11 gsm bss network kpi (paging success rate) optimization manual

GSM BSS Network KPI (Paging Success Rate) Optimization Manual INTERNAL
Product Name Confidentiality level
G3BSC INTERNAL
Product Version Total 28 pages
GSM BSS Network KPI (Paging Success Rate)
Optimization Manual
(For internal use only)
Prepared by Yang Chunjie (00119951),
WCDMA&GSM Network
Performance Research Dept.
Date 2008-9-2
Reviewed by Date
Reviewed by Date
Approved by Date
Huawei Technologies Co., Ltd.
All rights reserved
2014-6-18 Huawei Confidential Page 1 of 27

Contents
1.1 Definition..................................................................................................................................................................6
1.2 Recommended Formula...........................................................................................................................................6
1.3 Signaling Procedure and Measurement Point...........................................................................................................7
2.1 Hardware Fault.........................................................................................................................................................8
2.2 Transmission Problem..............................................................................................................................................8
2.3 Parameter Setting Problem.......................................................................................................................................8
2.4 Interference Problem................................................................................................................................................9
2.5 Coverage Problem....................................................................................................................................................9
2.6 Uplink and Downlink Balance Problem.................................................................................................................10
3.1 Analysis Procedure.................................................................................................................................................11
3.2 Problem Location of the Paging Success Rate and Optimization Method.............................................................12
3.2.1 Hardware and Transmission Problems.............................................................................................................13
3.2.2 SDCCHs Occupied Due to Paging Overload and Heavy Burst Traffic............................................................13
3.2.3 Parameter Configuration...................................................................................................................................14
3.2.4 Interference ......................................................................................................................................................19
3.2.5 Coverage...........................................................................................................................................................19
3.2.6 Balance Between Uplink and Downlink...........................................................................................................20
5.1 Case 1: Paging Success Rate Drops Due to a Hardware Fault...............................................................................22
5.2 Case 2: Paging Success Rate Drops Due to a Transmission Fault.........................................................................22
5.3 Paging Success Rate Drops Due to Improper Parameter Configuration................................................................23
5.3.1 Case 3: Paging Success Rate Drops When the Pre-paging Function Is Enabled ............................................23
5.3.2 Case 4: Paging Success Rate Drops When BS-PA-MFRAMS Is Set Improperly............................................23
5.3.3 Case 5: MS Cannot Respond to a Paging Message When the Number of Pagings on the N Side Is Set
Improperly.................................................................................................................................................................24
5.3.4 Case 6: BSC Paging Is Abnormal When the LAC Is Configured Improperly for the BSC.............................24
5.3.5 Case 7: Paging Success Rate Increases After the A-interface Collaboration Paging Function Is Enabled......25
5.4 Case 8: Paging Success Rate Drops Due to Poor Coverage...................................................................................25

Figures
Intra-BSS Paging Procedure...........................................................................................................7

Revision Record
Date Revision
version
Change Description Author
2008-09-02 V1.0 Draft completed Yang
Chunjie
References
SN Document Author Date
1 G-Guide to Eliminating Interference-20050311-
A-1.0
Chen Baolin 2005-3-11
2 GSM BSS Network KPI (Paging Success Rate)
Baseline Specification
Wu Zhen 2007-8-14
　　　　

GSM BSS Network KPI (Paging Success Rate)
Optimization Manual
Keyword: paging success rate
Abstract: This document provides the method for optimizing the paging success rate.
Acronyms and abbreviations:
Acronym and Abbreviation Full Spelling
MSC Mobile Switching Center
BSC Base Station Controller
BTS Base Transceiver Station
HLR Home Location Register
MS Mobile Station
IMSI International Mobile Station Identification Code
TMSI Temporary Mobile Station Identity

1 Definition of the Paging Success Rate
1.1 Definition
The paging success rate is the ratio of the paging responses received by the system to the
initial paging requests sent by the system. It indicates the paging capability of the system.
The paging consists of the voice call paging, short message paging, PSI paging, and Gs
paging. For the area that does not enable the Gs interface, the paging consists of only the
voice call paging, short message paging, and PSI paging.
The wireless services are performed on the basis of paging. A high paging success rate can
improve multiple service KPIs in the case of certain hardware capacity. A high paging success
rate helps to improve user satisfaction and to promote the brands of the operators. The paging
success rate is one of important KPIs related to the network access. It is also one of important
KPIs for the operators.
1.2 Recommended Formula
The paging success rate can be obtained from the traffic statistics and drive test (DT). If you
want to obtain the paging success rate from the traffic statistics, the paging success rate must
be obtained on the core network (CN) side. The measurement object is location area. The CN
decides whether the paging success rate is qualified or not. The recommended formula used
for calculating this KPI is as follows:
Number of paging request responses/Number of paging requests The specific formulas are as
follows:
Paging success rate (all the pagings) = (Number of first paging responses of common calls on
the A interface + Number of repeated paging responses of common calls on the A interface +
Number of first paging responses of short messages on the A interface + Number of repeated
paging responses of short messages on the A interface + Number of first paging responses of
the Gs on the A interface + Number of repeated paging responses of the Gs on the A interface
+ Number of first paging responses of the PSI on the A interface + Number of repeated paging
responses of the PSI on the A interface + Number of first paging responses on the Gs interface
+ Number of repeated paging responses on the Gs interface)/(Number of first pagings of
common calls on the A interface + Number of first pagings of short messages on the A
interface + Number of first pagings of the Gs on the A interface + Number of first pagings of
the PSI on the A interface + Number of first pagings on the Gs interface)
Paging success rate (MTC call access measurement)note 1
= (Number of first paging responses
of common calls on the A interface + Number of repeated paging responses of common calls
on the A interface)/Number of first pagings of common calls on the A interface
Paging success rate (main services)note 2
= (Number of first paging responses of common calls
on the A interface + Number of repeated paging responses of common calls on the A interface

+ Number of first pagings of short messages on the A interface + Number of repeated paging
responses of short messages on the A interface)/(Number of first pagings of common calls on
the A interface + Number of first pagings of short messages on the A interface)
Paging success rate (paging process measurement)note 3
= (Number of first paging responses on
the A interface + Number of repeated pagings on the A interface)/Number of first pagings on
the A interface
Note 1: Number of pagings involved in the MTC call access measurement consists of only the number of
pagings of common calls. The number of pagings of short messages, PSI, and Gs is not measured. It indicates
the success rate of the pagings initiated by the call.
Note 2: This formula is used to calculate the paging success rate of all the common CS services. It indicates
the paging processing of voice calls and short message calls. This formula is used for determining whether the
KPI reaches the standards.
Note 3: This formula is used to calculate the KPI of the MSC paging measurement corresponding to the
paging success rate. This formula is calculated according to the KPI measured on the OMC.
1.3 Signaling Procedure and Measurement Point
The KPIs related to the paging success rate are measured on the CN side. Figure 1 shows the
procedure for the paging on the BSS side.
Figure 1.1 Intra-BSS Paging Procedure
Measurement points on the CN side:
A: Number of paging requests
B: Number of paging request responses

2 Influencing Factors
The factors of the NEs (such as the MSC, BSC, BTS, and MS), network coverage,
interference, channel congestion, and hardware may influence the paging success rate. The
main influencing factors are listed as follows:
 Hardware fault
 Transmission problem
 Parameter setting problem
 Interference problem
 Coverage problem
 Uplink and downlink balance problem
 Other causes
2.1 Hardware Fault
When the TRX or the combiner is faulty, the MS cannot perform paging, which leads to a
decrease in the paging success rate.
2.2 Transmission Problem
The transmission quality of the links on the Abis and A interfaces is poor and transmission
links are unstable because of various causes, which also leads to an increase in the paging
success rate.
2.3 Parameter Setting Problem
The parameter settings on the BSC side and MSC side may influence the paging success rate.
The main parameters are as follows:
The parameters related to the paging on the MSC side are as follows:
 Location update time on the N side (IMSI invisible separation timer)
 First paging mode
 First paging interval
 Second paging mode
 Second paging interval
 Third paging mode
 Third paging interval

 Number of paging retransmissions by the MSC
 Network-wide paging
 Pre-paging
 Location update optimization (MSC software parameter)
 Call early release (MSC software parameter)
 Paging optimization control (MSC software parameter)
The parameters related to the paging on the BSC side are as follows:
 CCCH Conf
 RACH Min.Access Level
 RXLEV_ACCESS_MIN
 Paging Times
 BS_AG_BLKS_RES
 BS-PA-MFRAMS
 MS MAX Retrans
 SDCCH Dynamic Allocation Allowed
 Random Access Error Threshold
 T3212
 RACH Busy Threshold
 CCCH Load Threshold
 Abis Flow Control Permitted
 A-interface collaboration paging switch (software parameter)
 Paging lifecycle (software parameter 29)
2.4 Interference Problem
The intra-network and inter-network interference may influence the access success rate of the
system. In this case, the paging response of the system is directly influenced, thus decreasing
the paging success rate.
For more information about how to troubleshoot the interference problem, see the G-Guide to
Eliminating Interference - 20050311-A-1.0.
2.5 Coverage Problem
The coverage problems that influence the paging success rate are as follows:
1. Discontinuous coverage (with blind areas)
In complex terrains such as mountainsides, the radio propagation environment is complex, the
signals are blocked and thus the transmission is discontinuous. As a result, the MS cannot
respond to the paging.
2. Poor indoor coverage
The densely distributed buildings and thick walls cause great signal attenuation, great
penetration loss, and low indoor signal level. As a result, the MS cannot respond to the

paging.
3. Cross coverage (isolated BTS)
The cross coverage occurs in the serving cell because of various causes such as high power
and antenna azimuth angle. As a result, the MS can receive the downlink signal but the BTS
cannot receive the corresponding message sent by the MS, which leads to a decrease in the
paging success rate.
2.6 Uplink and Downlink Balance Problem
If the transmit power of the BTS is high or the tower mounted amplifier (TMA), BTS
amplifier, and antenna interface are faulty, the difference between the uplink and the downlink
levels are great. As a result, the access success rate of the MS may occur at the edge of the
BTS coverage area.

3 Analysis Procedure for the Paging Success
Rate and Optimization Method
3.1 Analysis Procedure

3.2 Problem Location of the Paging Success Rate and
Optimization Method

3.2.1 Hardware and Transmission Problems
When the TRX or combiner is faulty, the sending of the paging request or the assignment
fails. In this case, the paging success rate decreases.
You can check for the hardware faults by viewing BTS alarms or viewing the status of the
hardware on the LMT. The following table lists main BSC alarms.
Alarm ID Alarm Name
1000 LAPD OML Fault
2204 TRX Communication Alarm
4414 TRX VSWR Alarm
3606 DRU Hardware Alarm
<Related Cases> <Related Cases>
The counters related to the hardware fault are as follows (the following parameters are based
on BSC6000V900R008B048):
Cause BSC-level Counter Cell-level Counter
Device
fault
[BSC Measurement]->[Access
Measurement per BSC]->
SDCCH Availability per BSC
Configured SDCCHs per BSC
Available SDCCHs per BSC
[KPI Measurement per Cell]->
SDCCH Availability
Available SDCCHs
Configured SDCCHs
3.2.2 SDCCHs Occupied Due to Paging Overload and Heavy
Burst Traffic
When the LACs are divided improperly, the parameters are configured incorrectly, or there is
heavy burst traffic, the paging overload may occur. In this case, the paging success rate
decreases.
1. When the LACs are divided improperly and large-scale location updates are performed,
the PCH overload may occur.
2. When some cell parameters (such as "BS_AG_BLKS_RES", "BS-PA-MFRAMS", and
"MS MAX Retrans") are set improperly, PCHs may be insufficient. When there are
many paging messages, the cell reports an overload message to the BSC. In this case,
PCH overload occurs.
3. When there is heavy burst traffic (for example, assemblies), paging overload occurs.
Eliminate the paging overload according to generation causes. If the paging overload
persists for a long period, adjust the parameter configuration. If the paging overload is
caused by the heavy burst traffic, eliminates the paging overload after the traffic
decreases.
The counters related to paging overload are as follows:

Cause BSC-level Counter Cell-level Counter
Paging
overload
[Paging Measurement]->[A Interface Paging
Measurement]->
A0300: MSC-Initiated Paging Requests for
CS Service
A0301: SGSN-Initiated Paging Requests for
CS Service
A031: SGSN-Initiated Paging Requests for
PS Service
A032: Delivered Paging Messages to BTS
for CS Service
[Paging Measurement]->[Measurement of
Discarded Paging Messages due to Overload
per LAPD]
[Call Measurement]->[Calls Discarded due to
Overload per LAPD]
[Call Measurement]-
>[Flow Control
Measurement per Cell]
L3188L: Paging Messages
Discarded from the PCH
Queue
L3188M: Maximum
Seizure Ratio of PCH
Paging Queue
3.2.3 Parameter Configuration
If some parameters are set improperly on the BSC side and MSC side, the paging success rate
may decrease. Especially, the paging policy on the MSC side greatly affects the paging
success rate. You can check the problem causes through the following parameters.
Paging-related parameters on the MSC side
1. Location update time on the N side (IMSI invisible separation timer)
The value of this parameter must be greater than the value of T3212. Otherwise, when
the MS serves as a called party on a normal network, you are prompted that the
subscriber you dialed is powered off.
2. First paging mode
To improve the paging capability of the system and improve the PCH usage, the TMSI is
used for the first paging and the IMSI is used for the last paging in normal cases. In
addition, the IMSI-based paging can be done when some TMSIs are incorrect
temporarily. Therefore, the IMSI is mandatory for paging and it must be also carried in
the TMSI-based paging. The TMSI-based paging saves resources but does not reduce the
number of pagings. One PCH can page only two IMSIs at the same time, but can page
four TMSIs at the same time, which is considered as the capacity expansion of one PCH.
3. First paging interval
If the interval is set a small value or a large value, the paging success rate may decrease.
If the paging interval is set to a small value and the MSC does not receive a paging
response within the specified number of pagings, the MSC considers that the paging fails
and the paging message should be cleared. Even if the paging response is received later,
the MSC still sends a CLEAR_COMMAND message to clear the radio channel on the
called MS side because the paging message is cleared. The paging interval must be
properly related to the paging response time on the BSS side. In this way, the paging
success rate can be increased.
4. Second paging mode
The IMSI is used for the paging in normal cases. Because the TMSI sent by the system
cannot be identified by the MS, at least one IMSI paging must be set to enhance the

paging reliability.
5. Second paging interval
Omitted.
6. Third paging mode
Omitted.
7. Third paging interval
Omitted.
8. Number of paging retransmissions by the MSC
If the capacity of a location area is large, you are advised to set the number of paging
retransmissions to a small value. If the number of paging retransmissions is set to a large
value, the paging overload may occur.
9. Network-wide paging
If the MS roams to a new location area but does not initiate a location update request in
time (the probability of this case is low), a network-wide paging request can be initiated
to increase the paging success rate. When the network-wide paging request is initiated,
the paging traffic volume on the BSS side is greatly increased. In this case, the PCH may
be congested. You are not advised to enable the network-wide paging function for a
location area with large capacity. If the function is enabled, the BTS and BSC CPU may
be overloaded. In this case, a large number of paging messages are discarded and the
paging success rate sharply decreases. For a location area with small capacity, however,
you can enable the network-wide paging function to increase the paging success rate. If
the coverage is poor and the paging load on the BSS side is low, you can enable the
function for the last paging. <Related Cases>
10. Pre-paging
Pre-paging is a network function. When the HLR attempts to obtain a roaming number
from the VMSC Server, the VMSC Server initiates a paging procedure to the called MS
and then returns the roaming number to the HLR before the GMSC Server initiates a call
setup request to the VMSC Server. In this way, when the VMSC Server receives the call
setup request from the GMSC Server, the radio connection between the VMSC Server
and the MS is already established.
A pre-paging request is initiated when a roaming number is obtained. Thus, the system
can know whether the called MS can be paged before allocating the roaming number.
This helps to avoid the access failure of the called MS when the GMSC server is
connected to the VMSC server according to the roaming number. In this way, the
network resources can be saved. In addition, before the pre-paging, if the data restoration
is required, you can restore the data. In this way, the efficiency of incoming calls can be
improved.
During the pre-paging, however, the seizure duration of the SDCCH is increased. If the
configuration is improper, the congestion may occur, and thus the paging success rate
decreases. <Related Cases>
11. Location update optimization (MSC software parameter)
P1100.Bit1. When the MS performs location updates and pagings, this parameter is used
to control whether to optimize pagings. That is, the location update is performed and
then the paging is performed in a new location area after the location update succeeds. If
the location update fails or a follow-on request is initiated, a paging failure message is
returned. After the function is enabled, the MS can perform location updates and pagings
at the same time. In this way, the paging success rate can be increased.
0: to optimize the paging.
1: not to optimize the paging. The default value is 1.

12. Call early release (MSC software parameter)
P166.Bit15. This parameter specifies whether to measure PAGING RESP messages
when the MS is released early. If the function is enabled and the calling MS is released
early, the number of paging responses increases. Thus, the paging success rate can be
increased.
0: to enable the function.
1: to disable the function. The default value is 1.
13. Paging optimization control (MSC software parameter)
P164.BIT8. If no paging response is received from an MS, the number of pagings is
controlled by this parameter when the MS is called next time. When the MS can be
paged, the number of pagings is restored to the original value. If the function is enabled
but the MS cannot be paged, the number of pagings decreases.
0: to use the number configured in the paging control table.
1: to use the number configured in the paging control table minus 1. If the number
configured in the paging control table is 1, the number of pagings is 1.
The default value is 1.
Paging-related parameter on the BSC side:
14. CCCH Conf
The CCCH needs to be properly configured on the basis of the number of channels in a
cell and the paging capability of the location area. The configuration of the parameter
determines the number of PCHs in a cell.
The CCCH can be configured on TS0 of C0 (BCCH+CCCH can be configured in this
case). In addition, the CCCH configuration can be used to extend three combination sets
on TS2, TS4, and TS6. The configuration includes all combinations on TS0 except the
SCH and FCCH.
The CCCH configuration is represented by CCCH_CONF. The value must be consistent
with the actual configuration of the CCCH. The following table lists the CCCH_CONF
codes and their meanings.
CCCH-CONF codes
CCCH-CONF Meaning Number of CCCH Blocks in One
BCCH Multi-Frame
000 One physical channel is used for the CCCH but
not combined with the SDCCH.
9
001 One physical channel is used for the CCCH and
combined with the SDCCH.
3
010 Two physical channels are used for the CCCH but
18
100 Three physical channels are used for the CCCH
but not combined with the SDCCH.
27
110 Four physical channels are used for the CCCH but
36
15. RACH Min.Access Level
This parameter indicates the level threshold for the random access of the MS. If the level
of the received RACH burst pulse is smaller than the minimum access level of the

RACH, the BTS regards the access as an invalid access and does not decode the access
request. If the level of the received random access burst timeslot is greater than the
minimum access level of the RACH, the BTS regards the access request from the
timeslot as a valid request, and then determines whether the RACH access is valid based
on the value of Random Access Error Threshold.
16. RXLEV_ACCESS_MIN
This parameter indicates the minimum RX level required when the MS accesses the
BSS. If this parameter is set to a small value, the level of the access signal is low and
thus many MSs attempt to reside in the cell. In this case, the cell may be overloaded and
the call drops may occur. Therefore, you must properly set the parameter based on the
balance between uplink and downlink.
17. Paging Times
The paging retransmission function is added to the BTS side to improve the paging
success rate and paging efficiency. If the function is enabled and the transmission quality
of the radio link is poor occasionally, the MS can still receive paging commands. If the
transmission quality of the radio link is poor continuously, you can enable the paging
retransmission function on the MSC side to ensure that the MS correctly receives paging
commands. In addition, when the paging retransmission function is enabled on the BTS
side, the number of paging retransmissions on the MSC side is decreased. In this case,
the signaling load on the network side is decreased to a certain extent.
This parameter indicates whether the BTS retransmits a paging message. The number of
paging retransmissions is determined by the parameter and the number of pagings
configured on the MSC side. The total number of pagings is approximate to the number
of pagings on the BTS side multiplied by the number of pagings on the MSC side.
18. BS_AG_BLKS_RES
This parameter indicates the number of CCCH message blocks reserved for the AGCH.
After the CCCH configuration is complete, the parameter reflects the proportion of
AGCHs and PCHs on the CCCH. The setting of this parameter affects the MS paging
response time and system service performance.
19. BS-PA-MFRAMS
This parameter indicates the number of multi-frames as a cycle of the paging sub-
channel. Actually, the parameter determines the number of paging sub-channels into
which the PCH in a cell is divided. <Related Cases>
20. MS MAX Retrans
This parameter indicates the maximum number of retransmissions of the Channel
Request message in an immediate assignment procedure. After initiating the immediate
assignment procedure, the MS keeps monitoring BCCHs and all CCCH messages in its
CCCH group. If no Immediate Assignment message or Immediate Assignment Extend
message is received, the MS retransmits the Channel Request message periodically.
21. SDCCH Dynamic Allocation Allowed
The SDCCH dynamic allocation function can be enabled to add the number of available
SDCCHs. When the number of MSs in a cell increases sharply and many MSs cannot
access the network due to the failure to request SDCCHs, TCHs (including TCHs and
dynamic PDCHs as TCHs) are converted to SDCCHs to ensure that most MSs access the
network. The dynamic adjustment of SDCCHs can increase the system capacity.
22. Random Access Error Threshold
The system checks whether the received signal is a random access signal from the MS
based on the relativity of the training sequence code (TSC) (41 bits). In addition, the TA
value can be calculated at the same time. If this parameter is set to a small value, the
allowable error extent for a random access signal is high and the random access of the

MS is easy. The error reporting rate, however, is high. If this parameter is set to a large
value, the error reporting rate of the MS is low. The normal access request, however,
cannot be reported.
23. T3212
This parameter indicates the period when the MS performs location updates. Generally,
the T3212 values of all the cells are the same in a location area. Otherwise, the implicit
shutdown may occur.
24. RACH Busy Threshold
This parameter indicates the level threshold for MS random access when the RACH is
busy. If the level of the received random access burst timeslot is greater than the
threshold, the BTS regards the timeslot as a busy timeslot.
25. CCCH Load Threshold
This parameter indicates that the BTS notifies the BSC of the load on the CCCH
timeslot. The load refers to the access requests on the RACH and all the messages (such
as the paging and PS immediate assignment) on the PCH. For details, see the protocol
0858. If the load on the CCCH timeslot exceeds the value specified by this parameter,
the BTS sends a CCCH overload message to the BSC at regular intervals. The interval
for sending the overload message is the value specified by CCCH Load Indication
Period.
26. Abis Flow Control Permitted
This parameter indicates whether the Abis flow control is allowed. The flow control
function is used for the call management. When the system is congested, some services
are rejected or the service request time is prolonged to reduce the system load. The Abis
flow control function is used to reduce the system load from the Abis traffic. If this
parameter is set to a small value, the BTS reports an RACH overload message to the
BSC. In this case, the BSC starts the flow control for a cell, that is, the minimum RX
level of the MS in the system message is increased to reduce the RACH access. If this
parameter is set to a large value, the BTS reports an overload message to the BSC only
when many MSs access the network and the system resources are insufficient. In this
case, the system may be faulty.
27. A-interface collaboration paging switch (software parameter)
This parameter indicates whether CS paging messages can be received on the A interface
when the MS performs GPRS services.
If the switch is turned off and the MS performs GPRS services, the MS cannot serve as a
called party for paging response.
If the switch is turned on and the MS performs GPRS services, the MS can serve as a
called party. (Note: The function is supported only in the BSC6000V900R008 and later
versions and in built-in PCU mode.) <Related Cases>
28. Paging lifecycle (software parameter 29)
This parameter determines the waiting time of paging messages in the PCH queue. If the
MSC transmits a paging request but does not receive a paging response after the
specified interval, the MSC retransmits the paging request. The retransmission interval
can be configured on the MSC side. Therefore, if a paging request message is not
transmitted to the MS within the retransmission interval on the BTS side and no response
is returned from the MSC, the paging message is retransmitted on the MSC side. If the
buffering time of a paging request in the PCH queue exceeds the paging lifecycle, the
paging request is not transmitted on the Um interface. In this way, the valid paging
requests can be transmitted in time to ensure the validity of paging request messages
transmitted on the Um interface. The value of the parameter must be smaller than or
equal to the paging interval on the MSC side. Otherwise, the paging success rate
decreases.

3.2.4 Interference
When the intra-network or inter-network interference occurs, the Um quality is poor. Thus,
the MS cannot receive a paging message or the BTS cannot receive a paging response from
the MS. In this case, the paging success rate decreases.
You can obtain the uplink interference information through the distribution of interference
bands in the traffic statistics. If interference bands 3 to 5 are found, it indicates that the serious
uplink interference occurs. You can obtain the downlink interference information through the
DT or RX quality counter.
For the details about interference check, see the G-Guide to Eliminating the Interference.
The following table lists the traffic measurement counters related to the interference.
Cause Cell-level Counter TRX-level Counter
Interference [MR Measurement]->
[Interference Band Measurement per
TRX]->
Uplink/downlink Interference
Indication Messages (TCH)
Mean Number of TCHFs/TCHHs in
Interference Band 1
Interference Band 2
Interference Band 3
Interference Band 4
Interference Band 5
[MR Measurement]->
[Receive Quality Measurement per
TRX]
3.2.5 Coverage
You can check the coverage through the outdoor DT and indoor dialing test. If the downlink
RX level is small (smaller than –100 dBm), the following cases may occur: (1) The MS
cannot access the network; (2) The quality is poor; (3) No neighboring cell is available for the
handover for a long time; (4) The level quality is poor. If any of the preceding cases occurs, it
indicates that the coverage is poor.
When the coverage of a cell is poor, the call drop rate on the TCH is high, the handover
success rate is low, and more handovers are performed due to the signal strength. You can
check whether the coverage of a cell is poor by viewing the traffic measurement counters. The
following table lists the related traffic measurement counters.

Coverage [Call Measurement]-> [Outgoing
Internal Inter-Cell Handover Measurement per
Cell]->
Outgoing Internal Inter-Cell Handover
Requests (Uplink/Downlink Strength)
[Call Measurement]-> [Outgoing
External Inter-Cell Handover Measurement per
Cell]->
Outgoing External Inter-Cell Handover
Requests (Uplink Strength)
Outgoing External Inter-Cell Handover
Requests (Downlink Strength)
[MR Measurement]->
[TCHF Receive Level Measurement per
TRX]
[MR Measurement]->
[TCHH Receive Level Measurement per
TRX]
When the coverage is poor, you can adjust the antenna tilt, increase the transmit power, add a
repeater, or change the combination mode to solve the coverage problem. For the details about
the solution, see the GSM BSS Network KPI (Network Coverage) Optimization Manual.
<Related Cases>
3.2.6 Balance Between Uplink and Downlink
If the imbalance between uplink and downlink occurs, the MS at the edge of a cell cannot
access the network. In this case, the paging success rate decreases. If the downlink quality is
poor, the MS cannot receive a Paging message. If the uplink quality is poor, the BTS cannot
receive a Paging Response message from the MS. You can check whether the imbalance
between uplink and downlink occurs in a cell through the counters related to the balance
between uplink and downlink.
Uplink and
downlink
balance
[MR Measurement]->
[Uplink-and-Downlink Balance
Measurement per TRX]->
S462A:TRX_BALANCE_LEV_1
S462B:TRX_BALANCE_LEV_2
S462C:TRX_BALANCE_LEV_3
S462D:TRX_BALANCE_LEV_4
S462E:TRX_BALANCE_LEV_5
S462F:TRX_BALANCE_LEV_6
S462G:TRX_BALANCE_LEV_7
S462H:TRX_BALANCE_LEV_8
S462I:TRX_BALANCE_LEV_9
S462J:TRX_BALANCE_LEV_10
S462K:TRX_BALANCE_LEV_11

4 Test Methods
The paging success rate is a traffic measurement counter. You can obtain the counter through
traffic measurement or DT. Because the DT data sample is limited, the paging success rate
obtained through the DT has a large error. The special DT equipment is required in the DT.
During the DT, you can observe the network counters of the serving cell and neighboring cells
such as the level, interference, and uplink/downlink quality and save the DT signaling file that
is used to identify the causes for no paging response. Considering the limited DT data sample,
you are not advised to obtain the paging success rate through the DT method. If the DT is
required, a short call must be made in the DT.
When the blind areas and limited frequency resources cause co-channel or adjacent-channel
interference, repeater interference, or cross coverage, no paging response occurs. The cause of
no paging response should be identified according to the actual situation.
The paging success rate is shown by the traffic measurement data on the MSC side. If the
paging data on the MSC side cannot be extracted in real time, you can extract the traffic
measurement data on the BSC side to linearly indicate the change trend of the paging success
rates on the MSC side. The procedure is as follows:
Extract the traffic measurement counters on the BSC side. 1. Measure the counter "A330:
Delivered Paging Messages for CS Service" in Paging Measurement, and then sum the
counters measured in 24 hours in a cell. The sum determines the number of paging messages
delivered by the BSC (including the first paging messages and second paging messages).
2. Measure the counter "A3030C: Call Setup Indications (MTC) (SDCCH)" in Immediate
Assignment Measurement per Cell in Call Measurement, and then sum the counters
measured in 24 hours in a cell. The sum determines the number of paging response messages
received by the BSC (including the first paging response messages and second paging
response messages).
You can calculate the paging success rate on the BSC side through the two counters. As the
number of first paging response messages cannot be distinguished from the number of second
paging response messages on the BSC side, the paging success rate cannot be shown
correctly. The changes in the paging success rate, however, can be shown indirectly.
Therefore, you can obtain the change trend of the paging success rate when the paging data on
the MSC side is unavailable.

5 Cases for Optimization of the Paging
Success Rate
5.1 Case 1: Paging Success Rate Drops Due to a Hardware
Fault
Description: The paging success rate in a site is low (18% to 25%), other counters are
normal, and no alarm is reported to the alarm console.
Analysis and solution: According to the check result, the power amplifier in sector 2 of BTS
1 is faulty. Thus, no signal output from sector 2 is available. Because 90% of MSs in the site
are located in sector 2, most MSs can use only the edge signals of the adjacent sector (sector
0) for communication instead of the signals of sector 2. When the number of MSs increases,
the signal quality is poor. In this case, the paging success rate decreases. After the power
amplifier is replaced, the problem is solved.
5.2 Case 2: Paging Success Rate Drops Due to a
Transmission Fault
Description: The site type is S4/4/4, and two EDUs and Huawei MSC are configured.
According to the traffic measurement result, the number of PCH CS/PS overloads on the Abis
interface is 476 in a time segment. In this case, the paging success rate decreases.
Analysis and solution: When the transmission link is disconnected frequently, some
messages are discarded due to the BCCH aiding and switchback. After receiving system
message 3, the non-BCCH TRX receives a large number of paging messages. In this case, the
overload message is reported when the messages cannot be delivered and the overload
detection conditions are met. As shown in the BTS logs, the aiding of three TRXs occurs due
to the transmission fault. According to the signaling tracing result, the non-BCCH TRX1 and
TRX3 report the overload message.
After the transmission fault is rectified, the problem is solved. Note that the problem is
already solved in the BSS of the latest version.

5.3 Paging Success Rate Drops Due to Improper Parameter
Configuration
5.3.1 Case 3: Paging Success Rate Drops When the Pre-paging
Function Is Enabled
Description: When the pre-paging function is enabled, the alarm related to SDCCH
congestion is generated when the BSC is busy.
Analysis and solution: According to the analysis of the paging procedure on the BSS side,
the BSC delivers a paging message through the PCH. After the MS responds to the paging
message, the BSC allocates an SDCCH to the MS. The MS then reports the paging response
message through the SDCCH and seizes the SDCCH. After the BSC allocates the TCH to the
MS and the MS is handed over from the SDCCH to the TCH, the MS releases the seized
SDCCH. According to the field feedback, the pre-paging function is enabled, and the MS
independently seizes an SDCCH after the paging response is received. Generally, the
MSC/VLR allocates the roaming number, analyzes the number, and selects the route after the
paging response is received. Because the pre-paging request is initiated early, the SDCCH is
always seized during the interval. In a normal paging procedure, however, a paging message
is delivered after the roaming number is allocated and the number analysis and route selection
are performed. In this case, the time of seizing the SDCCH is shorter than that when the pre-
paging function is enabled. After the pre-paging function is disabled, the SDCCH congestion
problem on the BSC side is solved.
5.3.2 Case 4: Paging Success Rate Drops When BS-PA-MFRAMS
Is Set Improperly
Description: The paging overload occurs in some sites in Russia, and the paging success rate
decreases.
Analysis and solution: According to the analysis, the value of the parameter
BS_PA_MFRMS in the sites is 6 or 8. After the value is set to 2, the overload does not occur
and the paging success rate increases.
The BS_PA_MFRMS parameter indicates the number of multi-frames as a cycle of the
paging sub-channel. Actually, the parameter determines the number of paging sub-channels
into which the PCH in a cell is divided.
If the BCCH is configured, the number of paging sub-channels = (9 - BS_BLKS_RES) x
BS_PA_MFRMS.
BS_BLKS_RES indicates the number of blocks reserved for immediate assignment.
According to the preceding formula, if the value of BS_PA_MFRMS is large, the number of
paging sub-channels is large. The value of BS_PA_MFRMS ranges from 2 to 9.
The paging delivery procedure on the BTS side is as follows: The paging message from the
BSC is stored in the paging queue for buffering, and the paging message in the buffer of the
BTS is delivered on the paging sub-channel (Um interface).
When the paging messages in the buffer of the BTS overflow, the paging overload message is
reported. The factors that affect the paging capacity (overflow) are as follows:
1. Buffering capacity of the paging queue.
2. Delivery efficiency of the Um interface.

For the delivery efficiency of the Um interface, the number of paging messages carried
in a paging block is fixed. Thus, when the value of BS_PA_MFRMS is small, the
number of paging sub-channels in a cell is small. That is, the number of MSs on each
paging sub-channel is large and the probability of fully loaded messages on the Um
interface is high. In addition, when the value of BS_PA_MFRMS is small, the delivery
period of a paging group is short. That is, the delay for the paging message waiting for
delivery is short. If the buffer of the paging queue is not overloaded and the value of
BS_PA_MFRMS is set to a small value, the efficiency of the Um interface is high.
In practice, you need to modify the parameter and other paging-related parameters to
optimize the paging performance.
5.3.3 Case 5: MS Cannot Respond to a Paging Message When the
Number of Pagings on the N Side Is Set Improperly
Description: In a local network, the VMSC is connected to the M900 and M1800 BSSs. The
M1800 BSS is provided for the capacity expansion in phase II. To reduce the load on the BSC
side, we change the number of pagings on the VMSC from 5 to 2. After the data is changed,
the MS in the M1800 BSS can serve as the calling party but not the called party.
Analysis and solution: When the number of pagings on the VMSC is set to 5, you can set the
pagings for a single location area or the entire network. Generally, the first four pagings are
set for a single location area and the last paging is set for the entire network. As the MS can
serve as the called party, it indicates that the MS can be paged in the five pagings. The
possible cause is as follows: The previous pagings are not sent to a correct BSC, but the last
network-wide paging is sent to all the BSCs. In this case, the MS can be paged.
According to the data check result, no destination signaling point of the BSC is set in the
location area data of the M1800. For the paging in a single location area, the paging message
is delivered to the BSC signaling point corresponding to the location area. If no signaling
point is set, the MSC cannot deliver a paging message to the BSC. For the paging in the entire
network, the paging message is delivered to each BSC in the BSC table. After the BSC
signaling point corresponding to the location area is set, the MS can be paged in the first
paging procedure. Now, the problem is solved.
5.3.4 Case 6: BSC Paging Is Abnormal When the LAC Is
Configured Improperly for the BSC
Description: After the BSC6000 is cut over in an office, the number of CS paging requests
processed by the BSC rises sharply. The BSC is configured with more than 30 BTSs, and the
number of pagings in busy hours reaches about 100,000.
Analysis and solution: The problem can be analyzed in the following aspects: paging policy
of the MSC, paging mechanism on the BSC side, signaling congestion, and more than one
location area of Huawei BSC.
Check the data configuration on the BSC side, and find that the BTSs controlled by the BSC
belong to an LAC. Trace the messages on the A interface, and find that the paging message
carries the LAC of the BSC and the LAC of another BSC. Ask the MSC engineer to check
data, and find that more BTS data (the LAC of another BSC) is configured in the BSC. After
asking the engineering supervisor, find that the BTS data is test data before the cutover. After
the cutover, the BSC supervisor deletes the BTS data without notifying the MSC engineer of
the relevant information. In this case, the MSC sends more paging messages to the BSC (the
MSC sends a paging message based on the LAC).

5.3.5 Case 7: Paging Success Rate Increases After the A-interface
Collaboration Paging Function Is Enabled
Description: After a project is relocated, the paging success rate in some location areas
decreases.
Analysis and solution: After the project is relocated, all the original parameters are used but
the location areas change. Analyze the traffic measurement counters on the MSC side and
BSC side, and find that the paging success rate on the B side decreases.
Adjust other parameters, and find that the paging success rate is not improved. According to
the traffic statistics, PS traffic in the entire traffic reaches a certain proportion. After enabling
the A-interface collaboration paging function, the paging success rate in the entire network
increases by 1%, as shown in the following figure.
5.4 Case 8: Paging Success Rate Drops Due to Poor
Coverage
Description: After a GSM network is expanded, the subscribers complain that the called
party is out of the service area. When the signal quality is good and the MS is called, the
calling party hears a prompt tone "The subscriber you dialed is unreachable, please redial
later."
Analysis and solution: The problem is caused by the following two cases: (1) The prompt
tone is reported incorrectly, for example, the prompt tone is reported when the MS is powered
off or in call state. The error is caused by the abnormal NSS processing. (2) The prompt tone
is reported when the called MS does not respond to a paging message during the immediate
assignment. The immediate assignment process is contained in the following procedures: (1)
The MS serves as a called party; (2) The MS responds to a paging message; (3) The MS
performs a location update. Currently, the system cannot eliminate the collision between the
paging and the immediate assignment. You can reduce the probability of the collision only by
properly setting parameters, for example, prolongs the location updates time in a location area
with good network coverage or increases the number of pagings.

In addition, the problem may be caused when the MS cannot access the network normally.
The causes are as follows:
A. When the downlink signal quality is poor, the MS does not receive a paging message.
B. When the uplink signal quality is poor or the access signals collide, the network does not
receive a paging response from the MS.
In this case, there are many three-TRX cells and the antenna system is configured with many
SCUs. Because the insertion loss of the SCU is 3 dB to 4 dB higher than that of the CDU and
the power level is high in the original data configuration, the coverage in some areas is poor.
After the TRX power level of the SCU is decreased by two levels (the static power is
increased by 4 dB), the coverage in some cells is improved greatly. In this case, the paging
success rate increases.

6 Information Feedback
When the paging success rate decreases, you need to report the following data for the problem
analysis and location:
1. MSC software version and vendor information, BSC software version, and BTS software
version
2. Paging policy and paging measurement counters on the MSC side: used to obtain the
data configuration on the N side and the change trend of paging success rates
3. *.dat files: used to obtain the parameter configuration on the BSS side
4. Signaling: signaling messages traced on the faulty BTS
5. Traffic measurement: traffic measurement counters related to paging
6. Alarm information: used to check whether the hardware or transmission link is faulty

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