Research On High Spectrum Efficiency DCSK System Based On Time-Delay Overlapping Modulation

With the rapid development of communication technology,the pace of "Intelligent Connection of Everything" is accelerating,and more and more smart devices will be connected to the Internet in the future.In order to support the "Intelligent Connection of Everything",the communication system must have a higher data transmission rate and spectrum efficiency.At the same time,the "Intelligent Connection of Everything" will cause more and more private and sensitive information to be transmitted on the network,making the importance of safe and confidential transmission of information more and more prominent.Therefore,it is of great significance to study a communication technology that satisfies both high spectrum efficiency and strong confidentiality.Chaotic secure communication technology has been widely studied in recent years because of its advantages such as simple implementation,high confidentiality and strong real-time performance.In chaotic secure communication,differential chaotic shift keying(DCSK),as the most typical incoherent chaotic digital secure communication system,has inherent superiorities such as avoiding channel estimation and chaotic synchronization,being simple to implement,having strong ability to resist multipath fading,and a wide range of application prospects.However,the DCSK system has shortcomings such as low transmission rate,poor confidentiality,low spectrum efficiency and low energy efficiency,so that it must be improved when applied to current and future communication scenarios.Multi-carrier modulation technology has advantages in terms of transmission rate and spectrum efficiency.The combination of multi-carrier technology and chaotic communication technology can ensure the security and confidentiality of the system while accelerating the information transmission rate and improving the spectrum efficiency.Therefore,this thesis focuses on a high spectrum efficiency multicarrier communication technology--Multi-Carrier Time-Delay Overlapping Modulation(MC-TDOP)technology,and carries out systematic in-depth theoretical research and numerical simulation verification for the new multicarrier chaotic communication system formed by the fusion of this communication technology and chaotic communication technology.The main work is as follows.(1)Study a new type of high spectral efficiency multi-carrier time-delay overlapping modulation technology,and a numerical simulation research and analysis discussion on the communication performance of this technology in the maritime VHF frequency band.The results show that the proposed maritime MC-TDOP technology has the higher spectrum efficiency can achieve its peak communication rate--307.2 kbps while occupying only one-fifth of the VDES bandwidth.(2)Aiming at the insufficient spectrum efficiency of the existing Multi-Carrier Differential Chaos Shift Keying(MC-DCSK)system,a single Sub-Channel Multi-Carrier Differential Chaotic Shift Keying(SC-MC-DCSK)is proposed.The principle of modulation and demodulation of the SSC-MC-DCSK system is explained,and carry out numerical simulation research and analysis on the system’s spectrum efficiency,energy efficiency,Additive White Gaussian Noise(AWGN)and multipath Rayleigh fading channel communication performance and factors affecting communication performance,and compared with the communication performance of the traditional MC-DCSK system.The results show that the proposed SSC-MC-DCSK can simultaneously transmit the chaotic reference signal and the chaotic communication signal in a single frequency sub-channel,which means a higher spectral efficiency and energy efficiency,and the communication performance is better than the traditional MC-DCSK system.(3)In order to further improve the spectrum efficiency and energy efficiency of the DCSK system,a Time-Delay Overlapping Modulation Differential Chaos Shift Keying(TDOP-DCSK)system is proposed based on the idea of delay overlap modulation technology.The principle of modulation and demodulation of the TDOP-DCSK system is explained,the spectrum efficiency,energy efficiency and confidentiality of the system are theoretically analyzed,and the source and formula of the Bit Error Rate(BER)of the system are theoretically deduced.In addition,the communication performance of the system under AWGN and multipath Rayleigh fading channel is studied by numerical simulation.The correctness of the theoretical deduction is verified,and the factors affecting the bit error rate of the system are studied,and the communication performance of the system is compared with that of the traditional DCSK system.Theoretical analysis and numerical simulation results show that the proposed TDOP-DCSK system has high spectral efficiency and energy efficiency,and can increase the system symbol rate by dozens of times while ensuring that the system’s bit error rate is close to that of the traditional DCSK system.At the same time,the proposed TDOP-DCSK system reduces the correlation between the chaotic reference signal and the chaotic communication signal,and has higher confidentiality.