Time of Arrival (TOA) method measures the round-trip time (RTT) of a signal. Half of the RTT corresponds to the distance of the mobile device from the stationary device. Once the distances from a mobile device to three stationary devices are estimated, the position of the mobile device with respect to the stationary devices can easily be determined using the intersecting circles of trilateration. TOA requires very accurate and tightly synchronized clocks since 1.0 μs error corresponds to a 300 m error in the distance estimate [2]. Thus inaccuracy in measuring time differences should not exceed tens of nanoseconds since the error is propagated to the distance estimate [4]