The UWB indoor channel: large and small scale modeling

In this paper we examine large and small scale channel modeling for ultra-wideband signals. Specifically, we examine the impact of UWB signals on traditional channel modeling techniques. This examination is based on measurements taken in an indoor office environment as part of the DARPA NETEX Program. Our findings suggest that while traditional channel modeling approaches are appropriate, care must be taken in both applying the results and interpreting them. In particular, the wide bandwidths do not invalidate the traditional exponential decay versus distance approach to path loss, although it is important to separate antenna effects from path effects. Additionally, the traditional small scale approach which uses the time-invariant linear filter to represent the channel impulse response can still be applied to UWB signals. However, one must use the model with caution as "paths" from the model may no longer represent physical transmission paths but rather may simply represent frequency distortion of individual pulses. We also examine the path loss exponents obtained from measurements and compare them to previous measurement campaigns. Finally, small scale statistics such as delay spread and the energy per "path" are also examined and compared to previous results