## 1 Introduction  
Wireless communication systems have many advantages compared with their wired counterparts, including easy setup, flexibility, and delivering broadcasting information without cables. Wireless systems using radio frequencies (RFs) are broadly used in communication networks. However, RF waves can become exhausted during the formation process of wireless communication technology. To increase the data rate, the communication frequencies must be increased. Many research groups and organizations have investigated ways by which to improve sixth-generation (6G) cellular networks in the sub-THz waveband, which promises a data rate of up to 1-10 Tbps [1]. However, to communicate information, an RF system employs electromagnetic waves that are potentially harmful to human health [2]. This issue must be carefully considered in settings that include the elderly, teenagers, and patients, e.g., nursing homes, schools, and hospitals. Researchers worldwide are looking for new technologies that can substitute RF techniques in specific applications owing to the potentially detrimental effects of these systems. The use of visible light to transfer data has emerged as a viable alternative to RF methods. Optical Wireless Communication has many candidate solutions, some of which are as follows: Visible Light Communication (VLC), Light Fidelity (LiFi), Free-Space Optical (FSO), Optical Camera Communication (OCC), etc. The advantages of OWC systems over the RF approach are as follows:  
* The human body is unaffected by visible light waves [3]. In addition to the negative impact of RF waves on human health, they can also degrade system performance owing to electromagnetic interference (EMI). * Visible light waveforms have a much larger bandwidth compared with RF waves (more than 1000 times that of RF waveforms). * Visible light waveforms are safer and more efficient when the line-of-sight transmission is acquired by the optical channel. * Based on the following benefits, several organizations have suggested research funding to develop and investigate OWC systems. The OWC approach was introduced with its complexity protocol in the Institute of Electrical and Electronics Engineers (IEEE, 2011) 802.15.7-2011 standard [4]. The IEEE 802.15.7-2018 [5] standard was published in 2018, and it added the following four modes to the previous standard. * The IEEE 802.15.7-2011 standard [4] included VLC modes information. * Optical Camera Communication: By using image sensors, modulation systems can decode OCC information from a variety of LED sources. * High-speed LiFi: Using high-rate photodiode modulation techniques, the data rate can be increased to higher than 1 Mbps. * Photodiode identification: Photodiodes are used in communication techniques to transmit data at a low rate (less than 1 Mbps). Based on innovative manufacturing technologies, light-emitting diodes (LEDs) have several benefits as next-generation light sources with specific potential. These advantages include long life, efficient power consumption, low cost, and a variety of sizes. Additionally, LEDs are compatible and useful with high-rate OWC technologies, which enables ON/OFF status-switching at a high frequency [6; 7; 8]. For LiFi and VLC, photodiodes have been used as detectors [4], which can receive the intensity values of transmitters in real-time. In the case of OCC, a camera was used as a detector, which captured images and decoded data derived from LEDs. Global and rolling-shutter cameras are two general types that are deployed in OCC technologies. Accordingly, suitably designed OCC modulation schemes can be developed. RF systems are used in a variety of current applications including communication, monitoring, and mobile communication systems. These systems generate EMI, which can impact human health and especially brain function [9; 10]. As noted, OWC technologies have attracted significant research interest worldwide because it is EMI-free and, accordingly, is a good candidate for replacing RF technology [11].