Subspace-tracking methods for channel estimation in OFDM systems

Supervised channel estimation in OFDM systems typically consists in the interpolation/smoothing over the entire time-frequency grid of the channel gains estimated on the pilot subcarriers. In this process, only statistical informations about the propagation channel are exploited (i.e., Doppler spectrum and power-delay profile). We propose a novel technique that is based on a general parametric model of the multipath channel . Our method adds an intermediate step between the evaluation of the channel gains over the pilot subcarriers and the interpolation/smoothing. It performs an ustructured tracking of the delays of the multipath by a subspace tracking technique and a simultaneous tracking of the faded amplitudes by LMS (or modifications of the latter). Simulations and analysis show the relevant benefits of the proposed technique.