Design of an M-ary Chaos Shift Keying System Using Combined Chaotic Systems

TL;DR

The paper addresses the challenge of chaotic synchronization in CSK by proposing CCS-$M$-CSK, which combines two chaotic sequences from different systems with distinct lengths to enable $M$-ary modulation without synchronization. A DNN-based receiver, featuring BiLSTM and self-attention, demodulates by detecting the embedded short chaotic sequence within the longer one, leveraging a symbol-to-position mapping and Gray coding for efficient transmission. Offline training on simulated AWGN and Rayleigh channels, along with a complexity-aware architecture, demonstrates superior SER/BER performance over existing CSK schemes, including robustness to misalignment and multipath fading. The work highlights significant potential for high-reliability, secure communications in V2X and related applications, where conventional chaos synchronization is impractical.

Abstract

In traditional chaos shift keying (CSK) communication systems, implementing chaotic synchronization techniques is costly but practically unattainable in a noisy environment. This paper proposes a combined chaotic sequences-based $M$-ary CSK (CCS-$M$-CSK) system that eliminates the need for chaotic synchronization. At the transmitter, the chaotic sequence is constructed by combining two chaotic segments of different lengths, where each is generated from distinct chaotic systems and only one kind of chaotic segment modulates the information signal. At the receiver, a deep learning unit with binary classification is meticulously designed to recover information symbols. The symbol error rate (SER) performance of the proposed system is evaluated over additive white Gaussian noise (AWGN) and multipath Rayleigh fading channels. Specifically, the impact of varying misalignment lengths on the SER performance of the system is analyzed when the received sequence is misaligned. Furthermore, the proposed system demonstrates significant performance advantages over existing CSK-based systems in multipath Rayleigh fading channels. These features establish CCS-$M$-CSK as a promising candidate for various applications, including Vehicle-to-Everything (V2X).

Figures (9)

• Figure 1: The transmitter of CCS-$M$-CSK system.
• Figure 2: Composition of transmit signals corresponding to different information symbols.
• Figure 3: Mapping table of symbols to information chaotic sequence positions when $M = 4$.
• Figure 4: The receiver of CCS-$M$-CSK system. (a) DNN-based receiver. (b) DNN architecture.
• Figure 5: SER performances of CCS-$M$-CSK system over different channels for different $M$ and $\beta$. (a) AWGN channel. (b) Multipath Rayleigh channel.