Combining Index Modulation with Codebooks for Noncoherent Reception

Index modulation (IM) allows to improve spectral efficiency of digital transmission. Recently, IM has been combined with various types of linear modulation. However, in such a case, it is necessary to transmit pilot symbols, which ultimately reduces the spectral efficiency. Noncoherent reception does not use channel state information and therefore does not require pilot symbols, so it is useful in various applications. In this paper, the combination of IM with codebooks obtained using neural networks and suitable for noncoherent reception is considered. A comparison of the quality and complexity of two reception methods, optimal and energy-based, is made. It turned out that the loss in power efficiency provided by the simplified receiver is approximately equal to 1 dB. In addition, with high spectral efficiency, both receivers show approximately the same results. However, the computational complexity of the simplified method is noticeably lower.