The physical basis for wireless communications is the radio channel whos properties are determined by the effects of multipath propagation. A basic description of the channel is easily found. The received signal is a sum of delayed and attenuated copies of the transmitted signal, due to reflections at any kind of objects in the propagation environment. But the technical implication of these meachanisms is tremendous.

A simple narrowband signal, for example, undegoes signal fading due to the interfering multipath components and measures must be taken to avoid data loss. In fact, the whole field of wireless communications evolves from the properties of the multipath channel and techniques to ensure robust communication.

Our research in this topic concerns ultra-wideband (UWB) channels. Taking into consideration the correlation processing performed in the frontends of typical wireless receivers, we characterize the channel impact in a statistical sense. We obtain rather simple descriptions that are useful, e.g., for characterizing the fading in UWB systems, or inter-symbol or multiple-access interferences. The simplicity is due to the collapsed dimensionality of the received signal at the correlator output. The opposite holds for channel models for advanced localization systems. Here the propagation mechanisms have direct impact on the system performance, hence potentially very complex models are needed to characterize the impact of the radio channel.