# The Concept regarding Vehicular Communications Based on Visible Light Communication and the IoT
## 2 Methodology and Design Parameters
### Li-Fi Communication System Proposal  
The most important advantage that this new Li-Fi technology brings to the field of communications is greater security through the lower radius of the coverage area, as well as data encoding. As a consequence of limiting the coverage area, VLC cannot penetrate opaque surfaces or obstacles, even when geographically limited. In addition, VLC systems can employ connectivity based on unique IDs to encrypt the information in a format that can only be decoded with an adapted receiver. Therefore, this approach is extremely important in terms of the security and integrity of data communication, both for users and within vehicular networks. In the design process for a VLC system, the transmitter is not necessarily the central component, although it is important for the communication process, but an extremely volatile and important part of the system rests on the shoulders of the receiver. This idea was deduced from the specialized literature [45; 46] (see Figure 3). The IEEE 802.15.7 standard provides additional functions, some of which are complementary to lighting devices, and, in this case, they do not negatively influence the process [47]. Even if these systems have to be able to provide both lighting and data communication, they must not induce a flickering effect perceptible to the human eye, and it is necessary to implement functions capable of diminishing the light intensity if this is required. Hardware and software solutions have been found for this problem. Figure 4 shows a complete VLC diagram, as well as a way to secure the communication. The diagram includes an ARM Cortex M7 microcontroller component with a frequency of 1008 MHz, which is the central element around which the entire system gravitates. The basic function of the microcontroller is to transmit the data and transform/demodulate them to obtain a continuous stream of information/bitstream [48; 49]. Thus, the microcontroller facilitates the processing, encoding, modulation, and contouring of bit matrices to expose them and transmit them further. Through the prism of its versatility, its performance and data security can be substantially improved, including by using on-off keying (OOK) at the emission and modulation side. The improved security process is also based on the central anti-flicker aspect; the VLC transmitter runs a code based on unique IDs and a run-length-limited (RLL) code, which can overlap the logic levels \"1\" and \"0\" at the same light intensity. Encrypting data by using security keys with unique IDs assigned to each data matrix also increases the data transmission speed and the instantiation capacity; in some cases, the speeds are around 250-300 kb/s [50]. To validate the security process carried out, the GVLC comparator structured based on the message intent iterates a log with the purpose of validating the receiver as a part of the system; everything is undertaken based on unique IDs. Subsequently, the message header provides the VLC receiver with information regarding the modulation technique, coding, transfer rate, and length of the message, aspects that ultimately validate the communication and security process. The instance frame contains all the transmitted data, and it is followed  
Figure 3: Illustration presenting Li-Fi technology and its general utility. by a stop and validate header, the purpose of which is to inform the VLC receiver that the data have arrived. As shown by communications tests, the intermittency of the signals between data frames also facilitates the implementation of an additional security protocol. The top microcontroller component can generate data and transmit them to other devices, but, at the same time, it can be interfaced with other devices through CAN, I2C, or SPI ports, which increases the safety and veracity of the information [51]. Regarding the level of frame data and the data quantity, solutions related to the cadence of the data transmission can be established with the help of an LED driver.