GPRS OverviewIUP STRI Master 1ère année09/12/04

Valérie Floch

2

Agenda

• GPRS vs GSM for Data transmission

• System architecture

• Functions of the GPRS Elements

• Main GPRS Procedures

• MS-SGSN interface

• PCUSN-SGSN Interface (Gb)

• SGSN-GGSN Interface (Gn)

• GGSN-PDN Interface (Gi)

3

General Packet Radio Service (GPRS) -Background• General Packet Radio Service (GPRS) is an extension of the popular GSM

mobile standard that offers packet data to a mobile user. Before GPRS, data service on a GSM network was generally limited to 9.6 kilobits per second.

• With GPRS the theoretical maximum speed is 171.2 kilobits per second however there are no terminals that support these speeds today. The realistic speeds are more in line with dialup modem access.

• Apart from speed GPRS offers significant advantages to the network operator and the end user.

• GSM Circuit switch data utilized a full rate voice channel (Timeslot) on the air interface for the entire duration of the data connection whether or not data is being transferred. These connections are normally billed according to airtime.

• GPRS uses virtual connections for multiple users. Scarce radio resources are only allocated to a mobile if there is data waiting to be sent or received. As a result GPRS connections can be left ‘always on’ and are normally billed by data volume rather than time.

4

GPRS is an IP network

FrameRelay

GTP

Application

IP / X.25

SNDCP

LLC

RLC

MAC

GSM RF

SNDCP

LLC

BSSGP

L1bis

RLC

MAC

GSM RF

BSSGP

L1bis

LLC Relay

L2

L1

IP

L2

L1

IP

GTP

IP / X.25

Um Gn GiMS BSS SGSN GGSN

UDP /TCP

UDP /TCP

Gb

FrameRelay

Application part

Packet layer

NSAPI

Application

TFI TLLI

TIDSAPI

5

GPRS network overlaid on GSM network

Three new elements added to existing GSM network – PCU, SGSN, GGSN.

BSS: Base Station system

PCU: Packet Control Unit

SGSN: Serving GPRS Support Node

GGSN: Gateway GPRS Support Node

6

GPRS Packet Data Service

In GPRS some timeslots are dedicated to providing packet data service. The Packet Control Unit (PCU) controls the fair allocation of GPRS radio resources in real-time. If there are multiple users in the cell they can share different data frames on the same timeslot. This arrangement works great with bursty data like web browsing. Data resources on the uplink and downlink are allocated independently. Throughput for a user depends on the number of GPRS timeslots and the amount of resource requested.

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Mobile Network

(GPRS)

RadioRadio

TS 2TS 2

TS 1TS 1

TS 3TS 3

TS 4TS 4TS 5TS 5

TS 4TS 4 TS 5TS 5

7

Techniques used to improve throughput

• Multislots terminals

• User data’s security decrease

• More efficient spectrum modulations: — 4 Coding Schemes defined in GPRS

– CS-1: best data’s security: 9.05 Kbit/s– CS-2: 13.4 Kbit/s– CS-3: 15.6 Kbit/s– CS-4: 21.4 Kbit/s

8

GPRS Terminals

• The number of timeslots a GPRS mobile can use when sending (uplink) or receiving (downlink) is communicated to the network in the form of a Multislot class.

• Classes exist all the way to 8 + 8 (Class 29) but these require the handsets to send and receive at the same time. Currently there are no mobiles that can do this.

• 1 TS = 21.4 Kbit/s in Coding Scheme-4

54412

53411

52410

5239

5148

4337

4236

4225

4134

3223

3122

2111

Simultaneous Active Slots

Uplink Slots Downlink Slots Multislot Class

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Mobile Identity – International Mobile Subscriber IdentityInternal number that identifies the subscriber to the GSM network. This

to the subscriber and is no longer than 15 digits.uniquenumber is

•MCC: Mobile Country Code (3 digits)•MNC: Mobile Network Code (2 or 3 digits)•MSIN: Mobile Subscriber Identification Number

The IMSI contains information about the network it belongs to and a unique identity in the network.

•The IMSI is stored in the SIM card.

NOTE : THIS IS NOT THE SUBSCRIBER’S PHONE NUMBER (MSISDN)

10

Possible GPRS Applications

• Personal Messaging: e-mail, schedule update

• Mobile office: internet e-mail, file transfer, database access

• E-Commerce: interactive shopping, ticket sales, interactive banking and gambling

• On-line information access: news, web browsing, directory service, yellow pages, traffic information, train/plane time table, stock prices, real estate information

• Telemetry: simple messaging ( remote monitoring and reporting ofmetering devices such as vending machines, bank teller machines,taxis)

Section 1:System Architecture

12

Network architecture

PSPDN

A

PSTN/ISDN

Agprs

Gr

Gs

Gc

Gn

GGSN

Gb

Ater

BTSSMSC

Gd

Gp

SGSN ofother PLMN

HLREIR

Gf

BSC

TCU

Gi

SGSNPCU

GaGa

CGF

MSC-VLR

13

Backbones Used

Frame Relay Network

PCUs

GbGbBSCs

BSCs

IntranetsSGSNs

Gi

Gi

Gn

Gn

Gn

Gn

Gn

GGSNs

IP BackboneGn

InternetSS7 Network

Existing GSM

Components

SGSNs

Section 2:Functions of the GPRS Elements

15

GPRS impact on BSS

PCU: Packet Control UnitPCU provides interworking function between GPRS and BSS.

PCU can be located in the BTS, the BSC or the SGSN

Proprietary Interface

GPRSnetwork

NSS

PCU

BTS

Abis

Gb

BSC

16

Packet Control Unit (PCU) functions

BSC

RLC/MAC Block Management

Gbasynchronous

BSSGP Flow ControlFrame Relay Links

synchronous

PCU

MS

SGSN

The main function of the PCU is to provide the interworking function between two interfaces

•Packetized radio interface Agrs •Packet network interface Gb

17

Signaling Gateway Support Node (SGSN) functions

DNS

PCU

GGSN

MS

Routing Resolution

Gr

Mobility ManagementBilling RecordsGa

GnGTP Tunneling

Ciphering &

Compression

GbFram

e rela

y

LICP

Location

Services

LiG

GMLCCGF

HLR

SGSN

18

Domain Name Server (DNS) Functions

Internet

DNS

End user enters the URL:http://www.google.com

www.google.com(136.147.68.68)

(1) What is the IP address of

www.google.com?

(2) 136.147.68.68(3) 1

36.14

7.68

.68

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Remote Authentication Dial-In User Service (RADIUS) Functions

FrameRelay

Network

IP Backbone

MS

Is this alegitimate user?

RADIUS server

SGSNSGSN

GGSNGGSN

Log-in, Password

Authenticates remote users and performs accounting functions

20

Dynamic Host Configuration Protocol (DHCP) Functions

GPRS Network

(1) I need an IP address

(4) Use this address:

136.147.102.26

SGSN

Internet

GGSN

This will be my address:136.147.102.26

IP Backbone

DHCP

(2)E

nd u

ser n

eeds

IP a

ddre

ss

(3) G

ive

the

end

user

this

one

:13

6.14

7.10

2.26

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Charging Gateway Function (CGF) Functions

Corenetwork

SGSN

Aggregator&

Distributor

CGF

Billing FilesTransfer

Billing Center

Get billing files

G-CDR

GGSN

S-CDR and M-CDR

Collector

GTP’

GTP

Billing Records:• PDP session duration• GPRS QoS Negotiated• Input Octets• Output Octets• Hot Billing

The CGF is responsible for aggregating and sorting billing records and then translating them into a format that is useable by the downstream billing system.

22

Home Location Register (HLR) Functions• SGSN sends MAP messages over Gr to the HLR.

• The HLR is queried by the SGSN to verify subscription to the network and to retrieve the mobile’s subscription records (GPRS services, APN,

QOS etc.).

• The HLR keeps track of what SGSN the mobile is currently attached to.

Visiting Location Register (VLR) Functions• SGSN sends BSSAP+ messages over Gs to the VLR.

• The MSC/VLR notified by the SGSN when a mobile is attached for circuitservice.

• The VLR keeps track of what SGSN the mobile is currently residing withinand can use this information to page the mobile for circuit services.

23

Signaling Control Point (SCP) Functions

• SGSN sends CAMEL messages over Ge to SCP.

• The SCP is notified by the SGSN when a mobile is activate and requires CAMEL services.

• The SCP is used for pre-paid service. It keeps track of a resource and letsthe SGSN know when no more resources are available. The common example is to limit the amount of data traffic for a given mobile.

24

Short Message Service Center (SMSC)

• SGSN sends SMS messages over Gd to SMSC.

•For SMS, the SGSN sends SMs to the SMSC for a mobile initiated SMS.

• For SMS, the SMSC sends SMs to the SGSN for a mobile terminated SMS.

Gateway Mobile Location Center (GMLC) (R4)

• SGSN sends Location Service Messages over the Lg to the GMLC.

• The SGSN manages location requests from the GMLC, and tells the GMLCthe location of the MS.

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Lawful Intercept (LI) System Architecture

Allows Law Enforcement Agencies (LEAs) the ability to monitor target subscribersLiG (Lawful Intercept Gateway) [LIGD-LiG Delivery Function, LIGA-LiG Administration Function]; CF-Collection Function)

LEAs

LiG

GGSN

Gn

GbFuture

Development

SGSN

SGSN

Other PLM

IP Network

Router w IPSEC

LICP

LIGA

LIGD CF

CF

26

GPRS Gateway Support Node (GGSN) functions

DHCP

GGSN

Intranet

Intranet Switch

Gn

GTP Tunneling

SGSN

ChargingGatewayFunction

VPNTunneling

Gi

IP address Management

Billing Records

Ga

Authentication Radius

Section 3:Main GPRS Procedures

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Functional MM State Model

of SGSN

Mobility management

READY

IDLE

STANDBY

GPRS Attach

GPRS Detachor

Cancel Location

PDU reception

READY timer expiryorForce to StandbyorAbnormal RLC condition

Implicit Detachor

Cancel Location

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BSS SGSN GGSN HLR

Attach Request

Identity Request

GPRS Auth Request

Identity ResponseSend Auth Info

SAI Ack

GPRS Auth Response

GPRS Attach Procedure (normal) 1/2

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Attach Accept

Attach Complete

ISD Ack

UGL Ack

Update GPRS Location

Insert Subsciber Data

BSS SGSN GGSN HLR

GPRS Attach Procedure (normal) 2/2

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Packet Data Protocol Context ActivationMS Initiated

BSS SGSN GGSN HLR

Activate PDP Context Request

Security Functions

Activate PDP Context Response

Create PDPContext Resp

Create PDPContext Req

DNS DHCP

32

Packet Data Protocol Context Activation

@ MS

Mobile Subscribed

PDP contexts

PDP Type: IPAPN: SFR.com

PDP Type: IPAPN : Internet

PDP Type: X25APN: Transpac

10. @ MS PDP context

activation accept1. Activate PDP Context APN

= SFR.com

ISP

IntranetSFR.com

7. @ M

S6. @

: “ _

”

GGSN X

DNS

DHCP

8. Start billing record

CGF

5. Tunnel Creation

GGSN Y

4. Create PDP Context Req

9. Create PDP Context

Accept (@ MS)

@ MS@ SGSN

SGSN@GGSN X

@ MS

3. @ GGSN X

2. SFR.com.MNC.MCC.gprs

APN Operator Id

In this diagram, @ represents “the IP address of”

33

PDP Context DeactivationMS Initiated

Deactivate PDP Context Request

Security Functions

Deactivate PDP Context Response

Delete PDPContext Resp

Delete PDPContext Req

BSS SGSN GGSN HLR

34

PDP Context DeactivationNetwork Initiated

Deactivate PDP Context Request

Deactivate PDP Context Response Delete PDPContext Resp

Delete PDPContext Req

BSS SGSN GGSN HLR

35

MS-Initiated Detach Procedure

Detach Accept

Detach Request

Delete PDPContext Request

Delete PDPContext Response

BSS SGSN GGSN HLR

36

SGSN-Initiated Detach Procedure

Detach RequestDelete PDP

Context Request

Delete PDPContext Response

Detach Accept

BSS SGSN GGSN HLR

37

BSS SGSN GGSN HLR MSC/VLR

Modify PDP Context Request

Modify PDP Context Response

Update PDPContext Response

Update PDPContext Request

SABM

UA

PDP Context Modification Sequence MS Initiated

38

PDP Context Modification Sequence SGSN Initiated

BSS SGSN GGSN HLR MSC/VLR

Modify PDP Context Request

Modify PDP Context Response

Update PDPContext Response

Update PDPContext Request

ISD Ack

Insert Subsciber Data

SABM

UA

39

Security functionsAuthentication

BSS SGSN HLR

Attach Request

GPRS Auth Request

Send Auth Info

SAI Ack

GPRS Auth Response

RAND

A3

(IMSI, unknown CKSN) Ki(IMSI)

(Triplets - RAND, SRES, Kc)(RAND)

A3

Ki

(MS calculated SRES)

RANDSGSN

calculatedSRES

=Yes

No ForbiddenSubscriber

Authentiicated Subscriber

40

Example: WEB Access

IDLE

READY

GPRS Attachment

MS

PDP ContextActivation

GGSN

WEBServer

Home Page Request

PCUSN

SGSN

Section 4:MS-SGSN interface

42

LLC main function is to provide a reliable logical link layer • Sequential order of delivery, flow control, and error detection &

recovery.• User data ciphering.• Acknowledged & unacknowledged data transfers.• Information transfer between SGSN and MS.

Logical Link Layer (LLC) Function And Service

Relay

SGSN

LLC

BSSGPNetworkService

L1

GMM SNDCP SMS

MS

LLC

RLC

MAC

GSMRF

GMM SNDCPSMS

BSS

BSSGPNetworkService

L1

RLCMAC

GSMRFUm Gb

43

GPRS Ciphering Environment

A8

Store Kc

MS SGSN

A8

Store Kc

Ki KiRAND

RAND

HLR

Ciphered LLC frames

KcKc

A5 A5

Inputs (IOV), Direction

44

The GMM/SM main function is to support the mobility and session management of users terminals by:

• Informing the network of the MS location.

• Providing user identity confidentiality.

• Managing data sessions

GPRS Mobility Management/Session Management Layer Function and Service

SGSN

LLC

BSSGP

NetworkServiceL1bis

GMM/SM

MS

LLC

RLC

MAC

GSMRF

GMM/SM

Relay

BSS

BSSGPNetworkService

L1bis

RLCMAC

GSMRFUm Gb

45

Mobility Management

SGSN XBSS ABTS 1

GPRS attach procedure Cell update

SGSN YBSS CBTS 4

Inter RA update

SGSN XBSS BBTS 3

Intra RA update

SGSN XBSS ABTS 2

46

Transmission Plane

FrameRelay

GTP

Application

IP / X.25

SNDCP

LLC

RLC

MAC

GSM RF

SNDCP

LLC

BSSGP

L1bis

RLC

MAC

GSM RF

BSSGP

L1bis

LLC Relay

L2

L1

IP

L2

L1

IP

GTP

IP / X.25

Um Gn GiMS BSS SGSN GGSN

UDP /TCP

UDP /TCP

Gb

FrameRelay

Application part

Packet layer

NSAPI

Application

TFI TLLI

TIDSAPI

• The Temporary Flow Identity (TFI) is the unique identification of a Temporary Block Flow (TBF) throughout the TBF life, used by the MS and the BTS/CCU function.

• The Network layer Service Access Point Identifier (NSAPI), allocated dynamically by the MS, at the PDP Context Activation, identifies a specific PDP type and PDP address pair.

• The Tunnel IDentity (TID) used by GTP, identifies a PDP context in the IP backbone (between SGSN and GGSN); TID consists of an IMSI and a NSAPI.

47

Subnetwork-Dependent Convergence Protocol (SNDCP) Layer: N-SAPIs

Signaling SMS

SNDCP

LLC

RLC or BSSGP

TLLI

SAPI

N-SAPI

E-businessFTP WEBE-mailApplication Layer

PDP contextTranspac

X.25

PDP context

Nortel.comIP-V4

PDP contextAOL.com

IP-V6

48

IP data

SNDCP: Compression and Segmentation

compressed IP data

IP header

SNDCP header

SNDCP header

SNDCP header

N_201

Compressed header

49

Bit 8 7 6 5 4 3 2 1

Oct 1 X F T M NSAPI

2 DCOMP PCOMP

3 Segment number N-PDU number

4 N-PDU number (continued)

... Data segment

N

Information Mapping on SNDCP Frames

Bit 8 7 6 5 4 3 2 1

Oct 1 X F T M NSAPI

2 DCOMP PCOMP

3 N-PDU Number- ack’ed mode

... Data segment

N

Number of segment in a N-PDU (0-15)

N-PDU numberunack’ed mode

(0-4095)

SN-Data PDU FormatSN-Unitdata PDU Format

Headercompression type

Data compression type

N-SAP Identity(5-15)

N-PDU numberack’ed mode

(0-255)

X – SpareF – First SegmentT – Type (data or unitdata)M – More (to come, segmentation)

Section 5:PCU-SGSN Interface (Gb)

51

Gb Interface

NS

BSSGP

Physical

NS

LLC GMM NM

BSSGP

Relay GMM NM

PhysicalGb

PCU SGSN

• Physical layer - Currently T1 or E1 PCM channellized transport • Network Service (NS) layer includes the layer-2 protocol Frame Relay

and some specific procedures for GPRS (e.g.. NS-Test).• Base Station Subsystem GPRS Protocol (BSSGP) mainly manages

buffers for flow control between PCU and SGSN. It provides services for the upper layers entities:

• Network Management (NM): a local entity that manage buffers and virtual circuits between the two nodes,

52

Network Service sublayers

NS Control Part

BSSGP

Physical

NS Sub-network Part NS Layer

Frame Relay

Independent from FR or ATM

53

Identifiers Managed by NS Layer

NS Control

Frame Relay

Network

Sub-Network

NS Layer

Physical Port

PCU A

PCU B

SGSN

NSVCI 3 NSVCI 7 NSVCI 4 NSVCI 8

NSEI 1

DLCI 41 DLCI 221 DLCI 51 DLCI 44

NSVCI 1 NSVCI 5 NSVCI 2 NSVCI 6

NSEI 0

DLCI 51 DLCI 32 DLCI 66 DLCI 124NSEI0

NSEI1

NSVCI 1NSVCI 2NSVCI 3NSVCI 4

NSVCI 5NSVCI 6NSVCI 7NSVCI 8

DLCI 31DLCI 88DLCI 68DLCI 77

DLCI 28DLCI 18DLCI 85DLCI 98

54

BSSGP Identifiers

NSE

LLC NMGMM

Buffers « buckets »

BSSGP

BVC 5BVC 4BVC 3BVC 2BVC 1

NSVCI

NS

One BVC defined per cell

BVC 6

55

PDU Transmission

USER DATA

TLLI

LLC

BSSGP

MS buffer

BVC buffer

BVCI = 1 BVCI = 2 BVCI = 1

TLLI

NSEI 0 NSEI 1

NSEI

BVCI

56

Flow Control

BSS/PCU SGSN

BVC Flow ControlIncludes: BVC Bmax, BVC R, Default MS Bmax, Default MS R

BVC Flow Control Ack

MS Flow ControlIncludes: MS Bmax, MS R

MS Flow Control Ack

The PCU can send BVC or MS flow control messages to the SGSN to change the characteristics of the buffers managed by BSSGP

The procedure aims at adapting data rate on radio interface (RLC/MAC protocol) to the GPRS network.

Section 6:SGSN-GGSN Interface (Gn)

58

GPRS Tunneling Protocol (GTP) – Gn/Gp

Frame Relay

NetworkService

BSSGP

LLC

SNDCP

SGSN

IP

UDP/TCP

GTP

UDP/TCP

GTP

IP

Gn

RelayI P

Relay

GGSN

Ethernet Ethernet

UDP/TCP

IPIP

GTP is the protocol used between GSN nodes, it allows multi-protocol packets to be tunneled through the GPRS backbone on Gn and between GSNs in different PLMNs at the Gp interface.

In the signaling plane, GTP specifies a tunnel control and management protocol which allows the SGSN to provide GPRS network access to the MS. Used to create, modify and delete tunnels. In the transmission plane, GTP uses a tunneling mechanism to provide a service for carrying user data packets

59

GPRS Tunneling Protocol (GTP)

SGSN 1IP Backbone

Gn

Other PLMN

SGSN B

Gp

GTP

GTP

GGSN

Gi PublicData

Network

SGSN 2

GTPGTP

GTPGnGn

Gp

Section 7:GGSN-PDN Interface (Gi)

61

Gi Interface as a Reference Point

GPRS network looks like any other IP network with the GGSN as a router. Network Configuration mode for connectivity based on

• Users’ Authentication and Authorization • Allocation of dynamic address belonging to the PLMN/Intranet/ISP

addressing space• End to End Encryption between MS and Intranet/ISP

Leads to two different access modes• Transparent Access to Internet/Intranet• Non-Transparent Access to Intranet or ISP

G i

IP

G G S N

G P R S B earer

IP

L 2

L 1

62

Access Point Name (APN)

• The APN used to identify the data session requested by the mobile.

• APN is received in Create PDP Context Request

APN determines: • mobile subscriber user authentication (transparent and non-

transparent)• the method of subscriber authentication (Radius details)• the method of IP address allocation (local pools vs. DHCP)• if subscription is required for the GTP session• GGSN accounting information Quality of Service • Wireless services ( tariff or WAP)• IP Services

• APN is associated with subscriber template.

63

Transparent Access to IntranetTransparent = Basic Internet Access

• MS given an address (Static/Dynamic) belonging to the operator addressing space• Normal GPRS MS authentication is done by network to validate the subscriber. GGSN need not do any user authentication/authorization process.

• No specific security protocol required between GGSN and Intranet because security is ensured between MS and Intranet using IP protocols e.g. IPSec for data security; PPP, PPTP, L2TP for user authentication

P P P o r L 2

G P R S b e a re r

M T

G P R S b e a re r

L 2

IP IP

G G S N

L 2

IP

In tra n e t P ro to c o l

In tra n e t

IP

In tra n e t P ro to c o l

P P P o r L 2

T E

Can be direct linkOr through internet

64

Transparent ModeDHCP

Intranet

VPN Tunnel Dial UpPrivate IP @ for MS

TunnelPublic

IP@ of MS

PublicIP

@ of CES

Private IP

@ of MS

PrivateIP @ of server Data

PDP Context Activation

Public IP @ for MS

Radius

ServerSGSN GGSN CES

65

Non-Transparent Access to Intranet or ISP

PPP/L2

PPP/L2

SM

SM

GTP

GTP

Phy. layer Phy. layer

Lower layers

Lower layers

Lower layers

Lower layers

Lower layers

IP

UDP

DHCP/ RADIUS

IP

UDP

DHCP/RADIUS

TE MT SGSN GGSN ISP

Lower layers

MS given an address belonging to Intranet/ISP address space. GGSN needs to communicate with RADIUS or DHCP belonging to Intranet/ISPGGSN deduces from APN

• Server to be used for Address Allocation and Authentication• Communication/security features (L2TP, IPSec) to dialog

with servers in Intranet

66

Non-Transparent

PCUSN SGSN CES

PDP Context Activation

PDP Context Activation AcceptPrivate IP @ for MS

Intranet

MS AuthenticationRadius Query

MS IP @ allocationDHCP Query

DHCP

Radius

ServerLeasedLine

Tunneling signaling

GGSN

67

Non-Transparent Non-tunneled Mode

PCUSN SGSN CES

PDP Context Activation

PDP Context Activation AcceptPrivate IP @ for MS

Intranet

MS AuthenticationRadius Query

MS IP @ allocationDHCP Query

LeasedLineGGSN

DHCP

Radius

Server

68

Enhanced Non-Transparent Mode

PCUSN SGSN

PDP Context ActivationPDP Context Activation Accept

Intranet

VPN tunnel Creation

L2TPPPP connection: authentication, IPCP

Private IP @ for MS

PDNGGSN RadiusCES

69

Future of GPRS - Enhanced Data rates for GSM Evolution (EDGE)• EDGE is a radio based high-speed mobile data standard. It allows

data transmission speeds of 384 Kbit/s to be achieved when all eight timeslots are used.

• In fact, EDGE was formerly called GSM384. This means a maximum bit rate of 84 Kbit/s per TDMA frame timeslot.

• EDGE was initially developed (by Ericsson) for mobile network operators who fail to win Universal Mobile Telephone System (UMTS) spectrum. EDGE gives incumbent GSM operators the opportunity to offer data services at speeds that are near to those available on UMTS networks.

• Upgrades to radio software, new EDGE transceivers and new mobileterminals are required to handle the new modulation scheme –8PSK.

A graceful upgrade from GPRS to EDGE is envisaged with reuse of the existing circuit and GPRS networks.

70

The Specifications List of various useful GPRS/UMTS specifications

Specification TITLE NOTE GSM 01.04 Abbreviations and acronyms22.003 Teleservices - used for SMS23.003 Numbering, addressing and identificationGSM 03.13 Discontinuous Reception (DRX)GSM 03.20 Security related network functions - 2G Auth, etc.33.102 3G Security23.040 SMS23.060 General Packet Radio Service - Your GPRS/UMTS bible24.008 Layer 3 Specs - GMM/SM25.413 UTRAN Iu Interface RANAP Signalling - RANAP messaging29.002 MAP GSM 09.60 GTP (Rel97) - see ver 7.3 and ver 7.629.060 GTP (3G)32.015 Charging and Billing24.011 PP-SMSGSM 08.16 Network Services (NS) - GPRS only (Gb)GSM 08.18 BSSGP - GPRS only (Gb)GSM 04.64 LLC - GPRS only (Gb)GSM 04.65 SNDCP - GPRS only (Gb)29.018 VLR23.107 QoS - Rel99->Rel97 QoS mapping, etc.