OMF010001 System Information ISSUE1.5

System information SYS INFO contains network parameters sent to MS through Um interface network identity parameters,  cell selection parameters  system control parameters  network f

Wireless Curriculum Development Section

ISSUE

OMF010001 System Information

1.5

System Information Overview

Parameters Introduction Case Study

Course Contents

System information (SYS INFO) contains network parameters sent to MS through Um interface

 network identity parameters,

 cell selection parameters

 system control parameters

 network function parameters

System information can be sent through two kinds of logical channels

 System information on BCCH

 System information on SACCH

System Information Overview

 SYS INFO 1

SYS INFO 1

Cell Channel Description

(cell channel description format)

 RACH Control Parameter

(random access channel control parameter)

 Content

SYS INFO 1

It contains random access control information (RACH) and cell frequency allocation table (i.e CA table) It is transmitted on BCCH

SYS INFO 1 - Control Parameter

These control parameters include:

 Maximum re-transmitting times (MAX retrans)

 Extended transmission timeslots (Tx_interger)

 Common access control level (AC)

 Call reestablish permitted (RE)

 Emergency call permitted (EC)

SYS INFO 2

It contains access control information (RACH), network color code permitted (NCC Permitted), and neighbor cell frequency allocation list (BA1 list) It is transmitted on BCCH Generally speaking, SYS INFO 2, 2BIS, 2TER contains different parts of the neighbor cell BCCH frequencies Via reading and decoding BA1 list, MS can perform cell reselection in idle mode For a

MS of GSM900 PHASE I, it only reads the neighbor cell BCCH frequencies defined in SYS INFO 2, and ignores those carried by 2BIS and 2TER

SYS INFO 2BIS

2BIS contains RACH control data and neighbor cell BCCH frequencies

(part of BA1 list) It is optional and transmitted on BCCH As the number

of frequencies in BA1 list carried by SYS INFO 2 is limited, SYS INFO 2BIS carries the rest of the BCCH frequencies in the BA1 list that are from the same band as in SYS INFO 2

 SYS INFO 2BIS

 Content

SYS INFO 2BIS

- Neighbor Cell Desc

2TER contains neighbor BCCH frequencies (part of BA1 list) It is transmitted on BCCH Only dual band MS can read this information, and single band 900 or 1800 MS will ignore it Since this information carries BCCH frequencies that belong to different band other than those in SYS INFO 2, it is unnecessary for single band MS to read.

SYS INFO 2TER - - Neighbor Cell Description (extended)

 SYS INFO 2TER

 Content

SYS INFO 2TER

It contains LAI, cell identity, RACH control parameters and cell selection related parameters It is transmitted on BCCH It is one of the most important information.

SYS INFO 3 - - Cell Identity

- - LAI( location area identity)

- - Control Channel Description

- - Cell Option （ BCCH （

 SYS INFO 3

 Content

SYS INFO 3

Cell Identity and Location Area Identity

Cell Global Identity (CGI) consists of Location Area Identity (LAI) and Cell

Identity (CI) And LAI includes Mobile Country Code (MCC), Mobile Network

Code (MNC), and Location Area Code (LAC) SYS INFO 3, 6, and 4 contain

all or part of the information of CGI According to the received SYS INFO,

MS decodes the CGI, and decide whether it can register in the network

based on the MCC and MNC indicated by CGI At the same time, it can

judge whether the current location area is changed, so as to decide whether

it is necessary to start the location updating process

Control Channel Description

Control channel description includes the following parameters

 IMSI Attach-Detach Allowed (ATT)

 Common Control Channel Configuration (CCCH_CONF)

 Access Granted Blocks Reserved (BS_AG_BLKS_RES)

 Paging Channel Multi-frames (BS_PA_MFRAMES)

 Periodic Location Update Timer (T3212)

Cell Option

Cell option contains the following parameters:

 Power control indication (PWRC)

 Discontinuous transmission (DTX)

 Radio link timeout

Cell Selection Parameter

Cell selection parameters indicate how the MS should behave after t

he MS is powered on It includes the following parameters:

 Cell Reselection Hysteresis (CRH)

 Maximum power level of control channel (MS_TXPWR_MAX_CCH)

 Minimum receiving level of MS permitted to access (RXLEV_ACCESS_

MIN)

 Additional reselection parameter indicator (ACS)

 Half-rate supported (Support Half-Rate)

 SYS INFO 4

 Content

SYS INFO 4 - - LAI

- - Cell Selection Parameters

- - RACH Control Parameters

- - CBCH Channel Description (optional)

- - CBCH Mobile Allocation (optional)

SYS INFO 4

It consists LAI, RACH control parameters, cell selection parameters and optional CBCH channel information It is transmitted on BCCH When the system supports cell broadcast function, CBCH together with the CBCH MA describe the configuration of CBCH and the relevant frequency information

CBCH Channel Description and CBCH MA

These two parameters are optional When system supports cell

broadcast, CBCH Channel Description explains the CBCH channel

configuration situation When CBCH Channel is in frequency

hopping mode, CBCH MA is also needed.

SI4 Rest Octets

It contains the following parameters:

 Cell Reselection Parameter Indicator (PI)

 Cell Bar Qualify (CBQ)

 Cell Bar Access (CBA)

 Cell Reselect Offset (CRO)

 Temporary Offset (TO)

 Penalty Time (PT)

 Content

SYS INFO 5

SYS INFO 5

 It describes the neighbor cell BCCH frequencies(BA2 list) It is

mandatory and is transmitted on SACCH Different from SYS INFO 2,

MS can read the frequency described in SYS INFO 5 in dedicated mode, report the relevant information of neighbor cells in measurement reports, and use it as the basis for handover Similarly, for 900 MS of PHASE 1, it only recognizes the neighbor cell frequencies described by SYS INFO 5, and ignores those carried by SYS INFO 5BIS and 5TER

SYS INFO 5BIS

SYS INFO 5BIS

 5BIS describes neighbor cells’ BCCH frequencies.These frequencies

are part of BA2 list It is optional and is transmitted on SACCH

Generally, as the number of frequencies which can be described by SYS INFO 5 is limited, SYS INFO 5BIS carries the rest BCCH frequencies in the BA2 which belong to the same band as SYS INFO 5

Content

 SYS INFO 5BIS - - Neighbor Cell Description

 SYS INFO 5TER

 Content

SYS INFO 5TER - - Neighbor Cell Description (Extended)

SYS INFO 5TER

5TER describes neighbor cells’ BCCH frequencies, these frequencies are also a part of the BA2 list It is transmitted on SACCH Similarly, only dual band MS can read this information, and single band GSM900 or GSM1800 MS will ignore it It carries the BCCH frequencies of neighbor cells whose band are different from the serving cell’s

System Information Overview

Parameters Introduction

Case Study

Course Contents

Introduction to SYS INFO Parameters

 Huawei GSM System Information Parameters:

 Network Identity Parameters

 System Control Parameters

 Cell Selection Parameters

 Network Functional Parameters

Network Identity Parameter — CGI

Network identity parameters mainly include cell global identity (CGI)

and base station identity code (BSIC).

CGI=MCC+MNC+LAC+CI

 Once MS receives SYS INFO, it decodes the CGI information, and

decides whether it can stay in the cell according to the MCC and MNC indicated by CGI At the same time, it judges whether the current location area is changed, so as to decide whether to execute location update During the location update process, MS will report the new LAI

to the network, so that the network can know the LA in which MS is currently located

Network Identity Parameter — BSIC

BSIC=NCC+BCC

 In GSM system, each BTS is allocated with a color code, which is

called BSIC MS can identify two cells with the same BCCH by the help of BSIC In network planning, effort should be made to make sure that BCCH of neighbor cells are different from the serving cell’s BCCH

to reduce the interference Practically it is still possible that a same BCCH is re-used in the surrounding cells For cells using the same BCCH in a relevant near distance, their BSIC must be different so that

MS can identify two neighbor cells with same BCCH

Mobile Country Code （ MCC （

 MCC is composed of 3 decimal numbers The coding range is decimal 000-999

Definition

 MCC consists of 3 decimal numbers It indicates the home country of the mobile subscriber

Format

Mobile Network Code （ MNC （

 MNC is composed of two decimal numbers The coding range is decimal 00-99

 MNC is used to uniquely identify a specific GSM PLMN network in a certain country (decided by MCC)

Definition

Format

Location Area Code （ LAC （

 LAI contains LAC, which is composed of two bytes LAC

adopts hexadecimal coding The available range is from 0001H to FFFEH The code 0000H and FFFFH cannot be used (please refer to specification GSM0303, 0408, and 1111) One location area can contain one or more cells

 To locate the location of MS, the whole area covered by

each GSM PLMN is divided into different location areas

LAC is used to identify different location areas

Definition

Format

Format

Network Color Code （ NCC （

 NCC is composed of 3 bits, with the range of 0 to 7

 NCC is a part of BSIC MS uses it to distinguish adjacent BTS that belong to different GSM PLMN

Format

Definition

Radio Link Timeout

Neighbor Cell Description

ATT

Value range: Yes, No

Content （ It is used to inform MS whether IMSI attach-detach is allow

ed in this cell If it is set to “Yes”, the network will not process the conn

ection to the called mobile subscriber when MS is power-off Thus netw

ork processing time and radio resources are saved Otherwise the netw

ork will process the connection even though the MS has been powered

off

Recommendation （ Yes

CCCH_CONF

Value range: 1 Non-Compounding CCCH, 1 Compounding CCCH,

2 Compounding CCCHs, 3 compounding CCCHs, 4

Non-compounding CCCHs.

Content: It is “Common Control Channel Configuration” CCCH conf

iguration determines the capacity of PCH, AGCH and RACH This pa

rameter can be automatically configured by the BSC Data Auto Config

uration System according to the TRX channel configuration.

Recommendation: When there is one TRX in the cell, one combin

ed CCCH is recommended (in a system with few paging messages in

location area) For others, it is configured according to the number of

BS_PA_MFRAMES

Value range: 2 （ 9

Unit: Multi-frame period (51 frames)

Content: It is Paging Channel Multi-frames It defines the number

of multi-frames used as a cycle of paging sub-channels

Recommendation: 2

Radio Link Timeout

Value range: 4~64, the step size is 4

Unit: SACCH period (480ms)

Content: This parameter is used for MS to decide down-link disconnection in case of SACCH decoding failures

Recommendation: 20~56

•

Application of Radio Link Timeout

Impact of radio link timeout

Poor coverage

Neighbor Cell Description

There are table BA1 and table BA2.

Table BA1 describes BCCH frequencies of the adjacent cells to be

measured when the MS is in idle mode.

Table BA2 describes BCCH frequencies of the adjacent cells to be

measured when the MS is in dedicated mode.

Application of Neighbor Cell Description

Theoretical Neighbor Cells Actual Neighbor Cells

D

NCC Allowed

Value range: Check box, including options 0~7

Content: Network Color Code, sent in system information 2 and 6 It

lists NCC that need be measured by MS If a neighbor cell’s NCC is

permitted, MS will report MRs of it to the network

Recommendation: Subject to the concrete conditions

MS MAX Retrans

Value range: 1, 2, 4, 7

Unit: Time

Content: It is one of the random access control parameters MS MAX Ret

rans is the upper limit of times that MS is allowed to send “Channel Reque

st” in one immediate assignment procedure

 Set to 2 for micro-cell

 Set to 1 for micro-cell with heavy traffic or with obvious congestion

Value range: 3~12, 14, 16, 20, 25, 32, 50

Unit: RACH timeslot (equals to a TDMA frame, 4.615ms)

Content: Used to calculate the number of timeslots in the interval between

multiple channel requests sent by MS

Recommendation: 20 (If the cell immediate assignment success rate is

low, set the S with a larger value Select 32 for satellite transmission, so as

to reduce satellite transmission delay)

Common Access Control Class

Value range: Check box, including level 0 forbidden,lever 1

forbidden,…, till level 9 forbidden

Content: One of the parameters of random access control

information It is used for load control of ordinary subscribers, to

permit or forbid the network access of some common level users “1”

stands for forbidden and “0” for permitted

Recommendation: 0000000000

Special Access Control Class

Value range: Check box, including level 11 forbidden,level12

forbidden,…, till level 15 forbidden

Content: It is used for load control, permitting or forbidding the network

access of some special level users “1” stands for forbidden and “0” for

permitted

Recommendation: 00000

Value range: 0~3

Content: Multi-band Reporting It is used to inform MS to report the adjacent cells in a controllable way It is sent in the System Information 2ter and 5ter

Value range: Yes, No

Content: Early Classmark Sending Control It indicates if an MS in t

he cell is allowed to use early Classmark sending See Protocol 0408

Recommendation: No

Cell Selection Parameter

CBQ(Cell Bar Qualify)

CBA (Cell Bar Access)

MS_TXPWR_MAX_CCH

RXLEV_ACCESS_MIN

PI (Cell Reselect Parameters Indication)

CRO(Cell Reselection Offset)

TO(Temporary Offset)

PT(Penalty Time)

CRH( Cell Reselection Hysteresis)

Cell Selection Process

There are two kinds of cell selection.

 Normal cell selection

 Stored list cell selection

In fact, the process might be different for different MSs

Cell Reselection Process

 Cell reselection for cells in same location area

seconds, a cell reselection process will be performed and the MS tunes to the new cell.

 Cell reselection for cells in different location areas

of CRH for longer than 5 seconds, a location update process and the cell reselection process will be performed.

 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

 If current serving cell is prohibited, or down link fails, or C1 is less than 0 continuously

for 5s, cell reselection will also be triggered.

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

Recommendation: No.

Value range: Yes, No

Content: Cell Bar Access, worked together with CBQ to set the

priority status of the cell in idle mode for cell selection and reselection

Recommendation: Yes