A Simple and Effective Post-FFT Beamforming Technique for QAM-OFDM Systems

In this paper, a maximum ratio combining (MRC) approach is proposed for space-frequency processing in antenna-array-based OFDM systems with M-QAM demodulation. The proposed approach is a modified version of MRC for processing QAM signals. It combines the outputs of spatial filter-bank in frequency domain by using the estimated space-frequency channel. Compared with the existing post-FFT beamforming techniques, such as the typical DOA-based approach or the eigenvector-based approach, it exhibits computational simplicity. In addition, the IEEE 802.11g WLAN indoor channel model is used to investigate the performance of the proposed scheme.