Combined time and frequency domain OFDM channel estimation

In this paper we present a novel channel impulse response estimation technique for block-oriented OFDM transmission based on combining estimators: the estimates provided by a Kalman Filter operating in the time domain and a Wiener Filter in the frequency domain are optimally combined by taking into account their estimated error covariances. The frequency domain Wiener Filter smoothes Maximum-Likelihood estimates of the channel frequency response obtained by the Expectation-Maximization algorithm. Different variants of the proposed scheme are experimentally investigated in an IEEE 802.11a-like system setup. They compare favourably with known approaches from the literature resulting in reduced mean square estimation error and bit error rate. Further, robustness and complexity issues are discussed.