Gprs edge radio network optimization by Emerson Eduardo Rodrigues

GPRS Principles

www.huawei.com

Foreword z

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.

Page1

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

Page2

Contents 1. GPRS System Overview 2. GPRS Architecture 3. GPRS Network Interfaces & Protocols 4. GPRS Wireless Subsystem 5. GPRS Location Area

Page3

Circuit Switch (CS) G

A CS

B H C

E K F

Page4

Packet Switch (PS) PS

1 1

2 3

3 2 1

1 2 3

2 1 3

Page5

GSM Development Evolution 3G

2.75 G

ECSD 38.8 Kb/s

2.5 G

HSCSD 14.4 Kb/s

UMTS

384 Kb/s

EGPRS EDGE 59.2 Kb/s

GPRS 21.4 Kb/s

GSM

9.6 Kb/s

Page6

What is GPRS and EDGE? z

Abbreviation of General Packet Radio Service.

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 (Enhanced Data Rates for GSM Evolution)

EGPRS (Enhanced GPRS)

EGPRS supports wireless access rate of up to 473.6Kbps.

ECSD (Enhanced CSD, Enhanced HSCSD-High Speed Circuit Switched Data)

Page7

•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 Kbps

59.2

60.00

54.4

50.00

GPRS

44.8

EGPRS

40.00

29.6

30.00 22.4

21.4

20.00 13.4

10.00 0.00

17.6

15.6

14.8

9.05

CS-1

8.8

CS-2

CS-3

CS-4

MCS-1

11.2

MCS-2

MCS-3

MCS-4

MCS-5

MCS-6

GMSK

MCS-7

MCS-8

MCS-9

8PSK

Page8

Adjustments to GSM Network

BSS

CS Core Network

PCU Gs Gb

PS Core Network

BSS

NSS

Page9

Most Popular GPRS Applications z

E-mail

Web Browsing

Information Services

Moving Images

Still Images

Remote LAN Access

File Transfer

Sport Report Public Information Weather Forecast Service Traffic Information

Stock Market

Still Images

Job Despatch

Live News

Moving Bank

Personal Information Service

File Transfer

Web Browsing

Page10

Advantages and Disadvantages of GPRS z

Advantages

Share resource with GSM

High resource utilization

Fast transmission rate

Always on line

Short access time

Disadvantages

Slower data rates in practice than anticipated in theory

Suboptimal modulation technique

Page11

Contents 1. GPRS System Overview 2. GPRS Architecture 3. GPRS Network Interfaces & Protocols 4. GPRS Wireless Subsystem 5. GPRS Location Area

Page12

CS & PS Logic Structure C

GMSC

PSTN

E D CS

B T S

Abis

G-Abis

MSC/VLR

TRAU

BSC

PCU

HLR AUC GPRS Register

Gs Gb

Gr SGSN

BSS Gn Gc

Internet

GGSN Gi

Page13

GPRS System Structure HLR

SMS-GMSC SMS-IWMSC

MSC/VLR

EIR

SS7 WAP Gateway BSS MS

BSC

Gf Gn

Firewall

GGSN

Abis BTS

Intranet/Internet RADIUS

PCU

SGSN

GPRS Backbone

ATM/DDN/ISDN/Ethernet, etc

X.25 BSS

SGSN

BSC

GGSN

CNCN-PS

Abis BTS

DNS

PCU

Other PLMN

Page14

GPRS MS z

Class A

Class B

The MS is attached to both GPRS and other GSM services and the MS supports simultaneous operation of GPRS and other GSM services.

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.

Class C

The MS is attached to either GPRS or other GSM services. Alternate use only. services are selected manually or default selected service.

Page15

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

G-Abis interface processing function

Function related with GPRS BTS

Page16

Functions of PCU (Packet Control Unit) z

Pb interface processing function

LAPD link between BSC and PCU

Layer-3 signaling between BSC and PCU

Gb interface processing function

Data packet relay on wireless interface and Gb interface

Mobility management (cell updating procedure)

Downlink traffic control (wireless QoS guarantee)

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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

Functions of SGSN (Serving GPRS Support Node) z

Packet routing

MS Session management

Authentication and Ciphering

Mobility management

Billing information collection

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Functions of GGSN (Gateway GPRS Support Node) z

Interface between GPRS backbone and external PDNs.

PDP Conversion and context management

IP address assignment management

Packet routing to/from SGSNs

Billing information collection

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Functions of CG (Charging Gateway) z

Real-time collection of GPRS bills

Temporary storage and buffering of GPRS bills

Pre-processing of GPRS bills

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

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

GPRS combined mobility management procedure.

Combined IMSI/GPRS attachment/detachment.

Combined location area/routing area updating.

Circuit paging coordination function.

The wireless resource usage can be greatly improved.

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Functions of HLR/AUC z

Saving and updating GPRS subscriber subscription data

User authentication

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.

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.

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.

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

SGSN

SMS-IWMSC SMS-GMSC Page23

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)。

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

It is normally based on routers

It can be combined with GGSN in physical.

BG does not exclusively belong to the GPRS network. Gp GSN PLMN A

R R

PLMN B

GSN

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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.

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. DNS Server

DNS does not exclusively belong to the GPRS network. SGSN

GPRS Backbone

SGSN

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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.

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.

The RADIUS server stores the authentication and authorization information of subscribers.

It also performs subscriber identity authentication in the case of non-transparent access.

RADIUS Server does not exclusively belong to the GPRS network.

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Contents 1. GPRS System Overview 2. GPRS Architecture 3. GPRS Network Interfaces & Protocols 4. GPRS Wireless Subsystem 5. GPRS Location Area

Page27

Contents 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

Page28

Network interface types SGSN SGSN

GPRS backbone network

IP interface

GGSN GGSN

PDP network (IP/X.25)

SGSN SGSN

SS7 interface Gc

Gb Gr Gs

MT TE

MSC

HLR

Page29

BSS

SMSGMSC

Interface in GPRS Network Interface R

Description The reference point between the Mobile Terminal (MT) (for example, mobile phone) and the Terminal Equipment (TE) (for example, the portable computer).

The interface between MS and GPRS network side

The interface between the SGSN and BSS.

The interface between the GGSN and HLR (optional).

The interface between SMS and GMSC The interface between SMS-IWMSC and SGSN

The reference point between the GPRS and external packet data

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

The interface between GSNs of different PLMNs.

The interface between the SGSN and HLR.

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

The interface between the SGSN and EIR (optional).

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Data transmission plane Application

IP/X.25

relay

SNDCP LLC RLC

z z

relay

BSSGP

MAC

Network Service

Physical Layer

MS z

RLC

BSS

MAC: Media Access Control RLC: Radio Link Control LLC: Logical Link Control

z z z

GTP

SNDCP

LLC

UDP/TCP

BSSGP

Network Service

Physical Layer

SGSN

IP/X.25

L2 (MAC)

Physical Layer GGSN

BSSGP: BSS GPRS Protocol SNDCP: Sub-Network Dependency Convergence Protocol GTP: GPRS Tunneling Protocol

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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.

MS-SGSN signaling plane GMM/SM

GMM/SM

LLC

LLC relay Relay

RLC

BSSGP

MAC

Network Service

GSM RF

L1bis

BSS

GMM: GPRS Mobility Management

SM: Session Management

SGSN

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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

Contents 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

Page33

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

SNDCP (Subnetwork Dependent Convergence Protocol): Multiplexing of several PDPs, compression / decompression and Segmentation of user data.

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

RLC:Segmentation and re-assembly between LLC PDUs and RLC blocks.

MAC: defines the procedures that enable multiple mobile stations to share a common transmission medium.

SMS

GMM (GPRS Mobility Management): operates in the signalling plane of GPRS supports mobility management functionality.

SNDCP

GMM/SM

Protocol Layer of Um Interface

LLC RLC MAC Physical Link

Page34

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.

MM State >GMM context is not established; MS is not reachable. IDLE

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

STANDBY

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

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.

>MS can implement data transmission. READY

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

SGSN performs the MM on cell level.

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The Mobility Management (MM) activities related to a GPRS subscriber are characterised by one of three different MM states.

MM State Model READY timer expiry or Force to STANDBY

GPRS Attach

MM State Model of MS

READY

IDLE GPRS Detach

PDU transmission READY timer expiry or Force to STANDBY or Abnormal RLC condition

GPRS Attach

MM State Model of SGSN

IDLE

STANDBY

READY GPRS Detach or Cancel Location

STANDBY PDU reception

Implicit Detach or Cancel Location

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RLC/MAC Block Generation Subscriber IP packet (N-PDU)

Network Layer

SNDCP PDU(SN-PDU)

SNDCP Layer

LLC Layer

LLC frame

RLC/MAC Layer

Subscriber data

RLC/MAC block

SNDCP head

LLC head

LLC FCS

RLC/MAC head

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Physical Channel z

The same as in GSM

The same frequency

The modulation mode

The same TDMA frame definition

The same burst pulse definition

…

The differences between GPRS and GSM

The Multi-frame structure

RLC

The channel coding

MAC

…

Application IP/X25 SNDCP LLC

Physical Layer MS

RLC

Relay

BSSGP

Frame relay

MAC Physical Layer

Physical Layer

BSS

Page38

Packet Logic Channels Packet Logic Channel Packet control channel

Packet service channel

PBCCH

PCCCH

PDCCH

BCCH PDTCH/U

TCH

PDTCH/D

PPCH

PRACH

PAGCH

PNCH

PCH, RACH, AGCH,NCH

PACCH PTCCH/U PTCCH/D

SACCH z

Page39

Channel Abbreviation z z z z z z z z z z z z

Packet Data Traffic CHannel Uplink - PDTCH/U Packet Data Traffic CHannel Downlink - PDTCH/D Packet Broadcast Control CHannel - PBCCH Packet Common Control CHannel - PCCCH Packet Dedicated Control Channel - PDCCH Packet Paging CHannel - PPCH Packet Random Access CHannel - PRACH Packet Access Grant CHannel - PAGCH Packet Notification CHannel - PNCH Packet Associated Control CHannel - PACCH Packet Timing advance Control CHannel Uplink - PTCCH/U Packet Timing advance Control CHannel Downlink PTCCH/D

Page40

PDTCH (Packet Data Traffic CHannel) z

All packet data traffic channels are uni-directional.

Uplink (PDTCH/U) for a mobile

Packet service channel

originated packet transfer.

Downlink (PDTCH/D) for a mobile

PDTCH/U

PDTCH/D

terminated packet transfer.

Page41

PBCCH (Packet Broadcast Control CHannel) z

The PBCCH broadcasts parameters used by the MS to access the network for packet transmission operation. The PBCCH also carries the information transmitted via the BCCH to allow circuit switching operation.

Packet control channel

PBCCH

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.

Page42

PCCCH (Packet Common Control CHannel) z

PPCH

PRACH

PCCCH

Downlink only, used to allocate one or several PDTCHs.

PNCH

Uplink only, used to request allocation of one or several PDTCH/Us or PDTCH/Ds.

PAGCH

Downlink only, used to page MS.

PPCH

PRACH

PAGCH

PNCH

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

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.

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PDCCH (Packet Dedicated Control Channels) z

PACCH PDCCH

Bi-directional, used to transmit the packet signaling in data transmission.

PTCCH/U

PACCH

Used to transmit random access bursts to allow estimation of the timing advance for

PTCCH/U

PTCCH/D

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.

Page44

Combinations of Packet Logic Channel Mode 1: PBCCH+PCCCH+PDTCH+PACCH+PTCCH Mode 2: PCCCH+PDTCH+PACCH+PTCCH

Mode 3: PDTCH+PACCH+PTCCH

Mode 4: PBCCH+PCCCH (PCCCH=PPCH+PRACH+PAGCH+PNCH）

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.

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.

Page45

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.

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.

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Mapping of Packet Logic Channel z

A radio block is a 4-normal-burst sequence that carries a RLC/MAC PDU (Protocol Data Unit). 25

B2 T B3

B5 I B6

B8 T B9

B10 B11 I

456 bits

01234 567

012 34 567 01234 567

01234 56 7

I = Idle frame T = Frame used for PTCCH B0 ~ B11 = Radio blocks

1 TDMA frame

Page48

Mapping of Packet Logic Channel 0

BCCH 0

F 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

1 12

PDCH

2 B0

B2 T B3

B5 I B6

B8 T B9

B10 B11 I

3 25

TCH

4T T T T T T T T T T T TSTT T T T T T T T T T T I 5 6 7

Page49

Transmission Principle of Data Packet on Um Interface Subscriber IP packet

SNDCP PDU

LLC PDU

RLC/MAC block N B

N B

Physical layer

B0 B1 B2 T B3 B4 B5 I B6 B7 B8 T B9 B10 B11 I Subscriber data

SNDCP head

LLC head

LLC FCS

RLC/MAC head

Page50

Allocation of Wireless Packet Resources TS 0

B1 0

B1 1

TS 1

B1 0

B1 1

TS 2

B10

B11

MS1 z

MS2

MS3

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

Each PDCH can be used by several MSs; each MS can use multiple PDCHs at the same time.

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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.

The USF field is three bits in length DL

=1 SF

……

F=1 US

B B1 1

=1 SF

F=2 US

B 9T

F=3 US

5 I B B6

T F=3

F=4 US

T B3

F=4 US

=4 SF

USF=1

MS1

USF=2

MS2

USF=3

USF=4

MS3

MS4

Page52

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.

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.

TFI (Temporary Flow Identity)

Each TBF is assigned a Temporary Flow Identity (TFI) by the network.

The TFI field is five bits in length.

Page53

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.

Contents 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

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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.

Downlink resource allocation mode

Dynamic allocation and fixed allocation.

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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

Contents 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

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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)

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

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Contents 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

Page58

Power Control z

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

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

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

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.

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Contents 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

Page60

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

The network subsystem must support NC0 and should gradually support NC1 and NC2.

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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.

Network Control Modes MS

NC0

NC1

The MS shall send measurement reports to the network

The MS shall perform autonomous cell re-selection

NC2 MR The

BTS

MS Cell re-selection

shall

not

perform autonomous cell re-selection

command

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Contents 1. GPRS System Overview 2. GPRS Architecture 3. GPRS Network Interfaces & Protocols 4. GPRS Wireless Subsystem 5. GPRS Location Area

Page63

Relationship among Location Areas SGSN1 SGSN2 BSC1 BSC3

BSC2 CELL CELL

CELL CELL CELL

RA2 CELL RA1

RA3 LA1

LA2

Page64

LAI (Location Area Identification) z

MCC：Mobile Country Code, it consists of 3 digits. For example: The MCC of China is "460"

MNC：Mobile Network Code, it consists of 2 digits. For example: The MNC of China Mobile is "00"

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

For example: 460008C90

MCC

MNC

LAC

Location Area Identification

Page65

RAI z

Routing area is the sub-set of the location area. In special cases, the two areas are equal

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

MCC

MNC

LAC

RAC

Location Area Identification Routing Area Identification

Page66

CGI z

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

RAC is only unique when presented together with LAI.

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

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

MCC

LAC

MNC

RAC

Location Area Identification Routing Area Identification CGI

Page67

Relationship among location areas z

LAI MCC+ MNC+ LAC

LAI

RAI

MCC+ MNC+ LAC+RAC RAI

CGI /CellID

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

Page68

Summary z

GPRS System Overview

GPRS Architecture

GPRS Network Interfaces & Protocols

GPRS Wireless Subsystem

GPRS Location Area

Page69

Thank you www.huawei.com

GPRS EDGE Mobile Management Algorithm www.huawei.com

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.

Page1

References z

GBSS8.1 BSC6000 Feature Description

Page2

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

Page3

Contents 1. Overview of GPRS Mobile Management 2. Location Update 3. GPRS Cell Selection & Reselection

Page4

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.

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.

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).

Page5

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

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

STANDBY

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

The location information in the SGSN MM context contains only the GPRS RAI.

> MS can implement data transmission. READY

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

SGSN performs the MM on cell level.

Page6

GMM State Model READY timer expiry or Force to STANDBY

GPRS Attach

MM State Model of MS

READY

IDLE GPRS Detach

PDU transmission READY timer expiry or Force to STANDBY or Abnormal RLC condition

GPRS Attach

MM State Model of SGSN

IDLE

STANDBY

READY

STANDBY PDU reception

GPRS Detach or Cancel Location

Implicit Detach or Cancel Location

Page7

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. 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. 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. 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.

GMM State vs Location Information z

During GMM IDLE state, MS is detached from GPRS. Thus MS can not receive paging nor data transmission.

During GMM STANDBY state, MS is attached to the GPRS network and it will perform routing area update (RAU), MScontrolled cell reselection and monitor paging. It only report RA changes.

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.

Page8

Contents 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

Page9

Relationship among Location Areas SGSN1 SGSN2 BSC1 BSC3

BSC2 CELL CELL

CELL CELL CELL

RA2 CELL RA1

RA3 LA1

z z z

LA2

Page10

When MS across Location Area border, LAU & RAU is necessary When MS moves within same LA and across Routing Area boarder, RAU is necessary 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.

Relationship among Location Areas z

LAI

MCC+ MNC+ LAC LAI

RAI

MCC+ MNC+ LAC+RAC RAI

CGI /CellID

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

Page11

3. GPRS Cell Selection & Reselection

Page12

LAI (Location Area Identification) z

MCC：Mobile Country Code, it consists of 3 digits. For example: The MCC of China is "460"

MNC：Mobile Network Code, it consists of 2 digits. For example: The MNC of China Mobile is "00"

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

For example: 460008C90

MCC

MNC

LAC

Location Area Identification

Page13

RAI (Routing Area Identification) z

Routing area is the sub-set of the location area. In special cases, the two areas are equal.

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

MCC

MNC

LAC

RAC

Location Area Identification Routing Area Identification

Page14

CGI (Cell Global Identity) z

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

RAC is only unique when presented together with LAI.

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

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

MCC

LAC

MNC

RAC

Location Area Identification Routing Area Identification CGI

Page15

3. GPRS Cell Selection & Reselection

Page16

Cell Update Flow MS

Old Cell

Uplink LLC-PDU

New Cell PDU (CGI) in BSSGP-PDU

[MS ID]

RLC Radio Block

SGSN SGSN received and recorded the cell update

SGSN send the subsequence service to MS through the new cell

Page17

When the MS moves from one cell to another within the same RA and LA, cell update procedure will happen during the READY state. 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. MS make an access in the new cell and send a cell update to the SGSN (transparent to the PCU). SGSN will obtain the cell update (cell change information) from the uplink LLCPDU and record the cell update information and discovers that there was already an ongoing downlink packet transfer. 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. 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. 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.

Intra-SGSN Routing Area Update Flow MS

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

SGSN ROUTING AREA UPDATE REQUEST [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]

Page18

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. 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. Security function: authentication and ciphering/encrpytion

Inter-SGSN Routing Area Update Flow MS

BSS

New SGSN

Old SGSN

GGSN

HLR

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

PDP CTT REQ PDP CTT ACK [GGSN address] PDP CONTEXT UPDATE PDP CONTEXT UPDATE ACK

DATABASE UPDATE ROUTING AREA UPDATE ACCEPT

INSERT SUBCRIBER DATA

ROUTING AREA UPDATE COMPLETE

Page19

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

Contents 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

Page20

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. 2. 3.

Page21

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

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

Cell reselection between different RA/LA: C2(nei) > C2 (serving) + CRH for t>5s

1. 2. 3.

Page22

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

Cell Reselection in Standby Mode

RA 2 RA 1 CC2>BC2＋CRH

AC2>BC2 Cell B Cell A

Cell C

Page23

Cell Reselection in Ready Mode RA 1 BC2>AC2＋CRH Cell A Cell B

Page24

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

z z

Page25

C31 = signal threshold criterion/ signal level threshold criterion of HCS and is used to judge whether to adopt preference cell reselection HCS_THR = Hierarchical Cell Structure signal level threshold of cell reselection of HCS GPRS. It is broadcast on PBCCH of the service cell. RLA_P = Received level of the GPRS cell TO = Temporary offset given to the neighbor when the neighbor cell’s PRIORITY_CLASS is different from the PRIORITY_CLASS of the serving cell

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)

Page26

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

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

Page27

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

Cell Reselection Trigger Condition Cell reselection triggering condition:

With C1, C2 criterion

With C’1, C31, C32 criterion

C1 < 0

C’1 < 0

Downlink signaling failure

Serving cell is barred

Random access attempt is

Random access attempt is unsuccessful

unsuccessful after MAX_RETRANS

after MAX_RETRANS

Better neighbor cell detected:

Better cell with the highest C32 among:

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

(a) Highest PRIORITY_CLASS, C31>=0

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

(b) All cell, if no cell fulfils C31 criterion

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100

Contents 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

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101

Network Control Mode z

Cell Attribute -> GPRS Attributes

z z

Page30

Parameter Name: Network Control Mode Description: In the cell reselection required by the network, the network requests the MS to send measurement reports to control its cell reselection. There are three network control modes. nc0: Normal MS control. The MS performs automatic cell reselection.nc1: MS control with measurement reports. The MS sends measurement reports to the network and performs automatic cell reselection.nc2: Network control. The MS sends measurement reports to the network but does not perform automatic cell reselection. GUI Value Range: [nc0,nc1,nc2] Default Value: nc0

102

Parameter for GPRS Cell Reselection z

Network Control Mode (NCO)

Mode

Definition

Whether the MS send the M.R

MS mode

Cell Selection Mode

NC0

Normal MS Control Mode

Ready & Standby

Controlled by MS

NC1

MS Control with M.R Mode

Yes

Only Ready

Controlled by MS

NC2

Network Control Mode

Yes

Only Ready

Controlled by network

Page31

NC0: MS performs autonomous cell reselection without sending measurement reports to the network. NC1: MS performs autonomous cell reselection and sends measurement reports to network. NC2: Network controls cell reselection and MS sends measurement reports to the network.

103

Support NC2 z

Cell Attributes -> Other Attributes

z z z

z z

Page32

Parameter Name: Support NC2 Description: This parameter specifies whether the cell supports the Network Control 2 (NC2) function. In NC2, the MS reports the measurement report of the reference cell and neighbor cells to the BSC. The BSC controls cell reselection (including normal reselections and loadbased reselections) of the MS. GUI Value Range: [No,Yes] Default Value: No

104

NC2 Support in External Neighbour Cell z

BSC6000 -> Configure 2G External Cell

z z

Page33

Parameter Name: NC2 Support in External Neighbour Cell Description: This parameter specifies whether the GSM external cell supports NC2. GUI Value Range: [Not Support,Support] Default Value: Not Support

105

Parameter for GPRS Cell Reselection z

Cell Attributes -> GPRS Attributes -> Advanced -> Ps Other Parameters

z z

Page34

Parameter Name: Cell Urgent Reselection Allowed Description: This parameter specifies whether enabling the critical cell reselection algorithm is allowed. GUI Value Range: [Forbid,Permit] Default Value: Permit Parameter Name: Cell Load Reselection Allowed Description: This parameter specifies whether enabling the cell load-based reselection algorithm is allowed. GUI Value Range: [Forbid,Permit] Default Value: Permit Parameter Name: Cell Normal Reselection Allowed Description: This parameter specifies whether enabling the normal cell reselection algorithm is allowed. GUI Value Range: [Forbid,Permit] Default Value: Permit

106

Support NACC z

Cell Attributes -> Other Attributes

z z

Page35

Parameter Name: Support NACC Description: This parameter specifies whether the cell support the Network Assisted Cell Change (NACC) function.In network control mode NC0, NC1, or NC2, when the MS is in the packet transmission mode, the network informs the MS of the system information about neighbor cells in advance. Therefore, the cell reselection of the MS is accelerated. GUI Value Range: [No,Yes] Default Value: No

107

Contents 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

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108

GPRS Cell Reselection Type z

There are 3 type of cell reselections:

MS controlled cell reselection

Network controlled cell reselection

Network assisted cell reselection

Page37

109

MS-Controlled Cell Reselection z

MS-Controlled Cell Reselection

MS periodically measures the RX levels of all the BCCH carriers of the serving cell and its neighboring cells.

With no PBCCH configured, MS calculates C2 value.

With PBCCH configures, MS calculates C31/C32 value.

Based on the calculated value, MS decided whether to reselect a new serving cell.

Also call as autonomous cell reselection.

Parameter setting:

Support NC0/ NC1 to YES

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110

Network-Controlled Cell Reselection z

Network-Controlled Cell Reselection

MS periodically sends measurement reports to the BSC based on the parameters in the SYSINFO broadcast in the cell.

Based on the measurement reports and neighboring cell load, BSC sends a cell change command to the MS if all conditions are met, leading the MS to a suitable cell.

Parameter setting:

Support NC2 to YES

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111

Network-Controlled Cell Reselection (NC2) MS

BSS PACKET MEASUREMENT REPORT PACKET ENHANCED MEASUREMENT REPORT NC2 Cell Reselection Algorithm

PACKET NEIGHBOR CELL DATA

PACKET CELL CHANGE ORDER

PACKET CELL CHANGE FAILURE

[P-TMSI] optional]

Page40

MS in the GMM Ready mode state periodically sends PACKET MEASUREMETN REPORT to the BSC. After receive the MR, NSC process the MR. According to the NC2 cell reselection algorithm, BSC determines whether to perform cell reselection. If BSC determines to initiate a cell reselection, it send PACKET CELL CHANGE ORDER to MS to instruct MS to reselect the target cell. If NACC support, PACKET NEIGHBOR CELL DATA containing SYSINFO will be sent before the PACKET CELL CHANGE ORDER so that the reselection can be accelerated. If cell reselection fails, MS sends PACKET CELL CHANGE FAILURE message to BSC. After receive this message, BSC subtracts CELL PENALTY LEVEL from the RxLev of the target cell.

112

NC2 Cell Reselection Algorithm z

The NC2 cell reselection algorithm follows the priority sequence in descending order of:

Urgent reselection algorithm

Load reselection algorithm

Normal reselection algorithm

Page41

Urgent reselection is based on the receive quality of the radio link on the Um interface. If BER increases, the possible reason is that the signal level is too low or there is interference on the channel. In the network, load in some cells are heavy and some are light. To balance the load in these cells, load reselection is performed. In load reselection procedure, MS in heavy-loaded cell are directed to light-loaded cell. MS in neighbouring cell should not be reselected to the heavy-loaded cell. Normal reselection is based on Receive Level. When urgent reselection an load reselection are not met, normal reseelction is started to handover MS to a neighboring cell with higher signal strength if the RxLev (serving cell) < [Min Access Level Threshold]

113

NC2 Cell Reselection Algorithm Begin

Measure RxLev & RxQual MS in the MR

[Cell Urgent Reselection Allowed]?

Yes

[Cell Load Reselect Allowed]?

MS RxQual deterioration ratio > [MS Rx Qual Worsen Threshold]

Yes

[Cell Normal Reselect Allowed]?

Channel multiplexing rate>[Load Reselect Start Thres]

Yes

Any MS RxLev<[Load Reselect Level Thres] No

Yes

Receive Level (serving cell) < [Min Access Level Thres]

Yes

Satisfy P/N?

Trigger urgent cell reselection and select cell with the highest priority in cell list.

No No

Continue End

Page42

NC2 cell reselection algorithm follow the priority of: urgent reselection -> load reselection -> normal reselection Each type of reselection have different trigger condition.

114

NC2 Cell Reselection Algorithm Continue

Trigger urgent cell reselection and select cell with the highest priority in cell list.

For GSM Cell

For FDD Cell

RxLev>MAX(RxLev(s), [Min_Acc_Level_Thres])+ [Cell Reselect Hyst] AND non-congestion state

Ec/No>[PS FDD EcNo Quality Thres] or RSCP>[PS FDD RSCP Quality Thres]

For TDD Cell

RSCP>[PS FDD RSCP Quality Thres] No

End Yes

Yes

Cell reselection successful?

[Cell Penalty Level] given to target cell with [cell Penalty Last Time]

Yes

End

z z

Page43

The priority of the target cell is determined by receive level and the characteristics information such as cell type, cell priority, support for EDGE, and load status. Different cell type will need to fulfill the specified condition to be the candidate cell. When cell reselection fails, penalty is given to the target cell. If penalty time within [Cell Penalty Last Time (s)], [Cell Penalty Level] is subtracted from the receive level of the target cell.

115

NC2 Cell Reselection Algorithm z

Each NC2 cell reselection algorithm contains three NC2 cell reselection type: Cell

Serving cell

Reselection &Target cell

Condition

Type

position

Intra-BSC

Same BSC

Highest priority in the cell list.

Inter-BSC

Different BSC,

RxLev (Ext nei) = RxLev (n) – MAX(2, [Cell

both GSM cell

Reselection Hyst/2])

GSM to

Serving cell is

For FDD cell : Ec/No>[PS FDD EcNo Quality Thres]

UTRAN

GSM cell, target or RSCP>[PS FDD RSCP Quality Thres] cell is UTRAN

For TDD cell: RSCP>[PS TDD RSCP Quality Thres]

Page44

Intra-BSC cell reselection: Serving cell and target cell are controlled by same BSC. The selected target cell is the one that has highest priority in the cell list.

Inter-BSC cell reselection: Serving cell and target are in different BSC and both is GSM cell. The priority for the external neighbouring cell is lower. Thus, RxLev (Ext nei) = RxLev (n) – external cell reselection offset RxLev (Ext nei) = RxLev (n) – MAX(2, [Cell Reselection Hyst/2])

GSM to UTRAN cell reselection: Serving cell is GSM cell and target cell is UTRAN cell. The 3G MR and the 2G/3G cell priority strategy should be processed during the cell reselection. For FDD cell: Ec/No>[PS FDD EcNo Quality Thres] or RSCP>[PS FDD RSCP Quality Thres] For TDD cell: RSCP>[PS TDD RSCP Quality Thres] [2G/3G Cell Reselection Strategy] : Preference for 2G cell, Preference for 3G cell

116

Network-Assisted Cell Reselection z

Network-Assisted Cell Reselection

It is also known as NACC, Network Assisted Cell Change.

MS originates a cell change notification (CCN) procedure, and the BSC sends the system information (SYSINFO) about the neighboring cell to the MS before the cell reselection.

NACC accelerates the cell reselection and shortens the service disruption time during cell reselection.

Parameter setting:

Support NC0/ NC1/ NC2 to YES

Support NACC to YES

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117

Network Assisted Cell Change (NACC) z

Purposes:

MS is able to request BSC to send the target cell’s SYSINFO during the cell reselection.

Advantages:

According to the SYSINFO, MS accelerates the packet service access in the target cell.

Reduce the period of packet service disruption during a cell reselection .

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118

Network Assisted Cell Change (NACC)

Receive System information of cell B before reselection

Cell A

Cell B

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119

Network Assisted Cell Change (NACC) z

MS can initiate an NACC procedure only when autonomous cell reselection is triggered:

In NC0/ NC1 mode and packet transfer mode:

C1 <0

C2/ C23 is met

Downlink signaling reception fails

Authentication fails

NACC procedure is not initiated when:

In GMM standby state

In DTM mode

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120

Network Assisted Cell Change (NACC) z

The system supports:

Intra-BSC NACC

Inter-BSC NACC

UTRAN to GERAN NACC (Gb must support RIM procedure)

The system does not support the GERAN to UTRAN NACC procedure.

When PBCCH exists in target cell, the system does not support NACC procedure or the PACKET SI STATUS procedure.

z z z

Page49

GERAN : GPRS EDGE Radia Access Network RIM : RAN Information Management RIM procedure refer to the procedure of getting SYSINFO about the external neighboring cell from the serving cell 2 types of RIM procedures in the inter-BSC and UTRAN to GERAN NACC a) Inter RAN SYSINFO request procedure: initiated by controlling BSC/RNC to request the SYSINFO about the serving BSC b) Inter RAN SYSINFO update procedure: initiated by the serving BSC to ask the controlling BSC/RNC to update SYSINFO about the external neighboring cell RIM association between a cell in the serving BSS and the controlling BSS that requests the application information about this cell. It consists of 3 identities: a) ID of the cell in the controlling BSS b) ID of the cell in the serving BSS c) RIM application identity

121

Intra-BSC NACC Flow MS

BSS PACKET CELL CHANGE NOTIFICATION Obtain system messages of the target cell

PACKET NEIGHBOR CELL DATA

PACKET CELL CHANGE CONTINUE

PACKET SI STATUS

PACKET SERVING CELL DATA [P-TMSI] optional]

Page50

After MS determines to initiate an autonomous cell reselection, it enter CCN mode. But the MS does not change the cell immediately, it sends a PACKET CELL CHANGE NOTIFICATION to BSC to request SYSINFO about the target cell. When BSC received PACKET CELL CHANGE NOTIFICATION, it sends a PACKET NEIGHBOUR CELL DATA that contains SI1, SI3, SI13. Then BSC send PACKET CELL CHANGE CONTINUE to ask the MS to proceed the cell reselection. After receive PACKET NEIGHBOUR CELL DATA, MS save the SYSINFO. After receive the PACKET CELL CHANGE CONTINUE, MS changes from CCN mode to NC0/NC1 mode and continue cell reselection. After MS changes the cell, the MS uses the SYSINFO for initial packet access procedure. If target cell support PACKET SI STATUS (YES), MS does not receive all SYSINFO. MS needs to send PACKET SI STATUS message to request the SYSINFO. After BSC received PACKET SI STATUS, it sends PACKET SERVING CELL DATA which contain the SYSINFO of the serving cell. Then MS saves the SYSINFO in the PACKET SERVING CELL DATA.

122

Inter-BSC NACC Flow Control BSS/RNC

Serving BSS

RIM Procedure PACKET CELL CHANGE NOTIFICATION Obtain system messages of the target cell

PACKET NEIGHBOR CELL DATA

PACKET CELL CHANGE CONTINUE

PACKET SI STATUS

PACKET SERVING CELL DATA

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123

Summary z

We have understand the below from this training:

GPRS Mobility Management procedure

Cell reselection algorithm

Cell reselection and routing area update flow

Parameters related to GMM.

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124

Thank you www.huawei.com

125

GPRS EDGE Radio Network Optimization Parameters www.huawei.com

126

Foreword z

The PCU performance parameters are essential to the GPRS network. Proper setting of such parameters can improve performance of the packet services.

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Contents z GPRS Cell Parameters z GPRS Power Control z GPRS Cell Reselection z Performance Parameters

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128

GPRS Cell Parameters z

NOM

PAN

T3168

N3101

T3192

N3103

DRX_TIMER_MAX

N3105

BS_CV_MAX

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129

Network Operation Mode

Network Configure Mode Gs

Yes

Configur e PCCH

Yes

III

Yes

Channel for circuit paging

GPRS Paging Channel

PPCH

PCH

PACCH

PCH

PPCH

PCH

Idle Mode PCCCH Or CCCH

PACCH

CCCH

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130

T3168 T3168 is used to set the maximum duration for the MS to wait for the packet uplink assignment message PCU PACKET CHANNEL REQUEST PACKET UPLINK ASSIGNMENT/ IMMEDIATE ASSIGNMENT COMMAND PACKET RESOURCE REQUEST

T3168

PACKET UPLINK ASSIGNMENT

Very Good

BLER<2%

T3168 recommendation （ms） 500

Good

2%<BLER<5%

1000

Bad

5%<BLER<10%

2000

Condiction

BLER

Page5

The timer T3168 is used to set the maximum duration for the MS to wait for the packet uplink assignment message. The MS should start the timer T3168 to wait for the packet uplink assignment message after sending the packet resource request message. If the MS receives the packet uplink assignment message before timeout of T3168 and gets into the status of waiting for packet uplink assignment message, the MS will reset T3168; if T3168 times out, the MS will trigger the packet access process again until this process repeats for 4 times. Then the MS will believe that TBF establishment failure occurs. If the value of this paramter is smaller, the period of the MS determining failure of TBF establishment will be shorter, and the average time of packet access will be shorter. However, in severe wireless conditions, that will make the TBF establishment success rate lower. Moreover, too low values will make the MS increase the probability of retransmitting the packet access requests, which will increase the probabilty of the PCU performing repeated assignment and lead to waste of system resources. On the other hand, if this value is higher, the period of the MS determining failure of TBF establishment will be longer, and the average delay of the packet access will be longer.Value range: This parameter value is measured in 500ms, and its range is: 500ms, 1000ms, 1500ms… 4000ms. The recommended value is 500ms.

131

T3192 The timer is for the MS to wait for TBF release after receiving the last data block. PCU PACKET DOWNLINK ACK/NACK （FAI=1） Final ACK Identifier

T3192 PACKET DOWNLINK ASSIGNMENT TFI

value（ms） 500

1000

1500

120

160

200

Page6

After receiving the RLC data block which contains the Final Block Identifier (FBI) and confirming that all RLC data blocks in TBF are received, the MS should send the packet downlink acknowledgement/unacknowledgement message, set its Final Acknowledgement Identifier (FAI) to 1 and start T3192. If T3192 times out, the MS will stop all allocated listening tasks on PDCH, begin to listen to the paging channel and get into the packet idle status. If this parameter value is greater, the time for the MS to reserve the TFI and timeslot assigned by the system will be longer, and the risk of congestion will be higher. On the other hand, if this value is smaller, the MS will release TBF quickly. If new downlink packet data comes to the network, the network will have to originate the paging again or assign the program promptly, which prolongs the time of establishing the downlink TBF greatly. Value range: This parameter value is measured in 500ms, and its range is: 0ms, 80ms, 120ms, 160ms, 200ms, 500ms, 1000ms and 1500ms. The recommended value is 500ms.

132

DRX_TIMER_MAX The MS request keeps the maximum value of nonDRX mode.

Non_DRX

Packet transmission mode

Non_DRX

Packet idle mode

DRX

Packet idle mode

DRX_TIMER_MAX (s)

Value（Sencond） 0

Page7

Set the maximum value of the duration for MS to execute the non-DRX mode when shifting from the packet transmission mode to the packet idle mode. This parameter value is measured in seconds. Values: “0” – Get into the DRX mode immediately after the transmission mode, “1s” - 1 second, “2s” - 2 seconds, “4s” – 4 seconds… “64s” – 64 seconds. The typical value is “4s". If the value is higher, the TBF establishment duration will be shorter, but the MS power consumption will increase. If the value is lower, the battery consumption is lower, but the paging process will be longer, the system signaling load will be heavier and the data transmission delay will be longer.

133

Packet Signaling Processing RLC DATA BLOCK RLC DATA BLOCK (FBI) PACKET DOWNLINK ACK/NACK （FAI=1）

T3192=500ms Ready Mode Non DRX mode= 4s

DRX mode

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134

BS_CV_MAX PCU CV=X

设BS_CV_MAX=10

RLC DATA BLOCK

T3198

200ms

RLC DATA ACK

CV=X

RLC DATA BLOCK Timeout

z z

Page9

Set BS_CV_MAX. It is a parameter used for the MS to calculate the Countdown Value (CV). If the PBCCH channel does not exist, this parameter will be broadcast in the system message 13. When the RLC data block to be sent is the last but (x-1) data block, if x<= BS_CV_MAX, CV=x; otherwise CV=15. Ensure that the last RLC data block is being sent in case CV=0. Value range of BS_CV_MAX: 0~15 When the MS sends an RLC data block, the MS starts the timer T3198. After timeout of the timer, the MS will allow the status of this RLC data block to be “unacknowledged” and retransmit the data block. The default value of T3198 is duration of BS_CV_MAX blocks. The duration of each block is 20ms. The empiric value of transmission delay between MS and PCU is 100ms, so T3198 value > 100ms, i.e., BS_CV_MAX >5.1. If the BS_CV_MAX value is higher, the efficiency of the slide window program will be lower; 2. If the BS_CV_MAX value is lower, the probability of retransmission will be higher, and more wireless resources will be occupied.

135

BS_CV_MAX suppose BS_CV_MAX= 3

CV=0

CV=1

CV=2

CV=3

CV=15

PCU

CV=15

CV=3

CV=15

MS buffer – UL RLC blocks More data

CV=0

CV=1

CV=2

Page10

The default value of the MS-side timer T3198 is duration of BS_CV_MAX RLC blocks. The T3198 begins counting after the MS sends the RLC block. After timeout of T3198, the block is marked as “unacknowledged” and needs to be retransmitted.

To retransmit the erroneous RLC Block as soon as possible, the value of the BS_CV_MAX should be as small as possible, but cannot be less than the delay of transmission from MS to PCU. According to empiric values, the BS_CV_MAX value should be over 5.

136

PAN z

PAN_DEC

PAN_INC

Set the decrease step length of the N3102 counter of the MS

Set the increase step length of the N3102 counter of the MS

PAN_MAX

Set the maximum value of the N3102 counter of the MS

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137

PAN

N3102

Packet Uplink Ack/Nack - PAN_DEC + PAN_INC

PAN_MAX

Abnormal Release Perform Cell Re-selection

T3182 T3182

T3182

Page12

This parameter is used to avoid unpredictable link failure. It is used together with the MS-side counter N3102, and consists of three sub-parameters. PAN_DEC: Decremental value of PAN counter PAN_INC: Incremental value of PAN counterPAN_MAX: Maximum value of PAN counter The MS sets the counter N3102 according to PAN_MAX. When the MS receives a Packet ACK/NACK message, the N3102 increases by PAN_INCWhen N3102=PAN_MAX, the MS starts the timer T3182If the MS still receives no acknowledgement message upon timeout of T3182, the MS will decrease N3102 by PAN_DEC. In case N3102<=0, the MS will execute exception release of this TBF, and trigger cell reselection.

138

PAN PCU 设PAN_INC=2

RLC DATA BLOCK

PACKET DATA ACK N3102+2

RLC DATA BLOCK

设PAN_DEC=1

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139

N3101 PCU RLC DATA BLOCK/PACKET UPLINK ASSIGNMET (valid USF) RLC DATA ACK N3101+1

POLLING REQUEST

Page14

If N3101 expires, the network release the uplink TBF.

140

N3103 PCU PACKET UPLINK ACK/NACK (FAI=1) PACKET CONTROL ACK N3103+1

PACKET UPLINK ACK/NACK (FAI=1)

Page15

If N3103 expires, the network release the uplink TBF.

141

N3105 PCU RLC DATA BLOCK (RRBP) PACKET DOWNLINL ACK/NACK N3105+1

RLC DATA BLOCK (RRBP)

Page16

If N3105 expires, the network release the uplink TBF.

142

Case 1 z

Phenomenon Description: Â&#x2021;

Three cells of a satellite transmission BTS under a BSC are unable to access the network through GPRS. View the cell status and channel status. They are all normal. The PCU traffic measurement, Um interface and cell signaling tracing, and configuration data are collected on site.

The possible causes are as follows:

The configuration data of the PCU and BSC is incorrect.

The PCU version is incorrect.

The cell is exceptional for various reasons.

Page17

The parameter related to satellite transmission is not properly set.

Handling Process: a. Check the data. No exception occurs in other cells and the satellite transmission parameter on the PCU is set to Yes.

b. View the traffic measurement. The traffic measurement item "number of uplink assignment successes on PACCH" is 0. The traffic measurement item "number of uplink TBF establishment successes" is also 0 and the basic cause value is "uplink TBF establishment failures owing to no response from the mobile station".

c. View signaling messages. There are only a large number of RACK_RES_REQ and PACK_UL_ASSI messages over the air interface. This is obviously abnormal.

d. Analyze the traffic and signaling messages. After the MS sends a RACK_RES_REQ message and the PCU returns a PACK_UL_ASSI message, the MS makes no response and continues sending a RACK_RES_REQ message.5. Check the GPRS table about the PCU cell data. Timer T3168 is set to 500 ms, which is the same as that for other GPRS cells of terrestrial transmission. 6. Run the mt sattrans show delay command to view the transmission delay of the satellite transmission cells. The transmission delay is 725 ms.7. Find the cause. After the MS sends a RACK_RES_REQ message, timer T3168 is started. If the timer expires before a PACK_UL_ASSI message is received, the MS resends a RACK_RES_REQ message 143 for four times at most. The duration of the onsite timer T3168 is less than the delay of

Contents z GPRS Cell Parameters z GPRS Power Control z GPRS Cell Reselection z Performance Parameters

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144

GPRS Power Control z

GPRS Power Control Purpose

Save the power

Reduce the interference of the network

GPRS Power Control is complex than GSM for discontinuous transmission.

Normally now just uplink power control is implemented.

Page19

Because for the downlink blocks, it is not only contained TFI for downlink but also USF which may be is for another MS. The two subscribers perhaps one is near the BTS, one is far away. So downlink power control is not implemented for GPRS.

145

GPRS Power Control z

According GPRS principle, GPRS MS output power as below：

Pch = Min〔 Ro - Rch – a*( C+48) , Pmax〕

Pmax: GPRS MS max transmitting power

a：ALPHA，normally is 1

Ro：39dBm for 900M cell, and 36dBm for 1800M cell

Rch：GAMMA

C：MS receiving level

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GPRS Power Control

Page21

The ALPHA parameter is used by the MS to calculate the output power value PCH of its uplink PDCH For open loop power control, it should be set to 1.0. GAMMA:Expected receiving signal strength at the BTS side when the MS GPRS dynamic power control is active Value range: 0~62dB, default value is 14

147

Contents z GPRS Cell Parameters z GPRS Power Control z GPRS Cell Reselection z Performance Parameters

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148

GPRS Cell Reselection z

During ready and standby mode, MS will occur cell

reselection z

Cell reselection will be triggered upon the following 5

kinds conditions.

current serving cell is prohibited

down link fails

C1 of serving cell is lower than 0 last 5s

Neighbor cell C32 and C31 higher than serving cell last 5S

MS starts a cell reselection if the access times exceed the MAX

retrans.

Page23

If the C2 value of the target cell is higher than that of the serving cell by at least the value of CRH for longer than 5 seconds, a location update process and the cell reselection process will be performed. Only after the PBCCH is configured, C31 and C32 will be worked.

149

NETWORK_CONTROL_ORDER

Definition

Whether the MS send the M.R

MS mode

Cell Selection Mode

NC0

Normal MS Control Mode

Ready & Standby

Controlled by MS

NC1

MS Control with M.R Mode

Yes

Only Ready

Controlled by MS

NC2

Network Control Mode

Yes

Only Ready

Controlled by network

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150

NETWORK_CONTROL_ORDER

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151

NC2 Feature

change to cell C

Neighbor cell B

Neighbor cell c

Serving cell A

Page26

For MS receiving level of cell B is higher than cell C, but the load of cell B is too higher. So PCU will make the MS cell change to cell C instead of cell B. NC2 is just like load handover.

152

GPRS Cell Reselection z

If PBCCH no exists, the cell reselection is basically the same as GSM cell reselection

When the two cells locates in the different routing areas or the MS is in READY mode, the NC2 must be greater than SC2+CRH (>5s)

When the two cells locates in the same routing area and the MS is in STANDBY mode, the NC2 must be greater than SC2 (>5s)

Page27

Two consecutive cell reselections caused by C2 have a time interval of 15 seconds. In other words to say, if because of C2 a MS reselected to a cell, then the MS cannot reselect to another cell by the cause of C2 within 15 seconds.

153

Cell Reselection in Standby Mode

RA 2

RA 1 CC2>BC2＋CRH

AC2>BC2 Cell B Cell A

Cell C

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Cell Reselection in Ready Mode

RA 1 BC2>AC2＋CRH Cell A

Cell B

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NACC System information of cell B

Cell A

Cell B

Page30

In network control mode NC0, NC1, or NC2, when the MS is in the packet transmission mode, the network informs the MS of the system information about neighbor cells in advance. Therefore, the cell reselection of the MS is accelerated.

156

NACC

z z

Page31

NACC (Network Assisted Cell Change): shorten the duration of cell reselection NACC will be used during packet transmission mode, network will inform neighbor cell system information to make the cell reselection quickly. NC0:Before the cell reselection decision, MS will send “PACKET CELL CHANGE NOTIFICATION” to BSC, which carry ARFCN and BSIC of target cell. If serving cell support NACC, BSC will send the SI1,SI3 and SI13 of target cell . Before the GBSS8.1 version, just support intra-BSC NACC; GBSS8.1 or later version also can support inter BSC or inter RNC NACC. For Inter-BSC NACC,BSC and core network should support RIM （RAN Information Management）to get external cell system information. RIM flow means BSS requires the target cell system information from target BSC/RNC through core network. BSC implements RIM flow during provider service, and stores all the external cell system information. BSC also will update these external cell system information periodical. And during the interBSC NACC, if BSS did not find the target cell system information, it will trigger RIM flow.

157

Contents z GPRS Cell Parameters z GPRS Power Control z GPRS Cell Reselection z Performance Parameters

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Dynamic PDCH Channel Conversion z

When dynamic PDCH conversion will be triggered?

PDCH required failure (such as reach the max threshold)

No meet the multiple timeslot

The TBF numbers higher than ”Uplink (Downlink) Multiplex Threshold of Dynamic Channel Conversion”

z z

z z z

z z

Page33

Parameter Name Uplink Multiplex Threshold of Dynamic Channel Conversion Description This parameter specifies the uplink multiplex threshold of dynamic channel conversion.When the number of subscribers carried over the channel reaches the threshold/10, dynamic channels are used. GUI Value Range [10,70] Default Value 20 Configuration Policy If this threshold is high, it is difficult to seize dynamic channels. If this threshold is low, it is easy to seize dynamic channels.

Parameter Name Downlink Multiplex Threshold of Dynamic Channel Conversion Description This parameter specifies the downlink multiplex threshold of dynamic channel conversion.When the number of subscribers carried over the channel reaches the threshold/10, dynamic channels are used. GUI Value Range [10,80] Default Value 20

159

Dynamic PDCH Channel Conversion z

Which channel will be convert to dynamic PDCH

TCH/F channels can be converted to dynamic PDCH, the maximum dynamic PDCH number will be restricted by reasons listed below：

The max PDCH number restricted by License

Maximum Ratio Threshold of PDCHs in a Cell

Maximum PDCH numbers of carrier

Reservation Threshold of Dynamic Channel Conversion

Page34

Maximum PDCHs number in a Cell= ( TCH/F channels number + PDCH channels number) * Maximum Ratio Threshold of PDCHs in a Cell

160

Dynamic PDCH Channel Conversion z

When the dynamic PDCH channel will be converted to TCH channel?

Timer of Releasing Idle dynamic Channel

CS services preemption

All dynamic channels can be preempted

Control channels cannot be preempted

Dynamic channels carrying services cannot be preempted

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Dynamic PDCH Channel Conversion

Page36

Parameter Name

Maximum Ratio Threshold of PDCHs in a Cell

Description This parameter specifies the maximum ratio of PDCHs in a cell. The total number of TCHs and PDCHs available in a cell is fixed. The PDCH ratio is equal to PDCHs / (TCHs + static PDCHs). This parameter determines the proportion of PDCHs to the total number of TCHs + PDCHs.

GUI Value Range

[0,100]

Default Value

Configuration Policy If this parameter is set to an excessive value, there are excessive PDCHs and insufficient TCHs. This affects CS services. If this parameter is set to a modest value, there are insufficient PDCHs and excessive TCHs. This affects PS services.

Parameter Name

Description This parameter specifies the PDCH uplink multiplex threshold.The uplink PDCH can carry a maximum of (threshold/10) TBFs.

GUI Value Range

[10,70]

Default Value

Configuration Policy If this parameter is set to a lower value, the TBFs established on the PDCH and the subscribers are fewer, and the uplink bandwidth for each subscriber is higherIf this threshold is set to a higher value, the TBFs established on the PDCH and the subscribers are more, and the uplink bandwidth for each subscriber is lower.

Parameter Name

PDCH Downlink Multiplex Threshold

Description PDCH

This parameter specifies the PDCH downlink multiplex threshold.The downlink i f (th h ld/10) TBF

PDCH Uplink Multiplex Threshold

162

z z

z z z

z z

Parameter Name Level of Preempting Dynamic Channel Description This parameter specifies the levels of dynamic channels preempted by CS services and PS services. Only full-rate TCHs are the dynamic channels that can be preempted. All dynamic channels can be preempted: It indicates that the CS services can preempt all the dynamic channels.Control channels cannot be preempted: It indicates that the CS services can preempt all the dynamic channels except for the control channels.Dynamic channels carrying services cannot be preempted: It indicates that the CS services cannot preempt the dynamic channels that carry services. GUI Value Range [Preempt all dynamic TCHFs,No preempt of CCHs,No preempt of service TCHF] Default Value All dynamic channels can be preempted

Parameter Name Reservation Threshold of Dynamic Channel Conversion Description This parameter specifies the number of channels reserved for the CS services. GUI Value Range [0,8] Default Value 2 Configuration Policy If this parameter is set to an excessive value, the PS services are affected.If this parameter is set to a modest value, the CS services are affected when there are too many PS services.

Parameter Name Description allocated to a TRX. GUI Value Range Default Value

Maximum PDCH numbers of carrier This parameter specifies the maximum number of PDCHs [0,8] 8

163

GPRS Channel Priority Type

Page38

Value Range GPRS Channel, EGPRS Normal Channel, EGPRS Priority Channel, EGPRS Special Channel, NoneGPRS Channel

Default Value When Channel Type is set to non-PDTCH, the default value is None-GPRS Channel. When Channel Type is set to PDTCH and the cell does not support EDGE services, the default value is EGPRS Normal Channel. When Channel Type is set to PDTCH and the cell supports EDGE services, the default value is EGPRS Normal Channel.

Description

When Channel Type is set to PDTCH and the cell does not support EDGE services, the default value is EGPRS Normal Channel.

When Channel Type is set to PDTCH and the cell supports EDGE services, the default value is EGPRS Normal Channel.

When Channel Type is set to non-PDTCH, the default value is None-GPRS Channel.

164

GPRS Channel Priority Type TRX2 EGPRS Normal

EDGE MS

GPRS MS

Page39

EGPRS normal channel can support GPRS MS and EDGE MS at the same time. But sometimes it will decrease the EDGE MS speed.

165

GPRS Channel Priority Type TRX2 EGPRS

EGPRS Priority

Priority

× reject GPRS MS

EDGE MS GPRS MS

Page40

EGPRS normal channel can support GPRS MS and EDGE MS at the same time. But sometimes it will decrease the EDGE MS speed.

166

GPRS&EDGE Coding Scheme Kbps

59.2

60.00

54.4

50.00

GPRS

44.8

EGPRS

40.00

29.6

30.00 22.4

21.4

20.00 13.4

10.00 0.00

17.6

15.6

14.8

9.05

CS-1

8.8

CS-2

CS-3

CS-4

MCS-1

11.2

MCS-2

MCS-3

MCS-4

MCS-5

MCS-6

GMSK

MCS-7

MCS-8

MCS-9

8PSK

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167

Appendix

Codec

Idle timeslot

CS1

CS2 CS3

MC S1

MC S2

1+0

CS4

MCS MCS 3 4

MC S5

1+1

MC S6

MCS 7

MCS 8

1+2

1+3

MCS 9

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Appendix

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169

In this course, we have learned:

Summary

The function of GPRS cell parameters

The function of GPRS cell reselection parameters

The function of GPRS performance parameters

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Thank you www.huawei.com

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GPRS EDGE Build-in PCU Packet Radio Resource Management Algorithm and Parameters www.huawei.com

172

Foreword z

Radio resource management (RR) is an important protocol in the GSM system.

The channel management and load control is a part of the GPRS resource management.

The appropriate channel management and load control algorithm can improve the PS assignment success rate, decrease the congestion ratio, provide proper service resources for subscribers, and improve the network service quality.

This document describes the specific algorithms and parameters of the GPRS/EDGE channel management and load control.

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Objectives z

After studying this course, you will:

Understand the purposes of the PS resource management and load control.

Master the procedure for allocating channels and main factors to be considered.

Master the percentage of each factor in the channel allocation and adjustment method.

Master the dynamic channel allocation and release algorithm principles.

Be familiar with the main parameters of the dynamic channel allocation and release algorithm.

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Contents 1. Packet Radio Resource Management Algorithm Overview 2. Packet Channel Assignment Algorithm 3. Packet Channel Conversion Algorithm 4. Packet Channel Release Algorithm

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Overview of PS Resource Management Algorithm Phase 1 access on CCCH/PCCCH

Phase 2 access on CCCH/PCCCH

Establishment of the downlink TBF on the CCCH/PCCCH

PDCH allocation algorithm

Idle dynamic PDCH released

TBF reassignment/ timeslot re-configuration

Establishment of the downlink TBF on the PACCH

Establishment of the uplink TBF on the PACCH

Conversion algorithm of dynamic PDCH

For CS service, no idle radio channel resources available for preemption

For CS service, no idle Abis resources available for preemption

Dynamic PDCH release algorithm

Page4

The PS resource management algorithm is intended to guarantee the load balance between channels by allowing a single subscriber to obtain a high throughput rate simultaneously, thus improving the channel usage efficiency of the entire network. Upon the receipt of the service application from a subscriber, the BSS allocates appropriate resources to the subscriber after the processing through the PS resource management algorithm. The PS resource management algorithm consists of the following parts: PS channel allocation algorithm Dynamic channel conversion algorithm Dynamic channel release algorithm

176

Basic Concepts of PS Resource Management Algorithm RLC/MAC Block resource Radio channel resource

Abis timeslot resource

PS resource management

TFI resource

USF resource

TAI resource

Page5

Radio channel resources For the PDCH resources of a cell, one TBF can occupy multiple channels. At least one timeslot among the timeslots occupied by the uplink/downlink TBF of the same subscriber is shared. Multiple MSs can be multiplexed on the same channel. Available channel resources in the cell can be taken into account on the basis of these conditions. Abis resource In Fix Abis mode, the channel is fixedly bound to an active link (16 kbps) after configuration. After code adjustment, the idle timeslots can be bound. Flex mode

For static PDCHs, the description is the same as the preceding description.

The active link is not bound after the dynamic PDCH is configured. The active link is bound after the activation of the channel. A proper idle timeslot is applied for the binding. When no Abis resources are available, the channel cannot be allocated. Block resource One block budget is required for every 60 blocks. For a guaranteed bit rate (GBR) subscriber, the maximum number of occupied blocks is specified according to the TBF rate threshold/100 of the GBR. For other types of subscribers, the maximum number of blocks is allocated according to the priority of remaining blocks.

177

The GBR service can be applied for through registration. If the GBR attribute is subscribed to during registration, the service rate is guaranteed. For streaming subscribers, the rate is fixed. The corresponding resource is provided according to rate evaluation. The rate requirement is met after evaluation. USF resource The uplink status flag is used to control multiple MSs to use radio channels in dynamic allocation mode. The USF has three bits in total, labeling eight (0-7) uplink subscribers in total. For Huawei devices, the setting of USF to 7 is reserved. For example, if the USF of the RRBP block is set to 7, seven (0 – 6) USFs are left for allocation to subscribers. The USF applies to data transmission. The RRBP subscribers make response to corresponding data, for example, Ack or Nack. TFI resource TFI is an identity of the TBF. The TBF is uniquely identified through the TFI and data transmission direction. The TFI has five bits in total, identifying subscribers of 0-31 bits. There are 32 independent TBFs at the uplink and downlink respectively.

Different channels of the same TRX can use the same TFI value.

Any TFI value of the same channel at the same time belongs to a unique uplink or downlink TBF.

The uplink and downlink TBFs of the same MS can use different TFIs or the same TFI.

TAI resource

A total of 16 TAIs are available for allocation to subscribers for the TA adjustment.

178

Basic Concepts of PS Resource Management Algorithm z

PDCH types - by configuration mode

Static channel: fixedly unconvertible in the case of use by PS service

Dynamic channel: applies to CS or PS services

PDCH types - by PS service bearer capability

GPRS channel: applies to only GPRS services

EGPRS normal channel: applies to both GPRS and EGPRS services

EGPRS priority channel: preferentially applies to EGPRS services

EGPRS special channel: applies to only EGPRS service

Page7

179

Data Configuration

Page8

Common EGPRS channel GPRS and EGPRS subscribers can use this channel, with the same priority. Therefore, GPRS subscribers and EGPRS subscribers may exist in this channel at the same time. The modulation mode corresponding to the channel encoding used by these subscribers must be the GMSK. Therefore, the configuration may affect the high speed performance of the EDGE. EGPRS preferred channel The GPRS service can use this channel when it is idle. When the EGPRS service is available on this channel, the GPRS service is swapped and relevant resources are allocated for the EGPRS subscribers. If no channel is available for the GPRS service in the case of swap, call drop occurs in the GPRS service. Therefore, only GPRS subscribers or EGPRS subscribers can use this channel at the same time. This channel is allocated for EGPRS subscribers with priority. The GPRS channel assignment is initiated by MSs, which is similar to the GSM channel assignment. One channel may be applied for signaling and data transmission, which is similar to the early assignment in the GSM system. Alternatively, one PDCH is applied for and then PS resources are applied for on the basis of this PDCH. This is similar to the immediate assignment and then assignment in the GSM.

180

Contents 1. Packet Radio Resource Management Algorithm Overview 2. Packet Channel Assignment Algorithm 3. Packet Channel Conversion Algorithm 4. Packet Channel Release Algorithm

Page9

181

PS Channel Assignment Process TRX:0

TRX:1

Main BCCH

SDCCH

TCH

SDCCH

TCH

PDTCH

TCH

PDTCH

TCH

PDTCH

TCH

TRX:2

TRX:3

TCH

TCH/H

TCH

TCH/H

TCH

TCH/H

TCH

TCH/H

TCH

TCH/H

TCH

TCH/H

TCH

TCH/H

TCH

TCH/H

RACH-Channel Request Cause: PS access, random number

Imm Assignment decision AGCH-Imm Assignment (random number, PDCH channel description) PDCH-Packet Resource Request (TLLI, pre-emption decision)

Packet assignment decision

PDCH-Packet Assignment (TLLI)

Page10

The GPRS channel assignment is initiated by the MS, which is similar to channel assignment in the GSM system. One channel may be applied for signaling and data transmission, which is similar to early assignment in the GSM system. Alternatively, one PDCH is applied for and then PS resources are applied for on the basis of this PDCH, which is similar to the immediate assignment in the GSM.

182

PS Channel Assignment Process Immediate assignment request

Reassignment request

Assignment request on the PACCH

Channel assignment pre-processing

PS channel allocation algorithm

Yes

Is the channel assignment successful? No Processing after the initial assignment failure

End

Page11

According to the received assignment request, the BSS checks the assignment request type during channel assignment pre-processing to determine the channel type of the assignment and assignment process. The PS channel allocation algorithm is used to find the proper TRX, channel group, and calculation weight for the allocation processing. If once assignment is successful, the assignment process ends. If no appropriate channel is used for the assignment, it is subject to the processing after the initial assignment failure. The dynamic channel conversion and twice assignment are performed until the assignment is complete after the initial assignment failure.

183

General Process of PS Channel Allocation Algorithm Start Obtain the assignable channel group

Obtain the assignable TRX

Is the assignable channel group available?

Yes Is the assignable TRX available?

Yes

Calculate the weight of the assignable channel group

No Maximum channel group of the allocation weight

End

Page12

The PS channel allocation algorithm includes four steps: Obtaining the assignable TRX information. Obtaining the assignable channel group information from the assignable TRX. Performing the weight calculation for all assignable channel groups to obtain the appropriate channel group. Selecting the channel group with the greatest weight for allocation.

184

Obtaining the Allocable TRX No Start

Concentric cell or not? Yes

No Multi-band cell or nor?

Specify the overlaid subcell or underlaid subcell?

Yes

Yes Is the MS band support capability known?

Yes

Specify the TRX of the concentric subcell attribute

No Main BCCH TRX band and TRX of the band being compatible with the main BCCH TRX

Bands supported by the MS No Do the MS and cell support the EGPRS? No

Yes

Double-timeslot extension cell? TRX supporting the EGPRS

Yes No TA>63? Yes

End Select the double-timeslot extension TRX

Page13

The procedure for obtaining the assignable TRX is as follows: TRX requirement: To allocate the PDCH for MSs, check whether the cooperative TBF exists according to the ingress TRX index. If yes, allocate the PDCH for the MS on the specified TRX. For a multi-band cell, the capability of the MS supporting the frequency bands must be taken into account when assigning the PDCHs.

If the BSC does not know the radio access capability of the MS, only the PDCHs over the main BCCH frequency band and the frequency bands compatible with the main BCCH frequency band should be assigned.

If the BSC knows the radio access capability of the MS, only the PDCHs over the frequency bands supported by the MS are assigned. If the cell is a double timeslot extended cell as defined by the cell attribute parameter 【Cell Ext Type】, and if the TA reported by the MS is greater than 63, then the PDCHs on a double timeslot extended TRX should be assigned to the MS. If the cell is a concentric cell as defined by the cell attribute parameter 【Cell Type】, and if the BSC specifies the overlaid subcell or underlaid subcell upon a PDCH request, then the PDCHs on an overlaid TRX or underlaid TRX should be assigned accordingly. If the overlaid subcell or underlaid subcell is not specified, the PDCHs on a concentric TRX should be assigned without specific tendency. In the case of applying for the allocation of channels, the service type (EDGE or GPRS service, or EDGE + GPRS service) is contained. According to the TRX attribute parameter 【TRX capability】, the TRX supporting the EGPRS is selected if the MS and cell support the EGPRS.

185

Obtaining the

Allocable Channel

Start

Is the idle PDCH with normal statusY& available Abis timeslot & channel priorityemeeting the service requirement s available?

Yes

Match the service type to the channel priority type

Perform polling for all PDCHs

Yes Allow E Down G Up Switch?

Does the number of MSs multiplexed on the PDCH reach the threshold?

No No

Yes

Perform processing related to Prohibit E Down G Up Switch?

The corresponding PDCH is unavailable End

Page14

To obtain the assignable channels, do as follows: Check whether the channel type of the sub timeslot is PDCH. Check whether the valid status of the PDCH is configured, that is, whether the location occupied by the channel can be replaced. If it is not configured, it is unavailable. If it is configured, it is available. Obtain the management status of the current channel. Check the channel management status. If the channel is in the blocked state, do not perform the processing. Check the resource status recorded through 8 bits on the left and the control status recorded through 8 bits on the right. Make sure that they are normal. Check whether the main control status of the channel is in the idle state. Check whether the channel recorded in the radio resource management module is available. Make sure that the number of available Abis is not zero. Check whether the channel priority meets the service type.

For GPRS services, the GPRS channel group, EGPRS normal channel group, and EGPRS priority channel group can be allocated.

For EDGE services, the EGPRS special channel group, EGPRS normal channel group, and EGPRS priority channel group can be allocated.

186

According to the cell attribute parameter 【 PDCH Uplink/Downlink Multiplex 】 Threshold, make sure that the number of MSs multiplexed on the channel does not reach the upper threshold. For the PBCCH or PCCCH, the number of MSs multiplexed on the channel must be smaller than 7. Otherwise, the number of MSs multiplexed on the uplink PDTCH should be equal to or smaller than 7, and the number of MSs multiplexed on the downlink PDTCH should be equal to or smaller than 8. In the latest version, the downlink PDTCH supports 16 MSs. Match the service type with the channel priority type: The GPRS services cannot occupy the EGPRS special channels. If an EGPRS priority channel bears the EGPRS services, the EGPRS priority channel cannot be assigned to the GPRS services. Make decision according to the BSC attribute parameter 【 Allow E Down G Up Switch 】. If the switch is off (that is, the EGPRS OFF GPRS ON is prohibited), If a channel carries the EGPRS downlink services, the channel cannot be assigned to the GPRS uplink services. If a channel carries the GPRS uplink services, the channel cannot be assigned to the EGPRS downlink services. Obtain the assignable channel groups. If an available channel exists according to the preceding decision, obtain all channel groups that can be allocated to MSs based on the MS multi-timeslot capability.

187

Data Configuration

Page16

PDCH Uplink Multiplex Threshold Description: This parameter specifies the PDCH uplink multiplex threshold.The uplink PDCH can carry a maximum of (threshold/10) TBFs. Value Range: [10,70] Default Value: 70 Configuration Policy: If this parameter is set to a lower value, the TBFs established on the PDCH and the subscribers are fewer, and the uplink bandwidth for each subscriber is higherIf this threshold is set to a higher value, the TBFs established on the PDCH and the subscribers are more, and the uplink bandwidth for each subscriber is lower. PDCH Downlink Multiplex Threshold Description: This parameter specifies the PDCH downlink multiplex threshold.The downlink PDCH can carry a maximum of (threshold/10) TBFs. Value Range: [10,160] Default Value: 80 Configuration Policy: If this parameter is set to a lower value, the TBFs established on the PDCH and the subscribers are fewer, and the downlink bandwidth for each subscriber is higher.If this threshold is set to a higher value, the TBFs established on the PDCH and the subscribers are more, and the downlink bandwidth for each subscriber is lower.

188

Data Configuration

Page17

Allow E Down G Up Switch Description: This parameter specifies whether to enable the multiplexing of EDGE download and GPRS upload onto the same channel. If this parameter is set to Open, the EDGE download and GPRS upload can use the same channel;If this parameter is set to Close, the EDGE download and GPRS upload cannot use the same channel.In dynamic allocation or extended dynamic mode, the downlink block must use the GMSK coding scheme (including CS1-4, MCS1-4) to detect the USF assigned for the uplink by the GPRS MS. Then, the downlink cannot use the high-rate coding scheme, thus decreasing the EGPRS rate.If the Allow E Down G Up Switch is set to Open, this can prevent the EGPRS downlink and GPRS uplink from multiplexing the same channel to ensure the EGPRS rate. However, the channel needs to be properly allocated, the GPRS channel configured is to prevent decreasing the access of the GPRS MS due to no GPRS channel.If the Allow E Down G Up Switch is set to Close, the downlink uses the GMSK coding scheme, thus decreasing the EGPRS rate.At present, this parameter is usually set to Open. Value Range: [Open,Close] Default Value: Open

189

BITMAP Mapping of Available Channel 1

0 B

SD TF GS

GPRS service BITMAP mapping: 00011101

GPRS service BITMAP mapping: 00010100 EGPRS service BITMAP mapping: 00000111

User multiplexing is full.

EGPRS service BITMAP mapping: 00001111

0 B

SD TF GS

Allow E Down G Up Switch is OFF. The EGPRS downlink multiplexing is not full.

0 B

The EGPRS subscriber is available and the multiplexing is not full.

SD TF GS

EGPRS service BITMAP mapping: 00001111

Downlink GPRS service BITMAP mapping: 00011101

Page18

Channel type:

B: BCCH channel

SD: SDCCH channel

TF: TCH full rate channel

GS: GPRS special channel

EN: EGPRS normal channel

ES: EGPRS special channel

EP: EGPRS priority channel In the case of the existing channel resources, generate the corresponding available channel BITMAP according to the service type. See the preceding example. In the case of the request for allocating uplink channel, the allocation fails when the number of the multiplexed uplink TBFs on the channel is equal to or greater than 【PDCH Uplink Multiplex Threshold】. In the case of the request for allocating downlink, the allocation fails when the number of the multiplexed downlink TBFs on the channel is equal to or greater than 【PDCH Downlink Multiplex Threshold】. The EGPRS special channel cannot be allocated for the GPRS request. The GPRS channel cannot be allocated for the EGPRS request. The EGPRS priority channel occupied by the EGPRS (including the uplink and downlink) cannot be allocated for the GPRS. When 【Allow E Down G Up Switch】 is off, if the EGPRS downlink is available, the resource should be allocated to the GPRS uplink. If the GPRS uplink is available, the resource cannot be allocated to the EGPRS downlink. 190 All available channel groups are generated through the AND and OR operations among the BITMAP mapping of available channels and all possible BITMP tables of

Uplink GPRS service BITMAP mapping: 00010101

Obtaining the Assignable Channel Group z

The bitmap mapping of multi-timeslot ability. For example for 4 multi-timeslots ability Enable “Allocate Continuous Timeslot Switch” (by default )

Disable “Allocate Continuous Timeslot Switch”

Page19

“Allocate Continuous Timeslot Switch” can not be configured.

191

Obtaining the Downlink Channel Group

Consecutive timeslot

TAI/TFI Resource

Number of Channels Contained in the Channel Group/ MS Multi-timeslot Capability

Obtain the downlin k channel group

Frequency Hopping Parameter

EDA Function

Cooperation TBF

Receive/send Sharing Timeslot

Page20

After obtaining the allocable channel group, attempt to obtain available uplink or downlink channel group of a TRX according to the service status. The method for obtaining the downlink channel group is as follows:

If the number of channels contained in the assignable channel group in the TRX is smaller than or equal to the MS multi-timeslot capability channel group, these channel groups can be used for the allocation.

If the MS multi-timeslot capability is unknown, up to one PDCH is allocated.

If the MS multi-timeslot capability is known, the maximum number of channels supported by the MS multi-timeslot capability is allocated.

The channel group supports multi-timeslot capability meeting the MS. For type 1 or 2 MS, check the following (for type 1 MS, the simultaneous receiving and transmitting is not allowed. For type 2 MS, the simultaneous receiving and transmitting is allowed).

Calculate the number of received and transmitted timeslots of a TDMA frame.

Check whether the number of received and transmitted timeslots meets the multi-timeslot capability.

For the MSs with the multi-timeslot levels from 1 to 12, check whether the timeslot sum of the receiving and transmitting is in the range [1, Sum].

Make sure that the transmitting timeslot does not exist between two receiving timeslots in a TDMA frame.

Make sure that the receiving timeslot does not exist between two transmitting timeslots in a TDMA frame. 192

Check whether the Tta, Ttb, Tra, and Trb conditions of multi-timeslot capability are met, that is,

Time of the channel group supporting the MS from neighbor cell power measurement to transmitting (number of timeslots) Tta

Time of the channel group supporting the MS transmitting (number of timeslots) Ttb

Time of the channel group supporting the MS from neighbor cell power measurement to receiving (number of timeslots) Tra

Time of the channel group supporting the MS receiving (number of timeslots) Trb

193

Obtaining the Uplink Channel Group (Non-EDA Mode) Consecutive Timeslot

TAI/TFI Resource

Frequency Hopping Parameter

Number of Channels Contained in the Channel Group

Obtain the Uplink Channel Group

MS multi-timeslot Capability

Cooperation TBF

Page22

In non-EDA mode, consider the following factors when obtaining the uplink channel group: The number of channels contained in the channel group is less than or equal to the maximum number of assignable channels. The timeslots that carry the channels must be consecutive. For the cooperation TBF, consider the following items:

If the cooperation TBF does not exist, the channel with the largest timeslot number in the uplink channel group must able to be assigned to the downlink.

If the cooperation TBF exists, the control channel of the channel group must be the same as the control channel of the cooperation TBF, and the control channel of the cooperation TBF must have TAI resources. If there are m timeslots allocated to the channel group and n timeslots allocated to the cooperation TBF, there should be Min (m, n) timeslots for transmission and reception. The frequency parameters (MAIO, HSN) of the channels in the channel group must be the same. The channel group assigned to the MS must match the multislot capability of the MS. The TFI and TAI resources are available for assignment.

194

Obtaining the Uplink Channel Group (EDA Mode) Downlink Channel

TAI/TFI Resource

Channel Group including Channel Number

Obtaining the Uplink Channel Group

Frequency Hopping Parameters

Cooperation TBF

EDA Function

z z

Page23

When the BSC software parameter 【Support EDA】 is set to “Support”, and if the MS supports EDA, then only one channel should be assigned on the downlink. Note this channel corresponds to the timeslot numbered smallest of the uplink channel group. If the cooperation TBF exists, the control channel of the channel group must be the same as the control channel of the cooperation TBF, and the control channel of the cooperation TBF must have TAI resources. If there are m timeslots allocated to the channel group and n timeslots allocated to the cooperation TBF, there should be Min (m, n) timeslots for transmission and reception. Note: The uplink (or downlink) TBF of the MS is the cooperation TBF of the downlink (or uplink) TBF. If the number of receiving timeslots of the MS is m and the number of transmitting timeslots of the MS is n, there must be Min (m, n) same timeslots in the transmitting and receiving timeslots. The frequency parameter (MAIO, HSN) of the channel in the channel group must be the same. If the frequency parameter of the channel in the channel group is different, the channel group cannot be allocated. The TFI and TAI resources exist in the channel group. The timeslots that carry the channels must be consecutive.

195

Data Configuration

Page24

Support EDA Description：This parameter specifies whether the EDA is supported. Value Range：[Not Support,Support] Default Value：Not Support Allow EDA Multiplex Description：This parameter specifies whether the EDA multiplexing is allowed. Value Range：[Not Allow,Allow] Default Value：Not Allow

196

Calculating the Weight of the Allocable Channel Weight table Priority of Priority of non-double timeslot service type channels 31

Priority of number of channels in the channel group

Priority of the load of channel groups

Priority of number of estimated downlink channels

29-27

26-20

19-17

Priority of the channel group bandwidth

Reserved

16-1

Higher priority

Weight table

Extended weight table Lower priority

Reserved

Priority of the downlink bandwidth of the estimated channel group 30-15

Priority of channel type 14-10

Priority of the channel group timeslot ID

Reserved 5-0

9-6

Page25

If there are channels groups available for assignment, their weight must be calculated to select the optimal channel group for the MS. The following describes the channel weight table and channel extension weight table. After comparing the weights of the assignable channel groups on the basis of the channel weight table and channel extension weight table, the optimal channel group for assignment is determined. The channel extension weight table is used only when two channel groups have the same weight. The following describes the factors listed in the channel weight table. Bit 31 service type priority: When the EGPRS service is requested, the EGPRS channel is allocated with priority and is set to 1. Bit 30 Non- double timeslot channel priority: Check whether it is the double timeslot channel. According to the situation of the actual TA, set the weight of the non double-timeslot channel and double-timeslot channel. If TA is larger than 63, it indicates the high priority for the double timeslot TRX. Otherwise, it indicates the high priority for the common TRX. Bits 29 to 27 (priority of the number of channels in the channel group): This field specifies the number of channels in a channel group. Bit 26-30 channel group load priority: It indicates the total number of MSs multiplexed on the channel. The larger the total number of MSs, the lower the assigned value and the priority. Bit 19-17 number of estimated downlink channels priority: For the uplink TBF, the number of allocable channels can be estimated when the service type is neutral or downlink priority. The larger the number of downlink channels, the higher the priority. 197

Bits 16 to 1 (priority of the bandwidth of the channel group): The higher the bit rate provided by a channel group, the higher the priority of the channel group. When the BSC software parameter 【Support EDA】 is set to 【Support】, and if the MS supports EDA and uplink service is preferred, the rules for determining the uplink channel group are as follows: The number of channels contained in the channel group is less than or equal to the maximum number of assignable channels. The number of channels contained in the channel group is greater than or equal to 3. If the cooperation TBF does not exist, the downlink channel corresponding to the timeslot numbered smallest of the uplink channel group must be assignable; that is, the uplink threshold is not exceeded. Only one channel is assigned on the downlink, and the timeslot number of the timeslot that carries the channel must be the smallest. If the BSC software parameter 【Allow EDA Multiplex】 is set to 【Not Allow】, then any channel in the channel group cannot be multiplexed with other MSs. The frequency parameters (MAIO, HSN) of the channels in the channel group must be the same. The TFI and TAI resources are available for assignment.

198

Contents 1. Packet Radio Resource Management Algorithm Overview 2. Packet Channel Assignment Algorithm 3. Packet Channel Conversion Algorithm 4. Packet Channel Release Algorithm

Page27

199

Triggering Conditions of Dynamic Channel Application Failure to allocate the PDCH

Failure to assign a single block

Multitimeslot capability is not met

Channel reserved

Channel load exceeding the threshold

EGPRS preemption

Apply for the dynamic channel

Page28

In the case of applying for dynamic channels, check whether the cell is allowed to trigger the dynamic channel conversion to increase the number of PDCHs according to the cell channel resource, CPU load, and license. The number of PDCHs does not increase by triggering the dynamic channel conversion in the cell when one of the following cases occurs. Channel resources

The number of PDCHs activated in the cell is greater than the upper threshold of the maximum PDCH ratio.

The number of convertible TCHs in the cell is equal to or smaller than the number of reserved TCHs (specified by the Reservation Threshold of Dynamic Channel Conversion).

EGPRS MSs occupy the GPRS channel. CPU load: If the CPU utilization is high, the dynamic channel conversion is stopped. License: In the case of the license control, the dynamic channel conversion is not triggered if the activated PDCH channel is available (that is, the current logical type is PDCH). When any of the preceding conditions is not met, cell conversion is allowed. According to the triggering condition of the dynamic channel conversion, determine whether the subscriber needs to triggers the dynamic channel conversion. That is, dynamic channel application is triggered when any of the following conditions occurs: Multi-timeslot capability

The assignment of the PDCHs to the MS fails.

The assignment of the PDCHs to the MS succeeds, but the PDCHs do not meet the multislot capability requirement of the MS.

Load

200

Failure to assign a single block for MSs

Data Configuration

Page29

Maximum Ratio Threshold of PDCHs in a Cell

Description：This parameter specifies the maximum ratio of PDCHs in a cell. The total number of TCHs and PDCHs available in a cell is fixed. The PDCH ratio is equal to PDCHs / (TCHs + static PDCHs). This parameter determines the proportion of PDCHs to the total number of TCHs + PDCHs.

Value Range：[0,100] Default Value：30 Unit：%

Configuration Policy：If this parameter is set to an excessive value, there are excessive PDCHs and insufficient TCHs. This affects CS services. If this parameter is set to a modest value, there are insufficient PDCHs and excessive TCHs. This affects PS services.

Uplink Multiplex Threshold of Dynamic Channel Conversion

Description：This parameter specifies the uplink multiplex threshold of dynamic channel conversion.When the number of subscribers carried over the channel reaches the threshold/10, dynamic channels are used.

Value Range：[10,70] Default Value：20

Configuration Policy：If this threshold is high, it is difficult to seize dynamic channels. If this threshold is low, it is easy to seize dynamic channels.

201

Downlink Multiplex Threshold of Dynamic Channel Conversion

Description：This parameter specifies the downlink multiplex threshold of dynamic channel conversion.When the number of subscribers carried over the channel reaches the threshold/10, dynamic channels are used.

Value Range：[10,80] Default Value：20

Level of Preempting Dynamic Channel

Description：This parameter specifies the levels of dynamic channels preempted by CS services and PS services. Only full-rate TCHs are the dynamic channels that can be preempted. Preempt all dynamic TCHFs: It indicates that the CS services can preempt all the dynamic channels.No preempt of CCHs: It indicates that the CS services can preempt all the dynamic channels except for the control channels.No preempt of service TCHF: It indicates that the CS services cannot preempt the dynamic channels that carry services.

Value Range：[Preempt all dynamic TCHFs,No preempt of CCHs,No preempt of service TCHF] Default Value：Preempt all dynamic TCHFs

Reservation Threshold of Dynamic Channel Conversion

Description：This parameter specifies the number of channels reserved for the CS services.

Value Range：[0,8] Default Value：2

202

Process of Dynamic Channel Application Start

Obtain the number of applied dynamic channels

Is the convertible TRX available? Yes Obtain the weight maximum TRX

Obtain the convertible dynamic channel

End

Page31

When the condition for triggering dynamic channel application is met, start the dynamic channel application process. The procedure is as follows: Obtain the number of dynamic channels through calculation. Calculate the TRX weight and obtain the highest TRX of the weight. Locate the dynamic channel bitmap on the TRX and start to apply for the appropriate dynamic channel.

203

Obtaining the Number of Applied Dynamic Channels z

Multi-timeslot capability:

Fail to allocate the PDCH. The MS multi-timeslot capability is unknown.

The allocation of the PDCH for the MS is successful. The MS multitimeslot capability is not met.

Load:

The load reaches Uplink/Downlink Multiplex Threshold of Dynamic Channel Conversion

Pre-application for the PDCH

Failure to assign a single block for terminals

Page32

The method for obtaining the number of dynamic channels for request conversion is as follows: Multi-timeslot capability If the assignment of the PDCH to the MS fails, and if the multislot capability of the MS is unknown, then the number of dynamic channels requested for conversion is 1; if the multislot capability of the MS is known, the number of dynamic channels requested for conversion is equal to the number of timeslots supported by the MS. If the assignment of the PDCHs to the MS succeeds, but the PDCHs do not meet the multislot capability of the MS, then the number of dynamic channels requested for conversion is: maximum number of channels supported by the multislot capable MS – number of channels assigned to the MS. The channel conversion type of the preceding two causes is the multi-timeslot capability. Load The dynamic channel conversion is triggered due to the restriction by 【Uplink/Downlink Multiplex Threshold of Dynamic Channel Conversion】, to request for calculating the number of converted dynamic channels. The method is as follows:

Assume that the number of dynamic channels requested for conversion is X, the multiplexing dynamic channel conversion threshold is H, total number of uplink TBFs of the cell downlink PDCH channels is S, and the number of downlink PDCHs in the cell is M. The formula is as follows: X = S × 10/H – M + 1 This formula is used to check whether the channel resources are sufficient. The dynamic channel can be applied for when the multiplexing 204 dynamic channel conversion threshold is exceeded. The number of dynamic channels applied for is equal to the number of the part of load

Obtaining the Convertible TRX

No Concentric cell or not? Yes Specify the overlaid subcell or underlaid subcell?

Start

Yes

No Multi-band cell?

Specify the TRX of the concentric subcell attribute

Yes

Is the MS band support capability known?

Main BCCH TRX band and TRX of the band being compatible with the main BCCH TRX

Yes

Select the TRX corresponding to the service of triggering dynamic channel application

Bands supported by the MS

No Double-timeslot extension cell?

Select the TRX where the number of PDCHs is smaller than Maximum PDCH number of carrier.

Yes No TA>63?

Obtain the convertible channel bitmap on the TRX

Yes Select the double-timeslot extension TRX

End

Page33

The TRXs that carry the dynamic channels must be specified prior to the dynamic channel conversion. The rules for determining the TRXs are as follows: For a multi-band cell, the band supported by MSs must be taken into account. If the MS radio access capability is unknown, only the main BCCH band and the frequency bands compatible with the main BCCH band is selected. If the MS radio access capability is known, only the band supported by the MS is selected. For a double timeslot extended cell, if the TA reported by the MS is greater than 63, the double timeslot extended TRXs should be selected. For a concentric cell, the concentric attribute of the TRX carrying the dynamic channels must be taken into account when performing dynamic channel conversion. The cell attribute parameter concerned is 【Dynamic Channel Conversion Parameter of Concentric Cell】. See the following table for details. If the overlaid subcell or underlaid subcell is specified when requesting PDCH assignment, and if the channel assignment on the specified subcell fails, then the dynamic channel conversion in the specified subcell is triggered. The TRX of supporting the service is selected according to the service type. For the dynamic channel conversion triggered by the EDGE service, the minimum type of the converted dynamic channel is EGPRS TRX TCH. For the dynamic channel conversion triggered by the GPRS service, the minimum type of the converted dynamic channel is GPRS TRX TCH. Select the TRX on which the number of PDCHs carried is less than that specified by the TRX attribute parameter 【Maximum PDCH numbers of carrier】. Obtain the convertible channel bitmap on the TRX for selecting the optimal dynamic channel (group). If the dynamic channel conversion type is the multi-timeslot capability, the convertible channel bitmap on the TRX consists of the TCH channel and available 205 PDCH channel. If the dynamic channel conversion type is load, the convertible channel

Obtaining the TRX

Weight Maximum

TRX conversion weight table

Weight table

31 30 29

2 10

Higher priority

Priority Priority of main BCCH of the number of PDCHs TRX 19

Lower priority

Priority of the number of static PDCHs

Priority of number of convertible dynamic channels

Priority of number of maximum consecutive convertible dynamic channels

Distance priority

14-12

11-9

8-6

5-3

18-15

Priority of Priority of Concentric power amplifier double timeslot cell Switch TRX priority 31-30

Priority of the Priority of EDGE conversion TRX request satisfaction 27

Priority of the dynamic PDCH channel

Frequency hopping priority

25-24

Band priority 2-0

Interference priority 22-20

Page34

The TRX with the highest weight should be selected as the optimal TRX for conversion. The following describes the factors listed in the TRX extension weight table: Bits 31 and 30 (priority of the TRX power amplifier switch): If the switch of the power amplifier of a TRX is turned on, the priority of the TRX is higher; if the switch of the power amplifier of a TRX is turned off, the priority of the TRX is lower. Bit 29 (Subcell priority): When the requested subcell attribute and the TRX subcell attribute are the same, the value is 1. Otherwise, the value is 0. If the subcell attribute is not specified or the access is initial, the underlaid subcell is preferred. Bit 28: Double-timeslot TRX priority. For the single timeslot TRX, the priority is high. For the double timeslot TRX, the priority is lower. Bit 27: EDGE TRX priority (valid only for BTS in the earlier versions such as BTS312 and BTS3012). For the EGPRS TBF, the EGPRS TRX is preferred. For the GPRS TBF, the GPRS TRX is preferred. Bit 26 (priority indicating whether the TRX meets the conversion request): If the number of convertible dynamic channels on the TRX is equal to or greater than the number of dynamic channels for request conversion, it is set to the higher priority. Bit 25 to 24 (TRX dynamic PDCH attribute priority): The highest priority in the channel attribute priority of all TRX traffic channels (including the converted or configured static PDCHs) is the priority of the TRX. For the EGPRS TBF, the priorities of the PDCH attributes from the high to low is {EGPRS special channel, EGPRS priority channel, EGPRS normal channel, and GPRS channel}, with the corresponding weights 3, 2, 1, and 0 respectively. For the GPRS TBF, the priorities of the PDCH attributes from the high to low is {GPRS channel, EGPRS normal channel, EGPRS priority channel, EGPRS special channel}, with the corresponding weights 3, 2, 1, and 0 respectively.

206

Please refer to the notes

Page35

Bit 23 (frequency hopping attribute priority): The priority of the TRX without involving the TRX is higher.

Bit 22 to 20 (TRX interference priority): The priority of the TRX with lower interference is higher.

Bit 19 (priority indicating whether the TRX is the main BCCH TRX): The priority of the main BCCH TRX is higher.

Bit 18 to 15 (PDCH quantity priority over the TRX): The more the PDCH quantity is, the higher the priority is (the weight is valid when the number of convertible dynamic channels over the TRX is equal to or greater than 1).

Bit 14 to 12 (static PDCH quantity priority over the TRX): The more the static PDCH is, the higher the priority is (the weight is valid when the number of convertible dynamic channels over the TRX is equal to or greater than 1). The maximum value is 7.

Bit 11 to 9 (priority of the number of convertible dynamic channels on the TRX): The more the convertible dynamic channels are, the higher the priority is (When the number of convertible dynamic channels on the TRX is smaller than the number of dynamic channels requested for the conversion, the weight is valid).

Bit 8 to 6 (priority of the maximum number of consecutive convertible dynamic channels on the TRX): The larger the maximum number of consecutive convertible dynamic channels is, the higher the priority is.

Bit 5 to 3 (priority of distance between the maximum number of consecutive convertible dynamic channels on the TRX and other convertible dynamic channel groups): The shorter the distance is, the higher the priority is.

Bit 2 to 0 (TRX band priority): The priority of the band differing from the main BCCH TRX band is high. Otherwise, the priority is low. The priority of two sets of main BCCH same band or main BCCH different band are as follows (from high to low):

900M band: P band < E band < R band

1800M/1900M band: Only 1800M band or 1900M band exists on a network. Therefore, only one priority needs to be defined.

850 band

450 band

480 band

207

Obtaining the z

Convertible Dynamic Channel

Select the timeslot where the initial configuration is set to TCHF

You are not allowed to adjust the timeslot where the initial configuration is set to TCHH.

Consider the value of 【Whether to Allow to Re-adjust the PDCH】

When the value is set to Not allow, select only the idle TCHF or the timeslot where two TCHHs of the same timeslot are idle.

When the value is set to Allow, all timeslots of the TCH type can be selected, regardless of whether the TCHH or TCHF of this timeslot is occupied.

If an independent GPRS request triggers the dynamic conversion, the EGPRS special channel is not selected. If an independent EGPRS request triggers the dynamic channel conversion, the GPRS channel is not selected.

When multiple dynamic channels are selected for the conversion, the conversion is performed according to the sequence of the timeslot numbers 6, 5, 7, 4, 3, 2, 1, and 0.

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After selecting the optimal conversion TRX, select the convertible dynamic channel on the TRX according to the requirement. The dynamic channel is not converted when any of the following occurs: The number of channels to be converted is equal to or smaller than the number of channels being converted. The number of Abis timeslots on the TRX is greater than or equal to the number specified by the TRX attribute parameter MaxAbisTSOccupied. The number of PDCHs on the TRX is greater than or equal to the number specified by the TRX attribute parameter Maximum PDCH numbers of carrier. The number of PDCHs in a cell is greater than or equal to the maximum number of PDCHs allowed in a cell. The maximum number of PDCHs allowed in a cell can be calculated on the basis of the cell attribute parameter Maximum Ratio Threshold of PDCHs in a Cell. The formula is as follows: Maximum number of PDCHs allowed in a cell = Maximum Ratio Threshold of PDCHs in a Cell x number of TCHs and PDCHs in a cell/100 CS Repacking function is controlled by PDCH reforming. When PDCH reforming is set to Allow, the CS Repacking is functional. That is, it is functional when the dynamic PDCH applying for the conversion is occupied by CS services. If the local cell has the idle TCH resources, these CS services are switched to the idle TCH. If the idle TCH is unavailable and Level of Preempting Dynamic Channel is set to All dynamic channels carrying services not-preempted, the system initiates the forcible release for the CS service. As a result, the CS calls are dropped. If Level of Preempting Dynamic Channel is set to All dynamic channels preempted or control channel notpreempted, the application for converting the dynamic PDCH fails.

208

Data Configuration

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Maximum PDCH numbers of carrier

Description：This parameter specifies the maximum number of PDCHs allocated to a TRX.

Value Range：[0,8] Default Value：8

MaxAbisTSOccupied

Description：This parameter specifies the maximum number of Abis timeslots occupied by the PDCHs on a TRX.

Value Range：[0,32] Default Value：32

209

Contents 1. Packet Radio Resource Management Algorithm Overview 2. Packet Channel Assignment Algorithm 3. Packet Channel Conversion Algorithm 4. Packet Channel Release Algorithm

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210

General Process of Dynamic Channel Release CS channels are insufficient and CECHM receives the request for releasing channels

Obtain the TRX of releasing dynamic channels

Is the TRX obtained successfully? Yes Release the channel with the highest priority

Recall the dynamic PDCH with load Release the PDCH resource

End

When CS services are busy, the CS services may preempt the dynamic channel of the PS according to the data configuration because the TCH of the CS is deficient. As a result, the preceding process is triggered. The first step to release channel is to obtain the appropriate TRX of dynamic channel, with considering the requirements of the band and concentric cell. The band must be available and the congestion cannot occur. The frequency bands supported by the TRX must be the same as requested by the CS services. For the concentric cell, the overlaid/underlaid subcell attribute of the TRX must meet the requirement of the CS services on the overlaid/underlaid subcell.

When the CS requests the overlaid subcell or underlaid subcell, only the overlaid subcell or underlaid subcell can be selected.

When the CS requests the preferred underlaid subcell, the priority of the underlaid TRX is higher.

When the CS requests the preferred overlaid subcell, the priority of the overlaid TRX is higher. Determine the TRX to release the dynamic channel information. Release the weight ratio for the target TRX. Then select the channel with the maximum weight for initiating the release. In another case, the timing release of the idle dynamic channel is controlled by Timer of Releasing Idle Dynamic Channel. If the value is large, the idle channel fails to be released. As a result, resource is wasted. If the value is small, the dynamic channel can be released easily. The conversion may be triggered if required. As a result, the conversion is performed 211 repeatedly.

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Obtaining the Dynamic Channel to be Released Channel release weight table

Weight table

31 30 29

2 10

Higher priority

Lower priority

Priority of the number of fixed channels

Priority of the number of PDCHs

Priority of TRX type

Priority of channel type

19-17

16-14

12-11

z z

Reserved

7-0

10-8

Concentric cell priority

Priority of idle dynamic channels

Priority of the number of control channels

Priority of reserved channels

Priority of the number of dynamic TBFs

31-30

28-25

23-20

Priority of timeslot ID sequence

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Whether to release the channel is specified by 【Level of Preempting Dynamic Channel】. When the value is set to 【Preempt all dynamic TCHFs】, the dynamic PDCH can be released. When the value is set to 【No preempt of CCHs】, the dynamic PDCH of the control channel cannot be released. When the value is set to 【No preempt of service TCHF】, the channels cannot be preempted if a service exists on this channel. If this channel is idle, the resource is released actively after relevant PS timers expire when 【PDCH reforming】 is set to Allow. Release the dynamic channel with the highest priority. To select the optimal dynamic channel, calculate the priority of each dynamic channel in the TRX of the dynamic channel to generate the dynamic channel release weight table. See the preceding table. The factors in detail to be considered are as follows (select the dynamic channel with the greatest weight value for the release): Bits 31 and 30: priority of the concentric cell attribute Bit 29 (priority of the idle dynamic channel): An idle dynamic channel has a higher priority of being released.

212

Bits 28 to 25 (priority of the number of control channels): The less number the dynamic channels are used as control channels, the higher the priority of the dynamic channels are being released. Bit 24 (priority of reserved channels): During the PDCH pre-application conversion, the priority of the pre-applied channel is low. Bits 23 to 20 (priority of the number of TBFs on the dynamic channel): If fewer TBFs are multiplexed on a dynamic channel, the priority of the dynamic channel being released is higher. Bits 19 to 17 (priority of the number of fixed channels on the TRX): If fewer fixed channels are carried on the TRX that carries a dynamic channel, the priority of the dynamic channel being released is higher. Bits 16 to 14 (priority of the number of PDCHs on the TRX): If fewer PDCHs are carried on the TRX that carries a dynamic channel, the priority of the dynamic channel being released is higher. Bit 13 (priority of the TRX type): The dynamic channel carried on the GPRS capable TRX has a higher priority of being released. Bits 12 and 11 (priority of channel type): The release priority in descending order is as follows: GPRS channel, EGPRS normal channel, and EGPRS priority channel. Bits 10 to 8 (priority of the timeslot sequence): The priorities of the dynamic channels being released are decreased in the following order: TS0, TS1, TS2, TS3, TS4, TS7, TS5, and TS6.

213

Data Configuration

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Timer of Releasing Idle Dynamic Channel

Description：This parameter specifies the timer set to release the idle dynamic channel after all TBFs on the dynamic channel are released.If all TBFs on a dynamic channel are released, the dynamic channel is not released immediately. Instead, a timer is started when the channel is idle.Before the timer expires, if there are new services, the dynamic channel continues to be used and the timer is stopped. When the timer expires, the dynamic channel is released.

Value Range：[10,3600]

Default Value：20

Unit：Seconds

Configuration Policy：If this parameter is set to an excessive value, the dynamic channel resources may be wasted when there are no services for a long time. If this parameter is set to a modest value, it is possible that a dynamic channel is requested immediately after being released. Therefore, the dynamic channel request is sent frequently.

214

Data Configuration

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PDCH reforming

Description：This parameter specifies whether the PS services are allowed to preempt the ongoing channel for CS services when "Level of Preempting Dynamic Channel" is set to "No preempt of service TCHF".This parameter must be used together with "Level of Preempting Dynamic Channel", the condition as follows:1. When "Level of Preempting Dynamic Channel" is set to "No preempt of service TCHF" and "PDCH Reforming" is set to Yes, PS services can preempt the CS channel.2. When "Level of Preempting Dynamic Channel" is set to "No preempt of service TCHF" and "PDCH Reforming" is set to No, PS services cannot preempt the CS channel.

Value Range：[No,Yes]

Default Value：No

Caution：When this parameter is used:1. "Level of Preempting Dynamic Channel" must be set to "No preempt of service TCHF"; otherwise this parameter is invalid.2. The number of TCH/F of current TRX must be more than the value of the Reservation Threshold of Dynamic Channel Conversion parameter.3. "Maximum Ratio Threshold of PDCHs in a Cell" must be set properly; otherwise the TCH/F can not be changed to the PDCH because of the low ratio.2 and 3 are optional.

215

Summary z

After studying this course, you will learn:

PS channel allocation algorithm

Dynamic channel conversion algorithm

Dynamic channel release algorithm

By learning the three algorithms, you should master the PS channel management algorithm and load control policy of the BSC6000.

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216

Thank you www.huawei.com

217

GPRS EDGE Radio Network Optimization Problem Analysis www.huawei.com

218

Objectives z

Upon completion of this course, you will :

Be familiar with the common problems arising in GPRS and EDGE network optimization

Master the common troubleshooting measures for the problems discovered during GPRS and EDGE network optimization

Page 1

219

Contents 1. Low TBF Setup Success Ratio 2. Low Downloading Rate

Page 2

220

TBF Setup Success Ratio

Formula

Common Analysis Method

Page 3

221

Uplink TBF Setup Success Ratio Formula 1 – Air Interface Measured Uplink GPRS TBF setup success ratio =

A9004: Number of Failed Uplink GPRS TBF Establishments due to MS No Response

X 100%

A9001: Number of Uplink GPRS TBF Establishment Attempts

Uplink EGPRS TBF setup success ratio = A9204: Number of Failed Uplink EGPRS TBF Establishments due to MS No Response

A9201: Number of Uplink EGPRS TBF Establishment Attempts

X 100%

Page 4

The formula of the TBF setup success ratio varies with the measured objects.

If the measured object is the air interface, the preceding formulas are used.

For uplink TBF assignment: If the first uplink data block from the MS is not received at the network side after an assignment command is sent from the network side, an uplink TBF setup failure due to no response from MS is counted.

All the preceding counters are cell-level counters. The system also supports BSC-level counters as follows:

ZA9001: uplink GPRS TBF setup attempts within the BSC

ZA9004: uplink GPRS TBF setup failures due to no response from MS within the BSC

ZA9201: uplink EGPRS TBF setup attempts within the BSC

ZA9204: uplink EGPRS TBF setup failures due to no response from MS within the BSC

For particular values of the preceding counters, see the GPRS and EDGE traffic statistics.

222

Downlink TBF Setup Success Ratio Formula 1 – Air Interface Measured Downlink GPRS TBF setup success ratio =

A9104: Number of Failed Downlink GPRS TBF Establishments due to MS No Response A9101: Number of Downlink GPRS TBF Establishment Attempts

x 100%

Downlink EGPRS TBF setup success ratio =

A9304: Number of Failed Downlink EGPRS TBF Establishments due to MS No Response x 100% A9301: Number of Downlink EGPRS TBF Establishment Attempts

Page 5

The formula of the TBF setup success ratio varies with the measured objects.

If the measured object is the air interface, the preceding formulas are used.

For downlink TBF assignment: If no Packet Control Acknowledgement message from the MS is received at the network side after an assignment command is sent from the network side, a downlink TBF setup failure due to no response from MS is counted.

All the preceding counters are cell-level counters. The system also supports BSC-level counters as follows:

ZA9101: downlink GPRS TBF setup attempts within the BSC

ZA9104: downlink GPRS TBF setup failures due to no response from MS within the BSC

ZA9301: downlink EGPRS TBF setup attempts within the BSC

ZA9304: downlink EGPRS TBF setup failures due to no response from MS within the BSC

For particular values of the preceding counters, see the GPRS and EDGE traffic statistics.

223

Uplink TBF Setup Success Ratio Formula 2 – Resources Measured Uplink GPRS TBF setup success ratio =

A9003: Number of Failed Uplink GPRS TBF Establishments due to No Channel

x 100%

A9001: Number of Uplink GPRS TBF Establishment Attempts

Uplink EGPRS TBF setup success ratio = A9203: Number of Failed Uplink GPRS TBF Establishments due to No Channel

A9201: Number of Uplink EGPRS TBF Establishment Attempts

X 100%

Page 6

The formula of the TBF setup success ratio varies with the measured objects.

If the measured object is the channel resources, the preceding formulas are used.

For uplink TBF assignment: If the network side sends an assignment rejection message upon the channel request from the MS due to lack of channel resources (including channels, TFI, and USF), an uplink TBF setup failure due to lack of channel resources is counted.

All the preceding counters are cell-level counters. The system also supports BSC-level counters as follows:

ZA9001: uplink GPRS TBF setup attempts within the BSC

ZA9003: uplink GPRS TBF setup failures due to lack of channel resources within the BSC

ZA9201: uplink EGPRS TBF setup attempts within the BSC

ZA9203: uplink EGPRS TBF setup failures due to lack of channel resources within the BSC

For particular values of the preceding counters, see the GPRS and EDGE traffic statistics.

224

Downlink TBF Setup Success Ratio Formula 2 – Resources Measured Downlink GPRS TBF setup success ratio = A9103: Number of Failed Downlink GPRS TBF Establishments due to No Channel

x 100%

A9101: Number of Downlink GPRS TBF Establishment Attempts

Downlink EGPRS TBF setup success ratio = A9303: Number of Failed Downlink EGPRS TBF Establishments due to No Channel

x 100% A9301: Number of Downlink EGPRS TBF Establishment Attempts

Page 7

The formula of the TBF setup success ratio varies with the measured objects.

If the measured object is the channel resources, the preceding formulas are used.

For downlink TBF assignment: If the downlink TBF setup fails due to lack of channel resources (including channels, TFI, and USF) at the network side, a downlink TBF setup failure due to lack of channel resources is counted.

All the preceding counters are cell-level counters. The system also supports BSC-level counters as follows:

ZA9101: downlink GPRS TBF setup attempts within the BSC

ZA9103: downlink GPRS TBF setup failures due to lack of channel resources within the BSC

ZA9301: downlink EGPRS TBF setup attempts within the BSC

ZA9303: downlink EGPRS TBF setup failures due to lack of channel resources within the BSC

For particular values of the preceding counters, see the GPRS and EDGE traffic statistics.

225

Uplink TBF Setup Success Ratio Formula 3 – Both Air Interface and Resources Measured Uplink GPRS TBF setup success ratio = A9002: Number of Successful Uplink GPRS TBF Establishments

x 100%

A9001: Number of Uplink GPRS TBF Establishment Attempts

Uplink EGPRS TBF setup success ratio = A9202: Number of Successful Uplink EGPRS TBF Establishments

x 100%

A9201: Number of Uplink EGPRS TBF Establishment Attempts

Page 8

The formula of the TBF setup success ratio varies with the measured objects.

If the measured object are the air interface and the channel resources, the preceding formulas are used

For uplink TBF assignment: Both the uplink TBF setup failures due to no response from MS and those due to lack of channel resources are counted as uplink TBF setup failures.

All the preceding counters are cell-level counters. The system also supports BSC-level counters as follows:

ZA9001: uplink GPRS TBF setup attempts within the BSC

ZA9002: uplink GPRS TBF setup successes within the BSC

ZA9201: uplink EGPRS TBF setup attempts within the BSC

ZA9202: uplink EGPRS TBF setup successes within the BSC

For particular values of the preceding counters, see the GPRS and EDGE traffic statistics.

226

Downlink TBF Setup Success Ratio Formula 3 – Both Air Interface and Resources Measured Downlink GPRS TBF setup success ratio = A9102: Number of Successful Downlink GPRS TBF Establishments

x 100%

A9101: Number of Downlink GPRS TBF Establishment Attempts

Downlink EGPRS TBF setup success ratio = A9302: Number of Successful Downlink EGPRS TBF Establishments

x 100%

A9301: Number of Downlink EGPRS TBF Establishment Attempts

Page 9

The formula of the TBF setup success ratio varies with the measured objects.

If the measured object are the air interface and the channel resources, the preceding formulas are used.

For downlink TBF assignment: Both the downlink TBF setup failures due to no response from MS and those due to lack of channel resources are counted as downlink TBF setup failures.

All the preceding counters are cell-level counters. The system also supports BSC-level counters as follows:

ZA9101: downlink GPRS TBF setup attempts within the BSC

ZA9102: downlink GPRS TBF setup successes within the BSC

ZA9301: downlink EGPRS TBF setup attempts within the BSC

ZA9302: downlink EGPRS TBF setup successes within the BSC

For particular values of the preceding counters, see the GPRS and EDGE traffic statistics.

227

TBF Setup Success Ratio

Formula

Common Analysis Method

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228

Low TBF Setup Success Ratioâ&#x20AC;&#x201C; Common Analysis Process Start Analyze causes for the low TBF setup success ratio

Yes

Is the Abis interface faulty?

Check transmission

No Is the assignment message delivered normally?

CCCH overload

No channel

Yes No

Check traffic statistics

Is the air interface normal? Perform a CQT

Yes Is a response to the assignment and polling available?

End

No Inappropriate power control parameter settings High rate coding scheme

Errors of important message

Other incorrect parameter settings

Check CS domain parameters

Unbalanced uplink and downlink

Page 11

229

Low TBF Setup Success Ratio – Abis Interface Transmission z

Check whether the Abis link is faulty.

The downlink TBF setup might fail due to transmission problems such as outof-synchronization frames and intermittent interruption of the Abis link.

Locate the transmission problems of the Abis interface by checking the G-Abis frame error rate (FER) in the traffic statistics.

Page 12

RL9A08: FER = ([L9A02: number of received out-of-synchronization frames] + [L9A03: number of received check error TRAU frames]) x {100}/([L9A02: number of received outof-synchronization frames]+[L9A03: number of received check error TRAU frames] + [L9A01: number of received normal TRAU frames] + [L9A07: number of received information TRAU frames])

The number of received information TRAU frames equals the number of empty TRAU frames.

1. In normal cases, the FER is lower than 10e-5 (that is, one out of ten thousand) and one error frame occurs every four minutes in each channel. In this case, the link quality is high and the MSs transfer data stably.

2. If the FER is lower than 10e-4 (one out of one thousand), one to three error frames occur every minute and the link quality degrades. In this case, the affected MSs easily suffer rate drop, longer transmission delay, or even call drops due to error frame bursts.

3. If the FER is higher than 10e-4, the transmission link is unstable and might easily suffer out-of-synchronization. The number of out-of-synchronization frames increases. In this case, the MSs support services with low data traffic (such as high-layer signaling and low-volume WAP) only. Transmission of large-volume data (such as the FTP service) is not supported.

If a leased link (for example, microwave satellite) is used, an FER lower than 5‰ is acceptable because the link quality is not controlled by the mobile operator. If the FER of a cell remains high for a long time, it is regarded as a transmission problem and the transmission link needs to be checked and optimized.

230

Low TBF Setup Success Ratio – Abis Interface Transmission z

The transmission quality of the Abis interface can also be monitored through the maintenance console.

Monitoring BER

Monitoring port fault seconds

Page 13

Function supported by both monitoring options:

Monitor the BER of the E1/T1 ports and optical ports, thus learning the operation conditions of the transmission link and ports.

Definition of fault seconds:

If one or more block errors are detected in a certain second, the second is called a fault second.

Differences between the two monitoring options:

The Monitor BER function requires that remote loopback needs to be enabled at the opposite end of the monitored port. The Monitor Port Fault Seconds function, however, does not require remote loopback at the opposite end of the monitored port.

The unit sampling time of the Monitor BER function is configurable (ranging from 30 to 1000 milliseconds), while that of the Monitor Port Fault Seconds function is fixed to 1 second.

231

Low TBF Setup Success Ratio – the Assignment Message Fails to Be Delivered z

The assignment message might fail to be delivered due to the following cause:

CCCH overload

Refer to the following counters: – L3188A: number of reported DELETE IND messages of the Abis interface – L3188D: number of reported PACKET CCCH LOAD IND messages of the Abis interface – L3188E: number of reported OVERLOAD (CCCH overload) messages of the Abis interface

To remove CCCH overload, add CCCH channels, split the location area, or modify the CCCH load threshold and the T3168 timer.

Page 14

L3188A: number of reported DELETE IND messages of the Abis interface

If the BTS deletes the IMM ASS CMD message sent by the BSC due to downlink CCCH overload of the cell, the BTS reports a DELETE IND message to the BSC. This counter is used to measure the number of the DELETE IND messages received by the BSC from the measured cell.

L3188D: number of reported PACKET CCCH LOAD IND messages of the Abis interface

The BTS stores the paging messages sent through the downlink CCCH (PCH channel) for circuit services and those for packet services in two different receive buffer queues. If the length of either receive buffer queue exceeds the specified threshold, it is indicated that downlink CCCH overload occurs. In this case, the judges whether the overload is caused by excessive downlink packet services or excessive circuit services. If the overload is caused by excessive circuit services, the BTS reports a CCCH LOAD IND message to the BSC. If the overload is caused by excessive packet services, the BTS reports a PACKET CCCH LOAD IND message to the BSC. The BSC then forwards the PACKET CCCH LOAD IND message to the PCU. This counter is used to measure the number of PACKET CCCH LOAD IND messages received by the BSC from the BTSs within the measured cell.

L3188E: number of reported OVERLOAD (CCCH overload) messages of the Abis interface

If the BTS detects the CCCH overload, the BTS reports an OVERLOAD (cause: CCCH overload) message and a CCCH LOAD IND message to the BSC. This counter is used to measure the OVERLOAD (cause: CCCH overload) messages

232

Low TBF Setup Success Ratio – the Assignment Message Fails to Be Delivered z

The assignment message might fail to be delivered due to the following cause:

No channel is available (including insufficient channel resources and hardware faults).

Check whether the hardware is faulty by referring to the following counters: – RR307: TCH availability – RK3255: TRX carrier availability

Check whether channel resources are insufficient by referring to the following counters (take the uplink GPRS TBF setup as an example): – A9003: uplink GPRS TBF setup failures due to lack of channel resources – A9010: uplink GPRS TBF abnormal releases due to lack of channel resources – AA9013: average number of concurrent uplink GPRS TBF – R9343: callbacks of dynamic PDCH – R9344: callbacks of loaded dynamic PDCH

Page 15

Channel resources are insufficient in any of the following cases:

1. The cell is configured with a small number of channels when heave traffic of packet services exists. As a result, the channels reach the maximum capacity of MS multiplexing. To solve the problem, add more dynamic and static channels or set the PDCH uplink multiplexing threshold in the PS domain channel management parameters to a higher value.

2. Check whether the resources are insufficient because voice services preempt the dynamic PDCHs. If counters A9343 (callbacks of dynamic PDCH) and A9344 (callbacks of loaded dynamic PDCH) record high values, in indicates that circuit services preempt the channel resources of data services due to heavy traffic. To solve the problem, add more dynamic PDCHs or set Dynamic Channel Preemption Level to Control Channel Preemption Forbidden.

3. If the uplink GPRS TBF setup success ratio is low due to lack of channel resources but the uplink EGPRS TBF setup success ratio is high, check whether the GPRS channels are insufficient due to the configuration of dedicated or preferred EGPRS channels. If dedicated or preferred EGPRS channels are configured, modify some of them into common EGPRS channels and, if necessary, turn on the EGPRS Downlink and GPRS Uplink Allowed switch.

233

Low TBF Setup Success Ratio – Air Interface Abnormal z

The MS might fail to receive the downlink assignment message or polling message due to poor quality of the air interface.

Check the BEP distribution based on the following traffic statistics:

Number of different 8PSK_MEAN_BEP values

Number of different GMSK_MEAN_BEP values

Locate the problem through a CQT.

Locate the air interface problem through the traffic statistics of the CS domain.

Page 16

If the air interface suffers severe interference, adjust the frequency points to improve the quality of the air interface.

234

Question z

What are the CS domain traffic statistics items that help to locate air interface problems?

Page 17

Answers:

Measurement report — interference band measurement (carrier)

Measurement report — full-rate channel Rx level measurement (carrier)

Measurement report — half-rate channel Rx level measurement (carrier)

Measurement report — Rx quality measurement (carrier)

Measurement report — radio link exception measurement (carrier)

Measurement report — measurement of TA-based distribution of radio link exceptions (carrier)

Measurement report — measurement of TA-based RQI distribution (carrier)

Measurement report — RQI distribution measurement (carrier)

Measurement report — Rx quality distribution measurement (carrier)

……

235

Low TBF Setup Success Ratio – No Response from the MS z

Check the following counters to determine whether the MS responds to the assignment or polling message:

A9004: uplink GPRS TBF setup failures due to no response from MS

A9104: downlink GPRS TBF setup failures due to no response from MS

A9204: uplink EGPRS TBF setup failures due to no response from MS

A9304: downlink EGPRS TBF setup failures due to no response from MS

The MS might fail to respond to an assignment or polling message due to any of the following causes:

High rate uplink coding scheme

Inappropriate settings of uplink power control parameters

Inappropriate settings of other parameters

Incorrect cells in the assignment message

Unbalanced uplink and downlink

Inappropriate CS domain parameters

Page 18

When the radio environment is poor, the BLER is extra high and the uplink data blocks cannot be decoded correctly at the network side if a high rate uplink coding scheme is used.

If the uplink power control parameters are configured improperly, the MS supports low Tx power and the uplink data blocks cannot be decoded correctly at the network side.

Other parameters that might be configured improperly are as follows:

Downlink reassignment attempts (affecting the downlink TBF setup): During the setup process of a downlink TBF, the network side fails to receive a valid Packet Control Acknowledge message on the reserved uplink RLC block and then resends a downlink assignment message. This parameter specifies the maximum number of downlink reassignment attempts. If the downlink reassignment attempts exceed the value of this parameter, the network side releases the downlink TBF.

Polling retransmission times (affecting the downlink TBF setup): This parameter specifies the maximum number of polling messages retransmitted by the network side during the setup process of a downlink TBF.

Check whether the important cells in the assignment message are incorrect, including frequency hopping parameters and uplink power control parameters.

Frequency hopping parameters: Check whether GPRS Mobile Allocation in the SI 13 message and the Frequency Parameters in the assignment message are consistent with the actual configurations.

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Uplink power control parameters: Check whether the Alpha and GAMMA t

di t A

d P

k t U li k

Unbalanced uplink and downlink: If the uplink and the downlink are unbalanced, the uplink or downlink signals might fail to be received at the edge of coverage, thus resulting in a failure of TBG setup.

To verify whether the uplink and the downlink are balanced, check the uplink Rx level and the downlink Rx level in the measurement report. Refer to the measurement unit in Huawei traffic statistics: measurement report â&#x20AC;&#x201D; uplink and downlink balance measurement (carrier). Â&#x2021;

Usually, the uplink and the downlink are regarded as unbalanced (the downlink signals are too weak or the uplink signals are too strong) if the sum of the percentage of uplink and downlink balance level 1 plus the percentage of uplink and downlink balance level 2 is higher than 15%.

Â&#x2021;

The uplink and the downlink are regarded as unbalanced (the downlink signals are too strong or the uplink signals are too weak) if the percentage of uplink and downlink balance level 11 is higher than 30%.

The low TBF setup success ratio might also result from incorrect settings of CS domain parameters. Check the KPI of the CS domain to identify any exceptions. The relevant CS domain parameters include the call drop rate, congestion rate, assignment success ratio, balance between uplink and downlink, and call setup success ratio.

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Question z

What are the respective solutions to the exceptions that prevent the MS from responding to an assignment or polling message?

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Answers:

If a high rate uplink coding scheme is used, modify the default uplink MCS and the maximum value of the counter N3101. Inappropriate settings of uplink power control parameters: Modify the Alpha parameter and the initial power class. Inappropriate settings of other parameters: Modify the number of downlink reassignment attempts and the number of polling retransmissions. If the uplink and the downlink are unbalanced, check the following factors:

Installation of antenna feeder: Usually, a small antenna, lightning arrester, conversion connector, grounding solder connection, and antenna (and a power splitter in some cases) are installed between the BTS top interface and the antenna. The installation of such components might affect the receiving and transmitting performance of the BTS. For example, a loosened jumper connector results in severe influence on the uplink Rx level but no significant influence on the downlink level. This is because the transmitted signals are often strong (usually 30 dBm inside the feeder) while the received signals are weak (usually 80 dBm). Installation of the tower amplifier: Tower amplifiers are active components that amplify uplink signals only. If a tower amplifier is installed, the Tower Amplifier Attenuation Factor parameter is configured as follows at the RF front end of Huawei BSC6000: If the actual gain of the tower amplifier is G, the tower amplifier attenuation factor equals G minus 4 (4 dB here is the estimated compensation for the feeder loss). Therefore, the value of downlink level minus uplink level in the uplink/downlink balance measurement report decreases by 4 dB if an uplink tower238 amplifier is installed. Particularly, the uplink level increases by 4 dB.

Contents 1. Low TBF Setup Success Ratio 2. Low Downloading Rate

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239

Downloading Rate Measurement z

Measurement methods

CQT

Drive test (DT)

The maximum downloading rate at the application layer under idle conditions is as follows:

225 kbit/s

CQT: Call Quality Test

The CQT is often performed in a good radio environment where the C/I seldom fluctuates. The CQT in idle hours can verify whether all NEs and transmission from the Um interface to the Gi interface are faulty. In this case, the CQT reflects the equipment performance directly and accurately. The CQT in busy hours can also verify the performance of the resource (such as channels, Abis resources, and Gb resources) management algorithms. The CQT in busy hours, however, features randomness. For example, the tested downloading rate might be severely affected if another subscriber is also downloading data during the CQT. In this case, the CQT cannot reflect equipment performance accurately because the test results are significantly related to the quantity of configured resources. Therefore, the CQT in busy hours is used only for performance comparison before and after migration.

DT: Drive Test

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Compared with the CQT, the DT faces severe C/I fluctuation and cell reselection. Differing from the CQT, the DT can measure radio coverage and interference, performance of the coding scheme adjustment algorithm, and system processing in the case of cell reselection (since PS handover is not really supported yet). The DT, however, also feature randomness. For example, the radio conditions (high C/I or deep fading point) at the location where the testing vehicle waits for traffic light affect the tested average rate obviously.

The maximum downloading rate at the application layer under idle conditions is as follows: 59.2 Kbit/s x (4 2%) x 95.52% = 225.06 Kbit/s

The items in the equation are defined as follows:

59.2 Kbit/s: the theoretical rate of a single channel when the MCS-9 coding scheme is used

4: the assumed number of channels for transmission

2%: the minimum ratio of control messages in a single channel to all messages in the channel

95.52%: LLC layer efficiency (The efficiency is lower than 100% due to frame header overhead in each layer)

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An Example of Idle Conditions

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Differing from the CQT, the DT faces cell reselection and change of the coding scheme due to C/I fluctuation (The link quality control algorithm achieves a compromise between higher coding scheme and fewer retransmissions. The bandwidth of the air interface changes as the coding scheme changes). Compared with downloading of large files, the downloading of small files features severer influence brought by the slow start process upon setup of the TCP connection. Therefore, to locate the cause for a low downloading rate, download large files in idle hours at a place where the C/I is high.

Slow start means that the data is delivered slowly to avoid network congestion when the TCP layer is not aware of the transmission bandwidth and quality or when it is known that the transmission bandwidth decreases or the transmission quality degrades. Therefore, the amount of initially delivered data is insufficient. In addition, loss of packets, frames, or blocks needs to be minimized in all stages (including IPBB, core network, GB interface, PCU, G-Abis interface, BTS, and Um interface).

If control blocks (actually dummy blocks) exist in a non-control channel or a high percentage of control blocks exist in the control channel, it indicates that the system transmits dummy control blocks because no data needs to be sent.

Dummy control block: The system sends a block every one millisecond (transmission priorities: NACK block > VS block > PACK block). If none of those blocks is available, the system sends dummy control blocks that are counted by the TEMS as control blocks. That is to say, the control blocks counted by the TEMS include control messages and dummy control blocks.

NACK block: the block that the MS fails to receive as indicated in the Packet Downlink ACK/NACK message

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Common Causes for a Low Downloading Rate Common causes

Insufficient channel occupation

Low coding rate

High block error rate

High percentage of control blocks

Abnormal TBF release

Unmatched rate between the RLC layer and the application layer

Degrading the QoE of customers

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Quality-of-experience (QoE) describes the system-level activities focusing on the joint optimization of experienced multimedia quality and energy consumption in wireless multimedia systems.

242

Insufficient Channel Occupation z

To check the number of channels occupied by MSs, check the latest Packet Downlink Assignment or Packet Timeslot Reconfiguration message, as shown in the following figures.

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The figure on the left shows the Packet Downlink Assignment message, while that on the right shows the Packet Timeslot Reconfiguration message.

243

Insufficient Channel Occupation z

The possible causes for insufficient channel occupations are as follows:

Symptom 1: Failing to assign multiple channels

Cause 1: The channel resources are insufficient.

Cause 2: The MS does not support sufficient multi-slot capability.

Cause 3: The channels suffer out-of-synchronization.

Cause 4: The Abis interface resources are insufficient.

Symptom 2: Failing to occupy multiple channels stably

Cause 1: The channels are preempted by voice services.

Cause 2: The channels suffer out-of-synchronization.

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To verify whether the channel resources are sufficient, check the channel configuration.

To verify whether the MS supports sufficient multi-slot capability, check the Packet Resource Request massage for two-stage access or the 11-bit access request and Attach message (for 8-bit one-stage access, the MS indicates its multi-slot capability in the Attach request message) for one-stage access.

To verify out-of-synchronization, check the alarms by running the relevant commands. For example, run the mt pdch show state <cell ID> all command to check the status of all PDCHs in the specified cell if the external PCU is used. If the built-in PCU is used, run the DSP PDCH command to check the channels status.

To verify whether the Abis interface resources are sufficient, check the idle timeslot configurations.

To verify channel preemption of voice services, check the following traffic statistics:

R9343: callbacks of dynamic PDCH

R9344: callbacks of loaded dynamic PDCH

No channel preemption of voice services is detected during a test in idle hours.

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Abis Interface Timeslots Required by Different Coding Schemes EGPRS

GPRS

Number of Required Abis Interface 16 bit/s Timeslots

MCS1–MCS2

CS1–CS2

MCS3–MCS6

CS3–CS4

MCS7

MCS8–MCS9

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245

Low Coding Rate z

The possible causes for a low coding rate are as follows:

Symptom 1: using low-rate coding schemes

Cause 1: insufficient timeslots at the Abis interface

Cause 2: poor quality of the air interface

Cause 3: inappropriate initial coding rate or inappropriate conversion threshold for coding schemes

Cause 3: EDGE services not used

Cause 4: limited license

Symptom 2: changing coding schemes

Cause 1: error bits at the G-Abis interface

Cause 2: inappropriate conversion threshold for coding schemes (for GPRS services only)

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Solutions to insufficient timeslots at the Abis interface:

If Flex Abis is not used, configure all Abis interface timeslots that are not configured as idle timeslots.

Increase the multiplexing ratio of signaling links to improve the Abis transmission capacity.

Use Flex Abis.

Expand the transmission capacity.

Solutions to bit errors at the G-Abis interface:

Transmission problems: Perform local loopback and remote loopback at the TMU side to locate the problems.

Faults of the interface board

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Air Interface Requirements of Different Coding Schemes Coding Scheme

Rx Level of MS (dBm)

TU3 C/I (dB)

MCS-1

>= –102

MCS-2

>= –101

MCS-3

>= –99

16.5

MCS-4

>= –98

MCS-5

>= –97

MCS-6

>= –96

MCS-7

>= –93

23.5

MCS-8

>= –90.5

28.5

MCS-9

>= –86

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TU3: The speed is 3 km/h in typical urban scenarios.

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Question z

Where can we check the block error rate?

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Answers:

1. The figure in page 43 shows that the BLER/TS(%) parameter indicates the block error rate calculated by the TEMS based on a certain number of received blocks.

2. For fixed MSs, the Packet Downlink ACK/NACK message also indicates the block error rate.

The message shows that starting sequence number (SSN) is 64 and that a bitmap exists. This indicates that block 63 is not received. Check the blocks following block 64 (1 indicates that the block is received, while 0 indicates that the block is not received). The message shows that blocks 63, 65, 66, 68, 69, and 71 to 84 are not received.

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High Block Error Rate z

The possible causes for a high block error rate are as follows:

Bit errors at the air interface

A large number of error frames and out-of-synchronization frames at the G-Abis interface

The MS performs another process such as decoding neighbor cell messages.

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If a large number of neighbor cells are configured, the block error rate often increases because the MS needs to update the system messages of neighbor cells frequently. According to the relevant protocol, the MS must decode the BCCH data of a new carrier in 30 seconds. If the signal strength fluctuates and a large number of neighboring cells are configured, the MS has to parse the system messages of neighboring cells frequently. To solve this problem, reduce the number of neighboring cells and eliminate unnecessary neighboring cell configurations.

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High Percentage of Control Blocks z

The possible causes for a high percentage of control blocks are as follows:

The contracted peak rate is not high enough.

The LLC layer adopts the acknowledged mode.

The transmission window stops.

The bandwidth at the Gb interface is insufficient.

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The system assigns only one bidirectional control channel for the MS. Therefore, the same timeslot is occupied as the control channel in both the uplink and the downlink. In this way, the control channel can be located.

The PDP context shows the contracted peak rate. As shown in the following figure, the peak rate is 128000 octets/s = 128000 x 8/1024 = 1000 Kbit/s that exceeds the theoretical maximum rate.

250

If the LLC layer uses the acknowledged mode, the next frame is not sent until the current frame is acknowledged by the opposite end. In addition, the LLC layer connection needs to be set up and released, thus resulting in more signaling transmissions in the LLC layer. In a word, the downloading rate decreases significantly if the LLC layer uses the acknowledged mode.

You can also check the MS's PDP context in the TMES to view the operation mode of the LLC layer . If the LLC uses the acknowledged mode, modify it to the unacknowledged mode at the SGSN and modify the subscription information of the SIM card.

Usually, the transmission window stops only in the GPRS network because the GPRS system supports 64-block window only. If an error block occurs, the RRBP delay is about 200 ms regardless of the cause for the error block. When the MS reports the reception of the error block, 200 ms passed. If the MS occupies four timeslots, the system has transmitted 40 blocks (200 ms/(20 ms/block)). In this case, the transmission window may stop. Â&#x2021;

To verify whether the transmission window stops, check whether the amount of data received at the Gb interface is larger than the amount of data delivered by the system within a certain period.

If the traffic at the Gb interface exceeds 70% of the actual bandwidth, it indicates that the bandwidth is insufficient. Â&#x2021;

To view the traffic at the Gb interface, check the Downlink data kbytes sent to FR per NSVC item measured at the SGSN.

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Abnormal TBF Release z

The possible causes for abnormal TBF release are as follows:

The uplink TBF is released exceptionally when timers N3101 and N3103 expire.

The downlink TBF is released exceptionally when timer N3105 expires.

The TBF is released exceptionally when the control channel is preempted.

The TBF is released exceptionally due to cell reselection.

The TBF is released exceptionally due to some internal processing.

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Loss of packet is not a necessary result of abnormal TBF release, because the PCU stores the data that the MS has not transmitted and that the MS has transmitted without acknowledgement within 30 seconds after the TBF is released exceptionally. Usually, the MS initiates TBF re-setup soon. In this case, the TLLI remains unchanged. Therefore, the context of the MS can be detected according to the TLLI and then the data stored by the PCU is sent to the MS.

According to the TBF release process, the MS sets the FAI bit in the Packet Downlink ACK/NACK message to 1 if the download TBF is released normally. The system sets the FAI bit to 1 in the Packet Uplink ACK/NACK message if the uplink TBF is released normally. To verify whether a TBF is released exceptionally, check whether the FAI bit in the relevant message is set to 1. If the network side sends a Packet TBF Release message, the TBF is released exceptionally (the TBF is released exceptionally because timer N3105 expires if the cause value is normal release).

The abnormal TBF release decreases the rate because data transmission is not supported during the abnormal release.

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Unmatched Rate Between the RLC Layer and the Application Layer z

This problem often results from careless operations of the relevant test engineers.

How to identify the software applications and services that support automatic connection to the network?

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This problem often results from careless operations of the relevant test engineers. The software applications and services (such as automatic update) that support automatic connection to the network must be disabled during the test. If such software applications or services are not disabled, the rate at the application layer decreases when they connect to the network automatically.

How to identify the software applications and services that support automatic connection to the network: Â&#x2021;

After the test, check whether all the packets captured by the Ethereal software are the data interacted with the IP address of the server. If data interacted with another IP address exists, enter the IP address into the IE to identify the connected network.

253

Summary z

The GPRS/EDGE network optimization focuses on the downloading rate and the TBF setup success ratio. Pay attention to the relevant parameters and configurations.

Traffic statistics and signaling analysis help to solve the problems discovered in GPRS/EDGE network optimization more quickly.

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Thank you www.huawei.com

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