Optimal pre-weighting design using pilot sub-carrier cluster in MIMO-OFDM channel application

Instead of using eigen-beamforming approach to increase capacity gain, an optimal weight scheme is employed in the closed-loop multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (MIMO-OFDM) wireless system design. In particular, this scheme provides an uplink scale weight vector pre-weighting space-time block code (STBC) signals at each transmit sub-carrier in accordance to its space-time constellation, without utilizing the transmit channel state information (TCSI). A Bayes decision rule is adopted to generate the optimum weights using channel statistics measured from pilot sub-carriers cluster per OFDM symbol. Analytical expressions of the signal-to-noise power ratio (SNR) improvement, based on the 2 × 2 MIMO-OFDM system model, are derived and discussed over spatially correlated fading channel. From our Monte Carlo simulations, the proposed scheme outperforms the Alamouti´s detection in terms of the bit-error-rate (BER) performance with respect to various OFDM symbol size and pilot interval. The Doppler effect causes the inter-subcarrier-interference (ISI) are also taken into account. Hence, the derived analytical expressions of the SNR improvement are validated.