Section: 4.9.1 Handover procedures in 3GPP access 4.9.1.1 General
Content: These procedures are used to hand over a UE from a source NG-RAN node to a target NG-RAN node using the Xn or N2 reference points. This can be triggered, for example, due to new radio conditions, load balancing or due to specific service e.g. in the presence of QoS Flow for voice, the source NG-RAN node being NR may trigger handover to E-UTRA connected to 5GC. As defined in TS 38.413[ NG-RAN; NG Application Protocol (NGAP) ]  [10] a generic mechanism exists for the source NG-RAN node to retrieve information on the level of support for a certain feature at the target NG-RAN side associated with an NGAP IE. The mechanism makes use of the Source to Target and Target to Source transparent containers. The Inter NG-RAN node N2 based handover procedure specified in clause 4.9.1.3 may also be used for intra-NG-RAN node handover. NOTE: One use case for intra-NG-RAN handover to be performed by the Inter NG-RAN node N2 based handover procedure is when an NG-RAN node serves a satellite access system that covers more than one country. In such a situation, the UE might move from a "cell" in one country into a "cell" in another country and the NG-RAN node may need to cause the AMF to change to an AMF serving the UE's new country. The RRC Inactive Assistance Information is included in N2 Path Switch Request Ack message for Xn based handover or Handover Request message for N2 based handover (see clause 5.3.3.2.5 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2]).