Standard time and frequency signal broadcast via INSAT-accuracy improvements using differential mode

We describe the standard time and frequency signal (STFS) broadcast via the INSAT satellite and its use in accurate time synchronization and frequency calibration anywhere in India. Under normal operation it is possible to achieve a synchronization accuracy of better than /spl plusmn/20 /spl mu/s. For users with higher accuracy requirements we discuss the capability of the STFS broadcast to provide time synchronization with an accuracy better than 1 /spl mu/s using a mode of operation which we call differential STFS. Here we further correct the error residuals in the received STFS using data from a reference station collocated with the uplinking site. Both analytical and actual experimental data are presented.