Comparison of System Configurations Achieving 3 Bits per Symbol in Spatial Modulation (SM) Systems

When achieving 3 bits per symbol (i.e., 3 bit/s/Hz spectral efficiency) in Spatial Modulation (SM) systems, we compare two configurations: 4 transmit antennas with BPSK modulation versus 2 transmit antennas with 4-QAM modulation. This analysis includes implementation considerations such as antenna indexing, constellation mapping, and spectral efficiency calculations.