Selective Noise Cancellation for Spread Spectrum Signals
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Solution Overview
Problem
Communications systems face challenges in improving the signal-to-noise ratio (SNR) of spread spectrum signals, particularly when the spread power level is below the noise floor, leading to reduced data estimation capability and increased computational requirements for synchronization with non-square wave spreading sequences.
Innovation Solution
A method and receiver configuration that selectively eliminate samples with low instantaneous signal amplitudes by comparing the magnitude of random numbers in the spreading sequence to an adaptable threshold, using a digitized chaos generator to generate both the spreading and de-spreading sequences, and employing a selective noise cancellation device to improve the SNR by discarding samples with magnitudes below the threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If spread spectrum signals operate with spread power level below the noise floor to achieve low detectability, then the probability of detection is reduced, but the signal-to-noise ratio deteriorates and data estimation capability is reduced
Solution Approach 1:
The patent extracts and removes noise components from the received spread spectrum signal by comparing the magnitude of random numbers in the spreading sequence against an adaptable threshold. Samples where the random number magnitude falls below the threshold are identified as containing predominantly noise and are excluded from further processing, while samples above the threshold are retained for data recovery. This selective extraction improves the effective signal-to-noise ratio without requiring the signal to operate above the noise floor.
2Reliability
If non-square wave spreading sequences are used to improve security and robustness, then the communications system becomes more secure and robust to interferers, but the computational power required for synchronization increases significantly
Solution Approach 1:
The patent applies the same threshold-based extraction principle to reduce computational requirements for synchronization with non-square wave spreading sequences. By comparing random number magnitudes against an adaptable threshold and excluding samples below the threshold from correlation and de-spreading operations, the system reduces the number of computational operations required for synchronization while maintaining robustness to interferers through the use of non-square wave sequences in the samples that are processed.
Data Source
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AI summary
A method is provided for improving a signal-to-noise ratio in a received signal. The method involves receiving a spread spectrum signal (SSS) with a power level below a noise floor of a receiver. The SSS is generated by modulating a data signal using a spreading sequence (SS) comprised of a random number sequence (RNS). The SS can be generated using a chaos generator or any other deterministic means. The method also involves comparing a magnitude of each number of the RNS which was used to generate the SSS to an adaptable threshold value. The adaptable threshold value is selected based on a minimum magnitude of each number necessary to produce samples having a predetermined signal-to-noise ratio. Notably, samples of the received SSS are excluded from a receiver processing based on a result of the comparison. Similarly, each number of a random number sequence is excluded from the receiver processing based on the comparison.