Hughes Electronics Corporation

James Eryx Malcolm

Robert Carroll Marquart

Adrian J Morris

Enrique Laborde

David Alan Roos

Kumar Swaminathan

Seok Ho Kim

Daniel Fraley

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.

Method and system of frequency stabilization in a mobile satellite communication system

A method and system for synchronizing transmission TDMA frames in a mobile satellite communication system are disclosed herein. The method of synchronizing a transmitted frame timing in a mobile satellite communication system comprises the steps of broadcasting a frame timing offset from a satellite to a mobile terminal having a timer, receiving the frame timing offset information transmitted by the satellite in the mobile terminal, and adjusting the timer in the mobile terminal based on the timing offset information. The system includes a plurality of mobile terminals; a satellite adapted to communicate with each of the mobile terminals, the satellite having a satellite reference frame timing; at least one gateway in communication with the satellite, the gateway having a digital processor, the digital processor including a routine for calculating a frame timing offset; with the gateway transmitting the timing offset to at least one of the mobile terminals, the at least one mobile terminal receiving the timing offset and adjusting the mobile terminal transmit frame timing to compensate for the timing offset.

Method and system of frame timing synchronization in TDMA based mobile

A method and system for adjusting the transmission power of a transmitter during a communication with a receiver in a mobile satellite communication system is disclosed herein. The method comprises establishing at least one threshold signal strength value for a transmitted burst; measuring the received signal strength of the burst received by the receiver; comparing the received signal strength with the threshold value; and setting a power control bit based on the comparison. The system comprises a plurality of mobile terminals having a first stored threshold value; a satellite adapted to communicate with each of the mobile terminals; at least one gateway in communication with the satellite, the gateway having a second stored threshold value, and including a routine for measuring the received signal strength of a burst signal transmitted from the mobile terminal, for comparing the received signal strength with the second stored threshold value, and for adjusting the transmission power of the gateway based on the comparison; and each of the mobile terminals including a routine for measuring the received signal strength of a burst signal transmitted from the gateway to the mobile terminals, for comparing the received signal strength with the first stored threshold value, and for adjusting the transmission power of the mobile terminal based on the comparison.

Power control for TDMA mobile satellite communication system

The present invention relates to a device and a method for communicating in a mobile communication system. The method provides a carrier signal having a plurality of frames. Each frame has a plurality of time slots, and each time slot comprises a plurality of transmission bits. A group of time slots are assigned to a communication channel. A traffic burst signal having a plurality of traffic symbols is transmitted over the communication channel by transmitting a first preamble over one of the assigned time slots, and transmitting a second preamble and at least one of the traffic symbols over at least one of the other assigned time slots. The second preamble occupies fewer transmission bits than the first preamble. The apparatus for transmitting a telephony signal over an RF channel includes a modem receiving a digitized PCM telephony signal and producing a traffic burst signal, and a transmitting unit in communication with the modem for transmitting a FDMA/TDMA signal carrying a plurality of traffic burst signals. At least one of the traffic burst signals carries a limited preamble message including a header field and a unique word field and at least one digitized voice message associated with a telephone call. Another traffic burst signal carries at least one signal acquisition message including a unique word field.

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Bethesda, MD, United States of America

James Eryx Malcolm