Secure Beamforming Design for Rate-Splitting Multiple Access in Multi-antenna Broadcast Channel with Confidential Messages

Abstract

As physical layer security evolves to multi-user systems, multi-user interference (MUI) becomes an unavoidable issue. Recently, rate-splitting multiple access (RSMA) emerges as a powerful non-orthogonal transmission framework and interference management strategy with high spectral efficiency. Unlike most works fully treating MUI as noise, we take all users' secrecy rate requirements into consideration and propose an RSMA-based secure beamforming approach to maximize the weighted sum-rate (WSR), where MUI is partially decoded and partially treated as noise. User messages are split and encoded into common and private streams. Each user not only decodes the common stream and the intended private stream, but also tries to eavesdrop other users' private streams. A successive convex approximation (SCA)-based approach is proposed to maximize the instantaneous WSR under perfect channel state information at the transmitter (CSIT). We then propose a joint weighted minimum mean square error and SCA-based alternating optimization algorithm to maximize the weighted ergodic sum-rate under imperfect CSIT. Numerical results demonstrate RSMA achieves better WSR and is more robust to channel errors than conventional multi-user linear precoding technique while ensuring all users' security requirements. Besides, RSMA can satisfy all users' secrecy rate requirements without introducing WSR loss thanks to its powerful interference management capability.

Rate-Splitting Multiple Access for Secure Communications Over CR MISO SWIPT Systems With Non-Linear EH Users

“…The rate-splitting multiple access (RSMA) approach has been introduced in the literature as a powerful multiple access method aimed at enhancing spectral efficiency, and energy efficiency, particularly in scenarios with both perfect and imperfect Channel State Information at the Transmitter (CSIT) [9]- [17]. RSMA holds promise for addressing the challenges posed by varying channel conditions and interference levels, offering improved performance metrics across a range of wireless communication scenarios.…”

“…RSMA holds promise for addressing the challenges posed by varying channel conditions and interference levels, offering improved performance metrics across a range of wireless communication scenarios. Moreover, it has been shown that RSMA method and AN beamforming are promising solutions to improve the wireless security, especially in the presence of numerous eavesdroppers that may seize from a high transmit power [7], [9]. Particularly, RSMA relies on the rate-splitting technique to divide the message into the private and common parts [10].…”

“…Accordingly, prior research confirmed that RSMA is a potential multiple access technique that overcame baseline schemes and improved wireless security to legitimate users [9]. Although these studies have underscored the potential of RSMA in bolstering wireless security and efficiency, they have yet to explore the synergistic of underlay CR technology with RSMA and non-linear SWIPT featuring a power-splitting (PS) structure.…”