asr improvement

Guidelines for ASR Improvement Security Level

2012-06-25 Huawei Proprietary - Restricted Distribution Page2, Total23

Contents

1 Purpose

2 Scope

3 Reasons of ASR DIP and Solutions

3.1 Dual Seizure

3.2 Circuit Status

3.3 EOS(End of Selection)

3.4 MSC Utilization

3.5 B –Table routing

3.6 POI Trunk route Utilization

3.7 Subscriber behavior

3.8 Release cause

4 Counter for ASR:

5 Requirement for Analysis

6 Recommendations



1 Purpose

This document describes the guidelines for Selecting the ASR Strategy for a Network keeping in View

the Traffic Profile of the Network.

2 Scope

This document describes the guidelines for Selecting the ASR Strategy keeping in view the Traffic

Profile of the Network and ASR capacity of different interface in the Network.

3 Reasons of ASR DIP and Solutions

The Answer Success Rate can be optimize by adjusting the Call Answer strategy through the following

parameters:

Dual Seizure

Equipment Congestion

Circuit Channel

Call Rejection -



3.1 Dual Seizure

Dual seizure substitutes in ASR dip as the call may fail.

The calls that are failing due to “Dual Seizure” will be recorded in the field “DUAL SEIZURE_CV44”

in the performance measurement task “Failure Reason Traffic”.

If the field is 0 then, it implies no call failing due to “Dual Seizure” though in the “TKGRP Outgoing

Traffic” you can find lot of “Dual Seizure”.

The call failing happens only if the time for IAM/IAI message time outs in the CIC reselection

process (In case of non-controlling or salve Dual Seizure) or in IAM/IAI sending delay (In case of

controlling or Master Dual seizure).

For eg: If MSC A is configured as controlling office and MSC B as non-controlling office then if

MSC B sends an IAM message to MSCA while its is trying to send the IAM message using the

same CIC then MSC A will reject the IAM/IAI message from MSC B.

MSC B will then try to select another free CIC towards MSC A for sending the IAM/IAI message.

This is called controlling Dual Seizure with respect to MSC A and non-controlling Dual Seizure with

respect of MSC B.

For non-controlling “Dual Seizure” the fields “DUAL SEIZURE TIMES SLAVE’ and “TK RETRY

TIMES” are increased by 1. However in case of controlling Dual Seizure as there is no circuit

reselection involved only the “DUAL SEIZURE TIMES MASTER” field is increased by 1 for every

controlling Dual Seizure not the “TK RETRY TIMES” filed like non-controlling Dual Seizure.

Huawei MSCs are designed to retry 5 times after dual seizure happens. Actually the circuit

reselection times isn’t confined by any protocol constraint and is open for the vendor. This CIC

reselection times isn’t controlled by any software parameter or timer. It is defined while coding the

software of MSC i.e. CIC reselection is controlled as an embedded function of MSC and can’t be

modified through timer or software parameter.

Screen shot for Dual seizure details as per ITU standards attached below .



3.2 Circuit Status

Primary status: Not installed, faulty, manually blocked, peer blocked, idle, and busy

Combined status: Peer manually blocked, manually blocked and faulty, peer blocked and faulty,

manually blocked in the busy hour, peer blocked in the busy hour, and peer manually blocked in

the busy hour

Basic principles and illustration of circuit status: Except for not installed, other states can be

combined; only idle circuits can turn to busy; the manual blocking and peer blocked options can be

applied to busy circuits, and calls will not be affected; when faults occur, a busy circuit releases

calls immediately and enters into faulty status. The original book status and coexistence of busy

and faulty states do not exist any more. Major state transitions are illustrated in the following figure:



B_FAULT B_UNINSTALLHW－OK

B_IDLE

HW－OKB_OAM_BLOCK

B_PEER_BLOCK

B_OAM_PEER_BLOCK

OAM－BLOCK

PEER－BLOCK

OAM－BLOCK

PEER-BLOCK

B_BUSY

BOOK

B_BUSY_OAM_BLOCK

B_BUSY_PEER_BLOCK

B_BUSY_OAM_PEER_BLOCK

OAM－BLOCK

PEER－BLOCK

OAM－BLOCK

PEER-BLOCK

B_FAULTHW－FAULT

When faults occur on the c ircuit, three combined faulty s tates will be added

B_OAM_BLOCK_FAULTHW－FAULT

B_PEER_BLOCK_FAULTHW－FAULT

B_OAM_PEER_BLOCK_FAULTHW－FAULT

HW－FAULT

HW－FAULT

HW－FAULT

HW－FAULT

B_IDLE

B_OAM_BLOCK

B_PEER_BLOCK

B_OAM_PEER_BLOCK

B_BUSY

B_BUSY_OAM_BLOCK

B_ BUSY_PEER_BLOCK

B_ BUSY_OAM_PEER_BLOCK

B_FAULT

B_OAM_BLOCK_FAULT

B_PEER_BLOCK_FAULT

B_OAM_PEER_BLOCK_FAULT



3.2.1 Collecting Basic Information

Use the following MML commands on the MSOFTX3000 to collect only the information about the

circuits in faulty status a certain BSC:

LST MGW, DSP MGW: MGW-related configuration information and the status of each MGW

LST MCLNK, DSP MCLNK: Configuration information and status of the H248 link

LST N7LNK, DSP N7LNK: Configuration information and status of the BSC destination signaling

point

LST ACPOOL: Configuration information of circuit pools

LST AIETG,N7TG: Configuration information of A-interface and POI trunk groups

LST TKC,N7TKC: Circuit configuration information. Select YES to all options.

LST CIC: Circuit configuration information on each module

LST BSC: Configuration information of the processing modules reaching a certain BSC

DSP AIETKC,N7TKC: To query A-interface and POI circuit status. Use the parameter A-interface

and POI circuit number, which can be queried using the LST TKC command.

DSP OFTK: To make statistics on A-interface and POI circuit status by office

Save all these results and Check.



Use the following MML commands on the UMG8900 to collect only the information about the

circuits in faulty status on a certain BSC:

DSP VMGW: VMGW configuration information and status

DSP H248LNK: H248 link configuration information and status

DSP E1PORT: E1 port configured or not

LST TDMIU: VMGW correctly configured or not for the E1 link with specific TID

DSP TDMSTAT: Timeslots normal or not

LST TDMSPC: If there is a semi-permanent connection, use the DSP TDMSPC command.

Save all these results and Check.



3.3 EOS(End of Selection)

3.3.1 Definition:

For every failed call one End of Selection is generated by the switch with respect to the reason of the failure

of the call.

3.3.2 KPI Target:

The End of Selection should be as minimum as possible and should be consistent for every circle.

3.3.3 Reasons of High EOS(End of Selection):

Incorrect Definition of EOS(End of Selection) Table.

Incorrect mapping of announcement with EOS(End of Selection) Table.

C7 Signaling Congestion

Trunk route congestion.

Failures due to subscriber reasons.

3.3.4 Improvement Plans:

EOS(End of Selection) should be analyzed on daily basis.

In case of some major variation in EOS(End of Selection) for a particular circle, the reason for the same should be analyzed and RCA(Route Cause Analysis) for the same should be get.

Service Quality report or Traces can be used to get the EOS(End of Selection) for a particular time, but the trace should not be used if there is not any major problem and without the consultation

of Back Office.

3.4 MSC Utilization



3.4.1 Definition:

MSC Utilization is the utilization of all the MSC w.r.t to to its designed value in Erlang at a specific

Processor Load in busy hour. This parameter is calculated for Busy Hour.

3.4.2 KPI Target:

MSC Utilization should be equal to or less than ----------%.

3.4.3 Formula:

MSC Utilization% = 100*Switch NBH Traffic(Erls) / Switch Capacity (Erls)

3.4.4 Reasons of High MSC Utilization:

Trunk route Congestion.

Internal Congestion

Hardware fault.

Delay in MSC Deployment as per plan.

Uneven distribution of BSCs traffic for the MSCs.

Wrong forecast of subscriber behavior.

Subscriber abnormal behavior.

Transit Traffic.


All the BSCs should be evenly distributed to MSCs as per the BSC Traffic.

No. of BTS should be evenly distributed to MSCs as per the Traffic.

Trunk route utilization should not go above ------% and there should not be any congestion in the trunk route



There should not be any internal congestion in the switch.

3.5 POI Trunk route Utilization

3.5.1 Definition:

Trunk route Utilization is the Utilization of the circuits(Time Slots) in a given route w.r.t. to No. of Available

circuits(Time Slots) in that route. This parameter is calculated for Busy Hours.

3.5.2 KPI Target:

Trunk route Utilization should be equal to or less than 70%

3.5.3 Formula:

Trunk route Utilization% = No. of circuits(Time Slots) Utilized /

No. of Available circuits(Time Slots)

3.5.4 Reasons of High Trunk route Utilization:

POI Connectivity issue

Transmission Media Unavailability

Trunk route Dimensioning is not optimized and the Load is not evenly distributed to routes as per traffic requirement.


Trunk route dimensioning should be done properly and the load should be distributed as per traffic requirement.

POI Connectivity issue and Transmission Media unavailability situation should be avoided by taking the preventive action before the crises situation arises.



3.6 B-Table Routing

Check the routing of NLD/ILD and Local calls as per routing priority

All codes to be routed as per routing plan

Delete all the unnecessary codes from the switch

Alternate routes to be defined in MSC wherever applicable

Split the level where required e.g. 033-3 -Routed to RIL NLD and 022-4 Routed to BTSOL

Fixed the length of the codes(Min - Max Value )

Time Based routing can be implemented for congested routes, if possible

Put all major codes under observation



3.7 Subscriber behavior

• Calling party Subscriber disconnect the call

Dialing patterns -Check all the dailing patterns

• Called party Subscriber not Answer the call

• Called party Subscriber Make busy the call

3.8 Release cause

S.N. Cause code Release cause

1 CAUSE013 switch equipment congestion2 CAUSE014 no dialing in long time3 CAUSE015 no answer in long time4 CAUSE016 temporary failure5 CAUSE019 no alerting in long time6 CAUSE020 no release in long time7 CAUSE023 exceed maximum reattempt times8 CAUSE025 release before answer9 CAUSE027 switch equipment failure

10 CAUSE030 ST BUSY11 CAUSE031 SL BUSY12 CAUSE038 Exchange Route Error13 CAUSE042 remote equipment congestion14 CAUSE043 call failure15 CAUSE044 dual seizure16 CAUSE045 invalid directory number17 CAUSE060 CPU congestion or overload18 CAUSE062 no CCB resource19 CAUSE070 partial dial time out20 CAUSE075 signalling error21 CAUSE083 no A interface circuit22 CAUSE093 call release23 CAUSE097 time out of call limitation time24 CAUSE098 termination apply error



25 CAUSE100 callee do not exist

26 CAUSE105do not dial area code when call local

Subscriber27 CAUSE107 mobile callee is busy28 CAUSE108 callee power off29 CAUSE110 dial 0 when call PLMN user in other area30 CAUSE129 unallocated DN31 CAUSE130 no route to the selected transit network32 CAUSE131 no route to the callee33 CAUSE133 dial wrong prefix of long distance call34 CAUSE134 route unacceptable35 CAUSE137 preemption circuit reserved for reuse36 CAUSE145 user decide to busy37 CAUSE146 no response from callee38 CAUSE147 no answer from callee39 CAUSE149 call rejected40 CAUSE151 no free circuit41 CAUSE155 termination error42 CAUSE156 invalid DN format43 CAUSE158 response to status enquiry44 CAUSE166 network error45 CAUSE169 temporary error46 CAUSE170 device congestion47 CAUSE172 no route or circuit applied available48 CAUSE175 no resource available49 CAUSE186 no available bearer capability50 CAUSE209 invalid call reference51 CAUSE210 route identified do not exist52 CAUSE216 incompatible terminal53 CAUSE219 invalid transit network selection54 CAUSE230 recovery of time out55 CAUSE239 protocol error56 CAUSE254 interwork



4 Counter for ASR:

ASR (Answer to Seizure Ratio)

Formula: ( Incoming Traffic over A Interface Trunk Groups (Answer Times) +Outgoing Traffic

over A Interface Trunk Groups (Answer Times) ) / (Incoming Traffic over A Interface Trunk

Groups (Seizure Times ) + Outgoing Traffic over A Interface Trunk Groups (Seizure Times ) -

Trunk Group Traffic (MCA Call Attempt) ) * 100

4.1 Incoming Traffic over A Interface Trunk Groups (Answer Times)

4.1.1 Description

This measurement entity counts the number of times mobile originated (MO) calls are answered.

It provides a basis for calculating the call answer rate about which carriers are concerned.

4.1.2 Application Scenario

When you need to analyze the call answer rate and call answer traffic, create a measurement

task with this measurement entity to count the number of answered MO calls.

4.1.3 Measurement Point

In an MO call flow, the measurement is performed when the MSCa receives the Connect

message from the callee or the ANM message from the peer office. For details, see Figure 1.

For a multi-connection call, supplementary measurement is performed. For example, in an intra-

MSC call flow, subscriber A calls subscriber B and the A-B call is connected. If subscriber A

holds the A-B call and calls subscriber C and subscriber C is alerted, the MSC adds the answer

times counted in the A-C call to that counted in the A-B call. For details, see Figure 2.

Figure 1 Measurement point of Answer Times



Figure 2 Supplementary measurement point of Answer Times

4.2 Outgoing Traffic over A Interface Trunk Groups (Answer Times)

4.2.1 Description

This measurement entity counts the number of times the 2G mobile terminated (MT) calls are

answered, when the MSC receives the Connect message from the callee.

It provides a basis for calculating the call completion rate about which carriers are concerned.


When you need to analyze the call completion rate and call completion traffic, create a

measurement task with this measurement entity to count the number of answered 2G MT calls.


In a 2G MT call flow, the measurement is performed when the MSC receives the Connect

message from the callee. For details, see Figure 1.


MSC call flow, subscriber A calls subscriber B who has subscribed to the call waiting (CW)

service and the A-B call is connected. Then, if subscriber C calls subscriber B and subscriber B

answers the calls, the MSC adds the number of answered calls counted in the A-C call to that

counted in the A-B call. For details, see Figure 2.



Figure 1 Measurement point of Answer Times

Figure 2 Supplementary measurement point of Answer Times

4.3 Incoming Traffic over A Interface Trunk Groups (Seizure Times )

4.3.1 Description

This measurement entity counts the number of times the circuits in the A-interface incoming trunk

group are seized during the mobile originated (MO) calls.


This measurement entity counts the number of seize the circuits in the A-interface incoming trunk

group during the 2G MO calls. Create a measurement task with this measurement entity when

you need to learn the number of times the access bearer is seized in different traffic models.

4,3.3 Measurement Point

In a 2G MO call flow, the MSC hunt a circuit in the A-interface incoming trunk group successfully.

Then, the measurement is performed. For details, see Figure 1.




MSC call flow, subscriber A calls subscriber B and the A-B call is connected. If subscriber A

holds the A-B call and calls subscriber C and subscriber C is alerted, the MSC adds the seizure

times counted in the A-C call to that counted in the A-B call. For details, see Figure 2.

Figure 1 Measurement point of SEIZURE TIMESSeizure Times

Figure 2 Supplementary measurement point of SEIZURE TIMESSeizure Times

4.4 Outgoing Traffic over A Interface Trunk Groups (Seizure Times )

4.4.1 Description

This measurement entity counts the number of times circuits in the A-interface outgoing trunk

group are seized during the 2G mobile terminated (MT) calls. The measurement is performed

when the MSC successfully prepares the terrestrial resources.




This measurement entity counts the number of seize the circuits in the A-interface outgoing trunk

group during the 2G MT calls. Create a measurement task with this measurement entity when

you need to learn the number of times the access bearer is seized in different traffic models.


In a 2G MT call flow, the MSC hunt a circuit in the A-interface outgoing trunk group successfully.

Then, the measurement is performed. For details, see Figure 1.


MSC call flow, subscriber A calls subscriber B who has subscribed to the call waiting (CW)

service and the A-B call is connected. Then, if subscriber C calls subscriber B and subscriber B

is alerted, the MSC adds the seizure times counted in the A-C call to that counted in the A-B call.

For details, see Figure 2.

Figure 1 Measurement point of Seizure Times

Figure 2 Supplementary measurement point of Seizure Times



5 Requirement for Analysis

Reports required for analysis is given below

S.N. Details

1 POI Report

2 BICC / SIP report

3 A-Interface Report

4 Ater interface Report

5 All Link utilization report

6 Signaling report

7 EOS Report

8 MSC Hourly report

9 C7 traffic report

10 Source DATA Capacity report

11 Dest code report

Logs required for analysis is given below

S.N. Details

1 Circuit Selection detail

2 ALL Circuit detail

3 Announcement mapping Dump

4 Signaling circuits detail

5 Command Logs

6 Event Logs

7 Alarm Logs

8 Call logs

9 CP load



Traces required for analysis is given below

S.N. Details

1 POI Sig Traces

2 BICC/SIP Sig Trace

3 C7 Sig Trace

4 A,C,D Interface Traces

5 Looping

Configuration Data required for analysis is given below

S.N. Details

1 B-Table dump

2 New Augmentation Details

3 MSC Dump

4 Circuit Seizure/Hunting detail for both END

Connecting Node detail required for analysis is given below

S.N. Details

1 Code Routing Plan

2 Routine change tracker

3 GT Dump STP

4 LRN dump STP



6 Recommendations

• Identification of major rejection causes for outing call failures

• Audit of MSC- As per the action plan

• Circuit selection mode should be kept as per the standards at both POI ends in order

to avoid call failure due to dual

• EOS and Announcement mapping must be done as per the NOC guidelines, make

sure correct announcements are

• Remove congestion on all the POIs

• Start Dest Code monitoring on top 25 codes

• Further identification of low ASR codes/Routes and modification of routing plan

• Removal of crank bank feature on local POIs

• Time based routing of low ASR codes

• identify the codes rejected with release cause and check the route and take up with

the concerned operator

asr improvement

Documents

2g mobile

interface

call completion

intramsc call

measurement

seizure timesseizure

controlling

poi circuit