Non-uniform temporal dispersion in indoor wideband channels

The analysis of the time domain dispersion of wideband and ultrawideband (UWB) multipath channels is an active research topic. Such a channel can be viewed as an all pole filter and a joint time-frequency analysis of its frequency response can show the temporal dispersion characteristics of the channel. It has been assumed conventionally that the signal dispersion patterns at the temporal taps of the receiver should carry all of the frequency components that constitute the transmitted signal. However, some recent work has refined these simplistic propagation models and used physics-based propagation analysis to theorize the variation of the spectral content for the various multipath components. In this paper, we demonstrate experimentally that the uniform dispersion assumption is incorrect. We analyze the joint time-frequency spectra of the indoor UWB channels, from which it can be observed that there exist some missing frequencies corresponding to certain time instances within the impulse response.