02 LF_SP3001_E02_1 LTE Protocol Principle 74

LTE Protocol Principle

ZTE University

Objectives

After the course,you will: Understand the Protocol Structure of Control Plane and

User Plane Understand the Frame Structure Understand the Channel Know the MAC Layer Function Know the RLC Layer Function Know the PDCP Layer Function

Contents

Protocol Structure Physical Layer Protocol MAC Layer Protocol RLC Layer Protocol PDCP Layer Protocol

Protocol Structure on Control-Plane

UE eNodeB MME

eNB

PHY

UE

PHY

MAC

RLC

MAC

MME

RLC

NAS NAS

RRC RRC

PDCP PDCP

NAS functions: Certification Authentication, Security controlMobility processing in Idle modePaging launch in Idle mode

RRC functions: Broadcast Paging Link managementWireless bearing control MobilityUE measurement report and control

PDCP performs the function of encryption and integrity protectionRLC functions: PDU transmissionARQPacket assembly and disassembly

MAC functions: Scheduling HARQLogic channel priority processing PDU packetizing and demultiplexingPhysical layer

(L1) functions: Wireless access Power control MIMO

Protocol Structure on User-Plane

UE eNodeB MME

eNB

PHY

UE

PHY

MAC

RLC

MAC

PDCPPDCP

RLC

SAE Gateway

RLC performs the following functions: PDU transmissionARQPacket assembly and disassembly

PDCP performs the following functions: Header compression Encryption

MAC performs the following functions: Scheduling HARQLogic channel priority processing PDU multiplexing and de-multiplexing

Physical layer (L1) performs the following functions: Wireless access Power control MIMO

Contents

Protocol Structure Physical Layer Protocol

Basic Concepts Uplink and Downlink Physical Layer process Physical Procedure

MAC Layer Protocol RLC Layer Protocol PDCP Layer Protocol

Frame Structure

FDD frame structure

TDD frame structure

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

A wireless frame, Tf = 307200Ts = 10 ms

A timeslot, Tslot = 15360Ts = 0.5 ms

A sub-frame

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 Subframe #8 Subframe #9

Physical Resource Block

One physical resource block (RB) contain OFDM symbols on the time-domain and

sub-carriers on frequency-domain.

The number of and

are determined by the CP type and the subcarrier interval.

DLsymbN OFDM symbols

One downlink slot slotT

0l 1DLsymb Nl

RB

scD

LR

BN

N

subc

arri

ers

RB

scNsu

bcar

rier

s

RBsc

DLsymb NN

Resource block

resource elements

Resource element ),( lk

0k

1RBsc

DLRB NNk

DLsymbN

RBscN

DLsymbN

RBscN

Resource Grouping

RE (Resource Element): The minimum resource unit which is a symbol in time-domain and a subcarrier in frequency-domain

RB (Resource Block): A resource unit allocated by service channel resource. It is a timeslot in time-domain and 12 subcarriers in frequency-domain.

REG (Resource Element Group): a resource unit and it is allocated for control channel resource, it composed of 4 REs

CCE (Channel Control Element): A resource unit allocated by PDCCH resource, it composed of 9 REGs

RBG (Resource Block Group): A resource unit and it is allocated for the service channel resource, it composed of a group of RBs.

Concept of REG

l = 0

RS

RS

RS

RS

l = 1

k = 77

k = 72

k = 78

k = 83

l = 2

1Tx or 2Tx configured

l = 0 l = 1

k = 77

k = 72

k = 78

k = 83

l = 2

4Tx configured

7261212 PRB0 nk6min,

PRB DLRBNn

RS

RS

RS

RS

RS

RS

RS

RS

REG Diagram

464 – 110

327 – 63

211 – 26

1≤10

(P)

RBG SizeSystem Bandwidth

DLRBN

Concept of RBG

RBG is used for resource allocation of service channel One RBG is composed of a group of RBs. The number of RBG is related with the system bandwidth.

Concept of CCE

CCE is used in PDCCH allocation. PDCCH allocation is made after PCFICH and

PHICH. One CCE include 9 REGs. CCE is numbered from

0. Total number of CCEs is determined by the

number of PDCCH-occupied symbols.

CP,Subcarrier interval and OFDM Symbol

Relations between CP Type and Subcarrier Interval and OFDM Symbols

Subcarrier Interval

Number of OFDM Symbols (one slot)

Number of RB-Occupied Subcarriers

Corresponding REs in One RB

Normal CP 15KHz 7 12 84

Extended CP

15KHz 6 12 72

7.5KHz 3 24 72

One RB is composed of 12 subcarriers in the frequency-domain, i.e. 180KHz=15 x 12

(for normal CP)

RB and Bandwidth

The Number of RBs in Different Bandwidths

Occupied bandwidth = subcarrier interval x number of subcarriers in one RB x number of RBs

Subcarrier Interval = 15KHz The Number of subcarriers in one RB = 12 Remark: Maximum number of RBs is 110 in current protocols

Nominal bandwidth

(MHz)

1.4 3 5 10 15 20

Number of RBs 6 15 25 50 75 100

Actually occupied

bandwidth

(MHz)

1.08 2.7 4.5 9 13.5 18

Contents




Physical Downlink Channel and Signal

The LTE downlink includes the following physical channels: Physical-control-format indication channel (PCFICH) Physical broadcast channel (PBCH) Physical Hybrid-ARQ indicator channel (PHICH) Physical downlink control channel (PDCCH) Physical downlink shared channel (PDSCH) Two physical-layer signals: RS (reference signal) P (S) -SCH (synchronized channel)

Resource Allocation

Remark:This diagram is to display the effect of the resource allocation. Each square indicates “time-domain length of a symbol x resource of 12 subcarriers”. It is neither RE nor RB.

SCH (synchronization channel)

SCH includes P_SCH and S_SCH. The frequency-domain is located in the 72 subcarriers near direct current. Only 62 subcarriers are actually occupied. Other 10 subcarriers do not hold synchronization sequences.

There are two same P-SCHs in a wireless frame. Their time-domain is located in the last symbol of the slot no.0 and the slot no. 10.

There are also two S-SCHs in a wireless frame. Their time-domain is located in the penultimate symbol of the slot no.0 and the slot no. 10.

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

Slot no. 0

10ms radio frame

S-SCHP-SCH

Slot no. 10

Location of PSS and SSS

PBCH (physical broadcast channel)

PBCH bears the BCH-contained system information such as downlink system bandwidth, system frame number (SFN), PHICH duration, and resource-size indication information.

Each No.0 sub-frame has four PBCH signals of OFDM symbols.

Physical resource mapping on each antenna

port

OFDM modulation

OFDM modulation

OFDM modulation

An 1

An 0

An P

Cell interference enhancing

Modulation mapping

Layer mapping

Pre-programming

BCH TB

CRC adding

Signal program-

ming

Rate matching

PCFICH (physical-control-format indication channel)

PCFICH and E-Node B are transmitted in each sub-frame, informing UE of the OFDM symbols that PDCCH occupies in a sub-frame. The OFDM symbols are indicated by CFI which can be valued as 1, 2, 3, 4 (4 is reserved).

Signal program-

ming

Interference enhancing

Modulation mapping

Layer mapping

Pre-programming

RE mapping

OFDM symbol generating

CFI

PHICH (physical HARQ indication channel)

PHICH Channel bearing the NAK/ACK responding information of the eNodeB.

Two PHICH durations in one sub-frame ： 1. short PHICH 2. long PHICH; This duration is indicated by 1 bit in PBCH.

In each downlink sub-frame, PHICH needs to be sent. Multiple PHICH groups can be sent at the same time. Define one PHICH group to be mapped from multiple ones to a PHICH in the same RE.

Repetition(RF=3)

ModulationLayer

MappingPrecoding RE mapping

OFDM modulation

Spreading & scrambling

ACK/NACK

PDCCH (physical downlink control channel)

PDCCH bearing scheduling and other control information: Transmission format, resource allocation, uplink scheduling permission, power control and uplink-transmission-related ACK/NACK;

All the information can group multiple types of control information (DCI) format which is mapped to the first n (n<=4) OFDM symbols in each sub-frame. The value of n is indicated by CFI in the PCFICH channel.

In a sub-frame, we can transmit multiple PDCCHs. One UE can monitor one group of PDCCH. Each PDCCH is sent in one or more control channel elements (CCE) to achieve the different PDCH encoding rates by integrating various numbers of CCEs.

PDCCH supports 4 types of physical-layer formats which occupy one, two, four, and eight CCEs respectively.

CRC adding

User interference enhancing

Channel encoding

Rate matching

Merge the

PDCCH channels inside the

cell

CRC adding


Channel encoding

Rate matching

CRC adding


Channel encoding

Rate matching

Physical resource mapping on each antenna

port

OFDM modulation

OFDM modulation

OFDM modulation

An 1

An 0

An P

Cell interference enhancing

Modulation mapping

Layer mapping

Pre-coding

PDCCHDCIn

1DCI

2DCI

PDSCH (physical downlink service channel)

CRCadding

Bit block division

Turbo coding Bit block

cascading

1st data flow

Bit flow Interference

enhancing

Modulation mapping

Bit block cascadin

g

Bit flow Interference

enhancing

Modulation mapping

Layer mapping

1. Single antenna 2. Multiplexing 3. Diversity

Pre-coding

1. Single antenna 2. Multiplexing 3. Diversity

RE mapping

RE mapping

OFDM signal generating

OFDM signal generating

Symbol flow

Symbol flow

E-Node B baseband – Service channel processing link Antenna

port0

Antenna port

P

Turbo coding

Rate matching

Rate matching

CRCadding

Bit block division

Turbo codingM data

flow Turbo coding

Rate matching

Rate matching

Power factor

Power factor

Physical Uplink Channel and Signal

The LTE uplink includes the following physical channels: Physical random access channel (PRACH) Physical uplink control channel （ PUCCH） Physical uplink shared channel (PUSCH)

Two physical-layer signal: Demodulation reference signal (DRS) Sounding reference signal (SRS)

Enhance interference

ModulateTransfer pre-

programmed codesMap resource

Generate SC-FDMA signal

PUSCH (Physical Uplink Shared Channel)

Bearing uplink service information Adding interference: Using UE dedicated interference code Performing modulation: Supporting QPSK, 16QAM and

64QAM modulation Transmitting pre-programmed codes: Divide the input

symbols into groups and pre-program codes, i.e. DFT

Mapping to RE: From the 1st timeslot of the sub-frame, map k and I in turn.

Generating SC-FDMA signal: IDFT

PUSCHscsymb MM

PUCCH (Physical uplink control channel)

6 formats used to bear HARQ-ACK, CQI, SR information

For the same UE, PUCCH does not transmit with PUSCH.

Supports multiple formats: Different formats determine different modulations and different bytes in each sub-frame

PUCCH

formats

Modulati

on

Number of bytes in each

sub-frame

1 N/A N/A

1a BPSK 1

1b QPSK 2

2 QPSK 20

2aQPSK+BP

SK21

2bQPSK+Q

PSK22

PUCCH (Continuing)

Format 1 transfers SR information and sends constant 1.

Format 1a/1b transfers HARQ-ACK, BPSK modulation in 1 byte, and QPSK modulation in 2 bytes.

Format 2 transfers CQI information. Program CQI to 20 bit and performs QPSK modulation.

Format 2a/2b transfers the hybrid information of CQI and HARQ-ACK. Program CQI signal to 20 bit and perform QPSK modulation. For HARQ-ACK, perform BPSK/QPSK modulation.

PRACH (physical random access channel)

Frame structure

Different Preambles

Preamble generation Generated by the

Zadoff-Chu sequence in zero-related region

SequenceCP

CPT SEQT

6RB

10, ZC

)1(

ZC

Nnenx N

nunj

u

)mod)(()( ZCCS, NvNnxnx uvu

LTE Uplink/Downlink Mapping

BCCH PCCH CCCH DCCH DTCH MCCH MTCH

PCH DL-SCH MCHBCH

PBCH PDSCH PMCH

Logical Channel

Transmission Channel

Physical Channel

CCCH DCCH DTCH

UL-SCH

PRACH PUSCH

RACH

PUCCH

Downlink

Downlink

Logical Channel

Transmission Channel

Physical Channel

Contents




Physical-layer process – Cell SearchStart

End

Symbol timing, frequency shift estimating, sector ID

identifying

Frame synchronizing, cell group ID identifying, CP-

type blind detecting

RS identifying, cell identifying, antenna

configuration identifying

complete

with

primary

synchroni

zation

signal

and time-

domain

complete

with

secondar

y

synchroni

zation

signal

and

frequency

-domain

Physical-layer process –Power Control

Open-loop power control: Decide a starting transmit power of UE transmit power as the basis for closed-loop control adjustment.

Closed-loop power control: eNodeB measures SINR of PUCCH/PUSCH/SRS signal, then compares SINR with SINRtarge to determine the TPC command (what’s informed is power step size.), finally informs UE through PDCCH to determine the transmit power of uplink signal on the corresponding sub-frame.

Outer-loop power control: Controlled by the upper layer Inner-loop power control

Physical-layer process –Random Access

Random access process can be used in the following situations: Access at RRC_IDLE status Access when the wireless link fault occurs Access in handover Access at RRC_Connected status

When there are downlink data (eg. The uplink is at non-synchronization status.)

When there are uplink data (eg. The uplink is at non-synchronization status or no PUCCH resource can be used for scheduling request.)

Physical-layer process –Random Access

Random access based on competitiveness Used in the five mentioned situations UE selects a preamble sequence randomly in the

available preamble set in a competitive way. Possible collision: two UEs use the same preamble

sequence. Perform the synchronization process through four steps.

The fourth step is used to solve the collision. Random access based on non-competitiveness

In handover or when the downlink data arrive The BS allocates a preamble sequence. Perform the synchronization through three steps without

solving the collision.

Random Access Process (Based on Competitiveness)

Step1： UE sends Msg1 through PRACH, (RACH

－》 PRACH) eNB measures the distance between UE and BS

according to the received preamble, and generates timing adjustment quantity.

Step2： eNB sends Msg2 and Msg2 through PDSCH (DL-

SCH －》 PDSCH) The location is indicated by PDCCH, no HARQ. Msg2 is the grant of Msg4. If UE fails to receive the

RA respondence in a time window, this RA process is terminated; otherwise it goes to step3.

Step3： UE sends Msg3 and through PUSCH (UL-SCH

－》 PUSCH), HARQ eNB detects Msg3 and generates ACK/NACK.

Step4： eNB sends Msg4 for collision detection, HARQ UE finds that the UE of its own NAS-layer ID is

sending ACK.

UE eNB

MSG1

MSG2

MSG3

MSG4

1

2

3

4

Contents


Structure of Layer 2

PDCP

RLC

MAC

RRC

PHY

Layer 2 is split into the following sub layers ： MAC, RLC and PDCP.

Layer 2

Layer 3

Layer 1

Introduction to MAC

Resides on layer 2 of LTE wireless protocols (L2 ； L2 also includes RLC and PDCP)

Used to allocate the wireless resources (time, frequency (number of RBs and location), number of emission layers, number of antenna, and transmit power) to users

Resides in both E-Node B and UE, but has different functions.

Random Access Control

PCCH BCCH CCCH DCCH DTCH MAC-control

Upper layers

PCH BCH DL-SCH UL-SCH RACH

Lower layer

(De-) Multiplexing

Logical Channel Prioritization (UL only)

HARQ

Control

MAC structure overview, UE sideMAC structure overview, UE side

RLCRLC

PHYPHY

The Overview of MAC Structure

Functions of MAC sub layer

MAC

MultiplexingMultiplexing

UE priority handlingUE priority handling

TX Format SelectionTX Format Selection

De-multiplexingDe-multiplexing

Logical channels priorityLogical channels priority

Error correction (HARQ)Error correction (HARQ)

Scheduling Info ReportingScheduling Info Reporting

Mapping of ChannelsMapping of Channels

MAC Function

At UE side Mapping between the logic channel and transmission channel MAC SDUs multiplexing/de-multiplexing MAC PDU HARQ Buffer status report (BSR)

At eNodeB side Mapping between the logic channel and transmission channel MAC SDUs multiplexing/de-multiplexing MAC PDU HARQ Scheduling among UE of different priorities (dynamic scheduling,

semi-persistent scheduling) Selecting transmission format (MCS) Priority processing among different logic channels in the same UE

Functions of MAC sub layer

Services related to MAC sub layer

Data transfer Signalling of HARQfeedbackSignalling of Scheduling RequestMeasurements

RLCMACData transferRadio resource allocationPHY

Services expected from physical layer

Services provided to upper layers

Key Technology at MAC Layer- Fast Scheduling

Basic concept: Fast scheduling means fast service.

LTE FDD: 1ms. LTE TDD downlink: 1ms - 4ms

(related with uplink/downlink configuration)

LTE TDD uplink: 1ms - 10ms (related with uplink/downlink configuration) UMB: 1ms.

WiMAX TDD: 5ms. WCDMA HSDPA: 2ms. CDMA 2000 1x EV-DO:

1.667ms.

Scheduling modes: TDM, FDM, SDM

Key Technology at MAC Layer- Fast Scheduling-Classification

According to resource-occupied time:

Persistent scheduling (static scheduling)

Semi-persistent scheduling (semi-static scheduling)

Dynamic schedulingEvery M x TTI occupies N x RB. It turns to dynamic

scheduling in retransmission. For VoIP, every 20 TTIs occupies 2

RBs.

Determined according to channel status, buffer status, and remained resources.

Constantly occupies resources


According to resource-occupied time: Persistent scheduling (static

scheduling) Semi-persistent scheduling (semi-

static scheduling) Dynamic scheduling

Constantly occupies resources

Every M x TTI occupies N x RB. It turns to dynamic

scheduling in retransmission. For VoIP, every 20 TTIs occupies 2

RBs.

Determined according to channel status, buffer status, and remained resources.


Dynamic scheduling is classified according to multiplexing modes:

Time-domain scheduling (TDM) Frequency-domain scheduling

(FDM) Space-domain scheduling

(SDM)

Occupies part or all of RBs.

Occupies part or all of TTIs.

Occupies a part or all of RBs/TTIs but only a part of antenna resources.

Dynamic scheduling is classified according to fairness and throughput rate:

Polling (RR) MAX-C/I (MAX-TB). General proportional fairness (G-PF) Torsten proportional fairness (T-PF)

Best fairness but low

throughput

Better fairness and

higher throughput

Worse fairness but highest throughput

Better fairness and better throughput than G-PF



Dynamic scheduling is classified according to fairness and throughput rate:

Polling (RR) MAX-C/I (MAX-TB). General proportional

fairness (G-PF) Torsten proportional fairness

(T-PF)

Best fairness but low

throughput

Worse fairness but

highest throughput

oughputHistoryThr1

)(12

1

i

iTBFF

ngMultiplexi SpaceFor , oughput_2HistoryThr

)2(

oughput_1HistoryThr

)1(

Diversity TX , oughput_1HistoryThr

)1(

TBTB

ForTB

FF

Select the UE with the best fair factor (FF):

Round robin (RR)

MAX-C/I (MAX-TB).

General proportional fairness (G-PF)

Torsten proportional fairness (T-PF)

ngMultiplexi SpaceFor , oughput_2HistoryThr

)2(

oughput_1HistoryThr

)1(

Diversity TX , oughput_1HistoryThr

)1(

TBTB

ForTB

FFoughputHistoryThr1

)(12

1

i

iTBFF

2

1

)(i

iTBFFgtSchedulinI_SinceLasNumberOfTTFF

Key Technology at MAC Layer- Fast Scheduling-Classification, Algorithm

Dynamic scheduling is classified

according to the frequency selection

(FS):

Broadband scheduling (non-FS)

Sub-band scheduling (FS)

Operation is complicated but it can fully use the channel status. The

system performance is good.

Operation is simple but it cannot fully use the channel status.

The system performance is poor.


Dynamic scheduling is classified according to QoS:

QoS scheduling

BE scheduling

Can guarantee the QoS.

Cannot guarantee the QoS.


Key Technology at MAC Layer: AMC

Time-domain AMC

Frequency-domain

AMC

Space-domain AMC

SINR

Time

UE 1

UE 2

UE 3

TTI 1 TTI 2 TTI 3 TTI k TTI m

SINR

Frequency

UE 1

UE 2

UE 3

SubBand 1 SubBand 2 SubBand 3 SubBand k SubBand m

Key Technology at MAC Layer: AMC Principle

QPSK, 16QAM and 64QAM

“Continuous” encoding rate (0.07 - 0.93）

eNode B

UE

2. To check buffer.

3. To schedule a UE4. To issue a HARQ Process

UE

5. To set modulation, RBs, Layer, RV, etc.

0 5 10 15 20 25 300

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5x 10

7

Th

rou

gh

pu

t [b

ps

]

SNR [dB]

SCM-C 2x2, 50 RBs

chan_est ideal; 0.5 QPSK chan_est ideal; 0.5 16QAM chan_est ideal; 0.5 64QAM chan_est mmse; 0.5 QPSK chan_est mmse; 0.5 16QAM chan_est mmse; 0.5 64QAM

Key Technology at MAC Layer: HARQ

HARQ = FEC + ARQ. In LTE, FEC is a Turbo code attached with QPP.

SAW N-Channel (FDD uplink: 8; FDD downlink: 1 – 8; TDD uplink: related with timeslot configuration and a fixed number; TDD downlink: related with timeslot configuration).

Merging way of HARQ: CC/FIR/PIR. Synchronous HARQ and asynchronous HARQ Self-adaptive HARQ and non-self-adaptive HARQ

Key Technology at MAC Layer: HARQ Downlink Asynchronous Self-Adaptation

In order to make full use of channels, eNodeB can send new data blocks before receiving UE’s ACK/NACK.

P1 P2P1 P2P1 P2

P1

UE1 UE2 UE3 UE4

Key Technology at MAC Layer: HARQ Uplink Synchronous Self-Adaptation

Synchronous self-adaptation: When eNodeB sends UE NACK and PDCCH Format 0, it indicates that UE should resend in on this newly allocated RB.

PUSCH PHICH： sends NACK

PDSCH

>= 3ms

PDCCH Format 0: sends new authorization

Key Technology at MAC Layer: HARQ Uplink Synchronous Non-Self-Adaptation

Synchronous non-self-adaptation: When eNodeB sends UE NACK and does not send PDCCH Format 0, it indicates that UE should resend on the previously allocated RB.

PUSCH PHICH: sends NACK

PDSCH

>= 3ms

CCCH DTCHDCCH

RACH UP-SCH PCH DL-SCHBCH

PCCH DTCHBCCH CCCH DCCH

Transport CH

Logical CH

DOWN LINK UP LINK

MCH

Mapping between Logical CHs & Transport CHs

Contents


Overview of RLC

Overview model of the RLC sub layer

Functions of RLC

TM data transfer

UM data transfer

AM data transfer

Deliver indication

Data transfer

Transmissionopportunity

Total size of the RLC PDU(s)

MAC RLC PDCP

Services related to RLC sub layer

Transparent Mode

An RLC entity in transparent mode can send/receive RLC PDU through the logic channels, such as BCCH, DL/UL CCCH and PCCH

Transmissionbuffer

Transmitting TM-RLC entity

TM-SAP

radio interface

Receiving TM-RLC

entity

TM-SAP

UE/E-Node B E-Node B/UE

BCCH/PCCH/CCCH BCCH/PCCH/CCCH

Non-Confirmation Mode

An RLC entity in non-confirmation mode can send/receive RLC PDU through the logic channels, such as DL/UL DCCH, DL/UL DTCH, MCCH/MTCH.

Compared with 3G, the UM mode does not support the encryption/decryption function which is processed in PDCP.

Transmissionbuffer

Segmentation &Concatenation

Add RLC header

Transmitting UM-RLC entity

UM-SAP

radio interface

Receiving UM-RLC

entity

UM-SAP

UE/E-Node B E-Node B/UE

DCCH/DTCH/MCCH/MTCH DCCH/DTCH/MCCH/MTCH

Receptionbuffer & HARQ

reordering

SDU reassembly

Remove RLC header

Confirmation Mode

An RLC entity in confirmation mode can send/receive RLC PDU through the logic channels, such as DL/UL DCCH, DL/UL DTCH

Transmissionbuffer

Segmentation &Concatenation

Add RLC header

Retransmission buffer

RLC control

Routing

Receptionbuffer & HARQ

reordering

SDU reassembly

DCCH/DTCH DCCH/DTCH

AM-SAP

Remove RLC header

Contents


Overview of PDCP

The E-UTRAN protocol structure involves two layers: radio network layer (RNL) and transmission network layer (TNL).

PDCP separates the transmission technology on TNL from the air-interface processing technology on E-UTRAN.

PDCP maps the upper-layer protocol characteristics to the lower-layer air interface protocol characteristics and thus enables the LTE protocol to bear IP packets between UE and E-Node B through transparent transmission provides for the upper layer.

PDCP Structure

ROHC ROHC Integrity protection

Encryption Encryption

User Plane Control Plane

EPC Data from S-GW NAS Signal from MMERRC Signal from eNodeB

Structure of PDCP Entity

PDCP Functions

PDCP serves SRB and DRB mapped on the logic channels DTCH and DCCH. The functions provides on DTCH and DCCH are as follows:

DTCH channel PDCP packet transmission SN sequence number maintenance Header compression and decompression of IP data flow Encryption and decryption Resorting of lower-layer PDU data in switch-over

DCCH channel PDCP packet transmission SN sequence number maintenance Integrity protection Encryption and decryption

Transfer of user plane data

Transfer of control plane data

Header compression

Ciphering &integrity protection

Acknowledged data transfer

Unacknowledged data transfer

in-sequence delivery

Duplicate discarding

RLC PDCP RRC

Services related to PDCP sub layer

02 LF_SP3001_E02_1 LTE Protocol Principle 74

Documents