Chaotic Dithering for Spread Spectrum Signal Synchronization
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Solution Overview
Problem
Chaotic communication systems face challenges in achieving high data rates while maintaining low probability of interception (LPI) and low probability of detection (LPD) due to synchronization issues and limited practical chaos generation rates, which affect the robustness and throughput of spread-spectrum communications.
Innovation Solution
The introduction of a dithering mechanism that varies the sampling interval of chaotic spread waveforms, using a known pseudo-random or chaotic sequence, to enhance energy density suppression and synchronization between transmitter and receiver, thereby improving LPI/LPD characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If chaotic sequences are used for spreading to improve LPI/LPD characteristics, then spectral energy density is reduced, but synchronization difficulty increases and throughput decreases
Solution Approach 1:
The patent applies preliminary synchronization actions by exchanging state information between transmitter and receiver before high-rate data transmission begins. This preliminary synchronization establishes a foundation that allows subsequent high-throughput communication without requiring continuous state exchanges, thus maintaining low spectral energy density while achieving high throughput.
Solution Approach 2:
The patent implements periodic state information exchange at optimized intervals rather than continuous exchange. By determining appropriate synchronization intervals based on system parameters and maintaining synchronization within acceptable bounds during these periodic updates, the system achieves high data rates between synchronization events while preserving LPI/LPD characteristics.
2Measurement precision
If state information is exchanged frequently to improve synchronization accuracy, then synchronization is maintained, but data rate is reduced
Solution Approach 1:
The patent applies partial synchronization action by exchanging state information only when necessary to maintain synchronization within acceptable bounds, rather than continuously. The system determines appropriate intervals for state exchange based on drift rates and synchronization requirements, achieving sufficient synchronization accuracy without the overhead of continuous exchange, thus preserving high data rates.
Solution Approach 2:
The patent performs preliminary state information exchange to establish initial synchronization before high-rate data transmission. This preliminary action sets up the synchronization foundation that allows subsequent data transmission to proceed at high rates without requiring frequent intervention, balancing synchronization accuracy with data rate.
3Productivity
If chaos generation rate is increased to improve data rate, then throughput increases, but LPI/LPD characteristics deteriorate
Solution Approach 1:
The patent transitions from purely time-domain chaos generation to a multi-dimensional approach by incorporating state information exchange as an additional dimension for achieving high data rates. Instead of relying solely on increasing chaos generation rate in the time domain, the system uses the state information dimension to enable high throughput while maintaining lower chaos rates that preserve LPI/LPD characteristics.
Solution Approach 2:
The patent uses preliminary state information exchange to enable high data rate transmission without requiring high chaos generation rates. By establishing synchronization and exchanging state information in advance, the system can transmit data at high rates through efficient protocols while maintaining lower spreading rates that preserve spectral properties and LPI/LPD characteristics.
Data Source
AI summary
Embodiments of the present invention provide a system and method for further reducing cyclostationarity and correspondingly energy density in a chaotic spread spectrum data communication channel, by digitally generating a first chaotic sequence of values to form a spreading code. The spreading code is then used to form a digital IF spread spectrum signal having a uniform sampling interval. The digital IF spread spectrum signal is converted to a sampled analog IF spread spectrum signal at a conversion rate substantially equal to the uniform sampling interval. The duration of the sampling interval is then selectively varied in accordance with a first pseudo-random sequence, thereby introducing a known dither in the analog IF spread spectrum signal. After introducing the known dither, the analog IF spread spectrum signal is upconverted to an analog RF spread spectrum signal. The first pseudo-random sequences may be designed to be a chaotic sequence.