Generalized Spatial Modulation with Multi-index Modulation

In this letter, we propose a novel scheme extending index dimension with two distinct signal constellations, named as generalized spatial modulation with multi-index modulation (GSM-MIM). Through this scheme, which exploits the spatial domain and index domain, more extra information bits are transmitted by the spatial indexes as compared with the traditional GSM system. More specifically, with the aid of a vector index bit, a transmitted spatial vector (TSV) is derived by combining two spatial vectors, one of which is obtained by mapping $M$ -ary pulse amplitude modulation ( $M$ -PAM) symbol on an antenna index (AI) vector with the aid of both a key index bit and a group of AI bits, and the other one of which is obtained by mapping $L$ -quadrature amplitude modulation ( $L$ -QAM) symbol on another AI vector with another group of AI bits. Furthermore, the modified $M$ -PAM ( $M$ -MoPAM) is designed for increasing the squared minimum Euclidean distance (SMED) between the TSVs, the average bit error probability (ABEP) and the SMED are provided and analyzed. Finally, simulation results using Monte Carlo demonstrate that the GSM-MIM scheme has a significantly lower bit error ratio (BER) than other MIMO schemes.