SPIM: Split-Packet Interference Management for Uplink RSMA in Next-Generation Wireless Networks

Driven by the growing demands for reliability and high data rates, uplink rate-splitting multiple access (RSMA) has emerged as a promising technique for next-generation wireless networks. However, in practical scenarios, particularly under imperfect SIC (ipSIC), the presence of residual interference (RI) significantly degrades performance, especially at high transmit power levels. This RI stems from two key sources: intra-user split packet interference (SPI) due to imperfect cancellation of a user’s own split streams, and inter-user residual packet interference (IPI) from imperfect cancellation of other users’ signals. As these impairments accumulate across multiple SIC stages, the inherent benefits of rate splitting may progressively diminish, potentially resulting in performance degradation compared to conventional schemes such as non-orthogonal multiple access (NOMA). To address this challenge, we propose a split-packet interference management (SPIM) framework that enhances uplink RSMA performance under ipSIC by structurally enforcing orthogonality between a user’s own split streams. This design reduces the reliance on successive decoding and effectively limits the propagation of RI, especially from SPI, while preserving the benefits of rate-splitting. We consider a two-user system and perform a comprehensive outage probability analysis under both perfect SIC (pSIC) and ipSIC conditions, leveraging a copula-based statistical modelling framework to accurately model the dependency between streams. Additionally, we derive analytical expressions for the ergodic sum rate thus, providing insights into the long-term performance. While the core analysis focuses on a two-user setup, the SPIM RSMA architecture is extended to larger user groups with a scalable receiver design. Simulation results closely match analytical findings and demonstrate that while SPIM RSMA performs comparably to conventional RSMA under pSIC, it significantly outperforms both conventional RSMA and NOMA under ipSIC conditions in terms of outage probability, sum-rate, and sum-throughput. These results underscore the structural versatility of SPIM RSMA, which proactively mitigates SPI, thereby preserving the advantages of rate splitting in SIC-constrained environments.