【作者】 丁海洋；

【导师】 张延华；

【作者基本信息】 北京工业大学 ， 电路与系统， 2006， 硕士

【摘要】 近几年来,超宽带(Ultra-wideband简称UWB)技术得到了研究机构和工业界越来越广泛的关注。UWB技术采用超短脉冲发射技术(纳秒乃至皮秒量级),占用的频谱可达几个GHz,这使得其在短距离内可达到几百兆比特的传输速率[1-4],该技术因此而非常适于近距离高速无线个人域网[2](WPAN)。同时,由于UWB技术本身的特点,很多传统通信技术(如分集技术,调制技术等)在应用于UWB系统时性能发生了改变,为此需要重新评估这些技术在UWB系统中的适用性和可靠性。本文的工作主要分为以下几部分内容。1.采用标准高斯近似法及其改进方法对密集多径信道下(IEEE 802.15.3a CM1超宽带标准信道[1,2])多用户直扩-双相调制(Direct-Sequence Spread-Spectrum Binary Phase Shift Keying,简称DSSS-BPSK或DS-BPSK)超宽带系统的误码性能进行分析。首先由标准高斯近似法得到影响系统误码性能的几个关键因素。在此基础上证明改进型高斯近似法(Improved Gassian Approximation,简称IGA)在本文所述系统中的适用性,并利用其简化算法(Simplified IGA,简称SIGA)得到简洁的误码率近似表达式。进而通过蒙特卡罗仿真验证上述误码率近似表达式的正确性。此外,本文还比较了几种常见脉冲,常见伪随机码对系统误码率的影响,并对最优脉冲的设计进行了初步探讨。2.根据UWB密集多径信道的特点,提出了“复合对数正态随机变量”的概念。在此基础上,提出了一种新的对对数正态随机变量和的统计特性进行近似的方法,该方法对变量的分布参数和变量间的相关特性没有任何限制,且精度较已有方法有了进一步的提高。进而利用该法对复合对数正态信道下双集接收机(dual diversity receiver)的中断概率(Outage Probability)(分别采用最大比组合Maximal Ratio Combining和等增益组合Equal Gain Combining)进行了分析,并得到了精度较高的结果。此外,实验结果表明本文建议方法对多对数正态随机变量和的情况也适用,且精度很高。3.在IEEE802.15.3a UWB室内信道模型基础上,采用几种常见的RAKE分集接收方式,在考虑符号间串扰情况下对不同传输速率的BPSK调制信号进行了系统性能仿真实验。通过实验,得到了两种典型UWB信道中(0-4m视距和更多还原

【Abstract】 In recent years, ultra-wideband (UWB) communication has drawn considerable attention from both the research community and industry. Extremely short period pulses have been employed in this technology (usually as short as several nanoseconds or even several picoseconds), which results in the transmission capability of up to gigabits per second [1-4]. Because of the high transmission rate, UWB communications are best suited for wireless personal area networks (WPAN). Meanwhile, because of the characteristics of UWB, the performances of many traditional communication techniques (such as diversity, modulation and so on) change a lot when they are applied in the UWB communication systems, which results in the necessity of re-evaluating the performances of these techniques.The main contributions of this thesis are composed of the following three parts:1. A bit error rate (BER) analysis of an asynchronous DSSS-BPSK UWB system in dense multipath channels by means of standard Gaussian approximation (SGA) and simplified improved Gaussian approximation (SIGA) is presented. The standard UWB channel (proposed by IEEE 802.15.3a task group) is employed in the analysis to reflect the actual channel conditions. Several key parameters that affect the BER performance are obtained by means of SGA. On the basis of SGA, the validity of improved Gaussian approximation (IGA) method is established in our systems and the accuracy of the bit error rate expression obtained via SIGA is demonstrated with Monte-Carlo simulations. Besides, the impacts of several different kinds of transmitted pulses on BER performance are investigated with numerical examples. Further, we discuss the design of optimal pulse in the context of this thesis.2. According to the characteristics of UWB standard channel models, we propose the concept of“composite lognormal random variables (RVs)”. Based on this new concept, a new and precise approach is proposed to approximate the statistical distribution of lognormal RVs’sum, which places no restriction on the distributional parameters and correlation between the two branches. Then, we更多还原