Patent ID: 7120090

Claim:
A method for determining a timing offset between a first clock and a second clock at respective first and second points in a communications network, the method comprising: transmitting a plurality of request signals from the first point in the network to the second point in the network; receiving at the first point in the network a plurality of reply signals transmitted from the second point in the network, each reply signal corresponding to a respective one of the plurality of request signals; identifying a first request signal and a corresponding reply signal having a minimum round trip delay time; determining from the minimum round trip delay time a minimum single leg delay time; estimating a timing offset between the clock values of the first clock and the second clock at a first instance, the estimation being based upon the minimum single leg delay time, and a transmission time and a reception time of one of the identified request signal and the corresponding reply signal, as given by the respective clocks at the transmission and reception points of the signal; identifying a second request signal and a second corresponding reply signal having another minimum round trip delay time; and estimating a second timing offset between the clock values of the first clock and the second clock at a second instant, the estimation being based upon the another minimum single leg delay time, and a transmission time and a reception time of one of the second identified request signal and the second corresponding reply signal, as given by the respective clocks at the transmission and reception points of the signal; using the first timing offset and the second timing offset to estimate a third timing offset between the first and second clocks at a third instance, wherein the first and second timing offsets are treated as two terms in an arithmetic progression in order to estimate the third timing offset.