UTRAN KPI Analysis Guide
Huawei Technologies Co., Ltd
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UTRAN KPI Analysis Guide
For Internal Use Only
RAN Maintenance Dept.
Total 44 Pages
UTRAN KPI Analysis Guide
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RAN Maintenance Dept.
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Date
Aug. 10, 2005
Huawei Technologies Co., Ltd.
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UTRAN KPI Analysis Guide
For Internal
Only
Revision Edition
Date
Aug. 10, 2005
Version
Description
The first version is complete.
Author
Wang Wei
Use
UTRAN KPI Analysis Guide
For Internal Use Only
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
Call drop rate
VP Call Drop Rate
PS Call Drop Rate
Soft Handover Success Rate
Inter-Frequency HO Success Rate
Intra-Frequency HO Success Rate
Mobility management
CS Inter-RAT HO Success Rate
PS Inter-RAT HO Success Rate
Cell Update Success Rate
Equivalent User
Traffic
Cell Throughput
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 Name
Traffic
Access
HO
CDR
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)
CS AMR Call Drop Rate(<1.5%)
1.92%(19/990)
Video Call Drop Rate(<1.5%)
10.34%(3/29)
PS Service Drop Rate(<30%)
3.01%(30/997)
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:
y
RRC Setup Analysis
y
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_SUCC
7 RRC_REJ
2,186 RRC_SETUP_FAIL_NO_RSP
97.3 %
2.69 %
0.01 %
Figure 1-3 RRC Setup
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There are two reasons for RRC Setup Fail No Response:
y
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.
y
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_ORG
5,639 RRC_REQ_TERM
51,385 RRC_REQ_CELL_RESEL
16,387 RRC_REQ_REG
6.97 %
9.21 %
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:
y
RRC REQ CELL RESEL
If network coverage is poor, inter-system reselection may occur.
y
RRC REQ REG
If network coverage is poor, subscribers attempt to register for many times.
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0.99
0.985
0.98
Bar Value
0.975
0.97
0.965
0.96
0.955
0.95
0.945
0
Time
g
b
c
d
e
f
b
c
d
e
f
g
b
c
d
e
f
g
b
c
d
e
f
g
RNC:41(ID:41)-RRC_SETUP_SUCC_RATE_ORG
RNC:41(ID:41)-RRC_SETUP_SUCC_RATE_TERM
RNC:41(ID:41)-RRC_SETUP_SUCC_RATE_INTERRAT_CELL_RESEL
RNC:41(ID:41)-RRC_SETUP_SUCC_RATE_REG
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:
y
Admission reject due to crowded subscribers
y
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_CELL
0 RRC_REJ_CE_CONG_CELL
0 RRC_REJ_RL_FAIL_CELL
0 RRC_REJ_AAL2_FAIL_CELL
0 RRC_REJ_FP_FAIL_CELL
0 RRC_REJ_CODE_CONG_CELL
0 RRC_REJ_OTHER_CELL
100 %
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.
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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_32
101 CS_RAB_REQ_SETUP_CONV_32_64
5 PS_RAB_REQ_SETUP_64K
5 PS_RAB_REQ_SETUP_128K
749 PS_RAB_REQ_SETUP_384K
73.37 %
23.19 %
3.13 %
0.15 %
0.15 %
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.
1.1
1
0.9
Bar Value
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
Time
g
b
c
d
e
f
b
c
d
e
f
g
b
c
d
e
f
g
RNC:1(ID:1)-RB_SETUP_SUCC_RATE
RNC:1(ID:1)-CS_RAB_ SETUP_SUCC_RATE_AMR
RNC:1(ID:1)-CS_RAB_ SETUP_SUCC_RATE_VP
RNC:1(ID:1)-PS_RAB_SETUP_SUCC_RATE_64K
g
b
c
d
e
f
b
c
d
e
f
g
RNC:1(ID:1)-PS_RAB_SETUP_SUCC_RATE_128K g
b
c
d
e
f
RNC:1(ID:1)-PS_RAB_SETUP_SUCC_RATE_384K
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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UTRAN KPI Analysis Guide
99.05 %
0
%
0.63
0
% %
0
%
0.32
0
% %
For Internal Use Only
1,571 CS_RAB_SETUP_SUCC_CONV_CELL
0 CS_RAB_SETUP_SUCC_STR_CELL
0 CS_RAB_SETUP_FAIL_PARAM_CELL
0 CS_RAB_SETUP_FAIL_RELOC_CELL
10 CS_RAB_SETUP_FAIL_TNL_CELL
0 CS_RAB_SETUP_FAIL_CONG_CELL
0 CS_RAB_SETUP_FAIL_POWER_CONG_CELL
0 CS_RAB_SETUP_FAIL_CE_CONG_CELL
0 CS_RAB_SETUP_FAIL_CODE_CONG_CELL
5 CS_RAB_SETUP_FAIL_OTHER_CELL
0%
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)
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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.
84.09 %
0%
0%
0 PS_RAB_SETUP_SUCC_CONV_CELL
0 PS_RAB_SETUP_SUCC_STR_CELL
37 PS_RAB_SETUP_SUCC_INTER_CELL
0 PS_RAB_SETUP_SUCC_BKG_CELL
0 PS_RAB_SETUP_FAIL_PARAM_CELL
0 PS_RAB_SETUP_FAIL_RELOC_CELL
0 PS_RAB_SETUP_FAIL_CONG_CELL
3 PS_RAB_SETUP_FAIL_POWER_CONG_CELL
0 PS_RAB_SETUP_FAIL_CE_CONG_CELL
0 PS_RAB_SETUP_FAIL_CODE_CONG_CELL
4 PS_RAB_SETUP_FAIL_OTHER_CELL
9.09 %
0%
%
6.820 %
0%
0%
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.
99.76 %
0.18 %
1,645 RB_SETUP_SUCC_CELL
0 RB_SETUP_FAIL_CFG_UNSUPP_CELL
0 RB_SETUP_FAIL_PHYCH_FAIL_CELL
0 RB_SETUP_FAIL_SIMU_RECFG_INCOMP_CELL
0 RB_SETUP_FAIL_CELL_UPDT_CELL
3 RB_SETUP_FAIL_CFG_INVALID_CELL
1 RB_SETUP_FAIL_NO_RSP_CELL
0 RB_SETUP_FAIL_OTHER_CELL
0
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)
For Internal Use Only
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:
Aug. 10, 2005
y
Overview
y
Cell SHO Prepare Failure Analysis
y
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
Bar Value
handover prepare success rate), as shown in Figure 1-14.
1.005
1
0.995
0.99
0.985
0.98
0.975
0.97
0.965
0.96
0.955
0.95
0.945
0.94
0.935
0
Time
g
b
c
d
e
f
b
c
d
e
f
g
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RNC:1(ID:1)-SHO_SUCC_RATE
RNC:1(ID:1)-SHO_PREP_SUCC_RATE
b
c
d
e
f
g
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RNC:1(ID:1)-SOFTERHO_SUCC_RATE
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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:
y
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.
y
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_FAIL
7 SHO_PREP_AAL2_SETUP_FAIL
0 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)
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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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0
0.11
% %
99.75 %
0.14 %
0
0%
%
0%
0%
For Internal Use Only
2,797 SHO_SUCC_CELL
0 SHO_RL_ADD_FAIL_CFG_UNSUPP
0 SHO_RL_ADD_FAIL_SIMU_RECFG_INCOMP
0 SHO_RL_ADD_FAIL_CFG_INVALID
4 SHO_RL_ADD_FAIL_NO_RSP
0 SHO_RL_DEL_FAIL_CFG_UNSUPP
0 SHO_RL_DEL_FAIL_SIMU_RECFG_INCOMP
0 SHO_RL_DEL_FAIL_CFG_INVALID
3 SHO_RL_DEL_FAIL_NO_RSP
0 SHO_FAIL_OTHER_CELL
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)
For Internal Use Only
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:
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y
Overview
y
CS Inter-RAT Handover Prepare Failure Analysis
y
CS Inter-RAT Handover Failure Analysis
y
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_FAIL
2,735 CS_INTRAT_HO_OUT_SUCC
40 CS_INTRAT_HO_OUT_FAIL
17.9 %
1.18 %
80.92 %
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.
82.1 %
0%
%
0
0.95 %
0%
2,775 CS_INTRAT_HO_OUT_PREP_SUCC
0 CS_INTRAT_HO_OUT_PREP_FAIL_TARGET_FAIL
0 CS_INTRAT_HO_OUT_PREP_FAIL_TALLOC_EXPIR
0 CS_INTRAT_HO_OUT_PREP_FAIL_TARGET_UNSUPP
13 CS_INTRAT_HO_OUT_PREP_FAIL_RELOC_ABORT
560 CS_INTRAT_HO_OUT_PREP_FAIL_NO_RSRC_AVAIL
0 CS_INTRAT_HO_OUT_PREP_FAIL_UNKNOWTARGET
32 CS_INTRAT_HO_OUT_PREP_FAIL_REQINFNOTAVAI
0 CS_INTRAT_HO_OUT_PREP_FAIL_NO_RSP
0 CS_INTRAT_HO_PREP_FAIL_OTHER
16.57 %
0.38 %
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)
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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.
98.56 %
0.43 %
%
0.04
0%
0 CS_INTRAT_HO_OUT_FAIL_UNSPEC
0 CS_INTRAT_HO_OUT_FAIL_NO_RSP
12 CS_INTRAT_HO_OUT_FAIL_RELOC_ABORT
1 CS_INTRAT_HO_FAIL_OTHER
2,735 CS_INTRAT_HO_OUT_SUCC
0 CS_INTRAT_HO_OUT_FAIL_CFG_UNSUPP
27 CS_INTRAT_HO_OUT_FAIL_PHYCH_FAIL
0%
0.97
0
% %
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)
For Internal Use Only
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:
y
The signals of 2G network are weak or UE fails to access the network
due to serious interference.
y
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:
y
Overview
y
PS Inter-RAT Handover Failure Analysis
y
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_REQ
0 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
PS_INTRAT_HO_OUT_UTRAN_UE.
and
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.
0.9
0.8
0.7
Bar Value
0.6
0.5
0.4
0.3
0.2
0.1
0
0
Time
g
b
c
d
e
f
b
c
d
e
f
g
RNC:41(ID:41)-PS_INTRAT_HO_OUT_UTRAN_SUCC_RATE
RNC:41(ID:41)-PS_INTRAT_HO_OUT_UE_SUCC_RATE
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_SUCC
0 PS_HO_OUT_FAIL_CFG_UNSUPP
0 PS_HO_OUT_FAIL_PHYCH_FAIL
0 PS_HO_OUT_FAIL_UNSPEC
0 PS_HO_OUT_FAIL_NO_RSP
2 PS_HO_OUT_FAIL_OTHER
80 %
20 %
0%
0%
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)
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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:
y
Overview
y
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_REENTER
0 CELL_UPDT_PAGE
0 CELL_UPDT_UL_DATA_TRANS
211 CELL_UPDT_RLC_ERR
15 CELL_UPDT_RL_FAIL
0 CELL_UPDT_PRD
0 CELL_UPDT_RESEL
0 CELL_UPDT_OTHER
93.36 %
0%
0%
6.64 %
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%.
0.07
Bar Value
0.06
0.05
0.04
0.03
0.02
0.01
0
0
Time
g
b
c
d
e
f
b
c
d
e
f
g
b
c
d
e
f
g
b
c
d
e
f
g
b
c
d
e
f
g
b
c
d
e
f
g
b
c
d
e
f
g
b
c
d
e
f
g
RNC:41(ID:41)-CELL_UPDT_SUCC_RATE_RESEL
RNC:41(ID:41)-CELL_UPDT_SUCC_RATE_REENTER
RNC:41(ID:41)-CELL_UPDT_SUCC_RATE_PAGE
RNC:41(ID:41)-CELL_UPDT_SUCC_RATE_UL_DATA_TRANS
RNC:41(ID:41)-CELL_UPDT_SUCC_RATE_RLC_ERR
RNC:41(ID:41)-CELL_UPDT_SUCC_RATE_RL
RNC:41(ID:41)-CELL_UPDT_SUCC_RATE_PRD
RNC:41(ID:41)-CELL_UPDT_SUCC_RATE_OTHER
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:
y
Overview
y
CS Call Drop Analysis
y
PS Call Drop Analysis
y
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.
0%
75 RNC_CS_RAB_REL_AMR_TRIG_BY_RNC
8 RNC_CS_RAB_REL_CONV_64K_TRIG_BY_RNC
0 RNC_CS_RAB_REL_STR_TRIG_BY_RNC
515 RNC_PS_RAB_REL_REQ
1.34 %
12.54 %
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
Bar Value
process complexities, especially in the poor-covered areas.
0.65
0.6
0.55
0.5
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
0
Time
g
b
c
d
e
f
b
c
d
e
f
g
RNC:41(ID:41)-CS_RAB_AMR_DROP_RATE f
g
b
c
d
e
RNC:41(ID:41)-CS_RAB_STR_DROP_RATE g
b
c
d
e
f
RNC:41(ID:41)-CS_RAB_VP_DROP_RATE
RNC:41(ID:41)-PS_RAB_DROP_RATE
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.
0%
75 RNC_CS_RAB_REL_AMR_TRIG_BY_RNC
8 RNC_CS_RAB_REL_CONV_64K_TRIG_BY_RNC
0 RNC_CS_RAB_REL_STR_TRIG_BY_RNC
515 RNC_PS_RAB_REL_REQ
1.34 %
12.54 %
86.12 %
Figure 1-28 CS call drop reasons
CS call drops may be caused by the following reasons:
(1)
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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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40.39 %
15 RAB_PS_REL_RF_LOSS
26 RNC_PS_RAB_REL_TRIG_BY_RNC_TRB_RESET
208 RNC_PS_RAB_REL_TRIG_BY_RNC_SRB_RESET
0 RNC_PS_RAB_REL_TRIG_BY_RNC_GTPU_LOSS
266 PS_RAB_DROP_OTHER
5.05 %
0%
2.91 %
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)
For Internal Use Only
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%
33.33 %
0 RNC_CS_RAB_REL_CELL_TRIG_BY_RNC_OM
0 RNC_CS_RAB_REL_CELL_TRIG_BY_RNC_UTRAN
0 RNC_CS_RAB_REL_CELL_TRIG_BY_RNC_RAB_PREM
2 RNC_CS_RAB_REL_CELL_TRIG_BY_RNC_SRBRESET
0 RNC_CS_RAB_REL_CELL_TRIG_BY_RNC_AAL2LOSS
4 CS_RAB_DROP_CELL_OTHER
0%
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)
For Internal Use Only
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:
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y
Overview
y
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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0%
0%
14.49 %
4.388 CS_CONV_USER
0 CS_STR_USER
0 PS_CONV_USER
0 PS_STR_USER
25.808 PS_INTER_BKG_USER
0.09 UNKNOWN_USER
0.3 %
85.21 %
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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-65
-70
-75
Items
-80
-85
-90
-95
-100
-105
2005-04-21 00:00:00
2005-04-21 04:30:00
2005-04-21 09:30:00
2005-04-21 14:30:00
DateTime
b
c
d
e
f
g
2005-04-21 19:30:00
RTWP_MAX_CELL_DBM
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:
y
Narrowing down area range and time range
y
Analyzing abnormal logs
y
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.
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