Session establishment to join a group communication

1. A method comprising:

sending, by an access and mobility management function (AMF) to a network repository function (NRF), a query message to select a session management function (SMF) for a group communication session of a wireless device, the query message comprising an identifier associated with the group communication session;

receiving, by the AMF from the NRF, a query response message comprising an identifier of the SMF for the group communication session; and

sending, by the AMF to the NRF, a fourth message to update or register the SMF that supports the group communication session.

2. The method of claim 1 , wherein the identifier of the group communication session comprises at least one of:

a data network name; or

a single network slice selection assistance information (S-NSSAI).

3. The method of claim 1 , further comprising receiving, by the AMF from the wireless device, a first message indicating a request for the group communication session, the first message comprising the identifier associated with the group communication session.

4. The method of claim 3 , wherein the first message further comprises an identifier of the wireless device.

5. The method of claim 4 , wherein the identifier of the wireless device comprises a subscriber permanent identifier.

6. The method of claim 4 , wherein the identifier of the wireless device comprises a generic public subscription identifier.

7. The method of claim 1 , further comprising sending, by the AMF to a unified data management function (UDM), a second message to create a group context information, the second message comprising:

the identifier associated with the group communication session; and

the identifier of the SMF.

8. The method of claim 7 , wherein the group context information comprises:

the identifier of the SMF associated with the group communication session; and

an identifier of at least one user plane function (UPF) for the group communication session.

9. The method of claim 7 , wherein the group context information is stored in a network repository element wherein the network repository element comprises:

a network repository function;

a group management function;

a unified data repository; or

the UDM.

10. The method of claim 1 , further comprising sending, by the AMF to the SMF, a third message to establish a session to join the group communication session, the third message comprising:

the identifier associated with the group communication session; and

a wireless device identifier.

11. The method of claim 1 , further comprising receiving, by the AMF from the SMF, a response message indicating that joining the group communication session is successful.

12. The method of claim 1 , further comprising sending, by the AMF to a unified data management function (UDM) and based on a request to join the group communication session, a discovery request message comprising the identifier of the group communication session to determine the SMF associated with the group communication session.

13. The method of claim 1 , wherein the NRF maintains an association of the SMF with the identifier associated with the group communication session.

14. The method of claim 1 , wherein the query response message comprises a set of discovered SMF instances.

15. A method comprising:

receiving, by a network repository function (NRF) from an access and mobility management function (AMF), a query message to select a session management function (SMF) for a group communication session of a wireless device, the query message comprising a virtual local area network (VLAN) identifier associated with the group communication session; and

sending, by the NRF to the AMF, a query response message comprising an identifier of the SMF for the group communication session; and

receiving, by the NRF from the AMF, a fourth message to update or register the SMF that supports the group communication session.

16. The method of claim 15 , wherein the identifier of the group communication session comprises at least one of:

a data network name; or

a single network slice selection assistance information (S-NSSAI).

17. The method of claim 15 , wherein the NRF maintains an association of the SMF with the identifier associated with the group communication session.

18. The method of claim 15 , wherein the query response message comprises a set of discovered SMF instances.

19. An apparatus, comprising:

one or more processors; and

memory storing instructions that, when executed by the one or more processors, cause the apparatus to perform:

sending, to a network repository function (NRF), a query message to select a session management function (SMF) for a group communication session of a wireless device, the query message comprising an identifier associated with the group communication session;

receiving, from the NRF, a query response message comprising an identifier of the SMF for the group communication session; and

sending, to the NRF, a message to update or register the SMF that supports the group communication session.

20. The apparatus of claim 19 , wherein the NRF maintains an association of the SMF with the identifier associated with the group communication session.