Device and method for nodal multiple access into communications channels
First Claim
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1. A method for multiple access to a communications channel on a satellite comprising the steps of:
- 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 by applying coarse and fine synchronization processes, determining an estimate of satellite-to-ground distance and hence signal delay time, determining a time-rate-of-change of said satellite-to-ground distance and hence carrier frequency shift, 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 a database of outgoing signals stored in an archive; and
transmitting said outgoing signal from said at least two 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.
27 Citations
18 Claims
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1. 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 by applying coarse and fine synchronization processes, determining an estimate of satellite-to-ground distance and hence signal delay time, determining a time-rate-of-change of said satellite-to-ground distance and hence carrier frequency shift, 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 a database of outgoing signals stored in an archive; and transmitting said outgoing signal from said at least two sites. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. 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 local I/Q coordinate space for signal processing at one of said at least two transmit sites and wherein said local I/Q coordinate space is determined with respect to a local voltage control oscillator reference; determining an optimum I/Q location for said composite signal by maximizing a distance between signals in said composite signal, a local signal and a signal from said at least a second site; 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 (14, 15)
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16. 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 with an M-ARY phase/amplitude signal constellation; transmitting a first modulated signal from a first site to a transponder; receiving said first modulated signal at said at least a second site; obtaining a frequency of said first modulated signal; transmitting at least a second modulated signal having a frequency equal to said frequency of said first modulated signal from at least a second site to said transponder; transmitting a composite signal of said first and second carriers 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 local I/Q coordinate space for signal processing at one of said at least two transmit sites and wherein said local I/Q coordinate space is determined with respect to a local voltage control oscillator reference; determining an optimum I/Q location for said composite signal by maximizing a distance between signals in said composite signal, a local signal and a signal from said at least a second site; using orbital 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 (17, 18)
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Specification