M-ary PPM for Transmitted Reference Ultra-Wideband Communications

In this paper, we investigate the multiple-access (MA) performance of transmitted reference (TR) ultra-wideband (UWB) systems employing M-ary PPM in multipath environments. Because we assume there is no power control in the network, interfering power levels from users can vary over many 10's of dB. We categorize the interfering users into two groups with respect to power levels. A new method for deriving the variance of the Gaussian random variable resulting from multiple-access interference (MAI) is developed using the power delay profile (PDP) of the channel. This makes the theoretical analysis tractable and enables us to predict the system-level performance such as the supported number of users, the achievable data rate, and the required bit-energy-to-noise ratio. Chip discrimination is applied and shown to mitigate the effect of high-power users. Performance is quantified due to the combined effects of equal-power and high-power users.