Wi-Fi based fine ranging using carrier phase information

A device comprising:

• a transceiver;
• and
• a processor operably connected to the transceiver, the processor configured to:
• obtain Wi-Fi channel state information (CSI) parameters measured at an anchor and a target device from Wi-Fi frames transmitted between the anchor and the target device, the CSI parameters comprising, for each of the anchor and the target device, frame transmission and reception times, a carrier phase of the CSI, a crystal offset factor, and a packet detection time error, wherein each crystal offset factor is estimated based on a carrier frequency offset (CFO) between the target device and the anchor;
• determine a round trip time (RTT) estimate or a relative change in the RTT estimate as a function of the CSI parameters;
• and
• estimate a range between the anchor and the target device as a function of the RTT estimate, or estimate a change in the range between the anchor and the target device as a function of the relative change in the RTT estimate.

A non-transitory computer readable medium comprising program code that, when executed by a processor of a device, causes the device to:

• obtain Wi-Fi channel state information (CSI) parameters measured at an anchor and a target device from Wi-Fi frames transmitted between the anchor and the target device, the CSI parameters comprising, for each of the anchor and the target device, frame transmission and reception times, a carrier phase of the CSI, a crystal offset factor, and a packet detection time error, wherein each crystal offset factor is estimated based on a carrier frequency offset (CFO) between the target device and the anchor;
• determine a round trip time (RTT) estimate or a relative change in the RTT estimate as a function of the CSI parameters;
• and
• estimate a range between the anchor and the target device as a function of the RTT estimate, or estimate a change in the range between the anchor and the target device as a function of the relative change in the RTT estimate.