Channel recovery using group delay information

An apparatus comprising:

• at least one antenna;
• a transceiver coupled to the at least one antenna, the transceiver to transmit and receive radio frequency (RF) signals, the transceiver comprising:
• a RF circuit to transmit and receive the RF signals;
• and
• at least one digital circuit coupled to the RF circuit to process digital signals, the at least one digital circuit to initiate a channel sounding process with a device to couple to the apparatus via a wireless link to:
• determine, for each of a plurality of first channels of the wireless link, a channel response metric, and store the channel response metric in a channel sounding array;
• and
• provide, for each of a plurality of second channels of the wireless link comprising advertisement channels, a predetermined value for a channel response metric, and store the predetermined value in the channel sounding array;
• and
• a processor coupled to the transceiver, the processor to:
• access the channel sounding array and calculate a group delay for each of the plurality of first channels and each of the plurality of second channels based on the channel response metric for the corresponding channel and the channel response metric for a neighboring channel;
• determine a group delay metric based on the group delay for the plurality of first channels and the plurality of second channels;
• calculate, for each of the plurality of second channels, a channel response metric based on the channel response metric for the neighboring channel and the group delay metric;
• determine a distance between the apparatus and the device based at least in part on the channel response metric for each of the plurality of first channels and the calculated channel response metric for each of the plurality of second channels;
• and
• control access to a protected location based at least in part on the distance.

At least one non-transitory storage medium comprising instructions that when executed by at least one processor cause the at least one processor to perform a method comprising:

• determining, for each of a plurality of first channels of a wireless link between an initiator device and a reflector device, a channel response metric;
• providing, for each of a plurality of second channels of the wireless link, the plurality of second channels comprising advertisement channels, a predetermined value for a channel response metric;
• calculating a group delay for each of the plurality of first channels and each of the plurality of second channels based on the channel response metric for the corresponding channel and the channel response metric for a neighboring channel;
• determining a group delay metric based on the group delay for the plurality of first channels and the plurality of second channels;
• calculating, for each of the plurality of second channels, a channel response metric based on the channel response metric for the neighboring channel and the group delay metric;
• determining a distance between the initiator device and the reflector device based, at least in part, on the channel response metric for each of the plurality of first channels and the calculated channel response metric for each of the plurality of second channels;
• and
• enabling access to a protected location based, at least in part, on the distance between the initiator device and the reflector device.