Lte Channel Structure

8/18/2019 Lte Channel Structure

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Jaeho, Lee

Distribution

EnglishED01

Customer Training Center

http://www.samsung.co.kr/


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Contents

Chanel information

Physical channel structure

Basic procedure between eNB and UE


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Chanel information


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LTE/SAE Architecture

eNB

MME / S-GW MME / S-GW

eNB

eNB

S 1

S 1

S 1

S 1

X2

X 2X 2

E-UTRAN

SAE (System Architecture Evolution)

SAE = LTE packet core Network

(Evolved Packet Core : EPC)

LTE = evolved UMTS Radio Access Network

LTE (Long Term Evolution)

Use flat architecture without specific

radio network controller

LTE Base station = eNB

(eNB = „evolved‟ node B)


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PDCP/RLC/MAC sublayers terminated in eNB on the network side

User Plane Protocol Stack

eNB

PHY

UE

PHY

MAC

RLC

MAC

PDCPPDCP

RLC

Header compressionIn-sequency delivery at handover

Duplicate detectionCiphering for user/control plane

Integrity protection for control plane

AM/UM/TMARQ

(Re-)segmentationConcatenation

In-sequence deliveryDuplicate detection

Logical - transport channel mappingMultiplexing/demultiplexingTraffic volume measurement

HARQPriority handling

Transport format selection

* PDCP : Packet Data Convergence ProtocolRLC : Radio Link ControlMAC : Medium Access Control(H)ARQ : (Hybrid) Automatic Repeat Request


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Control Plane Protocol Stack

eNB

PHY

UE

PHY

MAC

RLC

MAC

MME

RLC

NAS NAS

RRC RRC

PDCP PDCP

Broadcast, Paging

RRC connection setupRadio bearer controlMobility functions

UE measurement control

EPS bearer managementAuthentication

ECM_IDLE mobility handlingPaging originated in ECM_IDLE

Security Control

* RRC : Radio Resource ControlNAS : Non Access StratumEPS : Evolved Packet SystemECM : EPS Connection Management


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Layer-2 Structure for Downlink

Segm. ARQ etc

Multiplexing UE1

Segm. ARQ etc

...

HARQ

Multiplexing UEn

HARQ

BCCH PCCH

Scheduling / Priority Handling

Logical Channels

Transport Channels

MAC

RLC Segm. ARQ etc

Segm. ARQ etc

PDCP

ROHC ROHC ROHC ROHC

Radio Bearers

Security Security Security Security

...CCCH


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Layer-2 Structure for Uplink

Multiplexing

...

HARQ

Scheduling / Priority Handling

Transport Channels

MAC

RLC

PDCP

Segm. ARQ etc

Segm. ARQ etc

Logical Channels

ROHC ROHC

Radio Bearers

Security Security

CCCH


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Logical Channel/Transport Channel/Physical Channel

Logical channel

Between RLC & MAC

Established per radio bearer

Defined by what kind of information is carried within

Transport channel

Between MAC&PHY

Used to define how traffics are processed (MCS level, TB size, CRC size)

Physical channel

Physical layer for the real transmission

7 types channels


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Channel Mapping - Downlink

BCH PCH DL-SCHMCH

Downlink

Physical channels

Downlink

Transport channels

PBCH PDSCHPMCH PDCCH

BCCH PCCH CCCH DCCH DTCH Downlink Logical Channels

System Info. Paging

CommonControl Infoat no RRC

Connection

DedicatedControl

DedicatedTraffic


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Channel Mapping - Uplink

Uplink

Physical channels

Uplink

Transport channels

UL-SCH

PUSCH

RACH

PUCCHPRACH

CCCH DCCH DTCH Uplink

Logical Channels


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BCCH/BCH/P-BCH

System information (MIB)

No PDCP, RLC TM, transparent MAC

BCCH/DL-SCH/PDSCH

System information (SIBs)


PCCH/PCH/PDSCH

Paging message




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CCCH/UL(DL)-SCH/PUSCH(PDSCH)

Initial RRC messages, fixed size in UL

Transmitted during random access

No PDCP, RLC TM, Transparent MAC

DCCH/UL(DL)-SCH/PUSCH(PDSCH)

RRC message (including NAS message coming from/going to MME)

PDCP/RLC AM/non-transparent MAC

DTCH/UL(DL)-SCH/PUSCH(PDSCH)

Normal user traffic

PDCP/RLC AM or UM/non-transparent MAC



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Example – Attach Procedure


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Physical Channels and Signals

Physical Downlink Channel (eNB UE)

PBCH (Physical broadcast channel)

DL bandwidth, system frame number, PHICH configuration transmission

PCFICH (Physical control format indicator channel)

Transmit the number of OFDM symbols with PDCCH on downlink subframe to UE

Transmit every subframe

PDCCH (Physical downlink control channel)

Transmit downlink resource allocation on downlink traffic and paging signal

Transmit Uplink scheduling grant

PDSCH (Physical downlink shared channel)

Transmit downlink traffic and paging signal (eNB -> UE)

PHICH (Physical hybrid ARQ indicator channel)

Transmit ACK/NACK for Uplink data(PUSCH)


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Physical Channels and Signals

Physical Uplink Channel (UE eNB)

PUSCH (Physical uplink shared channel)

Transmit uplink traffic

PUCCH (Physical uplink control channel)

Transmit ACK/NACK on Downlink data(PDSCH)

Transmit Scheduling request, downlink channel info.(CQI)

PRACH (Physical random access channel)

Transmit random access preamble when It need Initial access, re-access,requesting UL resources

Signal

Synchronization signal (primary, secondary)

Use it when UE get the synchronization with Base station

DL/UL reference signal

DL CQI measurement and DL / UL channel estimation

UL SRS (Sounding reference signal)

UE is periodically upload to eNB for checking the uplink channel status.


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Physical channel structure


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DL Frame Structure


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DL Frame Structure


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DL Physical Channels & Signals

Physical channels

A set of Resource Elements carrying information originating from higherlayers

Physical Downlink Shared Channel, PDSCH

Physical Broadcast Channel, PBCH

Physical Multicast Channel, PMCH

Physical Control Format Indicator Channel, PCFICH

Physical Downlink Control Channel, PDCCH

Physical Hybrid ARQ Indicator Channel, PHICH

Physical Signals

A set of Resource Elements NOT carrying information originating fromhigher layers

Reference signal

Synchronization signal


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Downlink Resource Grid


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Downlink Resource Grid

Physical resource block parameters

Number of symbols per slot

Number of RBs


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RS Pattern and Control Channel Region


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Initial Access

LTE Initial access procedure

Cell searchReceive System information

Attach

PowerON

Cell Searchand Selection

Receive SystemInformation Attach

User dataTx/Rx

Initial Access procedure

C S


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Cell Search

Cell search

Find a cell to connect and estimate frame timingProvide the primary and secondary synchronization signals on the

downlink to assist

Cell-specific sequences are inserted in synchronization signals

Support 504 unique physical-layer identities; N IDcell (168 unique physical-

layer cell-identity groups; N ID(1), each group containing three uniqueidentities; N ID

(2))

Physical-layer identity

S h i i Si l (FDD)


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Synchronization Signals (FDD)

PSS (primary synchronization signal)

Estimate 5 msec timing and physical-layer identityChannel estimation information for SSS

SSS (secondary synchronization signal)Physical-layer identity (Cell ID) is obtained

Mapped to one of 168 cell ID groups (168 ID groups for 504 Cell IDs)

Radio-frame timing (10msec) identification

Max # of hypotheses;336 hypotheses (2 for half frame x 168 for ID groups)

D li k R f Si l (RS)


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Downlink Reference Signal (RS)

Three types of downlink reference signal

Cell-specific reference signals, associated with non-MBSFN transmission(unicast RS)

MBSFN reference signals, associated with MBSFN transmission

UE-specific reference signals (Dedicated RS)

C ll ifi R f Si l


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Cell-specific Reference Signal

D di t d RS


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Dedicated RS

Three types of downlink reference signal

UE-specific reference signals are supported for single-antenna-porttransmission of PDSCH (transmitted on antenna port 5)

PBCH


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PBCH

PBCH

Master information block of system informationUse QPSK modulation

System information (14 bits) is included

DL system bandwidth (3 bits)

System frame number (SFN: MSB 8 bits explicit, LSB 2 bits implicit)

PHICH duration (1 bit)

PHICH resource (2 bits)

No explicit bits in PBCH to signal the number of TX antennas at the eNB

(1, 2, or 4)

Transmit 4 subframes with interval time(40 ms)

Transmit every Subframe #0

40 ms timing is blind detection on UE

PCFICH


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PCFICH

Use CFI (control format indicator) Transmission

Information about the number of OFDM symbols used for transmission ofPDCCH in a subframe is included

Transmit first OFDM symbol

The number of OFDM symbols using PDCCH

NRBDL > 10 : 1, 2, 3

NRBDL


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PDCCH

Transmit Scheduling assignment(physical downlink control channel)

Transmit the aggregation of one or several control channel element(CCE)

1 CCE = 9 REGs = 36 REs

1 PDCCH = 1, 2, 4, 8 CCEs

Possible to send several PDCCH in a subframe

PDCCH


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PDCCH

Resource Element Group (REG)

Basic RE mapping unit for downlink control information

PDCCH


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PDCCH

PDCCH


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PDCCH

DCI formats

DCI format 0 : UL-SCH assignments

DCI format 1 : DL-SCH assignments for SIMO operation

DCI format 1A : compact scheduling of one PDSCH codeword and for downlinktransmission of paging, RACH response and dynamic BCCH scheduling

DCI format 1B :used to support closed-loop single-rank transmission withpossibly contiguous resource allocation

DCI format 1C : downlink transmission of paging, RACH response and dynamicBCCH scheduling

DCI format 1D : compact scheduling of one PDSCH codeword with precodingand power offset information

DCI format 2 : scheduling PDSCH to UEs configured in closed-loop spatialmultiplexing mode

DCI format 2A : scheduling PDSCH to UEs configured in open loop spatialmultiplexing mode

DCI format 3 : transmission of TPC commands for PUCCH and PUSCH with 2-bit power adjustments

DCI format 3A : transmission of TPC commands for PUCCH and PUSCH withsingle bit power adjustments

PHICH


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PHICH

Transmit hybrid-ARQ ACK/NACK for PUSCH transmission

PHICH group1 PHICH group = 8 PHICHs (normal CP)

1 PHICH group = 4 PHICHs (extended CP)

The amount of PHICH resource is transmitted with 2 bits of PBCH

N h = 1/6, 1/2, 1, 2

The number of

PHICH group N

PHICH mapping

PHICH


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PHICH

Uplink Numerology


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Uplink Numerology

Number of symbols per slot

Bandwidth and number of RBs

UL

symb N SC-FDMA symbols

One uplink slot slotT

0l 1UL

symb N l

R B

s c

U L

R B

N

N

s u b c a r r i e r s

R B

s c

N

s u b c a r r i e r s

RB

sc

UL

symb N N

Resource block

resource elements

Resource element ),( l k

Uplink Basic Mapping Structure


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Uplink Basic Mapping Structure

Resource block (RB)

PUSCH mapping

Uplink Physical Channels and Signals


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Uplink Physical Channels and Signals

Physical Channels (Uplink)

Physical Uplink Shared Channel (PUSCH)

Physical Uplink Control Channel (PUCCH)

Physical Random Access Channel (PRACH)

Physical Signals (Uplink)Demodulation Reference Signal

Sounding Reference Signal

Mapping of Uplink Physical Channels


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Mapping of Uplink Physical Channels

PUCCH: frequency edge

PUSCH: between PUCCH RBsDemodulation reference signal : center symbol in each slot

Sounding reference signal : last symbol in a subframe

Frequency

Sub-frame

(1ms)

Slot

(0.5ms)

SC-FDMA

symbol

PUSCH

PUSCH RS

SRS

One example configuration for normal CP

PUCCH

RB

SC FDMA for LTE UL


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SC-FDMA for LTE UL

Equivalent to DFT-Precoded OFDMA

Low PAPR It‟s proper to Uplink

Overal l spectrum s ize

Low er symbol rate

Higher symbol rate

PUSCH Transmission


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PUSCH Transmission

Localized transmission Hopping transmission

PUCCH


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PUCCH

Format 1 (SR only with On-off Keying (OOK))

Format 1a and 1b (ACK/NACK only)Format 1a: BPSK ACK/NACK for 1 Codeword

Format 1b: QPSK ACK/NACK for 2 Codewords

Format 2 (CQI only)

Format 2a and 2b (CQI + ACK/NACK)

PUCCH (format 1)

PUCCH (format 1)

PUCCH (format 2)

PUCCH (format 2)

PUSCH

PUCCH format 1


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PUCCH format 1

PUCCH format 1 in RB (normal CP)

Cyclic shifts : 12 EA

Orthogonal cover sequence : 3 EA

Total available PUCCH format 1 resource in 1 RB = 36 EA

Decide available PUCCH format 1 resource as the value of

Ex) = 2 , can be used 18 PUCCH format 1 resources in 1 RB

PUCCH format 2


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PUCCH format 2

PUCCH format 2 resources in RB (normal CP)

Cyclic shifts : 12 EA

No orthogonal cover sequence for PUCCH format 2

Total available PUCCH format 2 resource in 1 RB = 12 EA

Decide available PUCCH format 2 resource as the value of

Ex) = 2, can be used 6 PUCCH format 2 resources in 1 RB

Sounding Reference Signal (SRS)


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UE is periodically upload to eNB for checking the uplink channelstatus.

Use checking of UL channel status for the bandwidth transmitted SRS to UE.

SRS cell-specific

Configuration

Configuration BinaryConfiguration Period

(subframes)

Transmission offset

(subframes)

0 0000 1 {0}

1 0001 2 {0}

2 0010 2 {1}

3 0011 5 {0}

4 0100 5 {1}

5 0101 5 {2}

6 0110 5 {3}

7 0111 5 {0,1}

8 1000 5 {2,3}

9 1001 10 {0}

10 1010 10 {1}

11 1011 10 {2}

12 1100 10 {3}

13 1101 10 {0,1,2,3,4,6,8}

14 1110 10 {0,1,2,3,4,5,6,8}

15 1111 Inf N/A



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SRS transmission bandwidths

Multiple SRS BW trees are predefined for each uplink system operating bandwidth

Cell-specific 3 bits are used to indicate one of 8 SRS BW configurations

One SRS BW configuration has Max. SRS BW and predefined SRS BW trees

UE specific 2 bits are given via higher layers to indicate one of 4 SRSBWs

For each SRS BW configurations, there exist 1~4 SRS BWs

SRS bandwidth configuration and SRS bandwidth for 40~60 RB uplink system BW

SRSbandwidth

configuration

SRSC

SRS-Bandwidth

0SRS B

SRS-Bandwidth

1SRS B

SRS-Bandwidth

2SRS B

SRS-Bandwidth

3SRS B

0SRS,m 0 N 1SRS,m 1 N 2SRS,m 2 N 3SRS,m 3 N

0 48 1 24 2 12 2 4 31 48 1 16 3 8 2 4 2

2 40 1 20 2 4 5 4 1

3 36 1 12 3 4 3 4 1

4 32 1 16 2 8 2 4 2

5 24 1 4 6 4 1 4 1

6 20 1 4 5 4 1 4 1

7 16 1 4 4 4 1 4 1



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Configuration Cell-specific SRS

SRS bandwidth configuration

SRS subframe configuration

Report the possibility for simultaneously transmission ACK/NACK and SRS

SRS Configuration per UE

SRS Transmission bandwidth

SRS hopping bandwidth

Cyclic shift

Frequency domain position

Comb

SRS Periods and offset per UE

PRACH Structure


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PRACH Structure

The number of RB for PRACH transmission = 6 RB

Transmit the subframe and frequency offset of PRACH using system information

Preamble format

SequenceCP

CPT SEQT

Preamble format CPT SEQT

0 s3168 T s24576 T

1 s21024 T s24576 T

2 s6240 T s245762 T

3 s21024 T s245762 T

4

(frame structure type 2 only)s448 T s4096 T

DL/UL Subframe Architecture


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DL/UL Subframe Architecture

DL Subframe Architecture

UL Subframe Structure


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Basic procedure betweeneNB and UE



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The procedure for synchronization and obtaining of system Info.

MIB : system frame number, DL bandwidth, PHICH information are included

SIB : Cell specific information are included for system operation except MIB

information

SIB1: cell access configuration, frequency band indicator, scheduling

information for syst other SIBs and systemInfoValueTag

SIB2: radio configuration information are included (PUCCH, PUSCH, SRS etc)

eNB

UEID 0~2 Cell ID

Group 0~167

Cell ID Detection 0~503

Cell specific RS

(Using cell ID info.)

System

Information (MIB)

System

Information (SIB)

Broadcast Information

PSS SSSDL Reference

Signal PBCH PDSCH

* MIB: Master Information Block

* SIB: System Information Block



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Call-Access procedure

UE specific resource allocation information in Msg 4 (RRC Connection Setup) are

transmitted

CQI Resorce index, Transmit period and subframe offset

SR Resource index, Transmit period and subframe offset

SRS Transmission bandwidth, Frequency location, comb, cyclic shift

eNB

UEMsg 1

(Random AccessPreamble)

Msg 2(Random Access

Response)

RACH DATA

UL Timing Advance

DATA+Msg 3

allocationinfo.

PDCCH PDSCH

Msg 3(RRC Connection

Request)

DATA

PUSCH

Msg 4(RRC Connection

Setup)

PDCCH PDSCH PDCCH

DATA

PUSCH

Msg 5(RRC ConnectionSetup Complete)

* CQI: Channel Quality Indicator (DL channel Quality index)

* SR: Scheduling Request (Using it when UE reports that UE has transmit data to eNB)

* SRS: Sounding Reference Signal (Using it when UE transmit it periodically for checking uplink-channel status data)

PRACH



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DL data-Transmission Procedure

UE transmit periodically CQI(channel quality indicator) which is DL channel

status after receiving CQI resource allocation per UE.

eNB allocates PDSCH considering DL channel status of a UE and DL buffer status

Transmit the information of PDSCH allocation per specific subframe withPDCCH.

When CRC is OK on PDSCH detection result in UE, transmit ACK to eNB.

Transmit ACK info. on PUSCH when PUSCH is allocated.

In other cases, Transmit ACK info on PUCCH .

eNB

UEDL CQI Estimation

DATA

PUSCH or PUCCH PDCCH PDSCH PUSCH or PUCCHDL Reference

Signal CQI CQI

DL Scheduling and

Link Adaptation

DL allocation info.

ACK/NACK DATA

PDCCH PDSCH

With there is ACK/NACK or not,

HARQ retransmission or new data transmission

PDSCH Detection

DL allocation info.



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UL data-Transmission Procedure

UE transmit periodically SRS signal after receiving SRS resource allocation per

UE.

eNB allocates PUSCH resource considering UL channel status of a UE and BSR.

When CRC is OK on PUSCH detection result in UE, transmit ACK to eNB.

Transmit ACK using PHICH (Downlink direction)

eNB

UETransmit SRS periodically0

PUSCH

Transmit

the buffer status of UE

SRS SRS

UL Channel Quality Estimation

PUCCH

SR

PDCCH

UL Scheduling and

Link Adaptation

UL allocation info.

DATA+ BSR

•BSR: Buffer Status Report Transmit the buffer status of uplink data to eNB

PDCCH

UL allocation info.

PHICH

ACK

PUSCH

DATA

HARQ



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Handover Procedure

UE sends measurement report to serving cell with the condition of comparing

Neighbor‟s cell signal and Serving cell signal.

If serving cell transmits “handover command” message to UE, UE orders target

cell to be handover.

After UE receives Handover command, UE will proceed the transmission of

RACH ,Handover procedure, to target cell.

Servingcell

UEMeasurement

Report Transmission

* Handover Command : RRC connection reconfiguration

PUSCH

MR

Targetcell

DL RS

DL RS

HandoverCommand

PDSCH

RACH RAR

PDSCHPUSCH

HandoverComplete

PRACH

Lte Channel Structure

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