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On the Performance of Spectrally-Encoded Spread-Time Ultrawideband CDMA Communication Systems

In this paper we study the performance of spectrally-encoded spread-time (SE/ST) technique when applied to ultrawideband (UWB) signals in the context of wireless code-division multiple-access (CDMA) communication. In this technique UWB pulses are spectrally encoded with pseudorandom codes that are assigned uniquely to each user. We shall show that the SE/ST ultrawideband system provides an appropriate multi-user capacity in realistic UWB channels, along with the ability of narrowband interference (NBI) suppression. To this end, after obtaining a suitable statistical model for spectrally encoded spread-time signals, we investigate the performance of the system in the presence of multiple-access and narrowband interferers, and simple and accurate approximations will also be developed which are in good agreement with simulation results. Furthermore, the effect of variations of the main system parameters and some of the relevant trade-offs will be numerically demonstrated.