Abstract
In this paper, a permutation-based chaos system, named as Single Reference Permutation Index with Dual Modulation Differential Chaos Shift Keying (SR-PIDM-DCSK), is developed and tested. The proposed system uses the chaotic segment and its reversed version to modulate two pairs of data sets simultaneously. It uses the same reference for multiple symbol modulation. This significantly reduces bit energy requirement and enhances the Bit Error Rate (BER). In addition, it reduces the complexity of the system. At the transmitter, the reference signal is sent first, then the same reference is delayed and permutated to send the first information set of bits, while the same version is time reversed and permutated to modulate the second set of bits. Both segments are added together on the same symbol duration slot for transmission. This process is repeated for multiple symbols in a frame. At the receiver, the incoming reference signal is delayed for several symbol durations for demodulation. The BER of the system is evaluated in various channel environments. Moreover, a theoretical prediction for BER formula is developed for the suggested model. Results show that the proposed system has superior BER performance compared with other standard chaos based systems by an average of 2 dB. It is evident that the BER performance is enhanced with the increase in the spreading factor and the number of symbols in a frame. The theoretical formula for BER prediction is validated by computer simulation. Excellent matching was found between the theoretical formula and simulation results.
Highlights
The chaos communications system is based on using a chaotic signal, which has the main function of carrying information signals to help recover the information signal through modulation and demodulation processes
The contributions of this paper are summarized as follows: 1) We propose a framework of SR-PIDM-Differential Coherent Shift Keying (DCSK) system, which uses a common reference signal to modulate multiple data symbols
In each SR-PIDM-DCSK symbol, β bits are mapped into a distinguished permutation of the chaotic sample while another β bits are mapped to the time reversal-permutated version
Summary
The chaos communications system is based on using a chaotic signal, which has the main function of carrying information signals to help recover the information signal through modulation and demodulation processes. Improved versions of PI-DCSK where reference chaotic segment and information-bearing signals are combined on one-bit duration are presented in [22]. The proposed system achieves anti-multipath fading capability without using channel estimators In this brief, a common reference signal is used to modulate the frame of information symbols, each symbol consisting of two parts. The first part is a normal permutation M-ARY DCSK system while the second part modulates other sets using a time reverse version of the same reference signal. Both parts are added together at the same time slot. The contributions of this paper are summarized as follows: 1) We propose a framework of SR-PIDM-DCSK system, which uses a common reference signal to modulate multiple data symbols. To have a fair comparison between systems, the BER performance is evaluated under fixed Eb/No and with the same spreading factor M (i. e chip rate)
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