Spectrally Efficient Nonorthogonal Frequency Division Multiplexing with Index Modulation

Spectrally Efficient Frequency Division Multiplexing (SEFDM) systems provide enhanced spectrum utilization compared with Orthogonal Frequency Division Multiplexing (OFDM) systems by relaxing the orthogonality condition among sub-carriers. However, in the SEFDM systems, the loss of orthogonality results in the inter-carrier-interference (ICI) thus reduces the transmission reliability. To alleviate the ICI and achieve better error performance, this paper proposes a novel SEFDM transmission scheme, called SEFDM with index modulation (SEFDM-IM). The index modulation, which was originally proposed for OFDM systems, performs an additional modulation besides conventional M-ary modulation by selecting the indices of the sub-carriers. Since a number of sub-carriers are switched off in index modulation, when the index modulation is applied in SEFDM systems, the ICI is reduced and better error performance can be obtained in comparison with the SEFDM systems using conventional Mary modulation. Simulation results confirm this conclusion that the joint applications of SEFDM and index modulation can effectively increase the transmission reliability.