Spatial diversity satellite communications system with error control
First Claim
1. In a TDMA satellite communications system employing a plurality of earth stations separated by a substantial distance one from another, each earth station having a transmitter and a receiver, the improvement comprising:
- means for selecting one of said transmitters to transmit an encoded modulated burst of information to said satellite,a plurality of demodulator means each connected to a corresponding one of said receivers for demodulating the message bursts received from the satellite according to a plurality of preselected thresholds and for producing demodulated output signals,probabalistic decoding means connected to receive said demodulated output signals for producing decoded output signals and providing for error correction according to the probability of maximum likelihood of occurrance of said demodulated output signals, andparity check means adapted to receive the decoded output signals from said probablistic decoding means for performing a parity check on said decoded output signals and for producing a single output signal representing the message transmitted by said selected transmitter.
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Accused Products
Abstract
A spatial diversity satellite communications system adapted to provide its own error control. The diversity communications system utilizes transmitting station selection or burst switching in the up-link and both probabalistic and algebraic error control in the down link to increase message accuracy and to overcome precipitation attenuation. Specialized multiple level decision demodulators are employed to exploit the inherent redundancy supplied by having available multiple signals embodying identical messages. Information is fedback, once the system is operating, and is used to select the optimum transmitter site. However, all available receivers are utilized and the received messages are statistically evaluated to accurately reproduce the received message.
103 Citations
12 Claims
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1. In a TDMA satellite communications system employing a plurality of earth stations separated by a substantial distance one from another, each earth station having a transmitter and a receiver, the improvement comprising:
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means for selecting one of said transmitters to transmit an encoded modulated burst of information to said satellite, a plurality of demodulator means each connected to a corresponding one of said receivers for demodulating the message bursts received from the satellite according to a plurality of preselected thresholds and for producing demodulated output signals, probabalistic decoding means connected to receive said demodulated output signals for producing decoded output signals and providing for error correction according to the probability of maximum likelihood of occurrance of said demodulated output signals, and parity check means adapted to receive the decoded output signals from said probablistic decoding means for performing a parity check on said decoded output signals and for producing a single output signal representing the message transmitted by said selected transmitter. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A satellite communication system comprising:
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a plurality of earth stations spaced apart one from another and each having a transmitter and a receiver for transmitting and receiving to and from the satellite coded burst modulated message signals; switch means connected to receive said message signals for selectively enabling only one of said transmitters at a time; control means connected to said receivers for actuating said switch means; demodulator means connected to each receiver for demodulating each received message signal into an output signal composed of binary words of a first number of bits; means connected to receive each output signal from said demodulator means for comparing the corresponding words in each signal one to another and producing output signals composed of binary words of a second number of bits wherein each bit is produced according to the probability of the maximum likelihood of occurrence of each bit; and decoder means connected to receive said output signals composed of said binary words of said second number of bits for parity checking said words and producing a single output signal representing the message transmitted by said enabled transmitter to the satellite. - View Dependent Claims (8, 9, 10, 11)
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12. In a TDMA satellite communications system employing a plurality of earth stations each containing an transmitter and receiver, the improvement comprising:
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switch means for connecting only one transmitter to an encoded modulated burst of information for transmitting said information via said satellite to said earth stations; control means connected to the outputs of said receivers for actuating said switch means in accordance with a predetermined algorithm; a plurality of four phase demodulator means one connected to the output of each receiver for demodulating each received signal into a demodulated signal comprised of binary words; synchronizing means connected to receive each demodulated signal for synchronizing the corresponding words in each demodulated signal to each other and producing parallel synchronized output signals therefrom; decoder means connected to receive said parallel synchronized output signals for detecting the corresponding bits in each binary word and producing a output signal composed of binary words wherein each bit value represents the majority of the bits detected; and means for performing parity check on said output signal from said decoder means and producing an output signal representing said encoded modulated burst of information.
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Specification