Research On DCSK In Chaos Communication

Currently,chaotic digital modulation is the most concerned chaotic communication technology,and its excellent chaotic characteristics ensure that the technology can be widely used in complex communication environments.Differential Chaos Shift Keying(DCSK)is a typical representative of chaotic digital modulation technology.Using chaotic signals as carrier signals,it not only realizes the modulation of bit information but also completes the spectrum expansion.In addition,it has the advantages of the circuit design is simple and does not require chaos synchronization,which has broad application prospects.However,due to the use of the Transmitted-Reference(T-R)method,half of the time and power are wasted,and there are disadvantages of low information transmission rate and poor information security.The combination of multiuser technology and DCSK satisfies the requirment of high speed for communication.However,due to the inter-user interference in most traditional multiuser DCSK systems,the bit error performance of the multiuser system is poor.Aiming at the disadvantages of DCSK and multiuser DCSK,the thesis proposes different solutions.The mathematical theory of this thesis is based on the Gaussian Approximation(GA)method,and the verification method is Monte Carlo simulation experiment.The thesis mainly introduces the following three aspects:(1)Aiming at the problems of DCSK low transmission rate and poor information security,a CD-DCSK communication system without inter-symbol interference is studied.Considering the serious transmission time and energy consumption of the DCSK system's transmitter modulation structure,it is integrated with the higher transmission efficiency of the Correlated Delay Shift Keying(CDSK),so as to achieve the goal of high transmission efficiency and high security.In order to solve the shortcomings of the poor bit error performance of the system after the combination,a generator which can generate two orthogonal chaotic signals is designed to eliminate the inter-symbol interference in the system.Through theoretical analysis and Monte Carlo simulation of the bit error performance of the system,the results show that the transmission efficiency and security of the system are greatly improved compared with DCSK.(2)Although traditional multiuser DCSK improves transmission efficiency,there is still room for improvement.In order to further improve the transmission efficiency,a Hilbert-Transform Multiuser(HMU)DCSK communication system is studied.The system uses Hilbert transform to double the capacity of the orthogonal basis signal set and double the transmission efficiency.The bit error rate of the HMU-DCSK system based on Rayleigh flat fading channel is analyzed,and the general expression of the optimal user's number of the system is obtained.The efficiency comparison and Monte Carlo simulation proves that the system has higher energy efficiency and transmission rate and has a better bit error performance than the traditional multiuser DCSK system.(3)Aiming at the poor bit error performance caused by inter-user interference in Variant Delay Multiple Access(VDMA)DCSK system,a Cyclic Shift Multiuser DCSK communication system is studied.The system uses a homogenizer and a cyclic shifter to uniformly divide and cyclically shift the chaotic signals to generate a plurality of different chaotic signals for the users to ensure that the user carriers are different.Utilizing the orthogonality of the Walsh codes,the orthogonality between the signals transmitted by the users is ensured.The system eliminates inter-user interference and greatly improves bit error performance.The fusion application of the scheme and Multiple Input and Single Output(MISO)technology is systematic analyzed,the bit error rate of the MISO-CSMUDCSK system based on Rayleigh flat fading channel is analyzed and the superiority of the system is verified by Monte Carlo simulation.