In order to design communication systems fully exploiting the FCC-defined ultra wideband (UWB) spectrum, an accurate knowledge of the propagation mechanisms is necessary. This paper presents a comprehensive UWB channel measurement campaign designed in the office indoor environment to cover the 3.1 GHz - 10.6 GHz frequency band. From an extensive set of recorded channel impulse responses (CIRs), statistical analyses permitted to extract the main UWB radio channel characteristics, such as the UWB path loss, delay spread and cluster and ray arrival rates. In particular, an alternative to the classical Saleh and Valenzuela approach is proposed for the description of UWB power delay profiles (PDPs). Our experimental set of collected parameters may be used to build a realistic model for the UWB radio channel.