1 GPRS Principles

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Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved.

GPRS Principles

Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved. Page1

ForewordGPRS principle is the basic part of the whole GPRS system

and the succeeding products learning.

This slide will help us to understand the GPRS system

networking and wireless subsystem etc.


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Circuit Switch (CS)

CS

F

CS

CS CS

CS

A

B

C

D

E

G

H

I

J

K

L


Packet Switch (PS)

PS

PS

PS PS

PS

PS

PS

PS

PS

PS PS

PS

PS

AC

B D


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GSM Development Evolution

GSM 9.6 Kb/s

GPRS21.4 Kb/s

EGPRS59.2 Kb/s

384 Kb/sUMTS

2 G

2.5 G

2.75 G

3 G

HSCSD14.4 Kb/s

ECSD38.8 Kb/s

CS

PS

EDGE


What is GPRS and EDGE?Abbreviation of General P acket Radio S ervice.

GPRS is an end-to-end packet switching technology

provided on the basis of GSM technology.

It has much interactive services with the existing GSM

circuit switching system.

GPRS supports wireless access rate of up to 171.2Kbps.

EDGE ( Enhanced Data R ates for GSM Evolution)EGPRS ( Enhanced GPRS )

EGPRS supports wireless access rate of up to 473.6Kbps.

ECSD ( Enhanced CSD , Enhanced HSCSD-High Speed Circuit

Switched Data)


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GPRS&EDGE Coding Rate

8PSKGMSK

9.05

13.415.6

21.4

8.811.2

14.817.6

22.4

29.6

44.8

54.4

59.2

0.00

10.00

20.00

30.00

40.00

50.00

60.00

CS-1 CS-3 CS-4 M CS-1 M CS-2 M CS-3 M CS-4 M CS-5 M CS-6 MC S-7 M CS-8 M CS-9

Kbps

GPRS

EGPRS

CS-2


Adjustments to GSM Network

BSS CS CoreNetwork

A

PS CoreNetwork

PCU

BSS NSS

Gb

Pb

Gs


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Most Popular GPRS Applications

E-mail

Web Browsing

Information Services

Moving Images

Still Images

Remote LAN Access

File Transfer

Job Despatch

Traffic Information

Sport Report

Weather Forecast

Stock Market

PublicInformation

Service

Email

Web Browsing

Still Images

File Transfer

Moving Bank

Live News

PersonalInformation

Service


Advantages and Disadvantages ofGPRS

Advantages

Share resource with GSM

High resource utilization

Fast transmission rate

Always on line

Short access time

Disadvantages

Slower data rates in practice than anticipated in theory

Suboptimal modulation technique


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Contents

1. GPRS System Overview

2. GPRS Architecture

3. GPRS Network Interfaces & Protocols

4. GPRS Wireless Subsystem

5. GPRS Location Area


CS & PS Logic Structure

HLRAUC

GPRSRegister

MSC/VLR

BSCAbis

D

C

CS

GMSCPSTN

BTS

BSS

CN

E

A

PS Gs

SGSN

GGSN

Gb

Gn

Gc

Gr

Gi

Internet

G-Abis Pb

PCU

TRAU


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Gf

GiGn

Gc

Gp

Gs

MSC/VLR

Gr

SGSN

Gd

SMS-GMSCSMS-IWMSC

GGSN

EIR

SGSN

Gn

GPRSBackbone

ATM/DDN/ISDN/Ethernet, etc

CNCN--PSPS

GGSN

GiCG

GPRS System Structure

Gb

SS7

HLR

Ga

Intranet/InternetFirewall

RADIUS

WAP Gateway

Other PLMN

BTS

BSCBSSBSS

AbisPCU

Gb

BTS

BSCBSSBSS

AbisPCU

X.25

DNS BG

MS

MS


GPRS MSClass A

The MS is attached to both GPRS and other GSM services and theMS supports simultaneous operation of GPRS and other GSMservices.

Class B

The MS is attached on GPRS network and GSM networksimultaneously but not enabling circuit switching and packet switchingservices at the same time.

services are selected automatically.

Class C

The MS is attached to either GPRS or other GSM services. Alternateuse only.

services are selected manually or default selected service.


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Functions of PCU (Packet Control Unit)

Packet wireless resource management function (RLC/MAC

protocol function)

Wireless resource management functions of GPRS BSS

Circuit paging coordination

G-Abis interface processing function

Function related with GPRS BTS


Functions of PCU (Packet Control Unit)Pb interface processing function

LAPD link between BSC and PCU

Layer-3 signaling between BSC and PCU

Gb interface processing function

Data packet relay on wireless interface and Gb interface

Mobility management (cell updating procedure)

Downlink traffic control (wireless QoS guarantee)


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PCU6000

External PCU & Built-in PCU

BSC6000


Functions of Built-in PCUProvides physical and logical data interface out of the BSS

for packet data traffic

Packet data transfer scheduling

Packet channel management function

Packet system messages


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Features of Built-In PCU

Resource sharing in a reliable and stable way

The packet service processing board works in the resource

pool mode

Supports the SGSN resource pool, ensuring the stability of

services


Introduction of the Boards

FG2a

IP route transmitting

protocol function

8FE ports or 2GE ports

Support IP over FE/GE

PEUa

Supply HDLC over

E1/T1

Support 32 E1/T1

GFGUG

GEPUG

DPUd

Support 48 packet

channel every DSP

GDPUP

TrafficProcessingBoard

Gb Interface

Board


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GDPUPGDPUP (GSM Data Processing Unit for PS

service):

According to the actual situations, the GDPUP can

be configured at slots 03, 813 or 1427 in the BM

subrack

The GDPUP delivers the PS processing function and

works in resource pool mode

PS data transmission and link management

BSSGP data transmission

Call state managementPacket resource allocation


GEPUGThe GEPUG is the Gb interface board of the

GDPUP. The GEPUG provides 32 E1 lines with

the SGSN by frame relay and supports

transmission capacity of up to 64 Mbps


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GFGUG

The GFGUG is the IP Gb interface board of the

GDPUP. The GFGUG provides 8 FE

connections (100 Mbit/s) and 2 GE connections

(1000 Mbit/s) with the SGSN, and supports

transmission capacity of up to 128 Mbps


New Functions of the GXPUMGXPUM can be configured at slots 01 in the

GMPS/GEPS subrack and there are 4 built-in CPUs on

the GXPUM board for core services

System PS domain resource management and channel

allocation message management

Gb interface state management, routing information

delivery and BVC management

Data transmission and link management on the NS-layer

signaling plane at the Gb interface

G X P U

P A R C

R U N

A L M

A C T

1 0 / 1 0 0 / 1 0 0 0 B A S E

- T

A C TL I N K

0

1

2

3


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Built-In PCU Specifications

Items for PCU configured quantities

GDPUP boards for full configuration 8+1=9pcs

GEPUG/GFGUG boards for full configuration 8 pairs

Maximum number of activated PDCHs supported by each

GDPUP

1024pcs

Maximum number of activated PDCHs supported by each

GDPUP

1024pcs

Maximum throughput at the Gb interface 512M


Configuration ExamplesBase on the 2048 TRX of Huawei BSC6000 maximal

configuration

If GPRS channel in the all of channel is 10%, the PS

channel number is 1639

GDPUP = 1639/1024=1.6 2 and 2+1=3 for N+1

In case of 1000 PDCHs are CS-2, the Gb interface speed of

every PS channel is 13.4kbit/s; 639 PDCHs are MSC-9, theGb interface speed of every PS channel is 59.2kbit/s


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Configuration Examples

Throughput of Gb = 1639

13.4kbit/s 1000/1639+59.2kbit/s 639/1639)=

51.23Mbit/s

E1 number = 51.23Mbit/s / 2.048Mbit/s 26

GEPUG or GFGUG on Gb interface

GEPUG board number = 51.23Mbit/s / 64Mbit/s 1

1+1=2 for N+1


Typical ConfigurationThe BSC configuration shown in the figure supports 512

full-rate/half-rate TRXsBM Subrack a


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Functions of SGSN (Serving GPRSSupport Node)

Packet routing

MS Session management

Authentication and Ciphering

Mobility management

Billing information collection


Functions of GGSN (GatewayGPRS Support Node)

Interface between GPRS backbone and external PDNs.

PDP Conversion and context management

IP address assignment management

Packet routing to/from SGSNs

Billing information collection


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Functions of HLR/AUC

Saving and updating GPRS subscriber subscription data

User authentication

Providing location/routing information and processing

needed in mobility management and routing, for example:

Saving and updating user service SGSN number and address

GPRS user location deletion indication

Whether MS is reachable.

Subscriber tracing (optional)


Contents1. GPRS System Overview






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Contents


3.1 Interface and Protocol Stack

3.2 Um Interface


Network interface types

SGSN

SGSNGGSN

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MS-SGSN signaling plane

GMM: GPRS Mobility Management

SM: Session Management

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Contents3. GPRS Network Interfaces & Protocols

3.1 Interface and Protocol Stack

3.2 Um Interface


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Protocol Layer of Um InterfaceGMM (GPRS Mobility Management): operates in the signallingplane of GPRS supports mobility management functionality.

SM (Session Management): processes procedure that GPRSMS connects to the external data network.

SNDCP (Subnetwork Dependent Convergence Protocol):Multiplexing of several PDPs, compression / decompressionand Segmentation of user data.

LLC (Logical Link Control ): This layer provides a highlyreliable ciphered logical link between an MS and its SGSN.

RLC:Segmentation and re-assembly between LLC PDUs and

RLC blocks.MAC: defines the procedures that enable multiple mobilestations to share a common transmission medium.

LLC

RLC

MAC

RF

Physical Link

S N D C P

S M S

G M M / S M


RLC/MAC Block Generation

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Contents

1. GPRS System Overview






Contents4. GPRS Wireless Subsystem

4.1 Packet Channels

4.2 Medium Access Modes

4.3 MS Multi-TS Ability

4.4 Power Control

4.5 Network Control Modes


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Physical ChannelThe same as in GSM

The same frequency

The modulation mode

The same TDMA frame definition

The same burst pulse definition

The differences between GPRS and GSM

The Multi-frame structure

The channel coding

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Packet Logic Channels

The specific type of PDCH (except PRACH) is determined by

RLC/MAC head and RLC/MAC control message type.

TCH

BCCH

PCH, RACH, AGCH,NCH

Packet service channel

PACCH

Packet Logic Channel

Packet control channel

PBCCH

PPCH PRACH PAGCH

PCCCH PDCCH

PDTCH/U PDTCH/DPNCH

PTCCH/U PTCCH/DSACCH


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PDCCH (Packet Dedicated ControlChannels)

PACCH

Bi-directional, used to transmit the packet

signaling in data transmission.

PTCCH/U

Used to transmit random access bursts to

allow estimation of the timing advance for

one MS in packet transfer mode.

PTCCH/D

Used to transmit timing advance updates for

several MS. One PTCCH/D is paired withseveral PTCCH/U's.

PACCH

PDCCH

PTCCH/U PTCCH/D


Combinations of Packet LogicChannel

Mode 3: PDTCH+PACCH+PTCCH

Mode 1: PBCCH+PCCCH+PDTCH+PACCH+PTCCHMode 2: PCCCH+PDTCH+PACCH+PTCCH

In case of small GPRS traffic , GPRSand circui t services share the sameBCCH and CCCH in the cell. In thiscase, only combination mode 3 isneeded in the cell.

With the increase of traffic, thepacket public channel should beconfigured in the cell. Channelcombination mode 1 and mode 2should be adopted.

Mode 4: PBCCH+PCCCH

(PCCCH=PPCH+PRACH+PAGCH+PNCH


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Packet Wireless ChannelConfigurations

Reason of adopting static PDCH

To enable that GPRS MS is constantly online in the cell.

To ensure certain QoS of GPRS services.

Reason of adopting dynamic PDCH

GPRS and GSM share wireless resources.

Wireless resources should be adopted in priority; on the other hand,QoS of voice services should be ensured.

In a cell, the percentage of packet switching services and thepercentage of circuit switching services are constantly changing.

Dynamic PDCH is not visible for voice services.


Packet Wireless ChannelConfigurations

General principlesThe cell should be configured with static PDCH to enable MS to

be normally attached on GPRS network as well as certain QoS of

GPRS services.

Dynamic PDCH should be configured according to the GPRS

traffic forecast, which should be adjusted as TCH or PDCH usable

in the operation process according to the cell traffic status.

Circuit switching services can seize the channel used by GPRS

services.


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Basic Conceptions about Radio Block

USF(Uplink State Flag) is sent in all downlink

RLC/MAC blocks and indicates the owner or use

of the next uplink Radio block on the same

timeslot.

The USF field is three bits in length

USF=1

USF=2

USF=3

USF=4

MS1

MS2

MS3

MS4


Basic Conceptions about Radio BlockTBF (Temporary Block Flow)

A Temporary Block Flow (TBF) is a physical connection used by the

two RR entities the RR entity of the MS and that of the BSS to

support the unidirectional transfer of LLC PDUs on packet data

physical channels.

A TBF is temporary and is maintained only for the duration of the data

transfer.

TFI (Temporary Flow Identity)Each TBF is assigned a Temporary Flow Identity (TFI) by the network.

The TFI field is five bits in length.


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Contents


4.1 Packet Channels

4.2 Medium Access Modes

4.3 MS Multi-TS Ability

4.4 Power Control

4.5 Network Control Modes


Medium Access ModesUplink resource allocation mode

Dynamic allocation (supported by all MSs and all networks)

The mobile station detecting an assigned USF value for each assigned PDCH andblock or group of four blocks that it is allowed to transmit on that PDCH.

Fixed allocation (supported by all MSs and all networks)

Fixed bit mapping is adopted to determine the allocated blocks in the allocation periodwithout an assigned USF.

Extended dynamic allocation (optional for the network)

The mobile station detecting an assigned USF value for any assigned PDCH allowing

the mobile station to transmit on that PDCH and all higher numbered assignedPDCHs in the same block or group of four blocks.

Downlink resource allocation mode

Dynamic allocation and fixed allocation.


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Network Control Modes

MS NC0 NC1

NC2

The MS shall perform autonomous cell re-selection

MS

TheMS shall perform autonomous cellre-selection

The MS shall send

measurement reports

to the network

MS BTS

MR

Cell re-selection

command

The MS shall not

perform autonomous cell

re-selection


Contents1. GPRS System Overview






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Relationship among LocationAreas

CELL

CELL

CELL

CELL

RA1

RA2

CELL

CELL

RA3

CELL

CELL

CELL

SGSN1SGSN2

BSC1

BSC2

BSC3

LA1 LA2


SummaryGPRS System Overview

GPRS Architecture

GPRS Network Interfaces & Protocols

GPRS Wireless Subsystem

GPRS Location Area


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