Opportunistic Group Antenna Selection in Spatial Modulation Systems

This paper proposes an opportunistic spatial modulation (OSM) scheme where the transmit antennas are divided into K >= 1 equal groups, and the hest antenna from each group is selected to form a K transmit antenna subset for implementing spatial modulation (SM). Thus, the activation of one antenna from the subset to transmit one of the M-ary modulation symbols achieves a data rate of log(2) (K) log(2) (M) bits per channel use. Notably, special cases of OSM include conventional SM and pure single transmit antenna selection. To characterize and comparatively evaluate OSM, we first consider phase-shift keying modulation and derive a closed-form, improved unionbound of symbol error probability (SEP) with a single-antenna receiver. Explicit expressions for the SEP in the high signal-tonoise ratio regime are also presented. Extensions to quadrature amplitude modulation analysis and simulations of multi-pleantenna reception case are also provided. Simulation results corroborate the analytical results and reveal the interesting interplay between the signal and spatial constellation diagrams. For a given number of transmit antennas and targeted data rate, asymptotically, the SEP can be minimized by using only one antenna group and the largest size of signal constellation, as this configuration achieves the full-diversity order.