Offset Space-Frequency Index Modulation

In this paper, a novel offset-based space-frequency index modulation (OSFIM) design is developed, for the sake of improving the bit error ratio (BER) performance. The proposed OSFIM scheme utilizes the channel state information (CSI) to precode the transmit signals so as to activate the optimal space-frequency resource units for offset-aided index mapping. Furthermore, aiming at enlarging the minimum Euclidean distance of the received signal, we further propose a modified scheme termed as enhanced OSFIM (E-OSFIM). Through theoretical analysis, the analytical BER upper bound for E-OSFIM is also quantified. Finally, simulation results show that, compared with conventional SFIM and offset SM-OFDM (OSM-OFDM), the proposed schemes can significantly improve the BER performance when the freedom of spatial degrees is large, while the proposed E-OSFIM scheme outperform its counterparts in terms of the BER performance.