Handover is initiated by ENB on receiving MEASUREMENT_REPORT from the UE’s. The handover decision is also taken by the ENB and not the MME. Handover also involves the exchange of various packets. 

  1. First UE’s send MeasurementReport packets to the ENB. 
  2. ENB takes Handover decision and sends HandoverRequest packet to the target ENB. 
  3. In response the Target ENB sends HandoverRequestAck packet back to the source ENB. 
  4. This completes the process of Handover.
  5. After this LTE Association happens between the target ENB and the UE that was handed over.                                                       (Refer: https://tetcos.freshdesk.com/solution/articles/14000059953-how-does-association-happen-in-lte)