Prediction of urban propagation characteristics for low base-station antennas

Effective use of frequency is extremely important for land mobile communication where the number of users is steadily increasing. One means of achieving frequency efficiency is to employ the microcell in which the service area is subdivided into a minimum unit to increase geographical frequency reuse. One implementation of the microcell system is to position the base‐station antenna at a level below the tops of surrounding build ings. Estimation of the radio wave propagation characteristics is indispensable for implementing such a microcell system. In this paper, a method of estimating the wave propagation characteristics between arbitrary transmission and reception points based on a building database is modeled theoretically on a computer using geometrical optical methods such as the geometrical theory of diffraction (GTD). Up to two reflections and diffractions are considered. Comparison of theoretical and measured results of the estimated propagation loss show that the estimated average error was less than about 10 dB for distances of less than 500 m from the transmitter to the receiver for streets on which the transmitting antenna is visible from the receiving antenna. By contrast, the error was about +20 dB to ‐10 dB within 600 m on a street crossing one where the transmitting antenna is visible.