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 (SNRinput). 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 SNRinput, (30dB). In terms of the delayed CSI, the capacity of all multiplexing schemes converges and multiplexing schemes are only beneficial for large antenna systems (4×2) and high SNRinput (20dB). When the CSI is corrupted by thermal noise, a 20dB SNR can be tolerated in the CSI estimation.