Precoded dual - polarized spatial modulation over correlated fading channels

Abstract

In wireless communication systems, multiple-input multiple-output (MIMO) sys tems have been emerged and widely used during past decades to achieve higher data rates, better quality of service and higher network capacity. However, using multiple antennas results in an inevitable problem which is known as inter-channel interfer ence. This is not the only issue due to the usage of multi-antennas, but also spatial correlation, which is the result of insufficient spacing among antennas. These effects deteriorate the performance of the system. Spatial modulation (SM) and using dual polarizated (DP) antennas are introduced in MIMO systems to combat with the pro posed problems respectively. In addition the joint utilization of both the antenna and signal spaces to convey information in SM causes a main drawback, specifically, if there is a direct line-of-sight (LOS) channel component (i.e., Rician fading) and/or spatial correlation among transmit antennas. This causes a significant degradation in the per formance of the receiver in resolving the active transmit antenna and results in a large increase in the overall average bit-error rate performance of the DP-SM system. In this work, we address the effects of precoding for dual-polarized antennas over MIMO systems employing SM. This approach is based on phase-rotation of the transmitted symbols according to the active transmit antenna. The optimum values of the precod ing coefficients are determined so as to minimize the asymptotic average bit-error rate. It is shown that there is a high performance improvement even in the case of heavily correlated transmit antennas and Rician channels in comparison to conventional DP SM systems, and precoded uni-polarized SM systems.Later on, the results are extended to the case where the receiver estimates the channel imperfectly.