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Mobile Communication. MMS / GPRS. What is GPRS ?. General Packet Radio Service (GPRS) is a new bearer service for GSM that greatly improves and simplifies wireless access to packet data networks

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Mobile Communication

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Mobile Communication

MMS / GPRS


What is GPRS ?

  • General Packet Radio Service (GPRS) is a new bearer service for GSM that greatly improves and simplifies wireless access to packet data networks

  • GPRS applies packet radio principal to transfer user data packets in an efficient way b/w MS & external packet data network


Benefits of GPRS

  • New Data Services

  • High Speed (Data Rate 14.4 – 115 kbps)

  • Efficient use of radio bandwidth (Statistical Multiplexing)

  • Circuit switching & Packet Switching can be used in parallel

  • Constant connectivity


Comparison of GSM & GPRS


High Data Rate

  • GPRS uses radio channel i.e. 200 kHz wide

  • Radio channel carries digital data stream of 271 kbps

  • This rate is divided into 8 time slots each carrying 34 kbps per time slot

  • Data rate 14 kbps per time slot achieved after corrections

  • GPRS can combine upto 8 time slots giving data rate of 114 kbps


GPRS Terminals

  • Class A

    • MS supports simultaneous operation of GPRS and GSM services

  • Class B

    • MS able to register with the n/w for both GPRS & GSM services simultaneously. It can only use one of the two services at a given time.

  • Class C

    • MS can attach for either GPRS or GSM services


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

  • GPRS Register


  • GSM SYSTEM ARCHITECTURE

    PSTN

    ISDN

    PDN

    BSC

    MS

    BTS

    MSC/VLR

    GMSC

    BTS

    BSC

    MS

    EIR

    BTS

    AUC

    MS

    HLR


    GPRS SYSTEM ARCHITECTURE

    Other GPRS

    PLMN

    Gd

    SMS-GMSC

    SMS-INMSC

    SGSN

    Gp

    GGSN

    Gb

    Gn

    GGSN

    Gf

    BTS

    BSC

    Gr

    Gs

    PDN

    Gi

    Gc

    BTS

    EIR

    HLR+GPRS Register

    MS

    D

    MSC/VLR


    SGSN – Serving GPRS Support Node

    • Delivers data packets to mobile stations & vice-versa

    • Detect and Register new GPRS MS in its serving area

    • Packet Routing, Transfer & Mobility Management

    • Authentication, Maintaining user profiles

    • Its location register stores location info. & user profiles


    GGSN – Gateway GPRS Support Node

    • Interfaces GPRS backbone network & external packet data networks

    • Converts the GPRS packets from SGSN to the PDP format

    • Converts PDP addresses <Packet Data Protocol> change to GSM addresses of the destination user

    • Stores the current SGSN address and profile of the user in its location register

    • Performs authentication

    • Many-to- many relations among SGSNs & GGSNs


    SESSION MANAGEMENT IN GPRS


    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)


    Session Management

    • Mobile Station applies for PDP address <link-local address>

    • For each session PDP context is created & it contains

      • PDP type

      • PDP addressed assigned to MS

      • Address 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


  • PDP Context Activation


    Channels in GPRS

    • Logical Channel

      • Traffic Channels

      • Signaling Channels (Control Channels)

    • Physical Channels


    Logical Channels


    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


    Multiframe Structure of PDCH

    Four consecutive TDMA frame forms one block - B0 – B11

    Two TDMA frames for transmission of PTCCH - T

    Two Idle frames - X


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