wireless networks - cs718 power point slides lecture 17

8/3/2019 Wireless Networks - CS718 Power Point Slides Lecture 17

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Wireless Networks

Lecture 17

GPRS: General Packet Radio Service (Part I)

Dr. Ghalib A. Shah


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Outlines

Review of last lecture

Identifiers in GSM Network and Call Routing

Introduction to GPRS

GPRS Architecture

Registration and Session Management

Routing Scenario in GPRS

Channels Classification


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Last Lecture

GSM Introduction

GSM System Architecture

GSM Network Areas

Specifications

Subscriber Services dual-tone multifrequency (DTMF)

facsimile group III

short message services

cell broadcast

Voice and fax mail

Mobility

Identifiers in GSM Network


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Identifiers in the GSM Network

GSM uses several identifiers for

the routing of calls,

identifying subscribers (e.g. for charging),

locating the HLR, identifying equipment, etc.

International Mobile Subscriber Identity (IMSI) It is embedded on the SIM card and is used to identify a

subscriber.

The IMSI is also contained in the subscription data in the HLR.


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International Mobile Equipment Identifier Each ME has a unique IMEI which is hard-coded in

the ME and cannot be modified.

(IMEI) is used to identify the ME.

Mobile Station Roaming Number (MSRN) is used in the GSM network for routing a

call to a MS.

The MSRN is allocated to a subscriber during MT

call handling and is released when the call to thatsubscriber is established.

Each MSC in a PLMN has a (limited) range ofMSRNs allocated to it.


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Mobile Station Integrated Services Digital Network

Number (MSISDN Number)

The MSISDN is used to identify the subscriber when, among

other things, establishing a call to that subscriber or sending an

SMS to that subscriber. The MSISDN is not stored on the subscribers SIM card and is

normally not available in the MS.

The MSISDN is provisioned in the HLR, as part of the

subscribers profile, and is sent to MSC during registration.


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Call Routing in GSM

Fixed

Subscriber

PSTN/ISDN

exchange

Gateway

MSC

HLR PSTN/ISDN

exchange

MSC/VLR MS

MSISDN

MSISDN

MSISDN

IMSIMSRN

MSRN

MSRN

SS SS


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General Packet Radio Service in GSM, Jian Cai and David J. Goodman, Rutgers University,

IEEE Communications Magazine,Oct 1997


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GPRS

GPRS is an enhancement over the GSM and

adds some nodes in the network to provide the

packet switched services. These network

nodes are called GSNs (GPRS Support Nodes)and are responsible for the routing and delivery

of the data packets to and from the MS and

external packet data networks (PDN).


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Introduction to GPRS

Goals of GPRS: Efficient bandwidth usage for bursty data traffic (e.g.

Internet)

Higher data rates

New charging models

Initially specified by ETSI

A lot of releases (R97, R98, R99, R4 etc.)

Specifications handed over to 3GPP

A lot of specifications considered in thisoverview: Release 5 (Ganz) / 6 (most recent TS at 3GPP)


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GPRS Release 5/6

Two modes determined by generation of core

network:

2G core => A/Gb

3G core => Iu Iu interface added in rel. 5 to align with UMTS


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GERAN Reference Architecture

GSM/UMTSCore Network

GERAN

Gb

A

Iu

MSUm

Iur-g

BSC

BTS

BTS

BSS

BSS

MS

Iur-g

UTRAN

RNC

3GPP TS 43.051 (Release 6)


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GPRS Architecture


IEEE Communications Magazine,Oct 1997

c


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A/Gb mode

Class A: MS can operate simultaneous packet

switched and circuit switched services

Class B: MS can operate either one at one time

Most common for handsets today Class C: MS can operate only packet switched

services

E.g. expansion cards for laptops


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Iu mode

CS/PS mode: Same as Class A in A/Gb mode

PS mode: MS can only operate packet

switched services

CS mode: MS can only operate circuit switchedservices


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Service Types

Point-to-Point

Internet access by user

Point-to-Multipoint

Delivery of information (e.g. news) to multiplelocations or interactive conference applications


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GPRS BSS

A software upgrade is required in the existingBase Transceiver Site (BTS).

The Base Station Controller (BSC) alsorequires a software upgrade, and theinstallation of a new piece of hardware called apacket control unit (PCU).

The PCU directs the data traffic to the GPRSnetwork and can be a separate hardware

element associated with BSC. The PCU provides a physical and logical data

interface out of BSS for packet data traffic.


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Registration of a Mobile Node

A mobile station must register itself with GPRS network.

GPRS attach

The device sends message to the new SGSN containing the

last assigned Temporary Mobile Subscriber Id (TMSI), location

area information, etc. The new SGSN queries the old SGSN for the identity of this

mobile device.

Then the new SGSN requests more information from the

mobile device to authenticate itself against the new SGSN

GPRS detach GPRS detach can be initiated by the MS or the network.


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Session Management

After Successful attach, when it wishes to begin a packetdata, it must activate Packet Data Protocol (PDP)address.This address is unique only for a particular session. Itconsists of,

PDP type

PDP address assigned to MS Requested QoS

Once PDP Context is activated, a two-way tunnel is establishedbetween the device current SGSN and the corresponding GGSN.

GGSN hides the mobility from onward

PDP-Address allocation:

Static:Assigned by network operator of Users home PLMN.

Dynamic:Assigned by Corresponding GGSN.


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PDP Context Activation

MS SGSN GGSN

Activate PDP Context Request

Security Functions

Activate PDP Context Accept

Create PDP Context Request

Create PDP Context Response

PDP type,PDP Address

QoS Requested,Access Point,

PDP type,PDP AddressQoS Negotiated,Access Point,

PDP type, QoS Negotiated,PDP type,PDP AddressQoS Negotiated,


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IEEE Communications Magazine,O

ct 199

7

c


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Physical Channels

Defined by timeslot (0-7) and radio frequency

channel

Shared Basic Physical Sub Channel

Shared among several users (up to 8) Dedicated Basic Physical Sub Channel

One user


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Physical Channels

Packet Data Channel (PDCH)

Dedicated to packet data traffic from logical

channels (next slide)

Control

User data


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Logical Channels

wireless networks - cs718 power point slides lecture 17

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