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The determination of the path clearance is one of the most important factors for channel propagation models because most of them classify their models into line-of-sight (LOS) and non-LOS (NLOS) environments. In particular, the path for vehicle-to-vehicle (V2V) communication is more easily obstructed owing to its characteristics such as low antenna heights and high mobility. In this paper, we verify the first Fresnel zone clearance, which is a widely employed method for the determination of path clearance in V2V scenarios. In the analytical model of the first Fresnel zone in V2V scenarios, the ground acts as an obstacle and thus induces NLOS environments for farther than a certain distance. In contrast, our measurement results reveal no additional loss due to the ground obstruction. Therefore, we conclude that the first Fresnel zone calculation is not applicable for determining the path clearance in V2V scenarios, which has significant impact on the accuracy of channel propagation modeling. [ABSTRACT FROM AUTHOR]

The results of signal strength measurements and ray tracing model calculations of indoor propagation at 900 and 1800 MHz are presented. Corridors are being illuminated by ceiling mounted 2 dB gain omni antennas. The objectives of these experiments are to study behavior of the received signal strength at 900 and 1800 MHz in comparison of cell coverage, signal attenuation and variation through the line of sight (LOS) and non line of sight (NLOS) orientation of halls. It is shown that large fluctuations occur between average signal levels in LOS and NLOS case of propagation. It is also obtained that ray tracing model neglecting diffraction effects work better for LOS then NLOS, and requires detailed database information for better prediction. [ABSTRACT FROM AUTHOR]

As a remedy to multipath fading in land mobile communication, adaptive antenna arrays combined with equalizers have been proposed. For hardware realization and adaptive algorithm development in order to alleviate fading by temporal and spatial processing, it is necessary to clarify the spatiotemporal characteristics of the propagation channel such as the delay time and direction of arrival of multipath waves. In a microcell using a low antenna-height base station, the spatiotemporal propagation characteristics are measured for line-of-sight and non-line-of-sight propagation at 3.35 GHz. Characteristics of these channels have been presented. With regard to non-line-of-sight propagation, the measured spatiotemporal characteristics are modeled and the angular spread and the delay spread of the arriving waves are quantitatively evaluated. Also, when the transmission characteristics of fading prevention techniques by spatiotemporal processing are evaluated by computer simulation, an example of the delay-azimuth profiles that is usable as a reference for setting the conditions for fading is presented. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(7): 11–21, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10032 [ABSTRACT FROM AUTHOR]

In a low-antenna-height line-of-sight (LOS) microcell, the delay spread characteristic strongly depends on the road shape, the location of the transmitting and receiving points, and so on. To analyze this propagation mechanism, it is necessary to deal with location-specific properties. This paper describes analyzed results for the multipath delay mechanism in a rectilinear street with intersections where both transmitting and receiving stations exist. Special focus is placed on reflection at LOS building walls and on diffraction at building corners at street intersections, and their effect as a factor creating multipath delay is investigated numerically. We show that waves created by their reflection and/or diffraction are significant multipath delays making a major contribution to delay spread in microcells. This paper also presents a comparison between the calculated and measured delay spread, and discusses the effectiveness of the propagation mechanism described. © 1998 Scripta Technica, Electron Comm Jpn Pt 1, 82(4): 56–70, 1999 [ABSTRACT FROM AUTHOR]

In the area of mobile communications, there has been increasing demand and development for new technologies and services such as digitalization and personalization. With this as background, this paper studies the use of adaptive antenna technology for mobile communication. In the area of mobile communications, the adaptive antenna technology has been studied with a view to reducing the fading for reception by the mobile station. In the case of microcells and indoor communication for which an expanded use is anticipated, arrivals of multiple waves tram various directions are expected even for the base station so that the application of the adaptive antennas to the base stations is effective. In the case of high-speed data transmission such as wireless local wireless networks (LAN), further reduction of fading and interference is required. Also, the frequency sharing among different radio services is an area in which the adaptive antenna is useful. Introductions of dynamic control of the systems are expected for mobile communications in time, space, and frequency domains. The adaptive antenna is effective for control in space. The dynamic zone configuration will he a new application area in which, depending on the distributions of the users, the zone shape is varied. [ABSTRACT FROM AUTHOR]