Multitone frequency hop communications system
First Claim
1. In a method of communicating information between at least two points using spread spectrum communications technology wherein said information is digitized and encoded, said encoded information is used to modulate a baseband signal having greater bandwidth than the bandwidth of said information, said baseband signal is in turn used to modulate a carrier signal to be transmitted from a first point, and wherein said transmitted signal is received, demodulated and decoded at a second point so as to replicate the information sent, the improvement wherein:
- said information encoding step comprises the substeps of;
establishing a plurality of subsets of tones to represent each possible state of said digitized information during a given timing interval, the tones comprising each said subset being selected from a set of N frequencies;
for selected successive timing intervals, establishing a new plurality of said subsets of tones from said set N, wherein selection of said tones comprising each of said subsets of tones is established based on a known coding sequence; and
said baseband modulation step comprises the substep of;
selecting the subset of tones corresponding to an increment of said digitized information to be transmitted during a timing interval.
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Abstract
An improved spread spectrum communications system is disclosed in which M-ary symbols are defined corresponding to each state of digital data to be transmitted and in which each of those M-ary symbols are represented by a plurality of tones selected from a set of N frequencies. A different plurality of tones out of the set N is established to represent each of the M-ary symbols during each successive timing interval, with selection of the tones comprising each such plurality of tones being determined in accordance with a known coding pattern. Phasing of the tones comprising each such plurality is also determined in accordance with a known coding sequence. After selection of the symbol corresponding to the data to be transmitted during a given timing interval, the frequency domain representation of the plurality of tones corresponding to that symbol is converted to the time domain for transmission. That time domain signal is converted back to the frequency domain by the receiver and the resultant signal processed by M-ary signal correlators synchronized with coding established by the transmitter to determine the transmitted symbol.
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Citations
33 Claims
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1. In a method of communicating information between at least two points using spread spectrum communications technology wherein said information is digitized and encoded, said encoded information is used to modulate a baseband signal having greater bandwidth than the bandwidth of said information, said baseband signal is in turn used to modulate a carrier signal to be transmitted from a first point, and wherein said transmitted signal is received, demodulated and decoded at a second point so as to replicate the information sent, the improvement wherein:
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said information encoding step comprises the substeps of;
establishing a plurality of subsets of tones to represent each possible state of said digitized information during a given timing interval, the tones comprising each said subset being selected from a set of N frequencies;
for selected successive timing intervals, establishing a new plurality of said subsets of tones from said set N, wherein selection of said tones comprising each of said subsets of tones is established based on a known coding sequence; and
said baseband modulation step comprises the substep of;
selecting the subset of tones corresponding to an increment of said digitized information to be transmitted during a timing interval. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. In a method of communicating information between at least two points using spread spectrum communications technology wherein said information is digitized and encoded, said encoded information is used to modulate a baseband signal having greater bandwidth than the bandwidth of said information, said baseband signal is in turn used to modulate a carrier signal to be transmitted from a first point, and wherein said transmitted signal is received, demodulated and decoded at a second point so as to replicate the information sent, the improvement wherein:
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said information encoding step comprises the substeps of;
establishing a plurality of subsets of tones to represent each possible state of said digitized information during a given timing interval, the tones comprising each said subset being selected from a set of N frequencies;
for selected successive timing intervals, establishing new plurality of said subsets of tones from said set N, wherein selection of said tones comprising each of said subsets of tones is established based on a known coding sequence;
said baseband modulation step comprises the substep of selecting the subset of tones corresponding to an increment of said digitized information to be transmitted during a timing interval and causing a frequency domain representation of said corresponding subset of tones to be operated on by an inverse finite Fourier transform thereby producing a time domain representation of said corresponding subset of tones; and
said step of demodulating said received signal includes the substep of operating on said received signal by a finite Fourier transform thereby reproducing a frequency domain representation of said corresponding subset of tones. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. In a method of communicating information between at least two points using spread spectrum communications technology wherein said information is digitized and encoded, said encoded information is used to modulate a baseband signal having greater bandwidth than the bandwidth of said information, said baseband signal is in turn used to modulate a carrier signal to be transmitted from a first point, and wherein said transmitted signal is received, demodulated and decoded at a second point so as to replicate the information sent, the improvement wherein:
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said information encoding step comprises the substeps of;
defining M-ary symbols to represent each possible state of said digitized information;
assigning subsets of Nt tones out of a set of N available tones to represent each of said M-ary symbols;
for selected successive timing intervals, assigning new subsets of Nt tones, each said Nt subset being drawn from said set N, to represent each of said M-ary symbols, wherein selection of tones comprising each said Nt tones representing said M-ary symbols is established based on a known coding sequence;
said baseband modulation step comprises the substep of;
selecting the symbol representing the information state to be transmitted during a timing interval and causing a frequency domain representation of the Nt tones corresponding to said selected symbol to be operated on by an inverse finite Fourier transform thereby producing a time domain representation of said corresponding Nt tones; and
said step of demodulating said received signal includes the substep of operating on said received signal by a finite Fourier transform thereby reproducing a frequency domain representation of said corresponding Nt tones. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. In a spread spectrum communications system comprising at least one transmitting means operative to encode, modulate and transmit digitized information and at least one receiving means operative to receive, demodulate, decode and thereby replicate such digitized information, the improvement comprising:
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selection means associated with said transmitting means for defining M-ary symbols to represent each possible state of said digitized information;
generation means associated with said transmitting means for assigning a subset of Nt tones out of a set of N available tones to represent each of said M-ary symbols in selected successive timing intervals, wherein selection of said Nt tones representing each of said M-ary symbols is established based on a known coding sequence;
transforming means associated with said transmitting means for causing a frequency domain representation of the subset Nt tones corresponding to the symbol to be transmitted during a timing interval to be transformed to a time domain representation of said corresponding Nt tones; and
reverse transforming means associated with said receiving means to reproduce the frequency domain representation of said corresponding Nt tones. - View Dependent Claims (27, 28, 29, 30)
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31. A receiver for a spread spectrum communications system operative to receive, demodulate, decode and thereby replicate transmitted digital information comprising:
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means for establishing a timing reference corresponding to timing information embedded in said transmitted information;
means for establishing a coding sequence corresponding to coding embedded in said transmitted information, wherein said embedded transmitted coding is characterized as having a plurality of subsets of tones established to represent each possible state of said transmitted digital information during a timing interval, the tones comprising each said subset being selected from a set of N frequencies, and further wherein a new plurality of said subsets of tones is established for selected successive timing intervals; and
means for decoding one of M symbols corresponding to an increment of digitized information transmitted during a given timing interval. - View Dependent Claims (32)
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33. A receiver for a spread spectrum communications system operative to receive, demodulate, decode and thereby replicate transmitted information comprising:
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means for establishing a timing reference corresponding to timing information embedded in said transmitted information;
means for establishing a coding sequence corresponding to coding embedded in said transmitted information;
means for decoding one of M symbols corresponding to an increment of digitized information transmitted during a given timing interval; and
a reverse transforming means to reproduce the frequency domain representation of a transmitted time domain representation of said transmitted symbol;
wherein said decoding means further includes a plurality of signal correlator means corresponding to each of said M symbols, and wherein the signal correlator means having the largest output magnitude is determined to represent the transmitted symbol.
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Specification