Design of Enhanced Permutation Differential Chaos Shift System Using Signal Reference With Dual Modulation

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.