GPRS ArchitectureGPRS Architecture

BSS Rao GSM FacultyBSS Rao GSM Faculty

NEs Involved in Data callNEs Involved in Data call MSMS BTSBTS BSCBSC PCUSNPCUSN SGSNSGSN GGSNGGSN CGFCGF

GPRS ArchitectureGPRS Architecture

Mobile StationMobile Station GPRS MS includes two components:GPRS MS includes two components:

MT (Mobile Terminal). Typically a handset MT (Mobile Terminal). Typically a handset used to access the radio interface.used to access the radio interface.

TE (Terminal Equipment). Typically a laptop TE (Terminal Equipment). Typically a laptop or a Personal Digital Assistant (PDA).or a Personal Digital Assistant (PDA).

Could be one unit combing the Could be one unit combing the functionalities of a MT and a TE.functionalities of a MT and a TE.

PCUSN(Packet control PCUSN(Packet control unit support Node)unit support Node)

The PCU The PCU separatesseparates the circuit switched the circuit switched and packet switched traffic from the user and packet switched traffic from the user and sends them to the GSM and GPRS and sends them to the GSM and GPRS networks respectively.networks respectively.

PCUSN is introduced as separate PCUSN is introduced as separate element in BSS to introduce the function element in BSS to introduce the function of PCUof PCU

SGSNSGSNDNS

PCUSN

GGSN

MS

Routing Resolution

Gr

Mob ManagementBilling RecordsGa

GnGTP Tunneling

Ciphering &

Compressio

n

GbFram

e rela

y

LICP

Location

Services

LIG

GMLCCGF

HLR

SGSN

SGSNSGSN SGSN is hosted on the Passport

platform.

SGSN performs: Mobility management, routes packet data, authentication, encryption, compression

GGSN (Gateway GPRS GGSN (Gateway GPRS Support Node)Support Node)

A packet processing node in the wireless A packet processing node in the wireless packet networkpacket network

it serves as the boundary between the it serves as the boundary between the wireless network and other public or private wireless network and other public or private networks.networks.

Remote Authentication Remote Authentication Dial-In User Service Dial-In User Service (RADIUS) Functions(RADIUS) Functions

FrameRelay

Network

IP Backbone

MS

Is this alegitimate user?

RADIUS server

SGSNSGSN

GGSNGGSN

Log-in, Password

Function of RADIUS Function of RADIUS ServerServer

The authentication verifies that the user The authentication verifies that the user is a legitimate user by means of a is a legitimate user by means of a username and a password. This can be username and a password. This can be done by using an external done by using an external RADIUSRADIUS server.server.

DHCP( DHCP( Dynamic Host Dynamic Host Configuration Protocol )Configuration Protocol )

.. When a subscriber joins the network (upon When a subscriber joins the network (upon

activation):activation): The network sends a request for a temporary IP The network sends a request for a temporary IP

address to the DHCP server for a client.address to the DHCP server for a client. The DHCP server assigns host configuration The DHCP server assigns host configuration

information to this client from the pool of information to this client from the pool of dynamic addresses. It assigns dynamic IP dynamic addresses. It assigns dynamic IP addresses to networked devices as needed, and, addresses to networked devices as needed, and, by doing this, reduces the administrative burden by doing this, reduces the administrative burden of manually configuring computers for network of manually configuring computers for network use.use.

DHCP FunctionDHCP Function

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

) End

use

r nee

ds IP

add

ress

(3) G

ive

the

end

user

this

one

:13

6.14

7.10

2.26

CGFCGF The billing is always sent to the primary CGF The billing is always sent to the primary CGF

server if possible; the secondary is used only if server if possible; the secondary is used only if the primary cannot be reached.the primary cannot be reached.

The CGF is composed of three following The CGF is composed of three following entities:entities: Collection CartridgeCollection Cartridge Aggregation ProcessorAggregation Processor Distribution CartridgeDistribution Cartridge

Collection CartridgeCollection Cartridge Collects billing records from the GPRS nodes Collects billing records from the GPRS nodes

using GTP’. using GTP’. Aggregates several billing records produced Aggregates several billing records produced

during a PDP session into a single GPRS during a PDP session into a single GPRS accounting record. accounting record.

Note that billing records coming from Note that billing records coming from different Collectors cannot be aggregated different Collectors cannot be aggregated (two Collectors are seen as two different (two Collectors are seen as two different billing stream by an Aggregator)billing stream by an Aggregator)..

Aggregation ProcessorAggregation Processor Aggregates several billing records Aggregates several billing records

produced during a PDP session into a produced during a PDP session into a single GPRS accounting record. single GPRS accounting record.

Note that billing records coming from Note that billing records coming from different Collectors cannot be different Collectors cannot be aggregated (two Collectors are seen aggregated (two Collectors are seen as two different billing stream by an as two different billing stream by an AggregatorAggregator

Distribution CartridgeDistribution Cartridge

Provides access to the GPRS accounting Provides access to the GPRS accounting records by the customer Billing System. The records by the customer Billing System. The available interfaces are FTP of ASCII or ASN.1 available interfaces are FTP of ASCII or ASN.1 files. The Billing Center may request the files. The Billing Center may request the records, or the Distribution Cartridge may set records, or the Distribution Cartridge may set to “push” the records to the Center without to “push” the records to the Center without requestrequest..

(CGF) Functions(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

SMSC FunctionSMSC Function

• • SGSN sends SMS messages over Gd’ to SIG.•The SIG then sends this over SS7 to the SMSC

.

•

SMSCGd (SS7)

Gd’ (IP)

SIG

SGSN

Nortel Nortel ImplementationImplementation

SGSN of other PLMN

PSPDN

A

PSTN/ISDN

Agprs

Gs

Gn

GGSN

Gb

Ater

BTS

GpBSC

TCU

Gi

SGSNPCUSNGa

GaCGF

MSC-VLR

Gr

GeSMSC

GdLEA

LiG

Lh

HLR External LCSClients

GMLCLg

Le

SIG

SCP

InterfacesInterfaces GaGa - between SGSN or GGSN and a - between SGSN or GGSN and a

CGF CGF GbGb - between PCUSN and SGSN - between PCUSN and SGSN GrGr - between SGSN and HLR - between SGSN and HLR extension of MAP.extension of MAP. GeGe - between SGSN and SCP- between SGSN and SCP

InterfacesInterfaces GnGn - between SGSN and GGSN using GTP - between SGSN and GGSN using GTP

protocol (tunnel).protocol (tunnel). GiGi - between GGSN and PDNs (Public Data - between GGSN and PDNs (Public Data

Networks - IP and X.25).Networks - IP and X.25). GsGs - between SGSN and MSC/VLR (via SIG), for - between SGSN and MSC/VLR (via SIG), for

some simultaneous GPRS andsome simultaneous GPRS and GSM operation (same as BSSMAP but optional).GSM operation (same as BSSMAP but optional).

GdGd - between SGSN and SMS-C (via SIG) to - between SGSN and SMS-C (via SIG) to deliver SMS messages via GPRSdeliver SMS messages via GPRS (same as MAP).(same as MAP).

InterfacesInterfaces LgLg - between GMLC (- between GMLC (Gateway Mobile Gateway Mobile

Location Center) and SIGLocation Center) and SIG LeLe - between GMLC and LCS (Location - between GMLC and LCS (Location

Services) clientsServices) clients LhLh - between GMLC and HLR- between GMLC and HLR

GPRS WorkingGPRS Working When a user begins on GPRS service,typically When a user begins on GPRS service,typically

it will run automatically scan for local GPRS it will run automatically scan for local GPRS channelchannel

If an appropriate channel is detected, the If an appropriate channel is detected, the device will attempt to attach to the networkdevice will attempt to attach to the network

SGSN receives the attach request,fetches the SGSN receives the attach request,fetches the subscriber profile info. From the HLR and subscriber profile info. From the HLR and authenticated userauthenticated user

GPRS Working GPRS Working SGSN uses the profile info. Including SGSN uses the profile info. Including

Access point name (which identifies the Access point name (which identifies the network and operator) to determine network and operator) to determine which GGSN to route towhich GGSN to route to

The selected GGSN perform RADIUS The selected GGSN perform RADIUS authentication and allocate dynamic IP authentication and allocate dynamic IP address before setting up the connection address before setting up the connection to outside networksto outside networks

GPRS workingGPRS working This process is called the “ Packet data This process is called the “ Packet data

profile context activation”.profile context activation”. When the mobile device is powered off or When the mobile device is powered off or

moved out of GPRS coverage area, moved out of GPRS coverage area, PDP context is deactivated and the PDP context is deactivated and the device is detached from the networkdevice is detached from the network

GPRS Attach function

Authenticate the mobile Generate the ciphering key Enable the ciphering Allocate temporary identity (TLLI) Copy subscriber profile from HLR to

SGSN

After GPRS AttachmentAfter GPRS Attachment The location of the mobile is tracked Communication between MS and SGSN is

secured Charging information is collected SGSN knows what the subscriber is allowed

to do HLR knows the location of the MS in

accuracy of SGSN

GPRS DetachmentGPRS Detachment MS initiated Detachment:

Network Initiated Detachment

MS Initiated DetachmentMS Initiated Detachment

Network Initiated Network Initiated DetachmentDetachment