Time-Reversal (TR) technique has opened a new area of investigation for wireless ultra-wide band (UWB) communications applications especially for indoor environments. Such interest is based on the space and timefocusing properties of TR. In high reverberating media with large delay spread, time-focusing induces an equivalent impulse response almost free from side-lobes lowering drastically the risk of Intersymbol Interference (ISI) and allowing much higher data rates. However, in a real channel the delay spread may not be enough to expect such a good performance. We show that in realistic indoor standard environment, the scattering level of the channel is really poor inducing a TR gain collapse to few decibels. These results give an insight of the real effectiveness of TR UWB communications in realistic channels.