14 GSM BSS Network KPI (Call Setup Time) Optimization Manual[1].Doc

GSM BSS Network KPI (Call Setup Time) Optimization Manual

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Confidentiality Level

G3BSC

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Product Version

Total 26 pages

GSM BSS Network KPI (Call Setup Time) Optimization Manual For internal use only

Prepared by

Date

2008-12-24

Reviewed by

Date

yyyy-mm-dd

Reviewed by

Date

yyyy-mm-dd

Approved by

Date

yyyy-mm-dd

Yang Chunjie (ID: 00119951) from the GSM&UMTS Network Performance Research Dept.

Huawei Technologies Co., Ltd. All rights reserved

GSM BSS Network KPI (Call Setup Time) Optimization Manual

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Contents 1 Overview of the Call Setup Time.....................................6 1.1 Definition of the Call Setup Time.................................................................................................6 1.2 Recommended Formulas...............................................................................................................6 1.3 Signaling Procedure and Measurement Points..............................................................................7

2 Influencing Factors........................................................9 2.1 Procedure Configuration...............................................................................................................9 2.2 Parameter Settings.........................................................................................................................9 2.3 Routing..........................................................................................................................................9 2.4 Hardware, Transmission, Coverage, and Interference................................................................10

3 Analysis Process and Optimization Method....................11 3.1 Analysis Process..........................................................................................................................11 3.2 Process Description.....................................................................................................................12 3.2.1 Procedure Configuration.......................................................................................................12 3.2.2 Parameter Setting..................................................................................................................14 3.2.3 Routing..................................................................................................................................17 3.2.4 Hardware, Transmission, Coverage, and Interference..........................................................18

4 Test Method................................................................20 5 Optimization Cases......................................................21 5.1 Long Call Setup Time Due to Long Period of Assignment Command Delivery........................21 5.1.1 Problem Description.............................................................................................................21 5.1.2 Problem Analysis..................................................................................................................21 5.1.3 Suggestion and Summary......................................................................................................21 5.2 Long Call Setup Time Due to Reporting of Two Classmark Change Messages........................22 5.2.1 Problem Description.............................................................................................................22 5.2.2 Problem Analysis..................................................................................................................22 5.2.3 Suggestion and Summary......................................................................................................23 5.3 Long Call Setup Time Due to Calling and Called MSs Under Different MSCs........................23 5.3.1 Problem Description.............................................................................................................23 5.3.2 Problem Analysis..................................................................................................................23 2012-12-12

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5.3.3 Suggestion and Summary......................................................................................................23 5.4 Long Call Setup Time Due to Inconsistency in Signaling Procedures.......................................24 5.4.1 Problem Description.............................................................................................................24 5.4.2 Problem Analysis..................................................................................................................24 5.4.3 Suggestion and Summary......................................................................................................25

6 Information Feedback..................................................26

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Revision Record Date

Revisio n

Change Description

Author

2008-12-24

V0.3

Draft completed.

Yang Chunjie

2009-1-20

V1.0

This document is modified according to review comments.

Yang Chunjie

References

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SN

Document

Author

Date

1

GSM BSS Network KPI (Call Setup Time) Baseline

Wu Zhen

2007-08-24

2

GSM Call Setup Time (CS) Analysis Report

Zha Shuangliu, Li Xiaomeng, Zhang Lida, and Wu Baishan

2008-10-25

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GSM BSS Network KPI (Call Setup Time) Optimization Manual Keywords Call setup time

Abstract This document describes the method of optimizing the call setup time.

Acronyms and Abbreviations

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MOC

Mobile Originated Call

MTC

Mobile Terminated Call

PSTN

Public Switched Telephony Network

TMSI

Temporary Mobile Station Identity

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Overview of the Call Setup Time

1.1 Definition of the Call Setup Time The call setup time indicates the mean time from the originating of a call by a subscriber to the setup of the call. A long call setup time will severely affect the user experience. Therefore, the call setup time is one of the KPIs that operators are most concerned about.

1.2 Recommended Formulas The call setup time is obtained through drive tests. It refers to the time for an MS to set up an end-to-end call through radio network equipment. There are three types of call setup time: 

MS to PSTN: average interval between the transmission of the Channel Request message from the MS and the MS's reception of the Alerting message sent from the MSC



MS to MS: average interval between the transmission of the Channel Request message from the calling MS and the calling MS's reception of the Alerting message sent from the MSC



PSTN to MS: average interval between MS's receiving of the paging message from the MSC and sending of the Alerting message from the MS to the MSC

Note that the call setup time is the average setup time of multiple successful calls. You need to conduct multiple dialing tests.

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1.3 Signaling Procedure and Measurement Points Figure 1.1 Measurement points in an MOC setup procedure (with the early assignment procedure as an example) BTS

M S

Channel Request A

BSC Channel Requi red Channel Acti ve

Channel Acti ve ACK Im m edi ate Assi gnm ent Com m and SABM U A Establ i shed I ndi cati on

CR CC

CMServi ce Accepted Setup Cal l Proceedi ng Channel Acti ve Channel Acti ve ACK Assi gnm ent Com m and SABM U A Establ i shed I ndi cati on Assi gnm ent Com pl ete

B

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Al erti ng

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Assi gnm ent Request

Assi gnm ent Com pl ete

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Figure 1.2 Measurement points in an MTC setup procedure (with the early assignment procedure as an example) MS

BTS

BSC

MSC pagi ng

C

Pagi ng Requi red

Pagi ng Com m and

Channel Request Channel Requi red Channel Acti ve Channel Acti ve ACK Im m edi ate Assi gnm ent Com m and SABM UA Establ i shed I ndi cati on

CR CC

CMServi ce Accepted Setup Cal l Control Channel Acti ve Channel Acti ve ACK Assi gnm ent Com m and SABM UA Establ i shed I ndi cati on Assi gnm ent Com pl ete Al erti ng

Assi gnm ent Request

Assi gnm ent Com pl ete

D

In 1.1 and 1.2: 

A is the time when the MS sends a Channel Request message.



B is the time when the MS receives the Alerting message from the MSC.



C is the time when the MS receives a paging message.



D is the time when the MS sends an Alerting message.

In the tests of MS-to-MS or MS-to-PSTN calls, the call setup time is equal to B minus A; in the tests of PSTN-to-MS calls, the call setup time is equal to D minus C.

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Influencing Factors

2.1 Procedure Configuration The setup of either an MOC or an MTC involves many procedures such as authentication and ciphering mode setting and relates to multiple NEs such as the MSC, BSC, BTS, and MS. Therefore, the configuration of the call procedures directly determines the length of the call setup time.

2.2 Parameter Settings The call setup time is related to the entire procedure of an MOC or MTC, and therefore, many parameters can affect the call setup time. The following are some examples: 

BS-PA-MFRAMS



Use Imm_Ass Retransmit Parameter



Max Delay of Imm_Ass Retransmit and Max Transmit Times of Imm_Ass



Pre-paging function, which is set on the MSC



Immediate Assignment Opt.



ECSC, which means early classmark sending control



Allow Reassign



Late assignment function, which is set on the MSC



Assignment command optimization



Force Queue In Assignment



T11(s)

2.3 Routing The network equipment of different manufacturers varies. Therefore, in the case of interworking between equipment of different manufacturers or change in routing, analysis and handling should be performed, on the basis of drive test results.

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2.4 Hardware, Transmission, Coverage, and Interference A problem in hardware, transmission, coverage, or interference may result in an increase in the call setup time.

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Analysis Process and Optimization Method

3.1 Analysis Process Figure 1.1 Analysis process Call setup time too long

Collect the test data

Is it due to a problem in procedure configuration?

Yes

Optimize the procedure configuration and then verify the optimization

Yes

Adjust the parameter settings and then verify the adjustment

Yes

Analyze the problem based on the signaling and data configuration and take proper measures

Yes

Solve the problem according to the related optimization manual

No Is it due to a problem in parameter settings? No Is it due to a problem in routing? No

Is it due to a problem in hardware, transmission, coverage, or interference? No No

Is the problem solved? Yes End

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3.2 Process Description 3.2.1 Procedure Configuration During the setup of a call, some procedures are optional, such as authentication, ciphering mode setting, and TMSI reallocation, and independent of each other. Therefore, flexible configuration of the procedures according to operators' requirements is applicable. On the existing networks, ciphering is generally enabled, and authentication and TMSI reallocation are enabled on a proportion (that is, 10% to 20%) of MSCs.

Authentication For a 3G subscriber, during the authentication when the mobile accesses a GSM network, the MSC sends an authentication message to the mobile. The message contains the RAND, AUTN, and RES, and is longer than 23 bytes. Therefore, the LAPDm needs to divide the message into two and deliver them separately. Thus, in a GSM network, a 3G subscriber requires 240 ms to 260 ms more than a 2G subscriber in terms of the call setup time. In addition, when the BSC assigns an AMR channel, the Assignment Command message will be longer than 23 bytes if the frequency hopping MA is too long. This results in 240 ms to 260 ms more in the call setup time.

Ciphering Mode Setting During the setup of an MOC, if the ciphering mode setting procedure is not performed, the MS does not send a Setup message until it receives a CM Service Accepted message from the MSC; if ciphering is to be enabled, however, the MS can send a Setup message immediately after the ciphering mode setting procedure is performed. Therefore, for an MOC, the call setup time in the case of ciphering enabled is generally only 250 ms to 300 ms longer than the call setup time in the case of ciphering not enabled. This is because the MS sends one more message (that is, the Ciphering Mode Complete message) to the network in the case of ciphering enabled.

TMSI Reallocation The TMSI is reallocated according to the settings on the network side after each operation or several operations on the air interface, such as a call or a location update.

Classmark Enquiry The Core Network (CN) can obtain the MS's information about their multiband and multislot capabilities through the classmark enquiry procedure.

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At the BSS, the cell-oriented parameter ECSC is set. The BSS sends the parameter through the system information type 3. Once an MS accesses the network, the MS reports Classmark3. According to the protocol, this must be implemented at MSs that support multiband, multislot, and Voice Group Call Service (VGCS). In practice, competitors generally do not enable classmark enquiry in their CNs but use ECSC. Thus, the LAPDm signaling interaction on the air interface is reduced, and the call setup time is shortened. Huawei, however, enables classmark enquiry in all its CNs by default. In addition, the classmark enquiry is not user-configurable. It can be controlled by the related reserved software parameter only. Therefore, when ECSC is enabled at both competitor's BSS and Huawei BSS, Huawei CN results in at least 240 ms more than competitor's CN in terms of the call setup time. For specific cases, see sections 5.2"Long Call Setup Time Due to Reporting of Two Classmark Change Messages" and 5.4"Long Call Setup Time Due to Inconsistency in Signaling Procedures."

Optimization on I frames at the LAPDm Before the optimization, Huawei BTS does not support the function of downlink I frames acknowledging uplink I frames at the LAPDm. That is, after receiving an uplink I frame from an MS, the BTS immediately sends an RR response message to the MS. During this process, if the BTS receives a downlink I frame from the BSC, the BTS has to postpone the delivery of the downlink I frame, that is, the BTS sends the downlink I frame in the next delivery period. Thus, the delay increases. This problem can be solved after the upgrade. With the optimization, the BTS can acknowledge uplink I frames by downlink I frames. That is, after receiving an uplink I frame from an MS, the BTS does not send an RR frame immediately. Instead, the BTS waits a period of time and checks whether it receives a downlink I frame. If the BTS receives a downlink I frame during this period, it acknowledges the uplink frame by the downlink I frame. Thus, the delay is decreased by one delivery period.

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1.1 shows the effect of the optimization. Figure 1.1 Optimization on I frames at the LAPDm

The optimization can be achieved by BTS upgrade only. It is incorporated into V300R008C11B337 of the BTS. During the optimization on the call setup time on site, the optimization on I frames can be considered.

3.2.2 Parameter Setting The main parameters that affect the call setup time are as follows: 

BS-PA-MFRAMS This parameter specifies the number of multi-frames used as a unit of the paging sub-channel. If this parameter is set to a high value, the average paging delay is great. Thus, the MS-to-MS call setup time and the PSTN-to-MS call setup time are prolonged.



Use Imm_Ass Retransmit Parameter If this parameter is set to Yes, the BSC sends the immediate assignment retransmission parameter to the BTS. Otherwise, the BSC does not send the immediate assignment retransmission parameter to the BTS. The immediate assignment retransmission function can help increase the call completion rate of MSs but may increase the access delay of MSs and the load of the BSC. It is recommended that this function be disabled.



Max Delay of Imm_Ass Retransmit and Max Transmit Times of Imm_Ass These two parameters specify the maximum delay of the immediate

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assignment retransmission and the maximum number of immediate assignment retransmissions respectively. When the network quality is poor, an immediate assignment message may need to be retransmitted. If these parameters are set to high values, the average call setup time may be prolonged. 

Pre-paging function This parameter is set on the MSC. −

If the pre-paging function is enabled, the MSC pages the called party as soon as the MSC receives the Setup message from the calling party.

−

If this function is not enabled, the MSC pages the called party as soon as the MSC sends the Call Proceeding message.

Therefore, for MS-to-MS calls, the call setup time can be shortened if the pre-paging function is enabled. It is recommended that this function be enabled. 

Immediate Assignment Opt. The channel activation and immediate assignment commands are sent at the same time to accelerate the signaling processing, thus improving the response speed of the network. It is recommended that this function be enabled.



ECSC This parameter specifies whether the MSs in a cell use early classmark sending.



−

If this parameter is set to Yes, after a successful immediate assignment, the MS sends additional classmark information to the network as early as possible.

−

For dual-band MSs, if this parameter is set to No, the MSC sends a Classmark Request message after the MS reports an Establish Indication message. The MS then reports the Classmark Update message. The access delay of the MS is affected.

Allow Reassign If this parameter is set to Yes, the BSC initiates a reassignment when receiving an assignment failure message over the Um interface. This helps increase the call completion rate and improve the QoS of the network. The successful reassignment, however, results in an increase in the access delay of MSs and the load of the BSC. It is recommended that this function be disabled.



Late assignment procedure This parameter is set on the MSC. With the late assignment function, the assignment command is sent after alerting. This can shorten the call setup time. In the late assignment procedure, however, the reception of the Alerting message does not necessarily indicate the establishment of a call. Therefore, the call setup time is not measured in the late assignment procedure. It is recommended that this function be disabled.



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If frequency hopping is enabled at Huawei BTS, the ARFCNs in the assignment command are delivered in the form of CA+MA by default, which may result in the assignment command longer than 23 bytes. Then, the message is divided into two I frames at the LAPDm, which are delivered separately. Thus, the delay is increased by about 230 ms because of the addition of a delivery period. To shorten the call setup time, the ARFCNs can be delivered in the form of frequency list so that the assignment command can be delivered in one I frame. On live networks, the frequency list mode is recommended. 3.2.2 describes how to set this parameter. Figure 1.1 Setting of the assignment command optimization parameter Paramete r

Setting

Decrease in the Delay

Assignment command optimization parameter

Bit 1 of the celloriented reserved parameter 1 is 1, that is, the parameter value is 65535.

CA+MA

Bit 1 of the celloriented reserved parameter 1 is 0, that is, the parameter value is 65533.

Bit 2 of reserved parameter 1 is 0, that is, the parameter value is 65529.

Frequency list with the variable bit map coding scheme

Bit 2 of reserved parameter 1 is 1, that is, the parameter value is 65533.

Frequency list with the bit map 0 coding scheme

No

About 200 ms

NOTE

The assignment command optimization is incorporated into BSC6000 V900R008C11B168SP11 and later releases.

For specific cases, see chapter 5"Optimization Cases." 

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Force Queue In Assignment −

When this parameter is set to Yes, the BSC puts an assignment request message into the assignment request message queue if no TCH is available for assignment, or the BSC assigns a TCH to the MS if the TCH is available for assignment.

−

If this parameter is set to No, the value of queuing allowed indicator in the assignment request message is 0, which means that the assignment request message cannot be put into the assignment request message queue. Then, the channel request is rejected when no TCH is available for assignment. Huawei Proprietary and Confidential

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The default value of this parameter is No. 

T11(s) This parameter specifies the length of the timer that is started to wait for a channel requested by an assignment request message. When the BSC receives an assignment request but no channel is available for assignment, the BSC starts the queuing procedure and this timer. If the channel request is accepted before the timer expires, the timer stops. If the timer expires, the channel assignment fails. When queuing is enabled, a high value of this parameter directly leads to a long call setup time.

3.2.3 Routing On live networks, when swapping is performed, the BSC and MSC are redeployed and thus the call routing changes. Therefore, the setup time of interMSC calls is affected. In this case, tests should be conducted, and the analysis should be performed on the basis of the test results obtained before and after the swapping. For a specific case, see section 5.3"Long Call Setup Time Due to Calling and Called MSs Under Different MSCs." 3.2.3 lists the example values of delay during an MS-to-MS call made in the lab. On live networks, the delay values are related to the actual situations. The data in 3.2.3 is provided only for reference. Figure 1.2 Example values of delay during an MS-to-MS call made in the lab Signaling of an Outgoing MS-to-MS Call (Authentication, Ciphering, and TMSI Reallocation Enabled, Whereas Classmark Enquiry Disabled)

Relative Delay (Unit: s)

Channel Request (UL) -> Immediate Assignment (DL)

00.050

Immediate Assignment (DL) -> SABM-CMD (UL)

00.132

SABM-CMD (UL) -> Authentication Request (DL)

00.708

Authentication Request (DL) -> Authentication Response (UL)

00.125

Authentication Response (UL) -> Ciphering Mode Command (DL)

00.564

Ciphering Mode Command (DL) -> Ciphering Mode Complete (UL)

00.000

Ciphering Mode Complete (UL) -> Setup (DL)

00.005

Setup (UL) -> TMSI Reallocation Command (DL)

00.458

TMSI Reallocation Command (DL) -> TMSI Reallocation Complete (UL)

00.001

TMSI Reallocation Complete (UL) -> Call Proceeding (DL)

00.466

Call Proceeding (DL) -> Assignment Command (DL)

00.466

Assignment Command (DL) -> Assignment Complete (UL)

00.011

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Signaling of an Outgoing MS-to-MS Call (Authentication, Ciphering, and TMSI Reallocation Enabled, Whereas Classmark Enquiry Disabled)

Relative Delay (Unit: s)

Assignment Complete (UL) -> SABM-CMD (UL)

00.039

SABM-CMD (UL) -> Alerting (DL)

04.797

Total delay

07.822

The versions of NEs used in the test are as follows: 

CN: G9MSC90 MSOFTX3000V100R003



BSC: V900R008C01B051



BTS: V3.03R002.20011015

3.2.4 Hardware, Transmission, Coverage, and Interference If a TRX or combiner is faulty or if an RF cable is incorrectly connected, seizing the SDCCH or TCH becomes difficult, and thus the call setup time increases. Faults such as poor transmission quality, instability of transport links, insufficiency of resources, or bit errors on the Abis and A interfaces may lead to an increase in the error rate on the links, which results in more message retransmissions between switches. Thus, the message transfer delay increases and congestion may occur on the links. In severe cases, routes change frequently, which leads to instability and congestion on the links. If the preceding problem occurs during call setup, the call setup time increases. The problem can be identified from traffic statistics. 3.2.4 lists the transmission-related alarms at the BSC. Figure 1.3 Transmission-related alarms at the BSC Alarm ID

Alarm Name

1000

LAPD OML Fault

11270

LAPD Alarm

11278

E1 Local Alarm

11280

E1 Remote Alarm

20081

Loss of E1/T1 Signals (LOS)

20082

Loss of E1/T1 Frames (LOF)

Coverage or interference problems can be identified from the traffic statistics 2012-12-12

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or KPIs. For example, the interference information can be obtained on the basis of the interference band distribution in the traffic measurement results. If a large proportion of interference levels belong to interference bands 3–5, you can infer that there is strong interference in the uplink. To obtain the downlink interference information, you can perform drive tests or analyze the traffic measurement results that are related to receive quality. Strong interference affects the call drop rate on TCH, the TCH assignment success rate, and the SDCCH setup success rate, thus affecting the call setup time. The interference elimination can be classified into intra-network interference elimination and inter-network interference elimination. For details about interference elimination, see the G-Guide to Eliminating Interference. If a coverage problem exists, you can solve the problem by using the methods such as adjusting the tilt of the antenna, increasing the transmit power, adding repeaters, and changing the combining mode. For details, see the GSM BSS Network Performance KPI (Coverage) Optimization Manual.

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Test Method

The call setup time is one of drive test KPIs. It can be obtained from the results of call quality tests or drive tests for calls between MSs or between MS and PSTN. The method is to perform a short MOC test. During the test, the interval between two calls is 5s, each call lasts 10s, and the interval between a call failure and the next call attempt is 30s. The recommended number of calls during the test is 100. The number of calls can be changed as required. During the test, the signaling on the Um and A interfaces needs to be traced. If a value of call setup time is abnormal, analyze the signaling to check whether the abnormal value is due to failure of the first paging. If the abnormal value is due to failure of the first paging, do not take this value into measurement of the call setup time. Otherwise, take this value into the measurement. Check the signaling on the A interface. If the MSC sends two Paging messages for one call, you can infer that the first paging for the call fails.

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Optimization Cases

5.1 Long Call Setup Time Due to Long Period of Assignment Command Delivery 5.1.1 Problem Description After swapping of Ericsson equipment for Huawei equipment at a site, the call setup time became longer. It was found that the delivery of an assignment command from Huawei equipment took two or three periods whereas that from Ericsson equipment generally took only one period.

5.1.2 Problem Analysis In frequency hopping mode, the BSC6000 currently delivers the ARFCNs in CA+MA form through the assignment command. CA uses the TV format and its length is fixedly 17 bytes, and MA uses the TLV format and its length is 3– 10 bytes. If an AMR channel is to be assigned (coded in TLV format in the command), the length of the assignment command increases by 4–8 bytes. Thus, the assignment command is longer than 23 bytes. Therefore, at the LAPDm, the assignment command is divided for delivery. Before the swapping, however, the ARFCNs are delivered in the form of frequency list, which uses the TLV format, and therefore in most cases, the assignment command can be delivered with one frame.

5.1.3 Suggestion and Summary When setting the assignment command optimization parameter, which is available only when frequency hopping is enabled in a cell, at the BSC, note that:

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

If this parameter is set to CA+MA, the original Huawei ARFCN delivery form is retained.



If this parameter is set to Frequency List, the coded ARFCNs for Huawei Proprietary and Confidential

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frequency hopping will be delivered in the form of frequency list. Therefore, the assignment command will be delivered in one period, thus shortening the call setup time.

5.2 Long Call Setup Time Due to Reporting of Two Classmark Change Messages 5.2.1 Problem Description After swapping for Huawei equipment at a site, the call setup time became longer.

5.2.2 Problem Analysis When Huawei CN is used, an additional Classmark Change message is reported during the call setup procedure if ECSC is set to Yes. The reason is that the classmark enquiry procedure is enabled by default in Huawei CN. 1.1 shows the difference in the signaling procedure before and after the swapping. Figure 1.1 Classmark enquiry procedure enabled after the swapping

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5.2.3 Suggestion and Summary To avoid the preceding problem, set ECSC to Yes and CM Update Optimize Type to 2, or coordinate with the CN to disable classmark enquiry at the CN.

5.3 Long Call Setup Time Due to Calling and Called MSs Under Different MSCs 5.3.1 Problem Description After swapping of some BSC in country R, the drive test results indicated that the call setup time was about 3,000 ms longer than that before the swapping. The call setup time is one of the acceptance check items of the project. It refers to the delay between sending of the Channel Request message and reception of the Alerting message.

5.3.2 Problem Analysis As indicated by the parameter check result, the parameters in the network are inherited from the previous network. Therefore, the parameters related to the call setup time remain unchanged. As indicated by the call signaling on the TEMS, the duration of the ciphering mode setting procedure after the swapping is the same as that before the swapping. Compared with the signaling messages before the swapping, the signaling messages after the swapping include another two Progress messages, which are present between the Assignment Complete message and the Connect message. The description in the progress messages is "Call is not end-to-end PLMN/ISDN, further call progress information may be available in-band." As indicated by messages traced at the CN, after the swapping, though the called number under the test is the same as that before the swapping, the test call is an inter-MSC one. That is because the calling MS is controlled by Huawei MSC whereas the called number remains under its original MSC.

5.3.3 Suggestion and Summary During the drive test on site after the swapping, the called number was the same as that before the swapping, but the fact that the calling MS and the called number were under different MSCs was not noticed. Therefore, when checking consistency between test conditions before and after swapping, pay attention to such hidden changes.

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5.4 Long Call Setup Time Due to Inconsistency in Signaling Procedures 5.4.1 Problem Description After swapping for Huawei equipment at a site, the call setup time became longer.

5.4.2 Problem Analysis The comparison between the call setup signaling procedures before swapping and those after swapping should be performed. If the call setup after swapping includes more procedures than that before swapping, remove them. Take the GP swapping in Bengal as an example. 1.1 shows the difference between the signaling procedures before and after the swapping. Figure 1.1 GPRS suspension procedure enabled after the swapping

As shown in 1.1, the difference between the signaling procedures was the presence of a GPRS suspension procedure in the test after the swapping. The presence of this procedure is related to whether the MS in the test has performed GPRS attach. According to 3GPP TS 44.108, as shown in 1.2, the MS sends a GPRS Suspension Request message to suspend PS services, regardless of whether the MS has any PS service in progress.

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Figure 1.2 GPRS suspension procedure described in the protocol

5.4.3 Suggestion and Summary For CS call setup time test, the GPRS suspension procedure should be removed. To remove this procedure, change the related setting of the mobile. The following are two examples: 

On a NOKIA N73 mobile, set Tools > Settings > Connection > Packet data > Packet data conn > When needed.

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On a Sony Ericsson K790 mobile, set Settings > Connectivity > Data communication > Preferred service > CS only.

The GPRS suspension procedure is always present in the test after swapping. If this procedure is not or seldom present in the test before swapping, this procedure can be removed to reduce the delay.

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Information Feedback

The following information is required:

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Data configuration file in .dat format

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Log files and comparison data obtained from drive tests

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Settings on the MSC, such as pre-paging and late assignment

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