Secrecy Rate Analysis of RSMA-Aided Cell-Free Massive MIMO with Non-Ideal Hardware

Abstract

In this work, we delve into the secure transmission within the downlink of a cell-free massive multiple-input multiple-output (MIMO) system leveraging rate-splitting multiple access (RSMA) technique, where the system’s secrecy performance is compromised by hardware impairments (HWIs) originating from non-ideal access points (APs), user equipment (UEs), and eavesdroppers (Eves). Within this system, numerous active Eves execute pilot spoofing attacks targeting a specific UE and intercept communications from both common and private streams. Considering spatially correlated Ricean fading channels, we derive closed-form expressions for the achievable secrecy rate and conducted a comprehensive secrecy rate assessment across diverse system configurations. Our simulation results indicate that RSMA’s common stream, in contrast to space-division multiple access, acts as an effective artificial noise and enhances the system’s secrecy rate. Nonetheless, HWIs are detrimental, as they substantially diminish the legitimate rate for UEs while concurrently increasing the rate of information leakage to Eves.