1 GPRS_GRX Overview

8/2/2019 1 GPRS_GRX Overview

http://slidepdf.com/reader/full/1-gprsgrx-overview 1/18

18.03.2012 1

GPRS/GRX Training

GPRS/GRX Overview

• GSM vs. GPRS Network

• GPRS Roaming Scenarios



18.03.2012 2

Circuit Switched Networks vs. Packet Switched

PSTN

Internet

MSC

BTS BSC

SGSN GGSN

GPRSBackboneIP Network

GPRS Core

http://intra.comfone.com/Intranet/01_General/Cliparts/cliparts/handy.gif



18.03.2012 3

GSM System Architecture

GSM elements

• MSCperforms telephonyswitching functions ofCircuit Switched System

• VLR

• HLRGSM and GPRSsubscription data androuting information

• BSChandles transmission

and reception of Radiosignals

• BTS-interface to MS

BSCBTS

BTS

BSCBTS

BTS

ISDN, PSTN

Other PMNs

SMS-CHLRMSC/VLR

OSS

GPRS NetworkManagement

BGwR8






18.03.2012 4

GPRS System Architecture

GPRS elements

• PCUPacket ControlUnit

•SGSNServing GSN

• GGSNGateway GSN

• DNSDomain Name

Server

SMS-CHLRMSC/VLR

BTS

BTS

BSCPCU

BTS

BTS

BSC

PCU

IP

Network:•ISP

•Internet

Other PMNs

FRBackbone

SS7

IP

Backbone

SGSN

SGSN

GGSN

GGSN

NTP

GPRS NetworkManagement

DNS rootserver

BGwR8

PXM





18.03.2012 5

Call related vs. non call related SignallingThere is more and more SMS, MAP, CAP

HLRVLR

SGSN

G-MSC

PSTN

VLR

MSC

LE

TE

LE

BSC

BTS

BTS

MS

Location updating

M S R N p r o v i

d i n g

s e n d

r o u t i n

g i n

f o r m

a t i o

n

I n i t i a

l A d d r e s s

M e s s a

g eInitial Address Message

non-circuit related signalling

circuit related signalling

cicuit

Databases

Switches

SCP

GGSNGTP PDPcontext

DCN

G T P P D P c o n t e x t

ISP

GTP related signalling

O p t i o

n a l i n

t e r f a

c e



18.03.2012 6

MAP/CAP Procedures for GPRS

The relevant MAP procedures have beenextended to suit GPRS:

•

MAP GPRS IMSI attach procedure• MAP Location update procedures

• MAP GPRS detach procedures

• CAP CAMEL procedures


http://slidepdf.com/reader/full/1-gprsgrx-overview 7/1818.03.2012 7

GPRS SS7 Case Study

•

GPRS Location Update• GPRS Authentication


http://slidepdf.com/reader/full/1-gprsgrx-overview 8/1818.03.2012 8

Case Study GPRS Authentication and Attach

1. VSGSN (VLR) requests authentication from HLR (AuC) basedon IMSI

2. HLR sends authentication sets (n) – SRES, RAND, Kc - toVSGSN for authentication

(comp with SIM generated SRES)3. VSGSN sends Location Update to HLR

4. Since first LU HLR sends subscriber data

5. VSGSN acknowledges receipt of subscriber data

6. HLR acknowledges Location Update

-> GPRS device is in Attached mode

Visiting Net:41799x

TOGEWAnet

Home Net:4237x

Orange Li

Comfone

STP

CSP1I

VSGSN

GT: 41799901201 IP: 132.161.141.195

HLR

GT:423783820005365

HGGSN

1/2) Authentication

3/6) Location Update

4/5) Insert Subs Data

GRX

PDP Context Activation

Sig System 7

IP/GTP



18.03.2012 9

New Elements in GPRS System Architecture

GPRS elements:

• PCU: Packet Control Unit - separates circuit data and packet data fromeach other

• SGSN: Serving GPRS Support Node- forwards IP packets addressed to/from MS

- session / mobility Management- connections to HLR, MSC, BSC, SMS-C, GGSN

• GGSN: Gateway GPRS Support Node- Interface toward external IP Networks (ISP, Internet)- contains access functionality like routers for security purposes

•

DNS: Domain Name System- Repository of all APN and their respective IP Addresses- web.SwissGPRS.ch => 10.7.2.1



18.03.2012 10

GPRS Roaming will be of Importance from Start

•Most operators are currently implementing GPRS networks. Many alreadylaunched national.

• GPRS roaming is expected to be required from the beginning (similar toGSM roaming).

• Market Comparison:

–GSM NW: ca. 400 worldwide

– GPRS NW: currently ca. 150 NW mostly in Europe and Asia,ca. 120 NW have implemented GPRS Roaming

• IR Docs:

– IR.33 GPRS Roaming in general

– IR 34 Role of the GRX

– IR.35 IREG Testing



18.03.2012 11

Pre-Requisites for GSM/GPRS Roaming

• Billing link for transfer of TAP Files between thebilling systems of the PMNs

– TAP 3.2 required

CCITT# 7 A B

• Signalling link for SS7 Signalling between the PMNs

–

GSM test cases IR.24/27 – GPRS test cases IR.35

• Legal link for contractual Roaming Relationship

– New Roaming Relations: bilateral IRA with AA.12, AA.13, AA.14

– Existing Roaming Relations: AA.31 as addendum to IRA

• Data link for Data Transfer via GRX betweenthe PMNs

IP A B

EDI A B

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18.03.2012 12

A B

GPRS Roaming Interfaces

BG GRX 1 GRX 2 BG

BS BSDCHDCH

MSC MSCSS7

RD RDIRA

RD : Roaming DepartmentMSC : Mobile Switching CenterBS : Billing SystemBG : Border Gateway





18.03.2012 13

GPRS Roaming Agreements

• Existing Roaming Relations

– Negotiate Addendum AA.31 to existing IRA

• Non-existing Roaming Relations

– Negotiate IRA incl. GPRS Services (AA.12-14)



18.03.2012 14

GPRS Charging, yes but how?

Different GPRS charging models under discussions:

•

Volume• time: attach, PDP context active

• monthly flat fee

• APN



18.03.2012 15

VPMN vs. HPMN Routing

Two roaming routing scenarios were defined:

• ISP Roaming: direct routing within visited network (VSGSN-VGGSN)

• HPMN Roaming: routing via home network (VSGSN-HGGSN)



18.03.2012 18

Data Connections to all Roaming Partners required

n*(n-1)/2 dedicated links would be needed; with significantimpact on network complexity and maintenance costs.

A

B

C

D

EF

G



18.03.2012 19

GRXPeering

DNS.gprs

DNS DNS

GRXBG

GRXBG

GRX

BG

One Roaming Connection to one GRX Provider

• Comfone has peering agreements with all leading GRX providers

• Worldwide .gprs DNS administration

A

B

C

D

F

E

BGBG

BG

BG

BG

BG

BG

G

BG



18.03.2012 20

Two main MS Procedures

Before sending IP packets, the MS must perform two actions:

• MS attach

• PDP Context Activation

1 GPRS_GRX Overview

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