【作者】 梁华林；

【导师】 曾凡仔；

【作者基本信息】 湖南大学 ， 计算机体系结构， 2008， 硕士

【摘要】 随着通信技术的发展,短距离无线通信技术近年来发展迅速,给人们带来了越来越多的便捷。作为短距离无线通信技术中最具有前景的技术,UWB(超宽带,Ultra-Wide-Band)无线电技术近年来受到了广泛而深刻的关注。它具有极高的带宽和数据速率,而且抗多径能量特别强,因此特别适合室内密集多径环境,具有其它无线技术无法比拟的优势。论文首先介绍了UWB无线电技术的概念、特点和研究现状。接着介绍了超宽带的脉冲形成方式、调制方式、收发机系统结构、信号衰减模型、室内多径信道模型以及各种多址系统,为后面的章节做好铺垫。常见的UWB多址系统有2PPM-TH-UWB、2PAM-TH-UWB和DS-UWB系统。一方面由于上述三种多址系统有其自身的不足,另一方面由于用户需求的多样性,可变速率将是未来通信系统的一个基本需求。针对这些问题,本文提出了一种新颖的基于OVSF码(正交可变扩频因子码,Orthogonal Variable Spread Factor code)和TH码(跳时码,Time Hopping code)的混合OVSF-TH-UWB通信系统。利用OVSF码的正交性来降低各个用户之间的干扰,利用TH码的随机性将冲突随机分散在时域上面。从理论上分析了其抗AWGN(加性高斯白噪声, Additive White Gaussian Noise)噪声以及抗多用户干扰的性能,并且通过仿真实验进行了验证。超宽带直接发射脉冲,具有非常高的时间分辨率,从而可以精确估计信号传输时延,比较适应精确定位。但是在实际应用中,在合理的时间内估计信号传输时延是一个难题,因为传统的滑动相关是一个非常耗时的工作。本文提出了一种分步的快速时延估计算法,该算法分为两个步骤:首先通过RSSI(接收信号强度指示,Received Signal Strength Indication)进行粗粒度的时延估计,得出时延大概在哪个分块里面。然后通过基于符号采样率的相关运算估计精确的时延。在理论上该算法的时延估计可以达到一个码片时间的精度。更多还原

【Abstract】 Along with the development of communication technology, short distance wireless communication develops fast in resent years, and brings conveniences to people. UWB has attracted profound and comprehensive interests. It has a very broad bandwidth, very high data rate, and is suitable for the indoor multipath environment. It is superior to other wireless technologies.This paper first introduces the conception, the characteristic and the present research status of UWB radio. Then introduces the pulse waveform, the architecture of the UWB transceiver, the fading models of the signal, the indoor channel models, at last some multiple access systems are presented as follow.The current UWB multiple access communication systems, such as 2PPM-TH-UWB, 2PAM-TH-UWB, DS-UWB have some drawbacks and do not provide the variable rate service. However, in the next generation communication systems, the variable rate is a basic need. Thus, the hybrid OVSF-TH-UWB is proposed to address the above problems, and a corresponding correlation mask is designed. It uses the OVSF code to reduce the interference and uses the TH code to disperse the collision in time domain. Because UWB transmits the pulses immediately, so it can estimate the timedelay accurately. This makes it suitable for accurate positioning. But it still remains a difficult problem to estimate the time delay in an appropriate time interval. The accustomed method to estimate the delay is sliding correlation, but it is very time-consuming to implement. To improve the sliding correlation method, this paper presents the two-step rapid method to estimate the time delay. First step is to use the RSSI to implement the coarse-grained estimate, and then use the sliding correlation method to implement the fine-grained estimate. In theory, this algorithm can achieve the accuracy of one chip time.更多还原