Compensation of frequency offset

Claim 1

Frequency offset compensation system in a satellite mobile communication system including a plurality of land earth stations each coupled with a terrestrial network and a satellite through a first radio link, a reference earth station coupled with said satellite through a second radio link to monitor and control said land earth stations, and at least one mobile earth station coupled with said satellite through a third radio link, said system comprising: means installed in a land earth station of the plurality of land earth stations for measuring a first frequency offset in a request signal or a response signal in a received signal from said mobile earth station through said satellite through the third radio link due to a second frequency offset by a transponder in said satellite and a local oscillator in said mobile earth station, and third frequency offset due to doppler shift by movement of said satellite, means for informing the first frequency offset thus measured to said mobile earth station which transmits said request signal or said response signal through a communication channel through the third radio link through said satellite, means installed in said mobile earth station for controlling local frequency for the communication channel based upon said first frequency offset informed by said land earth station so that said first frequency offset thus measured becomes a minimum.