GBO_003_E1_1 GPRS and EDGE Introduction-44

7/27/2019 GBO_003_E1_1 GPRS and EDGE Introduction-44

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GPRS and EDGE Introduction

ZTE University


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Objective

At the end of this course, you will be able tounderstand:

Learn the background, standards and evolution of

GPRS and EDGE

Master structure and protocol of GPRS/EDGE network

Master radio block structure and channel code of GPRS

and EDGE

Learn the difference of GPRS and EDGE

Learn cell reselection procedure and RLC/MAC

procedure


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Content

Review of GPRS and EDGE Technologies

Channel Combination and Frame Structure

Comparison of GPRS and EDGE

Data Transferring Process Process of Evolution from GPRS and EDGE to 3G


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What is GPRS?

GPRS General Packet Radio Service Packet switch is most efficient way of using frequency

in data application.

GPRS = mobile + IP, which is the integration of GSM

radio access technique and internet packet switchtechnique.


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What is EDGE?

EDGE Enhanced Data Rate for GSM Evolution Improve the data transmission rate through radio

connections in GSM.

Including EGPRS and ECSD, it can be used to transmit

PS and CS data. It can fully make use of existing GSM resources.


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Technical Features of GPRS

Seamless Connection to IP Network High Transmission

Always Online and Traffic Accounting

Provides existing mature GSM technologies anddata service deployment schemes.


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Technical Features of EDGE

A kind of modulation coding technology, which haschanged the rate of air interface.

The characteristics of air interface in EDGE are

same as those in GSM.

EDGE just upgrades BTS and PCU.

The core network of EDGE adopts a three-layer

model.

EDGE supports both packet switching and circuitswitching modes for data transmission.


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R

R

BSS

MSC

PSTN

SS7 Network

EIR

HLR/AUC

SMS-GMSC

Firewall

Firewall

Firewall

Router

Router

Server

Server

SGSN

Inter-PLMNnetwork

PTM-SC

GGSN

Border

GatewayGPRS

Backbone

IP based

GPRS

Infrastructure

Data Network

(Internet)

Data Network

X.25

UmR/S

PCU

Network Structure of GPRS and EDGE


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Transmission Protocol Platform of GPRS and EDGE


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Signaling Protocol Platform of GPRS and EDGE(1)


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Signaling Protocol Platform of GPRS and EDGE(2)


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Content

Review of GPRS and EDGE Technologies

Channel Combination and Frame Structure




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Frame Structure and Channel Combination

52 Multiframe Structure

Logical Channel Classification


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T = PTCCH,

I= Idle frame

B0 - B11 = Radio blocks

52 TDMA Frames

B0 B1 B2 T B3 B4 B5 I B6 B7 B8 T B9 B10 B11 I

0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 70 1 2 3 4 5 6 7

TDMA frame

RLC Block

Except PRACH and PTCCH/U, the unit of logical channels is Block with the

occupancy sequence is B0, B6, B3, B9, B1, B7, B4, B10, B2, B8, B5, B11.



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PDCH frame organization One 52 multi-frame includes 12 radio blocks

In circuit domain, one TDMA frame is divided into 8 TSL

TSL assigned to GPRS is PDCH

Multiple TSL can constitute one PDCH group, each including 8 TSL

at most.

Basic unit of radio resource allocation and radio transferring is

BLOCK.

One BLOCK includes 4 TDMA frame which is the smallest unit of

user occupancy.

Surplus 4 burst is used for measuring and reporting TA

Multiple users scramble for these blocks, in this way the goal of

packet share is achieved.


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Logical CH

Traffic CH

Control CH

PBCCH

PCCCH

PRACH

PAGCH

PPCH

PDCCH

PACCH

PTCCH/D

PS

CSPDTCH/CS1

PDTCH/CS2

PDTCH/CS3

PDTCH/CS4

PNCH

PTCCH/U


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Packet Data Channel (PDCH) include packet service channel and packet control

channel

Packet Data Traffic Channel (PDTCH)

Unidirectional traffic channelPDTCH/UPDTCH/D

Packet Control Channel

Broadcasting control channelPBCCH

Common control channelPPCHPRACHPAGCHPNCHsend notification message

Dedicated control channelPACCHPTCCH/Uto

estimate TAPTCCH/Dsend TA upgrading

message


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Packet Logical Channel to Physical Channel

Mapping

Combination of logical channels Mode 1PBCCHPCCCHPDTCHPACCH

PTCCH

Mode 2PCCCHPDTCHPACCHPTCCH

Mode 3PDTCHPACCHPTCCH

PCCCH = PPCH + PRACH + PAGCH + PNCH Service Volume

When GPRS traffic is not intense, GPRS and circuittraffic generally share BCCH and CCCH in cells. In thiscase, mode 3 is needed.

With the accumulation of traffic Packet common channel is needed to be configured in

the cell. Channel combination is either mode 1 or mode2.


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RLC / MAC header RLC Data BCSRLC / MAC layerRadio block

CS-1 9.05 kbit/s

CS-2 13,4 kbit/s

CS-3 15,6 kbit/s

CS-4 21,4 kbit/s

Coding scheme Bit rate

1/2

~ 2/3

~ 3/4

1

Code rate

184

274

318

440

Radio block excl. BCS

40

16

16

16

BCS

4

4

4

-

Tail

456

588

676

456

Coded bits

0

132

220

0

Punctured bits

Convolutional coding

Puncturing

456 bits

4 bursts

Physical layer

GPRS Channel Coding


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GPRS Channel Coding

GPRS defines four channel coding mode from CS-1 to CS-4

Data rate is 9.05 Kbps, 13.4 Kbps, 15.6 Kbps21.4 Kbps

accordingly.

Channel coding of CS-1 is the same with that of SDCCH. C/I of

CS-1 and CS-2 is the same with that of voice service with thecoverage of 90100C/I of CS-3 is higherC/I of CS-4 is

much higher and favorable radio environment are required.

Network will adjust channel coding mode based on real-

time monitoring of radio transmission

Different TSL can select different channel coding mode

When the quality radio transmission is good, its necessary to use

more efficient coding mode.


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EDGE Channel Coding

EDGE Coding Schemes MCS-1 to MCS-9


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EDGE Channel Coding

Coding Family Family A: The payload of family A code has 37 bytes. It

corresponds to MCS-3, MCS-6 or MCS-9 coding

scheme.

Family A padding: The payload of family A paddingcode has 34 bytes. It corresponds to MCS-3, MCS-6,or

MCS-8 coding schemes.

Family B: The payload of family B code has 28 bytes. It

corresponds to MCS-2, MCS-5 or MCS-7 codingscheme.

Family C: The payload of family C code has 22 bytes. It

corresponds to MCS-1 or MCS-4 coding scheme.


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Content

Review of GPRS and EDGE Technologies Channel Combination and Frame Structure




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Overview Comparison of GPRS and EDGE

EDGE is built on the basis of GPRS. EDGE has great influence on GPRS RF, physical

layer at radio interface, and RLC/MAC protocol.

Relative to GPRS, EDGE changed Link Quality

Control (LQC).


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Comparison of Physical Layer: GMSK and 8-PSK

GPRS uses Gaussian Minimum Shift Keying(GMSK) as the modulation mode.

In addition to GMSK (MCS1~MCS-4), EGPRS

also uses 8-PSK modulation mode

(MCS5~MCS9).


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Comparison of RLC/MAC Layer

Comparison of Coding Scheme GPRS uses CS1~CS4 modulation and coding schemes.

EGPRS uses MCS1~MCS9 modulation and coding

schemes.

RLC/MAC Radio Block Structure In GPRS, a RLC radio block only corresponds to a RLC

data block.

In EGDE, a RLC radio block can correspond to two RLC

data blocks using MCS7~MCS9 coding scheme,


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Link Quality Control

In GPRS, it only supports adaptive link mode. In EDGE, it not only supports adaptive link mode

(mixed ARQ type 1), but also supports incremental

redundancy (mixed ARQ type 2).


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Channel Quality Report

In GPRS, two measurements can be done up towithin 240 ms.

In EDGE, measurement can be done on the basis

of each pulse.


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Content





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UL TBF Access

TBF establishment process on the following channels CCCH

PCCCH

PACCH

Access Mode

ONE PHASE

means network assigns adequate resource one time upon network

receiving channel request.

TWO PHASE

means network assigns single RLC & MAC block the first time andassign corresponding RR upon MSs specific request.


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MS Network

Packet Channel Request

Packet Immediate Assignment

Uplink Data (TLLI)

Uplink Data (TLLI)

PRACH or RACH

PAGCH or AGCH

PDTCH

PDTCH

Uplink Data (TLLI)PDTCH

Packet Uplink Ack/NackPACCH

PDTCHUplink Data

. . . . . .

CCCH One-phase Access


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MS NetworkPacket Channel Request

Packet Immediate AssignmentPacket Resource Request

Packet Resource Assignment

PRACH or RACH

PAGCH or AGCHPACCHPACCH

Uplink Data PDTCHUplink Data

PDTCH

CCCH Two-phase Access


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Packet Uplink Ack/Nack

Data Block (last)

Access and Assignment

MS BSS

PACCH

PDTCH

Packet Uplink AssignmentPACCH

PACCH

Data BlockPDTCH

Data BlockPDTCH

Data Block (last in send window)PDTCH

Data BlockPDTCH

Data BlockPDTCH

Data Block

final Packet Ack/NackPACCH

LLC PDU

SGSN

GPRS UL Data Transfer


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MS Network

Packet Channel Request

Packet Immediate Assignment

Packet Paging Response (LLC frame)

PRACH or RACH

PAGCH or AGCH

PACCH

PPCH or PCHPacket Paging Request

GPRS Paging


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Packet Downlink Ack/Nack

MS Network

PACCH

Packet Downlink AssignmentPACCH

PDTCH

PACCHfinal Packet Ack/Nack

Data BlockPDTCH

Data BlockPDTCH

Data Block (polling)PDTCH

PDTCHData Block

PDTCHData Block

Data Block

Data Block (last, polling)PACCH

Immediate AssignmentAGCH

Packet Downlink Assignment

LLC PDU

SGSN

PACCH

GPRS DL Data Transfer


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Obtain TA in GPRS Data Transferring

TA Initialization Initial TA value isnt contained in Immediate Assignment

message, indicating UL data transmission will not be

conducted before TA value is gotten from TA update

System sends Packet Polling Message requesting MSto send access burst for computing of initial TA value

Use default TA value as initial TA for cell radius is not

great.

Continuous TA update Update once every 8x52multi-frame (1920ms,

approximately 2 second)


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Continously TA Update Process

For UL & DL data transferring, TAI will be gotten

upon getting PDCH. TAI is from 0 to 15 and

indicates 16 idle frame location of constant 8*52

multi-frame.

On UL channel, MS sends access burst on Idle

frame assigned by specified TAI. On DL,

corresponding idle frame sends TA Message.

TAI

TA message 4

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

TA message 3TA message 2TA message 1

26 TDMA frames

416 TDMA frames

Downlink:

Uplink:

Idle frame


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Power Control in GPRS Transferring Process

MS UL transmission power formulapower unit is dBMP = min(0 - CH - * (C + 48), PMAX)

CH is power control parameter constant through control

message from network to MS related to MS and channels,

0 is a constant and the value is 39dBm in the case GSM900 and

36dBm in the case of DCS1800

is notified to MS by control message of BCCH or RLC , and is

a weighting factor of receiving factor when MS computing TxPwr

with the value of 0~1.

Cstandardized value of MS receiving signaling level.

PMAX is maximum transmission power allowed in cell and the

value is GPRS_MS_TXPWR_MAX_CCH when PBCCH exists

otherwise it is MS_TXPWR_MAX_CCH


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BSCBTS

Server

BTSBSC

GGSN

SGSN

HPLMN VPLMNGGSN

BG

BG

SGSN

Intra-PLMNBackboneNetwork

DataNetwork

Intra-PLMNBackboneNetwork

Inter-PLMNBackboneNetwork

Graph of GPRS Data Transmission


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Content



Data Transferring Process Process of Evolution from GPRS and EDGE to

3G


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Channel Coding of GPRS& EDGE


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GPRS Evolution

According to tradition, GSM-GPRS-EDGE-WCDMA is the right path from GSM to 3G. But in

GSA case, EDGE parallels WCDMA. i.e the roll of

EDGE changes in evolution from one stop to the

destination. According to the definition of 3G setby ITU, 384kbps is the criterion of 3G.

Theoretically EDGE rate reaches 473.6kbps, So

for small or middle sized operators without 3G

license, EDGE is their destination.


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GPRS Evolution


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Documents

GBO_003_E1_1 GPRS and EDGE Introduction-44