Active geo-location for orthogonal frequency division multiplex wireless local area network devices

A first wireless device (WD) configured to determine at least a round trip time (RTT) associated with a plurality of ranging signals transmitted by the first WD to a second WD, the first WD comprising:

• a receiver configured to:
• receive a plurality of response signals from the second WD in response to the plurality of ranging signals;
• and
• processing circuitry in communication with the receiver, the processing circuitry being configured to:
• determine a plurality of expected response signals, each expected response signal having a scrambling seed number and an expected sequence of time domain symbols corresponding to the scrambling seed number;
• for each response signal of the plurality of response signals:
• determine a plurality of frequency shifted time domain samples from each response signal, each frequency shifted time domain sample corresponding to a frequency shift of a plurality of frequency shifts;
• cross-correlate each frequency shifted time domain sample of the plurality of frequency shifted time domain samples with the expected sequence of time domain symbols of each expected response signal of the plurality of expected response signals, the cross-correlating being performed for each scrambling seed number of each expected response signal;
• determine a maximum correlation value for each frequency shift and each frequency shifted time domain sample;
• sum the maximum correlation value for each frequency shift, each frequency shifted time domain sample, and each response signal;
• determine a peak correlation value based on the summed maximum correlation value;
• and
• determine at least the RTT associated with the plurality of ranging signals based at least in part on the peak correlation value.

An airborne station configured to determine at least a round trip time (RTT) associated with a plurality of ranging signals transmitted by the airborne station to a target station, the airborne station comprising:

• a receiver configured to:
• receive a plurality of response signals from the target station in response to the plurality of ranging signals;
• and
• processing circuitry in communication with the receiver, the processing circuitry being configured to:
• determine a plurality of expected response signals, each expected response signal having a scrambling seed number and an expected sequence of time domain symbols corresponding to the scrambling seed number;
• for each response signal of the plurality of response signals:
• determine a plurality of frequency shifted time domain samples from each response signal, each frequency shifted time domain sample corresponding to a frequency shift of a plurality of frequency shifts;
• cross-correlate each frequency shifted time domain sample of the plurality of frequency shifted time domain samples with the expected sequence of time domain symbols of each expected response signal of the plurality of expected response signals, the cross-correlating being performed for each scrambling seed number of each expected response signal;
• determine a maximum correlation value for each frequency shift and each frequency shifted time domain sample;
• sum the maximum correlation value for each frequency shift, each frequency shifted time domain sample, and each response signal;
• determine a peak correlation value based on the summed maximum correlation value;
• and
• determine at least the RTT associated with the plurality of ranging signals based at least in part on the peak correlation value.