Gprs Gsm Packet Radio Service1691

8/13/2019 Gprs Gsm Packet Radio Service1691

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GPRS-1School of Information Technologies

GPRS: GSM Packet Radio Service

InternetGPRS


Data Services in GSM

Data transmission standardized with only 9.6 kbit/s

advanced coding allows 14.4 kbit/s

not enough for Internet and multimedia applications

HSCSD (High-Speed Circuit Switched Data)

mainly software update

bundling of several time-slots to get higherAIUR (Air Interface User Rate)(e.g., 57.6 kbit/s using 4 slots, 14.4 each)

advantage: ready to use, constant quality, simple

disadvantage: channels blocked for voice transmission

AIUR [kbit/s] TCH/F4.8 TCH/F9.6 TCH/F14.44.8 19.6 2 114.4 3 119.2 4 228.8 3 238.4 443.2 357.6 4


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GPRS: GSM Packet Radio Service

Packet-switched data over GSM

Interconnects to Internet

Strict separation between radio subsystem andnetwork subsystem

GPRS does not mandate changes to an installed

MSC base

InternetGPRS


GPRS Channels

1 to 8 radio interface slots can be allocated perTDMA frame

timeslots are shared by the active users

uplink and downlink slots are allocated separately

radio resources can be shared dynamically betweenspeech and data

4 Coding Schemes CS1, CS2, CS3, CS4 giving user data rates of approx. 6, 9, 10, 14 kbps per slot,

raw data rates 9.05, 13.4, 15.6, 21.4 kbps per slot


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GPRS Raw Data Rates (kbps)

171.2149.8128.410785.664.242.821.4CS-4

124.8109.293.67862.446.831.215.6CS-3

107.293.880.46753.640.226.813.4CS-2

72.463.3554.345.2536.227.1518.29.05CS-1

8 slots7 slots6 slots5 slots4 slots3 slots2 slots1 slotCodingscheme


GPRS Traffic

Supports various traffic classes, from intermittent and

bursty transfers, to occasional transfer of large

volumes of data

Four different QoS levels

Fast reservation to begin transmission of packets,typically 0.5 to 1.0 sec


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GPRS MSs

Three classes of MS

Class A MSClass A MS can operate GPRS and other GSMservices simultaneously

Class B MSClass B MS can monitor control channels for GPRSand other GSM services simultaneously, but can

operate only one set of services at a time Class C MSClass C MS can operate GPRS services only


GPRS

GGSNSGSNGTP

GGSN: Gateway GPRS Support Node

SGSN: Service GPRS Support Node

GTP: GPRS Tunneling Protocol

GPRS Architecture (GSM view)

BTS BSC MSC

VLR

PSTN

GSMInternet

HLR


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GPSR Architecture (data view)

MS BSS GGSNSGSN

MSC

Um

EIR

HLR/GR

VLR

PDN

Gb Gn Gi

SGSN

Gn


Serving GPRS Support Node (SGSN)

at same hierarchical level as MSC

delivers packets to MS within its service area

queries HLRs for profile data of GPRS subscribers detects new GPRS mobile stations in a given service

area

processes registration of new MSs and keeps a

record of their location


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Gateway GPRS Support Node (GGSN)

used as interface to external packet-switchednetworks

connected to SGSN via an IP-based GPRS backbone

network

maintains routing information that is necessary to

tunnel the Protocol Data Units (PDUs) to the SGSNsthat service particular mobile stations

one or more GGSNs may support multiple SGSNs


GPRS Network Enhancements

Base Station System (BSS):Base Station System (BSS):

must be enhanced to recognize and send user data to theSGSN that is serving the area

Home Location Register (HLR):Home Location Register (HLR):

must be enhanced to register GPRS user profiles andrespond to queries originating from SGSNs regarding theseprofiles

MSC/VLR:MSC/VLR:

optionally enhanced to coordinate GPRS and non-GPRS

e.g. combined location updates, SGSN paging for GSM calls


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GPRS Network Operations

For GPRS user, network is connectionless

HOWEVER, a network connection must beestablished for each transaction, and released once

the transaction is completed


Network Access

GPRS attachGPRS attach request from MS to begin a transaction

GPRS detachGPRS detach request from MS to end a transaction

Attach/detach requests are infrequent e.g. daily Location updates much more frequently


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Network Access...User RegistrationUser Registration associates the MS ID with the user

address

In home area, HLR is enhanced to reference GPRS data

Outside home area, dynamically allocated records are

references in VLRs

AuthenticationAuthentication - via GSM mobility management protocols

Call Admission ControlCall Admission Control determines n/w resources for

QoS


Routing and Data Transfer

Routing is performed by the GSNs on a hop-by-hopbasis, using the destination address

Routing tables are maintained by the GSNs using the

GTP layer Data may be

Forwarded

Tunneled

Compressed

Encrypted


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Mobility Management

Mobility Management used to track the MS

SGSNs communicate to update the user location

Logical link is established between the MS and theSGSN


From http://www.trillium.com/whats-new/wp_gprs.html

GPRS Protocol Architecture

apps.

IP/X.25

LLC

GTP

MAC

radio

MAC

radioFR

RLC BSSGP

IP/X.25

FR

Um Gb Gn

L1/L2 L1/L2

MS BSS SGSN GGSN

UDP/TCP

Gi

SNDCP

RLC BSSGP IP IP

LLC UDP/TCP

SNDCP GTP


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GPRS Network Protocols

SubSub--Network Dependent Convergence ProtocolNetwork Dependent Convergence Protocol(SNDCP):(SNDCP): maps a network-level protocol, such as IP or X.25, to the

underlying logical link control.

provides compression, segmentation and multiplexing ofnetwork-layer messages to a single virtual connection

Logical Link Control (LLC):Logical Link Control (LLC): a data link layer protocol for GPRS which functions similar

to Link Access Protocol - D (LAPD). This layer assures thereliable transfer of user data across a wireless network.


GPRS Network Protocols...

Base Station System GPRS Protocol (BSSGP):Base Station System GPRS Protocol (BSSGP):

BSSGP processes routing and quality of service (QoS)information for the BSS. BSSGP uses the Frame Relay

Q.922 core protocol as its transport mechanism.

GPRS Tunnel Protocol (GTP):GPRS Tunnel Protocol (GTP):

tunnels the protocol data units through the IP backbone byadding routing information.

GTP operates on top of TCP/UDP over IP


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GPRS Mobility Management (GMM):GPRS Mobility Management (GMM):

handles mobility issues such as roaming, authentication,and selection of encryption algorithms.

Network Service:Network Service:

manages the convergence sub-layer that operatesbetween BSSGP and the Frame Relay Q.922 Core by

mapping BSSGP's service requests to the appropriateFrame Relay services.



BSSAP+:BSSAP+:

protocol that manages paging for voice and dataconnections and optimizes paging for mobile subscribers

BSSAP+ is also responsible for location and routingupdates as well as mobile station alerting


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EDGE

(Enhanced Data rate for GSM Evolution)

Uses GSM/GPRS, but with higher-level modulation(8-PSK instead of GMSK)

Choice of 9 modulation schemes

Allows up to 48 kbps per timeslot,

384 kbps using 8 time slots


References

Christian Bettstetter, Hans-Jrg Vgel, and Jrg Eberspcher ,GSM Phase 2+ General Packet Radio Service GPRS: Architecture, Protocols and Air Interface,IEEE Communications Surveyshttp://www.comsoc.org/pubs/surveys, Third Quarter 1999, vol. 2 no. 3

A. K. Salkintzis,A survey of Mobile Data Networks,

IEEE Communications Surveyshttp://www.comsoc.org/pubs/surveys, Third Quarter 1999, vol. 2 no. 3

Trillium Digital Systems,Generalised Packet Radio Service (GPRS) White Paper, http://www.trillium.com/whats-new/wp_gprs.html

Hannu H. Kari ,General Packet Radio Service (GPRS), http://www.ee.oulu.fi/~fiat/gprs.html

Hannu H. Kari ,GPRS overview and links,http://www.cs.hut.fi/~hhk/GPRS/gprs_index.html

GPRS links:http://www.topology.org/gprs.html

EDGE:http://www.dataonsms.com/edge.htm

Gprs Gsm Packet Radio Service1691

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