179846784 2G Huawei Performance Monitoring
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179846784 2G Huawei Performance Monitoring...
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HUAWEI 2G PERFORMANCE MONITORING AND ANALYSIS
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Contents 1. Overview 2. 2G Performance Monitoring and Analysis
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Document Information Document Version: 1.0 Issue Date: September 8, 2010 Author: Christos Kyriazopoulos Document Owner: Ville Salomaa SOFTWARE RELEASE: GBSS9.0 SCOPE: 2G performance monitoring and analysis CONVENTION: Raw counters are marked in BLUE Formulas are marked in GRAY Parameters are marked in RED MML commands are marked in GREEN
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Contents 1. Overview 2. 2G Performance Monitoring and Analysis
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Overview The purpose of this document is to describe the BSS KPI performance monitoring and analysis of problems that bad KPI values indicate. The following analysis contains a list of the most common KPIs used in Huawei networks. These KPIs are monitored constantly. When the value of a KPI goes below the defined threshold, then detailed analysis should be performed in order to identify the reasons of this deterioration. Once the reasons are found, proper solutions will be proposed and implemented. This document focuses more in the analysis of failure causes rather than the KPI monitoring itself. The most common use cases for monitoring and analysis of bad values are presented for 2G BSS.
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2G Performance Analysis Use Cases 2G Performance Analysis Use Cases: CS: 1.High SDCCH Blocking 2.High SDCCH Drop rate 3.CSSR 4.High TCH blocking 5.High TCH Drop call rate 6.High HO fail 7.Low Coverage – how to identify coverage problems (e.g. TA vs. cell radius, Rxlevel measurements, HO distribution…) 8.High Interference – how to identify interference problem in cell (idle UL interference, Rxlevel & Quality distributions, TA measurements) PS: 9.High Signaling Failures Before TBF Establishment 10.High TBF Establishment Failures 11.High TBF Drops 12.Low Throughput (Um, Abis, PCU, Gb)
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General Methodology General Methodology: 1. Define BSS KPI class required (Accessibility, Retainability, Mobility, Resource Usage). 2. Define KPI per service (Voice, Packet Service). 3. Define KPI formulas. 4. Define target or guaranteed KPI values. 5. Assess weekly average PLMN/BSC KPI performance in order to identify KPIs below target. 6. Assess BSC/Area level performance in order to check if bad performance occurs across network or only in specific areas. 7. Analyze bad performing KPIs in cell level in order to identify failure causes. (this point is the focus of this document) 8. Use TopN cell approach to identify the worst performers. Identify top 20 worst cells. 9. Look at failure distribution in network topology (urban, rural, motorway, RNC border, etc.). 10. Propose solution to improve KPI value.
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Contents 1. Overview 2. 2G Performance Monitoring and Analysis
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1. High SDCCH Blocking (1) - KPI formula: SDCCH Congestion Rate (Overflow) = ([Failed SDCCH Seizures due to Busy SDCCH]/[SDCCH Seizure Requests])*{100} Analysis process: 1.High SDCCH blocking is due to congestion on the SDCCH channel. Check what causes the high SDCCH usage. Then appropriate actions can be taken: •Check Call Setups: - CELL_ESTB_IND_MOC_NONSMS_SD: Number of Call Setup Indications for MOC on SDCCH - CELL_ESTB_IND_MTC_SD: Number of Call Setup Indications for MTC on SDCCH •Check amount of SMS. Check and verify with Core engineers SMS Center parameterization. - A3030B: CELL_ESTB_IND_MOC_SMS_SD: Number of Call Setup Indications for SMS on SDCCH - CA3340: CELL_Pt_to_Pt_SMS_SD: Number of Point-to-Point Short Messages on SDCCH (includes UL+DL) •Check LAU/RAU requests: - A300F: CELL_CH_REQ_LOC_UPDATE: Number of Channel Requests for Location Update - A3030F: CELL_ESTB_IND_LOC_UPDATE_SD: Number of Call Setup Indications on SDCCH for Location Update.
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1. High SDCCH Blocking (2) 2.
If high SCDDH usage is due to LAU then: • Check if the problem is caused by roamers that do not have access to the network, thus causing big amount of failed LAUs/RAUs. • Check if cell is in LA border: if yes, then we can increase CRH parameter value - CRH: Cell Reselect Hysteresis Parameters (Cell reselection hysteresis. This is one of the parameters used for deciding whether to reselect cells in different location areas.) • Check LA border planning. Verify LA borders by checking HO statistics between cells in LA border: - H380:CELLCELL_INCELL_HO_REQ: Incoming Inter-Cell Handover Requests between 2 cells • Check the value of T3212; if too low, increase - T3212: T3212 (This parameter specifies the length of the timer for periodic location update). Recommended value: as high as possible, usually 4h. • Check whether moving LA borders (if possible to move) could help relieving the congestion. • Check the pattern of LAU requests. Check hours and duration of high number of such requests. Check whether the problem is constant throughout the day or it occurs only during 1 hour for example. If the problem occurs only on specific hour of day check if it is worth acting to solve it (costs vs. benefits).
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1. High SDCCH Blocking (3) 3.
Check if TCH Immediate Assignment is allowed: - IMMASSEN: TCH Immediate Assignment (Whether to allow immediate TCH assignment. If this parameter is set to YES, the BSC can assign a TCH immediately when there is no available SDCCH for a channel request.) Note: It is not recommended to activate this in congested LA borders.
4.
Activate SDCCH dynamic conversion feature: Dynamic SDCCH conversion can be triggered if the SDCCH resource is insufficient or the SDCCH allocation fails during the channel assignment - SDDYN: SDCCH Dynamic Allocation Allowed (Whether to allow SDCCH dynamic allocation, that is, whether to allow dynamic conversion between TCHs and SDCCHs.) - IDLESDTHRES: Idle SDCCH Threshold N1 (When the number of idle SDCCH channels in a cell is smaller than this parameter, the system searches for available TCHs and transforms them into SDCCH channels) - CELLMAXSD: Cell SDCCH Channel Maximum (Maximum number of SDCCHs in the cell. Before converting a TCH into an SDCCH, the BSC compares the number of SDCCHs after the conversion in the cell with "Cell SDCCH Channel Maximum". If the number of SDCCHs after the conversion in the cell exceeds this parameter, the BSC does not convert the TCH into an SDCCH.)
5.
Add SDCCH/8 channel
6.
Add TRX
Note: for more details on SDCCH capacity optimisation check “HUA_2G_Capacity_Optimization_v1.0.pptx” document from Multivendor Team in IMS. For internal use 11 © Nokia Siemens Networks
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2. High SDCCH Drop Rate (1) - KPI formula: SDCCH Drop Rate = ([Call Drops on SDCCH]/[Successful SDCCH Seizures])*{100} Analysis process: 1.Identify the route cause of SDCHH drops by checking the following counters. The total number of SDCCH drops is given by: Call Drops on SDCCH = [Call Drops on Radio Interface (SDCCH)]+[Call Drops due to No MRs from MS for a Long Time (SDCCH)]+[Call Drops due to Abis Terrestrial Link Failure (SDCCH)]+[Call Drops Due to Equipment Failure (SDCCH)]+[Call Drops due to Forced Handover (SDCCH)]: •Call Drops on Radio Interface (SDCCH): the drop is due to radio. Check for missing neighbours. Check radio environment/signal strength at drop points. Adjust antenna parameters appropriately to improve coverage if this is the problem. Check whether the drops are during handover. Check interference. •Call Drops due to No MRs from MS for a Long Time (SDCCH): After seizing an SDCCH, the MS sends a measurement report to the BSC every 470 ms. When the BSC does not receive a measurement report within a certain period of time, the BSC sends a CLEAR REQUEST message to the MSC to release the call, and this counter is incremented by one. Check UL coverage and quality (interference). Check for possible MS problem. •Call Drops due to Abis Terrestrial Link Failure (SDCCH): transmission problem on Abis. Check relative alarms. •Call Drops Due to Equipment Failure (SDCCH): BSC hardware or software failure. Check alarms to discover the exact cause. For internal use 12 © Nokia Siemens Networks
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2. High SDCCH Drop Rate (2) •
Call Drops due to Forced Handover (SDCCH): After an MS seizes a channel, if the system initiates a forced handover and the handover fails, the BSC may initiate a call release procedure. Check why the handover failed: Timer expired? Check whether the emergency handover is due to preemption, or blocking of cell/TRX/channel.
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3. CSSR (1) - KPI formula: BSS Call Setup Success Rate = (([Immediate Assignment Success Rate]*[TCH Assignment Success Rate])*(1-[SDCCH Drop Rate]))*{100} The CSSR combines 3 other KPIs: - Immediate Assignment Success Rate = ([Call Setup Indications (Circuit Service)]/[Channel Requests (Circuit Service)])*{100} - TCH Assignment Success Rate = ([Successful Assignments]/[Assignment Requests])*{100} - SDCCH Drop Rate = ([Call Drops on SDCCH]/[Successful SDCCH Seizures])*{100} Analysis process: 1.Each of the 3 component-KPIs will affect CSSR: - Low Immediate Assignment Success Rate will decrease CSSR - Low TCH Assignment Success Rate will decrease CSSR - High SDCCH Drop Rate will decrease CSSR 2.Examine at which point most of the failures appear by checking thoroughly the 3 component-KPIs. Find out the corresponding failure causes for Immediate Assignment, Assignment and SDCCH Drops.
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3. CSSR (2) 3.
Low Immediate Assignment Success Rate
Basic Immediate Assignment signalling procedure:
Fig.1 Successful Immediate Assignment
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Fig.2 Failed Immediate Assignment A: The BSC sends an IMM ASS REJ message due to no available channel B: The BSC sends an IMM ASS REJ message due to channel activation failure C: The BSC sends an IMM ASS REJ message due to channel activation timeout
3. CSSR (3) • If Immediate Assignment failures are due to no channel available (point A in Figure 2), this means that there is SDCCH congestion. Refer to Case 1 of present document for handling. • If Immediate Assignment failures are due to channel activation failure or channel activation timeout (points B, C in Figure 2) check hardware/software alarms. 4.Low TCH Assignment Success Rate Basic Assignment signalling procedure:
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3. CSSR (4) • Check following counters to identify the reason for Assignment failure: (1) Failures due to mismatch between the state machine of the BSC and the ASS REQ message or due to the abnormality of the ASS REQ message: - A3129I: CELL_ASS_FAIL_INVALID_STATE: This counter provides the number of ASS FAIL messages sent by the BSC to the MSC when the BSC receives an ASS REQ message that is not expected by the internal state machine of the BSC (for example, the state machine is in release status). - A3129J: CELL_ASS_FAIL_INVALID_MSG_CONTENTS: This counter provides the number of ASS FAIL messages sent by the BSC to the MSC when the BSC receives an ASS REQ message but the ASS REQ message fails to be decoded (for example, an error occurs during the decoding of an IE, such as CHANNEL TYPE, CIC, or Layer 3 header information). - A3129E: CELL_ASS_FAIL_NO_CIC: This counter provides the number of ASS FAIL messages sent by the BSC to the MSC when the BSC receives an ASS REQ message that carries an unavailable A interface CIC. - A3129F: CELL_ASS_FAIL_CIC_ALLOC: This counter provides the number of ASS FAIL messages sent by the BSC to the MSC when the BSC receives an ASS REQ message that carries an A interface CIC that is already occupied by another call.
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3. CSSR (5) (2) Failures due to abnormal radio resource allocation: - A312A: CELL_ASS_FAIL_Frst_ASS_NO_CH: This counter provides the number of ASS FAIL messages sent by the BSC to the MSC when the cell does not have available channels and the directed retry procedure fails to be initiated or the directed retry is prohibited by the data configuration in the first air interface assignment procedure. - A312L: CELL_ASS_FAIL_RECONN_SUCC_ASS_NO_CH: This counter provides the number of ASS FAIL messages sent by the BSC to the MSC when the cell does not have available channels and the directed retry procedure fails to be initiated or the directed retry is prohibited by the data configuration in the air interface assignment procedure except for the first air interface assignment procedure. - A312K: CELL_ASS_FAIL_Frst_DR_NO_CH: This counter provides the number of ASS FAIL messages sent by the BSC to the MSC when the cell does not have available channels and the directed retry procedure is successfully initiated but failed due to no available channel in the first air interface assignment procedure. - A312M: CELL_ASS_FAIL_RECONN_SUCC_DR_NO_CH: This counter provides the number of ASS FAIL messages sent by the BSC to the MSC when the BSC attempts to make a directed retry but the directed retry failed because the target cell does not have available channels in the air interface assignment procedure except for the first air interface assignment procedure.
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3. CSSR (6) - A312F: CELL_ASS_FAIL_NO_IDLE_ABIS: This counter provides the number of ASS FAIL messages sent by the BSC to the MSC when the dynamic allocation of Abis resources is enabled on the BSC but the assignment fails due to no available Abis resources. - A3129S: CELL_ASS_FAIL_NO_SPEECH_VER: This counter provides the number of ASS FAIL messages sent by the BSC to the MSC when the assignment fails because the intersection between the speech version set carried in the ASS REQ message from the MSC and the speech version set supported by the current cell of the MS does not have available speech versions.
(3) Failures due to abnormal air interface access: - A3129C: CELL_ASS_FAIL_Frst_ASS_EXP: This counter provides the number of ASS FAIL messages sent by the BSC to the MSC when the timer for the BSC to wait for an ASS CMP message expires after the BSC sends an ASS CMD message to the MS in the first air interface assignment procedure. - A3129P: CELL_ASS_FAIL_RECONN_SUCC_ASS_EXP: This counter provides the number of ASS FAIL messages sent by the BSC to the MSC when the timer for the BSC to wait for an ASS CMP message expires after the BSC sends an ASS CMD message to the MS in the air interface assignment procedure except for the first air interface assignment procedure.
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3. CSSR (7) - A3129O: CELL_ASS_FAIL_Frst_DR_EXP: This counter provides the number of ASS FAIL messages sent by the BSC to the MSC when the cell does not have available channels and the directed retry procedure is successfully initiated but failed due to the expiry of the timer for waiting for an HO CMP message in the first air interface assignment procedure. - A3129Q: CELL_ASS_FAIL_RECONN_SUCC_DR_EXP: This counter provides the number of ASS FAIL messages sent by the BSC to the MSC when the timer for waiting for an ASS CMP message expires after the BSC sends an HO CMD message to the MS in the air interface assignment procedure except for the first air interface assignment procedure. - A3129D: CELL_ASS_FAIL_RECONN_SUCC_ASS_RECONN_SUCC: This counter provides the number of ASS FAIL or RR STATUS messages reported by the MS to the BSC when the MS attempts but fails to access the new channel and then successfully reconnects to the old channel after receiving an ASS CMD message. - A3129R: CELL_ASS_FAIL_RECONN_SUCC_DR_RECONN_SUCC: This counter provides the number of HO FAIL or RR STATUS messages reported by the MS to the BSC when the MS attempts but fails to access the new channel and then successfully reconnects to the old channel after receiving an HO CMD message.
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3. CSSR (8) (4) Failures due to the abnormality of terrestrial resources or the call clearing performed by the MSC. - A3129B: CELL_ASS_FAIL_Frst_APPLY_TRSL_FAIL: This counter provides the number of ASS FAIL messages sent by the BSC to the MSC when the MS drops from the connection to the air interface, or a circuit fails to be obtained for the call, or the obtained circuit is faulty during the circuit connection of the BSC in the first air interface assignment procedure. - A3129N: CELL_ASS_FAIL_RECONN_SUCC_APPLY_TRSL_FAIL: This counter provides the number of ASS FAIL messages sent by the BSC to the MSC when the MS drops from the connection to the air interface, or a circuit fails to be obtained for the call, or the obtained circuit is faulty during the circuit connection of the BSC in the air interface assignment procedure except for the first air interface assignment procedure. - A3129G: CELL_ASS_FAIL_A_INTERF_FAIL: This counter provides the number of times that the BSC locally releases the call when the BSC receives an SS7 link abnormality indication in the assignment procedure. - A3129H: CELL_ASS_FAIL_MSC_CLR_CMD: This counter provides the number of times that the BSC releases the call after receiving a CLEAR CMD message from the MSC in the assignment procedure.
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3. CSSR (9) 5.
High SDCCH Drop Rate
In case high SDCHH Drop Rate causes deterioration of CSSR, refer to Case 2 of present document for handling. 6.
Parameters that affect CSSR
- RACHACCLEV: RACH Min. Access Level This parameter affects the coverage area. If this parameter is set to a higher value, the actual coverage area of the network becomes small; if this parameter is set to a lower value, call drops are likely to occur because of invalid access or too weak access signals, thus decreasing the success rate of BSS call setup. - RACHBUSYTHRED: RACH Busy Threshold This parameter affects the coverage area. If this parameter is set to a higher value, the actual coverage area of the network becomes small; if this parameter is set to a lower value, call drops are likely to occur because of invalid access or too weak access signals, thus decreasing the success rate of BSS call setup. - RANERRTHRED: Random Access Error Threshold This parameter affects the coverage area. If this parameter is set to a higher value, the actual coverage area of the network becomes small; if this parameter is set to a lower value, call drops are likely to occur because of invalid access or too weak access signals, thus decreasing the success rate of BSS call setup. - CIC No. / Author / Datethat on the MSC side. The values of CICs must be Presentation consistent with
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3. CSSR (10) 7.
Network functions that affect CSSR
- Directed retry When TCHs in a cell are insufficient, TCHs in other cells can be assigned through directed retry, thus increasing the BSS CSSR. By default, this function is enabled. - SDCCH dynamic adjustment When SDCCHs are insufficient, this function can be enabled to convert some TCHs into SDCCHs to increase the success rate of immediate assignment, thus increasing the BSS CSSR. By default, this function is enabled. - TCH reassignment When this function is enabled, the BSC initiates a re-assignment procedure after receiving the failure indication of the TCH assignment on the Um interface. This function can be used to increase the success rate of TCH assignment, thus increasing the BSS CSSR. By default, this function is enabled. - Flex Abis This function is implemented in the BSC6000V900R003 and later versions. This function enables dynamic assignment of Abis timeslots to more efficiently utilize the Abis link resources; however, assignment may fail because of congestion on the Abis links. This function may decrease the BSS CSSR.
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4. High TCH Blocking (1) - KPI formula: TCH Congestion Rate (Overflow) = (([Failed TCH Seizures due to Busy TCH (Signaling Channel)]+[Failed TCH Seizures due to Busy TCH (Traffic Channel)]+[Failed TCH Seizures in TCH Handovers due to Busy TCH (Traffic Channel)])/([TCH Seizure Requests (Signaling Channel)]+[TCH Seizure Requests (Traffic Channel)]+[TCH Seizure Requests in TCH Handovers (Traffic Channel)]))*{100} Analysis process: 1.High TCH blocking means congestion on the Traffic Channel: there are not enough free TCHs to accept new service requests. 2.Check cell traffic channel availability in order to verify that congestion is not due to availability issue. Check cell alarms. 3.Check availability of neighboring sites. If neighboring cells are unavailable this will cause big amount of HOs directed to our current cell thus leading to congestion. 4.Check cell traffic channel configuration. Check if all HR resources are in use before TCH congestion occurs. Verify that HR is enabled. In case AMR is supported by the operator, verify that is enabled. 5.Load balancing between cells: certain features can be activated to manage the traffic sharing between cells: - Enable LO handover algorithm: LoadHoEn: Load Handover Support - Enable Directed Retry due to load: DIRECTRYEN: Directed Retry
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4. High TCH Blocking (2) 6.
Load balancing between cells: - Concentric Cells: check relative parameters so as to implement optimal traffic sharing between underlaid-overlaid cells. - Enhanced Dual Band Network: check relative parameters so as to implement optimal traffic sharing between underlaid-overlaid cells.
7.
Check if additional capacity related features can be activated in the network in order to improve the utilisation of TCH resources: - BCCH Dense Frequency Multiplexing: enables the BCCHs to reuse frequencies more tightly to free more frequencies for non-BCCH TRXs, thus increasing the system capacity. TIGHTBCCHSWITCH: TIGHT BCCH Switch (Whether to enable the BCCH aggressive frequency reuse algorithm) - Interference Based Channel Allocation (IBCA): The IBCA algorithm requires the BSC to estimate the C/I ratio of the new call in every channel assignment procedure; it also requires the BSC to estimate the interference caused to the established calls on the network when an idle channel is assigned to a new call. In this way, the optimal channel, that is, the one that meets the C/I ratio requirement of the new call and causes the least interference to the established calls after being occupied, is assigned to the new call to alleviate the interference and ensure the full use of the frequency resources. IBCAALLOWED: IBCA Allowed (Whether to enable the IBCA algorithm) - Flex MAIO: BSC dynamically adjusts the MAIO according to the current interference level of a channel when assigning an MAIO to the channel . FLEXMAIO: Start Flex MAIO Switch (Whether to enable the function of Flex Mobile Allocation Index Offset)
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4. High TCH Blocking (3) 8.
If congestion is still present although the previous described fine tuning and features activation, then: - Check Interference in the network (C/I); check frequency plan - Check coverage: maybe network layout should be changed in traffic hot spots - We can use TA distribution in order to identify traffic distribution among cells. In some cases overshooting can be detected, so we can check the possibility to reduce service area of the overshooting cell. Before doing so, we need, of course, to make sure that there is clear dominance in the area that we are going to shrink serving cell’s coverage. - Implement physical network changes where necessary and feasible: tilt, azimuth, antenna type, etc. - Add TRX - Long term monitoring (e.g. one month) can be used to identify whether we have constant growth in traffic in a site and area close by. If traffic increases in area level and we have already high HR/AMR HR utilization then there are not too many other options than implement a new site. - Add Site
Note: for more details on TCH capacity optimisation check “HUA_2G_Capacity_Optimization_v1.0.pptx” document from Multivendor Team in IMS. For internal use 26 © Nokia Siemens Networks
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5. High TCH Drop Call Rate (1) - KPI formula: TCH Call Drop Rate (including handovers) = ([Call Drops on TCH]/([Successful TCH Seizures (Signaling Channel)]+[Successful TCH Seizures (Traffic Channel)]+[Successful TCH Seizures in TCH handovers (Traffic Channel)]))*{100} Analysis process: 1.Identify the route cause of the call drops by checking the Call Drops on TCH counter: Call Drops on Traffic Channel = [Call Drops on Radio Interface in Stable State (Traffic Channel)]+ [Call Drops on Radio Interface in Handover State (Traffic Channel)]+ [Call Drops due to No MRs from MS for a Long Time (Traffic Channel)]+ [Call Drops due to Abis Terrestrial Link Failure (Traffic Channel)]+ [Call Drops due to Equipment Failure (Traffic Channel)]+ [Call Drops due to Forced Handover (Traffic Channel)]+ [Call Drops Due to Loopback Start Failure]+ [Call Drops Due to Failures to Return to Normal Call from Loopback] •Call Drops on Radio Interface in Stable State (Traffic Channel): indicates RF issue. Check coverage at drop points; check interference in the cell; check for missing neighbours. •Call Drops on Radio Interface in Handover State (Traffic Channel): drops during handover procedure; check the handover failure counters to get more details for the handover failure cause.
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5. High TCH Drop Call Rate (2) •
• • • •
•
Call Drops due to No MRs from MS for a Long Time (Traffic Channel): After seizing a TCH, the MS sends a measurement report to the BSC every 480 ms. If the BSC does not receive any measurement report within a certain period, call drop occurs on the Um interface. Check UL coverage/UL interference at drop points. Check for possible MS problem. Call Drops due to Abis Terrestrial Link Failure (Traffic Channel): indicates Abis transmission problem. Check relative alarms. Call Drops due to Equipment Failure (Traffic Channel): indicates BSS hardware or software problem. Check relative alarms. Call Drops due to Forced Handover (Traffic Channel): After the MS seizes a traffic channel, the BSC initiates forced handover in the case of channel preemption, channel failure, or channel blocking. If the handover of the MS fails, the BSC releases the call. Call Drops Due to Loopback Start Failure: After seizing a channel, the MS starts the local switching. This measurement provides the number of call drops due to the failure in starting the local switching caused by different reasons. The cause value can be Terrestrial Resource Request Failure, Failures on the BTS Side, or Timer Expired. Call Drops Due to Failures to Return to Normal Call from Loopback: After a call is in the BSC/BTS local switch state, it incurs a handover. The local switch, however, cannot be continued because the target cell of the handover may not support local switch, the outgoing BSC handover fails, the TRX that carries the target channel of the handover may not support local switch, or the specified handover fails. The BSC attempts to restore the call to a normal one. The restoration may fail due to various reasons. If the restoration fails, the MS incurs call drop.
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5. High TCH Drop Call Rate (3) 2.
Parameters that affect TCH Drop Call Rate:
Check and tune appropriately, if needed, the values of the following parameters: - RLT: Radio Link Timeout; recommended value: 52 - SAMULFRM: SACCH Multi-Frames; recommended value: 32
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6. High HO fail (1) - KPI formula: Handover Success Rate = (([Successful Outgoing Internal Inter-Cell Handover]+[Successful Outgoing External Inter-Cell Handovers])/([Outgoing Internal Inter-Cell Handover Requests]+[Outgoing External InterCell Handover Requests]))*{100} Analysis process: 1.Identify the possible cause of the handover failures by checking the following counters: A. Internal HO (intra-BSC): Basic intra-BSC inter-cell handover signalling procedure:
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6. High HO fail (2) The main causes for a failed outgoing internal inter-cell handover include: 1) Causes related to resource allocation: - No traffic channel is available. - No speech version is available. - No Abis resource is available. - The BSC fails to obtain the terrestrial resources. 2) Causes related to access on the Um interface - The MS fails to access the new channel and then reconnects to the old channel. - The timer for the BSC to wait for an HO CMP message expires. 3) Abnormal causes - The BSC fails to activate the allocated channel. - A fault occurs on the A interface.
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6. High HO fail (3) (1) The following counters are measured when the outgoing internal inter-cell handover fails because of failed allocation of relevant resources. - H312A:CELL_INTRABSC_OUTCELL_HO_FAIL_CONG: no channel is available in the target cell (congestion) - H312L: CELL_INTRABSC_OUTCELL_HO_FAIL_NO_IDLE_ABIS: no circuit resource is available on the Abis interface in the target cell when the Abis dynamic allocation is enabled (congestion on Abis) - H312H:CELL_INTRABSC_OUTCELL_HO_FAIL_NO_SPEECH_VER: no proper speech version is available in the target cell; check speech version configuration - H312B:CELL_INTRABSC_OUTCELL_HO_FAIL_APPLY_TRSL_FAIL: BSC fails to obtain circuit resource when establishing the terrestrial connection; check A interface circuit status; check A interface alarms
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6. High HO fail (4) (2) The following counters provide the numbers of failed internal intra-cell handovers when the MS fails to access the new channel on the Um interface. In the outgoing internal inter-cell handover procedure, the BSC sends an HO CMD message to the MS through the originating cell and initiates a timer (T3103) to wait for a HO CMP message. If the MS reconnects to the old channel and sends a HO FAIL message on the old channel before the timer expires, the following counters are measured in the originating cell based on the failure cause value: - H312Da:CELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_ABNORM_REL_UNS: Abnormal Release, Unspecified - H312Db:CELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_ABNORM_REL_CHN: Abnormal Release, Channel Unacceptable - H312Dc:CELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_ABNORM_REL_EXP: Abnormal Release, Timer Expired - H312Dd:CELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_ABNORM_REL_NO_ACT: Abnormal Release, No Activity on the Radio Path - H312De:CELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_PREEMPT: Preemptive Release - H312Df:CELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_HO_TA: Timing Advance out of Range - H312Dg:CELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_CH_MODE: Channel Mode Unavailable - H312Dh:CELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_FREQ: Frequency Unavailable For internal use 33 © Nokia Siemens Networks
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6. High HO fail (5) - H312Di:CELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_C_CLR: Call Already Cleared - H312Dj:CELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_SEMANT: Semantically Incorrect Message - H312Dk:CELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_INV_MAN: Invalid Mandatory Information - H312Dl:CELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_M_T_NE: Message Type Non-existent or Not Implemented - H312Dm:CELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_M_T_NC: Message Type Not Compatible with Protocol State - H312Dn:CELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_CONDIT: Conditional IE Error - H312Do:CELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_NO_CA: No Cell Allocation Available - H312Dp:CELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_PROTOCL: Protocol Error Unspecified - H312Dq:CELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_OTHER: Other Causes
For internal use 34 © Nokia Siemens Networks
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6. High HO fail (6) During the handover procedure excluding directed retry, after the BSC successfully allocates and activates the channel in the target cell, it sends an HO CMD message to the MS and starts the timer T3103 to wait for the HO CMP message. If no HO CMP is received by the BSC before T3103 expires, the BSC releases the call. Then, the specific one of the following counters is measured in the target cell based on the type of the target channel, that is, signalling channel (SDCCH/TCHF/TCCH) or traffic channel (TCHF/TCHH): - H3120C:CELL_INTRABSC_OUTCELL_HO_FAIL_EXP_SD_NOT_INCLUDE_DR - H3127Cb:CELL_INTRABSC_OUTCELL_HO_FAIL_EXP_TCHF_SIG_NOT_INCLUDE_DR - H3128Cb:CELL_INTRABSC_OUTCELL_HO_FAIL_EXP_TCHH_SIG_NOT_INCLUDE_DR - H3127Ca:CELL_INTRABSC_OUTCELL_HO_FAIL_EXP_TCHF_TRAF_NOT_INCLUDE_DR - H3128Ca:CELL_INTRABSC_OUTCELL_HO_FAIL_EXP_TCHH_TRAF_NOT_INCLUDE_DR In directed retry procedure, the BSC sends an HO CMD message to the MS through the originating cell and starts timer T3103 to wait for an HO CMP message. If no HO CMP is received by the BSC before T8 expires, the following counter is measured: - H3121C:CELL_INTRABSC_OUTCELL_HO_FAIL_EXP_DR
Note: The counter CH312C:CELL_INTRABSC_OUTCELL_HO_FAIL_EXP is the sum of all the above counters, i.e. the six counters above are sub-items of this counter.
For internal use 35 © Nokia Siemens Networks
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6. High HO fail (7) (3) The following counters are measured when the outgoing internal inter-cell handover fails because of equipment faults. After the BSC successfully performs channel allocation and speech version confirmation in the target cell, it sends a CH ACT message to the BTS for activating the channel, and starts the corresponding timer to wait for the response. If the BSC receives a CH ACT NACK or no response from the BTS before the timer expires, the following counter is measured: - H312I:CELL_INTRABSC_OUTCELL_HO_FAIL_CHACT_FAIL If an outgoing internal intra-cell handover fails because the BSC locally releases the call after receiving an SS7 link abnormality indication, the following counter is measured: - H312G:CELL_INTRABSC_OUTCELL_HO_FAIL_A_INTERF_FAIL
For internal use 36 © Nokia Siemens Networks
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6. High HO fail (8) B. External HO (inter-BSC): Basic inter-BSC inter-cell handover signalling procedure:
The main causes for a failed outgoing external inter-cell handover include: 1. The timer T7 for the BSC to wait for a HO CMD message, after having sent a HO RQD message, expires. 2. The BSC receives a HO RQD REJ message from the MSC. 3. The MS fails to access the new channel and then reconnects to the old channel, sending a HO FAIL message. 4. The timer T8 for the BSC to wait for a CLEAR CMD message , after having sent a HO CMD message, expires. 5. The BSC receives a CLEAR CMD message from the MSC which contains a failure handover cause. 6. An SS7 link failure occurs on the A interface
For internal use 37 © Nokia Siemens Networks
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6. High HO fail (9) (1) During the outgoing external inter-cell handover procedure, timer T7 is started after the BSC sends the HO RQD to the MSC and waits for the HO CMD command from the MSC. If no HO CMD is received by the BSC before T7 expires, the BSC re-sends the HO RQD message. The specific counter provides the number of failed outgoing external inter-cell handovers when the number of resending times has exceeded the maximum configuration. In the outgoing external inter-cell handover (excluding directed retry) procedure, the following counters are measured when T7 expires based on the channel type: - H3320L:CELL_INTERBSC_OUTCELL_HO_FAIL_T7_EXP_SD_NOT_INCLUDE_DR - H3327Lb:CELL_INTERBSC_OUTCELL_HO_FAIL_T7_EXP_TCHF_SIG - H3328Lb:CELL_INTERBSC_OUTCELL_HO_FAIL_T7_EXP_TCHH_SIG - H3327La:CELL_INTERBSC_OUTCELL_HO_FAIL_T7_EXP_TCHF_TRAF_CH - H3328La:CELL_INTERBSC_OUTCELL_HO_FAIL_T7_EXP_TCHH_TRAF_CH In the outgoing external inter-cell handover (directed retry) procedure, the following counter is measured: - H3321L:CELL_INTERBSC_OUTCELL_HO_FAIL_T7_EXP_DR
For internal use 38 © Nokia Siemens Networks
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6. High HO fail (10) (2) The following counters provide the number of times that the BSC terminates the outgoing external intercell handover because it receives an HO RQD REJ message from the MSC after sending the HO RQD message to the MSC. - H332Ka:CELL_INTERBSC_OUTCELL_HO_REQ_REJ_OM_INTERVENTION: OM Intervention - H332Kb:CELL_INTERBSC_OUTCELL_HO_REQ_REJ_EQUIP_FAIL: Equipment Failure - H332Kc:CELL_INTERBSC_OUTCELL_HO_REQ_REJ_NO_RADIO_RES: No Radio Resource Available - H332Kd:CELL_INTERBSC_OUTCELL_HO_REQ_REJ_REQ_NO_TER_RES: Requested Terrestrial Resource Unavailable - H332Ke:CELL_INTERBSC_OUTCELL_HO_REQ_REJ_BSS_NOT_EQUIP: BSS not Equipped - H332Kf:CELL_INTERBSC_OUTCELL_HO_REQ_REJ_INVALID_CELL: Invalid Cell - H332Kg:CELL_INTERBSC_OUTCELL_HO_REQ_REJ_REQ_TRANS_NO_ADAPT: Requested Transcoding/Rate Adaption Unavailable - H332Kh:CELL_INTERBSC_OUTCELL_HO_REQ_REJ_CIRCUIT_POOL_MISMATCH: Circuit Pool Mismatch - H332Ki:CELL_INTERBSC_OUTCELL_HO_REQ_REJ_REQ_NO_SV: Requested Speech Version Unavailable - H332Kj:CELL_INTERBSC_OUTCELL_HO_REQ_REJ_CIPH_ALG_NOT_SUPPORT: Ciphering Algorithm not Supported - H332Kk:CELL_INTERBSC_OUTCELL_HO_REQ_REJ_TER_CIR_ALLOC: Terrestrial Circuit Already Allocated - H332Kl:CELL_INTERBSC_OUTCELL_HO_REQ_REJ_INVALID_MSG: Invalid Message - H332Km:CELL_INTERBSC_OUTCELL_HO_REQ_REJ_PROTOCOL_ERR: Protocol Error between BSS and MSC - H332Kn:CELL_INTERBSC_OUTCELL_HO_REQ_REJ_OTHER: Other Causes For internal use 39 © Nokia Siemens Networks
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6. High HO fail (11) (3) In the outgoing external inter-cell handover procedure, the BSC sends a HO CMD message to the MS through the originating cell and initiates timer T8 to wait for a CLEAR CMD message from the MSC which will indicate Successful Handover. If the MS reconnects to the old channel and sends an HO FAIL message on the old channel before T8 expires, the specific one of the following counters is measured in the target cell based on the cause value in the HO FAIL message. - H332Da:CELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_ABNORM_REL_UNS: Abnormal Release, Unspecified - H332Db:CELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_ABNORM_REL_CHN: Abnormal Release, Channel Unacceptable - H332Dc:CELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_ABNORM_REL_EXP: Abnormal Release, Timer Expired - H332Dd:CELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_ABNORM_REL_NO_ACT: No Activity on the Radio Path - H332De:CELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_PREEMPT: Preemptive Release - H332Df:CELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_HO_TA: Timing Advance out of Range - H332Dg:CELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_CH_MODE: Channel Mode Unavailable - H332Dh:CELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_FREQ: Frequency Unavailable - H332Di:CELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_CALL_CLR: Call Already Cleared For internal use 40 © Nokia Siemens Networks
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6. High HO fail (12) - H332Dj:CELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_SEMANT: Semantically Incorrect Message - H332Dk:CELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_INVALID_MAN: Invalid Mandatory Information - H332Dl:CELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_MSG_TYPE_NEXISTENT: Message Type Non-existent or Not Implemented - H332Dm:CELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_MSG_TYPE_NOT_CO MPATIBLE: Message Type Not Compatible with Protocol State - H332Dn:CELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_CONDIT: Conditional IE Error - H332Do:CELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_NO_CA: No Cell Allocation Available - H332Dp:CELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_PROTOCL: Protocol Error Unspecified - H332Dq:CELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_MS_RPT_OTHER: Other Causes
For internal use 41 © Nokia Siemens Networks
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6. High HO fail (13) (4) In the outgoing external inter-cell handover procedure, after sending the HO CMD message to the MS, the BSC starts the timer T8 to wait for the CLEAR CMD message from the MSC. The specific counter provides the number of times that the BSC terminates the handover due to the expiration of T8. In the outgoing external inter-cell handover (excluding directed retry) procedure, the following counters are measured when T8 expires based on the channel type: - H3320C:CELL_INTERBSC_OUTCELL_HO_FAIL_T8_EXP_SD_NOT_INCLUDE_DR - H3327Cb:CELL_INTERBSC_OUTCELL_HO_FAIL_T8_EXP_TCHF_SIG - H3328Cb:CELL_INTERBSC_OUTCELL_HO_FAIL_T8_EXP_TCHH_SIG - H3327Ca:CELL_INTERBSC_OUTCELL_HO_FAIL_T8_EXP_TCHF_TRAF_CH - H3328Ca:CELL_INTERBSC_OUTCELL_HO_FAIL_T8_EXP_TCHH_TRAF_CH In the outgoing external inter-cell handover (directed retry) procedure, the following counter is measured: - H3321C:CELL_INTERBSC_OUTCELL_HO_FAIL_T8_EXP_DR
Note: The counter CH332C:CELL_INTERBSC_OUTCELL_HO_FAIL_T8_EXP is the sum of all the above counters, i.e. the six counters above are sub-items of this counter.
For internal use 42 © Nokia Siemens Networks
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6. High HO fail (14) (5) The following counters provides the number of times that the BSC terminates the outgoing external intercell handover because the BSC receives a CLEAR CMD message from the MSC and the cause value carried in the message is not Handover successful. - H332Ha:CELL_INTERBSC_OUTCELL_HO_FAIL_MSC_CLR_RADIO_INTF_MSG_FAIL: Radio Interface Message Failure - H332Hb:CELL_INTERBSC_OUTCELL_HO_FAIL_MSC_CLR_RADIO_INTF_FAIL: Radio Interface Failure - H332Hc:CELL_INTERBSC_OUTCELL_HO_FAIL_MSC_CLR_OM_INTERVENTION: OM Intervention - H332Hd:CELL_INTERBSC_OUTCELL_HO_FAIL_MSC_CLR_EQUIP_FAIL: Equipment Failure - H332He:CELL_INTERBSC_OUTCELL_HO_FAIL_MSC_CLR_PREEMPTION: Preemption - H332Hf:CELL_INTERBSC_OUTCELL_HO_FAIL_MSC_CLR_INVALID_MSG: Invalid Message - H332Hg:CELL_INTERBSC_OUTCELL_HO_FAIL_MSC_CLR_PROTOCOL_ERR: Protocol Error between BSS and MSC - H332Hh:CELL_INTERBSC_OUTCELL_HO_FAIL_MSC_CLR_OTHER: Other Causes
(6) The following counter provides the number of failed outgoing external inter-cell handovers when the BSC detects an SS7 link failure on the A interface and releases the call: - H332G:CELL_INTERBSC_OUTCELL_HO_FAIL_MSC_CLR_A_INTF_FAIL
For internal use 43 © Nokia Siemens Networks
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6. High HO fail (15) 2.
Check interference in source and target cells. High interference can cause handover failure.
3.
Check whether ping-pong handover occurs due to no dominant server in the area. Ping-pong may lead to HO failures.
4.
Parameters that affect HO Success Rate:
- T3103A: Timer started after the BSC delivers a HANDOVER COMMAND in an intra-BSC inter-cell handover. If the BSC receives a HANDOVER COMPLETE message before this timer expires, the timer stops. If this timer expires, the BSC considers the handover as failed. Recommended value: 10000 ms - T7: Timer is started after the BSC sends the HO RQD to the MSC and waits for the HO CMD command from the MSC in an inter-BSC inter-cell handover procedure. Recommended value: 10000 ms - T8: After sending the HO CMD message to the MS, the BSC starts this timer to wait for the CLEAR CMD message from the MSC in an inter-BSC inter-cell handover procedure. Recommended value: 10000 ms
For internal use 44 © Nokia Siemens Networks
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7. Low Coverage (1) 1.
TA measurements vs. cell radius
The following counters provide TA distribution per TRX in the cell. The measurements can be checked versus cell radius to identify possible coverage problems. - S4400A:TRX_MR_NUM_BY_TA_0 - S4401A:TRX_MR_NUM_BY_TA_1 - S4402A:TRX_MR_NUM_BY_TA_2 - S4403A:TRX_MR_NUM_BY_TA_3 - S4404A:TRX_MR_NUM_BY_TA_4 - S4405A:TRX_MR_NUM_BY_TA_5 - S4406A:TRX_MR_NUM_BY_TA_6 - S4407A:TRX_MR_NUM_BY_TA_7 - S4408A:TRX_MR_NUM_BY_TA_8 - S4409A:TRX_MR_NUM_BY_TA_9 - S4410A:TRX_MR_NUM_BY_TA_10 - S4411A:TRX_MR_NUM_BY_TA_11 - S4412A:TRX_MR_NUM_BY_TA_12 - S4413A:TRX_MR_NUM_BY_TA_13 - S4414A:TRX_MR_NUM_BY_TA_14 - S4415A:TRX_MR_NUM_BY_TA_15 - S4416A:TRX_MR_NUM_BY_TA_16 - S4417A:TRX_MR_NUM_BY_TA_17 - S4418A:TRX_MR_NUM_BY_TA_18 - S4419A:TRX_MR_NUM_BY_TA_19 For internal use 45 © Nokia Siemens Networks
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- S4420A:TRX_MR_NUM_BY_TA_20 - S4421A:TRX_MR_NUM_BY_TA_21 - S4422A:TRX_MR_NUM_BY_TA_22 - S4423A:TRX_MR_NUM_BY_TA_23 - S4424A:TRX_MR_NUM_BY_TA_24 - S4425A:TRX_MR_NUM_BY_TA_25 - S4426A:TRX_MR_NUM_BY_TA_26 - S4427A:TRX_MR_NUM_BY_TA_27 - S4428A:TRX_MR_NUM_BY_TA_28 - S4429A:TRX_MR_NUM_BY_TA_29 - S4430A:TRX_MR_NUM_BY_TA_30_TO_31 - S4432A:TRX_MR_NUM_BY_TA_32_TO_33 - S4434A:TRX_MR_NUM_BY_TA_34_TO_35 - S4436A:TRX_MR_NUM_BY_TA_36_TO_37 - S4438A:TRX_MR_NUM_BY_TA_38_TO_39 - S4440A:TRX_MR_NUM_BY_TA_40_TO_44 - S4445A:TRX_MR_NUM_BY_TA_45_TO_49 - S4450A:TRX_MR_NUM_BY_TA_50_TO_54 - S4455A:TRX_MR_NUM_BY_TA_55_TO_63 - S4463A:TRX_MR_NUM_BY_TA_GT_63
7. Low Coverage (2) 2.
Rxlevel & Rxquality measurements
BSC receives reports that contain the uplink and downlink receive level rank and the uplink and downlink receive quality rank. - The receive level ranges from rank 0 to rank 7. Each rank corresponds to a receive level range. - The receive quality ranges from rank 0 to rank 7. Each rank corresponds to a bit error rate range. Receive Level Rank Receive Level (dBm)
Receive Quality Rank Bit Error Rate
0
≤ -100
0
< 0.2%
1
(-100,-95]
1
0.2%-0.4%
2
(-95,-90]
2
0.4 %-0.8%
3
(-90,-85]
3
0.8%-1.6%
4
(-85,-80]
4
1.6%-3.2%
5
(-80,-75]
5
3.2%-6.4%
6
(-75,-70]
6
6.4%-12.8%
7
> -70
7
> 12.8%
Receive Level Measurement, together with Receive Quality Measurement per TRX, reflects the radio signal coverage and interference of a cell. For example, a high ratio of high level and low quality suggests possible interference; a high ratio of low level and low quality suggests poor coverage. For internal use 46 © Nokia Siemens Networks
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7. Low Coverage (3) • TCHF Receive Level Measurement per TRX provides the number of measurement reports from the TCHF that contain receive level rank and receive quality rank. TCHF receive level and quality measurements for UL and DL are given by following counters: - S4100A:TRX_FR_UP_LEV_0_RX_QLTY_0 - S4101A:TRX_FR_UP_LEV_0_RX_QLTY_1 - S4102A:TRX_FR_UP_LEV_0_RX_QLTY_2 …………………………………………………... Saaaaa:TRX_FR_UP_LEV_x_RX_QLTY_y
- S4100B:TRX_FR_DOWN_LEV_0_RX_QLTY_0 - S4101B:TRX_FR_DOWN_LEV_0_RX_QLTY_1 - S4102B:TRX_FR_DOWN_LEV_0_RX_QLTY_2 ……………………………………………………….. Saaaaa:TRX_FR_UP_LEV_x_RX_QLTY_y
where: aaaaa=counter ID, x=receive level rank (0~7), y=receive quality rank (0~7)
• TCHH Receive Level Measurement per TRX refers to the measurement of the sampled receive level ranks and receive quality ranks in the MRs on the TCHH. TCHH receive level and quality measurements for UL and DL are given by following counters: - S4100C:TRX_HR_UP_LEV_0_RX_QLTY_0 - S4101C:TRX_HR_UP_LEV_0_RX_QLTY_1 - S4102C:TRX_HR_UP_LEV_0_RX_QLTY_2 …………………………………………………… Saaaaa:TRX_HR_UP_LEV_x_RX_QLTY_y
- S4100D:TRX_HR_DOWN_LEV_0_RX_QLTY_0 - S4101D:TRX_HR_DOWN_LEV_0_RX_QLTY_1 - S4102D:TRX_HR_DOWN_LEV_0_RX_QLTY_2 ………………………………………………………… Saaaaa:TRX_FR_UP_LEV_x_RX_QLTY_y
where: aaaaa=counter ID, x=receive level rank (0~7), y=receive quality rank (0~7) For internal use 47 © Nokia Siemens Networks
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8. High Interference (1) 1.
Idle UL Interference
The interference band is the uplink interference level of a channel reported by the BTS to the BSC in the RF RESOURCE INDICATION message when the channel is idle. There are five levels of interference bands. The threshold of each interference band can be configured: Parameter ID
Interference Band Recommended Value (dBm)
INTERFTHRES1 1
-105
INTERFTHRES2 2
-98
INTERFTHRES3 3
-92
INTERFTHRES4 4
-87
INTERFTHRES5 5
-85
Higher rank suggests higher interference level.
For internal use 48 © Nokia Siemens Networks
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8. High Interference (2) The following counters provide the average number of idle channels (TCHF, TCHH, or SDCCH) whose interference level are in each interference band (1-5) per granularity period. - AS4200A:TRX_CH_IN_INTFR1_AVR_NUM_SD - AS4200B:TRX_CH_IN_INTFR2_AVR_NUM_SD - AS4200C:TRX_CH_IN_INTFR3_AVR_NUM_SD - AS4200D:TRX_CH_IN_INTFR4_AVR_NUM_SD - AS4200E:TRX_CH_IN_INTFR5_AVR_NUM_SD - AS4207A:TRX_CH_IN_INTFR1_AVR_NUM_FR - AS4207B:TRX_CH_IN_INTFR2_AVR_NUM_FR - AS4207C:TRX_CH_IN_INTFR3_AVR_NUM_FR - AS4207D:TRX_CH_IN_INTFR4_AVR_NUM_FR - AS4207E:TRX_CH_IN_INTFR5_AVR_NUM_FR - AS4208A:TRX_CH_IN_INTFR1_AVR_NUM_HR - AS4208B:TRX_CH_IN_INTFR2_AVR_NUM_HR - AS4208C:TRX_CH_IN_INTFR3_AVR_NUM_HR - AS4208D:TRX_CH_IN_INTFR4_AVR_NUM_HR - AS4208E:TRX_CH_IN_INTFR5_AVR_NUM_HR
2. Rxlevel & Quality distributions can be used to identify interference in a cell. Refer to Case 7 of present document for details. 3. TA measurements can be used to identify interference in a cell. Refer to Case 7 of present document for details. For internal use 49 © Nokia Siemens Networks
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9. High Signalling Failures Before TBF Establishment (1) - KPI formula: Success Rate of Random Access (Packet Service) = [A301H:CELL_IMM_ASS_CMD_PS]/[A300H:CELL_CH_REQ_PACKET_CALL] AGCH Blocking = ([L3188A:CELL_DEL_IND]/[Channel Requests (all reasons)])*{100} Paging Overload Rate PS = ([PACKET CCCH LOAD IND Messages Sent on Abis Interface])/([Delivered Paging Messages for PS Service])*{100} Analysis process: 1.High signalling failures before TBF establishment refers to failures on the CCCH. During one-phase access or two-phase access on the CCCH, the MS fails to proceed to TBF establishment process due to failures on the CCCH channel: AGCH or PCH. The failures most likely will be due to CCCH congestion. 2.Check the above KPIs to identify congestion on the AGCH or PCH. 3.Check relative alarms on the BSC/BTS in order to locate any hardware/software fault. 4.If blocking is the problem, proceed to the following steps in order to relieve congestion on the CCCH. Note: For more details on CCCH capacity optimisation refer to “HUA_2G_Capacity_Optimization_v1.0.ppt” document from Multivendor team in IMS.
For internal use 50 © Nokia Siemens Networks
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9. High Signalling Failures Before TBF Establishment (2) 5.
Check the values of following parameters: - BSAGBLKSRES: Blocks Reserved for AGCH. Value range: 0-7. Recommended: 2 - BSPAMFRAMS: Multi-Frames in a Cycle on the Paging CH. Value range: 2-9. Value depends on paging load. Increase value when paging load increases. Value should be kept as small as possible. - PAGTIMES: Paging Times. Value range: 1-8 (For the BTS, this parameter is used to determine paging retransmissions. This parameter and the number of paging times configured in the MSC determine the number of paging retransmissions.)
6.
Check if Flow Control feature is enabled. Recommendation is that Flow Control is always enabled. Flow Control, controls the arrival of paging messages on the A interface (MSC-BSC) and on the LAPD links (BSC-BTS).
7.
Check volume of PS pagings (A331:CELL_PAGES_PS: Delivered Paging Messages for PS Service). If too high then check if PCCCH is configured. If PCCCH is configured then packet pages can be transmitted through PPCH, thus reducing PCH load. CS pages can also be transmitted through packet control channels (PACCH or PPCH). For this to work, Gs interface needs to be configured between SGSN-MSC. Also Network Mode of Operation should be set to 1. - NMO: Network Operation Mode
8.
Check Location Area: re-size might be required (make smaller).
9.
Consider splitting cells in the paging overload area. This will grow CCCH capacity.
10. Add CCCH capacity (Extended BCCH). For internal use 51 © Nokia Siemens Networks
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9. High Signalling Failures Before TBF Establishment (3) Packet access on the CCCH signalling procedure:
MS
BTS
BSC
Channel Request Immediate Assignment RLC data block(with TLLI) Packet Uplink Ack/Nack(with TLLI)
MS
BTS Channel Request Immediate Assignment Packet Resource Request(with TLLI) Packet Uplink Assignment(with TLLI)
RLC data block(without TLLI)
RLC data block
RLC data block(without TLLI)
RLC data block
……… Packet Uplink Ack/Nack(without TLLI) RLC data block(without TLLI)
Fig.1 One-phase packet access on the uplink CCCH
For internal use 52 © Nokia Siemens Networks
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BSC
……… Packet Uplink Ack/Nack RLC data block Fig.2 Two-phase packet access on the uplink CCCH
10. High TBF Establishment Failures (1) - KPI formula: Uplink Assignment Success Rate = (([Number of Successful Uplink GPRS TBF Establishments]+[Number of Successful Uplink EGPRS TBF Establishments])/([Number of Uplink GPRS TBF Establishment Attempts]+[Number of Uplink EGPRS TBF Establishment Attempts]))*{100} Downlink Assignment Success Rate = (([Number of Successful Downlink GPRS TBF Establishments]+[Number of Successful Downlink EGPRS TBF Establishments])/([Number of Downlink GPRS TBF Establishment Attempts]+[Number of Downlink EGPRS TBF Establishment Attempts]))*{100}
Analysis process: 1.Identify the possible cause of the TBF establishment failures by checking the following counters: A. UL GPRS TBF establishment failures: - A9003:UP_GPRS_TBF_ESTB_FAIL_NO_CHAN_RES: number of failed uplink GPRS TBF establishments due to no channel available. Indicates congestion on the TCH; refer to Case 4 of present document for handling suggestions. - A9004:UP_GPRS_TBF_ESTB_FAIL_MS_NO_RESP: number of failed uplink GPRS TBF establishments due to no response from MS. Indicates bad RF conditions in the cell. Check cell coverage and interference. - A9037:UP_GPRS_TBF_ESTB_FAIL_SEND_ASSMSG_FAIL: In dedicated mode, the BSS sends the resource assignment command to the MS over the DCCH if both the network and the MS support DTM (Dual Transfer Mode – simultaneous support of CS+PS service). If the resource assignment command is not sent successfully and the establishment of the uplink GPRS TBF thus fails, this counter is incremented by one. For internal use 53 © Nokia Siemens Networks
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10. High TBF Establishment Failures (2) - A9038:UP_GPRS_TBF_ESTB_FAIL_MS_RESP_ASS_FAILURE: In dedicated mode, the BSS sends the resource assignment command to the MS over the DCCH if both the network and the MS support DTM (Dual Transfer Mode – simultaneous support of CS+PS service). If the MS responds with the resource assignment failure message and the establishment of the uplink GPRS TBF thus fails, this counter is incremented by one. - A9016:UP_GPRS_TBF_ESTB_FAIL_OTHER_CAUSE: This measurement provides the number of failed uplink GPRS TBF establishments due to other causes in a granularity period. This may happen because an exception or failure occurs in the resource assignment or the overload protection (flow control) is triggered. Check BSS alarms in order to locate possible faults in the equipment (h/w or s/w). B. UL EGPRS TBF establishment failures: - A9203:UP_EGPRS_TBF_ESTB_FAIL_NO_CHAN_RES: number of failed uplink EGPRS TBF establishments due to no channel available. Indicates congestion on the TCH; refer to Case 4 of present document for handling suggestions. - A9204:UP_EGPRS_TBF_ESTB_FAIL_MS_NO_RESP: number of failed uplink EGPRS TBF establishments due to no response from MS. Indicates bad RF conditions in the cell. Check cell coverage and interference. - A9235:UP_EGPRS_TBF_ESTB_FAIL_SEND_ASSMSG_FAIL: In dedicated mode, the BSS sends the resource assignment command to the MS over the DCCH if both the network and the MS support DTM. If the resource assignment command is not sent successfully and the establishment of the uplink EGPRS TBF thus fails, this counter is incremented by one. - A9236:UP_EGPRS_TBF_ESTB_FAIL_MS_RESP_ASS_FAILURE: In dedicated mode, the BSS sends the resource assignment command to the MS over the DCCH if both the network and the MS support DTM. If the MS responds with the resource assignment failure message and the establishment of the uplink EGPRS TBF thus fails, this counter is incremented by one. For internal use 54 © Nokia Siemens Networks
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10. High TBF Establishment Failures (3) - A9216:UP_EGPRS_TBF_ESTB_FAIL_OTHER_CAUSE: This measurement provides the number of failed uplink EGPRS TBF establishments due to other causes in a granularity period. This may happen because an exception or failure occurs in the resource assignment or the overload protection (flow control) is triggered. Check BSS alarms in order to locate possible faults in the equipment (h/w or s/w). C. DL GPRS TBF establishment failures: - A9103:DOWN_GPRS_TBF_ESTB_FAIL_NO_CHAN_RES: number of failed downlink GPRS TBF establishments due to no channel available. Indicates congestion on the TCH; refer to Case 4 of present document for handling suggestions. - A9104:DOWN_GPRS_TBF_ESTB_FAIL_MS_NO_RESP: number of failed downlink GPRS TBF establishments due to no response from MS. Indicates bad RF conditions in the cell. Check cell coverage and interference. - A9135:DOWN_GPRS_TBF_ESTB_FAIL_SEND_ASSMSG_FAIL: In dedicated mode, the BSS sends the resource assignment command to the MS over the DCCH if both the network and the MS support DTM. If the resource assignment command is not sent successfully and the establishment of the downlink GPRS TBF thus fails, this counter is incremented by one. - A9136:DOWN_GPRS_TBF_ESTB_FAIL_MS_RESP_ASS_FAILURE: In dedicated mode, the BSS sends the resource assignment command to the MS over the DCCH if both the network and the MS support DTM. If the MS responds with the resource assignment failure message and the establishment of the downlink GPRS TBF thus fails, this counter is incremented by one. - A9115:DOWN_GPRS_TBF_ESTB_FAIL_OTHER_CAUSE: This measurement provides the number of failed downlink GPRS TBF establishments due to other causes in a granularity period. This may happen because an exception or failure occurs in the resource assignment or the overload protection (flow control) is triggered. Check BSS alarms in order to locate possible faults in the equipment (h/w or s/w). For internal use 55 © Nokia Siemens Networks
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10. High TBF Establishment Failures (4) D. DL EGPRS TBF establishment failures: - A9303:DOWN_EGPRS_TBF_ESTB_FAIL_NO_CHAN_RES: number of failed downlink EGPRS TBF establishments due to no channel available. Indicates congestion on the TCH; refer to Case 4 of present document for handling suggestions. - A9304:DOWN_EGPRS_TBF_ESTB_FAIL_MS_NO_RESP: number of failed downlink EGPRS TBF establishments due to no response from MS. Indicates bad RF conditions in the cell. Check cell coverage and interference. - A9333:DOWN_EGPRS_TBF_ESTB_FAIL_SEND_ASSMSG_FAIL: In dedicated mode, the BSS sends the resource assignment command to the MS over the DCCH if both the network and the MS support DTM. If the resource assignment command is not sent successfully and the establishment of the downlink EGPRS TBF thus fails, this counter is incremented by one. - A9334:DOWN_EGPRS_TBF_ESTB_FAIL_MS_RESP_ASS_FAILURE: In dedicated mode, the BSS sends the resource assignment command to the MS over the DCCH if both the network and the MS support DTM. If the MS responds with the resource assignment failure message and the establishment of the downlink EGPRS TBF thus fails, this counter is incremented by one. - A9315:DOWN_EGPRS_TBF_ESTB_FAIL_OTHER_CAUSE: This measurement provides the number of failed downlink EGPRS TBF establishments due to other causes in a granularity period. This may happen because an exception or failure occurs in the resource assignment or the overload protection (flow control) is triggered. Check BSS alarms in order to locate possible faults in the equipment (h/w or s/w).
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10. High TBF Establishment Failures (5) Summary of corrective actions: 1. If TBF establishment failure is due to congestion in TCH, refer to Case 4 of present document for handling suggestions. In brief: - Check availability of current and neighbouring sites in order to make sure that TCH congestion is not due to unavailability issues. - Check FR/HR parameterization (including AMR if enabled in the network). Check usage of HR resources. - Check Load balancing configuration between cells. - Add TRX. 2. If TBF establishment failure is due to poor RF quality, then: - Check cell coverage and interference. Refer to Cases 7, 8 of present document for more details on how to check signal strength and quality in Huawei 2G system. - Adjust antenna parameters (tilt, azimuth) to improve coverage and/or suppress interference in the problematic areas. - Check antenna line (feeders, jumpers) to identify faulty connections. - Check BTS hardware (relative alarms) to identify faulty TRXs. 3. If TBF establishment failure is due to equipment fault, check relative BSS alarms (hardware and software alarms) in order to identify the faulty part. Repair or replace the faulty equipment once found.
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11. High TBF Drops (1) - KPI formula: Uplink GPRS TBF Drop Rate = (([Number of Uplink GPRS TBF Abnormal Releases due to N3101 Overflow (MS No Response)]+[Number of Uplink GPRS TBF Abnormal Releases due to N3103 Overflow (MS No Response)])/[Number of Successful Uplink GPRS TBF Establishments])*{100} Uplink EGPRS TBF Drop Rate = (([Number of Uplink EGPRS TBF Abnormal Releases due to N3101 Overflow (MS No Response)]+[Number of Uplink EGPRS TBF Abnormal Releases due to N3103 Overflow (MS No Response)])/[Number of Successful Uplink EGPRS TBF Establishment])*{100} Downlink GPRS TBF Drop Rate = ([Number of Downlink GPRS intermit transfers]/[Number of Successful Downlink GPRS TBF Establishments])*{100} Downlink EGPRS TBF Drop Rate = ([Number of Downlink EGPRS intermit transfers]/[Number of Successful Downlink EGPRS TBF Establishments])*{100} Analysis process: 1.Identify the possible cause of the TBF drops by checking the following counters: A. UL GPRS TBF Drops: - A9006:UP_GPRS_TBF_ABNORM_REL_N3101_OVERFLOW: Number of Uplink GPRS TBF Abnormal Releases due to N3101 Overflow (MS No Response). Indicates poor radio conditions in the cell. Check signal level, signal quality and interference in the cell. - A9007:UP_GPRS_TBF_ABNORM_REL_N3103_OVERFLOW: Number of Uplink GPRS TBF Abnormal Releases due to N3103 Overflow (MS No Response). Indicates poor radio conditions in the cell. Check signal level, signal quality and interference in the cell. For internal use 58 © Nokia Siemens Networks
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11. High TBF Drops (2) Additional UL GPRS TBF abnormal releases: - A9008:UP_GPRS_TBF_ABNORM_REL_SUSPEND: number of uplink GPRS TBF abnormal releases due to cell suspension. This may happen because the MS often initiates CS services during the process of PS services. Another possible cause is that the cell is on the edge of the network location area and therefore the location update of the MS is frequent. - A9009:UP_GPRS_TBF_ABNORM_REL_FLUSH: number of uplink GPRS TBF abnormal releases due to cell flush. This may happen because the cell reselection procedure is frequently initiated by the MS. - A9010:UP_GPRS_TBF_ABNORM_REL_NO_CHAN_RES: number of uplink GPRS TBF abnormal releases due to no channel. Indicates that the channel malfunction is frequent or the channel is blocked manually. Also indicates congestion on the traffic channel. To guarantee stable PS service in a cell with heavy CS traffic, add fixed packet channels. - A9017:UP_GPRS_TBF_ABNORM_REL_CHAN_PREEMPT: number of uplink GPRS TBF abnormal releases due to channel preemption. Preemption may happen because congestion occurs on the Abis interface or the dynamic PDCHs in use are occupied by the CS services. Check relative alarms to locate the cause. - A9018:UP_GPRS_TBF_ABNORM_REL_OTHER_CAUSE: number of uplink GPRS TBF abnormal releases due to other causes. This may happen because of incorrect parameters or the number of uplink GPRS TBFs on the PDCH reaches the limit or the cell is manually blocked. Check relative alarms to locate the cause. - A9034: UP_GPRS_TBF_ABNORM_REL_EGPRS_TBF_CONNECT: number of abnormal uplink GPRS TBF releases due to the access of the EGPRS service. - A9039:UP_GPRS_TBF_ABNORM_REL_CS_HO: number of uplink GPRS TBF abnormal releases due to CS handover.
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11. High TBF Drops (3) B. UL EGPRS TBF Drops: - A9206:UP_EGPRS_TBF_ABNORM_REL_N3101_OVERFLOW: Number of Uplink EGPRS TBF Abnormal Releases due to N3101 Overflow (MS No Response). Indicates poor radio conditions in the cell. Check signal level, signal quality and interference in the cell. - A9207: UP_EGPRS_TBF_ABNORM_REL_N3103_OVERFLOW: Number of Uplink EGPRS TBF Abnormal Releases due to N3103 Overflow (MS No Response). Indicates poor radio conditions in the cell. Check signal level, signal quality and interference in the cell. Additional UL EGPRS TBF abnormal releases: - A9208:UP_EGPRS_TBF_ABNORM_REL_SUSPEND: number of uplink EGPRS TBF abnormal releases due to cell suspension. This may happen because the MS often initiates CS services during the process of PS services. Another possible cause is that the cell is on the edge of the network location area and therefore the location update of the MS is frequent. - A9209:UP_EGPRS_TBF_ABNORM_REL_FLUSH: number of uplink EGPRS TBF abnormal releases due to cell flush. This may happen because the cell reselection procedure is frequently initiated by the MS. Check and tune if necessary cell reselection parameters in the area. - A9210:UP_EGPRS_TBF_ABNORM_REL_NO_CHAN_RES: number of uplink EGPRS TBF abnormal releases due to no channel. Indicates that the channel malfunction is frequent or the channel is blocked manually. Also indicates congestion on the traffic channel. To guarantee stable PS service in a cell with heavy CS traffic, add fixed packet channels. - A9217:UP_EGPRS_TBF_ABNORM_REL_CHAN_PREEMPT: number of uplink EGPRS TBF abnormal releases due to channel preemption. Preemption may happen because congestion occurs on the Abis interface or the dynamic PDCHs in use are occupied by the CS services. Check relative alarms to locate the cause. For internal use 60 © Nokia Siemens Networks
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11. High TBF Drops (4) - A9218:UP_EGPRS_TBF_ABNORM_REL_OTHER_CAUSE: number of uplink EGPRS TBF abnormal releases due to other causes. This may happen because of incorrect parameters or flow control or the cell is manually blocked. Check relative alarms to locate the cause. - A9237:UP_EGPRS_TBF_ABNORM_REL_CS_HO: number of uplink EGPRS TBF abnormal releases due to CS handover. C. DL GPRS TBF Drops: - A9118:DOWN_GPRS_TRANS_INTERRUPT_TIMES: number of intermitted downlink GPRS TBF transfers in a granularity period. The counter is incremented because the downlink PDU buffer is emptied upon abnormal downlink GPRS TBF releases due to SUSPEND, FLUSH, or failed downlink re-establishments due to other causes. - A9106:DOWN_GPRS_TBF_ABNORM_REL_N3105_OVERFLOW: number of downlink GPRS TBF abnormal releases due to N3105 overflow. Indicates bad radio conditions in the cell. Check coverage and interference in the cell. - A9107:DOWN_GPRS_TBF_ABNORM_REL_SUSPEND: number of downlink GPRS TBF abnormal releases due to cell suspension. This may happen because the MS often initiates CS services during the process of PS services. Another possible cause is that the cell is on the edge of the network location area and therefore the location update of the MS is frequent. - A9108:DOWN_GPRS_TBF_ABNORM_REL_FLUSH: number of downlink GPRS TBF abnormal releases due to cell flush. This may happen because the cell reselection procedure is frequently initiated by the MS. Check and tune if necessary cell reselection parameters in the area. - A9109:DOWN_GPRS_TBF_ABNORM_REL_NO_CHAN_RES: number of downlink GPRS TBF abnormal releases due to no channel. Indicates that the channel malfunction is frequent or the channel is blocked manually. Also indicates congestion on the traffic channel. To guarantee stable PS service in a cell with heavy CS traffic, add fixed packet channels. For internal use 61
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11. High TBF Drops (5) - A9116:DOWN_GPRS_TBF_ABNORM_REL_CHAN_PREEMPT: number of downlink GPRS TBF abnormal releases due to channel preemption. Preemption may happen because congestion occurs on the Abis interface or the dynamic PDCHs in use are occupied by the CS services. Check relative alarms to locate the cause. - A9117:DOWN_GPRS_TBF_ABNORM_REL_OTHER_CAUSE: number of downlink GPRS TBF abnormal releases due to other causes. This may happen because of incorrect parameters or the number of uplink GPRS TBFs on the PDCH reaches the limit or the cell is manually blocked. Check relative alarms to locate the cause. - A9132:DOWN_GPRS_TBF_ABNORM_REL_EGPRS_TBF_CONNECT: number of abnormal downlink GPRS TBF releases due to the access of the EGPRS service. - A9137:DOWN_GPRS_TBF_ABNORM_REL_CS_HO: number of downlink GPRS TBF abnormal releases due to CS handover. D. DL EGPRS TBF Drops: - A9318:DOWN_EGPRS_TRANS_INTERRUPT_TIMES: number of intermitted downlink EGPRS TBF transfers in a granularity period. The counter is incremented because the downlink PDU buffer is emptied upon abnormal downlink GPRS TBF releases due to SUSPEND, FLUSH, or failed downlink reestablishments due to other causes. - A9306:DOWN_EGPRS_TBF_ABNORM_REL_N3105_OVERFLOW: number of downlink EGPRS TBF abnormal releases due to N3105 overflow. Indicates bad radio conditions in the cell. Check coverage and interference in the cell. - A9307:DOWN_EGPRS_TBF_ABNORM_REL_SUSPEND: number of downlink EGPRS TBF abnormal releases due to cell suspension. This may happen because the MS often initiates CS services during the process of PS services. Another possible cause is that the cell is on the edge of the network location area and therefore the location update of the MS is frequent. For internal use 62
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11. High TBF Drops (6) - A9308:DOWN_EGPRS_TBF_ABNORM_REL_FLUSH: number of downlink EGPRS TBF abnormal releases due to cell flush. This may happen because the cell reselection procedure is frequently initiated by the MS. Check and tune if necessary cell reselection parameters in the area. - A9309:DOWN_EGPRS_TBF_ABNORM_REL_NO_CHAN_RES: number of downlink EGPRS TBF abnormal releases due to no channel. Indicates that the channel malfunction is frequent or the channel is blocked manually. Also indicates congestion on the traffic channel. To guarantee stable PS service in a cell with heavy CS traffic, add fixed packet channels. - A9316:DOWN_EGPRS_TBF_ABNORM_REL_CHAN_PREEMPT: number of downlink EGPRS TBF abnormal releases due to channel preemption. Preemption may happen because congestion occurs on the Abis interface or the dynamic PDCHs in use are occupied by the CS services. Check relative alarms to locate the cause. - A9317:DOWN_EGPRS_TBF_ABNORM_REL_OTHER_CAUSE: number of downlink EGPRS TBF abnormal releases due to other causes. This may happen because of incorrect parameters or overload protection (flow control) or the cell is manually blocked. Check relative alarms to locate the cause. - A9335:DOWN_EGPRS_TBF_ABNORM_REL_CS_HO: number of downlink EGPRS TBF abnormal releases due to CS handover.
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12. Low Throughput (1) - KPI formula: A. Average cell throughput: Average Throughput of Uplink GPRS RLC (kbit/s) = ([Total Number of Uplink RLC Data Blocks Using CS1]*{23}+ [Total Number of Uplink RLC Data Blocks Using CS2]*{34}+ [Total Number of Uplink RLC Data Blocks Using CS3]*{40}+ [Total Number of Uplink RLC Data Blocks UsingCS4]*{54})*{8}/({1000}*[Total time of Uplink GPRS TBFs exist period]) Average Throughput of Downlink GPRS RLC (kbit/s) = ([Total Number of Downlink RLC Data Blocks Using CS1]*{23}+ [Total Number of Downlink RLC Data Blocks Using CS2]*{34}+ [Total Number of Downlink RLC Data Blocks Using CS3]*{40}+ [Total Number of Downlink RLC Data Blocks Using CS4]*{54})*{8}/({1000}*[Total time of Downlink GPRS TBFs exist period])
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12. Low Throughput (2) Average Throughput of uplink EGPRS RLC (kbit/s) = ([Total Number of Uplink EGPRS MCS1 RLC Data Blocks]*{22}+ [Total Number of Uplink EGPRS MCS2 RLC Data Blocks]*{28}+ [Total Number of Uplink EGPRS MCS3 RLC Data Blocks]*{37}+ [Total Number of Uplink EGPRS MCS4 RLC Data Blocks]*{44}+ [Total Number of Uplink EGPRS MCS5 RLC Data Blocks]*{56}+ [Total Number of Uplink EGPRS MCS6 RLC Data Blocks]*{74}+ [Total Number of Uplink EGPRS MCS7 RLC Data Blocks]*{56}+ [Total Number of Uplink EGPRS MCS8 RLC Data Blocks]*{68}+ [Total Number of Uplink EGPRS MCS9 RLC Data Blocks]*{74})*{8}/({1000}*[Total time of Uplink EGPRS TBFs exist period]) Average Throughput of Downlink EGPRS RLC (kbit/s) = ([Total Number of Downlink EGPRS MCS1 RLC Data Blocks]*{22}+ [Total Number of Downlink EGPRS MCS2 RLC Data Blocks]*{28}+ [Total Number of Downlink EGPRS MCS3 RLC Data Blocks]*{37}+ [Total Number of Downlink EGPRS MCS4 RLC Data Blocks]*{44}+ [Total Number of Downlink EGPRS MCS5 RLC Data Blocks]*{56}+ [Total Number of Downlink EGPRS MCS6 RLC data blocks]*{74}+ [Total Number of Downlink EGPRS MCS7 RLC Data Blocks]*{56}+ [Total Number of Downlink EGPRS MCS8 RLC Data Blocks]*{68}+ [Total Number of Downlink EGPRS MCS9 RLC Data Blocks]*{74})*{8}/({1000}*[Total time of Downlink EGPRS TBFs exist period])
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12. Low Throughput (3) B. Average throughput per TBF: Average Throughput of Uplink GPRS TBF (kbit/s) = [Average Payload of Single Uplink GPRS TBF (KB)]*{1024}*{8}/[Average Duration of Uplink GPRS TBF (s)] Average Throughput of Uplink EGPRS TBF (kbit/s) = [Average Payload of Single Uplink EGPRS TBF (KB)]*{1024}*{8}/[Average Duration of Uplink EGPRS TBF (s)] Average Throughput of Downlink GPRS TBF (kbit/s) = [Average Payload of Single Downlink GPRS TBF (KB)]*{1024}*{8}/[Average Duration of Downlink GPRS TBF (s)] Average Throughput of Downlink EGPRS TBF (kbit/s) = [Average Payload of Single Downlink EGPRS TBF (KB)]*{1024}*{8}/[Average Duration of Downlink EGPRS TBF (s)] Analysis process: 1.Low throughput may be due to problems across the packet service transmission path. Thorough checks should be done in Gb, Abis, Um interfaces. Also in SGSN, PCU, BSC systems. 2.Gb interface: - Check usage of Gb links. Expand Gb capacity if congestion appears. Gb usage can be checked through Real Time Monitoring function of BSC LMT: On the Trace & Monitor tab page, choose Monitor > Monitor GPRS Flux. Also Gb utilization can be checked through following counters: - RL9608:BC_TRAN_UP_UTILIZATION_RATE: Uplink Utilization Rate on BC (%) - RL9610:BC_TRAN_DOWN_UTILIZATION_RATE: Downlink Utilization Rate on BC (%) Both counters above provide the ratio of actually used bandwidth over configured bandwidth on a BC of Gb. For internal use 66 © Nokia Siemens Networks
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12. Low Throughput (4) - Check alarms on GDPUP board (BSC6000) or DPUd board (BSC6900) which are the boards that provide PCU functionality in BSC (internal PCU). 3.Abis interface: - Check for congestion on Abis interface. Congestion will lower the throughput. - Higher CS and MCS coding schemes will occupy higher number of Abis timeslots. Check relative parameters for CS transition: - UPTHDCSUPGRADE1: Uplink TBF Threshold from CS1 to CS2 - UPTHDCSUPGRADE2: Uplink TBF Threshold from CS2 to CS3 - UPTHDCSUPGRADE3: Uplink TBF Threshold from CS3 to CS4 - UPTHDCSDEGRADE1: Uplink TBF Threshold from CS2 to CS1 - UPTHDCSDEGRADE2: Uplink TBF Threshold from CS3 to CS2 - UPTHDCSDEGRADE3: Uplink TBF Threshold from CS4 to CS3 - DNTHDCSUPGRADE1: Downlink TBF Threshold from CS1 to CS2 - DNTHDCSUPGRADE2: Downlink TBF Threshold from CS2 to CS3 - DNTHDCSUPGRADE3: Downlink TBF Threshold from CS3 to CS4 - DNTHDCSDEGRADE1: Downlink TBF Threshold from CS2 to CS1 - DNTHDCSDEGRADE2: Downlink TBF Threshold from CS3 to CS2 - DNTHDCSDEGRADE3: Downlink TBF Threshold from CS4 to CS3
Note: For more details on how to cope with Abis interface congestion refer to “HUA_2G_Capacity_Optimization_v1.0.pptx” document from Multivendor Team in IMS.
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12. Low Throughput (5) 4. Um interface: - Check if TCH congestion exists on air interface. High CS usage will leave less dynamic PDCHs free for PS service. Refer to Case 4 of present document for handling suggestions on TCH blocking. - Check Radio quality in the cell. Bad quality will negatively affect throughput. Refer to Case 7 of present document for more details on RxQual measurements. - Check UL interference in the cell. High interference will negatively affect UL throughput. Refer to Case 8 of present document for more details on UL interference measurements.
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References • HUA_2G_Capacity_Optimization_v1.0, Multivendor Team, IMS: https://sharenet-ims.inside.nokiasiemensnetworks.com/Overview/D420911578
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THANK YOU
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