Asynchronous DS-UWB communication using spatiotemporal chaotic waveforms and sequences

It is known that in a direct-sequence (DS) ultrawideband (UWB) system, a single type of UWB pulse is used in all bits for all users. In this paper, we address a method to generate varying waveforms based on spatiotemporal chaotic approach. Regarding spreading sequences, we consider the two cases of short and long sequences. In particular, we propose the use of a family of spatiotemporal chaotic systems, namely Piecewise Coupled Map Lattices (PCML), as spatiotemporal chaotic waveforms and spreading sequences. Such sequences are shown to reduce the multi-user interference (MUI) variance with regard to i.i.d. and Gold sequences for both short and long cases. On the other hand, we evaluate and compare the DS-UWB system performance by using conventional waveform such as Gaussian monocycle pulse and PCML pulses. Finally, we show that the use of long PCML codes with PCML pulses, results in an improvement of the system average BER, hence an increase of the system capacity in terms of number of active users.