Constructive Artificial Noise Aided Secure Rate Splitting Multiple Access

The demand for accommodating multiple users within the same bandwidth has increased in recent times. In this direction, rate splitting multiple access (RSMA) has gained significant attention among other multiple access techniques. In this article, we propose a novel method for the secure transmission of phase shift keying (PSK) modulated private messages in downlink RSMA. Unlike in conventional physical layer security(PLS) techniques, where random artificial noise(AN) is injected into the null space of the legitimate user, we propose to inject AN constructively towards legitimate user's private message such that it improves the performance of the system while degrading the performance of the eavesdropper. We analyze the secrecy sum rate of the system for both the conventional null steering (NS) method and the proposed constructive interference (CI) method. It is observed that the secrecy sum rate of the proposed CI method outperforms the conventional NS method. Interesting observations are drawn while varying different parameters such as the number of transmit antennas, number of private users, etc.