lte channel structure .eng

1. Jaeho, Lee
Distribution
EnglishED01
Customer Training Center

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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
S1
S1
S1
S1
X2
X2
X2
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 compression
In-sequency delivery at handover
Duplicate detection
Ciphering for user/control plane
Integrity protection for control plane
AM/UM/TM
ARQ
(Re-)segmentation
Concatenation
In-sequence delivery
Duplicate detection
Logical - transport channel mapping
Multiplexing/demultiplexing
Traffic volume measurement
HARQ
Priority handling
Transport format selection
* PDCP : Packet Data Convergence Protocol
RLC : Radio Link Control
MAC : 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 setup
Radio bearer control
Mobility functions
UE measurement control
EPS bearer management
Authentication
ECM_IDLE mobility handling
Paging originated in ECM_IDLE
Security Control
* RRC : Radio Resource Control
NAS : Non Access Stratum
EPS : Evolved Packet System
ECM : 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
Common
Control Info
at no RRC
Connection
Dedicated
Control
Dedicated
Traffic

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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)
No PDCP, RLC TM, transparent MAC
PCCH/PCH/PDSCH
Paging message
No PDCP, RLC TM, transparent MAC
Logical Channel/Transport Channel/Physical Channel

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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
Logical Channel/Transport Channel/Physical Channel

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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 higher
layers
 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 from
higher 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 search
Receive System information
Attach
Power
ON
Cell Search
and Selection
Receive System
Information Attach
User data
Tx/Rx
Initial Access procedure

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Cell Search
Cell search
Find a cell to connect and estimate frame timing
Provide 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; NID
cell (168 unique physical-
layer cell-identity groups; NID
(1), each group containing three unique
identities; NID
(2))
Physical-layer identity

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Synchronization Signals (FDD)
PSS (primary synchronization signal)
Estimate 5 msec timing and physical-layer identity
Channel 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)

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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)

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Cell-specific Reference Signal

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Dedicated RS
Three types of downlink reference signal
UE-specific reference signals are supported for single-antenna-port
transmission of PDSCH (transmitted on antenna port 5)

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PBCH
PBCH
Master information block of system information
Use 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

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PCFICH
Use CFI (control format indicator) Transmission
Information about the number of OFDM symbols used for transmission of
PDCCH in a subframe is included
Transmit first OFDM symbol
The number of OFDM symbols using PDCCH
NRB
DL > 10 : 1, 2, 3
NRB
DL <= 10 : 2, 3, 4

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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

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PDCCH
Resource Element Group (REG)
Basic RE mapping unit for downlink control information

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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 downlink
transmission of paging, RACH response and dynamic BCCH scheduling
DCI format 1B :used to support closed-loop single-rank transmission with
possibly contiguous resource allocation
DCI format 1C : downlink transmission of paging, RACH response and dynamic
BCCH scheduling
DCI format 1D : compact scheduling of one PDSCH codeword with precoding
and power offset information
DCI format 2 : scheduling PDSCH to UEs configured in closed-loop spatial
multiplexing mode
DCI format 2A : scheduling PDSCH to UEs configured in open loop spatial
multiplexing 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 with
single bit power adjustments

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PHICH
Transmit hybrid-ARQ ACK/NACK for PUSCH transmission
PHICH group
1 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
Nh = 1/6, 1/2, 1, 2
The number of
PHICH group N
PHICH mapping

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PHICH

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Uplink Numerology
Number of symbols per slot
Bandwidth and number of RBs
UL
symbN SC-FDMA symbols
One uplink slot slotT
0l 1
UL
symb  Nl
RB
sc
UL
RBNNsubcarriers
RB
scNsubcarriers
RB
sc
UL
symb NN 
Resource block
resource elements
Resource element ),( lk

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Uplink Basic Mapping Structure
Resource block (RB)
PUSCH mapping

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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

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Mapping of Uplink Physical Channels
PUCCH: frequency edge
PUSCH: between PUCCH RBs
Demodulation 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

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SC-FDMA for LTE UL
Equivalent to DFT-Precoded OFDMA
Low PAPR  It‟s proper to Uplink
Overall spectrum size
Lower symbol rate
Higher symbol rate

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PUSCH Transmission
Localized transmission Hopping transmission

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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

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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

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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

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Sounding Reference Signal (SRS)
UE is periodically upload to eNB for checking the uplink channel
status.
Use checking of UL channel status for the bandwidth transmitted SRS to UE.
SRS cell-specific
Configuration
Configuration Binary
Configuration 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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Sounding Reference Signal (SRS)
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 SRS
BWs
For each SRS BW configurations, there exist 1~4 SRS BWs
SRS bandwidth configuration and SRS bandwidth for 40~60 RB uplink system BW
SRS
bandwidth
configuration
SRSC
SRS-Bandwidth
0SRS B
SRS-Bandwidth
1SRS B
SRS-Bandwidth
2SRS B
SRS-Bandwidth
3SRS B
0SRS,m 0N 1SRS,m 1N 2SRS,m 2N 3SRS,m 3N
0 48 1 24 2 12 2 4 3
1 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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Sounding Reference Signal (SRS)
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

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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

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DL/UL Subframe Architecture
DL Subframe Architecture
UL Subframe Structure

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Basic procedure between
eNB and UE

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Basic procedure between eNB and UE
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
UE
ID 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 SSS
DL Reference
Signal PBCH PDSCH
* MIB: Master Information Block
* SIB: System Information Block

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Basic procedure between eNB and UE
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
UE
Msg 1
(Random Access
Preamble)
Msg 2
(Random Access
Response)
RACH DATA
UL Timing Advance
DATA
+Msg 3
allocation
info.
PDCCH PDSCH
Msg 3
(RRC Connection
Request)
DATA
PUSCH
Msg 4
(RRC Connection
Setup)
PDCCH PDSCH PDCCH
DATA
PUSCH
Msg 5
(RRC Connection
Setup 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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Basic procedure between eNB and UE
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 with
PDCCH.
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
UE
DL CQI Estimation
DATA
PUSCH or PUCCH PDCCH PDSCH PUSCH or PUCCH
DL 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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Basic procedure between eNB and UE
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
UE
Transmit 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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Basic procedure between eNB and UE
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.
Serving
cell
UE
Measurement
Report Transmission
* Handover Command : RRC connection reconfiguration
PUSCH
MR
Target
cell
DL RS
DL RS
Handover
Command
PDSCH
RACH RAR
PDSCH
PUSCH
Handover
Complete
* Handover Complete : RRC connection reconfiguration complete
PRACH