Adaptive MIMO-OFDM based on partial channel state information

Relative to designs assuming no channel knowledge at the transmitter, considerably improved communications become possible when adapting the transmitter to the intended propagation channel. As perfect knowledge is rarely available, transmitter designs based on partial channel state information (CSI) are of paramount importance, not only because they are more practical, but also because they encompass the perfect- and no-knowledge paradigms. Relying on partial CSI, the paper designs adaptive orthogonal frequency division multiplexed (OFDM) transmissions, that maximize the transmission rate over frequency-selective multi-input multi-output (MIMO) fading links. The adaptive transmitter parameters include beamformer weights and their power per OFDM subcarrier, as well as the power and bit loading across OFDM subcarriers. Our simulations confirm that adaptive two-directional beamforming combined with adaptive MIMO-OFDM improves the transmission rate considerably.