call drop statistic and analysis_doc9

HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential

Slide title :32-35pt Color: R153 G0 B0

Corporate Font :FrutigerNext LT Medium

Font to be used by customers and

partners : Arial

Slide text :20-22ptBullets level 2-5:

18pt Color:Black



partners : Arial

Call Drop Statistic and Optimization

NPI Project





partners : Arial


18pt Color:Black



partners : Arial

Statistics of Call Drops

• A call drop indicates that a call ends exceptionally. During a call drop, the service of the subscriber is

interrupted because the BSC or MS releases the business channel.

• Statistics of call drops by counters: Upon receiving the connection failure and error indication messages

from the BTS, the BSC sends the clear request message to the MSC to apply for disconnection. In this

case, the number of call drops is counted according to the reason for call drops.

• Statistics of DT call drops: Usually, a normal call release is counted when either of the two messages,

Disconnect or Channel Release appears during a call. A call drop is counted only when neither of these

two messages appears and the MS converts from dedicated mode to idle mode.

cal cul at drop counter

connecti on fai l ure

error i ndi cati on

cl ear request

MS BTS BSC MSC





partners : Arial


18pt Color:Black



partners : Arial

Classification of Traffic Call Drops• According to the reason for call drops, the BSC classifies call drops into various categories.

This helps to identify the type of a call drop and to locate problems.

• Typically, most call drops in a network are call drops occurred over radio interface (CM33C call drops). This type of call drops are divided into call drops occurred in stable state and call drops occurred during handover and should be given special attention.

• Other types of call drops seldom occur in the network. Among these types of call drops, pay attention to CM334 call drops and CM333 call drops. The loopback function is seldom used in the network. Therefore, loopback call drops are seldom concerned.

CM33:CELL_TRAF_CH_CALL_DROPS

CM33C:CELL_TRAF_CH_UM_CALL_DROPS

CM332:CELL_TRAF_CH_CALL_DROPS_NO_MR

CM333:CELL_TRAF_CH_CALL_DROPS_ABIS_LNK_FAIL

CM334:CELL_TRAF_CH_CALL_DROPS_EQUIP_FAIL

CM335:CELL_TRAF_CH_CALL_DROPS_FORCE_

HO

CM397:CELL_LOOP_START_FAIL_DROPS

CM385:CELL_LOOP_RESTORE_FAIL_DROPS

CM330:CELL_TRAF_CH_CALL_DROPS_IN_STABLE_STATE

CM331:CELL_TRAF_CH_CALL_DROPS_HO_FAIL





partners : Arial


18pt Color:Black



partners : Arial

Classification of Call Drops occurred over radio interface

• Call drops occurred over radio interface

are divided into call drops occurred in

stable state and call drops occurred

during handover.

• Among call drops occurred in stable

state , pay attention to CM3300 call

drops and CM3301 call drops. In a

normal network, CM3301 call drops

account for the largest proportion.

• Usually, most call drops occurred during

handover in a network are caused by

inter-cell handover. Therefore, H3127Ca

call drops and H3128Ca call drops

account for a large proportion.

• According to the proportion of various

types of call drops, you can preliminarily

determine whether the problem is

caused by the increase of a type of call

drops. For example, if a type of call

drops that originally account for a small

proportion increase suddenly, you should

pay special attention to this type of call

drops.

CM33C:CELL_TRAF_CH_UM_CALL_DROPS

CM330:CELL_TRAF_CH_CALL_DROPS_IN_STABLE_

STATE

CM3302:CELL_TRAF_CH_STATIC_STATE_CALL_DROPS_REL_IND

H3128Ca:CELL_INTRABSC_OUTCELL_HO_FAIL_EXP_TCHH_TRAF_NOT_INCLUDE_DR

H3027Ca:CELL_INTRACELL_HO_FAIL_EXP_TCHF_TRAF

H3028Ca:CELL_INTRACELL_HO_FAIL_EXP_TCHH_

TRAF

H3127Ca:CELL_INTRABSC_OUTCELL_HO_FAIL_EXP_TCHF_TRAF_NOT_INCLUDE_DR

CM331:CELL_TRAF_CH_CALL_DROPS_HO

_FAIL

CM3300:CELL_TRAF_CH_STATIC_STATE_CALL_DROPS_ERR_IND

CM3301:CELL_TRAF_CH_STATIC_STATE_CALL_DROPS_CONN_FAIL

H3227Ca:CELL_INTRABSC_INCELL_HO_FAIL_EXP_TCHF_TRAF

H3228Ca:CELL_INTRABSC_INCELL_HO_FAIL_EXP_TCHH_TRAF





partners : Arial


18pt Color:Black



partners : Arial

Proportions of Various Types of Call Drops in CJV

• In the CJV Telkomsel 2G network, the distribution of various types of call drops is counted as follows:

• Call drops occurred over radio interface account for 98.21%. Other types of call drops, however, account for a small proportion. This is the case for most networks. If a type of call drops rather than Call drops occurred over radio interface , CM334 call drops (call drops due to equipment failure), for example, account for a large proportion, you need to check the hardware and alarms.

• Among Call drops occurred over radio interface , many are call drops due to connection failure. Among this type of call drops, call drops due to radio link failure (M3101A call drops and M3201A call drops) account for the largest proportion.





partners : Arial


18pt Color:Black



partners : Arial

Basic Process of Troubleshooting Call Drop Problems

• If the call drop rate is high in a network, need

first analyze the problem to make clear what

causes the problem and what is the scope of

the problem. Then, you can find the solution

according to the analysis result.

• First, should analyze the call drop traffic,

determine whether the high call drop rate exists

in the entire network or only in some cells,

analyze the proportions of various types of call

drops, and finally determine the problem is

caused by a type of call drops.

• If call drops due to equipment failure and

transport failure (CM334 call drops and CM333

call drops) that do not occur over radio interface

increase, need pay attention to hardware failure

and transport failure.

• If wireless port call drops increase, need pay

attention to factors such as network

parameters, interference, and coverage and

solve the problem by improving the quality of

the air interface.

In a normal network, most call drops are call drops occurred over radio interface. This

type of call drops may be caused by improper parameter settings, cross coverage,

improper relation between neighboring cells, interference, and poor coverage. Usually,

problems exist in only few cells. Call drops not occurred over radio interface seldom occur

and usually occur in only few cells. When such call drops occur, you just need to analyze

the few cells.

Cal l Drop Problems

Anal ysi s of Proporti onsof Vari ous Types of

Cal l Drops

Proporti ons ofCM33C i s hi gh

hardware failuretransport failure

alarminformation

parameters

interference

coverage

Proporti ons ofCM334 and CM333

i s hi gh

Channel Conversion、Mutual aid of TRXs

Yes

No

Yes

No

enti re network/some cel l

BSCparameters

core networkparameters

networkplanning

software versionproblems

TOP cel lenti renetwork

Anal ysi s of Proporti onsof Vari ous Types of

Cal l Drops

hardware fai l uretransport fai l ure

neighboringcel l s

frequency





partners : Arial


18pt Color:Black



partners : Arial

Analysis of Proportions of Various Types of Call Drops

• The call drop rate is counted in two modes: including handovers and excluding handovers.

Call drop rate (including handovers) =

CM33/(K3013A+K3013B+K3023);

Call drop rate (excluding handovers) =

CM33/(K3013A+CH323+CH343-CH313-CH333);• The proportion of a type of call drops can be counted as follows:

Proportion of a type of call drops = Indicator of this type of call drops/CM33. For example,

Proportion of call drops due to equipment failure = CM334/CM33

The call drop counters during busy hours

in a week are obtained and the concrete

indicators are as shown in the figure on

the right.





partners : Arial


18pt Color:Black



partners : Arial

Troubleshooting of Call Drops Occurred over Radio Interface in the Entire Network

• If call drops occurred over radio interface account for a large proportion in the entire network, this problem is

usually caused by improper parameter settings in the entire network. In this case, you can check the settings

of various parameters according to the parameter baseline.

• Incoordination between settings of core network parameters and settings of BSC parameters may also cause a

high call drop rate in the entire network.

• Improper network planning and frequency planning of the entire network also cause call drops in the entire

network.

• Equipment-level problems, for example, software version problems, may cause a high call drop rate in the

entire network. Such problems, however, seldom occur.





partners : Arial


18pt Color:Black



partners : Arial

Troubleshooting of Call Drops Not Occurred over Radio Interface

• For call drops not occurred over radio interface, pay attention to CM333

call drops and CM334 call drops. Currently, local switch of BSC/BTS is

not enabled. Therefore, you do not need to pay attention to call drops

caused by loopback start failure and failure of failing to return to normal

call from loopback.

• For CM333 call drops, determine whether they are caused by links on

the Abis interface according to the proportion and number of call drops.

Disconnection of RSL links may also cause CM333 call drops.

• For CM334 call drops, determine whether they are caused by equipment

failure according to the proportion and number of call drops. The

following factors may cause increase of call drops due to equipment

failure:

Mutual aid of TRXs, dynamic modification of cell

attributes, dynamic modification of frequencies on TRXs,

dynamic modification of frequency hopping data of TRXs,

dynamic deletion of cells, dynamic deletion of TRXs,

blocking of cells, blocking of TRXs, blocking of channels

Software exceptions

• If CM333/CM334 call drops increase, check the related alarm

information, rule out possible reasons that cause call drops according to

the alarm information, and locate the problem. If necessary, troubleshoot

transmission equipment and hardware on site.





partners : Arial


18pt Color:Black



partners : Arial

TOP Cell Idea

• Problem analysis: Narrow down the scope of the problem, find what causes

the problem, and find the solution accordingly.

• TOP cell/area filtering: Find what are TOP cells and determine whether a

TOP area exists according to the geographical display.

• Alarm analysis: Check the related alarm information and solve the problems

for which alarms are reported.

• Engineering check: Check whether the engineering quality is high, whether

the hardware is in good condition, whether the connecting lines are correctly

connected, and whether the feeders are not inversely connected.

• Parameter check: Check the parameters according to the parameter

baseline provided by the Performance Department and the actual situation

of the existing network and adjust the parameters that are improperly set.

• Interference check: Check whether any repeater interference, external

interference, and intermodulation interference exists.

• Coverage check: Check whether any poor coverage area or any coverage

blind area exists in the TOP cells or in the TOP area.

• RF optimization: Check whether any missing configuration of neighboring

cells, frequency interference, cross coverage, and signal leakage of indoor

coverage sites exists.

TOP cel lfi l teri ng

Al arm anal ysi s

Parameter check

Interferencecheck

Coverage check

cal l drop probl em

TOP areafi l teri ng

Engi neeri ngcheck

RF opti mi zati on





partners : Arial


18pt Color:Black



partners : Arial

Analysis of Call Drop Counters

• Extract the data related to call drops and calculate the call drop

rate. Do this by using the PRS if one is available.

• Filter TOP cells where call drops occur frequently according to

the call drop rate. Consider the number of calls at the same

time because a cell where few calls are made has small effect

on the entire network even it has a high call drop rate. Such a

cell, however, should not be neglected. If not many call drops

occur in the entire network, be sure to check such cells.

Focus on TOP20 cells and focus on TOPn cells according to

the actual situation.

• Calculate the call drop rate of the entire network after removing

the call drops occurring in TOP cells and determine whether

the call drop problem is caused by TOP cells.

• Calculation of the call drop rate and templates for calculating

the proportions of various call drops

1. Extract the data and post the data below the table header

according to the format and sequence defined in the header of

the Traffic Data sheet (you can also define a template on the

M2000 according to the sequence defined in the table header).

2. On the Call Drop Rate Calculation sheet, refresh the pivot

table and obtain the call drop rates of various cells to manually

filter the TOP cells.

3. The Call Drop Rate & Proportions of Various Call Drops sheet

can display the data calculated according to the filtering

conditions set according to the Traffic Data sheet.

Template for analyzing call drop data:

Calculation result on the Call Drop Rate & Proportions of Various Call Drops sheet:

Place the data according to the sequence defined in the table header:

Template for analyzing call drop data





partners : Arial


18pt Color:Black



partners : Arial

TOP Cell Filtering

• After calculating the call drop rates of various cells, rank the call drop rates according to the call drop rate (excluding handovers) and filter the TOP cells.

• Through the geographical display function of the MapInfo, analyze whether TOP cells appear in patches, that is, whether a TOP area exists.

• Calculate the proportion of various call drops in each TOP cell and make clear which type of call drop dominates in each cell. For example, most call drops are caused by equipment failure in cell A and most call drops are caused by transmission failure in cell B. In this way, exclude possible reasons that cause call drops and make clear what causes the call drops in TOP area.

• After obtaining the TOP cell list and making clear which type of call drops dominate in each cell, focus on this type of call drops and make analysis accordingly. For example:





partners : Arial


18pt Color:Black



partners : Arial

Engineering Quality/Core Parameter Checking

• The engineering quality directly determines the performance of a network. For example, inverse connection of feeders and loose connectors directly affect the network quality. Therefore, it is necessary to make clear what causes engineering problems first. For details, see the Engineering Quality Problem Troubleshooting.

• Checking of hardware failure and transmission failure: Usually, an alarm is reported when a problem occurs. Sometimes, however, no alarm is reported when a problem occurs. In this case, you can analyze the traffic to determine whether the problem exists and check the problem on site if necessary. You can determine how many resources are available according to TCH Usage and TRX Usage and determine whether the links are normal according to Channel Active NACK and Channel Active Timeout.

Checking of call drop-related parameters: Parameters that have great effect on call drops on the BSC side

include SACCH Multi-Frames, Radio Link Timeout, T200, and N200. These parameters should be set

properly. In addition, core network parameters should also be checked because they involve the

coordination between the core network and the BSC. For details, see page 10. For what parameters should

be checked, see the Core Parameter Checking.

Related Problems Abbreviated Name Meaning

hareware Failure

RR300 SDCCH Availability

RR307 TCH Availability

K3015 Available TCHs

K3015 Configured TCHs

S3655 Activated TRXs in Cell

S3656 Available TRXs in Cell

Transport Failure

CR33A Channel Activation Attempts

CR33B CHAN ACTIV NACK Messages Sent By BTS

CR34C Channel Activation Timeouts





partners : Arial


18pt Color:Black



partners : Arial

Interference/Coverage Checking

• Interference checking: whether strong interference exists according to the proportion of level 4 and level 5

interference bands. Count the call drop rates of various cells at various intervals. If you use the average value of

call drop rates, you may cannot find the interference bands easily. According to the drive test result, analyze

whether co-frequency/adjacent-frequency interference or external interference exists. Then, find what causes the

interference by checking the possible reasons that cause the interference.

• Coverage checking: Analyze the traffic and find whether problems such as high proportion of great TAs,

imbalance between uplink and downlink, and high proportion of low levels exist. Preliminarily determine whether

problems of poor coverage and imbalance of uplink and downlink exist. According to the drive test result,

determine in what areas poor coverage exists. If the problem of imbalance between uplink and downlink exists,

check whether the transmitting power and tower amplifier are set properly.





partners : Arial


18pt Color:Black



partners : Arial

Related Traffic Analysis Templates

• As mentioned before, you can analyze the related traffic data when

analyzing call drop problems. This provides reference basis and data

support for you to analyze problems.

• The main involved traffic items are as shown in the figure on the right.

Templates for analyzing related traffic data:

TRX-level data and cell-level data should be extracted and analyzed

separately.

1. Extract TRX-level data and cell-level data and post the data below the

table header according to the format and sequence defined in the

headers of the TRX-Level Data sheet and Cell-Level Data sheet (you

can also define a template on the M2000 according to this sequence).

2. On the Calculation of TRX-Level Indicators and Calculation of Cell-

Level Indicators sheets, refresh the pivot table and obtain the TRX-

level data and cell-level data.

3. Set filtering conditions on the TRX-Level Data or Cell-Level Data sheet,

and the corresponding calculation result will be displayed on the

Calculation Result sheet.Template for analyzing call drop traffic data Templates for

analyzing related call dro





partners : Arial


18pt Color:Black



partners : Arial

Some cases illustration





partners : Arial


18pt Color:Black



partners : Arial

THANK YOU!

call drop statistic and analysis_doc9

Documents