Site-dependent BER due to MIMO beamforming predicted by using ray tracing

MIMO SDM (multiple-input multiple-output space division multiplexing) transmission is a promising technology to improve the frequency usage in mobile radio communications. SDM transmission uses mutually orthogonal channels to simultaneously transmit different substreams at the same frequency. An SDM system that uses the eigenbeams is focused on, and the site dependence of bit error rate (BER) for each substream is predicted by using ray tracing. Results show that the SDM beamforming does not significantly alleviate the BER degradation due to multipath, and that the SDM transmission is sensitive to an environmental change. We conclude that the robustness is a key to implement the SDM eigenbeam transmission.