Study on Analysis of Multipath Propagation for Indoor Radio Digital Communications

实现室内无线电通信系统的想法是如此有吸引力，因为高移动性和布线没有麻烦。然而，室内无线电多径传播环境限制了这些系统的设计。因此，本项目的研究重点是澄清室内无线电传播的特性。为此，估计多径波的到达方向和延迟时间是最有效的方法。到目前为止，我们提出并发展了一种估计到达方向和延迟时间的方法。该方法利用了MUSIC或ESPRIT算法这两种具有高分辨率的频谱分析技术。在1992年和1993年期间，我们通过计算机模拟和室内实验继续改进估算方法。所得结果如下：1。首先，我们提出了一种同时估计多径波到达方向和延迟时间的方法。该方法的最大优点是可以根据估计结果很容易地识别出入射波的传播路径。除了计算机模拟外，我们还在有限的区域内进行了实验。从估计结果中，我们识别出5 ~ 10个有效波，它们的方向在空间上几乎均匀分布，并且延迟时间小于50 ns。这些结果表明，室内无线电环境非常复杂。因此，我们证实了分集接收，特别是指向性分集，对于多径传播环境下的室内无线电通信系统是非常有效的。该方法根据到达方向和传播延迟时间对多径波进行分类。然而，对于低信噪比的到达波，它在估计延迟时间和到达方向上存在一定的误差。因此，我们进一步提出了一种对MUSIC或ESPRIT估计器应用自适应（最优）滤波的技术，以提高估计精度。我们的自适应滤波原理是基于方向约束的自适应阵列。通过计算机仿真，我们证明了该算法在低信噪比的多径环境下更有效。少

The idea of implementing indoor radio communication systems is so attractive because of high mobility and no trouble in wiring. However, indoor radio multipath propagation environments limit the design of these systems. Therefore, this project of research is concerned with clarifying the characteristics of indoor radio propagation. For this pupose, it is most effective to estimate the directions of arrival and delay times of multipath waves. So far, we proposed and developed a method of estimating the directions of arrival and delay times. This method utilized the MUSIC or ESPRIT algorithms which are spectrum analysis techniques with high resolution property. During 1992 and 1993, we continued to improve the estimation method through computer simulation and indoor experiments. The results obtained are described below.1. First, we proposed a method of simultaneously estimating both the directions of arrival and delay times of multipath waves. The great advantage of this method is that w … More e can easily identify the propagation paths of incident waves based on the estimation results. In addition to computer simulation, we carried out experiments in a limited region. From the estimation results, we recongnized 5 to 10 significant waves, the directions of which are almost uniformly distributed in space and also the delay times of which are less than 50 ns. These results demonstrated the indoor radio environments are much complicated. Thus, we confirmed that diversity reception, especially the directivity diversity, is much effective for indoor radio communication systems under multipath propagation environments.2. The proposed method has great capability of classifying the multipath waves in terms of directions of arrival and propagation delay times. For the arriving waves with the low signal-to-noise ratio (SNR), however, it has some errors in the estimates of delay times and directions of arrival. Therefore, we further presented a technique of applying an adaptive(optimum) filtering to the MUSIC or ESPRIT estimator to enhance the estimation accuracy. The principle of our adaptive filtering is based on the directionally constrained adaptive array. Via computer simulation, we showed that the presented algorithm is more effective in multipath environments of the low SNR. Less