Estimation of clock skew in telephony over packet switched networks

This study deals with some synchronization issues occurring in telephony over asynchronous packet switched networks. A method for estimation of clock skew i.e. difference between the transmitter and receiver clock frequencies is described. The method is based on modeling the clock skew as a linear trend and the network delay jitter as an exponentially distributed i.i.d. random process. The corresponding maximum likelihood parameter estimator of the trend and jitter parameters is derived and expressions for the mean squared estimation error are provided. Simulation results for computer generated data and for delay data recorded in some existing networks are given.