5G: Is it necessary to support LTE interfaces at next generation core network (NGCN) ?

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

Hi,

Yes your understanding is right, if operator wants to implement option 7 then eLTE should evolve s1-AP to NG-AP. This scenario will reduce deployment cost for stadalone NG, where you require either EPC or NG_C

Answer 2

Technically, option 7 requires eNB to be upgraded to ng-eNB and therefore would not require S1-AP anymore. However, upgrading all eNBs to ng-eNBs will not be feasible for many operators, so vendors are offering 5GC with built in EPC+ functionalities.