GSM P&O Training Material for Skill Certificate-GPRS Basic Principle

GPRS Basic Principle

GSM P&O Department

Objective

At the end of this course, you will be able to understand: GPRS network architecture and characteristics GPRS interfaces and protocols GPRS air interface technology GPRS working flow Evolution from GPRS to 3G

Content

GPRS Network Overview

GPRS Radio Interface technology

GPRS Mobility Management

GPRS Session Management

GPRS Data Transferring Process

Process of Evolution from GPRS to 3G

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 integratio

n of GSM radio access technique and inter

net packet switch technique.

GPRS network overview

Production & Evolution of GPRS

GPRS Production & Evolution

GPRS is mobile packet data service based on GSM mobile

Telecommunication system. GPRS system is a subsidiary of

previous GSM circuit switch system for fulfilling user’s demand as to

use MS to access internet or other packet data network.

GPRS realizes packet data transmission by adding series of

functional entities based on previous GSM network. Newly-added

entities and existing entities after software upgrading constitute

GSM-GPRS network providing GPRS data service while existing

GSM network providing circuit service.


GPRS Features

GPRS features

adapted to aperiodic bursty data service

uplink and downlink can be asymmetrical. Data rate is changeable.

flexible resource management style

GSM voice and GPRS data service share RR dynamically.

MS has various mapping relationships with channels.

One MS can has multiple data sessions simultaneously.

Coding mode: CS-1 ～ CS-4 ， data rate ： 9.05 ～ 171.2kbit/s

Major interface protocols (Internet ， X.25 和 SMS) are supported.

Shared GSM infrastructure to reduce network operation cost. Char

ge fees based on data quantity.


GPRS Services

Bearing service

WWW scanning, FTP, WAP and E-mail etc.

PTP

Unconnected PTP service (PTP-CLNS) like IP

Connected PTP service (PTP-CONS) like X.25

PTM ： GPRS provide in the second phase

PTM-M （ multicasting ） PTM-G （ group calling ） IP-M （ multicasting ）


GPRS Services

Telecom Service

PTP: E-mail, electronic monitoring, online games

PTM ： weather forecast

Mobile IP

Complementary service

GSM phase2 supplementary service supported by GPRS

GPRS specified supplementary service


GPRS service & existing service

Relationship with GSM SMS service

Relationship with circuit switch service

three network working mode

three kinds of terminals

conditions in which two services are applied

United GPRS & IMSI attachment and detachment

United router area & location area upgrading

B series MS suspension & restoration

GPRS network encourages the function of CS paging


System message

System message1

System message 3

System message 5 System message 13

System message 4

System message 2

GPRS System Message


GPRS Network Infrastructure


RLC/MAC layer function Radio resource management function

PCU Function

DL ： PDU at LLC divided into R

LC data block

UL ： RLC data block recompos

ed into PDU at LLC layer

PDCH UL & DL ARQ protocol

Allocate UL & DL radio resource

Channel access control function

such as access request and

access permission

Radio channel management

function such as power control,

congestion control and

broadcasting control messages.


Network Access Control

Authentication encrypti

on IMEI check

Path Management

SGSN-BSS data tra

nsferring path mana

gement SGSN-GGSN and S

GSN-SGSN path m

anagement

Logical Link Management

Management of SG SN-MS logical links Acknowledgement or un

acknowledgement transf

er

Path and Tunnel Transferring

Storage and transferring of user data

Router selection Address translation and

mapping Package and tunneling tr

ansferring

User Info Management

Mobility information Endorsement info.

Charge Management

……

SGSN Function


Network Access Control

Message filtering Charging info collection

Dynamic allocate IP address

SGSN-BSS data transfe

rring path management SGSN-GGSN and SGS

N-SGSN path managem

ent

Mobility and session

management

Service Management

Storage and transferring

of user data Management of APN

Router selection

and transferring

Mobility info Endorsement info

Charge Management

CG charging Radius charging

GGSN Function


HLR Function

GPRS subscriber subscription data

User authentication

GMM or router selection information upgrading and manipula

tion

Save and upgrade SGSN number and address of user service

GPRS user location deleting indication

MS availability

user tracing (optional)


MSC/VLR additional function

SGSN connection with MSC by Gs interface (Gs interface

is optional ） United IMSI/GPRS attachment & detachment

United location area & router area upgrading

Circuit paging coordination function

Enhance radio resource utilizing rate


GPRS Support SMS

SGSN connects with SMSC via Gd interface to send SMS

by GPRS

SMS service effect on voice service

SMS resource can be shared

operator can choose to transmit SMS either by MSC or SG

SN


BTS SGSN GGSNBSC

MSC/VLR

Gi

Gn

GrGs

Gb

Gn

A

HLR

IP Network

GPRSBackbone

BG

Other PLMN

Gp

PCU

SGSN

GGSN

Gn

GnBG

SS7

GPRS Network Interface

MS

Um

Abis


Major Interfaces Function

Um interface Through which MS communicate with GPRS network supporting functi

ons such as packet data transferring, SMS, SM and RRM.

Gb interface SGSN communicates with BSS and MS via Gb interface which supports

the function of packet data transferring, GMS and SM. This interface is a must in GPRS network.

Gi interface Gi interface connects GPRS with exterior packet data network. GPRS c

onnects with PDN including internet or ISDN via Gi interface. Operations such as Encapsulation, decapsulation, address conversion, user authentication are needed on this interface.


Major Interfaces Function

Gn interface Gn interface is interface between GPRS service supporting nodes, i.

e. interfaces between SGSN, between SGSN and GGSN, and wor

ks based on GTP.

Gs interfaces Via Gs interface , SGSN together with MSC realizes the function of

GMM including united Attach & Detach, upgrading of united router a

rea & location area. SGSN will also receive CS paging info from M

SC and transmit to MS through PCU.

Others Gr 、 Gd 、 GP 、 Gc 、 Gf.


GSM RF

MAC

RLC

LLC

SNDCP

IP/X.25

Application

GSM RF

MAC

RLC

L1 bis

NetworkService

BSSGP

Relay

L1 bis

NetworkService

BSSGP

L1

L2

IP

L1

L2

IP

UDP/TCP

GTP

IP/X.25

LLC

SNDCP

UDP/TCP

GTP

Relay

MS BSS/PCU SGSN GGSNUm Gb Gn Gi

GPRS Data Transferring Platform



Physical layer

It’s categorized into radio frequency layer and physical layer

Protocol of L1bis 、 L1 、 L2

There are no fixed regulations on that. Different manufactur

ers may have different solutions.

RLC/MAC

RLC provides reliable RL for upper service and MAC is res

ponsible for channel positioning and reuse. RLC and MAC c

onstitute OSI layer protocol with Um interface, and use servi

ce provided by physical link layer.



NS NS realizes transferring function based on BSSGP which lays on the basis

of flame layer connection between BSS and SGSN and passes through switch nodes of frame layer.

BSSGP In DL, SGSN provides BSS with radio information to realize RLC&MAC fu

nction; In UL, BSS provides SGSN with radio information gotten from RLC&MAC. BSSGP enables function of BSS and SGSN management. This layer transmits router and Qos information between BSS and SGSN without error correction function.

Relay Relay in BSS is relay LLC PDU between Um and Gb while Relay in SGSN

is to relay PDP PDU between Gb and Gn.



LLC

LLC is reliable and protective logical link between MS and SGSN

and is dependent of lower layer radio interface protocol. It has two

transferring mode: acknowledgement and non-acknowledgement.

SNDCP

It’s network protocol which is responsible for mapping,

compression, subsection, sequence and reuse. Main function

include reuse multiple PDP, compress or decompress user data

and protocol control information, partition N-PDU into LL-PDU or

encapsulate reversely.



GTP This protocol encourages data and signaling transferring between supporting

nodes of GPRS key network. PTP PDU PD should be encapsulated with GTP.

UDP/TCP They belongs to transmit layer protocol , providing end-to-end reliable link.

TCP (connection protocol) provides with flow protection and control function and guarantee the correctness of data transferring while UDP (non-connection) is just the transceiver of datagram without error correcting capability and not caring about whether the datagram has been correctly received.

IP GPRS backbone network protocol is used for router selection and signaling

control. GPRS backbone network preliminarily use IP V4, later will use IP V6.


BSSGPRelay

GMM/SM

LLC

RLC

MAC

GSM RF

GMM/SM

LLC

BSSGP

L1bis

Um GbMS BSS SGSN

NetworkService

RLC

MAC

GSM RF L1bis

NetworkService

SCCP

MTP2

MTP3

MTP2

MTP3

SCCP

Gr/Gf/Gd SGSN HLR

TCAP

MAP

TCAP

MAP

L1 L1

SCCP

MTP2

MTP3

MTP2

MTP3

SCCP

GsSGSN MSC/VLR

BSSAP+ BSSAP+

L1 L1

UDP

L2

L1

IP

L2

L1

IP

UDP

GnGSN GSN

GTP GTP

SCCP

MTP2

MTP3

MTP2

MTP3

SCCP

GcGGSN HLR

TCAP

MAP

TCAP

MAP

L1 L1

Gn

UDP

L2

IP

GGSN

L1

L2

IP

GSN

GTP

L1

MTP2

MTP3

SCCP

MAP

L1

MTP2

MTP3

SCCP

HLR

TCAP

MAP

L1

GTP

Gc

Interworking

TCAP

UDP

MS-SGSN SGSN-HLR/EIR/SMS SGSN-MSC/VLR

GSN-GSN

GPRS Signaling Platform


Content







GPRS radio interface technology

GPRS Logical Channel Type

Logical CHTraffic CH

·Control CH

PBCCH

PCCCH

PRACH

PAGCH

PPCH

PDCCH

PACCH

PTCCH/D

PS

CSPDTCH/CS1

PDTCH/CS2

PDTCH/CS3

PDTCH/CS4

PNCH

PTCCH/U

GPRS Logical Channel Type

Packet Data Channel (PDCH)

include packet service channel and packet control channel

Packet Data Traffic Channel (PDTCH)

Unidirectional traffic channel ： PDTCH/U ， PDTCH/D

Packet Control Channel

Broadcasting control channel ： PBCCH

Common control channel ： PPCH ， PRACH ， PAGCH ，PNCH （ send notification message ）

Dedicated control channel ： PACCH ， PTCCH/U （ to esti

mate TA ）， PTCCH/D （ send TA upgrading message ）


Packet Logical Channel Combining mode

Combination of logical channels Mode 1 ： PBCCH ＋ PCCCH ＋ PDTCH ＋ PACCH ＋ PTCCH Mode 2 ： PCCCH ＋ PDTCH ＋ PACCH ＋ PTCCH Mode 3 ： PDTCH ＋ PACCH ＋ PTCCH PCCCH = PPCH + PRACH + PAGCH + PNCH

Service Volume When GPRS traffic is not intense, GPRS and circuit traffic generall

y share BCCH and CCCH in cells. In this case, mode 3 is needed.

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

hannel combination is either mode 1 or mode 2.


MS Multi-slot Class

Concept of MS multi-slot class Element: maximum receiving TSL number (DL TS), maximum transmi

ssion TSL number (UL TS), and maximum TSL number Definition ： level 1-29. multi-slot class get boosted as level mounts

Factors affecting MS multi-slot class Whether transmit and receive can be done simultaneously Time for MS to make adjacent measurement, transceiver transmission

and reception preparation Frequency hopping affecting time range Target market thinning

BSS should make best resource allocation according to MS multi-slot class, Qos requested and current resource allocation condition.


MS Mobile Capability Series

A series

Can attach GPRS network and GSM network simultaneously

and PS and CS traffic can be conducted simultaneously.

B series

Can attach GPRS network and GSM network simultaneously

and PS and CS traffic can be conducted simultaneously.

C series

Can’t attach GPRS network and GSM network simultaneously.

Select either PS traffic or CS traffic to conduct and unselected

traffic is in disconnected state.


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 oc

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

Logical Channels Mapping


52 Multiframe Description

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.


RLC / MAC header RLC Data BCSRLC / MAC layerRadio block

CS-1 9.05 kbit/sCS-2 13,4 kbit/sCS-3 15,6 kbit/sCS-4 21,4 kbit/s

Coding scheme Bit rate1/2

~ 2/3~ 3/4

1

Code rate184274318440

Radio block excl. BCS40161616

BCS444-

Tail456588676456

Coded bits0

132220

0

Punctured bits

Convolutional coding

Puncturing

456 bits

4 burstsPhysical layer

CS Coding Scheme


CS Coding Scheme

GPRS defines four channel coding mode from CS-1 to CS-4 Data rate is 9.05 Kbps, 13.4 Kbps, 15.6 Kbps ， 21.4 Kbps accordingly.

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

nd CS-2 is the same with that of voice service with the coverage of 90

％－ 100 ％； C/I of CS-3 is higher ； C/I of CS-4 is much higher and f

avorable radio environment are required.

Network will adjust channel coding mode based on real-time monito

ring of radio transmission Different TSL can select different channel coding mode

When the quality radio transmission is good, it’s necessary to use more

efficient coding mode.


PDTCH Allocation

Concepts

USF Control different MS to reuse Blocks on PDCH UL. USF is used in dynamic

and extensible media access mode. On PCCCH, one USF is used to mark PRACH(USF equals to idle) , the remaining is left to 7 MS. (USF = R1/R2 … R7 ）

TBF TBF is physical link used by RR identity to transmit LLC PDU unidirectional

ly on PDCH. It’s RR allocated on one or more PDCH on which RLC & MAC blocks carrying one or more LLC PDU are transmitted.

TFI Each TBF is assigned one TFI, and it’s possible to use one TFI in different

directions. TFI assignment before LLC frame transmission. RLC & MAC related to one specified TBF must include one TFI.


PDTCH Assignment

GPRS and GSM share the same air interface channel

Three modes of RR assignment are:

static assignment

dynamic assignment

extend dynamic assignment mode


CS PS PS PS CS CS PS CS

Speechcall 1

Speechcall 2

Speechcall 3

GPRS user 1

GPRS user 2

GPRS user 3

GPRS user 4

TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7

GPRS user 5

GPRS user 6

Idle

PDTCH Assignment


P : packet channel C: voice channel

PDTCH Assignment

P2 P1 P3 P3 P3 P3 P3 P3 P3P2 P1 P3 P4 P4 P5 C8 C8 C8P1 P1 P1 P4 P4 P5 C9 C9 C9P1 P1 P1 P1 P5 P5 P5 P5 P5C4 P1 P1 P1 P1 P1 P1 C10 C10C3 C3 C3 C3 C3 C3 C3 C3 C3C2 C2 C2 C6 C6 C6 C6 C6 P1C1 C1 C5 C5 C5 P5 C7 C7 C7

7

Time210123456

83 75 64 9


PDTCH Assignment

Reason to use static PDCH

Ensure that GPRS MS in the cell is on line

Ensure Qos of GPRS service

Reason to use dynamic PDCH

GPRS and GSM share radio resource

consider the best utility of radio resource with voice traffic as the

top priority

The ratio of PS traffic and Cs traffic in one cell always changes

Dynamic PDCH is unusable


C/I(dB)

0

5

10

15

20

25

0 4 8 12 16 20 24

CS1CS2CS3CS4

Typical urban area with moving speed at 3 kil per hour

Packet Data Transmission


One PDCH can be used by multiple MS While one MS can use multiple PDCH.

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

MS1 MS3MS2



LLC

SNDCP

IP

RLC

MAC

GSM RF

N-PDU

SN-DATA PDUsLLC Frames

RLC Blocks

RLC/MAC Blocks

TDMA Bursts


Each IP package can be divided into blocks on one or more SNDCP layer. each SNDCP PDU is mapped to one LLC layer. LLC Frame shall be transferred into many RLC Block. RLC Block together with MAC header are sent into air by 4 bursts.


0 7

TDMA frame = 4.615 ms

= BURST PERIOD

0 70 70 7

RLC/MAC Blocks

TDMA Bursts

RLC Blocks

4 x TDMA Frames = 4 Bursts = 1RLC block ~ 20 ms



Content







Mobility Management Concepts & Procedures

Specified Procedures of Mobility Management Attach & detach Periodic location upgrading & router area upgrading Normal area location upgrading & router area upgrading

Unified Procedures of Mobility Management authentication P-TMSI reallocation ID identifier

Connection Management Procedures of Mobility Management

Establishment of connection and release

GPRS mobility management

Major Function of Mobility Management

General Function GPRS attach: establish MM context and MM state changes to be ready GPRS detach: delete MM context and MM state changes to be idle (eithe

r MS or network initiates) Security function includes authentication, encrypt and identifier verification

etc. Location management include normal or periodical router area upgrading

and cell upgrading

Network Function Work with HLR to erase GMM context. User data management MS class mark handling Work with MSC/VLR for united location upgrading and united paging etc.


GMM Status Migration Model


GMM State Transit

GMM State Idle: GMM context isn’t established and MS is unavailable Standby: GMM context has been established and MS can receive

paging but not transfer data; router area at which MS located Ready: MS can transfer data and cell in which MS belongs to

GMM context MS flag GMM state location information of MS (router area flag and cell flag) Serving SGSG location and VLR serial number (MS only) Encryption algorithm and authentication parameter


GMM Status migration

Idle (Idle)

When GPRS is in Idle state, GMM is not activated by the user.

There’s no effective location information or router information

concerning this user in MS and SGSN environment. In this

case MM is not supported.

Under this circumstances, MS makes selection and reselection

of PLMN and GPRS. Establish MM environment in MS and

SGSN by activating GPRS function.


GMM Status Migration

Standby In standby state, IMSI of the user in MM environment has been

created in MS and SGSN, and MS can receive paging message but not to send packet data. In SGSN, if it receives response to paging from MS , MM state migrates to Ready. And MM state of MS will return to Ready when data or signaling transmit from MS. Accordingly when SGSN gets data and signaling from MS, MM state will migrate to Ready. MS can process GRPS detach function to enter Idle state.

When Ready state timer times out SGSN know router information of MS MS can receive paging information MS can have router upgrading


GMM Status Migration

Ready

In this state, information of cells in which MS belongs to can be fou

nd in SGSN MM environment, and MS can transceive PTP PDU. R

eady state is monitored by a counter and MM environment will migr

ate from Ready to Standby. MS can invoke GPRS traffic detach fun

ction to realize the migration from Ready to Idle.

When GPRS attach is completed

SGSN know CELL ID of MS

MS can transceive PTP data

MS can have cell upgrading function


7d. Cancel Location Ack

7c. Cancel Location

7b. Update Location

7g. Update Location Ack

7e. Insert Subscriber Data

7f. Insert Subscriber Data Ack

6d. Insert Subscriber Data

6c. Cancel Location Ack

6b. Cancel Location

3. Identity Response

2. Identification Response

2. Identification Request 1. Attach Request

5. IMEI Check

3. Identity Request

4. Authentication

6a. Update Location

7a. Location Update Request

7h. Location Update Accept

6f. Update Location Ack

6e. Insert Subscriber Data Ack

MS BSS new SGSN old SGSN GGSN HLREIRold

MSC/VLRnew

MSC/VLR

9. Attach Complete

8. Attach Accept

10. TMSI Reallocation Complete

GPRS Attach Procedure


1. Send Authentication Info

2. Authentication and Ciphering Request 1. Send Authentication Info Ack

2. Authentication and Ciphering Response

MS BSS HLRSGSN

GMM Authentication Procedures

Identity Response Check IMEI

Identity Request

Check IMEI Ack

MS BSS EIRSGSN

GMM authentication

procedure

GMM Identifier

verification


3. IMSI Detach Indication

2. Delete PDP Context Response

1. Detach Request 2. Delete PDP Context Request

5. Detach Accept

MS BSS GGSNSGSN MSC/VLR

4. GPRS Detach Indication


1. Detach Request

2. Delete PDP Context Request

4. Detach Accept

MS BSS GGSNSGSN MSC/VLR


HLRMS BSS GGSNSGSN MSC/VLR


1. Cancel Location


2. Detach Request

6. Cancel Location Ack


5. Detach Request

MS originate SGSN originate

HLR originate

Detach Signaling Procedures


Location Management

Cell update: cell identifier changes and router identity

unchanged

Router area update: router area identity changes

Router area update in SGSN

router update cross-SGSN

United update of router area & location area

United RA/LA update in SGSN

RA/LA update cross-SGSN

Periodic location update


1. Routing Area Update Request

3. Routing Area Update Accept

2. Security Functions

MS BSS SGSN

4. Routing Area Update Complete

Router Area Update Procedure (Intra SGSN)


MS BSS new SGSN HLRGGSNold SGSN MSC/VLR

2. SGSN Context Response


1. Routing Area Update Request 2. SGSN Context Request

5. Update PDP Context Request5. Update PDP Context Response

6. Update Location

9. Update Location Ack

11. Routing Area Update Accept

10. Location Updating Request

10. Location Updating Accept

7. Cancel Location


8. Insert Subscriber Data Ack

8. Insert Subscriber Data

12. Routing Area Update Complete

3. Forward Packets

Router Area Update Procedures (Inter SGSN)


12b. Cancel Location

12c. Cancel Location Ack 12d. Insert Subscriber Data

16. TMSI Reallocation Complete

12f. Update Location Ack 13. Location Update Accept

15. Routeing Area Update Complete

14. Routeing Area Update Accept

8. Cancel Location


6. Update PDP Context Response

6. Update PDP Context Request

7. Update Location

10. Update Location Ack

12a. Update Location 11. Location Update Request

2. SGSN Context Response 3. Security Functions

2. SGSN Context Request 1. Routeing Area Update Request

9. Insert Subscriber Data

9. Insert Subscriber Data Ack

12e. Insert Subscriber Data Ack

MS BSS GGSNold SGSNnew SGSN HLRnew

MSC/VLRold

MSC/VLR

5. Forward Packets

4. SGSN Context Acknowledge

United Location Update Procedure


BSC SGSN

1.1.

RA1

1. Send LLC PDU

From one cell to another in the same RAC

Cell Update Procedures


Content







GPRS session management

SM Concept

There is one or multiple PDP address in GPRS authentication

data with each PDP address corresponding to one PDP context

SM management entity: SGSN,GGSN, MS

PDP content:

PDP type, address (dynamic and static) and status

APN

NSAPI

Activated and inactivated

Exclusive correlation between PDP context and MM context

Deactivate PDP Contextor

MM state change to IDLEor PMM-DETACHED

Activate PDPContext

INACTIVE

ACTIVE

PDP Context Status Migration


Function of SM Management

PDP context activation: either MS or network originates this function and PDP context status migrates to ACTIVE

Authentication SGSN gets GGSN address through analysis of APN QoS negotiation, address assignment and start charging etc.

PDP context modification Execute this process when some parameters (serving SGSN, Qos) in PD

P context need to be changed.

PDP context deactivation Either MS or network originates and PDP context status migrates to INAC

TIVE Delete PDP context Retrieve dynamic PDP address


GGSN

4. Activate PDP Context Accept

3. Create PDP ContextResponse

3. Create PDP Context Request

1. Activate PDP Context Request

SGSNMS


PDP Activation Process：MS Originate

MS SGSN GGSN

3. PDU Notification Request

HLR

1. PDP PDU

2. Send Routeing Info for GPRS

2. Send Routeing Info for GPRS Ack

4. Request PDP Context Activation

5. PDP Context Activation procedure

3. PDU Notification Response

MS originate

Network

originate


GGSN

4. Deactivate PDP Context Accept



1. Deactivate PDP Context Request

SGSNMS


GGSN


SGSN

3. Delete PDP Context Response 2. Deactivate PDP Context Accept

2. Deactivate PDP Context Request

MS

MS originate

GGSN originate

PDP Context Deactivation


BTS BSC

SGSN

GGSN

Intranet

GPRS Core

Network

SS7

HLR

DNS

Internet

1.

AccessPoint

PDP Context Activation Scene - 1

MS sends “PDP activation

request” to SGSN

SGSN verify user data

APN

dynamic & static IP address


BTS BSC

SGSN

GGSN

GPRS Core

Network

DNS

Intranet

Internet

1.

2.

AccessPoint


SGSN gets GGSN address from DNS

SGSN sends “setup PDP context

request” to GGSN


BTS BSC

SGSN

GGSN

GPRS Core

Network

Intranet

Internet

1.

2.


External data network wanted by APN identity user Dynamic address is assigned by GGSN interior IP

address pool or exterior DHCP server GGSN returns “ establish PDP context response” to

SGSN SGSN return “activate PDP context” to MS SGSN can establish router between MS and GGSN


Content







GPRS data transfer process

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 receivi

ng channel request.

TWO PHASE

means network assigns single RLC & MAC block the first time and assign

corresponding RR upon MS’s specific request.

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


MS Network



Packet Resource Request

Packet Resource Assignment

PRACH or RACH

PAGCH or AGCH

PACCH

PACCHUplink Data

PDTCH

Uplink DataPDTCH

CCCH Two-phase Access


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


MS Network



Packet Paging Response (LLC frame)

PRACH or RACH

PAGCH or AGCH

PACCH

PPCH or PCHPacket Paging Request

GPRS Paging


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 PDUSGSN

PACCH

GPRS DL Data Transfer


TA Initialization

Initial TA value isn’t contained in Immediate Assignment message, in

dicating UL data transmission will not be conducted before TA value i

s gotten from TA update

System sends Packet Polling Message requesting MS to send acces

s 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 seco

nd)

Obtain TA in GPRS Data Transferring


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 frames416 TDMA frames

Downlink:

Uplink:

Idle frame


Power Control in GPRS Transferring Process

MS UL transmission power formula （ power unit is dBM ）P = min(0 - CH - * (C + 48), PMAX)

CH is power control parameter constant through control message from ne

twork to MS related to MS and channels,

0 is a constant and the value is 39dBm in the case GSM900 and 36dBm i

n the case of DCS1800 ；： is notified to MS by control message of BCCH or RLC , and is a weigh

ting factor of receiving factor when MS computing TxPwr with the value of

0~1.

C ： standardized value of MS receiving signaling level.

PMAX is maximum transmission power allowed in cell and the value is GP

RS_MS_TXPWR_MAX_CCH when PBCCH exists otherwise it is MS_TX

PWR_MAX_CCH


BSCBTS

Server

BTSBSC

GGSN

SGSN

HPLMN VPLMNGGSN

BG

BG

SGSN

Intra-PLMNBackbone Network

Data Network

Intra-PLMNBackbone Network

Inter-PLMNBackbone Network

Graph of GPRS Data Transmission


Content






Evolution from GPRS to 3G

GPRS =GPRS = GGeneraleneral PPacketacket RRadioadio SSystemystem

EDGE =EDGE = Enhanced Data rates for Global Evolution

EGPRSGPRS = GPRS + EDGE modulation= GPRS + EDGE modulation


Concept of GPRS & EDGE

Channel Coding of GPRS& EDGE


GPRS Evolution

According to tradition, GSM-GPRS-EDGE-WCDMA is the

right path from GSM to 3G. But in GSA case, EDGE parall

els WCDMA. i.e the roll of EDGE changes in evolution fro

m one stop to the destination. According to the definition

of 3G set by ITU, 384kbps is the criterion of 3G. Theoretic

ally EDGE rate reaches 473.6kbps, So for small or middl

e sized operators without 3G license, EDGE is their desti

nation.


GPRS Evolution


Documents

GSM P&O Training Material for Skill Certificate-GPRS Basic Principle