SVM-Assisted Realization and Demonstration of Indoor 4 Mb/s Non-Line-of-Sight Visible Light Communication With Second-Order Reflection

Abstract

Non-line of sight (NLOS) visible light communication (VLC) from reflections can expand the application beyond the line-of-sight (LOS) link. We demonstrate the experimental results on such indoor NLOS VLC, up to the second-order reflection. We employ an avalanche photodiode (APD) receiver due to the strong ambient light background. Manchester coding is adopted at the transmitter, and digital filtering is adopted at the receiver. We propose an Support Vector Machine (SVM) detection method to solve the significant distortion issue due to weak signal of the NLOS link. Experimental results on the second-order reflection-based VLC demonstrate that the detection error probability of the proposed SVM detection can be reduced up to at least two orders of magnitude compared with the Gaussian approximation-based detection, and can reach $10^{-4}$ at bit rate 4Mbps. Thus, low-data rate applications can be achieved by VLC with only the second-order reflection, which implies the potential in speech/image/control message transmission and Internet of Things (IoT) applications, for example the mobile robots that may operate in the shadow or even under a table. Experimental results on the second-order reflection at different transmission rates, different sampling rates, different AC signal amplitudes, and different DC voltages of bias-tee are also demonstrated.