OMF010001 System Information ISSUE1.4.ppt

7/30/2019 OMF010001 System Information ISSUE1.4.ppt

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Wireless Curriculum Development Section

ISSUE

OMF010001

System Information

1.4


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Introduction to BSS Timers

System Information Overview

Parameters Introduction

Case Study

Course Contents


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System information (SYS INFO) contains network parameters

sent to MS through air interface(Um), including network identity

parameters, cell selection parameters, system control

parameters and network function parameters. By reading system

information, MS can access the network, perform cell selection,

fully utilize various services provided by the network, and

achieve favorable cooperation with the network. SYS INFO can

be divided into two parts:

SYS INFO sent on BCCH, including SYS INFO 1, 2, 2BIS, 2TER,

3, and 4, which are used by MS in idle mode.

SYS INFO sent on SACCH, including system information 5, 5BIS,

5TER, and 6, which are used by MS in dedicated mode.

Additionally Huawei BSC supports the system information 7 and

13 to support GPRS.



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SYS INFO 1

SYS INFO 1 - - Cell Channel Desc.

(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.


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Bit8 Bit7 Bit4 Bit3 Bit2 Format Type

0 0 X X X bit map 0

1 0 0 X X 1024 range

1 0 1 0 0 512 range

1 0 1 0 1 256 range

1 0 1 1 0 128 range

1 0 1 1 1 variable bit map

The above cell channel description formats correspond to different

requirements on the configured frequencies in a cell.

SYS INFO 1 - CA Description Format


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SYS INFO 1 - RACH Control Parameter

These control parameters include:

Maximum re-transmitting times (MAX retrans)

Extended transmission timeslots (Tx_interger)

Cell Bar access (CBA, CELL_BAR_ACCESS)

Common access control level(AC)

Call reestablish permitted (RE)

Emergency call permitted (EC)


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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 2

Content

SYS INFO 2 - - Neighbor Cell Desc.

- - NCC permitted



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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.


(Same as that in SYS INFO 1.)


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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 differentband as those in SYS INFO 2, it is unnecessary for single band

MS to read.

SYS INFO 2TER - - Neighbor Cell Desc. (extended)

SYS INFO 2TER

Content

SYS INFO 2TER


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It contains LAI, cell identity, RACH and parameters related to cell

selection. It is transmitted on BCCH. It is one of the most

important information in SYS INFO.

SYS INFO 3 - - Cell Identity

- - LAI( location area identity)

- - Control Channel Desc

- - Cell OptionBCCH

- - Cell Selection Parameter


SYS INFO 3

Content

SYS INFO 3


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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, Attach-Detach allowed)

Common Control Channel Configuration (CCCH-CONF)

Access Granted Blocks Reserved (BS_AG_BLKS_RES) Paging Channel Multi-frames (BS-PA-MFRAMS)

Periodic Location Updating 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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Cell Selection Parameter

Cell selection parameters indicate how the MS will behave

after the MS is powered on. It includes the following

parameters:

Cell Selection Hysteresis 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(NECI)


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SYS INFO 4

Content

SYS INFO 4 - - LAI

- - Cell Selection Parameter


- - CBCH Channel Desc. (optional)

- - CBCH Mobile Allocation(optional)

- - SI4 Rest Oct.(parameters related to cell reselection)

SYS INFO 4

It consists LAI, RACH, 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 Desc. and CBCH MA

These two parameters are optional. When system supports

cell broadcast, CBCH Channel Desc. explains the CBCH

channel configuration situation. When CBCH Channel Desc.

is in frequency hopping mode, CBCH MA is also needed.


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SI4 Rest Oct.

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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Content

SYS INFO 5 - - Neighbor Cell Desc.

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 report, and use it as the basis for handover.

Similarly, for 900 MS of PHASE 1, it only recognizes the

neighbor cell frequency information described by SYS INFO 5,

and ignores that carried by SYS INFO 5BIS and 5TER.


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SYS INFO 5BIS

SYS INFO 5

5 BIS 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 5 BIS carries

the rest BCCH frequencies in the BA2 that are belong to the

same band as SYS INFO 5 for transmitting to MS.

Content

SYS INFO 5BIS - - Neighbor Cell Desc.


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SYS INFO 5

ContentSYS INFO 5TER - - Neighbor Cell Desc.(Extended)

SYS INFO 5TER

5 TER describes neighbor cells BCCH frequencies,these

frequencies are also part of the BA2 list. It is transmitted on

SACCH channel. 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 cells.


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SYS INFO 6

Content

SYS INFO 6 - - Cell Identity

- - LAI

- - Cell Option

- - NCC Permitted

SYS INFO 6

It describes LAI, cell identity, and some parameters

describing functions of the cell. It is transmitted on

SACCH. It is also one of the most important informationin system information.


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Case Study

Course Contents


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Introduction to SYS INFO Parameters

Huawei GSM System Information Parameters:

Network Identity Parameters

System Control Parameters

Cell Option Parameters Network Functional Parameters


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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 updating. During the location updating process,

MS will report the new LAI information to the network, so that

the network can know exactly the LA in which MS is currently

located.


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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 different from the

serving cells 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.


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Mobile Country CodeMCC

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


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Mobile Network CodeMNC

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


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Location Area CodeLAC

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

adopts hexadecimal coding. The available range is from

0001H to FFFEH. Code group 0000H and FFFFHcannot 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


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Cell IdentityCI

CI is composed of 16 bits, The available range is

from 0 to 65535.

To uniquely identify each cell in the GSM PLMN, the

network operator needs to allocate one code for each

cell, which is the cell identity (CI). Cell identity, together

with LAI, is used for identity of each cell in the world.

(specification 0303).

Definition

Format


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Network Color CodeNCC

NCC is composed of 3 bits, with

coding capacity of 8.

NCC is part of BSIC. MS uses it to distinguish

adjacent BTS that belong to different GSM PLMN.

Format

Definition


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BS Color CodeBCC

BCC is composed of 3 bits. The available

range is from 0 to 7.

BCC is part of BSIC. For its function, please refer

to above sections.

Format

Definition


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ATT

CCCH-CONF

BS-AG-BLKS-RES

BS-PA-MFRAMST3212

Cell Channel Description format

Radio Link Timeout

Neighbor Cell Desc.

NCC Permitted

MS MAX re-trans

Tx-integer

CBA

Common Access Control Class

Wait-for-indication (T3122)MBR

ECSC

Power Deviation Indication

Power Deviation

CBCH Channel Description

CBCH Mobile Allocation

System Control Parameters


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ATT

Value range:Yes, No

ContentIt is Attach-Detach allowed (ATT) in Huawei data

management system. It is used to inform MS whether IMSI

attach-detach is allowed in this cell. If it is set to Yes, thenetwork will not process the connection to the subscriber called

when MS is power-off. Thus network processing time and

resource 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-combined CCCH, 1 combined CCCH, 2 non-

combined CCCH, 3 non-combined CCCH, 4 non-combined CCCH.

Content: It is Common Control Channel Configuration.The number of

CCCH message blocks in one corresponding BCCH multi-frame are 9,

3, 18, 27, and 36 respectively. CCCH configuration determines the

capacity of PCH, AGCH and RACH.

Unit: None

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

CCCH is recommended (in a system with few paging messages 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 for access granted channels(AGCH).

Recommendation: 2


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BS-PA-MFRMS

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 loop of paging sub-

channels.

Recommendation: 2


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T3212

Value range: 0~255

Unit: 6 minutes

Content: It is Periodic Location Update Timer. It defines

the period length of location updating.

Recommendation: 30 (for urban area), 20 (for suburban

area)


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Application of T3212

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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Cell Channel Description Format

Value range: Bitmap, 1024, 512, 256, 128,

variable length

Content: That is CA table. Presently, the parameter

has been automatically selected by the program

according to actual CA configurations.


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Application of CA Table

Module ID Cell ID Effectivefrequency 0

Effective

frequency 1

Effective

frequency 2

Effective

frequency 3

Effective

frequency 5

...

2 51 45 59 68 77 86 ...

2 52 49 62 71 80 89 ...

2 53 53 65 74 83 92 ...

This table describes all the effective frequencies configured in a cell.


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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-linkdisconnection 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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Neighbor Cell Description

I.e. Huawei BA tables. 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 cellsto be measured when the MS is in dedicated mode.


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Application of Neighbor Cell Description

Theoretical Neighbor Cells Actual Neighbor Cells

B

CA

D

B

CA

D


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B

C

A

Application of Neighbor Cell Description

A


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NCC Permitted

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

Content: Network Color Code, to be sent in system messages

2 and 6. It lists NCC that need be measured by MS. If a

neighbor cell with NCC permitted, MS will report M.R. Of the

neighbor cell to the network.

Recommendation: Subject to the concrete conditions.


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MS MAX Re-trans

Value range: 1, 2, 4, 7

Unit: Times

Content: One of the parameters of random access control

information. i.e. MS MAX. Re-trans Times. It is the upper limit of

times that MS is allowed to send Channel Request in oneimmediate 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

less than 3km. Set to 2: For micro-cellular Set to 1: For micro-

cellular with heavy traffic or with obvious congestion. And 4 or more

is recommended to set for satellite transmission BTS.


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Tx-integer

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

Unit: Number of RACH timeslots (equivalent to one timeslot,

0.577ms)

Content: Extended Transmission Timeslots(T), used to calculate the

number of timeslots in the interval between two channel requests

sent by MS.

Recommendation: 25 (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

ST

Combined

CCCH

Non-combined

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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CBA

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

Unit: None

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 CBA

CBQ(A)= NO

CBA(A)= NO

A

C

B

D


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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. i.e. 0~9 bits of AC. 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: 000000000


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Special Access Control Class

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

forbidden,till level 15 forbidden

Content: I.e. 11~15 bits of AC. 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


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When the network receives channelrequest message sent by MS,

if there is no appropriate channel assigned to MS, the network will

send immediate assignment rejection message to MS. To avoid the

congestion of radio channel which is caused by MSs frequently

sending of channel request, immediate assignment rejection

message contains the timer T3122 (the wait-indication). After MS

receives immediate assignment rejection message, only after T3122

is timeout MS can send a new channel request.

T3122

Definition

Format

T3122 is 8-bit binary. It indicates the time that MS has to wait before

sending the second request.Its timing length is 0-255 seconds.


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MBR

Value range: 0~3

Unit: None

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.

i i f


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Application of MBR

-92dBm-82dBm

AB

C -68dBm

D -90dBm

E -78dBm

F -88dBm

G -96dBm

H -84dBm

GSM1800

GSM900S

ECSC


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ECSC

Value range: Yes, No

Unit: None

Content: Early Classmark Sending Control. It informs MS in a

cell whether class-mark 3 should be sent in advance actively or

not.

Recommendation: No.

P D i i I di i


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Power Deviation Indication


Unit: None

Content: Determine whether to adjust the output the power for

class 3 MS of GSM1800.

Recommendation: None

P D i ti


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Power Deviation

Value range: 0~3, corresponding value: 0dB, 2dB, 4dB, 6dB

Unit: None

Content: After random access, when the initial power command is

not received, the power used by GSM1800 Class 3 MS is MS max.

transmitting power plus the value of power offset.

Recommendation: 1

C ll S l ti P t


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Cell Selection Parameter

MS_TXPWR_MAX_CCH

RXLEV_ACCESS_MIN

ACS(Additional Reselect Parameter

Indication)

PI(Cell Reselect Parameters Indication)

CBQ(Cell Bar Qualify)

CRO(Cell Reselection Offset)

TO(Temporary Offset)

PT(Penalty Time)

CRH( Cell Reselection Hysteresis)

C ll S l ti P


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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

C ll R l ti P


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Cell Reselection Process

Cell reselection for cells in same location area

If the C2 value of the target cell is higher than that of the serving cell and

last for longer than 5 seconds, a cell reselection process will be

performed and the MS tunes to the new cell.

Cell reselection for cells in different location areas

If the C2 value of the target cell is higher than that of the serving cell by

at least the value of CRH and last for longer than 5 seconds, a location

updating process and the cell reselection process will be performed.

Cell reselections caused by C2 have a time interval of 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 .

MS TXPWR MAX CCH


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MS_TXPWR_MAX_CCH

Value range: 0~31

Unit: level

Content: This parameter determines the max. allowed output

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

yet received power command.

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

RXLEV ACCESS MIN


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RXLEV_ACCESS_MIN

Value range: 0~63

Unit: Level

Content: It means the minimum received signal level

required for MS to access a cell.

Recommendation: 8

ACS


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ACS

Value range:Yes, No.

Unit:None

Content: Additional Reselect Parameter Indication. It is

used to inform MS of the location of reselection parameter in

the cell.

Recommendation: No.

PI


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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 of existenceof Cell Reselect Offset(CRO), Temporary Offset(TO)

and PenaltyTime(PT).

Recommendation: Yes.

CBQ


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CBQ

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

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.

Application of CBQ


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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

Application of CBA


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Application of CBA

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

B

A

CRO


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CRO

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

stepped every 2dB.

Unit: None

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

calculation to give a manual modification in MS cell reselection.

Recommendation: 0

TO


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TO

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

corresponds to Infinite

Unit: None

Content: Cell Reselect Temporary Offset. It is a parameter inC2 criterion to give a temporary modification within PT time.

Recommendation: 0

PT


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PT

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

31 is to change the function direction of CRO on C2.

Unit: None

Content: Cell Reselect Penalty Time.

Recommendation: 0

CRH


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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

Network Function Parameter


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Network Function Parameter

PWRC (Power Control Permitted)

UL DTX(Uplink Discontinuous Transmission)

NECI(New-Establishment Cause Indication)

Call Re-establish Allowed(RE)

EC Allowed(Emergency Call Allowed)

Frequency Hopping

PWRC


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PWRC

Value range: Yes, No.

Unit: None

Content: It is used to indicate MS weather to reduce

received level value obtained from the timeslots of BCCH

when MS measures receiving level during base band

hopping mode. When it is set to No, it means the

influence of receiving level on BCCH is not in

consideration. If it is set to Yes, process it in the way

mentioned above.

Recommendation: Yes

UL DTX


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UL DTX

Value range: May use, Must use, Can not use.

Unit: None

Content: It is used to indicate whether MS uses DTX

function. In System Information 3, it is 2 bits coding. InSystem Information 6, 3 bits coding. It shows the DTX

state of the MS in the previous measurement period.

Recommendation: Must use.

NECI


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NECI

Value range: Yes, No.

Unit: None

Content: Informing MS whether half-rate service aresupported in the cell.

Recommendation: No

Call Re-establishment Allowed


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Call Re establishment Allowed


Unit: None

Content: RE, Informing MS whether call reestablishment is

supported or not.

Recommendation: No

EC Allowed


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EC Allowed


Unit: None

Content: Emergence Call Allowed . When EC is set to

Yes, it means emergency call is permitted.

Otherwise it is prohibited.

Recommendation: Yes.

Others in Data Management system


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Others in Data Management system

System Information Used

Regular Transmission

Regular Transmission Interval



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Value Range: It is a check box, including system information

1~12, 2bis, 2ter, 5bis, 5ter, 10bis.

Unit: None

Content: It is used to determine whether a type of systeminformation should be sent. A selected box means support,

Recommendation: Select system information: 1~6, 2bis, 2ter,

5bis, 5ter



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Unit: None

Content: It shows whether BSC chooses to perform timing

update of system information contents transmitted by BTS. If it

is Yes, BSC will send system information to BTS at a certain

interval (it is decided by timing updating interval.). Otherwise, it

must be transmitted through operating the BSC.

Recommendation: Yes



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Value range: 0~255

Unit: Minute

Content:It stipulates the time interval that BSC

sends system information to BTS.

Recommendation: 10 minutes

Course Contents


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Case Study

Cou se Co e s

Case Study


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y

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 BA1 table. Cell A-3 and B-3 add adjacent data for each

other. The coverage problem is thus solved.

Summary and Suggestions

There is a lot of signals received in this area, it is difficult to solve the coverageproblem if we check data independently. Try to conduct frequency scanning in

highway sections where the signal is poor, find out the receiving frequency with

the highest signal level, check BA1 table, BA2 table, and the neighbor cell

relationship, and modify the data. In this way, problem can be solved quickly.

Case 1: Incorrect Configuration of BA Table

Case Study


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y

Case description

The subscriber complains that MS cannot register to the network, or

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

network mark is displayed on the MS, but MS indicates that the

signal is very good. Some subscribers also complain that MS canmake MTC but cannot make MOC.

Cause analysis

CGI of the cell is modified. So the network register flow is not

normal. Although the signal is very good, MS cannot 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

same.

Case 2: Incorrect CGI causes MS unable to register on the network.

Case Study


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Case description

SDCCH congestion rate is as high as 4.91% in 2 cells of an urban BTS. The

configuration of this BTS is S1/1/1. And the busy hour TCH traffic of each

cell does not exceed 3 Erl.

Handling procedure

Modify the LAC of this BTS into 0520, which is the same as the surrounding

cells. And the problem is solved.


LAC configurations of all the cells in the same location area must be the

same. Different cells must have different CGI. When there is modification on

BSS side, corresponding modification should be made on MSC.

Case 3: Incorrect LAC configuration causes high SDCCH congestion rate.

y

Case Study


88/99

y

Case description

After Huawei BSC has been running successfully in a network. Some subscribers

complain that they cannot be called. The system announcement that the subscriber

called is powered off. After they make a call, this phenomenon disappears.

Handling procedure 1. When analyzing the distribution of the complaining subscribers, it found the

distribution are very dispersed. So this should not be caused by poor coverage.

2. Use the complaining subscribers mobile for dial test, And the result shows tested

mobiles are okay.

3. Trace the cause from MSC. After checking location update time of MSC with the

operator, we reduce T3212 of BSC to 30 minutes.


T3212 in BSC must be less than that in MSC.

Case 4: MSC T3212 is too small caused part of MS cannot be called.

Case Study


89/99

y

Case description

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

tests 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 parameterRXLEV_ACCESS_MIN of all cells in urban area and

make them consistent with each other. The problem of signal fluctuation

is solved.


In area with complicated coverage, the RXLEV_ACCESS_MIN of each

cell should be kept same.

Case 5: MS Min-access Level causes the fluctuation of MS signal.

Case Study


90/99

y

Case description

A network operator finds that the SDCCH call drop rate is about 2% after

BSC cutover. This is far away from the acceptable standard.

Handling procedure

1. Modify relevant parameters in system information and cell attribute

tables. The modification helps to avoid the radio link failure which will

cause call drop, and to adjust the balance between uplink and downlink.

2. Check the situation of other indices, especially handover successful rate

and TCH related indices. Analyze hardware and parameters and see if

they are in compliance with the actual running situation of the network.

3.Check the performance of the hardware on-site. Analyze the drive test

result. Check and make proper adjustment to the azimuth and downtilt of

the antenna system. Check whether the connectors are loosened.

Case 6: High SDCCH call drop rate

Case Study


91/99

Case description

In a dual-band network, performing GSM1800 single network drive test, during

the driver test, MS often lost connection with the network. But when MS

reconnects with the network, the signal level is very strong.

Handling procedure

After analyzing the actual traffic in each cell of GSM900 network in details, MS

minimum access level and cell reselection offset (CRO) of GSM1800 are

adjusted to make C2 of cells in GSM1800 close to one another when received

signal levels are the same. At the same time, the traffic carried by equipment of

other network is not reduced. After several times of adjustment, CRO of most

1800 cells are 30dB, MS minimum access level is -90dBm. For GSM900 cells,

CRO is 0, MS minimum access level is -100dBm. The cross-cell coverage

phenomenon is basically eliminated.

Case 7: Cell reselection caused fluctuation of signals.

y

Case Study


92/99

Case description

A local GSM network has more than 6000 subscribers. There are four BTS. The

network has been working properly. But from sometime on, some MS often lost

connection with network suddenly. The complaint from subscribers in urban

area increased.

Handling procedure

Modify the time of BSC periodic location update (T3212) to 10, i.e. 60 minutes.

Modify the corresponding time of MSC to 180 minutes. Two days observation

shows no subscriber complains and the problem is solved.

Case 8Too small T3212 causes MS lose connection with network.

y

Course Contents


93/99




Case Study

Some of the BSC Timers -T3101


94/99

Definition It is used in the immediate assignment process. During the

process of immediate assignment, T3101 is activated when

BSC sends CHANNEL-ACTIVE to BTS, and reset when it

receives ESTABLISH INDICATION sent from BTS.

Value range 0~255s



95/99

Definition T3103 defines the time that BSC reserves the TCH of both the

target cell and the original cell simultaneously during the

handover process. T3103 starts when BSC originates handover

command and resets when handover complete (intra BSC

handover) or clear command is received (inter-BSC handover).

Value range

0~255s



96/99

Definition It is used in the TCH assignment process. BSC starts T3107.

when TCH assignment command is sent to BTS, and stop

after receiving assignmentcomplete from BTS.

Value range 0~255s



97/99

Definition SACCH release time allowed is indicated by this timer.

Value range

0~255s



98/99

Definition According to timer T3111, BSC delays the channel release

at BTS side. After BSC receives information of BTS

channel releasing, it start T3111. BSC will not send

channel release command to BTS until T3111 is timeout.

Value range 0~255s


99/99

Documents

OMF010001 System Information ISSUE1.4.ppt