1. lte uu interface protocol stack with comments.pdf

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


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


Contents


LTE Protocol stack Introduction

NAS, RRC, PDCP, RLC & MAC Functions

Signal processing in PHY layer

OFDM & SC-FDMA overview

MIMO Introduction.

Page2


Introduction

eNB

UE

E-UTRA

1.4MHz, 3MHz,

5MHz, 10MHz,

15MHz, 20MHz

Uu

Page3

Copyright 2015 Huawei Technologies Co., Ltd. All rights reserved. Page4

Introduction


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


Control plan Protocol stack

Page6


User plan Protocol stack

Page7


DL & UL Data processing of User Plan

Page8


DL & UL Signaling processing of

Control Plan

Page9


Contents






MIMO Introduction.

Page10


NAS Signaling

UE eNB

MME

EMM (EPS Mobility

Management)

ESM (EPS Session

Management)

Page11


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


Radio Resource Control

Page13


RRC States

Page14


RRC Signaling Radio Bearer

Page15


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


IP Header Compression

Page17


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


Transmission Modes

Page19


AM Use ARQ

Page20


Concatenation & Segmentation

Page21


Medium Access Control

eNB

RLC

MAC

PHY

PDCP

RRC

NAS Signaling

Channel Mapping and Multiplexing

Error Correction - HARQ

QoS Based Scheduling

Page22


Scheduling

Page23


Scheduling strategies

Page24


TB, TTI & Transmission Format

Page25


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.


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


LTE Channels

RLC

MAC

PHY

Logical

ChannelsTransport

Channels

Physical

Channels Radio

Channel

Page28


LTE Release 8 Transport Channels

BCH

eNBUE

PCH

DL-SCH

RACH

UL-SCH

Page29


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


Contents






MIMO Introduction.

Page31


LTE Transport Channel Processing


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


Transport Block CRC

CRC

Calculate

CRCTransport Block

Transport Block

Transmitter

Possible radio

interface errors

CRCTransport Block

Calculate

CRCCRC

Compare

Receiver


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


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


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


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


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


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


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


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


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


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


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


Comment

Code block concatenation effectively concatenates the

previously segmented code blocks.

Page48


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


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


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.


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


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


Comment

The modulation mapper converts the scrambled bits to

complex-valued modulation symbols (BPSK, QPSK,

16QAM or 64QAM).

Page54


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


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


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


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


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


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


Contents





OFDM & SC-FDMA Overview

MIMO Introduction.

Page63


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?


Frequency Division Multiplexing

Frequency

Guard Band

Channel

Bandwidth

Subcarrier

Page65


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


OFDM Subcarriers

Frequency

Channel

Bandwidth

Orthogonal

SubcarriersCentre Subcarrier

Not Orthogonal

Page67


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


Inverse Fast Fourier Transform

Coded

Bits

Serial

to

Parallel

Subcarrier

Modulation

IFFT

Inverse Fast

Fourier

Transform

RF

Complex

Waveform

Page69


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


FFT

Fast Fourier

Transform

Fast Fourier Transform

Receiver

Subcarrier

Demodulation

Coded

Bits

Parallel

to

Serial

Page71


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


OFDM Symbol Mapping

Time

Frequency

Amplitude

OFDM

Symbol

Cyclic

Prefix

Modulated

OFDM

Symbol

Page73


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


Inter Symbol Interference

1st Received

Signal Delayed

Signal

Interference

Caused

Page75


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


OFDM & SC-FDMA

Page77


OFDM

Peak to Average Power Ratio

Amplitude

Time

OFDM

Symbol

PAPR (Peak to Average

Power Ratio) Issue

Peak

Average

Page78


Contents



RRC, PDCP, RLC & MAC Functions



MIMO Introduction

Page79


MIMO Historical Overview


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.


Benefit of MIMO


MIMO Channel Model


MIMO Modes

Page84


UL MIMO Technology

Page85


Comment

No Spatial Multiplexing in UL because no mobiles with multiple

antennas

UL MU-MIMO used to improve UL cell throughput.

Page86


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


MIMO Transmission modes

Page88


Adaptive MIMO scheme

CQI, RI & PMI

Page89

1. lte uu interface protocol stack with comments.pdf

Documents