Effects of fading correlation on multiple antenna reception mobile OFDM systems

WE investigate the impact of fading correlation on multiple antenna reception mobile OFDM systems. Based on the unbiased minimum mean square error criterion we derive the carrier-based optimum combiner. We show that for purely noise-limited systems, the optimum combiner reduces to the well-known maximum ratio combiner (MRC). For these systems, a general performance assessment is performed. We adopt the antenna and the diversity gain, which were recently introduced in [4], and derive a closed form analytical expression for omnidirectional wave incidence. For the interference-limited case, we focus on a single user system with intercarrier interference (ICI) that originates from the channel variations during one OFDM symbol. Then, optimum combining involves knowledge of the spatial interference and noise covariance matrix. The structure of this matrix is investigated and for omnidirectional wave incidence we derive closed-form analytical expressions for the interference correlation coefficients.