On the secrecy sum-rate of MU-VLC broadcast systems with confidential messages

This paper studies the secrecy sum-rate in multi-user multiple-input single-output (MU-MISO) broadcast visible light communication (VLC) systems with confidential messages. The well-known Zero-Forcing (ZF) precoding is utilized to ensure confidentiality among users. Different from radio frequency (RF) counterpart, input data signals of VLC systems are amplitude constrained. This fundamental difference makes the derivation of the secrecy capacity more complex. In this study, we investigate a lower bound on the secrecy sum-rate of all users, which is valid in high signal-to-noise ratio (SNR) regime. The secrecy sum-rate is derived for two scenarios: known and unknown eavesdropper's channel state information (CSI) at the transmitter.