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31-03-99 Industry confidential 1

GPRS

General Telecom Presentation

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GPRS General Telecom Presentation

Agenda

Service overview

General architecture

GPRS Network Operations

Radio interface

Gb interface

Data transfer

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GPRS


SERVICE OVERVIEW

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Service overview

Data transfer with GSM Circuit-Switched

Internet

GSM

network

Air interfaceAccess node

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Service overview

Data transfer with GPRS

GPRS

network

Packet

datanetwork

Internet

LAN

Air interface

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Service overview

GPRS provides end-to-end packet-switched data transmission between

MS users and fixed packet data networks

GPRS is a GSM feature

GPRS provides efficient utilization of the radio resources:

multislot operation flexible sharing of radio resources between MS

bit rates up to 160 kbit/s per carrier, approximately

resources are allocated only when data are transmitted

charging is based on data volume transmitted, not on connection time

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Service overview

Market Examples

Wireless Network Computer

(Laptop, PDA, Notepad)

Mobile offices, Corporate Network access (e.g. E-mail)

Internet access, Information retrieval

Optimal support of Java applications

On-line banking, Mobile games (e.g. chess)

Traffic management GPRS Mobile in car

Fleet management

Railway, Automatic train control

Road Transport Informatics

Remote Telematics Security supervision

Utility meter reading, Remote control, POS

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Service overview

Three MS class modes of operation are defined:

class A :

simultaneous attach + traffic

class B :

simultaneous attach but exclusive traffic (the MS can be paged fora CS call, while performing GPRS)

class C :

exclusive attach

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GPRS


GENERAL ARCHITECTURE

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General Architecture

The BSS is used for both circuit-switched and GPRS services

GPRS backbone network in between the PDN and the BSS

The BSS has 2 clients:

The MSC, for circuit-switched services (A interface)

The GPRS backbone network, for GPRS (Gb interface)

The GPRS mobility is managed by the SGSN (Gb interface)

The A interface is unchanged

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PDN

e.g. X25

GPRS

Backbone

BSS

MSC/VLR PSTN

PDN

e.g. IP

A

Gb

Gi

Gi

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GPRS Interfaces

Gp

Gc

PDNBSS SGSN GGSN

MSC/

VLR

Gb

Gs

HLR

Gr

Gn

EIR

Gf

GGSN

other PLMN

Gi

Signalling and data interface

Signalling interface

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GPRS Interfaces

Gr: SGSN-HLR interface

MAP (Mobile Application Part), TCAP, SCCP, MTP3/2

update/cancel location

Gs: MSC/VLR-SGSN interface

BSSAP+ (Base Station System Application Part +), SCCP, MTP3/2 attach, update location, circuit paging

Gf: SGSN-EIR interface


Ge: GGSN-HLR interface


Gn: SGSN-GGSN interface

GTP, UDP, IP

PDP context creation/deletion/modification

route monitoring

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GPRS backbone architecture

GPRS backbone is an IP network which is composed of routers

Serving GPRS Support Node (SGSN)

At the same hierarchical level as the MSC.

Linked to several BSSs

Keeps track of the individual MSs location Performs security functions and access control

Gateway GPRS Support Node (GGSN)

Linked to one or several data networks

Provides interworking with external packet-switched networks

Connected with SGSNs via an IP-based GPRS backbonenetwork

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GPRS backbone architecture

other PLMN

PLMN

IP-based GPRS

ackbone

BSS

BSS

SGSN

SGSN

GGSN PDN

GGSN PDN

GGSN

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GPRS Transmission Plane

Relay

Network

Service

GTP

Application

IP / X.25

SNDCP

LLC

RLC

MAC

GSM RF

SNDCP

LLC

BSSGP

L1bis

RLC

MAC

GSM RF

BSSGP

L1bis

Relay

L2

L1

IP

L2

L1

IP

GTP

IP / X.25

Um Gb Gn Gi

MS BSS SGSN GGSN

Network

Service

UDP /

TCP

UDP /

TCP

Transmission Plane

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GTP (GPRS Tunneling Protocol)

tunnels user data and signaling between GSNs, in the GPRS backbone

network

TCP (Transmission Control Protocol)

carries GTP PDUs in the GPRS backbone network for protocols that

need a reliable data link

UDP (User Datagram Protocol)

carries GTP PDUs in the GPRS backbone network for protocols that

dont need a reliable data link

IP (Internet Protocol)

SNDCP (SubNetwork Dependent Convergence Protocol)maps network-level characteristics onto the characteristics of the

underlying network (packet segmentation, data compression)

GSM-RF layer

radio sub-system

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LLC (Logical Link Control)

provides a highly reliable ciphered logical link which is independent of

the underlying radio interface protocols

BSSGP (Base Station System GPRS Protocol)

conveys user and GMM/SM signalling LLC-PDUs, offers primitives for

management of the BVCs between BSS and SGSN

NS (Network Service)

transports BSSGP PDUs and is based on frame relay connection

between BSS and SGSN

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

RLC provides segmentation/reassembly of LLC-PDUs andtransport in acknowledged or unacknowledged mode of RLC data

blocks.

MAC controls the access signaling procedures for radio channel

and the mapping of RLC frames onto the GSM physical channel

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GPRS Signalling Plane

BSSGP

Relay

GMM/SM

LLC

RLC

MAC

GSM RF

GMM/SM

LLC

BSSGP

L1bis

Um Gb

MS BSS SGSN

Network

Service

RLC

MAC

GSM RF L1bis

Network

Service

Signalling Plane MS - SGSN

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GPRS Signalling Plane

GMM (GPRS Mobility management)

GPRS attach / detach, routeing area update, paging,

security (authentication, ciphering command),...

SM (Session management)

PDP context activation / deactivation, modification, GPRS attach/detach

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GPRS


GPRS NETWORK OPERATIONS

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GPRS Attach

GPRS Attach function is similar to IMSI Attach

Authenticates the MS

Generates the Ciphering Key

Allocates TLLI

Copy subscriber profile from HLR to SGSN After GPRS Attach

The location of the MS is tracked

Communication between MS and SGSN is secured

Charging information is collected

SGSN knows what the subscriber is allowed to do

HLR knows the location of the MS in accuracy of SGSN

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PDP Context Activation

An user can activate each of the subscribed PDP addresses

separately

User may have several PDP contexts but zero, only one or a few of

them are active

No data transmission is possible before the PDP address isactivated

Activation procedure

MS sends Activation Request to SGSN

SGSN verifies the subscription information of MS

SGSN informs GGSN about new PDP type and address

GGSN creates a context and acknowledge to SGSN

SGSN sends acknowledge to MS

Mobile Originating and Mobile Terminating data transmission is

now possible

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PDP Context Activation

When a PDP Context is activated:

SGSN has a logical bidirectional tunnel between the MS and the

GGSN

GGSN has a PDP address activated and mapped to the MS

Location of the MS is known in accuracy of SGSN Data Transfer

MS can send Mobile Originating data packets

Computers in external data network can send packets to MS using

MSs PDP address as destination

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Mobility Management

Instead of Location Area, GPRS uses Routing Areas to group cells. RA

is a subset of LA.

MM States:

IDLE :

MS is not known by the network READY :

MSs location is known in accuracy of cell

MS must inform its location after every cell change

MS can initiate Mobile Originating transfer at any time

SGSN does not need to page MS before Mobile Terminatingdata transfer

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Mobility Management

STANBY :

MSs location is known in accuracy of Routing Area

MS must inform its location after every Routing Area change (

no need to inform if MS changes from one cell to another within

the same Routing Area ) Before the network can perform Mobile Terminating data

transfer MS must be paged within the Routing Area

MS may initiate Mobile Originating data transfer at any time

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Mobility Management

Inter-SGSN RA update MS sends Routing Area Update request to new SGSN

New SGSN asks from old SGSN the context of the MS

New SGSN updates GGSN

New SGSN updates HLR

HLR cancels the context in old SGSN

HLR loads the subscriber data to new SGSN

New SGSN acknowledges to the MS

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Interworking with GSM services

Interworking with GSM services is offered by the Gs

interface Combined GPRS and IMSI Attach :

to save Radio Resources

MS sends combined GPRS and IMSI Attach to SGSN ( SGSN

may authenticate the MS )

SGSN informs MSC/VLR about the new MS

VLR set MS reachable by GPRS flag and stores SGSN

address

MSC may allocate new TMSI for MS

SGSN sends acknowledge ( and new TMSI and TLLI ) to MS

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Combined Location and Routing Area update :

to save Radio Resources

MS indicates its request for combined update

This is done when both Location and Routing Area changes in

the same time Combined Location and Routing Area update is not done if MS

has CS connection

MS sends combined Location and Routing Area update to

SGSN

SGSN derives the MSC/VLR address from Location Area Id

and informs MSC/VLR

MSC/VLR updates its location area info

SGSN acknowledges to MS

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Paging CS services via GPRS network :

MSC/VLR gets Mobile Terminating call or SMS

In VLR, presence of SGSN address tells that the MS is in

GPRS attached state

MSC/VLR sends the paging request to SGSN address ( not toBSC )

SGSN checks the location of MS ( identified by IMSI )

SGSN pages the MS via GPRS channels indicating CS Page

status

MS replies to the page using normal GSM channels

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Network Modes of Operation

Three network operation modes are defined:

Network operation mode I

The network sends a CS paging message for a GPRS-attached

MS, either on the same channel as the GPRS paging channel,

or on a GPRS traffic channel This means that the MS needs only to monitor one paging

channel and that it receives CS paging messages on the PDCH

when it has been assigned a PDCH.

Network operation mode II


MS, on the CCCH paging channel, which is also used for

GPRS paging

This means that the MS needs only to monitor the PCH, but

that CS paging continues on the PCH even if the MS has been

assigned a PDCH.

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Network Modes of Operation

Network operation mode III


MS, on the CCCH paging channel, and sends a GPRS paging

message either on PPCH (if there is a master PDCH) or on

PCH.

This means that the MS that wants to receive pages for both

CS and PS shall monitor PCH and PPCH (if there is a master

PDCH)

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Network Operation Mode I

MSC

SGSNBSS

CS paging

PS paging

Gs

PPCH or

PCH or

PACCHMS

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Network Operation Mode II

MSC

SGSNBSS

CS paging

PS paging

PCHMS

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Network Operation Mode III

MSC

SGSNBSS

CS paging

PS paging

PCH

MS

PPCH

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GPRS


RADIO INTERFACE

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Radio Interface

Time-slots and Frames

50 51

1 (52-frame) multiframe = 52 TDMA frames (240 ms)

49483210

0 2 7 0 2 7 0 2 7

1 TDMA frame = 8 TS (4,615 ms)

frame 0 4 8 12

13 17 21 25

26 30 34 38

39 43 47 51

block B0 B1 B2 B3 B4 B5 x B6 B7 B8 B9 B10 B11 x

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Radio Interface

Time-slots and Frames

The access scheme is Time Division Multiple Access (TDMA), with 8

basic physical channels (time-slots) per carrier

A GPRS time-slot is named a Packet Data Channel (PDCH)

The sharing of the physical channels is based on blocks of 4

consecutive bursts.

A PDCH is mapped dynamically on a 52-multiframe

The 52-multiframe consists of

12 blocks of 4 consecutive frames

2 idle frames (frames 25 and 51)

2 frames used for the PTCCH (frames 12 and 38)

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Radio Interface

Packet data logical channels

PCCCH (Packet Common Control Channel)

PRACH (Packet Random Access Channel)

PPCH (Packet Paging Channel)

PAGCH (Packet Access Grant Channel)

PBCCH (Packet Broadcast Control Channel) PTCH (Packet Traffic Channel)

PDTCH (Packet Data Traffic Channel)

PACCH (Packet Associated Control Channel)

PTCCH (Packet Timing Advance Control Channel)

PBCCH and PCCCH are optional

When they are present, they are called Master PDCH

When they are not present, CCCH and BCCH are used for common

signalling purposes

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Radio Interface

Channel Coding

On the radio interface, data can be coded according to 4 different

coding schemes:

CS1: 8 Kbit/s, per PDCH

(always used for signalling)


CS3: 14.4 Kbit/s, per PDCH


Dynamic coding scheme adaptation is handled, according to radio

conditions

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Radio Interface

Timing Advance

The timing advance procedure comprises 2 parts:

Initial Timing advance estimation

Continuous timing advance index

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Radio Interface

Initial timing Advance

Initial timing advance estimation

UL data transfer

It is based on BTS measurements, on the single access burst

carrying the Packet Channel Request (on PRACH) or Channel

Request (on RACH)

The Packet UL Resource Assignment (on PAGCH) or the UL

Immediate assignment (on AGCH) carries the estimated timing

advance value to the MS

This value is used by the MS until the continuous timing

advance update provides a new value

DL data transfer

The polling indication is sent in the Packet DL Resource

Assignment to request to the MS a Packet Control Ack as four

access bursts, on which the timing advance will be calculated,

by the BTS

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Radio Interface

Continuous timing Advance

Continuous timing advance update

This procedure is carried only on the PDCH which carries PACCH.

For packet transfer (UL or DL), the MS is assigned a Timing

Advance Index (TAI) which determines on which UL frame an

access burst has to be sent

The TAI allows 16 different positions in groups of eight 52-

multiframes (frames 12 and 38: PTCCH)

The BTS analyses the received access burst and determines a new

timing value

Timing advance values are broadcast DL, on frames 12 and 38

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Radio Interface

RLC Layer

RLC layer handles the following functions

Data transmission in an Acknowledged mode

(unsuccessfully delivered RLC data blocks are selectively

retransmitted)

Data transmission in an Unacknowledged mode

LLC-PDU segmentation, in the DownLink direction

LLC-PDU re-assembly, in the UpLink direction

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Radio Interface

MAC Layer

Multiplexing principles

Temporary Block Flow (TBF)

A TBF is a physical connection used by 2 RR entities to support the

unidirectional transfer of LLC-PDUs on PDCHs

The TBF is allocated radio resource on one or more PDCHs and

comprises a number of RLC blocks carrying one or more LLC

PDUs

A TBF is temporary and is maintained only for the duration of the

data transfer.

A TBF is identified by a Temporary Flow Identity (TFI)

Medium access modes

Three modes exist:

Dynamic allocation

Extended dynamic allocation

Fixed allocation

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Radio Interface

MAC Layer

Dynamic allocation

The control of the multiplexing of different MSs on an uplink PDCH

uses the USF (Uplink State Flag) mechanism.

The USF is a token which is distributed, by the network, at UL TBF

establishment (one USF per allocated PDCH)

The uplink multiplexing is scheduled by USF values included in the

header of each RLC downlink block

The USF value in downlink block Bn schedules the uplink block Bn+1.

(i.e. MS which has been allocated this USF, can use Bn+1 either as a

PDTCH or a PACCH)

On the master PDCH, a specific USF value is reserved (USF = FREE)

to schedule a PRACH. Another USF value is reserved to schedule a block for PACCH related

to a downlink TBF

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Radio Interface

System information

The MS shall monitor the System Information broadcast in the cell.

If PBCCH is present in the serving cell:

The MS shall receive the PSI messages broadcast on PBCCH

The presence of an activated PBCCH in the cell is indicated by the

PBCCH location description, in the SI13 message on BCCH When camping on a cell where PBCCH is present the MS shall

attempt to receive the PSI1 message at least every 30s

If PBCCH is not present in the serving cell:

The MS shall receive the SI messages broadcast on BCCH

The absence of an activated PBCCH in the cell is notified by anSI13 message without a PBCCH description

When camping on a cell where PBCCH is not present the MS shall

attempt to receive the SI13 message or the PSI13 message at least

every 30s (PSI13 may be broadcast on PACCH to avoid the MS in

transfer mode to have to read BCCH)

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Radio Interface

Radio Resource Management

The allocation of physical channels to Circuit Switched services and

GPRS is done dynamically according to the capacity-on-demand (i.e.

GPRS load is supervised to allocate or deallocate PDCHs)

Common control signalling, required by GPRS, in the initial phase of

the packet transfer is conveyed on PCCCH, when allocated, or on

CCCH.

GPRS doesnt require permanently allocated PDCHs.

GPRS master channel allocation may be dynamic, according to GPRS

signalling load.

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Radio Interface

TBF establishment

The establishment of a TBF can be initiated either by the MS or by the

network.

UL TBF establishment

The packet access can be done in either one phase or 2

phases

(2 phase access is necessary to request a RLC unacknowledge

mode and to send the MS multi-slot class, when the access is

on CCCH)

The packet access uses either the PCCCH (if there ia a master

PDCH) or the CCCH

The establishment can also be done on PACCH if a DL TBF ison-going.

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Radio Interface

TBF establishment

DL TBF establishment

The procedure may be entered either when the MS is in packet

idle mode (access on PCCCH or CCCH) or when the MS is in

packet transfer mode (i.e. an UL TBF is already established)

(access on PACCH)

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Radio Interface


One phase access on PCCCH

MS Network

Packet Channel Request (PRACH)

Packet Uplink Assignment + polling (PAGCH)(1)

(2)Packet Control Ack (PACCH)

(3)RLC data block (PDTCH)

Packet Uplink Ack/Nack (PACCH)

(4)

(5)

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Radio Interface



(1):

The Packet Channel Request is received on the PRACH and

indicates one phase access.

In case the request can be satisfied, a Packet UL Assignment

message is sent to the MS with a TFI, the allocated PDCHs with

their USF, the initial timing advance value (calculated on reception

of the Packet Channel Request) and the Timing advance Index (to

be used for continuous timing advance index).

(2):

The network forces the MS to send a Packet Control

Acknowledgement (polling indication) to be sure that the UL TBFhas been successfully established

The MS listens to the allocated PDCHs to detect its USF.

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Radio Interface



(3):

On reception of the Packet Control Ack, the network begins to

schedule UL blocks, with the USF mechanism

(4):

The MS transmits UL blocks when allowed by the network.

The MS shall provide its TLLI in RLC data blocks, until the end of

the contention resolution (i.e. reception of the Packet UL ack/Nack

with its TLLI)

(5):

The network acknowledges as soon as one of these blocks is

correctly received (i.e. the MS using the TBF is non-ambiguously

identified)

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Radio Interface


One phase access on CCCH

MS Network

Channel Request (RACH)

Packet Uplink Assignment + polling (PACCH)

(1)

(2)

Packet Control Ack (PACCH)(3)

RLC data block (PDTCH)

Packet Uplink Ack/Nack (PACCH)

Immediate Assignment (AGCH)

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Radio Interface



(1):

The Channel Request is received on the RACH and indicates one

phase access.

In case the request can be satisfied, an Immediate Assignment

message is sent to the MS with a TFI, one allocated PDCH with its

USF, the initial timing advance value (calculated on reception of the

Packet Channel Request) and the Timing advance Index (to be

used for continuous timing advance index).

A timer is activated to give time to the MS to take into account this

message

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Radio Interface



(2):

At timer expiry, a Packet UL Assignment message is sent to MS,

assigning the same resources as those assigned previously, but

without initial timing advance value.

The network forces the MS to send a Packet Control

Acknowledgement (polling indication) to be sure that the UL TBF

has been successfully established

(3): Then, the same process than on PCCCH occurs.

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Radio Interface


Two phase access on PCCCH

MS Network

Packet Channel Request (PRACH)

Packet Uplink Assignment (PAGCH) (1)

(2)

Packet Control Ack (PACCH)

(3)


(4)

Packet Resource Request (on allocated block)

Packet Uplink Assignment + polling

(5)

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Radio Interface



(1):

The Packet Channel Request is received on the PRACH and

indicates two phase access.

A Packet UL Assignment message is sent to the MS with the

definition of one UL block and the initial timing advance value

(calculated on reception of the Packet Channel Request).

No TFI, no USF and no TAI are assigned to the MS

(2):

At the occurrence of the allocated UL radio block, the MFS sends a

Packet Resource Request.

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Radio Interface



(3):

A Packet UL Assignment is sent to the MS on the PDCH from

which it received the Packet Resource Request

A TFI, PDCHs with their respective USF and the Timing Advance

Index are allocated

(4):

The network forces the MS to acknowledge the resource allocation

(with the polling indication)

The MS listens to the allocated PDCHs to detect its USF.

(5):

The network schedules UL blocks with the USF mechanism

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Radio Interface


Two phase access on CCCH

MS Network

Channel Request (RACH)

Immediate Assignment (AGCH) (1)

(2)


(3)


(4)

Packet Resource Request (allocated block)

Packet Uplink Assignment + polling

(5)

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Radio Interface


Two phase access on CCCH

(1):

The Channel Request is received on the RACH and indicates two

phase access.

An Immediate Assignment message is sent to the MS with the

definition of one UL block and the initial timing advance value

(calculated on reception of the Channel Request).

No TFI, no USF and no TAI are assigned to the MS

(2):

At the occurrence of the allocated UL radio block, the MFS sends a

Packet Resource Request.

(3):

Then same procedure as with PCCCH

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Radio Interface


(MS in packet transfer mode)

MS Network

RLC data block, polling (PDTCH)

Packet Downlink Ack/Nack (PACCH)

(1)

(2)


(3)


Packet Uplink Assignment + polling (PACCH)

R di I f

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Radio Interface



(1):

A DL transfer is on-going.

(2):

The MS requests establishment of an UL TBF by including a

Channel Request description IE in the Packet downlink Ack/Nack

message.

(3):

The Packet UL assignment is sent on the PACCH of the DL TBF,

assigning an UL TFI, the PDCH(s) carrying the TBF with their

respective USF and a TAI (no initial timing advance value is

provided)

R di I t f

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Radio Interface


on PCCCH

MS Network

Packet Downlink Assignment, polling (PPCH) (1)

(2) Packet Control Ack (on the allocated block)

(3)


Packet power ctrl/timing advance (PACCH)

(4)

R di I t f

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Radio Interface


on PCCCH

(1):

A packet DL Assignment message is sent with a TFI, PDCHs and a

Timing Advance Index (no initial timing advance value is provided)

(2):

The network forces the MS to acknowledge to be sure that the DL

TBF has been successfully established and to be able to compute

an initial timing advance value

(3):

The initial timing advance value is sent to the MS

(4):

Then, data transfer begins

R di I t f

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Radio Interface


on CCCH

MS Network

Immediate Assignment (PCH) (1)

(2)Packet Control Ack (on the allocated block)

(3)



(4)

Packet Downlink Assignment, polling (PPCH)

R di I t f

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Radio Interface


on CCCH

(1):

An Immediate assignment is sent with a TFI, one PDCH and a

Timing Advance Index (no initial timing advance value is provided).

A timer is activated to give time to the MS to take into account this

message.

At timer expiry, a packet DL Assignment message is sent with the

TFI, PDCHs (additional PDCHs may be allocated, since only one

PDCH can be allocated when using CCCH) and the Timing

Advance Index

(2), (3) and (4)

same procedure as on PCCCH

R di I t f

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Radio Interface



MS Network


(1)

(2)Packet Control Ack (on the allocated block)

(3)



(4)

Packet Downlink Assignment, polling (PACCH)

R di I t f

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Radio Interface



(1):

An UL TBF is on-going.

A Packet DL Assignment message is sent, on the PACCH of the

UL TBF, with a DL TFI, PDCHs and a Timing Advance Index (no

initial timing advance value is provided)

(2):

The network forces the MS to acknowledge to be sure that the DL

TBF has been successfully established

(3):

The initial timing advance value is sent to the MS (not necessary,

but sent to have only one process for DL TBF establishment)

(4):

Then, DL data transfer begins

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GPRS


Gb INTERFACE

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Gb interface

BSSGPNS (NSC)

L1

BSSGPNS (NSC)

L1

NS (SNS) NS (SNS)

FR network

BSS SGSN

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Gb interface

L1

Physical layer

Network Service (NS)

Sub-Network Service (SNS): dependent of the network

Provides access to the frame relay network

Network Service Control (NSC): independent of the network

Manages end-to-end logical connections between the BSS and

the SGSN.

BSS GPRS Protocol (BSSGP)

Conveys LLC-PDUs and GPRS Mobility Management signalling

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Gb interface

Gb entities

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Gb interface

Gb entities

Bearer Channel (BC)

A BC is a n x 64 Kbit/s channel on a 2048 Kbit/s link and supports a set of PVCs

Permanent Virtual Channel (PVC)

A Frame Relay PVC allows the service of multiplexing on a BC.

At network, a PVC is identified by its Data Link Connection Identifier (DLCI)

which is independent of the one defined at SGSN side. DLCI 0 is used for

signalling.

Network Service Virtual Channel (NS-VC)

A NS-VC provides end-to-end communication between the BSS and the SGSN

irrespective of the exact configuration of the Gb interface.

There is a one-to-one mapping between one NS-VC and one FR PVC.

Network Service Entity (NSE)

A NSE manages the resources associated to one BSS.It groups several NS-VCs

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Gb interface

Gb entities

BSSGP Virtual Connection (BVC)

A BVC is a virtual end-to-end path between the BSS and the SGSN.

Three types of BVCs exist:

Point-To-Point (PTP) BVC devoted to the GPRS traffic of one cell

signalling BVC which is the signalling circuit of all the BVC-PTPs of one

NSE

Point-To Multipoint (PTM)

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Gb interface

NS functions

BSSGP PDU transfer (NS UNITDATA PDUs are unacknowledged)

UL BSSGP PDUs load-sharing, among all the NS-VCs of one NSE

NS-VC management procedures

Blocking/unblocking of an NS-VC

When a NS-VC becomes locally unavailable either at the BSSor at the SGSN side, the remote NS enity is informed by means

of a blocking procedure.

A NS-VC may be blocked, because of:

O&M command

equipment failure

test procedure failure

When a NS-VC becomes available again, the NS entity which

initiated the blocking procedure (or the reset procedure) informs

the remote entity, by means of an unblocking procedure

Gb interface

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Gb interface

NS functions

Blocking/Unblocking procedures

NS entity NS entity

NS-BLOCK

NS-BLOCK-ACK

NS-VC

unavailable

NS-UNBLOCK

NS-UNBLOCK-ACK

NS-VC

available

(These PDUs are sent onany enabled NS-VC

belonging to the same

NSE)

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Gb interface

NS functions

NS RESET procedure

The reset procedure is used when a new NS-VC is set-up, after

processor restart, after failure recovery, or when its state is

undetermined

Upon completion of the reset procedure, the NS-VC is

blocked and its operational state is enabled

NS-VC TEST procedure

This procedure is used to check that end-to-end communication

exists between peer NS entities, on a given NS-VC

This procedure is intialised upon successful completion of the

reset procedure and shall be then periodically repeated When the procedure is successful, the operational state is

enabled otherwise it is disabled and the NS-VC becomes

blocked

Gb interface

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Gb interface

NS functions

Reset and Test procedures

NS entity NS entity

NS-RESET

NS-RESET-ACK(These PDUs are sent on

the NS-VC being reset)

NS entity NS entity

NS-ALIVE

NS-ALIVE-ACK(These PDUs are sent on

the NS-VC being tested)

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Gb interface

BSSGP functions

LLC PDU transfer (BSSGP UNITDATA PDUs are unacknowledged)

GMM procedures

Paging

To intiate a packet-switched transmission between the SGSN

and an MS, the SGSN sends a Paging PS PDU to the BSS

When instructed by the MSC/VLR to initiate circuit-switched

transmission between the MSC and an MS, the SGSN sends a

Paging CS PDU to the BSS (network mode operation I)

Radio status procedure

This PDU notifies bad conditions on the radio interface, for a

MS involved in a DL transfer

Gb interface

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Gb interface

BSSGP functions

GMM procedures procedures

BSS SGSN

PAGING CS (This PDU is sent either

on the BVC-SIG or on

the BVC-PTP)

BSS SGSN

PAGING PS (This PDU is sent on

the BVC-SIG)

BSS SGSN

RADIO STATUS (This PDU is sent on

the BVC-PTP)

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Gb interface

BSSGP functions

Network management procedures

FLUSH-LL procedure

The SGSN sends a FLUSH-LL to the BSS to ensure that LLC-

PDUs queued at a cell for a MS, are deleted or rerouted (e.g.

on MS location update)

LLC-DISCARD procedure

The BSS sends a LLC-DISCARDED PDU to the SGSN, when a

local LLC-PDU deletion has been performed (e.g. following a

PDU life-time expiry)

Flow control procedure

Downlink flow control is handled both at BVC and MS level

The BSS uses FLOW-CONTROL-BVC and FLOW-CONTROL-

MS PDUs to adjust the flow of BSSGP UNITDATA PDUs

Gb interface

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Gb interface

BSSGP functions

Network Management procedures

BSS SGSN

FLUSH-LL (This PDU is sent on

the BVC-PTP)FLUSH-LL-ACK

BSS SGSNLLC-DISCARDED (This PDU is sent on

the BVC-PTP)

BSS SGSN

FLOW-CONTROL-BVC/MS (This PDU is sent on

the BVC-PTP)FLOW-CONTROL-BVC/MS-ACK

Gb i f

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Gb interface

BSSGP functions

BVC Blocking/Unblocking procedures

These procedures are intiated by the BSS (cannot be initiated

by the SGSN) to remove from use, or bring into use a BVC-

PTP

The BSS may block a BVC-PTP because of:

O&M command

equipment failure at the BSS

cell equipment failure at the BSS

Gb interface

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Gb interface

BSSGP functions

Blocking/Unblocking procedures

BSS SGSN

BVC-BLOCK

BVC-BLOCK-ACK

BVC-PTP

unavailable

BVC-UNBLOCK

BVC-UNBLOCK-ACK

BVC-PTP

available

(These PDUs are sent on

the BVC-SIG)

Gb i t f

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Gb interface

BSSGP functions

BVC Reset procedure

This procedure is used to synchronise BVC states between the

BSS and the SGSN

This procedure may be initiated either by the SGSN or by the

BSS, on the following events:

BVC creation

processor recovery

underlying network recovery

After performing a BVC-RESET procedure, the affected BVC is

assumed to be in the unblocked state in the SGSN. So theBSS has to initiate a block procedure if the affected BVC-PTP

is marked blocked in the BSS (no block procedure for the

BVC-SIG)

Gb interface

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Gb interface

BSSGP functions

Reset procedure

BSS SGSN

BVC-RESET

BVC-RESET-ACK(These PDUs are sent on

the BVC-SIG)

BSS SGSN

BVC-RESET

BVC-RESET-ACK(These PDUs are sent on

the BVC-SIG)

Gb interface

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Gb interface

BSSGP functions

Reset procedure

RESET

O&M

lockingor

failure

O&M

unblockingor

recovery

unblocked

BVC-BLOCKBVC-UNBLOCK

or

RESET

unblocked

RESET

(1)locked

locked

BSS SGSN

(1): In this case, a block procedure has to be initiated

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GPRS


Data Transfer

D t t f

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Data transfer

Mobile terminating data transfer

SGSNBSSMS

Stand-by

(1)PAGING-PSPPCH or PCH (2)

Packet Channel Request (3)

Packet UL Assignment (4)

LLC PDU (5) UL TBF

UL-UNITDATA

Ready

DL-UNITDATA (6)Packet DL Assignment (7)

DL TBF. . . . . . . . .

Data transfer

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Data transfer


(1):

The SGSN receives a downlink PDP PDU, for an MS in stand-by

state (location of the MS is known at routing area accuracy)

A paging request is sent to the BSS

(2):

Packet Paging requests are sent in all the cells belonging to the

routing area, either on the PPCH, if there is a master PDCH in the

cell or otherwise on the PCH

(3):

To answer to the paging request the MS has to send a LLC-PDU

and to send this LLC-PDU, the MS has to request theestablishment of an UL TBF (either on PRACH, if there is a master

PDCH or otherwise on the RACH)

Data transfer

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Data transfer


(4):

An UL TBF is established (all the signalling messages exchanged

during the TBF establishment phase are not shown on the MSC

diagram)

(5):

The MS sends a LLC-PDU to answer to the paging of the SGSN

(6)

On the reception of the paging response, the SGSN knows the MS

cell location, the BSS adds the cell identifier in the UL message

(the MS is now in the ready state) and is now able to send data

LLC-PDUs to the BSS (7)

On the reception of the first LLC-PDU, the BSS establishes a DL

TBF.

This DL TBF is released, when there is no more LLC-PDUs to send

Data transfer

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Data transfer

Mobile originating data transfer

SGSNBSSMS

Packet Channel request (1)

Packet UL Assignment (2)

RLC PDU (3) UL TBF

UL-UNITDATA (5)Packet UL ACK/NACK (4)

Packet UL ACK/NACK UL-UNITDATA

(6)

..

Data transfer

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Data transfer


(1):

When the MS has data to send, the MS requests an UL TBF

establishment (either on PRACH, if there is a master PDCH or

otherwise on the RACH)

(2):

An UL TBF is established (all the signalling messages exchangedduring the TBF establishment phase are not shown on the MSC

diagram)

(3):

Data are sent to the network through RLC PDUs

(4) RLC PDUs are acknowledged by the network

Data transfer

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Data transfer


(5):

RLC PDUs are re-assembled into LLC PDU and then sent to the

SGSN

(6)

At reception of the last RLC PDU, an acknowledgement is returned

and the UL TBF is released

Documents

GPRS_tel