Method and Arrangement for Managing Security Reconfiguration in a Cellular Communication System

1. A method of managing security reconfiguration and cell update procedures in a user equipment in a cellular communication system, the method comprising: receiving a security reconfiguration request from a node of the cellular communication system at the user equipment, wherein the security reconfiguration request is to request a security reconfiguration for the user equipment; initiating and confirming a security reconfiguration procedure responsive to receiving the security reconfiguration request from the node; after receiving the security reconfiguration request and after initiating and confirming the security reconfiguration procedure, detecting a cell update trigger event; aborting the security reconfiguration procedure in said user equipment in response to detecting the cell update trigger event without previously receiving a security mode complete acknowledge for the security reconfiguration procedure while the security reconfiguration procedure is ongoing; providing a security status indication at the user equipment in response to aborting the security reconfiguration procedure; and jointly transmitting a cell update message and the security status indication from the user equipment to the node of the cellular communication system wherein the security status indication informs about the security reconfiguration procedure being aborted in the user equipment.

2. The method according to claim 1 , wherein providing the security status indication comprises setting the security status indication to a predetermined value.

3. The method according to claim 1 , wherein jointly transmitting the cell update message and said security status indication comprises transmitting the cell update message and said security status indication in a same cell update message.

4. The method according to claim 3 , wherein the security status indication is provided as a boolean information element in the cell update message.

5. The method of claim 1 wherein jointly transmitting the cell update message and the security status indication comprises transmitting the security status indication as an information element of the cell update message.

6. The method of claim 1 wherein the security reconfiguration procedure comprises a security reconfiguration procedure for the user equipment to reconfigure from a previous security configuration to a new configuration, and wherein aborting the security reconfiguration procedure comprises reverting back to the previous security configuration.

7. The method of claim 6 wherein receiving the security reconfiguration request comprises receiving a security mode command from the node of the cellular communication system, wherein confirming the security reconfiguration procedure comprises transmitting a security mode complete message to the node of the cellular communication system, and wherein jointly transmitting the cell update message and the security status indication comprise transmitting the cell update message and the security status indication in a same cell update message.

8. The method according to claim 1 wherein the node in the cellular communication system is a Radio Network Controller (RNC).

9. The method according to claim 1 wherein providing a security status indication comprises setting the security status indication to a predetermined value at the user equipment in response to aborting the security reconfiguration procedure and in response to the cell update message being triggered to be sent during an ongoing security reconfiguration procedure.

10. A method of managing security reconfiguration and cell update procedures in a node in a cellular communication system, the method comprising: transmitting a security reconfiguration request from the node in the cellular communication system to a user equipment wherein the security reconfiguration request is to request a security reconfiguration for the user equipment; receiving a security reconfiguration confirmation at the node in the cellular communication system from the user equipment for the security reconfiguration; acknowledging and performing the security reconfiguration for the user equipment, wherein acknowledging the security reconfiguration comprises transmitting an acknowledgment for the security reconfiguration to the user equipment; after transmitting the acknowledgment for the security reconfiguration to the user equipment, jointly receiving a cell update message and a security status indication at the node in the cellular communication system from the user equipment, wherein the security status indication informs about the security reconfiguration being aborted in the user equipment; and after transmitting the acknowledgment for the security reconfiguration to the user equipment, managing the security reconfiguration for the user equipment at the node in the cellular communication system based on the security status indication received from the user equipment wherein the security status indication informs about the security reconfiguration being aborted in the user equipment.

11. The method according to claim 10 , wherein managing the security reconfiguration comprises retransmitting the aborted security reconfiguration request from the node in the cellular communication system to the user equipment in response to receiving the security status indication.

12. The method of claim 10 wherein jointly receiving the cell update message and the security status indication comprises receiving the security status indication as an information element of the cell update message that informs about the security reconfiguration being aborted in the user equipment after transmitting the acknowledgment for the security reconfiguration to the user equipment, and wherein managing the security reconfiguration comprises managing the security reconfiguration responsive to receiving the security status indication as the information element of the cell update message.

13. The method of claim 10 wherein the security reconfiguration request for the user equipment comprises a request to reconfigure from a previous security configuration to a new configuration, and wherein managing the security reconfiguration comprises reverting to the previous security configuration for the user equipment in response to receiving the security status indication at the node in the cellular communication system from the user equipment.

14. The method of claim 13 wherein transmitting the security reconfiguration request comprises transmitting a security mode command from the node of the cellular communication system to the user equipment, wherein receiving the security reconfiguration confirmation comprises receiving a security mode complete message at the node of the cellular communication system, and wherein jointly receiving the cell update message and the security status indication comprises receiving the cell update message and the security status indication in a same cell update message.

15. The method according to claim 10 , wherein managing the security reconfiguration comprises reverting to a previous security configuration for the user equipment in response to receiving the security status indication at the node in the cellular communication system from the user equipment.

16. The method according to claim 10 wherein the node in the cellular communication system is a Radio Network Controller (RNC).

17. The method according to claim 12 , wherein managing the security reconfiguration comprises retransmitting the aborted security reconfiguration request from the node in the cellular communication system to the user equipment in response to receiving the security status indication as the information element of the cell update message after transmitting the acknowledgment for the security reconfiguration to the user equipment.