Orthogonal Frequency Division Multiplexing with Generalized Index Modulation

Recently, an Orthogonal Frequency Division Multiplexing (OFDM) with index modulation (OFDM-IM) [1] was proposed. By selecting a fixed number of subcarriers as active subcarriers to carry constellation symbols, the indices of these active subcarriers may carry additional bits of information. In this paper, a generalization of OFDM-IM, named as OFDM with generalized index modulation (OFDM-GIM) is proposed. In this scheme, the number of active subcarriers in an OFDM subblock of the overall structure is no longer fixed. Dependent on the input binary string, different number of active subcarriers are assigned to carry constellation symbols. In such a way, a higher spectral efficiency than that of OFDM-IM may be achieved. To facilitate the implementation of our scheme, a generalized index modulation block for the active subcarrier selection and an upgraded Log-likelihood Ratio (LLR) detector for the active subcarriers and symbol constellation detection have also been proposed. Computer simulation results show that our proposed scheme does offer us a much higher spectral efficiency at the cost of a marginal error performance loss.