# A Survey of Vehicular VLC Methodologies
## 3 Vehicular VLC Overview
### Infrastructure-to-vehicle reviews
Additionally, [82] studied the bit error rate (BER) in the infrastructure-to-Vehicle (I2V) system, considering the effects of both lateral and longitudinal shifts, as well as modeling the channel using the non-orthogonal multiple access method (NOMA). In summary, the above review indicates a pressing need to improve the overall channel model for VLC in vehicles, while considering factors such as weather conditions (clear, rainy, and foggy), the asymmetric beam pattern of headlights, lateral shifting between vehicles, the effects of road reflections, receiver aperture diameter, and transmitter beamdivergence angle. Table 2 summarizes the reviewed methodologies for channel modeling and the light sources of VLC utilized in establishing V2V and V2I/I2V links. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Ref.** & **Year** & **Application** & **Light Source** & **Channel Method** & \multicolumn{2}{c}{**Observations**} \\ \hline  & & & & & & The authors considered the following: & \\  & & & & & - & Line-of-sight (LoS) received power; & \\  & & & & & - & Effective scatterers on the Tx and Rx; & \\
2018 & V2V & Lambertian & GBSM & - & Single and double-bounced rays; & \\  & & & & & - & Lambertian light source, channel gain; & \\  & & & & & - & Different distance ranges; & \\  & & & & & - & PD is located at three different heights. \\ \hline  & & & & & - & Weather conditions (fog, rain); & \\
36 & 2018 & V2V & Asymmetrical & Ray tracing & - & Road reflection, achievable distance; & \\  & & & & & - & Asymmetrical headlight; & \\  & & & & & - & Multi-hop transmission; & \\  & & & & & - & Simulation built-in ray tracing. & \\ \hline  & & & & & - & Fog conditions; & \\
75 & 2019 & V2V & Lambertian & Experimental & - & LED in TX and camera in RX; & \\  & & & & & - & Experimental setup; & \\  & & & & & - & Effect of visibility levels; & \\  & & & & & & - & The modulation index (MI). & \\ \hline  & & & & & & - & Weather conditions (clear, rainy, foggy); & \\  & & & & & - & Dual photodetector; & \\
39 & 2019 & V2V & Asymmetrical & Ray tracing & - & Asymmetrical high-beam headlamp; & \\  & & & & & - & Achievable transmission distance; & \\  & & & & & - & Simulation built-in ray tracing. & \\ \hline  & & & & & & - & Various scenarios: (imperfect alignment, \\  & & & & & & - & lane changes); & \\
37 & 2019 & V2V & Asymmetrical & Ray tracing & - & Four photodetectors; & \\  & & & & & - & Asymmetrical high-beam lights; & \\  & & & & & & - & Achievable power percentage of each PD; & \\  & & & & & & - & Simulation built-in ray tracing. & \\ \hline  & & & & & - & Impact of optical CIRs; & \\  & & & & & - & The effect of lateral shifts; & \\  & & & & & - & Three photodetectors (traffic pole); & \\
74 & 2020 & V2I & Asymmetrical & Ray tracing & - & Two-lane road; & \\  & & & & & - & Two asymmetrical headlamps (TX); & \\  & & & & & - & Achievable data rate; & \\  & & & & & - & Achievable SNR; & \\  & & & & & - & Simulation built-in ray tracing. & \\ \hline  & & & & & - & Obtain the channel impulse (CIRs); & \\  & & & & & - & Two high-beam headlamps; & \\  & & & & & - & Investigate the maximum transmission; & \\  & & & & & - & Various weather conditions (clear, rainy, foggy); & \\
76 & 2020 & V2V & Asymmetrical & Ray tracing & - & Transmitter beam divergence angle; & \\  & & & & - & Receiver aperture diameter; & \\  & & & & & - & Lateral shift; & \\  & & & & - & Simulation built in non-sequential ray tracing. & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Vehicular VLC light sources and channel modeling summary.