Patent ID: 7051246
Filing Date: 2006-05-23
Classification: H04J

Abstract:
1. A method of calculating an estimate of a clock skew between a sender clock and a receiver clock in a packet-based communications network, the sender clock associated with a sending location in the communications network from which one or more packets have been transmitted to a receiving location in the communications network, the receiver clock associated with the receiving location in the communications network, the method comprising the steps of: calculating a first approximation of the clock skew between the sender clock and the receiver clock based on the transmission of one or more of said packets; evaluating the transmission of a current packet, said current packet having been transmitted subsequent to said transmission of said one or more of said packets, to measure a predetermined characteristic of said transmission of said current packet; computing a covariance matrix associated with said current packet based on a timestamp of the sender clock representative of said current packet being sent and on a previous covariance matrix associated with a packet transmitted prior to said transmission of said current packet; and calculating said estimate of the clock skew between the sender clock and the receiver clock based on said first approximation thereof and on said measured characteristic of said transmission of said current packet.