GSM
PS Performance Evaluation and Analysis Guide
Issue
01
Date
2011-07-20
HUAWEI TECHNOLOGIES CO., LTD.
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Issue 01 (2011-07-20)
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1
GSM PS Performance Evaluation and Analysis Guide
Change History
Change History Date
Issue
Description
Author
2011-04-13
V1.0
Completed the draft.
Shen Huafang, Zhang Yunfeng
2011-04-20
V1.1
Revised according to review comments.
Shen Huafang
2011-05-06
V1.2
Revised according to review comments.
Shen Huafang
2011-05-14
V1.3
Revised according to review comments.
Shen Huafang
2011-06-10
V1.4
Revised according to training comments.
Shen Huafang
2011-06-15
V1.5
Optimized the document.
Shen Huafang
2011-06-24
V1.6
Revised according to review comments.
Shen Huafang
2012-02-21
V1.7
Updated according to the latest draft rules.
Wang Xiaofen
GSM PS Performance Evaluation and Analysis Guide
Contents
Contents Change History................................................................................ ii 1 About This Document....................................................................1 2 Evaluation Items...........................................................................2 3 Analysis.......................................................................................4 3.1 KPI Performance Analysis.................................................................................................................................4 3.1.1 KPI Scoring..............................................................................................................................................4 3.1.2 Accessibility Analysis...............................................................................................................................5 3.1.3 Retainability Analysis.............................................................................................................................10 3.1.4 Transmission Performance Analysis.......................................................................................................14 3.2 User Experience Analysis................................................................................................................................18 3.2.1 LLC Throughput Analysis......................................................................................................................18 1. RLC Single-Timeslot Throughput Analysis................................................................................................19 2. TBF Multiplexing Degree Analysis.............................................................................................................21 3. Channel Satisfaction Degree Analysis.........................................................................................................22 3.2.2 Delay Analysis........................................................................................................................................22 3.2.3 Cell Reselection......................................................................................................................................23
4 Appendix.................................................................................... 25 4.1 Parameters........................................................................................................................................................25 4.2 Features............................................................................................................................................................28 4.2.1 NACC.....................................................................................................................................................28 4.2.2 Packet Si Status......................................................................................................................................28
GSM PS Performance Evaluation and Analysis Guide
1
3 Analysis
About This Document
This document describes how to analyze PS performance problems, including PS KPIs and user experience, based on the evaluation reports generated by the GSM_NetworkAudit tool of OMStar. This document is intended for:
R&D personnel for GSM Inventory Solutions Dept.
GNAC personnel
RNAC personnel
Marketing personnel
Field engineers
Before reading this document, familiar with GSM_NetworkAudit tool of OMStar and general packet radio service (GPRS) basic concepts.
2
Evaluation Items
PS performance is evaluated from the aspects of KPIs and user experience. The involved evaluation items can be obtained from the BSC6900 Check Item Summary worksheet in the Excel report generated by the OMStar. As shown in 1, you can choose Network Information > General Performance > Network Performance Audit to view all BSC-level KPIs. PS Network Performance lists the detailed analysis on the KPIs related to PS accessibility, retainability, transmission performance, and user experience. 1 Category
PS evaluation items
Evaluation Item
Name
Details
2. General Performance
Network Performance Audit
Network Performance Audit
PS Accessibility Performance Affect Factors Audit BSC Uplink EGPRS TBF Establishment Succ Rate Analysis BSC Uplink GPRS TBF Establishment Succ Rate Analysis BSC Downlink EGPRS TBF Establishment Succ Rate Analysis BSC Downlink GPRS TBF Establishment Succ Rate Analysis UL Assignment Success Rate Analysis
PS Accessibility Performance Affect Factors Audit BSC Uplink EGPRS TBF Establishment Succ Rate Analysis BSC Uplink GPRS TBF Establishment Succ Rate Analysis BSC Downlink EGPRS TBF Establishment Succ Rate Analysis BSC Downlink GPRS TBF Establishment Succ Rate Analysis UL Assignment Success Rate Analysis
DL Assignment Success Rate Analysis PS Retainability Performance Affect Factors Audi EGPRS_TBF_CALL_DROP_RATE
DL Assignment Success Rate Analysis PS Retainability Performance Affect Factors Audi EGPRS_TBF_CALL_DROP_RATE
GPRS_TBF_CALL_DROP_RATE
GPRS_TBF_CALL_DROP_RATE
3. Packet Service 1. PS Accessibility Performance
2. PS Retainability Performance
3. PS Transmission Performance
4. PS Resource
Analysis of Rate of BSC LLC
Analysis of Rate of BSC LLC
EGPRS_RLC_BLK_RESEND_RATE EGPRS Users Uplink and Downlink Throughput of LLC PDU in Cell GPRS Users Uplink and Downlink Throughput of LLC PDU in Cell RLC SingleSlot Rate Analysis
EGPRS_RLC_BLK_RESEND_RATE EGPRS Users Uplink and Downlink Throughput of LLC PDU in Cell GPRS Users Uplink and Downlink Throughput of LLC PDU in Cell RLC SingleSlot Rate Analysis
GPRS_RLC_BLK_RESEND_RATE PDCH TBF Multiplex Analysis
GPRS_RLC_BLK_RESEND_RATE PDCH TBF Multiplex Analysis
Utilization
PDCH Resource Utilization
PDCH Resource Utilization
3
Analysis
PS performance is analyzed by performing the following steps: 1.
Determine whether the overall PS performance meets the standards based on the values of the KPIs related to overall PS performance generated in the Network Performance Audit worksheet and the recommended values listed in this chapter.
2.
Analyze the cause for the KPIs that do not meet the standards based on the results of the corresponding evaluation items in the PS Network Performance worksheet and determine whether top N cells are available.
3.
Analyze top N cells in a detailed way.
PS KPIs are analyzed by KPI performance and user experience. KPI performance involves accessibility, retainability, and transmission performance. User experience involves throughput, service interaction delay, and cell reselection.
3.1 KPI Performance Analysis 3.1.1 KPI Scoring KPI scoring helps you determine the status of network KPIs and identify the key KPIs affecting scoring. BSC-level KPIs and KPI scoring are displayed in the Network Performance Audit worksheet of the OMStar report. The baseline value for PS KPI scoring is 85. Table 3.1.1.I.1.1.1.1 KPI scoring BSC Name
PS Accessibility
PS Retainability
PS Transmission Performance
PS LLC Throughput
PS KPI Scoring 85
3.1.2 Accessibility Analysis Accessibility measures the capability of an MS to access the network, which affects the network access success rate and access delay. Accessibility KPIs are displayed in the Network Performance Audit worksheet and are defined from the aspects of EGPRS/GPRS TBF establishment success rate and TBF congestion rate. In normal cases, the TBF establishment success rate is higher than 95% and the TBF congestion rate is lower than 3%. The actual values depend on operator's requirements. The TBF congestion rate is analyzed for resource capacity evaluation. Therefore, only the TBF establishment success rate is analyzed in this section. 2
Accessibility KPIs
KPI
Accessibilit y
Uplink GPRS TBF Establishment Succ Rate
> 95%
Downlink GPRS TBF Establishment Succ Rate
> 95%
Uplink EGPRS TBF Establishment Succ Rate
> 95%
Downlink EGPRS TBF Establishment Succ Rate
> 95%
Recommen ded Value
If the TBF establishment success rate is lower than the baseline value, perform the following detailed analysis.
TBF Establishment Success Rate Impact Analysis Table 3.1.2.I.1.1.1.1 lists the KPIs that can be queried by choosing Packet Service > PS Accessibility Performance > PS Accessibility Performance Affect Factors Audit. Table 3.1.2.I.1.1.1.1 BSC-level accessibility KPIs BSC Name
KPI
TBF Establishment Succ Rate Rate of Failed TBF Establishments due to No Channel Rate of Failed TBF Establishments due to MS No Response
Baseli ne Value
Actual Value
Deviati on
Affectin g Percent age
Rate of Failed TBF Establishments due to Others
Baseline value: The baseline value for TBF Establishment Succ Rate is 95%. Actual value: The actual value is obtained according to the statistical value of the live network. The value of Rate of Failed TBF Establishments due to MS No Response on the live network is excessively higher than that of Rate of Failed TBF Establishments due to Others. Therefore, the transmission quality on the Um interface needs to be optimized if the value of Rate of Failed TBF Establishments due to MS No Response exceeds 3%. The value of Rate of Failed TBF Establishments due to No Channel is 2%, and the value of Rate of Failed TBF Establishments due to Others is close to 0%. Deviation: It specifies the difference between the baseline value and the actual value. Affecting percentage: It specifies the percentage of deviation for different KPIs. Based on the affecting percentage, you can identify the main cause decreasing the TBF success rate and take measures accordingly.
Analysis on Rate of TBF Establishment Failures Due to Various Reasons on BSC for Top N Cells The KPIs noted by customers are usually BSC-level KPIs. This section describes how to optimize top N cells with poor accessibility based on the affecting percentage of BSC-level KPIs for each cell. This further improves BSC-level KPIs.
Rate of Cell TBF Establishment Failure
Succ Rate after Cell TBF Establishment
Succ Rate after Cell TBF Establishment
Succ Rate after Cell TBF Establishment
Succ Rate after Cell TBF Establishment
times(Other) to BSCRate of Cell TBF Failure
times(MS No Response) Rate of Cell TBF Failure
Sort data in descendin g order based on this column.
times(No Resource) to Rate of Cell TBF Failure
times to BSC
Establishment Attempt Rate of Cell TBF
Establishments due to Rate of Failed TBF
Cell TBF Establishment Succ Rate
Establishments due to Rate of Failed TBF
Establishments due to Rate of Failed TBF
Cell Name
BSC Name
Table 3.1.2.I.1.1.1.1 KPIs for measuring top N cells with poor accessibility
BSC Name Cell Name Cell TBF Establishment Succ Rate Rate of Failed TBF Establishments due to No Channel Rate of Failed TBF Establishments due to MS No Response Rate of Failed TBF Establishments due to Others Rate of Cell TBF Establishment Attempt times to BSC Rate of Cell TBF Establishment Failure times to BSC Rate of Cell TBF Failure times(No Resource) to BSC Rate of Cell TBF Failure times(MS No Response) to BSC Rate of Cell TBF Failure times(Other) to BSC Cell TBF Establishment Succ Rate after Optimize Cell TBF Establishment Succ Rate after Optimize PDCH resource Cell TBF Establishment Succ Rate after Optimize MS No Rsponse Cell TBF Establishment Succ Rate after Optimize Other reason
Quantified Analysis on Improvements in Accessibility KPIs Quantified analysis on improvements in accessibility KPIs quantifies how much BSC KPIs can improve when KPIs of top N cells reach their baseline values. Table 3.1.2.I.1.1.1.1 Quantified analysis on accessibility KPIs of top N cells
BSC Nam e
Top
Contribution Degree of TOP Cells
BSC TBF Establishmen t Succ Rate after Optimize
BSC TBF Establishmen t Succ Rate after Optimize PDCH resource
BSC TBF Establishmen t Succ Rate after Optimize MS No Rsponse
BSC TBF Establishmen t Succ Rate after Optimize Other reason
Performance after optimizing top 5 cells Performance after optimizing top 10 cells Performance after optimizing top 20 cells
Accessibility KPI Performance Analysis The TBF establishment failure causes of accessibility KPIs can be analyzed based on the data in the following worksheets:
BSC Uplink EGPRS TBF Establishment Succ Rate Analysis
BSC Uplink GPRS TBF Establishment Succ Rate Analysis
BSC Downlink EGPRS TBF Establishment Succ Rate Analysis
BSC Downlink GPRS TBF Establishment Succ Rate Analysis
As shown in Table 3.1.2.I.1.1.1.1 and Table 3.1.2.I.1.1.1.2 (using uplink EGPRS KPIs as an example), the TBFestablishment failure causes are as follows:
No channel resources (resource congestion)
No MS response (poor transmission quality on the Um interface, abnormal G-Abis transmission, and CCCH congestion)
Other causes (abnormal procedures and flow control, which account for a small percentage)
Table 3.1.2.I.1.1.1.1 Analysis on BSC-level uplink EGPRS TBF establishment success rate BSC Name
Uplink EGPRS TBF Establishm ent Succ Rate
Rate of Failed Uplink EGPRS TBF Establishme nts due to No Channel
Rate of Failed Uplink EGPRS TBF Establishme nts due to MS No Response
Rate of Failed Uplink EGPRS TBF Establishme nts due to Others
Table 3.1.2.I.1.1.1.2 Analysis on cell-level uplink EGPRS TBF establishment success rate
BS C Na me
Cel l Na me
Uplink EGPRS TBF Establis hment Succ Rate
Rate of Failed Uplink EGPRS TBF Establis hments due to No Channel
Number of Failed Uplink EGPRS TBF Establis hments due to No Channel
Rate of Failed Uplink EGPRS TBF Establis hments due to MS No Respons e
Number of Failed Uplink EGPRS TBF Establis hments due to MS No Respons e
Rate of Failed Uplink EGPRS TBF Establis hments due to Others
Number of Failed Uplink EGPRS TBF Establis hments due to Others
(1) TBF Establishment Failures Due to No Channel Resources TBF establishment failures indicate that no PDCH is available when a TBF attempts to establish. It corresponds to the PDCH congestion rate.
In normal cases, the GPRS PDCH congestion rate is almost the same as the EGPRS PDCH congestion rate. If the GPRS PDCH congestion rate is high but the EGPRS PDCH congestion rate is low, check whether GPRS PDCHs are insufficient because EGPRS dedicated PDCHs or EGPRS preferred PDCHs are configured. When this occurs, change EGPRS dedicated PDCHs or EGPRS preferred PDCHs to common EGPRS PDCHs and set Allow E Down G Up Switch to Yes.
If traffic in the underlaid subcell of a concentric cell is congested, set Dynamic Channel Conversion Parameter of Concentric Cell to Only convert dynamic channel at OL. Otherwise, set Dynamic Channel Conversion Parameter of Concentric Cell to Only convert dynamic channel at UL.
Perform capacity expansion or resource adjustment by referring to chapter "RF Resource and Capacity Evaluation" in the Guide to GSM Resource and Capacity Analysis. Suggestion: expand TRX capacity or deploy a new site when frequency resources are insufficient. (2) TBF Establishment Failures Due to No MS Response Due to poor transmission quality of the Um interface, abnormal G-Abis transmission or CCCH congestion, TBF establishment fails when the MS fails to receive or parse downlink messages or the BSC fails to parse the uplink response messages from an MS correctly. These TBF establishment failures are counted as TBF establishment failures due to no MS response.
Poor transmission quality of the Um interface Weak coverage, interference, and imbalance between the uplink and the downlink result in poor transmission quality of the Um interface. For details about how to analyze and optimize the transmission quality of the Um interface, see the Guide to GSM Network Evaluation of Coverage and Interference.
Abnormal G-Abis transmission If bit errors or channel out-of-synchronization occurs, uplink and downlink data fails to be decoded correctly. As a result, TBF establishment fails. In addition, the link delay
prolongs when the G-Abis transmission is abnormal. When this occurs, the timer at the receiving end may expire. As a result, TBF establishment fails. For details about how to analyze the G-Abis transmission, see "G-Abis Transmission."
CCCH congestion You can determine whether an assignment message is delivered normally based on the packet immediate assignment success rate and the Success Rate of PACCH assignment success rate. Table 3.1.2.I.1.1.1.3 and Table 3.1.2.I.1.1.1.4 list the KPIs related to BSClevel and cell-level uplink assignment success rates. Table 3.1.2.I.1.1.1.3 BSC uplink assignment success rate analysis BS C Na me
Succes sful UL Assign ment Rate (%)
Succes s Rate of UL PS Immedi ate Assign ment
Succes s Rate of UL Assign ment on PACCH
Table 3.1.2.I.1.1.1.4 Uplink assignment success rate analysis
BS C Na me
Cell Na me
Success ful UL Assign ment Rate (%)
Number of UL Assignm ents
Success Rate of UL PS Immedi ate Assign ment
Number of UL PS Immedia te Assignm ents
Success Rate of UL Assign ment on PACCH
Successf ul UL Assignm ents on PACCH
If the packet immediate assignment success rate is low, but the packet immediate assignment success rate on the PACCH is high, check whether CCCH overload occurs. If CCCH overload occurs, the Immediate Assignment messages sent over the CCCH may be discarded. As a result, TBF establishments fail. You can check whether CCCH overload occurs based on the Cell CS Service Paging Deletion Check and Paging Deletions Rate for PS Services Analysis worksheets. If CCCH overload occurs, set the CCCH load threshold to a large value to avoid TBF establishment failures due to flow control. The most effective method is to increase the number of extended BCCHs. In addition, increase the value of timer T3168 during two-phase access. This prevents MSs from frequently sending channel requests, alleviating CCCH overload. To reduce TBF establishment failures due to no channel available and no MS response, improve the transmission quality of the Um and G-Abis interfaces. Alternatively, optimize the settings of the following parameters:
Increase the value of T3168 for a satellite cell or a cell where transmission problems are serious and difficult to resolve, such as a cell where the transmission delay over the GAbis interface is long and unstable.
Increase the values of T3192, Release Delay of Downlink TBF(ms), Release Delay of Non-extended Uplink TBF(ms), and Inactive Period of Extended Uplink TBF(ms) to prolong the TBF release delay, increasing TBF establishment success rate on the PACCH.
Use a low-rate initial coding scheme to increase the TBF establishment success rate.
Suggestion: NPI services (parameter adjustment and optimization) (3) TBF Establishment Failures Due to Other Causes TBF establishment may fail when procedures are abnormal or flow control is enabled. TBF establishment failures of this type seldom occur.
3.1.3 Retainability Analysis Retainability measures whether call drops occur during conversation, which affect user throughput and delay. They are listed in the PS Retainability Performance Affect Factors Audit worksheet. Usually, the call drop rate for a common network should be lower than 5%, and the call drop rate for a network with excellent performance should be lower than 3%. The actual call drop rate depends on requirements of telecom operators. 3
BSC-level retainability KPIs
KPI
Recommen ded Value
Retainabilit y
Uplink GPRS TBF Call Drop Rate
< 5%
Downlink GPRS TBF Call Drop Rate
< 5%
UL EGPRS TBF drop rate
< 5%
DL EGPRS TBF drop rate
< 5%
If the TBF call drop rate is lower than the baseline value, perform the following detailed analysis.
Analysis on Affecting Percentage of Retainability KPIs Table 3.1.3.I.1.1.1.1 lists the KPIs that can be queried by choosing Packet Service > PS Retainability Performance > PS Retainability Performance Affect Factors Audit. Table 3.1.3.I.1.1.1.1 Analysis on BSC-level retainability KPIs BSC Name
KPI
TBF Call Drop Rate
Baseli ne Value
Actual Value
Deviati on
Affectin g Percent age
Rate of TBF Drop Due to MS No Response Rate of TBF Drop Due to FLUSH
Rate of TBF Drop Due to SUSPEND Rate of TBF Drop Due to No Resource Rate of TBF Drop Due to Other Reason
Baseline value: The baseline value for TBF establishment success rate is 95%. The baseline values are obtained based on network evaluation experience. The difference between these values depends on different network requirements. Actual value: The actual value is obtained according to the statistical value of the live network. Deviation: It is not considered for the KPIs Rate of TBF Drop Due to SUSPEND and Rate of TBF Drop Due to Other Reason because the optimization on abnormal TBF releases due to suspend and other reasons is unclear. Affecting percentage: It specifies the percentage of deviation for different KPIs. Based on the affecting percentage, you can identify the main cause decreasing the TBF success rate and take measures accordingly.
Analysis on Rate of TBF Call Drops Due to Various Reasons on BSC for Top N Cells The KPIs noted by customers are usually BSC-level KPIs. This section describes how to optimize top N cells with poor retainability based on the affecting percentage of BSC-level KPIs for each cell. This further improves BSC-level KPIs.
BSC Name Cell Name
FLUSHCell TBF Call Drop Rate after Optimize
No RsponseCell TBF Call Drop Rate after Optimize MS
Cell TBF Call Drop Rate after Optimize
Rate of Cell TBF Drop Times(FLUSH) to BSC
PDCH Resource Cell TBF Call Drop Rate after Optimize
Sort data in descend ing order based on this column.
Response) to BSCRate of Cell TBF Drop Times(MS No
BSCRate of Cell TBF Drop Times(No Resource) to
Rate of Cell TBF Drop Times to BSC
to BSCRate of Cell TBF Establishment Success times
Rate of TBF Drop Due to Other Reason
Rate of TBF Drop Due to SUSPEND
Rate of TBF Drop Due to FLUSH
Rate of TBF Drop Due to MS No Response
Rate of TBF Drop Due to No Resource
Cell TBF Call Drop Rate
Cell Name
BSC Name
Table 3.1.3.I.1.1.1.1 Top N cells with poor retainability
Cell TBF Call Drop Rate Rate of TBF Drop Due to No Resource Rate of TBF Drop Due to MS No Response Rate of TBF Drop Due to FLUSH Rate of TBF Drop Due to SUSPEND Rate of TBF Drop Due to Other Reason Rate of Cell TBF Establishment Success times to BSC Rate of Cell TBF Drop Times to BSC Rate of Cell TBF Drop Times(No Resource) to BSC Rate of Cell TBF Drop Times(MS No Response) to BSC Rate of Cell TBF Drop Times(FLUSH) to BSC Cell TBF Call Drop Rate after Optimize Cell TBF Call Drop Rate after Optimize PDCH Resource Cell TBF Call Drop Rate after Optimize MS No Rsponse Cell TBF Call Drop Rate after Optimize FLUSH
Quantified Analysis on Improvements in Retainability KPIs Quantified analysis on improvements in retainability KPIs quantifies how much improvements BSC KPIs can make when KPIs of top N cells reach their baseline values. Table 3.1.3.I.1.1.1.1 Quantified analysis on improvements in retainability KPIs
BSC Name
Top
Performance after optimizing top 5 cells Performance after optimizing top 10 cells Performance after optimizing top 20 cells
Contribution Degree of TOP Cells
BSC TBF Call Drop Rate after Optimiz e
BSC TBF Call Drop Rate after Optimiz e PDCH Resourc e
BSC TBF Call Drop Rate after Optimize MS No Rsponse
BSC TBF Call Drop Rate after Optimiz e FLUSH
Retainability KPI Analysis and Optimization For the cells with unsatisfied call drop rate, analyze the cause of abnormal TBF releases based on the analysis items in the EGPRS_TBF_CALL_DROP_RATE and GPRS_TBF_CALL_DROP_RATE worksheets. Table 3.1.3.I.1.1.1.1 and Table 3.1.3.I.1.1.1.2 list the KPIs related to BSC-level and cell-level abnormal TBF releases. Following uses abnormal uplink EGPRS TBF release as an example. Other abnormal TBF releases are similar to this type of abnormal TBF release. Table 3.1.3.I.1.1.1.1 Analysis on abnormal uplink EGPRS TBF releases Uplink EGPRS TBF Abnorma l Release No Channel Resource
BSC Name
Uplink EGPRS TBF Abnormal Release Suspend
Uplink EGPRS TBF Abnormal Release Flush
Uplink EGPRS TBF Abnormal Release MS No Response
Uplink EGPRS TBF Abnormal Releases Channel Preemption
Uplink EGPRS TBF Abnormal Releases Other Cause
Uplink EGPRS TBF Call Drop
Table 3.1.3.I.1.1.1.2 Top N cells with high abnormal uplink EGPRS TBF release rate
BSC Nam e
Cell Nam e
Uplink EGPRS TBF Abnorma l Release No Channel Resource
Uplink EGPRS TBF Abnorma l Release Suspend
Uplink EGPRS TBF Abnorma l Release Flush
Uplink EGPRS TBF Abnorma l Release MS No Response
Uplink EGPRS TBF Abnormal Releases Channel Preemptio n
Uplink EGPRS TBF Abnorma l Releases Other Cause
Uplink EGPR S TBF Call Drop
DL EGPR S TBF drop rate (%)
Sum of the precedin g abnorma l releases due to various reasons
(1) Abnormal TBF Releases Due to No MS Response N3101, N3103, and N3105 are counters for the BSC to measure uplink and downlink TBF quality. If abnormal TBF releases occur because these counters overflow, the uplink and downlink TBF quality is poor. Abnormal releases due to no MS response refer to uplink call drops due to N3101 and N3103 overflow and downlink call drops due to N3105 overflow. In normal cases, more than 80% call drops are due to N3101, N3103, and N3105 overflow. N3101, N3103, or N3105 overflows mainly because of poor transmission quality on the Um interface, unstable transmission quality on the G-Abis interface, or improper MS operations. In addition, call drops due to N3101, N3103, and N3105 overflow may occur when the settings of PS coding parameters are inappropriate, or an inappropriate algorithm is selected for adjusting the coding scheme.
To reduce TBF abnormal releases due to no MS response, improve the transmission quality on the Um and G-Abis interfaces. Alternatively, optimize the settings of the following parameters:
Increase the values of N3101, N3103, and N3105 to improve the link quality tolerance of the network.
Use a low-rate coding scheme to reduce call drops. For details, see the methods for selecting a low-rate coding scheme.
Select the BTS reporting BER algorithm for adjusting the uplink coding scheme. Call drops can be reduced by using the algorithm.
Suggestion: NPI services (parameter adjustment and optimization) (2) Abnormal TBF Releases Due to Suspended PS Services Ongoing PS services are suspended when MSs perform location updates or CS services. In this situation, abnormal TBF releases due to suspended PS services are measured. This type of abnormal release reflects the impact of CS services on PS services. If abnormal releases of this type occur, the location area settings for cells where the call drop rate is high and the setting of the timer for periodic location updates may be inappropriate. You are advised to check these settings. (3) Abnormal TBF Releases Due to FLUSH_LL Messages When the serving GPRS support node (SGSN) detects cell reselection initiated by an MS during PS services, it sends a FLUSH_LL message to the source cell. After the source cell receives the FLUSH_LL message, one abnormal TBF release due to the FLUSH_LL messages is counted. This type of TBF abnormal release reflects the frequency of cell reselection initiated by MSs. If a flood of abnormal releases of this type occur, check the settings of coverage parameters and reselection parameters of a serving cell and its neighboring cells to avoid ping-pong cell reselection. For details about the optimization method, see section 3.2.3"Cell Reselection." (4) Abnormal TBF Releases Due to No Channel The causes of abnormal TBF releases due to no channel available are as follows:
Unstable channel status
Frequent channel out-of-synchronization
Channel faults
Manual channel blocking
Channel deactivation
PDCH preemption by CS services
When abnormal releases of this type occur, you are advised to whether transmission or the clock is faulty. If the number of times the BSC reclaims dynamic PDCHs is equal to the number of times the BSC reclaims dynamic PDCHs in load state, ongoing CS services preempt channels occupied by PS services. In this situation, you need to add static PDCHs. In addition, set Level of Preempting Dynamic Channel to LEVEL1(No preempt of CCHs). Suggestion: expand TRX capacity or deploy a new site when frequency resources are insufficient.
3.1.4 Transmission Performance Analysis Transmission performance measures transmission quality of the network, which affects accessibility and retainability as well as user experience. 4 lists the transmission performance KPIs displayed in the Network Performance Audit worksheet. Usually, the downlink EGPRS RLC data block retransmission rate is lower than 10%, other retransmission rates are lower than 5%, and the transmission frame error rate is lower than 0.1%. The actual rates depend on the requirements of telecom operators. 4
BSC-level transmission performance KPIs
KPI
Recommen ded Value
Transmission performance
Retransmission rate of UL RLC data block (%)
< 5%
Retransmission rate of DL RLC data block (%)
< 5%
Retransmission rate of UL EGPRS RLC data block (%)
< 5%
Retransmission rate of DL EGPRS RLC data block (%)
< 10%
Rate of Transmitted Error Frames
< 0.10%
Cell transmission performance can be analyzed based on the analysis items that can be queried by choosing Packet Service > PS Transmission Performance. 5
Transmission performance evaluation items Evaluation Item
Details
EGPRS_RLC_BLK_RESEND_RATE
EGPRS_RLC_BLK_RESEND_RATE
GPRS_RLC_BLK_RESEND_RATE
GPRS_RLC_BLK_RESEND_RATE
RLC SingleSlot Rate Analysis
RLC SingleSlot Rate Analysis
RLC Retransmission Rate If RLC data blocks are lost or incorrect because of poor transmission quality on the Um or GAbis interface, the receiving end requests the sending end to retransmit data. Therefore, the RLC retransmission rate reflects the transmission quality of the Um and G-Abis interfaces to some extent. For details about how to analyze and optimize the transmission quality of the Um interface, see the Guide to GSM Network Evaluation of Coverage and Interference. You can determine the transmission quality of G-Abis interface based on the FER over the G-Abis interface, transmission alarms, and clock alarms.
The coding scheme is dynamically adjusted according to the transmission quality on the Um interface during GPRS data transmission. When a low-rate coding scheme is used, data blocks contain more redundant data and the data transmission rate is low, but the reliability of data transmission is high. When a high-rate coding scheme is used, data blocks contain less redundant data and the data transmission rate is high, but the reliability of data transmission is low. Therefore, if the transmission quality of the Um or G-Abis interface is poor, you are advised to use a low-rate coding scheme to obtain high-quality data transmission, improving user experience. Using a high-rate coding scheme may not improve user experience as expected and may even deteriorate user experience. The methods for selecting a low-rate coding scheme are as follows:
Select a low-rate initial coding scheme.
For GPRS services, increase difficulties in converting a low-rate coding scheme to a high-rate coding scheme and decrease difficulties in converting a high-rate coding scheme to a low-rate coding scheme.
For EGPRS services, shorten the BEP period to improve the sensitivity of measurement reports (MRs) to changes in the transmission quality of the Um interface to ensure that appropriate coding schemes are dynamically selected and used.
Select the BTS reporting BER algorithm for adjusting the uplink coding scheme to ensure that the uplink coding scheme is appropriate to the transmission quality of the Um interface.
6 lists the parameters related to the coding scheme. 6
Parameters related to the coding scheme
Category
Parameter
Default Value
Recommended Value
Setting Principle
Coding scheme adjustment
ADJUSTULMCSTYPE
2
2
The uplink coding scheme is adjusted according to uplink quality. The adjusted coding scheme can better suit the uplink quality.
BEP Period
5
5
When this parameter is set to a small value, the PS performance is sensitive to the changes in the transmission quality of the Um interface. If the transmission quality of the Um interface is poor, decrease the value of this parameter.
Uplink Fixed MCS Type
UNFIXED
UNFIXED
Uplink Default MCS Type
MCS2
MCS2
If the transmission quality of the Um interface is unstable and a high-rate initial uplink coding scheme is used, the TBF establishment success rate may be low. If a low-rate coding scheme is used, the TBF establishment success rate increases but the uplink throughput and proportion of high-rate coding schemes
decrease. Downlink Fixed MCS Type
UNFIXED
UNFIXED
Downlink Default MCS Type
MCS6
MCS6
Use a high-rate initial coding scheme to increase the proportion of high-rate coding schemes. This may increase the retransmission rate.
Uplink Fixed CS Type
UNFIXED
UNFIXED
Uplink Default CS Type
CS1
CS1
If the transmission quality of the Um interface is unstable and a high-rate initial uplink coding scheme is used, the TBF establishment success rate may be low. If a low-rate coding scheme is used, the TBF establishment success rate increases but the uplink throughput and proportion of high-rate coding schemes decrease.
Downlink Fixed CS Type
UNFIXED
UNFIXED
Downlink Default CS Type
CS2
CS2
Use a high-rate initial coding scheme to increase the proportion of high-rate coding schemes. This may increase the retransmission rate.
Suggestion: NPI services (parameter adjustment and optimization)
G-Abis Transmission FER over the G-Abis interface can be used to identify uplink transmission problems based on check error frames and out-of-synchronization frames received on the uplink. FER over the G-Abis interface mainly reflects the uplink transmission problems and reflects the downlink transmission problems to some extent. However, it does not map downlink KPIs. Therefore, you must analyze transmission alarms and clock alarms when analyzing downlink accessibility, retainability, and transmission performance KPIs. Table 3.1.4.I.1.1.1.1 lists the KPIs that are used for analyzing G-Abis frame error rate. These KPIs can be queried by choosing Packet Service > PS Transmission Performance > RLC SingleSlot Rate Analysis. Table 3.1.4.I.1.1.1.1 Cell-level transmission FER analysis BSC Nam e
Cell Name
Average Throughput of Uplink GPRS RLC per PDCH(kbps )
Uplink CS3CS4 Ratio
Rate of Fail Applicatio n Attempts of Abis Timeslot Because of
Rate of Transmitte d Error Frames
no Idle Timeslot
E432 E432
MD41964 MD42542
8.80
0.00%
0.00%
0.03%
8.85
0.00%
0.00%
0.06%
FER over the G-Abis interface can be used to preliminarily determine the transmission quality of the G-Abis interface.
In normal cases, the FER is less than 10e-5, that is, an average of one error frame is sent every four minutes on one channel. In this situation, the link quality is favorable, and MSs can transmit data properly.
For a transmission link with poor quality, the FER is less than 10e-4, that is, an average of one to three error frames are sent every minute on one channel. Due to the error frames, the affected MS may encounter the problems of decreased data rate, long transmission delay, and even call drops or disconnection from the network.
If the FER is greater than 10e-4, the link is quite unstable and tends to be out of synchronization. In this situation, the proportion of out-of-synchronization frames increases. The MS may only be able to perform small-traffic data services, such as the upper-layer signaling and some WAP services. Mass data transmission, such as FTP services, becomes difficult.
If the FER is less than 5‰, the link quality is acceptable. If the FER of a cell is always high, a transmission problem occurs in this cell. In this situation, check the transmission cables and improve the transmission quality.
3.2 User Experience Analysis This section describes how to analyze PS user experience from the aspects of LLC throughput, delay, and cell reselection.
3.2.1 LLC Throughput Analysis 7 lists the KPIs for reflecting the average LLC throughput per user on the BSC. 7
BSC-level LLC throughput KPIs KPI
Baseline Value
Uplink Throughput of GPRS Users LLC PDU(kbit/s)
> 16
Downlink Throughput of GPRS Users LLC PDU(kbit/s)
> 36
Uplink Throughput of EGPRS Users LLC PDU(kbit/s)
> 45
Downlink Throughput of EGPRS Users LLC PDU(kbit/s)
> 120
The LLC throughput on the live network can be obtained based on the weighted value of the uplink and downlink GPRS/EGPRS LLC throughputs obtained by choosing Packet Service > PS Transmission Performance > Analysis of Rate of BSC LLC. Then, check whether the LLC throughput meets the standards by comparing it with its baseline value. Table 3.2.1.I.1.1.1.1 BSC-level LLC throughput analysis BSC Name
LLC Throughput Baseline Value (kbit/s)
LLC Throughput on the Live Network (kbit/s)
Analysis Result
If the LLC throughput on the live network does not reach its baseline value, check the impact of each affecting factor on the LLC throughput. As listed in Table 3.2.1.I.1.1.1.2, the factors affecting the LLC throughput are RLC single-timeslot throughput, TBF multiplexing degree, and channel satisfaction degree. Table 3.2.1.I.1.1.1.2 Analysis on factors affecting BSC-level LLC throughput BSC Name DoubleHAJ J DoubleHAJ J DoubleHAJ J
Affecting Factor
KPI Baseline Value
Actual Value
Affecting Percentage
27.65
25.16
17.14%
2
1.91
0.00%
0.85
0.62
82.86%
Throughout Capacity of RLC Signal-time(kbps) Frequence of TBF Content of Channel
Obtain and analyze the top N cells with unsatisfied LLC throughput based on the cell-level LLC throughput analysis table. Table 3.2.1.I.1.1.1.3 Cell-level LLC throughput analysis
BSC Name
Cell Name
Rate of LLC(kbp s)
Signaltime Rate
Frequen ce
Conte nt of Chann el
Percenta ge of Signaltime Affect LLC Rate
DoubleHA JJ
MD3701 -1
24.91
10.26
2.45
0.78
84.31%
Percenta ge of Frequen ce Affect LLC Rate
Percenta ge of Content of Channel Affect LLC Rate
15.51%
0.18%
Suggestion: If only EGPRS-capable MSs experience low LLC throughput, EGPRS and GPRS channels can be separated. Following describes how to analyze each affecting factor.
1. RLC Single-Timeslot Throughput Analysis The average RLC single-timeslot throughput can be obtained based on the weighted value of the average uplink and downlink GPRS/EGPRS RLC single-timeslot throughputs obtained by choosing Packet Service > PS Transmission Performance > RLC SingleSlot Rate Analysis. Then, check whether the average RLC single-timeslot throughput meets the standards by comparing it with its baseline value. Table 3.2.1.I.1.1.1.4 BSC-level RLC single-timeslot throughput
BSC Name
Average Through put of Uplink GPRS RLC per PDCH(k bps)
Average Through put of Downlin k GPRS RLC per PDCH(k bps)
Average Through put of Uplink EGPRS RLC per PDCH(k bps)
Average Through put of Downlin k EGPRS RLC per PDCH(k bps)
Avg-Rate of RLC Signaltime(kbps)
Baseline of Avg-Rate of RLC Signaltime(kbps)
DoubleH AJJ
9.74
11.91
27.42
35.75
25.16
27.65
If the average RLC single-timeslot throughput does not meet the standards, isolate the main affecting factor based on the affecting percentages shown in Table 3.2.1.I.1.1.1.5. The two factors affecting the RLC single-timeslot throughput shown in Table 3.2.1.I.1.1.1.5 are BEP 19-31 ratio and proportion of Abis timeslot application failures due to no idle timeslots. Table 3.2.1.I.1.1.1.5 Analysis on BSC-level RLC single-timeslot affecting factors BSC Name
Affecting Factor
KPI Baseline Value
Actual Value
Affecting Percentage
DoubleHAJ J
BEP19~31 Ratio
85.00%
83.89%
5.85%
DoubleHAJ J
Rate of Fail Application Attempts of Abis Timeslot Because of no Idle Timeslot
30.00%
83.49%
94.15%
Obtain and analyze the top N cells with unsatisfied RLC single-timeslot throughput based on the cell-level single-timeslot throughput analysis table.
Table 3.2.1.I.1.1.1.6 Analysis on cell-level RLC single-timeslot throughput
BSC Name
Cell Name
Signaltime Rate of RLC(kbp s)
DoubleHAJ J2
MD37031
16.53
BEP19~3 1 Ratio
Rate of Fail Applicatio n Attempts of Abis Timeslot Because of no Idle Timeslot
94.45%
91.00%
Effect on Rate of RLC Caused by LinkQuali ty
Effect on Rate of RLC Caused by Abistime
0.00%
100.00%
BEP19-31 Ratio BEP means the bit error probability, which indicates the proportion of bit errors measured on the receiving end. The BEP is classified into 32 classes, ranging from 0 to 31. The higher the BEP, the more favorable the transmission quality of the Um and G-Abis interfaces. The BSC determines the coding scheme based on the BEP. The higher the BEP, the higher-rate the coding scheme. For the cells with BEP 19-31 ratio lower than the baseline value, locate the problems on the cells based on the transmission quality of the G-Abis and Um interfaces. For details about the analysis on the transmission quality of the G-Abis interface, see "G-Abis Transmission." For details about the transmission quality of the Um interface, see the Guide to GSM Network Evaluation of Coverage and Interference. Table 3.2.1.I.1.1.1.1 describes the receive level and carrier-to-interference ratio supported by each coding scheme. When the carrier-to-interference ratio is higher than 23.5 dB, the coding scheme higher than MCS7 can be used, and the corresponding BEP class must be 19 or higher. Table 3.2.1.I.1.1.1.1 Receive level and carrier-to-interference ratio supported by each coding scheme Coding Scheme MCS1 MCS2 MCS3 MCS4 MCS5 MCS6 MCS7 MCS8 MCS9
Receive Level (dBm) ≥ –102 ≥ –101 ≥ –99 ≥ –97 ≥ –98 ≥ –96 ≥ –93 ≥ –90.5 ≥ –86
TU3 Carrier-toInterference Ratio (dB) 13 15 16.5 19 18 20 23.5 28.5 30
Proportion of Abis Timeslot Application Failures Due to No Idle Timeslots Abis timeslot sufficiency is a prerequisite for cells using high-rate coding schemes. If idle timeslots are insufficient, channels cannot use high-rate coding schemes. Table 3.2.1.I.1.1.1.1 describes the mapping between the number of required idle timeslots and coding schemes. Table 3.2.1.I.1.1.1.1 Mapping between the number of idle timeslots and coding schemes Coding Scheme CS1-CS2 CS3-CS4 MCS1-MCS2 MCS3~MCS6 MCS7 MCS8-MCS9
Number of Required Idle Timeslots 0 1 0 1 2 3
In the TDM_Abis Interface Resource Evaluation worksheet of the OMStar report, check whether the number of idle timeslots is sufficient, the number of required idle timeslots, and whether to expand E1 timeslots in the site idle timeslot capacity analysis table. Field engineers can determine to add idle timeslots or expand E1 timeslots based on the number of required idle timeslots. Suggestion: transmission capacity expansion, and GBFD-117301 Flex Abis.
2. TBF Multiplexing Degree Analysis PDCHs carry RLC control signaling and RLC data. The rate for a single PDCH is definite. When multiple MSs are multiplexed onto the same channel, the single-user throughput will decrease because block resources on the channel are shared by MSs. In this situation, the PDCH multiplexing degree needs to decrease to improve the single-user throughput. For the cells whose uplink and downlink PDCH TBF multiplexing degrees are higher than 2, perform the following optimization operations:
For the cells where channels are insufficient and TCHs are not congested, more PDCHs can be obtained by improving the maximum PDCH rate threshold, decrease the uplink or downlink multiplexing dynamic channel conversion threshold, and set the PDCH downlink multiplexing threshold to 80. Suggestion: NPI services (parameter optimization)
For the cells where TCHs are congested, the recommended optimization operation is capacity expansion.
Suggestion: expand TRX capacity or deploy a new site when frequency resources are insufficient.
3. Channel Satisfaction Degree Analysis Channel satisfaction degree is the ratio of the actual number of allocated channels to the MS multi-timeslot capability. The higher the channel satisfaction degree, the more the number of channels allocated to cells, the higher the probability that the number of allocated channels meets the requirements of MS multi-timeslot capability.
If the channel satisfaction degree is lower than 85%, the number of PDCHs in the cell is insufficient. The optimization methods are as follows:
If the number of times the BSC reclaims dynamic PDCHs is equal to the number of times the BSC reclaims dynamic PDCHs in load state, ongoing CS services preempt channels occupied by PS services. In this situation, you need to add static PDCHs. In addition, set Level of Preempting Dynamic Channel to LEVEL1(No preempt of CCHs).
Check the analysis items in the DSP CPU Occuption Rate of DPUP worksheet. When the value of Average Number of PDCHs Activated on DSP is greater than 40, dynamic PDCHs in some cells cannot be converted because a single DSP reaches the channel activation upper limit. As a result, channels are insufficient. When this occurs, the number of activated channels on certain DSP is great. It is recommended that cell redistribution be performed to balance cell distribution on DSPs. If most DSPs experience this type of problem, it is recommended to add DPUPs. Suggestion: board expansion
For the cells where channels are sufficient and TCHs are not congested, improve the maximum PDCH rate threshold in the cell to obtain more PDCHs.
For the cells where TCHs are congested, the recommended optimization operation is capacity expansion. Suggestion: expand TRX capacity or deploy a new site when frequency resources are insufficient.
3.2.2 Delay Analysis Delay can be analyzed based on PCHR data instead of traditional traffic statistics. PCHRs are improved since GBSS 13.0, and therefore there is no tool for batch analyzing PCHRs. In this situation, you need to analyze PCHRs one by one by using the InsightSharp tool. Delay can be analyzed based on the data in the PCHR delay-sensitive service information area. The key KPI to be analyzed is average delay in service interaction response. The formula for calculating the average delay in service interaction response is as follows: Average delay in service interaction response = Average delay in sending PDUs + Average delay in receiving PDUs + Average delay in PDU round trip over the Gb interface Table 3.2.2.I.1.1.1.1 describes the formulas for calculating each KPIs. Table 3.2.2.I.1.1.1.1 Delay KPIs KPI Average delay in sending PDUs Average delay in receiving PDUs Average delay in PDU round trip over the Gb interface
Formula Total duration for sending PDUs/Total number of sent PDUs Total duration for receiving PDUs/Total number of received PDUs Total interval between uplink and downlink PDUs/Statistical times for measuring the interval between uplink and downlink PDUs
The average delay in sending PDUs and average delay in receiving PDUs reflect the downlink and uplink delays on the BSS side, respectively. The average delay in PDU round trip over the Gb interface reflects the delay above the Gb interface, including the uplink and downlink processing duration on the Gb interface and core network.
For the cells with long delay on the BSS side, check whether accessibility, retainability, and transmission performance KPIs are normal. If they are abnormal, optimize them by referring to associated methods. For the cells with long delay above the Gb interface, check the links over the Gb interface or contact core network engineers to locate problems on the core network.
3.2.3 Cell Reselection The key KPI for analyzing cell reselection on the BSS side is TBF abnormal release rate due to flush. If the value of this KPI is greater than 1%, cell reselection greatly affects services. In this situation, you need to set the cell reselection parameters and adjust coverage. The KPIs listed in Table 3.2.3.I.1.1.1.1 can be obtained by choosing Packet Service > PS Retainability Performance > PS Retainability Performance Affect Factors Audit. The baseline values for these KPIs are 1%. Table 3.2.3.I.1.1.1.1 BSC-level cell reselection analysis BSC Nam e
UL GPRS TBF drop rate due to Flush
DL GPRS TBF drop rate due to Flush
UL EGPRS TBF drop rate due to Flush
UL EGPRS TBF drop rate due to Flush
Obtain top N cells with high abnormal TBF release rate due to flush based on the cell-level cell reselection analysis table, and analyze whether short-interval cell reselection or ping-pong cell reselection occurs. Table 3.2.3.I.1.1.1.2 Cell-level cell reselection analysis
BSC Nam e
Cell Name
TBF drop rate due to Flush
Numbe r of Times a Cell Is Selecte d by MS
Ratio of Cell Reselection s by MS at Short Interval
Ratio of Cell PingPong Reselection s by MS
CR H
For the cells with high short-interval cell reselection rate, check whether they are under poor coverage due to incorrect power settings, hardware faults, or quick attenuation. For the cells with high ping-pong cell reselection rate, stabilize the serving cell by controlling coverage or adjusting CRH parameters. Suggestion: NPI services (cell reselection optimization), GBFD-116301 Network Assisted Cell Change (N/ACC), and GBFD-119801 Packet SI Status (PSI).
4
Appendix
4.1 Parameters 8
PS parameters
Category
Accessibilit y
Resource
Parameter Name
Default Value
Recommended Value
T3168
500
T3192
500
BS_CV_MAX
10
10
NO
YES
MODE4_1
MODE4_1
Support 11BIT EGPRS Access Multiplexing Mode
Maximum Ratio Threshold of PDCHs in a Cell(%) Uplink Multiplex
Setting Principle After eliminating the effect of link quality and radio resource congestion, increasing the value of T3168 can improve the uplink TBF assignment success rate. However, this also prolongs the delay. When network resources are sufficient, that is, the GPRS service congestion rate is low, set T3192 to a large value, accelerating TBF establishments and improve data transmission performance. If this parameter is set to a small value, the MS retransmits data before receiving an acknowledgement message. This increases retransmission rate and wastes resources.
30
2
2
When the number of MSs carried on a channel reaches the
Threshold of Dynamic Channel Conversion Downlink Multiplex Threshold of Dynamic Channel Conversion PDCH Uplink Multiplex Threshold PDCH Downlink Multiplex Threshold Timer of Releasing Idle Dynamic Channel Level of Preempting Dynamic Channel
threshold divided by 10, dynamic channel conversion is triggered. A high multiplexing degree may affect service rates for MSs. 2
2
7
7
8
20
8
20
LEVEL0
LEVEL0
Timer of Releasing Abis Timeslot
15
15
Dynamic Channel Conversion Parameter of Concentric Cell
Only convert dynamic channel at UL
Allow E Down G Up Switch
Yes
Yes
Resource Reallocation to Different Trx
ALLOW
ALLOW
Once
Multiple
Applying for Multiple Abis Timeslots
Decrease the value of this parameter when channels are insufficient. If TCHs are sufficient but the reclaimed dynamic PDCH proportion is high, set this parameter to LEVEL1. Set this parameter to prevent frequent Abis resource requests, shorten timeslot binding duration, and increase the rate. When the traffic is heavy and idle timeslots are insufficient, decrease the value of this parameter. If traffic in the underlaid subcell is congested, dynamic channels are converted in the overlaid cell. If traffic in the overlaid subcell is congested, dynamic channels are converted in the underlaid subcell. When this parameter is set to No, the number of available GPRS resources decreases. Set this parameter to Yes only if demonstrating the EGPRS downlink rate or the operator has a demanding requirement for EGPRS downlink rate. Set this parameter to accelerate channel assignment or coding scheme adjustment to improve
the rate.
Once
Coding scheme adjustment
EGPRS UL Coding Scheme Dynamic Conversion
BTS reporting BER
BTS reporting BER
BEP Period
5
5
Uplink Fixed MCS Type
UNFIXED
UNFIXED
Uplink Default MCS Type
MCS2
MCS2
Downlink Fixed MCS Type
UNFIXED
UNFIXED
Downlink Default MCS Type Uplink Fixed CS Type Uplink Default CS Type Downlink Fixed CS Type Downlink Default CS Type PS timer and counter
Release Delay of Nonextended Uplink TBF (ms)
MCS6
MCS6
UNFIXED
UNFIXED
CS1
CS1
UNFIXED
UNFIXED
CS2
CS2
120
120
The uplink coding scheme is adjusted according to uplink signal quality. The adjusted coding scheme can better suit the uplink signal quality. If this parameter is set to a small value, the PS performance is sensitive to changes in the transmission quality of the Um interface. If the transmission quality of the Um interface is poor, decrease the value of this parameter. If the transmission quality of the Um interface is unstable and the uplink coding scheme is high, the TBF establishment success rate may be low. If a low-rate coding scheme is used, the TBF establishment success rate increases but the uplink throughput and proportion of high-rate coding schemes decrease.
Use a high-rate initial coding scheme to increase the proportion of high-rate coding schemes. This increases the retransmission rate. Same as the setting principle of Uplink Default MCS Type. Use a high-rate initial coding scheme to increase the proportion of high-rate coding schemes. This increases the retransmission rate. Increase the value of this parameter to increase the probability of TBF establishment on the PACCH for
Inactive Period of Extended Uplink TBF (ms) Release Delay of Downlink TBF (ms) Maximum Value of N3101 Maximum Value of N3103 Maximum Value of N3105 Support NACC
PS cell reselection
2000
2000
2400
2400
20
20
3
3
10
10
NO
YES
PACKET SI
NO
YES
FLUSH-LL PDU Transfer Switch
OPEN
OPEN
MSs and increase the TBF establishment success rate. This wastes TBF resources.
When the Um interface quality fluctuates significantly, increase the value of this parameter to reduce call drops. However, resources may be occupied for a long time. Adjust the value of this parameter to reduce the interruption duration caused by cell reselection.
4.2 Features 4.2.1 NACC Before an MS reselects a cell, it reports the target cell to the BSC. The BSC sends the system information (SI) message about the target cell to the MS in advance through RLC data blocks. In this way, the MS hands over to the target cell without receiving the SI message about the target cell. This facilitates the MS to process PS services and reduces data transmission interruption caused by cell reselection.
4.2.2 Packet Si Status The MS can initial PS resource request in the target cell before receiving all SI messages. The MS sends a Packet Si Status message to the BSS to notify the network of system information messages that are not received. The BSS sends the requested SI messages through RLC data blocks. In this way, the MS does not need to exit from the PS state and enters the idle state to receive these messages.
