This is observed in intra MME handover
MME sends handover preparation failure to source eNB with cause unknown target ID
Both eNBs are under same TAC
What could be reason for this failure with this cause?
As you have mentioned that both the eNodeBs are under same TAC but it is not necessary that both the eNodeBs have connection with same MME. Please verify , Is s1 setup done for both the eNodeBs using wireshark or tcpdump ? I am suspecting that target eNodeB is not registered with MME.
Are you adding neighbor information in NRT using ANR or manually. If you are adding neighbor information in NRT manually then i think need to check the neighbor cell id in the NRT. It may be possible that neighbor cell id in NRT is different from the actual neighbor cell id. Due to this mismatch MME can not find the target eNB so that MME can send MME preparation failure to source eNB.
Newly integrated 3rd carrier is facing IRAT handover failure with reason "unknown-targetID" and "Failure In Target EPC/eNB Or Target System". Other carriers of same enodeB are doing successful handover with the same WCDMA cell. Sometimes for the affected cell, handover is successful.
Thanks in advance,
I found two MME UE S1-AP IDs i.e. MME UE S1AP ID (Mandatory) and MME UE S1AP ID 2 (optional).
I got why mandatory one is present but what's use of optional one.
Can someone please explain it ?
My friend was talking about ANR feature of LTE. By using, ANR feature neighboring eNodeBs update their NRT table. One of my friend was saying that it is not always X2 handover is allowed in X2 link. But he could not tell about cause/reason. I know when X2 handover can not perform, S1-handover shall be executed.