Contention window adaptation in multi-carrier listen-before-talk protocols

1. A method of adaptation of contention windows in a multicarrier wireless communication system implementing a listen-before-talk protocol, the multicarrier wireless communication system providing multiple secondary cells, SCells, that use multiple component carriers, CCs, the method comprising:

determining at least one first component carrier, CC, of the multiple CCs to serve as a backoff channel;

performing a listen-before-talk procedure on the at least one CC serving as a backoff channel, the listen-before-talk procedure including:

performing sensing for the backoff channel whether a clear channel exists during a backoff period drawn from a contention window, CW;

before an expected completion of the sensing for the backoff channel, performing a clear channel assessment, CCA, on a plurality of the multiple CCs that do not serve as a backoff channel;

transmitting on the first CC for which the sensing indicates a clear channel exists;

transmitting on CCs of the plurality of the multiple CCs for which the CCA indicates a clear channel; and

determining a size of the CW based on a ratio of a plurality of transmission feedback values associated with the multiple CCs, the ratio corresponding to a ratio of negative acknowledgments, NACKs, to acknowledgements, ACKs.

2. The method of claim 1 , wherein

the transmitting on CCs of the plurality of the multiple CCs for which the CCA indicates the clear channel occurring immediately after performing CCA.

3. The method of claim 1 , wherein only the first CC serves as a backoff channel.

4. The method of claim 1 , wherein the CW is increased only if the ratio of NACKs to ACKs exceeds a threshold.

5. The method of claim 1 , wherein the CW is increased only if the ratio of NACKs to ACKs on all backoff channels exceeds a threshold.

6. The method of claim 1 , wherein an increase of the size of the CW is obtained by multiplication of a CW by a factor greater than one.

7. The method of claim 1 , wherein the backoff period is drawn from a joint contention window, JCW, that is determined from CWs of the multiple component carriers.

8. The method of claim 7 , wherein the JCW is a maximum of the CWs of the multiple component carriers.

9. The method of claim 7 , wherein the JCW is an average of the CWs of the multiple component carriers.

10. The method of claim 1 , further comprising performing a listen-before-talk procedure on at least one CC not serving as a backoff channel.

11. A network node for adaptation of contention windows in a multicarrier wireless communication system implementing a listen-before-talk protocol, the multicarrier wireless communication system providing secondary cells, SCells, that use multiple components carriers, CCs, the network node comprising:

processing circuitry including:

a processor;

a memory in communication with the processor, the memory including executable instructions that, when executed by the processor, configure the processor to:

determine at least one first component carrier, CC, of the multiple CCs to serve as a backoff channel;

perform a listen-before-talk procedure on the at least one CC serving as a backoff channel, the listen-before-talk procedure including:

performing sensing for the backoff channel whether a clear channel exists during a backoff period drawn from a contention window, CW; and

before an expected completion of the sensing for the backoff channel, performing a clear channel assessment, CCA, on a plurality of the multiple CCs that do not serve as a backoff channel;

determine a size of CW based on a ratio of a plurality of transmission feedback values associated with the multiple CCs, the ratio corresponding to a ratio of negative acknowledgments, NACKs, to acknowledgements, ACKs; and

a transmitter configured to transmit on the first CC for which the sensing indicates a clear channel exists and transmit on CCs of the plurality of multiple CCs for which CCA indicates a clear channel.

12. The network node of claim 11 , wherein

the transmitting on CCs of the plurality of the multiple CCs for which the CCA indicates the clear channel occurs immediately after performing CCA.

13. The network node of claim 11 , wherein only the first CC serves as a backoff channel.

14. The network node of claim 11 , wherein the CW is increased only if the ratio of NACKs to ACKs exceeds a threshold.

15. The network node of claim 11 , wherein the CW is increased only if the ratio of NACKs to ACKs on all backoff channel exceeds a threshold.

16. The network node of claim 11 , wherein an increase of the size of the CW is obtained by multiplication of a CW by a factor greater than one.

17. The network node of claim 11 , wherein the backoff period is drawn from a joint contention window, JCW, that is determined from CWs of the multiple component carriers.

18. The network node of claim 17 , wherein the JCW is a maximum of the CWs of the multiple component carriers.

19. The network node of claim 17 , wherein the JCW is an average of the CWs of the multiple component carriers.

20. The network node of claim 11 , wherein the memory includes further executable instructions that, when executed by the processor, further configure the processor to perform a listen-before-talk procedure on at least one CC not serving as a backoff channel.

21. A network node for adaptation of contention windows in a multicarrier wireless communication system implementing a listen-before-talk protocol, the multicarrier wireless communication system providing multiple secondary cells, SCells, using multiple component carriers, CCs, the network node comprising:

a listen-before-talk module, configured to perform a listen-before-talk, LBT, procedure at least one first component carrier, CC, of multiple CCs serving as a backoff channel, the LBT procedure including:

determining whether a clear channel exists on the backoff channel during a backoff period drawn from a contention window, CW;

before an expected completion of the determining whether the clear channel exists on the backoff channel, performing a clear channel assessment, CCA, on a plurality of the multiple CCs that do not serve as a backoff channel; and

a contention window size determination module configured to determine a size of the CW based on a ratio of a plurality of transmission feedback values associated with multiple CCs, the ratio corresponding to a ratio of negative acknowledgments, NACKs, to acknowledgements, ACKs;

a transmitter module configured to:

transmit on the first CC for which the determination indicates a clear channel exists; and

transmit on CCs of the plurality of the multiple CCs for which the CCA indicates a clear channel.