Robust modified MMSE estimator for comb-type channel estimation in OFDM systems

Orthogonal frequency division multiplexing (OFDM) is used for wireless data transfer because of its robustness to narrow band interference, frequency selective fading and spectral efficiency. Channel estimation and equalization in OFDM is necessary to nullify impairments induced by the frequency selective fading environment. Frequency domain comb-type pilot assisted channel estimation has been used in this paper. Pilot subcarriers are used to implement Modified Minimum Mean Square Error (MMSE) estimator algorithm at pilot subcarriers. The performance and complexity comparison is made between the modified MMSE and MMSE estimator for fast fading Rayleigh channel. Linear, Low Pass and spline cubic interpolation techniques have been used with the MMSE estimator. The effect of increase in number of channel taps on the performance of both estimators is studied. Simulation results reveal that the performance of the modified MMSE estimator remains stable with an increase in channel taps, but significant degradation has been observed in the performance of the MMSE estimator with an increase in channel taps.