# A Survey of Vehicular VLC Methodologies
## 3 Vehicular VLC Overview
### Reviews on Vehicular VLC  
There is already a substantial amount of research to explore the performance of V2V and I2V VLC lines, and this research is expected to continue to expand. 1. Vehicle-to-vehicle reviews  
The authors in [36] presented a channel modeling study on a V2V link and used an asymmetrical high-beam headlight at the transmitter side. The study focuses on developing a path loss model under different weather conditions to determine a maximum distance of about 72 m in clear weather conditions and 26 m in fog conditions. Moreover, road reflection models and the intensity distributions of headlights were also considered. On the other hand, the proposed closed-form formulation for the path loss is only relevant for a minimum distance that does not exceed 20 m. Furthermore, a non-constant random geometry-based model (GBSM) is suggested for V2V VLC channels. According to the results, the amount of power loss varies greatly depending on the distance, the height of Rx, and the pattern of the optical source [72]. In order to support longer communication distances, the authors in [39] presented a negative exponential form, which produced a good fit with the findings of the ray tracing simulation under various atmospheric circumstances. The authors calculated the shortest distance to travel while meeting the BER requirement. According to the findings, it was possible to travel a maximum distance of approximately 72 m when the weather was clear, but this distance was only about 26 m when fog was present. Figure 4: Connections between vehicles that utilize vehicular VLC, comprising tail to head, head to tail, head-to-head, tail to tail, and infrastructure to vehicle (I2V). The implementation of a twin photodetector and an angle diversity receiver contributed to performance enhancements [56]. Moreover, there is a significant variance in the ray tracing scenario for path loss calculation when compared to the Lambert model, as shown in [73], where the authors present a non-sequential ray tracing simulation and focus on the radiation patterns of different taillights to investigate the performance of VLC, to examine the effect of neighboring vehicles when delays spread to various scenarios. Additionally, the effect of neighboring vehicles when delays spread to various scenarios. A precise channel characterization of VLC-based V2I systems is provided. [74]. This type of model is capable of being practically applied to TLs manufactured by a variety of different companies. As a result, it is simple enough to be utilized in estimating the network performance of V2V systems. According to this concept, the maximum transmission distance that could support reliable communications was as follows: contact was made possible with a bandwidth of 100 kHz and a range of up to 66 m thanks to this technology. The effect of fog on vehicle-to-vehicle (V2V) connections was studied in [75]. The authors presented an experimental method on a VLC link based on a camera at the receiver side using natural light in the transmitter, considering the distance and visibility levels between vehicles. Moreover, the results are shown when using the signal modulation index decreases from 1 to 0.75 and 0.5: the connection error rate is up to 20 m, and it deteriorates further at the 0 index to reach about 10 m.  
Furthermore, for achieving omnidirectional coverage for V2V under various practical scenarios of imperfect alignment and lane changes, and presenting the total contribution of received optical power considering all PDs, [37] proposed a VLC-based channel modeling method for a V2V link between a source vehicle equipped with a transmitter-side high-beam, where four photodiodes support the car on the destination side. The first two parking PDs are in the car's trunk, directly below the taillights. Moreover, another one is located on the left part of the vehicle, and the final one can be found in the right position.