Space modulation techniques ( SMTs ) like spatial modulation ( SM ) , generalized spatial modulation ( GSM ) , and fully generalized spatial modulation ( F - GSM ) have become known as encouraging candidates for spectral and energy - efficient wireless communication systems as they have a good balance between error performance , power efficiency , and spectrum efficiency . In the SMTs , the information is conveyed not only by the usual M - ary signal constellations but also by the indices of the transmit antennas . Fully generalized spatial modulation ( F - GSM ) is a promising transmission technique for multiple - input multiple - output ( MIMO ) systems because of its spectral