Methods of listen-before-talk mechanism for opportunistic spectrum access
A method of determining and adapting a contention window size (CWS) based on channel loading for load-based equipment (LBE) listen before talk (LBT) channel access mechanism is proposed. The historic observations obtained from carrier sensing can reflect the state of channel loading, which is then used to adapt the maximal contention window size. A wireless device collects historical channel loading information including the number of idle slots and the number of busy slots. The wireless device uses the historical information to estimate the total number of active devices M in the wireless network and the channel-loading factor. The wireless device then computes the thresholds using the long-term value of M and then adapts the value of the CWS based on the channel-loading factor and the thresholds.
1. A method, comprising:
determining a channel loading factor indicative of a channel loading of a channel by a wireless device adopting a load based equipment (LBE) listen-before-talk (LBT) mechanism in a wireless communication network, wherein the channel loading factor is an average channel loading factor determined based on historical backoff procedures performed by the wireless device;
determining a contention window size based on the channel loading factor;
performing another backoff procedure to access the channel based on a random backoff counter value that is determined according to the contention window size; and
transmitting radio signals using the channel if the wireless device during the another backoff procedure detects a channel idle condition for a period defined by the random backoff counter value.
2. The method of claim 1 , wherein the another backoff procedure is an extended clear channel assessment (CCA) channel access procedure.
3. The method of claim 1 , wherein the channel-loading factor is computed based on a relationship between historical random backoff counter values and corresponding backoff time values of the historical backoff procedures.
4. The method of claim 1 , wherein the contention window size is determined based on a high channel-loading threshold and a low channel-loading threshold.
5. The method of claim 4 , wherein the contention window size is increased if the channel loading factor is higher than the high channel-loading threshold.
6. The method of claim 4 , wherein the contention window size is decreased if the channel loading factor is lower than the low channel-loading threshold.
7. The method of claim 4 , wherein the thresholds are determined based on a total number of active devices in the wireless communication network.
8. The method of claim 7 , further comprising estimating, by the wireless device, the total number of active devices in the wireless communication network.
9. A wireless device, comprising:
a processing circuit configured to:
determine a channel loading factor indicative of a channel loading of a channel in a wireless communication network, wherein the channel loading factor is an average channel loading factor determined based on historical backoff procedures performed by the wireless device adopting a load based equipment (LBE) listen-before-talk (LBT) mechanism;
determine a contention window size based on the channel loading factor; and
perform another backoff procedure to access the channel based on a random backoff counter value that is determined according to the contention window size; and
a transmitter configured to transmit radio signals using the channel if the wireless device during the another backoff procedure detects a channel idle condition for a period defined by the random backoff counter value.
10. The wireless device of claim 9 , wherein the another backoff procedure is an extended clear channel assessment (CCA) channel access procedure.
11. The wireless device of claim 9 , wherein the channel-loading factor is computed based on a relationship between historical random backoff counter values and corresponding backoff time values of the historical backoff procedures.
12. The wireless device of claim 9 , wherein the contention window size is determined based on a high channel-loading threshold and a low channel-loading threshold.
13. The wireless device of claim 12 , wherein the contention window size is increased if the channel loading factor is higher than the high channel-loading threshold.
14. The wireless device of claim 12 , wherein the contention window size is decreased if the channel loading factor is lower than the low channel-loading threshold.
15. The wireless device of claim 12 , wherein the thresholds are determined based on a total number of active devices in the wireless communication network.
16. The wireless device of claim 15 , wherein the wireless device is further configured to estimate the total number of active devices in the wireless communication network.