Abstract:

Rate-splitting multiple access (RSMA) outperforming non-orthogonal multiple access (NOMA) in spectral efficiency and energy efficiency, stands as the most promising multiple access technology for sixth generation (6G) networks. Index modulation （IM） technology, which uses the index of communication system resources to send additional information bits, can improve the system’s energy efficiency, spectral efficiency, and bit error rate performance. To address the low spectral efficiency issue in IM-NOMA systems, IM is introduced into RSMA for the first time and an IM-RSMA system with two users and a single antenna is proposed. This system builds on orthogonal frequency division multiplexing （OFDM） RSMA by using subcarriers as index resources to transmit additional information bits. At the receiver end, it proposes maximum likelihood （ML） detection and low complexity log-likelihood ratio （LLR） detection that approaches ML performance. Through theoretical analysis and simulation, the performance of different systems is compared, and the results show that the proposed system has significant advantages over existing IM-NOMA in terms of spectral efficiency and bit error rate.

Key words: rate-splitting multiple access （RSMA）, index modulaiton （IM）, spectral efficiency, bit error rate