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An Overview of GPRS. Shourya Roy Pradeep Bhatt Gururaja K. What is GPRS?. A new bearer service for GSM that greatly improves and simplifies wireless access to packet data networks,e.g to the internet. Motivation . Speed Immediacy New and better applications User friendly billing.

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An overview of gprs

An Overview of GPRS

Shourya Roy

Pradeep Bhatt

Gururaja K.


What is gprs
What is GPRS?

  • A new bearer service for GSM that greatly improves and simplifies wireless access to packet data networks,e.g to the internet.


Motivation
Motivation

  • Speed

  • Immediacy

  • New and better applications

  • User friendly billing


Gsm architecture
GSM Architecture

PSTN

PDN

ISDN

GMSC

BSC

BTS

MS

MSC

BTS

BSC

EIR

MS

AUC

HLR

BTS

VLR

MS


Gprs architecture
GPRS Architecture

Other GPRS

PLMN

GGSN

Gp

Gn

SGSN

Gb

Gf

BSC

Gr

Gs

Gi

BTS

Gc

GGSN

PDN

EIR

D

BTS

HLR

MS

MSC/VLR


Protocol architechture
Protocol Architechture

  • Transmission Plane

    GPRS specifies a tunnel mechanism to transfer user data packets .

  • Signalling Plane

    GTP specifies a tunnel control management protocol.The signalling is used to create modify and delete tunnels.


Registration of a mobile node
Registration of a Mobile Node

A mobile station must register itself with GPRS network.

  • GPRS attach

  • GPRS detach

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


Session management
Session Management

After Successful attach a MS gets one or more Packet Data Protocol(PDP) address.This address is unique only for a particular session.

It consists of,

  • PDP type

  • PDP address assigned to MS

  • Requested QoS

  • Address of the corresponding GGSN


Session management contd
Session Management(Contd.)

PDP-Address allocation:

  • Static:Assigned by network operator of User’s home PLMN.

  • Dynamic:Assigned by Corresponding GGSN.


Pdp context activation
PDP Context Activation

MS SGSN GGSN

Activate PDP Context Request

PDP type,PDP Address

QoS Requested,Access Point,…

Security Functions

Create PDP Context Request

PDP type,PDP Address

QoS Negotiated,Access Point,…

Create PDP Context Response

Activate PDP Context Accept

PDP type,QoS Negotiated,…

PDP type,PDP Address

QoS Negotiated,…


Routing
Routing

BSC

BTS

BSC

BTS

SGSN

SGSN

MS

Inter-PLMN

GPRS Backbone

Gn

Intra-PLMN

GPRS Backbone

Intra-PLMN

GPRS Backbone

Gp

PLMN2

PLMN1

Border

Gateway

Gn

Border Gateway

Gn

GGSN

Packet Data Network(PDN)

Eg.Internet,Intranet

SGSN

Gi

GGSN

Host

Router

LAN


Location management
Location Management

  • MS frequently sends location update messages to inform the SGSN where it is.

  • Determining frequency of update messages is non-trivial.

  • The location update frequency is dependent on the state of the MS.


Location management contd
Location Management(Contd.)

A MS can be in 3 states:

  • IDLE

  • READY

  • STANDBY


Protocol architechture1

Protocol Architechture

Transmission Plane

The protocols provide transmission of user data and its associated signalling

Signalling Plane

Comprises protocols for the control and support of functions of the transmission plane


Transmission plane

Transmission Plane

GPRS Backbone:SGSN GGSN

GTP tunnels the user packets and related signalling information between the GPRS support nodes.

Subnetwork dependent convergence protocol

It is used to transfer packets between SGSN and MS

Data link layer

LLC(MS-SGSN)

RLC/MAC(MS-BSS)

Physical layer

PLL:channel coding,detection of errors, forward error correction, interleaving, detection of physical link congestion

RFL:modulation and demodulation


Network Layer

(IP or X.25)

Relay

SNDCP GTP

GTP

LLC TCP/UDP

TCP/UDP

Relay

RLC BSSP

BSSGP IP

IP

MAC Network

Service

Network Data Link

Service Service

Data Link

Layer

PLL

RFL Phy Layer

Phy Layer Phy Layer

Phy layer

Gm

Gb

Gi

BSS

SGSN

GGSN

RLC :Radio link control BSSGP:BSS GPRS Application protocol

PLL :Physical link layer GTP :GPRS tunneling protocol

RFL :Physical RF layer TCP :Transmission control protocol

MAC:Medium access control UDP :user datagram protocol

IP :Internet Protocol

Transmission Plane


MS

BSS

Application

Network Layer

SNDCP

LLC

RLC

Relay

RLC BSSGP

MAC

MAC Network

Service

PLL

RFL

PLL

PHY

RFL Layer

Um

SNDCP:Subnetwork dependent convergence protocol

LLC :Logical link control

RLC :Radio link control


SGSN

BSS

MS

GMM/SM

GMM/SM

LLC

LLC

Application

Relay

RLC BSSGP

BSSGP

RLC

Application

MAC

Network

layer

MAC Network service

GSM/RF

GSM RF Physical layer

Phy Layer

Um

Gb

GMM/SM:GPRS Mobilty Management and session Management Protocol

GSM/RF:GSM physical layer(radio interface) I.e.PLL and RFL

Signalling Plane:MSSGSN


SGSN

MSC/VLR

BSSAP

BSSAP

SCCP

SCCP

MTP3

MTP3

MTP2

MTP2

Phy Layer

Phy Layer

Gs

Signalling Plane SGSN

MSC/VLR


SGSN

HLR(and EIR)

MAP

MAP

TCAP

TCAP

SCCP

SCCP

MTP3

MTP3

MTP2

MTP2

Phy Layer

Phy Layer

Gr

MAP :Mobile Application Part

TCAP :Transaction capabilities and application part

SCCP :Signalling connection control part

MTP :Message transfer part

Signalling Plane SGSNHLR/SGSNEIR


Gsm tdma frame slots and bursts
GSM TDMA Frame Slots and Bursts

960 MHz

959.8 MHz

124

Time Slot

123

. . .

200 KHz

. . .

Downlink

1

2

3

4

5

6

7

8

1

2

TDMA Frame

935.2 MHz

1

935 MHz

915 MHz

Data Burst = 156.25 bit periods

914.8 MHz

124

123

. . .

200 KHz

. . .

1

2

3

4

5

6

7

8

1

Uplink

2

TDMA Frame

890.2 MHz

1

890 MHz


Gprs air inteface
GPRS Air Inteface

Time Slot Number

0

0

1

1

2

2

3

3

4

4

5

5

6

6

7

7

0

0

1

1

2

2

3

3

4

4

F1

Uplink

F2

F3

F4

Carrier

Frequency

0

0

1

1

2

2

3

3

4

4

5

5

6

6

7

7

0

0

1

1

2

2

3

3

4

4

F1

F2

Downlink

F3

F4

Voice User1

GPRS User1

GPRS User3

Voice User2

GPRS User2


Gprs air interface
GPRS Air Interface

  • Master slave concept

    • One PDCH acts as Master

    • Master holds all PCCCH channels

    • The rest of channels act as Slaves

  • Capacity on demand

    • PDCH(s) are increased or decreased according to demand

    • Load supervision is done in MAC Layer


  • Gprs logical channels
    GPRS Logical Channels

    Function

    Group

    Channel

    Direction

    Packet data

    Traffic channel

    PDTCH

    Data Traffic

    MS BSS

    Packet broadcast

    control channel

    PBCCH

    Broadcast Control

    MS BSS

    PRACH

    Random Access

    MS BSS

    Packet common

    Control Channel

    (PCCCH)

    PAGCH

    Access Grant

    MS BSS

    PPCH

    Paging

    MS BSS

    PNCH

    Notification

    MS BSS

    PACCH

    Associated Control

    MS BSS

    Packet Dedicated

    Control Channels

    PTCCH

    Timing Advance Control

    MS BSS


    Uplink data transfer
    Uplink Data Transfer

    MS

    BSS

    Packet channel Request

    PRACH or RACH

    Packet Immediate assignment

    PAGCH or AGCH

    Packet resource Request

    PACCH

    Packet resource assignment

    PACCH

    Random Access

    Transmission

    Frame Transmission

    PDTCH

    Negative Acknowledgement

    PACCH

    Retransmission of blocks in error

    PDTCH

    Acknowledgement

    PACCH


    Downlink data transfer
    Downlink Data Transfer

    MS

    BSS

    Packet paging request

    PPCH or PCH

    Packet channel Request

    PRACH or RACH

    Packet Immediate assignment

    PAGCH or AGCH

    Packet paging response

    PACCH

    Packet resource assignment

    PACCH or PAGCH

    Paging

    Frame Transmission

    Transmission

    PDTCH

    Negative Acknowledgement

    PACCH

    Retransmission of blocks in error

    PDTCH

    Acknowledgement

    PACCH


    Multi slot operation
    Multi Slot Operation

    • GPRS allows a mobile to transmit data in up to 8 PDCHs (eight-slot operation)

    • 3-bit USF at beginning of each radio block in downlink points to next uplink radio block

    • Comparison with single-slot GSM

      • Higher delay at higher load

      • Low blocking rate

      • Improved Throughput


    Conclusion
    Conclusion

    • GPRS provides efficient access to Packet Data Networks.

    • Multislot operation in GPRS leads to efficient channel utilization.

    • GPRS is more effective for long data packet transmission than short ones.


    References
    References

    • “General Packet Radio Service in GSM”, Jian Cai and David J. Goodman, Rutgers University, IEEE Communications Magazine, Oct 1997

    • http://www.comsoc.org/pubs/surveys/3q99issue/bettstetter.html

    • http://www.wsdmag.com/2000/aug2200/38-45.html

    • “Wireless Internet Access based on GPRS”, IEEE Personal Comm. April 2000.


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