An accurate and low complex channel estimator for OFDM WiMAX

In this paper, we present an approximate LMMSE (ALMMSE) channel estimator for OFDM WiMAX. The ALMMSE estimator utilizes the inherent correlation between the channels of neighboring subcarriers to improve the least squares estimate by a spectral smoothing filter. We show that the covariance matrix of the channel, required for the calculation of the spectral smoothing filter, can be estimated from the LS channel estimate of the same receive frame. The complexity of the proposed ALMMSE estimator is considerably lower than the complexity of the exact LMMSE estimator while the performance loss is only about 0.3 dB in SNR. Our evaluation of the channel estimator performance is based on outdoor measurements in realistic WiMAX scenarios.