Mitigation of cross-modulation interference in UWB energy detector receivers

For ultra-wideband (UWB) pulse position modulation (PPM) signalling, cross-modulation interference (CMI) occurs when the amount of the pulse-position shift is less than the maximum excess delay of the multipath channel. Such CMI severely degrades the bit error rate (BER) performance of energy detector (ED) receivers. To alleviate the adverse effect of CMI, in this letter we propose an enhanced energy detector (E-ED) combined with block-orthogonal-coded PPM (BOC-PPM). Each PPM frame is chopped into several sub-windows and the outputs of sub-windows are combined to form the decision statistic. The optimum combining scheme is derived based on the maximum likelihood (ML) criteria. Through analysis and simulations, we show that E-ED can significantly suppress CMI and thus performs well in the CMI region.