gsm handbook

GSM OPTIMIZATIONHANDBOOK

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1. Introduction.........................................................................................................32. Support Arrangement..........................................................................................43. Optimisation Team Structure..............................................................................54. Bad Perfromance FisH Bone diagram................................................................65. Information Preparation......................................................................................76. General Optimisation Proceedure......................................................................87. Alarm Analysis....................................................................................................98. Statistics Analysis Procedure...........................................................................109. Drive Test..........................................................................................................13

9.1. Drive Test Reminder..................................................................................139.2. Drive Test Log Investigation Consideration...............................................13

10. Frequeny Planning .........................................................................................1410.1. BCCH and BSIC planning criteria............................................................1410.2. Frequency Assignment Criteria................................................................1410.3. Frequency Retune Procedure..................................................................15

11. Add Neighbor Criteria.....................................................................................1512. High Rise Building Coverage..........................................................................1613. Maximum System Configuration.....................................................................1614. HDPC Setting Template.................................................................................18

14.1. TX Power and Power Control...................................................................1814.2. Handover..................................................................................................2114.3. Multiband..................................................................................................2314.4. Miscellaneous...........................................................................................23

15. Tools Available................................................................................................2516. Problem Root Cause ......................................................................................26

16.1. High SDCCH Blocking.............................................................................2616.2. High TCH Blocking...................................................................................2716.3. SDCCH Access Failure Rate...................................................................2816.4. Handover Failure & Loss..........................................................................2916.5. MSC Connection Rate ............................................................................3016.6. SDCCH and TCH RF Loss.......................................................................3116.7. Power Control...........................................................................................3216.8. Handover Problem...................................................................................3216.9. Others.......................................................................................................33

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1. INTRODUCTIONTeamwork, “listen to order”, cycle time reduction and follow procedure are critical to every successful optimisation.

Below is the optimisation flow chart:

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No

Yes

Data Analysis

Data Preparation

Complete

Optimisation

Data Collection

Satisfactory Result?

2. SUPPORT ARRANGEMENT

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Start optimisation and skill transfer and acquisition

PEG ArrangementOptimisation Flow

Account Team supplies required

information

PEG prepares INFORMATION FOR

OPTIMISTION

PEG audits network in Beijing

PEG derives optimisation plan

OMC Engineer arrives local office to setup data collection platform

Contractor prepares optimisation informationin Beijing

Engineers perform brief audit in Beijing to understand REAL situation

PEG discuss with account teams to identify optimisation targets.

Monthly performance meeting to identify optimisation targets.

Start optimisation

PEG arrives local office to discuss the

optimisation plan with Account Team and

Customer

All engineers return to Beijing to derive plan

Best engineering arrangement arrives at local office

3. OPTIMISATION TEAM STRUCTURE

Job FunctionBSS Controller- Understand fully on BTS maintenance, BSS configuration

Alarm Monitoring, - Monitor daily alarm

Statistics Monitoring- Investigate problem from statistics

D.B. & Feature Controller- Check database and monitor feature deployment process

Drive Test Log Investigator- Investigate problem from drive test log

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Team Leader

D.B. & Feature Controller

Drive Test Log Investigator

Alarm Monitoring

Statistics Monitoring

BSS Controller

MONITORING ACTION

4. BAD PERFROMANCE FISH BONE DIAGRAM

Example of each major problems:a. Database Setting – improper HOPC settingsb. Neighbor – wrong external neighbor’s BCCH or BSIC values, missing

neighborc. Coverage – weak, highly overlapped, improper antenna downtilt and

orientationd. External Interference – microwave, repeater, faulty alarme. Calculation – incorrect statistics equationsf. Cable Connection – no/cross connectiong. Statistics Pegging and Collection – SW problem on statistics pegging, or

retrievalh. Capacity – lack of TRCU, improper channel configuration, lack of RSL, MTL

linksi. Frequency Plan – co-channel, adj-channel, improper BSIC planningj. Software – bugk. Hardware – wrong cable connection, faulty combiner and filter, PCM link

downl. Network Topology – bad site location selection, redundant site deployedm. Signaling – Improper cause value and message sequencen. Mobile – faulty mobile in term of signaling or frequency hopping capabilityo. Documentation – wrong feature/parameter usage description

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FrequencyPlan

Network Topology

Signaling Mobile

Bad Performance

Database Setting Coverage

Software HardwareCapacity

ExternalInterference

Neighbor CalculationStatistics Pegging and Retrieval

Cable Connection

Documentation

5. INFORMATION PREPARATION

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6. GENERAL OPTIMISATION PROCEEDURE

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Data Collection & Check Local Office NetPlan

Information

Data Preparation & NetPlan Information

Correction

Network Audit from1. Alarm2. Statistics3. Database4. Check customer statistics equations

1. Suggest Better Database Setting (Channel Reconfiguration, Standard HOPC, Blocking Timer , Congestion Relief)

2. Capture External Interference3. Frequency Retune for high IOI, BER and TCH_RF_LOSS4. Audit External Neighbor5. Improper ARFCN:BSIC Planning6. GPROC loading7. RSL & MTL Usage

Statistics & DB. mainly on a. SDCCH Access Failureb. CSFRc. Drop Calld. TCH_RF_Losse. HO_Lossf. HO_Failureby ARFCN retune, neighor change and coverage

Hardware

Capacity

Database, Interference & Capacity

Network Topology

FP, Neighobr and Coverage

1 day

Solve Blocking by:a. BCCH Optimisationb. Neighor Optimisationc. Add Radiod. Site Reconfiguratione. Add Sitef. Antenna Refinement

Network Topology Problem due to no available ARFCN is found by:a. Site Replacementb. Coverage Optimisationc. Capacity Dimensioning

TEMS Log & FP. mainly ona. Undecoded BCCHb. Missing Neighborc. HO Failured. Incorrect External Neighbore. Weak Coveragef. High Overlapping

g. use non-dominant serverby ARFCN retune, neighor change and coverage

1. Hardware Fix (Sleeping Cell, OOS TCU, OOS TS2. Path Balance Issue, Faulty TCU from TCH_RF_Loss Issue)3. GCLK shift and frequent Phase Lock Loop failure from Alarm

2 days

2 days

12 days

2 days

2 days

2 days

7. ALARM ANALYSIS

Below lists some important alarms that we focus,a. Critical and major alarmb. Alarms affect voice quality like MSI, KSW, RXCDR, DRIM, DRIc. GCLK affects HOd. Link alarms affect site availability and voice qualitye. XBL alarm affects acknowledgement of OOS CIC

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8. STATISTICS ANALYSIS PROCEDURE

Statistics Tree Diagram

B A D G O O D

P a g i n g N o R e s p o n s eS D C C H A c c e s s F a i l u r e R a t e

M S C A s s i g n m e n t A t t e m p t R a t e( M A _ R E Q _ F R O M _ M S C )

C O N N R e f u s e d

S D R F L o s s

C i p h e r M o d e F a i l( T S M I , I M S I )

T C H B l o c k i n g

T C H A s s i g n m e n t S u c c e s s

C a l l S e t u p S u c e s s R a t e

T C H R F L o s s R a t e

I n t e r - B S S H O L o s s

I n t r a - B S S H O L o s s

I n t r a - c e l l H O L o s s

H O L o s s R a t e

D r o p C a l l R a t e

C a l l S u c e s s R a t e

M S C T C H C o n n e c t i o n R a t e

Firstly, we need to understand account teams and customer performance equation.

Problem Identification from Statistics1. per carrier on HW, external interference, channel interference, coverage

a. PATH_BALANCE for faulty hardware (Every 3 days)b. IOI for external interference and bad channel assignment (Every Day)c. BER for external interference and bad channel assignment (Every Day)d. TCH_RF_LOSS for faulty hardware and bad channel assignment (Every Day)e. CHAN_REQ_FAIL_ROLL for faulty hardware and BCCH and SDCCH coverage footprint difference (Every Day)

2. per cell on usagea. AVAILABLE_TCH and AVAILABLE_SDCCH (Every Day)b. BUSY_SDCCH_MAX, SDCCH Blocking for faulty hardware (Every Day)c. SDCCH_CONGESTION and BUSY_SDCCH_MEAN for phantom RACH (Weekly)d. BUSY_TCH_MAX, TCH Blocking for faulty hardware (Every Day)e. OK_ACC_PROC_SUC_RACH for sleeping cell (Every Day)f. No TOTAL_CALL, OUT_INTRA_BSS_ATMPT, OUT_INTER_BSS_ATMPT (Every Day)g. CONN_REFUSED { - IMSI_DETACH} for CIC blocking (Weekly)h. cell without any statistics for OOS cell (Every Day)

3. per cell on dual band mobile usagea. MA_ACCESS_BY_TYPE (Weekly)b. MS_TCH_USAGE_BY_TYPE (Weekly)

4. per cell on Cipher Modea. CIPHER_MODE_FAIL (Weekly)

5. per cell on loadinga. BSS GPROC loading mean 70% (Weekly)

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b. MSC Processor Loading and Subscriber (Weekly)c. RSL TX, RX Utilisation mean 25% (Weekly)d. MTL TX, RX Utilisation mean 20% (Weekly)e. Pages per second (Weekly)f. ALLOC_SDCCH, ALLOC_SDCCH_FAIL ,OK_ACC_PROC relationship (Weekly)g. HO per call (Weekly)

6. per cell on paginga. PCH_PAGE_Q_DISCARD (Weekly)

7. per cell for BCCH and BSIC planninga. INV_EST_CAUSE_RACH and BAD_HO_REFNUM_MS (Weekly)

8. per cell inter-BSS HO monitoringa. OUT_INTER_BSS_MS_FAIL + OUT_INTER_BSS_MS_LOST = HP_MSC_REQ_FAIL (not include blocking) (Weekly)b. OUT_INTER_BSS_MS_ATMPT = HO_MSC_REQ_FAIL + HO_MSC_REQ_OK (Weekly)

Below all are daily task:9. evaluate target

a. calculate system total call, total loss, ho loss, rf loss, drop call%b. calculate how many total loss reduction is required to achieve the goalc. do (b) again for other statistics

10. select worst cells and BSCsd. pick worst 20 cells and worst 5 BSCs

11. per cell on TCH Assignmenta. CONN_REQ_TO_MSCb. MA_REQ_FROM_MSC, CONN_REFUSED { - IMSI_DETACH}, if CONN_REFUSED is high, MSC procedure is required.c. MA_CMD_TO_MS_BLKD, MA_CMD_TO_MSd. MA_FAIL_FROM_MS, MA_COMPLETE_TO_MSC (same as TOTAL_CALL)

12. per cell on HO Causea. OUT_HO_CAUSE

13. per cell on HO Failurea. OUT_INTRA_BSS_HO_FAIL, OUT_INTER_BSS_HO_FAIL, IN_INTRA_BSS_HO_FAIL and IN_INTER_BSS_MS_NO_SEIZE for ho failues

14. per cell on TCH_RF_LOSS, SD_RF_LOSS, HO Lossa. TCH_RF_LOSS, OUT_INTRA_BSS_HO_REQ, OUT_INTRA_BSS_HO_ATMPT,

OUT_INTER_BSS_HO_REQ, OUT_INTER_BSS_HO_ATMPTb. SD_RF_LOSS and HO_LOSS relationship on cell coveragec. OUT_INTER_BSS_HO_LOSTMS, OUT_INTRA_BSS_HO_LOSTMS,

OUT_INTRA_CELL_HO_LOSTMS

For hardware fix, it usually takes 3 days to fix, hence we suggest to review those statistics every 3 days. For system loading and usage, we will visit them once in a week.Weekly and every 3 days statistics should be reviewed when that corrective action is done.

Special RequestFor growth planning per cell on blocked call setup, we can use ALLOC_TCH_FAIL – HO_FAIL_NO_RESUORCES_INTRA_BSS - HO_FAIL_NO_RESUORCES_INTER_BSS - HO_FAIL_NO_RESUORCES_INTRA_CELL to estimate expanded network total calls.

For coverage analysis and improve MSC connection rate, we can use per LAC ACCESS_PER_RACH – PAGING_RESPONSE. Difference tells us how many no page reponses.

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9. DRIVE TEST

9.1. Drive Test Reminder

i. prepare cell definition fileii. 2mins per calliii. 10-15mins per log fileiv. force to appropriate band (GSM only, DCS only or Dual)v. mark benchmark route per log file in mapvi. mark on maps about (a) drop call (b) weak coverage (c) lot of rxquality (d)

bad coveragevii. fill in drive test problem sheet

9.2. Drive Test Log Investigation Consideration

General TEMS Log Investigation Concern1. check undecoded BCCH – this affects RF loss and creates log of ping pong

handover2. decoded neighbor but no handover is attempted – due to missing neighbor or

incorrect external neighbor path3. focus on drop call and rxqual greater than 4 for non-hopping, 5 for hopping for

at least 4 seconds4. look for handover failure – investigation target cell assigned ARFCN/MA from

ASSIGNMENT COMMAND and HANDOVER COMMAND5. mark down weak coverage area, no dominant server, say less than –85dBm6. mark down highly overlapped area

Besides, be careful that when you see a decoded cell, that cell is not definitely a neighbor of serving, it can be due to serving cell having a neighbor which has same BCCH as decoded cell.

Note: (a) Focus on new site database (b) Due to CCB, no SFH can be deployed (c) Dedicated ARFCN/MA is different from BCCH (d) After Assignment and Handover, the cell ID may not be updated yet due to serious rxquality at DL.

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10. FREQUENY PLANNING

10.1. BCCH and BSIC planning criteria

a. Cells have same BCCH and BSIC that increases TEMS log review troublesome.

b. Nearby cells have same BCCH:BSIC with ARFCN:BSIC.c. Nearby cells have adjacent BCCH with ARFCN and same BSIC.

10.2. Frequency Assignment Criteria

Non-hopping Case

Hopping Case for non-BCCH

BCCH in hopping case is same as the non-hopping case.

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serving cell

serving cell can’t be co- or adj-cahannel

co-channeladjacentchannel

adjacent channel

co-channel

10.3. Frequency Retune Procedure

Frequencies can be grouped into 5 types, they are:-a. same site co- and adj-channel to BCCHb. adjacent site co- and adj-channel to BCCHc. adjacent site co-channel to ARFCNd. same site co-channel to ARFCNe. same site adj-channel to ARFCNf. adjacent site adj-channel to ARFCNg. others ARFCN

Priority of ARFCN retune is from g. to e. for fix and BBH, from g. to d. for SFH. If no available ARFCN can be found, site planning need to be reviewed.Besides, 400k separation is required for CCB.58, 70 shouldn’t be used for BCCH.MCell generates UL interference on channel 50 and 56.

11. ADD NEIGHBOR CRITERIAIn general, LOS and 2nd Round Interferer will be added as neighbor; however, for 3rd Round, this is very network dependant. field knowledge is required to make the decision.

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serving cell LOS interferer2nd Round Interferer

3rd Round Interferer

12. HIGH RISE BUILDING COVERAGEIntroduce high rise building coverage must make sure to have good street coverage.

High Rise Building – provide high level (likely above 8th floor) high rise building coverageMacro – provide low floors and street level coverageMicro – provide street level and indoor coverage

13. MAXIMUM SYSTEM CONFIGURATIONIt is important to understand how system grows from phase to phase. It can be described in 3 phases.

Phase 1: Only macro layer, antenna located at tower top with small downtilt. Antenna uses large vertical beam-width.

Phase 2: Start to introduce micro layer, and increase macro cell downtilt and lower macro cell height of macro antenna.

Phase 3: Introduce high rise building coverage to office building and hotel. Before deploying this kind of coverage, street level coverage MUST be strong enough (likely more than –75dBm) to protect interference from high rise building coverage.

For a mature network which its system rxlevel has reach average –75dBm, it is time for us to deploy SFH to expand system capacity.

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High Rise Building

Macro

Micro

盄盄

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14. HDPC SETTING TEMPLATE

14.1. TX Power and Power ControlTX Power

ParameterCurrentSetting

Suggest Setting

Reason

max_tx_msmax_tx_bts

Downlink Power Control due to Level


Suggest Setting

Reason

decision_alg_num bts_power_control_allowedbts_p_con_ack (TIMER)bts_p_con_interval (TIMER)pow_inc_step_sizepow_red_step_sizerxlev_dl_pc, hreqaverxlev_dl_pc, hreqtdecision_1_dl_rxlev_av_pl_rxlev_dl_pu_rxlev_dl_pdecision_1_n1decision_1_p1decision_1_n2decision_1_p2

Downlink Power Control due to Quality


Suggest Setting

Reason

decision_alg_num bts_power_control_allowedbts_p_con_ack (TIMER)bts_p_con_interval (TIMER)pow_inc_step_sizepow_red_step_sizerxqual_dl_pc, hreqaverxqual_dl_pc, hreqtrxqual_dl_pc, qual_weightdecision_1_dl_rxqual_av_pl_rxqual_dl_pu_rxqual_dl_pdecision_1_n3decision_1_p3decision_1_n4decision_1_p4w_qual

Uplink Power Control due to Level


Suggest Setting

Reason

decision_alg_num

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ms_power_control_allowedms_p_con_ackms_p_con_intervalpow_inc_step_sizepow_red_step_sizerxlev_ul_pc, hreqaverxlev_ul_pc, hreqtdecision_1_ul_rxlev_av_pl_rxlev_ul_pu_rxlev_ul_pdecision_1_n1decision_1_p1decision_1_n2decision_1_p2

Uplink Power Control due to Quality


Suggest Setting

Reason

decision_alg_numms_power_control_allowedms_p_con_ackms_p_con_intervalpow_inc_step_sizepow_red_step_sizerxqual_ul_pc, hreqaverxqual_ul_pc, hreqtrxqual_ul_pc, qual_weightdecision_1_ul_rxqual_av_pl_rxqual_ul_pu_rxqual_ul_pdecision_1_n3decision_1_p3decision_1_n4decision_1_p4w_qual

Data and Hopping Quality Power Control


Suggest Setting

Reason

data_qual_flagl_rxqual_dl_p_datal_rxqual_ul_p_datahop_qual_enabledl_rxqual_dl_p_hoppingl_rxqual_ul_p_hopping

Standard MS HO Power, MS Ho Power Level based on Path Loss Calculations (GSR3)


Suggest Setting

Reason

handover_power_leveluse_derived_ho_power 0 1 Reduce MS UL power and interference

Optimised Power Control (GSR4)


Suggest Setting

Reason

dyn_step_adjdyn_step_adj_fmprpow_inc_step_size_dlpow_inc_step_size_ulpow_red_step_size_dlpow_red_step_size_ul

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Oscillation Prevention for MS Power Control


Suggest Setting

Reason

mspwr_alg

Rapid MS Power Down


Suggest Setting

Reason

rpd_pwr_downrpd_period (TIMER)rpd_triggerrpd_offset

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14.2. HandoverInter-cell Handover


Suggest Setting

Reason

inter_cell_handover_allowed

Intra-cell Handover


Suggest Setting

Reason

intra_cell_handover_allowedho_ack (TIMER)hop_counthop_count_ timer

Uplink Quality


Suggest Setting

Reason

ul_rxqual_ho_allowedrxqual_ul_ho, hreqaverxqual_ul_ho, hreqtrxqual_ul_ho, qual_weightrxqual_ul_ho, qual_pwr_flagrxqual_ul_ho, qual_marginrxqual_ul_ho, adj_qual_margindecision_1_ul_rxqual_av_hl_rxqual_ul_hu_rxqual_ul_hdecision_1_n6decision_1_p6w_qual

Uplink Interference


Suggest Setting

Reason

interfer_ho_allowedrxlev_ul_ho, hreqaverxlev_ul_ho, hreqtrxlev_ul_ho, qual_marginrxlev_ul_ho, adj_qual_margindecision_1_ul_rxlev_av_ihu_rxlev_ul_ihdecision_1_n7decision_1_p7

Downlink Quality


Suggest Setting

Reason

dl_rxqual_ho_allowedrxqual_dl_ho, hreqaverxqual_dl_ho, hreqtrxqual_dl_ho, qual_weightrxqual_dl_ho, qual_pwr_flagrxqual_dl_ho,

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qual_marginrxqual_dl_ho, adj_qual_margindecision_1_dl_rxqual_av_hl_rxqual_dl_hu_rxqual_dl_hdecision_1_n6

decision_1_p6

w_qual

Downlink Interference


Suggest Setting

Reason

interfer_ho_allowedrxlev_dl_ho, hreqaverxlev_dl_ho, hreqtrxlev_dl_ho, qual_marginrxlev_dl_ho, adj_qual_margindecision_1_dl_rxlev_av_ihu_rxlev_dl_ihdecision_1_n7decision_1_p7

Uplink Level


Suggest Setting

Reason

ul_rxlev_ho_allowedrxlev_ul_ho, hreqaverxlev_ul_ho, hreqtdecision_1_ul_rxlev_av_hl_rxlev_ul_hu_rxlev_ul_hdeicion_1_n5decision_1_p5

Downlink Level


Suggest Setting

Reason

dl_rxlev_ho_allowedrxlev_dl_ho, hreqaverxlev_dl_ho, hreqtdecision_1_dl_rxlev_av_hl_rxlev_dl_hu_rxlev_dl_hdecision_1_n5decision_1_p5

Distance


Suggest Setting

Reason

ms_distance_allowedrel_tim_adv, hreqaverel_tim_adv, hreqtdecision_1_tim_adv_av_algms_max_rangedecision_1_n8decision_1_p8

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poor_initial_assignmenttiming_advance_period (TIMER)

Define the interval between timing advance changes

Power Budget


Suggest Setting

Reason

pwr_handover_allowedrxlev_dl_ho, hreqaverxlev_dl_ho, hreqtsurround_cell, hreqavedecision_1_pbgt_rxlev_av_hdecision_1_ncell_rxlev_av_h_calcmax_tx_ms (serving cell)ms_tx_pwr_max_def (internal neighbor default)ms_tx_pwr_max_cell (external neighbor)use_neighbor_pbgt_hreqave

1

Data and Hopping Quality Handover Control


Suggest Setting

Reason

data_qual_flagl_rxqual_dl_h_datal_rxqual_ul_h_datahop_qual_enabledl_rxqual_dl_h_hoppingl_rxqual_ul_h_hopping

14.3. Multiband

Multiband Handover


Suggest Setting

Reason

mb_preferencephase2_classmark_ allowedearly_classmark_sendingearly_classmark_delayinterband_ho_allowedband_preferenceband_preference_modemultiband_reporting

14.4. MiscellaneousCriteria 1


Suggest Setting

Reason

rxlev_min_def 5 rxlev_min_def (internal neighbor default)rxlev_min_cell 5 rxlev_min_cell (external neighbor)

Criteria 2


Suggest Setting

Reason

ho_margin_def 4,5

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Neighboring Cell Processing


Suggest Setting

Reason

ncell_pro 0disuse_cnt_hreqave 0ho_only_max_pwr 1neighbor_journal 0worse_neighbor_ho 0

Alternative Processing of Rxqual Measurements


Suggest Setting

Reason

alt_qual_proc 0 0 Quality Band Unit

Broadcast Control Channel Allocation (BA) Reinitialization


Suggest Setting

Reason

ba_alloac_proc 1

Missing Report


Suggest Setting

Reason

missing_rpt 0 0 Waiting for the actual data

Handover Timer


Suggest Setting

Reason

handover_recongnized_periodbssmap_t7

Link Disconnection


Suggest Setting

Reason

radio_link_timeoutrr_t3109link_about_to_faillink_failfull_pwr_rfloss

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15. TOOLS AVAILABLECOP – Event Counting Tool, Call Trace Product, Generic Look Up, Cell Analysis Tool 2TEMS and SafcoK1103Web StatisitcsNetPlanBSS DatabaseGEP

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16. PROBLEM ROOT CAUSE

16.1. High SDCCH Blocking

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HIGH SD BLOCKING

BUSY_SD_MAX=MAX CONFIGUREDSD

Find faulty TS from BER stats or check alarm

SD_MEAN_HOCDING TIME CONVERGES to

T3101

May due to Phantom RACH and HO access burst, check any same ARFCN and BSICPath Imbalance (SDCCH not on BCCH carrier)

Check Neighbor BCCH being Interfered

Missing Neighbor or incorrect neighbor DB Path, TOTAL_CALL/ALLOC_TCH may be used

Review OK_ACC_PROC like CM_SERVICE_REQ_CALL, PAGE_RESPONSE,LOCATION UPDATE

Neighbor Cell Outage or own cell carrier outage (l carrier can have max 2 SD)

Coverage HoleLot of location

Update?END

Is out_INTRA_BSS_HO_RETURN AND out_INTER_BSS_HO_RETURN A LOT? END

Check neighbor in_intra_BSS_ho_return and in_inter_bss_ho_Seize, if high, Check neighbor 磗 fp

LAC BORDER REDESIGN ，check t3121

No TCH BLOKING, ENABLE CHANNEL RE CONFIGUPATION

Neighbor 磗 tx power reduced

N

N

N

N

Y

Y

Y

Y

16.2. High TCH Blocking

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HIGH TCH BLOCKING

BUSY_TCH_MAX=MAX_CONFIGURED_TCH

Find faulty TS From BER Stats or check alarm

1. Any neighbor 磗 BCCH interfered

2. Missing Neighbor or incorrect Neighbor BSIC

3. Its GCLK SHIFT causes neighbor 磗 bsic undecoded

4. Long timer settingintra_BSS HO_rrt3103 channel release_rrt3109

5. check out_intra_bss_no_return and out_inter_bss_ho_return, it is high

END

6. Check any co-located or close micro-cell,see whether traffic offload is possible by optismisig DB

7. If SD has no blocking. May reconfigure channels or enable channel reconfiguration feature

Find neighbors which has high in_intra_bss_ho_return in_inter_bss_ho_seize then check its fp

9. Coverage hole and improper DT & orientation

10. Add radio to cell without adding new cabinet

8. check adjacent cell busy_tch_max, if the busy_tch_max-8>configured TCH

Site reconfiguration

Reduce ho margin and enable congestion relief

N

Y

Y

N

N

Y

11. Increase of single or dualband MSs.

12. Inappropriate congestion HO setting

16.3. SDCCH Access Failure Rate

Note: SDCCH blocking is excluded.

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LOW SDCCH ACCESS SUCCESS RATE

1. Phantom RACH, check any same ARFCN and BSIC

2. Path Balance, BCCH is OK bat SD carrier not OK

3. Link balance, DB power setting

4. HW Problem, check per carrier chan_req_ms_fail stats. or check alarm

5. UL InterferenceExternal check night line IOIHigh cell siteHigh UL Path LossCo. or adj. channel interference�

6. Excessive TA

16.4. Handover Failure & Loss

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High HO Loss / Failure

1. Poor serving cell HDPC setting

2. Short rr_t31034. Bad fp or external Interference -find % of UL/DL Quality by out_ho_cause

5. HO Failure- Incorrect External Neighbor Database

7. HO failure- Check target cell fp

3. MSC Problem

6. Handover_power_level is max?

8. HW (DRCU, Filter F� ault 9. Radio Calibration

16.5. MSC Connection Rate

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Low MSC Connection Rate

1. Paging Overflow Causing Discard

2. Coverage Hole 3. SD RF loss

4. TCH BLOCKING 5. Infrequent Location Update 6. Cipher Mode Fail

8. MSC Connection Refused (MTL Congested)

7. Proper setting on ms_txpwr_max_cch and ms_txpwr_max_def

9. Call clearing timer (t3109<<radio_link_timeout) causing unclear call generating UL interference

16.6. SDCCH and TCH RF Loss

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High SD & TCH RF LOSS

a. Neighbor´s BCCH Interfered b. External Interferencec. Use guard bandd. Use AMPS frequency

2. Hardware (a)Path balance -idea is 108;≥ 120 (serious UL Path Loss) ;≤ 100 (serious DL Path Loss) (b)Radio -check per carrier RF loss stats (c) Neighbor cell outage (d) GCLK SHIFT

Neighbor Blocking-check (OUT_INTRA_BSS_HO_REQ_OUT_INTRA_BSS_HO_ATTEMPT) or (OUT_INTER_BSS_REQ_TO_MSC_OUT_TNETER_BSS_HO_ATTEMPT) and check neighbor′ s ALLOC_TCH_FAIL

Missing Neighbor, usually by drive test or trace-call

5. Coverage hole, check UL Path Loss

7. SD RF LOSSInconsistent coverageNot enough overlappingNo SDCCH HO

8. Poor HDPC setting

9. Is out_intra_bss_ho_returnand out_inter_bss_ho_return a lot?

END

Check neighbor in_intra_bss_ho_return and in_inter_bss_ho_seize if high, check neighbor′ s fp

N

Y

16.7. Power ControlSudden Power Drop1. Incorrect call clearing timer setting2. Faulty hardware

Slow Power Control1. ho_only_max_pwr is turned on2. Bad xx_p_con_ack and xx_p_con_interval

Power Control Window1. Any external interference2. Frequency planning technique3. Speed of power down and up4. Street or indoor coverage

16.8. Handover ProblemPing Pong Handover1. Bad radio calibration2. Hardware fault3. Negative handover allowed4. Quality handover without turning on qual_pwr flag5. Especially air combing, one of TX, RX antenna is blocked by building

Negative Handover1. Neighbor journal2. qual_margin_flag=03. Bad radio calibration between BCCH and non-BCCH4. Turn on ho_magrin_rxqual feature with default value

No and Delay Handover1. Inappriorate hreqave, hreqt and N & P voting2. Negative handover margin3. Improper setting on handover_recognised_period and bssmap_t74. Improper HO algorithm (Type 4, 6)5. Blocking

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16.9. OthersLow Erlang Usage1. Inappropriate C1, C2 and handover criteria

High Rxqual1. Adjacent site interference2. Same site MAIO assignment problem3. High internal same site hit rate4. External interference like cordless phone, alarm, BTS hardware

Undecode BSIC1. GCLK shift2. BCCH interfered

Spurious Coverage1. Coverage optimization2. TA control

Killed Paging1. Too many access grant block reserved2. Location area too large

No Paging After Mobile is on certain time period1. MSC Location Update Timer < BSS Location Update Timer

No Call Setup1. LACI is different between BSS and MSC2. Cell BAR

Immediate Assignment Reject1. NO SDCCH

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gsm handbook

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