Low Complexity Estimation of LTV Channels for OFDM Systems with Uniformly Spaced Pilots

We propose a novel pilot-based method for the estimation of linear time-varying (LTV) channels in OFDM systems with uniformly spaced pilots. Our method is based on the basis expansion model (BEM) for LTV channels and it can be applied to any BEM. Exploiting the periodicity induced by the uniformly spaced pilots, we show how the joint estimation of BEM coefficient vectors is decoupled into several indepen-dent subproblems. The closed form formula is derived for the least-squares (LS) estimation of each BEM coefficient vector. The proposed method can be implemented using fast Fourier transforms and thus its complexity is low. Moreover our method only requires the number of pilots greater than or equal to the channel length. Simulation results show that the proposed method compares favorably with existing methods.