Patent ID: 6058306
Filing Date: 2000-05-02
Classification: H04B

Abstract:
A communication system providing a feeder link to an earth orbiting satellite transponder having a mobile link illuminating several spot beams with associated access, control and traffic channels for multiple user terminals on the earth, the system comprising:means for using the satellite transponder as a reference point to correct for dynamic Doppler caused by satellite motion;means for performing Doppler correction for each of the channels of the feeder link to the satellite transponder;means for calculating Doppler frequency shift in the mobile link between the satellite transponder and a median Doppler line of each spot beam on the earth;means for using the calculated Doppler frequency shift in the mobile link to establish a forward link to the user terminals via the satellite transponder such that when the signal of each control channel is received by any user terminal on the median Doppler line of each spot beam, the carrier frequency of the control channel is received by the user terminal at a preassigned nominal frequency;means for measuring the user terminal Doppler over the access channel and for deriving the Doppler frequency in the traffic channel from the measured Doppler in the access channel of the user terminals; andmeans for facilitating a forward link and a return link over the traffic channel between the user terminal and a satellite base station via the satellite transponder for achieving minimal frequency error at the input of demodulators of the user terminal and the satellite base station.