The development of efficient ultra-wideband (UWB) systems providing high data rates requires an accurate description of the propagation channel. This paper develops a comprehensive statistical model for the UWB indoor transmission channel, based on an extensive set of experimental measurements. We first detail a procedure for the random generation of static channel impulse responses presenting the main channel characteristics within the 3.1 GHz-10.6 GHz band. Spatial variations due to the displacement of the antennas are then taken into account. Finally, the model is adapted to emulate temporal variations such as people moving in the vicinity of the radio link. A dedicated sounding experiment allowed us to simulate realistic temporal variations over frequency bandwidths of up to 1 GHz.