80139282 Omf810001 Gsm Cell Parameters Issue1 0

7/28/2019 80139282 Omf810001 Gsm Cell Parameters Issue1 0

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Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.

GSM Cell Parameters


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Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved. Page2

Descriptions

1. Cell Parameters Overview

2. Cell Parameters Introduction

3. Case Study


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Cell ParametersOverview

Cell Parameters include the most of radio network

parameters transmitted via Um interface.

Via receiving cell parameters, MS is able to exactly select,

access and coordinate with the network through which

different kinds of service is provided.

Via reasonably cell parameters, BTS can run in high point

and whole system can be effectively utilized to provide moreand better services although basing on limited resources.


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Cell ParametersOverview

Cell Parameterscan be sent through two kinds of logical channels

BCCH (in idle mode)

SACCH (in dedicated mode)


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Descriptions



3. Case Study


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Introduction to Cell Parameters

Huawei GSM cell parameters:

Network Identity Parameters

Idle Mode Parameters

Call Control Parameters

Cell Selection and Reselection Parameters

Other Parameters


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Power on

Access Network

(Call Control Para.)

Select Network

(Network Identity Para. )

Cell Data Mapping in Different Statuses of MS

Cell Selection

(Cell Selection Para.)

Paging Mode

(Idle Mode Para.)

Dedicated Mode


Cell Reselection Mode

(Cell Reselection Para.)Idle Mode

(Idle Mode Para.)


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Network Identity Parameter CGI

Network identity parameters mainly include

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 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.


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Mobile Country CodeMCC

Definition: MCC consists of 3 decimal numbers. It indicates the

home country of the mobile subscriber.

Format: MCC is composed of 3 decimal numbers. The coding

range is decimal 000~999.

Location: Cell Attributes


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Mobile Network CodeMNC

Definition: MNC is used to uniquely identify a specific GSM PLMN

network in a certain country (decided by MCC).

Format: MNC is composed of two decimal numbers. The coding

range is decimal 00~999.



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Location Area CodeLAC Definition: 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.

Format: 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.



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Cell IdentityCI

Definition: 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.

Format: CI is composed of 16 bits, The available range is 0~65535.



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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, make sure that BCCH of neighbor cells are

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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Network Color CodeNCC

Definition: NCC is a part of BSIC. MS uses it to distinguish

adjacent BTS that belong to different GSM PLMN.

Format: NCC is composed of 3 bits, with the range of 0 to 7.



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BTS Color CodeBCC

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

to above sections.

Format: BCC is composed of 3 bits. The available range is 0~7.



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Idle Mode Parameters

ATT

CCCH Conf

BS_AG_BLKS_RES

BS_PA_MFRAMES

Paging Times

Period of Periodic Location Update(T3212)

Neighbor Cell Description (BA Table)


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ATT

Value Range: Yes, No

Default ValueYes

Description: It is Attach-detach allowed. It 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. Location: Cell Attributes/Idle Mode/Basic Idle Parameters


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CCCH Conf

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

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

compounding CCCHs.

Default Value: 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.

Description: It is Common Control Channel Configuration. CCCH

configuration determines the capacity of PCH, AGCH and RACH. This

parameter can be automatically configured by system according to the

TRX channel configuration.

Location: Cell Attributes/Idle Mode/Basic Idle Parameters


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BS_AG_BLKS_RES

Value Range: 0~7 (Non-Compounding CCCHs), 0~2 (1 combinedCCCH)

Unit: Block

Default Value: 2 (Non-combined CCCH), 1(1 combined CCCH)

Description: 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).



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BS_PA_MFRAMES

Value Range: 2~9

Unit: Multi-frame period (51 frames)

Default Value: 2 Multi-frame period

Description: It is Paging Channel Multi-frames. It defines thenumber of multi-frames used as a cycle of paging sub-channels.



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Paging Times

Value Range:1~8

Unit: Times

Default Value: 4

Description: This parameter is used for BTS to determine whetherpaging is resent. Together with the paging times configured in MSC,

they jointly control the paging resend times. The total paging times

are approximate to be the multiplication of the two.

Location: Cell Attributes/Call Control/Basic Call Control Parameters


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Period of Periodic Location Update(T3212)

Value Range: 0~255

Unit: 6 minutes

Default Value: 20

Description: It is the Periodic Location Update Timer. It definesthe interval of periodic location update.



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LA 1

LA 2

Definition of Location Update

Inform the system the LA (Location Area) where the MS is to be paged.


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LA 2

LA 3

Condition of Location Update

Periodical location update

Moving into a new LA

LA 1


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Procedure of Location Update

BSC

MSC

MS

1 Hour 1 Hour 1 Hour

++ ++ +


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Abnormal Occasion

LA 3

LA 2

LA 1

But I am always

powered on

The subscriber

you dialed has

been powered off


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Reason1 of Abnormal Occasion

BSC

MSC

MS

1 Hour 1 Hour1 Hour


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Reason2 of Abnormal Occasion

BSC

MSC

MS

1 Hour 1 Hour 1 Hour


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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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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.

Location: Cell Attributes/Idle Mode/Advanced

Table BA2 describes BCCH frequencies of the adjacent cells to

be measured when the MS is in dedicated mode.

Location: Cell Attributes/Handover data/Advanced


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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


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Call Control Parameters

MS MAX Retrans

TX-integer

RACH Min. Access Level

NCC Allowed

RLT

SACCH Multi-Frames

Common Access Control Class

Special Access Control Class

MBR

ECSC

Emergent Call Disable


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MS MAX Retrans

Value Range: 1, 2, 4, 7 Unit: Time(s)

Default Value: 4 Times

Description: 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.



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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)

Default Value: 32

Description: Used to calculate the number of timeslots in theinterval between multiple channel requests sent by MS.



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Calculation of S

STX-integer

Non-Combined CCCH Combined CCCH

3, 8, 14, 5055 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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RACH Min. Access Level

Value Range: -121~-47 Unit: dbm

Default Value: -115

Description: The parameter affects the access of an MS. That is to say,

the BTS determines the threshold of the level for the random access of

the MS. When the receive level of the RACH burst is lower than the

threshold, the BTS regards this access as an invalid access and no

decoding is performed. Only when the receive level for the burst

timeslot of the random access is greater than the threshold, the BTS

regards that this timeslot has an access request. Location: Cell Attributes/Call Control/Advanced/Access Control


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Radio Link Timeout

Value Range: 4~64, the step size is 4

Unit: SACCH period (480ms)

Default Value: 52

Description: This parameter is used for MS to decide downlinkdisconnection in case of SACCH decoding failures.



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Application of Radio Link Timeout

Impact of radio link timeout

A B

P Q

Poor coverage


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Radio Link Timeout

To increase the robustness of the SACCH channel, to improve theAMR network coverage performance, and to lower the call drop rate, in

practice the AMR FR/HR RLT should be set higher.

Normal Call Radio Link Timeout (SACCH period(480ms))

AMR FR AFR Radio Link Timeout (SACCH period(480ms))

AMR HR AHR Radio Link Timeout (SACCH period(480ms))

Default Value

52

Call Type Parameter

64

52


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SACCHMulti-Frames Value Range: 0~63

Unit: SACCH period (480ms)

Default Value: 31

Description: It is a timer used to determine whether the uplink radio link

connection fails. BSS judges the uplink radio link failure according to

uplink SACCH BER.

Every time BTS fails to decode the MR sent from MS, this timer decreases by 1;

Every time BTS succeeds to decode the MR, this timer increases by 2.

When this timer reaches 0, BTS judges that the uplink radio connection fails,

then BTS sends a radio connection failure message to BSC.

This parameter and the radio link timeout (RLT) are used to judge the

uplink/downlink radio connection failure.



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SACCHMulti-Frames

To increase the robustness of the SACCH channel, to improve the AMRnetwork coverage performance, and to lower the call drop rate, in practice

the AMR FR/HR SACCH Multi-Frames should be set higher.

Normal Call SACCH Multi-Frames (SACCH period(480ms))

AMR FR AFR SACCH Multi-Frames (SACCH period(480ms))

AMR HR AHR SACCH Multi-Frames (SACCH period(480ms))

Default Value

31

Call Type Parameter

48

32


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NCC Permitted

Value Range: Selection of 0~7 Perm.

Default Value: 11111111

Description: Network Color Code. It lists NCC that need be

measured by MS. If a neighbor cells NCC is permitted, MS willreport MRs of it to the network.



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Common Access Control Class

Value Range: Level 0~9 Forbidden


Description: 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.



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Special Access Control Class

Value Range: Level 10~14 Forbidden


Description: 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.



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MBR

Value Range: 0~3

Default Value: 0

Description: Multi-Band Reporting. It is used to inform MS to report

the adjacent cells in a controllable way.



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Application of MBR

-92dBm -82dBmA B

C -68dBm

D -90dBm

E -78dBm

F -88dBm

G -96dBm

H -84dBm

GSM1800

GSM900

S


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ECSC


Default Value: No

Description: Early Classmark Sending Control. It indicates if an MS

in the cell is allowed to use early Classmark sending.

Yes: The MS reports Classmark3 to the network immediately

after link setup.

No: The MS is forbidden to report its Classmark3 to network

initiatively.



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Definition of Classmark In GSM system, the abilities that MS supports, such as service ability,

band ability, power ability, encryption ability, is described by the classmark.

BSC decodes the information according to the requirement of network and

transfer to the network.

There are 3 kinds of classmark:Classmark1Classmark2Classmark3.

Network knows about abilities of MS either via inquiring for MSs

CLASSMARK or via requiring MS to report CLASSMARK3 immediately by

itself after link setup.


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Classmark Update Flow

For dual-band MS, after the SCCPconnection is established and before

receiving message "CM Service

Accepted" there will be a class mark

update flow.

CR message reports the information of

Classmrk 2. And in the class mark

update flow, MS will report Classmark

3 information which is related to the

dual-band capability.

Classmark Change

Classmark Enquiry

MS BSS MSC

Classmark Request

Classmark Update


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Information about Classmark 2/3


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Emergent Call Disable


Default Value: No

Description: Emergence Call Disable. When EC Disable is set to

No, it means emergency call is permitted. Otherwise it is

prohibited.



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Cell Selection/Reselection Parameters

RXLEV_ACCESS_MIN MS_TXPWR_MAX_CCH

CBQ (Cell_Bar_Qualify)

CBA (Cell_Bar_Access)

CRO (Cell Reselection Offset)

TO (Temporary Offset)

PT (Penalty Time)

PI (Cell Reselect Parameters Indication)

CRH ( Cell Reselection Hysteresis)


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Cell Selection Process

There are two kinds of cell selection

Stored list cell selection

Normal cell selection

In fact, the process might be different for different MSs


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Stored List Cell Selection

Search the BCCH which

have been stored

Normal cell selection

Can decode

any frequency?

Come into

idle mode

Yes

No

Can reside in

any cell ?

No Try to reside in its

neighbor cell?

Yes

No

Yes


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Normal Cell SelectionSearch all

frequency

Rank according to

receiving level

Come into

idle mode

Is it a BCCH carrier?

Right PLMN&C1>0&

priority isNormal ?

Select the next frequency

with the higher Rx_level

YES No

YES

Try the cell of other PLMN

allowed in the SIM card

Stay in a cell(RX-LEV is strongest, C1>0 ,

cell priority is not prohibited) without

considering the PLMN

All frequency not satisfy

No

YES

Emergency call

mode

Select the frequency with

the highest Rx_level

Decode SCH, read

cell para. on BCCH

No

All frequency not satisfy

No

No YES

Right PLMN&C1>0&

priority is Low ?


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Cell Selection Parameter

C1=RLA_C-RXLEV_ACCESS_MIN-

MAX((MS_TXPWR_MAX_CCH - P), 0)

RLA_C: Receiving level of MS

RXLEV_ACCESS_MIN: Minimum receiving level of MS permitted to access

MS_TXPWR_MAX_CCH: Maximum transmit power level of MSs

P: Maximum Physical supported transmitting power of MS.


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RXLEV_ACCESS_MIN

Value Range: 0~63 (-110 dBm ~ -47 dBm)

Default Value: 8

Description: It means the minimum receive signal level

required for MS to access a cell.



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MS_TXPWR_MAX_CCH

Value Range: 0~19

Unit: level

Default Value: 5 (900MHz cell),0 (1800/1900MHz cell)

Description: This parameter determines the maximum transmitpower level of the MS when it begins to access a cell and has

not yet received power control command.

Location: Cell Attributes/Other Attributes/Advanced/Public

Channel Control


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CBA

Value Range: 0, 1

Default Value: 0

Description: Cell_Bar_Access, worked together with CBQ to set

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

reselection.



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CBQ

Value Range: 0 , 1

Default Value: 0

Description: Cell_Bar_Qualify. CBQ only affects the cell

selection, but is not related to cell reselection. It works with CBA

to define the access priorities of cells.



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Application of CBA and CBQ

CBA CBQ Cell SelectionPriorityCell Reselection

Priority0 0 Normal Normal

1 0 Forbidden Forbidden0 1 Low Normal

1 1 Low Normal


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Application of CBQ

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

CBA=1, CBQ=0.

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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Cell Reselection Process Cell reselection for cells in the same location area

If the C2 value of the target cell is higher than that of the serving cell for longerthan 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 for longer than 5 seconds, a location update process and thecell 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.


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Cell Reselection Parameter

C2=C1+CRO-TO*H(PT-T) When PT is not equal to 31

C2=C1-CRO When PT is equal to 31

For neighbour cell:

H(PT-T)=0, when PT-T


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CRO Value Range: 0~63( the corresponding level value: 0~126dB,

stepped every 2dB).

Unit: 2dB

Default Value: 0

Description: 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).

Default Value: 0

Description: Cell Reselect Temporary Offset. It is a parameter in

C2 criterion to give a temporary modification within PT time.

Location: Cell Attributes/Idle Mode/Advanced/Idle Parameter


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PT

Value Range: 0~31(the corresponding time is 20~620s), 31(reserved forchanging the effect of CRO on C2)

Unit: Second

Default Value: 0

Description: Cell Reselect Penalty Time. It is used to ensure the safetyand validity of cell reselection because it helps to avoid frequent cell

reselection.

Location: Cell Attributes/Idle Mode/Advanced/Idle Parameter


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PI

Value Range: Yes , No

Default Value: Yes

Description: 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

Penalty Time(PT).



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CRH

Value Range: 0~14, the step size is 2dB

Unit: dB

Default Value: 6

Description: Cell Reselection Hysteresis. It is the parameter used

when cell reselection happens between two location areas.



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Other Parameters

Call Reestablishment Forbidden

TCH Immediate Assignment

Immediate Assignment Optimization

Direct Retry

Assignment Cell Load Judge Enable

Cell Direct Try Forbidden Threshold

Directed Retry Load Access Threshold

Min Power Level for Direct Try

Max Resend Times of Phy. Info. T3105

PWRC

Cell Extension Type

Max TA

Interference Band Threshold

Interference Calculation Period

UL DTX

DL DTX

T200 and N200

Use LAPDm N200


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Call Reestablishment Forbidden


Default Value: Yes

Description: Informing MS whether call reestablishment is

allowed or not.



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TCH Immediate Assignment


Default Value : No

Description: Option "Yes" means that TCH channel can be

immediately assigned as signaling and traffic channel when

SDCCH has no available resource. The option "No" means that

only SDCCH can be assigned.



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Immediate Assignment Optimization


Default Value : No

Description: This parameter is mainly used for satellite transmission,

i.e., to reduce the impact of satellite transmission delay.

Yes: when the Transmission Mode of the BTS is Satellite transmission

No: when the Transmission Mode of the BTS is Terrestrial transmission

Location: Cell Attributes/Call Control/Advanced/Call Control

Signaling Flow of Immediate


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Signaling Flow of Immediate

Assignment Optimization

MS BTS BSC MSC

Channel_req Channel_Required

Channel_ActiveChannel_Active_Ack

IMMEDIATE ASSIGN COMMAND

Establish_IND (CM Service Req)

CR(Complete_L3_

information)

CM Service Accepted

CC

(NOTE 1)

First SABM

UA

CHAN_ACT

IMM_ASS_CMD

MS BTS BSC


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Direct Retry


Default Value : Yes

Description: 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.



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Assignment Cell Load Judge Enable

Value Range: Enable, Disable Default Value: Disable

Description: When the Assignment Cell Load Judge Enabled is set

to Yes, the direct try flow is allowed if the following two conditions

are met:

The cell supports the direct retry function.

The load of the cell is larger than or equal to the Cell Direct Try

Forbidden Threshold.


C


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Cell Direct Try Forbidden Threshold

Value Range: 0~100(%) Unit: None

Default Value: 50

Description: If the parameterAssignment Cell Load Judge

Enabled is set to Yes, the direct retry process is started and

channels are assigned when the cell supports direct retry and the

load of the current cell is equal to or greater than the value ofCell

Direct Try Forbidden Threshold during channel assignment.

Location: Cell Attributes/Other Attributes/Advanced/Other

Parameters

Di d R L d A Th h ld


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Directed Retry Load Access Threshold

Value Range: 0~100(%) Unit: None

Default Value : 85

Description: This parameter is used to adjust the candidate target

cells during direct retry.

When target cells are selected during direct retry, only the cells whose

loads are smaller than or equal to the DirectedRetryLoadAccess

Threshold are selected as candidate target cells.


Mi P L l f Di t T


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Min Power Level for Direct Try

Value Range: 0~63 (-110dBm~-47dBm)

Default Value :16

Description: This parameter indicates the selection of candidate cell

for direct try. If the receiving level of the cell exceeds the value of

this parameter, this cell can be selected as candidate target cells.

Location: Cell Attributes/ Handover Data/Advanced/HO Control

M R d Ti f Ph I f


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Max Resend Times of Phy. Info.

Range Value :1~255

Unit: Times

Default Value :30

Description: This parameter specifies the maximum times Ny1 for re-

sending physical information.

If the number of resending times exceeds Ny1 and BTS still has not

received any correct SAMB frame from MS, BTS will send BSC the

connection failure message and handover failure message.

After BSC receives the messages, it will release the newly assigned

dedicated channel and stop timer T3105.

Location: Cell Attributes/Handover Data/Advanced/Cell HO Data

T3105


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T3105

Range Value : 0~255

Unit: 10ms

Default Value : 7

Description: When BTS sends physical information to the MS,

the BTS starts the timer T3105. If the timer T3105 times outbefore receive the SAMB frame from MS, BTS re-sends physical

information to MS and restarts the timer T3105.

Location: Cell Attributes/Handover Data/Advanced/Cell HO Data

I t BSC H d Si li Fl


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Intra-BSC Handover Signaling Flow

MS BTS1 BSC BTS2 MS MSC

Channel_ActiveChannel_Active_Ack

Measure Report from MS

HANDOVER COMMANDHandover Access

Handover_DetectPHYINFO

PHYINFO

First SABM

Establish_IND

HANDOVER COMPLETE

Handover_Performed

UA

PWRC


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PWRC

Value range: Yes, No.

Default Value: Yes

Description: It is used to indicate MS whether to delete received level value

obtained from the timeslots ofBCCH 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 in

consideration.

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

Location: Cell Attributes/Other Attributes/Advanced/Public Channel Control

C ll E t i T


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Cell Extension Type

Value Range: Normal cell, Double TS Ext cell Default Value: Configure this parameter according to the

practical situation.

Description: It indicates whether a cell is an extended cell and

the extended cell mode.


M TA


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Max TA Value Range:

0~63 (Normal cell)

0~255 (Double TS Ext cell)

Unit: Bit period (1 bit = 0.55km)

Default Value

62 for normal cell

219 for dual TS extended cell

Description: Maximum Time Advance. It determines the actual coverage

area of BTS. When BTS receives the channel request message, it

determines whether channel assignment should take place in the currentcell by comparing the TA with the value of this parameter.


Interference Band Threshold 0~5


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Value Range: 110~85

Unit: -dBm

Default Values

110 ( Interference band threshold 0)


98 ( Interference band threshold 2 )




Description: It decides the corresponding value for each interference

band (from band 0 to band 5) and used to measure the uplink

interference during the SDCCH/TCH(F)/TCH(H) timeslot is in idle mode.

Location: Cell Attributes/Other Attributes/Advanced/Other Parameters



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Value range: 1~31

Unit: SACCH period (480 ms)

Default Values: 20

Description: Before the BTS transmits the radio resource indication

message to the BSC, the interference levels measured on idle channels in

the period defined by this parameter are averaged. The average

interference level is used to classify the interference levels on idle channels

into five interference bands. A too big value of this parameter cannot reflect

the change of interference. A too small value of this parameter wastes the

resources.

Location: Cell Attributes/Other Attributes/Advanced/Other Parameters

UL DTX


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UL DTX

Value Range: May use, Shall use, Shall not use Default Value: Shall use

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

shows the DTX state of the MS in the previous measurement period.


DL DTX


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DL DTX

Value range: Yes, No

Default Value: Yes

Description: This parameter indicates whether downlink DTX

is used in a cell. The use of downlink DTX is also controlled by

the DTX switch in the MSC. If downlink DTX is forbidden in theMSC, 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.


T200 and N200


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T200 and N200 T200 :

T200 timers are used to avoid deadlock during data transfer on the data link layer. On the LAPDm layer, every time a message is sent, the opposite end is

requested to acknowledge the reception. If this message is lost for unknown

reasons, it will occur that both ends keep waiting, leading to system deadlock.

Therefore, a timer should be started when the sender sends a message. If the

timer times out, the sender will regard that the receiver has not received themessage and will resend the message.

N200

The maximum resend times are determined by N200.

Different timer values should be set for different LAPDm channels such as

SDCCH, FACCH and SACCH. This is because these channels have differenttransmission rate.

Location: Cell Attributes/Call Control/Advanced/Timer

Use LAPDm N200


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Use LAPDm N200

Range: Yes, No

Default Value : No

Description: Determines whether BSC delivers LAPDm N200

parameters to BTS. If it configured as Yes, then LPADm N200

parameters will be delivered to BTS, otherwise not.

Location: Cell Attributes/Call Control/Advanced/Timer

Cell Data Mapping in Different Statuses of MS


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Power on

BA2 / RLT / MBR

NCC Allowed / PWRC

Emergent Call Disabled

Call Re-establishmentForbidden

UL DTX / DL DTX

SACCH Multi-Frames

Max Resend Times of

Phy. Info. / T3105

Max TA

T200 and N200

Use LAPDm N200TCH immediate

assignment

Immediate assignment

optimization

Direct Retry Para.

MS MAX Retrans/ ECSCTX-integer / RACH Min. Access Level

Common/Special Access Control Class

CGI, BSIC

ATT

T3212

CCCH Conf

BS_AG_BLKS_RES

BS_PA_MFRAMES

Paging Times

C2 (CRO,TO,PT,PI)

CRHDSC

C1(RXLEV_ACCESS_MIN/

MS TXPWR_MAX_CCH)

CBA, CBQ

BA1

Interference

Band Threshold/

Interference

Calculation

Period

pp gSelect Network

(Network Identity

Para. )

Cell Selection

(Cell Selection

Para.)

Access Network


Idle Mode

(Idle Mode Para.)

Paging Mode

(Idle Mode Para.)

Cell Reselection Mode

(Cell Reselection Para.)

Dedicated Mode


Descriptions


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Descriptions



3. Case Study

Case 1: Island Effect


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Case 1: 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 for each other. The coverage problem is thus solved.

C

BA-92

-80 -95

Case 2: Incorrect CGI Causes MS


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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.

Default Value 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.

Case 3: RXLEV_ACCESS_MIN


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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.

Default Value and summary

In area with complicated coverage, the RXLEV_ACCESS_MIN of

each cell should be kept same.

Case 4Too Small T3212 Causes


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MS Lose Connection with Network

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 urban area increased.

Handling procedure

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

MSC to 180 minutes. Two days observation shows no subscriber

complaint and the problem is solved.


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Documents

80139282 Omf810001 Gsm Cell Parameters Issue1 0