Closed-Loop MIMO-OFDM Wireless System Using Long-Term Pre-Weighting Scheme

Instead of using a codebook-based or quantized channel feedback, a long-term pre-weighting scheme incorporated with optimum decision algorithm is employed in a closed-loop multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (MIMO-OFDM) wireless system. In particular, this approach provides an up-link scale weight vector pre-weighting space-time block code (STBC) signals in a clustered subcarriers base, in accordance with its space-time constellation, without the necessity of using transmit channel state information (TCSI). Quasi-static fading channel is assumed over a channel block length. We present an analytical expression for the signal-to-noise power ratio (SNR) in the basis of a 2-by-2 closed-loop MIMO-OFDM system, taking into account spatially correlated channel parameters. Using Monte Carlo simulations, our proposed scheme outperforms the Alamouti´s detection in terms of the bit-error-rate (BER) performance. Maximization of eigenvalue decomposition (EVD) is also shown for providing channel enhancement and robustness to spatial correlation effects.