A sensible structure and high performance DCSK system using normalized Walsh codes for two dimensional index modulation

This paper proposes a sensible structure and high performance differential chaos shift keying system using normalized Walsh codes for two dimensional index modulation (SHTDIM-DCSK). At the transmitter of the system, the chaotic signal is expanded by an all-1 vector and modulated onto the 0-th time slot for transmission as a reference signal. Together with its Hilbert-transformed signal, the reference signal carries joint code and reference indices in subsequent information time slots. Among them, the code indices adopt normalized Walsh codes to achieve the goal of power coefficient optimization, which not only effectively reduces the transmission power but also improves the bit error performance. At the receiver, a moving average technique is used to denoise the received reference signal, further enhancing the bit error performance, and a joint demodulation algorithm is designed. This paper derives the theoretical bit error rate expressions of the SHTDIM-DCSK system over AWGN channels and multipath Rayleigh fading channels, and verifies the correctness of these theoretical expressions through simulation experiments. In addition, simulation results demonstrate that the proposed system exhibits superiority over other advanced chaotic communication schemes in terms of performance metrics such as data rate, spectral efficiency, energy efficiency, and bit error rate.