Physical layer security for MISO vehicle-to-vehicle visible light communication systems

Security is a fundamental requirement for communication systems. Although conventional methods rely on the complexity of the code used to encrypt the data, physical layer security (PLS) leverages information theory by exploiting differences between legitimate and wiretapped channels. This concept has been investigated for indoor environments where light sources have a Lambertian pattern. However, there is a notable gap in the literature on PLS schemes for vehicle-to-vehicle visible light communication (V2V-VLC), where irregular headlight radiation patterns complicate secure transmission. This paper proposes a PLS scheme to secure the data in V2V-VLC system, experimentally validated in an outdoor environment. The proposed scheme utilizes the vehicle’s headlights to implement a multi-input-single-output (MISO) system that beamforms the transmission toward the legitimate receiver and zero-forces (ZF) it into the eavesdropper’s null space. We derive the achievable secrecy rate of the system and analyse its performance under different legitimate receiver’s (Bob) channel conditions. Additionally, we establish a physical key considering the geometry of the legitimate link in the presence of an eavesdropper. To validate the proposed approach, we conducted an experiment using the GNU Radio platform, implementing the MISO system via software-defined radio (SDR). The results prove the efficacy of the ZF beamforming scheme in securing the V2V-VLC link by nullifying the transmission directed toward the eavesdropper. A key conclusion is that security is guaranteed when the transmitter and legitimate receiver are traveling alone in the same lane. Otherwise, Bob is further to the left on the road than Eve because the DPR values are high.