Path loss and delay profile characteristics of the 3-GHz band are measured and compared for line-of-sight (LOS) and non-line-of-sight (NLOS) paths in a suburban residential area. For the LOS path, the path loss increases as a function of distance squared; and hence the propagation is considered as the free space propagation. For the NLOS paths, it is found that corner losses occur ranging from 28 to 40 dB, and subsequent losses increase as a function of distance squared, but in case of there are open spaces, spaces between the rows of houses or roads intersecting LOS road, the increase was small. The delay spread for the LOS path increased in proportion to power of the distance; and the exponents ranging from 1.9 to 2.9 is found smaller than in urban areas. The delay spreads for the NLOS paths were several times greater than that for the LOS path, and the rate of delay spread increase with distance was found to be several orders of magnitude greater for NLOS paths than the LOS path.

We have measured the non line-of-sight (NLOS) propagation characteristics of microwave frequencies in an urban environment with a base station antenna situated well above the surrounding buildings. When these characteristics are compared with the results of measurements made in the same environment with a low base station antenna height, it can be seen that with a low base station antenna height the attenuation coefficient varies greatly between line-of-sight (LOS) and NLOS environments, whereas with a high base station antenna height there is no variation of this sort. This is because the waves arriving NLOS environments from a high base station antenna do so primarily as a result of rooftop diffraction, and the path loss does not vary much over regions of equal distance between the base station and mobile station. We have confirmed that the frequency characteristics of relative loss in NLOS environments with a high antenna height follow a relationship of 22.8 log f, which is more or less the same as the characteristic for the UHF band. By modifying the frequency terms of the Sakagami model (used for UHF band) based on this trend to allow it to handle microwave frequencies, a close correspondence is seen between the results of actual measurements and the values predicted by the extended model.

We investigate the relationship between microwave path-loss characteristics and line-of-sight (LOS) blocking in an urban environment with a low base-station antenna using LOS-blocking measurement equipment that we have developed. Changes in path loss, traffic conditions, and LOS-blocking caused by vehicles were measured simultaneously. It was found that path loss exhibits a Rayleigh distribution even in a LOS environment if the amount of traffic is such that LOS- blocking occurs for 80% of the time or more, but the other case path loss exhibits a Nakagami-Rice distribution. It was also found that ratio of coherent wave level to envelope level (c/r) depends heavily on rate of road traffic flow.

To generalize characteristics of a received signal level distribution from narrow- to wide-bands in a mobile radio channel, a new propagation parameter called equivalent received bandwidth (2ΔfΔLmax) has been proposed. The distributions are discussed mainly with computer simulation results. The simulation results shows the level distribution depends on 2ΔfΔLmax and power ratio a of direct to indirect waves, and the value of 2ΔfΔLmax classifies the radio channel as narrow- or wide-bands transmission. To confirm these simulated results, a field test was performed with a 3.35 GHz radio wave. This paper describes that the field test demonstrated the simulation results. It is concluded that the equation representing received signal level in the computer simulation is valid. And the fading depth depends directly on 2ΔfΔLmax, and the 2ΔfΔLmax is effective for generalizing the received signal level distribution. Furthermore, a method for calculating the power ratio was found to be better for a peak level model.