The new elements in 5G are gNB, AMF, UPF, which are using new interfaces as the XN and N2 interface to link the AMF with gNB and vice versa, replacing X2 and S1 AP interfaces.
There are also several other components as follows:
There in 5G the handover is called Xn Handover and N2 Handover
The NG-RAN sends the UE Notification message to report the current RRC state for the UE (i.e. RRC Inactive state or RRC Connected state). The current UE location information (i.e. TAI + Cell Identity) is always included when RRC state information is reported.
The differences are subtle, and the main difference is that the X2 handover. We server that Location Information is mandatory, but it was after LTE
Rel-13 as well. The changes are minimum and this facilitates the understanding of all functions including AMF / UPF in 5G. In TS 38.423 V.15, the Xn-AP commands are shown, which is a similar document to the X2-AP specification.
If the Location Reporting InformationIE is included in the HANDOVER REQUEST message, then the target NG-RAN node should initiate the requested location reporting functionality as defined in TS 38.413 .
Similarly this is shown in TS 123.502 with
In the 4G LTE System, we would have an ENodeB, MME, S-GW, PDN-GW, as common elements of the network, hence the X2 and S1 interfaces were used for handover.
In this design, X2 handover facilitates handoff between eNodeBs and relies on the MME for S1-AP handoff only.
In 5G, things have changed a bit:
In comparison, UEs are the same, different radios, on one end LTE, and into the future a 5G radio.
What are the main actors for handover on LTE
There are multiple specifications related to handover on LTE and defined by ETSI/3GPP organizations.