On Secure NOMA-CDRT Systems with Physical Layer Network Coding

TL;DR

This paper introduces a secure NOMA-CDRT system leveraging physical layer network coding, user-assisted jamming, and analytical secrecy performance evaluation to enhance confidentiality against untrusted relays.

Contribution

It proposes a novel scheme combining physical-layer network coding with user-assisted jamming to improve secrecy in NOMA-based relay systems with untrusted relays.

Findings

Closed-form ergodic secrecy sum rate expression derived

Asymptotic analysis provides high SNR insights

Simulations confirm scheme effectiveness and theoretical accuracy

Abstract

This paper proposes a new scheme to enhance the secrecy performance of a NOMA-based coordinated direct relay transmission system (NOMA-CDRT) with an untrusted relay. The physical-layer network coding and the non-orthogonal multiple access scheme are combined to improve the spectrum efficiency. Furthermore, inter-user interference and friendly jamming signals are utilized to suppress the eavesdropping ability of the untrusted relay without affecting the acceptance quality of legitimate users. Specifically, the far user in the first slot and the near user in the second slot act as jammers to generate jamming signals to ensure secure transmissions of the confidential signals. We investigate the secrecy performance of the proposed scheme in NOMA-CDRT systems and derive the closed-form expression for the ergodic secrecy sum rate. The asymptotic analysis at high signal-to-noise ratio is performed to obtain more insights. Finally, simulation results are presented to demonstrate the effectiveness of the proposed scheme and the correctness of the theoretical analysis.