Abstract-In measurements of in-room radio channel responses an avalanche effect can be observed: earliest signal components, which appear well separated in delay, are followed by an avalanche of components arriving with increasing rate of occurrence, gradually merging into a diffuse tail with exponentially decaying power. We model the channel as a propagation graph in which vertices represent transmitters, receivers, and scatterers, while edges represent propagation conditions between vertices. The recursive structure of the graph accounts for the exponential power decay and the avalanche effect. We derive a closed form expression for the graph's transfer matrix. This expression is valid for any number of interactions and is straightforward to use in numerical simulations. We discuss an example where time dispersion occurs only due to propagation in between vertices. Numerical experiments reveal that the graph's recursive structure yields both an exponential power decay and an avalanche effect.
Abstract-A model based on experimental observations of the delay power spectrum in closed rooms is proposed. The model includes the distance between the transmitter and the receiver as a parameter which makes it suitable for range based radio localization. The experimental observations motivate the proposed model of the delay power spectrum with a primary (early) component and a reverberant component (tail). The primary component is modeled as a Dirac delta function weighted according to an inverse distance power law (d −n ). The reverberant component is an exponentially decaying function with onset equal to the propagation time between transmitter and receiver. Its power decays exponentially with distance. The proposed model allows for the prediction of e.g. the path loss, mean delay, root mean squared (rms) delay spread, and kurtosis versus the distance. The model predictions are validated by measurements: they show good agreement with respect to distance dependent trends.
The delay power spectrum is widely used in both communication and localization communities for characterizing the temporal dispersion of the radio channel. Experimental investigations of in-room radio environments indicate that the delay power spectrum exhibits an exponentially decaying tail. This tail can be characterized with Sabine's or Eyring's reverberation models, which were initially developed in acoustics. So far, these models were only fitted to data collected from radio measurements, but no thorough validation of their prediction ability in electromagnetics has been performed yet. This paper provides a contribution to fill this gap.We follow Sabine's original experimental approach, which consists in comparing model predictions to experimental observations in a room, while varying its mean absorption coefficient and total room surface. We find that Eyring's model provides a more accurate prediction of the parameters characterizing the decaying tail, like the reverberation time, than Sabine's model.We further use the reverberation models to predict the parameters of a recently proposed model of a distance-dependent delay power spectrum. This model enables us to predict the path loss, mean delay and rms delay spread versus transmitter-receiver distance. We observe good agreement between predictions and experimental results. Gerhard Steinböck received the DI (FH) degree in telecommunications from Technikum Wien, Austria in 1999. From 2000 to 2006, he worked as a R&D engineer at the Austrian Institute of Technology (AIT), Vienna, Austria, contributing among other things in the hard-and software development of a real-time radio channel emulator. Gerhard Steinböck received the M.Sc.E. (cum laude) degree in wireless communications in 2008 and the Ph.D. degree in wireless communications in 2013 from Aalborg University, Denmark. Since 2013 he is a postdoctoral researcher at Aalborg University. His research interests lie in the area of wireless communications, radio channel modeling, radio channel estimation and sounding, and radio geolocation techniques. Troels Pedersen received the M.Sc.E. degree in digital communications and the Ph.D. degree in wireless communications from Aalborg University, Denmark, in 2004 and 2009, respectively. Since 2009 he has been with the
We formulate a model for the outdoor-to-indoor radio channel in terms of a propagation graph. The model accounts for outdoor scattering and in-room reverberation. It is observed from the model how such a scenario results in channels with several room excitations leading to "clusters" in the simulated channel impulse responses. Simulation studies further indicate that the outdoor-to-indoor and inroom channels differ in terms of spatial envelope correlation.
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