Beamforming Based MIMO-OFDMA System for Performance Improvement in Harsh Downlink Channels

We propose a MIMO-OFDMA (multi input multi output-orthogonal frequency division multiple access) system based on beamforming for harsh downlink channels with low CIR (carrier-to-interference ratio). In the proposed system, we consider an effective CSI (channel state information) calculation based on spatial resource grouping, which is adequate for a combination of MRT (maximum ratio transmission) beamforming in the BS (base station) and MRC (maximum ratio combining) in the MS (mobile station). In addition, to reduce feedback information for the beamforming, we apply the Grassmannian beamforming scheme. Furthermore, for fair and efficient resource allocation in multi-user environment, we propose a simple resource allocation algorithm composed of three steps. Simulation results reveal that the proposed MIMO-OFDMA system achieves significant improvement of spectral efficiency in low CIR region as compared to a typical open-loop MIMO-OFDMA system using pseudo-orthogonal space time block code