LTE's Handovers (by Qualcomm)

https://www.qualcomm.com/media/documents/files/lte-mobility-enhancements.pdf

1. Backward Handover

Backward handover can be described as network-controlled/UE-assisted mobility. Handover related information is exchanged between the UE and the source eNB via the old radio path (thus, the usage of the term ‘backward’). Specifically, the radio conditions need to be good enough for the source eNB to be able to decode the Measurement Report from the UE and subsequently prepare the target cell for handover. The radio conditions also need to be good enough for the UE to be able to decode the Handover Command from the source eNB.


2. RLC Handover

RLF handover is UE-based mobility and provides a recovery mechanism when the backward handover signaling with the source cell partially fails due to poor radio conditions. Specifically, the radio conditions are good enough for the source eNB to be able to decode the Measurement Report from the UE and subsequently prepare the target cell for handover, but not good enough for the UE to be able to decode the Handover Command from the source eNB1.