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Abstract The general packet radio service is being operated by gsm operator’s world wide used to offer services on data access at bandwidths comparable to that of fixed telephone modem which is used for providing fast and inexpensive internet links . GPRS offers packet based radio services and allow data information to be sent and received across mobile networks The main benefits of GPRS are that it reserves radio resources efficiently and sends data when ever user need and also reduces wastage of bandwidth.
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Page 1: Gprs

Abstract

The general packet radio service is being operated by gsm operator’s world wide used to offer services on data access at bandwidths comparable to that of fixed telephone modem which is used for providing fast and inexpensive internet links .

GPRS offers packet based radio services and allow data information to be sent and received across

mobile networks The main benefits of GPRS are that it reserves radio

resources efficiently and sends data when ever user need and also reduces wastage of bandwidth.

Page 2: Gprs

ContentsContents

Overview of GSM

What is GPRS? Network Architecture Protocol Stack Air Interface

Page 2

Page 3: Gprs

Overview of GSMOverview of GSM Second Generation

Technology Groups Special Mobile Developed by ETSI International wireless

standard Based on the cellular

concept Frequency reuse

implementation Over 480 million

subscribers

Page 3

Introduction to GPRS

F1

F2

F3

F4

F1

F2

F3

F4

F2

F1

F2

N=4 Frequency Reuse Concept

100 200 300 400 5000

GSM

IS-95

IS-136

PDC (Japan)

Analog

Millions of subscribers (Feb 2001)source: EMC

Page 4: Gprs

ContentsContents Overview of GSM

What is GPRS? Network Architecture Protocol Stack Air Interface HSCSD, EDGE, and 3G Growth Path

Page 4

Introduction to GPRS

Page 5: Gprs

What is GPRS? - Circuit vs What is GPRS? - Circuit vs Packet SwitchPacket Switch

2G technologies are circuit switched

Dial-up type connections A single user occupies a

channel for the entire transmission

Requires time-oriented billing GSM transmissions are bursty Bursty nature favors data

services

Page 5

• GPRS is packet switched technology

• More appropriate for data services

• Continuous flow is not required

• Access is based on demand only

• Several users can be multiplexed

• Billing based on negotiated QoS and usage

Introduction to GPRS

Page 6: Gprs

What is GPRS? - Types of What is GPRS? - Types of Data ServicesData Services

Most popular Internet data applications include:

E-mail Web browsing File transfers Real time audio Streaming video

Different services have different throughput requirements

GSM evolution is expected to provide services at throughputs similar to their landline counterparts

Page 6

Introduction to GPRS

Page 7: Gprs

ContentsContents Overview of GSM What is GPRS?

Network Architecture SGSN, GGSN GR, PCU Mobile Station

Protocol Stack Air Interface

Page 7

Introduction to GPRS

Page 8: Gprs

GPRS Network GPRS Network ArchitectureArchitecture GPRS introduces new entities to support data packet transmissions

New entities are PCU, GSN, Border Gateway, and GPRS register

Page 8

GPRS Network Architecture

ForeignPLMNBG

M S

BSC

DATA-BASESUBSYSTEM

Other SGSNBG

VLR H LRG R

EXTERNALNETW ORKS

BTS

BTS

GSMRADIOSUBSYSTEM

GPRSSUBSYSTEM

PDNGGSNSGSNPCU

AirInterface

GbInterface

GnInterface

GnInterface

GpInterface

GiInterface

GcInterface

GrInterface

GsInterface

AbisInterface

BTS - Base Transceiver StationBSC - Base Station ControllerPCU - Packet Control UnitSGSN - Service GPRS Support NodeGGSN - Gateway GPRS Support NodeBG - Border GatewayHLR - HomeLocation RegisterVLR - Visitor Location RegisterGR - GPRS RegisterPDN- Packet Data Netw ork

Introduction to GPRS

Page 9: Gprs

GPRS Network Architecture - GPRS Network Architecture - SGSNSGSN

Serving GPRS support nodeDelivers data packets to

the mobile stationsEach SGSN is assigned to a

specific service areaAllows for very little

change in the BTS and BSC

Page 9

SGSNPCU

BSS

BSS

BSS

SGSNPCU

SGSNPCU

GGSN

• All mobile stations communicate to the SGSN in the area

• Provides authentication

• Handles mobility management

• Introduction of the routing area - RA

• Also responsible for billing over the air interface

Introduction to GPRS

Page 10: Gprs

GPRS Network Architecture - GPRS Network Architecture - GGSNGGSN

Gateway GPRS support node Allows the GPRS network to

communicate with external PDNs

Routes all packet data units through the corresponding SGSN

Whereas the SGSNs can change during cell reselections, the GGSN remains the same during an on going packet transaction

Responsible for billing related to connections with external PDNs

Page 10

GGSN

GGSN GGSN

PDNPDN

PLMN

PDN

Introduction to GPRS

Page 11: Gprs

GPRSGPRSGPRS standard defines three mobile station

classesClass A supports simultaneous circuit and packet

switched communicationsClass B supports packet and circuit switched

sequentially Currently only Class B mobiles being developed

Class C does not support parallel operationOperates in either packet or circuit mode only

Page 11

Introduction to GPRS

Page 12: Gprs

GPRS Network Architecture - GPRS Network Architecture - GSM and GPRSGSM and GPRS

Page 12

GMSC

M S

ForeignPLMNBG

BSC

BSC

Other MSC

DATA-BASESUBSYSTEM

Other SGSNBG

VLRH LRG R

EXTERNALNETW ORKS

BTS

BTS

BTS

GSMRADIOSUBSYSTEM

GSMSW ITCHINGSUBSYSTEM

GPRSSUBSYSTEM

PDN

ISDN

MSCTRAU

GGSNSGSNPCU

AirInterface

AbisInterface

GbInterface

GnInterface

GnInterface

GpInterface

GiInterface

GcInterface

GrInterface

GsInterface

AInterface

BInterface

CInterface

EInterface

DInterface

AbisInterface

AirInterface

PSTNBTS

M S

Introduction to GPRS

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ContentsContents What is GPRS? Network Architecture

Protocol Stack OSI/ISO Model GPRS Protocol Stack GTP SNDCP and BSSGP RLC/MAC and LLC

Air Interface

Page 13

Introduction to GPRS

Page 14: Gprs

GPRS Protocol Stack - GPRS Protocol Stack - ISO/OSI ModelISO/OSI Model

International Telecommunications Union (ITU) and International Standardization Organization (ISO) developed Open Systems Interconnect (OSI)

Allows for compatibility between different equipment manufacturers

Page 14

Session Layer

Transport Layer

Netw ork Layer

Data Link Layer

PresentationLayer

Physical Layer

ApplicationLayer

1

2

3

4

5

6

7

Session Layer

Transport Layer

Netw ork Layer

Data Link Layer

PresentationLayer

Physical Layer

ApplicationLayer

1

2

3

4

5

6

7

Netw ork Layer

Data Link Layer

Physical Layer

Node A Node B Node C

peer-to-peer protocol

Introduction to GPRS

Page 15: Gprs

GPRS Protocol Stack - GPRS Protocol Stack - ISO/OSI ModelISO/OSI Model

Each layer adds its own header to the message

Same layer at destination node removes its corresponding header

Physical layer delivers message from one node to the next

In GSM, layer 1 corresponds to the air interface

GPRS layers fall between OSI layers 2 and 3

Page 15

Node A Node C

Application Layer

Presentation Layer

Session Layer

Transport Layer

Netw ork Layer

Data Link Layer

Physical Layer

234567Info

Info

2

3

4

5

6 7

7 Info

Info

6 7 Info

5 6 7 Info

4 5 6 7 Info

5 4 5 6 7 Info

6 5 4 5 6 7 Info 1

2

3

4

5

6

7

2

3

4

5

67

7Info

Info

67Info

567Info

4567Info

34567Info

234567Info1

2

3

4

5

6

7

Info

Introduction to GPRS

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GPRS Protocol StackGPRS Protocol Stack

Page 16

M SBTS

BSC PCU SGSN GGSN

RFL PhysicalLayer

PhysicalLayer

PhysicalLayer

PhysicalLayer

PhysicalLayer

PhysicalLayer

PhysicalLayer

PhysicalLayer

MACNSFR

RLC BSSGP

NSFR

L2

BSSGP IP

LLC UDP

SNDCP GTP

L2

IP

UDP

GTP

RFL

MAC

RLC

LLC

SNDCP

Netw orkLayer

Netw orkLayer

AbisInterface

AirInterface

InternalInterface

GbInterface

GnInterface

OSILayer 1

OSILayer 2

OSILayer 3

Introduction to GPRS

Page 17: Gprs

GPRS Protocol Stack - GTPGPRS Protocol Stack - GTP GPRS Tunneling protocol

Allows communication between the GGSN and SGSN Data transfer is done via encapsulation and tunneling GTP header includes such as PDU type, QoS parameters, and

tunnel identifier (TID) TID differentiates PTP from PTM transactions

Page 17

Introduction to GPRS

GTP PDU

N PDUTCP/IPHeader

User Data

Netw ork Layer

GTP Layer

GTPHeader

TID User Data

Page 18: Gprs

GPRS Protocol Stack - SNDCP GPRS Protocol Stack - SNDCP & BSSGP& BSSGP

Sub network Dependent Convergence Protocol

Makes GPRS network transparent to the common subscriber regardless of what application is running

Responsible for converting network packet data units into GPRS suitable format Multiplexing of SN packet data units over the LLC layer Segmentation and Desegmentation of SN packets into LLC packets Compression of the IP header information

Page 18

• Base Station Subsystem GPRS Protocol

– Routing between SGSN and PCU

– Provide radio related info for RLC/MAC

– Routing goes via Network Relay

– Transparent transfer of LLC frames

– Convey QoS information

Introduction to GPRS

TCP/IPHeader

User Data

Netw ork Layer

SNDCP Layer

SN-PDUHeader

Com pressed Inform ation TailSN-PDUHeader

Com pressed Inform ation Tail

Page 19: Gprs

GPRS Protocol Stack - LLCGPRS Protocol Stack - LLC Logical Link Control

Provides a logical reliable link between MS and SGSN Designed as independent as possible from the radio interface

layers Encapsulation of SNDCP packet data units Detection and recovery of lost LLC packet data units Responsible for acknowledged/unacknowledged operation

Page 19

Introduction to GPRS

Fram eHeader

Radio Blocks

SNDCP Layer

SN-PDUHeader

Compressed Inform ation TailSN-PDUHeader

Compressed Inform ation Tail

FCS

LLC Layer

Fram eHeader

Radio Blocks FCS Fram eHeader

Radio Blocks FCS

Page 20: Gprs

GPRS Protocol Stack - RLC / GPRS Protocol Stack - RLC / MACMAC

RLC sublayer Transmission of data blocks across the air interface Retransmission of error data blocks using ARQ

Page 20

• MAC sublayer

– Provides access to a given transmission medium

– Controls access signaling, medium sharing by multiple users

– Release operations over the radio channel

– Access is based on slotted ALOHA

– Performs mapping of RLC blocks onto the GSM physical channels

Introduction to GPRS

PC PCT TRLC

HeaderRLC/MAC Signaling

Inform ationUSF BCS USF BCS

RLC/MACLayer

RLC Data

RLC Data B lock RLC/MAC S ignaling B lock

Fram eHeader Radio Blocks FCS

LLC Layer

Fram eHeader Radio Blocks FCS Fram e

Header Radio Blocks FCS

Page 21: Gprs

ContentsContents Network Architecture Protocol Stack

Air Interface GPRS Logical Channels The Master Slave Concept The 52-Multiframe Timing Advance

Mobility Management HSCSD, EDGE, and 3G Growth Path

Page 21

Introduction to GPRS

Page 22: Gprs

GPRS Air InterfaceGPRS Air Interface Air interface continues to be

limiting factor in terms of capacity

GPRS shares the same interface with GSM

Recall GSM has 200 kHz and eight TS

GPRS utilizes multiplexing and dynamic channel allocation to use the air interface more efficiently

Some channels can be configured for data traffic and others for voice traffic

Channels are reconfigured accordingly based on demand

Page 22

GPRS Air Interface

Introduction to GPRS

PhysicalLayer

MAC

RLC

RFL

MAC

RLC

MS BSS

RLC - Radio Link ControlM AC - M edium Access ControlRFL - Radio Frequency LinkM S - M obile StationBSS - Base Station Subsystem

Page 23: Gprs

GPRS Logical ChannelsGPRS Logical Channels Signaling and traffic channels are also required for GPRS A new family of packet data channels PDCHs has been

defined Some of the existing GSM signaling channels can still be

used for GPRS The GPRS mobile still requires to listen to the GSM

broadcast channel for GPRS channel information

Page 23

Introduction to GPRS

Page 24: Gprs

GPRS 52-MultiframeGPRS 52-Multiframe Each radio block is transmitted over 4 TDMA

frames Resource allocation is done in terms of

blocks for both uplink and downlink A 52-Multiframe consists of:

twelve blocks for PDCHs signaling and traffic two timing advance frames two idle frames (for neighbor list and power control) 12 x 4 +2 + 2 = 52 frames

Page 24

0

Block 0 Block 1 Block 2TA

1 2 3 4 5 6 7 8 9 10 11 12 13

Block 3 Block 4 Block 5 I

14 15 16 17 18 19 20 21 22 23 24 25 26

Block 6 Block 7 Block 8TA

27 28 29 30 31 32 33 34 35 36 37 38 39

Block 9 Block 10 Block 11 I

40 41 42 43 44 45 46 47 48 49 50 51

TA - T im ing A lignm ent F ram eI - Id le F ram e

Introduction to GPRS

Page 25: Gprs

GPRS 52-MultiframeGPRS 52-Multiframe The PDCHs are mapped and organized into a 52-Multiframe

Page 25

0 1 2 3 4 5 6 7 21 22 23 24 25.5

0 1 2 3 4 49 50 51

0 1 2 3 4 5 6 7 21 22 23 24 25

1 TDM A Frame4.615 ms

26 M ultiframe120 ms

51 M ultiframe235.4 ms

Hyperframe3 h 28 min 53 s 760 ms

0 1 2 3 4 48 49 50

0 1 2 3 4 5 6 7 2043 2044 2045 2046 2047

0 1 2 3 4 5 6 7 46 47 48 49 50

0 1 2 3 4 23 24 25

52 M ultiframe240 ms

51 x 26 Superframe or 26 x 51 Superframe or 25.5 x 52 Superframe6s 120 ms

0 1 2 3 4 5 6 7

Introduction to GPRS

Page 26: Gprs

GPRS Timing Advance - GPRS Timing Advance - UplinkUplink

The PTCCH/U is divided into 16 subchannels with eight 52-multiframes

The 16 subchannels can be assigned to 16 different active mobile stations

Every PTCCH/U has a cycle of 1.92 s

Active mobile stations will transmit one access burst with TA=0 to the BTS once per eight 52-multiframes within their subchannel

Based on the PTCCH/U message, the BTS can recalculate the timing advance value Pa

ge 26

0 1

2 3

4 5

6 7

8 9

10 11

12 13

14 15

8 x 52-multiframe = 416 framesTAI = 0 - 15

Introduction to GPRS

Page 27: Gprs

GPRS Timing Advance - GPRS Timing Advance - DownlinkDownlink

Each mobile is assigned a timing advance index (TAI) value via the PTCCH/D

The TA message sent on the downlink can convey timing advance information for up to 16 mobile stations

The timing advance message contains the TAI values associated with each mobile station

Since the message requires 4 frames, it is carried within four consecutive TA frames

Page 27

One TA message in 4 normal burstsfor up to 16 MS

0 1

3 4

Introduction to GPRS

Page 28: Gprs

ContentsContents Network Architecture Protocol Stack Air Interface

Mobility Management Mobility Management States GPRS Attach

HSCSD, EDGE, and 3G Growth Path

Page 28

Introduction to GPRS

Page 29: Gprs

GPRS Mobility Management GPRS Mobility Management StatesStates

Mobility management states apply for both the mobile and the SGSN

Idle: Mobile is powered on but not attached to GPRS

Standby: Mobile is powered on and attached to GPRS. No packet transfer is in progress. Routing area updates are sent as needed.

Ready: The mobile is currently engaged in packet transfer or recently terminated a packet transfer. The Ready state is determined by a timer. No need to page a mobile in Ready state

Page 29

GPRS Mobility Management States for MS

Introduction to GPRS

Idle

Ready

Standby

Ready-TimerExpiry

PDUTransfer

GPRSDetach

GPRSAttach

PDUTransfer

Page 30: Gprs

GPRS Attach ProcessGPRS Attach Process Process of registration of the mobile into the GPRS

network Occurs when mobile is first powered on and can occur

afterwards based on network settings Mobile registers directly with the SGSN

Page 30

M S BTS

BSC SGSN

AirInterface

GbInterface

GsInterface

VLRH LRG R

DInterface

Attach Request

Authentication and Ciphering Authentication and Ciphering

Routing Area Update

Location Area Update

Attach Acknow ledged

For GPRS

For GSM

• Information Exchanged

– IMSI or P-TMSI

– TLLI

– RA, LA

– Power class mark

– Type of registration (GSM, GPRS)

– Authentication

– Ciphering

Introduction to GPRS

Page 31: Gprs

GPRS PDP Context GPRS PDP Context ActivationActivation

Page 31

M S BTS

BSC SGSN

AirInterface

GbInterface

GnInterface

Request PDP Context Create PDP Context

PDP Context ActivatedPDP Context Granted

GGSN

Message Includes:§ IP Address (Static of Dynamic)§ Access Point-AP(ie yahoo.com)§ QoS§ NSAPI

Message Includes:§ IP Address (Static of Dynamic)§ Access Point-AP(ie yahoo.com)§ QoS§ Tunneling ID (TID)

Message Includes:§ IP Address (Static of Dynamic)§ UPD Protocol Header§ QoS§ Tunneling ID (TID)

Message Includes:§ IP Address (Static of Dynamic)§ Priority Level§ QoS§ Tunneling ID (TID)§ NSAPI§ GGSN Address

• The mobile need to activate a packet data protocol context before it can transmit or receive information

Introduction to GPRS

Page 32: Gprs

GPRS Measurements - End-GPRS Measurements - End-to-End Processto-End Process

End-to-end test process is best approach towards measuring performance at the application layer

Client - Server configuration On the uplink, the mobile sends packets over the

GPRS network. A test server measures the performance and reports results back to the mobile

On the downlink, the test server sends packets over the GPRS network. The test mobile measures performance and stores the results

Page 32

Test Server

GPRS Netw ork

GiInterface

M SDrive Test System

Introduction to GPRS

Page 33: Gprs

HSCSD, EDGE and 3G HSCSD, EDGE and 3G Growth PathGrowth Path

Page 33

EDGE

SMS, Data (9.6Kbit/s)

UMTS

2 Mbit/s

GPRS

171.2 kbit/s

HSCSD

60 kbit/s

Bandwidth

Technology

384 kbit/s

9.6 kbit/s

1997 1998 1999 2000 2001 2002 2003

Introduction to GPRS

Page 34: Gprs

Conclusion An understanding of the above

technology and changes it brings will be a vital for successful deployment of gprs and full realization of benefits to mobile network

Page 35: Gprs

Any queries

Page 36: Gprs

Thank you