Importance

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Abstract

The present invention relates generally to satellite communication systems, and more particularly to a method and system for stabilizing transmission frequencies in a mobile satellite communication system. The preferred embodiment of the invention involves adjusting the transmit frequency of the gateway to account for a frequency shift from the reference frequency on the link between the gateway and the satellite. The preferred method of stabilizing the transmission frequency of a mobile terminal in a mobile satellite communication system involves receiving frequency offset information transmitted by a gateway in the mobile satellite system, and adjusting a reference oscillator in a mobile terminal based on the frequency offset information. The preferred embodiment of the system includes a plurality of mobile terminals, a satellite adapted to communicate with the mobile terminals, and a gateway in communication with the satellite. Each mobile terminal has a mobile terminal reference oscillator, and the satellite has a satellite reference oscillator. The gateway has a high-stability reference oscillator and a digital processor. The digital processor includes a routine for calculating a frequency offset, such as reference oscillator drift. The gateway transmits the frequency offset to at least one of the mobile terminals via the satellite. At least one of the mobile terminals receives the frequency offset and adjusts the mobile terminal reference oscillator to compensate for the received frequency offset.

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First Claim