Modified signal design for multistream spatial modulation over spatially correlated channels

In this paper, we describe a modified signal design for Multistream Spatial Modulation (MSM). The fundamental idea behind MSM is to activate multiple antennas and transmit complex symbols along with active antenna indices. Here, a modified MSM technique explicitly designed to combat the effect of spatial correlation in realistic channel scenarios is proposed. In this MSM scheme, two antennas are made active all the time, mapping for antenna selection is judiciously adopted from primary and secondary constellation points. Secondary constellations are obtained through single geometric interpolation of the primary constellation points. Simulation studies show that for a fixed number of antenna combinations and spectral efficiency, the proposed scheme produces a performance improvement of at least 4 dB at a ABER of 10^-5 over all traditional Spatial Modulation (SM) systems, more specifically Enhanced Spatial Modulation (ESM), Quadrature Spatial Modulation (QSM) and Double Spatial Modulation (DSM) systems when employed over dense spatially correlated channels. Furthermore, an upper bound on the average bit error probability (ABEP) for the modified MSM scheme has been derived and quantified. Monte Carlo simulation results corroborate the close correspondence between analytical and the obtained simulation results.