Patent ID: 7450069

Claim:
A method of determining a time of flight between first and second wireless communication devices, comprising the steps of: conducting a first estimate of a time of flight of a signal between the first and second wireless communication devices, the first estimate being conducted by timing a transmission and response between the first wireless communication device and the second wireless communication device; conducting a subsequent estimate of a time of flight of a signal between the first and second wireless communication devices, the subsequent estimate being conducted by timing another transmission and response between the first wireless communication device and the second wireless communication device, wherein the subsequent estimate is performed with a clock phase in the first device that is offset by a known amount relative to the clock phase used for the first time-of-flight estimate; comparing the first and the subsequent time of flight estimates; and computing a refined estimate of the time of flight of a signal between the first and second wireless communication devices by combining the estimates based on the difference between the subsequent and the first time-of-flight estimates and the known clock phase offset.