An MMSE channel estimation algorithm based on the conjugate gradient method for OFDM systems

In this report, we propose a new scheme in order to implement an MMSE channel estimator for OFDM systems. We know that the time domain maximum likelihood estimator (MSE) can achieve highly accurate impulse response estimation by using a time domain long preamble of an OFDM frame. On the other hand, the impulse response estimation based on the minimum mean square error (MMSE) criterion can achieve superior channel estimation in low SNR conditions; however, it requires prior statistical information such as delay profiles of channels. In addition, the computational complexity becomes large because of the inverse matrix calculation. In order to overcome these implementation issues, we propose to estimate the statistical values based on the observed information of the channel. In addition, we show that we can suppress the increase of the computational complexity for the matrix inverse calculation by applying the conjugate gradient method while achieving the same performance with the ideal MMSE estimator.