As I know, 5G network performs signal quality measurements on BRS ( Beam reference signal ) from different 5G cells & in LTE 3GPP defines several set of predefined set of measurement report mechanism to be performed by UE called Event for handover(A1,A2..) based on RSRP/RSRQ.
In 5G, handovers are network controlled handover & UE based handover.
In network controlled handover-• UE receives handover information from serving cell (NB1).
• Next, UE performs quality measurements on BRSs (Beam Reference Signals) from neighbor cells.
• Once measurement event is triggered, UE sends measurement report to serving cell.
• serving cell replies with handover command containing RRC connection re-configuration along with target cell NB2.
• UE completes handover with target cell NB2 by transmitting "RRC connection reconfiguration complete".
UE based handover-
When UE receives measurement configuration from serving cell , it performs quality measurements on BRSs from neighboring cells.
• As per measurement event triggering, UE sends measurement report to serving cell .
• Serving cell responds UE with list of possible neighboring cells to complete the handover. This is provided in message "RRC connection reconfiguration".
• Serving cell provides measurement configuration for UE to complete the handover with target NBs.
• From the list of cells, UE selects the best cell for handover using "RRC Connection Reestablishment procedure". .