Prediction Method for Propagation Path Loss Obstructed by Dielectric Material in the 920-MHz Band

This paper presents a simple calculation method for predicting the propagation path loss of a radio wave passing through a dielectric obstruction between a transmitter (Tx) and receiver (Rx). In this paper, the propagation characteristics of a radio that is obstructed by a concrete beam on a ceiling in a large indoor environment, such as those seen in factories and warehouses, are investigated. The radio frequency is the 920-MHz band, used for Internet-of-Things (IoT) wireless communications in Japan. The proposed calculation method is based on forbidden region (FR) theory, with the radius defined as 0.6 times that of the first Fresnel zone. In our proposed method, a three-wave model in the FR area at an obstructing object between Tx and Rx is considered for predicting the propagation path loss. The model consists of a wave propagating through the air, a wave penetrating the concrete beams, and a wave traveling inside the concrete ceiling. The path losses using the proposed calculation method are in good agreement with those of a Finite Difference Time Domain (FDTD) simulation and the measured data. We conclude that the proposed calculation method effectively predicts the path loss characteristics of radio waves obstructed by a dielectric material, such as a concrete beam on a concrete ceiling.