The Handover is the process of transferring an ongoing data session/Call from
one (source) cell connected to the core network to another (target) cell. Handovers are needed when UE moved out of its serving cell’s coverage or for load balancing purposes.
In mobile communication, Handover can either be Network controlled (i.e. HO decision is with network) or Mobile Evaluated (i.e. Mobile terminal makes HO decision and inform Network to arrange resources on target cells)
LTE uses both the approaches in a way that, LTE capable UE sends measurement report to network and based on this report; network directs UE to move to a target cell.
Handover Types in LTE:
- Intra-LTE Handover: Source and target cells are part of the same LTE network.
- Handover using X2 Interface
- Handover using S1 Interface
If more than one frequencies/carrier are being in use for LTE then HO can further be distinguished with (Inter or Intra eNodeB) InterFreq and (Inter or Intra eNodeB) IntraFreq Hand overs.
- Inter-LTE Handover: Handover happens towards other LTE nodes. (Inter-MME and Inter-SGW
- Inter-MME Handover
- Inter-MME/SGW Handover
- Inter-RAT Handover: Handover between different radio technologies. For example handover from LTE to WCDMA.