Hybrid Model for Reverberant Indoor Radio Channels Using Rays and Graphs

Ray tracing tools allow for deterministic simulation of the channel impulse response. Studies show that these tools work well when the impulse response consists only of a few distinct components. However, measurements of the channel impulse response in indoor environments reveal a diffuse tail. This diffuse tail is difficult to include in ray tracing due to the computational complexity. We propose a hybrid model to include deterministic components and the diffuse tail by combining ray tracing with a propagation graph. The recursive structure of the propagation graph allows for a computationally efficient calculation of the channel transfer function considering infinitely many components. We use ray tracing and the theory of room electromagnetics to obtain the parameter settings for the propagation graph. Thus, the proposed hybrid model does not require new or additional parameters in comparison to ray tracing. Simulation results show good agreement with measurements with respect to the inclusion of the diffuse tail in both the delay power spectrum and the azimuth-delay power spectrum.