This paper presents a prediction formula of propagation loss for low antenna height scenarios on a line-of-sight (LOS) straight-line road having an intersection, for modeling the propagation loss characteristic in inter-vehicle communications (IVCs). The regression analysis is applied to the propagation loss data generated by computer simulation based on the geometrical optics theory, and the regression formula is established as a dual-slope model having variables of propagation distance, frequency, road width, and antenna height. In this analysis, the position of breakpoint is determined so that the RMS error of the regression becomes the smallest on both slope regions because its position is an important factor for good prediction accuracy. Furthermore, the comparison between predicted and measured propagation losses is performed in 2 GHz and 5 GHz bands, and the effectiveness of the prediction formula is confirmed by evaluating the prediction errors.

This paper presents a path-shadowing model in indoor populated environments based on computer simulations. The propagation paths between the transmitting and receiving points in an empty rectangular space are determined by a ray tracing method, moving quasi-human bodies modelled as a cylinder with finite height are generated in this space, and intersections of the paths with the bodies are counted. As a result, the shadowing probabilities, durations, and intervals are evaluated for each propagation path, and this shadowing process is characterized as a Markov process. This paper proposes a method for individually generating the shadowing effects on each propagation path. The measurement results of path shadowing characteristics using a photoelectric sensor are also presented, and the validity of this model is confirmed.

This paper presents a path-shadowing model in indoor populated environments based on computer simulations. The propagation paths between the transmitting and receiving points in an empty rectangular space are determined by a ray tracing method, moving quasi-human bodies modeled as a cylinder with finite height are generated in this space, and intersections of the paths with the bodies are counted. As a result, the shadowing probabilities, durations, and intervals are evaluated for each propagation path, and this shadowing process is characterized as a Markov process. This paper proposes a method for individually generating the shadowing effects on each propagation path. The results of 5.2 GHz propagation measurements in indoor populated space using a high resolution channel sounder is also presented, and the validity of this model is confirmed.

This paper proposes a new propagation model to accurately predict outdoor-to-indoor propagation loss. Account is taken of the structural openings along the paths; it is assumed that outdoor-to-indoor paths are possible only through wall openings such as doors and windows. Introducing the angle dependency of the losses with the paths that penetrate the indoor area makes it possible to accurately predict outdoor-to-indoor propagation loss. Measurements in a microcellular environment show that the proposed model can predict outdoor-to-indoor propagation loss more accurately than the COST231 model.

This paper presents the clustering mechanism of multipath components in urban environments. A cluster in an urban area originates from a scattering point located atop a building or on a wall. The degrees of visibility both between the base station and the scattering point, and between mobile station and the scattering point determine the incoming scattering waves. Shadowing caused by surrounding buildings determines the degree of visibility, and this depends on the base station height and the arrangement and irregularity in height of the surrounding buildings. Vector channel measurements at 5.2 GHz in an urban area in Tokyo verify the clustering mechanism.

In systems beyond IMT-2000, the microcell structure will be adopted to achieve adequate system capacity and link budget. Thus base stations (BS) would be mounted closer to the road than heretofore, and the shadowing effects due to buildings will be more serious in the entrance radio link between BS. This paper uses the ray-tracing calculation method to predict the propagation characteristics of microwave entrance radio links. The increases in excess path loss and delay spread due to shadowing are characterized as a function of the clearance factor for the first Fresnel zone along direct paths. When the clearance is more than 5 m, the path loss can be taken as free space loss; smaller clearance values yield average excess loss values of several dB, and the path loss increases strongly at negative clearance values. These results agree very well with the experimental results.

The pattern averaging gain (PAG) method to estimate the average gain of mobile antennas in a multipath propagation environment is proposed. By using this method and a wire-grid model, the radiation characteristics of the planar invertedFantenna (PIFA) mounted on a portable radio case is analyzed. In particular, the variation of the antenna gain with the radio case dimensions and inclination angle of the radio case during operation is clarified. Also, the effect on antenna patterns of the operator holding the portable radio is experimentally investigated. Based on this analysis, the antenna configuration with the PIFA element mounted on the lateral side of the radio case is found to be most suitable for portable radio units. In addition, an appropriate selection of the radio case dimensions is found to result in further improvements in the antenna bandwidth.