Study of Communication Methods Combining Multiple Transmitted and Received Signals inside a Limited Space Region

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The idea of implementing indoor radio communication systems appears to be an attractive proposition. 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 purpose, it is most effective to estimate the directions of arrival and delay times of multipath waves. The results obtained are described below.1. We first proposed a method of estimating the directions of arrival. This method utilizes the MUSIC algorithm which is a spectrum analysis technique owning high resolution property and applied to the data obtained by the rotatory scanning of antenna. As a result of computer simulation and some experiments, it is shown that the proposed method has high resolution of 5 degrees with the rotation radius of 1 wavelength.2. Next, we proposed a method of estimating propagation delay time of multipath waves which also applies the MUSIC alg … More orithm to the conventional frequency sweeping method. The results of computer simulation and experiments have shown that the proposed method has high resolution of 3ns with the frequency bandwidth of 100MHz.3. Finally, 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 we can easily identify the propagation paths of incident waves based on the estimation results. This method also utilizes the MUSIC algorithm. We carried out experiments in a limited region. From the estimation results, we recognized 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 very complicated. Thus, we confirmed that diversity reception, especially the directivity diversity, is effective for indoor radio communication systems under multipath propagation environments. Less