Composite spread spectrum signal including modulator demodulator
First Claim
1. A method of transmitting information by generating a spread-spectrum modulated signal and transmitting the signal over a communications link, the method comprising:
- determining selected chipping sequences from a plurality of possible chipping sequences for message bundles in response to data to be transmitted;
determining starting positions of said selected chipping sequences in response to data to be transmitted;
modulating a carrier signal with the selected chipping sequences and beginning the selected chipping sequences at the starting positions to perform simultaneously code shift key modulation and pulse position modulation for the message bundles; and
repeating at least a portion of said selected chipping sequences beginning at the starting positions in every message bundle for at least as long as multipath delays over the communications link.
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Accused Products
Abstract
A composite spread spectrum signal including modulator and demodulator therefor is disclosed. The composite signal having a multi-dimensional signal space, comprising a pulse position modulation dimension generated by varying starting positions of cyclically repeated chipping sequences, a frequency shift key dimension generated by varying a carrier frequency between a plurality of frequencies, code shift keyed dimensions generated by selecting the chipping sequences from among a plurality of orthogonal sequences, and amplitude shift key dimensions generated by selecting amplitudes of each subcarrier for each message bundle. This signal may further comprise a phase shift key dimension generated by assigning a phase relationship of the orthogonal subcarriers.
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Citations
32 Claims
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1. A method of transmitting information by generating a spread-spectrum modulated signal and transmitting the signal over a communications link, the method comprising:
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determining selected chipping sequences from a plurality of possible chipping sequences for message bundles in response to data to be transmitted; determining starting positions of said selected chipping sequences in response to data to be transmitted; modulating a carrier signal with the selected chipping sequences and beginning the selected chipping sequences at the starting positions to perform simultaneously code shift key modulation and pulse position modulation for the message bundles; and repeating at least a portion of said selected chipping sequences beginning at the starting positions in every message bundle for at least as long as multipath delays over the communications link. - View Dependent Claims (2, 3, 4, 5)
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6. A method for transmitting information across a communications link by generating a spread-spectrum modulated signal temporally divided into message bundles, said method comprising:
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generating a first modulated subcarrier by linearly modulating a first subcarrier with a first selected chip sequence being a pseudo-random sequence of plural bits in which starting positions of the transmission of the first selected chip sequence for each message bundle between a first through last bit are determined in response to data to be transmitted, wherein said first selected chip sequence is one of a first plurality of mutually orthogonal chip sequences chosen in response to data to be transmitted; generating a second modulated subcarrier by linearly modulating a second subcarrier with a second selected chip sequence being a pseudo-random sequence of plural bits in which starting positions of the transmission of the second selected chip sequence between a first through last bit are determined in response to data to be transmitted, wherein said second selected chip sequence is one of a second plurality of mutually orthogonal chip sequences chosen in response to data to be transmitted; generating a combined signal by combining said first modulated subcarrier and said second modulated subcarrier in phase quadrature; and inducing frequency shifts in said combined signal corresponding to one of a plurality of frequencies in response to data to be transmitted. - View Dependent Claims (7, 8, 9, 10, 11)
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12. A method for demodulating a spread-spectrum modulated signal to receive transmitted information, said method comprising:
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cross-correlating a received chip sequence of the spread-spectrum modulated signal with a plurality of possible chip sequences each beginning at a predetermined bit; determining to which one of said plurality of possible chip sequences said received chip sequence corresponds; determining a time delay until a correlation peak is generated; determining a frequency shift in a frequency of the spread-spectrum modulated signal; and decoding said time delay, said received chip sequence, and the frequency shift as transmitted information. - View Dependent Claims (13, 14, 15)
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16. An apparatus for transmitting information over a communications link, the apparatus comprising:
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a synthesizer for generating a carrier signal; a modulator for spectrally spreading said carrier signal with a selected chipping sequence, information being encoded into said carrier signal by determining said selected chipping sequence from a plurality of possible chipping sequences and determining a start bit among the bits comprising said selected chipping sequence for each message bundle, the modulator further repeating at least a portion of said selected chipping sequence beginning at the start bit in every message bundle for at least as long as multipath delays over the communications link; and a transmitter for transmitting the modulated carrier signal over the communications link. - View Dependent Claims (17)
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18. An apparatus for transmitting information over a communications link, the apparatus comprising:
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a synthesizer for generating a carrier signal a modulator for phase shift key modulating said carrier signal by a selected chipping sequence, information being encoded into said carrier signal by determining the selected chipping sequence from a plurality of possible chipping sequences and by determining a start bit among the bits comprising said selected chipping sequence for each message bundle; and a modulator for modulating a frequency of said carrier signal encode information. - View Dependent Claims (19, 20)
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21. An apparatus for transmitting information over a communications link, the apparatus comprising:
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a synthesizer for generating a first subcarrier and a second subcarrier in phase quadrature; a first modulator for phase shift key modulating said first subcarrier by first chipping sequences selected from a first set of orthogonal sequences, the first modulator including a first selector for selecting a start bit among the bits comprising said first chipping sequences for each message bundle; a second modulator for phase shift key modulating said second subcarrier by second chipping sequences selected from a second set of orthogonal sequences, each one of said chipping sequences of said first set being orthogonal to every chipping sequence of said second set, the second modulator including a second selector for selecting a start bit from among the bits comprising said second chipping sequences for each message bundle; an adder for combining the modulated first subcarrier and the modulated second subcarrier to generate a composite signal; and a frequency modulator for modulating a frequency of the composite signal. - View Dependent Claims (22, 23, 24)
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25. A demodulator for receiving information over a communications link contained in a spread-spectrum signal, the demodulator comprising:
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a filter for cross-correlating a received chipping sequence with a plurality of possible chipping sequences each beginning at a predetermined bit; a comparator for determining to which one of said plurality of possible chipping sequences said received chipping sequence corresponds; a delay detector for determining a time delay until a correlation peak is generated by said filter relative to a received chipping sequence beginning at the predetermined bit; and a frequency detector for determining a frequency of the spread-spectrum signal; a decoder for decoding said time delay, said received chipping sequence, and the frequency as transmitted data. - View Dependent Claims (26, 27, 28)
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29. A method transmitting information by generating a spread-spectrum modulated signal and transmitting the signal over a communications link, the method comprising:
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determining selected chipping sequences from a plurality of possible chipping sequences in response to data to be transmitted; determining starting positions of the selected chipping sequences in response to data to be transmitted; determining frequency shifts in response to data to be transmitted; modulating a carrier signal with the selected chipping sequences, beginning the selected chipping sequences at the starting positions, and modulating a frequency of the carrier signal in response to the determined frequency shifts to perform simultaneously code shift key modulation, pulse position modulation, and frequency shift key modulation. - View Dependent Claims (30, 31, 32)
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Specification