Multi-dimensional spread spectrum modem
First Claim
1. A multi-dimensional spread spectrum modulator comprising:
- a spreading sequence generator for generating a set of substantially mutually orthogonal spreading sequences;
a first frequency spreading means comprising a first input for a first set of parallel input data streams;
a second input for the set of spreading sequences, respective input data streams being associated with respective spreading sequences in the set of spreading sequences; and
an output;
a second frequency spreading means comprising a first input for a second set of parallel input data streams;
a second input for the set of spreading sequences, respective input data streams being associated with respective spreading sequences in the set of spreading sequences; and
an output; and
a quadrature modulator comprising first and second inputs and an output, the first input of the quadrature modulator being connected to the output of the first frequency spreading means and the second input of the quadrature modulator being connected to the output of the second frequency spreading means, wherein the set of spreading sequences are derived from at least one complex sequence comprising a real part and an imaginary part, wherein each spreading sequence in the set of spreading sequences comprises a combination of at least two parts of the at least one complex sequence, wherein the combination is an arithmetic sum of the real part and the imaginary part, and wherein a first spreading sequence in the set comprises the sum of the real part and a negative of the imaginary part of the complex sequence and wherein a second spreading sequence in the set comprises a negative sum of said real part and said imaginary part of the complex sequence.
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Abstract
An n-dimensional direct sequence spread spectrum modulator (10) comprises a spreading sequence generator (21) for generating a set of n/2 substantially mutually orthogonal spreading sequences. The spreading sequences each comprises combinations of the real and imaginary parts of complex sequences. A first frequency spreading arrangement (24,26) comprises a first input (24.1,26.1) for a first set of n/2 parallel input data streams (d1(t) d2(t)), a second input (24.2, 26.2) for the set of spreading sequences and an output (24.3, 26.3). Respective input data streams are associated with respective spreading sequences in the set of spreading sequences. A second frequency spreading arrangement (28,30) comprises a first input (28.1, 30.1) for a second set of n/2 parallel input data streams (d3(t), d4(t)), a second input (28.2, 30.2) for the set of spreading sequences and an output (28.3, 30.3). Respective input data streams being associated with respective spreading sequences in the set of spreading sequences. A quadrature modulator (42) comprises a first input (36.1) and a second input (38.1) and an output (40). The first input (36.1) is connected to the output of the first frequency spreading arrangement and the second input (38.1) is connected to the output of the second frequency spreading arrangement. An associated demodulator is also disclosed.
21 Citations
28 Claims
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1. A multi-dimensional spread spectrum modulator comprising:
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a spreading sequence generator for generating a set of substantially mutually orthogonal spreading sequences;
a first frequency spreading means comprising a first input for a first set of parallel input data streams;
a second input for the set of spreading sequences, respective input data streams being associated with respective spreading sequences in the set of spreading sequences; and
an output;
a second frequency spreading means comprising a first input for a second set of parallel input data streams;
a second input for the set of spreading sequences, respective input data streams being associated with respective spreading sequences in the set of spreading sequences; and
an output; and
a quadrature modulator comprising first and second inputs and an output, the first input of the quadrature modulator being connected to the output of the first frequency spreading means and the second input of the quadrature modulator being connected to the output of the second frequency spreading means, wherein the set of spreading sequences are derived from at least one complex sequence comprising a real part and an imaginary part, wherein each spreading sequence in the set of spreading sequences comprises a combination of at least two parts of the at least one complex sequence, wherein the combination is an arithmetic sum of the real part and the imaginary part, and wherein a first spreading sequence in the set comprises the sum of the real part and a negative of the imaginary part of the complex sequence and wherein a second spreading sequence in the set comprises a negative sum of said real part and said imaginary part of the complex sequence. - View Dependent Claims (12)
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2. A multi-dimensional spread spectrum modulator comprising:
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a spreading sequence generator for generating a set of substantially mutually orthogonal spreading sequences;
a first frequency spreading means comprising a first input for a first set of parallel input data streams;
a second input for the set of spreading sequences, respective input data streams being associated with respective spreading sequences in the set of spreading sequences; and
an output;
a second frequency spreading means comprising a first input for a second set of parallel input data streams;
a second input for the set of spreading sequences, respective input data streams being associated with respective spreading sequences in the set of spreading sequences; and
an output; and
a quadrature modulator comprising first and second inputs and an output, the first input of the quadrature modulator being connected to the output of the first frequency spreading means and the second input of the quadrature modulator being connected to the output of the second frequency spreading means, wherein the first input of the first frequency spreading means comprises n/2 branches for n/2 input data streams, wherein the first spreading means comprises n/2 spreading multipliers and the set of spreading sequences comprises n/2 spreading sequences connected to respective multipliers, to spread the n/2 data streams, wherein the first input of the second frequency spreading means comprises n/2 branches for n/2 input data streams, wherein the second spreading means comprises n/2 spreading multipliers and respective ones of the n/2 spreading sequences are connected to the n/2 multipliers of the second frequency spreading means to spread the n/2 data streams at the first input of the second frequency spreading means, wherein output signals of the n/2 multipliers of the first frequency spreading means are added by a first adder to provide a first spreaded signal; and
wherein output signals of the n/2 multipliers of the second frequency spreading means are added by a second adder to provide a second spreaded signal.- View Dependent Claims (3, 4, 5)
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6. An n-dimensional spread spectrum demodulator wherein n is larger than two, the demodulator comprising:
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an input for a received modulated spread spectrum signal comprising n mutually orthogonal data signals spreaded with a set of n/2 substantially mutually orthogonal spreading sequences, wherein the set is derived from at least one non-binary complex sequence comprising a real part and an imaginary part utilizing combinations of the real part and the imaginary part;
the input being connected to a circuit for recovering quadrature carriers in the received signal;
a local despreading sequence generator for generating a set of n/2 mutually orthogonal despreading sequences, wherein the set is derived from at least one non-binary complex sequence comprising a real part and an imaginary part utilizing combinations of the real part and the imaginary part;
the input also being connected to a tracking and synchronizing circuit for tracking the n/2 spreading sequences in the received signal and synchronizing the locally generated despreading sequences with the tracked spreading sequences; and
circuitry connected to the carrier recovery circuit and the spreading sequence synchronization circuit for extracting the n data signals from the received signal, utilizing the recovered quadrature carriers and the n/2 despreading sequences. - View Dependent Claims (7, 8, 9, 10, 11)
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13. A method of frequency spread modulating n data streams wherein n is larger than two, the method comprising the steps of:
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dividing the n data streams into first and second groups of n/2 streams each;
utilizing n/2 substantially mutually orthogonal spreading sequences respectively to frequency spread the streams in the first group, thereby to provide a first group of n/2 mutually orthogonal frequency spreaded signals, wherein the n/2 spreading sequences are derived from at least one non-binary complex sequence comprising a real part and an imaginary part utilizing combinations of the real part and the imaginary part;
utilizing the n/2 spreading sequences respectively to frequency spread the streams in the second group, thereby to provide a second group of n/2 mutually orthogonal frequency spreaded signals; and
modulating the first group of frequency spreaded signals and the second group of frequency spreaded signals on first and second quadrature carriers respectively, thereby to generate n mutually orthogonal modulated data signals.
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14. A method of demodulating n substantially mutually orthogonal data streams in an incoming spread spectrum signal and wherein n is larger than two, the method comprising the steps of:
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utilizing one of;
(a) a set of n/2 substantially mutually orthogonal despreading sequences derived from at least one non-binary complex sequence comprising a real part and an imaginary part utilizing combinations of the real part and the imaginary part; and
(b) first and second quadrature signals, to separate the n data streams into first and second substantially mutually orthogonal groups of signals; and
utilizing another of (a) and (b) to extract the n data streams from the first and second groups.
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15. An n-dimensional spread spectrum modulator having n data inputs and wherein n is larger than two, comprising:
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a spreading sequence generator for generating a set of n/2 substantially mutually orthogonal spreading sequences, wherein the set is derived from at least one non-binary complex sequence having a real part and an imaginary part utilizing combinations of the real part and the imaginary part;
a first frequency spreading arrangement comprising a first set of n/2 inputs for n/2 parallel input data streams, a second set of n/2 inputs one for each of said spreading sequences, each input of the first set being associated with a respective input of the second set and an output, so that each input data stream is associated with a respective spreading sequence to provide at the output of the first arrangement n/2 mutually orthogonal frequency spreaded data signals;
a second frequency spreading arrangement comprising a first set of n/2 parallel inputs for n/2 parallel input data streams, a second set of n/2 inputs one for each of said spreading sequences, each input of the first set being associated with a respective input of the second set and an output, so that each input data stream is associated with a respective spreading sequence to provide at the output of the second arrangement n/2 mutually orthogonal frequency spreaded data signals; and
a quadrature modulator comprising first and second inputs and an output, the first input being connected to the output of the first frequency spreading arrangement and the second input being connected to the output of the second frequency spreading arrangement, to provide at the output of the quadrature modulator n mutually orthogonal spreaded and modulated data signals. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A multi-dimensional spread spectrum modulator comprising:
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a spreading sequence generator for generating a set of substantially mutually orthogonal spreading sequences, the set of spreading sequences being derived from at least one complex sequence comprising a real part and an imaginary part, wherein a first spreading sequence in the set comprises a sum of the real part and a negative of the imaginary part of the at least one complex sequence and wherein a second spreading sequence in the set comprises a negative sum of said real part and said imaginary part;
a first frequency spreading means comprising a first input for a first set of parallel input data streams;
a second input for the set of spreading sequences, respective input data streams being associated with respective spreading sequences in the set of spreading sequences; and
an output;
a second frequency spreading means comprising a first input for a second set of parallel input data streams;
a second input for the set of spreading sequences, respective input data streams being associated with respective spreading sequences in the set of spreading sequences; and
an output; and
a quadrature modulator comprising first and second inputs and an output, the first input of the quadrature modulator being connected to the output of the first frequency spreading means and the second input of the quadrature modulator being connected to the output of the second frequency spreading means.
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Specification