Research On Chaotic Digital Modulation Technologies Based On Differential Chaos Shift Keying

Chaotic communication has attracted wide attention in terms of low power consumption and low complexity,and its excellent anti-fading and anti-eavesdropping capabilities make it applicable to the field of wireless communications.Differential Chaos Shift Keying(DCSK)is a classical modulation technique in chaotic digital modulation due to its simple structure and good performance.DCSK system replaces the carrier synchronization of the Chaos Shift Keying(CSK)by using the Transmitted-Reference(T-R)method.The T-R transmission mode makes the DCSK system transmit the chaotic carrier through the reference time slot,but this reduces the transmission rate of the DCSK system.Based on the above description,three improvements are proposed in this paper.The Gaussian Approximation(GA)method is used as a tool to derive the theoretical bit error rate(BER),and the Monte Carlo experiments is used as a simulation test method.The main work of this article will be developed from the following aspects:1.Due to the low transmission efficiency caused by the fact that the reference time slot of the DCSK system does not transmit information,a high-rate DCSK(HR-DCSK)communication system is studied.This scheme used the idea of Correlation Delay Shift Keying(CDSK)and reduces the length of the reference time slot to achieve the purpose of improving the transmission rate.The transmitter uses the normalized chaotic sequence mapping to achieve constant signal energy during different bit-periods.The receiver uses related demodulation,and simultaneously demodulates the transmission bits through two separate circuits.The BER formula of the HR-DCSK system in the Additive White Gaussian Noise(AWGN)channel and the length of the optimal reference slot are deduced and verified by Monte Carlo simulation.Meanwhile,HR-DCSK compares the performance with three classical modulation methods.2.In order to further improve the data transmission rate of HR-DCSK system,a Short Reference Multiple Rate DCSK(SRMR-DCSK)communication scheme is proposed.This scheme is a general case of the HR-DCSK system and extends the frame structure of the HR-DCSK system.The BER formula of the SRMR-DCSK system in the AWGN channel and the length of the optimal reference sequence length under different transmission bits are deducted by using the GA method.The feasibility of the SRMRDCSK scheme in Multiple Input and Single Output(MISO)is further studied.The BER formula of the MISO-SRMR-DCSK communication system in the multipath Rayleigh channel is derived and the effect of parameters on system performance is analyzed.3.For the above two improved schemes,the BER performance is unsatisfactory.For this purpose,Orthogonal Multiple Code DCSK(OMC-DCSK)scheme is studied.This scheme uses Hadamard matrix combined with Kronecker operation.As the number of transmission bits increasing,the length of the reference signal is reducing.Because this system reduces the length of the reference signal,it improves the data transmission rate compared to the DCSK system that transmits the same bit.The chaotic signal transmitter is designed to eliminate interference between transmission bits,and all data signals share a reference signal,which effectively reduces the average bit energy.The BER formula of OMC-DCSK in multi-path Rayleigh channel is deduced by GA method,and the simulation and comparison experiments are carried out.