Convolutional ambiguity multiple access (CAMA) transmission system
First Claim
1. A multiple access processing system for processing an input signal for transmission as an output signal, said system comprising:
- first means for taking a Fourier transform of a known original signal corresponding to the input signal, using at least one predetermined index, and providing a first result;
second means for taking the Fourier transform of the output signal and providing a second result;
third means for multiplying the first and second results together to provide a product;
fourth means for taking the inverse Fourier transform of the product and providing a further result; and
fifth means for reindexing the Fourier transform computed by the first means by shifting the at least one predetermined index to provide a reindexed first result;
wherein said third means multiplies the reindexed first result and the second result, said fifth means providing reindexing a predetermined number of times and said third means operating on each reindexed first result and the second result, so as to generate a decoded input signal at an appropriate time delay and doppler shift.
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Abstract
A communication system that reduces significantly the processing required to search over unknown time delays and unknown frequency shifts. Convolutional type processing with a unique re-indexing of the desired signal'"'"'s Fourier transform is provided so as to allow for the design of a communication system that is invariant to time of arrival and frequency shift such as that caused by doppler effects from moving vehicles or moving satellites. The processing required is several orders of magnitude less computationally intensive than conventional approaches to solving this problem. In addition, the inventive convolutional ambiguity multiple access (CAMA) system can be used in conjunction with M-Ary FSK (Frequency Shift Keying) and other coding techniques to decode the various frequency codes efficiently. The technique also can be used as a processing system for radar, sonar, ultrasound, ladar, and other reflective transmission signals to generate a full ambiguity function, utilizing an arbitrary waveform efficiently. In addition, by processing each frequency independently, it is possible to remove frequency distortion (or time distortion that is frequency dependent) more accurately.
39 Citations
22 Claims
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1. A multiple access processing system for processing an input signal for transmission as an output signal, said system comprising:
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first means for taking a Fourier transform of a known original signal corresponding to the input signal, using at least one predetermined index, and providing a first result; second means for taking the Fourier transform of the output signal and providing a second result; third means for multiplying the first and second results together to provide a product; fourth means for taking the inverse Fourier transform of the product and providing a further result; and fifth means for reindexing the Fourier transform computed by the first means by shifting the at least one predetermined index to provide a reindexed first result; wherein said third means multiplies the reindexed first result and the second result, said fifth means providing reindexing a predetermined number of times and said third means operating on each reindexed first result and the second result, so as to generate a decoded input signal at an appropriate time delay and doppler shift. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A multiple access processing and transmission method for processing an input signal and transmitting an output signal accordingly, said method comprising the following steps:
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a) taking a Fourier transform of a known original signal corresponding to the input signal, using at least one predetermined index, and providing a first result; b) taking a Fourier transform of the output signal and providing a second result; c) multiplying the first and second results together to provide a product; d) taking an inverse Fourier transform of the product and providing a further result; e) reindexing the Fourier transform computed in said step a) by shifting the at least one predetermined index to provide a reindexed first result; f) multiplying the reindexed first result and the second result; g) performing said reindexing step a predetermined number of times and operating on each reindexed first result and the second result accordingly; h) generating a decoded input signal at an appropriate time delay and doppler shift in accordance with said steps a)-g); and i) generating and transmitting said output signal in accordance with said step h). - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification