Secrecy Sum-Rate Enhancement for NOMA-VLC System With Pseudo User

Non-orthogonal multiple access (NOMA) enabled visible light communication (VLC) system is vulnerable to malicious eavesdropping, mainly because of the inherent broadcast nature of VLC technology. To this end, this letter proposes a novel concept called pseudo user (PU), which obstructs the successive interference cancellation (SIC) procedures of the eavesdropper. The minimum-feasible (MF) power allocation policy toward the PU is obtained under different power allocation strategies. Then, the secrecy sum-rate and user fairness along with the sum-rate are evaluated under both perfect SIC (pSIC) and imperfect SIC (ipSIC) scenarios. Results show that compared with the benchmark scheme without PU, the secrecy sum-rate and user fairness are both greatly enhanced with slight sum-rate loss. Furthermore, this letter proves that with much lower computations, the proposed scheme yields close-to-optimum secrecy sum-rate and user fairness performance provided by the exhaustive search algorithm in the pSIC scenario.