Simulation And Research Of Hybrid Chaotic Sequence Spread Spectrum Code In Spread Spectrum Communication System

Nowdays,with the rapid development of communication technology,spread spectrum technology has been widely concerned that because of its good anti-jamming capability, low intercept resistance and multiple access capability.And a key factor that influence spread spectrum technology lies on the choice of the spread spectrum code.As we all know,in the practical application common spread spectrum code include m sequence,Gold sequence and the like.Although these spread spectrum code have a good correlation and randomness, however, their periodicity makes their number limited.With the increase of communication users,the demand for pseudo-random sequences' number is growing,the traditional spread spectrum code already cannot satisfy the requirements of users.In recent years, studies have shown that because of its rich sequence and good anti-interception capability, chaotic sequence can be used as spreading code.However,single chaotic map has disadvantage in the aspects of balance and randomness.To solve these problems,a new method of generating new chaotic sequence has been proposed.This article's main research content is how to make use of a variety of common one-dimensional chaotic systems to produce new chaotic sequence.Like Gold sequence generator structure,we can combine two chaotic systems together in the way of XOR to form a new hybrid chaotic system.Reasonably selecting the appropriate chaotic systems by the simulation analysis of the performance of the single map chaotic systems,then combine them into a new hybrid chaotic system.The following step is to simulate and analysis the performance of chaotic sequence while is generated by the hybrid system.Meanwhile, in the MATLAB/Simulink platform, design a model of a direct sequence spread spectrum system, and validate the feasibility of hybrid chaotic sequence as spread spectrum code.This paper first introduces the research background, significance and research status of relevant theories, and then made a comprehensive overview of the spread spectrum system from the aspects of theoretical basis, main parameters and the main advantages, especially focusing on several common spread spectrum code.As following, briefly describe the definition, the main characteristics, classification of chaotic systems and an important indicator-Lyapunov index.After that make the simulate and analysis about the relative performance of a single chaotic sequence.The simulation results show that the improved Logistic system and Chebyshev system can be combined into a new hybrid chaotic system.And compared with other sequences, hybrid chaotic sequence has more excellent performance.Based on the analysis of relevant properties of this hybrid chaotic sequence,this sequence will be applied to the direct sequence spread spectrum system.The simulation results show that either in single user or multiple users, hybrid spread spectrum sequence can greatly improve the performance of system.And this paper also demonstrates that the proposed method can produce spread spectrum code with good performance.Finally, according to the results of previous research, designe a direct spread spectrum system model, and describe the internal module and its parameter setting in detail.Through the simulation on the system of Simulink model, further verify that the new hybrid chaotic sequence can be regarded as spread spectrum code instead of single chaotic sequence.At the end of this article, summarize the main content of the full text, and pointed out that further improvement and research are needed in this paper.