gprs presentation

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GENERAL PACKET GENERAL PACKET RADIO SERVICE RADIO SERVICE

(GPRS) (GPRS)

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ObjectivesObjectives Understand the GPRS network architecture and

fundamental concepts. Understand the nodes that make up the GPRS network. Understand the key interfaces between GPRS nodes. Examine usage scenarios to see how data is routed through

the GPRS network Understand all the layers of the GPRS stack

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ContentsContents Mobile Wireless data Introduction to GPRS

General Aspects Quality Of Service Network Architecture

GPRS Protocol Stack Physical Layer RLC/MAC (Radio Link Control/Medium Access

Control) RRM (Radio Resource Management) Frame/Relay/Network Service BSSGP (Base Station Subsystem GPRS Protocol) LLC (Logical Link Control) SNDCP (SubNetwork Dependent Convergence

Protocol) GTP (GPRS Tunneling Protocol) GMM (GPRS Mobility Management) SM (Session Management)

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Mobile Wireless Mobile Wireless DataData

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What is Mobile Wireless data?What is Mobile Wireless data?• Transmission of data using wireless interface

Cellular Wireless Network

Wireline Data Network

Fixed User

Air Interface

DataVoice

Mobile Users

Wireless data networks should provide the following functionalities:

•Network access•Radio resource management•Logical link management•Packet routing and transfer•Mobility management•Network management

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Differences between wireless and Differences between wireless and wireline networkswireline networks

Mobile Wireless DataMobile Wireless Data

•Air Interface- Error prone medium- Spectrum is limited

•Wireless Network- Link Layer must be established- Delay of data transmissions

•User can move- Mobile location not always known- Handoffs required

•Wireless data terminal- Power consumption- limited battery life- smaller devices

•Additional security issues

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Access Requirements for Wireless Access Requirements for Wireless DataData

Mobile Wireless DataMobile Wireless Data

•Radio Link Protocol (RLP) for error recovery

- L2 protocol over the air interface

- Designed specifically to support data services

- Provides reliable data links between mobile and wireless system

•Fraud prevention - need stringent security

•Mobility support for wireless data

•Enhanced privacy for sensitive data

•Support for existing wireline protocols

•Compensation for slower data rates over wireless than wireline

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Network Requirements for Wireless Network Requirements for Wireless DataData

•How does network know about mobile?

- Registration

•How does mobile originate/terminate a data session?

- Call setup/termination (circuit)

- Packet delivery (packet)

•What happens when user moves around?

- Nomadic computing: access the network from any fixed location.

- Mobile computing: ability to be mobile while the data user is still connected to network.

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Network Requirements… contdNetwork Requirements… contd •How are computing addresses mapped to MS addresses

- e.g. for IP, need IP address/IMSI mapping functionality

•How does network deter fraud?

- Additional security and privacy mechanisms

•How do data applications work over wireless?

- Adaptation with WAP, etc

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GPRS - General GPRS - General AspectsAspects

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Why GPRS ?Why GPRS ? Provide true packet data on GSM networks

Faster data rates than Circuit Switched data More bandwidth efficient for asymmetric bursty traffic

Cost effective for network operator Allows for effective resource management (bandwidth

and hardware) Use of existing GSM radio physical layer

Provides evolution path for the future higher layers are independent of the radio technology

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GPRS is defined in the ETSI standardsGPRS is an entirely new GSM service

Targeted toward computer applications (email, Web)

9.05 Kbps to 171.4 Kbps to one user Allows for higher speed and bandwidths

GPRS - General AspectsGPRS - General Aspects

GPRS - GPRS - ServiceService

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Point to multipoint broadcast services

• traffic messaging• weather conditions

subscribed services• market reports

support of different protocols• IP• X.25

GPRS – GPRS – Service … contdService … contd

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Class A simultaneous execution of circuit switched and

GPRS operation is possibleClass B

simultaneous execution of signalling for both circuit switched and GPRS operation is possible

GPRS traffic will be suspended during a pending or an established circuit switched connection

Class C alternate use of circuit switched and GPRS operation

Classes of MobileClasses of Mobile

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Network Mode I paging coordination

• same channel for circuit switched and packet switched services

• either CCCH or PCCH in idle mode• packet data channel in transfer mode

combined procedures performed by Class A and B radios

Network Mode II no paging coordination always use CCCH PCCCH not present in the cell

Network Modes of Network Modes of OperationOperation

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Network Mode III no paging coordination circuit switched services always on CCCH packet switched services either on CCCH or

packet data channel

Network Modes … contdNetwork Modes … contd

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Typical GPRS mobile operationTypical GPRS mobile operation

Power On - Carrier selectionPLMN selectionCell selectionRegistration - GPRS AttachConnection set up - PDP context

activationTraffic exchange or Data TransferConnection termination - PDP context

deactivationPower Off - GPRS detach

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Call Flow DiagramCall Flow Diagram

BSS SGSN GGSN PDN

Registration (Authentication/Identification)

Session Deactivation

Data Transfer (Mobile to Network and Network to Mobile)

De-Registration

Session Activation

Link Establishment

Link Release

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Basic GPRS operationBasic GPRS operation Attachment:

mobile sends attach request to SGSN via the BSS SGSN performs authorization check, authenticates user, and

determines if it is willing / able to provide requested QoS if attach request is accepted, SGSN must keep track of

mobile as it moves around within the SGSN’s coverage area PDP context activation:

PDP addresses are anchored by a GGSN, i.e. all packet data traffic from the public PDN for a particular PDP address goes through the GGSN

activating a PDP address sets up an association between the mobile’s current SGSN and the GGSN that anchors that PDP address

the record that the GSNs use to record this association is called a PDP context

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Basic GPRS operation... contdBasic GPRS operation... contd

Data transferNetwork to mobile: packets originating in the public PDN reach the GGSN

that anchors the PDP address which was previously activated by the mobile

the GGSN uses the PDP context information to route the packets to the mobile’s serving SGSN

the SGSN forwards the packets to the mobileMobile to network: packets sent by the mobile are received by the serving

SGSN the SGSN then forwards the packets to the GGSN which

anchors the mobile’s activated PDP address

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Basic GPRS operation... contdBasic GPRS operation... contd

Data transferNetwork to mobile: packets originating in the public PDN reach the GGSN

that anchors the PDP address which was previously activated by the mobile

the GGSN uses the PDP context information to route the packets to the mobile’s serving SGSN

the SGSN forwards the packets to the mobileMobile to network: packets sent by the mobile are received by the serving

SGSN the SGSN then forwards the packets to the GGSN which

anchors the mobile’s activated PDP address

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Basic GPRS operation... contdBasic GPRS operation... contd Inter-GSN communication is done using tunnelling Tunnelling involves wrapping network-layer packets

inside another header so that they can be carried as normal IP traffic through the intra-PLMN backbone network

Once received by the far-end GSN, the extra header is discarded an the packets are routed to their final destination based on the original header information

Tunnelling takes place in both the MS to network and Network to MS directions

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Mobile IdentitiesMobile Identities

External Identities Internal Identities

Global Over Radio Over Network

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External IdentitiesExternal Identities Visible to user or external networks

IPV4 Address or IPV4 logical name• static or dynamic

IPV6 Address or IPV6 logical name X.25 Address Phone number

• used for circuit switch call Other protocol address

Access Point Name (APN) Defines GGSN that handles the context of MS In addition, a route from GGSN to external networks

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Internal Identities GlobalInternal Identities Global IMSI (International Mobile Subscriber Identity)

Similar to GSM, stored in SIM Three parts

• MCC : Mobile Country Code (Identify country)• MNC : Mobile Network Code (Identify PLMN)• MSIN : Mobile Subscriber Identification Number

(Identify subscriber)• Used for generating other identities

IMEI (International Mobile Equipment Identity) Similar to GSM, the identifier of the device

IMEI-SV Similar to GSM, software version of the MS

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Internal Identities over networkInternal Identities over network TID (Tunnel Identifier) GSN Number GSN Address GSN Name BSSGP Virtual Connection Identifier (BVCI) Network Service Virtual Connection Identifier (NS-VCI) Network Service Virtual Link Identifier (NS-VLI)

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Mobile-originated packet Mobile-originated packet transfertransfer

Packet Channel Request (PRACH)

Packet Uplink Assignment (PAGCH)

RLC/MAC data block

Packet Uplink ACK/NACK

TBF

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Quality of ServiceQuality of Service

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QoS ParametersQoS Parameters QoS requirements of typical mobile packet data

applications are very diverse (Eg. Real-time multimedia, web browsing, e-mail, chat, etc).

GPRS allows defining QoS profiles by using the parameters:

Service precedence Reliability Delay Throughput

QoS profiles are negotiated between the MS and the network for each session, depending on the QoS demanded and the current available resources.

Billing of the service is based on transmitted data volume, type of service and the chosen QoS profile.


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QoS Parameters - Service PrecedenceQoS Parameters - Service Precedence It is the priority of a service in relation to another service. There exists 3 levels of priority: high, normal and low.


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QoS Parameters - ReliabilityQoS Parameters - Reliability It indicates the transmission characteristics

required by an application.Each reliability class guarantees certain max

values for probability of loss, duplication, mis-sequencing and corruption (undetected error) of packets.


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QoS Parameters - DelayQoS Parameters - DelayDelay is the end-to-end transfer time between two

communicating MSs or between a MS and the Gi interface to an external PDN, it includes the delay for request and assignment of radio resources and the transit delay in the GPRS backbone network.


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QoS Parameters - ThroughputQoS Parameters - ThroughputThroughput specifies the maximum/peak bit rate

and the mean bit rate.


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Network ArchitectureNetwork Architecture

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TE MT BSS SGSN GGSN

EIR

SM-SC

HLR

SMS-GMSCSMS-IWMSC

E C

DA

Gb

Gd

GrGs

MSC/VLR

PDN

GGSN

Other PLMN

Gc

R Um

Gn

Gf

GiTE

SGSNGn

SignalingSignaling & Data

Gp

GPRS - Network ArchitectureGPRS - Network Architecture

Network ArchitectureNetwork Architecture

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GPRS – Signaling PlaneGPRS – Signaling Plane

GSM RF

MAC

L1bis

NetworkService

LLC

BSSGP

NetworkService

L1bis

BSSGPRLC

LLC Relay

GMM/SM

L1

L2

IP

UDP /TCP

GTPRelay

L1

L2

IP

UDP /TCP

GTP

IP/X.25 IPX.25

GGSN End nodeUm BSS Gb Gn GiSGSN

Application

IWU

GMM/SM

LLC

GSM RF

MS

RLC

MAC

RRM

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GPRS – Data Transmission PlaneGPRS – Data Transmission Plane

Application

IP / X.25/IWU

SNDCP

LLC

GSM RFGSM RF

MAC

L1bis

NetworkService

LLC

BSSGP

NetworkService

L1bis

BSSGPRLC

LLC Relay

SNDCP

L1

L2

IP

UDP /TCP

GTPRelay

L1

L2

IP

UDP /TCP

GTP

IP/X.25 IPX.25

MS GGSN End nodeUm BSSGb

GnGiSGSN

RLC

MAC

RRM

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TE MT BSS SGSN GGSN

EIR

SM-SC

HLR

SMS-GMSCSMS-IWMSC

E C

DA

Gb

Gd

GrGs

MSC/VLR

PDN

GGSN

Other PLMN

Gc

R Um

Gn

Gf

GiTE

SGSNGn


Gp

GPRS - Network ArchitectureGPRS - Network ArchitectureExisting Circuit Mode Existing Circuit Mode EntitiesEntities

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Class 4 switchGSM Mobility ManagementGSM Supplementary ServicesVisiting Location Register (VLR)

Local cache of HLR data for users in MSC coverage area

Interworking Function (IWF) Modem bank for circuit mode data service

interworking into POTS network

GPRS - Network ArchitectureGPRS - Network ArchitectureMobile Switching Centre + Mobile Switching Centre + VLRVLR

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Database of User Account informationGSM Mobility ManagementGenerates Authentication

challenge/response VLR caches several challenge/response pairs to

minimizeVLR-HLR traffic

GPRS - Network ArchitectureGPRS - Network ArchitectureHome Location Register - Home Location Register - HLRHLR

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SMS-GMSC and SMS-IWMSCSMS-GMSC and SMS-IWMSC

Gateway between MSC and SMS Service Center


SMS-GMSC => Short Message Service Gateway MSC

SMS-IWMSC => Short Message Service InterWorking MSC

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Point-to-point SMS (not Cell Broadcast)

Forwards and stores SMS messagesInterface between GSM PLMN and rest of

the world (email, Web, etc.) for SMS


SMS – Service CentreSMS – Service Centre

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Database of valid/invalid IMEIs

GPRS - Network ArchitectureGPRS - Network ArchitectureEquipment Identity Register - Equipment Identity Register - EIREIR

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Base Transceiver Station (BTS) Up to 250 per BSS, trend is towards more Abis is typically daisy chained to reduce costs

Base Station Control (BSC)Transcoder (XCDR)

BTS

BSC XDCR

BTSAbis

Ater A

GPRS - Network ArchitectureGPRS - Network ArchitectureBase Station Subsystem - Base Station Subsystem - BSSBSS

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Mobile Station (MS) MS consists of Mobile Equipment (ME) plus

SIM ME contains IMEI SIM contains IMSI, TMSI, Kc and A3/8

algorithmTerminal Equipment (TE) is data terminal

May be external to ME or internal External is typically a notebook computer, etc. Internal is Nokia 9000, etc.

GPRS - Network ArchitectureGPRS - Network ArchitectureMobile Station – MS Mobile Station – MS

Terminal Equipment - TETerminal Equipment - TE

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TE MT BSS SGSN GGSN

EIR

SM-SC

HLR

SMS-GMSCSMS-IWMSC

E C

DA

Gb

Gd

GrGs

MSC/VLR

PDN

GGSN

Other PLMN

Gc

R Um

Gn

Gf

GiTE

SGSNGn


Gp


Entities New for GPRSEntities New for GPRS

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Gateway between GPRS PLMN and other packet data networks IP networks / Internet X.25

Functions Message screening Billing data collection Relaying and Routing Address Translation and Mapping Encapsulation and Tunnelling (GTP) Mobility Management (PDP context management)

toSGSN

PDN

Gc

Gn Gi

to HLR

GGSN

GPRS - Network GPRS - Network ArchitectureArchitectureGateway GPRS Support Node - Gateway GPRS Support Node -

GGSNGGSN

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Authentication and Admission ControlBilling Data CollectionRelay, Routing, Address Translation

and MappingEncapsulation and TunnellingDomain Name ServerMobility ManagementCiphering (LLC Layer)Logical Link Management (LLC)

Compression (SNDCP Layer)

toBSS

HLR

toSMS-GMSCSMS-IWMSC

Gb

Gd

Gs

Gn

toGGSN

Gr

SGSN

GnTo SGSN

(or GGSN in other PLMN)

GPRS - Network ArchitectureGPRS - Network ArchitectureServing GPRS Support Node - Serving GPRS Support Node - SGSNSGSN

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TE MT BSS GGSN

EIR

SM-SC

HLR

SMS-GMSCSMS-IWMSC

E C

DA

Gb

Gd

GrGs

MSC/VLR

PDN

GGSN

Other PLMN

Gc

R Um

Gn

Gf

GiTE

SGSNGn


SGSN

Gp

GPRS - BackboneGPRS - Backbone

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Gn Interfaces SGSN<->GGSN internal to PLMN SGSN<->SGSN internal to PLMN

Gp Interface SGSN<->GGSN external to PLMN

IP based TCP or UDP allowed

GPRS Tunnel Protocol (GTP)NEWNEW Tunneling (Data plane) Mobility Management (Signaling

plane) GSM 09.60

Lower Layer(s)

IP

TCP UDP

GTP

IP X.25

SignalingPlane

DataPlane


GPRS – Backbone … contdGPRS – Backbone … contd

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GPRS - PROTOCOL STACKGPRS - PROTOCOL STACK• Physical LayerPhysical Layer• Physical Link LayerPhysical Link Layer• RLC/MAC (Radio Link Control/Medium Access Control)RLC/MAC (Radio Link Control/Medium Access Control)• RRM (Radio resource Management) RRM (Radio resource Management) • LLC (Logical Link Control)LLC (Logical Link Control)• SNDCP (SubNetwork Dependent Convergence Protocol)SNDCP (SubNetwork Dependent Convergence Protocol)• BSSGP (Base Station Subsystem GPRS Protocol)BSSGP (Base Station Subsystem GPRS Protocol)• GTP (GPRS Tunneling Protocol)GTP (GPRS Tunneling Protocol)• GMM (GPRS Mobility Management)GMM (GPRS Mobility Management)• SM (Session Management)SM (Session Management)• Recap of the State Models.Recap of the State Models.

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Radio Link Control/Medium Access Control (RLC/MAC) Layer

GPRS Physical Layer

Logical Link Control (LLC) Layer

Subnetwork Dependent Convergence Protocol (SNDCP)

IP X.25

Implementedin BSS

Implementedin SGSN

Implementedin GGSN

GPRS - Protocol StackGPRS - Protocol Stack

The Protocol SuitThe Protocol Suit

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Physical LayerPhysical Layer

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CCCH used for initial access in some cells

Packet Data Channel (PDCH) Packet Common Control Channel (PCCCH)

• 52 multiframe or existing CCCH 51 multiframe

• Packet Broadcast Control Channel (PBCCH)

• Packet Access Grant Channel (PAGCH)

• Packet Paging Channel (PPCH) Packet Data Traffic Channel (PDTCH) Packet Associated Control Channel (PACCH) Packet Timing Control Channel (PTCCH)

PHYSICAL LAYERPHYSICAL LAYER

Logical ChannelsLogical Channels

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3 additional packet channel combinations (multiframe types) Type 11 : PBCCH+PDTCH+PACCH+PTCCH Type 12 :

PBCCH+PCCCH+PDTCH+PACCH+PTCCH Type 13: PDTCH+PACCH+PTCCH

Type 13 is used for packet channel set up with CCCH.

Channel CombinationsChannel Combinations PHYSICAL LAYERPHYSICAL LAYER

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Similar to TCH multiframe but twice as long Blocks are rectangularly interleaved on 4 bursts as on

CCCH and SDCCH No predefined substructure, contents of each block

determines the logical channel type of the block

TCH 26 Multiframe

GPRS 52 multiframe

4 bursts = 1 block

Idle frame (used for measurements)

52 Multiframe Structure52 Multiframe Structure PHYSICAL LAYERPHYSICAL LAYER

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29 multislot classesSemi-duplex (12 classes)

cannot TX and RX simultaneously but must TX and RX every TDMA frame

Similar multiplexing to GSM voice mobile Up to 4 TS downlink and 1 TS uplink, or 2

TS downlink and 2 TS uplink

Full duplex (6 classes) TX and RX are not coordinated Up to 8 TS downlink and 8 TS uplink

Half duplex (11 classes) cannot TX and RX simultaneously but can

TX or RX continuously for long intervals Up to 8 TS downlink OR 8 TS uplink Cheaper and lower power than Full duplex and more

throughput than Semi-duplex

TDMA frame

TDMA frame

TDMA frame

Multislot Mobile StationsMultislot Mobile Stations PHYSICAL LAYERPHYSICAL LAYER

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4 new channel coding schemes defined CS-1 is identical to CCCH and SDCCH coding CS-2 and CS-3 are punctured versions of CS-1 with

precoded USF bits and a 16 bit CRC CS-4 has USF precoding and 16 bit CRC only, no

coding

CodingScheme

CodeRate

Block Size(Octets)

Data Rate(Kbits/sec)

CS-1 1/2 23 9.05

CS-2 ~2/3 33 13.4

CS-3 ~3/4 39 15.6

CS-4 1 53 21.4

Channel CodingChannel Coding PHYSICAL LAYERPHYSICAL LAYER

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MS performs cell reselection in Idle Mode and in Transfer Mode No handovers MS aborts data transfer when it decides to

reselect to a new cellMS monitors neighbour cell BCCH/PBCCH

in Idle Mode and in Transfer ModeNew reselection criteria are used when

PBCCH is present in the cell

Cell ReselectionCell Reselection PHYSICAL LAYERPHYSICAL LAYER

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Radio Link Control/Medium Access Radio Link Control/Medium Access Control [ RLC/MAC ]Control [ RLC/MAC ]

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Layered OverviewLayered Overview RLC/MACRLC/MAC

RR management

RR-SAP GMMRR-SAP GRR-SAP

RR sublayer

PD

RRnon-RR

MM sublayer

LLC sublayer

Data Link layer (signalling layer 2)

SAPI 0 SAPI 3

RACHBCCH

PCHAGCH

SDCCHSACCH

FACCHSDCCH

SACCH

Physical Link layer

PDCH

RLC/MAC

RRupper layers'

PDUs

PDTCHPACCH

PCCCHPBCCH

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RLC/MAC

RLC/MAC BLOCK [ RADIO BLOCK ]

Input-OutputInput-Output

UPPER LAYER PDU [ LLC FRAME ]

RLC/MACRLC/MAC

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TBF : The K(ey) - wordTBF : The K(ey) - word

• A Temporary Block Flow (TBF) is a physical connection used by the two RR entities to support the unidirectional transfer of LLC PDUs on packet data physical channels • The TBF is allocated radio resource on one or more PDCHs and comprises a number of RLC/MAC blocks carrying one or more LLC PDUs.

• A TBF is temporary and is maintained only for the duration of the data transfer

• Each TBF is assigned a Temporary Flow Identity (TFI) by the network that is unique among concurrent TBFs in the same direction (uplink or downlink) on all PDCHs used for the TBF

RLC/MACRLC/MAC

64

Idle<->Transfer ModesIdle<->Transfer Modes

• mobile does not occupy a radio resource

• TBF does not exist

• mobile monitors PBCCH and PCCCH

•mobile occupies a radio resource

•TBF exists

•mobile is transferring LLC frames

PACKET IDLE

MODE

PACKET TRANSFER

MODE

Trigger from

upper layer

No more blocks to transmit

RLC/MACRLC/MAC

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Functional SplitFunctional Split

•Segmentation•Re-assembly•Sequencing•Backward Error Correction

RLC/MAC

•Procedures that enable multiple user equipment to share a common transmission medium.•Contention resolution •Queuing and scheduling of access attempts

MAC

RLC

RLC/MACRLC/MAC

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Packet Data CHannel CharacteristicsPacket Data CHannel Characteristics

PDCH

• Shared Channel

• Assigned to one or more UEs

• One phase or Two phase access procedures

•Different Medium Access Modes

• Can be assigned for both uplink and downlink TBF

RLC/MACRLC/MAC

67

Nearly identical procedures are defined for the CCCH and PCCCH

If PCCCH exists in a cell, these MAC procedures are performed on PCCCH

If no PCCCH exists in a cell, these MAC procedures are performed on CCCH

Initial AccessInitial Access RLC/MACRLC/MAC

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Initiation of Packet Access ProcedureInitiation of Packet Access Procedure

• Mobile schedules PACKET CHANNNEL REQUEST on PRACH channel

• 8 bit or 11 bit format

• Indication of the purpose of radio resource like user data/ page response/ MM procedure/ measurement report

• Indication about the preferred access type

• Monitors PCCCH group for an assignment message

RLC/MACRLC/MAC

69

Packet Assignment ProcedurePacket Assignment Procedure

•On receipt of PACKET CHANNEL REQUEST, network sends PACKET UPLINK ASSIGNMENT on the

same PCCCH on which it has received PACKET CHANNEL REQUEST

•On receipt of a PACKET CHANNEL REQUEST message with establishment cause indicating

Two Phase Access Request or Single block without TBF establishment, the network may

allocate a single radio block on an uplink PDCH

•In order to force the mobile station to make a two phase access, the network may

allocate a single radio block on an uplink PDCH with any of the other access types

•If the mobile station has been allocated a single block in the PACKET UPLINK ASSIGNMENT

message and the mobile station has not indicated Single block without TBF establishment

in the PACKET CHANNEL REQUEST message, the mobile station shall proceed with the

two phase packet access procedure

•If the mobile station has been allocated a single block in the PACKET UPLINK ASSIGNMENT

message and the purpose of the packet access procedure is to send a Measurement Report

message and the mobile station has indicated Single block without TBF establishment in the

PACKET CHANNEL REQUEST message, the mobile station shall proceed with measure report

procedure

RLC/MACRLC/MAC

70

Channel AssignmentsChannel Assignments

• A set of PDCHs to be used for the uplink transfer and the associated paramenters• A unique Temporary Flow Identity • A TBF Starting Time indication

Uplink Assignment

Downlink Assignment

• A set of PDCHs to be used for the downlink transfer and the associated parameters• A unique Temporary Flow Identity • A TBF Starting Time indication

RLC/MACRLC/MAC

71

Access + Transfer mode Access + Transfer mode

ParametersParameters

Access Type

PDCH

Access Mode

TBF mode

RLC mode

RLC/MACRLC/MAC

72

Access TypesAccess Types

One Phase Access

Two Phase Access

•All the resource is Allocated at one step•A defined contentionResolution mechanism

•Resource is Allocated in two steps•A defined contentionResolution mechanism

RLC/MACRLC/MAC

73

One Phase Access – Contention ResolutionOne Phase Access – Contention Resolution

1. The UE shall send RLC data blocks with the extended RLC Header to include the TLLI of the user equipment. 2. The network shall respond by including the TLLI in the PACKET UPLINK ACK/NACK message after the first correctly received RLC data block that comprises the TLLI.

3. The contention resolution is completed on the network side when the network receives a TLLI value identifying the user equipment.4. The contention resolution is completed on the user equipment side when the UE receives a PACKET UPLINK ACK/NACK message with the same TLLI as the user equipment has included in the RLC header of the first RLC data blocks.

5. if the user equipment receives a PACKET UPLINK ACK/NACK message with the right TFI but with another TLLI than the user equipment has included in the RLC header of the first RLC data blocks, the contention resolution is declared failed.

RLC/MACRLC/MAC

74

1 Phase – Contention Resolution1 Phase – Contention Resolution

PRACH

PAGCH

PACKET CHANNEL REQUEST

PACKET UPLINK ASSIGNMENT

REF NO, PDCHS, TFI, TBF ST

REF NO, CAUSE/ACCESS TYPE

PDTCHRLC DATA

TLLI

PACCHPACKET UPLINK ACK/NAK

TLLI

PDTCHRLC DATA

TLLI

NW MS

RLC/MACRLC/MAC

75

Two Phase Access – Contention ResolutionTwo Phase Access – Contention Resolution

1. The network sends PACKET UPLINK ASSIGNMENT message with a Single Block allocation, denoting two phase access to the user equipment. 2. UE sends a PACKET RESOURCE REQUEST message in that single block PDPCH. In this message, the UE shall indicate TLLI value and the number of data octets it has to deliver. The value = 0 => an open ended TBF. 3. The network shall respond by sending PACKET UPLINK ASSIGNMENT message including the TLLI value.

4. The contention resolution is completed on the network side when the network receives a TLLI value identifying the user equipment.5. The contention resolution is completed on the user equipment side when the user equipment receives a PACKET UPLINK ASSIGNMENT message with the same TLLI as the user equipment has included in the PACKET RESOURCE REQUEST message.

6. The contention resolution has failed on the user equipment side when the user equipment does not receive a PACKET UPLINK ASSIGNMENT message with its TLLI.

RLC/MACRLC/MAC

76

2 Phase – Contention Resolution2 Phase – Contention Resolution

PRACH

PAGCH

PACKET CHANNEL REQUEST


REF NO, CAUSE/ACCESS TYPE

PACCH

PACCH

PACKET RESOURCE REQUEST


TLLI, ACCESS MODE, RLC MODE, OCTET COUNT

TLLI, PDCHs, TFI,

SINGLE BLOCK ALLOC STRUCTURE

NW MS

RLC/MACRLC/MAC

77

(Medium)Access Modes(Medium)Access Modes

Fixed mode

Dynamic mode

Extended Dynamic mode

Fixed Allocation characterised by fixed allocation of radio blocks and PDCHs in the assignment message without an assigned USF

Dynamic Allocation, characterised by that the mobile station detecting an assigned USF value for each assigned PDCH and block or group of four blocks that it is allowed to transmit on that PDCH

Extended Dynamic Allocation characterised by the mobile station detecting an assigned USF value for any assigned PDCH allowing the mobile station to transmit on that PDCH and all higher numbered assigned PDCHs In the same block or group of four blocks

RLC/MACRLC/MAC

78

Fixed Access ModeFixed Access Mode

• The network sends PACKET UPLINK ASSIGNMENT or PACKET TIMESLOT RECONFIGURE message containing a Fixed Allocation structure.

• The fixed allocation structure contains the TIMESLOT_ALLOCATION flag that indicates 1 to 8 time slots that are allocated for packet data transmission, taking into account the multi-slot restrictions of the user equipment.

• It also contains the ALLOCATION_BITMAP that indicates blocks/block periods that are assigned to the allocation.

• The user equipment shall transmit an RLC/MAC block on each assigned PDCH on those time slots indicated in the TIMESLOT_ALLOCATION flag field in each

block period indicated in the ALLOCATION_BITMAP.

RLC/MACRLC/MAC

79

B4

B11

B10

B5

Multi-frame blocks

. . . . . .

B2

B3

B0

B1

TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7

Fixed AllocationFixed Allocation

Indicates the allocated blocks

RLC/MACRLC/MAC

80

Dynamic Access ModeDynamic Access Mode

• The network sends PACKET UPLINK ASSIGNMENT or PACKET TIMESLOT RECONFIGURE message containing a Dynamic Allocation structure.

• The dynamic allocation structure contains one USF value / PDCH for all the PDCHs assigned to that UE.

• Whenever the user equipment detects the assigned USF value, on an assigned PDCH, it shall transmit either a single RLC/MAC block or a sequence of four RLC/MAC blocks on the same PDCH.

• The time relation between the uplink block, which the mobile station shall use for transmission, and the occurrence of the USF value is pre-defined

• The number of RLC/MAC blocks to transmit is controlled by the USF_GRANULARITY parameter characterising the uplink TBF.

RLC/MACRLC/MAC

81

USF=MY_USF

MYDATA

B4

B5


Dynamic AllocationDynamic Allocation RLC/MACRLC/MAC

82

Extended Dynamic Access ModeExtended Dynamic Access Mode

•The Extended Dynamic Allocation medium access method extends the Dynamic

Allocation medium access method to allow higher uplink throughput

•The network sends PACKET UPLINK ASSIGNMENT that allocates to the mobile a

subset of 1 to N PDCHs based on the multislot class

•The mobile station shall monitor its assigned PDCHs starting with the lowest

numbered PDCH, then the next lowest numbered PDCH, etc

•Whenever the user equipment detects the assigned USF value, on an assigned

PDCH, it shall transmit either a single RLC/MAC block or a sequence of four

RLC/MAC blocks on the same PDCH and all the higher numbered PDCHs

•The time relation between the uplink block, which the mobile station shall use

for transmission, and the occurrence of the USF value is pre-defined

•The number of RLC/MAC blocks to transmit is controlled by the USF_GRANULARITY

parameter characterising the uplink TBF.

RLC/MACRLC/MAC

83

USF=MY_USF

MYDATA

B4

B5


Extended Dynamic AllocationExtended Dynamic Allocation

MYDATA

MYDATA


Allocated timeslots as PDCHs

Sending data on all higher numbered PDCHs

RLC/MACRLC/MAC

84

TBF ModesTBF Modes

Open Ended

Close Ended

• The UE can indicate in the PACKET RESOURCE REQUEST message, the number of data octets it has to deliver in the RLC_OCTET_COUNT field. The value = 0 => a request for open ended TBF.• If the PACKET UPLINK ASSIGNMENT / PACKET TIMESLOT RECONFIGURE message contains the RLC_DATA_BLOCKS_GRANTED field, the TBF is a close-ended TBF. else, the TBF is open-ended.• During a close-ended TBF the UE shall transmit only the number of RLC data blocks indicated in the RLC_DATA_BLOCKS_GRANTED field. • RLC/MAC control blocks and retransmissions of RLC data blocks do not count towards the limit. • If the number of RLC data blocks granted is not sufficient to empty the UEs send buffer, the UE shall attempt to establish a new uplink TBF by sending a PACKET RESOURCE REQUEST message

RLC/MACRLC/MAC

85

RLC ModesRLC Modes

Ack Mode

Unack Mode

• The transfer of RLC data blocks in the acknowledged mode uses selective retransmissions of RLC data blocks. • The transmitting side numbers the RLC data blocks via the block sequence number BSN. • The BSN is used for retransmission and for re-assembly. • The receiving side sends PACKET Ack/Nack messages to request retransmission of RLC data blocks.

• The transfer of RLC data blocks in the unack mode does not include any retransmissions, except during the release of an uplink TBF where the last transmitted uplink block may be retransmitted. • The block sequence number BSN in the RLC data block header is used to number the RLC data blocks for re-assembly. • The receiving side sends Packet Ack/Nack messages to convey the necessary control signalling (e.g. monitoring of channel quality for downlink transfer or timing advance or transmit power correction for uplink transfers)

RLC/MACRLC/MAC

86

MS BSSRLC Data Block

RLC Data Block

RLC Data Block

...

PDTCH

PDTCH

PDTCH

Packet Uplink Ack/Nack PACCH

RLC Data Block

RLC Data Block

RLC Data Block

...

PDTCH

PDTCH

PDTCH

RLC ARQ OperationRLC ARQ OperationRLC/MACRLC/MAC

87

ARQ Bit MapARQ Bit Map

64 63 62

8 17 6 5 4 3 2

61 60 59 58 57

56 55 54 53 52 51 50 49

48 47 46 45 44 43 42 41

40 39 38 37 36 35 34 33

32 31 30 29 28 27 26 25

24 23 22 21 20 19 18 17

16 15 14 13 12 11 10 9

Start Sequence Number (SSN)Final

SSN-x, for x=1 to 640 = NACK1 = ACK

Final Ack Indication0 = entire TBF NACKed1 = entire TBF ACKed

RLC/MACRLC/MAC

88

General Procedures : UE sideGeneral Procedures : UE side

Cell reselection

TLLI Management

Frequency Parameters

Discontinuous Reception

Acquisition of SI System info on

BCCH

System info on PBCCH

MeasurementReporting

RLC/MACRLC/MAC

89

General Procedures : N/W sideGeneral Procedures : N/W side

Cell change procedure

System info On PACCH

System info broadcasting

on BCCH

System info Broadcasting

on PBCCH

Measurementprocedure

RLC/MACRLC/MAC

90

• Paging for circuit mode establishment

– Sent on PCH or PPCH in Idle Mode

– Sent on PACCH in Transfer Mode

• Paging for downlink packet transfer

– MS is paged only if SGSN Ready Timer is expired

Packet Paging Request Paging PS

LLC frame LLC frameLLC frameLLC frame

Packet Paging Request Paging PS

LLC frame LLC frameLLC frameLLC frame

Ready Timer

running

LLC frameLLC frame

MS BSS SGSN

Paging ProcedurePaging Procedure RLC/MACRLC/MAC

91

MAC Header RLC Header RLC data unit spare

MAC Header RLC Header RLC/MAC control message

RLC/MAC Block

RLC/MAC Block

RLC/MAC Block StructureRLC/MAC Block StructureRLC/MACRLC/MAC

92

MAC header

RLC Header

RLC Header

E

Control message

MAC header

Control message

optional

UplinkDownlink

2323

RLC/MAC Control BlockRLC/MAC Control BlockRLC/MACRLC/MAC

93

MAC header

RLC Header

RLC Header E

User Data

MAC header

optional

UplinkDownlink

RLC Header E...

RLC Header

RLC Header E

RLC Header E...

TLLI

User Data

optional

RLC/MAC Data BlockRLC/MAC Data BlockRLC/MACRLC/MAC

94

Radio Resource Management Radio Resource Management [RRM][RRM]

95

RRMRRM Between MS and BSS Asymmetric MS

Cell Selection, reselection Measurement reporting Camping

BSS channel allocation based on demand Handoff, command cell change load balance

RRMRRM

96

Radio resource statesRadio resource states

Mobile can be in one of two states: Packet idle:

mobile does not occupy a radio resource

TBF does not exist mobile monitors PBCCH and

PCCCH Packet transfer:

mobile occupies a radio resource TBF exists mobile is transferring LLC frames

Packet Idle

Packet transfer

No LLC framesto send

LLC framesSet up TBF

RRMRRM

97

Logical Link Control Logical Link Control [ LLC ][ LLC ]

98

SGSNMS

GPRS Mobility Management

LogicalLink

ManagementEntity

Multiplex Procedure

LL5 LL9LL3 LL11

SNDCP

LLGMM LLSMS

SMS

LogicalLink

EntitySAPI=7

RLC/MAC

LogicalLink

EntitySAPI=11

LogicalLink

EntitySAPI=9

LogicalLink

EntitySAPI=5

LogicalLink

EntitySAPI=3

LogicalLink

EntitySAPI=1

GRR

LLGMM

RLC/MAC layer

LLC layer

Layer 3

LLC layer

BSSGP

BSSGP

BSSGP layer

Signalling

Signalling and data transfer

Functional ModelFunctional Model LLCLLC

99

Operates between MS and SGSN Common signaling and data planes Provides framing for higher layer packets Addressing is provided by the lower layer

RLC/MAC or BSSGP Acknowledged mode

Optional Protects against LLC PDUs lost on Gb interface Protects against lost or duplicated LLC PDUs during

cell change Unacknowledged mode

Framing only, no reliability

LLC BasicsLLC Basics LLCLLC

100

Address field SAPI 1 = GMM SAPI 2, 3, 9 and 11 = User Data SAPI 7 = SMS

Control field Similar to LAPD control field SACK is bit field selective repeat acknowledgement

Frame check sequence (24 bit CRC)

Address Control Information Field FCS(SAPI)

1 octet variable(36 max)

variable(1520 max)

3 octets

LLC PDULLC PDULLCLLC

101

Subnetwork Dependent Subnetwork Dependent Convergence Protocol Convergence Protocol

[SNDCP][SNDCP]

102

Adapts IP or X.25 to ride on top of the GPRS air interface

Multiplexing N‑PDUs from one or several NSAPIs onto one LLC SAPI

Compression of protocol control information and user data

TCP/IP header compression V.42 bis data compression

Segmentation and reassembly

SNDCP - PurposeSNDCP - PurposeSNDCPSNDCP

103

NSAPICspare T MDCOMP PCOMP

Data Segment

NSAPICspare T MDCOMP PCOMP

Data Segment

Segment Number N-PDU number

E N-PDU number (continued)

N-PDU number (extended)

SN-Data PDU(acknowledged mode)

SN-Unitdata PDU(unacknowledged mode)

SN - PDUSN - PDUSNDCPSNDCP

104

Compression

Segmentation Reassembly

De-compression

SNDC Primitive SNDC Primitive

LLC Primitive LLC Primitive

Network Layer

SNDC Layer

LLC Layer

SNDCP - FunctionalitySNDCP - FunctionalitySNDCPSNDCP

105

SessionManagement entity

QoS 2 QoS 3QoS 1 QoS 4

2 3

PDPor

Relay

SNDCP entity

LLC layer

SNDCP users

SNDCPmanagement

entity

PDPor

Relay

15 NSAPI

SAPI

. . .

SNDCP layer

SNSM

ControlEntity

SNDCP – Service Access PointsSNDCP – Service Access PointsSNDCPSNDCP

106

Originator

SNDCP LLC

XID

XID

LL-XID.res

LL-XID.req

LL-XID.ind

LL-XID.cnf

SNDCP user

Receiver

SNDCPLLC SNDCP user

SN-XID.req

SN-XID.cnf

SN-XID.res

SN-XID.ind

SNDCP : XID NegotiationSNDCP : XID NegotiationSNDCPSNDCP

107

Originator

SNDCP LLC

LL-DATA.res

LL-DATA.req

LL-DATA.ind

LL-DATA.cnf

SNDCP user

Receiver

SNDCPLLC SNDCP user

SN-DATA.req

SN-DATA.ind

Acked Information TransferAcked Information TransferSNDCPSNDCP

108

Originator

SNDCP LLC

LL-UNITDATA.req

LL-UNITDATA.ind

SNDCP user

Receiver

SNDCPLLC SNDCP user

SN-UNITDATA.req

SN-UNITDATA.ind

Unacked Information TransferUnacked Information TransferSNDCPSNDCP

109

GPRS Tunneling Protocol GPRS Tunneling Protocol [GTP][GTP]

110

GTP - FunctionalityGTP - Functionality

Protocol used to transfer information between SGSN and GGSN

Creates “tunnel” between GPRS support nodes for user data and signaling messages

Defined for inter-PLMN and intra-PLMN

GTPGTP

GTP TID 1

GTP TID 2

GTP TID 3

Web Browsing

FTP

E-mail

111

GTP - Functionality… contdGTP - Functionality… contd Allows multi-protocol packets to be “tunneled” through

the GPRS backbone Tunnels are established on activation of PDP context and

destroyed on deactivation of PDP context Each tunnel between two GSNs has a unique tunnel ID

(TID) During handover queued packets stored in the old SGSN

are tunneled to the new SGSN

GTPGTP

112

GPRS Mobility Management GPRS Mobility Management [GMM][GMM]

113

GMM - PurposeGMM - PurposeGMMGMM

Administration of the MS in combination with Circuit Switched Services.

Attach/Detach proceduresRouting area updatesAuthenticationUpdate HLR/VLRPaging

114

MobilityMobility

LAI=1

LAI=3

LAI=2

RAU-A

SGSN

SGSN

BSC

BSC

BSC

GGSN

RAU-B

GMMGMM

115

Mobility LevelsMobility Levels

Micro mobility intra-SGSN RA update no need to inform other

network elements track the current RA or cell of

the mobile station Macro mobility

inter-SGSN RA update need to inform other network

elements (e.g., GGSN, MSC/VLR, HLR)

track the current SGSN of the mobile station

SGSN

RA

SGSN

RARA

RA

Intra-SGSN

Inter-SGSN

Micro mobility

Macro mobility

GMMGMM

116

PDUtransmission

GPRS Attach

READY timerexpiry or Forceto STANDBY

GPRSDetach

GPRS Attach

PDUreception

GPRS Detachor CancelLocation

MM State Model of MS MM State Model of SGSN

IDLE

READY

STANDBY

IDLE

READY

STANDBY

READY timerexpiryorForce to STANDBYorAbnormal RLCcondition

GMM – State ModelGMM – State ModelGMMGMM

IDLE

•Routing Area update not required.

READY

•Inform every movement to a new cell.

•Paging not required.

STANDBY•Inform every movement to a new RA (Routing Area).•Paging required.

117

GMM-NULLGMM-ROUTING-

AREA-UPDATING-INITIATED

GMM-DEREGISTERED

- enableGPRS mode

- DETACH requested(not power off)

GMM-REGISTERED

Any state

GMM-DEREGISTERED-

INITIATED

- ATTACHrequested - ATTACH rejected

DETACH requested (power off)

- Network init. DETACH requested

- Lower layer failure

- ATTACHaccepted

- RAU rejected- Network init. DETACH requested- implicit DETACH

- DETACH accepted- Lower layer failure

- disableGPRS mode

- RAUrequested

- RAU accepted- RAU failed

GMM-REGISTERED-

INITIATED

GMM States in MSGMM States in MS GMMGMM

118

GPRS Attach Detach P-TMSI Reallocation Authentication Identification Paging PDP Context Activation PDP Context Deactivation

GMM ProceduresGMM ProceduresGMMGMM

119

3. Identity Response

2. Identification Response

2. Identification Request

1. Attach Request

3. Identity Request

4. Authentication

MS BSS new SGSN old SGSN HLR

9. Attach Complete

5. Attach Accept

10. TMSI Reallocation Complete

GPRS Attach Procedure GPRS Attach Procedure (normal)(normal)

GMMGMM

120

3. IMSI Detach Indication

2. Delete PDP Context Response

1. Detach Request

2. Delete PDP Context Request

5. Detach Accept

MS BSS GGSNSGSN MSC/VLR

4. GPRS Detach Indication

MS Initiated Detach MS Initiated Detach ProcedureProcedure

GMMGMM

121


1. Detach Request


4. Detach Accept

MS BSS GGSNSGSN MSC/VLR

3. GPRS Detach Indication

Network Initiated Detach Network Initiated Detach ProcedureProcedure

GMMGMM

122

1. Routeing Area Update Request

3. Routeing Area Update Accept

2. Security Functions

MS BSS SGSN

4. Routeing Area Update Complete

Routing Area Update Routing Area Update ProcedureProcedure

GMMGMM

123

5. Any LLC Frame

4. Any LLC Frame

3. GPRS Paging Request

2. Paging Request

1. PDP PDU

MS BSS SGSN

GPRS Paging ProcedureGPRS Paging ProcedureGMMGMM

124

Session Management [SM]Session Management [SM]

125

Activate/Deactivate PDP contexts (MS and Network initiated)

Assign/Negotiate QoSCreate connection with GGSN

SM - PurposeSM - PurposeSMSM

126

Deactivate PDPContext or MM statechange to IDLE

ActivatePDPConext

INACTIVE

ACTIVE

PDP – State ModelPDP – State ModelSMSM

127

AA PDP Context Activation

AA PDP Context Deactivation

Routing Area UpdateCombined Routing

Area/Location Area Updates

SM ProceduresSM ProceduresSMSM

128

GGSN

4. Activate PDP Context Accept

3. Create PDP Context Response

3. Create PDP Context Request

1. Activate PDP Context Request

SGSNMS


MO PDP Context Activation MO PDP Context Activation ProcedureProcedure

SMSM

129

MS SGSN GGSN

3. PDU Notification Request

HLR

1. PDP PDU

2. Send Routeing Info for GPRS

2. Send Routeing Info for GPRS Ack

4. Request PDP Context Activation

5. PDP Context Activation procedure

3. PDU Notification Response

MT PDP Context Activation MT PDP Context Activation ProcedureProcedure

SMSM

130

4. Modify PDP Context Accept

2. Update PDP Context Response

1. Update PDP Context Request

3. Modify PDP Context Request

SGSN GGSNMS

PDP Context Modification PDP Context Modification ProcedureProcedure

SMSM

131

GGSN

4. Deactivate PDP Context Accept



1. Deactivate PDP Context Request

SGSNMS


MS Initiated PDP Context De-MS Initiated PDP Context De-activation Procedureactivation Procedure

SMSM

132

GGSN


SGSN


2. Deactivate PDP Context Accept

2. Deactivate PDP Context Request

MS

NW Initiated PDP Context De-NW Initiated PDP Context De-activation Procedureactivation Procedure

SMSM

133

REFERENCESREFERENCES

gprs presentation

Documents