Super-Resolution Estimation of UWB Channels including theDense Component — An SBL-Inspired Approach

In this paper, we present an iterative algorithm that detects and estimates the specular components (SCs) and estimates the dense component (DC) of singleinput—multipleoutput (SIMO) ultrawideband (UWB) multipath channels. Specifically, the algorithm superresolves the SCs in the delay–angleofarrival domain and estimates the parameters of a parametric model of the delayangle power spectrum characterizing the DC. Channel noise is also estimated. In essence, the algorithm solves the problem of estimating spectral lines (the SCs) in colored noise (generated by the DC and channel noise). Its design is inspired by the sparse Bayesian learning (SBL) framework. As a result the iteration process contains a threshold condition that determines whether a candidate SC shall be retained or pruned. By relying to results from extremevalue analysis the threshold of this condition is suitably adapted to ensure a prescribed probability of detecting spurious SCs. Studies using synthetic and real channel measurement data demonstrate the virtues of the algorithm: it is able to still detect and accurately estimate SCs, even when their separation in delay and angle is down to half the Rayleigh resolution limit (RRL) of the equipment; it is robust in the sense that it tends to return no more SCs than the actual ones. Finally, the algorithm is demonstrated to outperform a state-of-the-art superresolution channel estimator in terms of robustness in the estimation of the amplitudes of specular components closely spaced in the dispersion domain.