Radio link recovery for user equipment

1. An apparatus comprising:

one or more processors; and

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

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

receiving, at the apparatus, within the non-access stratum security context previously established between the user equipment and the apparatus, a message from the user equipment, the message being encrypted using a cryptographic key associated with the non-access stratum context previously established between the user equipment and the apparatus; and

in an instance in which the 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, enabling 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.

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 1 , wherein the cryptographic key is derived using an uplink message count or a downlink message count.

4. The apparatus of claim 1 , wherein the instructions stored on the one or more memory, when executed by the one or more processors, further cause the apparatus to perform at least:

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

5. The apparatus of claim 4 , wherein the instructions stored on the one or more memory, when executed by the one or more processors, further cause the apparatus to perform at least:

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

6. The apparatus of claim 5 , wherein the instructions stored on the one or more memory, when executed by the one or more processors, further cause the apparatus to perform at least:

sending, from the apparatus, within the non-access stratum security context previously established between the user equipment and the apparatus in the communication system, a second message to the user equipment through the target access node, wherein the second message indicates an acknowledgment of the radio link failure, and is protected using the cryptographic key created within the non-access stratum security context previously established between the user equipment and the apparatus.

7. The apparatus of claim 6 , wherein the second message comprises data associated with the data transfer.

8. The apparatus of claim 7 , wherein the data is at least one of previous buffered data and new data.

9. The apparatus of claim 7 , 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.

10. The apparatus of claim 9 , wherein the encryption key comprises a non-access stratum encryption key.

11. The apparatus of claim 3 , wherein the instructions stored on the one or more memory, when executed by the one or more processors, further cause the apparatus to perform at least:

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

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

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

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

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

16. The apparatus of claim 1 , wherein the apparatus is configured to function as a mobility management node of the communication system, and 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.

17. 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, a message from the user equipment, the message being encrypted using a cryptographic key associated with the non-access stratum context previously established between the user equipment and the apparatus; and

in an instance in which the 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.

18. An apparatus comprising:

one or more processors; and

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

determining, during a data transfer operation over a control plane between the apparatus and a mobility management node of a communication system, via a source access node of the communication system, that a radio link failure has occurred; and

initiating recovery of the radio link for the apparatus, through a target access node of the communication system, by sending a message to the mobility management node of the communication system through the target access node within a non-access stratum security context previously established between the apparatus and the mobility management node, the message comprising an indication that the radio link failure has occurred,

wherein the message is encrypted using a cryptographic key associated with the non-access stratum security context previously established between the apparatus and the mobility management node.

19. A method comprising:

determining, during a data transfer operation over a control plane between a user equipment and a mobility management node of a communication system, via a source access node of the communication system, that a radio link failure has occurred; and

initiating recovery of the radio link, through a target access node of the communication system, by sending a message to the mobility management node of the communication system through the target access node within a non-access stratum security context previously established between the user equipment and the mobility management node, the message comprising an indication that the radio link failure has occurred,

wherein the message is encrypted using a cryptographic key associated with the non-access stratum security context previously established between the user equipment and the mobility management node.

20. An apparatus comprising:

one or more processors; and

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

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

receiving, at the apparatus, within the non-access stratum security context previously established between the user equipment and the apparatus, a message from the user equipment, the message being protected by a key associated with the non-access stratum security context previously established between the user equipment and the apparatus;

in an instance in which the 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, enabling 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; and

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

21. A mobility management entity (MME) device configured to communicate in a communication system, the MME device comprising:

one or more processors; and

one or more memory storing instructions thereon that, when executed by the one or more processors, cause the MME device to perform at least:

causing establishment of a non-access stratum (NAS) security context between a user equipment (UE) and the MME device in the communication system;

in response to a radio link failure of a radio link occurring between the UE and a source access node of the communication system during a data transfer operation over a control plane, receiving, at the MME device, from the UE, via a target access node of the communication system, a first message indicating that the radio link failure has occurred, the target access node being different than the source access node, the first message received at the MME device via the target access node being protected using a key associated with the NAS security context previously established between the UE and the MME device of the communication system;

verifying the UE, at the MME device, using the key associated with the NAS security context previously established between the UE and the MME device;

retrieving, using the MME device, from the source access node, the data that previously failed to be delivered to the UE when the radio link failure occurred during the data transfer operation over the control plane between the MME device and the UE;

initiating, at the MME device, set-up of a signaling interface with the target access node; and

recovering the radio link for the UE, at the MME device, by sending via the signaling interface a second message, the second message being protected using the key associated with the NAS security context previously established between the UE and the MME device, the second message comprising the data that previously failed to be delivered to the UE when the radio link failure occurred during the data transfer operation over the control plane between the MME device and the UE.