Uplink small data transmission in inactive state

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

generating, while in a state with no dedicated resources allocated to the UE, a message with a first UE identification security protected using a first key and uplink data encrypted using a second key derived based on information obtained from a first cell prior to transitioning to the state;

transmitting the message to a second cell; and

receiving, from the second cell, a message indicating a second UE identification and information regarding a third key to use for encrypting uplink data sent in a third cell.

2. The method of claim 1 , wherein the state comprises at least one of: a radio resource control (RRC) state, a substate of an RRC state, or a configuration of an RRC state.

3. The method of claim 1 , further comprising:

generating a reconfiguration complete message encrypted using the second key; and

transmitting the reconfiguration complete message to the second base station.

4. The method of claim 3 , further comprising:

receiving a message from the second base station with downlink data; and

decrypting the downlink data using the second key.

5. The method of claim 1 , further comprising:

generating a message with uplink data encrypted using the third key; and

transmitting the message to a third base station in the third cell while the UE is in a state in the third cell with no dedicated resources allocated to the UE.

6. The method of claim 1 , further comprising receiving signaling, from the first cell, placing the UE in the state with no dedicated resources and indicating a configuration for sending uplink data while the UE is in the state.

7. The method of claim 1 , further comprising providing an indication of at least one of a call type or a cause type to allow for network access control of the uplink data.

8. A method for wireless communications by a serving base station, comprising:

receiving, from a user equipment that is in a state with no dedicated resources allocated to the UE, a message with a first UE identification security protected using a first key and uplink data encrypted using a second key derived by the UE based on information obtained from a first cell prior to the UE transitioning to the state;

sending a request to the other base station to transfer a context of the UE to the serving base station;

receiving a response to the request, the response including information regarding the second key;

decrypting the uplink data using the second key; and

transmitting, to the UE, a reconfiguration message indicating a second UE identification and information regarding a third key for the UE to use for encrypting uplink data sent in a third cell.

9. The method of claim 8 , wherein the state comprises at least one of: a radio resource control (RRC) state, a substate of an RRC state, or a configuration of an RRC state.

10. The method of claim 8 , further comprising:

receiving, from the UE, a reconfiguration complete message encrypted using the second key.

11. The method of claim 10 , further comprising:

transmitting, to the UE, a message with downlink data encrypted using the second key.

12. The method of claim 8 , further comprising obtaining an indication of at least one of a call type or a cause type to allow for network access control of the uplink data.

13. The method of claim 12 , further comprising providing the indication to an application server.

14. The method of claim 13 , further comprising providing, based on the indication, radio resource control (RRC) signaling for a connection reject after the a context transfer of the UE to the serving base station.

15. A method for wireless communications by an anchor base station, comprising:

providing, to a user equipment configured with a first key used to encrypt uplink data to be sent to another base station while the UE is in a state with no dedicated resources allocated to the UE, information for deriving a second key;

receiving a request from the other base station to transfer a context of the UE from the anchor base station to the other base station, wherein the request indicates a first UE ID and the anchor base station verifies the UE based on the first UE ID and using the first key; and

transmitting a response to the request, the response including information regarding the second key.

16. The method of claim 15 , wherein the state comprises at least one of: a radio resource control (RRC) state, a substate of an RRC state, or a configuration of an RRC state.

17. The method of claim 15 , wherein the information for deriving the second key is provided to the UE when reconfiguring the UE to the state.

18. The method of claim 15 , further comprising signaling the UE to enter the state with no dedicated resources and indicating a mechanism for sending uplink data while the UE is in the state.

19. The method of claim 18 , further comprising selecting the mechanism based on at least one of a service type of the UE, a user preference, or network operator configuration.

20. A method for wireless communications by an anchor base station, comprising:

placing a user equipment (UE) in a state with no dedicated resources allocated to the UE, the UE configured with a first key;

receiving, from a serving base station, a first message with a first UE identification and uplink data encrypted by the UE using the first key;

verifying the UE using the first key;

receiving, from the serving base station, a preference for a context transfer from the other base station to the serving base station; and

deciding whether to transfer context of the UE to the serving base station.

21. The method of claim 20 , further comprising:

sending a message to the other base station with downlink data encrypted using the first key to be forward to the UE.

22. The method of claim 20 , wherein the state comprises at least one of: a radio resource control (RRC) state, a substate of an RRC state, or a configuration of an RRC state.

23. The method of claim 20 , further comprising signaling the UE to enter the state with no dedicated resources and indicating a mechanism for sending uplink data while the UE is in the state.

24. The method of claim 23 , further comprising selecting the mechanism based on at least one of a service type of the UE, a user preference, or network operator configuration.

25. The method of claim 20 , further comprising obtaining an indication of at least one of a call type or a cause type to allow for network access control of the uplink data.

26. The method of claim 25 , further comprising providing the indication to an application server.

27. The method of claim 1 , wherein the security protection comprises an integrity protection.

28. The method of claim 1 , wherein the state with no dedicated resources allocated to the UE comprises an RRC_INACTIVE state.