Joint scale-lag diversity in mobile ultra-wideband systems

In this paper, we consider the effect of mobility on an ultra-wideband (UWB) direct sequence spread spectrum communication system. Based on a uniform ring of scatterers model, we determine that the wideband scattering function has a "bathtub-shaped" scale spectrum. We compare the performances of a scale-lag Rake and a frequency-lag Rake, each capable of leveraging the diversity that results from mobility. The scale-lag Rake receiver, whose scale- and lag-shifted basis functions are matched to the dilation-delay dynamics of the wideband channel, exploits greater diversity. Finally, we suggest a low-complexity implementation of the scale-lag Rake receiver.