Short distance attenuation measurements at 900 MHz and 1.8 GHz using low antenna heights for microcells

Short-distance, low-antenna-height signal attenuation measurements are presented in connection with their use in the design of future microcell cellular radio networks. Measurements presented are based on the propagation along busy city streets in a direction radial to a fixed antenna site. Antenna heights between 5 m and 20 m were chosen for the fixed site, while 1.5 m was chosen for the mobile vehicle. The signal strength was then measured out to a distance of 1 km in a line-of-sight path from the fixed site at both 870.15 MHz and 1.8 GHz. The measurements show that extrapolation of the M. Hata (1980) and Y. Okumura et al. (1968) formulas into the low-antenna-height, short-distance area is not valid and can lead to inaccuracies. The results show that at short distances from the antenna the signal attenuation slope is very much less than that predicted by extrapolating the results of Hata and Okumura et al.>