【作者】 胡君萍；

【导师】 杨杰；

【作者基本信息】 武汉理工大学 ， 交通信息工程及控制， 2008， 博士

【摘要】 由于超宽带技术能够与其它通信系统共享频谱资源,所以当FCC在2002年2月开放超宽带技术在民用领域的应用后,引起了超宽带技术的研究热潮。超宽带技术首要解决的问题是避免对其它通信系统产生干扰,基本标准是系统的能量辐射满足FCC的辐射限制。脉冲波形在脉冲方式超宽带系统的能量辐射中起决定作用。因此,脉冲波形设计是超宽带的一项关键技术,同时,设计既时限又频限,满足FCC频谱掩蔽且频谱利用率高的脉冲波形是一项具有挑战性的工作。本文对脉冲方式超宽带系统的脉冲波形展开研究,以FCC频谱掩蔽为基本衡量标准,按照从时域到频域和从频域到时域的两种设计模式,研究超宽带脉冲波形的设计方法,并进行具体的脉冲波形设计;研究超宽带脉冲对系统性能的影响,系统地研究了所设计脉冲的系统误码率和多址容量。本文的主要工作和研究成果如下:(1)超宽带实现技术的研究:在研究了IR-UWB、DS-UWB和MB-UWB三种制式的超宽带系统的原理、技术特点的基础上,研究三种制式超宽带信号功率谱密度对FCC的辐射掩蔽的适应性,得到DS-UWB和MB-UWB适合于高速通信,IR-UWB不适合于高速通信只适用于成像系统和探地雷达的结论;综合分析和比较系统的成本、功耗、干扰性以及误码率等性能,得到DS-UWB在实现复杂性、系统误码率和适应FCC的辐射限制方面优于MB-UWB的结论。这些结论对超宽带技术的研究具有指导意义。(2)基于时域的超宽带脉冲波形研究:论文提出了超宽带脉冲的基本设计原则,该原则比原有的仅匹配FCC频谱掩蔽更全面;在从时域到频域优化设计UWB脉冲方面,提出使脉冲最佳匹配FCC频谱掩蔽最小差值积分算法,与最小方差算法相比,实现简单,运行速度快;通过全面、深入地研究现有各种脉冲波形的时域特性、频域特性以及匹配FCC频谱掩蔽的程度,提出一种适合于直接序列超宽带系统的脉冲波形,按照最小差值积分法优化了该脉冲参数;运用优化组合方法,给出了复杂度稍高但FCC频谱匹配度更高的组合脉冲形式的超宽带脉冲。与传统的超宽带脉冲相比,它们具有实现简单、频谱利用率高的优点。(3)基于频域的超宽带脉冲波形的研究:通过研究现有的从频域到时域的UWB脉冲设计方法,提出了新的超宽带设计方法——直接频域法,该方法可灵活适应不同国家的UWB辐射限制,用此方法设计的超宽带脉冲在频谱利用率、干扰性、保密性方面具有优势。论文按此方法为直接序列超宽带系统设计出了两个超宽带脉冲——平方根升余弦脉冲和升余弦脉冲,它们在频谱利用率、干扰性、保密性方面明显优于现有的超宽带脉冲。(4)不同脉冲波形下超宽带系统的性能研究:论文分析了IEEE推荐的UWB无线多径信道模型,建立了直接序列超宽带系统模型,仿真实验了不同脉冲的直接序列超宽带系统在多径信道下的系统误码率,实验结果表明:所设计的超宽带脉冲在多径信道下的误码率性能优于传统脉冲。理论推导出本文的多用户直接序列超宽带系统的误码率公式,得到多用户干扰MUI受用户数量、数据比特率、脉冲波形的自相关函数等因素影响的重要结论,该结论对超宽带脉冲设计具有指导意义。根据理论推导的误码率公式分析和仿真实验,均得到基于时域设计的组合脉冲和基于频域设计的升余弦脉冲在多用户下的误码率性能和多址容量优于传统的Scholtz脉冲和近似扁长椭球波脉冲。综合各方面的性能,本文所设计的四种脉冲均可用于直接序列超宽带系统。其中,基于时域设计的单脉冲适合于系统成本要求低、0～4米LOS信道的应用场合;基于时域设计的组合脉冲适合于对多址容量要求很高的系统,尤其适合于多址容量要求很高的0～4米NLOS信道的应用场合;升余弦脉冲和平方根升余弦脉冲适合于对多址容量、误码率、干扰性、保密性等各项指标综合要求高的系统,平方根升余弦脉冲尤其适合于综合指标要求高的0～4米LOS信道的应用场合,升余弦脉冲尤其适合于综合指标要求高的4～10米NLOS信道和很差的NLOS信道应用场合。这些结论对直接序列超宽带系统的脉冲波形设计具有实际应用价值。更多还原

【Abstract】 As the ultra-wideband technology can share spectrum resources with other communications systems,the ultra-wideband technology caused the extensive attention when the FCC permitted the Ultra-Wideband technology for civilian applications in February 2002.The first problem of Ultra-wideband technology to solve is to avoid interference with other communications systems.And the basic standard estimating interference is that the radiation energy of system must meet the FCC’s radiation limit.The pulse shape of Ultra-Wideband System determines the energy radiation of pulse-mode UWB system.For this reason,this paper studies on pulse shape of the pulse-mode ultra-wideband system.It researches the UWB pulse shape design according FCC spectrum mask,from the time-domain to frequency domain,and frequency domain to the time-domain design points of view.It also researches the affect of UWB pulse on the ultra-wideband system performance in order to evaluate the UWB pulse and guide the design of ultra-wideband pulse.The main work and research results are as follows.1.The study of realization technology of ultra-widebandIt studies the working principles of IR-UWB,DS-UWB and MB-UWB,and analysis their technical characteristics.Then,The system cost,power consumption, interference,bit error rate of the three ultra-wideband are analyzed and compared.It establishes the UWB system scheme for this article which is direct sequence spread spectrum,BPM modulation ultra-wideband system with frequency shifting.The research results concluded that:DS-UWB and MB-UWB suitable for high-speed communications;IR-UWB is not applicable to high-speed communications but imaging systems and ground-penetrating radar.Compared with MB-UWB,DS-UWB is simpler,lower error rate,adaptive FCC’s radiation restrictions better.2.UWB pulse study based on time-domainIt discusses the basic design principles of Ultra-Wideband pulse.It studies on time-domain characteristics and frequency-domain characteristics of existing pulses, analyses whether they meet the FCC spectrum mask,discusses the algorithms of optimizing and combining pulse to best match with the FCC spectrum mask.Based on the front research results,it designs two ultra-wideband pulses,single-Gaussian pulse and Gaussian-combination pulse,in accordance with the optimization and combination algorithms for the direct sequence ultra-wideband system.The two pulses are easy to realization and have high frequency spectrum utilization as opposed to the previous ultra-wideband pulse.3.UWB pulse study based on frequency-domainIt studies the UWB pulse design from frequency domain to the time-domain design point of view.It proposes a new ultra-wideband design method,direct frequency-domain method.It designs two UWB pulse,the square-root raised cosine pulse and raised cosine pulse,for the direct sequence UWB system according to the new method.The two designed pulses have better Spectrum utilization,less interference to other communication systems,more secret than the existing ultra-wideband pulses.This indicates that the direct frequency-domain method is fine.4.UWB pulse study based on system performance Scholtz pulse,It analyses the AWGN channel model and UWB wireless multi-path channel model recommended by the IEEE,and constructs the direct sequence ultra-wideband system model.It realize the system bit error rate simulation using Scholtz pulse,the single-Gaussian pulse,the combination-Gaussian pulse,the approximate prolate spheroidal wave pulse,the square raised root cosine pulse,and raised root cosine pulse in the AWGN,CM1,CM2,CM3,and CM4 channel.The results show that the bit error rate of single-user direct sequence ultra-wideband system using six kind of pulses is not very different.Then,it researches and simulates the performance of multi-user direct sequence ultra-wideband system.It first derives bit error rate formula of the multi-user direct sequence ultra-wideband system.The bit error rate formula indicates that the Multi-user interference MUI is determined by the number of users,data bit rate,and auto-correlation function of the pulse.Through analyzing MUI of the six pulses System,it obtains the conclusion that combination-Gaussian pulse,raised cosine pulse,and square root raised cosine pulse have strong resistance on MUI,and Scholtz pulse has weak resistance on MUI. It establishes the multi-user direct sequence ultra-wideband system model,simulates bit error rate of multi-user system using different pulse,and obtains the multi-user capacity of six pulses.Combination-Gaussian pulse,and raised cosine pulse have big multi-site capacity,Scholtz pulse has small multi-site capacity.According to the results of the performance simulation,the designed four pulses by this paper,the single-Gaussian pulse,the combination-Gaussian pulse,the raised cosine pulse,and the square root raised cosine pulse can be used to direct sequence ultra-wideband system.Considering the interference to other systems,the bit error rate performance,multi-site capacity,difficulty to achieve,the raised cosine pulse is best.更多还原