Performance Evaluation of Impulse Radio UWB Systems with Pulse-Based Polarity Randomization in Asynchronous Multiuser Environments

In this paper, we analyze the performance of a binary phase shift keyed time-hopping impulse radio system with pulse-based polarity randomization. Effect of multiple access interference is investigated for both chip-synchronous and asynchronous systems. It is shown that the performance of a chip-synchronous system is the same as the symbol-synchronous case studied in [7]. The asynchronous system is modelled as a chip-synchronous system with uniformly distributed timing jitter at transmitted pulses of interfering users. By so doing, we extend the analysis technique developed for chip-synchronous case to the asynchronous case. An approximate closed-form expression for probability of error, expressed in terms of the autocorrelation function of the transmitted pulse, is derived for the asynchronous case. Our analysis shows that the chipsynchronous assumption can result in over-estimating the error probability, hence the system design based on this approximation will be on a safe side. The degree of over-estimation mainly depends on the autocorrelation function of the UWB pulse and signal-to-interferenceplus -noise-ratio (SIR) of the system. Simulations studies support our approximate analysis.