Device and method for nodal multiple access into communications channels
First Claim
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1. A system for nodal division multiple access communication signal processing comprising:
- a single satellite transponder;
a plurality of modulated signals transmitted to said satellite transponder from at least first and second sites;
a composite signal of said plurality of signals transmitted to at least one receive location;
a modulating subsystem for modulating a carrier of said composite signal with an information bit stream by removing local modulation from said incoming composite signal, determining an estimate of signal delay time and carrier frequency shift of the composite signal, using said estimate to modify an outgoing signal thereby defining a replica of said outgoing signal, and subtracting said replicated signal from said composite signal, said outgoing signal being selected from stored outgoing signals;
a transmitter for transmitting said outgoing signal from said at least first and second sites.
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Abstract
A nodal division multiple access technique for multiple access to a communications channel such as a satellite transponder. The present invention provides multiple access into a communications channel where each accessing site utilizes one signal from a composite amplitude/phase digital signal constellation, such that demodulators receive the composite signal without changes in the system design related to the multiple access operation.
23 Citations
22 Claims
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1. A system for nodal division multiple access communication signal processing comprising:
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a single satellite transponder; a plurality of modulated signals transmitted to said satellite transponder from at least first and second sites; a composite signal of said plurality of signals transmitted to at least one receive location; a modulating subsystem for modulating a carrier of said composite signal with an information bit stream by removing local modulation from said incoming composite signal, determining an estimate of signal delay time and carrier frequency shift of the composite signal, using said estimate to modify an outgoing signal thereby defining a replica of said outgoing signal, and subtracting said replicated signal from said composite signal, said outgoing signal being selected from stored outgoing signals; a transmitter for transmitting said outgoing signal from said at least first and second sites. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A system for nodal division multiple access to a satellite communications channel comprising:
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a modulation scheme having an M-ARY phase/amplitude signal constellation; a first modulated signal transmitted from a first site to a transponder; a second modulated signal transmitted from a second site to said transponder; a composite signal of said first and second modulated signals transmitted to at least one receive location; local modulation being removed from said transmitted composite signal at at least one of said at lest two transmit sites; a local I/Q coordinate space defined by In-phase and Quadrature components of said composite signal; an optimum I/Q location for said composite signal determined by maximizing a distance between signals in said composite signal, a local signal and a signal from said at least a second site; geometric data used to remove effects of a changing geometry for said transponder from said composite signal; a modulator for modulating said composite signal with an information bit stream to define an outgoing modulated signal; and a transmitter for transmitting said outgoing modulated signal. - View Dependent Claims (9)
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10. A method for multiple access to a communications channel on a satellite comprising the steps of:
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transmitting a first modulated signal from a first site to a transponder; transmitting at least a second modulated signal from at least a second site to said transponder; transmitting a composite signal of said first and second signals to at least one receive location; modulating a carrier of said composite signal with an information bit stream by removing local modulation from said incoming composite signal, determining an estimate of signal delay time and carrier frequency shift of the composite signal, using said estimate to modify an outgoing signal thereby defining a replica of said outgoing signal, and subtracting said replicated signal from said composite signal, said outgoing signal being selected from stored outgoing signals; and transmitting said outgoing signal from said first site and second site. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A nodal division multiple access method for multiple access to a satellite communications channel comprising the steps of:
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utilizing a modulation scheme having an M-ARY phase/amplitude signal constellation; transmitting a first modulated signal from a first site to a transponder; transmitting at least a second modulated signal from at least a second site to said transponder; transmitting a composite signal of said first and second modulated signals to at least one receive location; removing, at one of said at least two transmit sites, local modulation from said incoming composite signal; recovering a frequency of said composite signal; converting said composite signal into In-phase and Quadrature components, thereby defining a I/Q coordinate space for signal processing at one of said at least two transmit sites and; determining an optimum I/Q location for said composite signal by maximizing a distance between signals the first modulated signal and the second modulated signal in the I/Q coordinate space; using geometric data to remove effects of a changing geometry for said transponder from said composite signal; modulating said composite signal with an information bit stream to define an outgoing modulate signal; and transmitting said outgoing modulated signal. - View Dependent Claims (21, 22)
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Specification