TCH Drop Analysis KPI Formula Total TCH Drop
Total TCH Loss Connection when HO intracell & HO intercell
TCH Drop Rate = NRFLTCH [1-17] + UNIHIALC + UNIHIRLC TNTCHCL [1,2] Total TCH Connection
BSC Surabaya2, Semarang, and Bandung2 have same drop reason series as high contributor, that are : Analysis
Rank 1 2 3 4 5
Reason to Drop _TCHDropD _TCHDropDistRa istRadLinkF dLinkFail ail rate_Nr rate_Nr _TCHDropD _TCHDropDistT20 istT200 0 rate_Nr _TCHDropD _TCHDropDistIn istInterCe terCellHO llHO rate_Nr rate_Nr _TCHDropD _TCHDropDistEq istEquipFai uipFaill rate_Nr rate_Nr _TCHDropD _TCHDropDistHO istHOAccess Access rate_Nr
Correlated with Radio Interface Problems Causing : Radio Link Failure , many loss message until T200 ex AND any unnecessary DB setting : - RDLNKTO / BS - T200 - T3105 , NY1 - T8
While for BSC Yogya have drop reason series as shown below : Rank 1 2 3 4 5
Reason to Drop _TCHDropD _TCHDropDistRa istRadLinkF dLinkFail ail rate_Nr rate_Nr _TCHDropD _TCHDropDistRe istRemTrans mTranscFail cFail rate_Nr rate_Nr _TCHDropD _TCHDropDistT20 istT200 0 rate_Nr _TCHDropD _TCHDropDistIn istInterCe terCellHO llHO rate_Nr rate_Nr _TCHDropD _TCHDropDistHO istHOAccess Access rate_Nr
Call Drop Related Events Can be explained by the following message diagram : TCH Drop with Radio Link Failure Reason
TCH Drop with T200 Expiry Reason
Correlated with Radio Interface Problems Causing : Radio Link Failure , many loss message until T200 exp AND HW problems & wrong DB setting might cause Remote Transc - TRACK Modul Failure -> can be detected from BSC fermaint al will be distributed on whole sites which access to the broken trac - COBA / CU failure - Transmission Flicker - timer setting in DB doesn't meet rule : TTRAU > T8 , TTRAU > ensuring that a signaling failure (T8 and T10) is detected before t
TCH Drop with HO Access Failure Reason
Loss Connection when Intercell HO
TCH Drop with Remote Transcoder Failure Reason
Action
iry, many HO access fail
- Radio Analysis include aspects : - Freq interference analysis - Coverage Analysis - HW &Installation Problems - DB setting review - Followed by Radio Optimization based on analysis result
iry, many HO access fail oder Failure, that are : arm, if this happen, the Remote Transcoder Failure k
10 , TTRAU = TSYNC => This setting is for ranscoder failure (TSYNC and TTRAU)
- Radio Analysis include aspects : - Freq interference analysis - Coverage Analysis - HW &Installation Problems - Fermaint Alarm analysis to find broken TRACK/TRAU module possibi - Transmission Alarm - Timer Rule checking within DB - Followed by Optimization based on analysis result
Every unsuccessful decoding of uplink SACCH message (indicates any radio problems) will lead decrease of S c ounter in MS by 1. If the S counter reaches 0, the MS regards the dedicated radio connection as failed and stops any further transmission on the dedicated channel, also the BTS cannot correctly decode any uplink SACCH frames anymore because the MS has stopped transmitting them. When the radio link counter in BTS (RDLNKTBS) reaches 0, a CONNECTION FAILURE INDICATION (BTS>BSC) is sent and indicates call drop. S counter in MS and RDLNKTBS should follow the same rule, that is : S = (4 * RDLNKTO)+4 Reccomendation : - Fix any radio problem (interference, coverage, HW&Installation) => can be checked by optimization engineer in area - Increase RDLNKTO from 4 to 6 (RDLNKTBS from 20 to 28
+
from MS (reasons : any radio problems exist ) until T200 timer expired, then the connections are dropped. Messages with acknowledged mode are SABM, DISCONNECT and I-frames. All messages within this acknowledged mode are checked by the LAPDm flow control mechanisms based on sequence numbers that are assigned to each transmitted LAPD message. Reccomendation : - Fix any radio problem (interference, coverage, HW&Installation) => can be checked by optimization engineer in area - Increase T200 timer for FACCH TCHF, FACCH TCHH, SACCH TCH SAPI0, SACCH TCH SAPI3 from T200 = 29-31-38-90-70-29-168 to T200 = 29- 62-76-180-70-29-200
MS doesn't react to PHYS INFO sent by BTS (could be caused by any radio problems ), no SABM is received at the BTS until NY1 repetition with period time T3105. Reccomendation : - Fix any radio problem (interference, coverage, HW&Installation) => can be checked by optimization engineer in area - Check if DB ti mer meet rule : NY1*T3105 ≥ 2 sec , and (NY1+1)* T3105 << T8 < TTRAU
Loss HO CMD (caused by any radio problems) cause loss connection when intercell HO occurred. Reccomendation : - Fix any radio problem (interference, coverage, HW&Installation) => c an be checked by optimization engineer in area - Check T8 setting, must follow rule : T8 < TTRAU, and (NY1+1)* T3105 << T8 < TTRAU - Increase T8 timer for HLFSEC-12 to HLFSEC-14 (T8 determines the time to receive HANDOVER COMPLETE message)
Drop call due to Remote Transcoder Failures might be triggered by : - TRACK/TRAU Module Failure - COBA / CU Failure - Transmission Flicker - Wrong timer setting in DB, doesn't meet rule : TTRAU > T8 , TTRAU > T10, TTRAU = TSYNC => This setting is for ensuring that a signaling failure (T8 and T10) is detected before transcoder failure (TSYNC and TTRAU) Reccomendation : - Fermaint BSC alarm analysis to detect any TRACK/TRAU broken module - HW check - DB setting review
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