Research On Key Technology Of Trellis-Coded Modulation Adapted To Differential Chaotic Communications

Chaotic signals have inherent spread spectrum characteristics,so chaotic digital modulation system is usually used in broadband scene,but the bandwidth in real scene is often limited.Traditional trellis-code modulation has good bandwidth utilization,but its anti-fading capacity is poor,the chaotic digital modulation system can make up for the shortage,so this thesis studies trellis-code modulation technology based on dual mode differential chaos shift keying modulation index system(DM-DCSK-IM)and vector multivariate differential chaos shift keying multicarrier system(V-MM-DCSK).The main contributions of this thesis are summarized as follows:(1)Trellis-coding modulation based on the mapping bits of DM-DCSK-IM.In the DM-DCSK-IM system,the information bits is mainly composed of mapping bits and modulation bits.The mapping bits determine the constellation mode of each time slot.Firstly,the concept of multidimensional coordinate and distance is proposed,and each time slot is regarded as a coordinate dimension,and the energy on the time slot is regarded as the coordinate value.Finally,the constellation mode is determined by distance decision,so as to demodulate the mapping bits.The results show good robustness in Gaussian white noise channel and Rayleigh multipath fading channel.(2)Trellis-coding modulation based on the modulation bits of DM-DCSK-IM system.In the DM-DCSK-IM system,since the mapping bits determine the constellation mode of each time slot,the influence of constellation mode decision error on the modulation bits cannot be corrected by coding.Therefore,a repeated-transmission diversity scheme is proposed to improve the detection performance of the mapped bits,and then a coding modulation scheme is designed for the modulation bits.Simulation results in additive white Gaussian noise(AWGN)show that the proposed scheme has obvious performance gain.(3)Trellis-coding modulation based on V-MM-DCSK system.V-MM-DCSK system is a multi-carrier chaotic communication system with high throughput and excellent performance in time-frequency dual extended channels.Therefore,this thesis designs the Trellis-code modulation based on V-MM-DCSK system architecture,and simulates the trellis-code modulation system under AWGN and underwater acoustic channel,and the simulation results show that the system can achieve considerable performance improvement under the same bandwidth efficiency.