Gprs

GENERAL PACKET RADIO SERVICE

Professor Hrushikesha Mohanty Department of Computer & Information Sciences University of Hyderabad

10/14/08

Prof.H.Mohanty, UoH

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GENERAL PACKET RADIO SERVICE GSM follows • Circuit switched Radio Transmission(earlier) • Packet Switched Bearer Services(later)

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Prof.H.Mohanty, UoH

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GPRS applies packet radio principle to transfer user data packets • between GSM mobile stations • to external packet data networks ( IP, X.25) • friendly billing based on volume of transfer

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GSM SYSTEM ARCHITECTURE • A cell : radio coverage of a BTS • several BTSs connected by a BSC • BTS & BSC together make BSS • Traffics among MHs routed through MSC • GMSC interfaces a mobile network to fixed network • GSM networks structured hierarchically • MSC keeps HLR,VLR, AUC, EIR data bases 10/14/08

Prof.H.Mohanty, UoH

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GSM components • BSS

Base Support Station

• BSC

Base Station Controler

• BTS

Base Tranciever Station

• MSC

Mobile Switching Controler

• GMSC Gateway Mobile Switching Controler • MS

Mobile Station

• HLR

Home Location Register

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• VLR

Visited Location Register

• EIR

Equipment Identity Register

• AUC

Authentication center

• PLMN Public Land Mobile Network

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Address, Authenticity • Distinguishes device & user identities • IMEI : International Mobile Equipment Identity • IMSI : International Mobile Subscriber Identity • MSISDN : Mobile Subscriber ISDN • VLR contains current location of a subscriber • A MS can subscribe to several MSIDN 10/14/08

Prof.H.Mohanty, UoH

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GSM SYSTEM ARCHITECTURE PSTN ISDN PDN

BSC MS

BTS GMSC

BTS

BSC

MSC

MS EIR

BTS MS 10/14/08

Prof.H.Mohanty, UoH

AUC

HLR

VLR 8

GPRS SYSTEM ARCHITECTURE • Existing GPRS includes GSNs • SGSN : Serving GPRS Support Node • Delivers data packets from and to mobile stations • Packet Routing and Transfer • Mobility Management • Logical Link Management • Authentication • Billing, Maintaining user profiles

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GPRS SYSTEM ARCHITECTURE

Other GPRS PLMN

Gd

SMS-GMSC SMS-INMSC

SGSN

Gp GGSN

Gb

Gn Gf

BTS

BSC

GGSN

Gr Gs

PDN Gc

BTS MS 10/14/08

EIR

Gi

HLR

Prof.H.Mohanty, UoH

MSC/VLR

D

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• GGSN : Gateway GPRS support node • interfaces GPRS backbone network & external packet data networks • PDP addresses change to GSM addresses • performs authentication & billing • many-to- many relations among SGSNs & GGSNs 10/14/08

Prof.H.Mohanty, UoH

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• Routing in GPRS system • Gb interface connects BSC to SGSN • Gn interface connects SGSN to GGSN while both in the same PLMN • Gp interface connects SGSN to GGSN located in different PLMNs • All GSNs connect via IP-based GPRS backbone network • GSNs follow GPRS Tunneling Protocol (GTP), encapsulate PDN packets 10/14/08

Prof.H.Mohanty, UoH

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• Gd interface for SMS (Short Message Service) • Gs interface connects SGSN and MSC/VLR • Gc interface connects GGSN and HLR • Gf interface to query on IMEI of a MS • Gi interface connects PLMN with external public/private PDN (IP, X.25)

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GPRS ROUTING BSC MS

BSC

BTS

BTS

inter-PLMN GPRS backbone Gn

SGSN

SGSN

Boarder gateway

intra-PLMN GPRS backbone PLMN1 Gn

Gp Boarder gateway

intra-PLMN GPRS backbone

Gn

PLMN2

Gi GGSN

SGSN

Packet data network(PDN) 10/14/08

Prof.H.Mohanty, UoH

GGSN

Router

Host 14

Lan

• SERVICES • offers end-to-end packet switched data transfer

PTP - Point-To-Point service PTM - Point-To-Multi point service • PTM-M

multicast service

• PTM-G

group call service

• SMS

Short Message Service

• CFU

Call Forwarding Unconditional

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• CFNRc Call Forwarding on mobile subscriber not reachable • CUG

Closed User Group

• tele action , data bases, electronic monitoring surveilance • Quality Of Service • GPRS allows defining QOS profiles • loss, duplication, mis-sequencing, corruption 10/14/08

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• SESSION & MOBILITY MANAGEMENTS • Session management SGSN

MS

GGSN

Activate PDP context request [PDP type, PDP address, QoS requested, access point,...] Security functions

Create PDP context request [PDP type, PDP address, QoS requested, access point,...]

Activate PDP context accept [PDP type, PDP address, QoS requested,...] 10/14/08

Create PDP context response [PDP type, QoS requested,…]

Prof.H.Mohanty, UoH

PDP context activation

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• A user can have several simultaneous PDP contexts active at a given time • Allocation of PDP address could be static/dynamic • GPRS supports anonymous PDP context activation • Location Management • intra SGSN routing area update • inter SGSN routing area update 10/14/08

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State model of a GPRS mobile station IDLE GPRS attach STANDBY time expired

GPRS dispatch

READY READY time expired or forced to STANDBY

Transmission of a packet

STANDBY

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Intr-SGSN routing area update BSS

MS

Routing area update request [old RAI, old P-TMSI signature, update type]

SGSN Routing area update request [old RAI, old P-TMSI signature, update type, CI]

Security functions Routing area update accept [P-TMSI, P-TMSI Signature] Routing area update complete [P-TMSI](optional) 10/14/08

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• Multiple Access & Radio Resource Management principles • Physical Layer • Uses both FDMA & TDMA for multiple access • 890 – 915 MHz for mobile station for up linking 935 – 960 MHz for BTS for down link • Each of the above two bands divided to 124 single carrier channels of 200 kHz width • Each 200 kHz channel has 8 time slots TDMA channels • 8 time slots form a TDMA frame • Recurrence of a time slot defines a Physical Channel 10/14/08

Prof.H.Mohanty, UoH

Packet Data Channel

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• Logical Channel

• Logical Channels are divided to – traffic channels – signaling (control) Channels

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Logical channels in GPRS GROUP Packet data traffic channel

CHANNEL

FUNCTION

DIRECTION

PDTCH

Data traffic

MS

BSS

Packet broadcast control channel

PBCCH

Broadcast control

MS

BSS

Packet common control channel (PCCCH)

PRACH PAGCH PPCH PNCH

Random access Access agent paging Notification

MS MS MS MS

BSS BSS BSS BSS

MS

BSS

MS

BSS

Packet dedicated control channels 10/14/08

PACCH

Associated control

PTCCH

Timing advance control Prof.H.Mohanty, UoH

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• Protocol Architecture Defined on – Transmission Plane – Signaling Plane

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• Transmission Plane • Provides transmission of user data and its associated signaling eg: Flow control , error detection and correction

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MS

BSS

SGSN

GGSN

Application Network layer (IP,X.25)

Network layer (IP,X.25)

SNDCP

Relay SNDCP

LLC RLC

Relay RLC BSSGP

MAC

MAC

PLL

PLL

RFL

RFL

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U m

Network service Phy. layer

LLC

TCP/UDP

TCP/UDP

BSSGP

IP

IP

Network service

Data link layer

Data link layer

Phy. layer

Phy. layer

Phy. layer

Prof.H.Mohanty, UoH

Gb

GTP

GTP

Gn

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Gi

SNDP

Sub Network Dependent Protocol

LLC

Logical Link Control

RLC

Radio Link Control

MAC

Medium Access Control

PLL

Physical Link Layer

RFL

Physical RF Layer

BSSGP BSS GPRS application Protocol GTP

GPRS Tunneling Protocol

TCP

Transmission Control Protocol

UDP

Use Datagram Protocol

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• Signaling Plane • for control and support the functionalities of the transmission plane eg: GPRS attach / detach PDP Context activation Control of routing paths Allocation of network resources 10/14/08

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• Internetworking with IP Networks GGSN Router

IP

IP Layer 2

GPRS bearer

Layer 1 Gi

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Protocols Prof.H.Mohanty, at the GiUoH IP interface

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