OFDM With Dual Frequency Index Modulation

This letter presents a novel index modulation framework called OFDM with Dual Frequency Index Modulation (OFDM-DFIM) to reduce the complexity of index modulation technology. We split subcarriers in subblock into two equal parts and original indices are derived from only one part. To compensate for lessened SE, the in-phase and quadrature components of M-ary symbols are independently index modulated, which depends on indices and input strings, jointly. The OFDM-DFIM principle is applied in two different implementations, i.e., OFDM-DFIM-I and OFDM-DFIM-II. Specifically, all symbols in OFDM-DFIM-I share the same sequence to determine active positions, which can achieve diversity gain and result in better BER performance. In OFDM-DFIM-II, different symbols are controlled by different sequences to get higher SE. Moreover, a two-stage log-likelihood ratio detector is proposed to ease the computational burden. Simulation results show that the proposed two schemes exhibit promising results in both SE and BER performances.