Ray-Tracing-Aided Modeling of User-Shadowing Effects in Indoor Wireless Channels

The user body inevitably located near a portable wireless terminal is known to dominantly affect the wireless link. In this communication, user-shadowing effects are investigated at 2.4 GHz by using a ray-tracing technique comprising the following three steps. First, the shadowing effects depending on the states and relative positions of the user are examined to determine the power loss on a single propagation path based on the uniform theory of diffraction (UTD), which has been verified by measurements in an anechoic chamber. Next, we combine the single path models with the multipath channel profiles obtained from the ray-tracing prediction, which also has been validated by comparison with in-building measurements. Finally, a user-shadowing path loss model is established by a statistical analysis of the ray-tracing simulations taking into consideration the randomness of the user's positions. Nakagami- m distributions well describe the user-shadowing effects over diverse indoor propagation scenarios. We found that the K-factor can be a major indicator of the user-shadowing effects. Consequently, we propose the statistical user-shadowing model in which m exponentially decreases as the K-factor increases whereas Ω is independent of the K-factor.