7745 – Alarm TRX
CHANNEL FAILURE RATE ABOVE DEFINED
THRESHOLD
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7745 - CHANNEL FAILURE RATE ABOVE DEFINED
THRESHOLD
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.
Alarm in TRXlevel, reported in BSC
Category
Quality of Services Alarm, Severity Medium
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.
NSN Default Threshold :
TCHFR = TCH failure rate (20 % or 30%)
SCHFR = SDCCH failure rate (80 %)
PRDCFR = length of supervision period (60 min)
CS = channel seizure threshold value (10)
7745 - CHANNEL FAILURE RATE ABOVE DEFINED
THRESHOLD
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
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7745 - CHANNEL FAILURE RATE ABOVE DEFINED
THRESHOLD
TCH Failure
0A Channel state conflict between RRMPRB and ABIPRB 0B Channel type conflict between RRMPRB and ABIPRB 0D TCH radio failure
0E Source TCH radio failure in HO 0F Target TCH radio failure in HO 1D TCH transcoder failure
1E Source TCH transcoder failure in HO 1F Target TCH transcoder failure in HO 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
03 SDCCH radio failure
04 Source SDCCH radio failure in HO 05 Target SDCCH radio failure in HO
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 Network
Around 90% is affected in TCH, around 10% is affected in SDCCH
Abnormal relase cause defined below :
7745 - Alarm Information
<HIST> AKSES_UI BCF-0065 BTS-0156 QUAL 2009-01-13 13:51:49.59
** ALARM TRX -006 JNCSILIWANGIMD2
DISABLED
(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
ENABLED
(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/percentage of TCH or SDCCH subchannel releases due to failure in all
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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
•
KPI Browser
Cell Doctor (report 211 Network Doctor) OSS
Cell KPI (report 204 Network Doctor) OSS
•
Basic verification of site condition – for new sites
VSWR test verification (VSWR, RL, DTF verification)
Verification of Main and Diversity receive level
Step By Step - Flowchart for investigation methodology
Root Cause & Suplementary information SD & TCH TCH : 59, 0F, 0D SDCCH : 4B, 4D Audit Neighbours Retune, Check Parameter ARFCN orAudit Antenna tilting Action
ND 195 : Unbalanced Uplink & downlink per TRX ND 196 : Uplink/Downlink Quality
1. Check VSWR / cross feeder, Check Antenna/feeder/arrester/grounding. 2. Check cable connection & Hardware inspection, swap existing module 3. Hardware replacement if needed. i.e : TRX, DVXX, BB2X, etc
Check TSC TRX using ZERO command BCC using ZEQO command
Switch BCCH Frequency to another TRX Change Request & Execute End Start 7745 Site Visit ND 196 > uplink & downlink Quality
ND 195 > TRX by downlink /uplink level balance ND 232 > Time advance ND 153 > Handover KPI OK Alarm ND 232 : Time Advanced (from drive test)
Coordinate with OSS
Investigation together with PLO
Y
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BTS installation standard
TX1,2 and RX main
If we have 7745, 7743 alarms in our network, what is really
happening?
Before Site Visit :
Make sure Audit neighbor, TSC checking and TRXtest
Action on site :
1.
7745, 7743 at one TRX only
- Check SMA cable at Tx connector to WCXA of the TRX, make sure properly connected
- Replace TRX, BB2F and SMA cables if needed
2.
7745, 7743 at two TRX
- Try to switch BCCH, if still appear potential have a partial cross feeder
- Replace TRX, BB2F WCXA, or DVXA if needed
- Check alarms of other sector to ensure analysis
3.
7745, 7743 at all TRXs under same cell
- Possibilities error : full partial cross feeder, bad feeder quality and its connection,
interference, broken DVXA
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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.
Sample ND 196
Performance Analysis:
IF: band q5 value is under 90%
THEN: we suspect that the TRX have bad
quality uplink or Downlink ( in this case
downlink issue)
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Sample ND 195
Base on BTS installation standard that :
“Uplink and Downlink between TRX in one sector
is maks 3db”
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 SAMPLE ABOVE :
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
Sample ND 232 ( Time advance)
this site having overshoot issue
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Sample ND 232
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Sample ND 153 ( handover)
•
MancagarMD3 to CiropohMG2 and cisarunimg having 100% fail
•
MancagarMD3 to mancagar MG3 having 85 of 2144 sample call Fail
Exception for 7745
•
7745 will keep occur for this condition :
1.
No have neighbors cell ( island or remote standalone)
2.
Landscape contour ( hill and valley)
3.
Obstacle
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Summary
1. Alarm 7745 occur due to Abnormal release Channel
-
Mostly in TCH 53,56,59 because of Handover, Call Setup Issue
-
SDCCH 4B because of antenna and feeder installation
2. Module M6HA should be part of BTS High Capacity
3. Correction related alarm 7745 software CX5 CD4 (replace CX4.1 CD4)
4. Many things that can lead to alarm 7745, it can be categorized as below :
Transmission issue, Power Related issue
Environment Related, Air Conditioning, Temperature
BTS HW problem related, Cooling Fan, Module faulty
BTS Antenna Line
Coverage Issue
Configuration Mismatch between BSC and BTS/MMI
Some existing problem in the old SW
RFI Site Procedure
Objective:
1. To have better site integration verification procedure
2. To make sure that all functionality of the integration site already
in place and being verified
3. To avoid unnecessary mistake on integration such as cross feeder
(partial and full), Loose feeder and others functionalities.
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