2G Planning & Optimization - Part-4

8/13/2019 2G Planning & Optimization - Part-4

1/62

2G, 3G Planning & Optimization

ventinel Page 1


Part 4

GSM Parameter Configuration and Adjustment


2/62


ventinel Page 2

Contents

4 GSM Parameter Configuration and Adjustment .................................................................................... 5

4.1 Network and Cell ID ....................................................................................................................... 5

4.1.1 Cell Global ID........................................................................................................................... 5

4.1.2 Base Station Identity Code ...................................................................................................... 7

4.2 Paging and Access Control Parameters .......................................................................................... 8

4.2.1 Number of Access Grant Reserved Blocks (BS_AG_BLK_RES or AG)......................................... 8

4.2.2 Frame Number Coding Between Identical Paging ................................................................... 9

4.2.3 Common Control Channel Configuration (CCCH-CONF) ......................................................... 10

4.2.4 Extended Transmission Slots (TX_INTEGER) .......................................................................... 12

4.2.5 Minimum Access Level of RACH ............................................................................................ 13

4.2.6 Random Access Error Threshold ........................................................................................... 14

4.2.7 Access Control Class (ACC) .................................................................................................... 15

4.2.8 Maximum Retransmission Times (RET) ................................................................................. 16

4.2.9 Control Class of MS Maximum Transmit Power (MS-TXPWR-MAX-CCH)................................ 17

4.2.10 Power Offset (POWEROFFSET) ............................................................................................ 18

4.2.11 IMSI Attach/Detach Allowed............................................................................................... 18

4.2.12 Direct Retry (DR) ................................................................................................................ 19

4.3 Serial Parameters of Cell Selection and Reselection..................................................................... 20

4.3.1 cell_bar_access .................................................................................................................... 20

4.3.2 cell_bar_qualify .................................................................................................................... 20

4.3.3 Minimum Received Level Allowing MS to Access (RXLEV_ACCESS_MIN) ............................... 22

4.3.4 Additional Reselection Parameter Indicator .......................................................................... 22

4.3.5 Cell Reselection Parameter Indicator .................................................................................... 23

4.3.6 Cell Reselection Offset, Temporary Offset, and Penalty Time ................................................ 23

4.3.7 Cell Reselection Hysteresis (CRH).......................................................................................... 25

4.4 Parameters Affecting Network Functions .................................................................................... 26

4.4.1 Newly Established Cause Indicator (NECI) ............................................................................. 26


3/62


ventinel Page 3

4.4.2 Power Control Indicator (PWRC) ........................................................................................... 27

4.4.3 Discontinuous Transmit of Uplink ......................................................................................... 28

4.4.4 Discontinuous Transmit of Downlink .................................................................................... 28

4.4.5 Call Resetup Allowed ............................................................................................................ 29

4.4.6 Emergency Call Allowed ....................................................................................................... 29

4.4.7 Early Classmark Sending Control ........................................................................................... 30

4.5 Frequency Hopping Parameters .................................................................................................. 31

4.5.1 Frequency Hopping Sequence Number ................................................................................. 31

4.5.2 Mobile Allocation ................................................................................................................. 32

4.5.3 Mobile Allocation Index Offset ............................................................................................. 32

4.6 Distance Control Parameters....................................................................................................... 33

4.6.1 Call Clearing ......................................................................................................................... 33

4.6.2 TA Handover Threshold (MSRANGEMAX) ............................................................................. 33

4.6.3 TA Restriction (MS_BS_DIST_USED) ...................................................................................... 34

4.7 Radio Link Failure Process and Parameters .................................................................................. 34

4.7.1 Radio Link Failure Counter (RLC or Radio Link Timeout) ........................................................ 35

4.7.2 SACCH Multiframe (RLTO_BS) ............................................................................................... 36

4.8 Handover and Related Parameters .............................................................................................. 37

4.8.1 PBGT Handover Threshold (HoMargin) ................................................................................. 37

4.8.2 Minimum Downlink Power of Handover Candidate Cells (rxLevMinCell) ............................... 37

4.8.3 Handover Threshold at Uplink Edge ...................................................................................... 38

4.8.4 Handover Threshold at Downlink Edge ................................................................................. 38

4.8.5 Downlink Quality Restriction of Emergency Handover .......................................................... 39

4.8.6 Uplink Quality Restriction of Emergency Handover ............................................................... 39

4.8.7 Uplink Quality Threshold of Interference Handover .............................................................. 40

4.8.8 Downlink Quality Threshold of Interference Handover ......................................................... 40

4.8.9 Uplink Received Power Threshold of Interference Handover ................................................ 41

4.8.10 Downlink Received Power Threshold of Interference Handover .......................................... 41

4.8.11 Maximum Repeated Times of Physical Messages (NY1) ...................................................... 42

4.8.12 Multiband Indicator (multiband_reporting) ........................................................................ 43

4.8.13 Permitted Network Color Code (ncc permitted) .................................................................. 44


4/62


ventinel Page 4

4.9 Power Control and Related Parameters....................................................................................... 45

4.9.1 Maximum Transmit Power of MS (MSTXPWRMX) ................................................................. 45

4.9.2 Received Level Threshold of Downlink Power Increment (LDR) ............................................. 46

4.9.3 Received Level Threshold of Uplink Power Increment (LUR) ................................................. 47

4.9.4 Received Quality Threshold of Downlink Power Increment (LDR) .......................................... 47

4.9.5 Received Quality Threshold of Uplink Power Increment (LUR) .............................................. 48

4.9.6 Received Level Threshold of Downlink Power Decrement (UDR) ........................................... 49

4.9.7 Received Level Threshold of Uplink Power Decrement (UUR) ............................................... 50

4.9.8 Received Quality Threshold of Downlink Power Decrement (UDR)........................................ 50

4.9.9 Received Quality Threshold of Uplink Power Decrement (UUR) ............................................ 51

4.9.10 Power Control Interval (INT) ............................................................................................... 52

4.9.11 Power Increment Step (INC) ............................................................................................... 52

4.9.12 Power Decrement Step (RED) ............................................................................................. 53

4.10 Systematic Important Timers .................................................................................................... 53

4.10.1 T3101 ................................................................................................................................. 53

4.10.2 T3103 ................................................................................................................................. 54

4.10.3 T3105 ................................................................................................................................. 54

4.10.4 T3107 ................................................................................................................................. 55

4.10.5 T3109 ................................................................................................................................. 55

4.10.6 T3111 ................................................................................................................................. 56

4.10.7 Parameter T3212 ................................................................................................................ 56

4.10.8 T3122 ................................................................................................................................. 58

4.10.9 T3124 ................................................................................................................................. 58

4.10.10 T11 ................................................................................................................................... 59

4.10.11 T200 ................................................................................................................................. 60

4.10.12 N200 ................................................................................................................................ 61


5/62


ventinel Page 5

4 GSM Parameter Configuration and Adjustment

When operators prepare to construct a mobile communication network, they must predict

coverage according to traffic prediction and local radio propagation environment. Thisguides project design of the system and parameter configuration of radio network.

The project design includes the following aspects:

Network topology design

Selecting the location of base station

Frequency planning

Cell parameter configuration

The RF planning determines the coverage range of a cell, and the serving range of the cell is

determined based on the combination of RF planning and cell parameter configuration. By

this, the MS always enjoys optimal services and maximum network capacity at the best cell.

This chapter discusses the meaning and effect of important parameters in GSM radio

communication. Mastering the effect and impact of these parameters helps to configure

network parameters and optimize the network in later stages.

In a GSM network, abundant radio parameters are configured according to cells or partial

areas; however, the parameter configuration might affect neighbor areas. Therefore, while

configuring and adjusting parameters, you must pay attention to the impact of configuring

parameters on other areas, especially neighbor areas.

4.1 Network and Cell ID

4.1.1 Cell Global ID

I. Definition

GSM is a global cellular mobile communication system. To ensure that each cell

corresponds to a unique ID globally, the GSM system numbers the following items:

Each GSM network in each country

Each location area

Each base station

Each cell

Numbering the previous items aims as follows:

An MS can identify the serving network so that the MS can select a network in

any environment.

The network can obtain the precise location of the MS so that the network can

process various service requests involving the MS.


6/62


ventinel Page 6

The MS can report information about neighbor cells to the network during

calling to avoid call drop.

The cell global identity (CGI) is a major network identity parameter. CGI consists of location

area identity (LAI) and cell identity (CI). LAI includes mobile country code (MCC), mobile

network code (MNC), and location area code (LAC).

The system transmits CGI information through system information (SI) transmitted by cell

broadcast. When an MS receives SI, it demodulates SI for CGI information. The MS judge

whether to camp on the cell according to the MCC and MNC. It also judges whether the

current location area changes to determine updating location. While updating location, the

MS reports LAI information to the network so that the network can know the location area

of the MS.

II. Format

The CGI is MCC-MNC-LAC-CI, with details as follows:

MCC consists of three decimal digits, ranging from 000 to 999.

MNC consists of two decimal digits, ranging from 00 to 99.

LAC ranges from 0 to 65535

CI ranges from 0 to 65535.

III. Configuration and Influence

As a globally unique mobile identity, the MCC is uniformly distributed and managed by

international telecommunication union (ITU). The MCC for China is 460 (decimal).

The MNC is uniformly distributed by state telecommunication management organs. Now

two GSM networks exist in China. The MNC for China Mobile is 00. The MNC for ChinaUnicom is 01.

The method for coding LAC is ruled by each country accordingly. This caters for China also

(refer to GSM system from Ministry of Information Industry). At the early stage of network

construction, the LAC is coded and distributed. The LAC is seldom changed in the later

stages.

The coverage areas related to the LAC is vital in the network. You can configure it as great

as possible.

No special restriction is on the distribution of CI. The CI ranges from 0 to 65535 (decimal). It

must be ensured that two equivalent CIs exist in the same location area. This is determinedin the system design. Except for special situations (such as constructing base stations), the

CI must not be changed during the system operation.

IV. Precautions

You must pay attention to the following aspects:

The MNC is unchangeable.


7/62


ventinel Page 7

While configuring the LAC, you must follow related regulations. Equivalent

LACs must not exist in the state network.

Equivalent CIs must not exist in the same location area.

4.1.2 Base Station Identity Code

I. Definition

In a GSM network, each base station corresponds to a distributed local color code, called

base station identity code (BSIC). When the MS receives broadcast control channel (BCCH)

carriers of two cells at the same time, with same channel number, the MS distinguishes

them by BSIC.

In network planning, the BCCH carriers of neighbor cells are different in frequency to

reduce intra-frequency interference. The cellular communication system features that the

BCCH carrier might be reused. Therefore, the BSIC of the cells with the same BCCH carrier

must be different.

The system transmits BSIC on synchronization channel (SCH) of each cell. The effect of BSIC is as follows:

The BSIC involves in decoding process of random access channel (RACH) to

prevent base stations from connecting to the RACH sent to the neighbor cells

by the MS by error.

After the MS receives SCH messages, it judges that it has been synchronous to

the cell. Decoding information on the downlink common signaling channel

correctly requires training sequence code (TSC) used on common signaling

channel.

GSM regulations describe TSC in eight fixed formats, and the sequence numberof them is 07. The cell BCC determines the TSC used by the common signaling

channel of a cell. Therefore the BSIC helps inform the MS of the TSC used by the

common signaling channel of the serving cell.

In a call, the MS must measure the level of BCCH carrier of neighbor cells and

report it to the base station according to regulations to neighbor cell list of

BCCH. Meanwhile, the MS must provide measured BSIC of the carrier in the

uplink measurement reports. When the neighbor cells of a cell include two or

more cells with the same BCCH carrier, the base station can distinguish the cells

by BSIC to avoid incorrect handover.

In a call, the MS must measure signals of neighbor cells, and sends

measurement reports to the network. The measurement report can contain

information about six neighbor cells only, so the MS must be controlled to

report the cells actually related to handover. The first three digits of BSIC

(namely, NCC) aims as previously mentioned. Operators control the MS to

report the neighbor cell information permitted by the serving cell NCC by

broadcast parameters NCC permitted.


8/62


ventinel Page 8

II. Format

The BSIC is NCC-BCC, with details as follows:

The NCC ranges from 0 to 7.

The BCC ranges from 0 to 7.III. Configuration and Influence

Usually different GSM PLMNs use the same frequency resource, but, to some degree, their

network planning is independent. The neighbor GSM PLMNs use different NCCs according

to regulations. This ensures that the neighbor base stations with same frequency use

different BSICs.

The BCC is part of the BSIC. It helps identify different base stations with same BCCH carrier

number in the same GSM PLMN. The values of BCC must meet the previous requirements.

According to GSM regulations, the TSC of cell BCCH carrier must be same as that of cell BCC.

The equipment providers must ensure the TSC consistency.

IV. Precautions

The neighbor cells or cells nearby using the same BCCH carrier must use different BSICs.

Especially when two or more cells use the same BCCH carrier in the neighbor cell list of a

cell, theses cells must use different BSIC. Pay attention to cells at the bordering areas

between provinces and cities, and otherwise cross-cell handover might fail and abundant

mistaken access problems might occur.

4.2 Paging and Access Control Parameters

4.2.1 Number of Access Grant Reserved Blocks (BS_AG_BLK_RES or AG)

I. Definition

The common control channel consists of access grant channel (AGCH) and paging channel

(PCH).

For different CCCHs, each BCCH multiframe (including 51 frames) contains CCCH message

blocks different number. The CCCH is shared by AGCH and PCH. According g to regulations,

partial message blocks on CCCH are especially reserved for AGCH. This avoids that the

AGCH messages are blocked when the PCH traffic is great.The number of parameter access grant reserved blocks (AG) refers to the number of

message blocks reserved for AGCH on CCCH in each BCCH multiframe.

II. Format

The AG ranges from 0 to 2 when CCCH shares physical channel (CCCH_CONF = 1) with

stand-alone dedicated control channel (SDCCH).


9/62


ventinel Page 9

The AG ranges from 0 to 5 when CCCH does not share physical channel (CCCH_CONF=0)

with stand-alone dedicated control channel (SDCCH).


When the channel combination of the cell is fixed, the parameter AG adjusts the ratio ofAGCH and PCH in CCCH. When the PCH is idle, it can send immediate assignment messages.

The AGCH does not transmit paging messages. Equipment operators can balance AGCH and

PCH by adjusting AG, with the following principles.

The principle for AG value is that based on no overload of AGCH, you must reduce the

parameter to shorten the time for MS to respond to paging, and to improve system service

performance. When the immediate assignment messages are superior to paging messages

to be sent, configure AG to 0.

The value of AG is recommended as follows:

AG is 1 when the CCCH and SDCCH share a physical channel.AG is 2 or 3 in other situations.

In network operation, take statistics of overload situations of AGCH and adjust AG

accordingly. By default the immediate assignment messages are superior to paging

messages to be sent in the network, so you need not reserve a channel for immediate

assignment messages. In this situation, configure AG to 0.

4.2.2 Frame Number Coding Between Identical Paging

Frame number coding between identical paging is BS_PA_MFRMS (MFR for short).

I. Definition

According to GSM regulations, each MS (corresponding to an IMSI) belongs to a paging

group (for calculation of paging groups, see GSM regulation 05.02). Each paging group in a

cell corresponds to a paging subchannel. According to its IMSI, the MS calculates the paging

group that it belongs to, and then calculates the location of paging subchannel that belongs

to the paging group. The MS only receives the signals of the paging subchannel that it

belongs to, and neglects that of other paging subchannels. In addition, the MS even powers

off some hardware of itself during other paging subchannel to lower power cost of itself.

The number of paging channel multiframe (MFR) is the number of multiframes used in a

period of paging subchannel. The MFR determines the number of paging subchannels that

the cell PCH is divided into.

II. Format

The MFR ranges from 2 to 9, which respectively means that the same paging group cycles in

a period of 2 to 9 multiframes.


10/62


ventinel Page 10


According to the definition of CCCH, AG, and MFT, you can calculate the number of paging

channel in each cell.

When the CCCH and SDCCH share a physical channel, there is (3 - AG)MFRs.

When the CCCH and SDCCH share a physical channel, there is (9 - AG)

MFRs.

According to the previous analysis, the greater the MFR is, the more the paging channels of

the cell are (see the calculation of paging groups in GSM regulation 05.02). Theoretically,

the capacity of paging channels does not increase with the increase of MFR. The number of

buffers for buffering paging messages on each base transceiver station (BTS) increases. The

paging messages are sent more evenly both in time and space, so it seldom occurs that the

paging messages overflow in the buffers so call lost occurs (related to functions by

equipment providers).

However, to enjoy the previous advantages, you will have a longer delay of paging

messages on the radio channels. The greater the MFR is, the greater the delay of paging

messages in the space is, and the lower the average service performance of the system is.

Therefore, the MFR is an important parameter in network optimization.

The following principle caters for configuring MFR:

The configured strategy for buffers of each equipment provider is different, so you must

select the MFR properly so that the paging messages do not overflow on PCH. Based on

this, configure the parameter as small as possible. In addition, you must measurement the

overflow situations of PCH periodically while the network is running, and adjust MFRaccordingly.

IV. Precautions

Any paging message of the same location area must be sent to all cells in the location areas

at the same time, so the PCH capacity of each cell in the location area must be equivalent or

close to each other. Otherwise, you must consider smaller PCH capacity as the evidence for

designing location area.

4.2.3 Common Control Channel Configuration (CCCH-CONF)

I. Definition

The CCCH includes AGCH and PCH. It sends immediate assignment messages and paging

messages. In each cell, all traffic channels (TCHs) share CCCH. According to the TCH

configuration and traffic model of the cell, the CCCH can be one or more physical channels.

In addition, the CCCH and SDCCH share a physical channel. The combination methods for

CCH are determined by CCCH parameter CCCH_CONF.


11/62


ventinel Page 11

II. Format

The CCCH_CONF consists of three bits, with the coding methods listed in CCCH configuration coding

CCCH configuration coding

CCCH_CONF MeaningNumber of CCCH message blocks in a

BCCH multiframe

000One physical channel for used

for CCCH, not shared with

SDCCH9

001One physical channel for used

for CCCH, shared with SDCCH3

010Two physical channels for used


SDCCH

18

100Three physical channels for

used for CCCH, not shared with

SDCCH27

110Four physical channels for used


SDCCH36


When the CCCH and SDCCH share one physical channel, the CCCH has the minimum

channel capacity. When the CCCH and SDCCH do not share a physical channel, the morephysical channels that the CCCH uses, the greater the capacity is.

The CCCH_CONF is determined by the operators based on combination of cell traffic model

and paging capacity of the location area where a cell belongs to. It is determined in system

design, and adjusted in network expansion. According to experiences, when the paging

capacity in the location area is not high and cell has one or two carriers, it is recommended

that the CCCH uses one physical channel and share it with SDCCH (in combination CCCH

methods). This spares a physical channel for paging. Otherwise, the method that CCCH and

SDCCH do not share one physical channel is used.

When the cell TRX exceeds 6 and CCCH OVERLOAD occurs in the cell, it is recommended

that the CCCH uses two or more basic physical channel and does not share them with

SDCCH.

IV. Precautions

The CCCH_CONF must be consistent with the actual configuration of cell CCCH. In addition,

you must consider the influence on the access grant reserved blocks.


12/62


ventinel Page 12

4.2.4 Extended Transmission Slots (TX_INTEGER)

I. Definition

In a GSM network, a random access channel (RACH) is an ALOH. To reduce the conflicting

times on RACH when an MS accesses the network, and to increase RACH efficiency, GSM

regulations (sections 3.3.1.2 of 04.08) prescribe the compulsory access algorithm for MS.

The algorithm defines three parameters as follows:

Extended transmission slots T

Maximum retransmission times RET

T

It is the number of slots between two sending when the MS keeps sending

multiple channel request messages.

S

It is related to channel combination, and is an intermediate variable of access

algorithm. It is determined by T and CCCH configuration.

II. Format

The value of T is from 3 to 12, 14, 16, 20, 25, 32, and 50.

The value of S ranges as listed in Values of S

Values of S

T

S in different CCCH combination methods

The CCCH and SDCCH does not

share a physical channel

The CCCH and SDCCH share a physical

channel3, 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


To access the network, the MS must originate an immediate assignment process. To begin

the process, the MS sends (RET + 1) channel request messages on RACH. To reduce conflicts

on RACH, the time for MS to send channel request messages must meet the following

requirements:

The number of slots (not including slots for sending messages) between

originating immediate assignment process by MS and sending the first channel


13/62


ventinel Page 13

request messages is random. Its range is {0, 1, , MAX (T, 8) - 1}. When the MS

originates the immediate assignment process, it takes a value from the range

according to even distribution probability.

The number of slots (not including slots for sending messages) between a

channel request message and the next is from {S, S + 1, , S + T - 1} according toeven distribution probability.

According to previous analysis, the greater the T is, the larger the range of intervals

between one channel request message and the next, and the less the RACH conflicting

times is. The greater the S is, the greater the interval between one channel request

message and the next, the less the RACH conflicting times is, and the more efficiently the

SDCCH is used. However, the increase of T and S leads to longer time for MS to access the

network, so the access performance of the whole network declines. Therefore you must

configure T and S properly.

S is calculated by MS according to T and combination of CCH. You can configure T freely and

sends it to MS by system information. Usually, you need configure T properly to make T + S

as small as possible (to reduce the time for MS to access the network); meanwhile you must

ensure an effective assignment of SDCCH to avoid overload (for all random access requests,

the system does not distinguish whether they are from the same MS, but assigns a SDCCH).

In operation, you can adjust the value according to traffic measurement of cell immediate

assignment.

4.2.5 Minimum Access Level of RACH

I. Definition

The minimum access level of RACH is the level threshold for the system to judge whether

there is a random access request.

II. Format

The minimum access level of RACH ranges from 0 to 63 (corresponding to 110 dBm to47

dBm).

The unit is level grade value.


When the access burst level of RACH is greater than the threshold, the BTS judges thatthere is an access request. The BTS, together with the parameter random access error

threshold, determines whether the random access burst is valid. To configure the

parameter properly, you must combine actual sensitivity of the base station and the

parameter minimum received level permitted for MS to access. This prevents the MS from

failing in calling though there are signals. The access burst level of RACH affects call drop


14/62


ventinel Page 14

rate and access range (coverage), so you must pay attention to the influence on access of

MS.

4.2.6 Random Access Error Threshold

I. Definition

GSM protocols prescribe that by relativity of judgment training sequence (41 bits) the

system can judge whether the received signals are the random access signals of MS.

II. Format

The value ranges from 0 to 255. The recommended value is 180.


The random access error threshold defines the relativity of training sequence. If the smaller

it is, the more errors of random access signals permitted by the network are, the easily the

MS randomly accesses the network, and the greater the report error rate is. If the greater

the random access error threshold is, the smaller the report error rate is, and the more

difficult the access to the network is when signals are weak. See protocol 0408, 0502.

The system requires the random access error threshold transferred by current bit of 41 bit

training sequence.

90100 33

101120 34

121140 35141160 36

161175 37

176195 38

196221 39

222243 40

244250 41

089 or 251

255

38

The two parameters random access error threshold and minimum access level of RACH

determine the validity of random access burst.


15/62


ventinel Page 15

4.2.7 Access Control Class (ACC)

I. Definition

GSM regulations (02.11) prescribe that each GSM user (common user) corresponds to an

access class, ranging from class 0 to class 9. The access class is stored in SIM of mobile

users. For special users, GSM regulations reserves five special access classes, ranging from

class 11 to class 15. Theses classes are prior to other classes in accessing. Special users

might have one or more access classes (between 11 and 15), which are also stored in user

SIM. Users of class 11 to 15 are prior to that of class 0 to 9. However, the class between 0

and 9 or between 11 and 15 does not mean priority.

The access class is distributed as follows:

Class 09: common users

Class 11: users for PLMN management

Class 12: users for security departmentsClass 13: common business departments (in charge of water, gas)

Class 14: emergency services

Class 15: PLMN staff

Users of class 09 have its access rights catering for home PLMN and visited PLMN. Users of

class 11 and 15 have its access rights catering for visited PLMN only. Users of class 12, 13,

and 14 have its access rights catering for in the country where home PLMN belongs to.

II. Format

The access control class consists of two parts:

Common access control class

Value range: a check option, including class 0 disabled, , class 9 disabled.

Recommended value: all 0.

Special access control class

Value range: a check option, including class 11 disabled, , class 15 disabled.

Recommended value: all 0.

If a class is configured to 1, it means that access is forbidden. For example, a common

access class is configured to 1000000000; common users excluding class 0 users can access

the network.


C0C15 (excluding C10) are set by equipment room operators. Usually these bits are

configured to 1. Proper configuration contributes to network optimization as follow:

When installing a base station, starting a base station, or maintaining and

testing in some cells, configure C0C15 (excluding C10) to 1. In this way,

different users are prevented from accessing the network, so the installing and

maintenance is less influenced.


16/62


ventinel Page 16

During busy hours of cells with high traffic, congestion occurs, RACH

conflicting time increase, AGCH traffic overloads, and Abis interface traffic

overloads. When you configure class of some users to 1, you can reduce the

traffic of the cell.

4.2.8 Maximum Retransmission Times (RET)

I. Definition

See GSM regulation 04.08. When an MS originates an immediate assignment process, it

sends a channel request message to the network on RACH. The RACH is an ALOH, so the MS

can send multiple channel request messages before receiving immediate assignment

messages, to increase access success rate of MS. The maximum retransmission times M

(RET) is determined by equipment room operators, and sent to MS by SI.

II. Format

The maximum retransmission times consists of two bits, with the meanings listed in Coding

of maximum transmission times M

Coding of maximum transmission times M

M maximum transmission times

00 1

01 2

10 4

11 7


The greater the M is, the higher the success rate of call attempt is, and the higher the

connection rate is, but the load of RACH, CCCH, and SDCCH increase. In cell with high traffic,

if the RET is over great, overload of radio channels and congestion occur, so the connection

rate and radio resource utilization declines sharply. If the RET is over small, the call attempttimes of MS reduces, success rate reduces, so the connection rate reduces. Therefore,

proper configuration of RET for each cell help utilize network radio resources and improve

connection rate.

For configuration of RET M, refer to the following methods:

For areas with low traffic, such as in suburban or rural areas, configure RET

to 7 to increase the access success rate of MS.


17/62


ventinel Page 17

For areas with average traffic, such as common urban areas, configure RET

to 4.

For microcell with high traffic and of apparent congestion, configure RET to 1.

4.2.9 Control Class of MS Maximum Transmit Power (MS-TXPWR-MAX-CCH)

I. Definition

MS-TXPWR-MAX-CCH is sent in BCCH SIs. It affects behavior of MS in idle mode. It is also

used in calculating C1 and C2, and determines cell selection and reselection.

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

RLA_C: average received level by MS

RXLEV_ACCESS_MIN: minimum received level permitted for MS to access

MS_TXPWR_MAX_CCH: maximum power level of control channel (control

class of MS maximum transmit power)

P: Maximum transmit power level of MS

II. Format

The range of MS-TXPWR-MAX-CCH is 031. For cells of GSM900 and GSM1800, the dBm

values corresponding to the control class are different.

In a GSM900 network, the 32 control class of maximum transmit power

corresponding to 031 is as follows:

the 32 control class of maximum transmit power

corresponding to 031 is as follows:

{30, 28, 26, 24, 22, 20, 18, 16, 14, 12, 10, 8, 6, 4, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

0, 0, 36, 34, 32}

Recommended values are 5 for GSM900 and 0 for GSM1800.


MS-TXPWR-MAX-CCH determines the power class used before MS receives power control

messages. For details, seeprotocol 0508.

The smaller it is, the greater the output power of MS is. The MS near the base station

interferes with neighbor channels of the cell, so the access to the network by other MSsand communication quality are influenced. The greater it is, the smaller the output power

of MS is, and the lower the access success rate of MS at cell borders is. You must configure

MS-TXPWR-MAX-CCH properly according to the serving range of the cell.


18/62


ventinel Page 18

4.2.10 Power Offset (POWEROFFSET)

I. Definition

When the MS accesses the network and before it receives the initial power control

messages, all GSM900 MSs and type 1 and type 2 DCS1800 MSs use MS_TXPWR_MX_CCH

of BCCH. If the MS_TXPWR_MX_CCH exceeds the maximum transmit power of MS, the MS

uses the closest power.

The parameter POWEROFFSET is effective to type 3 DCS1800 MSs. When the type 3

DCS1800 MS accesses the network, it use total power of MS_TXPWR_MX_CCH +

POWEROFFSET before receiving the initial power control message. See protocol GSM0508.

II. Format

The values of 03 correspond to 0 dB, 2 dB, 4 dB, and 6 dB.

The recommended value is 2.


The greater the parameter is, the more easily the type 3 DCS1800 MS accesses the network.

A great POWEROFFSET enables MS to access the network afar, but does not help control

cross-cell interference, so the network quality is influenced.

4.2.11 IMSI Attach/Detach Allowed

I. Definition

The IMSI detach means that the MS informs the network of itself work state changing from

working to non-working. Usually it refers to when the MS powers off or the SIM is taken off

MS. After receiving the inform from MS, the network sets the IMSI as in non-working state.

The IMSI attach is opposite of IMSI detach. It means that MS informs the network of itself

work state changing to working. Usually it refers to when the MS powers on or the SIM is

put into MS again. After the MS turns to working state again, it detects whether the current

location areas (LAI) is the same as that recorded in MS at last.

If yes, the MS starts IMSI attach process (this is one of location updating).

If no, the MS starts location updating process of cross location area.

After receiving the location updating message or IMSI message from MS, the network setsthe IMSI as in working state.

The parameter IMSI attach/detach allowed (ATT) is used for informing MS of the IMSI

attach/detach process.


19/62


ventinel Page 19

II. Format

The value of ATT includes YES/NO. NO means that starting IMSI attach/detach process by

MS is forbidden. YES means that starting IMSI attach/detach process by MS is compulsory.


Usually configure ATT to YES so that the network will not process the proceeding of the MS

after the MS powers off. This frees system resources (such as PCH).

IV. Precautions

The ATT of different cells in the same location area must be the same to avoid

abnormalities while the MS is called. For example, in a cell with YES as the value of ATT,

when the MS powers off, it starts IMSI detach process. Therefore the network records that

the MS is in non-working state, so it does not page the MS. In a cell with No as the value of

ATT and the cell being different from the one where the MS powers off, when the MS

powers on again in the cell, the MS does not start IMSI attach process. In this situation, the

MS cannot be called normally until it starts location updating process.

4.2.12 Direct Retry (DR)

I. Definition

During the assignment process of call setup, congestion might cause assignment failure.

The assignment failure causes failure of the whole call. GSM networks has a function to

avoid such failures, namely, DR. The DR is that the BSS directly assign MS to TCH of

neighbor cells. The parameter is used by system to set whether to allow direct retryfunction.

II. Format

The value of DR includes YES and NO. YES means that the system allows directional retry.

NO means that the system does not support direction retry function.


DR improves call success rate. If conditions are ready, start DR. On the contrary, DR is that

the BSS directly assign MS to TCH of neighbor cells when congestion occurs in the cell

where the MS camps, so the MS can originates a call in the non-best cell with lowestreceived level, and extra interference might be brought about in frequency reuse networks.

Therefore, you must use the function properly according to comprehensive network

situations.


20/62


ventinel Page 20

4.3 Serial Parameters of Cell Selection and Reselection

4.3.1 cell_bar_access

I. Definition

In the SI broadcasted in each cell, a bit indicates whether the MS is allowed to access the

network in the cell, namely, cell_bar_access.

II. Format

The value of cell_bar_access includes 1 and 0. The value 0 indicates that MS is allowed to

access the network from the cell. The value 1 indicates that the MS is barred to access the

network from the cell. Actually whether to allow MS to access the network from the cell is

determined by both cell_bar_access and cell_bar_qualify.


The cell_bar_access is configured by equipment room operators. Usually the MS is allowed to access the

network from all the cells, so cell_bar_access is configured to 0. In special situations, the operators want

some cell for handover service only, so cell_bar_access is configured to 1

The MS usually works in microcells (you can configure the priority of cells and reselection parameters to

enable this). When the MS is calling while moving fast, the network force MS to hand over to the base

station G. The signals of base station G are stronger than microcell base station in most areas. When the

call terminates, the MS just camps near base station G and at edge of microcell cells, the MS will not

reselect a cell according to GSM regulations, therefore the MS cannot return to microcell.

The capacity of base station G is usually small, so the previous phenomenon leads to

congestion of base station G. To solve the problem, you can configure the cell_bar_access

to 1, namely, to forbid MS directly accessing base station G. In area A, handover is allowed

to base station G.

IV. Precautions

The cell_bar_access is used only in some special areas. For common cells, it is configured to

0.

4.3.2 cell_bar_qualify

I. Definition

The cell_bar_qualify determines the priority of cells, namely, it enables MS to select some

cell by preference.


21/62


ventinel Page 21

II. Format

The value of cell_bar_qualify includes 1 and 0. The cell_bar_qualify and cell_bar_access

determine the priority state of cells, as listed in Table 7-1 Cell priorit.

Table 7-1 Cell priorities

cell_bar_qualify cell_bar_access Cell selection priority Cell reselection state

0 0 Normal Normal

0 1 Barred Barred

1 0 Low Normal

1 1 Low Normal

An exception is that the cell selection priority and cell reselection state are normal when

the following conditions are met:

The cell belongs to the PLMN which the MS belongs to.

The MS is in cell test operation mode.

The cell_bar_access is 1.

The cell_bar_qualify is 0.

The access control class 15 is disabled.


The priority of all the cells are usually configured to normal, namely, cell_bar_qualify = 0. In

microcell and dualband networking, operators might want MS to camps on the cell of some

type by preference. In this situation, the equipment room operators can configure the

priority of these cells to normaland other cells to low.

During cell selection, when the proper cells with normal as the priority is not present

(proper cells means that all parameters meet the conditions for cell selection, namely, C1 >

0, and the cell is allowed to access), the MS will select cells with low priority.

IV. Precautions

Pay attention to the following aspects:

When cell priority is used as a method to optimize network, the

cell_bar_qualify only affects cell selection, without any influence on cell

reselection. You must optimize the network by combining cell_bar_qualify andC2.

During cell selection, when the proper cells with normal as the priority is

not present, the MS will select cells with low priority. Therefore when the level

of the cell with normal priority is low, and cells with low priority and high level

are present, the MS will access the network slowly while powering on.


22/62


ventinel Page 22

4.3.3 Minimum Received Level Allowing MS to Access (RXLEV_ACCESS_MIN)

I. Definition

To avoid bad communication quality, call drop, and a waste of network radio resources due

to MS accessing the network at low received signal level, GSM regulations prescribe that

when an MS accesses the network the received level must be greater than the threshold

level, namely, the minimum received level allowing MS to access.

II. Format

The value range of RXLEV_ACCESS_MIN is from110 dBm to47 dBm.


The recommended RXLEV_ACCESS_MIN needs to be approximately equal to the receiving

sensitivity of MS. The RXLEV_ACCESS_MIN affects cell selection parameter C1, so it is

important to traffic adjustment and network optimization.

For cells with over high traffic and severe congestion, you can increase

RXLEV_ACCESS_MIN. In this way, the C1 and C2 of the cells decrease, and the effective

coverage range decreases. You must not configure RXLEV_ACCESS_MIN over great, because

this might cause non-seamless coverage and complaints for signal fluctuation. It is

recommended that the RXLEV_ACCESS_MIN is smaller than or equal to 90 dBm.

IV. Precautions

Except for areas of high density of base stations and of qualified coverage, adjusting cell

traffic by RXLEV_ACCESS_MIN is not recommended.

4.3.4 Additional Reselection Parameter Indicator

I. Definition

The cell selection and reselection by MS depends on the parameters C1 and C2. Whether C2

is the cell reselection parameter is determined by network operators. Additional reselection

parameter indicator (ADDITIONAL RESELECT) informs MS of whether to use C2 in cell

reselection.

II. Format

ADDITIONAL RESELECT consists of 1 bit. In SI3, it is meaningless, and equipment

manufacturers configure it to N. The MS uses ADDITIONAL RESELECT of SI4.

When ADDITIONAL RESELECT is configured to N, the meaning is: if the rest

bytes of SI4 (SI4RestOctets) are present, the MS must abstract and calculate

parameters related to C2 and related cell reselection parameter PI.


23/62


ventinel Page 23

When ADDITIONAL RESELECT is configured to Y, the meaning is that the MS

must abstract and calculate parameters related to C2 and related cell

reselection parameter PI.


Cells seldom use SI7 and SI8, so you can configure ADDITIONAL RESELECT to N. When cells

use SI7 and SI8, and the parameter C2 is used in cell reselection, you can configure

ADDITIONAL RESELECT to Y.

4.3.5 Cell Reselection Parameter Indicator

I. Definition

The cell reselection parameter indicator (CELL_RESELECT_PARAM_IND) is used in informing

MS of whether C2 is a cell reselection parameter and whether C2 is present.

II. Format

The value of CELL_RESELECT_PARAM_IND includes Y and N, with the meanings as follows:

Y: The MS must calculate C2 by abstracting parameters from SIs of cell

broadcast, and set C2 as the standard for cell reselection.

N: The MS must set C1 as the standard, namely, C2 = C1.


The equipment room operators determine the value of PI. Configure PI to Y if related cells

set C2 as the standard for cell reselection; otherwise, configure it to N.

4.3.6 Cell Reselection Offset, Temporary Offset, and Penalty Time

I. Definition

After the MS selects a cell, without great change of all the conditions, the MS will camp on

the selected cell. Meanwhile, it does as follow:

Starts measuring signals level of BCCH carrier in neighbor cells.

Records the 6 neighbor cells with greatest signal level.

Abstract various SI and control information of each neighbor cell from the 6

cells.When conditions are met, the MS hands over from the selected cell to another. This

process is called cell reselection. The conditions include:

Cell priority

Whether the cell is barred to access

Radio channel level (important)


24/62


ventinel Page 24

When the signal level of neighbor cells exceeds that of the serving cell, cell reselection

occurs. The channel level standard used in cell reselection is C2, with the calculation as

follows:

1) When PENELTY_TIME 11111:

C2 = C1 + CELL_RESELECT_OFFSET - TEMPORARY_OFFSET * H (PENALTY_TIME -T)

Wherein, if PENALTY_TIME - T (x) < 0, the function H(x) = 0; if x 0, H(x) = 1.

2) When PENELTY_TIME = 11111:

C2 = C1 - CELL_RESELECT_OFFSET

T is a timer, with 0 as the initial value. When a cell is listed by MS in the list of cells with

maximum signal level, start T with step of 4.62ms (a TDMA frame). When the cell is

removed from the list, the associated T is reset.

After cell reselection, the T of original cell works as PENALTY_TIME. Namely, temporary

offset is not performed on the original cell.

CELL_RESELECT_OFFSET (CRO) modifies cell reselecting time C2.

TEMPORARY_OFFSET (TO) is supplemented to C2 from starting working of T to the

prescribed time.

PENALTY_TIME is the time for TEMPORARY_OFFSET having effect on C2. When

PENALTY_TIME = 11111, the MS is informed of using C2 = C1 CRO.

CELL_RESELECT_OFFSET, TEMPORARY_OFFSET, and PENALTY_TIME are cell reselection

parameters.

When the cell reselection parameter PI is 1, the MS is informed of receiving

values of three parameters on BCCH.If PI is 0, the MS judges that the previous three parameters are 0, namely

C2 = C1.

If the C2 of a cell (in the same location area as the serving cell) calculated by MS is greater

than the C2 of the cell where MS camps, and this lasts for over 5s, the MS reselects to camp

on the cell.

If the C2 of a cell (in different location area as the serving cell) calculated by MS is greater

than the sum of C2 of the cell where MS camps and cell reselect hysteresis, and this lasts

for over 5s, the MS reselects to camp on the cell.

The interval between two reselections is at least 15s, and this avoids frequent cell

reselection by MS.

C2 is formed on the combination of C1 and artificial offset parameters. The artificial offset

parameters help MS camp on or prevent MS from camping on some cell. This balances the

traffic of the network.


25/62


ventinel Page 25

II. Format

1) The cell reselection offset (CRO) is in decimal, with unit of dB. It ranges

from 0 to 63, which means 0 to 126 dB (2 dB as the step). The recommended

value is 0.

2) The temporary offset (TO) is in decimal, with unit of dB. It ranges from 0 to

7, which means 0 to 70 dB (10 dB as the step). The recommended value is 0.

3) The penalty time (PT) is in decimal, with unit of second. It ranges from 0 to

31. The value 0 to 30 means 20s to 620s (20s as the step). The value 31 is

reserved for changing the effect direction of C2 by CRO. The recommended

value is 0.

III. Configurationa and Influence

The previous parameters can be adjusted accordingly in the following three situations:

1) When the communication quality is bad due to heavy traffic or other

causes, change the parameters to enable MS not camps on the cell (the cell is

exclusive from the MS). For this situation, configure PT to 31, so TO is

ineffective. C2 = C1CRO. The C2 is artificially lowered. So the probability for

MS to reselect the cell decreases. In addition, the equipment room operators

can configure CRO to a proper value according to the exclusive level of the cell

by MS. The greater the exclusion is, the greater the CRO is.

2) For cells with low traffic and equipment of low utilization, change the

parameters to enable MS to camp on the cell (the cell is prior). In this situation,

configure CRO to 020 dB according to the priority. The higher the priority is,

the greater the CRO is. TO is configured the same as or a little greater than

CRO. PT helps avoid over frequent cell reselection, the recommended value ofPT is 20s or 40s.

3) For cell with average traffic, configure CRO to 0, PT to 11111 so that C2 =

C1. No artificial influence is on the cell.

IV. Precautions

In whatever situations, the CRO must not be greater than 30 dB, because over great CRO

leads to unstable network, such as complaints about signal fluctuation.

4.3.7 Cell Reselection Hysteresis (CRH)

I. Definition

CRH affects cell reselection of cross location area. The MS starts cell reselection if the

following conditions are met:

The signal level of neighbor cell (in different location area) is greater than

that of the serving cell.


26/62


ventinel Page 26

The difference between the signal levels of the neighbor cell and the

serving cell must be greater than the value prescribed by cell reselection

hysteresis.

The difference is based on the cell reselection methods used by MS. If the MS reselects a

cell with C2, then compare values of C2.

II. Format

CRH is in decimal, with unit of dB. The range is 0 to 14, with step of 2 dB. The recommended

value is 4.


If the original cell and target cell belongs to different location areas, the MS must originate

a location updating process after cell reselection. Due to the attenuation feature of radio

channels, the C2 of two cells measured at the bordering area of neighbor cells fluctuates

much, so the MS reselect cells frequently. The interval between two reselections is over

15s, which is rather short for location updating. The signal flow of network increases

sharply, radio resources cannot be fully utilized.

During location updating, the MS cannot respond to paging, so the connection rate

decreases. Adjust CRH according to signal flow and coverage. When signal flow overloads or

location updating of cross location area is frequent, the cell reselection hysteresis is

increased as recommended. You must avoid abnormal coverage due to over large location

area.

IV. Precautions

Do not configure CRH to 0 dB.

4.4 Parameters Affecting Network Functions

4.4.1 Newly Established Cause Indicator (NECI)

I. Definition

In a GSM network, the traffic channel (TCH) consists of full-speed TCH and half-speed TCH.

When the network supports half-speed TCH, the MS is informed of whether the area

supports half-speed TCH by NECI.

II. Format

The value of NECI includes Y and N, with the meaning as follows:

Y means that the area support half-speed TCH.

N means that the area cannot support half-speed TCH.


27/62


ventinel Page 27


Half-speed TCHs enable each carrier to support more traffic channel, but you must confirm

whether the system support half-speed TCH.

4.4.2 Power Control Indicator (PWRC)

I. Definition

The PWRC informs MS of whether to take statistics of downlink level of BCCH carrier slot for

measuring average value when the BCCH frequency participates in frequency hopping. The

causes to configuring PWRC are as follows:

GSM regulations allow frequency hopping channels to use BCCH (frequency

hopping not in BCCH slots) .

GSM regulations allow downlink power control over frequency hopping

channels.The MS needs signal level of the measured neighbor cells, so the power of

each slot on BCCH frequency is prohibited to change. The downlink power

control does not involve carrier slots for BCCH which includes the frequency

hopping.

For previous causes, when the MS measures the average downlink channel level with

common methods, the measurement result is inaccurate for power control because the

average value includes the downlink received level of BCCH carriers the power of which are

not controlled, so the measurement report is inaccurate for power control.

To avoid the influence on power control, when the MS calculates average received level

during frequency hopping, the received level obtained from BCCH carrier slot must be

removed (see GSM regulations 05.08).

II. Format

The value of PWRC includes 0 and 1, with meanings as follows:

When PWRC is 0, the measurement result by MS includes BCCH carrier.

When PWRC is 1, the measurement result by MS does not include BCCH

carrier.


The PWRC is usually configured to 0. Configure it to 1 if all the following conditions are met:

Channels have frequency hopping on two or more frequencies.

One of the frequency is BCCH carrier frequency.

The system uses downlink power control.

IV. Precautions

The value of PWRC depends actually on the following parameters:


28/62


ventinel Page 28

Whether to use frequency hopping.

Whether the hopping frequency includes BCCH carrier.

Whether the system uses downlink power control.

4.4.3 Discontinuous Transmit of Uplink

I. Definition

Discontinuous transmit of uplink (DTXU) refers to the process for MS not to transmit signals

during silent period (see description about DTX in Chapter 2).

II. Format

Whether the network allows uplink to use discontinuous transmit (DTX) is set by equipment

room operators. DTX ranges from 0 to 2, with the following meanings:

0: MS can use DTXU.

1: MS must use DTXU.

2: MS cannot use DTXU.


Using uplink DTX affects call quality, but it is helpful in the following aspects:

Lower interference to radio channels.

Due to this, the average call quality of network is improved.

Cut power consumption by MS

For the previous advantages, DTX is recommended to use.

4.4.4 Discontinuous Transmit of Downlink

I. Defintion

Discontinuous transmit of downlink (DTXD) means the network does not transmit signals

during silent period.

II. Definition

DTXD is in string, and the range is YES and NO. The meanings are as follows:

YES: Downlink uses DTX.

NO: Downlink does not use DTX.


Using downlink DTX affects call quality in a limit scale, but it is helpful in the following

aspects:

Lower interference to radio channels.

Due to this, the average call quality of network is improved.


29/62


ventinel Page 29

Reduce load of base station CPU

Therefore, if possible, you use DTX.

IV. Precautions

According to GSM regulations, downlink DTX is optional. If the base station equipment

supports DTXD, then use it. However, you must ensure that voice transcoder is available to

support DTXD.

4.4.5 Call Resetup Allowed

I. Definition

When coverage voids cause radio link failure, consequently call drop, the MS starts to

resetup the call for recovery. Whether resetting up the call is allowed depends on the

parameter call resetup allowed (RE).

II. Format

The values of call resetup allowed are 1 and 0, with meanings as follows:

1: Call resetup is allowed in the cell.

0: Call resetup is forbidden in the cell.


When a connected MS passes coverage voids, call drop occurs easily. If call resetup is

allowed, the average call drop rate (CDR) is lowered. However, call resetup takes longer

time, and most users disconnects before completion of call resetup. Therefore call resetupis difficult to achieve, and even wastes abundant radio resources. In a word, call resetup is

disabled.

4.4.6 Emergency Call Allowed

I. Definition

The following MSs cannot enjoy various services:

MS without SIM

MS with ACC as one of C0 to C9 and with cell_bar_access

The parameter emergency call allowed (EC) determines whether the MS is allowed for

emergency calls, such as police emergency call.

II. Format

EC consists of 1 bit. For the MS with ACC of C0 to C9 or without SIM, the EC is NO, meaning

emergency call forbidden. YES means emergency call allowed. For the MS with ACC of C11


30/62


ventinel Page 30

to C15, when both the access control bit and EC are configured to forbidden, it is forbidden

for emergency calls.


According to the GSM regulations, the emergency number is 112, different from that inChina. The Chinese emergency call cannot function as prescribed in GSM regulations. For

international roaming users, set 112 to answerphone to inform users of various special

service numbers. Therefore, setting emergency call must be allowed through configuring

radio parameters, namely, configure EC to 1.

4.4.7 Early Classmark Sending Control

I. Definition

In a GSM network, the MS classmark marks the following aspects:

Service capacity

Supported frequency band

Power capacity

Encryption capacity

Classmark consists of classmark1, classmark2, and classmark3. A GSM MS. In a GSM

network, the MS reports Classmark1 or Classmark2 information immediately after

ESTIND (corresponding to L2-SABM at Um interface) is allocated.

Classmark3 (CM3) information includes power information of various frequency band of

multi-frequency MS.

During handover between different bands, the power class must be correctly described.When the GSM system pages and transmits BA2 in different bands, it must know the CM3

message. In GSM regulation Phase2plus, early classmark sending control (ECSC) is added.

ECSC means that by SI the system informs MS of reporting Classmark3 after link setup. This

avoids querying process by network.

II. Format

The values of ECSC are Y and N, with the following meanings:

Y: The MS reports Classmark3 to the network immediately after link setup.

N: The MS is forbidden to report its Classmark3 to network initiatively.


The major information of Classmark3 is for dualband network, so do as follows:

Configure ECSC to N in single frequency GSM application areas.

Configure ECSC to Y in dualband GSM application areas.


31/62


ventinel Page 31

IV. Precautions

In a dualband network, configure the parameter of all cell to the same value. Configuring

the parameter to different values in one or more cells is forbidden; otherwise, the network

quality declines.

4.5 Frequency Hopping Parameters

4.5.1 Frequency Hopping Sequence Number

I. Definition

In a GSM network, the cell allocation (CA) means the set of carriers used by each cell,

recorded as {R0, R1, , Rn - 1}. Wherein, Ri indicates the absolute channel number. For

each communication process, the set of carriers used by base station and MS is mobile

allocation (MA), recorded as {M0, M1, , Mn - 1}. Wherein, Mi indicates the absolutechannel number. Obviously MA is a subset of CA.

During a communication process, the air interface uses a carrier number, one element of

MA. The variable mobile allocation index (MAI) determines an exact element of MA.

According to the frequency hopping algorithm in GSM regulation 05.02, the MAI is the

TDMA frame number (RN) or reduced frame number (RFN), frequency hopping sequence

number (HSN), and mobile allocation index offset (MAIO).

Wherein, the HSN determines two aspects:

Track of frequency points during frequency hopping

The asynchronous neighbor cells using the same MA can avoid continuous

frequency collision during frequency hopping by using different HSNs.

II. Format

HSN is in decimal, ranging from 0 to 63, wherein:

0: cyclic frequency hopping

163: pseudo frequency hopping


You can choose any HSN in cells using frequency hopping, but you must ensure that the

cells using same frequency group must use different HSN. The following paragraph is anexception:

In an 1X1 network, three cells under a base station use the same frequency group, but they

are synchronous cells because of same FN. Therefore the three cells use the same HSN. You

must plan MAIO properly to avoid frequency collision of the three cells under the same

base station.


32/62


ventinel Page 32

4.5.2 Mobile Allocation

I. Definition

The mobile allocation (MA) in the GSM network indicates a frequency set for frequency

hopping. Namely, when the MA of a cell is fixed, the communication frequency points of

the cell performs transient in the set by MA according to rules.

The parameter MA determines all the elements in MA.

II. Format

MA is a set, with all GSM frequency points as its element, namely:

For GSM900 networks: 1124 and 9751023.

For GSM1800 networks: 512885


MA is configured according to network designing requirements.

IV. Precautions

Chinese GSM networks do not cover all available frequency bands of GSM system, so

configure MA in available frequency bands.

The number of elements in each MA set cannot exceed 63.

The MA cannot include BCCH carriers.

The number of MA must not be multiples of 13 if all the following conditions are met:

Using DTXHSN = 0 (cyclic frequency hopping)

You must avoid SACCH to appear usually at the same frequency point.

4.5.3 Mobile Allocation Index Offset

I. Definition

During communication, the air interface uses a carrier frequency, one element of MA set.

MIO determines an exact element of MA set. According to the frequency hopping algorithm

in GSM regulation 05.02, the MAI is the TDMA frame number (RN) or reduced frame

number (RFN), frequency hopping sequence number (HSN), and mobile allocation index

offset (MAIO). MAIO is an initial offset of MAI, and it aims to avoid multiple channels to use

the same frequency carrier in the same time.

II. Format

MAIO ranges from 0 to 63.


33/62


ventinel Page 33


MAIO is configured by equipment room operators.

IV. Precautions

The different cells using same group of MA must use consistent MAIO.

Using different MAIOs enables different sectors in the same location to use the same

frequency group (MA) without frequency collision.

4.6 Distance Control Parameters

4.6.1 Call Clearing

I. Definition

Call clearing (CallClearing) means that the maximum allowed distance threshold is clearedbetween MS and base station in talk.

II. Format

CallClearing ranges from 0 to 63, with unit of TA.


Configure CallClearing according to actual coverage range of a cell. Proper configuration of

CallClearing helps check whether the handover threshold of the cell is properly defined,

especially for urban cells.

If the call is frequently cleared after CallClearing threshold is defined according to cell

radium, probably the handover threshold is improperly configured. This is due to that the

MS cannot hand over to the best server cell after exceeding designed coverage range.

Define CallClearing according to msRangeMax, namely, CallClearing > msRangeMax.

In actual network operation, call clearing is unusually performed, because radio link fails

due to over poor coverage before call clearing. Defining CallClearing aims to restrict the

distance between MS and base station and to avoid MSs in allowed coverage range to

interfere other MSs, especially in areas with complex landform.

The cell coverage range is irregular, so island effect might occur. For this phenomenon,

define CallClearing to clear calls in island areas.

4.6.2 TA Handover Threshold (MSRANGEMAX)

I. Defintion

When the distance between MS and base station reaches or exceeds MSRANGEMAX,

distance handover is triggered.


34/62


ventinel Page 34

II. Format

MSRANGEMAX ranges from 0 to 63, with unit of TA. The reference is 63.


MSRANGEMAX must be smaller than CallClearing, and otherwise the handover function will

be actually unavailable. While configuring MSRANGEMAX, you must adjust the threshold of

other types of handover; otherwise ping-pong handover occurs. one occasion might be as

follows:

The distance between MS and the serving cell exceeds the threshold, but the signals of

target cell are weaker than that of original cell. Consequently the PowerBudget handover is

triggered immediately after distance handover is triggered.

4.6.3 TA Restriction (MS_BS_DIST_USED)

I. Definition

The maximum allowed access distance between base station and MS. If the distance

between an MS and base station exceeds the maximum allowed access distance, the MS is

forbidden to access cells.

II. Format

The range is 0 to 63, with unit of TA. The reference is 63.


For its configuration, refer to the method for configuring CallClearing. Adjust the parameter

to enable it consistent with the geographic coverage range of the cell. Set a proper

threshold to filter pseudo RACH requests to avoid unnecessary assigning SDCCH.

According to tests, for mountain-mounted base stations, the coverage and interference is

difficult to control. If you define the maximum allowed access distance to 63, the RACH

misjudgment increases (the system demodulates interference to RACH bursts by mistake).

Therefore the radio performance and traffic measurement indexes of the cell are affected.

4.7 Radio Link Failure Process and Parameters

The radio link failure is detected from uplink and downlink. The MS completes downlink

detection, while the base station completes uplink detection.


35/62


ventinel Page 35

4.7.1 Radio Link Failure Counter (RLC or Radio Link Timeout)

I. Definition

The MS originates call resetup or disconnects by force if all the following conditions are

met:

The voice or data quality is too poor to be received.

Power control and handover cannot help to improve the quality.

A disconnection by force actually brings about a call drop, so the MS considers it a radio link

failure that the voice or data service is actually too poor to be received. GSM regulations

provide solutions to the previous problems as follows:

Set a counter S in the MS. The initial value of S is provided at the beginning of talk, and it is

the value of the parameter radio link failure counter. S changes as follows:

S decreases by 1 if the MS fails in decoding a correct SACCH message when

the MS should receive the SACCH message.

S increases by 2 if the MS succeed in decoding a correct SACCH message.

S cannot exceed the value for radio link failure counter. When S equals to 0, the MS

originates call resetup or disconnects by force.

II. Format

The step from 4 to 64 is 4, with unit of SACCH period as follows:

For TCH, the SACCH period is 480ms.

For SDCCH, the SACCH period is 470ms.


The value of the parameter radio link failure counter affects CDR and utilization of radio

resources.

Assume that cell A is a neighbor cell to cell B and the bordering coverage is poor. When an

MS moves from P to Q while in talk,

If the radio link failure counter is over small, call drop occurs before cross-

cell handover.

If the radio link failure counter is over great, the network releases related

resources until radio link expires, though the voice quality is too poor when MS

camps on cell B near P. Therefore, the utilization of radio resources declines.

Proper configuration of radio link failure counter is important, and is related to the actual

situations. To configure radio link failure counter, refer to the following rules:

Configure it to between 52 and 64 in areas with over low traffic.

Configure it to between 36 and 48 in areas with low traffic and great

coverage radium

Configure it to between 20 and 32 in areas with heavy traffic.


36/62


ventinel Page 36

IV. Precautions

Configure radioLinkTimeout to smaller than T3109. This contributes to success of call

resetup and avoids the following situation effectively:

Before the MS releases radio resources due to expiration, the network side completesreleasing channels resources and reallocates resources to other MSs. Therefore two MSs

might use the same slot and this causes interferences even call drop.

4.7.2 SACCH Multiframe (RLTO_BS)

I. Definition

Refer to the description of radio link failure counter. A counter is set accordingly to radio

link at base station side for managing radio link failures. The solutions vary due to different

equipment providers, but a general method is as follows:

Set a counter S in the base station. The initial value of S is provided at the beginning of talk,

and it is the value of the parameter radio link failure expiration. S changes as follows:

S decreases by 1 if the MS fails in decoding a correct SACCH message when

the MS should receive the SACCH message.

S increases by 2 if the MS succeed in decoding a correct SACCH message.

S cannot exceed the value for radio link expiration of base station. When S equals to 0, the

MS originates call resetup or disconnects by force, as shown in Error! Reference source not

found..

II. Format

RLT0_BS ranges from 4 to 64.


Proper configuration of radio link expiration of base station affects CDR and utilization of

radio resources. It is related to the actual situations. To configure radio link failure counter,

refer to the following rules:

Configure it to between 52 and 64 in areas with over low traffic.

Configure it to between 36 and 48 in areas with low traffic and great

coverage radium

Configure it to between 20 and 32 in areas with heavy traffic.Configure it to a greater value in areas with apparent voids or where call

drop occurs frequently while the MS moves.

IV. Precautions

RLT0_BS and RLC must be consistent.


37/62


ventinel Page 37

4.8 Handover and Related Parameters

4.8.1 PBGT Handover Threshold (HoMargin)

I. Definition

The PBGT handover threshold is power handover tolerance (handover in serving areas).

When the signal level of neighbor cell is hoMargin (dB) higher than that of the serving cell,

handover occurs. Complex radio propagation conditions cause fluctuation of signal level.

Using handover tolerance avoids frequent handover at bordering areas. The PBGT handover

threshold is similar to HO_MARGIN (GSM 05.08).

II. Format

The PBGT handover threshold ranges from 0 to 127, corresponding to 64 dB to +63 dB.

The reference value for suburban areas is 68. The reference value for urban areas is 70 to

72.


The PBGT handover threshold aims to adjust handover difficulty properly, and to avoid

ping-pong handover. If it is configured over great, the handover is delayed and handover is

less efficient. When it is smaller than 64, the MS hands over from the serving cell to the

neighbor cell with lower level.

4.8.2 Minimum Downlink Power of Handover Candidate Cells (rxLevMinCell)

I. Definition

It is the minimum allowed access level for a cell to be a neighbor cell. When the cell level

measured by MS is greater than the threshold, the BSS list the cell into candidate cell list for

handover judgment.

II. Format

It ranges from110 dBm to47 dBm.


It is helpful in the following two aspects:

It guarantees communication quality.

For a common single layer network structure, the value ranges from90 dBm

to80 dBm.

It helps allocate traffic between cells averagely.

Especially in multi-layer network structure, to maintain MS in a network layer,


38/62


ventinel Page 38

you can increase the level of the cell of the network layer (such as 70 dBm),

and also decrease that in other cells.

IV. Precautions

You cannot configure rxLevMinCell over great (over65 dBm) or over small (lower than95dBm), and otherwise communication quality is affected.

4.8.3 Handover Threshold at Uplink Edge

I. Definition

If the uplink received level keeps being smaller than the handover threshold at uplink edge

for a period, edge handover can be performed.

II. Format

It ranges from 0 to 63, corresponding to110 dBm to47 dBm. The recommended values

are as follows:

Configure it to 25 in urban areas without PBGT handover.

Configure it to 20 in single site of suburban areas.

Configure it to 20 in urban areas with PBGT handover


When PBGT handover is enabled, the corresponding edge handover threshold can be

lowered. When PBGT handover is disabled, and the edge handover threshold is over low, an

artificial cross-cell non-handover occurs. Therefore call drop occurs or intra-frequency and

side interference occur due to cross-cell talk.

4.8.4 Handover Threshold at Downlink Edge

I. Definition

If the downlink received level keeps being smaller than the handover threshold at downlink

edge for a period, edge handover can be performed.

II. Format

It ranges from 0 to 63, corresponding to110 dBm to47 dBm. The recommended valuesare as follows:

Configure it to 30 in urban areas without PBGT handover.

Configure it to 25 in single site of suburban areas.

Configure it to 25 in urban areas with PBGT handover


39/62


ventinel Page 39


When PBGT handover is enabled, the corresponding edge handover threshold can be

lowered. When PBGT handover is disabled, and the edge handover threshold is over low, an

artificial cross-cell non-handover occurs. Therefore call drop occurs or intra-frequency and

side interference occur due to cross-cell talk.

4.8.5 Downlink Quality Restriction of Emergency Handover

I. Definition

If the downlink received quality is lower than the threshold of downlink quality restriction

of emergency handover, the quality difference emergency handover occurs.

II. Format

It ranges from 0 to 70, corresponding to RQ (QoS 0 to 7) x 10.The recommended value is 50.


When frequency hopping is enabled, the voice quality is better with the same RQ, you can

configure it to 60 or 70. When emergency handover occurs, the intracell handover occurs

first. If there are no other candidate cells, and the intracell handover is enabled, the

intracell handover occurs.

4.8.6 Uplink Quality Restriction of Emergency Handover

I. Definition

If the uplink received quality is lower than it, quality difference emergency handover is

triggered.

II. Format

It ranges from 0 to 70, corresponding to RQ (QoS 0 to 7) x 10.

The recommended value is 50.


When frequency hopping is enabled, the voice quality is better with the same RQ, you can

configure it to 60 or 70. When emergency handover occurs, the intracell handover occurs

first. If there are no other candidate cells, and the intracell handover is enabled, the

intracell han

Documents

2G Planning & Optimization - Part-4