Description

Dual-mode index modulation aided orthogonal frequency division multiplexing (DM-OFDM) is recently proposed, where subcarriers are partitioned into OFDM sub-blocks, divided into two groups within each sub-block, and modulated by two differentiable alphabets. In DM-OFDM, additional bits can be transmitted through indices of subcarriers modulated by the same alphabet. In this letter, generalized DM-OFDM (GDM-OFDM) is proposed, where the number of subcarriers modulated by the same constellation mode in each sub-block is alterable. By applying such enhancement, the spectral efficiency can be improved at the cost of marginal performance loss. Moreover, since the BER performance of GDM-OFDM degrades at low signal-to-noise ratios (SNRs), an interleaving technique is employed to address this issue. At the receiver, a maximum-likelihood (ML) detector and a reduced-complexity log-likelihood ratio (LLR) detector are employed for demodulation. Simulation results demonstrate that the proposed GDMOFDM is capable of enhancing the spectral efficiency compared with DM-OFDM at the cost of negligible performance loss, and the interleaved GDM-OFDM (IGDM-OFDM) can harvest on performance gain over GDM-OFDM.