【作者】 张朝霞；

【导师】 王华奎；

【作者基本信息】 太原理工大学 ， 电路与系统， 2010， 博士

【摘要】 超宽带脉冲通信是一种与其它通信技术有很大不同的无线通信技术,它具有辐射功率密度低、通信容量大、抗多径干扰、结构简单、处理增益高和保密性好等优点。超宽带(UWB)脉冲通信是对无线频谱资源的利用进行的新探索,这项新技术对方兴未艾的无线通信技术是一个强有力的支持。UWB脉冲通信技术已经被广泛应用于无线多媒体家域网、个域网、雷达定位和智能交通等系统,以及在军事通信、医用检测器等多个领域都有广泛的应用前景。因此,人们需要深入研究并掌握这项新兴技术。目前提出的超宽带的实现方式有三种:跳时超宽带、直接序列超宽带、多频带OFDM超宽带。本文采用了最常用和最传统的方法:即发射时域上很短的脉冲,这种传输技术也称为“冲激无线电”。为了形成所要产生的频谱,除了对脉冲进行调制外,还要用伪随机码对数据符号进行编码,这样,编码后的数据符号引起了脉冲在时间轴上的偏移,这就是跳时超宽带通信系统。本文即是从跳时入手,进行了大量的分析与研究工作,主要有:1.分析了超宽带无线通信技术的理论基础以及超宽带技术的发展现状,研究了可应用于超宽带技术的调制技术及多址方式,重点研究了采用脉冲位置调制(PPM)和脉冲幅度调制(PAM)时系统的模型,分析了其信道模型与接收方式,阐述了超宽带中跳时的定义、重要性和必要性。2.探讨了平衡Gold码和截短平衡Gold码的生成机理,研究了这两种码的自相关与互相关特性,比较了它们与m序列等伪随机序列的性能,提出将平衡Gold码和截短平衡Gold码分别应用于超宽带的跳时技术中,解决了超宽带通信系统中对多址码数量和平衡性的要求,仿真了两种信道下多径和多址的误码率,表明它们比已提出的伪随机序列具有更好的性能。3.在Logistic映射和Tent映射产生伪混沌序列研究的基础上,探讨了Hybrid映射产生的数学机理,研究了Hybrid映射产生的伪混沌码的自相关与互相关特性,比较了它与Logistic映射产生的伪混沌序列的相关性能,分析了Hybrid映射优选的准则,提出将Hybrid映射产生的伪混沌码用于超宽带通信系统中跳时码的研究方案,解决了混沌系统对码的数量、安全性、保密性等方面的关键问题。仿真结果也显示该混沌序列的各项特性均满足伪随机序列的要求,具有较高的安全性和保密性,是一类具有广泛应用前景的伪随机跳时序列。仿真结果表明,在多用户的跳时超宽带系统中,该序列比传统的伪随机序列具有更好的误码性能。4.在阐述RS码基本原理的基础上,研究了它的相关性能,探讨了RS码作为跳频序列族的机理,分析了跳频与跳时码置换的关系,采用时间反转技术,提出将RS码用于超宽带的跳时多址技术中。解决了RS码可以用于跳时码的关键问题,仿真结果表明,将RS码用于UWB系统的跳时序列是一种不错的选择,同时验证了理论的正确性。更多还原

【Abstract】 Ultra-Wideband (UWB) pulse communication is a very different communication technique from other wireless communication. It has characteristics of low power spectral densities, high system capacity, exceptional multiple-path immunity, simple structure, high process gain and good confidentiality. The UWB pulse communication is new exploration of radio spectrum and it is the strong support for wireless communication. So far it has been widely used for wireless multimedia family area network, personal area network, radar positioning, intelligent transportation systems, and military communications, medical detector etc. fields. Therefore, it is necessary to study and grasp the new technology.At present, the realization methods of UWB are three: time-hopping UWB, direction sequence UWB and multiple-band OFDM UWB. The paper introduces the most frequently-used and the most traditional method: transmitting the very short pulse in time domain, the transmission technology is also called“pulse radio”. For forming the spectrum, we not only modulate the pulse, but also encode the data symbols by utilizing pseudo-random code. This is the time-hopping ultra wide-band communication system. A lot of analysis and study about time-hopping code are carried out in the paper.The major contribution of this paper is summarized as follows:1. In the paper, the principle of wireless communication technology and the development status quo of ultra wide-band system are analyzed systematically. The modulation methods and multi-Access of ultra wide-band system are studied and the priority research is the system models using pulse position modulation and pulse amplitude modulation. The channel models and receiver of ultra wide-band are analyzed, and the importance and necessity of time-hopping code are elaborated.2. The paper discussed the generating mechanism of balance Gold code and shortened balance Gold code and studied the auto-correlation and cross-correlation of the two codes. And the paper compared the correlation performance between the aforementioned two codes with m sequence. Using balance Gold code and shortened balance Gold code for the time-hopping technology of UWB are presented in the paper. And the technology solves the commands of numbers and balance for multi-access codes. At last, the paper simulates the bit error ratio of multi-path and mutli-access in two channels. The simulation results specify that the present time-hopping codes have high error probability performance over traditional pseudo-random code.3. On the basis of the study of the pseudo-chaotic sequence generated through Tent and Logistic mapping in the other literatures, the paper discussed the mathematics mechanism of Hybrid mapping and studied the auto-correlation and cross-correlation of the pseudo-chaotic sequence generated by Tent mapping. And the paper compared the correlation performance between the aforementioned codes with the pseudo-chaotic sequence generated by Logistic mapping. The criterion of selective preference of Hybrid mapping is analyzed in the paper. Utilizing the pseudo-chaotic (PC) code which is generated by Hybrid mapping in the time-hopping technology of UWB is presented in the paper. The key problems of codes’numbers and system’s confidentiality and security are solved. Hybrid mapping not only inherits the characteristics of easy generation of Logistic mapping and Tent mapping, but also the output sequence is more random and unpredictable. And the number of the sequence is very much and this increases the system’s confidentiality and the pseudo-chaotic system’s security. Simulation results also indicate all features of the pseudo-chaotic sequence need the requirements of pseudo-random sequence and have high confidentiality and security. It is a promising pseudo-random time-hopping sequence. Simulation results indicate the pseudo-chaotic sequence has the higher performance than traditional pseudo-random code in time-hopping ultra wide band system.4. On the basis of the elaboration of the RS codes’fundamental theory, the paper studied the auto-correlation and cross-correlation of RS codes and discussed its mechanism of using for frequency-hopping code. The transposing relationship from frequency-hopping to time-hopping is analyzed in the paper. Introducing time reverse technology, and using the RS code in the time-hopping technology of UWB is presented in the paper. The problem which RS can be used for time-hopping code is solved. Simulation results verify that using Reed-Solomon code for time-hopping code in UWB system is a good choice. Simulation results verify the correctness of the theory.更多还原