Slide 17745 – Alarm TRX
7745
Meaning
The rate of calls terminating in failure on a channel is above the threshold value set by the operator. The alarm is used to supervise the functioning of traffic and signaling channels, and to detect the possible faulty channels.
Category
KeyWord
Whenever a channel is released with a release cause other than a normal one,
the counter of channel failures for the released channel is incremented.
Default Threshold
SCHFR = SDCCH failure rate (80 %)
PRDCFR = length of supervision period (60 min)
CS = channel seizure threshold value (10)
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7745
Channel Release procedure
Whenever a channel is released with a release cause other than a normal one,
the counter of channel failures for the released channel is incremented.
After a certain observation time and a certain threshold it will reported in the 7745 alarm. It give an indication that there’s a failure that need to be addressed, but overall KPI need to be used as a first priority.
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7745
TCH Failure
0D TCH radio failure
1D TCH transcoder failure
2E TCH failure due to a LAPD failure
2F TCH failure due to a BTS failure
30 TCH failure due to user actions
31 TCH failure due to a BCSU reset
32 TCH failure due to radio network reconfiguration actions
51 TCH activation failure during call set-up
53 Target TCH activation failure in HO
54 TCH failure due to an Abis interface failure in call set-up
55 Source TCH failure due to an Abis interface failure in HO
56 Target TCH failure due to an Abis interface failure in HO
57 TCH failure due to an A interface failure in call set-up
58 Source TCH failure due to an A interface failure in HO
59 Target TCH failure due to an A interface failure in HO
FF Actually no release cause, but causes all channels with
an abnormal release cause to be listed
SDCCH Failure
0A Channel state conflict between RRMPRB and ABIPRB
0B Channel type conflict between RRMPRB and ABIPRB
23 SDCCH failure due to a LAPD failure
24 SDCCH failure due to a BTS failure
25 SDCCH failure due to user actions
26 SDCCH failure due to a BCSU reset
27 SDCCH failure due to radio network reconfiguration actions
48 SDCCH activation failure during call set-up
4A Target SDCCH activation failure in HO
4B SDCCH failure due to an Abis interface failure in call set-up
4C Source SDCCH failure due to an Abis interface failure in HO
4D Target SDCCH failure due to an Abis interface failure in HO
4E SDCCH failure due to an A interface failure in call set-up
4F Source SDCCH failure due to an A interface failure in HO
50 Target SDCCH failure due to an A interface failure in HO
7745 alarm occurance in Telkomsel Netowrk
Around 90% is affected in TCH, around 10% is affected in SDCCH
Abnormal relase cause defined below :
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7745
** ALARM TRX -006 JNCSILIWANGIMD2
(60756) 7745 CHANNEL FAILURE RATE ABOVE DEFINED THRESHOLD
01 00 01 01 01 01 01 00 00 04 00 48d
<HIST> AKSES_UI BCF-0065 BTS-0156 QUAL 2009-01-13 13:51:49.59
.. CANCEL TRX -007 JNCSILIWANGIMD2
(60755) 7745 CHANNEL FAILURE RATE ABOVE DEFINED THRESHOLD
01 00 00 00 00 00 00 00 00 00 00 0d
Supplementary information fields
1 indicates if the alarm is on the TCH or on the SDCCH channel 01: TCH 02: SDCCH
2..9 indicates if the channel failure rate is above the defined threshold in time slot 0 00: belove threshold (no alarm) 01: above threshold (alarm)
10 time slot with the highest failure rate
11 subchannel identification TCH: 00: TCH/H -subchannel 0 01: TCH/H -subchannel 1 02: TCH/F -subchannel subchannel identification SDCCH: 00 - 07: SDCCH -subchannel 0 – 7
12 proportion of TCH or SDCCH subchannel releases due to failure in all channel releases on a given channel during the measurement period
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Tools or verification that have been performed so far by NSN before/during site visit
Basic SW for Monitoring NE
MML, BTS Manager
Basic verification of site condition – for new sites
VSWR test verification (VSWR, RL, DTF verification)
Verification of Main and Diversity receive level
TRX Test function from BTS manager
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Step By Step Summary
Flowchart for investigation methodology
Root Cause & Suplementary information
Check cross sector founded
Troubleshoot Report
ND 196 > uplink & downlink Quality ND 195 > TRX by downlink /uplink level balance ND 232 > Time advance
Audit Neighbour & Paramater ADCE
Action
Troubleshooting if before VSWR OK > check cable connection & arester / grounding
VSWR Check Coverage
Monitoring Alarm & KPI
KPI OK Alarm
Justification for alarm : 1. Countur 2. Remote 3. Blocking & Fading 4. Etc
CR & Execute
BTS installation standart
TX 3 , 4 dan RX div
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If we have 7745, 7604 alarms in our network, what is really happening?
If: VSWR have been checked,
Then: we can find out from hardware by checking its transmit path from
TRx unit, Tx port, SMA-cables from Tx port to WCxA, WCxA itself, and
so on, until its feeder connection and antenna.
Thus:
7604 alarm is usually related to degraded receive quality of one
sector or one TRx.
From hardware point of view:
check its receive path from TRx unit, Rx main and RxDiv port,
SMA cables from Rx port to M2xA, M2xA itself, and so on, until its
feeder connection and antenna.
Futher investigation:
if we have feeder antenna cable broken, it may raise 7745, and
7604 as feeder is used as transmit and receive paths. Use ND report to strengthen your analysis. Usually ND report 195, 196,153 and 232.
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Sample ND 196
IF: band q5 value is under 90%
THEN: we suspect that the TRX have bad quality uplink or
Downlink ( in this case downlink issue)
Solution:
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Sample ND 195
Base on BTS installation standard that :
For Down link TX 1 and TX 2 have big differences , also for TX5 and TX6 for sec 2
For Uplink RX main having 3db diff in sec 1, for sec 2 have 9 db diff
This report shows for each TRX:
Ave MS pwr attn /lb_11 Average MS power attenuation (dB)
Ave BS pwr attn /lb_12 Average BS power attenuation (dB)
Ave UL str /lb_9 Average UL signal strength
Ave DL str /lb_10 Average DL signal strength
. The signal (UL, DL) strength is given as value 0..63 (GSM 5.08)
. 0 =less than -110dBm, 1= -110 to -109 dBm, 3= -109 to -108dBm
. ... 62 = -49 to -48, 63=greater than -48
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Sample ND 232 ( Time advance)
this site having overshoot issue
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Sample ND 232
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AUDIT ANTENNA and Neighbour
Sample ND 153 ( handover)
MancagarMD3 to CiropohMG2 and cisarunimg having 100% fail
mancagarMD3 to mancagar MG3 having 85 of 2144 sample call Fail
this report showing incoming and Outgoing handover
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Exception for 7745
No have neighbors cell ( island or remote standalone)
Landscape contour ( hill and valley)
Obstacle
This exception need to be justify as long as the KPI value achieve
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Summary
& Recommendation
Summary of findings from 7745 alarm in TELKOMSEL network (March – May 09) :
Many things that can lead to alarm 7745, it can be categorised as below :
Transmission issue, Power Related issue
Environment Related, Air Conditioning, Temperature
BTS HW problem related, Cooling Fan, Modul faulty
BTS Antena Line
Some existing problem in the old SW
Other maintenance activity in the BSC level
RECOMMENDATION
The affected factor need to be investigated carefully by understanding the root cause.
This alarm give information that there’s an abnormal channel release that we need to be aware.
KPI verification need to be addressed first rather than looking at the amount of this alarm appear.
Root Cause
ND 195 > TRX by downlink /uplink level balance
ND 232 > Time advance
& arester / grounding