gprs theory arian

7/29/2019 GPRS Theory Arian

http://slidepdf.com/reader/full/gprs-theory-arian 1/40

TP-0094.3, February 2000, Slide 1

GPRS: General Packet

Radio Service




What Is GPRS?

GPRS is the integration of the two strongestworldwide trends:

In ternet and GSM




What Is GPRS? (Cont.)

Packet data network connectivity for GSMnetworks

Allows completely transparent IP support

Billing according to actual bandwidth consumed!

• As opposed to billing by calls, or billing by

bandwidth provisioned

User can stay connected (on-line) for long

periods of time without sending any data and

without paying

Dynamically variable data rates: from 9 to 150

Kbits/s per user




Data will account for up to 75% of total mobile traffic

Source:

Siemens

Mbytes per user per month

Today

0.8 Mb/user/month

Huge Increase of Mobile Data

Volume

0

5

10

15

20

25

30

35

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005




GPRS Applications

Two classes of applications :

• Horizontal applications – Are not specific to any

business segment.

• Vertical applications – Are tailormade for specific

business segment.




GPRS Applications(Cont.)

Horizontal applications :• Company e-mail

• Document and data sharing

• Sales and customers support

•Corporate news and phone directories

• Job postings

Vertical applications :

• Vending and lottery machines

• Dispatch operations(taxi, field services)• Police operations

• Medical emergency operations

• Traffic and weather conditions


http://slidepdf.com/reader/full/gprs-theory-arian 7/40TP-0094.3, February 2000, Slide 7

GPRS Main Concepts

Optimizes the use of RF network and resources

Strict separation between the RF subsystem and

data network

Datacom internetworking performed by the

tunneling concept

Internetworking defined for IP and X.25 networks

• Seamless connectivity to the internet

Does not force any changes to GSM’s MSCs Other GSM entities need only software updates



GSM Architecture

GSM Network

Mobile

PSTN

BSS



GPRS Architecture



GPRS Architecture (Cont.)

GPRSBackbone

SS7

PSTN

Data

Network

Internet

Mobile

PC E t h e r n e t

BSS

BTS

EIR

MSC

SGSN

BSC

VLR

GGSN

Workstation

FW

Router

Border GWInter PLMN

Network

X.25

Network

Corporate

Network



GPRS Add-ons to GSM

SGSN: the serving GSN (GPRS support node)• Keeps track of individual MS location

• Performs security and access control functions

• Is connected to the BSS via frame relay

GGSN: the gateway GSN (GPRS support node)

• Provides interworking with external packet-switched

networks(IP, X.25)

•Is connected to the SGSN via an IP-based GPRSbackbone network



GPRS Add-ons to GSM(Cont.)

Other additions• HLR – is enhanced with GPRS subscriber

information

• SMS – is upgraded in order to support SMS

transmission via the SGSN

• MSC/VLR – optionally, the MSC/VLR can be

enhanced for more efficient co-ordination of GPRS

and non-GPRS services and functionality



Transmission Plane

Consists of a layered protocol structureproviding:

• User information transfer

• Information transfer control procedures

•

Flow control• Error detection,

• Error correction

• Error recovery



Transmission Plane Protocol

Stack

Relay

Network

Service

GTP

Application

IP / X.25

SNDCP

LLC

RLC

MAC

GSM RF

SNDCP

LLC

BSSGP

L1bis

RLC

MAC

GSM RF

BSSGP

L1bis

Relay

L2

L1

IP

L2

L1

IP

GTP

IP / X.25

Um Gb Gn GiMS BSS SGSN GGSN

Network

Service

UDP /TCP

UDP /TCP




Stack(Cont.)GTP – GPRS tunnelling protocol.

SNDCP – maps network-level characteristics

onto the characteristics of the underlying

network.

BSSGP – conveys routing and QoS information

between the BSS and SGSN.




Stack(Cont.)NS – performs the transport of BSSGP PDUs

between the BSS and SGSN.

LLC – defines the logical link control layer protocol to be used for packet data transfer

between the MS and the SGSN.

Relay – relays LLC or PDP PDUs between

different interfaces(Um/Gb or Gb/Gn).RLC/MAC – provides radio link control function.



Signalling Plane

Consists of protocols for control and support of the transmission plane functions:

• Controlling the GPRS network access connections

• Controlling the attributes of an established network

access connection

• Controlling the routing path of an established

network connection

• Controlling the assignment of network resources

• Providing supplementary services



Signalling Plane MS-SGSN

BSSGP

Relay

GMM/SMLLC

RLC

MAC

GSM RF

GMM/SMLLC

BSSGP

L1bis

Um Gb

MS BSS SGSN

Network

Service

RLC

MAC

GSM RF L1bis

Network

Service

GMM/SM:

• GPRS Attach/Detach

• Security, routing area, location update

• PDP context activation/modification/deactivation




Signalling Plane SGSN-HLR

MAP - with additional functionalities to handleGPRS subscribers information, among other functions

TCAP, SCCP, MTP3 and MTP2 – SS7 protocols

SCCP

MTP2

MTP3

MTP2

MTP3

SCCP

Gr

SGSN HLR

TCAP

MAP

TCAP

MAP

L1 L1




Signalling Plane GSN-GSN

GTP – GPRS Tunnelling protocol.

• This protocol tunnels user and signalling data between

GPRS support nodes(GSNs) in the GPRS backbone.

• Create/update/delete PDP context request/response.

UDP

L2L1

IP

L2L1

IP

UDP

GnGSN GSN

GTP GTP




Signalling Plane-Interfaces

MS - SGSN : Um and Gb interfaces

GSN - GSN : Gn interface

SGSN - HLR : Gr interfaceOther signalling planes:

• SGSN - MSC/VLR : Gs interface

• SGSN - EIR : Gf interface

• SGSN - SMS-GMSC or SMS-IWMSC : Gd interface• GGSN - HLR : Gc interface




GPRS Protocols - Interfaces

Protocol Interface

GTP Gn

SNDCP Gb

LLC Gb

NS Gb

GMM Gb

BSSGP Gb

BSSAP+ Gs

MAP Gr , Gf , Gd and Gc




MS Identities

IMSI – International Mobile Subscriber Identity.• A unique identity allocated to each mobile

subscriber in GSM/GPRS.

P-TMSI – Packet Temporary Mobile Subscriber

Identity.TLLI – Temporary Logical Link Identity.

• Is derived from a P-TMSI and provides user identity

confidentiality.

PDP Address – Packet Data Protocol Address• A GPRS Subscriber(identified by IMSI) shall have a

network layer address(IP version 4/6).




MM Functionality

Mobility management(MM) states

• Three different MM states :

• IDLE

• STANDBY

• READY

• Each state describes a level of functionality and

information

• The information sets held at MS and SGSN are

denoted MM context




MM Functionality(Cont.)

IDLE

READY

STANDBY

GPRS Detach

PDU transmission

GPRS Attach

READY timer expiryor Force to STANDBY

STANDBY timer

expiry

State model of MS - Transitions and Functions




MM Functionality(Cont.)

State model of SGSN - Transitions and Functions

IDLE

READY

STANDBY

GPRS Detach

or

Cancel Location

PDU reception

GPRS Attach

READY timer expiry

or Force to STANDBY

or Abnormal RLC condition

STANDBY timer

Expiry or Cancel

Location




GPRS Attach Procedure

MS Network

ATTACH REQUESTStart T3310

ATTACH ACCEPT

ATTACH REJECTStop T3310

Stop T3310

or

ATTACH COMPLETEStop T3350

ATTACH REQUEST

Start T3310

If P-TMSI

and/or

TMSI allocated

Start T3350If P-TMSI

and/or

TMSI allocated




GPRS MM TimersTIMER

NUM.

TIMER

VALUE

STATE CAUSE OF START NORMAL STOP ON THE

1st

, 2nd

, 3rd

, 4th

EXPIRY Note 3

T3310 15s GMM-REG-INIT

ATTACH REQ sent ATTACH ACCEPTreceived

ATTACH REJECTreceived

Retransmission of ATTACH REQ

T3311 15s GMM-DEREG ATTEMPTINGTO ATTACH or

GMM-REG ATTEMPTING

TO UPDATE

ATTACH REJ with othe r causevalues as described in chapter ‘GPRS Attach’

ROUTING AREA UPDATE REJwith other cause values asdescribed in chapter ‘Routing

Area Update’

Low layer failure

Change of therouting area

Restart of the Attach or th e RAUprocedure withupdating of therelevant attemptcounter

T3321 15s GMM-

DEREG-INIT

DETACH REQ sent DETACH ACCEPTreceived

Retransmission of the DETACH REQ

T3330 15s GMM-ROUTING-UPDATING-INITIATED

ROUTING AREA UPDATEREQUEST sent

ROUTING AREAUPDATE ACCreceived

ROUTING AREAUPDATE REJreceived

Retransmission of the ROUTING AREA UPDATEREQUESTmessage

TIMERNUM.

TIMERVALUE

STATE CAUSE OF START NORMAL STOP ON THE

1st

, 2nd

, 3rd

, 4th

EXPIRY Note 3

T3322 6s GMM-DEREG-INIT DETACH REQ sent DETACH ACCEPTreceived Retransmission of DETACHREQUEST

T3350 6s GMM-COMMON-PROC-INIT

ATTACH ACCEPTsent with P-TMSI and/or TMSI

RAU ACCEPT sent with P-TMSIand/or TMSI

P-TMSI REALLOC COMMANDsent

ATTACHCOMPLETEreceived

RAU COMPLETEreceived

P-TMSI REALLOCCOMPLETEreceived

Retransmission of the same messagetype, i.e. ATTACH ACCEPT, RAU ACCEPT or REALLOCCOMMAND

T3360 6s GMM-COMMON-PROC-INIT

AUTH AND CIPH REQUESTsent

AUTH AND CIPHRESPONSEreceived

Retransmission of AUTH AND CIPHREQUEST

T3370 6s GMM-COMMON-

PROC-INIT

IDENTITY REQUEST sent IDENTITYRESPONSE

received

Retransmission of IDENTITY

REQUEST

GSM 04.08: GPRS Mobility management timers - network side

GSM 04.08: GPRS Mobility management timers - MS side




GPRS Detach Procedure

MS Network

DETACH REQUESTStart T3321

DETACH ACCEPTStop T3321

or at MS power switch off

DETACH RE UEST

MS initiated GPRS detach procedure




GPRS Detach Procedure(Cont.)

MS Network

DETACH REQUEST Start T3322

DETACH ACCEPTStop T3322

SGSN initiated GPRS detach procedure




PDP Procedure

Packet Data Protocol(PDP):• PDP context - Procedure that allows an MS to

transfer data.

• PDP Address – Network layer address(IP version 4,

IP version 6).

• Each PDP address – Described by an individual PDP

context in the MS/SGSN/GGSN.

• There are two PDP states:

• Inactive State.

• Active State.




INACTIVE State:

• No routing or mapping information to process PDUs

•

No data can be transferred ACTIVE State:

• MM state of subscriber is STANDBY or READY

• Moves to INACTIVE when MM state changes to IDLE

PDP States

ACTIVE

INACTIVE

Deactivate PDP Context

or

MM state change to IDLE Activate PDP Context




PDP Context Activation,

Modification and DeactivationA MS can initiate those functions at any time

A GGSN may request the PDP context activation

and initiate the PDP context deactivation

Static and Dynamic PDP Addresses:

• Static address : The PLMN operator assigns a PDP

address permanently to the MS

• Dynamic address : The PLMN operator assigns a

PDP address to the MS when a PDP context isactivated




MS-PDP Context Activation

Procedure

MS GGSNSGSN

1.Activate PDP Context Request

3.Create PDP Context Request

3.Create PDP Context Response

4.Activate PDP Context Accept

2.Security Functions




GGSN-PDP Context Activation

ProcedureMS GGSNSGSN

2.Send Routing Info for GPRS

3.PDU Notification Request

4.Request PDP Context Activation

HLR1.PDP PDU

2.Send Routing Info for GPRS Ack

3.PDU Notification Response

5.PDP Context Activation Procedure




PDP Context Modification

Procedure

MS GGSNSGSN

1.Update PDP Context Request

3.Modify PDP Context Request

2.Update PDP Context Response

4.Modify PDP Context Accept




MS-PDP Context Deactivation

Procedure

MS GGSNSGSN

1.Deactivate PDP Context Request

3.Delete PDP Context Request

3.Delete PDP Context Response

4.Deactivate PDP Context Accept

2.Security Functions




GGSN-PDP Context

Deactivation Procedure

MS GGSNSGSN

1.Delete PDP Context Request

2.Deactivate PDP Context Request

3.Delete PDP Context Response

2.Deactivate PDP Context Accept




GPRS Tunnelling Protocol

GPRS Tunnelling Protocol(GTP) - Allows multi-protocol packets to be tunnelled through the

GPRS Backbone between GSNs

Two modes of operation for information transfer

are supported:• Unacknowledged Mode – UDP/IP

• Acknowledged Mode – TCP/IP

Uses a tunnelling mechanism to provide services

for carrying PDUs over an IP or X.25 networks



GTP Signalling Messages

Path management messages:• Echo Request

• Echo Reply

Tunnel management messages:

• Create PDP Context Request (SGSN to GGSN)• Create PDP Context Response (GGSN to GGSN)

• Update PDP Context Request / Response

• Delete PDP Context Request / Response

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