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High SDCCH assignment failure rate


Dear all, I have a high SDCCH assignment failure rate. It has reached 100%. What action should I take?


Is there congestion?

Check the TCH.

May be the issue is at trx level . Like trx faulty, hardware issue etc.
If the site is carrying heavy traffic, we have to add sd in new trx

What is the site TRX configuration?? And how many SD’s are there per TRX???

Also share alarms


a 100% fail rate cannot be due to insufficient number of SDCCH. Which Vendor? Alarms on site? The Fail Rate is constant 100% or just reached 100 in some hours? TRX quality from statistics during hour when SD fail is high? During the period of 100% fail is there a surge of SD attempts mostly LU?


The vendor is Alcatel


Have you tried a soft reset?


Let me try a soft reset. But i did it before and there was no improvement


You should first mention all the actions and steps you have taken so that someone does not suggest them again



i think the TRX is not working right


This is normal if all SDs are failing. You cant assign TCH. Maybe check ul-dl path balance.


it is Alcatel, you know the indicator ?


I am not sure if u can find in alcatel, in huawei exist


Check if this site is a border to other LAC too, There are many possibilities for failure, like interference, alarm (Check availability) because trx down, LAC border if only traffic increase and check paging. Check the BCCH and TCH power and the if subcell structure is OK


Please i have the same problem with E\ vendor. when i check the trend of SD Assignement failure per BSC i’ve 60%.per hour

How i can solve the problem?

Thank You