POR channel estimation for UWB communications

Power of R (POR) technique has been successfully applied to multiuser detection for a direct sequence code-division multiple access (CDMA) system even when multipath channel is unknown. It yields channel estimate asymptotically converged to that of the ideal subspace approach while without request of estimation of the noise subspace of the received data covariance matrix. Its applicability in multiple access ultra-wideband (UWB) systems is investigated in this paper. First, a time-hopping (TH) UWB system using pulse position modulation (PPM) is converted to a linear form similar to a multirate CDMA system, after transforming modulation delays to amplitudes of pulses and then defining a new set of virtual inputs for each user. Based on the new multirate model, POR technique is applied to estimate unknown channel parameters. Performance of the proposed channel estimator is analyzed and verified. Comparisons with other approaches are also performed.