Reduced complexity turbo equalization for MIMO channels using random signal mapping

Abstract —Multiple-input multiple-output (MIMO) wirelesssystems are known to be robust against fading, providing whatis known as diversity gain. However, if traditional techniques toobtain diversity are used, the receiver complexity for a MIMOchannel with intersymbol interference (ISI) may be unfeasible.In this paper, we investigate the use of random signal mappingas a source of diversity gain for MIMO channels with ISI. Wetheoretically demonstrate that the proposed system has muchlower complexity than existing solutions and is robust againstchannel mismatch. Simulation results also show that the newscheme provides good diversity gain. I. I NTRODUCTION Wireless systems with multiple transmit and/or receiveantennas have been the topic of intense research activity lately.The interest in these multiple-input multiple-output (MIMO)systems was spurred by two results. First, in two independentworks, Telatar [1], and Foschini and Gans [2] showed that asignificant increase in capacity can be obtained in wirelesssystems when multiple antennas are employed at both thetransmitter and the receiver. Besides this increased capacity,multiple antennas can also lead to increased robustness againstfading, even without channel knowledge at the transmitter.Indeed, in [3], Tarokh