A Novel Uplink Positioning and SVD-Based Physical Layer Security Scheme for VLC Systems

In this paper, two techniques including uplink positioning and multiple-input multiple output (MIMO) singular value decomposition (SVD) beamforming are proposed and utilized to provide a novel physical layer security (PLS) scheme for visible light communication (VLC) systems, which much enhance the integrated location-sensing and data security strength. The paper first develops a closed-form mathematical model for ubiquitous uplink positioning using a single light-emitting diode with the trilateration algorithm, considering the field-of-view constraints due to the user’s optical transmitter and access point receivers. SVD in MIMO VLC is subsequently introduced to exploit the acquired user’s location to form a pair of public and private keys for secure data transfer over the physical medium. The proposed system performance is evaluated in terms of the root mean square positioning error εX and the achieved bit error rate (BER) for the uplink positioning and the downlink data transmission, respectively. Results show that the effective area of the photodiode significantly impacts εX, with smaller areas resulting in higher εX. It is also observed that the εX directly relates to the strength of ambient light inducing noise in the system. However, the proposed uplink positioning is less prone to natural ambient light as compared to the traditional downlink visible light positioning. The BER analysis of the downlink data transmission shows that the proposed SVD-based PLS enhances the system’s confidentiality by significantly narrowing the communication zone area by over 90% in comparison to the zero-forcing beamforming scheme and achieves reasonable secrecy capacity.