eNodeBs in LTE are interconnected with the X2 interface. If two eNodeBs are served by the same MME, handover from the source to the target eNodeB will take place over the X2 interface.
Get an overview of the interactions between a UE, eNodeBs and the Core Network
Focus on UE interactions in a X2 handover
Source eNodeB role in an X2 interface handover
Target eNodeB interactions in an X2 handover
RRC signaling interactions in an X2 handover
X2AP signaling in an X2 handover
Data flow during an X2 handover