7745 Alarm Troubleshoot

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7745 – Alarm TRXCHANNEL FAILURE RATE ABOVE DEFINED THRESHOLD


7745 - CHANNEL FAILURE RATE ABOVE DEFINED THRESHOLD

MeaningThe 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)



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.



TCH Failure0A Channel state conflict between RRMPRB and ABIPRB0B Channel type conflict between RRMPRB and ABIPRB0D TCH radio failure0E Source TCH radio failure in HO0F Target TCH radio failure in HO1D TCH transcoder failure1E Source TCH transcoder failure in HO1F Target TCH transcoder failure in HO2E TCH failure due to a LAPD failure2F TCH failure due to a BTS failure30 TCH failure due to user actions31 TCH failure due to a BCSU reset32 TCH failure due to radio network reconfiguration actions51 TCH activation failure during call set-up53 Target TCH activation failure in HO54 TCH failure due to an Abis interface failure in call set-up55 Source TCH failure due to an Abis interface failure in HO56 Target TCH failure due to an Abis interface failure in HO57 TCH failure due to an A interface failure in call set-up58 Source TCH failure due to an A interface failure in HO59 Target TCH failure due to an A interface failure in HOFF Actually no release cause, but causes all channels with

an abnormal release cause to be listed

SDCCH Failure03 SDCCH radio failure04 Source SDCCH radio failure in HO05 Target SDCCH radio failure in HO0A Channel state conflict between RRMPRB and ABIPRB0B Channel type conflict between RRMPRB and ABIPRB23 SDCCH failure due to a LAPD failure24 SDCCH failure due to a BTS failure25 SDCCH failure due to user actions26 SDCCH failure due to a BCSU reset27 SDCCH failure due to radio network reconfiguration actions48 SDCCH activation failure during call set-up4A Target SDCCH activation failure in HO4B SDCCH failure due to an Abis interface failure in call set-up4C Source SDCCH failure due to an Abis interface failure in HO4D Target SDCCH failure due to an Abis interface failure in HO4E SDCCH failure due to an A interface failure in call set-up4F Source SDCCH failure due to an A interface failure in HO50 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 SDCCHAbnormal 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 fields1 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 rate11 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 – 712 proportion/percentage of TCH or SDCCH subchannel releases due to failure in all

channel releases on a given channel during the measurement period


Tools or verification that have been performed so far by NSN before/during site visit

• Basic SW for Monitoring NEMML, BTS Manager

• KPI BrowserCell Doctor (report 211 Network Doctor) OSSCell KPI (report 204 Network Doctor) OSS

• Basic verification of site condition – for new sitesVSWR test verification (VSWR, RL, DTF verification)Verification of Main and Diversity receive levelTRX Test function from BTS manager


Step By Step - Flowchart for investigation methodology

Root Cause

&

Suplementary

information

SD

& TCH

TCH : 59, 0F, 0D

SDCCH : 4B, 4DAudit 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


BTS installation standard

TX1,2 and RX main

TX 3 , 4 and RX div


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


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)


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


Sample ND 232this site having overshoot issue


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


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


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


RFI Site Procedure

Objective:1. To have better site integration verification procedure2. To make sure that all functionality of the integration site already

in place and being verified3. To avoid unnecessary mistake on integration such as cross feeder

(partial and full), Loose feeder and others functionalities.

Additional :


RFI Site Procedure Methodology:

There are 3 group of site check of this test call procedure: a. Connected Mode

- Mobile originated calls of voice servicesb. 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 sectors5.Failed TRXs can trigger further analysis with the site inspection on possible wrong

connection or swapped feeder/antennac. 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

Documents

7745 Alarm Troubleshoot