Adaptive Precoding for Switching Between Spatial Multiplexing and Diversity in MIMO OFDM With Transmit Antenna and Path Correlations
The path and antenna correlations significantly degrade the system capacity in spatially-multiplexed Multiple-Input Multiple-Output (MIMO) Orthogonal Frequency-Division Multiplexing (OFDM) systems and increase Bit Error Rate (BER) in Orthogonal Space-Time Block Coded (OSTBC) OFDM. The authors develop adaptive dual-mode precoding to improve system performance with transmit antenna and path correlations. Both linear and non-linear Tomlinson-Harashima (TH) precoders are considered. In the proposed approach, precoding for maximizing capacity in spatially-multiplexed OFDM or precoding for minimizing error rate in OSTBC OFDM is adaptively chosen at the receiver, and only one-bit decision information per subcarrier needs to be sent back to the transmitter.