Patent ID: 7969963

Claim:
A method for improving two-way radio ranging accuracy by estimating a relative clock frequency offset between a first clock X of a first transceiver and a second clock Y a second transceiver, comprising: transmitting, by the first transceiver, a first packet at time t 0 of the first clock X; receiving, by the second transceiver, the first packet at a time t 1 of the second clock Y; transmitting, by the second transceiver, a second packet at a time t 2 of the second clock; receiving, by the first transceiver, the second packet at a time t 3 of the first clock X; transmitting, by the second transceiver, a third packet at a time t 4 of the second clock Y; receiving, by the first transceiver, the third packet at a time t 5 of the first clock X, and calculating the relative clock frequency offset by the first transceiver in which the relative clock frequency offset is Δ ⁢ ⁢ f XY ′ ≅ 2 ⁢ ⁢ f ⁡ ( N 24 Y - N 35 X ) N 24 Y + N 35 X , where f is a nominal clock frequency of the first and second clocks, N Y 24 is a measured first delay between times t 2 and t 4 of the second clock, N X 35 is a measured second delay between times t 3 and t 5 of the first clock X; and canceling an effect of channel impulse response, RF circuit and baseband circuit imperfection while determining the relative clock frequency offset.