Hybrid ray-mode modelling of indoor propagation for wireless applications

One ofthe key factors in designing microcellular mobile radio systems is a comprehensive knowledge of propagation characteristics into and within buildings. Ray tracing propagation models are commonly used to characterize the channel response for wireless systems in indoor areas. The model proposed makes use of a judiciously chosen hybrid combination of ray and mode fields to predict the dependence of indoor channel fading characteristics and to estimate the RMS delay spread. We consider the canonical problem presented by a rectangular enclosure and we derive the construction of the hybrid ray-mode representations and the conversion of a portion of the ray series into a portion of mode series, and vice versa. The proposed method provides a physical insight into the local and global features of wave propagation in indoor environments and their relative importance. Moreover, it is shown that the hybrid representation permits systematic identification of ray fields for a given number of boundary reflections thereby also improving the efficiency of ray-based propagation models