Analytical unequal-spreading factor DCSK: A robust chaotic modulation framework for noisy channels

Abstract

In the present paper, an Analytical Unequal-Spreading Factor Differential Chaotic Shift Keying (USF-DCSK) modulation scheme is proposed to enhance the reliability and energy efficiency of chaotic communications in noisy and fading propagation environments. The proposed system contains an analytical beta-allocation function that adjusts the spreading factor dynamically both as a function of the instantaneous signal-to-noise ratio (SNR) and the perceptual significance of each bit-plane. This adaptive allocation balances robustness and power efficiency, providing improved protection for perceptually important bits while simultaneously reducing redundancy in good channel conditions. Simulation trials run over additive white Gaussian noise (AWGN) and Rayleigh fading channels support the model efficiency and show the maximum mean-square-error (MSE) reduction of 94% and 12 dB peak signal-to-noise ratio (PSNR) improvement in the AWGN case and a consistent 36% MSE reduction and approximately 1.5 dB PSNR improvement in the Rayleigh fading channel. Besides performance improvement, the modulator itself provides an additional degree of data confidentiality by its non-uniform chaotic spread, which makes statistical interception significantly harder than without this overhead. Furthermore, it is found in the investigation that wireless sensor networks (WSNs) and wireless visual sensor networks (WVSNs) are especially favorable application domains for the proposed modulation framework. These networks are mainly battery powered, so the use of energy-efficient modulation is the key to increasing the lifetime of nodes; additionally, because they are static or semi-static networks, it is possible to make approximate predictions of the channel conditions at the transmitter, thus allowing the practical and cost-effective implementation of adaptive chaotic spreading without the need for frequent feedback. The results validate the idea that the USF-DCSK model provides a theoretically valid and practical solution for robust, energy-aware, and perceptually optimized wireless multimedia communication solutions.