Channel Estimation in Time and Frequency Domain in OFDM Systems

In Orthogonal Frequency Division Multiplexing (OFDM) systems over fading channels, channel estimation is carried out by transmitting pilot symbols in different patterns. The process consists of two steps. First, the estimation of channel at pilot frequencies is done based on LS criteria. Then, this estimation is interpolated using linear interpolation, cubic interpolation, and spline interpolation. In this paper, we propose a two dimensional (2-D) pilot-aided channel estimator for OFDM systems, whose purpose is to reduce bit error rate by using different pilot arrangement in fast fading channels. The major concept behind the proposed scheme is to estimate the channel in time and frequency domain. So we first obtain the channel frequency response of a number of subcarriers via before-mentioned interpolators in time domain. Next, using this estimations and the channel responses, which obtained in pilot frequencies we estimate the channel in frequency domain and achieve the channel in all frequencies. Consequently, using the fewer pilots, the more accurate channel estimation will be obtained. We have compared the performance of our proposed 2-D channel estimator with conventional channel estimators.