Chaotic Spread Spectrum Receiver Synchronization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Chaotic communications systems face throughput limitations due to drift in analog chaos generators, leading to synchronization challenges and reduced data transmission rates, while non-coherent systems suffer from lower throughput and error rates.
Innovation Solution
A coherent chaotic spread-spectrum communications system using residue number system (RNS) arithmetic and discrete time chaotic samples to synchronize and demodulate chaotic sequences, minimizing timing and frequency offsets, and adjusting local oscillators and amplifiers to maintain signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If analog chaotic circuits are used to generate chaotic sequences, then the system can achieve coherent communication, but the circuits drift over time requiring frequent state information exchange which reduces throughput
Solution Approach 1:
The patent replaces analog chaotic circuits with a digital chaotic sequence generator that uses a deterministic algorithm (e.g., logistic map or tent map) implemented in digital logic or software. This substitution eliminates hardware drift while maintaining chaotic signal properties, allowing the receiver to generate identical sequences without continuous state exchange, thereby resolving the contradiction between synchronization reliability and data transmission rate
Solution Approach 2:
The receiver generates a local copy of the chaotic sequence using the same deterministic algorithm and initial conditions as the transmitter. This copying approach eliminates the need for continuous state information exchange while maintaining synchronization, as both transmitter and receiver independently produce identical chaotic sequences through the deterministic algorithm
2Reliability
If state information is exchanged frequently between transmitter and receiver to counteract drift, then synchronization is maintained, but the increased exchange rate causes faster relative drift and reduces throughput
Solution Approach 1:
The system enables self-synchronization where both transmitter and receiver independently generate identical chaotic sequences using the same deterministic algorithm and initial conditions. The receiver autonomously maintains synchronization without requiring external state information from the transmitter, eliminating the throughput-reducing state exchange while maintaining synchronization stability
3Device complexity
If non-coherent chaotic waveforms are used, then synchronization complexity is reduced, but throughput and error rate performance deteriorate
Solution Approach 1:
The patent implements coherent demodulation using a digital chaotic sequence generator that reproduces the transmitted chaotic sequence at the receiver. This digital implementation maintains the benefits of coherent detection (high throughput and low error rates) while eliminating the drift problems of analog circuits, achieving both low complexity and high performance
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A method is provided for coherently demodulating a chaotic sequence spread spectrum signal at a receiver (104). The method includes receiving a chaotic sequence spread spectrum signal including a plurality of information symbols. The method also includes generating a first string of discrete time chaotic samples. The first string of discrete time chaotic samples is identical to a second string of discrete time chaotic samples generated at a transmitter. The method further includes processing the chaotic sequence spread spectrum signal at the receiver to identify a time offset and a frequency offset relative to the first string of discrete time chaotic samples. Each of the discrete time chaotic samples of the first string of discrete time chaotic samples has a shorter sample time interval than the duration of the information symbols.