Alternating sequential half duplex communication system
First Claim
1. A communication system for transferring messages between central communication stations and one or more of a plurality of mobile terminals through Earth orbital relay satellites, comprising:
- at least one central communication station having first transceiver means for transmitting a first communication signal in the form of Time Division Multiplexed communication signals, which comprise a series of N channels which are separated into A address channels and D data channel;
said central communication station further comprising;
receiver assignment means for detecting which of said plurality of mobile terminals each message is directed to;
channel assignment means for assigning at least one channel to each of said messages at a time from said D channels;
address control means for transferring a terminal address and an associated channel assignment onto one of said A channels in response to input messages intended for a corresponding terminal; and
message input means connected to said channel assignment means for receiving digital messages and transferring said messages onto said D channels in response to an assignment from said channel assignment means; and
at least one mobile terminal having second transceiver means for receiving and demodulating said first communication signal, and for transmitting at a predetermined transmit duty cycle, second communication signals to at least one of said central communication stations.
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Accused Products
Abstract
A message communication system employing one or more centralized communication stations transferring messages through Earth orbit repeater satellites to or from mobile terminals with at least one central communication station having a first transceiver for transmitting a first communication signal to one or more mobile terminals and at least one mobile terminal having a second transceiver for receiving the first communication signal and demodulating it, and for transmitting at a predetermined duty cycle of the second transceiver, a second communication signal to at least one of the central communication stations. The preferred duty cycle over which the second communication signal is transmitted is about fifty percent of the second transceiver duty cycle. The communication system uses Time Division Multiplexed (TDM) communication signals using a number of channels as designated address channels with the remainder being used for data transfer. Information transmitted on the address channels is used by terminals to determine both the presence of a message and its corresponding data transmission or reception channel. In addition the terminals use the reception of the first communication signal to adjust return link transmission frequency to compensate for transmission path errors. The alternating duty cycle allows mobile terminals to use a single set of local oscillators for both transmission and reception modes of operation. To decrease interference with other systems the present system employs a power dispersal modulation function to achieve the footprint of a video signal for high transfer rate digital communication signals.
291 Citations
58 Claims
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1. A communication system for transferring messages between central communication stations and one or more of a plurality of mobile terminals through Earth orbital relay satellites, comprising:
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at least one central communication station having first transceiver means for transmitting a first communication signal in the form of Time Division Multiplexed communication signals, which comprise a series of N channels which are separated into A address channels and D data channel; said central communication station further comprising; receiver assignment means for detecting which of said plurality of mobile terminals each message is directed to; channel assignment means for assigning at least one channel to each of said messages at a time from said D channels; address control means for transferring a terminal address and an associated channel assignment onto one of said A channels in response to input messages intended for a corresponding terminal; and message input means connected to said channel assignment means for receiving digital messages and transferring said messages onto said D channels in response to an assignment from said channel assignment means; and at least one mobile terminal having second transceiver means for receiving and demodulating said first communication signal, and for transmitting at a predetermined transmit duty cycle, second communication signals to at least one of said central communication stations. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A communication system for transferring messages between central communication stations and one or more of a plurality of mobile terminals through Earth orbital relay satellites, comprising:
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at least one central communication station having transceiver means for transmitting a first communication signal; and at least one mobile terminal having second transceiver means for receiving and demodulating said first communication signal, and for transmitting at a predetermined transmit duty cycle, second communication signals to at least one of said central communication stations, said second transceiver means having a demodulator/modulator apparatus, comprising; up/down conversion means for converting received signals at extra high frequencies to a first preselected intermediate frequency range and for converting signals to be transmitted from said first intermediate frequency range to said extra high frequencies; a tunable band pass filter connected in series with said up/down conversion means, said tunable band pass filter capable of having a preselected band pass range tuned in response to a control signal; a power signal splitter connected at a first input/output port in series with said tunable band pass filter; a first mixer connected at a first input to a second input/output port of said signal splitter; a coarse frequency synthesizer connected to said first mixer at a second input; a second band pass filter connected in series with an output of said first mixer; a second mixer connected in series with said second band pass filter and connected thereto at a first input; a fine frequency synthesizer connected to said second mixer at a second input; a crystal output filter connected to an output of said second mixer; a third mixer connected at a first input to said fine synthesizer and at a second input to said coarse synthesizer, having an output connected to a third input/output port of said power splitter; and transmit modulation means connected to said fine synthesizer for modulating a frequency input thereof in response to transmission of desired message signals.
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10. A communication system for transferring messages between central communication stations and one or more of a plurality of mobile terminals through Earth orbital relay satellites, comprising:
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at least one central communication station having first transceiver means for modulating a carrier wave of preselected frequency components with said messages and for transmitting a resulting signal as a first communication signal; and at least one mobile terminal having second transceiver means for receiving, demodulating, and detecting transmission characteristics of said first communication signal, and for transmitting at a predetermined transmit duty cycle during a preselected transmit and receive period, second communication signals to at least one of said central communication stations, and for adjusting transmission characteristics of said second communication signals in response to said first communication signal detected transmission characteristics, and wherein said second transceiver means further comprises data modulation means for applying a direct spread spectrum coding function to message data of said second communication signals. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 29)
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21. A communication system for transferring messages between central communication stations and one or more of a plurality of mobile terminals through Earth orbital relay satellites, comprising:
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at least one central communication station having first transceiver means for modulating a carrier wave of preselected frequency components with said messages and for transmitting a resulting signal as a first communication signal; at least one mobile terminal having second transceiver means for receiving, demodulating, and detecting transmission characteristics of said first communication signal, and for transmitting at a predetermined transmit duty cycle during a preselected transmit and receive period, second communication signals to at least one of said central communication stations, and for adjusting transmission characteristics of said second communication signals in response to said first communication signal detected transmission characteristics; and wherein said at least one central communication station first transceiver means further comprises modulation means for modulating said carrier wave with said messages and said carrier wave is a periodic triangle wave in frequency with respect to time. - View Dependent Claims (22, 23, 24, 25)
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26. A communication system for transferring messages between central communication stations and one or more of a plurality of mobile terminals through Earth orbital relay satellites, comprising:
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at least one central communication station having first transceiver means for modulating a carrier wave of preselected frequency components with said messages and for transmitting a resulting signal as a first communication signal; and at least one mobile terminal having second transceiver means for receiving, demodulating, and detecting transmission characteristics of said first communication signal, and for transmitting at a predetermined transmit duty cycle during a preselected transmit and receive period, second communication signals to at least one of said central communication stations, and for adjusting transmission characteristics of said second communication signals in response to said first communication signal detected transmission characteristics, and wherein said second transceiver means further comprises adjustment means for adjusting said transmit duty cycle to zero when said first communication signal reception degrades below a desired level. - View Dependent Claims (27, 28)
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30. A method of transferring messages between central communication stations and one or more of a plurality of mobile terminals through one or more Earth orbital relay satellites, comprising the steps of:
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modulating a carrier wave comprising preselected frequency components with said messages to form a first communication signal; transmitting said first communication signal from at least one central communication station through said satellites; receiving and demodulating said first communication signal at said one or more mobile terminals with a transceiver to produce at least one message; tracking and substantially locking onto locations of said satellites using said first communication signal during reception; directing signal transmission from said transceiver to said satellites according to acquired tracking information for signal reception direction; and transmitting at a predetermined transmit duty cycle, a second communication signal from said transceiver to said central communication stations through said locked on and tracked satellites. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45)
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46. A demodulator/modulator apparatus for use in communication transceivers, comprising:
- up/down conversion means for converting received signals at predetermined high frequencies to a first preselected intermediate frequency range and for converting signals to be transmitted from said first intermediate frequency range to said predetermined high frequencies;
a tunable band pass filter connected in series with said up/down conversion means, said tunable band pass filter capable of having a preselected band pass range tuned in response to a control signal; a power signal splitter connected at a first input/output port in series with said tunable band pass filter; a first mixer connected to a second input/output port of said signal splitter; a coarse frequency synthesizer connected to said first mixer; a second band pass filter connected in series with an output of said first mixer; a second mixer connected in series with said second band pass filter; a fine frequency synthesizer connected to said second mixer at a second input; a crystal output filter connected to an output of said second mixer; a third mixer connected at a first input to said fine synthesizer and at a second input to said coarse synthesizer, having an output connected to a third input/output port of said power splitter; and transmit modulation means connected to said fine synthesizer for modulating a frequency input thereof in response to transmission of desired communication signals. - View Dependent Claims (47, 48)
- up/down conversion means for converting received signals at predetermined high frequencies to a first preselected intermediate frequency range and for converting signals to be transmitted from said first intermediate frequency range to said predetermined high frequencies;
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49. A communication system for transferring messages between central communication stations and more or more of a plurality of mobile terminals through Earth orbital relay satellites, comprising:
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at least one central communication station each having first transceiver means for, generating Time Division Multiplexed data from ones of said messages, modulating said data upon a first carrier wave wherein said first carrier wave is a periodic triangle wave in frequency with respect to time, and transmitting said data modulated first carrier wave as a first communication signal; and at least one mobile terminal each having second transceiver means for, receiving said first communication signal, demodulating said received first communication signal, providing from said demodulated first communication signal certain ones of said messages intended for a corresponding one of said mobile terminals, spread spectrum modulating other ones of said messages, and transmitting said spread spectrum modulated messages as a second communication signal to at least one of said central communication stations, said second transceiver means receiving and transmitting respectively during alternating sequential receive and transmit periods. - View Dependent Claims (50, 51, 52, 53, 54, 55, 56, 57, 58)
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Specification