UTRAN KPI Analysis Guide 20051010 B 1 0

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UTRAN KPI Analysis Guide For Internal Use Only Document name Confidentiality level UTRAN KPI Analysis Guide For Internal Use Only Huawei Technologies Co., Ltd RAN Maintenance Dept. Total 44 Pages UTRAN KPI Analysis Guide Prepared by RAN Maintenance Dept. Date Aug. 10, 2005 Reviewed by Date Reviewed by Date Approved by Date Huawei Technologies Co., Ltd. All Rights Reserved

Transcript of UTRAN KPI Analysis Guide 20051010 B 1 0

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UTRAN KPI Analysis Guide

For Internal Use Only

Document name Confidentiality levelUTRAN KPI Analysis Guide For Internal Use OnlyHuawei Technologies Co., Ltd RAN Maintenance Dept. Total 44 Pages

UTRAN KPI Analysis Guide

Prepared by RAN Maintenance Dept. Date Aug. 10, 2005

Reviewed by Date

Reviewed by Date

Approved by Date

Huawei Technologies Co., Ltd. All Rights Reserved

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UTRAN KPI Analysis Guide

For Internal Use Only

Revision Edition

Date Version Description Author

Aug. 10, 2005 The first version is complete. Wang Wei

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Table of Contents

1. Overview ..............................................................................................................................4 1.1 Intended Audience ......................................................................................................4 1.2 Objectives....................................................................................................................4

2. Introduction to Nastar...........................................................................................................5 3. UTRAN KPI Analysis ...........................................................................................................5

3.1 Nastar Tasks ...............................................................................................................5 4. Detailed UTRAN KPI Analysis .............................................................................................7

4.1 Call Completion Rate ..................................................................................................7 4.1.1 RRC Setup Analysis ............................................................................................7 4.1.2 RAB Setup Analysis ..........................................................................................11

4.2 Soft Handover Analysis.............................................................................................18 4.2.1 Overview............................................................................................................19 4.2.2 Cell SHO Prepare Failure Analysis ...................................................................20 4.2.3 Cell SHO Failure Analysis .................................................................................22

4.3 CS Inter-RAT Handover Analysis..............................................................................24 4.3.1 Overview............................................................................................................25 4.3.2 CS Inter-RAT Handover Prepare Failure Analysis ............................................26 4.3.3 CS Inter-RAT Handover Failure Analysis..........................................................28 4.3.4 Cell Inter-RAT Handover Analysis.....................................................................30

4.4 PS Inter-RAT Handover Analysis..............................................................................30 4.4.1 Overview............................................................................................................30 4.4.2 PS Inter-RAT Handover Failure Analysis ..........................................................31 4.4.3 Cell Inter-RAT Handover Analysis.....................................................................33

4.5 Cell Update Analysis .................................................................................................33 4.5.1 Overview............................................................................................................33 4.5.2 Cell Update Failure Analysis .............................................................................34

4.6 Call Drop Analysis.....................................................................................................35 4.6.1 Overview............................................................................................................35 4.6.2 CS Call Drop Analysis .......................................................................................36 4.6.3 PS Call Drop Analysis .......................................................................................37 4.6.4 Cell Call Drop Analysis ......................................................................................39

4.7 Traffic Load Analysis.................................................................................................40 4.7.1 Overview............................................................................................................41 4.7.2 Cell Traffic Analysis ...........................................................................................42

5. Analyzing Complicated Problems ......................................................................................44 5.1 Narrowing Down Area Range and Time Range........................................................44 5.2 Analyzing Abnormal Logs .........................................................................................44 5.3 Analyzing Repeated Problems..................................................................................44

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UTRAN KPI Analysis Guide

1. Overview

In a commercial network, the QoS and network operation are reflected through

KPI. UTRAN KPI analysis is a major method used for monitoring and evaluating

network operation. UTRAN KPI analysis is also served to track the network traffic,

monitor the resource distribution, and facilitate the network expansion and

optimization. Huawei UTRAN traffic statistics provides sufficient KPI for network

operation, algorithm management, and resource distribution. These traffic

statistics can be used to locate network problems and optimize network KPI.

UTRAN KPI analysis is a major method for RAN maintenance engineers and

network optimization engineers to evaluate network performance. Comparing with

drive tests, call detail logs, and alarms, KPI analysis can be used to monitor

network operation directly and conveniently. To better locate network problems

and optimize network KPI, abnormal indices, call detail logs, tracked messages,

and drive tests can be used together.

Huawei provides a traffic statistics analysis tool Nastar for UTRAN KPI analysis.

Nastar can be used to obtain and analyze UTRAN KPI. This guide introduces how

to use Nastar to analyze UTRAN KPI. For more information, refer to GENEX

Nastar V400R001C01 User Manual.

1.1 Intended Audience

This guide, intended for network maintenance engineers and site audit engineers,

introduces Nastar V400R001, which supports the KPI analysis of RNC

V100R002C03B092 and RNC V100R002C03B151.

1.2 Objectives

This guide aims to provide guidance for network maintenance personnel to

monitor network KPI on a timely basis, analyze abnormal indices, and find out

practical solutions.

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2. Introduction to Nastar

Nastar provides such functions as index defining, query defining, and report

generating. For more information, refer to GENEX Nastar V400R001C01 User

Manual.

3. UTRAN KPI Analysis

The QoS of communication network is defined in ITU-T E.800. Considering the

features of wireless communication network, the following KPI must be considered

for WCDMA RAN, as shown in Table 1-1.

Network performance KPI

RRC Setup Success Rate Call completion rate

RAB Setup Success Rate

Voice Call Drop Rate

VP Call Drop Rate Call drop rate

PS Call Drop Rate

Soft Handover Success Rate

Inter-Frequency HO Success Rate

Intra-Frequency HO Success Rate

CS Inter-RAT HO Success Rate

PS Inter-RAT HO Success Rate

Mobility management

Cell Update Success Rate

Equivalent User

Cell Throughput Traffic

Cell Resource Allocation

Table 1-1 WCDMA RAN KPI

3.1 Nastar Tasks

Figure 1-1 shows a list of Nastar tasks.

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Figure 1-1 Nastar tasks

Perf Daily Report and Perf Weekly Report can be generated in .xls file by Nastar.

An object can be a self-defined clutter or RNC. Perf Daily Report is used to

monitor network performance. By default, Perf Daily Report includes the following

KPI, as shown in Table 1-2.

RNC:1

CS User Based on Equivalent User 17.13(16:00 ~ 17:00)

PS User Based on Equivalent User 54.09(12:00 ~ 13:00)

RRC Connection Setup Success Rate(service)(>95%) 98.64%(2468/2502)

RRC Connection Setup Success Rate(other)(>95%) 96.87%(36445/37624)

AMR RAB Assignment Success Rate(>95%) 99.00%(990/1000)

Video Call RAB Assignment Success Rate(>95%) 100.00%(29/29)

PS RAB Assignment Success Rate(>95%) 99.60%(997/1001)

RB Setup Success Rate(>95%) 99.31%(2016/2030)

Soft Handover Success Rate(>98%) 99.75%(17090/17132)

Softer Handover Success Rate(>98%) 99.66%(3509/3521)

Soft Handover Factor based on Radio Link Number(<40%) 18.85%

Inter-Freq Hard Handover Success Rate(>85%) 100.00%(16/16)

CS Inter-RAT Handover Success Rate( from UTRAN to GSM)(>85%) 100.00%(4/4)

PS Inter-RAT Handover Success Rate( from UTRAN to GSM)(>85%) 66.67%(4/6)

1.92%(19/990)

10.34%(3/29)

CS AMR Call Drop Rate(<1.5%)

Video Call Drop Rate(<1.5%)

PS Service Drop Rate(<30%) 3.01%(30/997)

CDR

RNC Name

Traffic

HO

Access

Table 1-2 Perf Daily Report

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If network performance cannot meet the previous KPI or the KPI is changed, refer

to Section 4 UTRAN KPI Analysis.

4. UTRAN KPI Analysis

4.1 Call Completion Rate

This section consists of the following parts:

RRC Setup Analysis

RAB Setup Analysis

4.1.1 RRC Setup Analysis

1. Overview

RRC Setup Analysis is included in Nastar, as shown in Figure 1-1. Double click

RRC Setup Analysis to display the RRC setup details, as shown in Figure 1-3.

RRC setup success rate is 97.3%. Most RRC setup failures result from RRC

Setup Fail No Response while few RRC setup failures (seven times) result from

RRC Setup Reject.

78,961 RRC_SETUP_SUCC7 RRC_REJ

2,186 RRC_SETUP_FAIL_NO_RSP

97.3 %

0.01 %2.69 %

Figure 1-3 RRC Setup

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There are two reasons for RRC Setup Fail No Response:

Downlink FACH and RACH are covered unevenly.

The networks, built during the early period, are covered poorly. In particular,

inter-system reselection areas are covered poorly.

A certain area has too many subscribers or any equipment in this area is

faulty.

2. RRC Setup Scenario Analysis

One of the reasons for RRC Setup Fail No Response is poor coverage, so RRC

setup reasons and RRC setup success rate can be used for further analysis. Start

Scenario Analysis to display a pie or bar chart for presenting RNC indices.

7,451 RRC_REQ_ORG5,639 RRC_REQ_TERM

51,385 RRC_REQ_CELL_RESEL16,387 RRC_REQ_REG

9.21 %

6.97 %

63.55 %

20.27 %

Figure 1-4 RRC setup scenario (pie chart)

Use Scenario Analysis to analyze RRC setup scenarios, as shown in Figure 1-5.

Most RRC setup requests are caused by:

RRC REQ CELL RESEL

If network coverage is poor, inter-system reselection may occur.

RRC REQ REG

If network coverage is poor, subscribers attempt to register for many times.

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RNC:41(ID:41)-RRC_SETUP_SUCC_RATE_ORGgfedcbRNC:41(ID:41)-RRC_SETUP_SUCC_RATE_TERMgfedcbRNC:41(ID:41)-RRC_SETUP_SUCC_RATE_INTERRAT_CELL_RESELgfedcbRNC:41(ID:41)-RRC_SETUP_SUCC_RATE_REGgfedcb

Time0

Bar V

alue

0.99

0.985

0.98

0.975

0.97

0.965

0.96

0.955

0.95

0.945

Figure 1-5 RRC setup scenario (bar chart)

Figure 1-5 shows RRC setup success rates. RRC SETUP SUCC RATE ORG is

very high while RRC SETUP SUCC RATE REG is very low. On Huawei networks,

resident threshold Ec/Io is greater than -18 dB while inter-system reselection start

threshold Ec/Io is less than -14 dB. Low RRC SETUP SUCC RATE REG indicates

that many registrations are attempted within the area (Ec/Io falls between -14 dB

and -18 dB), which has poor coverage. High RRC SETUP SUCC RATE ORG

(99%) indicates that the network is covered by PCH and RRC SETUP SUCC

RATE can be high in a well-covered network.

3. RRC Setup Reject Analysis

RRC setup reject are caused by:

Admission reject due to crowded subscribers

Access failure due to equipment faults

RRC setup reject may occur no matter how poor network coverage is; however,

RRC setup reject occurs in a small-scale network. Therefore, only the areas of

RRC setup reject must be analyzed.

In RRC Setup Analysis, start Cell RRC Analysis to query the TOPN. The queried

results are outputted in three pages:

(1) The top ten cells that have the highest RRC setup reject times.

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(2) The top ten cells that have the highest RRC setup success rates.

(3) The top ten cells that have the highest RRC setup failure rates.

For the top ten cells that have the maximum RRC setup fail rates, start Cell

Scenario Analysis for further analysis. For the top ten cells that have the

maximum RRC setup rejects, start Cell RRC Reject Analysis for further analysis.

2 RRC_REJ_POWER_CONG_CELL0 RRC_REJ_CE_CONG_CELL0 RRC_REJ_RL_FAIL_CELL0 RRC_REJ_AAL2_FAIL_CELL0 RRC_REJ_FP_FAIL_CELL0 RRC_REJ_CODE_CONG_CELL0 RRC_REJ_OTHER_CELL

100 % 0 %0 %0 %0 %0 %0 %

Figure 1-6 RRC setup reject analysis

Figure 1-6 shows the results of Cell RRC Reject Analysis. In this figure, two RRC

setup rejects are caused by Power Congestion. RRC setup reject may be caused

by the following reasons:

(1) Power Congestion

RRM performs the admission algorithm decision but uplink or downlink

admission decision is rejected, so RRC setup reject occurs. If network load

is heavy, power congestion may occur. To locate the problem, start Cell

Traffic Load Analysis to check whether uplink or downlink is congested by

focusing on the maximum RTWP and the maximum TCP. If power

congestion is confirmed, check whether the threshold is reasonable, check

whether there is any interference, and check whether the network capacity

is insufficient.

(2) CE Congestion

If there are many subscribers, CE resources may become insufficient in

RNC. To locate the problem, start Cell Traffic Load Analysis to check the

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DCH user number and forecast the required CE quantity in accordance with

the traffic model.

(3) RL Fail

During the RRC setup process, NodeB recognizes RRC setup fail because

NodeB fails or NodeB resource is insufficient. To locate the problem start

Cell Traffic Load Analysis to check the DCH user number. Analyze the

data and logs of the boards or CEs in NodeB to check whether NodeB fails

or NodeB resource is insufficient.

(4) AAL2 Fail

If transmission resource is insufficient or any transmission equipment is

faulty, the AAL2 path setup of lub interface may fail. To locate the problem,

start Cell Traffic Load Analysis to check the DCH user number and the

bandwidth of AAL2 path. Check whether transmission resource is

insufficient or any transmission equipment is faulty.

(5) FP Fail

If the transmission fails or an equipment is faulty, FP synchronization may

fail. To locate the problem, check whether there is any BTS alarm.

(6) Code Congestion

If there is high traffic in the indoor micro cell, code resource may be

insufficient. To locate the problem, start Cell OVSF Code Allocation Analysis

to analyze the code allocation and confirm major services.

(7) Other

If there is any problem in RNC, RRC setup reject may occur. To locate the

problem, analyze call detail logs.

4.1.2 RAB Setup Analysis

1. Overview

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Figure 1-7 Nastar tasks

Figure 1-7 shows a list of Nastar tasks. RAB Setup Analysis is included in Nastar.

Double click RAB Setup Analysis to display RAB setup details, as shown in

Figure 1-8.

2,370 CS_RAB_REQ_SETUP_CONV_0_32101 CS_RAB_REQ_SETUP_CONV_32_64

5 PS_RAB_REQ_SETUP_64K5 PS_RAB_REQ_SETUP_128K

749 PS_RAB_REQ_SETUP_384K

73.37 %

3.13 % 0.15 %0.15 %

23.19 %

Figure 1-8 RAB setup analysis

Check such RAB setup rates as CS_RAB_REQ_SETUP_CONV_0_32 (AMR),

CS_RAB_REQ_SETUP_CONV_32_64 (VP), 64 K (PS), 128 K (PS), and 384 K

(PS) to confirm major services in the network.

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Click Produce a Bar Chart to display the RB and RAB setup success rates, as

shown in Figure 1-9.

RNC:1(ID:1)-RB_SETUP_SUCC_RATEgfedcb RNC:1(ID:1)-CS_RAB_ SETUP_SUCC_RATE_AMRgfedcbRNC:1(ID:1)-CS_RAB_ SETUP_SUCC_RATE_VPgfedcb RNC:1(ID:1)-PS_RAB_SETUP_SUCC_RATE_64KgfedcbRNC:1(ID:1)-PS_RAB_SETUP_SUCC_RATE_128Kgfedcb RNC:1(ID:1)-PS_RAB_SETUP_SUCC_RATE_384Kgfedcb

Time0

Bar V

alue

1.11

0.90.80.70.60.50.40.30.20.1

0

Figure 1-9 RB and RAB setup success rates

2. RAB Setup Fail Analysis

In RAB Setup Analysis, start Cell RAB Analysis to query the TOPN. The queried

results are outputted in four pages:

(1) The top ten cells that have the highest CS RAB setup failures.

(2) The top ten cells that have the lowest CS RAB setup failures.

(3) The top ten cells that have the highest PS RAB setup failures.

(4) The top ten cells that have the lowest PS RAB setup failures.

Low RAB setup success rate may occur in the cells that have lowest setup times.

To locate the problem, focus on the cells that have the lowest setup failures

because the KPI is affected mostly by these cells.

If CS RAB setup fail rate is high in a cell, start Cell CS RAB Setup Fail Analysis

to display the CS RAB setup fail rates, as shown in Figure 1-10.

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1,571 CS_RAB_SETUP_SUCC_CONV_CELL0 CS_RAB_SETUP_SUCC_STR_CELL0 CS_RAB_SETUP_FAIL_PARAM_CELL0 CS_RAB_SETUP_FAIL_RELOC_CELL

10 CS_RAB_SETUP_FAIL_TNL_CELL0 CS_RAB_SETUP_FAIL_CONG_CELL0 CS_RAB_SETUP_FAIL_POWER_CONG_CELL0 CS_RAB_SETUP_FAIL_CE_CONG_CELL0 CS_RAB_SETUP_FAIL_CODE_CONG_CELL5 CS_RAB_SETUP_FAIL_OTHER_CELL

99.05 %

0 %0 %0 %

0.63 %0 %0 %0 %0 %0.32 %

Figure 1-10 Cell CS RAB setup fail analysis

Cell CS RAB setup failures may be caused by the following reasons:

(1) PARAM_CELL

RNC regards the parameters transmitted by core network as invalid

parameters. This reason seldom occurs. To locate the problem, track the

signaling and check the RAB setup messages in specific cells.

(2) RELOC_CELL

When initializing the migration process, RNC receives the RAB setup

request messages but RNC does not process the request. This reason is

mainly caused by the process integration related to subscriber action

sequence, so this reason seldom occurs. In a core network, this situation is

always avoided.

(3) TNL_CELL

RAB setup fails because IU transmission setup fails. To locate the problem,

check the transmission capacity and operation stability.

(4) CONG_CELL

This may be caused by RNC resource allocation failure. To locate the

problem, analyze the RNC logs and obtain the detailed resource failure

information.

(5) POWER_CONG_CELL

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According to RRM admission decision, new RAN cannot be set up because

cell load is too heavy. To locate the problem, check whether the parameters

of admission algorithm are reasonable. If yes, consider to optimize the

coverage and expand the capacity.

(6) CE_CONG_CELL

CE resource admission fails in RNC. CE must be expanded.

(7) CODE_CONG_CELL

During the RAB setup process, code resource allocation fails because too

many subscribers are crowded on the network or code resource allocation

fails. To locate the problem, analyze the code resource of cell traffic to

check whether code resource is restricted due to cell overload.

(8) OTHER_CELL

This may caused by RB setup failure or other reasons. To locate the

problem, analyze RB setup success rates.

If PS RAB setup fail rate is high, start Cell PS RAB Setup Fail Analysis to display

the PS RAB setup fail rates, as shown in Figure 1-11.

0 PS_RAB_SETUP_SUCC_CONV_CELL0 PS_RAB_SETUP_SUCC_STR_CELL

37 PS_RAB_SETUP_SUCC_INTER_CELL0 PS_RAB_SETUP_SUCC_BKG_CELL0 PS_RAB_SETUP_FAIL_PARAM_CELL0 PS_RAB_SETUP_FAIL_RELOC_CELL0 PS_RAB_SETUP_FAIL_CONG_CELL3 PS_RAB_SETUP_FAIL_POWER_CONG_CELL0 PS_RAB_SETUP_FAIL_CE_CONG_CELL0 PS_RAB_SETUP_FAIL_CODE_CONG_CELL4 PS_RAB_SETUP_FAIL_OTHER_CELL

0 %0 %

84.09 %

0 %0 %0 %0 %

6.82 %

0 %0 %

9.09 %

Figure 1-11 Cell PS RAB setup fail analysis

Cell CS RAB setup failure may be caused by the following reasons:

(1) PARAM_CELL

RNC regards the parameters transmitted by core network as invalid

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parameters. This reason seldom occurs. To locate the problem, track the

signaling and check the RAB setup messages in specific cells.

(2) RELOC_CELL

When initializing the migration process, RNC receives the RAB setup

request messages but RNC does not process the request. This reason is

mainly caused by the process integration related to subscriber action

sequence, so this reason seldom occurs. In a core network, this situation is

always avoided.

(3) TNL_CELL

RAB setup fails because IU transmission setup fails. To locate the problem,

check the transmission capacity and operation stability.

(4) CONG_CELL

This may be caused by RNC resource allocation failure. To locate the

problem, analyze the RNC logs and obtain the detailed resource failure

information.

(5) POWER_CONG_CELL

According to RRM admission decision, new RAN cannot be set up because

cell load is too heavy. To locate the problem, check whether the parameters

of admission algorithm are reasonable. If yes, consider to optimize the

coverage and expand the capacity.

(6) CE_CONG_CELL

CE resource admission fails in RNC. CE must be expanded.

(7) CODE_CONG_CELL

During the RAB setup process, code resource allocation fails because too

many subscribers are crowded on the network or code resource allocation

fails. To locate the problem, analyze the code resource of cell traffic to

check whether code resource is restricted due to cell overload.

(8) UNSUP_CELL

During the RAB setup process, the QoS is not supported by RNC or RRM

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admission fails in RAB.

(9) OTHER_CELL

This may caused by RB setup failure or other reasons. To locate the

problem, analyze RB setup success rates.

In a commercial network, RAB setup is mainly caused by admission failure and RB

setup failure. To analyze the RB setup failure, start Cell RB Setup Fail Analysis

to display the RB setup fail rates, as shown in Figure 1-12.

1,645 RB_SETUP_SUCC_CELL0 RB_SETUP_FAIL_CFG_UNSUPP_CELL0 RB_SETUP_FAIL_PHYCH_FAIL_CELL0 RB_SETUP_FAIL_SIMU_RECFG_INCOMP_CELL0 RB_SETUP_FAIL_CELL_UPDT_CELL3 RB_SETUP_FAIL_CFG_INVALID_CELL1 RB_SETUP_FAIL_NO_RSP_CELL0 RB_SETUP_FAIL_OTHER_CELL99.76 %

0 %0 %0 %0 %

0.18 %0.06 %0 %

Figure 1-12 Cell RB setup fail analysis

Cell RB setup failure may be caused by the following reasons:

(1) CFG_UNSUPP

UE acknowledges the RB setup failure because of configuration

unsupported. This reason seldom occurs in the network. It is mainly caused

by compatibility problem of UE in some unknown scenarios.

(2) PHYCH_FAIL

The RB setup failure may occur if FACH is migrated to DCH but downlink

physical layers are not synchronized during the RB setup process. The

rooted reason is poor coverage.

(3) SIMU_RECFG_INCOMP

UE regards that the RB setup process and other processes simultaneously

occur and they are incompatible. RNC processing ensures RRC processes

nesting. This reason seldom occurs. It is mainly caused by UE defects.

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(4) CELL_UPDT

During the RB setup process, the Cell Update process occurs. The RB

setup failure is caused by process nesting.

(5) CFG_INVALID

UE regards the configured parameters are invalid ones. This reason seldom

occurs. It is mainly caused by inconsistent understanding of network and

UE.

(6) NO_RESPONSE

UE does not acknowledge the RB setup request. This reason frequently

occurs. It is mainly caused by poor coverage, so UE cannot receive the RB

setup request message.

(7) OTHER

Cell RB setup failure is caused by other reasons. To locate the problem,

analyze call detail logs.

4.2 Soft Handover Analysis

This section consists of the following parts:

Overview

Cell SHO Prepare Failure Analysis

Cell SHO Failure Analysis

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4.2.1 Overview

Figure 1-13 Nastar Tasks

Soft Handover Analysis is included in Nastar tasks, as shown in Figure 1-13.

Double click Soft Handover Analysis to display the RNC soft handover details

(including soft handover success rate, softer handover success rate, and soft

handover prepare success rate), as shown in Figure 1-14.

RNC:1(ID:1)-SHO_SUCC_RATEgfedcb RNC:1(ID:1)-SOFTERHO_SUCC_RATEgfedcbRNC:1(ID:1)-SHO_PREP_SUCC_RATEgfedcb

Time0

Bar V

alue

1.0051

0.9950.99

0.9850.98

0.9750.97

0.9650.96

0.9550.95

0.9450.94

0.935

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Figure 1-14 Soft Handover Analysis

In the previous figure, soft handover factor is used to measure the proportion and

cost of soft handover. SHO_FACTOR_RL and SHO_FACTOR_UE are defined as

follows:

SHO_FACTOR_RL

SHO_FACTOR_RL is used to measure average link number.

SHO_FACTOR-RL can be calculated as follows:

(Subscriber number of link 1 of active set*1 + Subscriber number of link 2 of

active set*2 + Subscriber number of link 3 of active set*3)/Total subscriber

number – 1

SHO_FACTOR_RL is used to indicate the influence of soft handover

exerted on NodeB CE and to evaluate the subscriber resource utililization.

SHO_FACTOR_UE

SHO_FACTOR_UE is used to measure the proportion of soft handover

subscribers. SHO_FACTOR_UE can be calculated as follows:

(Subscriber number of link 2 of active set + Subscriber number of link 3 of

active set)/Total subscriber number

SHO_FACTOR_UE is used to indicate the subscribers in the soft handover

area, which is similar to the proportion of soft handover area by making drive

tests. SHO_FACTOR_UE is used to measure the reasonable relationship

between soft handover area and soft handover distribution.

SHO_FACTOR_UE is greater than SHO_FACTOR_UE. The greater the

difference between them is, the greater the subscriber number of link 3 of active

set is. If the subscriber number of link 3 of active set is very great,

SHO_FACTOR_RL is greater than 1 while SHO_FACTOR_UE is less than 1.

4.2.2 Cell SHO Prepare Failure Analysis

In the Soft Handover Analysis, start Cell SHO Analysis to query the TOPN. The

queried results are outputted in four pages:

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(1) The top ten cells that have the highest soft handover failure times

(2) The top ten cells that have the lowest soft handover success rates

(3) The top ten cells that have the highest soft handover prepare failure times

(4) The top ten cells that have the lowest soft handover prepare success rates

During the early period, low soft handover success rates may exist in the cells that

have less soft handover times. Attention must be paid to the cells that have the

highest soft handover failure times and the highest soft handover prepare failure

times because they affect the KPI of soft handover greatly.

To query the cells that have the highest soft handover prepare failure times, start

Cell SHO Prepare Failure Analysis to display the soft handover prepare failure

details, as shown in Figure 1-15.

0 SHO_PREP_RL_SETUP_FAIL7 SHO_PREP_AAL2_SETUP_FAIL0 SHO_PREP_FP_SYNC_FAIL

67 SHO_PREP_FAIL_OTHER_CELL

0 %

9.46 %

0 %

90.54 %

Figure 1-15 Cell SHO Prepare Failure Analysis

Cell SHO prepare failure may be caused by the following reasons:

(1) SHO_PREP_RL_SETUP_FAIL

The links cannot be added during the soft handover because NodeB CE

resource is insufficient or NodeB is faulty. Internal NodeB logs, Cell Traffic

Load Analysis, and data configuration of NodeB boards can be used to

locate the problems. If NodeB CE resource is insufficient, one or more

boards must be added for expansion.

(2) SHO_PREP_AAL2_SETUP_FAIL

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When the links are added during the soft handover, the AAL2 setup of lub

interface fails because the transmission bandwidth is insufficient. If the

transmission bandwidth is insufficient, transmission equipments must be

expanded.

(3) SHO_PREP_FP_SYNC_FAIL

When the links are added during the soft handover, the synchronization of

AAL2 and FP of lub interface fails. To locate the problem, check whether the

intermittent transmission interruption occurs or the IMA group transmission

is incorrectly configured.

(4) SHO_PREP_ FAIL_OTHER_CELL

Soft handover prepare failure is caused by other reasons, such as

insufficient RNC resource, radio resource admission reject, and RNC link

state reject. To locate the problem, RNC logs must be used for further

analysis.

4.2.3 Cell SHO Failure Analysis

In the Soft Handover Analysis, start Cell SHO Analysis to query the TOPN. The

queried results are outputted in four pages:

(1) The top ten cells that have the highest soft handover failure times

(2) The top ten cells that have the lowest soft handover success rates

(3) The top ten cells that have the highest soft handover prepare failure times

(4) The top ten cells that have the lowest soft handover prepare success rates

During the early period, low soft handover success rates may exist in the cells that

have less soft handover times. Attention must be paid to the cells that have the

highest soft handover failure times and the highest soft handover prepare failure

times because they affect the KPI of soft handover greatly.

In the Cell SHO Analysis, start Cell SHO Failure Analysis to display the soft

handover failure details, as shown in Figure 1-16.

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2,797 SHO_SUCC_CELL0 SHO_RL_ADD_FAIL_CFG_UNSUPP0 SHO_RL_ADD_FAIL_SIMU_RECFG_INCOMP0 SHO_RL_ADD_FAIL_CFG_INVALID4 SHO_RL_ADD_FAIL_NO_RSP0 SHO_RL_DEL_FAIL_CFG_UNSUPP0 SHO_RL_DEL_FAIL_SIMU_RECFG_INCOMP0 SHO_RL_DEL_FAIL_CFG_INVALID3 SHO_RL_DEL_FAIL_NO_RSP0 SHO_FAIL_OTHER_CELL

99.75 %

0 %0 %0 %

0.14 %0 %0 %0 %

0.11 %0 %

Figure 1-16 Cell SHO Failure Analysis

Soft handover failure may be caused by the following reasons:

(1) SHO_RL_ADD_FAIL_CFG_UNSUPP

UE does not support to add radio links in RNC during the active set update.

This reason seldom exists in a commercial network.

(2) SHO_RL_ADD_FAIL_SIMU_RECFG_INCOMP

UE feeds back that the soft handover process is incompatible with other

concurrent processes when radio links are added in RNC. When handling

the processes, RNC performs the serial connection. The problem is mainly

caused by some handsets.

(3) SHO_RL_ADD_FAIL_CFG_INVALID

UE regards active set update of adding radio links in RNC as invalid

configuration. This reason seldom occurs in a commercial network.

(4) SHO_RL_ADD_FAIL_NO_RSP

RNC does not receive the acknowledgement of active set update of adding

radio links. Soft handover failure is mainly caused by this reason. If network

coverage is poor or soft handover area is small, soft handover failure easily

occurs. Thus, the RF optimization is required.

(5) SHO_RL_DEL_FAIL_CFG_UNSUPP

UE does not support to delete radio links in RNC during the active set

update. This reason seldom occurs in a commercial network.

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(6) SHO_RL_ADD_FAIL_SIMU_RECFG_INCOMP

UE feeds back that the soft handover is incompatible with other concurrent

processes when radio links are deleted in RNC. When handling the

processes, RNC performs the serial connection. The problem is mainly

caused by some handsets.

(7) SHO_RL_ADD_FAIL_CFG_INVALID

UE regards the active set update of deleting radio links in RNC as invalid

configuration. This reason seldom occurs in a commercial network.

(8) SHO_RL_ADD_FAIL_NO_RSP

RNC does not receive the acknowledgement of active set update of deleting

radio links. Soft handover failure is mainly caused by this reason. If network

coverage is poor or soft handover area is small, soft handover failure easily

occurs. Thus, the RF optimization is required.

(9) SHO_FAIL_OTHER_CELL

Soft handover failure is caused by other reasons; however, soft handover

failure is seldom caused by other reasons. If soft handover failure is caused

by other reasons, analyze the logs to locate the problems.

4.3 CS Inter-RAT Handover Analysis

This section consists of the following parts:

Overview

CS Inter-RAT Handover Prepare Failure Analysis

CS Inter-RAT Handover Failure Analysis

Cell Inter-RAT Handover Analysis

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4.3.1 Overview

Figure 1-17 Nastar tasks

CS Inter-RAT Handover Analysis is included in Nastar tasks, as shown in Figure

1-17. Double click CS Inter-RAT Handover Analysis to display the CS inter-RAT

handover details between a 2G network and a 3G network (including CS

inter-RAT handover success rate, CS inter-RAT handover prepare failure rate,

and CS inter-RAT handover failure rate), as shown in Figure 1-18. In a commercial

network, CS inter-RAT handover between a 2G network and a 3G network seldom

occurs.

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605 CS_INTRAT_HO_OUT_PREP_FAIL2,735 CS_INTRAT_HO_OUT_SUCC

40 CS_INTRAT_HO_OUT_FAIL17.9 %

80.92 %

1.18 %

Figure 1-18 CS Inter-RAT Handover Analysis

4.3.2 CS Inter-RAT Handover Prepare Failure Analysis

In the CS Inter-RAT Handover Analysis, start CS Inter-RAT Handover Prepare

Failure Analysis to display the CS inter-RAT handover details, as shown in

Figure 1-19.

2,775 CS_INTRAT_HO_OUT_PREP_SUCC0 CS_INTRAT_HO_OUT_PREP_FAIL_TARGET_FAIL0 CS_INTRAT_HO_OUT_PREP_FAIL_TALLOC_EXPIR0 CS_INTRAT_HO_OUT_PREP_FAIL_TARGET_UNSUPP

13 CS_INTRAT_HO_OUT_PREP_FAIL_RELOC_ABORT560 CS_INTRAT_HO_OUT_PREP_FAIL_NO_RSRC_AVAIL

0 CS_INTRAT_HO_OUT_PREP_FAIL_UNKNOWTARGET32 CS_INTRAT_HO_OUT_PREP_FAIL_REQINFNOTAVAI0 CS_INTRAT_HO_OUT_PREP_FAIL_NO_RSP0 CS_INTRAT_HO_PREP_FAIL_OTHER

82.1 %

0 %0 %0 %

0.38 %

16.57 %

0 %0.95 %0 %0 %

Figure 1-19 CS inter-RAT handover prepare failure analysis

CS inter-RAT handover prepare failure may be caused by the following reasons:

(1) CS_INTERRAT_HO_PREP_FAIL_TARGET_FAIL

CS inter-RAT handover prepare failure is caused by Relocation Failure

Target CN/RNC or Target System (cause value) because the data

configuration of core network is incorrect or BSS does not support the

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handover. To locate the problem, track the signaling of core network and

BSS for further analysis.

(2) CS_INTERRAT_HO_PREP_FAIL_TALLOC_EXPIR

CS inter-RAT handover prepare failure is caused by TRELOCalloc Expiry

(cause value) because the data configuration or link connection of core

network is incorrect. To locate the problem, track the signaling of core

network and BSS for further analysis.

(3) CS_INTERRAT_HO_PREP_FAIL_TARGET_UNSUPP

CS inter-RAT handover prepare failure is caused by Relocation Not

Supported in Target RNC or Target System (cause value) because BSC

does not support some parameters of handover requests. To locate the

problem, track the signaling of core network and BSS for further analysis.

(4) CS_INTERRAT_HO_PREP_FAIL_RELOC_ABORT

After sending the handover prepare request, RNC receives the release

message from core network. This may be caused by two reasons:

(1) Inter-RAT handover is requested during the signaling processes,

such as location update. Location update process is complete

before inter-RAT handover process is complete. Thus, core network

initializes the release.

(2) When inter-RAT handover prepare process is performed, an MS

hangs up the call. Thus, core network initializes the release.

Although the previous inter-RAT handover processes are incomplete, they

are normal nested processes.

(5) CS_INTERRAT_HO_PREP_FAIL_NO_RSRC_AVAIL

CS inter-RAT handover prepare failure is caused by No Resource Available

(cause value) because the data configuration of MSC is incorrect or there is

no available resource in BSC. To locate the problem, track the signaling of

core network and BSS for further analysis.

(6) CS_INTERRAT_HO_PREP_FAIL_UNKNOWTARGET

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CS inter-RAT handover prepare failure is caused by Unknown Target RNC

(cause value) because the data configuration of MSC is incorrect or the LAC

of target cell is not configured. To locate the problem, check whether any

data is incorrectly configured in the core network. This problem frequently

occurs if a 2G network is adjusted.

(7) CS_INTERRAT_HO_PREP_FAIL_ REQINFNOTAVAI

CS inter-RAT handover prepare failure is caused by Requested Information

Not Available because the data configuration is incorrect or target BSC does

not support the handover. To locate the problem, track the signaling of core

network and BSS for further analysis.

(8) CS_INTERRAT_HO_PREP_FAIL_NO_RSP

CS inter-RAT handover prepare failure occurs because core network does

not respond to the handover prepare request. This may be caused by

incorrect data configuration or link connection of core network. To locate the

problem, track the signaling of core network and BSS for further analysis.

4.3.3 CS Inter-RAT Handover Failure Analysis

In the CS Inter-RAT Handover Analysis, start CS Inter-RAT Handover Failure

Analysis to display the CS inter-RAT handover details (including CS inter-RAT

handover success and failure rates), as shown in Figure 1-20.

0 CS_INTRAT_HO_OUT_FAIL_UNSPEC0 CS_INTRAT_HO_OUT_FAIL_NO_RSP

12 CS_INTRAT_HO_OUT_FAIL_RELOC_ABORT1 CS_INTRAT_HO_FAIL_OTHER

2,735 CS_INTRAT_HO_OUT_SUCC0 CS_INTRAT_HO_OUT_FAIL_CFG_UNSUPP

27 CS_INTRAT_HO_OUT_FAIL_PHYCH_FAIL

0 %0 %

0.43 %0.04 %98.56 %

0 %0.97 %

Figure 1-20 CS inter-RAT handover failure analysis

CS inter-RAT handover failure may be caused by the following reasons:

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(1) CS_INTERRAT_HO_ FAIL_UNSPEC

CS inter-RAT handover failure is caused by Unspecified (cause value). This

reason seldom occurs in a network.

(2) CS_INTERRAT_HO_ FAIL_PHYCN_FAIL

CS inter-RAT handover failure is caused by Physical Channel Failure

(cause value). CS inter-RAT handover failure is mainly caused by:

The signals of 2G network are weak or UE fails to access the network

due to serious interference.

Some parameters (such as ciphering mode) transmitted to UE are

inconsistent with that of BSC.

To locate the problem, compare the parameters of UE with that of BSC.

(3) CS_INTERRAT_HO_ FAIL_ CFG_UNSUPP

CS inter-RAT handover failure is caused by Configuration Unsupported

(cause value) because UE does not support the handover request. This

reason may be mainly caused by abnormal UE.

(4) CS_INTERRAT_HO_ FAIL_ RELOC_ABORT

After sending the handover request message to UE, RNC receives the

release message from core network. However, the cause is not Normal

Release because the link is released abnormally due to other reasons. This

reason is caused by the nesting of handover process and release process.

(5) CS_INTERRAT_HO_ FAIL_NO_RSP

After RNC sends the handover request message to UE, UE does not

acknowledge the request because network coverage is poor.

(6) CS_INTERRAT_HO_ FAIL_OTHER

CS inter-RAT handover failure is caused by other reasons. To locate the

problem, analyze the RNC logs.

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4.3.4 Cell Inter-RAT Handover Analysis

In the CS inter-RAT Handover Analysis, start Cell inter-RAT Handover Analysis

to query the TOPN. The queried results are outputted to list:

(1) The cell that have the lowest CS inter-RAT handover success rate

(2) The cell that have the greatest CS inter-RAT handover prepare failure times

(3) The cell that have the greatest CS inter-RAT handover failure times

(4) The cell that have the greatest CS inter-RAT handover times

Through the previous results, you can find the cell that has the greatest CS

inter-RAT handover times. Thus, the network coverage must be improved. In

addition, you can find the cell that has the greatest CS inter-RAT handover failure

times. Thus, the data configuration must be checked.

4.4 PS Inter-RAT Handover Analysis

This section consists of the following parts:

Overview

PS Inter-RAT Handover Failure Analysis

Cell Inter-RAT Handover Analysis

4.4.1 Overview

PS inter-RAT Handover Analysis is included in Nastar tasks. Double click PS

Inter-RAT Handover Analysis to display the PS inter-RAT handover details

between a 2G network and a 3G network, as shown in Figure 1-21. PS inter-RAT

handover from a 2G network to a 3G network need not be analyzed because PS

inter-RAT handover from a 2G network to a 3G network cannot be identified in

access network.

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10 PS_INTRAT_HO_OUT_UTRAN_REQ0 PS_INTRAT_HO_OUT_UE_REQ

100 % 0 %

Figure 1-21 PS inter-RAT handover analysis

Figure 1-22 shows PS_INTRAT_HO_OUT_UTRAN_REQ and

PS_INTRAT_HO_OUT_UTRAN_UE. PS_INTRAT_HO_OUT_UTRAN_REQ

indicates that the PS inter-RAT handover is initialized by the UE in a dedicated

channel. PS_INTRAT_HO_OUT_UTRAN_UE indicates that the PS inter-RAT

handover is initialized by combined services or the PS inter-RAT reselection is

initialized by the UE that is not in a dedicated channel.

RNC:41(ID:41)-PS_INTRAT_HO_OUT_UTRAN_SUCC_RATEgfedcbRNC:41(ID:41)-PS_INTRAT_HO_OUT_UE_SUCC_RATEgfedcb

Time0

Bar V

alue

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

Figure 1-22 PS inter-RAT handover success rate

4.4.2 PS Inter-RAT Handover Failure Analysis

In the PS inter-RAT Handover Analysis, start PS inter-RAT Handover Failure

Analysis to display the PS inter-RAT handover success and failure rates, as

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shown in Figure 1-23.

8 PS_INTRAT_HO_OUT_UTRAN_SUCC0 PS_HO_OUT_FAIL_CFG_UNSUPP0 PS_HO_OUT_FAIL_PHYCH_FAIL0 PS_HO_OUT_FAIL_UNSPEC0 PS_HO_OUT_FAIL_NO_RSP2 PS_HO_OUT_FAIL_OTHER

80 %

0 %0 %0 %0 %

20 %

Figure 1-23 PS inter-RAT handover failure analysis

PS inter-RAT handover failure may be caused by the following reasons:

(1) PS_INTERRAT_HO_ FAIL_UNSPEC

PS inter-RAT handover failure is caused by Unspecified (cause value). This

reason seldom occurs in a network.

(2) PS_INTERRAT_HO_ FAIL_PHYCN_FAIL

PS inter-RAT handover failure is caused by Physical Channel Failure (cause

value) because the signals of 2G network are weak or UE fails to access the

network due to serious interference.

(3) PS_INTERRAT_HO_ FAIL_ CFG_UNSUPP

PS inter-RAT handover failure is caused by Configuration Unsupported

(cause value) because UE does not support the handover request. This

reason may be mainly caused by abnormal UE.

(4) PS_INTERRAT_HO_ FAIL_NO_RSP

After RNC sends the handover request message to UE, UE does not

acknowledge the request because network coverage is poor or UE does not

support the handover.

(5) PS_INTERRAT_HO_ FAIL_OTHER

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PS inter-RAT handover failure is caused by other reasons. To locate the

problem, analyze the RNC logs.

4.4.3 Cell Inter-RAT Handover Analysis

In the PS Inter-RAT Handover Analysis, start Cell Inter-RAT Handover Analysis

to query the TOPN. The queried results are outputted to list:

(1) The cell that have the lowest PS inter-RAT handover success rate

(2) The cell that have the greatest PS inter-RAT handover prepare failure times

(3) The cell that have the greatest PS inter-RAT handover failure times

(4) The cell that have the greatest PS inter-RAT handover times

Through the previous results, you can find the cell that has the greatest PS

inter-RAT handover times. Thus, the network coverage must be improved.

4.5 Cell Update Analysis

This section consists of the following parts:

Overview

Cell Update Failure Analysis

4.5.1 Overview

Cell Update Analysis is included in Nastar tasks. Double click Cell Update

Analysis to display the cell update details (including cell update times and cell

update success rate). Cell update process is initialized because the links of UE are

abnormal or RLC is reset. Cell update process is mainly caused by poor network

coverage. This cell update process is different from that of cell reselection, so you

must be familiar with diverse cell update processes. In the Cell Update Analysis,

start Cell Update Scenario Analysis to display different cell update scenarios, as

shown in Figure 1-24. If the state transition is disabled in a network, the cell update

is caused by abnormal links or RLC reset if UE is not in CELL_FACH or

CELL_PCH state.

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0 CELL_UPDT_REENTER0 CELL_UPDT_PAGE0 CELL_UPDT_UL_DATA_TRANS

211 CELL_UPDT_RLC_ERR15 CELL_UPDT_RL_FAIL0 CELL_UPDT_PRD0 CELL_UPDT_RESEL0 CELL_UPDT_OTHER

0 %0 %0 %

93.36 %

6.64 %

0 %0 %0 %

Figure 1-24 Cell update scenarios

In the Cell Update Scenario Analysis, click Create a Bar Chart to display the cell

update success rates, as shown in Figure 1-25. In general, the cell updates are

caused by abnormal links (RL) or RLC reset (RLC_ERR), thus low cell update

success rate may be caused by poor network coverage. If cell update is caused by

other reasons, cell update success rate must be greater than 85%.

RNC:41(ID:41)-CELL_UPDT_SUCC_RATE_RESELgfedcbRNC:41(ID:41)-CELL_UPDT_SUCC_RATE_REENTERgfedcbRNC:41(ID:41)-CELL_UPDT_SUCC_RATE_PAGEgfedcbRNC:41(ID:41)-CELL_UPDT_SUCC_RATE_UL_DATA_TRANSgfedcbRNC:41(ID:41)-CELL_UPDT_SUCC_RATE_RLC_ERRgfedcbRNC:41(ID:41)-CELL_UPDT_SUCC_RATE_RLgfedcbRNC:41(ID:41)-CELL_UPDT_SUCC_RATE_PRDgfedcbRNC:41(ID:41)-CELL_UPDT_SUCC_RATE_OTHERgfedcb

Time0

Bar V

alue

0.07

0.06

0.05

0.04

0.03

0.02

0.01

0

Figure 1-25 Cell update success rates

4.5.2 Cell Update Failure Analysis

In the Cell Update Analysis, start Cell Update Analysis to query the TOPN. The

queried results are outputted to list:

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(1) The cell that has the lowest cell update success rate

(2) The cell that has the greatest cell update failure times

If a cell has the lowest cell update success rate, cell update times are less.

Attention must be paid to the cell that has the greatest cell update failure times.

In the queried results of Cell Update Analysis, start Cell Update Scenario

Analysis for Cell to analyze the cell update failure and summarize the cell update

failure scenarios.

4.6 Call Drop Analysis

This section consists of the following parts:

Overview

CS Call Drop Analysis

PS Call Drop Analysis

Cell Call Drop Analysis

4.6.1 Overview

Call Drop Analysis is included in Nastar tasks. Double click Call Drop Analysis to

display the RNC call drop details. Then, click Create a Pie Chart to display the call

drop details for different services (including voice, VP, CS, and PS), as shown in

Figure 1-27.

75 RNC_CS_RAB_REL_AMR_TRIG_BY_RNC8 RNC_CS_RAB_REL_CONV_64K_TRIG_BY_RNC0 RNC_CS_RAB_REL_STR_TRIG_BY_RNC

515 RNC_PS_RAB_REL_REQ

12.54 %

1.34 %0 %

86.12 %

Figure 1-26 Call drop analysis

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In the Cell Drop Analysis, click Create a Bar Chart to display the call drop rates

for different services (including voice, VP, CS, and PS), as shown in Figure 1-27.

In general, the call drop rate of CS service is less than that of VP service or PS

service because of their different service coverage capabilities and service

process complexities, especially in the poor-covered areas.

RNC:41(ID:41)-CS_RAB_AMR_DROP_RATEgfedcb RNC:41(ID:41)-CS_RAB_VP_DROP_RATEgfedcbRNC:41(ID:41)-CS_RAB_STR_DROP_RATEgfedcb RNC:41(ID:41)-PS_RAB_DROP_RATEgfedcb

Time0

Bar V

alue

0.650.6

0.550.5

0.450.4

0.350.3

0.250.2

0.150.1

0.050

Figure 1-27 Call drop rates

4.6.2 CS Call Drop Analysis

In the CS Call Drop Analysis, click Create a Pie Chart to display the CS call drop

reasons, as shown in Figure 1-28.

75 RNC_CS_RAB_REL_AMR_TRIG_BY_RNC8 RNC_CS_RAB_REL_CONV_64K_TRIG_BY_RNC0 RNC_CS_RAB_REL_STR_TRIG_BY_RNC

515 RNC_PS_RAB_REL_REQ

12.54 %

1.34 %0 %

86.12 %

Figure 1-28 CS call drop reasons

CS call drops may be caused by the following reasons:

(1) RAB_CS_REL_RF_LOSS

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CS call drop may be caused by abnormal release caused by the lost

synchronization of links because of poor network coverage (including

adjacent cell missing, small handover area. As a result, UE closes the

transmitter abnormally or uplink demodulation is asynchronous. To solve the

problem, network coverage must be improved. In the early network, call

drops are mainly caused by this reason.

(2) RNC_CS_RAB_REL_TRIG_BY_RNC_SRB_RESET

CS call drops may be caused by link releasing due to downlink SRB reset.

This reason is mainly caused by poor network coverage (including adjacent

cell missing and small handover area). To solve the problem, the network

coverage must be improved. In the early network, call drops are mainly

caused by this reason.

(3) RNC_CS_RAB_REL_TRIG_BY_RNC_AAL2_LOSS

If IU CS interface (AAL2 path) is abnormal, RNC initializes the release. In

practice, this reason seldom occurs. If this reason occurs, the problem may

be caused by any faulty or defective equipment. In some versions of RNC,

normal release is recorded as abnormal release during the RB setup

process.

(4) CS_RAB_DROP_OTHER

CS call drops may be caused by other reasons. There are few call drop

statistics in RNC (Version 12). Such reasons as process interaction timeout

and cell update failure are recorded in CS_RAB_DROP_OTHER. In practice,

many call drops are caused by process interaction timeout and cell update

failure. Therefore, these call drops are recorded in

CS_RAB_DROP_OTHER.

4.6.3 PS Call Drop Analysis

In the Call Drop Analysis, start PS Call Drop Analysis. Then, click Create a Pie

Chart to display the PS call drops, as shown in Figure 1-29.

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15 RAB_PS_REL_RF_LOSS26 RNC_PS_RAB_REL_TRIG_BY_RNC_TRB_RESET

208 RNC_PS_RAB_REL_TRIG_BY_RNC_SRB_RESET0 RNC_PS_RAB_REL_TRIG_BY_RNC_GTPU_LOSS

266 PS_RAB_DROP_OTHER

2.91 %

5.05 %

40.39 %

0 %

51.65 %

Figure 1-29 PS call drop reasons

PS call drop may be caused by the following reasons:

(1) RAB_PS_REL_RF_LOSS

PS call drops may be caused by abnormal release because the links are

asynchronous. This reason is mainly caused by poor network coverage

(including adjacent cell missing and small handover area). As a result, UE

closes the transmitter abnormally or uplink demodulation is asynchronous.

To solve the problem, network coverage must be improved. In the early

network, call drops are mainly caused by this reason.

(2) RNC_PS_RAB_REL_TRIG_BY_RNC_SRB_RESET

PS call drops may be caused by link releasing due to downlink SRB reset.

This reason is mainly caused by poor network coverage (including adjacent

cell missing and small handover area). To solve the problem, the network

coverage must be improved. In the early network, call drops are mainly

caused by this reason.

(3) RNC_PS_RAB_REL_TRIG_BY_RNC_TRB_RESET

PS call drops may be caused by link releasing due to downlink TRB reset.

This reason is mainly caused by poor network coverage (including adjacent

cell missing and small handover area). To solve the problem, the network

coverage must be improved. In the early network, call drops are mainly

caused by this reason.

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(4) RNC_PS_RAB_REL_TRIG_BY_RNC_GTPU_LOSS

If IU CS interface (AAL2 path) is abnormal, RNC initializes the release. In

practice, this reason seldom occurs. If this reason occurs, the problem may

be caused by any faulty or defective equipment.

(5) PS_RAB_DROP_OTHER

PS call drops may be caused by other reasons. There are few call drop

statistics in RNC (Version 12). Such reasons as process interaction timeout

and cell update failure are recorded in PS_RAB_DROP_OTHER. In practice,

many call drops are caused by process interaction timeout and cell update

failure. Therefore, these call drops are recorded in

PS_RAB_DROP_OTHER.

4.6.4 Cell Call Drop Analysis

In the Cell Drop Call Analysis, query the TOPN to find the cell that has the greatest

CS call drop rate, start Cell Call Drop Analysis, and then click Create a Pie

Chart to display the cell drop reasons, as shown in Figure 1-30.

0 RNC_CS_RAB_REL_CELL_TRIG_BY_RNC_OM0 RNC_CS_RAB_REL_CELL_TRIG_BY_RNC_UTRAN0 RNC_CS_RAB_REL_CELL_TRIG_BY_RNC_RAB_PREM2 RNC_CS_RAB_REL_CELL_TRIG_BY_RNC_SRBRESET0 RNC_CS_RAB_REL_CELL_TRIG_BY_RNC_AAL2LOSS4 CS_RAB_DROP_CELL_OTHER

0 %0 %0 %

33.33 %0 %

66.67 %

Figure 1-30 CS cell drop reasons

CS Cell call drops may be caused by the following reasons:

(1) RNC_CS_RAB_REL_CELL_TRIG_BY_RNC_OM

Cell call drops may be caused by CS link releasing due to operation and

maintenance (for example, cell block). Actually, cell call drops caused by

this reason are normal.

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(2) RNC_CS_RAB_REL_CELL_TRIG_BY_RNC_SRB_RESET

Cell call drops may be caused by link releasing due to downlink SRB reset.

This reason is mainly caused by poor network coverage (including adjacent

cell missing and small handover area). To solve the problem, the network

coverage must be improved. In the early network, call drops are mainly

caused by this reason.

(3) RNC_CS_RAB_REL_CELL_TRIG_BY_RNC_UTRAN

Cell call drops may be caused by abnormal link releasing due to UTRAN. To

solve the problem, use CDL for further analysis.

(4) RNC_CS_RAB_REL_CELL_TRIG_BY_RNC_AAL2_LOSS

If IU CS interface (AAL2 path) is abnormal, RNC initializes the release. In

practice, this reason seldom occurs. If this reason occurs, the problem may

be caused by any faulty or defective equipment.

(5) RNC_CS_RAB_REL_CELL_TRIG_BY_RNC_RAB_PREM

Cell call drops may be caused by CS link releasing due to high priority

preemption. If load or resource is insufficient, cell call drop may occur.

Check whether the expansion is required according to cell call drop times.

(6) CS_RAB_DROP_CELL_OTHER

Cell call drops may be caused by other reasons. There are few call drop

statistics in RNC (Version 12). Such reasons as process interaction timeout

and cell update failure are recorded in CS_RAB_DROP_CELL_OTHER. In

practice, many call drops are caused by process interaction timeout and cell

update failure. Therefore, these call drops are recorded in

CS_RAB_DROP_CELL_OTHER.

4.7 Traffic Load Analysis

This section consists of the following parts:

Overview

Cell Traffic Analysis

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4.7.1 Overview

Traffic Load Analysis is included in Nastar tasks. Double click Traffic Load

Analysis to display the RNC traffic load details. You can choose Time Range or

Query Object to query the RNC traffic load, as shown in Figure 1-32.

Figure 1-32 Query traffic load

Choose Busy Time (Busy Time can be Automatic Querying or Designated Time).

In the Traffic Load Analysis, click Create a Pie Chart to display the traffic load

details. Assume that the subscribers for different services are equivalent, traffic

load proportions are displayed in Figure 1-33. UNKNOWN_USER indicates that

the subscribers are from other RNC and service type is unknown. The unit of

traffic load is Erl.

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4.388 CS_CONV_USER0 CS_STR_USER0 PS_CONV_USER0 PS_STR_USER

25.808 PS_INTER_BKG_USER0.09 UNKNOWN_USER14.49 %

0 %0 %0 %

85.21 %

0.3 %

Figure 1-33 Traffic Load

4.7.2 Cell Traffic Analysis

If a cell has the highest traffic, it is the most important cell in a network. In addition,

the cell is easily congested and need to be expanded. In the Traffic Load Analysis,

start Cell Traffic Analysis to query the TOPN. The queried results are outputted

as follows:

(1) The cell that has the greatest RTWP

(2) The cell that has the greatest TCP

(3) The cell that has the greatest DCH UE

(4) The cell that has the greatest downlink admission rejects

The cell that has the greatest RTWP represents the cell that has the greatest

uplink radio load. In practice, this queried result can be used to find the cell that is

seriously interfered. If the RTWP of a cell is greater than -100 dBm, the cell must

be analyzed. Check whether it is the burst interference or continuous interference.

The burst interference exerts little influence on the system but the continuous

interference must be eliminated on a timely basis. If the cells have large

RTWP_MAX_CELL_DBM values, start Cell RTWP Analysis, as shown in Figure

1-34.

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RTWP_MAX_CELL_DBMgfedcb

DateTime2005-04-21 00:00:00 2005-04-21 04:30:00 2005-04-21 09:30:00 2005-04-21 14:30:00 2005-04-21 19:30:00

Item

s

-65

-70

-75

-80

-85

-90

-95

-100

-105

Figure 1-34 Cell RTWP analysis

The cell that has the greatest TCP represents the cell that has the greatest

downlink radio load. In practice, if the cell has the greatest downlink radio load, the

cell also has the greatest downlink admission rejects. For such cell, check whether

the cross coverage is serious and check whether the indoor coverage of high

traffic area must be improved to decrease large power consumption.

The cell that has the greatest DCH UE is used to measure the subscriber number

of a cell. Combined with the utilization of OVSF codes, the average CE and

transmission can be estimated to further check whether the resources are

sufficient.

The cell that has the greatest DL ADMSN DENY is used to measure the cell that

has the greatest downlink radio load. In practice, downlink radio load is a

bottleneck because the uplink is asymmetric to the downlink and the downlink is of

interference. If a cell has the greatest DL ADMSN DENY, check whether the cross

coverage is serious, the handover area is unreasonable, or the indoor coverage

for high traffic area must be improved.

For the cell that has the greatest DL ADMSN DENY, start Cell Resource

Analysis to display the admission reject proportions of call setup, incoming

handover, and re-configuration. In this way, you can further understand the

influence exerted on the subscribers.

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5. Analyzing Complicated Problems

Further analysis is necessary because the KPI of traffic statistics does not

represent the processes, but the results. Some reasons may not be found through

the KPI analysis. Therefore, it is necessary for us to use further analysis to locate

complicated problems. To analyze complicated problems, use the following

methods:

Narrowing down area range and time range

Analyzing abnormal logs

Analyzing repeated problems

5.1 Narrowing Down Area Range and Time Range

The area range of abnormal traffic statistics can be determined by querying the

TOPN. After determining the area range, query the time range of problem (The

time range falls within 30 minutes).

5.2 Analyzing Abnormal Logs

Execute the command LST CELL in MML on the RNC maintenance console to

find the service subrack. Then, send the CDL of service subrack from BAM to a

service engineer for further analyzing abnormal processes, reasons, and involved

subscribers.

5.3 Analyzing Repeated Problems

If time range or area range falls within a fixed scope after the KPI analysis is

performed for several days, use Sample Trace on the RNC maintenance console

in a given time to obtain the detailed call procedure for further analyzing problem

causes and involved subscribers.