Detection of a multi-sequence spread spectrum signal
First Claim
1. In the detection of a multi-sequence spread spectrum signal, a block correlation method for generating correlation values associated with a received signal and a plurality of candidate sequences, the method comprising:
- receiving a signal comprising a first transmitted sequence and a second transmitted sequence;
stripping the second transmitted sequence from the received signal to form a stripped signal; and
generating correlation values as a function of the stripped signal and a replica of the first transmitted sequence at a plurality of offsets,wherein the generating step comprises the substeps of;
padding the stripped signal with zeroes to form a first extended data sequence;
generating a first set of coefficients by performing a discrete Fourier transform on the first extended data sequence;
padding a replicated first transmitted sequence with zeroes to form a second extended data sequence;
generating a second set of coefficients by performing a discrete Fourier transform on the second extended data sequence;
generating a set of product coefficients by multiplying each coefficient in the first set by the complex conjugate of a corresponding coefficient in the second set; and
generating correlation values by computing the inverse discrete Fourier transform of the product coefficients.
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Abstract
A detector of a multiple-sequence spread spectrum signal uses a Hadamard transform (106) to simultaneously correlate a received signal comprising two sequences (64) with a plurality of candidate sequences. The received signal is stripped of the first sequence (65, 66), and the signal is permuted (via a table lookup) (104). A Hadamard transform is performed on the permuted data and the candidate sequences (106). After transformation, the data is permuted again (112 ) to determine the symbol (sequence) transmitted. Alternatively, Fast Fourier Transforms (FFTs) (FIG. 3), Winograd Fourier Transform Algorithms (WFTA), or other cyclic correlation algorithms (FIG. 5) may be used to compute the transformation. In a preferred embodiment, a "pilot" signal is transmitted in quadrature (90 degrees phase offset) with an information-bearing signal. And, a block error correcting code (150) (e.g., a modified Reed-Solomon code) is transmitted with the information-bearing signal a(t). The block length of the block error correcting code (150) is equal to an integral multiple of the period of the pilot signal. The period of the pilot signal is an integral multiple of the information bearing signal. Thus, carrier recovery, sequence synchronization, and block code synchronization are all achieved simultaneously by correlating (synchronizing) the received signal with a baseband version of the pilot signal.
112 Citations
9 Claims
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1. In the detection of a multi-sequence spread spectrum signal, a block correlation method for generating correlation values associated with a received signal and a plurality of candidate sequences, the method comprising:
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receiving a signal comprising a first transmitted sequence and a second transmitted sequence; stripping the second transmitted sequence from the received signal to form a stripped signal; and generating correlation values as a function of the stripped signal and a replica of the first transmitted sequence at a plurality of offsets, wherein the generating step comprises the substeps of; padding the stripped signal with zeroes to form a first extended data sequence; generating a first set of coefficients by performing a discrete Fourier transform on the first extended data sequence; padding a replicated first transmitted sequence with zeroes to form a second extended data sequence; generating a second set of coefficients by performing a discrete Fourier transform on the second extended data sequence; generating a set of product coefficients by multiplying each coefficient in the first set by the complex conjugate of a corresponding coefficient in the second set; and generating correlation values by computing the inverse discrete Fourier transform of the product coefficients. - View Dependent Claims (2, 3)
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4. In the detection of a multi-sequence spread spectrum signal, a block correlation method for generating correlation values associated with a received signal and a plurality of candidate sequences, the method comprising:
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receiving a signal comprising a first transmitted sequence and a second transmitted sequence; stripping the second transmitted sequence from the received signal to form a stripped signal; generating correlation values as a function of the stripped signal and a replica of the first transmitted sequence at a plurality of offsets; and selecting a subset from the correlation values generated.
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5. In the detection of a multi-sequence spread spectrum signal, a block correlation method for generating correlation values associated with a received signal and a plurality of candidate sequences, the method comprising:
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receiving a signal comprising a first transmitted sequence and a second transmitted sequence; stripping the second transmitted sequence from the received signal to form a stripped signal; and generating correlation values as a function of the stripped signal and a replica of the first transmitted sequence at a plurality of offsets, wherein the correlation values are generated by computing a fast cyclic convolution algorithm on the stripped signal and a replica of the first transmitted sequence at a plurality of offsets.
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6. In the detection of a multi-sequence spread spectrum signal, a block correlation method for generating correlation values associated with a received signal and a plurality of candidate sequences, the method comprising:
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receiving a signal comprising a first transmitted sequence and a second transmitted sequence; stripping the second transmitted sequence from the received signal to form a stripped signal; and generating correlation values as a function of the stripped signal and a replica of the first transmitted sequence at a plurality of offsets, wherein the generating step comprises the substeps of; permuting the stripped signal to form permuted data; and generating correlation values by performing a Hadamard transform on the permuted data. - View Dependent Claims (7)
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8. In a multi-sequence spread spectrum signal detector, a block correlator apparatus comprising:
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a receiver for receiving a signal comprising a first transmitted sequence and a second transmitted sequence; coupled to the receiver, a multiplier for multiplying the received signal by a replica of the second transmitted sequence to generate a stripped signal; and coupled to the multiplier, a block correlator for generating correlation values as a function of the stripped signal and a replica of the first transmitted sequence at a plurality of offsets, wherein the block correlator generates correlation values as a function of a Hadamard transformation. - View Dependent Claims (9)
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Specification