Gprs standards

GPRS Sales Training 1999 - Greater China Network Solutions Division

GPRS Standards Overview

By

Mohan Palat

GPRS Sales Training 1999 - Greater China Network Solutions Division GPRS Sales Training 1999 - Greater China Network Solutions Division

GPRS in a GSM Network

BTS

BSC

MSC

PSTN

VoiceCalls

GSM

SGSN GGSN

PacketDataNetwork

GPRS

Packet DataCalls


Main Concepts

Packet-based transmission

1 to 8 timeslots can allocated on the air interface per carrier

Timeslots can be shared between active users

Interworking with external IP and X.25 networks

QoS - different QoS levels defined


Main Concepts - continued

No handovers in GPRS (on the RF interface) only cell reselection

Uplink and Downlink timeslots allocated independently

1 2 3 4

1 2


Point to Point Point to MultiPoint (PTM)

Types of Services

• Requires knowledge of the location of receivers

ServiceRequester

GPRS Network

ServiceRequester

GPRS Network

• Service Requester specifies Receiver, Geographic Area (for PTM calls)


PTM - Multicast PTM - Group Call

Types of MultiPoint (PTM) Service

Message may be targeted to specific group orto all subscribers within a geographic area(s)

NOTE: No subscription is required to receive a PTM-Multicast message

Defined GPRS Geographic Area(s)

ServiceRequester

Message transmitted to a specific receiver group - messages are transmitted only to cells containingreceiver group members

ServiceRequester

Cells


PTM - IP Multicast

GPRS Network

ServiceRequester

Types of PTM Services (cont.)

IP Network

• IP messages are sent between participants• Group can be internal to PLMN or distributed across internet• Messages are compliant with Internet Protocols


GPRS Data Rates

Channel Coding Scheme Code Rate Data Rate

CS-1 1/2 9.05 Kbps

CS-2 2/3 13.4 Kbps

CS-3 3/4 15.6 Kbps

CS-4 1 21.4 Kbps

- Data Rates are per timeslot

- Maximum of 8 timeslots per carrier (shared among multiple users)

GPRS Data Rates


Data Rate for Mobile Classes

Rate Timeslots

1 2 3 4 5 6 7 8

9.05 9.05 18.1 27.15 36.2 45.25 54.3 63.35 72.4

13.4 13.4 26.8 40.2 53.6 67 80.4 93.8 107.2

15.6 15.6 31.2 46.8 62.4 78 93.6 109.2 124.8

21.4 21.4 42.8 64.2 85.6 107 128.4 149.8 171.2


SGSN

Intra PLMNBackbone

GPRS Backbone Networks

SGSN

GGSN BG

Inter PLMNBackbone

SGSN

Intra PLMNBackbone

SGSN

BG GGSN

• Every intra-PLMN network is a private IP network• Inter-PLMN networks based on agreements between operators

PLMN PLMN


BTS

BSC

MSC

PSTN

GSM

GPRS Network Interfaces

SGSN GGSN

PacketDataNetwork

GPRSA

Abis

All the GPRS interfaces start with “G”

Current GSM interfaces


GPRS Network Interfaces - Gb

SGSNGGSN

PacketDataNetwork

GPRS

BTS

BSC

MSC

PSTN

GSM

A

Abis

Gb• Used for both signalling and user data exchange• Based on Frame Relay link protocol• frame relay virtual circuits between BSS & SGSN• data (PDU) field: 1-600 octets in size

• Virtual circuits may be multi-hop• network of frame relay switching nodes

• Users multiplexed over the Gb link• Access rates can vary over the Gb link


GPRS Network Interfaces - Gs

SGSNGGSN

PacketDataNetwork

GPRS

BTS

BSC

MSC

PSTN

GSM

A

Abis

Gs

• SS7 link between SGSN and MSC• Mainly for signalling (no data flow)


GPRS Network Interfaces - Gr/Gc

SGSNGGSN

PacketDataNetwork

GPRS

BTS

BSC

MSC

PSTN

GSM

A

Abis

HLR

Gr

Gc

• SS7 link between SGSN/GGSN and HLR• Signalling link, no user data transfer• Primarily for

• lookup of GPRS subscriber info in HLR• GPRS mobile roaming (routing) information

•


GPRS Network Interfaces - Gn

SGSN GGSN

PacketDataNetwork

GPRS

BTS

BSC

MSC

PSTN

GSM

A

Abis

Gn

• IP network protocol (UDP/IP, TCP/IP)• Used for signalling and data transfer• GPRS Tunnelling Protocol (GTP) operates over IP

• User data encapsulated with GTP• May be multi-hop


GPRS Network Interfaces - Gi

SGSN GGSN

PacketDataNetwork

GPRS

BTS

BSC

MSC

PSTN

GSM

A

Abis

Gi

• IP or X.25 network protocol• Used for both signalling and data transfer• Main interconnection point between GPRS network and external packet data network


GPRS Network Interfaces - Gp

SGSNGGSN

PacketDataNetwork

GPRS

BTS

BSC

MSC

PSTN

GSM

A

Abis

Gp

• IP network protocol • Can be an Inter-PLMN backbone (internet, leased line)• Provides Gn interface + security• Connects to an external GPRS network

GGSN

External PLMN


GPRS Interfaces - Summary

GGSN

SGSN

Gb

MSC

Other Networks

Echo

XCDR

Voice

BSC

BTS BTSBTS

VLRA

Gs

Gi

Gn

Gp GPRS on adifferent PLMN

HLRGr


Packet Control Unit (PCU)

PCU

BTS BSC GSN

BTS BSC GSN

BTS BSC GSN

• Provides GPRS radio channel control functions

(1)

(2)

(3)

PCU

PCU

Circuit switched Packet switched


IMSI - same as GSM (Packet) TMSI -

local to an SGSN assigned both by MSC/VLR and SGSN MSC/VLR uses 00, 01, 10 & SGSN 11 as the two most

significant bits MS can be allocated 2 TMSIs simultaneously

PDP Address GPRS Mobile has one or more network layer addresses can be temporary or permanent (eg, IP address)

GPRS Mobile Identification


GPRS Subsystem Identities

GSN Address each SGSN and GGSN has an IP Address

GSN Number SGSN has a number for communication with HLR, etc.

TLLI (Temporary Logical Link Identity) identifies the logical link between MS and SGSN used for network layer routing


IMGI (International Group Mobile Identity) defines 2 levels of identification

Service provider

Application Level IMGI can be stored on SIM Card or on the ME 2 types of IMGIs: HPLMN IMGI or IMGIs that can be

used in multiple PLMNs IMSI used for authentication Subscriber Profile:

subscribed services (PTP, PTM-G etc) subscriber profile (priority, throughput, etc)

PTM Group Identification


Class A: supports both GPRS and Circuit-Switched (including SMS) user can make/receive calls on both services simultaneously mimimum of 1 timeslot available to each type of service

Class B: supports both GPRS and Circuit-Switched only one type of service at a time can be attached to both services

Class C: can be only attached to one service at a time can receive/make calls from default/manually selected

service

GPRS Mobile Classes


Type 1: Classes 1 through 12 Class 12: 4 consecutive ts receive, transmit on 3rd. ts OR 2

consecutive ts receive and transmit

Type 2: Classes 13 through 18 Can simultaneously transmit and receive on timeslots Classes 13 = 3 ts, Class 14 = 4 ts ….. Class 18 = 8 ts

Type 3: Half Duplex, power efficient mode Classes 19 through 28 Class 19-23 supports ts from 3-8 Classes 24-28 supports ts from 3-8

GPRS Mobile Types

Difference is thespacing of PACCH


GPRS must interwork with the following external data networks:

X.25 networks IP networks a. user’s IP address is allocated from a pool of unused IP

addresses upon activation of access to IP network

b. user’s IP address is permanently allocated

other GPRS PLMNs

GPRS Network Interworking


GPRS Support in Cells

A cell may or may not support GPRS

Non-GPRS Cells

GPRS Cells


Tunnelling in GPRS

GPRS Tunnelling Protocol (GTP)

Point to Point path through one or more intermediate nodes

Data Packet add GPRS Tunnelling Protocol header

• contains endpoint identifiers insert this in a TCP or UDP packet data unit insert this in an IP packet data unit

SGSN GGSN

IP Backbone

PLMN 2PLMN 1


“Anonymous Acess” concept

MS does not identify itself (IMSI) Authentication not required for Anonymous Access Temporary TLLI assigned to MS

Regular GPRS call: all GPRS activities can be traced to a GPRS subscriber

Anonymous GPRS call: all GPRS activities can be traced only to an auxiliary TLLI.

Mobile requests Anonymous Access, and a logical link to SGSN (TLLI) is established

Examples: Services where Service Provider pays for the call Services where user confidentiality is required


Half Duplex Mode

Fixed vs Dynamic Allocation Dynamic: MS must continuously monitor downlink

(USF bits) Fixed: MS is given specific time to start and stop

transmitting

Fixed Allocation Mode is the Half Duplex Mode of operation


GPRS Standards

GPRS Standards being done in phases

PHASE 1:

• PTP (TCP/IP, connectionless)• X.25 Support • Network Interfaces (Gn, Gb, Gr, Gp, Gs, Gi)• Security• Charging Issues (information to be collected)• SMS over GPRS• anonymous access

PHASE 1:

• PTP (TCP/IP, connectionless)• X.25 Support • Network Interfaces (Gn, Gb, Gr, Gp, Gs, Gi)• Security• Charging Issues (information to be collected)• SMS over GPRS• anonymous access

PHASE 2:

• PTM-Multicast• PTM-Group Call• Supplementary Services• Additional External Network Interfaces


STAGE 1STAGE 1

STAGE 2STAGE 2

STAGE 3STAGE 3

02.60General GPRS Overview

03.60 03.64 03.61 03.62 General System Radio Arch. Point to MultiPoint Point to MultiPointDesc. & Network Description Multicast Group CallArchitecture

02.60 04.65 09.60 04.61 04.62 LLC SNDCP Gb Interface PTM-M Services PTM-G Services

08.64 07.60 09.60 04.60 BSSGP User External NetworkGb Interface Interworking Interworking

• Plus modifications to existing standards (Stage 3)

GPRS Standards Breakdown

Read 03.60 if you have time to read only one document !


Air Interface - New Channels

PDTCH - Packet Data Traffic Channel PACCH - Packet Associated Control Channel

PBCCH - Packet Broadcast Control Channel

PCCCH PAGCH - Packet Access Grant Channel PPCH - Packet Paging Channel PNCH - Packet Notification Channel

PRACH - Packet Random Access Channel

Downlink Only

Uplink Only

Downlink Only

Uplink &Downlink


Air Interface Timeslot Allocation

Upto 8 timeslots can be allocated for GPRS maximum one GPRS carrier per cell (initial release)

Air interface timeslot configuration: GPRS only timeslots GPRS and Circuit Switched timeslots Circuit Switched (GSM voice) timeslots

BCCHCarrier

0 .

.

7

Second Carrier

BCCHCarrier

0 .

.

7

Second Carrier

BCCHCarrier

0 .

.

7

Second Carrier

Switchable

TCH

BCCH/CCCHwith GPRS msg

GPRS only


Mobile States and Transitions

IDLE

READY

STANDBY

GPRS Attach GPRS Detach

Packet DataTransmission

READY timer expiryorForce to STANDBY

STANDBYtimerexpiry

IDLE:

- not attached to GPRS

- MS, SGSN has no valid location routing information

- MS can only receive PTM-M STANDBY

- MS attached to GPRS network

- MS can receive pages for incoming data

- MS can receive CS pages READY

- MS sends and receives packet data

- MS remains in this state until it times out


Basic Call Processing

MS turns on. MS initiates LOGON procedure with SGSN

GGSN gets location update of MS.

HLR assigns IP address to MS from its static pool of IP addresses

MS goes into standby mode


Mobile Originated Call

Channel Request on PRACH or RACH

BSS assigns initial resources to MS (Timing Advance, Timeslots)

Data Blocks

Packet Acknowledge

Packet Data Channel

PACCH Channel

MS goes into STANDBY Mode


Mobile Terminated Call

Paging Request from BSS

BSS assigns initial resources to MS (Timing Advance, Timeslots)

Data Blocks

Packet Acknowledge

Packet Data Channel

PACCH Channel

MS goes into STANDBY Mode

Channel Request on PRACH or RACH

Technology

Gprs standards