Exact evaluation of M-ary TH-PPM UWB systems on AWGN channels for indoor multiple-access communications

Analysis of ultra-wideband (UWB) time-hopping spread-spectrum code division multiple-access system using binary PPM signaling has been considered previously. However, the representation of the multiple-access interference was based on assuming Gaussian random processes that resulted in inaccuracies in some scenarios. This analysis was improved by a more precise statistical analysis that dispensed with approximations based on using Gaussian process statistics. In the paper, this precise statistical analysis is extended for general M-ary PPM UWB modulations. Performance metrics of symbol error rate and capacity are evaluated. It is shown that there is a significant error in using the Gaussian approximation as it overestimates the capacity of the M-ary PPM modulation.