Nokia SDCCH A-IF Fail Call

[sachinsatija_in]

Hi Dear
Working on Nokia Systems and experiencing a strange phenomenon. First let me explain the network Heirarchy:
Nokia Ultra Site
Nokia S12 BSC
Nokia TCSM
Nokia MGW and Nokia MSS

I am facing a very high number of SDCCH A-if drops almost every 1-2 hours every day. This is not relevant to the BSC busy hour, neither the area it is serving. Now when this happens, obviously my SDCCH attempts increase and thus the SDCCH blocking.

I am not able to find any solid reason for this. But this is what I have seen only in the network where we have Nokia MGW in place. Also the MGW-MSS routing and balancing is ok, but still it happens.

kindly post your valuable experience, if you have faced the same.

Cheers

[kahnoie]

Wrong t3212 timer value for few cells in BSC lower than other cells means more periodic LU by MS and results in high SDCCH load.
SDCCH drops are linked to interference from other cells or due to large cell coverage (many subscribers at the cell border, with low RXLEV). Steps that can be taken to reduce SDCCH blocking are:
1. Increase T3212 from every 4 hours to every 6 or 8 hours.
2. SDCCH HO should be disabled as it does not improve the QoS
3. Try to reduce TA filter from 64 (32km) to 15 (7.5km) for a few hours.
4. Try to increase RXLEV_ACCESS_MIN from -104dBm to -98dBm for a few hours and observe the result


Regards,
Amit
agarwalamit081@gmail.com

[atese]

Hi.

Also check any possible co-channel, co-bsic in the area.

This is a ussual reason for SDCCH_DC.

Good luck

[sachinsatija_in]

Hi.

Also check any possible co-channel, co-bsic in the area.

This is a ussual reason for SDCCH_DC.

Good luck

no this was not the case here

[ddungu]

Hi,

check from the stats the reasons what causes the sd drops. from there you can start your troubleshooting..

regards,

[mojiiiiii]

hi
alse increase your SDCCH timesliots on trxs.

[faib]

Hi dude ,

we observed the same issue in S13 in one project and NSN did some upgradation in the NSN MGW and strange thing after the upgradation activity(some patches) A-interface failure just reduced to zero , do check with NSN Global support or u can open a ticket with local NSN.


Regards,
Faib

[ullazusman]

Hello,

This could be also due to CIC misalignment or unequal number of CIC circuits defined on the MSC server side and the BSC side.

I would advice you do a complete CIC aligment test on all the A-interface trunks to that BSC.

All the best.