Signal detection in a direct-sequence spread spectrum transmission system
First Claim
1. A method for improved detection of received signals transmitted by Direct Sequence Spread Spectrum Transmission, comprising the steps of:
- continuously correlating the received signals with each of N known symbol patterns, where N is an integer, to yield N correlated symbol patterns;
determining which of the N correlated symbol patterns has a largest peak power;
determining a running power average of the received signals;
computing a ratio of the largest peak power of the N correlated symbol patterns to the running power average; and
comparing the ratio to a threshold value to determine a first symbol in the received signals, an identity of the first symbol, and a true burst location of the first symbol relative to a receiver time base.
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Abstract
A receiver (10) achieves more reliable detection of signals transmitted by Direct Sequence Spread Spectrum Transmission by correlating received signals with a separate of N symbol patterns via N detector stages (181-18N). A maximum peak power detecting mechanism (241-24N, 261-26N and 28) detects which of the N correlated symbol patterns has a maximum peak power, as well as the identity of each of the N patterns actually received and an index of the peak power in each symbol. A computing mechanism (30, 32 and 34) computes a running power average of the received signals, while a ratio computing stage (36) computes the ratio of the largest peak power of the N correlated symbol patterns to the running power average. A comparator stage (38 and 40) compares the ratio to a threshold value to determine a first symbol in the received signals. From knowledge of the first symbol received, the identity of that symbol, and the true burst location of the received symbol relative to a receiver time base can be determined, thus providing more reliable signal detection.
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Citations
9 Claims
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1. A method for improved detection of received signals transmitted by Direct Sequence Spread Spectrum Transmission, comprising the steps of:
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continuously correlating the received signals with each of N known symbol patterns, where N is an integer, to yield N correlated symbol patterns;
determining which of the N correlated symbol patterns has a largest peak power;
determining a running power average of the received signals;
computing a ratio of the largest peak power of the N correlated symbol patterns to the running power average; and
comparing the ratio to a threshold value to determine a first symbol in the received signals, an identity of the first symbol, and a true burst location of the first symbol relative to a receiver time base. - View Dependent Claims (2, 3, 4, 5)
(a) determining a power value for each of the N correlated symbol patterns;
(b) detecting a peak within the power value for each of the N correlated symbol patterns; and
(c) determining from the peak power values for the N correlated symbol patterns which symbol pattern has a maximum value as well an identity of each of the N patterns actually received and an index of the peak power within each symbol in each symbol pattern.
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4. The method according to claim 1 wherein the identity of the first symbol corresponds to the one of the N correlated symbol patterns having the largest peak power.
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5. The method according to claim 1 wherein the threshold value is determined from knowledge of the sequence of the received signals.
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6. Apparatus for improved detection of signals transmitted by Direct Sequence Spread Spectrum Transmission, comprising:
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N detector stages, each correlating received signals with a separate one of N separate known symbol patterns where N is an integer, to yield N correlated symbol patterns;
a maximum peak power detecting mechanism for;
(a) detecting which of the N correlated symbol patterns output by the N detector stages has a maximum peak power, (b) determining an identity of each of the N symbol patterns actually received and (c) establishing an index of the peak power within the symbol in each received symbol pattern;
a first computing mechanism for computing a running power average of the received signals;
a second computing mechanism for computing a ratio of the maximum peak power, as established by the maximum peak power detecting mechanism, to the running power average;
as established by first computing mechanism, anda comparator stage for comparing the ratio to a threshold value to determine a first symbol in the received signals, the first symbol having an identity corresponding to the one of the N correlated symbol patterns having the largest peak power, and the first symbol having a true burst location relative to a receiver time base corresponding to the index of the peak power within that symbol. - View Dependent Claims (7, 8, 9)
a pattern generator for generating a separate one of N possible known symbol patterns; and
a pattern correlator for correlating the received signals with the separate one of the N known symbol patterns produced by the pattern generator.
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8. The apparatus according to claim 6 wherein the maximum peak power detecting mechanism comprises:
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N power monitors, each measuring the power of a corresponding one of the N correlated symbol patterns;
N peak detectors, each detecting a peak in the power measured by a corresponding one of the power monitors; and
a maximum peak power detecting stage for determining which of the N correlated symbol patterns has a peak power, as detected by a separate one of the peak detectors as well the identity of each of the N patterns actually received and the index of the peak power within each symbol in each symbol pattern.
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9. The apparatus according to claim 6 wherein the first computing mechanism comprises:
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a power monitor for measuring the power of the received signals;
a peak detector for detecting a peak in the power measured by the power monitor; and
a computing stage responsive to the peak in the power measured by the peak detector for computing a running power of the peaks measured by the peak detector.
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Specification