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

2023-4-12 Huawei Confidential of 28


Contents

1 Definition of the Paging Success Rate.............................................71.1 Definition...........................................................................................................................................................7

1.2 Recommended Formula.....................................................................................................................................7

1.3 Signaling Procedure and Measurement Point....................................................................................................8

2 Influencing Factors........................................................................92.1 Hardware Fault..................................................................................................................................................9

2.2 Transmission Problem........................................................................................................................................9

2.3 Parameter Setting Problem................................................................................................................................9

2.4 Interference Problem........................................................................................................................................10

2.5 Coverage Problem............................................................................................................................................10

2.6 Uplink and Downlink Balance Problem..........................................................................................................11

3 Analysis Procedure for the Paging Success Rate and Optimization Method..........................................................................................12

3.1 Analysis Procedure..........................................................................................................................................12

3.2 Problem Location of the Paging Success Rate and Optimization Method......................................................13

3.2.1 Hardware and Transmission Problems...................................................................................................14

3.2.2 SDCCHs Occupied Due to Paging Overload and Heavy Burst Traffic.................................................14

3.2.3 Parameter Configuration.........................................................................................................................15

3.2.4 Interference.............................................................................................................................................20

3.2.5 Coverage.................................................................................................................................................20

3.2.6 Balance Between Uplink and Downlink................................................................................................21

4 Test Methods...............................................................................22

5 Cases for Optimization of the Paging Success Rate........................235.1 Case 1: Paging Success Rate Drops Due to a Hardware Fault........................................................................23

5.2 Case 2: Paging Success Rate Drops Due to a Transmission Fault...................................................................23

5.3 Paging Success Rate Drops Due to Improper Parameter Configuration.........................................................24

5.3.1 Case 3: Paging Success Rate Drops When the Pre-paging Function Is Enabled...................................24

5.3.2 Case 4: Paging Success Rate Drops When BS-PA-MFRAMS Is Set Improperly.................................24

5.3.3 Case 5: MS Cannot Respond to a Paging Message When the Number of Pagings on the N Side Is Set Improperly.......................................................................................................................................................25

5.3.4 Case 6: BSC Paging Is Abnormal When the LAC Is Configured Improperly for the BSC...................25



5.3.5 Case 7: Paging Success Rate Increases After the A-interface Collaboration Paging Function Is Enabled.........................................................................................................................................................................26

5.4 Case 8: Paging Success Rate Drops Due to Poor Coverage............................................................................26

6 Information Feedback.....................................................................................28



Figures

Figure 1-1 Intra-BSS Paging Procedure..................................................................................................................8



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 FaultWhen 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 ProblemThe 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 ProblemThe 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 ProblemThe 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 ProblemThe 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 ProblemIf 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 ProblemsWhen 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 BSCConfigured SDCCHs per BSCAvailable 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 ConfigurationIf 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 not combined with the SDCCH.

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 not combined with the SDCCH.

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 1Mean Number of TCHFs/TCHHs in Interference Band 2Mean Number of TCHFs/TCHHs in Interference Band 3

Mean Number of TCHFs/TCHHs in Interference Band 4

Mean Number of TCHFs/TCHHs in Interference Band 5

[MR Measurement]->

[Receive Quality Measurement per TRX]

3.2.5 CoverageYou 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.


g00130220, 06/30/09,



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 DownlinkIf 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


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

Engineering

paging success rate

paging success rate

bsc paging

paging overload

paging message

coverage problem

interference problem

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