Enhanced SVD-based transmit pre-processing for single-user and multi-user MIMO wireless systems with imperfect CSIT

Transmit precoding techniques using the singular value decomposition of the downlink channel are well-known for the single-user (SU) multiple-input-multiple-output (MIMO) as well as multi-user (MU) MIMO downlink channel. The accuracy of channel state information at the transmitter (CSIT) has been shown to have a significant impact on system throughput. Different sources of errors can degrade the CSIT accuracy, such as the Gaussian noise from the estimation process, errors from the quantization of the channel estimate, and noise in the feedback channel in frequency-division duplexing (FDD) channels, among others. The objective of this paper is to design robust SVD-based precoding using an incremental SVD for both the SU-MIMO and MU-MIMO channels with imperfect CSIT. The proposed algorithm shows capacity gains of up to 20% as compared to existing SVD-based MIMO precoding algorithms such as block-diagonalization, orthogonal space-division multiplexing (OSDM and modified total-minimum mean square error (MT-MMSE).