CS Inter-RAT Fail with cause physicalChannelFailure (3G Huawei)

[Kitachi]

Dear Experts,
My network is Huawei(both 2G and 3G), I have problem with CS Inter-RAT HO with some cells (success only 44%); I have check:
+ Neighbour, External cell, BCCH, BSIC is OK.
+ 2G isn't congestion.
+ These cells are using Event trigger.
+ I haved adjust threholds for 2D/2F, but it not improved.
+ I haved driving test and see the message "Handover from UTRAN command-GSM(DL-DCCH)" but after that the HO fail. (see attachment).

Please help me to solve this problem.

Thanks.

[jayk]

The problem seems in GSM cell. Can you check the incoming Handover success rate of the 2G cell?

[paulus]

Hi,

Have you checked whether your 2G cells (as external cells) have been registered in RNC? (LST UEXT2GCELL).

Check 2G LAC also..

Then check the 2G neighbor list (LST U2GNCELL)..

You can check also on the layer 3 messages in TEMS, click on the Inter-Rat process, find out what's the missing compared to the successful inter-rat.

Br,

Paul

[BryxKeisha]

Hi,

You must check also if there are co-BCCH and/or adjacent BCCH on the area with low IRAT success rate. Next, if you can, maintain the 2G neighbor list (LST U2GNCELL) to 10-15 neighbors only. The reason is, if a UE attempts to handover from 3G to 2G, during compressed mode, it scans all the 2G cells on the neighbor list. If you have too much 2G neighbors, UE will take time to handover as it will take time to verify which cell is best suitable. The UE scans 3G cells for 80ms and 160ms for GSM cells. So with 10-15 GSM neighbors only, UE can finish the scanning from 1.6 seconds to 2.4 seconds and can avoid call drops. Hope this help.

Please add reps if you find this useful. Thanks!