7745-alarm-troubleshoot

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7745 – Alarm TRX
CHANNEL FAILURE RATE ABOVE DEFINED
THRESHOLD

2. 2 © Nokia Siemens Networks. All rights reserved.
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)

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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
addressed, but overall KPI need to be used as a first priority.

4. 4 © Nokia Siemens Networks. All rights reserved.
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 :

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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
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
• 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
TRX Test function from BTS manager

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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 or
Audit 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
N

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BTS installation standard
TX1,2 and RX main
TX 3 , 4 and RX div

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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.

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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

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Sample ND 232 ( Time advance)
this site having overshoot issue

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Sample ND 232
this site having overshoot issue

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AUDIT ANTENNA and Neighbour

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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
• This report showing incoming and outgoing handover

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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
This exception need to be justify as long as the KPI value achieve

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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
 Other maintenance activity in the BSC level

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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.
Additional :

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RFI Site Procedure Methodology:
There are 3 group of site check of this test call procedure:
a. Connected Mode
- Mobile originated calls of voice services
b. Cross feeder Check
1.Using Network Monitoring on TEMS/NEMO (for best result for recognizing cross feeder
symptom, Move along main lobe of each cell ± 500 m, and make sure that we have the
serving CI along the main lobe).
2.Make Test Call and notate the used TRX in case of Hopping TRX eg. (Synthesizer Hopping)
Specific MAIO will represent specific transceiver according to system Configuration or Site
parameter. In case of Baseband Hopping TRXs then Baseband hopping parameter shall be
disable then individual test shall be carried out individually per TRX according to Database
Site parameter.
3.Lock the Transceiver carrying BCCH Frequency and perform test number 2 until all TRXs in
the same cell have been successfully verified
4.Locate the same treatment in the different sectors
5.Failed TRXs can trigger further analysis with the site inspection on possible wrong
connection or swapped feeder/antenna
c. Hardware Inspection
- Antenna Type
- Antenna azimuth
- Antenna downtilt (Mechanical/Electrical)
- Have feeder label and match with antenna
d. Remarks for further finding on the field