LTE Basic Principle 20130820 a 1.1

7/24/2019 LTE Basic Principle 20130820 a 1.1

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HUAWEI TECHNOLOGIES CO., LTD.

LTE Basic Principle

Author/ Email:

Version:01(20130820)


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Charter 1 LTE Background IntroductionCharter 2 LTE Network Architecture and

Protocol Introduction

Charter 3 LTE Physical Layer Structure

Introduction

Charter 4 LTE Layer 2 Structure Introduction

Charter 5 LTE Air Interface Key Technology

Introduction


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Page 3HUAWEI TECHNOLOGIES CO., LTD.

LTE Background Introduction

What is LTE

LTE (Long Term Evolution)is known as the evolution of radio

access technology conducted by 3GPP. The radio access network will evolve toE-UTRAN (Evolved UMTS

Terrestrial Radio Access Network), and the correlated core

network will evolved to SAE(System Architecture Evolution).

LTE Design Target

Flexible bandwidth configuration: supporting 1.4MHz, 3MHz, 5MHz,

10Mhz, 15Mhz and 20MHz

Peak date rate (within 20MHz bandwidth): 100Mbps for downlink and

50Mbps for uplink

Time delay:


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Specification in 3GPP

R99 R4* R5 R6 R7 R8 (LTE/SAE) R9R

L

3GPP

1999 20102008 2009

05Q1, LTE project (Rel.

8) start

09Q1, LTE specification (Rel.

8) frozen

10Q1, Rel. 9

specification frozen

11Q1, Rel. 10 specification

( LTE-A) frozen

Oct. 2010, LTE-A accepted as 4G

(IMT-Advanced) technology by

ITU-R


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SAE Brief Introduction

SAE (System Architecture Evolution) considers evolution for the whole system architecture, i

Flat Functionality: Take out the RNC entity and part of the functions are moved to e-NodeBthe latency and enhance the schedule ability, such as interference coordination, internal load

Part of the RNC functions are moved to core network;

To enhance the mobility management, all IP technology is applied, user-plane and control-p

The compatibility of other RAT is considered.

SGi

S4

S3S1-MME

PCRFS7

S6a

HSS

Operators IP S(e.g. IMS, PSS

Rx+S10

UE

GERAN

UTRAN SGSN

LTE-UuEUTRAN

MME

S11

S5ServingSAE

Gateway

PDNSAE

GatewayS1-U

LTE Background Introduction


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Charter 1 LTE Background Introduction

Charter 2 LTE Network Architecture and



Introduction



Introduction


7/46

Charter 2 LTE Network Architecture and ProtocolIntroduction

2.1 LTE Network Architecture

2.2 LTE Network Element Function

2.3 LTE Protocol Stack Introduction


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LTE Network Architecture

Main Network Element of LTE

E-UTRAN: e-NodeBs, providing the user plane and control

plane.

EPC: MME, S-GWand P-GW.

eNB

MME / S-GW MME / S-GW

eNB

eNB

S1

S1

S1

S1

X2

X2

X2

Compare with traditional 3G network

becomes much more simple and flat,

to lower networking cost, higher netw

and shorter time delay of user data a

signaling.

Network Interface of LTE

The e-NodeBs are interconnected with each other by means of

the X2 interface, which enabling direct transmission of data

and signaling.

S1is the interface between e-NodeBs and the EPC, more

specifically to the MME via the S1-MME and to the S-GW via

the S1-U.


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eNB

RB Control

Connection Mobility Cont.

eNB Measurement

Configuration & Provision

Dynamic ResourceAllocation (Scheduler)

PDCP

PHY

MME

S-GW

S1

MAC

Inter Cell RRM

Radio Admission Control

RLC

E-UTRAN

RRC

MobilityAnchoring

EPS Bearer Co

Idle State Mob

Handling

NAS Securi

e-Node Functions:

Radio Resource Management: Radio Bearer Control, Radio

Admission Control, Connection Mobility Control, Dynamic

allocation of resources to UEs in both uplink and downlink ;

IP header compression and encryption of user data stream;

Routing of User Plane data towards Serving Gateway;

Paging and broadcast messages;

Measurement and measurement reporting configuration for

mobility and scheduling.

MME (Mobility Management Entity) Functions:

NAS signaling and security;

AS Security control; Idle state mobility handling;

EPS (Evolved Packet System) bearer control;

Support paging, handover, roaming and authentication. S-GW (Serving Gateway) hosts the

Packet routing and forwarding; Local m

handover; Lawful interception; UL and

and QCI; Accounting on user and QCI

charging.

P-GW (PDN Gateway) Functions:

Per-user based packet filtering; UE IP address allocation; UL and

DL service level charging, gating and rate enforcement;

LTE Network Element FunctionRRC: Radio Res

PDCP: Packet Da

RLC: Radio Lin

MAC: Medium A

PHY: Physical

EPC: Evolved P

MME: Mobility M

S-GW: Serving G

P-GW: PDN Gat


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Introduction of LTE Radio Protocol Stack

Two Planes in LTE Radio Protocol:

User-plane: For user data transfer

Control-plane: For system signaling transfer

Main Functions of User-plane:

Header Compression

Ciphering

Scheduling

ARQ/HARQ

eNB

PHY

UE

PHY

MAC

RLC

MAC

PDCPPDCP

RLC

eNB

PHY

UE

PHY

MAC

RLC

MAC

RLC

NAS

RRC RRC

PDCP PDCP

Main Functions of Control-plane:

RLC and MAC layers perform the same

plane

PDCP layer performs ciphering and inte

RRC layer performs broadcast, paging

RB control, mobility functions, UE mea

control

NAS layer performs EPS bearer manag

security control

User-plane protocol stack

Control-plane protocol stack


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Introduction



Introduction


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Charter 3 LTE Physical Layer Structure Introduction

3.1 LTE Supports Frequency Bands

3.2 Radio Frame Structure

3.3 Physical Channels

3.4 Physical Signals

3.5 Physical Layer Procedures


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Frequency Band of LTE

E-UTRABand

Uplink (UL) D

FUL_low

FUL_high FD

1 1920 MHz 1980 MHz 2110 MH

2 1850 MHz 1910 MHz 1930 MH

3 1710 MHz 1785 MHz 1805 MH

4 1710 MHz 1755 MHz 2110 MH

5 824 MHz 849 MHz 869 MHz

6 830 MHz 840 MHz 875 MHz

7 2500 MHz 2570 MHz 2620 MH

8 880 MHz 915 MHz 925 MHz

9 1749.9 MHz

1784.9 MHz 1844.9 MH

10 1710 MHz 1770 MHz 2110 MH

111427.9 MHz 1452.9 MHz 1475.9 MH

12 698 MHz 716 MHz 728 MHz

13 777 MHz 787 MHz 746 MHz

14 788 MHz 798 MHz 758 MHz

17 704 MHz 716 MHz 734 MHz

...

E-UTRA

Band

Uplink (UL) Downlink (DL) Duplex

ModeFUL_low

FUL_high FDL_low

FDL_high

33 1900 MHz 1920 MHz 1900 MHz 1920 MHz TDD








TDD Frequency Band

FDD Frequency Ban From LTE Protocol:

Duplex mode: FDD and TDD

Support frequency band form 700MHz to 2.6GHz

Support various bandwidth: 1.4MHz, 3MHz, 5MHz, 10MHz,

15MHz, 20MHz

Protocol is being updated, frequency information could be

changed.


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Radio Frame Structures Supported by LTE:

Type 1, applicable to FDD

Type 2, applicable to TDD

FDD Radio Frame Structure: LTE applies OFDM technology, with subcarrier spacing f=15kHz and 2048-order

IFFT. The time unit in frame structure is Ts=1/(2048* 15000) second;

FDD radio frame is 10ms shown as below, divided into 20 slots which are 0.5ms. One

slot consists of 7 consecutive OFDM Symbols under Normal CP configuration.

#0 #1 #2 #3 #19#18

One radio frame, Tf = 307200Ts = 10 ms

One slot, Tslot = 15360Ts = 0.5 ms

One subframe FDD Radio Frame Structure

Concept of Resource Block:

LTE consists of time domain and frequency domain resources. The minimum unit for schedule

is RB (Resource Block),which compose of RE (Resource Element);

RE has 2-dimension structure: symbol of time domain and subcarrier of frequency domain;

One RB consists of 1 slot and 12 consecutive subcarriers under Normal CP configuration.

Radio Frame Structure (1)


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TDD Radio Frame Structure:

Applies OFDM, same subcarriers spacing and time

unit with FDD;

Similar frame structure with FDD. radio frame is 10ms

shown as below, divided into 20 slots which are 0.5ms;

The uplink-downlink configuration of 10ms frame are

shown in the right table.

One slot,Tslot=15360Ts

GP UpPTSDwPTS

One radio frame, Tf= 307200Ts= 10 ms

One half-frame, 153600Ts= 5 ms

30720Ts

One subframe,

30720Ts

GP UpPTSDwPTS

Subframe #2 Subframe #3 Subframe #4Subframe #0 Subframe #5 Subframe #7

Uplink-downlink Configuratio

Uplink-downlinkconfiguration

Downlink-to-UplinkSwitch-point

periodicity 0 1 2

0 5 ms D S U

1 5 ms D S U

2 5 ms D S U

3 10 ms D S U

4 10 ms D S U

5 10 ms D S U

6 5 ms D S U

DwPTS

GP: GuUpPTS

TDD Radio Frame Structure



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Special Subframe Structure:

Special Subframe consists of DwPTS, GP and UpPTS .

9 types of Special subframeconfiguration;

Guard Period size determines the maximal cell radius. (100km);

DwPTS consists of at least 3 OFDM symbols, carrying RS,

control message and data;

UpPTS consists of at least 1 OFDM symbol, carrying sounding

RS or short RACH.

Configuration of specia

Special Subframe Structure

Special subframe

configuration

No

DwPTS

0 3

1 9

2 10

3 11

4 12

5 3

69

7 10

8 11


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CP Length Configuration:

Cyclic Prefix is applied to eliminate ISI of OFDM;

CP length is related with coverage radius. Normal

CP can fulfill the requirement of common

scenarios;

Extended CP is for wide coverage scenario;

Longer CP, higher overhead.

Configuration DL OFDM CP LengthUL SC-FDMA C

Length

Normal CP f=15kHz160 for slot #0

144 for slot #1~#6

160 for slot #0

144 for slot #1~#

ExtendedCP

f=15kHz 512 for slot #0~#5 512 for slot #0~#

f=7.5kHz 1024 for slot #0~#2 NULL

CP Configuration

Slot structure under Normal CP

configuration

(

f=15kHz)

Slot structure under Extended CP

configuration

(

f=15kHz)

Slot structure under Extended CP

configuration

(

f=7.5kHz)


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Brief Introduction of Physical Channels

Downlink Channels

Physical Broadcast Channel (PBCH): Carries system information for cell

search, such as cell ID.

Physical Downlink Control Channel (PDCCH) : Carries the resource

allocation of PCH and DL-SCH, and Hybrid ARQ information.

Physical Downlink Shared Channel (PDSCH) : Carries the downlink user

data.

Physical Control Format Indicator Channel (PCFICH) : Carriers

information of the OFDM symbols number used for the PDCCH.

Physical Hybrid ARQ Indicator Channel (PHICH) : Carries Hybrid ARQ

ACK/NACK in response to uplink transmissions.

Physical Multicast Channel (PMCH) : Carries the multicast information. Uplink Channels

Physical Random Access Channel (PRACH) : Carries the random

access preamble.

Physical Uplink Shared Channel (PUSCH) : Carries the uplink user data.

Physical Uplink Control Channel (PUCCH) : Carries the HARQ

ACK/NACK, Scheduling Request (SR) and Channel Quality Indicator

(CQI), etc.

BCH PCH DL-SMCH

PBCH PDSCHPMCH

UL-SCH

PUSCH

RACH

PUCCHPRACH

Mapping between downlin

channels and downlink ph

Mapping between uplink

and downlink physical c


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Downlink Physical Channel

ScramblingModulation

mapper

Layermapper

Precoding

Resource elementmapper

OFDM genera

Resource elementmapper OFDM generaScrambling Modulationmapper

layerscode words

Downlink Physical Channel Processing

scrambling of coded bits in each of the code words to be transmitted on a physical channel

modulation of scrambled bits to generate complex-valued modulation symbols

mapping of the complex-valued modulation symbols onto one or several transmission layers

precoding of the complex-valued modulation symbols on each layer for transmission on the antenna ports

mapping of complex-valued modulation symbols for each antenna port to resource elements

generation of complex-valued time-domain OFDM signal for each antenna port

Modulation Scheme of Downlink Channel

Phy Ch Modulation Scheme Phy Ch Modulation Scheme

PBCH QPSK PCFICH QPSK

PDCCH QPSK PHICH BPSK

PDSCH QPSK, 16QAM, 64QAM PMCH QPSK, 16QAM, 64QAM


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Downlink Resource Structure


Type I frame, single antenna, F = 15 kHz

Standard RB:

One of center 6 RBs:

Legend:Downlink Reference SignalsPBCH (Physical Broadcast Channel)

PSS (Primary Synchronisation Signal)

SSS (Secondary Synchronisation Signal)

PDCCH / PHICH / PCFICH (Physical - Downlink Control / HARQ Indicator / Control Format Indicator -

PDSCH (Physical Downlink Shared Data Channel)


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OFDM

Symbol 0CP

OFDM

Symbol 1CP

OFDM

Symbol 3CP

OFDM

Symbol 4CP

OFDM

Symbol 5CP

OFDM

Symbol 2CP

Legend:

Downlink Reference s

PBCH

PSS

SSS

PDCCH / PHICH / PCF

PDSCH

1 subframe = 2 slot (1 ms)

1 fra

10 s

SF 0 SF 1 SF 2 SF 3 SF 4 SF 5 SF 6 SF 7 SF 8 SF 9

7 OFDM symbols at normal CP per slot (0.5 ms)

0 1 2 3 4 5 6 0 1 2 3 4 5 6

Centre6RBs


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Uplink RS (Reference Signal):

The uplink pilot signal, used for synchronization between E-

UTRAN and UE, as well as uplink channel estimation.

Two types of UL reference signals:

DM RS (Demodulation Reference Signal), associated with

PUSCH and PUCCH transmission;

SRS(Sounding Reference Signal), without associated

with PUSCH and PUCCH transmission.

Characteristics:

Each UE occupies parts of the system bandwidth since SC-

FDMA is applied in uplink. DM RS only transmits in the

bandwidth allocated to PUSCH and PUCCH.

The slot location of DM RS differs with associated PUSCH andPUCCH format.

Sounding RSs bandwidth is larger than that allocated to UE, in

order to provide the reference to e-NodeB for channel estimation

in the whole bandwidth.

Sounding RS is mapped to the last symbol of sub-frame. The

transmitted bandwidth and period can be configured. SRS

transmission scheduling of multi UE can achieve

time/frequency/code diversity.

DM Rto the

Time

Freq

Time

Freq

Time

Freq

DM R

UL AC3 sym

DM RS

CQI si

slot

PUCCH is mapped to up & down

ends of the system bandwidth,

hopping between two slots.

Alloc

Sys

Uplink Physical Signals


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Uplink esource Structure

OFDM

Symbol 0CP

OFDM

Symbol 1CP

OFDM

Symbol 3CP

OFDM

Symbol 4CP

OFDM

Symbol 5CP

OFDM

Symbol 2CP

Legend:

UL DMRS (Uplink Demodulation Refe

UL SRS (Uplink Sounding Reference

PUCCH (Physical Uplink Control Cha

(incl.HARQ feedback and CQI report

Demodulation Reference Signal for P

PUSCH (Physical Uplink Shared Data

SF 0 SF 1 SF 2 SF 3 SF 4 SF 5 SF 6 SF 7 SF 8 SF 9

7 OFDM symbols at normal CP per slot (0.5 ms)

0 1 2 3 4 5 6 0 1 2 3 4 5 6

1 subframe = 2 slot (1 ms)

1 fra

10 s


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0l

0R

0R

0R

0R

6l 0l

0R

0R

0R

0R

6l

Resource element (k,l)

Not used for transmission on this antenna port

Reference symbols on this antenna port

0l

0R

0R

0R

0R

6l 0l

0R

0R

0R

0R

6l 0l

1R

1R

1R

1R

6l 0l

1R

1R

1R

1R

6l

0l

0R

0R

0R

0R

6l 0l

0R

0R

0R

0R

6l 0l

1R

1R

1R

1R

6l 0l

1R

1R

1R

1R

6l

0l 6l 0l

2R

6l 0l 6l 0l 6l

2R

2R

2R

3R

3R

3R

3R

even-numbered slots odd-numbered slots




Downlink Physical Signals (1) Downlink RS (Reference Signal):

Similar with Pilot signalof CDMA. Used for downlink physical ch

channel quality measurement (CQI)

Three types of RS in protocol. Cell-Specific Reference Signal is

types RS (MBSFN Specific RS & UE-Specific RS) are optional.

Cell-Specific RS

Mapping in Time-

Frequency DomainOne

AntennaPort

TwoAntennaPorts

FourAntennaPorts

Antenna Port 0 Antenna Port 1 Antenna Port 2 Antenna Port 3

Characteristics:

Cell-Specific Reference Signals are generate

and frequency shift mapping. RS is the pseud

the time-frequency domain.

The frequency interval of RS is 6 subcarriers.

RS distributes discretely in the time-frequenc

situation which is the reference of DL demodu

Serried RS distribution leads to accurate chan

overhead that impacting the system capacity.

M

S

RE

Not used for RStransmission on thisantenna port

RS symbols on thisantenna port

R1: RS

R2: RS

R3: RS

R4: RS


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Synchronization Signal:

synchronization signals are used for time-frequency synchronization between UE and E-UTRAN during cell se

synchronization signal comprise two parts:

a. Primary Synchronization Signal, used for symbol timing, frequency synchronization and part of the ce

b. Secondary Synchronization Signal, used for detection of radio frame timing, CP length and cell group

Synchronization Signals Structur

Characteristics:

The bandwidth of the synchronization signal

is 62 subcarrier, locating in the central part of

system bandwidth, regardless of system

bandwidth size.

Synchronization signals are transmitted only

in the 1st and 11rd slots of every 10ms frame.

The primary synchronization signal is located

in the last symbol of the transmit slot. The

secondary synchronization signal is located in

the 2nd last symbol of the transmit slot.

Downlink Physical Signals (2)


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Basic Principle of Cell Search:

Cell search is the procedure of UE synchronizes with E-UTRAN in time-

freq domain, and acquires the serving cell ID;

Two steps in cell search:

Step 1: Symbol synchronization and acquirement of ID within

Cell Group by demodulating the Primary Synchronization Signal;

Step 2: Frame synchronization, acquirement of CP length and

Cell Group ID by demodulating the Secondary Synchronization

Signal.

About Cell ID

In LTE protocol, the physical layer Cell ID comprises two parts: Cell

Group ID and ID within Cell Group. The latest version defines that

there are 168 Cell Group IDs, 3 IDs within each group. So totally

168*3=504 Cell IDs exist.

represents Cell Group ID, value from 0 to 167;

represents ID within Cell Group, value from 0 to 2.

(2)ID

(1)ID

cellID 3 NNN

(1)IDN

(2)IDN

Initial Cell Search:

The initial cell search is carried on after the UE

know the network bandwidth and carrier freque

UE repeats the basic cell search, tries all the ca

to demodulate the synchronization signals. Thistime requirement are typically relatively relaxed

time, such as recording the former available ne

search target.

Once finish the cell search, which achieve sync

and acquirement of Cell ID, UE demodulates th

information, such as bandwidth and Tx antenna

After the procedure above, UE demodulates the

that allocated by system. UE wakes up from the

paging period, demodulates PDCCH for monito

PDSCH resources will be demodulated to recei

Physical Layer Procedure Cell Search


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Basic Principle of Random Access :

Random access is the procedure of uplink

synchronization between UE and E-UTRAN.

Prior to random access, physical layer shall receive the

following information from the higher layers:

Random access channel parameters: PRACH configuration,

frequency position and preamble format, etc.

Parameters for determining the preamble root sequences and

their cyclic shifts in the sequence set for the cell, in order to

demodulate the random access preamble.

Two steps in physical layer random access:

UE transmission of random access preamble

Random access response from E-UTRAN

Detail Procedure of Random Access:

Physical Layer procedure is triggered up

transmission by higher layers.

The higher layers request indicates a prepreamble received power, a correspondi

resource .

UE determines the preamble transmissio

received power + Path Loss. The transm

the maximum transmission power of UE.

path loss estimate calculated in the UE.

A preamble sequence is selected from th

using the preamble index.

A single preamble is transmitted using th

sequence with calculated transmission p

PRACH resource.

UE Detection of a PDCCH with the indica

during a window controlled by higher laye

corresponding PDSCH transport block is

The higher layers parse the transport blo

grant.

RA-RNTI: Random Access Radio Netwo

Physical Layer Procedure Random Access


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Basic Principle of Power Control:

Downlink power control determines the EPRE (Energy

per Resource Element);

Uplink power control determines the energy per DFT-

SOFDM (also called SC-FDMA) symbol.

Uplink Power Control:

Uplink power control consists of opened loop power and closed loop power

control.

A cell wide overload indicator (OI) is exchanged over X2 interface for

integrated inter-cell power control, possible to enhance the system

performance through power control.

PUSCH, PUCCH, PRACH and Sounding RS can be controlled respectively by

uplink power control. Take PUSCH power control for example:

PUSCH power control is the slow power control, to compensate the path loss

and shadow fading and control inter-cell interference. The control principle is

shown in above equation. The following factors impact PUSCH transmission

power PPUSCH: UE maximum transmission power PMAX, UE allocated resource

MPUSCH, initial transmission power PO_PUSCH, estimated path loss PL,

modulation coding factor TFand system adjustment factor f (not working

during opened loop PC)

UE report CQI

DL Tx Power

EPRE: Energy per Resource Eleme

DFT-SOFDM: Discrete Fourier Trans

f(i)}(i)PL(j)(j)P(i))(M,{P(i)P TFO_PUSCHPUSCHMAXPUSCH 10log10min

Downlink Power Control:

The transmission power of downlink R

The transmission power of PDSCH is

transmission power.

Downlink transmission power will be a

comparison of UE report CQI and targ

power control.

UL Tx Power

System ad

parameter

Physical Layer Procedure Power Control


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Introduction

Charter 4 LTE Layer 2 Structure IntroductionCharter 5 LTE Air Interface Key Technology

Introduction


30/46

Charter 4 LTE Layer 2 Structure Introduction4.1 LTE Layer 2 Brief Introduction

4.2 MAC Layer Introduction

4.3 RLC Layer Introduction

4.4 PDCP Layer Introduction

4.5 Summary of Layer 1 & 2 Data Flow


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Layer 2 is split into the following layers:

MAC (Medium Access Control) Layer

RLC (Radio Link Control ) Layer

PDCP (Packet Data Convergence Protocol ) Layer

Main Functions of Layer 2:

Header compression, Ciphering

Segmentation and concatenatio

Scheduling, priority handling, mu

demultiplexing, HARQ

Segm.

ARQ etc

Multiplexing UE1

Segm.

ARQ etc...

HARQ

Multiplexing UEn

HARQ

BCCH PCCH

Scheduling / Priority Handling

Logical Channels

Transport Channels

MAC

RLCSegm.

ARQ etc

Segm.

ARQ etc

PDCP

ROHC ROHC ROHC ROHC

Radio Bearers

Security Security Security Security

...

Multiplexing

...

HARQ

Scheduling / Priority H

MAC

RLC

PDCP

Segm.

ARQ etc

Se

ARQ

ROHC RO

Security Sec

Layer 2 Structure for DL Layer 2 Structur

Overview of LTE Layer 2


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Main functions of MAC Layer:

Mapping between logical channels and transport channels

Multiplexing/demultiplexing of RLC PDUs (Protocol Data Unit)

belonging to one or different radio bearers into/from TB (transport

blocks ) delivered to/from the physical layer on transport channels

Traffic volume measurement reporting

Error correction through HARQ

Priority handling between logical channels of one UE

Priority handling between UEs (dynamic scheduling)

Transport format selection

Padding

Logical Channels of MAC Lay

Control Channel: For the transf

information

Traffic Channel: for the transfer

Multiplexing

HARQ

Scheduling / Priority Handling

Transport Channels

MAC

Logical Channels

MAC Layer

Structure

BCCHPCCH CCCH DCCH DTCH MCCH M

BCHPCH DL-SCH

Control Channel

Traffic Channel

Introduction of MAC Layer


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Main functions of RLC Layer:

Transfer of upper layer PDUs supports AM, UM or TM data

transfer

Error Correction through ARQ (no need RLC CRC check,

CRC provided by the physical) Segmentation according to the size of the TB: only if an RLC

SDU does not fit entirely into the TB then the RLC SDU is

segmented into variable sized RLC PDUs, no need padding

Re-segmentation of PDUs that need to be retransmitted: if a

retransmitted PDU does not fit entirely into the new TB used

for retransmission then the RLC PDU is re-segmented

Concatenation of SDUs for the same radio bearer

In-sequence delivery of upper layer PDUs except at HO

Protocol error detection and recovery Duplicate Detection

SDU discard

Reset

RLC PDU Structure:

The PDU sequence number carried

independent of the SDU sequence n

The size of RLC PDU is variable acc

scheme. SDUs are segmented /concsize. The data of one PDU may sour

...

RLCSegm.

ARQ etc

Segm.

ARQ etc

Logical Channels

RLC Layer

Structure

RLC PDU Structure

RLC header

RLC PDU

...

n n+1 n+2RLC SDU

Segmentation Concatenation

Introduction of RLC Layer

f C


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Main functions of PDCP Layer:

Functions for User Plane:

Header compression and decompression: ROHC

Transfer of user data: PDCP receives PDCP SDU from theNAS and forwards it to the RLC layer and vice versa

In-sequence delivery of upper layer PDUs at handover for RLC

AM

Duplicate detection of lower layer SDUs at handover for RLC

AM

Retransmission of PDCP SDUs at handover for RLC AM

Ciphering

Timer-based SDU discard in uplink

Functions for Control Plane:

Ciphering and Integrity Protection

Transfer of control plane data: PDCP receives PDCP SDUs

from RRC and forwards it to the RLC layer and vice versa

PDCP PDU Structure:

PDCP PDU and PDCP header a

PDCP header can be either 1 or

PDCP

ROHC RO

Security Sec

ROHC: Robust Header Com

PDCP header

PDCP P

PDCP PDU S

Introduction of PDCP Layer

S f D t Fl i L 1 & 2


35/46


Data Transfer in Layer 1 and Layer 2

Data from the upper layer are headed and packaged, sent to the lower layer, vice versa.

Scheduler effect in the RLC, MAC and Physical Layers. User data packages are multiplexed in the MAC Lay

CRC in Physical Layer.

Summary of Data Flow in Layer 1 & 2


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Introduction



Introduction


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Charter 5 LTE Air Interface Key Technology Introduction

5.1 OFDM & SC-FDMA

5.2 MIMO

5.3 Cell Interference Control

5.4 Schedule and Link Auto-Adaptation

5.5 E-MBMS

OFDMA & SC FDMA


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OFDM & OFDMA

OFDM(Orthogonal Frequency Division Multiplexing) is a

modulation multiplexing technology, divides the system bandwidth

into orthogonal subcarriers. CP is inserted between the OFDM

symbols to avoid the ISI.

OFDMAis the multi-access technology related with OFDM, is used

in the LTE downlink. OFDMA is the combination of TDMA and

FDMA essentially.

Advantage:High spectrum utilization efficiency due to orthogonal

subcarriers need no protect bandwidth. Support frequency link auto

adaptation and scheduling. Easy to combine with MIMO.

Disadvantage:Strict requirement of time-frequency domain

synchronization. High PAPR.

DFT-S-OFDM & SC-FDMA

DFT-S-OFDM (Discrete Fourie

OFDM) is the modulation multi

in the LTE uplink, which is simi

release the UE PA limitation ca

Each user is assigned part of th

SC-FDMASingle Carrier Fre

Accessingis the multi-access

DFT-S-OFDM.

Advantage:High spectrum uti

orthogonal user bandwidth nee

Low PAPR.

The subcarrier assignment sch

mode and Distributed mode.

OFDMA & SC-FDMA

TTI: 1ms

System Bandwidth

Sub-band12Sub-carriers

Time

TTI: 1ms

System Bandwidth


Time

Sub-carriers

TTI: 1ms

Frequency

Time

System Bandwidth


User 1

User 2

User 3

Sub-carriers

TTI: 1ms

Frequency

Time

System Bandwidth


User 1

User 2

User 3

User 1

User 2

User 3

MIMO


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Downlink MIMO

MIMO is supported in LTE downlink to achieve spatial

multiplexing, including single user mode SU-MIMO and

multi user mode MU-MIMO.

In order to improve MIMO performance, pre-coding is usedin both SU-MIMO and MU-MIMO to control/reduce the

interference among spatial multiplexing data flows.

The spatial multiplexing data flows are scheduled to one

single user In SU-MIMO, to enhance the transmission rate

and spectrum efficiency. In MU-MIMO, the data flows are

scheduled to multi users and the resources are shared

within users. Multi user gain can be achieved by user

scheduling in the spatial domain.

Uplink MIMO

Due to UE cost and power consump

implement the UL multi transmission

Virtual-MIMO, in which multi single a

associated to transmit in the MIMO munder study.

Scheduler assigns the same resourc

user transmits data by single antenn

data by the specific MIMO demodula

MIMO gain and power gain (higher T

freq resource) can be achieved by V

of the multi user data can be control

also bring multi user gain.

Pre-coding vectors

User k data

User 2 data

User 1 data

Channel Information

User1

User2

User k

Scheduler Pre-coder

S1

S2

Pre-coding vectors

User k data

User 2 data

User 1 data

Channel Information

User1

User2

User k

Scheduler Pre-coder

S1

S2

User 1 data

Channel

Scheduler

MIMO

DecoderUser k data

User 1 data

User 1 data

Channel

Scheduler

MIMO

DecoderUser k data

User 1 data

DL-MIMO Virtual-M

MIMO

DL MIMO


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DL MIMO

codeword

UE1

User1S

FB

C

Mod

SFBC (Transmit Diversity)

Same stream transmitted simultaneously in certain

form of MIMO coding at the same time-frequency

resource from both antenna ports (Rank = 1)

Depending on the environment & number of

antennas, SFBC can reduce fading margin by 2~8

dB, to extend coverage, and enhance system

capacity

Layer 1, CW1, AMC1

Layer 2, CW2, AMC2

MIMOencoder and

layer

mapping

MCW (Spatial Multiplexing)

Multiple data streams transmitte

frequency resource from differen

The terminal must have at least

spatial multiplexing (SM)

Cell Interference Control


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PowerPower

PowerPower

ICIC

Inter-Cell Interference Coordination

ICIC is one solution for the cell interference control, is essentially a schedule strategy. In LTE,

coordination schemes, like SFR (Soft Frequency Reuse) and FFR (Fractional Frequency Reus

the interference in cell edges to enhance the frequency reuse factor and performance in the ce

SFR Fundamentals

SFR is one effective solution of inter-cell interference control. The system bandwidth is separa

primary band and secondary band with different transmit power.

1

2

3

6

5

7

4

1

2

3

6

5

7

4

The primary band is assigned to the

users in cell edge. The eNB transmit

power of the primary band can be high.

SeconBand

Cell 2,4,6 Primary Band

Frequency

Cell 1Power

Frequency

Cell 1Power

Cell 1 Primary Band

Secondary Band

Cell 3,5,7P Prim

The secondary band is assigned to the usersin cell center. The eNB transmit power of thesecondary band should be reduced in orderto avoid the interference to the primary bandof neighbor cells.

SecondaryBand

SecondaryBand

Cell Interference Control

Huawei SFR 1 3 1 Frequency Planning


42/46


ICIC is introduced into 131 planning to reduce inter cell interference. Higher cell

service throughputenhances users experience.

Huawei SFR 1

3

1 Frequency Planning

SFR 131 UL ICIC

Cells from different sites:frequency division, could be

adjusted periodically due to edge load

Cells in the same site:time division. Edge users are

scheduled in odd and even subframe

SFR 131 DL ICIC

Cell edge:frequency division,se

power

Cell central:all bandwidthare tra

coverage to reduce interference

High sector throughput and spectrum efficiency

Suitable for high capacity scenarios (dense urban & urban) Expansion solution for traditional 131

Adaptive Modulation and Coding


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Adaptive Modulation and Coding

The most appropriate modulation and coding scheme can be adaptively selected according to t

propagation conduction, then the maximum throughput can be obtained for different channel sit

Schedule and Link Auto-adaptation


44/46


User Multiplexing and Scheduling

Large system bandwidth (10/15/20MHz) of LTE will facing the

problem of frequency selected fading. The fading

characteristic on subcarriers of one user can be regarded as

same, but different in further subcarriers.

Select better subcarriers for specific user according to the

fading characteristic. User diversity can be achieved to

increase spectrum efficiency.

The LTE schedule period is one or more TTI.

The channel propagation information is feed back to e-NodeB

through the uplink. Channel quality identity is the overhead of

system. The less, the better.

Schedule and Link Auto-adaptation

Link Auto-adaptation

LTE support link auto-adaptation i

frequency-domain. Modulation sch

on the channel quality in time/freq

In CDMA system, power control is

auto-adaptation technology, which

by far-near effect. In LTE system,

OFDM technology. Power control

uplink interference from adjacent c

path loss. It is one type of slow lin

scheme.

Channel Propagation FadingUser Multiplexing and Sch

Enhance MBMS


45/46

Page 45

HUAWEI TECHNOLOGIES CO., LTD.

E-MBMS

All e-NodeBs apply same frequency resource and send MBMS data simultaneously.

For UE, the signals from different e-NodeBs can be treat as component of multi paths. Not nec

signal from e-NodeBs, which can be soft combined by UE.

Enhance MBMS

E-MBMS Features SFN (Single Frequency Network) mode

MBMS is limited by the cell edge user performance. SFN enhance the performance in cell edg

MBMS effect.

Need downlink air-interface synchronization in SFN mode.

Time delay is much different for e-NodeBs, the signal combination will cause time delay increa

will be configured.


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Copyright2011 Huawei Technologies Co., Ltd. All Rights Reserved.

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