Location and context management in a RAN INACTIVE mode

1. A serving node of a radio access network (RAN), the serving node comprising:

a radio interface;

a network interface;

a processor; and

a non-transitory memory storing instructions that when executed by the processor cause the serving node to:

receive, using the radio interface, from a user equipment (UE) operating in an inactive mode, an identifier of the UE and a first message, the first message being protected with a first cryptographic key wherein the first cryptographic key is associated with a second network node of the RAN;

send, using the network interface, to the second network node, a UE context retrieval request, the UE context retrieval request including the identifier of the UE and the first message;

receive, using the network interface, from the second network node, a UE context retrieval response, the UE context retrieval response including a relocation indication of whether a UE context is to be relocated to the serving node, wherein when the relocation indication indicates that the UE context is not relocated to the serving node, the UE context retrieval response includes a second message protected with a second cryptographic key wherein the second cryptographic key is associated with the second network node; and

send, using the radio interface, the second message to the UE.

2. The serving node as claimed in claim 1 wherein the second network node is determined in accordance with the identifier of the UE.

3. The serving node as claimed in claim 1 , wherein the second message comprises at least one of:

an identifier to be used by the UE for further operations in the inactive mode;

an indication of a RAN notification area (RNA) where the UE can receive service while operating in the inactive mode; and

a maximum time between location notifications initiated by the UE.

4. A serving node of a radio access network (RAN), the serving node comprising a memory and at least one processor configured to:

a radio interface; a network interface; a processor; and

a non-transitory memory storing instructions that when executed by the processor cause the serving node to:

receive, using the radio interface, from a user equipment (UE) operating in an inactive mode, an identifier of the UE and a first message, the first message being protected with a first cryptographic key wherein the first cryptographic key is associated with a second network node of the RAN;

send, using the network interface, to the second network node, a UE context retrieval request, the UE context retrieval request including the identifier of the UE and the first message;

receive, using the network interface, from the second network node, a UE context retrieval response, the UE context retrieval response including a relocation indication that the UE context is relocated to the serving node and a context associated with the UE;

derive, based on the received UE context, a second cryptographic key wherein the second cryptographic key is associated with the serving node; and

send, using the radio interface, a second message to the UE protected with the second cryptographic key.

5. The serving node as claimed in claim 4 wherein the second network node is determined in accordance with the identifier of the UE.

6. The serving node as claimed in claim 4 , wherein the second message comprises any one or more of:

an identifier to be used by the UE for further operations in the inactive mode;

an indication of a RAN notification area (RNA) where the UE can receive service while operating in the inactive mode; and

a maximum time between location notifications initiated by the UE.

7. A method at a network node of a radio access network (RAN) for managing a UE context of a user equipment (UE) operating in an inactive mode, the method comprising:

receiving, from the UE, a UE identifier and a first message, the first message being protected with a first cryptographic key wherein the first cryptographic key is associated with a second network node of the RAN;

sending, to the second network node, a UE context retrieval request, the UE context retrieval request including the UE identifier and the first message; and

receiving, from the second network node, a UE context retrieval response, the UE context retrieval response containing a relocation indication of whether a UE context is to be relocated to the network node, wherein one the following holds;

when the relocation indication indicates that the UE context Is not relocated to the network node, the method further comprises: receiving, in the UE context retrieval response, a second message protected with a second cryptographic key, the second cryptographic key being associated with the second network node; and sending the second message to the UE; and

when the relocation indication indicates that the UE context is relocated to the network node, the UE context retrieval response includes a UE context associated with the UE, and the method further includes: using the UE context by the network node to derive a further cryptographic key wherein the further cryptographic key is associated with the network node; and sending a second message to the UE wherein the second message is protected using the further cryptographic key.

8. The method of claim 7 wherein the second network node is determined in accordance with the UE identifier.

9. The method of claim 7 wherein the second message comprises any one or more of:

an identifier to be used by the UE for further operations in the inactive mode;

an indication of a RAN notification area (RNA) where the UE can receive service while operating in the inactive mode; and

a maximum time between location notifications initiated by the UE.

10. The method of claim 7 wherein the second message is a radio resource control (RRC) message.

11. The method of claim 7 wherein the network node is a new serving node associated with the UE.

12. The method of claim 7 wherein the second network node is an old anchor node associated with the UE.