Radio link recovery for user equipment

1. An apparatus comprising:

one or more processors; and

one or more memory storing computer program instructions, the one or more memory and computer program instructions configured to, with the one or more processors, cause the apparatus to:

establish, in a communication system, a non-access stratum security context between user equipment and the apparatus;

receive, at the apparatus, within the non-access stratum security context previously established between the user equipment and the apparatus, an encrypted non-access stratum message from the user equipment; and

in an instance in which the encrypted non-access stratum message received from the user equipment indicates a radio link failure has occurred between the user equipment and the apparatus during a data transfer operation over a control plane, enable recovering of the radio link for the user equipment through a target access node of the communication system, using the non-access stratum security context previously established between the user equipment and the apparatus,

wherein the encrypted non-access stratum message is encrypted using a cryptographic key created from the non-access stratum security context between the user equipment and the apparatus.

2. The apparatus of claim 1 , wherein the cryptographic key comprises an integrity key from the non-access stratum security context.

3. The apparatus of claim 2 , wherein the cryptographic key is derived using an uplink message count or a downlink message count.

4. The apparatus of claim 1 , wherein the one or more memory and computer program instructions are further configured to, with the one or more processors, cause the apparatus to:

verify, at the apparatus, using the cryptographic key, an identify of the user equipment.

5. The apparatus of claim 4 , wherein the one or more memory and computer program instructions are further configured to, with the one or more processors, cause the apparatus to:

indicate set up of a signaling interface with the target access node.

6. The apparatus of claim 5 , wherein the one or more memory and computer program instructions are further configured to, with the one or more processors, cause the apparatus to:

send, from the apparatus, within the non-access stratum security context previously established between the user equipment and the apparatus in the communication system, an encrypted second non-access stratum message to the user equipment through the target access node.

7. The apparatus of claim 6 , wherein the encrypted second non-access stratum message indicates an acknowledgment of the radio link failure, and is protected using the cryptographic key created from the non-access stratum security context previously established between the user equipment and the apparatus.

8. The apparatus of claim 7 , wherein the encrypted second non-access stratum message comprises data associated with the data transfer.

9. The apparatus of claim 8 , wherein the data is at least one of previous buffered data and new data.

10. The apparatus of claim 8 , wherein the data is encrypted by an encryption key created during establishment of the non-access stratum security context previously established between the user equipment and the apparatus.

11. The apparatus of claim 10 , wherein the encryption key comprises a non-access stratum encryption key.

12. The apparatus of claim 4 , wherein the one or more memory and computer program instructions are further configured to, with the one or more processors, cause the apparatus to:

retrieve, by the apparatus, buffered data associated with the data transfer from the source access node.

13. The apparatus of claim 1 , wherein the radio link failure is detected by the user equipment.

14. The apparatus of claim 1 , wherein the radio link failure is detected by the source access node.

15. The apparatus of claim 1 , wherein an access stratum security context is not established between the user equipment and the source access point.

16. The apparatus of claim 1 , wherein the communication system comprises a Narrow Band Internet of Things (NB-IoT) network, and further wherein the user equipment comprises cellular IoT (CIoT) user equipment.

17. The apparatus of claim 1 , wherein the source access node and the target access node each comprise a base station distinct from the mobility management node of the communication system.

18. A method comprising:

establishing, in a communication system, a non-access stratum security context between user equipment and a mobility management node of the communication system;

receiving, at the mobility management node, within the non-access stratum security context previously established between the user equipment and the mobility management node of the communication system, an encrypted non-access stratum message from the user equipment; and

in an instance in which the encrypted non-access stratum message received from the user equipment indicates a radio link failure has occurred between the user equipment and a source access node of the communication system during a data transfer operation over a control plane, recovering, via the mobility management node, while maintaining the non-access stratum security context previously established between the user equipment and the mobility management node, the radio link for the user equipment through a target access node of the communication system,

wherein the mobility management node comprises a processor and memory configured to enable the recovery of the radio link between the user equipment and the mobility management node via the target access node, and

wherein the encrypted non-access stratum message is encrypted using a cryptographic key created from the non-access stratum security context between the user equipment and the mobility management node.

19. A non-transitory computer-readable storage medium having embodied therein executable program code that when executed by a processor causes the processor to:

establish, in a communication system, a non-access stratum security context between user equipment and a mobility management node of the communication system;

receive, at the mobility management node, within the non-access stratum security context previously established between the user equipment and the mobility management node of the communication system, an encrypted non-access stratum message from the user equipment; and

in an instance in which the encrypted non-access stratum message received from the user equipment indicates a radio link failure has occurred between the user equipment and a source access node of the communication system during a data transfer operation over a control plane, recover, via the mobility management node, while maintaining the non-access stratum security context previously established between the user equipment and the mobility management node, the radio link for the user equipment through a target access node of the communication system,

wherein the mobility management node comprises a processor and memory configured to enable the recovery of the radio link between the user equipment and the mobility management node via the target access node, and

wherein the encrypted non-access stratum message is encrypted using a cryptographic key created from the non-access stratum security context between the user equipment and the mobility management node.

20. An apparatus comprising:

one or more processors; and

one or more memory storing computer program instructions, the one or more memory and computer program instructions configured to, with the one or more processors, cause the apparatus to:

establish, between the apparatus and a mobility management node of a communication system, via a source access node of the communication system, a non-access stratum security context; and

in an instance in which a radio link failure occurs between the apparatus and the source access node of the communication system during a data transfer operation over a control plane, initiate recovery of the radio link for the apparatus, through a target access node of the communication system, by the apparatus sending an encrypted non-access stratum message to the mobility management node of the communication system through the target access node using the non-access stratum security context previously established between the apparatus and the mobility management node, the encrypted non-access stratum message indicating that the radio link failure has occurred,

wherein the encrypted non-access stratum message is encrypted using a cryptographic key created from the non-access stratum security context between the apparatus and the mobility management node.

21. A method comprising:

establishing, between user equipment and a mobility management node of a communication system, via a source access node of the communication system, a non-access stratum security context; and

in an instance in which a radio link failure occurs between the user equipment and the source access node of the communication system during a data transfer operation over a control plane, initiating recovery of the radio link for the user equipment, through a target access node of the communication system, by sending an encrypted non-access stratum message from the user equipment to the mobility management node of the communication system through the target access node using the non-access stratum security context previously established between the user equipment and the mobility management node, the encrypted non-access stratum message indicating that the radio link failure has occurred,

wherein the user equipment comprises a processor and memory configured to initiate the radio link recovery, and

wherein the encrypted non-access stratum message is encrypted using a cryptographic key created from the non-access stratum security context between the user equipment and the mobility management node.

22. A non-transitory computer-readable storage medium having embodied therein executable program code that when executed by a processor causes the processor to:

establish, between user equipment and a mobility management node of a communication system, via a source access node of the communication system, a non-access stratum security context; and

in an instance in which a radio link failure occurs between the user equipment and the source access node of the communication system during a data transfer operation over a control plane, initiate recovery of the radio link for the user equipment, through a target access node of the communication system, by sending an encrypted non-access stratum message from the user equipment to the mobility management node of the communication system through the target access node using the non-access stratum security context previously established between the user equipment and the mobility management node, the encrypted non-access stratum message indicating that the radio link failure has occurred,

wherein the encrypted non-access stratum message is encrypted using a cryptographic key created from the non-access stratum security context between the user equipment and the mobility management node.