Multichannel Ultra-Wideband Systems with Noncoherent Autocorrelation Detection

This thesis provides an in-depth analysis of a previously introduced noncoherent ultrawideband (UWB) receiver that uses a parallel autocorrelation frontend to separate a transmitted multichannel signal. The frontend calculates samples of the autocorrelation function of the received signal. Despite this nonlinear operation, a linear multiple-input multiple-output (MIMO) model can be found for the relation between the transmitted data symbols and the receiver outputs. According to the MIMO model, the subchannel data can be separated using well-known combiner structures. The nonlinear receiver frontend causes crossterms among the subchannel signals and the noise. It is shown that the MIMO model only holds if certain conditions for the mutual crosscorrelation of the subchannel signals are met. Violating this condition leads to a considerable number of performance-degrading crossterms. This thesis focuses on an analysis of the influence of these terms as well as on the introduction of several measures for the general invertibility of the problem. Simulation results for the performance of the originally proposed orthogonal frequency-division multiplexing (OFDM) transmission scheme are provided, which show that the impact of the nonlinear crossterms on the receiver performance is negligible. Another issue is the influence of the linear multipath channel on the subchannel signals’ orthogonality, which is shown to be benign. Furthermore, alternative signaling schemes are introduced. To exploit the increased fading resistance of higher bandwidth signals, these signaling schemes use signal waveforms where each subchannel uses the full signal bandwidth. This implies that the subchannel orthogonality can not be provided by frequency separation as in the OFDM scheme. The investigated schemes include Discrete Prolate Spheroidal Sequences, an orthogonal pulse amplitude modulation (OPAM) scheme based on code-division multiple access (CDMA) spreading codes, shift-added noise waveforms and signals obtained by genetic optimization. Their performance is analyzed and compared with the original OFDM scheme. It is shown that the OFDM scheme is the favourable signaling scheme concerning performance and robustness with respect to the transmission over the multipath channel for the proposed multichannel receiver.