Design Of Improved Differential Chaos Shift Keying System

Differential chaos shift keying(DCSK)is a typical chaotic shift keying system,belonging to the non-coherent chaotic digital modulation technique.The system uses the transmitted-reference(T-R)transmission mode,which transmits reference signal and information signal separately in consecutive two time slots.So that it brings two problems.First,it wastes half bit duration on sending the reference signal that carries no data,which results in low bit transmission rate of DCSK.Second,there is a certain similarity in reference signal and information signal of the same bit time,which leads to weak security.What's more,in DCSK system,both the transmitter and receiver contain radio-frequency(RF)delay components,which limits circuit implementation in high-speed wireless communications.Therefore,in order to improve the bit transmission rate,the performance of bit error rate(BER)and system security,besides,to solve the integration problem of the delay hardware,this paper studies on the improved DCSK system.First,in order to increase the system bit transmission rate,reverse-DCSK(RE-DCSK)system is proposed.The time reversal operation is used to generate an information signal orthogonal to the original one,and they are added together to transmit data information in one time slot.By using the Gaussian approximation(GA)analysis method in additive white Gaussian noise(AWGN)channel and Rayleigh fading channel(single-path,two-path),respectively,the BER expression of RE-DCSK system is derived,and Monte Carlo simulation is also performed in MATLAB.The experimental results show that the bit transmission rate of RE-DCSK is double that of DCSK system.At the same time,the performance of BER and security are improved.In order to further improve RE-DCSK bit transmission rate,remove the technical limitations of the integrated circuit and excess RF delay element,orthogonal frequency division multiplexing(OFDM)technology is utilized here.It has good network structure scalability,more flexible modulation,higher spectrum efficiency and stronger anti-multipath interference capability,so that we study RE-DCSK system based on OFDM(OFDM-RE-DCSK).The BER expression of the system is derived by GA method in AWGN channel and Rayleigh fading channel(single-path,two-path),respectively,and Monte Carlo simulation is carried out in MATLAB.The experimental results show that the bit transmission rate of OFDM-RE-DCSK system is higher than that of correlation delay shift keying(CDSK),DCSK and RE-DCSK system.At the same time,the amplification of the bit transmission rate is increased as the number of sub-carriers of OFDM signal increases.The BER performance is increased obviously,meanwhile,the performances of anti-multipath fading and security are also improved.