3g

what do you mean by “fail”? can you see 2G neighbors when on 3G?

if no check for classmark update message (with K15) when arriving on 3G cell. Some handset are failing on that point.

what brand of MS are you using?

dear
Thanks for the response but I would like generally the reason for the HO failure from one way WCDMA to GSM

Hi,
First of all 3g to 2g neighbour, the database should be defined in MSS, RNC.
in MSS, the external LAC, MSCID of 2G neighbour should be defined.
in RNC, the information about 2G (like LAC-CI, bcch no, bsic, etc) should consisten with real 2G database.

I’ve listed down some Common reasons for 3G-2G handover failures
1). Improper neighbour definition-this can be verified from SIB 11 message
2). Wrong settings for event 2D thresholds & TTT (time to trigger values)
3). Wrong Settings for event 3A (thresholds & TTT)
4.) Inaccurate Timer settings (eg for T309 it is recommended to have more than 5s)

above are related to wrong configurations, remember that there could be other reasons as well

furthermore if we consider the different phases of the HO process, followings can be identified as some of the reasons for failures;
1. failures During Preparation phase (eg- due to no radio resources in target cell)-these are generally called as “CS-iRAT-HO_Failure_1”

2. failures in IuB & generally called as “CS-iRAT-HO_Failure_2”

3. Due to NBAP link failures

thanks