Wireless Networks - CS718 Power Point Slides Lecture 17
Transcript of 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
General Packet Radio Service in GSM, Jian Cai and David J. Goodman, Rutgers University,
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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General Packet Radio Service in GSM, Jian Cai and David J. Goodman, Rutgers University,
IEEE Communications Magazine,O
ct 199
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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