Fig. 1. VLC system performances in recent references

Fig. 2. Schematics of various visible light transmitters and receivers. (a) Multicolor LED array photo, with colored boxes standing for their emission colors^[17]; (b) scanning electron microscope (SEM) image of V-pit in GaN based LED quantum well region, which increases luminous efficacy and device bandwidth^[17]; (c) micro-LED array in SEM image^[43]; (d) schematics and SEM images of GaN-based light detector array^[47]; (e) schematic of large angle of FOV luminous concentrator^[48]; (f) wearable perovskite receiver device illustration and SEM images of perovskite grains^[49]; (g) schematic of nanopatterned hyperbolic meta-material (HMM) structure with fluorescent coating^[50]

Fig. 3. Schematic diagrams of structures of channel modeling based on neural networks. (a) Dual-branch heterogeneous neural network^[53]; (b) physics-inspired three-branch neural network^[54]; (c) dual-branch network based on trainable noise module^[56]

Fig. 4. Principles of carrierless amplitude and phase (CAP) modulation. (a) Single band CAP modulation and demodulation principle^[61]; (b) multi-band CAP modulation and demodulation principle^[61]; (c) multi-dimension CAP modulation and demodulation principle^[62]

Fig. 5. Adaptive bit-power loading. (a) Diagram of improved MLC adaptive bit-power loading; (b) subcarrier modulation orders calculated by floor bit loading (FBL) after channel detection (subcarriers with cross mark are in low power margin or with overly high modulation order); (c) final modulation order distribution and subcarriers with reduced modulation orders

Fig. 6. Novel modulation formats. (a) APSK constellation design^[4]; (b) TDHQ principle^[74]; (c) TDHQ simulation rate^[74]

Fig. 7. Schematics of channel equalization. (a) Cascade amplitude equalization circuit^[77]; (b) software pre-equalization algorithm and (c) GK-DNN-based post-equalizer^[79]

Fig. 8. Design diagrams of post-equalizers. (a) Linear post-equalizer structure^[80]; (b) structure with cascaded linear and nonlinear equalizers^[36]

Fig. 9. Schematic diagrams of channel equalization structures based on neural networks. (a) Post-equalization algorithm based on sparse connection dual-branch multilayer perceptron^[82]; (b) post-equalization algorithm based on MIMO multi-branch hybrid neural network^[83]

Fig. 10. Schematic diagrams of large-scale MIMO visible light laser communication optical interconnect system^[31,93]. (a) System diagram, including transmitter module, optical lens antenna array, and receiver; (b) schematic of experimental setup and algorithm flowchart

Fig. 11. Schematic diagrams of visible light beamforming systems. (a) Wavelength-division multiplexed fiber integrated with visible light indoor access network^[97]; (b) MIMO visible light communication system assisted by intelligent optical reflecting surfaces^[98]; (c) active beam steering device based on meta-surfaces and liquid crystal spatial light modulators^[95]; (d) diagram of beamforming technology based on on-chip phased arrays^[99]

Fig. 12. VLC network designs. (a) Illustration of VLC network^[100]; (b) prototype of in-vehicle VLC system in internet of vehicles [geometry of VLC system consisting of two transmitters (Tx1 and Tx2) and two receivers (Rx1 and Rx2)]^[101]