Detection of Spatially-Modulated Signals in Doubly Selective Fading Channels With Imperfect CSI

To detect spatially-modulated signals, a receiver needs the channel state information (CSI) of each transmit- receive antenna pair. Although the CSI is never perfect and varies in time, most studies on spatial modulation (SM) systems assume perfectly known CSI and time-invariant channel. The spatial correlations among multiple spatial subchannels, which have to be considered when CSI is imperfect, are also often neglected. In this paper, we release the above assumptions and take the CSI uncertainty along with the spatial-temporal selectivities into account. We derive the channel estimation error aware maximum likelihood (CEEA-ML) detectors as well as several low- complexity alternatives for PSK and QAM signals. As the CSI uncertainty depends on the channel estimator used, we consider both decision feedback and model based estimators in our study. The error rate performance of the ML and some suboptimal detectors is analyzed. Numerical results obtained by simulations and analysis show that the CEEA-ML detectors offer clear performance gain against conventional mismatched SM detectors and, in many cases, the proposed suboptimal detectors incur only minor performance loss.
Comment: 15 pages, 9 figures, 4 tables, submitted to IEEE Trans. Veh. Techol. in May 2017