Mobility between areas with heterogeneous network slices

1. A method of wireless communications for a user equipment (UE), comprising:

receiving a first indication that a network slice is not available;

entering a connection management idle (CM-IDLE) state in response to the first indication;

initiating a registration procedure with an access and mobility management function (AMF) subsequent to entering the CM-IDLE state; and

obtaining a second indication from the AMF requesting the UE to provide a permanent identity of the UE in future mobility management procedures.

2. The method of claim 1 , wherein obtaining the second indication from the AMF requesting the UE to provide the permanent identity includes:

obtaining a third indication from the AMF that a current temporary identifier of the UE is invalid.

3. The method of claim 2 , further comprising:

removing the current temporary identifier from a configuration of the UE, based on the third indication.

4. The method of claim 1 , wherein an upper layer of a protocol stack of the UE transmits to a lower layer of the protocol stack at least one of:

a second indication to release a connection with a radio access network (RAN) and to re-establish the connection,

a network slice selection assistance information (NSSAI) request, or

a third indication to refrain from providing a current 5 th generation globally unique temporary identifier (5G-GUTI).

5. The method of claim 4 , wherein the upper layer comprises a non-access stratum (NAS) layer and the lower layer comprises an access stratum (AS) layer.

6. The method of claim 1 , wherein initiating the registration procedure comprises:

transmitting a registration request message comprising a subscription permanent identifier (SUPI) or a security protected version of the SUPI of the UE.

7. The method of claim 1 , further comprising:

receiving a new allowed network slice selection assistance information (NSSAI), from the AMF prior to entering the CM-IDLE state, wherein initiating the registration procedure comprises transmitting a registration request message comprising a requested NSSAI matching the new allowed NSSAI.

8. The method of claim 1 , further comprising:

connecting a first protocol data unit (PDU) session to a network slice associated with another AMF to convey data of a second PDU session active prior to receiving the first indication that the network slice is not available.

9. The method of claim 1 , wherein receiving the first indication comprises receiving the first indication in a non-access stratum (NAS) message.

10. The method of claim 1 , wherein receiving the first indication comprises receiving the first indication in an access resource reconfiguration message.

11. The method of claim 1 , wherein receiving the first indication comprises receiving a request from the AMF to re-register with a network.

12. A method of wireless communications for an access and mobility management function (AMF), comprising:

detecting that a network slice, with which a user equipment (UE) has at least one active protocol data unit (PDU) session corresponding to that network slice, has or will become unavailable;

sending a request to a session management function (SMF) for a modification of the PDU session, in response to the detection; and

sending, to the UE, an indication that a re-registration of the UE is required and that a current temporary identifier of the UE is invalid.

13. The method of claim 12 , further comprising:

sending, to the UE, a new allowed network slice selection assistance information (NSSAI) comprising a network slice instance (NSI) identifier (NSI ID) identifying the network slice with which the UE had the active PDU session.

14. The method of claim 12 , further comprising:

receiving a registration request message from the UE.

15. The method of claim 14 , further comprising:

sending, to a service management function (SMF), another indication to release the PDU session.

16. The method of claim 12 , further comprising:

sending, to a service management function (SMF), another indication to release the PDU session.

17. The method of claim 12 , wherein the detecting is based on another indication, received by the AMF, from a radio access network (RAN) entity communicating with the UE.

18. The method of claim 12 , wherein the detecting is based on a message received by the AMF from the UE.