Dynamic discovery of network functions in mobility interworking across radio access technologies

1. A method, comprising:

detecting, by a processing system including a processor, user equipment (UE) in a Long-Term Evolution (LTE) network, wherein a Packet Data Network Gateway Control/Session Management Function (PGW-C/SMF) provides the UE with access to a packet data network (PDN) through a Serving Gateway (SGW) of the LTE network, and wherein the UE has another radio technology capabilities;

determining, by the processing system, that the UE has crossed a threshold and entered a coverage area of another radio technology network;

discovering, by the processing system, an access mobility management function (AMF) in the another radio technology network responsive to a message received by a network repository function (NRF) from a mobile management entity (MME) in the LTE network;

transferring, by the processing system, metadata associated with the UE to the AMF responsive to discovering the AMF;

handing over, by the processing system, cellular services for the UE to the another radio technology network after the transferring; and

providing, by the processing system, the UE with access to the PDN through a user data plane function (UPF) of the another radio technology network after the handing over.

2. The method of claim 1 , wherein the AMF provides the cellular services to the coverage area of the another radio technology network, and wherein the another radio technology network is a fifth generation (5G) network.

3. The method of claim 2 , wherein the NRF discovers the AMF.

4. The method of claim 3 , wherein the NRF discovers the AMF without using a domain name service (DNS) protocol.

5. The method of claim 4 , wherein the message is passed over a first Representational State Transfer (REST) Application Programming Interface (API).

6. The method of claim 5 , wherein the MME performs the transferring by passing a second message over an enhanced N26 interface to the AMF using a second REST API.

7. The method of claim 3 , further comprising: checking, by the processing system, that the UE is authorized to access the 5G network before the handing over.

8. The method of claim 7 , wherein the NRF and the AMF are virtual network elements and wherein the metadata comprises status, heartbeat timer, Internet Protocol address, capacity, priority, load, locality, services supported, or a combination thereof.

9. A device, comprising:

a processing system including a processor; and

a memory that stores executable instructions that, when executed by the processing system, facilitate performance of operations, the operations comprising:

detecting a user equipment (UE) in a Long-Term Evolution (LTE) network, wherein a Packet Data Network Gateway Control/Session Management Function (PGW-C/SMF) provides the UE with access to a packet data network (PDN) through a Serving Gateway (SGW) of the LTE network, and wherein the UE has another radio technology capabilities;

determining that the UE has crossed a threshold and entered a coverage area of another radio technology network;

discovering an access mobility management function (AMF) in the another radio technology network responsive to a message received by a network repository function (NRF) from a mobile management entity (MME) in the LTE network;

transferring metadata associated with the UE to the AMF responsive to discovering the AMF;

handing over cellular services for the UE to the another radio technology network after the transferring; and

providing access to the PDN through a user data plane function (UPF) of the another radio technology network after the handing over.

10. The device of claim 9 , wherein the AMF provides services to the coverage area of the another radio technology network.

11. The device of claim 9 , wherein the NRF discovers the AMF.

12. The device of claim 11 , wherein the message is passed over a first Representational State Transfer (REST) Application Programming Interface (API).

13. The device of claim 11 , wherein the MME performs the transferring using a second REST API to the AMF over an enhanced N26 interface.

14. The device of claim 11 , wherein the NRF discovers the AMF without using a domain name service (DNS) protocol.

15. The device of claim 11 , wherein the NRF and the AMF are virtual network elements.

16. The device of claim 9 , wherein the processing system comprises a plurality of processors operating in a distributed computing environment.

17. A non-transitory, machine-readable medium, comprising executable instructions that, when executed by a processing system including a processor, facilitate performance of operations, the operations comprising:

detecting a user equipment (UE) in a Long-Term Evolution (LTE) network, wherein a Packet Data Network Gateway Control/Session Management Function (PGW-C/SMF) provides access to a packet data network (PDN) through a serving gateway (SGW) of the LTE network;

determining that the UE has crossed a threshold and entered a coverage area of another radio technology network;

discovering an access mobility management function (AMF) in the another radio technology network responsive to a message received by a network repository function (NRF) from a mobile management entity (MME) in the LTE network;

transferring metadata associated with the UE to the AMF responsive to discovering the AMF;

handing over cellular services for the UE to the another radio technology network after the transferring; and

providing access to the PDN through a user data plane function (UPF) of the another radio technology network after the handing over.

18. The non-transitory, machine-readable medium of claim 17 , wherein the processing system comprises a plurality of processors operating in a distributed computing environment.

19. The non-transitory, machine-readable medium of claim 17 , wherein the NRF discovers the AMF.

20. The non-transitory, machine-readable medium of claim 19 , wherein the message is passed over a first Representational State Transfer (REST) Application Programming Interface (API), and wherein the MME performs the transferring using a second REST API to the AMF over an enhanced N26 interface.