5G: What is the role of Xn interface between next generation radio network nodes ?

Question

I was going through deployment options 4A and 7, in which LTE eNodeB interacts with NGCN for control plane and user plane.
I am thinking the scenarios that when an operator would require particular option 7 in which eNodeB control and user plane both ends interface towards NGCN ? If this is the case then S1-AP and NG-AP both protocols will have to implement at next generation core network.
Is my understanding of option 7 is correct ?

Answer 1

Xn interface in the 5G RAN is as same as X2 interface of LTE RAN. It enables communication between the following nodes:
- ng-eNB and ng-eNB
- ng-eNB and gNB
- gNB and gNB

It is divided into control and user plane. Control plane of this interface uses SCTP as transport and it is mainly used for UE mobility, context transfer, RAN paging, Dual connectivity and interface management. The user plane part of Xn interface provides data forwarding and flow control. The user plane is based on GTP-U protocol stack.