1. lte uu interface protocol stack with comments.pdf
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www.huawei.com
Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
LTE Air Interface &
Signaling A-Z
Workshop
Prepared by: Ramy Khalil
NA NPS Department
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1- LTE Uu interface protocol Stack
2- LTE Physical layer Basic concepts and processing procedures
3- LTE Signaling procedures and UE initialization flow
4- LTE Typical signaling procedures
Page1
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1- LTE Uu interface protocol Stack
LTE Protocol stack Introduction
NAS, RRC, PDCP, RLC & MAC Functions
Signal processing in PHY layer
OFDM & SC-FDMA overview
MIMO Introduction.
Page2
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Introduction
eNB
UE
E-UTRA
1.4MHz, 3MHz,
5MHz, 10MHz,
15MHz, 20MHz
Uu
Page3
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved. Page4
Introduction
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
UE
PDN-GW
E-UTRAN EPC
MME
S-GW
eNB
S1-MME
S1-U
S5/S8
S11
LTE Control Plane and User Plane
NAS Control
Plane
RRC
Control
Plane
User
Plane
Page5
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Control plan Protocol stack
Page6
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
User plan Protocol stack
Page7
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
DL & UL Data processing of User Plan
Page8
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
DL & UL Signaling processing of
Control Plan
Page9
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1- LTE Uu interface protocol Stack
LTE Protocol stack Introduction
NAS, RRC, PDCP, RLC & MAC Functions
Signal processing in PHY layer
OFDM & SC-FDMA overview
MIMO Introduction.
Page10
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
NAS Signaling
UE eNB
MME
EMM (EPS Mobility
Management)
ESM (EPS Session
Management)
Page11
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NAS EMM and ESM Procedures EMM Procedures ESM Procedures
Attach Default EPS Bearer Context Activation
Detach Dedicated EPS Bearer Context Activation
Tracking Area Update EPS Bearer Context Modification
Service Request EPS Bearer Context Deactivation
Extended Service Request UE Requested PDN Connectivity
GUTI Reallocation UE Requested PDN Disconnect
Authentication UE Requested Bearer Resource Allocation
Identification UE Requested Bearer Resource Modification
Security Mode Control ESM Information Request
EMM Status ESM Status
EMM Information
NAS Transport
Paging
Page12
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Radio Resource Control
Page13
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
RRC States
Page14
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
RRC Signaling Radio Bearer
Page15
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
eNB
RLC
MAC
PHY
PDCP
RRC
NAS Signaling
Control Plane
Encryption
Integrity Checking
User Plane
IP Header Compression
Encryption
Sequencing and Duplicate Detection
Packet Data Convergence Protocol
Page16
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
IP Header Compression
Page17
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Radio Link Control
eNB
RLC
MAC
PHY
PDCP
RRC
NAS Signaling
TM (Transparent Mode)
UM (Unacknowledged Mode)
AM (Acknowledged Mode)
Segmentation and Re-assembly
Concatenation
Error Correction
Page18
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Transmission Modes
Page19
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
AM Use ARQ
Page20
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Concatenation & Segmentation
Page21
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Medium Access Control
eNB
RLC
MAC
PHY
PDCP
RRC
NAS Signaling
Channel Mapping and Multiplexing
Error Correction - HARQ
QoS Based Scheduling
Page22
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Scheduling
Page23
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Scheduling strategies
Page24
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
TB, TTI & Transmission Format
Page25
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
HARQ
Page26
If receiver demodulate Receiver will combine
The data in error, it will retransmitted data
Save the data and and initial data. If
Feedback NACK correct, receiver would
feedback ACK.
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
ARQ vs. HARQ
ARQ
Implemented at RLC Layer
Slow Retransmission
Not optimized for Radio Interference
HARQ
Not New used in HSPA and HSPA+Implemented at MAC and PHY Layers
Fast Retransmission
Optimized for Radio Interference
Improved system efficiency
eNBUE
Page27
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
LTE Channels
RLC
MAC
PHY
Logical
ChannelsTransport
Channels
Physical
Channels Radio
Channel
Page28
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
LTE Release 8 Transport Channels
BCH
eNBUE
PCH
DL-SCH
RACH
UL-SCH
Page29
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Physical Layer
eNB
RLC
MAC
PHY
PDCP
RRC
NAS Signaling
Error Detection
FEC Encoding/Decoding
Rate Matching
Mapping of Physical Channels
Power Weighting
Modulation and Demodulation
Frequency and Time Synchronization
Radio Measurements
MIMO Processing
Transmit Diversity
Beamforming
RF Processing
Page30
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1- LTE Uu interface protocol Stack
LTE Protocol stack Introduction
NAS, RRC, PDCP, RLC & MAC Functions
Signal processing in PHY layer
OFDM & SC-FDMA overview
MIMO Introduction.
Page31
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved. Page32
LTE Transport Channel Processing
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Comment
The term channel coding can be used to describe the overall coding for the
LTE channel. It can also be used to describe one of the individual stages.
LTE channel coding is typically focused on a TB (Transport Block). This is a
block of information which is provided by the upper layer, i.e. MAC (Medium
Access Control). The figure summarizes the typical processes performed by
the PHY (Physical Layer), these include:
CRC (Cyclic Redundancy Check) attachment for the Transport Block.
Code block segmentation and CRC attachment.
Channel Coding.
Rate Matching.
Code Block Concatenation.
Page33
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved. Page34
Transport Block CRC
CRC
Calculate
CRCTransport Block
Transport Block
Transmitter
Possible radio
interface errors
CRCTransport Block
Calculate
CRCCRC
Compare
Receiver
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Comment
The error detection method across the air interface is
based on the addition of a CRC (Cyclic Redundancy
Check). The figure illustrates the basic concept of
attaching a CRC to the Transport Block. The purpose of
the CRC is to detect errors which may have occurred
when the data was being sent. In LTE the CRC is based on
complex parity checking.
Page35
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved. Page36
Code Block CRC Attachment and
Segmentation
CRCTransport Block
Transport Block CRC
CRC
Code Block #1 Code Block #2 Code Block #3
Code Block CRCFiller Bits
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Comment
The next stage in the processing of the transport block is
code block segmentation and CRC attachment. The figure
illustrates the concept of code block segmentation. This
process ensures that the size of each block is compatible
with later stages of processing, i.e. the turbo interleaver.
In addition, each code bock (segment) has a CRC included
for the turbo coding.
Page37
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved. Page38
Channel Coding
Transport Channel Coding Options
Transport Channel Coding Method Rate
DL-SCH
Turbo Coding 1/3 UL-SCH
PCH
MCH
BCH Tail Biting Convolutional Coding 1/3
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Comment
Channel coding in LTE facilitates FEC (Forward Error Correction) across the air interface.
There are four main types:
Repetition Coding
Block Coding.
Tail Biting Convolutional Coding.
Turbo Coding.
The actual method used is linked to the type of LTE transport channel or the control
information type.
Page39
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Comment
The actual LTE tail biting convolutional coder is shown in
the figure. There are six shift registers and hence 6bits are
required to initialize the coder. The input bit stream is
identified by ck, dk(0), dk
(1) and dk(2) correspond to the first,
second and third parity streams, respectively.
Page41
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Comment1
Turbo coding defines a high-performance FEC mechanism.
The term Turbo coding can be used to describe many
different types of encoders. For example, in LTE the turbo
encoder is known as a PCCC (Parallel Concatenated
Convolutional Code) and it has two 8 state constituent
encoders and one contention-free QPP (Quadratic
Permutation Polynomial) turbo code internal interleaver.
As previously mentioned, the coding rate of the LTE turbo
encoder is 1/3.
Page43
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Comment2
i.e. for each input bit, three bits are produced. The structure of a
turbo encoder is illustrated in the figure.
The LTE turbo encoder employs two recursive convolutional encoders
connected in parallel, with the QPP turbo interleaver preceding the
second encoder. The outputs of the constituent encoders are
punctured and repeated to achieve the correct output. It can be seen
that the turbo coder encodes the input block twice, i.e. with and
without interleaving, to generate two distinct sets of parity bits.
Page44
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved. Page45
Rate Matching
dk(1)
dk(0)
dk(2)
Sub-block
Interleaver
Sub-block
Interleaver
Sub-block
Interleaver
vk(1)
vk(0)
vk(2)
Bit
Collection
wk
Virtual
Circular
Buffer
Bit Selection
and Pruning
ek
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Comment
The rate matching for turbo coded transport channels is
defined per coded block and consists of interleaving the
three information bit streams dk(0), dk
(1) and dk(2), followed
by the collection of bits and the generation of a circular
buffer as illustrated in the figure.
Page46
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved. Page47
Code Block Concatenation
4200bits
4224bits
3800bits
3840bits
Code Block CRC Attachment and Segmentation
Channel Coding
Rate Matching
Channel Coding
Rate Matching
ek
Code Block Concatenation
ek
fk
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Comment
Code block concatenation effectively concatenates the
previously segmented code blocks.
Page48
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Antenna
Ports
OFDM Signal Generation
Codewords
Scrambling
Scrambling
Modulation
Mapper
Modulation
Mapper
Layer
MapperPrecoding
Layers
Resource
Element
Mapper
Resource
Element
Mapper
OFDM
Signal
Generation
OFDM
Signal
Generation
Page49
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Comment
There are various Physical Layer stages involved in the
generation of the downlink and uplink signals. The figure
illustrates the possible stages for a PDSCH.
Page50
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Scrambling
eNB eNB
PRB PRB
F1 F1
Interference
No
Scrambling
PRB PRB
Less
Interference
Cell RNTI
specific
scrambling
Page51
The scrambling feature statistically improves the interference by scrambling the
information with a scrambling code based on the physical cell ID and RNTI.
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Comment
This stage is applied to the signal in order to provide
interference rejection properties. Scrambling effectively
randomizes interfering signals using a pseudo-random
scrambling process. The figure illustrates the concept of
scrambling, showing a Physical Resource Block on each of
the cells using the same frequency.
Page52
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Modulation Mapper
I
Q
1-1
1
-1
0
1
I
Q
1-1
1
-1
00
01
10
11
I
Q
1 3-1-3
1
3
-1
-3
0000 0010
0001 0011
0100 0110
0101 0111
1000
1001
1100
1101
1010
1011
1110
1111
BPSK QPSK 16QAM
Page53
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Comment
The modulation mapper converts the scrambled bits to
complex-valued modulation symbols (BPSK, QPSK,
16QAM or 64QAM).
Page54
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
64 QAM Modulation Mapper
I
Q
1 3 5 7-1-3-5-7
1
3
5
7
-1
-3
-5
-7
000011 000001 001001 001011
000010 000000 001000 001010
000110 000100 001100 001110
000111 000101 001101 001111
010011 010001 011001 011011
010010 010000 011000 011010
010110 010100 011100 011110
010111 010101 011101 011111
100011
100010
100110
100111
110011
110010
110110
110111
100001
100000
100100
100101
110001
110000
110100
110101
101001
101000
101100
101101
111001
111000
111100
111101
101011
101010
101110
101111
111011
111010
111110
111111
64QAM
Page55
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Codeword, Layer and Antenna Port
Mapping
1 Layer 2 Layers 3 Layers 4 Layers
1 1 2 1
Rank 1 Rank 2 Rank 3 Rank 4
2 2 2 21 1
Codeword
1, 2 or 4
Antenna
Ports
2 or 4
Antenna
Ports
4 Antenna
Ports
4 Antenna
Ports
Page56
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Comment1
To Map codeword into different antennas
Prior to identifying the various stages it is worth clarifying
the concept of codewords, layers and antenna ports. The
use of layers and multiple antenna ports is related to
diversity and MIMO (Multiple Input Multiple Output). In
addition, the term rank is typically applied to the
number of layers.
Page57
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Comment2
In LTE, when discussing the Physical Layer processing, a codeword
corresponds to a TB (Transport Block). One or two codewords can be
used and these are mapped onto layers. The number of layers can vary
from one up to a maximum which is equal to the number of antenna
ports. When there is one codeword, i.e. one transport block, a single
layer is used. In contrast, two codewords, i.e. two transport blocks, can
be used with two or more layers.
It is important to note that the number of modulation symbols on each
layer needs to be the same. As such, when operating with three layers,
the second codeword is twice as large as the first. This can be achieved
due to the supported TB sizes and the other Physical Layer stages.
Page58
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Comment
The next stage is precoding the complex-valued modulation symbols on each
layer for transmission. The figure illustrates the different precoding options:
Single Antenna Port.
Transmit Diversity.
Spatial Multiplexing - This includes two options, i.e. with CDD (Cyclic
Delay Diversity) and without.
Page60
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Comment
Following on from the precoding stage the resource
element mapper maps the complex-valued symbols to the
allocated resources.
Frequency selective scheduling is used to choose best
frequency for some Ues, to map the bits into the
frequency with good radio conditions, so it take channel
quality into consideration
Page62
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1- LTE Uu interface protocol Stack
LTE Protocol stack Introduction
NAS, RRC, PDCP, RLC & MAC Functions
Signal processing in PHY layer
OFDM & SC-FDMA Overview
MIMO Introduction.
Page63
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
OFDM(Orthogonal Frequency Division Multiple Access)
Page64
General Revision
OFDM is a type of Multi-Carrier Transmission.
OFDM is a special case of FDM Technology.
It is a way of FDM but with the condition of orthogonality
OFDM is the DL Accessing Technique for LTE.
Think About the benefits?
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Frequency Division Multiplexing
Frequency
Guard Band
Channel
Bandwidth
Subcarrier
Page65
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Comment
OFDM is based on FDM (Frequency Division Multiplexing) and is a
method whereby multiple frequencies are used to simultaneously
transmit information. The figure illustrates an example of FDM with
four subcarriers. These can be used to carry different information and
to ensure that each subcarrier does not interfere with the adjacent
subcarrier, a guard band is utilized. In addition, each subcarrier has
slightly different radio characteristics and this may be used to provide
diversity.
FDM systems are not that spectrally efficient (when compared to
other systems) since multiple subcarrier guard bands are required.
Page66
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OFDM Subcarriers
Frequency
Channel
Bandwidth
Orthogonal
SubcarriersCentre Subcarrier
Not Orthogonal
Page67
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Comment
OFDM follows the same concept as FDM but it drastically increases
spectral efficiency by reducing the spacing between the subcarriers.
The figure illustrates how the subcarriers can overlap due to their
orthogonality with the other subcarriers, i.e. the subcarriers are
mathematically perpendicular to each other. As such, when a
subcarrier is at its maximum the two adjacent subcarriers are passing
through zero. In addition, OFDM systems still employ guard bands.
These are located at the upper and lower parts of the channel and
reduce adjacent channel interference.
Page68
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Inverse Fast Fourier Transform
Coded
Bits
Serial
to
Parallel
Subcarrier
Modulation
IFFT
Inverse Fast
Fourier
Transform
RF
Complex
Waveform
Page69
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Comment
OFDM subcarriers are generated and decoded using
mathematical functions called FFT (Fast Fourier Transform)
and IFFT (Inverse Fast Fourier Transform). The IFFT is used
in the transmitter to generate the waveform. The figure
illustrates how the coded data is first mapped to parallel
streams before being modulated and processed by the
IFFT.
IFFT is used to convert signal from frequency domain into
time domain
Page70
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FFT
Fast Fourier
Transform
Fast Fourier Transform
Receiver
Subcarrier
Demodulation
Coded
Bits
Parallel
to
Serial
Page71
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Comment
At the receiver side, this signal is passed to the FFT which
analyses the complex/combined waveform into the
original streams. The figure illustrates the FFT process.
FFT is used to convert signal from time domain into
frequency domain
Page72
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OFDM Symbol Mapping
Time
Frequency
Amplitude
OFDM
Symbol
Cyclic
Prefix
Modulated
OFDM
Symbol
Page73
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Comment
The mapping of OFDM symbols to subcarriers is
dependent on the system design. The figure illustrates an
example of OFDM mapping. The first 12 modulated
OFDM symbols are mapped to 12 subcarriers, i.e. they are
transmitted at the same time but using different
subcarriers. The next 12 subcarriers are mapped to the
next OFDM symbol period. In addition, a CP (Cyclic Prefix)
is added between the symbols.
Page74
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Inter Symbol Interference
1st Received
Signal Delayed
Signal
Interference
Caused
Page75
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Comment
The delayed signal can manifest itself as ISI (Inter Symbol
Interference), whereby one symbol impacts the next.
ISI (Inter Symbol Interference) is typically reduced with
equalizers. However, for the equalizer to be effective a
known bit pattern or training sequence is required.
However, this reduces the system capacity, as well as
impacts processing on a device. Instead, OFDM systems
employ a CP (Cyclic Prefix).
Page76
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OFDM & SC-FDMA
Page77
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
OFDM
Peak to Average Power Ratio
Amplitude
Time
OFDM
Symbol
PAPR (Peak to Average
Power Ratio) Issue
Peak
Average
Page78
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1- LTE Uu interface protocol Stack
LTE Protocol stack Introduction
RRC, PDCP, RLC & MAC Functions
Signal processing in PHY layer
OFDM & SC-FDMA overview
MIMO Introduction
Page79
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
MIMO Historical Overview
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Overview
Multi antenna systems is the use of multiple receive and/or transmit antennas
If one transmitting and many receiving, is called SIMO(single input multi output)
If many transmitting and one receiving, is called MISO(multi input single output)
If many transmitting and many receiving, is called MIMO(multi input multi output)
Multi antenna techniques are used to increase system performance including
capacity, coverage, QoS.
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Benefit of MIMO
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
MIMO Channel Model
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MIMO Modes
Page84
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UL MIMO Technology
Page85
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Comment
No Spatial Multiplexing in UL because no mobiles with multiple
antennas
UL MU-MIMO used to improve UL cell throughput.
Page86
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Beam Forming
The idea of beam forming is to direct the antenna
radiation pattern towards a certain group of users in a
certain place
This is done by multiplying by a certain pre-coding
Matrix calculated from user feedback about the channel
spatial characteristics
Beam Forming increases the SINR and decreases the
interference
It is not used till now in any operator
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
MIMO Transmission modes
Page88
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
Adaptive MIMO scheme
CQI, RI & PMI
Page89
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Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved.
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