Fractionally Spaced Frequency-Domain MMSE Receiver for OFDM Systems

Based on frequency-domain oversampling and the Bayesian Gauss-Markov theorem, we propose a fractionally spaced frequency-domain minimum mean-square error (FSFDMMSE) receiver for orthogonal frequency-division multiplexing systems. It is shown that frequency diversity inherent in a frequency-selective fading channel can be extracted and exploited by the proposed FSFD-MMSE receiver. This diversity advantage outweighs the effect of intercarrier interference generated by frequency-domain oversampling, due largely to the MMSE receiver´s interference suppression capability. Numerical results show that the FSFD-MMSE receiver outperforms the conventional MMSE receiver under both ideal and practical situations (i.e., with frequency offset, channel estimation errors, and even doubly selective channel fading). In addition, the FSFD-MMSE receiver only needs a fast Fourier transform size that is no larger than N + Q -1 (TV = number of data subcarriers, and Q = number of resolvable multipath components).