UE receives the RRCReconfiguration msg from source eNB with mobility parameters then try to synchronize with target eNB. If UE is not able to send RRCReconfiguration complete msg to target eNB before expiring t304 timer due to any reason like RACH is not resolved, this will be considered as HO failure. Then UE will trigger rrc connection reestablishment request with cause as handover failure.
