RADIO PROPAGATION AT MICROWAVE-FREQUENCIES FOR LINE-OF-SIGHT MICROCELLULAR MOBILE AND PERSONAL COMMUNICATIONS

A current thrust in radio communications is to merge personal (portable) and mobile telephone service and make it universally available with high quality. The anticipated tremendous growth in demand for such a service could be accommodated by a radio network of "microcells." In such a network, portable users would communicate via line-of-sight (LOS) with fixed compact canisters mounted on lamp posts, utility poles, etc., with spacings of up to perhaps 2000 ft. We have designed and conducted a propagation experiment at 900 MHz and 11 GHz to characterize microcell channels employing various antennas at two distinct frequencies in different environments, from rural to dense urban. We find that propagation in rural areas is dominated by interference between the direct (LOS) ray and a specular roadway-reflected ray. In urban areas, the addition of four specular well-reflected rays adequately represents microcell propagation. Using this simple model, we can accurately predict the received signal power and structures-induced delay spread as functions of vehicle position in a microcell environment. A wide-band communication channel appears to be feasible, since the multiray interference effects and the random components of the received signals can be overcome by simple methods (e.g., higher antenna directivity or space diversity.