摘要
混沌科学作为一门新兴学科,越来越多的学者对其进行了研究,并被广泛应用于扩频通信技术中。随着混沌在扩频通信中的应用,使得电子侦察工作越来越困难,因此对混沌扩频通信系统的对抗研究成为现代电子战争的一个关键。本文中,对基带混沌扩频通信系统的特性进行了深入的分析,并对该系统的干扰技术做了进一步的研究。本文的主要工作如下:
第一部分重点研究了四种混沌序列优于传统扩频序列的统计特性。
主要研究了四种常用于扩频通信的混沌映射:Chebyshev映射、Logistic、改进型Logistic映射和Tent映射,仿真研究表明,在一定的条件下,这四种混沌映射都存在着一个或几个收敛点,因此在构造混沌序列时应避免这些收敛点;四种混沌序列误码性能要优于传统扩频序列--m序列和Gold序列。
第二部分采用了一种基于Gold序列的混沌扩频同步方法。
本文对一种基于Gold序列的混沌扩频同步方法进行了仿真分析。从仿真结果可以看出,该同步方法有效的实现了混沌扩频通信系统的同步问题,解扩后接收到的信息码比原始信息码延迟了一秒的时间,这在扩频通信系统的要求中是可以允许的。
第三部分重点研究了多用户基带混沌扩频通信系统原理及其性能。
理论分析了多用户基带混沌扩频通信系统的原理,强调了该系统的抗干扰能力强的特点,重点研究了产生混沌扩频码的映射参数对基带混沌扩频通信系统的影响,通过仿真比较,我们可以知道,该系统具有比传统扩频通信系统更优良的系统特性。
第四部分重点分析了对基带混沌直接序列扩频通信系统的四种干扰样式和比较。
首先对通信对抗技术的发展、干扰的不同分类以及干扰通信系统的分类进行了简单的介绍,其次,针对基带混沌直接序列扩频通信系统,说明影响通信系统性能的指标为系统输出端误码率,并说明了对混沌扩频通信系统的最佳干扰理论为具有混沌时频特性的随机信号。随后采用高斯白噪声信号、单频信号、线性调频信号、噪声调幅、噪声调频和噪声调相六种压制式干扰信号,对基带混沌直接序列扩频通信系统进行干扰仿真实验,分析各种信号的特性及在不同频率和不同带宽下的对其干扰效能的影响。
Chaos spread-spectrum communication has become a hotspot in the field of chaotic application research. Combined theoretical analysis with simulation approaches, the key technologies of multi-user chaotic direct sequence spread spectrum(DS-SS) communication are analyzed, especially in the generation of chaotic sequence, the optimizing of the chaotic sequence, the method of chaotic synchronization, and the simulation and performance analysis of the system. The chaos DS-SS communication’s availably jamming becomes the key to get the electronic war’s victory, so it is very important to research the effectiveness of jamming and interference referred to the chaos DS-SS communication system.
In the first part, the relation between the performance of balance and the parameter of four typical chaotic maps (Chebyshev, Logistic, Improved Logistic and Tent) is studied. The new numeric ranges of initial value and fractal parameter are decided, which provides reference for the generation of chaotic spread-spectrum sequence. The performance of balance and correlated characteristic of these four chaotic sequences with the length of 2000 to 3000 are studied. Compared with conventional spreading sequence (m sequence and Gold sequence), they have better performance of balance and correlated characteristic.
In the second part, the techniques of Costas carrier tracking and non-coherent PN sequence tracking in digital receiver are studied. Besides, based on m sequence, a new chaotic sequence synchronization method which has excellent anti-jamming capability is proposed. Through the capture of m sequence, the synchronization of chaotic sequence between transmitter and receiver is realized. This method not only solves the synchronization of the chaotic sequences with the finite length, but also founds the technology foundation for the practical application of chaotic DS-SS communication. In the third part, multi-user chaotic DS-SS communication systems are designed. The error-bit rate performance of this system with parameter of chaotic maps, signal to noise ratio, number of users, the length of sequence is investigated, and the results show that it has many merits, such as good anti-interference, low BER, great capacity, ideal secure properties, and good flexibility.
In the fourth part, the optimum jamming bandwidth and optimum jamming frequency for direct sequence system are mathematically analyzed. Based on DS-SS technology, the proposed chaos-based noise jamming technology is studied. Based on chaos DS-SS technology, this Master Dissertation profoundly studies five kinds of different jamming signals, including the white noise, the chirp signal, the noise AM jamming, the noise FM jamming and the noise PM jamming, evaluates the effectiveness of them and makes simulation. Combined theoretical deduction and the computer simulation results, jamming strategy in different situations and get relevant jamming condition is analyzed.
引文
[1]黄润生.混沌及其应用[M].武汉:武汉大学出版社,2005.
[2]张学义.混沌同步及其在通信中的应用研究[博士学位论文] [D].哈尔滨:哈尔滨工程大学,2002.
[3] Kohda T, Tsuneda A. Pseudonoise sequence by chaotic nonlinear maps and their correlation properties[C].IEICE Trans. on Commun, 1993,E76-B(8):855-862.
[4]周家令.多用户混沌扩频通信系统的研究[硕士学位论文] [D].湖南:中南大学,2006.
[5]王玫.混沌通信中的关键技术研究[博士学位论文] [D].西安:西安电子科技大学,2003.
[6]查光明.扩频通信[M].西安:西安电子科技大学出版社,1990.
[7] Chong F U. A fast chaotic spread spectrum communication system and its performance analysis[C]. 2005 Global Mobile Congress-Papers, Chongging, China. 2005:237-242.
[8] Liang M, Gang T. Long spreading sequences based on chaotic map for satellite communication system[C]. 2005 Global Mobile Congress-Papers, Chongging, China. 2005:558-562.
[9]求是科技,编著.MATLAB从入门到精通[M].北京:人民邮电出版社,2006.
[10] Leon W Couch罗新民等译.数字与模拟通信系统(第六版).北京:电子工业出版社2005.
[11] Roger L. Peterson沈丽丽等译.扩频通信导论[M].北京:电子工业出版社2006.
[12]易定海.对扩频通信系统干扰的仿真研究[硕士学位论文] [D].成都:电子科技大学,2008.
[13]胡健栋,郑朝辉,龙必起,等.码分多址与个人通信[M].北京:人民邮电出版社,1996.
[14]于银辉,刘卫东.两种混沌扩频序列平衡性分析[J].重庆邮电学院学报,2004,16(3):61-64.
[15]王亥,胡健栋.Logistic-map混沌扩频序列[J].电子学报, 1997, 25(7):95-97.
[16]王亥,胡健栋.改进型Logistic-map混沌扩频序列[J].通信学报, 1997, 25(1):19-23.
[17]姚海涛.产生混沌扩频序列及其在扩频通信中的应用[硕士学位论文] [D].广西:广西大学,2001.
[18]邱玲,朱近康,孙葆根,等.第三代移动通信技术[M].北京:人民邮电出版社,2001.
[19]沈允春.扩谱技术[M].北京:国防工业出版社, 1995.
[20]张厥盛,郑继禹,万心平.锁相技术[M].西安:西安电子科技大学出版社,1994.
[21]邓华,等.MATLAB通信仿真及应用实例详解[M].北京:人民邮电出版社,2003.
[22]陈树新,邓妍,等.现代通信系统建模与仿真[M].西安:西安电子科技大学出版社,2003.
[23]蔡国权,等.混沌直接序列扩频通信系统[J].信息工程学院学报,1999,18(1):25-28.
[24]杜月林,陆婷.混沌扩频序列在CDMA通信系统中的应用[J].国外电子测量技术,2006,25(7):69-73.
[25] Xu D L, Kyung H C. Optimal PN sequence design for quasi-synchronous CDMA communication systems[J]. IEEE Trans. on Commun,1997,45(2):221-226.
[26] Kurian A P, Sadasivan P K,Htut S M. Performance enhancement of DS/CDMA system using chaotic complex spreading sequence[J].IEEE Trans. On Wireless Communication, 2005,4(3):984-989.
[27] Wang X G, Lai C H. On generating binary spatiotemporal chaotic sequences and its application on spread-spectrum communication[J]. International Journal of Bifurcation and Chaos, 2006, 16(1):213-219.
[28] Vladeanu C, Lucaciu R. Second order moment estimation for multilevel quantized tailed shifts sequences optimizing BER for asynchronous DS-CDMA systems[C]. ISSCS 2005: International Symposium on Signal, Circuits and Systems-proceedings,2005(2):661-664.
[29] Torieri D J. Performance of direct-sequence systems with long pseudonoise sequence[J].IEEE J. on SAC,1992,10(4):770-781.
[30]孙克辉,周家令,牟俊.多用户混沌序列扩频通信系统的设计与仿真[J].计算机仿真,2007,24(8):112-115.
[31]孙克辉,周家令,牟俊.多用户混沌序列扩频通信系统设计与性能分析[J].电子与信息学报,2007,29(10):2436-2440.
[32]向春秋,胡修林.扩频通信抗干扰能力及其改进[J].船舰电子工程,2004,140(2):59-63.
[33]肖曼琳.直扩通信系统的干扰效能评估与仿真[硕士学位论文] [D].成都:电子科技大学,2006.
[34]刘杰,李艳斌.直扩通信最佳干扰形式分析[J].研究与分析,2001,27(6):27-29.
[35] Richard A Poisel著,陈鼎鼎,等译.现代通信干扰原理与技术[M].北京:电子工业出版社,2005.
[36]许靖,谷春燕.单频干扰在直扩系统中的误码性能分析[J].空间电子技术,2004,27(4):16-20.