Wireless time reference system and method

Abstract

Instead of normalizing time reference of independent spatially-located clocks using a reference tag transmission from known location, the present invention uses an interarrival time interval between a pulse pair of UWB pulses as a timing metric. Thus, a method of synchronizing spatially-located clock or normalizing time indications thereof comprises transmitting a UWB pulse pair, determining at first and second monitoring stations a respective count value indicative of a locally measured time interval between received pulse pairs, determining a ratio between clock counts of first and second monitoring stations, and utilizing the ratio to determine clock skew, e.g., a timing correction to be applied to respective local clocks of the monitoring stations. A corresponding system comprises a reference tag transmitter that transmits a pulse pair of UWB pulses to define a time reference interval, a first independent receiver that receives the pulse pair to generate a first count value indicative an interarrival interval between the pulse pair, a second independent receiver that receives the pulse pair to similarly generate a second count value, and a processor hub responsive to the count values to determine a ratio corresponding to the ratio of respective clock frequencies of the first and second receiver clocks. Once the correction is applied, time-of-arrival information from object tag transmissions may be used to determine object location with sub-foot position accuracies.