GSM SI.ppt

8/10/2019 GSM SI.ppt

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HUAWEI TECHNOLOGIES CO., LTD.

www.huawei.com

HUAWEI Confidential

Security Level:

GSM System

Information and Cell

DataV 1.0


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HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential Page 2

Upon completion this course, you will be

able to:

Master the characteristics of System

Information and Cell Data

Know the phenomenon and reason

of problem through Case Study


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Chapter 1 System Information Overview

Chapter 2 Parameters Introduction of

System Information and Cell Data


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1.1 System Information Usage

1.2 System Information Distribution

1.3 System Information Contents


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System Information Usage

By reading system information, MS can access

the network, perform cell selection and reselection,

fully utilize various services provided by the

network, and achieve favorable cooperation with

the network.


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SYS INFO 1

SYS INFO 1

It contains random access control information (RACH) and cell

frequency allocation table (i.e. CA table). It is transmitted on

BCCH.

Content

SYS INFO 1

Cell Channel Description

(cell channel description format) RACH Control Parameter

(random access channel control parameter)


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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 forbidden

Emergency call disable


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SYS INFO 2

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 ofGSM900 PHASE I, it only reads the neighbor cell BCCH frequencies defined

in SYS INFO 2, and ignores those carried by 2BIS and 2TER.

Content

SYS INFO 2

Neighbor cell BCCH frequency description

NCC permitted

RACH Control Parameter


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SYS INFO 2BIS

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.

Content

SYS INFO 2BIS

Neighbor Cell Desc.

RACH Control Parameter (Same as those in SYS INFO 1.)


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SYS INFO 3

SYS INFO 3

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.

ContentSYS INFO 3 - - Cell Identity

- - LAI( location area identity)

- - Control Channel Description

- - Cell OptionBCCH

- - Cell Selection Parameter

- - RACH Control Parameter


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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.


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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)


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Cell Option

Cell option contains the following parameters:

Power control indication (PWRC)

Discontinuous transmission (DTX)

Radio link timeout


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SYS INFO 4

Content SYS INFO 4 - - LAI

- - Cell Selection Parameters

- - RACH Control Parameters

- - CBCH Channel Description (optional)

- - CBCH Mobile Allocation (optional)

- - SI4 Rest Octets (parameters related to cell reselection)

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.


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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.


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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)


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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 carriesthe rest BCCH frequencies in the BA2 which belong to the

same band as SYS INFO 5.

Content

SYS INFO 5BIS - - Neighbor Cell Description


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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 GSM1800MS will ignore it. It carries the BCCH frequencies of neighbor cells whose

band are different from the serving cells.


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Chapter 2 Parameters Introduction of

System Information and Cell Data


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Chapter 2 Parameters Introduction

2.1 Network Identity Para. 2.6 Radio Link Control Para.

2.2 Paging Para. 2.7 BA1,BA2 Table

2.3 Cell Selection and Cell Reselection Para. 2.8 Dual-band Network Para.

2.4 Assignment Para. 2.9 Network Function Para.

2.5 Handover Para. 2.10 Interference Measurement Para.


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Network Identity Parameter

Cell Global Identity (CGI)

Base Station Identity Code (BSIC)


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Network Identity Parameter CGI

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 decidewhether 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.


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Network Identity Parameter CGI

MCC MNC LAC CI

Full Name Mobile Country

Code

Mobile Network

Code

Location Area

Code

Cell Identity

Type Dec Dec Hex Hex

Rage 000~999 00~99 0001~FFFE 0000~FFFF

LACLAC 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. The same LAC can

exist in different BSC, but can not exist in different MSC.


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Case Study: Incorrect CGI causes MS unable to

register on the network.

Case description

The subscriber complained that MS could not register to the network, or it

was difficult to register to the network between BTS A and B, or no network

mark was displayed on the MS, but MS indicated that the signal was very

good. Some subscribers also complained that MS could make MTC could

not make MOC.

Cause analysis

CGI of the cell was modified. So the network register flow was not normal.

Although the signal was very good, MS could not get registered in the

network.

Recommendation and summary

CGI is a very important parameter and should be configured correctly, thus

to ensured that the CGI data in BSC and MSC are the same.


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Network Identity Parameter BSIC

NCC BCC

Full Name Network Color

Code

Base Station Color

Code

Contain 3 bits 3 bits

Range 0~7 0~7

BSIC is transmitted on Synchronous Channel (SCH)

NCC is used to identify different Base Station from different GSM PLMN

NCC Permitted should work with NCC

BSIC=NCC+BCC


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Cell C: BCCH 97

Case Study BSIC

Base Station Identity Code

BSIC

Cell B: BCCH 97

Cell A

BSIC: 12

BSIC: 12

BSIC: 13

NeighborCell List

Serving

Cell

Neighbor

Cell

Cell A Cell B

Cell A .


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Paging Parameter

MSC can resend Paging Command 4 times in A Interface. The resendingtime intervals are 3, 3, 2, 2 seconds. 2 seconds after the last Paging

Command is sent, totally 12 seconds after first Paging Command is sent,

if MSC does not receive Paging Response, and then MSC report Voice

Announcement that subscriber is out of coverage.

BSC only transmits the Paging Command.

Whether BTS resends Paging Command, it depends on correspondingBTS version. (Refer to the Version Description documents)

MSC BSC BTS MS

PagingPaging CMD

PCH: Paging REQ


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Paging Parameter

T3212

ATT

CCCH Conf. BS_AG_BLKS_RES

BS_PA_MFRMS

Paging Times


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T3212

Value range: 0~255

Unit: 6 minutes

Content: It is the Periodic Location Update Timer. It defines the

interval of periodic location update.

Recommendation: 20~30 (urban), 10~20 (suburban),

8~10(mountain area)


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ATT

Value range: Yes, No

ContentIt is used to inform MS whether IMSI attach-detach is

allowed in this cell. If it is set to Yes, the network will not process

the connection to the called mobile subscriber when MS is power-

off. Thus network processing time and radio resources are saved.Otherwise the network will process the connection even though

the MS has been powered off.

RecommendationYes


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CCCH Conf

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

2 Non-Compounding CCCHs, 3 Non-compounding CCCHs, 4

Non-compounding CCCHs.

Content: It is Common Control Channel Configuration. CCCH

configuration determines the capacity of PCH, AGCH and RACH.This parameter can be automatically configured by the BSC Data

Auto Configuration System according to the TRX channel

configuration.

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

combined CCCH is recommended (in a system with few pagingmessages in location area). For others, it is configured according

to the number of TRX in the cell.


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BS_AG_BLKS_RES

Value range: 0~2 (1 combined CCCH), 0~7 (others)

Unit: Block

Content: It is also called Access Granted Blocks Reserved. It is

the number of CCCH channel message blocks that are reserved in

one multi-frame for access granted channels (AGCH).

Recommendation: 2 (non-combined CCCH)


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BS_PA_MFRAMES

Value range: 29

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


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Paging Times

Value range: The BTS24, BTS3Xr, BTS3001C, BTS3002C, and dual-

transceiver BTSs support paging re-sending. Paging times: 18

Unit: None

Default Value: 4

Content: The BTS2X supports the re-sending mechanism. Both the BTS3X

series and the dual-transceiver BTSs support paging re-sending. BTS3X

and double-transceiver BTSs will support paging resending function.


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Case Study: Wrong T3212 setting cause MTC failure

Even if T3212 setting is less than the system (MSC)

query time, the system will still sometimes voice The

subscriber you dialed is powered off.

A B

T3212=4 T3212=8

LAC

Ping-pong Reselect


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Case description

A local GSM network has more than 6000 subscribers. There

are four BTSs. The network has been working properly. But

from sometime on, some MS often lost connection with

network suddenly. The complaint from subscribers in urbanarea increased.

Handling procedure

Modify T3212 to 10, i.e. 60 minutes. Modify the corresponding

time of MSC to 180 minutes. Two daysobservation shows no

subscriber complaint and the problem is solved.

Case Study: Too small T3212 causes MS lose connection

with network.


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Cell Selection and Cell Reselection Parameter

MS_TXPWR_MAX_CCH

RXLEV_ACCESS_MIN

PI

CRO

TO

PT

Cell Bar AccessCBA

Cell Bar QualifyCBQ

Cell Selection HysteresisCRH


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C1 = RLA_C- RXLEV_ACCESS_MIN-MAX((MS_TXPWR_MAX_CCH- P), 0)

RLA_C: MS average receiving level

RXLEV_ACCESS_MINminimum level of received signals required for

the MS to access the system

MS_TXPWR_MAX_CCH: maximum transmit power level of MS

P: MS maximum transmit power

C1 Formula

Cell Selection Parameter


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MS TXPWR_MAX_CCH

Value range: 0~31

Unit: level

Content: This parameter determines the maximum allowed output

power of the MS when it begins to access a cell and has not yet

received power control command.

Recommendation: 5(900MHz), 0(1800MHz)


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RXLEV_ACCESS_MIN

Value range: 063 (110 dBm to47 dBm)

Unit: Level

Default Value: 8

Content: This parameter indicates the minimum level of received

signals required for the MS to access the system. If the parameter

value is small, the required level of received signals is low. If the

parameter value is great, the required level of received signals is

high.


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C2 = C1+ CRO- TO*H(PT-T), if PT31;

C2 = C1- CRO, if PT= 31

CRO: CELL_RESELECT_OFFSET

TO: TEMPORARY_OFFSET

PT: PENALTY_TIME , to determine the effect duration of TO

T: a Timer, initial value is 0. When one cell appears in six maximal the

neighbor cell list, the Timer to that cell starts. When one cell is deleted

from the neighbor cell list, the Timer is restored.

H(x): Neighbor Cell: H(x) = 0, when x < 0; H(x) = 1, when x >= 0.Serving Cell: H(x) = 0

C2 Formula

Cell Reselection Parameter


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PI

Value range: Yes (1), No (0).

Unit: None

Content: Cell Reselect Parameters Indication, sent on the

broadcast channel of the cell. It is an indication to the existence of

Cell Reselect Offset(CRO), Temporary Offset(TO) and PenaltyTime(PT).

Recommendation: Yes.


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CRO

Value range: 0~63, the corresponding level value: 0~126dB,

stepped every 2dB.

Unit: None

Default Value: 0

Content: Cell Reselect Offset. It is a parameter in C2 calculation to

give an intentional modification in MS cell reselection.


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TO

Value range: 0~7 , the corresponding value is 0~60dB, 7

corresponds to Infinite.

Unit: None

Default Value: 0

Content: Cell Reselect Temporary Offset. It is a parameter in C2

criterion to give a temporary modification within PT time.


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PT

Value range: 0~31, the corresponding time is 20~620s. 31 is to

change the formula of C2.

Unit: None

Content: Cell Reselect Penalty Time.

Recommendation: 0


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CBQ

Value range: Yes , No

Unit: None

Content: Cell Bar Qualify. CBQ only affects the selection of cells but is not related

to cell reselection. It works with CBA to define the access priorities of cells.

Recommendation: No.


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CBA


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


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Application of CBQ

The traffic of cell A and B is heavy. Set these two cells with

CBA=No, CBQ=No.

A B


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Application of CBA

B is a micro cell. Set B to Normal and A to Low.

B

A


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Application of CBA

CBQ(A) = NO

CBA(A) = NO

A

C

B

D


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CRH

Value range: 0~14 , the step size is 2

Unit: dB

Content: Cell Reselection Hysteresis. It is the parameter used

when cell reselection happens between two location areas.

Recommendation: 4


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Case Study: RXLEV_ACCESS_MIN causes signal

fluctuation

Case description

Subscribers complain that the signal fluctuates in a certain area. On-site test

shows that this phenomenon does exist. From the testing mobile, we can see

that there are a lot of cells signals in this area. Some frequencies are the

suburb BTS signals far away from this area. The cell reselection of MS is rather

frequent.

Handling procedure

Modify parameter RXLEV_ACCESS_MIN of all cells in urban area and make

them consistent with each other. The problem of signal fluctuation is solved.

Recommendation and summary In area with complicated coverage, the RXLEV_ACCESS_MIN of each cell

should be kept same.


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MS MAX Retrans

Value range: 1, 2, 4, 7

Unit: Time

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

Retrans is the upper limit of times that MS is allowed to send Channel

Request in one immediate assignment procedure.

Recommendation:

Set to 7 for areas with low traffic (suburban or rural area) and the cell

radius more than 3 km.

Set to 4 for areas with ordinary traffic (non-busy area in the city) and

the cell radius is less than 3km.

Set to 2 for micro-cell

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

Set to 4 or 7 for satellite transmission BTS.


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TX-Integer

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).


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Calculation of S

Interval of first time: {01MAXT81}

Interval of Resending: {SS1ST1}

TS

Combine CCCH Non-combine CCCH

3, 8, 14, 50 55 41

4, 9, 16 76 52

5, 10, 20 109 58

6, 11, 25 163 86

7, 12, 32 217 115


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TCH Immediate Assignment


Unit: None

Default Value: No

Content: Yes: It indicates that the TCH is immediately assigned

when the SDCCH has no available resource during the processing

of access request. No: It indicates that only the SDCCH can be

assigned.


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RACH Min Access Level

Value range: 0-63 (-110 dBm to -47 dBm)

Unit: None

Default Value: 5

Content: This parameter must be set according to the actual

sensitivity of the BTS and the minimum access level of the MS so

that calls can be made when there is signal.


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Handover Parameter

NCC Permitted

Max Resend Times of Phy. Info

T3105

Direct Retry

MS

Old

BTS BSC

Measure Report

New

BTS MS

Measure Report CHAN ACTIV

CHAN ACTIV ACKHO CMDHO CMD

HO ACCESS

PHYSICAL INFHO DETECTION

SABM

UAEST IND

HO COMPLETE


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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 cells

NCC is permitted, MS will report MRs of it to the network.

Recommendation: Subject to the concrete conditions.


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Max Resend Times of Phy. Info

Value range: 1255

Unit: None

Default Value: 30

Content: This parameter indicates the maximum times of resending

physical information.

Recommendation: Subject to the concrete conditions.


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T3105

Value range: 0255

Unit: 10ms

Default Value: 7

Content: When BTS sends physical information to the MS, the BTS

starts the timer T3105.If the timer T3105 times out before receive

the SAMB frame from MS, BTS re-sends physical information to MS

and restarts the timer T3105.


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Direct Retry


Unit: None

Content: This parameter indicates the whether the directed retry on

the TCH is allowed. If this parameter is set to Yes, the handover

procedure is used and the MS is handed over to the neighboring cell.Direct retry is an emergency measure for abnormal peak traffic in the

local wireless network. It is not a primary method of clearing traffic

congestion. If direct retry is preformed frequently in a local network,

you must adjust the sector carrier configuration of the BTS and the

network layout. Recommendation: Yes


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Radio Link Control Parameter

BS-PA-MFRMS (Idle Mode)

Radio Link Timeout

RLINKT (Active Mode, DL) SACCH Multi-frames (Active Mode, UL)


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BS_PA_MFRAMES

Value range: 29

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

Note: In idle mode MS camps in a cell. The DSC is initialized to

the integer part of 90/N (N is BS_PA_MFARMES, with the value

range: 2~9). when MS can successfully decode the message on

paging sub-channel, DSC will increase by 1, but it will not exceed

initially value. If decoding fails, DSC will decrease by 4. If DSC


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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


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Application of Radio Link Timeout

Impact of radio link timeout

A B

P Q

Poor coverage


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SACCH Multi-frames

Value range: 063

Unit: SACCH period (480ms)

Default Value: 31

Content: This parameter is used for MS to decide up-link disconnection

in case of SACCH decoding failures.


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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.


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Theoretical Neighbor Cells Actual Neighbor Cells

B

CA

D

B

CA

D

Application of Neighbor Cell Description


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B

C

A

A

Application of Neighbor Cell Description

Case Study: Island effect


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Case Study: Island effect

Case Description

During the process of optimization in a certain area, it is found out that

the signal is poor in a certain section of suburban highway. The signal

strength measured is less than -95dBm.

Handling Procedure

Modify the data in BSC. Add neighbor relationship to Cell A and B foreach other. The coverage problem is thus solved.

C

BA

-92

-80

-95


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Dual-band Network Parameter

ECSC

MBR


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ECSC


Content: Early Classmark Sending Control. It indicates if an MS in the cell

is allowed to use early Classmark sending. See Protocol 0408.

Recommendation: No.


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MBR

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.


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Application of MBR

-92dBm-82dBm

AB

C -68dBm

D -90dBm

E -78dBm

F -88dBm

G -96dBm

H -84dBm

GSM1800

GSM900S


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UL DTX

Value range: May use, Shall use, Shall not use.

Unit: None

Default Value: Shall use

Content: It is used to indicate whether MS uses DTX function. In

System Information 3, it is 2-bit coding. In System Information 6, itis 3-bit coding. It shows the DTX state of the MS in the previous

measurement period.

Recommendation: Shall use.


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DL DTX


Unit: None

Default Value: No

Content: This parameter indicates whether downlink DTX is used in a cell.

Remarks: The use of downlink DTX is also controlled by the DTX switch

in the MSC. If downlink DTX is forbidden in the MSC, downlink DTX is not

used regardless of the setting of this parameter. If downlink DTX is

allowed in the MSC, the setting of this parameter can determine whether

downlink DTX is used in the cell.


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Call Re-establishment Allowed


Unit: None

Default Value: Yes

Content: This parameter indicates whether the network allows call re-

establishment.Yesmeans do not allow to use call re-establishment.


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Emergent Call Disable


Unit: None

Default Value: No

Content: Emergence Call Disable. When EC Disable is set to No,

it means emergency call is permitted. Otherwise it is prohibited.


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Interference Measurement Parameter

Interference Average Period

Intf. band Distribution

Interference

f


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Interference Band Threshold 0~5

Value range: 110~85

Unit: -dBm

Content: It decides the corresponding value for each interference band (from

band 0 to band 5) and used to measure the uplink interference during the TCH

timeslot is in idle mode.

Recommended values:

110 ( Interference band threshold 0)


98 ( Interference band threshold 2 )




I t f C l l ti P i d


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Interf Calculation Period

Value range: 1-31

Unit: SACCH period (480 ms)

Default Value: 20

Content: Before the BTS transmits the radio resource indication

message to the BSC, the interference levels measured on idlechannels in the period defined by this parameter are averaged.


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Thank You

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