【作者】 王征；

【导师】 卢志茂；

【作者基本信息】 哈尔滨工程大学 ， 信号与信息处理， 2011， 硕士

【摘要】 码分多址(Code Division Multiple Access)是一种崭新而成熟的无线通信技术,在现代通信系统中有着广泛的应用。设计出数量足够多的、具有优良相关特性的扩频码是CDMA的技术基础,以满足多用户的需求。现有普遍应用在CDMA系统中的地址码是由最大长度线性移位寄存器生成的m序列以及Gold序列,虽然易于实现但是它们有长度和数量受限的缺陷。混沌现象的发现和混沌理论的成熟为扩频序列的研究提供了新思路。混沌现象是一种在非线性系统中出现的确定类随机过程,这种现象具有非周期、不收敛和对初值具有高度敏感性的特点。利用混沌映射可以产生数量众多具有优良相关特性的伪随机序列。本文主要围绕着数字混沌扩频序列展开研究。以Logistic和Chebyshev映射序列为代表,对序列的平衡性、相关性及旁瓣峰值和均方值进行了仿真分析。在上述研究的基础上,编制优选算法对混沌序列进行优选,并将优选序列应用到CDMA的系统模型中,最后给出了该模型在加性高斯噪声(Additive White Gaussian Noise,AWGN)信道模型下的单用户和多用户的误码率性能。仿真结果表明,上述混沌序列适合作为CDMA通信系统中的地址码。在对混沌序列性能分析的基础上,针对传统单峰映射生成扩频序列复杂度低,抗截获性能差的缺陷,本文提出了一种利用串联结构的混合映射模型产生混沌扩频序列的方法,并对序列的相关性、平衡性以及游程性进行了仿真分析。在序列的优选上,给出了一种根据初值区域来产生源序列作为搜索目标的方法,然后将优选序列应用于CDMA系统中仿真。结果表明,由这种混合映射模型产生的混沌扩频序列具有优良的性能和较高的保密性。更多还原

【Abstract】 Code Division Multiple Access is one kind of new and mature wireless communication technique, which has a great deal of applications in modern communication system. Designing a sufficient number of spread spectrum codes, which have excellent characteristics, are the basis of CDMA technology in order to meet the needs of many users. Commonly used in CDMA systems address code is generated by the maximum length of a linear shift register sequences such as m and Gold sequences, though easily to implement they have a length and quantity limited number of defects.The discovery of chaotic phenomenon and the maturity of chaotic theory offer the broad way of PN sequence. The chaos phenomenon is one kind of convinced and random course that appears in nonlinear system, which has the characteristic of a non-periodic, non-convergence and highly sensitive to initial values. Making use of chaotic mapping can generate enough PN sequence with good correlation property.This paper mainly centers on research of the chaotic digital spread-spectrum sequence. With Logistic and Chebyshev sequence represented, the balance, relevance and side-lobe peak and mean square value and other properties of performance of chaotic sequences are analyzed and simulated. On the basis of study, the optimization algorithm was complied to prepare for optimizing the chaotic sequence, and the optimal sequences are applied to CDMA system model, finally gives the BER performance in single user and multi-user circumstances under Additive White Gaussian Noise channel. The simulation results show that these chaotic sequences are suitable as address code in the CDMA communication system.Based on the analysis of the performance of chaotic sequence, aiming at overcoming the shortcoming that the spreading spectrums sequences generated by traditional single chaotic map has low complexity and poor performance against by intercepted, a method for generating chaotic spread-spectrum sequences based on the series hybrid mapping model was proposed, then do the simulation analysis about the performance of sequence such as correlation, balance, run-length and so on. In the sequence optimization process, this paper offers a method according to the initial value area to produce source sequence as a search target. Then make the simulation in the circumstances that optimal sequences are applied to CDMA system. The results of simulation show that the chaotic spread-spectrum sequences generated by the proposed method have good performance and more secure for communication.更多还原