Non-orthogonal Transmission in MIMO Systems with Imperfect Channel Estimation

In this paper, we investigate the capacity performance of non-orthogonal transmission schemes under imperfect channel state information (CSI) caused by feedback delay and thermal noise for various values of the signal to noise ratio (SNR_input). We use orthogonal transmission, i.e. singular value decomposition (SVD), as a benchmark. With perfect CSI, the multiplexing schemes achieve higher capacity than single data stream transmission under high SNR_input (30dB). In terms of the delayed CSI, the capacity of all multiplexing schemes converges and multiplexing schemes are only beneficial for large antenna systems (4times2) and high SNR_input (20dB). When the CSI is corrupted by thermal noise, a 20dB SNR can be tolerated in the CSI estimation.