Dual-Mode OFDM-IM by Encoding All Possible Subcarrier Activation Patterns

In traditional orthogonal frequency division multiplexing with index modulation (OFDM-IM), when the subcarrier activation patterns (SAPs) is not a power of 2, part of SAPs will not be used. This will result in low transmission efficiency and low bit error rate (BER) performance. We have proposed a new scheme namely bit-padding dual-mode orthogonal frequency division multiplexing (BPDM-OFDM). It exploits all of the possible SAPs to convey data to obtain a better BER performance. Meanwhile, the BPDM-OFDM uses the dual-mode orthogonal frequency division multiplexing (DM-OFDM) to improve the transmission efficiency. In addition, a subcarrier interleaving technique is adopted to further improve the BER performance and the idea of hard limit algorithm, which is applied to the log-likelihood ratio detector (LLR-HL) to reduce the detection complexity. Significant performance improvement of the proposed scheme, in terms of transmission rate, detection complexity and BER performance, over the traditional OFDM-IM scheme has been validated through theoretical analysis and extensive simulations.