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Investigation Flow Chart
Drop Call, Congestion, Handover Analysis & Procedure
Vendor: Ericsson
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Table of Contents
Investigation Flow Chart ....................................................... 1 I. Scope Of Work......................................................... 4
II. Introduction.......................................................... 4
III. Investigation Flow Chart ......................................... 4
IV. Drop Call Analysis .................................................. 5
V. Network Congestion ............................................. 13
VI. Handover Analysis ............................................... 15
VII. Metrica Related Reports ........................................ 26
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I. Scope Of Work
This document describes the procedure for investigating and diagnosing the performance-related network problems and recommends solutions and a checklist to identify and cease the causes thus improving network performance. Since RF parameters, counters, and tools are Vendor-Specific, the analysis described in this document is applicable only to Ericsson equipment. II. Introduction
The network’s key RF performance indices are drop call, congestion, and handover performance. In order to minimize the RF drop rate, resolve network congestion, and improve handover performance, a logical investigation flow chart is proposed in order identify the network faults and eliminate them. Recommendations, parameter check list is also proposed. III. Investigation Flow Chart The flow chart depicted in Fig-1 illustrates the methodology and the procedure used to identify the possible network problem and propose a check list to enable the RF engineer diagnosing the network performance degradation.
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Parameters set according to Best
Practices ?
Current Market Status:- KPI-Traffic
RN Database Audit
Correct Database Parameters
CNA (OSS) Consistency
Check
Any Inconsistencies
?
Correct InconsistenciesCongestion Audit
- Do Capacity Upgrade- Check CLS Parameters- Check Network Availability and Radio Blocked Resources
Any Congestion?
Drop Call Reason Analysis
Note: These steps can be done in parallel
Drops Other>10%, High Sudden Loss
Drops?
Low SS_UL Drops High?
O&M-Check H/W, T1s
Check for Faulty RBS H/W- Alarm Supervision- MRR
Identify cells needing TMAs(Using Stats and Link Budget)
Low SS_BL Drops High?
- Identify areas need Power Increase:TCC, S/W Power Boost, New Sites, High Gain Antennas, TDU
- Neighbor Optimization using NCS & Neighbor relations check
Quality Drops High?
Identify:- Boomer Sites- Areas with Bad Frequency Plan
Propose Solutions:- Power Decrease- Frequency Retunes- Antenna Downtilts- Antenna Changes- Antenna Height (RAD) Changes- BCCH in OL- AMR Parameter retune
Does Market meet KPI and Coverage Targets?
Performance Analysis using:- Metrica- Drive Test- MRR- NCS/NOX/FAS/FOX
Identify Worst Performing Cells
EXIT/FA
Possible Solutions:- Power Increase/Decrease- Frequency Retunes- Antenna Downtilts- Antenna Changes- Neighbor Addition/Deletion- Parameter retune
Investigation Flow Chart
No
Yes
Yes
No
Yes
No
Yes
No
Yes
No
Yes
No
Yes
No
YesNo
Fig-1 Investigation Flow Chart
IV. Drop Call Analysis
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Drop Call Reasons……… Low SS-UL Only Parameter Parameter Name MML Command Parameter Description
SSOFFSETULAFR RLIHP UL offset for signal strength in Db in AFR
SSDESULAFR RLAPP Signal strength for the UL AMR FR. Numeral 47 - 110
LOWSSUL RAEPP UL low SS limit used for counter – not used in HO algorithm
RLINKUP RLLDP Radio Link Timeout counter value on the uplink
SSDESUL RLPCP UL signal strength
SSLENUL RLPCP UL length of signal strength filter
Counter Counter Name Object Type Counter Description Metrica Report Heading
TFDISSUL CLTCHDRF Total No of dropped TCH-FR connections due to low SS on UL
CELLTCHD R1_30MIN
THDISSUL CLTCHDRF Total No of dropped TCH-HR connections due to low SS on UL
CELLTCHD R1_30MIN
TFDISSULA CLTCHDRF Total No of dropped AMR-FR TCH connections due to low SS on UL
CELLTCHD R1_30MIN
TFHISSULA CLTCHDRF Total No of dropped AMR-HR TCH connections due to low SS on UL
CELLTCHD R1_30MIN
TFNDROP CELTCHF Total No of dropped FR TCH in UL subcell.
CELLTCHF 1_30MIN
THNDROP CELTCHF Total No of dropped HR TCH in UL subcell.
CELLTCHF 1_30MIN
TFCASSALL CELTCHF No. of assignment complete messages on TCH-FR for all MS power classes.
CELLTCHF 1_30MIN
Low SS-DL Only Parameter
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Parameter Name Ass. MML CommandParameter Description
SSOFFSETDLAFR RLIHP DL offset for signal strength in dB in AFR
SSDESDLAFR RLAPP Signal strength for the DL AMR FR. Numeral 47 - 110
LOWSSDL RAEPP DL low SS limit used for counter – not used in HO algorithm
RLINKT RLSSP Radio link Timeout counter value for MS (D/L)
SSDESDL RLBCP Downlink desired signal strength at MS
REGINTDL RLBCP Downlink Power control regulation interval/period
SSLENDL RLBCP Length of Signal Strength averaging filter D/L DPC
BSPWRMIN RLBCP Minimum DL dynamic power level
MSTXPWR RLCPP Max. MS power while maintaining a TCH connection
BSPWRB RLCPP Base Station output power in dBm for the BCCH RF channel number.
BSPWRT RLCPP Base Station output power in dBm for the non-BCCH RF channel numbers.
BSPWR RLLOP Tx power on BCCH carrier (at reference point)
BSTXPWR RLLOP Tx power on non-BCCH carrier (at reference point)
Counter Counter Name Object Type Counter Description Metrica Report Heading
TFDISSDL CLTCHDRF Total No of dropped TCH-FR connections due to low SS on DL
CELLTCHD R1_30MIN
THDISSDL CLTCHDRF Total No of dropped TCH-HR connections due to low SS on DL
CELLTCHD R1_30MIN
TFDISSDLA CLTCHDRF Total No of dropped AMR-FR TCH connections due to low SS on DL
CELLTCHD R1_30MIN
TFHISSDLA CLTCHDRF Total No of dropped AMR-HR TCH connections due to low SS on DL
CELLTCHD R1_30MIN
TFNDROP CELTCHF Total No of dropped FR TCH in UL subcell.
CELLTCHF 1_30MIN
THNDROP CELTCHF Total No of dropped HR TCH in UL subcell.
CELLTCHF 1_30MIN
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TFCASSALL CELTCHF No. of assignment complete messages on TCH-FR for all MS power classes.
CELLTCHF 1_30MIN
Low SS-BL Parameter Parameter Name MML Command Parameter Description
BSRXMIN RLLOP Min. SS at BTS to consider n-cell a h/o candidate
MSRXMIN RLLOP Min. SS at MS to consider n-cell a h/o candidate
HIHYST RLNRP SS hysteresis when evaluating high SS cells
LOHYST RLNRP SS hysteresis when evaluating low SS cells
BSRXSUFF RLLOP Sufficient SS at a BTS to consider cell for PL rank
MSRXSUFF RLLOP Sufficient SS at MS to consider cell for PL ranking
SSEVALSD RLLFP RxLev averaging filter type on TCH
SSRAMPSD RLLFP Time to ramp up N-cell measurements on TCH
SSLENSD RLLFP Length of RxLev average. filter for SSEVALSD = 6 - 9
SSLENSI RLLFP Length of RxLev average filter for SSEVALSI = 6 - 9
MSTXPWR RLCPP Max. MS power while maintaining a TCH connection
BSPWRB RLCPP Base Station output power in dBm for the BCCH RF channel number.
BSPWRT RLCPP Base Station output power in dBm for the non-BCCH RF channel numbers.
BSPWR RLLOP Tx power on BCCH carrier (at reference point)
BSTXPWR RLLOP Tx power on non-BCCH carrier (at reference point)
Counter
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Counter Name Object Type Counter Description Metrica Report Heading
TFDISSBL CLTCHDRF Total No of dropped TCH-FR connections due to low SS on BL
CELLTCHD R1_30MIN
THDISSBL CLTCHDRF Total No of dropped TCH-HR connections due to low SS on BL
CELLTCHD R1_30MIN
TFDISSBLA CLTCHDRF Total No of dropped AMR-FR TCH connections due to low SS on BL
CELLTCHD R1_30MIN
TFHISSBLA CLTCHDRF Total No of dropped AMR-HR TCH connections due to low SS on BL
CELLTCHD R1_30MIN
TFNDROP CELTCHF Total No of dropped FR TCH in UL subcell.
CELLTCHF 1_30MIN
THNDROP CELTCHF Total No of dropped HR TCH in UL subcell.
CELLTCHF 1_30MIN
TFCASSALL CELTCHF No. of assignment complete messages on TCH-FR for all MS power classes.
CELLTCHF 1_30MIN
Bad RXQual-UL Only Parameter Parameter Name MML Command Parameter Description
QLIMUL RLLUP RxQual threshold on uplink (at BTS) for h/o. Lower threshold used for cells hopping over 6 or more frequencies
QLIMULAFR RLLUP Quality limit UL for handover. Numeral 0 - 100
QOFFSETULAFR RLIHP UL offset for quality in dtqu in AFR
QDESULAFR RLAPP Quality for the UL AMR FR. Numeral 0 - 70
QDESUL RLPCP Desired RxQual at BTS Rx QLENUL RLPCP Length of UL quality filter
BADQUL RAEPP UL BQ limit used for urgency counter – not used in HO algorithm
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Counter Counter Name Object Type Counter Description Metrica Report Heading
TFDISQAUL CLTCHDRF Total No of dropped TCH-FR connections due to bad quality on UL.
CELLTCHD R2_30MIN
THDISQAUL CLTCHDRF Total No of dropped TCH-HR connections due to bad quality on UL.
CELLTCHD R2_30MIN
TFDISQAULA CLTCHDRF Total No of dropped AMR-FR TCH connections due to bad quality on UL.
CELLTCHD R2_30MIN
THDISQAULA CLTCHDRF Total No of dropped AMR-HR TCH connections due to bad quality on UL.
CELLTCHD R2_30MIN
TFNDROP CELTCHF Total No of dropped FR TCH in UL subcell.
CELLTCHF 1_30MIN
THNDROP CELTCHF Total No of dropped HR TCH in UL subcell.
CELLTCHF 1_30MIN
TFCASSALL CELTCHF No. of assignment complete messages on TCH-FR for all MS power classes.
CELLTCHF 1_30MIN
Bad RXQual-DL Only Parameter Parameter Name MML Command Parameter Description
QLIMDL RLLUP
RxQual threshold on downlink (at MS) for h/o. Lower threshold used for cells hopping over 6 or more frequencies
QLIMDLAFR RLLUP Quality limit DL for handover. Numeral 0 - 100
QOFFSETDLAFR RLIHP DL offset for quality in dtqu in AFR
QDESDLAFR RLAPP Quality for the DL AMR FR. Numeral 0 - 70
QDESDL RLBCP Desired Qual in DL
BADQDL RAEPP DL BQ limit used for urgency counter – not used in HO algorithm
Counter Counter Name Object Type Counter Description Metrica Report Heading
TFDISQADL CLTCHDRF Total No of dropped TCH-FR connections due to bad quality on DL.
CELLTCHD R2_30MIN
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THDISQADL CLTCHDRF Total No of dropped TCH-HR connections due to bad quality on DL.
CELLTCHD R2_30MIN
TFDISQADLA CLTCHDRF Total No of dropped AMR-FR TCH connections due to bad quality on DL.
CELLTCHD R2_30MIN
THDISQADLA CLTCHDRF Total No of dropped AMR-HR TCH connections due to bad quality on DL.
CELLTCHD R2_30MIN
TFNDROP CELTCHF Total No of dropped FR TCH in UL subcell.
CELLTCHF 1_30MIN
THNDROP CELTCHF Total No of dropped HR TCH in UL subcell.
CELLTCHF 1_30MIN
TFCASSALL CELTCHF No. of assignment complete messages on TCH-FR for all MS power classes.
CELLTCHF 1_30MIN
Bad RXQual-BL Parameter Parameter Name MML Command Parameter Description
BQOFFSETAFR RLNRP Signal strength corridor in dB for bad quality urgency handover. Numeral 0 - 63
BQOFFSET RLNRP Bad RxQual h/o corridor or negative hysteresis
DMQB RLDMP Quality based switch from HR ->FR allow switch
DMQBAMR RLDMP Bad radio quality threshold to trigger for an IHO HR ->FR
DMQG RLDMP Quality based switch from FR ->HR allow switch
QEVALSD RLLFP RxQual averaging filter type on TCH
QLENSI RLLFP Length of RxQual average filter for QEVALSI = 6 - 9
QLENSD RLLFP Length of RxQual average filter for QEVALSD = 6 - 9
TINIT RLLBP Min. time before handover after call init. or handover
Counter Counter Name Object Type Counter Description Metrica Report Heading
TFDISQABL CLTCHDRF Total No of dropped TCH-FR connections due to bad quality on BL
CELLTCHD R2_30MIN
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THDISQABL CLTCHDRF Total No of dropped TCH-HR connections due to bad quality on BL
CELLTCHD R2_30MIN
TFDISQABLA CLTCHDRF Total No of dropped AMR-FR TCH connections due to bad quality on BL
CELLTCHD R2_30MIN
THDISQABLA CLTCHDRF Total No of dropped AMR-HR TCH connections due to bad quality on BL
CELLTCHD R2_30MIN
TFNDROP CELTCHF Total No of dropped FR TCH in UL subcell.
CELLTCHF 1_30MIN
THNDROP CELTCHF Total No of dropped HR TCH in UL subcell.
CELLTCHF 1_30MIN
TFCASSALL CELTCHF No. of assignment complete messages on FR-TCH for all MS power classes.
CELLTCHF 1_30MIN
Excessive TA Parameter Parameter Name MML Command Parameter Description
MAXTA RLLDP
Maximum timing advance permitted before disconnection. Normal cell can work to 63. RBS200 Xrange cell with SPP cards can work to 133 and new RBS2000 extended range hardware can work to 219.
TALIM RLLUP Timing advance threshold for handover
TAAVELEN RLLBP Timing Advance (TA) averaging window length
PTIMTA RLLPP Duration of penalty PSSTA for TA h/o
PSSTA RLLPP SS penalty on cell from which h/o occurs (TA)
Counter Counter Name Object Type Counter Description Metrica Report Heading
TFDISTA CLTCHDRF Total No of dropped FR TCH connections at excessive TA.
CELLTCHD R1_30MIN
THDISTA CLTCHDRF Total No of dropped HR TCH connections at excessive TA.
CELLTCHD R1_30MIN
TFDISTAA CLTCHDRF Total No of dropped AMR-FR TCH connections at excessive TA.
CELLTCHD R1_30MIN
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THDISTAA CLTCHDRF Total No of dropped AMR-HR TCH connections at excessive TA.
CELLTCHD R1_30MIN
TFNDROP CELTCHF Total No of dropped FR TCH in UL subcell.
CELLTCHF 1_30MIN
THNDROP CELTCHF Total No of dropped HR TCH in UL subcell.
CELLTCHF 1_30MIN
TFCASSALL CELTCHF No. of assignment complete messages on TCH for all MS power classes, FR-UL.
CELLTCHF 1_30MIN
Sudden Loss Parameter
Check the MAIO Assignment, HSN, Freq. Allocation of the DCHNO's, T1 and/or Radio Outages, DXU Faults, etc. Run RXMFP on the CF for faulty H/W, and run DTQDP on the DIP for T1 outages and slip freq errors.
Counter Counter Name Object Type Counter Description Metrica Report Heading
TFSUDLOS CLTCHDRF Sudden loss of FR-TCH connections.
CELLTCHD R1_30MIN
THSUDLOS CLTCHDRF Sudden loss of HR-TCH connections.
CELLTCHD R1_30MIN
TFSUDLOSA CLTCHDRF Sudden loss of AMR-FR TCH connections.
CELLTCHD R1_30MIN
THSUDLOSA CLTCHDRF Sudden loss of AMR-HR TCH connections.
CELLTCHD R1_30MIN
TFNDROP CELTCHF Total No of dropped FR TCH in UL subcell.
CELLTCHF 1_30MIN
THNDROP CELTCHF Total No of dropped HR TCH in UL subcell.
CELLTCHF 1_30MIN
TFCASSALL CELTCHF No. of assignment complete messages on TCH for all MS power classes, FR-UL.
CELLTCHF 1_30MIN
V. Network Congestion Feature/Parameter Cell Load Sharing Parameter Name MML Command Parameter Description
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CLSSTATE RLLCI/E Cell load sharing
active/inactive for a cell
HOCLSACC RLLCP
Enable/disable acceptance of incoming h/o due to Load Sharing
CLSLEVEL RLLCP
% Idle channel free level at which shedding of calls is started
CLSACC RLLCP
% Idle channel free level, below which no shedded call is accepted by target cell
RHYST RLLCP
Hysteresis reduction factor (how much of hysteresis zone is used for call shedding)
CLSRAMP RLLCP Time interval in which
hysteresis is ramped down Load Distribution SCLD RLLLC Subcell load distribution
SCLDLL RLLLC Subcell Load Distribution
Lower Limit
SCLDUL RLLLC Subcell Load Distribution Upper Limit
AMR DMQGAMR RLDMP Bad Radio Quality threshold to trigger for an IHO HR->FR
DMSUPP RLDMP
Switch to activate Dynamic allocation of HR & FR Codec Sets
DTHAMR RLDHP Packing threshold for AMR
HR Calls. Counters Counter Name Object Type Metrica Report Heading Counter Description
CCONG CLSDCCHO CELLSDCC H2_30MIN Congestion counter for UL subcell. Stepped each time an allocation attempt fails due to SDCCH congestion.
CTCONGS CLSDCCH CLSDCCH Congestion time counter for UL subcell. Stepped each second all available SDCCH channels are busy.
CNRELCONG CLSDCCH CELLSDCC H3_30MIN
Number of released connections on SDCCH due to TCH or Transcoder (TRA) congestion.
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TFNRELCONG CELTCHF CELLTCHF 2_30MIN
Number of released TCH-FR signaling connections due to transcoder resource congestion during immediate assignment on TCH.
THNRELCONG CELTCHF CELLTCHF 2_30MIN
Number of released TCH-HR signaling connections due to transcoder resource congestion during immediate assignment on TCH.
TFCONGSAS CELTCHF CELLTCHF 2_30MIN
Number of congestion at TCH-FR assignment or immediate assignment in UL subcell.
THCONGSAS CELTCHF CELLTCHF 2_30MIN
Number of congestion at TCH-HR assignment or immediate assignment in UL subcell.
TFCONGSHO CELTCHF CELLTCHF 2_30MIN Number of congestion at incoming handover in UL subcell- for TCH-FR
THCONGSHO CELTCHF CELLTCHF 2_30MIN Number of congestion at incoming handover in UL subcell- for TCH-HR
TFTCONGS CELTCHF CELLTCHF 2_30MIN Soft Congestion time counter for UL subcell- for TCH-FR
THTCONGS CELTCHF CELLTCHF 2_30MIN Soft Congestion time counter for UL subcell- for TCH-HR
TFTHARDCONGS CELTCHF CELLTCHF 2
Hard congestion time counter for UL subcell. The counter starts to increment only when it has not been possible to allocate a channel with the help of any type pf pre-emption.
VI. Handover Analysis
General HO Problems
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Internal HO Check List- Actions
Interference
Check the results from Co-Channel interference and Drop Call Analysis
Wrong Neighboring Cell Definition & Faulty Exchange Properties
Check the results from the radio related data check
Faulty Parameter Settings related to HO Check the results from the radio related data check
Too many Measurement Frequencies (more than 16) in theActive BA list
This can result in fewer samples per frequency and less accurate HO decision
Too few (or even too many) defined neighboring cells Check the results from the radio related data check
Software problems such as Congestion. Check the results from the SAE & EOS Analysis
Faulty H/W Check the faults by running the RXMFP on the TG
External HO & Inter MSC HO Check List- Actions
MSC Definition
The MSC's to which Inter-MSC HO shall be performed have to be defined as neighboring MSC.
Address Definition
The address definitions have to be consistent in all MSC's
Software Routes
SW Routes for the inter MSC HO have to be defined properly
C7 Links The C7 Link performance shall be checked
BSC Definition The BSCs have to be defined properly in the MSCs
Investigation Analysis Rules Description
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Rule # 1
The worst cell analysis is based on internal incoming HO on cell level
Rule # 2 The problem with HO can be traced on the target cell
Rule # 3
The worst cell analysis should not include cells with extremely low HO rates- At least 50 HO attempts..!
Worst Cell Analysis on Cell Level Check List- Actions
Follow the General Procedure described above Shown under "General HO Problems"
HO Reversion Rate
If the HO Reversion rate is high (>5-6%), for a cell, and there is no strong indication of interference problem in the target cell => Check the BTS error log and a site visit need to be scheduled to check the antenna and its near parts.
HO Lost calls
Check the HO lost of total dropped calls in the cell. If too many calls are dropped during HO=> Check the drop call report.
Congestion
Check the area around the investigated cell for cells with congestion (see the TCH and SDCCH analysis reports). Congestion in surrounding cells can lead to that a bad HO candidate has to be selected.
Worst Cell Analysis on Cell relation Level Check List- Actions
HO Behavior
Check the HO behavior for concerned cell relations (both ways); e.g. the number of HO decisions leading to HO attempts.
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HO reasons
Check the HO reasons related to HO decisions (bad quality, signal strength, etc) for concerned cell relations (both ways).
HO successful rates
Check the rate of successful HO back to old cell within 10 seconds for the concerned cell relations
Coverage Maps
Look for areas with bad coverage. Low signal strength during HO will make the MS more sensitive for UL- and DL interference.
Cell Map
Study the cell map. Check if there is any neighboring cells close to the concerned cell which are missing in the cell relation statistics of have low number of HO commands registered.
Results and Recommendations Actions
Missing Neighbors Cell Relations are found Add neighbors and/or run NCS reports
BTS Sites which are suspected to have H/W issues Recommend site visits and Field test=> contact FOPS
Faulty Parameter Settings affecting the HO performance
Recommend parameter changes- check the HO parameters and compare to the standard parameter settings
Too many Measurement Frequencies in the active BA list
Remove unnecessary cell relations and recommend fewer measurement frequencies
Coverage Holes are affecting HO performance Expand with more cells in affected areas.
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Problems with Congestion
Recommend expansion with more TRX's in affected cells or recommend cell splits, micro cells or new sites (This should be associated with the TCH/SDCCH analysis
Interference affecting the HO performance in specific areasBCCH Frequency change/retune
Troubleshooting Too Few Handover Attempts or No Handovers Possible Reasons Troubleshooting Cell Split Layout- Distance between cells or antenna directions Natural reasons
TCH Congestion- for Target Cell
Check HO congestion report and HO decision successful rate
Parameter settings: for CO-BCCH/CO-BSIC in 2 ncells Change BSIC for one or more ncells
Parameter settings: Missing MBCCHNO Add missing MBCCHNOs
Parameter settings: Too many MBCCHNO Remove unnecessary MBCCHNOs
Parameter settings: Too high hysteresis Adjust the hysteresis to lower value
Parameter settings: Low O/P Power in target cell Increase BTS Output Power
Parameter settings: NCCPERM wrong Add missing NCC to NCCPERM
HW-Errors: TRU/CDU error in target cell Check BTS Error Log- Site visit if necessary
HW-Errors: Antenna/Feeder installation error Check BTS Error Log- Site visit if necessary
HW-Errors: Synchronization problems Drive test- Site Visit HW-Errors: Target cell blocked by buildings Site visit
Interference: Target cell BCCH is interfered Frequency planning and drive test
Unsuccessful (Lost) Handovers Possible Reasons Troubleshooting
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Cell Split layout: The neighboring cell is far away
Investigate the ncell relation if it is possible to remove the relation
Congestion: High congestion in target cell may lead to dragged calls and unsuccessful HO's
Check TCH Congestion rate in target cell and/or HO decision success rate. Additional TCH capacity required. Short term solution is to activate the cell load sharing and/or use offsets to move the cell borders.
Interference: DL Interference in serving and/or target cell results in lost HO's
Check reasons for HO, check HO reasons for target cell in opposite direction. Check frequency plan. Run CTR or perform drive test using TEMS
Too many Measurement Freqs.
MBCCHNOs >16 will decrease the accuracy of the mobile measurements to locate the best 6 servers. Many measurement freqs mean fewer samples per frequency and problem for mobiles o decode the BSIC. Check the number of MBCCHNOs
Unbalanced Power Link Budget
DL is stronger than UL in serving cell. The MS cannot receive the HO command message. Drop call due to Low SS or handover lost as result. Too high BTS output power. Run CTR and/or MRR
Handover Reversions Possible Reasons Troubleshooting
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UL Interference in target cell
Check drop reasons for target cell. Check HO reasons for target cell. Run MRR and/or CTR. Check ICM band in target cell. Measure with spectrum analyzer on site for possible (external) source.
DL interference in Serving Cell- The MS cannot detect the HO Command Message
Check drop call reasons for serving cell. Check the HO reasons for serving cell. Run MRR and/or CTR. Check Freq Plan.
Unbalanced Link Power Budget- DL is stronger than UL in target cell
Too high BTS O/P Power. Too low MS power settings. Run MTR, CTR and/or MRR to check power balance.
Lower Power on TCH than on BCCH in Target Cell Check power parameter settings. Check BTS error Log
Receive Antenna Problems- Only if separate TX/RX antennas are installed
Run MTR/CTR and/or MRR to check power balance. Check antenna installation on site.
Co-BCCH/BSIC in two ncells- The MS measures BCCH from wrong cell
Run Consistency Check in OSS. Check BCCH/BSIC Plan
Co-BCCH/TCH & Co-BSIC in two ncells
The MS measures a strong TCH and detect BSIC from a weak BCCH in another ncell. Check the freq/BSIC plan and run CTR
Ping-Pong Handovers Possible Reasons Troubleshooting
Wrong Parameter Settings
Hysteresis can be too low. Urgency HO can be triggered too early. Check hysteresis parameters. Check HO reasons
Lower O/P Power on TCH than BCCH Check power parameter settings. Check BTS error log
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Coverage Holes
Coverage holes can lead to ping pong HOs especially for slow moving mobiles. The coverage problem might be shadowing by high buildings and straight streets with good coverage from another nearby BTS. Run CTR, MRR or drive test by TEMS. Reduce the Hysteresis and shorten the signal strength filters. Long term solutions is to add coverage.
No Dominant Server
Several possible equal signals from two or more base stations might lead to a Ping Pong effect. This is valid for slow moving vehicles. Often, this situation also causes bad quality and finally a high ratio of dropped calls. Long term solution is to add sites. A short term solution might be is to re-direct the antennas, change antenna types or tilt, to get sharper borders.
Parameters
Parameter Name MML Command Parameter Description
IBHOASS RLLBP Flag to enable assignment to another cell inter-BSC
IBHOSICH RLLBP Flag to enable SDCCH handover inter-BSC
IHOSICH RLLBP Flag for enabling intra-cell handover on SDCCH
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HOCLSACC RLLCP Enable/disable acceptance of incoming h/o due to Load Sharing
SCHO RLLCP Flag to enable SDCCH handover
EXTPEN RLLCP Flag to enable penalty "transfer" for inter-BSC h/o
HYSTSEP RLLCP SS separator for HIHYST and LOHYST
IHO RLIHP Flag enabling intra-cell handover on a sub-cell
MAXIHO RLIHP
Max. no. of consecutive intra-cell handovers allowed. For OL / UL cells it must always be less than the no of CHGR in the subcell
TMAXIHO RLIHP
Maximum time between intra-cell handovers to consider them as consecutive.
TIHO RLIHP Time for which intra-cell h/o inhibited
SSOFFSETUL RLIHP Offset FQSS function along RxLev axis (uplink)
SSOFFSETDL RLIHP Offset FQSS function along RxLev axis (downlink)
QOFFSETUL RLIHP Offset FQSS function along RxQual axis (uplink)
QOFFSETDL RLIHP Offset FQSS function along RxQual axis (downlink)
SSOFFSETULAFR RLIHP UL offset for signal strength in Db in AFR
QOFFSETULAFR RLIHP UL offset for quality in dtqu in AFR
SSOFFSETDLAFR RLIHP DL offset for signal strength in dB in AFR
QOFFSETDLAFR RLIHP DL offset for quality in dtqu in AFR
KHYST RLNRP Hysteresis applied when both cells ranked on SS
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KOFFSET RLNRP Offset applied when both cells are ranked on SS
LHYST RLNRP Hysteresis applied when both cells ranked on PL
LOFFSET RLNRP Offset applied when both cells are ranked on PL
TRHYST RLNRP Hysteresis when in transition between K and L
TROFFSET RLNRP Offset when in transition between K and L
AWOFFSET RLNRP Assignment to worse cell negative hysteresis
BQOFFSETAFR RLNRP
Signal strength corridor in dB for bad quality urgency handover. Numeral 0 - 63
BQOFFSET RLNRP Bad RxQual h/o corridor or negative hysteresis
LOHYST RLNRP SS hysteresis when evaluating low SS cells
HIHYST RLNRP SS hysteresis when evaluating high SS cells
OFFSET RLNRP SS offset
CAND RLNRP
Candidate type: Identifier AWN (assignment to worse cell), NHN (normal handover) or BOTH
SSRAMPSD RLLFP Time to ramp up N-cell measurements on TCH
SSRAMPSI RLLFP Time to ramp up N-cell measurements on SDCCH
QLIMULAFR RLLUP Quality limit UL for handover. Numeral 0 - 100
QLIMDLAFR RLLUP Quality limit DL for handover. Numeral 0 - 100
TALIM RLLUP Timing advance threshold for handover
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PTIMHF RLLPP Duration of penalty PSSHF for handover failure
PTIMBQ RLLPP Duration of penalty PSSBQ for RxQual h/o
PTIMTA RLLPP Duration of penalty PSSTA for TA h/o
PSSHF RLLPP SS penalty applied to a cell to which h/o fails
PSSBQ RLLPP SS penalty on cell from which h/o occurs (RxQual)
PSSTA RLLPP SS penalty on cell from which h/o occurs (TA)
PSSTEMP RLLHP Size of temp. penalty on meas. From new n-cells
PTIMTEMP RLLHP Time of temp. penalty on meas. From new n-cells
Counters
Counter Name Counter Description
HOVERCNT No of HO commands sent to the MS
HOVERSUC No of successful HO's to the neighboring cell
HORTTOCH
No of HO's that result in a return to the old channel after a failure of a HO attempt to a neighboring cell
HODUPFT
No of successful HO's back to the old cell within 10 seconds.
HOTOKCL HO attempts made to better K-Cell. (This is for Ericsson-1 Alg.
HOTOLCL HO attempts made to better L-Cell.
HOTOHCS HO attempts due to HCS
HODWNQA No of HO attempts due to bad DL quality
HOUPLQA No of HO attempts due to bad UL quality
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HOEXCTA No of HO attempts due to excessive TA
HOASBCL No of assignment attempts to better cell
HOASWCL No of assignment attempts to worst cell
HOSUCBCL No of successful assignment attempts to better cell.
HOSUCWCL No of successful assignment attempts to worst cell.
HOATTLSS No of HO attempts when the serving cell is a Low SS cell.
HOATTHSS No of HO attempts when the serving cell is a High SS cell.
HOATTHR No of HO attempts at high handover rate.
HOSUCHR No of successful HO's at high handover rate.
VII. Metrica Related Reports
Drop Call Analysis
Metrica Reports
Drop Call Analysis/Daily Reports/ Ericsson Drop Analysis Report
AMR Reports/Reports/Ericsson AMR Cell Drop Report
AMR Reports/Reports/Ericsson AMR BSC Drop Report
AMR Reports/Summary Reports/Ericsson AMR MOUs Per Drop calls Report
AMR Reports/Summary Reports/Ericsson AMR BSC MOUs Per Drop calls Report
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Congestion
Metrica Reports Radio Network BSS/Daily Reports/Cell TCH Traffic Report
Radio Network BSS/Summary Reports/Cell TCH Traffic
Radio Network BSS/Summary Reports/BSS Cell TCH
Radio Network BSS/Summary Reports/Cell Blocking BSS TCH Availability/Reports/BSS Avail Cell Report BSS TCH Availability/Reports/BSS Avail BSC Report AMR Reports/Reports/Ericsson AMR Cell Reports AMR Reports/Reports/Ericsson AMR Traffic Cell Report AMR Reports/Reports/Ericsson AMR Traffic BSC Report Radio Network BSS/Daily Reports/Cell SDCCH Traffic Report
H/O Analysis
Metrica Reports Radio Network BSS/Daily Report/Cell Handover
Radio Network BSS/Summary Reports/Cell Handover
Radio Network BSS/Summary Reports/HO Trending Report