Contention-free random access procedure in wireless networks

1. A radio access node in a wireless telecommunication network for performing a random access procedure with a User Equipment, UE, said radio access node comprising

a transceiver element for transmitting information to and receiving information from UEs,

wherein said transceiver element is configured to receive a first message from a UE, said first message containing a pre-assigned contention-free random access preamble and representing a start of a random access procedure and to respond to said received first message by sending a second message to said UE, the second message containing time alignment information for enabling a scheduled transmission of a third message by said UE to said radio access node,

wherein said transceiver element is further configured to:

ascertain that no third message is received from said UE within a predetermined period of time;

transmit a request to said UE at least a predetermined number of times, wherein said request requests a repeat transmission of the third message from said UE and the predetermined number of times comprises a predefined maximum number of requests stored in said radio access node; and

transmit a command to said UE ordering a restart of said random access procedure with the same assigned contention-free random access preamble after transmitting the request to said UE the predetermined number of times.

2. A radio access node according to claim 1 , wherein said transceiver element includes transceiver circuitry and a control module coupled to, and configured to control, said transceiver circuitry.

3. A radio access node according to claim 1 , wherein said transceiver element is further configured to transmit said command ordering the restart of said random access procedure to said UE on a downlink control channel, and to include the same assigned contention-free random access preamble in said command.

4. A radio access node according to claim 1 , wherein said predetermined period of time is selected to ensure that said UE does not return to an idle mode of operation.

5. A radio access node according to claim 1 , wherein said transceiver element is further configured to ascertain that said random access procedure relates to a handover procedure in which said radio access node is a target node before transmitting the command to said UE ordering the restart of said random access procedure.

6. A radio access node according to claim 1 , wherein said radio access node is further configured to pre-assign said contention-free random access preamble to said UE prior to the start of said random access procedure.

7. A radio access node according to claim 1 , wherein said radio access node is configured to operate in an LTE wireless network.

8. A method of performing a random access procedure in a radio access node that is arranged in a wireless network and configured to communicate with User Equipment, UE, said method comprising:

receiving, a first random access message from a UE, said first message containing a pre-assigned contention-free random access preamble and representing a start of a random access procedure

responding to the received first message by sending a second message to said UE, said second message containing time alignment information for enabling a scheduled transmission of a third message by said UE to said radio access node,

ascertaining that no third message is received from said UE within a predetermined period of time and

transmitting a command to said UE ordering a restart of said random access procedure with the same pre-assigned contention-free random access preamble after transmitting a request to said UE a predetermined number of times, each said request requesting a repeat transmission of the third message, wherein the predetermined number of times comprises a predefined maximum number of requests stored in said radio access node.

9. A method according to claim 8 , wherein said step of transmitting said command ordering a restart of said random access procedure includes transmitting a direct order to said UE on a downlink control channel, said direct order containing said assigned contention-free random access preamble.

10. A method according to claim 8 , wherein said predetermined time is selected to ensure that said UE will not return to an idle mode of operation.

11. A method according to claim 8 , further including: ascertaining that said random access procedure concerns a handover procedure in which said radio access node is the target node before transmitting said command ordering the restart of said random access procedure to said UE.

12. A method according to claim 8 , further including: pre-assigning and transmitting said contention-free random access preamble to said UE prior to the start of said random access procedure.

13. A computer program product for use in a radio access node of a wireless network, said computer program product comprising instructions stored on non-transient computer-readable media which, when executed by a processor, perform the method of claim 8 .