Secrecy-Oriented Transmitter Optimization for Visible Light Communication Systems

Securing visible light communication (VLC) systems with physical-layer technologies has drawn increasing attention. In this paper, we leverage both transmit beamforming and jamming techniques to enhance communication secrecy for a multiple-input single-output (MISO) VLC system with presence of multiple eavesdroppers. The transmit beamformer and jamming precoder are jointly optimized in the sense that the signal-to-noise ratio (SNR) of the legitimate user is maximized subject to maximum SNR constraints imposed on eavesdroppers, as well as light-emitting diode (LED) optical power constraints. Despite the fact that the corresponding optimization problem has a nonconvex fractional form, we are able to determine its locally optimal solution via Charnes-Cooper transformation and minorization-maximization algorithm. Furthermore, we study the extension to a more complicated scenario where perfect channel state information at the transmitter (CSIT) is not available. The superiority of the proposed algorithms is finally verified via simulations.