Skip-correlation based symmetric carrier sensing with multiple power levels

1. A method, comprising:

applying a receiver of a first wireless communications device to receive a transmission of a preamble of a transmitter of a neighboring wireless communications device;

selecting and correlating a subset of one or more samples of the preamble as a function of a transmission power level of a transmitter of the first wireless communications device;

applying the first wireless communications device to automatically choose a variable carrier sensing threshold as a combined function of the transmission power level of the transmitter of the first wireless communications device and the subset of the one or more samples of the preamble; and

applying the first wireless communications device to implement carrier sensing symmetry relative to the neighboring wireless communications device based on the variable carrier sensing threshold.

2. The method of claim 1 wherein the preamble further comprises an indication of the transmission power level that is encoded into the preamble by the neighboring wireless communications device as a function of the transmit power of the transmitter of the neighboring wireless communications device.

3. The method of claim 2 further comprising choosing the variable carrier sensing threshold as a combined function of the transmit power of the first wireless communications device and the transmit power of the neighboring wireless communications device.

4. The method of claim 2 wherein the indication of the transmission power level is encoded into the preamble by the neighboring wireless communications device by constructing a variable length preamble from a subset of samples of a corresponding Short Training Sequence (STS) as a function of the transmit power of the neighboring wireless communications device.

5. The method of claim 4 wherein choosing the variable carrier sensing threshold further comprises:

applying the first wireless communications device to automatically select and correlate the subset of samples of the preamble;

computing a total preamble energy of the correlated samples of the preamble; and

selecting the variable carrier sensing threshold as a function of the total preamble energy.

6. The method of claim 1 further comprising:

applying the first wireless communications device to maintain a table comprising a plurality of identified neighboring wireless transmitters and a transmit power of each of those neighboring wireless transmitters;

wherein the preamble further comprises an identification of the neighboring wireless transmitter from which the transmission of the preamble was received;

applying the first wireless communications device to perform a lookup on the table to determine the transmit power of the neighboring wireless transmitter identified by the preamble; and

choosing the variable carrier sensing threshold as a combined function of the transmit power of the first wireless communications device and the transmit power of the identified neighboring wireless transmitter.

7. The method of claim 1 wherein:

the preamble received from the transmitter of the neighboring wireless communications device is selected by the neighboring wireless communications device from a set of predefined preambles as a function of a transmit power of the neighboring wireless communications device; and

wherein the first wireless communications device applies a matched filter bank to correlate the received preamble against each possible preamble from the set of preambles to choose the variable carrier sensing threshold.

8. The method of claim 1 wherein implementing carrier sensing symmetry further comprises applying the variable carrier sensing threshold to determine whether a particular wireless channel is free for transmissions by the first wireless communications device.

9. The method of claim 1 wherein the receiver is a component of a physical radio of the first wireless communications device.

10. The method of claim 1 wherein the receiver is a component of a software-defined radio of the first wireless communications device.

11. A system, comprising:

a first wireless communications device having a receiver configured to receive a preamble of a transmitter of a neighboring wireless communications device and to select and correlate a subset of one or more samples of the preamble as a function of a transmission power level of a transmitter of the first wireless communications device;

the preamble including an indication of a transmission power level of the transmitter of the neighboring wireless communications device;

the first wireless communications device further configured to automatically determine a variable carrier sensing threshold as a combined function of the transmission power level of the transmitter of the first wireless communications device and the transmission power level of the transmitter of the neighboring wireless communications device; and

the first wireless communications device further configured to apply the variable carrier sensing threshold to implement carrier sensing symmetry between the first wireless communications device and the neighboring wireless communications device.

12. The system of claim 11 wherein the preamble is constructed by the neighboring wireless communications device from a subset of samples of a corresponding Short Training Sequence (STS) as a function of the transmit power of the transmitter of the neighboring wireless communications device.

13. The system of claim 12 wherein determining the variable carrier sensing threshold further comprises:

applying the first wireless communications device to automatically select and correlate the subset of samples of the preamble;

computing a total preamble energy of the correlated samples; and

determining the variable carrier sensing threshold as a function of the total preamble energy.

14. The system of claim 11 wherein implementing carrier sensing symmetry further comprises applying the variable carrier sensing threshold to determine whether a particular wireless channel is free for transmissions by the first wireless communications device.

15. The system of claim 11 wherein the preamble received from the transmitter of the neighboring wireless communications device is selected by the neighboring wireless communications device from a set of predefined preambles as a function of the transmit power of the transmitter of the neighboring wireless communications device; and

wherein the first wireless communications device applies a matched filter bank to correlate the received preamble against each possible preamble from the set of preambles to determine the variable carrier sensing threshold.

16. A wireless communications device comprising:

a receiver configured to receive a transmission of a preamble from one or more neighboring transmitters;

the wireless communications device configured to select and correlate a subset of samples of the received preamble as a function of a transmission power level of a transmitter of the wireless communications device;

the wireless communications device further configured to compute a total preamble energy of the correlated samples of the preamble; and

the wireless communications device further configured to apply the total preamble energy as a carrier sensing threshold to determine whether a wireless channel is free for transmissions by the transmitter of the wireless communications device.

17. The wireless communications device of claim 16 wherein the preamble further comprises an indication of a transmission power level of the neighboring transmitter from which the preamble was received.

18. The wireless communications device of claim 17 further comprising applying the wireless communications device to automatically determine the variable carrier sensing threshold as a combined function of the transmit power of the transmitter of the wireless communications device and the transmit power of the neighboring transmitter from which the preamble was received.

19. The wireless communications device of claim 17 , wherein the indication of the transmission power level is encoded into the preamble by the neighboring transmitter from which the preamble was received by constructing a variable length preamble from a subset of samples of a corresponding Short Training Sequence (STS) as a function of the transmit power of the neighboring transmitter.

20. The wireless communications device of claim 16 wherein the receiver and the transmitter of the wireless communications device further comprise any combination of physical radio devices and software-defined radio devices.