Orthogonal frequency division multiplexing with index modulation by using multiple constellation sets

In this article, a new transmission method named enhanced orthogonal frequency division multiplexing (E‐OFDM) is proposed to increase the spectral efficiency (SE) of the OFDM. The proposed method conveys information bits not only by the M‐ary symbols but also by the multiple different constellation sets. In the proposed method, we build the sub‐blocks by splitting the whole OFDM into pieces. Then, we use different constellation sets in each sub‐block and we assign the extra bits to them to increase the SE of the OFDM systems. Consequently, at the same modulation level, the proposed method has higher SE than the conventional OFDM system. The simulation results also show that the proposed method achieves better bit error rate (BER) performance than the conventional OFDM system with tolerable complexity. For example, the proposed method with a sub‐block size 2 doubles the SE of the conventional OFDM method with BPSK modulation, and also it has approximately 1.6 dB better BER performance than the conventional OFDM at BER =10−4. New constellation designs and receiver algorithm for the detection of additional bits are also presented. All sub‐carriers are activated unlike orthogonal frequency division multiplexing index modulation (OFDM‐IM) and modulated by multiple different constellation sets. The proposed method conveys information bits not only by the M‐ary symbols but also by the multiple different constellation sets. Therefore, the proposed method has higher SE than the conventional OFDM system.