Feasibility of UWB radio: Impulse radio versus chaos-based approach

Both the peak power and the average power of emission are limited in UWB systems in order to keep the interference caused in an already existing narrowband radio system low enough. It is frequently overlooked that these power limits have to be checked not over the transmitted UWB signal but at the output of a bandpass filter specified in the FCC regulations. A further constraint exists in the handheld cheap devices where the low supply voltage reduces even further the attainable energy available to carry one bit information. The bit energy determines the coverage, the larger the bit energy, the larger the coverage. Introducing a novel approach an exact link budget calculation is proposed here for UWB impulse radio. Since the NLOS coverage of impulse radio obtained from the link budget is less than 2 m, the implementation of WLAN systems is not feasible with UWB impulse radio devices. To increase the bit energy, the UWB carrier-based approach, where the duty cycle is considerably increased, is proposed here. More than 16-dB improvement in bit energy has been achieved by increasing the UWB carrier duration to 300 ns.