GPRS

byPrakshet ThapaMSD, Jawalakhel3G n GPRS SectionMob:9851144444

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Contents• Evolution of Wireless • Introduction of GPRS• GPRS Architecture

• SGSN, GGSN, BG, DNS, CG

• GPRS characteristics • GPRS data rate• Session management in GPRS• Location management in GPRS• Routine Area Code• Radio Channels in GPRS• GPRS Roaming and Billing• Application

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Cellular Evolution Timeline

Nepal TelecomMobile Service Directorate

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Evolution of WCDMA CN

GSM

GPRS Edge PS

CS

CDMA2000CDMA

2G 2.5G 2.75G 3G

3GPP

3GPP2

Organization

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What is GPRS•GPRS is the abbreviation of General Packet

Radio Service•GPRS provides end to end packet switch

service for user based on GSM•GPRS make the best use of existing GSM

network•GPRS provides highly efficient use of radio

resources•GPRS provides as high as 171.2Kbps

access rate

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What is PS• PS is the packet switch network in WCDMA core

network• PS provides end-to-end packet switch service for

users• PS has almost the same elements and network

structure with GPRS• PS can provides access for GPRS radio access

equipment and 2/3G hybrid network• WCDMA-PS provides as high as 2Mbps access

rate

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GPRS Network GMSC

ZXG10 GPRS System Structure

BSS

InternetX.25

ISDN

GPRS MS

TE

MSC

PCU

SGSN GGSN

GSNBackbone

Voice

Packet Data

CS service line

PS service line

GPRS Network

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RNC

Node B

TDM/ATM PSTN

IP

Iu-PS

Gn Gn

Gp

Gi

CG

Billing Center

Ga

HLR

MSC

GGSN

GMSC

Serving GPRS Support Node

Gateway GPRS Support Node

Inter-PLMN

Charging Gateway

BSCBTS

SGSN

Gb

Internet

PS Network

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Iu-CS

A

Gr Gc

GPRS Network Elements

GPRS Architecture is same as GSM except few hardware modifications :

GPRS includes GSNs SGSN : Serving GPRS Support

Node GGSN : Gateway GPRS Support

Node

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Interfaces• Gb – Connects BSC with SGSN

• Gn – SGSN – SGSN/GGSN (in the same network)

• Gp – SGSN –GGSN (in different networks)

• Gi – Connects PLMN with external PDNs

• Gr – To exchange User profile between HLR & SGSN

• Gs – To exchange Database between SGSN & MSC

• Gd – Interface between SMS & GPRS

• Gf – For equipment querying at registering time

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SGSN Function

•Perform mobility management for GPRS terminals (attach/detach, user authentication, ciphering, location management)

•Route packets between mobile terminals and the GGSN

▫Detect and Register new GPRS MS in its serving area

▫Its location register stores location info. & user profiles

•Charging information

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GGSN Function

•Routing Select, PDP PDU Transfer, Address Mapping

•Tunnel Capsulate and Transfer •Subscriber Data Management•Session Management•IP Address Management•Charging Information Select

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DNS Function

When activating PDP, APN is used to get the IP address of GGSN Get old SGSN IP address during the process of inter-SGSN routing area

update

SGSN GGSN(A)

MS

BSS

GPRS Core NetworkGPRS Core Network

ISP AISP A

ISP BISP B

Internet/IntranetGGSN(B)

DNS

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BC

GPRS Bore

TCP/IP

SGSN/GGSN SGSN/GGSN

CG

TCP/UDPGTP'

FTAM/FTPFTAM/FTP

CG OMM Server CG OMM Client CG OMM Client

CG Function

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CG Function

•CG implements the following functions:▫CDRs generated by GSNs collected in real

time▫Buffering the CDRs▫Preprocessing the CDRs, such as CDR

consolidation and filtering, deleting certain CDR fields, and modifying or adding some CDR fields.

▫Transferring the CDRs to the BC.

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SGSN GGSN

Backbone Network

S-SMT-CDRS-CDR M-CDRS-SMO-CDR G-CDR

CG CDRs

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BG Function

•BG implement these functions▫Security: IPSec and firewall ▫Routing protocol: BGP▫Billing protocol: negotiated by operators,

collect billing information•Usually based on router•Can be the same equipment as GGSN

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HLR/AUC Function

•Store and update GPRS user profile•User authentication•Processing the location/routing

information related to mobility management and route selection, such as▫Store and update user’s serving SGSN

number and address▫MS reachable or not flag

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MSC/VLR Function

•When Gs interface is installed, MSC/VLR can support:▫SGSN and MSC/VLR relationship

establishment and maintenance▫GPRS joint mobility management▫Joint IMSI/GPRS attach/detach▫Joint location area/routing area updating▫Circuit paging coordination function

Improve the radio resource utilization ratio

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GPRS characteristics•GPRS uses packet switched resource

allocation▫resources allocated only when data is to be sent/received

•Flexible channel allocation▫one to eight time slots

▫available resources shared by active users

▫up and down link channels reserved separately

▫GPRS and circuit switched GSM services can use same time slots alternatively

•Traffic characteristics suitable for GPRS▫Intermittent, bursty data transmissions

▫Frequent transmissions of small volumes of data

▫Infrequent transmission of larger volumes of data

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Air interface resources

0

2

4

6

8

10

12

14

16

1:00 PM 1:15 PM 1:30 PM 1:45 PM

TCH

An example of occupied TCH capacity by CS traffic during busy hour with n% blocking

0

2

4

6

8

10

12

14

16

3:00 6:00 9:00 12:00 15:00 18:00 21:00 0:00

TCH

Capacity occupied by CS traffic

FreeCapacityGPRS "steals" any TCH

capacity not used by CStraffic

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Statistical Multiplexing22

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GPRS Data Rates

Scheme Data Rate (kbps)

Note

CS-1 9.05 Best performance for low C/I values

CS-2 13.4 CS-2 and CS-3 have similar performance

CS-3 15.6 CS-2 and CS-3 have similar performance

CS-4 21.4 Needs high C/I values

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GPRS Terminals

•Class A – support simultaneous GPRS and GSM voice services with two channels

•Class B – support either GPRS and GSM voice services with simultaneous network attachment

•Class C – support only GPRS service

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 switched services

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APN information

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SESSION MANAGEMENT IN GPRS

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Attachment & Detachment Procedure

•GPRS attach- User is registered in SGSN, after authentication

check from HLR- SGSN assigns P-TMSI to MS

•GPRS detach- Disconnection of MS from GPRS network is called

GPRS detach- It can be initiated by MS or by network(SGSN or

HLR)

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Session Management

•Mobile Station applies for PDP address•For each session PDP context is created & it

contains PDP addressed assigned to MSAddress of GGSN that servers access point

to PDN

•With active PDP context MS able to send or receive data packets

•Allocation of PDP address can be static or dynamic

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PDP Context Activation30

LOCATION MANAGEMENT IN GPRS

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State Model of GPRS MS

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Location Management

Mobile station can be in 1 of the 3 states depending on traffic amount▫ Idle : MS is not using GPRS service

▫ Ready : Performing GPRS Attach, MS gets into READY State

▫ Standby : When MS does not send any packets for longer period of time,

Ready timer Expires

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Routing Area Update

•GSM Location Area(LA) is divided into several Routing Areas(RA)

•RA consists of several cells•SGSN is informed when MS moves to a new

RA•MS sends a “Routing Area Update Request”

to its assigned SGSN

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Routing Area Update35

Channels in GPRS

•Logical Channel▫Traffic Channels▫Signaling Channels (Control Channels)

•Physical Channels

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Logical ChannelsGroup Channel Function Direction

Packet data traffic channel

PDTCH Data traffic MS BSS

Packet broadcast control channel

PBCCH Broadcast control

MS BSS

PRACH Random access

MS BSS

PAGCH Access grant

MS BSS

PPCH Paging MS BSS

PNCH Notification MS BSS

PACCH Associated control

MS BSS

PTCCH Timing advance control

MS BSS

Packet common control channel (PCCCH)

Packet dedicated control channels

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Packet Data Channel(PDCH)

•Physical Channel for GPRS Traffic

•PDCH are taken from all channels available in the cell

•Depending on current traffic load and priority of service, the physical channel are allocated to either GPRS or GSM services.

•Physical channels not currently used by GSM can be allocated as PDCH to increase the QOS for GPRS

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BTS BSCSGSN

GGSN

Internet

VISITEDPLMN

HOMEPLMN

BG

BG

GGSN

Home Operator

Visited Operator

AP

Visiting user selects to use home APN1

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HomeDNS

my.isp.com

myoperator.fi.gprs

RootDNS

4 4Visited DNS asks GPRS root DNS:

"who knows the IP address for this name?”

VisitedDNS

3

3

SGSN asks for GGSN IP address (using APN as the key) from visited DNS

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GPRS root DNS replies the home DNS address to visited DNS GRX

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6

Visited DNS asks home DNS for GGSN address

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7

Home DNS replies the GGSN IP address

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8 Visited DNS replies SGSN

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SGSN creates PDP context with home GGSN

2 MS sends "activate PDP context”

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GPRS Roaming & GRX

Can pass through GRXs

BillingGGSN

MSC

PSTN

BSC

SGSN

GPRS Network

Charging Gateway

Mediation

MSC

Billing

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Other Data related VAS

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• MMS

• MVS

• Video On Demand

• Live TV

Applications

▫Standard data network protocol based IP based applications

WWW, FTP, Telnet, ...Any conventional TCP/IP based applications

▫GPRS specific protocol basedPoint-to-point applications

Toll road system, UIC train control systemPoint-to-multipoint applications

Weather info, road traffic info, news, fleet management

▫SMS delivery (GPRS as a bearer for SMS)

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Thanks for listening

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