Frequency Dependence of the UWB Indoor Propagation Channel

Ultra wideband (UWB) is seen as a major technology for future high rate, short range radio links. For the development of UWB-based communication systems for indoors, an accurate knowledge of the propagation channel is necessary. However, most of the available studies regarding the UWB radio channel concentrate on the lower frequencies of the FCC-defined spectrum mask, and experimental data is generally missing for the evaluation of the frequency dependence of the channel parameters. In this paper, an extensive sounding campaign is presented, where the UWB channel is probed from 3.1 GHz to 11.1 GHz in a typical indoor environment. Following a thorough analysis of the effect of the antennas on the measured data, a characterisation of the main propagation parameters is presented, with a specific interest on their frequency dependence. A frequency power decay close to the theoretical loss of 20 dB per decade is observed. Other typical parameters, such as the environment dependent path loss exponent, the delay spread or the power delay profile decay exponent show limited variations with increasing frequency. This behaviour may be explained by the characteristics of the main building materials constituting indoor environments, which present a relative stability in the frequency range of interest.