Constellation Design for Dual-Mode OFDM-IM

Dual mode Orthogonal Frequency Division Multiplexing with Index Modulation (DM-OFDM-IM) is a modified version of the orthogonal frequency division multiplexing with index modulation (OFDM-IM). In DMOFDM-IM, sub-carriers in each sub-block are divided into two groups. These two groups are modulated with two different signal constellations, chosen from available standard constellations, for example PSK or QAM. All the subcarriers are used to transmit data, while index bit is used to select the constellation. Therefore, in this system there is an improvement in the spectral efficiency which is always greater than OFDM-IM. In this paper we suggest a new signal constellation design to be used for DM-OFDM-IM that gives reduced bit error rate (BER) compared to conventional DMOFDM-IM system. We also discuss about the rationale between our design here.