tag:blogger.com,1999:blog-1708924581612271862024-03-14T01:11:03.387-07:00LTE Signaling: Troubleshooting and OptimizationUnknownnoreply@blogger.comBlogger45125tag:blogger.com,1999:blog-170892458161227186.post-45927186218699509902019-07-04T13:00:00.000-07:002019-07-04T13:00:01.041-07:00Optical Channel Layer <br />
<div class="MsoNormal">
<span style="color: #1c263d; font-family: "scala-sans-offc-pro--",serif; font-size: 12.0pt; line-height: 107%; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";">The Optical Channel Layer
is the highest level layer and interacts directly with the clients
system interface. It also provides the mechanism for transporting the
client's digital signal through into the OTH compliant network. The optical
channel trail from source to sink composes of two distinct
logical signals: <o:p></o:p></span></div>
<div class="MsoNormal">
<span style="color: #1c263d; font-family: "scala-sans-offc-pro--",serif; font-size: 12.0pt; line-height: 107%; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";"><br /></span></div>
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<span style="color: #1c263d; font-family: "scala-sans-offc-pro--",serif; font-size: 12.0pt; line-height: 107%; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";">1.The
optical client payload <o:p></o:p></span></div>
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<span style="color: #1c263d; font-family: "scala-sans-offc-pro--",serif; font-size: 12.0pt; line-height: 107%; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";">2.The
optical channel overhead ( the information added by OTH) <o:p></o:p></span></div>
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<br /></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjOcshvO3bWvodgsyrESKzkGQO6U8LwB_MSAlYwVcKtpRHPYQDYQCV6B1AswA33VNhQsEhqPeBxP6cuI453-xbJvqT_KybsdjAu-_6T2VcYP4EIgz-giwWPY2k4i2jdZIEq0YG6G0lWDwxr/s1600/1.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="270" data-original-width="594" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjOcshvO3bWvodgsyrESKzkGQO6U8LwB_MSAlYwVcKtpRHPYQDYQCV6B1AswA33VNhQsEhqPeBxP6cuI453-xbJvqT_KybsdjAu-_6T2VcYP4EIgz-giwWPY2k4i2jdZIEq0YG6G0lWDwxr/s1600/1.jpg" /></a></div>
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<o:p><br /></o:p></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in;">
<span style="color: #1c263d; font-family: "scala-sans-offc-pro--",serif; font-size: 12.0pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";">To provide for end-to-end networking the following
capabilities are included: </span><span style="color: #1c263d; font-family: "reader_ff",serif; font-size: 12.0pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";"> <o:p></o:p></span></div>
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<br /></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: .5in; margin-right: 0in; margin-top: 0in;">
<span style="color: #1c263d; font-family: "scala-sans-offc-pro--",serif; font-size: 12.0pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";">•Optical
Channel connection rearrangement <o:p></o:p></span></div>
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<br /></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: .5in; margin-right: 0in; margin-top: 0in;">
<span style="color: #1c263d; font-family: "scala-sans-offc-pro--",serif; font-size: 12.0pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";">•Processes
for ensuring the integrity of the information added by the optical channel
– This involves the introduction by OTH standards of bit-error rate
evaluation and FEC (forward error correction) <o:p></o:p></span></div>
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<br /></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: .5in; margin-right: 0in; margin-top: 0in;">
<span style="color: #1c263d; font-family: "scala-sans-offc-pro--",serif; font-size: 12.0pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";">•Supervisory
features for allowing network level management and control – this
function involves the introduction of OTH standards for provisioning
of connections, quality of service parameter exchange, and link
protection schemes for network survivability </span><span style="color: #1c263d; font-family: "reader_ff",serif; font-size: 12.0pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";"> <o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in;">
<br /></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in;">
<span style="color: #1c263d; font-family: "scala-sans-offc-pro--",serif; font-size: 12.0pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";">The process required to create an optical channel from
client data signal is: </span><span style="color: #1c263d; font-family: "reader_ff",serif; font-size: 12.0pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";"> <o:p></o:p></span></div>
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<br /></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: .5in; margin-right: 0in; margin-top: 0in;">
<span style="color: #1c263d; font-family: "scala-sans-offc-pro--",serif; font-size: 12.0pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";">1.To
create the optical channel from the client’s signal through interfacing
with a transponder/transceiver in order to generate a continuous data
stream that can be modulated onto a carrier wavelength <o:p></o:p></span></div>
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<br /></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: .5in; margin-right: 0in; margin-top: 0in;">
<span style="color: #1c263d; font-family: "scala-sans-offc-pro--",serif; font-size: 12.0pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";">2.The
generation of management/maintenance signals for the OS overhead </span><span style="color: #1c263d; font-family: "reader_ff",serif; font-size: 12.0pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";"><o:p></o:p></span></div>
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<br />Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-170892458161227186.post-43641966089528394372019-07-01T01:22:00.000-07:002019-07-01T01:22:01.187-07:00OTN Functional Architecture <br />
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<b><span style="font-family: inherit;">Bearing in mind the goals of the OTH initiative, we
can begin to visualize the structure and purpose of the OTN system. It
would be predominantly optical delivery, certainly in its transmission
path as it would be deployed over WDM. It would also retain one of
WDM's advantages that of frame, protocol and bit-rate transparency
independently of the client signals processing and transmission.
Furthermore, we can see that the OTN model will have to
provide telecommunications network management, monitoring and
administrative control. Last, but not least, the OTN will provide
necessary fault-tolerance, by providing protection mechanisms and
link fail-over for redundancy. <o:p></o:p></span></b></div>
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<br /></div>
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<b><span style="font-family: inherit;">Therefore, the OTN must deliver the
following functions on a per-client signal basis: <o:p></o:p></span></b></div>
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<b><span style="font-family: inherit;">•Transport <o:p></o:p></span></b></div>
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<b><span style="font-family: inherit;">•Routing <o:p></o:p></span></b></div>
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<b><span style="font-family: inherit;">•Multiplexing <o:p></o:p></span></b></div>
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<b><span style="font-family: inherit;">•Supervision <o:p></o:p></span></b></div>
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<b><span style="font-family: inherit;">•Survivability <o:p></o:p></span></b></div>
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<br /></div>
<br />Unknownnoreply@blogger.com1tag:blogger.com,1999:blog-170892458161227186.post-77529641388862277682019-06-27T03:30:00.000-07:002019-06-27T03:30:06.809-07:00The OTH Goals <br />
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<b>Some of the design goals of the OTH initiative were
to provide the following: <o:p></o:p></b></div>
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<b><br /></b></div>
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<b>1.Develop a holistic system to
handle rapid traffic growth <o:p></o:p></b></div>
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<b><br /></b></div>
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<b>2.Develop a system to handle
transparently diverse signal types, frames, bit-rates and protocols <o:p></o:p></b></div>
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<b><br /></b></div>
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<b>3.To develop management
OAM&P features through a supervisory information channel that did not
negatively impact payload bandwidth <o:p></o:p></b></div>
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<b><br /></b></div>
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<b>4.Preserve the natural
transparency and protocol independence of WDM and its
inherent advantages <o:p></o:p></b></div>
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<b><br /></b></div>
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<b>5.To develop OTN standards – for
optical termination, regeneration and cross-connects <o:p></o:p></b></div>
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<b><br /></b></div>
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<b>6.To work towards standards that
would make full mesh OTN network practical <o:p></o:p></b></div>
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<br /></div>
<br />Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-170892458161227186.post-1129242013593844762019-06-25T01:20:00.000-07:002019-06-25T01:20:00.391-07:00Optical Transport Hierarchy<br />
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Up until the advent of the OTN initiative, the optical
layer had been used simply as a physical medium over which to transmit
data. This was primarily because of the impossibility to
process optical data without first handling it over to the electrical
domain. The OTH principle was seen by many as the first step in rectifying
this shortcoming and in attempting to deliver some 'intelligence' to
a passive system. Now, the OTH does not rewrite the laws of physics
and it is still impossible to process data optically. However not to be
deterred by such detail they opted for reserving a specific
wavelength in order to use as a management or supervisor channel on
which they could transport management information between equipment.
Designers deemed this out-of-band supervisory channel a good
solution as it did not interfere or unduly affect <o:p></o:p></div>
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<br /></div>
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The payload of the underlying system was in contrast to
SDH's overhead bytes. The OTH out-of-band supervisor channel would carry
the same management information as SDH frames carried as overhead,
but without using up precious cargo space in the frames. <o:p></o:p></div>
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<br /></div>
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The OTH however would have to face come challenges as
WDM differed quite considerable from the SDH framed protocol. For
instance, there was no defined frame, DWM was light waves, without
any frame structure or protocol and that was one of its strengths.
Secondly, SDH handled one signal trail per path whereas WDM would be
carrying several client signals per path and each would have to
have its own individual management information with regards its own
client’s state and fault. <o:p></o:p></div>
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<br /></div>
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However, the challenge to delivering the project was
easily outweighed by the potential benefits. If the principles of the OTH
initiative could be applied to a working WDM out-of-band optical
supervisory channel (OSC) then the potential was massive. Optical
networks would be able to take on new topologies, such as partial and
complete mesh networks using optical add/drop multiplexors,
cross connects and optical switches in practical real
world deployments. This would be due to the underlying management
information being carried across the supervisory channel providing insight
into the state of the network at every optical termination point,
just like SDH. <o:p></o:p></div>
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<br /></div>
<div class="MsoNormal">
Furthermore, it would be possible to even implement
protection and link fail-over as a network reliability measure, again due
to having insight as to the link state between each optic termination
link. However, the comparisons with SDH don't end there the OSC could
also make provisioning of services possible, as it provides the ability to
create, delete, and manage a service remotely, as can be done
with SDH. <o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
In short, the OSC would do away with the WDM black-box
approach to service management and provide all the SDH style visibility,
manageability, flexibility and those precious OAM&P features
for which everyone was clamoring.<o:p></o:p></div>
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<br /></div>
<br />Unknownnoreply@blogger.com1tag:blogger.com,1999:blog-170892458161227186.post-83651208866825140562019-06-21T01:11:00.000-07:002019-06-21T01:11:01.973-07:00OTH (Optical Transport Hierarchy)<br />
<div class="MsoNormal">
The OTH (Optical Transport Hierarchy) was the initiative to
bring intelligence and OAM&P features to WDM. OTH is the underlying optical
multiplexing principles and techniques for aggregating several light wave
signals onto a single multiplexed signal, which is then transported as a single
signal across a single optical fiber. WDM's operation is independent of the
original signals format, frames or bit-rate so it can handle any signal type.
However, there are some physical restrictions in the WDM mode of operations. <o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoListParagraphCxSpFirst" style="margin-left: .75in; mso-add-space: auto; mso-list: l0 level1 lfo1; text-indent: -.25in;">
<!--[if !supportLists]--><span style="mso-bidi-font-family: Calibri; mso-bidi-theme-font: minor-latin;"><span style="mso-list: Ignore;">1.<span style="font: 7.0pt "Times New Roman";">
</span></span></span><!--[endif]-->All the client wavelengths must be different to avoid
interference. <o:p></o:p></div>
<div class="MsoListParagraphCxSpLast" style="margin-left: .75in; mso-add-space: auto; mso-list: l0 level1 lfo1; text-indent: -.25in;">
<!--[if !supportLists]--><span style="mso-bidi-font-family: Calibri; mso-bidi-theme-font: minor-latin;"><span style="mso-list: Ignore;">2.<span style="font: 7.0pt "Times New Roman";">
</span></span></span><!--[endif]-->All the wavelengths must be sufficiently separated
by a distance, a guard gap, to avoid signal cross talk. <o:p></o:p></div>
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<br /></div>
<div class="MsoNormal">
WDM's advantage though is that it can take many different
wavelengths (client signals) and multiplex them onto a single fiber, which had
previously been only capable of handling one wavelength (client signal). This
efficiency of resource usage is just one of WDM's beneficial features another
is that it can carry transparently any client signal type. For instance client
inputs can be from SDH, TDM, IP, ATM or any data stream as it is all
transparent to WDM, it concerns itself only with carrying wavelengths. <o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
At this point, it will be good to introduce the term Lambdas
as this term is often used to describe a single wavelength. Consequently, the
words wavelength and lambdas will be used inter-changeably in this book as the
terms are synonymous.<span style="mso-spacerun: yes;"> </span>On a similar note,
the term OTH (Optical Transport Hierarchy) is used to describe the efforts to
the OTH party to standardize the OTN network. However it can also be considered
to be interchangeable with the term G.709, which was the resultant standard. <o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
The OTH goal was to apply the principles of OTH design,
learned from SDH, with the technology of WDM to provide the basis for a
manageable fully meshed optical transport network, the OTN.<o:p></o:p></div>
<br />Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-170892458161227186.post-178339248219016222019-06-18T01:09:00.001-07:002019-06-18T01:09:51.550-07:00Narrowband-Internet of Things (NB-IoT)<br />
<div class="MsoNormal">
<span style="font-family: inherit;">The IoT and 5G massive Machine-Type Communications
(mMTC) will be a large market in 5G. NB-IoT is a Low Power Wide AreaNetwork
(LPWAN) radio technology 4G standard for IoT sensorsand devices to communicate
over cellular networks. However,unlike many other characteristics of 5G, NB-IoT
is not necessarily designed for speed. <o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span style="font-family: inherit;">Cat-NB1 uses a channel bandwidth of just200kHz, more akin
to the old Global System for Mobile Communications (GSM) standard than the
20MHz of LTE and 100MHz of5G NR.Cat-NB1 and its 5G derivative is the antithesis
of 5G enhanced Mobile Broadband (eMBB). It uses the narrowest bandwidth
andslowest data rate to lower costs and enable a ten-year (or
more) battery life. <o:p></o:p></span></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<span style="font-family: inherit;">Kbps stands for kilobits per second — and one
million kilobits equalsone gigabit — a popular measure of speed back when
modems used tone-modulated phone signals (accompanied by annoyingscreeching
sounds) and people still used the yellow pages.<o:p></o:p></span></div>
<div class="MsoNormal">
<span style="font-family: inherit;"><br /></span></div>
<div class="MsoNormal">
<span style="font-family: inherit;">NB-IoT is designed primarily for IoT sensors and devices.
Thelong range, using bands less than 1GHz, allows a vast network of low power
sensors, each sending small data reports, to be aggregated efficiently. For
these devices, it isn’t critical that the data they transmit is received with
ultra-low latency, or that every transmission be acknowledged by the receiver.
Thus, NB-IoT is an ideal technology for massive IoT use cases<o:p></o:p></span></div>
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<br /></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
<br /></div>
<br />Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-170892458161227186.post-45669632266248872772012-04-23T04:00:00.000-07:002012-04-23T04:00:11.775-07:00Medium Access Control (MAC) Protocol<br />
<h3 class="sect3-title" id="288-3" style="background-color: white; color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: medium; margin-bottom: 0.9em; margin-top: 1.3em; text-align: left;">
</h3>
<div class="first-para" id="289-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0em; margin-top: 0em; text-align: left;">
The MAC layer provides services through SAPs to the upper layer as all other sublayers of layer 2. The layer above MAC is the RLC layer; the lower layer is the physical layer which provides services to the MAC. In the case of the MAC, SAPs to the RLC layer are logical <span class="beginpage" pagenum="96"><a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="290" name="290" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="page96" name="page96" style="outline-color: initial; outline-style: none; outline-width: initial;"></a></span>channels. Logical channels are used by higher layers to differentiate between logical connections which may use different metrics, for example, in terms of quality or delay, and so on. Furthermore, logical channels are used to distinguish control plane connections, either CCCHs or DCCHs, from user plane connections (DTCHs).</div>
<div class="para" id="290-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<span class="beginpage" pagenum="97"><a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="291" name="291" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="page97" name="page97" style="outline-color: initial; outline-style: none; outline-width: initial;"></a></span>Services provided by the physical layer to the MAC layer are granted via another type of SAP. SAPs between the MAC and the physical layer are transport channels. Transport channels match data units to physical channels in which data is supposed to be transmitted. One exception is the PCH which is multiplexed into the PDSCH identified with the P-RNTI =0xFFFE.</div>
<div class="para" id="291-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Multiplexing of data units from logical channels to transport channels is one of the tasks of the MAC layer. Logical channels are differentiated with LCIDs. Tables 1 and 2 show the defined LCIDs and their values for DL and UL respectively. A CCCH always has LCID =0. Other UE dedicated channels start with LCID = 1.</div>
<a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="292" name="292" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; outline-color: initial; outline-style: none; outline-width: initial; text-align: left;"></a><a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="ch01table20" name="ch01table20" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; outline-color: initial; outline-style: none; outline-width: initial; text-align: left;"></a><span style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: x-small; text-align: left;"></span><br />
<table border="1" class="table" id="ch01table20" linktabletoexcel="yes" style="background-color: white; color: black; font-family: verdana, arial, helvetica, sans-serif; font-size: 11px; margin-bottom: 1em; margin-top: 1em; text-align: left;"><caption class="table-title" id="292-1" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small; font-weight: bold; margin-top: 0.3em; text-align: left;"><span class="table-title" style="margin-top: 0.3em;"><span class="table-titlelabel">Table 1: </span>Values of LCID for DL-SCH. </span></caption><thead>
<tr valign="top"><th align="left" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="292-2" style="margin-left: 0.3em; margin-right: 1em;">
Index</div>
</th><th align="left" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="292-3" style="margin-left: 0.3em; margin-right: 1em;">
LCID values</div>
</th></tr>
</thead><tbody>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="292-4" style="margin-left: 0.3em; margin-right: 1em;">
00000</div>
</td><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="292-5" style="margin-left: 0.3em; margin-right: 1em;">
CCCH</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="292-6" style="margin-left: 0.3em; margin-right: 1em;">
00001–01010</div>
</td><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="292-7" style="margin-left: 0.3em; margin-right: 1em;">
Identity of the logical channel</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="292-8" style="margin-left: 0.3em; margin-right: 1em;">
01011–11011</div>
</td><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="292-9" style="margin-left: 0.3em; margin-right: 1em;">
Reserved</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="292-10" style="margin-left: 0.3em; margin-right: 1em;">
11100</div>
</td><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="292-11" style="margin-left: 0.3em; margin-right: 1em;">
UE contention resolution identity</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="292-12" style="margin-left: 0.3em; margin-right: 1em;">
11101</div>
</td><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="292-13" style="margin-left: 0.3em; margin-right: 1em;">
Timing advance command</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="292-14" style="margin-left: 0.3em; margin-right: 1em;">
11110</div>
</td><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="292-15" style="margin-left: 0.3em; margin-right: 1em;">
DRX command</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="292-16" style="margin-left: 0.3em; margin-right: 1em;">
11111</div>
</td><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="292-17" style="margin-left: 0.3em; margin-right: 1em;">
Padding</div>
</td></tr>
</tbody></table>
<a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="293" name="293" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; outline-color: initial; outline-style: none; outline-width: initial; text-align: left;"></a><a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="ch01table21" name="ch01table21" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; outline-color: initial; outline-style: none; outline-width: initial; text-align: left;"></a><span style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: x-small; text-align: left;"></span><br />
<table border="1" class="table" id="ch01table21" linktabletoexcel="yes" style="background-color: white; color: black; font-family: verdana, arial, helvetica, sans-serif; font-size: 11px; margin-bottom: 1em; margin-top: 1em; text-align: left;"><caption class="table-title" id="293-1" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small; font-weight: bold; margin-top: 0.3em; text-align: left;"><span class="table-title" style="margin-top: 0.3em;"><span class="table-titlelabel">Table 1.21: </span>Values of LCID for UL-SCH. </span></caption><thead>
<tr valign="top"><th align="left" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="293-2" style="margin-left: 0.3em; margin-right: 1em;">
Index</div>
</th><th align="left" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="293-3" style="margin-left: 0.3em; margin-right: 1em;">
LCID values</div>
</th></tr>
</thead><tbody>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="293-4" style="margin-left: 0.3em; margin-right: 1em;">
00000</div>
</td><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="293-5" style="margin-left: 0.3em; margin-right: 1em;">
CCCH</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="293-6" style="margin-left: 0.3em; margin-right: 1em;">
00001–01010</div>
</td><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="293-7" style="margin-left: 0.3em; margin-right: 1em;">
Identity of the logical channel</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="293-8" style="margin-left: 0.3em; margin-right: 1em;">
01011–11001</div>
</td><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="293-9" style="margin-left: 0.3em; margin-right: 1em;">
Reserved</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="293-10" style="margin-left: 0.3em; margin-right: 1em;">
11010</div>
</td><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="293-11" style="margin-left: 0.3em; margin-right: 1em;">
Power headroom report</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="293-12" style="margin-left: 0.3em; margin-right: 1em;">
11011</div>
</td><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="293-13" style="margin-left: 0.3em; margin-right: 1em;">
C-RNTI</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="293-14" style="margin-left: 0.3em; margin-right: 1em;">
11100</div>
</td><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="293-15" style="margin-left: 0.3em; margin-right: 1em;">
Truncated BSR</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="293-16" style="margin-left: 0.3em; margin-right: 1em;">
11101</div>
</td><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="293-17" style="margin-left: 0.3em; margin-right: 1em;">
Short BSR</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="293-18" style="margin-left: 0.3em; margin-right: 1em;">
11110</div>
</td><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="293-19" style="margin-left: 0.3em; margin-right: 1em;">
Long BSR</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="293-20" style="margin-left: 0.3em; margin-right: 1em;">
11111</div>
</td><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="293-21" style="margin-left: 0.3em; margin-right: 1em;">
Padding</div>
</td></tr>
</tbody></table>
<div class="para" id="293-22" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
A MAC PDU consists of a MAC payload part and a MAC header part. The MAC payload conveys multiple units of MAC control elements and MAC SDUs from higher layers. Therefore, the MAC header is also divided into sub-headers depending on the units carried in the MAC payload as MAC sub-headers describe the MAC payload units. There are various possible combinations of MAC control elements, MAC SDUs, and MAC padding derivatives. An example of a MAC PDU with a combination of MAC sub-headers, MAC control elements, and MAC SDUs in the payload section is depicted in Figure 1.</div>
<div class="para" id="293-22" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgEaM9hVqGIg1tW9tbcA0-wZmUswq57V6SPdnmfnjMmvmyTbBa1hYDlUgPN9pssYj8mW6e5ppOcGRWa8vb-zRSmcSOT_tdTCLIQ9T3nO4gBps4zlUJAoF94eul1YXNPssxGRUyTLxbFSe_l/s1600/a.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgEaM9hVqGIg1tW9tbcA0-wZmUswq57V6SPdnmfnjMmvmyTbBa1hYDlUgPN9pssYj8mW6e5ppOcGRWa8vb-zRSmcSOT_tdTCLIQ9T3nO4gBps4zlUJAoF94eul1YXNPssxGRUyTLxbFSe_l/s640/a.jpg" width="640" /></a></div>
<div class="figure" id="ch01fig86" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="294" name="294" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="ch01fig86" name="ch01fig86" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><span class="figuremediaobject"></span><br />
<span class="figure-title" id="294-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 1: </span>Example of MAC PDU consisting of MAC header, MAC control elements, MAC SDUs, and padding (TS36.321). Reproduced with permission from © 3GPP<sup>™</sup></span></div>
<div class="para" id="294-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Logical channels which are multiplexed to transport channels are prioritized by the scheduling algorithm. The scheduling algorithm decides what to schedule on which physical resources as described in detail for DL scheduling. There is only one MAC entity per UE; thus, the UL within the UE has one MAC entity and the eNB executes multiple parallel MAC entities in the DL direction in case the eNB has to handle multiple UEs.</div>
<div class="last-para" id="294-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<span class="beginpage" pagenum="98"><a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="295" name="295" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="page98" name="page98" style="outline-color: initial; outline-style: none; outline-width: initial;"></a></span>The MAC layer implements a soft combining <i class="emphasis">N</i> -process stop-and-wait FEC and detection mechanism, or HARQ (Hybrid Automatic Repeat Request). Transport blocks are protected with a FEC algorithm known as turbo codes. Soft combining means not correctly decoded blocks are not acknowledged in order to conduct a retransmission, but the previous received not decoded block is held in a soft buffer to be recombined with the new retransmission. This process of soft combining two or more receptions increases the chance that the last received retransmission can be decoded error-free.</div>Unknownnoreply@blogger.com3tag:blogger.com,1999:blog-170892458161227186.post-13773087985192857302012-04-18T04:04:00.000-07:002012-04-18T04:04:00.167-07:00Stream Control Transmission Protocol (SCTP)<br />
<h3 class="sect3-title" id="280-4" style="background-color: white; color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: medium; margin-bottom: 0.9em; margin-top: 1.3em; text-align: left;">
<br /></h3>
<div class="first-para" id="281-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0em; margin-top: 0em; text-align: left;">
Originally the SCTP was defined as a transport protocol for SS7 messages to be transmitted over IP networks. As TCP and UDP it is seen as a layer 4 transport protocol in the ISO OSI model.</div>
<div class="para" id="281-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The SCTP frames are called chunks. All chunks are associated to a connection that guarantees in-order delivery. However, within the same chunk there might be data blocks of different connections transmitted simultaneously. In addition, it is also possible to send urgent packets "out of order" with a higher priority.</div>
<div class="para" id="281-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
SCTP also supports multihoming scenarios where one host owns multiple valid IP addresses.</div>
<div class="para" id="281-4" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Besides the data streams, SCTP frequently sends heartbeat messages to test the state of connection.</div>
<div class="para" id="281-5" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
How SCTP works will be demonstrated by means of an example. Figure 1 shows the message flow required to transport the NAS signaling message Attach Request from the eNB to MME across the S1 interface.</div>
<div class="para" id="281-5" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjhh5cs2A1arsd8EaprZ1OxaKYGqEBGN0m8sg-iVlhT3Mrq9RtAXnIgeOuqk1EzoAnaunZsQaPmtHYBAnq_aB8m2e0pWyEOMy9_NhMcmYgMiW52hHAcLMoSzXYV72PKdgHgZ0wwepn0IcP1/s1600/a.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjhh5cs2A1arsd8EaprZ1OxaKYGqEBGN0m8sg-iVlhT3Mrq9RtAXnIgeOuqk1EzoAnaunZsQaPmtHYBAnq_aB8m2e0pWyEOMy9_NhMcmYgMiW52hHAcLMoSzXYV72PKdgHgZ0wwepn0IcP1/s400/a.jpg" width="375" /></a></div>
<div class="figure" id="ch01fig82" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="282" name="282" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><a href="" id="ch01fig82" name="ch01fig82" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="282-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 1: </span>SCTP example</span></div>
<div class="para" id="282-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
After setting up a RRC connection on the Uu interface between the UE and the eNB, the UE sends the attach request message. When the appropriate RRC transport container is received by the eNB, the establishment of a dedicated SCTP stream on the S1 interface as shown in Figure 2 is triggered.</div>
<div class="para" id="282-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The establishment of the SCTP stream starts with a SCTP initiation message. It will always be sent by the eNB in the case of the attach procedure, because the RRC connection is established earlier and the request to transport the NAS message triggers the request to have a S1 connection. The SCTP initiation message contains the IP addresses of both the eNB and MME. The individual subscriber for which this connection is established is represented by a unique pair of SCTP source port and destination port numbers.</div>
<div class="para" id="282-4" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The SCTP initiation needs to be acknowledged by the peer SCTP entity in the MME. In the next step a SCTP cookie echo message is sent and acknowledged by Cookie Echo ACK. In the protocol world, this is called a heartbeat procedure. Such a procedure periodically checks the availability and function of the active connection. Similar functions with other message names are found, for example, in SS7 SCCP Inactivity Test or GTP Echo Request/Response.</div>
<div class="para" id="282-5" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
On SCTP higher layer messages are transported using SCTP datagram (SCTP DTGR) packets. Each SCTP DTGR contains a Transaction Sequence Number (TSN) in addition to source and destination address information. This TSN will later be used by the peer entity to acknowledge the successful reception of the DTGR by sending an SCTP selective ACK message on S1 that confirms error-free reception of the SCTP DTGR that carried the attach request message. Further S1AP and NAS messages of this connection will be transported in the same way and the Cookie Echo/Cookie Echo ACKs will be sent periodically as long as the connection remains active.</div>
<div class="para" id="282-6" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<span class="beginpage" pagenum="94"><a href="" id="283" name="283" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><a href="" id="IDX-94" name="IDX-94" style="outline-color: initial; outline-style: none; outline-width: initial;"></a></span>If the S1 signaling transport layer SCTP has problems in offering proper functionality, there will be no signaling transport on S1 if the problems are located in the eNB SCTP entity. If the MME suffers from congestion or protocol errors on the SCTP level as shown in <a class="internaljump" href="" style="color: green; cursor: pointer; outline-color: initial; outline-style: none; outline-width: initial;">Figure 1.83</a>, the expected selective ACK messages will be missing (maybe not sent at all, maybe sent with a TSN out of the expected range). This malfunction may be detected by a NACK Cookie Echo and as a result the connection will be terminated. Or the attach accept message expected to be received by the UE will be missed. The missing attach accept message will be recognized by the UE where a timer is guarding the NAS procedures. After the guard timer expires on the UE side the attach request message will be repeatedly sent up to <i class="emphasis">n</i> times (the counter value of <i class="emphasis">n</i> is configurable and typically signaled on the broadcast channel SIBs; the default value recommended by 3GPP is <i class="emphasis">n</i> = 5). If neither an attach request message nor an attach reject message is received by the UE the handset will go back to IDLE when the maximum number of attach request repetitions has been sent.</div>
<div class="para" id="282-6" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
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<div class="figure" id="ch01fig83" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="284" name="284" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><a href="" id="ch01fig83" name="ch01fig83" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="284-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 2: </span>Failure in SCTP signaling transport</span></div>Unknownnoreply@blogger.com3tag:blogger.com,1999:blog-170892458161227186.post-32976332131235199732012-04-15T20:01:00.000-07:002012-04-15T20:01:00.492-07:00Internet Protocol (IPv4/IPv6)<br />
<h3 class="sect3-title" id="269-2" style="background-color: white; color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: medium; margin-bottom: 0.9em; margin-top: 1.3em; text-align: left;">
<br /></h3>
<div class="first-para" id="270-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0em; margin-top: 0em; text-align: left;">
The IP frame is called the datagram and there exist two main versions of the IP: IPv4 and IPv6.</div>
<div class="section" id="ch01lev3sec24" style="background-color: white; font-family: Arial, Helvetica, sans-serif; text-align: left;">
<h4 class="sect4-title" id="annotationlabel-1" style="color: #010100; margin-bottom: 0em; margin-top: 0.9em;">
<span style="outline-color: initial; outline-width: initial;"><a href="" id="271" name="271" style="outline-color: initial; outline-style: none; outline-width: initial;"></a></span>IPv4</h4>
<div class="first-para" id="271-1" style="font-size: small; margin-bottom: 0em; margin-top: 0em;">
The IP header has a minimum size of 20 bytes (if no options are used) and a maximum size of 64 bytes (including options and padding bits). Due to a set of different options that can be appended to the IPv4 header, these headers can become very large.</div>
<div class="para" id="271-2" style="font-size: small; margin-top: 0.9em;">
<span class="beginpage" pagenum="90"><a href="" id="272" name="272" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><a href="" id="page90" name="page90" style="outline-color: initial; outline-style: none; outline-width: initial;"></a></span>The included information elements shown in Figure 1 are:</div>
<ul class="itemizedlist" style="font-size: small; list-style-image: initial; list-style-position: initial; list-style-type: square; margin-left: 3em; margin-top: 0.9em;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="first-para" id="272-1" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold">Version</b>: IP protocol version, here IPv4.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="272-2" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold">Internet header length</b> (IHL length): The length of the header.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="272-3" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold">Type of Service</b>: The QoS parameters for IP.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="272-4" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold">Total Length</b>: The length of the IP frame including header and payload field.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="272-5" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold">Identification, Fragment Offset</b>: Both used in case of fragmentation/reassembly.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="272-6" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold">Time to Live</b>: A hop counter to prevent circular routing.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="272-7" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold">Protocol</b>: Indicates the higher layer protocol that uses IP as the transport layer; typical examples are ICMP, TCP, UDP.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="272-8" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold">Source Address</b>: IP address of the sender of the datagram.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="272-9" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold">Destination Address</b>: IP address of the receiver of the datagram.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="272-10" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold">Options</b>: For example, the timestamp of each router that the IP packet passed.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="272-11" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold">Padding</b>: Fill bits to align the header to a multiple of 32 bits.</div>
</li>
</ul>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjoUTOloIl8WdnPYcqfjdT7K0omkmkuXvlULkl7s1q1WFW86erZAxqf1R4WcgnO0KyyX5MsYJrZ_lJXsMIaGNvD0pu55lXyTXnN3dTousKfnbMjHBSdp-DYBKCthm0GBuoABeb0ZYW3XSlW/s1600/a.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="286" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjoUTOloIl8WdnPYcqfjdT7K0omkmkuXvlULkl7s1q1WFW86erZAxqf1R4WcgnO0KyyX5MsYJrZ_lJXsMIaGNvD0pu55lXyTXnN3dTousKfnbMjHBSdp-DYBKCthm0GBuoABeb0ZYW3XSlW/s640/a.jpg" width="640" /></a></div>
<div class="figure" id="ch01fig78" style="font-size: small; margin-left: 2em; margin-top: 1em;">
<a href="" id="273" name="273" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><a href="" id="ch01fig78" name="ch01fig78" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><span class="figuremediaobject"><a href="http://www.books24x7.com/assetviewer.aspx?bookid=40946&chunkid=984807587&noteMenuToggle=0&leftMenuState=1" name="IMG_88" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;" target="_self"></a></span> <br style="line-height: 1;" /><span class="figure-title" id="273-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 1: </span>IP datagram structure</span></div>
<div class="para" id="273-2" style="font-size: small; margin-top: 0.9em;">
Since the maximum packet size of an IP datagram can vary from one local network to the next, the IP is equipped with fragmentation/reassembly functionality that allows the transmission of larger frames in series of smaller portions. Figure 2 shows an example where a frame with 1600 bytes of data is fragmented into two smaller frames with 1480 and 120 bytes of data each. Fragmented frames do all have the same frame ID (in the example: 1234). As long as more fragments are following the first one, the fragmentation flag MF is set to "1." The last frame in a series of fragments has fragmentation flag MF = "0," but a fragmentation offset that is required for proper reassembly on the receiver side.</div>
<div class="para" id="273-2" style="font-size: small; margin-top: 0.9em;">
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<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgrbWKX-kqPnjSGGtnV2knrK0HnmpMYSUGKzDrnWFyWfHB3APzr4kMgCLAcmU65yICZnY7tLhUTZdHiRLs_F4ARJl2a9DlLWJtRvUAw2ugJUiBiBbxLtkarIiJZBgxrakKFDMtupHEuVpoz/s1600/b.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="358" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgrbWKX-kqPnjSGGtnV2knrK0HnmpMYSUGKzDrnWFyWfHB3APzr4kMgCLAcmU65yICZnY7tLhUTZdHiRLs_F4ARJl2a9DlLWJtRvUAw2ugJUiBiBbxLtkarIiJZBgxrakKFDMtupHEuVpoz/s400/b.jpg" width="400" /></a></div>
<div class="figure" id="ch01fig79" style="font-size: small; margin-left: 2em; margin-top: 1em;">
<a href="" id="274" name="274" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><a href="" id="ch01fig79" name="ch01fig79" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="274-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 2: </span>IP fragmentation</span></div>
<div class="para" id="274-2" style="font-size: small; margin-top: 0.9em;">
IP fragmentation (Figure 2) may be found in the user plane data streams, but should be avoided on interfaces that carry 3GPP signaling.</div>
<div class="para" id="274-3" style="font-size: small; margin-top: 0.9em;">
IPv4 addresses are typically written in the so-called dotted decimal notation, for example, 195.24.1.2. There are 32 bits (= 4 bytes) reserved for the address fields in the IP datagram. Each number in the dotted decimal format represents the decimal value of a single byte. The dot "." is used as the separator between the different bytes of the IP address. Figure 3 shows a sample address in binary, hexadecimal, and decimal dotted notation format.</div>
<div class="para" id="274-3" style="font-size: small; margin-top: 0.9em;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhb0IJVthXUms9I3C3LmDjeuld6ZRcKoaLJVF_9kYw0zCC4qFkGmhpSSJszcV9yUVrSskdmbwDjdEYVIBdRQozewOZHd0q9kbhSevpfCptPLo1Dc4N6skodJpSJXZdcy0GocdpPoij3TXlt/s1600/c.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="114" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhb0IJVthXUms9I3C3LmDjeuld6ZRcKoaLJVF_9kYw0zCC4qFkGmhpSSJszcV9yUVrSskdmbwDjdEYVIBdRQozewOZHd0q9kbhSevpfCptPLo1Dc4N6skodJpSJXZdcy0GocdpPoij3TXlt/s320/c.jpg" width="320" /></a></div>
<div class="figure" id="ch01fig80" style="font-size: small; margin-left: 2em; margin-top: 1em;">
<a href="" id="275" name="275" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><a href="" id="ch01fig80" name="ch01fig80" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="275-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 3: </span>Example of IPv4 address format</span></div>
</div>
<div class="section" id="ch01lev3sec25" style="background-color: white; font-family: Arial, Helvetica, sans-serif; text-align: left;">
<h4 class="sect4-title" id="annotationlabel-2" style="color: #010100; font-size: small; margin-bottom: 0em; margin-top: 0.9em;">
<a href="" id="276" name="276" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><span class="section-titlelabel"> </span></h4>
<h4 class="sect4-title" id="annotationlabel-2" style="color: #010100; margin-bottom: 0em; margin-top: 0.9em;">
IPv6</h4>
<div class="first-para" id="276-1" style="font-size: small; margin-bottom: 0em; margin-top: 0em;">
<span class="beginpage" pagenum="91"><a href="" id="277" name="277" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><a href="" id="page91" name="page91" style="outline-color: initial; outline-style: none; outline-width: initial;"></a></span>The most important improvements that come with IPv6 are:</div>
<ul class="itemizedlist" style="font-size: small; list-style-image: initial; list-style-position: initial; list-style-type: square; margin-left: 3em; margin-top: 0.9em;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="first-para" id="277-1" style="margin-bottom: 0em; margin-top: 0em;">
A larger number of possible address values become available. In IPv4 the number of addresses is limited to 32 bits, which means in turn that 2<sup>32</sup> (<span class="unicode" style="font-family: 'Lucida Sans Unicode', Arial, Helvetica, sans-serif;">≈</span>4.3 billion = 4.3 × 10<sup>9</sup>) possible values can be addressed. IPv6 provides space for 2<sup>128</sup> (=3.4 × 10<sup>38</sup>) possible address values. This is an improvement by a factor of 2<sup>96</sup> and reached by a restructuring of the IP header. In the IPv6 header shown in Figure 4, 128 bits (16 bytes) is reserved for source and destination addresses. The larger address ranges available for IPv6 will also allow more direct end-to-end packet routing and, hence, less address translation in network nodes is required and the packet routing in the overall network is expected to be faster and more efficient.</div>
<div class="first-para" id="277-1" style="margin-bottom: 0em; margin-top: 0em;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiyXNnRBpeffhuQKdJ-aC74YKuHegtIVD3p-q8AsaDXcrqPZaajcs-CCGHk4ZleW1uCYY6fvB9bwOAjQ4Ogv5693ThP3bFHT6BxECEsbONkz2ctu1h6dXCI9KGla6mQGdqHKdvqPulCvXng/s1600/d.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="138" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiyXNnRBpeffhuQKdJ-aC74YKuHegtIVD3p-q8AsaDXcrqPZaajcs-CCGHk4ZleW1uCYY6fvB9bwOAjQ4Ogv5693ThP3bFHT6BxECEsbONkz2ctu1h6dXCI9KGla6mQGdqHKdvqPulCvXng/s400/d.jpg" width="400" /></a></div>
<div class="figure" id="ch01fig81" style="margin-left: 2em; margin-top: 1em;">
<a href="" id="278" name="278" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><a href="" id="ch01fig81" name="ch01fig81" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="278-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 4: </span>IPv6 header format</span></div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="278-2" style="margin-bottom: 0em; margin-top: 0em;">
The automatic configuration of dynamically assigned IP addresses is improved and in turn legacy procedures like DHCP (Dynamic Host Configuration Protocol) become unnecessary.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="278-3" style="margin-bottom: 0em; margin-top: 0em;">
<span class="beginpage" pagenum="92"><a href="" id="279" name="279" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><a href="" id="page92" name="page92" style="outline-color: initial; outline-style: none; outline-width: initial;"></a></span>IPv6 supports Mobile IP, simplifies renumbering (change of dynamically assigned IP addresses), and allows multihoming of subscribers. The purpose of multihoming is to increase the reliability of Internet connections by using two different Internet service providers simultaneously. If the access to one of the providers is interrupted a redirection of packets via the second connection is possible. Mobile IP means that the subscriber always gets the same IP address assigned, no matter if working at home or traveling around.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="279-1" style="margin-bottom: 0em; margin-top: 0em;">
IPsec is integrated into IPv6 to achieve a higher security of IP data transmission, while back in IPv4 no security functions were provided at all.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="279-2" style="margin-bottom: 0em; margin-top: 0em;">
All in all, the basic header of IPv6 has a simpler structure compared to the header of IPv4. Although the overall header size is larger than in IPv4 (40 bytes, most of them occupied by the longer IP addresses), there are less basic header fields.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="279-3" style="margin-bottom: 0em; margin-top: 0em;">
For the version, the decimal number 6 is encoded as binary bit sequence "0110."</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="279-4" style="margin-bottom: 0em; margin-top: 0em;">
The IPv6 traffic class indicates the packet priority and should not be mistaken for the traffic class QoS element introduced in 3GPP standards that classifies the throughput sensitivity and delay sensitivity of application services. IPv6 traffic class priority values subdivide into two ranges: traffic, where the source provides congestion control, and non-congestion control traffic.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="279-5" style="margin-bottom: 0em; margin-top: 0em;">
The flow label is used for QoS management and encoded in 20 bits. Packets having the same flow label value will be treated with the same priority and reliability. This is important for the routing of packets that contain real-time service data.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="279-6" style="margin-bottom: 0em; margin-top: 0em;">
The payload length indicates the size of the payload in octets and is encoded in 16 bits. When cleared to zero, the option is a "Jumbo Payload" (hop by hop). The size of the basic header is not counted by the payload length, but the optional header extensions are included. So payload length + 40 bytes (of basic header) = total length of the IPv6 packet.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="279-7" style="margin-bottom: 0em; margin-top: 0em;">
The next header information element specifies the next upper layer protocol of the transported payload such as UDP and TCP. The values are compatible with those specified for the IPv4 protocol field (8 bits). The next header information can also point to optional extension headers. In this case the upper layer payload protocol is not indicated by this field.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="279-8" style="margin-bottom: 0em; margin-top: 0em;">
The hop limit field (8 bits) indicates the maximum number of routers that are allowed to be involved in routing an IPv6 packet. It replaces the time to live field of IPv4. If the hop limit reaches the value "zero" the packet will be discarded by the router.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="279-9" style="margin-bottom: 0em; margin-top: 0em;">
Source and destination addresses, 128 bits each, represent the sender and receiver of the IPv6 datagram.</div>
</li>
</ul>
<div class="para" id="279-10" style="font-size: small; margin-top: 0.9em;">
IPv6 addresses are normally written as eight groups of 16 bits, where each group is separated by a colon (:). For example, 2001:0db8:85a3:0000:0000:8a2e:0370:7334 is a valid IPv6 address.</div>
<div class="para" id="279-11" style="font-size: small; margin-top: 0.9em;">
<span class="beginpage" pagenum="93"><a href="" id="280" name="280" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><a href="" id="page93" name="page93" style="outline-color: initial; outline-style: none; outline-width: initial;"></a></span>To shorten the writing and presentation of addresses, several simplifications to the notation are permitted. Any leading zeros in a group may be omitted; thus, the given example becomes: 2001:db8:85a3:0:0:8a2e:370:7334.</div>
<div class="para" id="280-1" style="font-size: small; margin-top: 0.9em;">
Also, one or any number of consecutive groups of value 0 may be replaced with two colons (::): 2001:db8:85a3::8a2e:370:7334.</div>
<div class="para" id="280-2" style="font-size: small; margin-top: 0.9em;">
It is possible to use IPv6 addresses in the URL notation format. In this case the IPv6 address information is enclosed in square brackets:</div>
<div class="para" id="280-2" style="font-size: small; margin-top: 0.9em;">
<br /></div>
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<div class="informalequation" id="N418" style="font-size: small;">
<span class="equation-image"></span></div>
<div class="para" id="280-3" style="font-size: small; margin-top: 0.9em;">
The brackets prevent that part of the IPv6 address being misinterpreted as port number information. A URL including IPv6 address and port number looks like this:</div>
<div class="para" id="280-3" style="font-size: small; margin-top: 0.9em;">
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<div class="informalequation" id="N429" style="font-size: small;">
<span class="equation-image"></span></div>
</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-170892458161227186.post-18317529988913865712012-04-11T05:55:00.000-07:002012-04-11T05:55:00.163-07:00Ethernet | Protocol Functions, Encoding, Basic Messages, and Information Elements<br />
<h3 class="sect3-title" id="265-1" style="background-color: white; color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: medium; margin-bottom: 0.9em; margin-top: 1.3em; text-align: left;">
<br /></h3>
<div class="first-para" id="266-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0em; margin-top: 0em; text-align: left;">
Ethernet is the typical transport layer protocol in IP networks. It is designed to transmit packets from a sender to a receiver, both identified on behalf of an address information element.</div>
<div class="para" id="266-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
According to this limited functionality, Ethernet has a very small header. The header field (Figure 1) contains only the information elements:</div>
<ul class="itemizedlist" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; list-style-image: initial; list-style-position: initial; list-style-type: square; margin-left: 3em; margin-top: 0.9em; text-align: left;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="first-para" id="266-3" style="margin-bottom: 0em; margin-top: 0em;">
Destination address.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="266-4" style="margin-bottom: 0em; margin-top: 0em;">
Source address.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="266-5" style="margin-bottom: 0em; margin-top: 0em;">
Ethernet type.</div>
</li>
</ul>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhYT0LgjEkjOL5AA7XgWlrNmnJPduORa52pgDwjtKmFp8bowE3InQP4s-sCmojQSuLKIexALaUo1DOis0Zy672jF0n6LqhyumqedfA2-Shh2ZfAaMWUvUah8LuNcXAlKgU_qHYQBdqxF-YW/s1600/a.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="124" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhYT0LgjEkjOL5AA7XgWlrNmnJPduORa52pgDwjtKmFp8bowE3InQP4s-sCmojQSuLKIexALaUo1DOis0Zy672jF0n6LqhyumqedfA2-Shh2ZfAaMWUvUah8LuNcXAlKgU_qHYQBdqxF-YW/s640/a.jpg" width="640" /></a></div>
<div class="figure" id="ch01fig76" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="267" name="267" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><a href="" id="ch01fig76" name="ch01fig76" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="267-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 1: </span>Ethernet header example</span></div>
<div class="para" id="267-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<span class="beginpage" pagenum="89"><a href="" id="268" name="268" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><a href="" id="page89" name="page89" style="outline-color: initial; outline-style: none; outline-width: initial;"></a></span>Ethernet type is similar to a SAPI (Service Access Point Identifier). It contains information about which higher layer protocol information is transported by Ethernet frames.</div>
<div class="para" id="268-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The Ethernet addresses, often called MAC addresses (but with nothing in common with RLC/MAC!), consist of 6 bytes. These MAC addresses are fixed hardware addresses and, due to a defined numbering scheme, each address is unique worldwide.</div>
<div class="para" id="268-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
If IP data is to be transmitted using Ethernet the hardware MAC address of the receiver of IP packets is unknown when the connection starts. Only the target IP address is known. However, since Ethernet is the lowest layer of the connection there must be a source and a destination MAC address included in each header. In other words, for each sender IP address there is an appropriate sender hardware address, and for each destination IP address there must be an appropriate target hardware address.</div>
<div class="para" id="268-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The target hardware address that is related to the target IP address is requested by the Address Resolution Protocol (ARP). Its sister protocol, the Reverse Address Resolution Protocol (RARP), can be used to find the target IP address (or, in terms of ARP/RARP, the target protocol address) to a known MAC address.</div>
<div class="para" id="268-4" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The address resolution procedure consists of two steps:</div>
<ol class="orderedlist" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px; margin-left: 3em; margin-top: 0.4em; text-align: left;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="first-para" id="268-5" style="margin-bottom: 0em; margin-top: 0em;">
ARP request (req) message with Target Hardware Address = "0" is sent to <i class="emphasis">all(!)</i> IP clients in the network.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="268-6" style="margin-bottom: 0em; margin-top: 0em;">
The client that has the target protocol address as set in the ARP req message sends ARP Replay (rpl). The sender hardware address in ARP rpl is the Ethernet MAC address related to the destination IP address that the sender of the ARP req is looking for. An example of the Ethernet address resolution procedure is shown in Figure 2.</div>
<div class="first-para" id="268-6" style="margin-bottom: 0em; margin-top: 0em;">
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</li>
</ol>
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<div class="figure" id="ch01fig77" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="269" name="269" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><a href="" id="ch01fig77" name="ch01fig77" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="269-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 2: </span>Ethernet address resolution</span></div>Unknownnoreply@blogger.com1tag:blogger.com,1999:blog-170892458161227186.post-252776066351268662012-04-07T19:51:00.000-07:002012-04-08T19:52:14.881-07:00S1 – Control/User Plane<br />
<h3 class="sect3-title" id="254-7" style="background-color: white; color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: medium; margin-bottom: 0.9em; margin-top: 1.3em; text-align: left;">
<br /></h3>
<div class="first-para" id="255-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0em; margin-top: 0em; text-align: left;">
On the S1 reference point the physical layer L1 will in most cases be realized by Gigabit Ethernet cables. L2 in this case will be Ethernet. On top of Ethernet we find IP, but used as a transport protocol between two network nodes: eNB and MME. This lower layer IP does not represent the user plane frames.</div>
<div class="para" id="255-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Instead, the user plane IP frames (higher layer IP) are carried by the GTP Tunneling Packet Data Unit (T-PDU). The GTP is responsible for the transport of payload frames through the IP tunnels on S1-U. The transport layer for GTP-U is the User Datagram Protocol (UDP). As IP this protocol may be found twice in the user plane stack: lower UDP for transport between the eNB and MME and higher UDP (not shown in Figure 1) that is transparently routed through the mobile network as the <span class="beginpage" pagenum="87"><a href="" id="256" name="256" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><a href="" id="page87" name="page87" style="outline-color: initial; outline-style: none; outline-width: initial;"></a></span>transport protocol for real-time application data. The higher layer IP on top of GTP-U as well as all application data on top of this higher layer IP are identical with the user plane information.</div>
<div class="para" id="255-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
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<div class="figure" id="ch01fig72" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="257" name="257" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><a href="" id="ch01fig72" name="ch01fig72" style="outline-color: initial; outline-style: none; outline-width: initial;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="257-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 1: </span>Protocol stack S1 control/user plane</span></div>
<div class="last-para" id="257-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
On the control plane side, the Streaming Control Transport Protocol (SCTP) provides reliable transport functionality for the very important signaling messages. S1AP is the communication expression between MME and S-GW while NAS</div>Unknownnoreply@blogger.com2tag:blogger.com,1999:blog-170892458161227186.post-78584706883310639822012-02-20T04:44:00.000-08:002012-02-20T04:44:00.222-08:00LTE Network Protocol Architecture<br />
<h3 class="sect3-title" id="251-1" style="background-color: white; color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: medium; margin-bottom: 0.9em; margin-top: 1.3em; text-align: left;">
Uu – Control/User Plane</h3>
<div class="first-para" id="252-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0em; margin-top: 0em; text-align: left;">
The protocol stack used on radio interface Uu is shown in Figure 1. The physical layer in this stack is represented by OFDM in the DL and SC-FDMA in the UL. Then we see the MAC protocol that is <span class="beginpage" pagenum="86"><a href="" id="253" name="253" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page86" name="page86" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>responsible for mapping the transport channels onto the physical channels, but also for such important tasks as packet scheduling and timing advance control. RLC provides reliable transport services and can be used to segment/reassemble large frames. The main purpose of PDCP is the compression of larger IP headers as well as ciphering of user plane data and integrity protection of both user plane and control plane data.</div>
<div class="first-para" id="252-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0em; margin-top: 0em; text-align: left;">
<br /></div>
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<div class="figure" id="ch01fig71" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="254" name="254" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig71" name="ch01fig71" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="254-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 1: </span>Protocol stack LTE Uu interface</span></div>
<div class="para" id="254-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
On top of PDCP the stack is split into the user plane and control plane parts. On the control plane side we see RRC protocol, that is, the expression for the communication between the UE and eNB. RRC provides all the necessary functions to set up, maintain, and release a radio connection for a particular subscriber. </div>
<div class="para" id="254-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
RRC also serves as a transport protocol for NAS signaling messages. NAS is the expression for the communication between the UE and MME in which MME represents the core network.</div>
<div class="para" id="254-4" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
On the user plane side we see IP as the transport layer for end-to-end applications. On the Uu stack the IP is always end-to-end IP, which means that all these IP packets are transparently routed, often tunneled through the mobile network. The user plane IP frames we see on Uu are the same IP frames that can be monitored at SGi reference points before or behind the PDN-GW.</div>
<div class="para" id="254-5" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The IP version can be Internet Protocol version 4 (IPv4) or Internet Protocol version 6 (IPv6). In the case of VPN (Virtual Private Network) traffic, IPsec will be used.</div>
<div class="last-para" id="254-6" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The applications on top of IP in the user plane stack are all protocols of the TCP/IP suite, such as the File Transfer Protocol (FTP), HTTP (web-browsing), and POP3/SMTP (for e-mail), but also Real-Time Transport Protocol (RTP) and SIP for real-time services like VoIP.</div>Unknownnoreply@blogger.com1tag:blogger.com,1999:blog-170892458161227186.post-60720978646894578182012-02-16T07:52:00.000-08:002012-02-16T07:52:00.145-08:00Initial UE Radio Access<br />
<h3 class="sect3-title" id="237-8" style="background-color: white; color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: medium; margin-bottom: 0.9em; margin-top: 1.3em; text-align: left;">
<br /></h3>
<div class="first-para" id="238-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0em; margin-top: 0em; text-align: left;">
Cell search is a procedure for synchronizing time and frequency to a base station sector. Additionally, cell search and synchronization include deriving basic information of the target cell.</div>
<div class="para" id="238-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
LTE defines a hierarchical cell search as it is deployed with WCDMA UMTS. PSS and SSS provide radio frame and slot synchronization, as well as information like the duplex mode TDD or FDD and the physical layer group and c-ID.</div>
<div class="para" id="238-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
UEs synchronizing to a new LTE cell start searching for a PSS which is a Zadoff–Chu sequence. Three sequences are defined indicating the physical cell group ID. Three physical layer c-ID groups with 168 physical layer c-IDs each are defined. After successfully detecting the PSS with its physical layer c-ID group and slot timing, the SSS is decoded which is broadcasted one OFDM symbol prior to the PSS. Now the UE retrieved DL slot, radio frame timing and frequency synchronization. With decoding successfully PSS and SSS, it obtained as well the complete 9-bit physical layer c-ID together with the radio frame type (either type 1 for FDD or type 2 for TDD) and the CP length.</div>
<div class="para" id="238-4" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Figure 1 illustrates the initial steps of cell synchronization and access. After synchronization, the UE is ready to detect and decode the PBCH in order to derive the system bandwidth, PHICH configuration, and the current System Frame Number (SFN). Other common system information now needs to be retrieved from the DL-SCH. SIBs are scheduled on regular shared channel resources by <span class="beginpage" pagenum="81"><a href="" id="239" name="239" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page81" name="page81" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>using a special C-RNTI = 0xFFFF. SIBs provide general system configuration information like UL configuration and random access configuration.</div>
<div class="para" id="238-4" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
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<div class="figure" id="ch01fig66" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="240" name="240" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig66" name="ch01fig66" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="240-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 1: </span>Initial cell access with level of retrieved information</span></div>Unknownnoreply@blogger.com1tag:blogger.com,1999:blog-170892458161227186.post-59894005806704088592012-02-12T08:09:00.000-08:002012-02-12T08:09:00.214-08:00Channel Mapping and Multiplexing<br />
<h3 class="sect3-title" id="233-1" style="background-color: white; color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: medium; margin-bottom: 0.9em; margin-top: 1.3em; text-align: left;">
<br /></h3>
<div class="first-para" id="234-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0em; margin-top: 0em; text-align: left;">
Besides physical and transport channels, LTE also defines logical channels. Logical channels are multiplexed to transport channels within the MAC layer. Logical channels map different content connections to transport channels, like CCCHs to multiple UEs or DCCHs to a specific UE or dedicated transport channels carrying higher layer application data.</div>
<div class="para" id="234-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Logical channels are addressed with a logical channel ID. The logical ID is a field within the MAC header PDU. Logical channels are multiplexed by using logical channel IDs to transport channels specifying where the information should be transmitted. Finally, transport channels are transferred with physical channels as a service provided by the physical channel.</div>
<div class="para" id="234-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Figures 1 and 2 show the above-described channel architecture from the basic physical channels via transport channels to logical channels bearing higher layer messages for DL and UL respectively.</div>
<div class="para" id="234-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgRmnmCM17mTGND5fQpifUTWaBSra9v5DoLDluFcDDqR5772G1_lQps3LA7x3Ka6XKVoocEfdzXIwxAQs1oiXipIUwDus6rKd3igIBr5pFXUBx2L3gE359J8cHOqcP1sDj7gL2Wxw_4G3c5/s1600/a.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="177" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgRmnmCM17mTGND5fQpifUTWaBSra9v5DoLDluFcDDqR5772G1_lQps3LA7x3Ka6XKVoocEfdzXIwxAQs1oiXipIUwDus6rKd3igIBr5pFXUBx2L3gE359J8cHOqcP1sDj7gL2Wxw_4G3c5/s400/a.jpg" width="400" /></a></div>
<div class="figure" id="ch01fig64" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="235" name="235" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig64" name="ch01fig64" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="235-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 1: </span>Downlink channel mapping and multiplexing from logical channels via transport channels to physical channels</span></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhb1IbWy1dpCFFq40BnilbDoBTY8tuRKvRn3xg-EURzjY9M8y1CIrX_F7PUKj1kPeieaz0XfKkO_tmnc-2tfZGlWotJZa0TFvfA1rmwobgNOGuiZXkFv5bxF8_uNxqwlbs5YpzthahhYKXw/s1600/b.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="177" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhb1IbWy1dpCFFq40BnilbDoBTY8tuRKvRn3xg-EURzjY9M8y1CIrX_F7PUKj1kPeieaz0XfKkO_tmnc-2tfZGlWotJZa0TFvfA1rmwobgNOGuiZXkFv5bxF8_uNxqwlbs5YpzthahhYKXw/s400/b.jpg" width="400" /></a></div>
<div class="figure" id="ch01fig65" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="236" name="236" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig65" name="ch01fig65" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="236-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 2: </span>Uplink channel mapping and multiplexing from logical channels via transport channels to physical channels</span></div>
<div class="para" id="236-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Two basic sets of logical channels are defined:</div>
<ul class="itemizedlist" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; list-style-image: initial; list-style-position: initial; list-style-type: square; margin-left: 3em; margin-top: 0.9em; text-align: left;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="first-para" id="236-3" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">Control channels</b>: CCCH and DCCHs.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="236-4" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">Traffic channels</b>: CCCH and DTCHs.</div>
</li>
</ul>
<div class="para" id="236-5" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The nature of common channels is such that no specific UE is addressed, but the information is either general for all cell-wide subscribers or a message from a UE which has not yet established a dedicated control/traffic channel. A typical example of a CCCH is the broadcast of SIBs.</div>
<div class="para" id="236-6" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Traffic channels carry user plane protocols like the Packet Data Convergence Protocol (PDCP) and application IP packets, while control channels carry control plane protocols as RRC and NAS.</div>
<ul class="itemizedlist" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; list-style-image: initial; list-style-position: initial; list-style-type: square; margin-left: 3em; margin-top: 0.9em; text-align: left;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="first-para" id="236-7" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">DL logical channels</b>:</div>
<ul class="simple-list" style="list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0em; margin-left: 3em; margin-top: 0.4em;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="first-para" id="236-8" style="margin-bottom: 0em; margin-top: 0em;">
– Broadcast Control Channel (BCCH).</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="236-9" style="margin-bottom: 0em; margin-top: 0em;">
– Paging Control Channel (PCCH).</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="236-10" style="margin-bottom: 0em; margin-top: 0em;">
<span class="beginpage" pagenum="80"><a href="" id="237" name="237" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page80" name="page80" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>– Common Control Channel (CCCH).</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="237-1" style="margin-bottom: 0em; margin-top: 0em;">
– Dedicated Control Channel (DCCH).</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="237-2" style="margin-bottom: 0em; margin-top: 0em;">
– Dedicated Traffic Channel (DTCH).</div>
</li>
</ul>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="237-3" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">UL logical channels</b>:</div>
<ul class="simple-list" style="list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0em; margin-left: 3em; margin-top: 0.4em;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="first-para" id="237-4" style="margin-bottom: 0em; margin-top: 0em;">
– Common Control Channel (CCCH).</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="237-5" style="margin-bottom: 0em; margin-top: 0em;">
– Dedicated Control Channel (DCCH).</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="237-6" style="margin-bottom: 0em; margin-top: 0em;">
– Dedicated Traffic Channel (DTCH).</div>
</li>
</ul>
</li>
</ul>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-170892458161227186.post-49755826044020478802012-02-09T07:27:00.000-08:002012-02-09T07:27:00.460-08:00Transport Channels in LTE<br />
<h3 class="sect3-title" id="231-1" style="background-color: white; color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: medium; margin-bottom: 0.9em; margin-top: 1.3em; text-align: left;">
<br /></h3>
<div class="first-para" id="232-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0em; margin-top: 0em; text-align: left;">
The physical layer provides a transport service for MAC PDUs. This service is accessed by transport channels. Most transport channels are directly mapped to physical channels. Thus, in other words, transport channels are the gateway to physical channels and a selection for MAC PDUs where they are to be transmitted.</div>
<div class="para" id="232-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The following DL transport channel types are defined:</div>
<ul class="itemizedlist" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; list-style-image: initial; list-style-position: initial; list-style-type: square; margin-left: 3em; margin-top: 0.9em; text-align: left;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-3" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">Broadcast Channel (BCH)</b>:</div>
<ul class="simple-list" style="list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0em; margin-left: 3em; margin-top: 0.4em;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-4" style="margin-bottom: 0em; margin-top: 0em;">
– Uses a static transport format and has the requirement that all UEs within the cell have to receive its information error-free. The reception of the BCH is mandatory for accessing any service of a cell.</div>
</li>
</ul>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-5" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">DL-SCH</b>:</div>
<ul class="simple-list" style="list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0em; margin-left: 3em; margin-top: 0.4em;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-6" style="margin-bottom: 0em; margin-top: 0em;">
– Carries all semi-static broadcast information (SIB) and all UE-specific traffic channels.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-7" style="margin-bottom: 0em; margin-top: 0em;">
– DL-SCH is secured with HARQ algorithms.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-8" style="margin-bottom: 0em; margin-top: 0em;">
– Efficiency is realized with AMC link adaptation.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-9" style="margin-bottom: 0em; margin-top: 0em;">
– Various TMs are defined to meet different environment scenarios to increase efficiency in respect of current conditions.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-10" style="margin-bottom: 0em; margin-top: 0em;">
– DRX is available in order to increase handset operating time.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-11" style="margin-bottom: 0em; margin-top: 0em;">
– Makes use of spatial algorithms like beamforming or MIMO.</div>
</li>
</ul>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-12" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">Paging Channel (PCH)</b>:</div>
<ul class="simple-list" style="list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0em; margin-left: 3em; margin-top: 0.4em;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-13" style="margin-bottom: 0em; margin-top: 0em;">
– Needs to be received in complete cell coverage area.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-14" style="margin-bottom: 0em; margin-top: 0em;">
– Supports DRX in order to increase battery operating cycle.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-15" style="margin-bottom: 0em; margin-top: 0em;">
– Dynamically allocated via own physical identifier (P-RNTI).</div>
</li>
</ul>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-16" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">Multicast Channel (MCH)</b>:</div>
<ul class="simple-list" style="list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0em; margin-left: 3em; margin-top: 0.4em;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-17" style="margin-bottom: 0em; margin-top: 0em;">
– Broadcast to entire cell coverage area.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-18" style="margin-bottom: 0em; margin-top: 0em;">
– MBMS transmission with use of multiple cells.</div>
</li>
</ul>
</li>
</ul>
<div class="para" id="232-19" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
A designated DL control channel is not defined as the PDCCH is used for physical channel control only. All the higher layer control plane is transmitted via the DL-SCH.</div>
<div class="para" id="232-20" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Defined UL transport channel types are shown in the following items:</div>
<ul class="itemizedlist" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; list-style-image: initial; list-style-position: initial; list-style-type: square; margin-left: 3em; margin-top: 0.9em; text-align: left;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-21" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">UL-SCH</b>:</div>
<ul class="simple-list" style="list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0em; margin-left: 3em; margin-top: 0.4em;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-22" style="margin-bottom: 0em; margin-top: 0em;">
– UL-SCH is secured with HARQ algorithms.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-23" style="margin-bottom: 0em; margin-top: 0em;">
– Fully dynamic and semi-static resource allocation schemes.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-24" style="margin-bottom: 0em; margin-top: 0em;">
– Can make use of multi-user MIMO (UL "virtual" MIMO).</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-25" style="margin-bottom: 0em; margin-top: 0em;">
– Uses dynamic link adaptation like AMC.</div>
</li>
</ul>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-26" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">RACH</b>:</div>
<ul class="simple-list" style="list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0em; margin-left: 3em; margin-top: 0.4em;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-27" style="margin-bottom: 0em; margin-top: 0em;">
– Accessible without UL synchronization.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-28" style="margin-bottom: 0em; margin-top: 0em;">
– Collision-based and collision-free operating modes.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="232-29" style="margin-bottom: 0em; margin-top: 0em;">
– Various modes depending on cell size and interference.</div>
</li>
</ul>
</li>
</ul>
<div class="last-para" id="232-30" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<span class="beginpage" pagenum="79"><a href="" id="233" name="233" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page79" name="page79" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>As in the DL direction, no UL control transport channel is defined as all the higher layer control plane is transmitted on the UL-SCH. The PUCCH is a control channel used by the physical layer only.</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-170892458161227186.post-3297273620426982202012-02-06T00:25:00.000-08:002012-02-07T07:25:41.280-08:00Link Adaptation in LTE<br />
<h3 class="sect3-title" id="187-1" style="background-color: white; color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: medium; margin-bottom: 0.9em; margin-top: 1.3em; text-align: left;">
<br /></h3>
<div class="first-para" id="188-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0em; margin-top: 0em; text-align: left;">
Mobile wireless reception conditions vary greatly over frequency and time as described in <a class="internaljump" href="" style="color: green; cursor: pointer; outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;">Section 1.8</a>. In order to cope with these circumstances and guarantee best possible QoS, a procedure is implemented known as Adaptive Modulation and Coding (AMC). AMC controls and changes transmission parameters to achieve a defined Transport Block Error Rate (BLER) of below 10%, in order to keep retransmissions in a suitable range. This is done by adapting the modulation scheme, in LTE on the shared channels between QPSK and 64QAM, and the Forward Error Correction (FEC) coding rate.</div>
<div class="para" id="188-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Different modulation schemes make the bit detection more robust against noise and other distortion caused by the wireless channel. Figure 1 shows the applied modulation scheme for the LTE shared channels. Most robust transmission is achieved by mapping just 2 bits to each modulation symbol as seen with QPSK, resulting in four stages. A large distance between modulation points as seen with QPSK allows a higher probability of the correct decision at the receiver even with noisy reception conditions. Both 16QAM and 64QAM map 4 and 6 bits respectively to one modulation symbol used with better wireless channel conditions to achieve a higher data throughput. It is to find the best compromise between the modulation scheme and code rate for a given channel quality. LTE defines a list of MCS combinations and just signals an MCS index.</div>
<div class="para" id="188-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPsjtYF0X8YsZc4aNmJdLzhykx0uG3vKhVVRjKvLbc1QNQfq2uzPETmHlGj6DXHoba-KQzJXRiNzgeWVosSIDkyUKBX4tsMu1pjkOsjSunOU84QP2J7UkhS0nqoc7BkitXCj7mxZgLBpmF/s1600/a.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="142" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPsjtYF0X8YsZc4aNmJdLzhykx0uG3vKhVVRjKvLbc1QNQfq2uzPETmHlGj6DXHoba-KQzJXRiNzgeWVosSIDkyUKBX4tsMu1pjkOsjSunOU84QP2J7UkhS0nqoc7BkitXCj7mxZgLBpmF/s400/a.jpg" width="400" /></a></div>
<div class="figure" id="ch01fig54" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="189" name="189" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig54" name="ch01fig54" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="189-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 1: </span>Different QAM schemes used with LTE and the number of bits mapped to each scheme</span></div>
<div class="para" id="189-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The data modulated with the different modulation schemes to subcarriers needs to be protected against transmission errors. LTE defines a turbo de-/encoder with trellis termination of a native code rate of one-third. The turbo coder adds redundancy bits to the data, which makes it possible to correct some bit errors. The code rate is a fraction of source data rate to resulting protected data rate; thus, a code rate of one-third encodes 1 bit into 3 bits. Other code rates are needed in order to optimize the trade-off between protection and efficiency. This is done by puncturing the native coded bit stream to a higher (less protection) code rate by deterministically leaving out coded bits, or by deterministically repeating coded bits if a smaller code rate is desired (more protection).</div>
<div class="para" id="189-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Additionally, one parameter being controlled is the UL transmit power. UL power control is implemented to deal with the near–far effect. Figure 2 shows an UL scenario with a near–far effect compared to a DL scenario without power differences between user signals as they are equally attenuated because the mix of the signal is transmitted from one position (eNB). This occurs when a user is close to the base station (near) and another user is far away from the base station, introducing a higher power path loss which leads to a lower receive power of the signal of the cell edge user. All <span class="beginpage" pagenum="67"><a href="" id="190" name="190" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page67" name="page67" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>UL receive signals should have equal power in order to have the same analog-to-digital converter saturation of each signal to reduce the quantization noise of users with low received signals, reducing inter-subcarrier interference between the users. This happens with imperfect UL synchronization within real-life scenarios.</div>
<div class="para" id="189-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQcMMspU5iUCXhbFEeeLcoOyIU_-K1NdegBoAxl0tpCpBoIOub7PhDYppTK74xVhQVh56kergPdVtkKFeD798lg-SF-kzDHGP9gZFyy-7wFTsK-jB4tlqrgS4dkRlgFMy2JDc5rhcRNK-G/s1600/b.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="337" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQcMMspU5iUCXhbFEeeLcoOyIU_-K1NdegBoAxl0tpCpBoIOub7PhDYppTK74xVhQVh56kergPdVtkKFeD798lg-SF-kzDHGP9gZFyy-7wFTsK-jB4tlqrgS4dkRlgFMy2JDc5rhcRNK-G/s400/b.jpg" width="400" /></a></div>
<div class="figure" id="ch01fig55" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="191" name="191" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig55" name="ch01fig55" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="191-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 2: </span>Near–far effect occurring in uplink direction, compared to equal signal strength reception in downlink</span></div>
<div class="para" id="191-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
UL TPC commands are sent via designated DCI formats 3 and 3A. DCI 3 and 3A are differential power control commands for PUCCH and PUSCH transmission in steps of decibels. DCI 3 is a 2bit assignment as opposed to DCI 3A which is a single bit command. These dedicated DCIs with TPC commands are only used when there is no data to be transmitted to the UE; otherwise, the TPC command is transmitted embedded in other control information on the PDCCH for this UE. An initial 3-bit TPC command is embedded in the RAR message. The different TPC commands are listed in Tables 1 and 2.</div>
<a href="" id="192" name="192" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; outline-color: initial; outline-style: none; outline-width: initial; text-align: left; text-decoration: none;"></a><a href="" id="ch01table13" name="ch01table13" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; outline-color: initial; outline-style: none; outline-width: initial; text-align: left; text-decoration: none;"></a><span style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: x-small; text-align: left;"></span><table border="1" class="table" id="ch01table13" linktabletoexcel="yes" style="background-color: white; color: black; font-family: verdana, arial, helvetica, sans-serif; font-size: 11px; margin-bottom: 1em; margin-top: 1em; text-align: left;"><caption class="table-title" id="192-1" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small; font-weight: bold; margin-top: 0.3em; text-align: left;"><span class="table-title" style="margin-top: 0.3em;"><span class="table-titlelabel">Table 1: </span>Mapping of TPC command field in DCI format 1A/1B/1D/1/2A/2/3 to <span class="unicode" style="font-family: 'Lucida Sans Unicode', Arial, Helvetica, sans-serif;">δ</span><sub>PUCCH</sub> values. Reproduced with permission from © 3GPP<sup>™</sup></span> </caption><thead>
<tr valign="top"><th align="left" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="192-2" style="margin-left: 0.3em; margin-right: 1em;">
TPC command field in DCI format 1A/1B/1D/1/2A/2/3</div>
</th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="192-3" style="margin-left: 0.3em; margin-right: 1em;">
<i class="emphasis"><span class="unicode" style="font-family: 'Lucida Sans Unicode', Arial, Helvetica, sans-serif;">δ</span></i><sub>PUCCH</sub> (dB)</div>
</th></tr>
</thead><tbody>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="192-4" style="margin-left: 0.3em; margin-right: 1em;">
0</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="192-5" style="margin-left: 0.3em; margin-right: 1em;">
-1</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="192-6" style="margin-left: 0.3em; margin-right: 1em;">
1</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="192-7" style="margin-left: 0.3em; margin-right: 1em;">
0</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="192-8" style="margin-left: 0.3em; margin-right: 1em;">
2</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="192-9" style="margin-left: 0.3em; margin-right: 1em;">
0</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="192-10" style="margin-left: 0.3em; margin-right: 1em;">
3</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="192-11" style="margin-left: 0.3em; margin-right: 1em;">
3</div>
</td></tr>
</tbody></table>
<a href="" id="193" name="193" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; outline-color: initial; outline-style: none; outline-width: initial; text-align: left; text-decoration: none;"></a><a href="" id="ch01table14" name="ch01table14" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; outline-color: initial; outline-style: none; outline-width: initial; text-align: left; text-decoration: none;"></a><span style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: x-small; text-align: left;"></span><table border="1" class="table" id="ch01table14" linktabletoexcel="yes" style="background-color: white; color: black; font-family: verdana, arial, helvetica, sans-serif; font-size: 11px; margin-bottom: 1em; margin-top: 1em; text-align: left;"><caption class="table-title" id="193-1" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small; font-weight: bold; margin-top: 0.3em; text-align: left;"><span class="table-title" style="margin-top: 0.3em;"><span class="table-titlelabel">Table 2: </span>Mapping of TPC command field in DCI format 3A to <i class="emphasis"><span class="unicode" style="font-family: 'Lucida Sans Unicode', Arial, Helvetica, sans-serif;">δ</span></i><sub>PUCCH</sub> values. Reproduced with permission from © 3GPP<sup>™</sup></span> </caption><thead>
<tr valign="top"><th align="left" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="193-2" style="margin-left: 0.3em; margin-right: 1em;">
TPC command field in DCI format 3A</div>
</th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="193-3" style="margin-left: 0.3em; margin-right: 1em;">
OPUCCH (dB)</div>
</th></tr>
</thead><tbody>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="193-4" style="margin-left: 0.3em; margin-right: 1em;">
0</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="193-5" style="margin-left: 0.3em; margin-right: 1em;">
-1</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="193-6" style="margin-left: 0.3em; margin-right: 1em;">
1</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="193-7" style="margin-left: 0.3em; margin-right: 1em;">
1</div>
</td></tr>
</tbody></table>
<div class="para" id="193-8" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
UEs report their received channel quality to the eNB by transmitting a CQI value. The CQI value represents either a wideband receive quality as a scalar or a more detailed report about frequency sections (sub-bands) as a vector. CQI reports are transmitted periodically or aperiodically configured by higher layers. Sub-band CQI reports indicate the receive quality of each sub-band relative to the wideband average with four steps: worse, equal, better, and much <span class="beginpage" pagenum="68"><a href="" id="194" name="194" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page68" name="page68" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>better. The UE reports the best M sub-bands compared to the average channel quality with the best M method as depicted in Figure 3.</div>
<div class="para" id="193-8" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<br /></div>
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<div class="figure" id="ch01fig56" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="195" name="195" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig56" name="ch01fig56" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="195-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 3: </span>CQI illustration with sub-bands and best M reporting. Reproduced with permission from Nomor</span></div>
<div class="para" id="195-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The UE should derive a MCS scheme from the above measurement information, which is indexing 1 MCS out of 16 to suit the target BLER of below 10%. This enables differentiation between high- and low-cost handsets which use more or less expensive RF hardware and/or a more sophisticated IQ signal processing engine.</div>
<div class="para" id="195-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Recapitulating, LTE link adaptation uses various stacked link adaptation techniques, securing transmission, or in order to make it more effective using different control loop delays regarding the process's dimension. The following items summarize the LTE link adaptation functions with their responsiveness:</div>
<div class="informaltable" id="N2634" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left; width: 995px;">
<table border="1" style="font-family: verdana, arial, helvetica, sans-serif; font-size: 11px;"><tbody>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="195-4" style="margin-left: 0.3em; margin-right: 1em;">
<br /></div>
<ul class="itemizedlist" style="list-style-image: initial; list-style-position: initial; list-style-type: square; margin-left: 3em; margin-top: 0.9em;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="table-para" id="195-5" style="margin-left: 0.3em; margin-right: 1em;">
<b class="bold" style="font-weight: bold;">Adaptive frequency-selective scheduling</b>: Assign frequency resource to UEs on a 1 ms basis, which provides each UE with the individual best reception quality.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="table-para" id="195-6" style="margin-left: 0.3em; margin-right: 1em;">
<b class="bold" style="font-weight: bold;">AMC</b>: Obtain the most efficient modulation and FEC code rate in order to balance retransmissions vs. maximization of throughput.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="table-para" id="195-7" style="margin-left: 0.3em; margin-right: 1em;">
<b class="bold" style="font-weight: bold;">HARQ</b>: Multiple retransmission process using prior transmission to increase the correct decoding probability.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="table-para" id="195-8" style="margin-left: 0.3em; margin-right: 1em;">
<b class="bold" style="font-weight: bold;">TPC</b>: Provides UL power control in order to minimize multiple user interference.</div>
</li>
</ul>
<br /></td><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="195-9" style="margin-left: 0.3em; margin-right: 1em;">
</div>
<div class="informalfigure" id="N2683" style="margin-left: 2em; margin-top: 1em;">
<span class="figuremediaobject"><img alt="Image from book" border="0" height="210" id="IMG_63" src="http://images.books24x7.com/bookimages/id_40946/figu68_1.jpg" title="" width="29" /></span></div>
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</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-170892458161227186.post-57487704845679971012012-01-25T01:31:00.000-08:002012-02-07T07:19:47.165-08:00Uplink Slot Structure<br />
<h3 class="sect3-title" id="181-1" style="background-color: white; color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: medium; margin-bottom: 0.9em; margin-top: 1.3em; text-align: left;">
</h3>
<div class="first-para" id="182-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0em; margin-top: 0em; text-align: left;">
The UL slot structure is similar to the DL slot structure. Differences are mainly due to simplifications of reference symbols, robustness, and physical UL channel multiplexing. A radio frame lasts 10 ms and is divided into 10 subframes with two slots of 0.5 ms duration as a DL radio frame is split into subframes and slots. Figure 1 shows an UL radio frame with its subframe and slot structure. An UL RB has 12 subcarriers on the frequency axis and on the time domain it has, seven SC-FDMA symbols per slot when normal CP is used, and six SC-FDMA symbols when extended CP is used (see Figure 2).</div>
<div class="first-para" id="182-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0em; margin-top: 0em; text-align: left;">
<br /></div>
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<div class="figure" id="ch01fig52" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="183" name="183" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="ch01fig52" name="ch01fig52" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span><br />
<span class="figure-title" id="183-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 1 </span>Uplink radio frame and subframe with two slots including PUSCH, PUCCH, PRACH, DMRS, and SRS. Reproduced with permission from Nomor</span></div>
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<a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="184" name="184" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="ch01fig53" name="ch01fig53" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span><br />
<span class="figure-title" id="184-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 2: </span>Uplink resource grid showing on UL RB. Reproduced with permission from © 3GPP<sup>™</sup></span></div>
<div class="para" id="184-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
UL synchronization signals are not used because all UL signals from UEs transmitting within the cell are time aligned at the eNB with an UL timing control procedure. The eNB signals a Timing Advance (TA) command to each UE to track the UL alignment. Timing varies due to the different special distribution of UEs within a cell region. Signals are delayed because of the propagation delay. Firstly, during the random access procedure a total timing offset to the UE is transmitted. After this there is a control loop just tracking and signaling differential timing offsets in steps of 0.52 <span class="unicode" style="font-family: 'Lucida Sans Unicode', Arial, Helvetica, sans-serif;">μ</span>s (16 × <i class="emphasis">T<sub>s</sub></i>).</div>
<div class="para" id="184-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The PRACH always uses six consecutive RBs on the frequency axis and is time-wise one subframe wide. Which six RBs are used is variable and set in SIB type 2. The PRACH configuration index is signaled in SIB type 2 as well, which defines the subframes which carry the PRACH's six RBs. This subframe configuration applies for either even or any radio frame. There are 64 possible PRACH configuration index permutations.</div>
<div class="para" id="184-4" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Resources at the upper and lower edges of the system bandwidth are used to carry the PUCCH. The frequency resources in between the PUCCH bands are designated to PUSCH transmission.</div>
<div class="para" id="184-5" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
UL reference signals are used for UL channel estimation. DL reference signals are spread over frequency and time as single REs, which leads to a two-dimensional spheric channel estimation. UL <span class="beginpage" pagenum="64"><a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="185" name="185" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="IDX-64" name="IDX-64" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span><span class="beginpage" pagenum="65"><a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="186" name="186" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="page65" name="page65" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>reference signals are similar to TDMA pilots in the middle of each time slot. LTE defines reference signals in the middle of each slot (on the fourth OFDM symbol assuming normal CP duration) and spanning via the complete allocated frequency range of each UE.</div>
<div class="para" id="186-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The eNB can instruct UEs to transmit special reference signals over the complete system bandwidth, or parts of it, independently of UL data transmission either on PUSCH or PUCCH. These reference signals are called Sounding Reference Signals (SRSs). SRSs are used to estimate UL channel quality of a wider frequency range in order to optimize frequency-selective UL scheduling.</div>
<div class="last-para" id="186-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<span class="beginpage" pagenum="66"><a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="187" name="187" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="http://www.blogger.com/blogger.g?blogID=170892458161227186" id="page66" name="page66" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>Figure 2 depicts, in addition to the radio frame, a zoomed UL subframe with a PUCCH and PUSCH example configuration with UL demodulation reference symbols (DMRS) and SRS symbols.</div>Unknownnoreply@blogger.com1tag:blogger.com,1999:blog-170892458161227186.post-28354557774118099302012-01-21T08:28:00.000-08:002012-01-21T08:28:00.351-08:00Scheduling on LTE Upload<br />
<h3 class="sect3-title" id="177-2" style="background-color: white; color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: medium; margin-bottom: 0.9em; margin-top: 1.3em; text-align: left;">
<br /></h3>
<div class="first-para" id="178-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0em; margin-top: 0em; text-align: left;">
The LTE UL scheduling is very similar to the DL scheduling, although the UL scheduler is a distinct entity. This section describes the difference from the DL scheduling only.</div>
<div class="para" id="178-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
UL scheduling grants are indicated to the UE by transmitting all relevant UL scheduling information within the PDCCH. This is done by using a dedicated DCI type, DCI 0. Each UE has to monitor the PDCCH in every subframe for DCI types 0 scrambled with their RNTI. This does not apply for the case when power saving mode DRX is enabled, which switches off the UE's receiver periodically. UL resources are allocated without a designated PDCCH UL grant in the case of SPS or for non-adaptive HARQ retransmissions. A non-adaptive HARQ retransmission is triggered by the transmission of a Negative Acknowledgment (NACK) by the UE.</div>
<div class="para" id="178-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyl2ZXSw7ibnq6JS4nus5fDNs6i4EU0LX9Se9glNf7CAxDrfSK_CEtiYkfz1Ozs1Vz9diuz9BOhPYLa_JlAmIhVZtMgmqREpXRBx61gM0xVa2PVeYT2T91C78QqbLoVi8LoXr7_KVQ8Phl/s1600/a.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="205" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyl2ZXSw7ibnq6JS4nus5fDNs6i4EU0LX9Se9glNf7CAxDrfSK_CEtiYkfz1Ozs1Vz9diuz9BOhPYLa_JlAmIhVZtMgmqREpXRBx61gM0xVa2PVeYT2T91C78QqbLoVi8LoXr7_KVQ8Phl/s400/a.jpg" width="400" /></a></div>
<div class="figure" id="ch01fig50" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="179" name="179" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig50" name="ch01fig50" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="179-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 1: </span>Example PDCCH message of DCI format 0 (uplink scheduling grant)</span></div>
<div class="para" id="179-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
In the UL only localized scheduling is allowed, which means that an integer number of consecutive RBs is allocated to one UE. Furthermore, there is only one scheduling process per UE, thus there is not a dedicated scheduling process per radio bearer.</div>
<div class="para" id="179-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The UE feeds the UL scheduler with CQI, Buffer Status Reports (BSRs), ACKs/NACKs, and Scheduling Requests (SRs). BSRs indicate the fill level status of the current transmit buffer. This buffer status is reported in bins, quantizing the fill level in bytes. Figure 2 shows an example of a MAC BSR message.</div>
<div class="para" id="179-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjpZIXTeWonn75Riq2td5sqwA0f-j_z1zQZ8wUyyqozyh14Vw6rWaIHKZLwAME7v7kcVzPHx01HMwqterS4uBNkB4B9fWFfIBZGfArLcjE_04VDA5hs6xgI-5r7UfsVgZjp8VKx7HfbooZ5/s1600/b.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="206" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjpZIXTeWonn75Riq2td5sqwA0f-j_z1zQZ8wUyyqozyh14Vw6rWaIHKZLwAME7v7kcVzPHx01HMwqterS4uBNkB4B9fWFfIBZGfArLcjE_04VDA5hs6xgI-5r7UfsVgZjp8VKx7HfbooZ5/s400/b.jpg" width="400" /></a></div>
<div class="figure" id="ch01fig51" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="180" name="180" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig51" name="ch01fig51" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="180-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 2: </span>Example MAC Buffer Status Report (BSR) message</span></div>
<div class="last-para" id="180-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<span class="beginpage" pagenum="63"><a href="" id="181" name="181" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page63" name="page63" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>LTE trial studies show that there are various cases of scheduled empty UL grants. This happens when the eNB assigns UL resources to a UE and the designated UE does not use those UL resources for an UL transmission. Operators should minimize such empty scheduled UL resource in order to optimize the usage of UL radio resources.</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-170892458161227186.post-6601402256124715082012-01-17T05:55:00.000-08:002012-01-17T05:55:00.207-08:00SC-FDMA Principles and Modulation<br />
<h3 class="sect3-title" id="173-2" style="background-color: white; color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: medium; margin-bottom: 0.9em; margin-top: 1.3em; text-align: left;">
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<div class="first-para" id="174-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0em; margin-top: 0em; text-align: left;">
The OFDM transmission scheme shows robustness against multipath fading and is especially useful for mobile communication systems due to various reasons. An example is the complexity of the receiver where fairly simple and channel estimation/equalization is done in the frequency domain. Why is another transmission scheme selected for the LTE UL? A major disadvantage of OFDM systems is <span class="beginpage" pagenum="61"><a href="" id="175" name="175" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page61" name="page61" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>that the time domain signal which is amplified and transmitted shows a large dynamic range after modulating symbols on subcarriers and transformation to a time signal. This leads to a high Peak-to-Average Power Ratio (PARP) of the signal, which should be avoided for battery-powered handsets, which underlies a limit on the budget to justify the business case. The linear transmission of such a signal needs a highly complex RF amplifier for the handsets in order not to run into the nonlinear region of the transmitter. Additionally, the power consumption is larger compared to a transmitter running a smaller linear dynamic range. The PAPR even increases with a wider OFDM bandwidth for a larger number of modulated subcarriers. This results in another transmission scheme for the UL: Single Carrier FDMA (SC-FDMA).</div>
<div class="para" id="175-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Actually SC-FDMA is very similar to OFDMA but shows a better PAPR, leading to a longer battery lifetime and a cost-effective RF amplifier design. Figure 1 illustrates the components of a SC-FDMA transmitter system with its block entities. Highlighted in the figure are the main differences from a regular OFDM system. The main difference is the Discrete Fourier Transform (DFT) in the transmitter and the inverse DFT (iDFT) in the receiver, respectively. Thus, SC-FDMA is sometimes called DFT-spread-OFDM. Due to this difference, we can picture the information to be transmitted as modulated (bits mapped to two-dimensional QAM symbols with an I and Q component) to a time domain signal instead of modulating subcarriers of a frequency domain signal. The output of the DFT can be interpreted as a spectrum of the previously modulated data symbols. This spectrum has the characteristic of consecutive modulated subcarriers; it has therefore no scattered spectral distribution. Thus, it has the inherent behavior of localized RE usage as described in Section 1.</div>
<div class="para" id="175-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEghQHuITOIy0aPGx_Pm2exbhUe_pCnn_F_lJdQOMIRi5Qbi8u2qUVQgvJKkVu1Un5J1zIhkArh_9k791PKCsKOQDcyy6d0Tl2hYne8w9_7FPNsPvMyva1i9u8NHUpy-GzM-U8Z_33gBCFAd/s1600/a.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="180" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEghQHuITOIy0aPGx_Pm2exbhUe_pCnn_F_lJdQOMIRi5Qbi8u2qUVQgvJKkVu1Un5J1zIhkArh_9k791PKCsKOQDcyy6d0Tl2hYne8w9_7FPNsPvMyva1i9u8NHUpy-GzM-U8Z_33gBCFAd/s640/a.jpg" width="640" /></a></div>
<div class="figure" id="ch01fig49" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="176" name="176" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig49" name="ch01fig49" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="176-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 1: </span>Block diagram of SC-FDMA transmitter with localized mapping to frequency resources</span></div>
<div class="para" id="176-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
This localized spectrum is now mapped to the consecutive frequency REs which are specified in the UL scheduling grant, as only localized frequency resource assignments are allowed with UL transmission, which refers to the intrinsic signal characteristic of DFT-spread-OFDM. The rest of the spectrum for the full system bandwidth is filled with zeros. This zero patched spectrum is fed to <span class="beginpage" pagenum="62"><a href="" id="177" name="177" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page62" name="page62" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>an iFFT unit transforming a full system-wide spectrum "back" to the time domain for transmission. Figure 1 shows this mapping of the DFT symbols to the full iFFT width by adding zeros to frequency positions at the block in the center. The zero patched frequency areas are not used by this user and could be assigned to other users transmitting in the same time slot.</div>
<div class="last-para" id="177-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
As for the future, a current research item is to overcome the lack of a high PAPR of OFDM signals in such a way that a digital reverse distorted signal is added to the signal which is to be transmitted. The nonlinear distortion is known for a given RF amplifier. Therefore, it is possible to pre-calculate the distortion applied to the transmitted signal. This distortion is inverted and joined to the signal to such a degree that the RF amplifier distortion eliminates the inverted signal again.</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-170892458161227186.post-21254589170479261452012-01-13T04:23:00.000-08:002012-01-13T04:23:00.734-08:00OFDM Scheduling on LTE DL<br />
<h3 class="sect3-title" id="163-2" style="background-color: white; color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: medium; margin-bottom: 0.9em; margin-top: 1.3em; text-align: left;">
<br /></h3>
<div class="first-para" id="164-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0em; margin-top: 0em; text-align: left;">
The eNB advises each UE when and on which resources to transmit its data or informs a UE where it should listen to receive data. The resources are defined by frequency and time units. This procedure <span class="beginpage" pagenum="57"><a href="" id="165" name="165" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page57" name="page57" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>of assigning system resource is called scheduling. The system resources are divided into units of RBs. Only integer numbers of RBs can be assigned to one user. Localized and distributed RB allocations are possible. Localized allocations assign adjacent RBs to one UE, distributed allocations distribute the scheduled RBs over the spectrum with gaps, for example, in order to achieve frequency diversity.</div>
<div class="para" id="165-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
A new scheduling assignment is transmitted for each subframe, thus the scheduling period on the time axis is 1 ms. The DL scheduling information is transmitted in the PDCCH. The assignments on the frequency scale vary between one RB (minimal scheduled transmission) and the maximum number of available RBs in respect of the system bandwidth.</div>
<div class="para" id="165-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Generally, the LTE scheduling algorithm is not defined by the standard; it is a matter for the eNB vendors. This enables the base station vendors to differentiate between each other and use different optimization goals. Various parameters can be used as input for the scheduling decisions: channel quality of different users (measured or reported by the UE with the Channel Quality Indicator, CQI), QoS, congestion/resource situation, fairness, charging policies, and so on. Most schedulers aim to maximize the cell throughput under consideration of fairness metrics between cell edge users and users with very good channel conditions. Figure 1 shows a screenshot of a typical scheduling and cell resource allocation analysis tool. It gives insight into the scheduling process of the eNB and is able to evaluate the scheduler performance and the utilization of cell resources.</div>
<div class="para" id="165-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
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<div class="figure" id="ch01fig46" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="166" name="166" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig46" name="ch01fig46" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="166-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 1: </span>Scheduling and cell resource allocation analysis</span></div>
<div class="para" id="166-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The CQI is reported in the UL direction and can be derived periodically or upon request by the eNB. It gives reception quality feedback to the scheduling algorithm in the eNB in order to schedule <span class="beginpage" pagenum="58"><a href="" id="167" name="167" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page58" name="page58" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>data on those frequency regions with the best possible reception characteristics. </div>
<div class="para" id="167-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The scheduling information is encoded as Downlink Control Information (DCI). The DCI is then mapped to REGs of the PDCCH. The length of the PDCCH can vary between one and three OFDM symbols depending on the load to be transmitted on the PDCCH. The number of used OFDM symbols is indicated in the PCFICH.</div>
<div class="para" id="167-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The DCI does not just transmit RB assignments and its assignment type, but also other information needed for the transmission or reception of data. This information is, for example, the Modulation and Coding Scheme (MCS), HARQ feedback information, or power control commands for UL transmission of the Physical Uplink Control Channel (PUCCH) or Physical Uplink Shared Channel (PUSCH) (see below).</div>
<div class="para" id="167-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The following DCI formats are defined and used for scheduling and UL Transmit Power Control (TPC) commands:</div>
<ul class="itemizedlist" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; list-style-image: initial; list-style-position: initial; list-style-type: square; margin-left: 3em; margin-top: 0.9em; text-align: left;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="first-para" id="167-4" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">DCI format 0</b>: UL scheduling grant.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="167-5" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">DCI format 1</b>: Single transport block (code word) scheduling assignment, for example, used for assigning resources to system information, paging, or random access. Further information: MCS, HARQ (New Data Indicator (NDI), redundancy version, HARQ process number), and TPC for PUCCH.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="167-6" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">DCI format 1A</b>: Compact single transport block scheduling assignment. Further information: MCS, HARQ (NDI, redundancy version, HARQ process number), and TPC for PUCCH.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="167-7" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">DCI format 1B</b>: A special DCI format for transmission mode 6 (MIMO closed loop rank 1 pre-coding). Further information: precoding vector, MCS, HARQ (NDI, redundancy version, HARQ process number), and TPC for PUCCH.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="167-8" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">DCI format 1C</b>: Even more compact scheduling format as DCI 1A. For example, used for assigning resources to SIBs, paging, or RARs. This DCI is always transmitted using frequency diversity via distributed virtual resource block assignments using resource allocation type 2 (see below). This is done because channel feedback cannot be derived for such common information, as it is received by multiple users. The modulation is fixed to QPSK. Further information: MCS, HARQ (NDI, redundancy version, HARQ process number), and TPC for PUCCH.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="167-9" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">DCI format 1D</b>: A special DCI format for transmission mode 5 (multi-user MIMO). Further information: MCS, HARQ (NDI, redundancy version, HARQ process number), power offset indicator if two UEs share power resources, and TPC for PUCCH.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="167-10" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">DCI format 2</b>: Scheduling for transmission mode 4 (closed loop MIMO), multiple antenna port transmission operation, addressing multiple transport blocks (code words) to be transmitted on different antenna ports (layers). Further information: MCS for each transport block, HARQ (NDI, redundancy version, HARQ process number), number of transmission layers, precoding, and TPC for PUCCH.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="167-11" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">DCI format 2A</b>: Used with transmission mode 3 (open loop MIMO using Cyclic Delay Diversity (CDD)), multiple antenna port transmission operation, addressing multiple transport blocks (code words) to be transmitted on different antenna ports (layers). Further information: MCS for each transport block, HARQ (NDI, redundancy version, HARQ process number), number of transmission layers, precoding, and TPC for PUCCH.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="167-12" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">DCI format 3</b>: A 2-bit UL TPC command applying for PUSCH and PUCCH. Multiple users are addressed.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="167-13" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">DCI format 3A</b>: A 1-bit UL TPC command applying for PUSCH and PUCCH. Multiple users are addressed.</div>
</li>
</ul>
<div class="para" id="167-14" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The resource allocation assignments of the above DCI formats can use different resource allocation types. Table 1 maps the DCI formats to the allowed resource allocation types:</div>
<ul class="itemizedlist" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; list-style-image: initial; list-style-position: initial; list-style-type: square; margin-left: 3em; margin-top: 0.9em; text-align: left;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="first-para" id="167-15" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">Resource allocation type 0</b>: With resource allocation type 0 a bit map is transmitted describing Resource Block Groups (RBGs). A RBG is a number of consecutive physical resource blocks (RBs). The number depends on the system bandwidth and has a range between one and four physical RBs. Table 1 maps the size of a RBG to the system bandwidth. The allocated RBGs do not have to be adjacent.</div>
<a href="" id="168" name="168" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01table11" name="ch01table11" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><table border="1" class="table" id="ch01table11" linktabletoexcel="yes" style="font-family: verdana, arial, helvetica, sans-serif; font-size: 11px; margin-bottom: 1em; margin-top: 1em;"><caption class="table-title" id="168-1" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small; font-weight: bold; margin-top: 0.3em; text-align: left;"><span class="table-title" style="margin-top: 0.3em;"><span class="table-titlelabel">Table 1: </span>Resource allocation types and the applying DCI formats TS36.213. Reproduced with permission from © 3GPP<sup>™</sup></span> </caption><thead>
<tr valign="top"><th align="left" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="168-2" style="margin-left: 0.3em; margin-right: 1em;">
<span class="beginpage" pagenum="59"><a href="" id="169" name="169" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page59" name="page59" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>Resource allocation type</div>
</th><th align="left" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="169-1" style="margin-left: 0.3em; margin-right: 1em;">
Applying DCI formats</div>
</th></tr>
</thead><tbody>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="169-2" style="margin-left: 0.3em; margin-right: 1em;">
Type 0</div>
</td><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="169-3" style="margin-left: 0.3em; margin-right: 1em;">
1, 2, 2A, and 2B</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="169-4" style="margin-left: 0.3em; margin-right: 1em;">
Type 1</div>
</td><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="169-5" style="margin-left: 0.3em; margin-right: 1em;">
1, 2, 2A, and 2B</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="169-6" style="margin-left: 0.3em; margin-right: 1em;">
Type 2</div>
</td><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="169-7" style="margin-left: 0.3em; margin-right: 1em;">
1A, 1B, 1C, and 1D</div>
</td></tr>
</tbody></table>
<a href="" id="170" name="170" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01table12" name="ch01table12" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><table border="1" class="table" id="ch01table12" linktabletoexcel="yes" style="font-family: verdana, arial, helvetica, sans-serif; font-size: 11px; margin-bottom: 1em; margin-top: 1em;"><caption class="table-title" id="170-1" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small; font-weight: bold; margin-top: 0.3em; text-align: left;"><span class="table-title" style="margin-top: 0.3em;"><span class="table-titlelabel">Table 2: </span>Type 0 resource allocation RBG size vs. DL system bandwidth</span> </caption><thead>
<tr valign="top"><th align="left" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="170-2" style="margin-left: 0.3em; margin-right: 1em;">
System bandwidth <i class="emphasis">N</i><sub>R</sub><sup>D</sup> <sub>B</sub><sup>L</sup></div>
</th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="170-3" style="margin-left: 0.3em; margin-right: 1em;">
RBG size (<i class="emphasis">P</i>)</div>
</th></tr>
</thead><tbody>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="170-4" style="margin-left: 0.3em; margin-right: 1em;">
<span class="unicode" style="font-family: 'Lucida Sans Unicode', Arial, Helvetica, sans-serif;">≤</span>10</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="170-5" style="margin-left: 0.3em; margin-right: 1em;">
1</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="170-6" style="margin-left: 0.3em; margin-right: 1em;">
11–26</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="170-7" style="margin-left: 0.3em; margin-right: 1em;">
2</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="170-8" style="margin-left: 0.3em; margin-right: 1em;">
27–63</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="170-9" style="margin-left: 0.3em; margin-right: 1em;">
3</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="170-10" style="margin-left: 0.3em; margin-right: 1em;">
64–110</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="170-11" style="margin-left: 0.3em; margin-right: 1em;">
4</div>
</td></tr>
</tbody></table>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="170-12" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">Resource allocation type 1</b>: The bit map transmitted with resource allocation type 1 makes use also of RBGs but can address single physical RBs by introducing additional flags. The number of RBGs is smaller than the ones used with resource allocation type 0, thus not reaching the complete bandwidth. The bit map addresses not whole RBGs, but a subset within each RBG which is pointed to by the bit map. A selection flag indicates the position within the RBG regions and a shift flag shows the position of the numbered RBGs within the system bandwidth as the number of RBGs does not address the complete system bandwidth: shift flag = 0 indicates that the RBGs start at the beginning of the system bandwidth leaving an unaddressable region at the end of the system bandwidth; shift flag = 1 indicates that the RBGs are shifted to the end of the system bandwidth leaving the unaddressable region at the beginning of the system bandwidth.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="170-13" style="margin-bottom: 0em; margin-top: 0em;">
<b class="bold" style="font-weight: bold;">Resource allocation type 2</b>: This resource allocation type uses virtual RBs as scheduling units. Two types of virtual RB scheduling assignments are used:</div>
<ul class="simple-list" style="list-style-image: initial; list-style-position: initial; list-style-type: none; margin-bottom: 0em; margin-left: 3em; margin-top: 0.4em;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="first-para" id="170-14" style="margin-bottom: 0em; margin-top: 0em;">
– A localized type, where the allocated virtual RBs equal a number of consecutive physical RBs addressed with a starting RB and a number of adjacently assigned RBs. This information is encoded into an 11-bit Resource Indication Value (RIV).</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="170-15" style="margin-bottom: 0em; margin-top: 0em;">
– A distributed type, where the addressed virtual RBs are distributed over the frequency with one or two gaps (depending on the system bandwidth) hopping at slot boundaries. Virtually distributed RB assignments are always used with DCI format 1C. There is a 1-bit flag indicating whether virtual distributed or virtual localized RB assignment is used in the case of DCI formats 1A, 1B, and 1D.</div>
</li>
</ul>
</li>
</ul>
<div class="para" id="170-16" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Instead of addressing a UE with a PDCCH scheduling assignment (DCI) directly by adding a UE ID (e.g., a RNTI) to the DCI, the 16-bit CRC of the PDCCH message is scrambled with the RNTI, introducing common and UE-specific search spaces. This CRC scrambling saves additional resources <span class="beginpage" pagenum="60"><a href="" id="171" name="171" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page60" name="page60" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>in DCIs, but increases slightly the chance of decoding a DCI for a different UE which is not intended to be addressed.</div>
<div class="para" id="171-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Figure 2 depicts an example PDCCH message of DCI format type 1 with all the transmitted information.</div>
<div class="para" id="171-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
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<div class="figure" id="ch01fig47" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="172" name="172" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig47" name="ch01fig47" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="172-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 2: </span>Example PDCCH message of DCI format 1 (downlink scheduling assignment)</span></div>
<div class="para" id="172-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Some special applications require the transmission of small data chunks in equidistant periods of time. An example is a VoIP application. In order to minimize the signaling overhead in such cases, a mode Semi Persistent Scheduling (SRS) is introduced. SPS parameters are configured by the RRC layer, enabling the transmission of data on defined RBs in frequency and time without further scheduling on the PDCCH.</div>
<div class="para" id="172-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Battery energy saving is always an important topic with mobile handset systems. A potential scheduling assignment could be sent in each PDCCH which occurs every millisecond. Therefore, each attached UE would need to monitor the PDCCH each millisecond for scheduling information. The DRX mode enables the UE just to listen to defined subframes for scheduling assignments and turn off its receiver in between, in order to save battery consumption. Short and long DRX cycle periods are defined. The DRX parameters are set by MAC and RRC. Figure 3 depicts a DRX cycle.</div>
<div class="para" id="172-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
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<div class="figure" id="ch01fig48" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="173" name="173" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig48" name="ch01fig48" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="173-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 3: </span>DRX cycle.</span></div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-170892458161227186.post-44607159590421081612012-01-09T01:19:00.000-08:002012-01-09T01:19:00.174-08:00Downlink Slot Structure | Radio Interface Basics<br />
<h3 class="sect3-title" id="152-21" style="background-color: white; color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: medium; margin-bottom: 0.9em; margin-top: 1.3em; text-align: left;">
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<div class="first-para" id="153-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0em; margin-top: 0em; text-align: left;">
This section introduces the LTE DL structure with respect to time. In the time domain, the DL is divided into slots and frames. A radio frame is the largest unit and lasts 10 ms. As both duplex modes, FDD and TDD, use similar timings, this makes a UE starting to synchronize to a LTE cell unaware of the duplex method used. Thus, TDD and FDD both introduce radio frames of 10 ms timing.</div>
<div class="para" id="153-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<span class="beginpage" pagenum="52"><a href="" id="154" name="154" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="IDX-52" name="IDX-52" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span><span class="beginpage" pagenum="53"><a href="" id="155" name="155" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page53" name="page53" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>Both duplex methods define different types of radio frames:</div>
<ul class="itemizedlist" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; list-style-image: initial; list-style-position: initial; list-style-type: square; margin-left: 3em; margin-top: 0.9em; text-align: left;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="first-para" id="155-1" style="margin-bottom: 0em; margin-top: 0em;">
Frame type 1 is the frame type used with FDD.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="155-2" style="margin-bottom: 0em; margin-top: 0em;">
Frame type 2 is the frame type used with TDD.</div>
</li>
</ul>
<div class="para" id="155-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
One radio frame is split into 10 subframes of 1 ms duration. A subframe is also the most important unit of scheduling and for physical control channel durations the PDCCH is found in the first OFDM symbols of each subframe. Furthermore, subframes are divided into two slots of 0.5 ms. The smallest unit is an OFDM symbol. Depending on the CP length (normal or extended) used, the length will be seven or six OFDM symbols transmitted within one slot, resulting in 14 or 12 OFDM symbols within one subframe, respectively. Figure 1 shows one radio frame of type 1 (FDD) with 20 slots and 10 subframes. The length of one radio frame is defined as <b class="bold" style="font-weight: bold;"><i class="emphasis">Tf</i></b> = 307 200 × <b class="bold" style="font-weight: bold;"><i class="emphasis">T<sub>s</sub></i></b> where<b class="bold" style="font-weight: bold;"><i class="emphasis">T<sub>s</sub></i></b> is the sampling period. Therefore, the base sampling frequency of 30.72 MHz (<b class="bold" style="font-weight: bold;"><i class="emphasis">T<sub>s</sub></i></b> = 1<i class="emphasis">/</i>30.72 MHz) is used.</div>
<div class="para" id="155-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
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<div class="figure" id="ch01fig42" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="156" name="156" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig42" name="ch01fig42" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="156-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 1: </span>Frame structure type 1 used with FDD TS36.211. Reproduced with permission from © 3GPP<sup>™</sup></span></div>
<div class="para" id="156-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Figure 2 shows a complete radio frame of type 1 as used with FDD. It illustrates all 10 subframes with areas for the PDSCH. The first OFDM symbols are allocated by the PDCCH. In the area of the PDCCH, additional physical channels for control information are embedded. These channels are the Physical HARQ Indicator Channel (PHICH) and the Physical Control Format Indicator Channel (PCFICH).</div>
<div class="para" id="156-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEivk5FcSWGOGLpiT0keAZde8zOingTyaEVi9Wgx2sr2Gm7p8n4B9IjogUbjfNUiZd6Yx6eaT8GHfNPUzhCFMdIMU-66aBIA4FnZmWoPRH0x5S1SmKAqMUWnDWahvT-P6gU6Je1sFqWXWisI/s1600/b.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="363" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEivk5FcSWGOGLpiT0keAZde8zOingTyaEVi9Wgx2sr2Gm7p8n4B9IjogUbjfNUiZd6Yx6eaT8GHfNPUzhCFMdIMU-66aBIA4FnZmWoPRH0x5S1SmKAqMUWnDWahvT-P6gU6Je1sFqWXWisI/s640/b.jpg" width="640" /></a></div>
<div class="figure" id="ch01fig43" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="157" name="157" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig43" name="ch01fig43" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="157-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 2: </span>Downlink FDD radio frame (normal cyclic prefix) with PDCCH, PDSCH, PBCH, reference signals, and synchronization signals. Reproduced with permission from Nomor</span></div>
<div class="para" id="157-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The PCFICH indicates the number of OFDM symbols allocated for the complete PDCCH in its current subframe. Thus, the PDCCH is transmitted on a variable number of OFDM symbols depending on how much control or scheduling information has to be transmitted, and the resulting number of OFDM symbols which are used for the PDSCH is variable as well. The PDCCH allocates between 1 and 3 OFDM symbols and the PDSCH between 13 and 11 for normal CP and between 11 and 9 OFDM symbols for extended CP, respectively.</div>
<div class="para" id="157-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
In the middle (around the DC subcarrier) of the bandwidth are six RBs used for some common signals and channels in some subframes. These locations are used for initial cell search and cell synchronization. This central location enables a bandwidth-independent cell and frame synchronization as well as initial cell access. Two step hierarchical synchronization signals are defined and located in the first and sixth subframes. The Primary Synchronization Signal (PSS) is transmitted on the seventh OFDM symbol and the Secondary Synchronization Signal (SSS) is transmitted on the sixth OFDM symbol of subframes described above. PSS and SSS can be seen in Figure 2 shows the bandwidth of the synchronization signals. Only 62 subcarriers of the 72 provided by six allocated RBs are used for synchronization signals. </div>
<div class="para" id="157-4" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<span class="beginpage" pagenum="54"><a href="" id="158" name="158" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page54" name="page54" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span><span class="beginpage" pagenum="55"><a href="" id="159" name="159" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page55" name="page55" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>Resources for the PBCH are allocated apart from the SSS. The PBCH is transmitted in each first subframe of all radio frames. Other than the synchronization signals, the PBCH uses all 72 subcarriers of the six central RBs </div>
<div class="para" id="159-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Reference signals are needed by the channel estimation process in order to correct the wireless channel distortion in the signal at the receiver. Four sets of reference signals are specified for each transmit antenna as LTE defines multi-antenna transmissions (DL MIMO). The receiver needs to know the propagation conditions of each transmit antenna for using the complete MIMO gain. Therefore, a defined signal (reference signal) is transmitted from each individual antenna completely independently and all other transmit antennas do not transmit any signals on those specific frequencies and time resources (REs). Figure 3 illustrates the frequency and time RE used for transmitting reference signals depending on the number of antennas configured.</div>
<div class="para" id="159-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgTY1S5sJ57lvnJqDo2rO0CIgx1wFXsvrV-YUyk66gFtn-7SykUPV9OsI-hECxOaRhbmBAQ4LiyR3qevDaIxKoPO19x_Mvszhfmd60tkrgmYTESNNctCzM28-xHZCuIAS2l7i-qfSzlmfLy/s1600/c.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="544" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgTY1S5sJ57lvnJqDo2rO0CIgx1wFXsvrV-YUyk66gFtn-7SykUPV9OsI-hECxOaRhbmBAQ4LiyR3qevDaIxKoPO19x_Mvszhfmd60tkrgmYTESNNctCzM28-xHZCuIAS2l7i-qfSzlmfLy/s640/c.jpg" width="640" /></a></div>
<div class="figure" id="ch01fig44" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="160" name="160" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig44" name="ch01fig44" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="160-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 3: </span>Mapping of downlink reference signals (normal cyclic prefix) (TS36.211). Reproduced with permission from © 3GPP<sup>™</sup></span></div>
<div class="para" id="160-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Frame type 2 is used with TDD. The general slot structure of a TDD frame is similar to a FDD frame, since a mobile is not aware of the duplex method before synchronizing to the cell. A radio frame of type 2 has a duration of 10 ms as its FDD equivalent. The TDD radio frame is also divided into 10 transmission time intervals of 1 ms duration called subframes. Furthermore, TDD subframes are split as well into two slots of 0.5 ms period.</div>
<div class="para" id="160-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
TDD systems switch on one frequency between DL and UL transmission. Therefore, TDD needs defined switch points and guard intervals between UL and DL transmission.</div>
<div class="para" id="160-4" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<span class="beginpage" pagenum="56"><a href="" id="161" name="161" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page56" name="page56" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>LTE defines two basic switch point interval durations of 5 and 10 ms. A switch point is a designated subframe divided into three zones which are already known from basic UMTS TDD: Downlink Pilot Time Slot (DwPTS), GP, and Uplink Pilot Time Slot (UpPTS). Other subframes are used for either UL or DL transmission. Operators can decide from UL–DL configurations which subframes are used as DL and UL depending on the UL and DL traffic mixture of a network. Seven different UL and DL structures are defined. The possible UL–DL configurations with the switch points and the subframe used for UL and DL transmission are given in Table 1.</div>
<a href="" id="162" name="162" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; outline-color: initial; outline-style: none; outline-width: initial; text-align: left; text-decoration: none;"></a><a href="" id="ch01table10" name="ch01table10" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; outline-color: initial; outline-style: none; outline-width: initial; text-align: left; text-decoration: none;"></a><span style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: x-small; text-align: left;"></span><table border="1" class="table" id="ch01table10" linktabletoexcel="yes" style="background-color: white; color: black; font-family: verdana, arial, helvetica, sans-serif; font-size: 11px; margin-bottom: 1em; margin-top: 1em; text-align: left;"><caption class="table-title" id="162-1" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small; font-weight: bold; margin-top: 0.3em; text-align: left;"><span class="table-title" style="margin-top: 0.3em;"><span class="table-titlelabel">Table 1: </span>Uplink–downlink configurations for TDD. Reproduced with permission from © 3GPP<sup>™</sup></span> </caption><thead>
<tr valign="top"><th align="left" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="162-2" style="margin-left: 0.3em; margin-right: 1em;">
Uplink-downlink configuration</div>
</th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="162-3" style="margin-left: 0.3em; margin-right: 1em;">
Downlink-uplink switch-point periodicity (ms)</div>
</th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"> </th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"> </th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"> </th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"> </th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"> </th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"> </th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"> </th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"> </th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"> </th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"> </th></tr>
<tr valign="top"><th align="left" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"> </th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"> </th><th align="center" class="th" colspan="10" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="162-4" style="margin-left: 0.3em; margin-right: 1em;">
Subframe number</div>
</th></tr>
<tr valign="top"><th align="left" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"> </th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"> </th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="162-5" style="margin-left: 0.3em; margin-right: 1em;">
<b class="bold" style="font-weight: bold;">0</b></div>
</th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="162-6" style="margin-left: 0.3em; margin-right: 1em;">
1</div>
</th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="162-7" style="margin-left: 0.3em; margin-right: 1em;">
2</div>
</th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="162-8" style="margin-left: 0.3em; margin-right: 1em;">
3</div>
</th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="162-9" style="margin-left: 0.3em; margin-right: 1em;">
4</div>
</th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="162-10" style="margin-left: 0.3em; margin-right: 1em;">
5</div>
</th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="162-11" style="margin-left: 0.3em; margin-right: 1em;">
6</div>
</th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="162-12" style="margin-left: 0.3em; margin-right: 1em;">
7</div>
</th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="162-13" style="margin-left: 0.3em; margin-right: 1em;">
8</div>
</th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="162-14" style="margin-left: 0.3em; margin-right: 1em;">
9</div>
</th></tr>
</thead><tbody>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-15" style="margin-left: 0.3em; margin-right: 1em;">
0</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-16" style="margin-left: 0.3em; margin-right: 1em;">
5</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-17" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-18" style="margin-left: 0.3em; margin-right: 1em;">
S</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-19" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-20" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-21" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-22" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-23" style="margin-left: 0.3em; margin-right: 1em;">
S</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-24" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-25" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-26" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-27" style="margin-left: 0.3em; margin-right: 1em;">
1</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-28" style="margin-left: 0.3em; margin-right: 1em;">
5</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-29" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-30" style="margin-left: 0.3em; margin-right: 1em;">
S</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-31" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-32" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-33" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-34" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-35" style="margin-left: 0.3em; margin-right: 1em;">
S</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-36" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-37" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-38" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-39" style="margin-left: 0.3em; margin-right: 1em;">
2</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-40" style="margin-left: 0.3em; margin-right: 1em;">
5</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-41" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-42" style="margin-left: 0.3em; margin-right: 1em;">
S</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-43" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-44" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-45" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-46" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-47" style="margin-left: 0.3em; margin-right: 1em;">
S</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-48" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-49" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-50" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-51" style="margin-left: 0.3em; margin-right: 1em;">
3</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-52" style="margin-left: 0.3em; margin-right: 1em;">
10</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-53" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-54" style="margin-left: 0.3em; margin-right: 1em;">
S</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-55" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-56" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-57" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-58" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-59" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-60" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-61" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-62" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-63" style="margin-left: 0.3em; margin-right: 1em;">
4</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-64" style="margin-left: 0.3em; margin-right: 1em;">
10</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-65" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-66" style="margin-left: 0.3em; margin-right: 1em;">
S</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-67" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-68" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-69" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-70" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-71" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-72" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-73" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-74" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-75" style="margin-left: 0.3em; margin-right: 1em;">
5</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-76" style="margin-left: 0.3em; margin-right: 1em;">
10</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-77" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-78" style="margin-left: 0.3em; margin-right: 1em;">
S</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-79" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-80" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-81" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-82" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-83" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-84" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-85" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-86" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-87" style="margin-left: 0.3em; margin-right: 1em;">
6</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-88" style="margin-left: 0.3em; margin-right: 1em;">
5</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-89" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-90" style="margin-left: 0.3em; margin-right: 1em;">
S</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-91" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-92" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-93" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-94" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-95" style="margin-left: 0.3em; margin-right: 1em;">
S</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-96" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-97" style="margin-left: 0.3em; margin-right: 1em;">
U</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-98" style="margin-left: 0.3em; margin-right: 1em;">
D</div>
</td></tr>
</tbody><tfoot>
<tr valign=""><td align="left" class="td" colspan="12" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="162-99" style="margin-left: 0.3em; margin-right: 1em;">
S = Swithching point.</div>
</td></tr>
</tfoot></table>
<div class="para" id="162-100" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Figure 4 shows a radio frame with frame structure type 2 used with TDD. This is an example with a 5 ms switch-point periodicity.</div>
<div class="para" id="162-100" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<br /></div>
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<div class="figure" id="ch01fig45" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="163" name="163" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig45" name="ch01fig45" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="163-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 4: </span>Frame structure type 2 used with TDD (for 5 ms switch-point periodicity) (TS36.211).</span></div>Unknownnoreply@blogger.com1tag:blogger.com,1999:blog-170892458161227186.post-31326989069918001672011-12-28T03:33:00.000-08:002011-12-28T03:33:00.458-08:00Resource Blocks | Radio Interface Basics<br />
<h3 class="sect3-title" id="147-1" style="background-color: white; color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: medium; margin-bottom: 0.9em; margin-top: 1.3em; text-align: left;">
<br /></h3>
<div class="first-para" id="148-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0em; margin-top: 0em; text-align: left;">
This section describes how LTE defines and divides the bandwidth from physical subcarriers of the OFDM symbol in the logical abstract sense used for scheduling shared channel data.</div>
<div class="para" id="148-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The smallest division of the LTE spectrum carrying data is a subcarrier, as described in more detail in the sections above. OFDM systems modulate all data in the frequency domain on the subcarrier of the OFDM spectrum. A modulated subcarrier is defined as a Resource Element (RE) and is the smallest logical unit of the LTE spectrum. One subcarrier or RE has a bandwidth of 15 kHz in normal and extended CP mode, but a special 7.5 kHz subcarrier spacing mode is defined with extended CP transmission. All physical LTE channels use REs to modulate the data. Each RE of the shared channel is modulated using a variable modulation scheme from Quadrature Phase Shift Keying (QPSK) to 64QAM as assigned by the scheduling process of the eNB. REs carry a variable number of data bits, due to the variable number of bits mapped to a RE because of the modulation order, but also because of applied CSs. CSs are used to make the data transmission more robust against transmission errors. They add redundancy to the transmitted information, which increases the probability of the receiver to retrieve the information error-free. LTE defines an Adaptive Modulation and Coding (AMC) process.</div>
<div class="para" id="148-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
A physical Resource Block (RB) defines the smallest unit used by the scheduling algorithm. Therefore, the minimal scheduled user transmission on the shared channels is one RB. A RB consists of 12 adjacent REs on the frequency axis. Consequently, it has a bandwidth of 180 kHz, since one RE is 15 kHz wide in normal and extended CP mode (additionally a mode with 7.5 kHz is defined for extended CP). The possible configurations of CPs are given in Table 1.</div>
<a href="" id="149" name="149" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; outline-color: initial; outline-style: none; outline-width: initial; text-align: left; text-decoration: none;"></a><a href="" id="ch01table08" name="ch01table08" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; outline-color: initial; outline-style: none; outline-width: initial; text-align: left; text-decoration: none;"></a><table border="1" class="table" id="ch01table08" linktabletoexcel="yes" style="background-color: white; color: black; font-family: verdana, arial, helvetica, sans-serif; font-size: 11px; margin-bottom: 1em; margin-top: 1em; text-align: left;"><caption class="table-title" id="149-1" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small; font-weight: bold; margin-top: 0.3em; text-align: left;"><span class="table-title" style="margin-top: 0.3em;"><span class="table-titlelabel">Table 1: </span>Configuration of cyclic prefix. Reproduced with permission from © 3GPP<span class="unicode" style="font-family: 'Lucida Sans Unicode', Arial, Helvetica, sans-serif;">™</span></span> </caption><thead>
<tr valign="top"><th align="left" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="149-2" style="margin-left: 0.3em; margin-right: 1em;">
Configuration</div>
</th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"> </th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="149-3" style="margin-left: 0.3em; margin-right: 1em;">
<i class="emphasis">N</i><sup>RB</sup><sub>sc</sub></div>
</th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="149-4" style="margin-left: 0.3em; margin-right: 1em;">
<i class="emphasis">N</i><sup>DL</sup><sub>symb</sub></div>
</th></tr>
</thead><tbody>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="149-5" style="margin-left: 0.3em; margin-right: 1em;">
Normal cyclic prefix</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="149-6" style="margin-left: 0.3em; margin-right: 1em;">
<span class="unicode" style="font-family: 'Lucida Sans Unicode', Arial, Helvetica, sans-serif;">Δ</span><i class="emphasis">f</i> = 15 kHz</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="149-7" style="margin-left: 0.3em; margin-right: 1em;">
12</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="149-8" style="margin-left: 0.3em; margin-right: 1em;">
7</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="149-9" style="margin-left: 0.3em; margin-right: 1em;">
Extended cyclic prefix</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="149-10" style="margin-left: 0.3em; margin-right: 1em;">
<span class="unicode" style="font-family: 'Lucida Sans Unicode', Arial, Helvetica, sans-serif;">Δ</span><i class="emphasis">f</i> = 15 kHz</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="149-11" style="margin-left: 0.3em; margin-right: 1em;">
24</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="149-12" style="margin-left: 0.3em; margin-right: 1em;">
6</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"> </td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="149-13" style="margin-left: 0.3em; margin-right: 1em;">
<span class="unicode" style="font-family: 'Lucida Sans Unicode', Arial, Helvetica, sans-serif;">Δ</span><i class="emphasis">f</i> = 7.5 kHz</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"> </td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="149-14" style="margin-left: 0.3em; margin-right: 1em;">
3</div>
</td></tr>
</tbody></table>
<div class="para" id="149-15" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<span class="beginpage" pagenum="51"><a href="" id="150" name="150" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page51" name="page51" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>From a time perspective, a RB spans one scheduling period which is defined as one subframe. One subframe has a duration of 1 ms. A subframe is divided into two slots of 0.5 ms. Within a subframe 14 OFDM symbols are transmitted in the case of normal CP length and 12 OFDM symbols in the case of extended CP length, hence a RB covers an area of, respectively, 12 × 14 and 12 × 12 REs. </div>
<div class="para" id="150-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
A third dimension is introduced by using multiple antenna ports with MIMO. The MIMO transport layers depend on and correlate with the number of used transmit antenna ports. Each antenna port layer adds additional RB elements to the antenna port dimension. Figure 1 shows the two-dimensional (frequency and time) area of a RB.</div>
<div class="para" id="150-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<br /></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgK6vfIS141Yv__QNpOub2TXKD26yb2736161Ym5clfFPfwszDjz8xh0MEILF03BFUi73badOWi2PSoG-umwW6cBGVyrcgwZCt0p4UMcnfPtICNcWkY3WtBsTJ12h4kTjSs1uvpXcacKg9J/s1600/a.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgK6vfIS141Yv__QNpOub2TXKD26yb2736161Ym5clfFPfwszDjz8xh0MEILF03BFUi73badOWi2PSoG-umwW6cBGVyrcgwZCt0p4UMcnfPtICNcWkY3WtBsTJ12h4kTjSs1uvpXcacKg9J/s640/a.jpg" width="420" /></a></div>
<div class="figure" id="ch01fig41" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="151" name="151" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig41" name="ch01fig41" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="151-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 1: </span>Downlink resource grid. Reproduced with permission from © 3GPP<sup>™</sup></span></div>
<div class="para" id="151-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
RBs have a primary role in the scheduling process, but are also used for describing the LTE overall cell bandwidth. The cell bandwidth is announced in the data transmitted in the Physical Broadcast Channel (PBCH) in number of resource blocks. Table 2 maps the number of RBs to the LTE spectrum bandwidth in megahertz.</div>
<a href="" id="152" name="152" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; outline-color: initial; outline-style: none; outline-width: initial; text-align: left; text-decoration: none;"></a><a href="" id="ch01table09" name="ch01table09" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; outline-color: initial; outline-style: none; outline-width: initial; text-align: left; text-decoration: none;"></a><table border="1" class="table" id="ch01table09" linktabletoexcel="yes" style="background-color: white; color: black; font-family: verdana, arial, helvetica, sans-serif; font-size: 11px; margin-bottom: 1em; margin-top: 1em; text-align: left;"><caption class="table-title" id="152-1" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small; font-weight: bold; margin-top: 0.3em; text-align: left;"><span class="table-title" style="margin-top: 0.3em;"><span class="table-titlelabel">Table 2: </span>Commonly used number of resource blocks</span> </caption><thead>
<tr valign="top"><th align="left" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="152-2" style="margin-left: 0.3em; margin-right: 1em;">
Bandwidth (MHz)</div>
</th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="152-3" style="margin-left: 0.3em; margin-right: 1em;">
Resource blocks</div>
</th></tr>
</thead><tbody>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="152-4" style="margin-left: 0.3em; margin-right: 1em;">
1.4</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="152-5" style="margin-left: 0.3em; margin-right: 1em;">
6</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="152-6" style="margin-left: 0.3em; margin-right: 1em;">
3</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="152-7" style="margin-left: 0.3em; margin-right: 1em;">
13</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="152-8" style="margin-left: 0.3em; margin-right: 1em;">
5</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="152-9" style="margin-left: 0.3em; margin-right: 1em;">
25</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="152-10" style="margin-left: 0.3em; margin-right: 1em;">
10</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="152-11" style="margin-left: 0.3em; margin-right: 1em;">
50</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="152-12" style="margin-left: 0.3em; margin-right: 1em;">
15</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="152-13" style="margin-left: 0.3em; margin-right: 1em;">
75</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="152-14" style="margin-left: 0.3em; margin-right: 1em;">
20</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="152-15" style="margin-left: 0.3em; margin-right: 1em;">
100</div>
</td></tr>
</tbody></table>
<div class="para" id="152-16" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The scheduling procedure defines virtual resource blocks. Virtual resource blocks and physical resource blocks are of equal size. The scheduler always uses virtual resource blocks for defining user allocations. There are two different types of virtual resource blocks:</div>
<ul class="itemizedlist" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; list-style-image: initial; list-style-position: initial; list-style-type: square; margin-left: 3em; margin-top: 0.9em; text-align: left;">
<li class="first-listitem" style="margin-top: 0.9em;"><div class="first-para" id="152-17" style="margin-bottom: 0em; margin-top: 0em;">
Localized virtual resource blocks.</div>
</li>
<li class="listitem" style="margin-top: 0.9em;"><div class="first-para" id="152-18" style="margin-bottom: 0em; margin-top: 0em;">
Distributed virtual resource blocks.</div>
</li>
</ul>
<div class="para" id="152-19" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Localized virtual RBs are equal to physical RBs. Therefore, localized virtual RBs address physical RBs directly. Distributed RB mapping enables the usage of frequency diversity without scheduling distributed RBs directly. Distributed virtual RBs split a physical RB at the slot boundary into two halves. The first half of the scheduled distributed virtual RB directly equals the physical RBs. The second slot is hopped to another second slot of another UE which is virtually scheduled in the distributed way. There is one hopping gap between the scheduled RBs at system bandwidths smaller 50 RBs and two gaps at systems with a larger number of RBs. Virtual RBs are used with resource allocation type 2.</div>
<div class="last-para" id="152-20" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Resource Element Groups (REGs) are defined to map physical channels to OFDM symbols, this is done especially in the first OFDM symbols used by the PDCCH. The maximum length of the PDCCH is three OFDM symbols, thus other PHY channels are mapped into the resources of the PDCCH. A REG is defined in such a way that it spreads the information over a bigger frequency range to gain frequency diversity</div>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-170892458161227186.post-55752131802498848212011-12-23T01:41:00.000-08:002011-12-23T01:41:00.103-08:00Multiple Access in OFDM – OFDMA | Radio Interface Basics<br />
<h3 class="sect3-title" id="142-2" style="background-color: white; color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: medium; margin-bottom: 0.9em; margin-top: 1.3em; text-align: left;">
<br /></h3>
<div class="first-para" id="143-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0em; margin-top: 0em; text-align: left;">
LTE uses OFDM as the transmission scheme, as described in the section above. Multiple access is realized with OFDMA with the base station (eNB) taking care of the resources within its cell; this procedure is also called scheduling as the eNB schedules the transmission <span class="beginpage" pagenum="49"><a href="" id="144" name="144" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page49" name="page49" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>of user data in the DL and UL direction on the transmission medium used by all users within this cell. The transmission is done on the basis of a shared channel. The control information for granting an UL transmission on the UL-SCH, or informing a UE about data that is transmitted for it on the DL-SCH, is done within the DL control channel with designated control information. Figure 1 shows the principle of an OFDM shared channel-based multiple user communication.</div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgynnHHqWtbQFxZxNiMcSTw_WkW2o3tRwWZ4AMZBEcqJVyJaCQ5tXjFS0RzEWleqXQNbCWNqPjMPpvxtVX7GR5momV661qzfip1iNySNla1ra_H_jc_tlNKDYMgobkOu6RbBxOScDwRs_B8/s1600/a.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="361" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgynnHHqWtbQFxZxNiMcSTw_WkW2o3tRwWZ4AMZBEcqJVyJaCQ5tXjFS0RzEWleqXQNbCWNqPjMPpvxtVX7GR5momV661qzfip1iNySNla1ra_H_jc_tlNKDYMgobkOu6RbBxOScDwRs_B8/s400/a.jpg" width="400" /></a></div>
<div class="figure" id="ch01fig39" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="145" name="145" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig39" name="ch01fig39" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="145-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 1: </span>OFDM shared channel-based multiple user communication. Reproduced with permission from Nomor</span></div>
<div class="para" id="145-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Resources to be scheduled with OFDMA systems are units of frequency resources and time units describing a time slot for which the scheduled frequency units are valid.</div>
<div class="para" id="145-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
This scheduling procedure not only adds overhead, but also enables the system to be more efficient by introducing a frequency-selective scheduling algorithm with feedback from the UEs regarding current reception quality, rather than use only diversity gains by spreading transmitted data.</div>
<div class="para" id="145-4" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Figure 2 compares a shared channel of an OFDMA system using localized and distributed scheduling of user data. In the localized mode, granted areas belonging to one user allocate adjacent frequency resources within one block. The distributed mode is used when frequency diversity is to be used by spreading the user data of the shared channel to distributed non-adjacent frequency resources. Simulations show that systems with frequency-selective scheduling with a fast channel quality feedback report from users can achieve higher cell throughput compared to systems just spreading data over the spectrum in order to achieve frequency diversity.</div>
<div class="para" id="145-4" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg-37mysXTpyuN7q1xjy9_hyphenhyphentQl6gKqBr1xw2SKp0STW9vR7XGaG7VDhnZLtUN8zcaEvGxNTJT-ur1Klzt6e2HzYndLAi315KiwhMHh0XsqsA11sCDN9nw9OfP66ZBpbl6KKgzDGAlpRm8l/s1600/b.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="235" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg-37mysXTpyuN7q1xjy9_hyphenhyphentQl6gKqBr1xw2SKp0STW9vR7XGaG7VDhnZLtUN8zcaEvGxNTJT-ur1Klzt6e2HzYndLAi315KiwhMHh0XsqsA11sCDN9nw9OfP66ZBpbl6KKgzDGAlpRm8l/s400/b.jpg" width="400" /></a></div>
<div class="figure" id="ch01fig40" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="146" name="146" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig40" name="ch01fig40" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="146-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 2: </span>Localized vs. distributed shared channel scheduling</span></div>
<div class="last-para" id="146-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<span class="beginpage" pagenum="50"><a href="" id="147" name="147" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page50" name="page50" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>LTE defines both localized and distributed scheduling in the DL direction but only localized scheduling in the UL direction in order to keep the PAPR small in the SC-FDMA symbols of each user.</div>Unknownnoreply@blogger.com1tag:blogger.com,1999:blog-170892458161227186.post-69166491327593140962011-12-20T07:28:00.000-08:002011-12-20T07:28:01.167-08:00OFDM Principles and Modulation | Radio Interface Basics<br />
<h3 class="sect3-title" id="134-2" style="background-color: white; color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: medium; margin-bottom: 0.9em; margin-top: 1.3em; text-align: left;">
<br /></h3>
<div class="first-para" id="135-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0em; margin-top: 0em; text-align: left;">
Most recent communication systems like WiFi, WiMAX, and digital audio and video broadcasts make use of OFDM, as in the LTE DL transmission scheme and a slightly modified version in the LTE UL transmission scheme.</div>
<div class="para" id="135-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<span class="beginpage" pagenum="46"><a href="" id="136" name="136" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page46" name="page46" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>OFDM systems have some advantages for mobile wireless transmission as signals are robust against frequency-selective fading. Systems which make use of OFDM have been known since the 1950s and 1960s in military applications. Their realization was expensive as all components and filters were implemented as analog circuits. Nowadays, a wide range of applications profit from the benefits of OFDM systems since digital signal processing has become inexpensive and available in consumer products.</div>
<div class="para" id="136-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Information is modulated on very small adjacent carriers within the allocated bandwidth (baseband). The intrinsic design of an OFDM system prevents interference among the carriers (also called subcarriers or tones). This is the reason why the subcarriers are orthogonal to each other. Figure 1 shows the basic components needed for OFDM signal generation. The realization of an OFDM signal generator and analyzer is simple to achieve as the main computational functions are transformations between time and frequency spectra which are easy to implement in modern digital signal processing integrated circuits by using the Fast Fourier Transform (FFT) algorithm.</div>
<div class="para" id="136-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjwlWzyIhk45fRg64YoiF-8-l4txoafhHt0NDEUu60tznBkx28JTZyWeGLdALQznXOoXkvf0W4IvBpYK6cFzGLucUKQrZRlA_SrhyphenhyphenZM50PIePQLS_W6hsw1UQeqKCjIxEz5SFtkPVL72ENo/s1600/a.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="188" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjwlWzyIhk45fRg64YoiF-8-l4txoafhHt0NDEUu60tznBkx28JTZyWeGLdALQznXOoXkvf0W4IvBpYK6cFzGLucUKQrZRlA_SrhyphenhyphenZM50PIePQLS_W6hsw1UQeqKCjIxEz5SFtkPVL72ENo/s640/a.jpg" width="640" /></a></div>
<div class="figure" id="ch01fig36" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="137" name="137" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig36" name="ch01fig36" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="137-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 1: </span>Block diagram of OFDM signal generation</span></div>
<div class="para" id="137-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The first step in the transmit chain is the serial-to-parallel conversion of the data to be transmitted. This is usually done within the transmit buffer. This binary data is now quadrature amplitude modulated by mapping bits to complex data symbols. The characteristic of complex data symbols is that each symbol describes a two-dimensional vector with a phase and amplitude. A complex data symbol is described with an in-phase and a quadrature component. These symbols are called IQ samples, as the modulated symbols are digitally sampled. It is possible to map a higher number of bits to symbols by using a higher modulation order like 16 or 64QAM resulting in a higher spectral efficiency, which means transmitting more bits per hertz of the utilized bandwidth. A higher spectral efficiency allows greater user and cell data throughput. The number of bits which are carried by the different modulation schemes can be seen in Table 1. Those numbers are OFDM independent and are equal to other transmission schemes.</div>
<a href="" id="138" name="138" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; outline-color: initial; outline-style: none; outline-width: initial; text-align: left; text-decoration: none;"></a><a href="" id="ch01table07" name="ch01table07" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; outline-color: initial; outline-style: none; outline-width: initial; text-align: left; text-decoration: none;"></a><table border="1" class="table" id="ch01table07" linktabletoexcel="yes" style="background-color: white; color: black; font-family: verdana, arial, helvetica, sans-serif; font-size: 11px; margin-bottom: 1em; margin-top: 1em; text-align: left;"><caption class="table-title" id="138-1" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small; font-weight: bold; margin-top: 0.3em; text-align: left;"><span class="table-title" style="margin-top: 0.3em;"><span class="table-titlelabel">Table 1: </span>Bits to be carried by the modulation schemes used with LTE</span> </caption><thead>
<tr valign="top"><th align="left" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="138-2" style="margin-left: 0.3em; margin-right: 1em;">
Modulation scheme</div>
</th><th align="center" class="th" scope="col" style="color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: small;"><div class="table-para" id="138-3" style="margin-left: 0.3em; margin-right: 1em;">
Number of bits which can be carried by one complex symbol</div>
</th></tr>
</thead><tbody>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="138-4" style="margin-left: 0.3em; margin-right: 1em;">
BPSK</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="138-5" style="margin-left: 0.3em; margin-right: 1em;">
1</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="138-6" style="margin-left: 0.3em; margin-right: 1em;">
QPSK</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="138-7" style="margin-left: 0.3em; margin-right: 1em;">
2</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="138-8" style="margin-left: 0.3em; margin-right: 1em;">
16QAM</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="138-9" style="margin-left: 0.3em; margin-right: 1em;">
4</div>
</td></tr>
<tr valign="top"><td align="left" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="138-10" style="margin-left: 0.3em; margin-right: 1em;">
64QAM</div>
</td><td align="center" class="td" style="font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0px;"><div class="table-para" id="138-11" style="margin-left: 0.3em; margin-right: 1em;">
6</div>
</td></tr>
</tbody></table>
<div class="para" id="138-12" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<span class="beginpage" pagenum="47"><a href="" id="139" name="139" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page47" name="page47" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>Mobile cell phone standards which do not use OFDM, like GSM, CDMA2000, or UMTS, modulate the data to complex symbols in the time domain. This means that the resulting sinusoid over time after modulation is the time domain signal of the baseband to be transmitted on the RF carrier frequency. OFDM systems interpret the modulated symbols as modulated frequency tones, which are to be transformed to a signal over time in order to be transmitted. Thus, the modulated symbols are mapped to orthogonal subcarriers (tones) of the baseband spectrum. The transformation to the time domain is done with an <i class="emphasis">n</i>-point inverse Fast Fourier Transform (iFFT). The Fourier transformation adds the orthogonal spectrum of each subcarrier to the resulting baseband spectrum. The spectrum of each subtone is a <i class="emphasis">si(x)</i> function (sin<i class="emphasis">(x)/x</i>), thus the resulting spectrum is an addition of <i class="emphasis">si(x)</i> functions as depicted in Figure 2. The inherent behavior of the Fourier transformation lets each <i class="emphasis">si(x)</i> maximum match zero transitions of all other <i class="emphasis">si(x)</i>functions, resulting in non-interfering subtones since the data was modulated to individual subcarriers (peaks of the <i class="emphasis">si(x)</i> functions). This characteristic is known as orthogonal behavior, which means data is perfectly demodulatable and no guard band between subcarriers is needed, in contrast to FDM, where intercarrier interference needs to be taken care of, for example, with guard bands.</div>
<div class="para" id="138-12" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
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<a href="" id="140" name="140" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig37" name="ch01fig37" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="140-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 2: </span>OFDM signal of orthogonal Si functions (subcarriers); subcarriers do not interfere because at each subcarrier the signals from other subcarriers are zero</span></div>
<div class="para" id="140-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
The designated system bandwidth (baseband bandwidth) is divided into <i class="emphasis">m</i> subcarriers which are sampled with an <i class="emphasis">n</i>-point Fourier transformation, where <i class="emphasis">n > m</i>, indicating oversampling. System bandwidth is defined by a number of resource blocks from 6 to 110, each resource block grouping 12 subcarriers. For approximately 20 MHz system bandwidth (100 resource blocks), 1200 subcarriers are defined and a common FFT size is 2048 samples. LTE defines the sampling frequency as <i class="emphasis">f<sub>s</sub></i> = 1<i class="emphasis">/T<sub>s</sub></i> = 30.72 MHz, which leads to a LTE OFDM symbol length of 66.67<span class="unicode" style="font-family: 'Lucida Sans Unicode', Arial, Helvetica, sans-serif;">μ</span>s for normal CP (Cyclic Prefix). The CP is 5.2 <span class="unicode" style="font-family: 'Lucida Sans Unicode', Arial, Helvetica, sans-serif;">μ</span>s or 160 samples in the first symbol and 4.7 <span class="unicode" style="font-family: 'Lucida Sans Unicode', Arial, Helvetica, sans-serif;">μ</span>s or 144 samples in the other symbols for normal CP. The CP lasts 16.7 <span class="unicode" style="font-family: 'Lucida Sans Unicode', Arial, Helvetica, sans-serif;">μ</span>s or 512 samples for extended CP. </div>
<div class="para" id="140-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<span class="beginpage" pagenum="48"><a href="" id="141" name="141" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page48" name="page48" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>OFDM systems show robust characteristics against frequency-selective fading caused by the wireless channel, because fading holes are bigger compared to the subcarrier bandwidth, leading to a flat fading of individual subcarriers which is equalized by interpolating between defined reference symbols (reference subcarriers).</div>
<div class="para" id="141-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
LTE defines a set of reference symbols in order to distinguish between various entities: cell-specific, UE-specific, antenna-port-specific, and MBMS-specific (Multimedia Broadcast/Multicast Service) reference symbols. MBMS data and reference symbols are always transmitted on antenna port 4 if MBMS data transmission is enabled.</div>
<div class="para" id="141-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
In other words, the time domain is just the "transmit domain" for OFDM systems. The resulting time domain signal after transforming the modulated frequency signal representing the data is, so to say, "just noise" and cannot be interpreted without transformation back to the frequency domain. All channel estimation, equalization, and interpretation of the data are done in the frequency domain within OFDM systems.</div>
<div class="para" id="141-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
A timely guard interval or GP between OFDM symbols is needed to prevent intersymbol interference due to channel delay spread (arrival of all reflections). This is realized by copying the end of each OFDM symbol in front of the OFDM samples to be transmitted. This GP, also known as the CP (Cyclic Prefix), decreases alias effects caused by a windowing effect of the Fourier spectrum as the Fourier transformation expects an infinite repeated spectrum, but the OFDM symbol has a time-limited duration. LTE defines two CP lengths, a normal CP and an extended CP, for cells with a larger channel delay spread. Additionally, the CP is used for frame synchronization using an auto/cross-correlation function.</div>
<div class="para" id="141-4" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
OFDM systems have the drawback of a high dynamic range after transforming the frequency signal to a time domain signal which is amplified and transmitted. This high Peak-to-Average Power Ratio (PAPR) (squared peak signal amplitude to average signal power level) leads to cost-intense RF amplifiers and shorter battery life. This is especially a disadvantage for mobile handset devices; thus, another transmission scheme needs to be found for the UL.</div>
<div class="para" id="141-5" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
LTE uses Single Carrier Frequency Division Multiple Access (SC-FDMA) or Discrete Fourier Transform (DFT) spread OFDM as the UL transmission scheme to overcome some drawbacks of pure OFDM systems. </div>
<div class="para" id="141-6" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Figure 3 presents an overview of the functional steps needed for physical channel processing.</div>
<div class="para" id="141-6" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
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<div class="figure" id="ch01fig38" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-left: 2em; margin-top: 1em; text-align: left;">
<a href="" id="142" name="142" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig38" name="ch01fig38" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="142-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 3: </span>Overview of physical channel processing. Reproduced with permission from © 3GPP<span class="unicode" style="font-family: 'Lucida Sans Unicode', Arial, Helvetica, sans-serif;">™</span></span></div>Unknownnoreply@blogger.com1tag:blogger.com,1999:blog-170892458161227186.post-4998914012999162112011-12-17T00:24:00.000-08:002011-12-17T00:24:00.101-08:00Multiple Access Methods | Radio Interface Basics<br />
<h3 class="sect3-title" id="125-4" style="background-color: white; color: maroon; font-family: Arial, Helvetica, sans-serif; font-size: medium; margin-bottom: 0.9em; margin-top: 1.3em; text-align: left;">
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<div class="first-para" id="126-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-bottom: 0em; margin-top: 0em; text-align: left;">
<span class="beginpage" pagenum="42"><a href="" id="127" name="127" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page42" name="page42" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>Multiple access has to be performed in systems where a medium is shared for transmission and reception by multiple users or entities. Those entities or users, sometimes also called nodes, are accessing the very same medium to transmit their information, other than, for example, in CS communication schemes. For example, within classical CS communications like Plain Old Telephone Systems (POTSs), each communication node gets a dedicated resource (a telephone landline) to dedicatedly access for the complete communication session. On the other hand, it is necessary to apply a multiple access method when multiple nodes share the same medium for their information transfer, in order to prevent or detect collisions on the shared medium.</div>
<div class="para" id="127-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
This implies that the users share the same resources for communication in a certain way. Multiple access methods are mainly used with PS data transmission, as multiple nodes usually share the same resources for efficiency reasons. Packet Switched (PS) data transmission is mostly characterized by bursty traffic patterns. There are different schemes which can be applied to share those resources. These access schemes are known as multiple access methods.</div>
<div class="para" id="127-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Multiple access methods introduce rules for accessing the shared medium, generally resources. Care has to be taken not to use the same resources by two or more nodes at once, because this would result in distortion of the transferred information.</div>
<div class="para" id="127-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Transmission/reception resources are one or multiples of the following: time, code, frequency, space, etc.</div>
<div class="para" id="127-4" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
One of the first radio-based multiple access scheme is Aloha. Early research in these schemes was carried out at the University of Hawaii in the early 1970s. In the Hawaiian language <i class="emphasis">Aloha</i> means "Hello" which indicates a fundamental mechanism: the university ran several campuses on different islands where an early radio-based packet data network was established. Stations immediately transmitted packets to be sent and waited for a fixed time (double the round-trip time of the most distant stations in the network plus the transmission and processing time of packets) for an acknowledgment (ACK) from the receiving station. If an ACK was received, the packet was retransmitted. Aloha shows that many collisions of packets occur when applying this scheme.</div>
<div class="para" id="127-5" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Most modern access methods use mechanisms of avoiding, detecting, or preventing collisions within the shared medium, in order to reach a certain system efficiency. A basic method to avoid collisions is sensing the medium before starting a transmission, to avoid interrupting or interfering with an ongoing transmission of other communication peers.</div>
<div class="para" id="127-6" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
This scheme is known as Carrier Sense Multiple Access (CSMA). Sensing the medium before transmission adds Collision Avoidance functionality (i.e., CSMA/CA). In addition to sensing the <span class="beginpage" pagenum="43"><a href="" id="128" name="128" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page43" name="page43" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>medium before transmission, one has to take care with detecting collisions when two terminals have started a transmission at the same time. This scheme, for example, is used with Ethernet local area networks, CSMA/CD. If a collision is detected from both transmit entities, a collision resolution mechanism must be applied. Both peers select a random time in a defined range in order to restart their transmission after this randomly selected period of time. The process starts by sensing the medium again, as the other collision peer (or a new transmission of a third node) could already have (re)started its transmission as it has selected a shorter back-off period. The efficiency can be increased by introducing discrete back-off slots.</div>
<div class="para" id="128-1" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
A special effect of wireless networks without infrastructure has to be taken care of. As mentioned above, a station listens to the channel before sending data to avoid a collision with an ongoing transmission from two other stations at that time. But this behavior is not fully sufficient to avoid collisions at all stations within the transmission range. If a node within the transmission range receives a data frame from another station which is not in the range of a node also trying to allocate the channel, this node will interfere with reception of the other node without warning. This unrecognized collision scenario is called the hidden terminal effect, because the sending node is "hidden" or out of range.</div>
<div class="para" id="128-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Figure 1 shows a typical scenario for the hidden terminal effect. The circles around the stations demonstrate the transmission ranges of the nodes. Node A has a link to node B but does not know about the existence of node C, which is the hidden terminal from the point of view of node A. Node B has a link to both node A and node C. In this scenario node C attempts to transmit data to node B and indicates this with a Request to Send (RTS) packet with the destination address of node B. The designated destination node B confirms this request with a Clear to Send (CTS) packet to node C; this CTS packet is also received by node A. Thereby, node A detects that there is another station while transmitting, until the reception node B sends an ACK packet to complete this transmission. Within <span class="beginpage" pagenum="44"><a href="" id="129" name="129" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page44" name="page44" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>that time, node A will not initiate any transmission, not to node B nor to any other possible node, in order not to corrupt reception at node B.</div>
<div class="para" id="128-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
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<a href="" id="130" name="130" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig32" name="ch01fig32" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="130-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 1: </span>Illustration of the hidden terminal effect</span></div>
<div class="para" id="130-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Note that this effect only occurs in mobile networks without fixed infrastructure, for example, mobile ad-hoc networks. Thus, the hidden terminal effect does not affect LTE.</div>
<div class="para" id="130-3" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
One way of sharing the same resources between communication entities is to introduce a master entity, which takes care of the usage of the shared medium. This scheme is widely used within mobile cell phone networks, as the base station controls and grants the access of resources within its cell. Within a Time Division Multiple Access (TDMA) mobile network, one frequency resource is divided into time slots which are used by different users. Mobile networks of the second generation (GSM) share eight time slots within a certain frequency band. Figure 2 illustrates the DL frame of a TDMA system which uses FDD. Thus, UL and DL utilize different frequency bands and both use TDMA. A Guard Period (GP) used between time slots serves to reduce the risk of multi-user interference. The training sequence in the middle of the time slot is used to estimate the wireless channel conditions. This information is extrapolated time-wise to the adjacent data sections.</div>
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<a href="" id="131" name="131" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig33" name="ch01fig33" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="131-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 2: </span>Schematic example of a Time Division Multiple Access (TDMA) system</span></div>
<div class="para" id="131-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
Non-overlapping frequency bands are assigned to different UEs within Frequency Division Multiple Access (FDMA). A single user allocates one frequency resource which is used for the complete active time. Guard bands need to be designed for the system in order to prevent multi-user interference. Systems (as GSM) often use a mixture of TDMA and FDMA, as multiple frequency channels with, for example, eight time slots serve as cell resources. Figure 3 depicts a FDMA system with five users assigned to five different frequency bands.</div>
<div class="para" id="131-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
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<a href="" id="132" name="132" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig34" name="ch01fig34" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="132-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 3: </span>Schematic of Frequency Division Multiple Access (FDMA)</span></div>
<div class="para" id="132-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
UMTS users share orthogonal codes which are used to spread transmission data in order to be transmitted on the same frequency resources within one cell. Picture this as a metaphor: each user uses the same time, space, and frequency resources, but communicates in a different language. This multiple access method is known as Code Division Multiple Access (CDMA) and illustrated in Figure 4.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhEmJJebI87y48K0lDCxC8-qIYkTaIEaAJkfUyZy1vtkOOasgnHUdNhDnaic4tBPENZpcbJzroVrLj7GPtiD8DTPCc0FN16B5obE3l5hO0pOhfi373C5P4rgfAmysWQo02T-GtZzb39BS6H/s1600/d.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="125" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhEmJJebI87y48K0lDCxC8-qIYkTaIEaAJkfUyZy1vtkOOasgnHUdNhDnaic4tBPENZpcbJzroVrLj7GPtiD8DTPCc0FN16B5obE3l5hO0pOhfi373C5P4rgfAmysWQo02T-GtZzb39BS6H/s320/d.jpg" width="320" /></a></div>
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<a href="" id="133" name="133" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="ch01fig35" name="ch01fig35" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><span class="figuremediaobject"></span> <br style="line-height: 1;" /><span class="figure-title" id="133-1" style="margin-left: 0em; margin-right: 8em; margin-top: 0.5em;"><span class="figure-titlelabel" style="font-weight: bold;">Figure 4: </span>Code Division Multiple Access (CDMA)</span></div>
<div class="para" id="133-2" style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: small; margin-top: 0.9em; text-align: left;">
<span class="beginpage" pagenum="45"><a href="" id="134" name="134" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a><a href="" id="page45" name="page45" style="outline-color: initial; outline-style: none; outline-width: initial; text-decoration: none;"></a></span>The shared resources in LTE are very small frequency bands and small transmission time slots. Thus, the method combines FDMA and TDMA behavior, but in a very agile way. Frequency and time resources are often reassigned for diversity or efficiency reasons during ongoing user transmissions. This method is known as Orthogonal Frequency Division Multiple Access (OFDMA). </div>
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Within mobile cell phone network systems, time slot resources, frequency resources, and code resources are controlled by the base station. This controlled multiple access method is known as scheduling. This scheduling case allows active transmission collision protection, as well as other parameters, to be taken into account when granting transmissions between users. These parameters can be fairness, QoS requests of nodes, medium/channel quality or (charging) policies.</div>Unknownnoreply@blogger.com0