Propagation Graph Modeling of Time-Varying Radio Channels
Radio systems operating in time-varying propagation environments are exposed to rapid fading in the transfer function due to multi-path effects. In general propagation environments, where recursive scattering may occur, modeling and simulating the channel is challenging. In this contribution, we model the channel as a time-varying propagation graph induced by vertices representing transmitters, receivers and scatterers and edges representing the propagation conditions between the vertices. For time-varying systems a closed form expression for the transfer matrix of the graph is not available and therefore we introduce an approximation by assuming the graph model to be an approximately underspread system. We give a bound for the resulting approximation error. Finally, simulations illustrate how the model can be applied for simulation of a vehicle-to-vehicle tunnel scenario with time-varying delays and Doppler-shifts.