Handover refers to a cell transition that occurs when a circuit-switched (CS) connection is in place (such as CS voice, CS data, or Dual Transfer Mode). Handovers can only be initiated by the network. During a handover, the network sends the mobile a Handover command, which provides information about the destination cell, including the traffic channel configuration.
The procedure for mobility from LTE to another RAT supports both handover and Cell Change Order (CCO).
The CCO procedure is applicable only for mobility to GERAN.
In case of handover (as opposed to CCO), the source eNodeB requests the target RAN node to prepare for the handover.
As part of the ‘handover preparation request’ the source eNodeB provides information about the applicable inter-RAT UE capabilities as well as information about the currently-established bearers. In response, the target RAN generates the ‘handover command’ and returns this to the source eNodeB.