Ultra-wideband (UWB) communications has emerged as a promising technology for high data rate wireless personal area networks (WPANs). Several proposals for UWB-based WPANs have been made. One widely popular proposal is based on multi-channel OFDM. This proposal was recently standardized by European Computer Manufacturers Association (ECMA). In this dissertation, we address several important aspects that impact the performance of OFDM-based UWB systems. First, we propose an interference management distributed reservation protocol (IMDRP) for these communications. IM-DRP aims at reducing interference between uncooperative beacon groups that operate simultaneously over the same area. We then integrate IM-DRP into the design of a rate adaptation strategy that exploits the multi-rate capability of OFDM-based UWB systems. Besides maintaining a target packet error rate, our proposed strategy attempts to reduce the required reservation time over a link, hence allowing more links to be concurrently activated. Second, we propose a novel overhearing-aware joint routing and rate selection (ORRS) scheme. For a given source-destination pair, ORRS aims at selecting a path and its transmission rates that achieve the minimum channel reservation time, leading to low blocking rate for prospective reservations and high network throughput. At the same time, ORRS takes advantage of packet overhearing, a typical characteristic of broadcast communications. Finally, we propose a novel resource utilization mechanism (RUM) for improving the throughput in multi-rate UWB-based WPANs. RUM exploits opportunistic-relaying and time-spreading techniques to improve link reliability and increase the transmission rate, and hence network throughput. Simulation results indicate that our proposed protocols and schemes achieve significant throughput improvement compared with other protocols.