Thanks a lot Pix.
i am going to check radio signalling link utilization as well.
if i would’t see any problem, i perform :
1. stop frequency hopping then check the SDCCH Failure rate
2. if continues , shift sdcch positon to next TS
3. if continues signaling card and TRX Harware replacement
4. if still continues checking whether cables are corrosed
5.if still continues, Jumper cable, feeder, connector finally Antenna replacement.
Best Regard Pix.
Thanks spending time for answer