Research On CDSK In The Chaotic Communication System

With the rapid development of information technology,the requirements for anti-interference ability and security of information transmission has been raised higher and higher in wireless communication.Therefore,the emergence of chaotic key-controlled communication technology has attracted widespread attention.Correlation Delay Shift Keying(CDSK)is one of the typical schemes in chaotic keying communication system.At the transmitter of the CDSK system,since the adder is used instead of the switching structure of the Differential Chaos Shift Keying(DCSK)system,the transmission rate is twice that of the DCSK and the continuity in the information transmission process can be ensured.However,since the signal transmitted by the CDSK transmitter is the sum of the reference signal and the information signal,the additional intra-signal interference will be introduced into the correlation demodulation at the receiver.Therefore,the Bit-Error Ratio(BER)of CDSK is higher than DCSK.At present,the improvement based on CDSK has not solved the problem of intra-signal interference well,and there are few studies on applying CDSK to multi-user systems.In order to reduce the BER of the CDSK,the thesis focuses on how to eliminate the intra-signal interference of the system.The main research work of this thesis will be developed from the following aspects:1.In order to solve the problem that the receiver of the CDSK system introduces intra-signal interference during demodulation,an improved Orthogonal Correlation Delay Chaos On-Off Keying(OCD-COOK)communication system is studied.This scheme combines the characteristics of CDSK and Chaos On-Off Keying(COOK)and introduces a pair of Walsh code sequences at the transmitter of the system.By the Walsh code sequence to distinguish the two modulation signal,so that the system does not generate intra-signal interference during the demodulation process.The BER formula of the OCD-COOK over the Additive White Gaussian Noise(AWGN)channel is deduced and the theoretical derivation of the system is verified by Monte Carlo simulation.Meanwhile,OCD-COOK compares the BER performance with CDSK and DCSK.2.In order to improve the information transmission rate and BER performance of CDSK system and apply it into the multiuser system,a Multiple Ary Multiple User CDSK with No Intra-Signal Interference(NISI-MAMU-CDSK)communication system is studied.This scheme makes each user's binary information sequence is grouped and mapping for Multiple Ary information symbol.By introduces a set of Walsh code sequence to distinguish the reference signal and the Multiple User information signal,so that the system does not generate intra-signal interference and inter-user interference in the demodulation process.The BER formula of the NISI-MAMU-CDSK over the AWGN channel and multipath Rayleigh fading channel is derived,and the simulation verification and system BER performance analysis is conducted.3.In order to improve the BER performance of CDSK system and apply it into the multiuser system,a multi-user CDSK(Multi-User CDSK with No Intra-Signal Interference,NISI-MU-CDSK)communication system based on Frequency Division Multiplexing(FDM)is studied.By introducing an orthogonal chaotic signal generator,the scheme generates two orthogonal chaotic signals,which are taken as reference signal by a linear superposition.The reference signal and the information signal are transmitted by means of FDM,so that the system does not generate intra-signal interference and inter-user interference in the demodulation process.The BER formula of the NISI-MU-CDSK over the AWGN channel is deduced.The feasibility of the NISI-MU-CDSK in Multiple Input and Single Output(MISO)environment is further studied.The BER formula of the MISO-NISI-MU-CDSK over the multipath Rayleigh fading channel is derived,and the effect of each parameter on system BER performance is analyzed.