Omq000001 Gprs Principle Issue2.0

HUAWEI TECHNOLOGIES CO., LTD. All rights reserved

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OMQ000001 GPRS Principle

ISSUE 2.0

HUAWEI TECHNOLOGIES CO., LTD. Page 2All rights reserved

GPRS 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.


References

� GPRS principle

� GPRS protocol

� 31025698 - M900/M1800 PCU

Technical Manual


� Upon completion of this course, you will

be able to:

�Know the GPRS system structure

�Describe the GPRS important

interfaces

�Understand the GPRS channel

structures

�Master the GPRS relevant numbering


Chapter 1 Chapter 1 GPRS System OverviewGPRS System Overview

Chapter 2 GPRS Achitecture Chapter 2 GPRS Achitecture

Chapter 3Chapter 3 GPRS Network Interfaces & ProtocolsGPRS Network Interfaces & Protocols

Chapter 4 Chapter 4 GPRS Wireless SubsystemGPRS Wireless Subsystem

Chapter 5 Chapter 5 GPRS Location AreaGPRS Location Area


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

12 3

12

3

1

3

2

2

1 3

2

2

1 3

1 2 3

12

3

PS

PS

PS

PS

PS

PS

PS

12 3

12

3

1

3

2

2

1 3

2

2

1 3

1 2 3

12

3

PS

PS

PS

AC

B D


GSM Development Evolution

GSM 9.6 Kb/s

GPRS21.4 Kb/s

EGPRS59.2 Kb/s

384 Kb/s UMTS

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 Packet Radio Service.

� 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 Rates 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)


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 MCS-1 MCS-2 MCS-3 MCS-4 MCS-5 MCS-6 MCS-7 MCS-8 MCS-9

Kbps

GPRS

EGPRS

CS-2


Adjustments to GSM Network

BSS CS Core Network

A

PS Core Network

PCU

BSS NSS

Gb

Pb

Gs


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 of GPRS

� 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








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


Modifications in BSS (GSM Evolves into GPRS)

Upgrade BSC software

Add new PCUUpgrade BTS software


Modifications in BSS (GPRS Evolves into EDGE)

Upgrade BSC software

Upgrade PCU software

Upgrade BTS software and hardware

TE

R


Modifications in Core Network（GSM Evolves into GPRS/EDGE）

� New GPRS CN equipments

�SGSN

�GGSN

�CG

� Upgraded GPRS CN equipments

�HLR

�MSC/VLR

�SMS-GMSC/SMS-IWMSC


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 MS� TE（Terminal Equipment）

� MT（Mobile Terminal）

� TA （Terminal Adapter）

TETEMTMT

UUmmR R GGii

GPRS Network1

GPRSNetwork2

PDN/Other Network

GGpp

TA

MSMS

S S

Reference Point Reference Point


GPRS MS

�Class A

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

�Class B

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

�services are selected automatically.

�Class C

�The MS is attached to either GPRS or other GSM services. Alternate use only.

�services are selected manually or default selected service.


Functions of PCU (Packet Control Unit)

� Provides physical and logical data interface out of the BSS for packet data traffic

� LLC layer PDU segmentation/reassembly of RLC blocks

� Packet data transfer scheduling

� Radio channel management function


Position of Huawei PCU

CCU

CCU

BSCBTS

SGSN

Um Gb

BSC

Pb

CCU

CCU

PCU

BTS

Abis


Functions of SGSN (Serving GPRS Support Node)

� Packet routing

� MS Session management

� Authentication and Ciphering

� Mobility management

� Billing information collection


Functions of GGSN (Gateway GPRS 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


Functions of CG (Charging Gateway)

� Real-time collection of GPRS bills

� Temporary storage and buffering of GPRS bills

� Pre-processing of GPRS bills

� Sending GPRS bills to the billing center


Functions of MSC/VLR

When Gs interface is installed, MSC/VLR can support

� Establishment and maintenance of the association between SGSN

and MSC/VLR.

� GPRS combined mobility management procedure.

� Combined IMSI/GPRS attachment/detachment.

� Combined location area/routing area updating.

� Circuit paging coordination function.

The wireless resource usage can be greatly improved.


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)


Functions of SMS-GMSC/SMS-IWMSC

� The SMS-GMSC and SMS-IWMSC are connected to the SGSN

via the Gd interface to enable GPRS MSs to send and receive

SMs over GPRS radio channels.

� After Gd interface is installed, short messages can be sent via

GPRS, which reduces the occupation on SDCCH and cuts down

the influence on voice services by SMS services.

� The operator can select to send SMS via MSC or SGSN.

MS SGSN SMS-IWMSCSMS-GMSC

GdSMS


Functions of BG (Border Gateway)� BG enables the following protocols necessary for in terworking between

operators

� Security protocol: IPSec and firewall are recommended

� Routing protocol: BGP is recommended

� Billing protocol: determined by the operators with negotiation; BG

might be needed in collecting billing information

� It is normally based on routers

� It can be combined with GGSN in physical.

� BG does not exclusively belong to the GPRS network.

Gp

PLMN AGSN RR

BG RR

BG GSN PLMN B


Functions of DNS (Domain Name System)� The following two types of DNSs may be adopted in the GPRS network:

�The DNS between the GGSN and external networks

�The DNS on the GPRS backbone network. Provides two types of

functions:

− a. Resolve the GGSN IP address based on the Access Point

Name (APN) in the process of the PDP context activation;

− b. Resolve original SGSN IP address based on the original routing area No. in the process of the update of inter-SGSN

routing area.

� DNS does not exclusively

belong to the GPRS network. GPRS BackboneSGSN

DNS Server

SGSN


Functions of RADIUS Server (Remote Authentication Dial In User Service Server)

� It is a protocol used by Remote Access Server's for user Authentication.

� The RADIUS server stores the authentication and authorization

information of subscribers.

� It also performs subscriber identity authentication in the case of non-

transparent access.

� RADIUS Server does not exclusively belong to the GPRS network.




Chapter 3 Chapter 3 GPRS Network Interfaces & ProtocolsGPRS Network Interfaces & Protocols





3.1 Interface and Protocol Stack

3.2 Um Interface

3.3 G-abis/Pb Interface

3.4 Gb Interface

3.5 Gs Interface


Network Interface Types

GPRS backbone network

SGSNSGSN

SGSNSGSNGGSNGGSNGn

IP interface

SS7 interface

BSS MSCSMS-GMSC

AUm

PDP network(IP/X.25)

Gi

TE

MT

MS

HLR

Gs

Gr

Gd

Gc

Gb


Interface in GPRS Network

The interface between MS and GPRS network sideUm

The interface between the SGSN and EIR (optional). Gf

The interface between the SGSN and MSC/VLR (optional). Gs

The interface between the SGSN and HLR. Gr

The interface between GSNs of different PLMNs. Gp

The interface between SGSNs and between SGSN and GGSN in the PLMN. Gn

The reference point between the GPRS and external packet dataGi

The interface between SMS and GMSCThe interface between SMS-IWMSC and SGSN

Gd

The interface between the GGSN and HLR (optional). Gc

The interface between the SGSN and BSS. Gb

The reference point between the Mobile Terminal (MT) (for example, mobile phone) and the Terminal Equipment (TE) (for example, the portable computer).

R

DescriptionInterfac

e


Data Transmission Plane

� MAC: Media Access Control

� RLC: Radio Link Control

� LLC: Logical Link Control

� BSSGP: BSS GPRS Protocol

� SNDCP: Sub-Network Dependency Convergence Protocol

� GTP: GPRS Tunneling Protocol

Application

IP/X.25 IP/X.25 IP/X.25

SNDCP GTP

LLC LLC UDP/TCP UDP/TCP

RLC BSSGP BSSGP IP IP

MAC MAC NetworkService

NetworkService L2 L2

L2 (MAC)

PhysicalLayer

PhysicalLayer

PhysicalLayer

PhysicalLayer

PhysicalLayer

PhysicalLayer

PhysicalLayer

MS BSS SGSN GGSN

relay

relaySNDCP GTP

Um Gb Gn Gi

RLC


MS-SGSN Signaling Plane

� GMM: GPRS Mobility Management

� SM: Session Management

MS BSS SGSN

BSSGP

GMM/SM

LLC

RLC

MAC

GSM RF

GMM/SM

LLC

BSSGP

L1bis

Um Gb

NetworkService

RLC

MAC

GSM RF L1bis

NetworkService

Relayrelay




3.2 Um Interface


3.4 Gb Interface

3.5 Gs Interface


Protocol Layer of Um Interface

� GMM (GPRS Mobility Management): operates in the signalling plane of GPRS supports mobility management functionality.

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

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

� LLC (Logical Link Control ): This layer provides a highly reliable 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 mobile stations to

share a common transmission medium.

LLC

RLC

MAC

RF

Physical Link

SN

DC

P

SM

S

GM

M/S

M


MM State

IDLE �GMM context is not established; MS is not reachable.

�MS can implement data transmission.

�GMM context is established; MS can receive paging but cannot implement data transmission.

− The MS performs MM procedures to provide the network with the actual

selected cell.

− SGSN performs the MM on cell level.

READY

STANDBY− The location information in the SGSN MM context contains only the GPRS RAI.

− Pages for data or signalling information transfers may be received. It is also

possible to receive pages for the CS services via the SGSN. Data reception

and transmission are not possible in this state.

− Data transmission to and from the mobile subscriber as well as the paging of

the subscriber are not possible


MM State Model

IDLE READY STANDBY

IDLE READY STANDBY

MM State Model of MS

MM State Model of SGSN

GPRS Attach

GPRS Detach

READY timer expiry or

PDU transmission

PDU reception

Implicit Detach or Cancel Location

GPRS Attach

Force to STANDBY

READY timer expiry orForce to STANDBY or

Abnormal RLC condition

GPRS Detach or Cancel Location


Transmission Principle of Data Packet on Um Interface

RLC/MAC block

Subscriber data

RLC/MAC headLLC headSNDCP head LLC FCS

LLC frame

Subscriber IP packet (N-PDU)

SNDCP PDU(SN-PDU)

Network Layer

SNDCP Layer

LLC Layer

RLC/MAC Layer




3.2 Um Interface


3.4 Gb Interface

3.5 Gs Interface


G-abis/Pb Interface

MS

BTS

PCU

MS

G-abisBSC

Abis Pb

�G-abis/Pb interface is not a standard interface




3.2 Um Interface


3.4 Gb Interface

3.5 Gs Interface


Protocol Stack of the Gb Interface

BSS SGSN

BSSGP

GMM/SM

LLC

BSSGP

L1bis

Gb

NetworkService

RLC

MAC

GSM RF L1bis

NetworkService

Relayrelay


NS Layer Definition

�The Network Service performs the transport of NS SDUs(Service Data Unit )

between the SGSN and BSS.

�The Network Service entity is composed of the Sub-Network Service and the

Network Service Control.

FR PVC（（（（DLCI））））

NSVC（（（（NSVCI））））


NS Layer Functions

� Sub-Network Service Functions

� The Sub-Network Service functions of the Network Service shall provide access to the intermediate network (or to the peer entity in case of direct point-to-point configuration) and shall provide NS-VCs between NS peer entities.

� Frame Relay shall be the network used on the Gb interface. The Sub-Network Service entity is the Frame Relay entity.

� Network Service Control Functions

� NS SDU transmission

� Load sharing� NS-VC management

BSS

FR Network

SGSN

DTE

DTEDTE

DCE

Gb Gb

Gb


NS Layer Parameters

� BC

� Bearer Channel: consist of one group of time slots in one E1

� DLCI� Data Link Connection Identifier: the identifier of PVC having end-to-end

significance across the Gb interface

� NSVC, NSVCI

� The NS-VCs are end-to-end virtual connections between the BSS and SGSN.

� NSE, NSEI� NS entity, NSE is responsible for management of all of NS-VC, e.g. NSVC

block /unblock /reset


NS Layer StructureBC1(TS1~TS3)

BC2(TS1~TS3)E1 link

TS0~TS31

SGSN

E1 linkTS0~TS31

BSS

NSVCI=10

DLCI=259

NSVCI=20

DLCI=16

NSVCI=20

DLCI=16

NSVCI=10

DLCI=259

NSVC collection

NSEI=1

NSVC collection

NSEI=1

TS3TS2TS1

TS3TS2 TS1

……


NS Layer Load-sharing

NSVC channel=10 DLCI=259

NSVC channel=20 DLCI=16

NS Layer

ms#1ms#2

cell

SGSN BSS

BSSGP Layer BVC1 BVC2

BVC1 BVC2

NSE1NSE1NSE2 NSE2

NSE3 NSE3

Two users in the same cell


Functions of BSSGP� The primary function of BSSGP is to provide the radio-related, QoS, and routing

information that is required to transmit user data between a BSS and an SGSN.

� A secondary function is to enable the SGSN and BSS to operate node

management control functions.

� BSSGP Virtual Connections (BVCs) provide communication paths between BSSGP entities. Each BVC is used in the transport of BSSGP PDUs between the

following entities:

− peer point-to-point (PTP) functional entities : PTP user data transmission. A

cell is identified by a BVCI.

− peer point-to-multipoint(PTM) functional entities: PTM user data

transmission. There is one or more PTM functional entities per BSS.

− peer signalling functional entities : Signaling transmission. Each NSE

corresponds a SIG BVC. There is one or more NSEs per BSS.


Realization of BSSGP Layer

GbSIG BVC

BVC1 1

BVC1 2

BVC1 3

BVC1 4

BVC1 5

BVC1 1

BVC1 2

BVC1 3

BVC1 4

cell1

cell2

cell3

cell4

PTP BVC

BSC SGSN


The Difference btw. PTP BVC and SIG BVC

NSE NSE

NSVC1

NSVC2

SIG BVC

PTP BVC

Signaling

User data

Cell1 Cell2 Cell1 Cell2




3.2 Um Interface


3.4 Gb Interface

3.5 Gs Interface


SCCP

MTP2MTP3

MTP2MTP3

SCCP

GsSGSN MSC/VLR

BSSAP+ BSSAP+

L1 L1

SGSN - MSC/VLR Signaling Plane

� Gs interface is the optional interface.

� It adopts BSSAP+ protocol to enable combined mobility management and

paging functions so as to improve the effective usage of wireless resources.

MSC/VLR

Gs

SGSN

BSCPCU

TRAU


Cooperation between GMM and MM

� Objectives

� To improve the effective usage of wireless resources

� To reduce the network signaling traffic

� Pre-condition

�SGSN and MSC/VLR support Gs interface

� Functions

�Combined IMSI/GPRS attachment and Combined IMSI/GPRS detachment

�Combined routing area/location area updating (including periodical)

�Paging Co-ordination


Network Operation Mode (Paging Co-ordination)�Paging co-ordination means that the network sends paging messages for circuit-switched services on the same channel as used for packet-switched services, i.e., on the GPRS paging channel or on the GPRS traffic channel, and the MS needs

only to monitor that channel.

CCCH Paging Channel

CCCH Paging Channel

CCCH Paging Channel

Packet Data Channel

CCCH Paging Channel

Packet Paging Channel

Circuit Paging Channel

CCCH Paging Channel

Packet Paging ChannelNetwork Operation Mode

III

No (Gs interface is not present, all MSC-originated paging of GPRS-attached MSs shall

go via the A interface)

CCCH Paging ChannelNetwork Operation Mode

II ��

Not Applicable

CCCH Paging Channel

Yes (Gs interface is present, all MSC-originated paging of GPRS-attached MSs shall

go via the SGSN)

Packet Paging ChannelNetwork Operation Mode

I

Paging co-ordinationGPRS Paging Channel

Mode









4.1 Packet Channels

4.2 Medium Access Modes

4.3 MS Multi-TS Ability

4.4 Power Control

4.5 Network Control Modes


Physical Channel

The 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

� …

Application

IP/X25

SNDCP

LLC

RLC RLC BSSGP

MAC MACFramerelay

PhysicalLayer

PhysicalLayer

PhysicalLayer

MS BSS

Relay


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/D PNCH

PTCCH/U PTCCH/DSACCH


Channel Abbreviation

� Packet Data Traffic CHannel Uplink - PDTCH/U

� Packet Data Traffic CHannel Downlink - PDTCH/D

� Packet Broadcast Control CHannel - PBCCH

� Packet Common Control CHannel - PCCCH

� Packet Dedicated Control Channel - PDCCH

� Packet Paging CHannel - PPCH

� Packet Random Access CHannel - PRACH

� Packet Access Grant CHannel - PAGCH

� Packet Notification CHannel - PNCH

� Packet Associated Control CHannel - PACCH

� Packet Timing advance Control CHannel Uplink - PTCCH/U

� Packet Timing advance Control CHannel Downlink - PTCCH/D


PDTCH (Packet Data Traffic CHannel)

� All packet data traffic channels are uni-

directional.

� Uplink (PDTCH/U) for a mobile

originated packet transfer.

� Downlink (PDTCH/D) for a mobile

terminated packet transfer.

Packet service channel

PDTCH/U PDTCH/D


PBCCH (Packet Broadcast Control CHannel)

� The PBCCH broadcasts parameters used by the MS to access the network for packet transmission operation.

� The PBCCH also carries the information transmitted via the BCCH to allow circuit switching operation.

�The MS in GPRS attached mode monitors the PBCCH only, if PBCCH is available, otherwise, the BCCH shall be used to broadcast information for packet operation.

�The existence of the PBCCH in the cell is indicated on the BCCH via SI13.

Packet control channel

PBCCH


PCCCH (Packet Common Control CHannel) � PPCH

� Downlink only, used to page MS.

� PRACH � Uplink only, used to request allocation of one

or several PDTCH/Us or PDTCH/Ds.

� PAGCH � Downlink only, used to allocate one or

several PDTCHs.

� PNCH� Downlink only, used to notify MS of PTM-M

call.

� If no PCCCH is allocated, the information for packet switching operation is transmitted on the CCCH. If a PCCCH is allocated, it may transmit information for circuit switching operation.

PPCH PRACH PAGCH

PCCCH

PNCH


PDCCH (Packet Dedicated Control Channels)

� 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 with several PTCCH/U's.

PACCH

PDCCH

PTCCH/U PTCCH/D


Combinations of Packet Logic Channel

Mode 3: PDTCH+PACCH+PTCCH

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

In case of small GPRS traffic, GPRS and circuit services share the same BCCH and CCCH in the cell. In this case, only combination mode 3 is needed in the cell.

With the increase of traffic, the packet public channel should be configured in the cell. Channel combination mode 1 and mode 2 should be adopted.

Mode 4: PBCCH+PCCCH

(PCCCH=PPCH+PRACH+PAGCH+PNCH）


Packet Wireless Channel Configurations

� 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 the

percentage of circuit switching services are constantly changing.

�Dynamic PDCH is not visible for voice services.


Packet Wireless Channel Configurations

� General principles

� The 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.


Mapping of Packet Logic Channel

I = Idle frame T = Frame used for PTCCHB0 ~ B11 = Radio blocks

51250

B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11T I T I

456 bits

0 1 2 3 4 5 6 7

1 TDMA frame

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

� A radio block is a 4-normal-burst sequence that carries a RLC/MAC PDU

(Protocol Data Unit).


Mapping of Packet Logic Channel

51

4

3

5

6

7

0

1

2 B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11T I T I

500

BCCH

PDCH

TCH

S B B B B C C C C F S CC C C C C C C F S C C CCC C C C F S C C C C C CC C F S C C C C C C C C I

T T T T T T T T T T T S T T T T T T T T T T T T IT

F

25

2512


Transmission Principle of Data Packet on Um Interface

Subscriber data

RLC/MAC headLLC headSNDCP head

Subscriber IP packet

LLC FCS

SNDCP PDU

LLC PDU

RLC/MAC block

Physical layer

B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11T I T I

NB

NB

NB

NB


Allocation of Wireless Packet Resources

� Wireless resource allocation and wireless transmission adopt the wireless block (BLOCK) as the

basic unit.

� Each PDCH can be used by several MSs; each MS can use multiple PDCHs at the same time.

B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11B0

B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11B0

B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11B0

MS3MS2

TS 0

TS 1

TS 2

MS1


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

B11B10 B9B8 B7 B6

B5 B4 B3B2 B1 B0

T

I

T

I

UL

DL

USF=1USF=1

USF=1USF=2

USF=2USF=3

USF=3USF=3

USF=3USF=4

USF=4USF=4

T

I

T

I

USF=1

USF=2

USF=3

USF=4

MS1

MS2

MS3

MS4

USF=1

……

B0 I……


Basic Conceptions about Radio Block

� TBF (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.



4.1 Packet Channels



4.4 Power Control



Medium Access Modes

� Uplink resource allocation mode

�Dynamic allocation (supported by all MSs and all networks)

− The mobile station detecting an assigned USF value for each assigned PDCH and block 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 period without 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 assigned PDCHs in the same block or group of four blocks.

� Downlink resource allocation mode

�Dynamic allocation and fixed allocation.



4.1 Packet Channels



4.4 Power Control



MS Multi-TS Ability

� Concept of MS multi-TS ability

� Types

− Type 1: Non-simultaneous TRX

− Type 2: Simultaneous TRX

� the multi-TS ability level is 1-29; the bigger the level, the stronger the multi-TS ability.

− 1~12 (Type 1),up to 4 timeslots in any direction

− 13~18 (Type 2),ranges between 3~8 timeslots

− 19~29 (Type 1)

� BSS allocates resources according to the MS multi-TS ability, requested QoS and

current resource configuration.



4.1 Packet Channels



4.4 Power Control



Power Control

� Power control can improve the spectrum usage and system capacity as

well as reduce MS power consumption.

� As there is no continuous bi-directional connection in the packet data

transmission process, GPRS power control is very complicated.

� Uplink power control includes open-loop and close-loop power control.

� About downlink power control, there is no specific definition in protocol. It

lies on the BTS and its algorithm needs information about downlink, so

downlink power control needs MS sends channel quality reports to BTS.



4.1 Packet Channels



4.4 Power Control



Network Control Modes

� During the network controlled cell re-selection, the network may request measurement reports from the MS and control its cell re-selection. Hence, three types of mode are defined as follows:

� NC0: Normal MS controls

� NC1: MS control with measurement reports

� NC2: Network control

� The network subsystem must support NC0 and should gradually support NC1 and NC2.


Network Control Modes

MS NC0 NC1

NC2

The MS shall perform autonomous cell re-selection

MS

The MS shall perform autonomous cell re-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








Relationship among Location Areas

CELL

CELL

CELL

CELL

RA1

RA2

CELL

CELL

RA3

CELL

CELL

CELL

SGSN1SGSN2

BSC1

BSC2

BSC3

LA1 LA2


� MCC：Mobile Country Code, it consists of 3 digits. For example:

The MCC of China is "460"

� MNC：Mobile Network Code, it consists of 2 digits. For example:

The MNC of China Mobile is "00"

� LAC：Location Area Code, it is a two bytes hex code. The value

0000 and FFFF is invalid

� For example: 460008C90

Location Area Identification

MCC MNC LAC

LAI (Location Area Identification)


RAI

� Routing area is the sub-set of the location area. In special cases, the two

areas are equal

� The division of the routing area is related with traffic distribution and

SGSN processing ability


MCC MNC LAC RAC

Routing Area Identification


CGI


MCC MNC LAC CI

CGI

� CI (Cell Identity): This code uses two bytes hex code to identify the radio cells within a LAI.

� RAC is only unique when presented together with LAI.

� CI is only unique when presented together with LAI or RAI.

� CGI = MCC+MNC+LAC+{RAC}+CI

RAC

Routing Area Identification


CGI

Relationship among Location Areas

� LAI

�MCC+ MNC+ LAC

LAI

� RAI

�MCC+ MNC+ LAC+RAC

� CGI /CellID

�MCC+ MNC+ LAC+{RAC}+CI

RAI


Summary

� GPRS System Overview

� GPRS Achitecture

� GPRS Network Interfaces & Protocols

� GPRS Wireless Subsystem

� GPRS Location Area

www.huawei.com

Thank You

Omq000001 Gprs Principle Issue2.0

Documents

logical link control

bytes hex code

circuit switching operation

mm state model

temporary flow identity

upgrade bts software

implement data transmission

circuit switching services