How long does ENB will hold the contention free pramble in Target ENB?

Question

If HO fails the UE will initiate contention based reestablishment and connect to some ENB, But target ENB have provided the contention free Rach preamble , at failure case how long ENB will hold this preamble because it has to release for other UE?

Answer 1

Since this is a failure handover case where UE never triggered RACH at target eNB (there is also a possibility of UE triggering RACH at target and still sending reestablishment at source with target PCI though), the handin procedure at target is bound to fail for this UE at the expiry of target HO timer or receiving HO cancel from MME/source. As part of UE context release at target eNB, the allocated preamble for contention free rach shall also be freed up.