Multiple Access Enabled Integrated Sensing and Communication With Imperfect SIC: Non-Orthogonal Versus Rate Splitting

Integrated sensing and communication (ISAC) technology presents promising prospects for improving spectral efficiency, enabling hardware resource sharing, and facilitating novel application scenarios. Nevertheless, the mutual interference between communication and sensing remains a critical barrier to overcome. As an effective interference management solution, both non-orthogonal multiple access (NOMA) and rate splitting multiple access (RSMA) demonstrate unique advantages in interference suppression, which are expected to substantially enhance the overall performance of ISAC systems. To this end, the design options of NOMA versus RSMA for the ISAC systems are investigated in this paper. Furthermore, due to the inherent complexities in both signal propagation characteristics and receiver processing architectures, channel estimation errors (CEEs) and imperfect successive interference cancellation (ipSIC) are incorporated during system modeling. Against the above background, the communication and sensing performance of the NOMA and RSMA ISAC systems is analyzed by respectively deriving the exact and asymptotic outage probabilities (OPs) and ergodic rates (ERs) for the users, the probability of detection (PoD) for the base station and Cramér-Rao bound (CRB). The numerical results demonstrate that RSMA outperforms NOMA in terms of OPs, ERs, PoD, and CRB.