Urban multipath propagation delay characteristics in mobile communications

Abstract In this paper, propagation delay measurements were carried out in Tokyo (metropolitan urban area) where high rises and other buildings are concentrated on a plane and in Kofu (urban area adjacent to mountains) surrounded by tall mountains. The delay characteristics such as delay spread and wave numbers were found. The principal results obtained in these areas are as follows. (1) In a metropolitan urban area, i.e., Tokyo, (a) the average delay spread in a high‐density residential district is less than about 1 μs and the delay profile consists of a group of direct waves arriving directly from the base station; and (b) the average delay spread in a location with high‐rise buildings is also less than 1 μs and the average number of arriving waves is about five with the delay profile consisting of a direct wave group and a reflected wave group from reflecting object. (2) In an urban area adjacent to mountains, i.e., Kofu, the average delay spread is less than about 2 μs and the average number of arriving waves is four. The delay profile consists of a direct wave group and a reflected wave group. The level of the reflected wave group decreases exponentially with the delay time in the case of reflection from buildings, while the level is almost constant within a certain range of delay time and is of a spread shape (rectangular) in the case of reflection from mountains. From these measured results, a simple propagation model consisting of a direct wave group and a reflected wave group is proposed. It is shown that the distance dependence of the delay spread has a peak between the base station and a reflecting object.