Omf810001 Gsm Cell Parameters Issue1.0

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GSM Cell Parameters

Page2Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.

Descriptions

1. Cell Parameters Overview

2. Cell Parameters Introduction

3. Case Study


Cell Parameters Overview

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 more and better services although basing on limited resources.


Cell Parameters Overview Cell Parameters can be sent through two kinds of logical channels

BCCH (in idle mode)

SACCH (in dedicated mode)


Descriptions



3. Case Study


Introduction to Cell Parameters

Huawei GSM cell parameters:

Network Identity Parameters

Idle Mode Parameters

Call Control Parameters

Cell Selection and Reselection Parameters

Other Parameters


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(Call Control Para.)

Cell Reselection Mode(Cell Reselection Para.)

Idle Mode(Idle Mode Para.)


Network Identity Parameter — CGI Network identity parameters mainly include

Cell Global Identity (CGI)

Base Station Identity Code (BSIC)


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.


Mobile Country Code （ MCC ） 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


Mobile Network Code （ MNC ） 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.



Location Area Code （ LAC ） 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.



Cell Identity （ CI ） 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.



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 cell’s BCCH to reduce the

interference.

Practically it is still possible that a same BCCH is re-used in

the surrounding cells. For cells using the same BCCH in a

relevant near distance, their BSIC must be different so that

MS can identify two neighbor cells with same BCCH.


Network Color Code （ NCC ） 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.



BTS Color Code （ BCC ） 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.



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)


ATT Value Range: Yes, No Default Value ： Yes 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


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.



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

d CCCH) 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).



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

the number of multi-frames used as a cycle of paging

sub-channels.



Paging Times Value Range:1~8

Unit: Times

Default Value: 4

Description: This parameter is used for BTS to determine

whether paging 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


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

defines the interval of periodic location update.



LA 1

LA 2

Definition of Location Update

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


LA 2

LA 3

Condition of Location Update Periodical location update

Moving into a new LA

LA 1


Procedure of Location Update

BSC

MSC

MS

1 Hour

1 Hour

1 Hour

++ ++ +


Abnormal Occasion

LA 3

LA 2

LA 1

But I am always powered on

The subscriber you dialed has been powered off


Reason1 of Abnormal Occasion

BSC

MSC

MS

1 Hour

1 Hour

1 Hour


Reason2 of Abnormal Occasion

BSC

MSC

MS

1 Hour

1 Hour

1 Hour


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”


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


Theoretical Neighbor Cells Actual Neighbor Cells

B

CA

D

B

CA

D

Application of Neighbor Cell Description


B

C

A

A

Application of Neighbor Cell Description


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


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. M

S MAX Retrans is the upper limit of times that MS is allowed to send “Channel Request” in one immediate assignment procedure.

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


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

the interval between multiple channel requests sent by

MS.



Calculation of S

STX-integer

Non-Combined CCCH 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


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 sa

y, 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


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

downlink disconnection in case of SACCH decoding failures.


Parameters


Application of Radio Link Timeout

Impact of radio link timeout

A BP Q

Poor coverage


Radio Link Timeout To increase the robustness of the SACCH channel, to improve

the AMR 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


SACCH Multi-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.

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


SACCH Multi-Frames To increase the robustness of the SACCH channel, to improve the AMR

network 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


NCC Permitted

Value Range: □Selection of 0~7 Perm. Default Value: 11111111 Description: Network Color Code. It lists NCC that need be mea

sured by MS. If a neighbor cell’s NCC is permitted, MS will report MRs of it to the network.



Common Access Control Class

Value Range: □Level 0~9 Forbidden

Default Value: 0000000000

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.


Parameters


Special Access Control Class

Value Range: □ Level 10~14 Forbidden

Default Value: 00000

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.


Parameters


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.


Parameters


Application of MBR

-92dBm -82dBmA B

C -68dBm

D -90dBm

E -78dBm

F -88dBm

G -96dBm

H -84dBm

GSM1800

GSM900

S


ECSC Value Range: Yes, No Default Value: No Description: Early Classmark Sending Control. It indicates if an MS i

n the cell is allowed to use early Classmark sending. Yes: The MS reports Classmark3 to the network immediately afte

r link setup. No: The MS is forbidden to report its Classmark3 to network initi

atively. Location: Cell Attributes/Call Control/Basic Call Control Parameter

s


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

and 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:Classmark1 、 Classmark2 、 Classmark3.

Network knows about abilities of MS either via inquiring for MS’s CLASSMARK or via requiring MS to report CLASSMARK3 immediately by itself after link setup.


Classmark Update Flow For dual-band MS, after the SCCP co

nnection 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


Information about Classmark 2/3


Emergent Call Disable

Value Range: Yes, No

Default Value: No

Description: Emergence Call Disable. When EC Disable is

set to “No”, it means emergency call is permitted.

Otherwise it is prohibited.


Parameters


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)


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


Stored List Cell Selection

Search the BCCH which have been stored

Normal cell selectionCan 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


Normal Cell SelectionSearch all frequency

Rank according to receiving level

Come into idle mode

Is it a BCCH carrier?

Right PLMN&C1>0& priority is Normal ?

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 conside

ring 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 ?


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.


RXLEV_ACCESS_MIN

Value Range: 0~63 (-110 dBm ~ -47 dBm) Default Value: 8 Description: It means the minimum receive signal level r

equired for MS to access a cell. Location: Cell Attributes


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

transmit power 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


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.



CBQ Value Range: 0 , 1 Default Value: 0 Description: Cell_Bar_Qualify. CBQ only affects the cell select

ion, but is not related to cell reselection. It works with CBA to define the access priorities of cells.



Application of CBA and CBQ

CBA CBQCell Selection

PriorityCell Reselection

Priority

0 0 Normal Normal

1 0 Forbidden Forbidden

0 1 Low Normal

1 1 Low Normal


Application of CBQ

The traffic of cell A and B is heavy. Set these two cells with CBA=“1”, CBQ=“0”.

A B


Application of CBA

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

BA


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 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 lea

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

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

If current serving cell is prohibited, or down link fails, or C1 is less than 0 continuously for 5s, cell reselection will also be triggered.

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


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<0

H(PT-T)=1, when PT-T ≥ 0

For serving cell:

H(PT-T) = 0


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.



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


PT

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

Unit: Second

Default Value: 0

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

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


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)”.



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.



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


Call Reestablishment Forbidden Value Range: Yes, No

Default Value: Yes

Description: Informing MS whether call

reestablishment is allowed or not.



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.



Immediate Assignment Optimization Value Range: Yes, No

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 Assignment Optimization

MS BTS BSC MSC

Channel_req Channel_Required

Channel_Active

Channel_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


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.



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.


Parameters


Cell Direct Try Forbidden Threshold Value Range: 0~100(%)

Unit: None

Default Value: 50

Description: If the parameter Assignment 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 of Cell Direct Try

Forbidden Threshold during channel assignment.

Location: Cell Attributes/Other Attributes/Advanced/Other

Parameters


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 Directed Retry Load Access

Threshold are selected as candidate target cells.


Parameters


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


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 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 out before 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


Intra-BSC Handover Signaling FlowMS BTS1 BSC BTS2 MS MSC

Channel_Active

Channel_Active_Ack

Measure Report from MS

HANDOVER COMMAND

Handover AccessHandover_Detect

PHYINFO

PHYINFO

First SABM

Establish_IND

HANDOVER COMPLETE

Handover_Performed

UA


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 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 in consideration.

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

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

Control


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.



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 current cell by comparing the TA with the value of this parameter.



Interference Band Threshold 0~5 Value Range: 110~85 Unit: -dBm Default Values

110 ( Interference band threshold 0) 105 ( Interference band threshold 1) 98 ( Interference band threshold 2 ) 92 ( Interference band threshold 3 ) 87 ( Interference band threshold 4 ) 85 ( Interference band threshold 5)

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


Interference Calculation Period 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

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 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 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.



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 the message 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, F

ACCH and SACCH. This is because these channels have different transmission rate. Location: Cell Attributes/Call Control/Advanced/Timer


Use LAPDm N200 Range: Yes, No Default Value : No Description: Determines whether BSC delivers LAPDm N200 pa

rameters 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


Power on

BA2 / RLT / MBRNCC Allowed / PWRC Emergent Call DisabledCall Re-establishment ForbiddenUL DTX / DL DTXSACCH Multi-FramesMax Resend Times of Phy. Info. / T3105 Max TAT200 and N200Use LAPDm N200TCH immediate assignmentImmediate assignment optimization Direct Retry Para.

MS MAX Retrans / ECSCTX-integer / RACH Min. Access LevelCommon/Special Access Control Class

CGI, BSIC

ATTT3212CCCH ConfBS_AG_BLKS_RESBS_PA_MFRAMESPaging Times

C2 (CRO,TO,PT,PI)CRHDSC

C1(RXLEV_ACCESS_MIN/MS TXPWR_MAX_CCH)CBA, CBQ

BA1InterferenceBand Threshold/Interference Calculation Period

Cell Data Mapping in Different Statuses of MS

Select Network(Network Identity

Para. )

Cell Selection(Cell Selection

Para.)

Access Network(Call Control Para.)

Idle Mode(Idle Mode Para.)

Paging Mode(Idle Mode Para.)

Cell Reselection Mode(Cell Reselection Para.)

Dedicated Mode(Call Control Para.)


Descriptions



3. Case Study


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 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 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 4 ： Too Small T3212 Causes 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.

Thank youwww.huawei.com

Documents

Omf810001 Gsm Cell Parameters Issue1.0