OFDM-RSMA: Robust Transmission under Inter-Carrier Interference

Rate-splitting multiple access (RSMA) is a multiple access method designated to counteract the effects of the multi-user interference (MUI) present in multi-antenna systems. In this study, RSMA's ability to manage interference is integrated with the flexibility of orthogonal frequency division multiplexing (OFDM) waveform incorporating multi-numerology concept. This fusion aims to confront the issue of inter-carrier interference (ICI) which compromises the orthogonality of OFDM subcarriers. Sum-rate maximization problem is formulated aiming to determine the optimal power and subcarrier allocation for downlink communication in a system with two users. We utilize a transformation grounded in the weighted minimum mean-square error (WMMSE) approach to address the non-convex problem. We show that the marriage of rate-splitting (RS) with OFDM provides complementary strengths to cope with peculiar characteristic of wireless medium and its performance-limiting challenges including ICI, inter-symbol interference (ISI), inter-numerology interference (INI), and MUI. The sum-rate and fairness performance of the proposed multi-numerology OFDM-RSMA approach is numerically evaluated against traditional orthogonal frequency division multiple access (OFDMA) and OFDM-non-orthogonal multiple access (NOMA).