GPRS-EDGE Radio Network Optimization

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www.huawei.com

GPRS Principles

(2)

Foreword

z

GPRS principle is the basic part of the whole GPRS system

and the succeeding products learning.

z

This slide will help us to understand the GPRS system

networking and wireless subsystem etc.

(3)

Objectives

z

Upon completion of this course, you will be able to:

Know the GPRS system structure

Describe the GPRS important interfaces Understand the GPRS channel structures Master the GPRS relevant numbering

(4)

1. GPRS System Overview

2. GPRS Architecture

3. GPRS Network Interfaces & Protocols

4. GPRS Wireless Subsystem

5. GPRS Location Area

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Circuit Switch (CS)

CS F CS CS _CS CS A B C D E G H I J K L 5

(6)

Packet Switch (PS)

PS PS PS 1 2 3 1 2 3 1 3 2 2 1 3 2 2 1 3 1 2 3 1 2 3 PS PS PS PS PS PS PS 1 2 3 1 2 3 1 3 2 2 1 3 2 2 1 3 1 2 3 1 2 3 PS PS PS A C B D 6

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GSM Development Evolution

GSM 9.6 Kb/s GPRS 21.4 Kb/s EGPRS 59.2 Kb/s 384 Kb/s UMTS 2 G 2.5 G 2.75 G 3 G HSCSD 14.4 Kb/s ECSD 38.8 Kb/s CS PS EDGE 7

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What is GPRS and EDGE?

z

Abbreviation of

G

eneral

P

acket

R

adio

S

ervice.

z

GPRS is an end-to-end packet switching technology

provided on the basis of GSM technology.

z

It has much interactive services with the existing GSM

circuit switching system.

z

GPRS supports wireless access rate of up to 171.2Kbps.

z

EDGE (

E

nhanced

D

ata R

ates for

G

SM

E

volution)

EGPRS (Enhanced GPRS)

EGPRS supports wireless access rate of up to 473.6Kbps.

ECSD (Enhanced CSD, Enhanced HSCSD-High Speed Circuit

Switched Data)

•GPRS is the abbreviation of General Packet Radio Service.

•GPRS network introduces packet switching functional entities in the GSM network

to implement data transmission in the packet mode.

•GPRS can be regarded as the service expansion based on the GSM network for

supporting mobile subscribers access the Internet of other packet data networks via

packet data mobile terminal. Making full use of the existing GSM network,small

investment and quick rewarding,all of these benefit to protect the existing

investment and obtain maximum benefits for the operators.

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GPRS&EDGE Coding Rate

8PSK GMSK 9.05 13.4 15.6 21.4 8.8 11.2 14.8 17.6 22.4 29.6 44.8 54.4 59.2 0.00 10.00 20.00 30.00 40.00 50.00 60.00 CS-1 CS-3 CS-4 MCS-1 MCS-2 MCS-3 MCS-4 MCS-5 MCS-6 MCS-7 MCS-8 MCS-9 Kbps GPRS EGPRS CS-2 9

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Adjustments to GSM Network

BSS CS Core Network A PS Core Network PCU BSS NSS Gb Pb Gs 10

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Most Popular GPRS Applications

z

E-mail

z

Web Browsing

z

Information Services

z

Moving Images

z

Still Images

z

Remote LAN Access

z

File Transfer

z

Job Despatch

Traffic Information Sport Report Weather Forecast Stock Market Public Information Service Email Web Browsing Still Images File Transfer Moving Bank Live News Personal Information Service 11

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Advantages and Disadvantages of

GPRS

z

Advantages

Share resource with GSM High resource utilization Fast transmission rate Always on line

Short access time

z

Disadvantages

Slower data rates in practice than anticipated in theory Suboptimal modulation technique

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1. GPRS System Overview

2. GPRS Architecture

3. GPRS Network Interfaces & Protocols

4. GPRS Wireless Subsystem

5. GPRS Location Area

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CS & PS Logic Structure

HLR AUC GPRS Register MSC/VLR BSC Abis D C CS GMSC PSTN B T S BSS CN E A PS Gs SGSN GGSN Gb Gn Gc Gr Gi Internet G-Abis Pb PCU TRAU 14

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Gf Gi Gn Gc Gp Gs MSC/VLR Gr SGSN Gd SMS-GMSC SMS-IWMSC GGSN EIR SGSN Gn GPRS Backbone ATM/DDN/ISDN/Ethernet, etc CN CN--PSPS GGSN Gi CG

GPRS System Structure

Gb SS7 HLR Ga Intranet/Internet Firewall RADIUS WAP Gateway Other PLMN BTS BSC BSS BSS Abis PCU Gb BTS BSC BSS BSS Abis PCU X.25 DNS BG MS MS 15

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GPRS MS

z Class A

The MS is attached to both GPRS and other GSM services and the

MS supports simultaneous operation of GPRS and other GSM services.

z Class B

The MS is attached on GPRS network and GSM network

simultaneously but not enabling circuit switching and packet switching services at the same time.

services are selected automatically.

z Class C

The MS is attached to either GPRS or other GSM services. Alternate

use only.

services are selected manually or default selected service.

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Functions of PCU (Packet Control Unit)

z

Packet wireless resource management function (RLC/MAC

protocol function)

Wireless resource management functions of GPRS BSS Circuit paging coordination

z

G-Abis interface processing function

Function related with GPRS BTS

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Functions of PCU (Packet Control Unit)

z

Pb interface processing function

LAPD link between BSC and PCU

Layer-3 signaling between BSC and PCU

z

Gb interface processing function

Data packet relay on wireless interface and Gb interface Mobility management (cell updating procedure)

Downlink traffic control (wireless QoS guarantee)

Provides physical and logical data interface out of the BSS for packet data

traffic

LLC layer PDU segmentation/reassembly of RLC blocks

Packet data transfer scheduling

ARQ functions

Radio channel management function

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Functions of SGSN (Serving GPRS

Support Node)

z

Packet routing

z

MS Session management

z

Authentication and Ciphering

z

Mobility management

z

Billing information collection

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Functions of GGSN (Gateway

GPRS Support Node)

z

Interface between GPRS backbone and external PDNs.

z

PDP Conversion and context management

z

IP address assignment management

z

Packet routing to/from SGSNs

z

Billing information collection

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Functions of CG (Charging

Gateway)

z

Real-time collection of GPRS bills

z

Temporary storage and buffering of GPRS bills

z

Pre-processing of GPRS bills

z

Sending GPRS bills to the billing center

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Functions of MSC/VLR

z When Gs interface is installed, MSC/VLR can support

z Establishment and maintenance of the association between SGSN and MSC/VLR.

z GPRS combined mobility management procedure.

Combined IMSI/GPRS attachment/detachment. Combined location area/routing area updating.

z Circuit paging coordination function.

z The wireless resource usage can be greatly improved.

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Functions of HLR/AUC

z

Saving and updating GPRS subscriber subscription data

z

User authentication

z

Providing location/routing information and processing

needed in mobility management and routing, for example:

Saving and updating user service SGSN number and address GPRS user location deletion indication

Whether MS is reachable.

z

Subscriber tracing (optional)

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Functions of SMS-GMSC/SMS-IWMSC

z The SMS-GMSC and SMS-IWMSC are connected to the SGSN via the Gd interface to enable GPRS MSs to send and receive SMs over GPRS radio channels.

z After Gd interface is installed, short messages can be sent via GPRS, which reduces the occupation on SDCCH and cuts down the influence on voice services by SMS services.

z The operator can select to send SMS via MSC or SGSN.

MS SGSN SMS-IWMSC_SMS-GMSC

Gd SMS

SMS-IWMSC(Interworking MSC For Short Message Service):A function of an MSC capable of receiving a short message from within the PLMN and submitting it to the recipient SC.

For example:The MSC forwards the SM to the SMS-IWMSC, which is responsible for processing SMs submitted by the MS.

SMS-IWMSC:The SMS Interworking MSC acts as an interface between the PLMN and a Short

Message Service Centre (SC) to allow short messages to be submitted from Mobile Stations to the SC.

SMS-GMSC(Gateway MSC For Short Message Service):A function of an MSC capable of receiving a short message from an SC, interrogating an HLR for routing information and SMS info, and delivering the short message to the VMSC of the recipient MSFor example:The SMS system submits the message transfer request to the SMS-GMSC, which is responsible for processing delivered SMs.

SMS-GMSC:The SMS Gateway MSC (SMS-GMSC) acts as an interface between a Short Message

Service Centre and the PLMN, to allow short messages to be delivered to mobile stations from the Service Centre (SC)。

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Functions of BG (Border Gateway)

z BG enables the following protocols necessary for interworking between

operators

Security protocol: IPSec and firewall are recommended Routing protocol: BGP is recommended

Billing protocol: determined by the operators with negotiation; BG might be

needed in collecting billing information

z It is normally based on routers

z It can be combined with GGSN in physical.

z BG does not exclusively belong to the GPRS network.

Gp PLMN A GSN RR BG R R BG _{PLMN B}GSN

IPsec (IP security) is a standardized framework for securing Internet Protocol (IP)

communications by encrypting and/or authenticating each IP packet in a data stream.

A protocol for exchanging routing information between gateway host s (each with

its own router ) in a network of autonomous system s. BGP is often the protocol

used between gateway hosts on the Internet.

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Functions of DNS (Domain Name System)

z The following two types of DNSs may be adopted in the GPRS network:

The DNS between the GGSN and external networks

The DNS on the GPRS backbone network. Provides two types of

functions:

a. Resolve the GGSN IP address based on the Access Point Name (APN)

in the process of the PDP context activation;

b. Resolve original SGSN IP address based on the original routing area No.

in the process of the update of inter-SGSN routing area.

z DNS does not exclusively belong to the GPRS network.

GPRS Backbone

SGSN

DNS Server

SGSN

DNS（Domain Name System）

The following two types of DNSs may be adopted in the GPRS network:

The DNS between the GGSN and external networks: Implements resolution of the

domain name of external network, and functions as the ordinary DNS on the Internet.

The DNS on the GPRS backbone network. Provides two types of functions:

a. Resolve the GGSN IP address based on the Access Point Name (APN) in

the process of the PDP context activation;

b. Resolve original SGSN IP address based on the original routing area No.

in the process of the update of inter-SGSN routing area. The DNS is not a

proprietary entity of the GPRS network.

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Functions of RADIUS Server (Remote

Authentication Dial In User Service Server)

z

It is a protocol used by Remote Access Server's for user

Authentication.

z

The RADIUS server stores the authentication and

authorization information of subscribers.

z

It also performs subscriber identity authentication in the

case of non-transparent access.

z

RADIUS Server does not exclusively belong to the GPRS

network.

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1. GPRS System Overview

2. GPRS Architecture

3. GPRS Network Interfaces & Protocols

4. GPRS Wireless Subsystem

5. GPRS Location Area

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3. GPRS Network Interfaces & Protocols

3.1 Interface and Protocol Stack 3.2 Um Interface

3.3 G-abis/Pb Interface 3.4 Gb Interface

3.5 Gs Interface

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Network interface types

GPRS backbone network

SGSN

GGSN

Gn IP interface SS7 interface BSS A MSC _GMSC SMS-Um PDP network (IP/X.25) Gi TE MT MS HLR Gs Gr Gd Gc Gb 30

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Interface in GPRS Network

The interface between MS and GPRS network side Um

The interface between the SGSN and EIR (optional). Gf

The interface between the SGSN and MSC/VLR (optional). Gs

The interface between the SGSN and HLR. Gr

The interface between GSNs of different PLMNs. Gp

The interface between SGSNs and between SGSN and GGSN in the PLMN. Gn

The reference point between the GPRS and external packet data Gi

The interface between SMS and GMSC

The interface between SMS-IWMSC and SGSN Gd

The interface between the GGSN and HLR (optional). Gc

The interface between the SGSN and BSS. Gb

The reference point between the Mobile Terminal (MT) (for example, mobile phone)

and the Terminal Equipment (TE) (for example, the portable computer). R

Description Interface

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Data transmission plane

z MAC: Media Access Control

z RLC: Radio Link Control

z LLC: Logical Link Control

z BSSGP: BSS GPRS Protocol

z SNDCP: Sub-Network Dependency Convergence Protocol

z GTP: GPRS Tunneling Protocol Application

IP/X.25 IP/X.25 IP/X.25

SNDCP GTP

LLC LLC UDP/TCP UDP/TCP

RLC BSSGP BSSGP IP IP

MAC MAC Network_Service Network_Service L2 L2

L2 (MAC) Physical Layer Physical Layer Physical

Layer Physical_Layer Physical_Layer Physical_Layer Physical_Layer

MS BSS SGSN GGSN relay relay SNDCP GTP Um Gb Gn Gi RLC

The Relay function provides buffering and parameter mapping between the RLC/MAC and the BSSGP. For example, on the uplink the RLC/MAC shall provide a TLLI. The Relay function shall then make it available to BSSGP.

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MS-SGSN signaling plane

z GMM: GPRS Mobility Management z SM: Session Management MS BSS SGSN BSSGP GMM/SM LLC RLC MAC GSM RF GMM/SM LLC BSSGP L1bis Um Gb Network Service RLC MAC GSM RF L1bis Network Service Relayrelay Um interface:

Physical layer: wireless coding/decoding, channel multiplexing and mapping, wireless link control and wireless measurement

RLC/MAC: wireless interface media access and link control function

LLC: providing a reliable logic link between MS and SGSN for data transmission. LLC protocol can support both acknowledged mode and unacknowledged mode. It supports both encryption and decryption modes

SNDCP: Layer-3 transmission protocol. As the transition between the network layer and the subnet layer, it implements segmentation/assembling and compression/decompression on IP/X.25 subscriber data

GMM/SM: Layer-3 signaling protocol

Gb interface:

L1bis: physical transmission layer based on E1 or T1

NS: based on FR; used to transmit BSSGP PDU of the upper layer

BSSGP: On the transmission platform, this protocol is used to provide a connectionless link between BSS and SGSN for unacknowledged data transmission; on the signaling platform, it is used to transmit QoS and routing information related with the wireless section; it is also used to process paging requests and implement traffic control on data transmission

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3. GPRS Network Interfaces & Protocols

3.1 Interface and Protocol Stack 3.2 Um Interface

3.3 G-abis/Pb Interface 3.4 Gb Interface

3.5 Gs Interface

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Protocol Layer of Um Interface

z GMM (GPRS Mobility Management): operates in the signalling

plane of GPRS supports mobility management functionality.

z SM (Session Management): processes procedure that GPRS MS connects to the external data network.

z SNDCP (Subnetwork Dependent Convergence Protocol):

Multiplexing of several PDPs, compression / decompression and Segmentation of user data.

z LLC (Logical Link Control ): This layer provides a highly reliable ciphered logical link between an MS and its SGSN.

z RLC:Segmentation and re-assembly between LLC PDUs and

RLC blocks.

z MAC: defines the procedures that enable multiple mobile

stations to share a common transmission medium.

LLC RLC MAC RF Physical Link SNDCP SMS GMM/SM

GMM (GPRS Mobility Management)

This protocol that operates in the signalling plane of GPRS supports

mobility management functionality such as GPRS attach, GPRS detach,

security, routing area update, location update, roaming, authentication, and

selection of encryption algorithms.

SM (Session Management)

It is the processing procedure that GPRS MS connects to the external data

network. The main function is to support the processing of PDP mobile

scenario.

Logical Link Control (LLC): This layer provides a highly reliable ciphered

logical link between an MS and its SGSN.

LLC includes functions for

the provision of one or more logical link connections discriminated between

by means of a DLCI.

sequence control, to maintain the sequential order of frames across a logical

link connection.

detection of transmission, format and operational errors on a logical link

connection.

recovery from detected transmission, format, and operational errors.

notification of unrecoverable errors.

flow control.

ciphering.

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MM State

IDLE

>GMM context is not established; MS is not reachable.

>MS can implement data transmission.

>GMM context is established; MS can receive paging but cannot implement data transmission.

The MS performs MM procedures to provide the network with the actual

selected cell.

SGSN performs the MM on cell level.

READY STANDBY

The location information in the SGSN MM context contains only the GPRS RAI. Pages for data or signalling information transfers may be received. It is also

possible to receive pages for the CS services via the SGSN. Data reception and transmission are not possible in this state.

Data transmission to and from the mobile subscriber as well as the paging of

the subscriber are not possible

The Mobility Management (MM) activities related to a GPRS subscriber are

characterised by one of three different MM states.

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MM State Model

IDLE READY STANDBY

MM State Model of MS MM State Model of SGSN GPRS Attach GPRS Detach

READY timer expiry or

PDU transmission

PDU reception

Implicit Detach or Cancel Location

GPRS Attach

Force to STANDBY

READY timer expiry or Force to STANDBY or Abnormal RLC condition

GPRS Detach or

Cancel Location

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RLC/MAC Block Generation

RLC/MAC block

Subscriber data SNDCP head LLC head LLC FCS RLC/MAC head LLC frame Subscriber IP packet (N-PDU)

SNDCP PDU(SN-PDU) Network Layer SNDCP Layer LLC Layer RLC/MAC Layer 38

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Physical Channel

z The same as in GSM

z The same frequency z The modulation mode

z The same TDMA frame definition

z The same burst pulse definition

z …

z The differences between GPRS and GSM z The Multi-frame structure

z The channel coding

z … Application IP/X25 SNDCP LLC RLC RLC _BSSGP

MAC MAC Frame_relay

Physical

Layer PhysicalLayer PhysicalLayer

MS BSS

Relay

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Packet Logic Channels

z The specific type of PDCH (except PRACH) is determined by

RLC/MAC head and RLC/MAC control message type.

TCH

BCCH

PCH, RACH, AGCH,NCH Packet service channel

PACCH

Packet Logic Channel

Packet control channel

PBCCH PPCH PRACH PAGCH PCCCH PDCCH PDTCH/U PDTCH/D PNCH PTCCH/U PTCCH/D SACCH 40

(41)

Channel Abbreviation

z

P

acket

D

ata

T

raffic

CH

annel

U

plink - PDTCH/U

z

P

acket

D

ata

T

raffic

CH

annel

D

ownlink - PDTCH/D

z

P

acket

B

roadcast

C

ontrol

CH

annel - PBCCH

z

P

acket

C

ommon

C

ontrol

CH

annel - PCCCH

z

P

acket

D

edicated

C

ontrol

Ch

annel - PDCCH

z

P

acket

P

aging

CH

annel - PPCH

z

P

acket

R

andom

A

ccess

CH

annel - PRACH

z

P

acket

A

ccess

G

rant

CH

annel - PAGCH

z

P

acket

N

otification

CH

annel - PNCH

z

P

acket

A

ssociated

C

ontrol

CH

annel - PACCH

z

P

acket

T

iming advance

C

ontrol

CH

annel

U

plink - PTCCH/U

z

P

acket

T

iming advance

C

ontrol

CH

annel

D

ownlink

-PTCCH/D

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PDTCH (Packet Data Traffic CHannel)

z

All packet data traffic channels are

uni-directional.

Uplink (PDTCH/U) for a mobile

originated packet transfer.

Downlink (PDTCH/D) for a mobile

terminated packet transfer.

Packet service channel

PDTCH/U PDTCH/D

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PBCCH (Packet Broadcast Control

CHannel)

z The PBCCH broadcasts parameters used by the MS to access the network for packet transmission operation.

z The PBCCH also carries the information transmitted via the BCCH to allow circuit switching operation.

The MS in GPRS attached mode monitors

the PBCCH only, if PBCCH is available, otherwise, the BCCH shall be used to broadcast information for packet operation.

The existence of the PBCCH in the cell is

indicated on the BCCH via SI13.

Packet control channel

PBCCH

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PCCCH (Packet Common Control

CHannel)

z PPCH

Downlink only, used to page MS.

z PRACH

Uplink only, used to request allocation of one or

several PDTCH/Us or PDTCH/Ds.

z PAGCH

Downlink only, used to allocate one or several

PDTCHs. z PNCH

Downlink only, used to notify MS of PTM-M call.

z If no PCCCH is allocated, the information for packet switching operation is transmitted on the CCCH. If a PCCCH is allocated, it may transmit information for circuit switching operation.

PPCH PRACH PAGCH

PCCCH

PNCH

(45)

PDCCH (Packet Dedicated Control

Channels)

z PACCH

Bi-directional, used to transmit the packet

signaling in data transmission. z PTCCH/U

Used to transmit random access bursts to

allow estimation of the timing advance for one MS in packet transfer mode.

z PTCCH/D

Used to transmit timing advance updates for

several MS. One PTCCH/D is paired with several PTCCH/U's.

PACCH PDCCH

PTCCH/U PTCCH/D

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Combinations of Packet Logic

Channel

Mode 3: PDTCH+PACCH+PTCCH

Mode 1: PBCCH+PCCCH+PDTCH+PACCH+PTCCH Mode 2: PCCCH+PDTCH+PACCH+PTCCH

In case of small GPRS traffic, GPRS and circuit services share the same BCCH and CCCH in the cell. In this case, only combination mode 3 is needed in the cell.

With the increase of traffic, the packet public channel should be configured in the cell. Channel combination mode 1 and mode 2 should be adopted.

Mode 4: PBCCH+PCCCH

(PCCCH=PPCH+PRACH+PAGCH+PNCH）

(47)

Packet Wireless Channel

Configurations

z Reason of adopting static PDCH

To enable that GPRS MS is constantly online in the cell. To ensure certain QoS of GPRS services.

z Reason of adopting dynamic PDCH

GPRS and GSM share wireless resources.

Wireless resources should be adopted in priority; on the other hand,

QoS of voice services should be ensured.

In a cell, the percentage of packet switching services and the

percentage of circuit switching services are constantly changing.

Dynamic PDCH is not visible for voice services.

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Packet Wireless Channel

Configurations

z

General principles

The cell should be configured with static PDCH to enable MS to

be normally attached on GPRS network as well as certain QoS of GPRS services.

Dynamic PDCH should be configured according to the GPRS

traffic forecast, which should be adjusted as TCH or PDCH usable in the operation process according to the cell traffic status.

Circuit switching services can seize the channel used by GPRS

services.

(49)

Mapping of Packet Logic Channel

z

A radio block is a 4-normal-burst sequence that carries a

RLC/MAC PDU (Protocol Data Unit).

I = Idle frame T = Frame used for PTCCH

B0 ~ B11 = Radio blocks 51 25 0 B0 B1 B2 T B3 B4 B5 I B6 B7 B8 T B9 B10 B11 I 456 bits 0 1 2 3 4 5 6 7 1 TDMA frame 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 49

(50)

Mapping of Packet Logic Channel

51 4 3 5 6 7 0 1 2 B0 B1 B2 T B3 B4 B5 I B6 B7 B8 T B9 B10 B11 I 50 0 BCCH PDCH TCH S B B B B C C C C F S C C C C C C C C F S C C CC C C C C F S C C C C C C C C F S C C C C C C C C_I T T T T T T T T T T T S T T T T T T T T T T T T I T F 25 25 12 50

(51)

Transmission Principle of Data Packet

on Um Interface

Subscriber data SNDCP head LLC head RLC/MAC head Subscriber IP packet LLC FCS SNDCP PDU LLC PDU RLC/MAC block Physical layer B0 B1 B2TB3 B4 B5 I B6 B7 B8TB9 B10 B11I N B N B N B N B 51

(52)

Allocation of Wireless Packet

Resources

z Wireless resource allocation and wireless transmission adopt the wireless block (BLOCK) as the basic unit.

z Each PDCH can be used by several MSs; each MS can use multiple PDCHs at the same time. B1 B2 B3 B4 B5 B6 B7 B8 B9 B1 0 B1 1 B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B1 0 B1 1 B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11 B0 MS3 MS2 TS 0 TS 1 TS 2 MS1 52

(53)

Basic Conceptions about Radio Block

z USF(Uplink State Flag) is sent in all downlink RLC/MAC blocks and indicates the owner or use of the next uplink Radio block on the same timeslot.

z The USF field is three bits in length

B11 B 10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0 T I T I UL DL USF= 1 US F=1 USF=1 USF= 2 US F=2 USF=3 USF= 3 US F=3 USF= 3 US F=4 USF= 4 US F=4 T I T I USF=1 USF=2 USF=3 USF=4 MS1 MS2 MS3 MS4 USF=1 …… B0 I ……

The USF field is three bits in length and eight different USF values can

be assigned, except on PCCCH, where the value '111' (USF=FREE)

indicates that the corresponding uplink Radio block contains PRACH.

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Basic Conceptions about Radio Block

z TBF (Temporary Block Flow)

A Temporary Block Flow (TBF) is a physical connection used by the

two RR entities（the RR entity of the MS and that of the BSS） to support the unidirectional transfer of LLC PDUs on packet data physical channels.

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

transfer.

z TFI (Temporary Flow Identity)

Each TBF is assigned a Temporary Flow Identity (TFI) by the network. The TFI field is five bits in length.

The same TFI value may be used concurrently for TBFs in opposite directions. The

TFI is assigned in a resource assignment message that precedes the transfer of LLC

frames belonging to one TBF to/from the MS. The same TFI is included in every

RLC header belonging to a particular TBF as well as in the control messages

associated to the LLC frame transfer (e.g. acknowledgements) in order to address

the peer RLC entities.

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4. GPRS Wireless Subsystem

4.1 Packet Channels

4.2 Medium Access Modes 4.3 MS Multi-TS Ability 4.4 Power Control

4.5 Network Control Modes

(56)

Medium Access Modes

z Uplink resource allocation mode

Dynamic allocation (supported by all MSs and all networks)

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.

Fixed allocation (supported by all MSs and all networks)

Fixed bit mapping is adopted to determine the allocated blocks in the allocation period

without an assigned USF.

Extended dynamic allocation (optional for the network)

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.

z Downlink resource allocation mode

Dynamic allocation and fixed allocation.

Three medium access modes are supported:

- 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

- Fixed Allocation characterised by fixed allocation of radio blocks and PDCHs in the assignment message without an assigned USF. Fixed Allocation may operate in half duplex mode, characterised by that downlink and uplink TBF are not active at the same time. Half duplex mode is only applicable for multislot classes 19 to 29.

Either the Dynamic Allocation medium access mode or Fixed Allocation medium access mode shall be supported by mobile stations and all networks that support GPRS. The support of Extended Dynamic Allocation is optional for the network.

The Dynamic Allocation and Fixed Allocation modes shall be supported in all mobile stations. The support of Extended Dynamic Allocation is mandatory for mobile stations of multislot classes 22, 24, 25 and 27. The support of Extended Dynamic Allocation for mobile stations of all other multislot classes are optional and shall be indicated in the MS Radio Access Capability.

In the case of a downlink transfer, the term medium access mode refers to the measurement time scheduling, for the MS to perform neighbour cell power measurements

(57)

4. GPRS Wireless Subsystem

4.1 Packet Channels 4.2 Medium Access Modes 4.3 MS Multi-TS Ability 4.4 Power Control

(58)

MS Multi-TS Ability

z Concept of MS multi-TS ability

Types

Type 1: Non-simultaneous TRX Type 2: Simultaneous TRX

the multi-TS ability level is 1-29; the bigger the level, the stronger the

multi-TS ability.

1~12 (Type 1),up to 4 timeslots in any direction 13~18 (Type 2),ranges between 3~8 timeslots 19~29 (Type 1)

z BSS allocates resources according to the MS multi-TS ability, requested QoS and current resource configuration.

(59)

4. GPRS Wireless Subsystem

4.1 Packet Channels

4.2 Medium Access Modes 4.3 MS Multi-TS Ability 4.4 Power Control

(60)

Power Control

z Power control can improve the spectrum usage and system capacity as well as reduce MS power consumption.

z As there is no continuous bi-directional connection in the packet data transmission process, GPRS power control is very

complicated.

z Uplink power control includes open-loop and close-loop power control.

z About downlink power control, there is no specific definition in protocol. It lies on the BTS and its algorithm needs information about downlink, so downlink power control needs MS sends channel quality reports to BTS.

(61)

4. GPRS Wireless Subsystem

4.1 Packet Channels

4.2 Medium Access Modes 4.3 MS Multi-TS Ability 4.4 Power Control

4.5 Network Control Modes

(62)

Network Control Modes

z

During the network controlled cell re-selection, the network

may request measurement reports from the MS and control

its cell re-selection. Hence, three types of mode are defined

as follows:

NC0: Normal MS controls

NC1: MS control with measurement reports NC2: Network control

z

The network subsystem must support NC0 and should

gradually support NC1 and NC2.

During the network controlled cell re-selection, the network may request

measurement reports from the MS and control its cell re-selection. Hence, three

types of mode are defined as follows:

NC0: Normal MS controls. The MS shall perform autonomous cell re-selection. NC1: MS control with measurement reports. The MS shall send measurement reports to the network. The MS shall perform autonomous cell re-selection.

NC2: Network control. The MS shall send measurement reports to the network. The MS shall not perform autonomous cell re-selection.

The network subsystem must support NC0 and should gradually support NC1 and

NC2.

(63)

Network Control Modes

MS NC0 NC1

NC2

The MS shall perform autonomous cell re-selection

MS

The MS shall perform autonomous cell re-selection The MS shall send measurement reports to the network MS BTS MR Cell re-selection command

The MS shall not perform autonomous cell re-selection

(64)

1. GPRS System Overview

2. GPRS Architecture

3. GPRS Network Interfaces & Protocols

4. GPRS Wireless Subsystem

5. GPRS Location Area

(65)

Relationship among Location

Areas

CELL CELL CELL CELL RA1 RA2 CELL CELL RA3 CELL CELL CELL SGSN1 SGSN2 BSC1 BSC2 BSC3 LA1 LA2 65

(66)

Location Area Identification

MCC MNC LAC

LAI (Location Area Identification)

z MCC：Mobile Country Code, it consists of 3 digits. For example: The

MCC of China is "460"

z MNC：Mobile Network Code, it consists of 2 digits. For example: The

MNC of China Mobile is "00"

z LAC：Location Area Code, it is a two bytes hex code. The value 0000

and FFFF is invalid

z For example: 460008C90

(67)

RAI

z Routing area is the sub-set of the location area. In special cases, the two

areas are equal

z The division of the routing area is related with traffic distribution and

SGSN processing ability

Location Area Identification

MCC

MNC

LAC

RAC

Routing Area Identification

(68)

CGI

z CI (Cell Identity): This code uses two bytes hex code to identify the radio cells within a LAI.

z RAC is only unique when presented together with LAI. z CI is only unique when presented together with LAI or RAI. z CGI = MCC+MNC+LAC+{RAC}+CI

MCC

MNC

LAC

CI

CGI

RAC

(69)

CGI

Relationship among location areas

z

LAI

MCC+ MNC+ LAC LAI z

RAI

MCC+ MNC+ LAC+RAC z

CGI /CellID

MCC+ MNC+ LAC+{RAC}+CI RAI 69

(70)

Summary

z

GPRS System Overview

z

GPRS Architecture

z

GPRS Network Interfaces & Protocols

z

GPRS Wireless Subsystem

z

GPRS Location Area

(71)

Thank you

www.huawei.com

(72)

www.huawei.com

GPRS EDGE Mobile

Management

Algorithm

(73)

Foreword

z

GPRS Mobility Management is a GPRS signaling

protocol that handles mobility issues such as roaming,

authentication and selection of encryption algorithms.

It is important to enable the network to keep track the

current location of the MS in order for the paging to be

performed smoothly. With the proper setting of the

GMM parameters, we can shorten the access delay of

the MS.

(74)

References

z

GBSS8.1 BSC6000 Feature Description

(75)

Objectives

z

Upon completion of this course, you will be able to:

Understand the GPRS Mobility Management procedure

Familiar with the GMM state model

Understand the cell reselection algorithm

Recognize the cell update and routing area update flow

Realize the GMM related parameters

(76)

1. Overview of GPRS Mobile Management

2. Location Update

3. GPRS Cell Selection & Reselection

(77)

Overview for GPRS Mobile Management

z

The main purpose of the mobility management is to keep track

of the user’s current location. Thus, the paging can be

performed.

z

MS perform cell selection and reselection when it moves

around the coverage area. It also sends the location update

message to the SGSN so that the network can be always

aware of the MS’s current location.

z

There are 3 states exist in the GPRS mobility management

and different location information is available in each state

(please see the following figure – MM State).

(78)

GMM State

IDLE

>GMM context is not established; MS is not reachable.

>MS can implement data transmission.

>GMM context is established; MS can receive paging but cannot implement data transmission.

The MS performs MM procedures to provide the network with the actual selected cell.

SGSN performs the MM on cell level. READY

STANDBY

The location information in the SGSN MM context contains only the GPRS RAI. Pages for data or signalling information transfers may be received. It is also

possible to receive pages for the CS services via the SGSN. Data reception and transmission are not possible in this state.

Data transmission to and from the mobile subscriber as well as the paging of the subscriber are not possible

.

(79)

GMM State Model

IDLE READY STANDBY

MM State Model of MS MM State Model of SGSN GPRS Attach GPRS Detach

READY timer expiry or

PDU transmission

PDU reception

Implicit Detach or Cancel Location

GPRS Attach

Force to STANDBY

READY timer expiry or Force to STANDBY or Abnormal RLC condition

GPRS Detach or

Cancel Location

z By performing GPRS attach, the MS gets into READY state and if the MS does not transmit any packet for a long period of time until the READY timer is expired, the MS will get into STANDBY state.

z It is possible to transmit data only if the MS is in READY state, thus the MS in STANDBY state can switch back to the READY state, if a PDU transmission occurs and in the same way, at READY state if the GPRS detach is performed, the MS will be back into IDLE state and all PDP context will be deleted.

z In STANDBY state, the MS sends the location update message seldom, so its location is not known exactly and the paging is necessary for every downlonk packet, resulting in a delivery delay.

z In READY state, the MS updates its location frequently. Consequently the MS‘s location is known precisely and no paging delay during delivery downlonk packet. Howeverm this consumes much more the uplink radio capacity and battery of the MS.

(80)

GMM State vs Location Information

z

During GMM IDLE state, MS is detached from GPRS. Thus

MS can not receive paging nor data transmission.

z

During GMM STANDBY state, MS is attached to the GPRS

network and it will perform routing area update (RAU),

MS-controlled cell reselection and monitor paging. It only report

RA changes.

z

During GMM READY state/ packet transfer mode, MS will

perform both routing area update (RAU) and cell update (both

MS-controlled and Network-controlled cell reselection). It

report the cell changes and RA changes.

(81)

1. Overview of GPRS Mobile Management

2. Location Update

2.1 Relationship between Cell, Routing Area & Location Area 2.2 LAI, RAI, CGI

2.3 Signaling flow for Cell Update, RA Update & LA Update

3. GPRS Cell Selection & Reselection

(82)

Relationship among Location Areas

CELL CELL CELL CELL RA1 RA2 CELL CELL RA3 CELL CELL CELL SGSN1 SGSN2 BSC1 BSC2 BSC3 LA1 LA2

z When MS across Location Area border, LAU & RAU is necessary

z When MS moves within same LA and across Routing Area boarder, RAU is necessary z When MS moves within the same LA and RA, cell update may be needed may be

needed. It depends on the current state of the MS.

a) READY state: MS updates the location every cell change. This strategy ensures that the accurate location of the MS is always known and packet data can be delivered faster as no paging procedure is necessary. However the MS battery is drained more and uplink radio capacity is wasted for cell updates.

b) STANDBY state: MS updates the location only when the MS moves to a new routing area (RA). In this strategy, when data packet is sent to the MS, paging is required in order to find out the current location of the MS. Thus, uplink capacity will be wasted for paging response and every downlink packet requires paging of the mobile delay.

(83)

CGI

Relationship among Location Areas

z

LAI

MCC+ MNC+ LAC LAI z

RAI

MCC+ MNC+ LAC+RAC z

CGI /CellID

MCC+ MNC+ LAC+{RAC}+CI RAI 83

(84)

1. Overview of GPRS Mobile Management

2. Location Update

3. GPRS Cell Selection & Reselection

(85)

Location Area Identification

MCC MNC LAC

LAI (Location Area Identification)

z MCC：Mobile Country Code, it consists of 3 digits. For example: The

MCC of China is "460"

z MNC：Mobile Network Code, it consists of 2 digits. For example: The

MNC of China Mobile is "00"

z LAC：Location Area Code, it is a two bytes hex code. The value 0000

and FFFF is invalid

z For example: 460008C90

(86)

RAI (Routing Area Identification)

z Routing area is the sub-set of the location area. In special cases, the two

areas are equal.

z The division of the routing area is related with traffic distribution and SGSN processing ability

MCC

MNC

LAC

RAC

(87)

CGI (Cell Global Identity)

z CI (Cell Identity): This code uses two bytes hex code to identify the radio

cells within a LAI.

z RAC is only unique when presented together with LAI. z CI is only unique when presented together with LAI or RAI.

z CGI = MCC+MNC+LAC+{RAC}+CI

MCC

MNC

LAC

CI

CGI

RAC

(88)

1. Overview of GPRS Mobile Management

2. Location Update

3. GPRS Cell Selection & Reselection

(89)

Cell Update Flow

MS Old Cell SGSN

Uplink LLC-PDU [MS ID]

SGSN received and recorded the cell update

New Cell

SGSN send the subsequence service

to MS through the new cell PDU (CGI) in BSSGP-PDU

RLC Radio Block

1. When the MS moves from one cell to another within the same RA and LA, cell

update procedure will happen during the READY state.

2. During the READY state/ packet transfer state, MS will keep monitor its current

location and cell reselection will happen. When MS discover another better cell according to its own measurement. The MS stops listening to the old cell and start to read the necessary SYSINFO in the new cell.

3. MS make an access in the new cell and send a cell update to the SGSN

(transparent to the PCU).

4. SGSN will obtain the cell update (cell change information) from the uplink

LLC-PDU and record the cell update information and discovers that there was already an ongoing downlink packet transfer.

5. SGSN will then sends a Flush message to the respective PCU. The Flush

message contains the addresses to both the old and new cell as well as the MS identity.

6. The PCU check whether it is responsible for the new cell. In that case all the

buffered frames/ the subsequence service will be moved to a queue towards the new cell. The PCU assign new resources to the MS in the new cell and

transmission is restarted.

7. If the PCU is not responsible for the new cell, it will delete all the frames

destined to the MS ang leave the retransmission to higher layers.

(90)

Intra-SGSN Routing Area Update Flow

MS BSS SGSN

ROUTING AREA UPDATE REQUEST ROUTING AREA UPDATE REQUEST

[Old RAI, old P-TMSI, update type] [Old RAI, old P-TMSI, update type, new CI]

SECURITY FUNCTIONS (optional)

ROUTING AREA UPDATE ACCEPT [P-TMSI, P-TMSI signature]

ROUTING AREA UPDATE COMPLETE [P-TMSI] optional]

1. When MS moves to new RA, it sends RA update request including the RAI of

the old RA to its assigned SGSN. When the message arrives at the BSS, the BSS adds the CI of the new cell. Based on the RAI and CI data, SGSN can derived the new RAI.

z Intra-SGSN routing area update: The MS has moved to an RA, assigned to the same SGSN as the old RA. In this case, the SGSN knows already all necessary user profile, and can assign a new packet temporary mobile subscriber identity (P-TMSI) to the user without the need to inform other network elements.

z Security function: authentication and ciphering/encrpytion

(91)

Inter-SGSN Routing Area Update Flow

MS BSS

New SGSN

ROUTING AREA UPDATE REQUEST [Old RAI, old P-TMSI, update type]

Old SGSN GGSN HLR PDP CTT REQ [GGSN address] PDP CTT ACK PDP CONTEXT UPDATE

PDP CONTEXT UPDATE ACK

DATABASE UPDATE

INSERT SUBCRIBER DATA

ROUTING AREA UPDATE COMPLETE ROUTING AREA UPDATE ACCEPT

z Inter-SGSN routing area update: In this case, the MS has moved to an RA, assigned to a different SGSN, thus, the new SGSN does not have the user profile of the MS. The new SGSN contacts the old SGSN and requests the PDP context of the user.

z After receiving the PDP context of the user, the new SGSN informs the involved network elements,

GGSN about the new PDP context of the user HLR about the user’s new SGSN

z HLR cancels the MS information context in the old SGSN and loads the subscriber data to the new SGSN. New SGSN acknowledges to the MS

z The old SGSN is requested to transmit the undelivered data to the new SGSN.

(92)

1. Overview of GPRS Mobile Management

2. Location Update

3. GPRS Cell Selection & Reselection

3.1 Cell Reselection Algorithm

3.2 Parameter for Cell Reselection 3.3 Type of Cell Reselection

(93)

GPRS Cell Reselection Algorithm

z

If no PBCCH exists, the GPRS cell selection &

reselection is basically the same as GSM cell

selection & reselection (C1, C2):

C2 = C1 + CRO – TO*H(PT-T) when PT=/31 C2 = C1 – CRO when PT=31 C1 = RLA_C – RxLev_Acc_Min –

Max((MS_TXPWR_MAX_CCCH – P), 0)

1. C1 = RLA_C - RxLev_Access_Min - Max((MS_TxPwr_MAX_CCH - P), 0) 2. C2 = C1 + CRO - TO * H(PT-T) when PT=/31

3. C2 = C1 - CRO when PT= 31

(94)

GPRS Cell Reselection Algorithm

z If no PBCCH exists, the GPRS cell selection & reselection is basically the same as GSM cell selection & reselection (C1, C2) excepts for the following conditions:

a) When MS in STANDBY mode,

Cell reselection within the same RA/LA:

C2(nei) > C2 (serving) for t>5s

Cell reselection between different RA/LA:

C2(nei) > C2 (serving) + CRH for t>5s

b) When MS in READY mode,

Cell reselection within the same RA/LA:

Cell reselection between different RA/LA:

1. C1 = RLA_C - RxLev_Access_Min - Max((MS_TxPwr_MAX_CCH - P), 0) 2. C2 = C1 + CRO - TO * H(PT-T) when PT=/31

3. C2 = C1 - CRO when PT= 31

(95)

Cell Reselection in Standby Mode

RA 1 RA 2 Cell A Cell B Cell C AC2>BC2 CC2>BC2＋CRH 95

(96)

Cell Reselection in Ready Mode

BC2>AC2＋CRH

RA 1

Cell A

Cell B

(97)

GPRS Cell Reselection Algorithm

z

If PBCCH exists, new cell selection & reselection algorithm

(C31, C32) is applicable:

C31(s) = RLA_P(s) – HCS_THR(s) (Serving cell) C31(n) = RLA_P(n) – HCS_THR(n) –

GPRS_TO(n)*H(GPRS_PENALTY_TIME-T)*L(n) (Neighbor cell)

C31 = signal threshold criterion

RLA_P = actual received level of the GPRS cell

HCS_THR = signal level threshold of cell reselection of HCS GPRS GPRS_TO = GPRS temporary offset

L = 0; when PRIORITY_CLASS (s) = PRIORITY_CLASS (n) L = 1; when PRIORITY_CLASS (s) =/ PRIORITY_CLASS (n)

z C31 = signal threshold criterion/ signal level threshold criterion of HCS and is used to judge whether to adopt preference cell reselection

z HCS_THR = Hierarchical Cell Structure signal level threshold of cell reselection of HCS

GPRS. It is broadcast on PBCCH of the service cell.

z RLA_P = Received level of the GPRS cell

z TO = Temporary offset given to the neighbor when the neighbor cell’s PRIORITY_CLASS is different from the PRIORITY_CLASS of the serving cell

(98)

GPRS Cell Reselection Algorithm

z

If PBCCH exists, new cell selection & reselection algorithm

(C31, C32) is applicable:

C32(s) = C’1 (Serving cell) C32(n) = C’1 + GPRS_RESELECT_OFF –

GPRS_TO*H(GPRS_PENALTY_TIME – T) * (1-L) (Neighbor cell)

H(X<0) = 0; T > GPRS_PENALTY_TIME H(X>0) = 1; T < GPRS_PENALTY_TIME

L = 0; when PRIORITY_CLASS (s) = PRIORITY_CLASS (n) L = 1; when PRIORITY_CLASS (s) =/ PRIORITY_CLASS (n)

C’1 = RxLev – GPRS_Acc_Level_Min – Max( (GPRS_MS_TXPWR_MAX_CCH – P), 0)

z C32 = Perfection of C2 applied to GSM. It applies the offset and the delay value to the cell reselection which needs execution of cell update program or route update program. When the PBCCH channel does not exist in the service cell, the MS will execute cell reselection according to the C2 algorithm.

z T = timer with initial value =0. When a cell is recorded by the MS into the 6 strongest cell, the counter corresponding to this cell, T will begin to count at a precision of one TDMA frame (4.62ms). When this cell is removed from the 6 strongest cell list, the timer is reset.

z GPRS TO = temporary offset, which counts from the counter T. T to the

(99)

GPRS Cell Reselection Algorithm

z

In additional, it is necessary to consider the routing area for

the serving cell and adjacent cell:

When MS in STANDBY mode, and within the same RA C32’(n) = C32(n)

When MS in READY mode, and within the same RA C32’(n) = C32(n) - CELL_RESELECT_HYSTERESIS

When MS in READY or STANDBY mode, with different RA C32’(n) = C32(n) - RA_RESELECT_HYSTERESIS

z C32’(n) = Final calculated/ actual value of the C32 criterion after consider the routing area of the serving cell and neighbor cell.

(100)

Cell Reselection Trigger Condition

z Cell reselection triggering condition:

Random access attempt is unsuccessful after MAX_RETRANS

Random access attempt is

unsuccessful after MAX_RETRANS 4 5 3 2 1 With C’1, C31, C32 criterion With C1, C2 criterion C’1 < 0 C1 < 0

Downlink signaling failure Downlink signaling failure

Better cell with the highest C32 among: (a) Highest PRIORITY_CLASS, C31>=0 (b) All cell, if no cell fulfils C31 criterion Better neighbor cell detected:

Same RA: C2(n) > C2(s) for t>5s Dif RA: C2(n) > C2(s)+CRH for t>5

Serving cell is barred Serving cell is barred

(101)

1. Overview of GPRS Mobile Management

2. Location Update

3. GPRS Cell Selection & Reselection

3.1 Cell Reselection Algorithm

3.2 Parameter for Cell Reselection 3.3 Type of Cell Reselection

GPRS-EDGE Radio Network Optimization

GPRS Principles

Foreword

GPRS principle is the basic part of the whole GPRS system

and the succeeding products learning.

This slide will help us to understand the GPRS system

networking and wireless subsystem etc.

Objectives

Upon completion of this course, you will be able to:

Contents

1. GPRS System Overview

2.

GPRS Architecture

3.

GPRS Network Interfaces & Protocols

4.

GPRS Wireless Subsystem

5.

GPRS Location Area

Circuit Switch (CS)

Packet Switch (PS)

GSM Development Evolution

What is GPRS and EDGE?

Abbreviation of

G

eneral

P

acket

R

adio

S

ervice.

GPRS is an end-to-end packet switching technology

provided on the basis of GSM technology.

It has much interactive services with the existing GSM

circuit switching system.

GPRS supports wireless access rate of up to 171.2Kbps.

EDGE (

E

nhanced

D

ata R

ates for

G

SM

E

volution)

•GPRS is the abbreviation of General Packet Radio Service.

•GPRS network introduces packet switching functional entities in the GSM network

to implement data transmission in the packet mode.

•GPRS can be regarded as the service expansion based on the GSM network for

supporting mobile subscribers access the Internet of other packet data networks via

packet data mobile terminal. Making full use of the existing GSM network,small

investment and quick rewarding,all of these benefit to protect the existing

investment and obtain maximum benefits for the operators.

GPRS&EDGE Coding Rate

Adjustments to GSM Network

Most Popular GPRS Applications

E-mail

Web Browsing

Information Services

Moving Images

Still Images

Remote LAN Access

File Transfer

Job Despatch

Advantages and Disadvantages of

GPRS

Advantages

Disadvantages

Contents

1.

GPRS System Overview

2. GPRS Architecture

3.

GPRS Network Interfaces & Protocols

4.

GPRS Wireless Subsystem

5.

GPRS Location Area