Secure Transmission in Uplink C-RAN Systems with RSMA, NOMA, and SDMA

Abstract

This paper investigates secure transmission in the uplink of a cloud radio access network (C-RAN) system incorporating rate-splitting multiple access (RSMA), non-orthogonal multiple access (NOMA), and space-division multiple access (SDMA). We derive closed-form expressions for the secrecy spectral efficiency (SSE) under Rician fading channels with imperfect channel state information. The security performance is comprehensively analyzed across diverse system parameters, including the density of access points, user distribution, line-of-sight (LoS) component intensity, and multiple access schemes. Numerical results corroborate the theoretical analysis and demonstrate that RSMA achieves superior SSE performance compared to conventional NOMA and SDMA schemes, particularly in scenarios characterized by severe inter-user interference and strong LoS components.