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Yoshihiko KUWAHARA Yoshimitsu IKI Kazuo NAGAO Shuichi OBAYASHI Keishi MURAKAMI Akio SATO Shoichiro KAWAMURA Masaharu HATA
Multi-path propagation structure in the urban mobile communication environment of 25 GHz band has been measured by means of newly developed "multi-path propagation parameter measurement equipment," which is capable of estimating coupled DOA (Direction Of Arrival), TOA (Time Of Arrival) and relative field strength by super resolution techniques. Before measurement, basic performance of the equipment has been evaluated in the anechoic chamber in order to ascertain limitation on measurement. For practice and verification of outdoor propagation characteristics, basic data have been collected in a works where accurate buildings and road layout is known. Sub-sequently, data have been collected in the urban mobile communication environment and following characteristics have been confirmed. 1) DOA and TOA of wave reflected by the side of building almost follow the ray-trace. 2) Street trees make 25 GHz band wave attenuate. 3) There are such unusual cases that it is possible to communicate in spite of out of line-of-sight by multi-path propagation. 4) Narrow streets have very complicated propagation structures. Finally, technologies that should be developed for the high-speed digital mobile communication are proposed based on the measurement results.