Optimised index modulation for filter bank multicarrier system

Orthogonal frequency division multiplexing with index modulation (OFDM-IM) has attracted considerable interest recently. The technique uses the subcarrier indices as a source of information. In filter bank multicarrier (FBMC) system, double-dispersive channels lead to inter-carrier interference and/or inter-symbol interference, which are caused by the neighbouring symbols in the frequency and/or time domain. When the authors introduce index modulation to the FBMC system, the interference power will be smaller comparing with that of the conventional FBMC system as some subcarriers carry nothing but zeros. In this study, the advantages of FBMC with index modulation (FBMC-IM) are investigated by comparing the signal to interference ratio with that of the conventional FBMC system. However, the bit error rate (BER) performance is affected since there exists interference in the FBMC-IM system. To improve the BER performance, the authors propose an optimal combination-selection algorithm and an optimal combination-mapping rule. By abandoning some combinations whose error probability are larger and by mapping the remaining combinations into specified bits, a better BER performance can be achieved compared with that without optimisation. The theoretical analysis and simulation results clearly show the FBMC-IM system has a good BER performance under double-dispersive channels.