## 1 Introduction  
Currently, the Internet of Things (IoT) is widely applied for various purposes in different areas such as system-monitoring systems for smart factories, smart agriculture, smart homes, and healthcare [1]. The purpose of IoT is to connect physical devices with the virtual world, using internet protocol as the intermediary to communicate data [2]. This system includes computing devices, machines, animals, and people, all of which are assigned unique identifiers and the capacity to transmit data over the network automatically, without human interaction. However, current techniques that involve IoT are mostly based on radio frequency (RF) technology, such as ZigBee, Bluetooth, and WiFi. It is important to note that radio frequencies come with potentially harmful effects on human health [3], especially for children, old people, and hospital patients. Therefore, many researchers focus on finding new wireless technologies to replace RF technologies. The use of visible light for data transmission highlights a good alternative to replace RF technologies, including new viable candidates such as visible-light communication (VLC), optical wireless communication (OWC), and optical camera communication (OCC), whose advantages over RF communication are as follows:  
* Visible-light wave bandwidth is more than 1000 times the RF bandwidth. * Visible light waves do not negatively affect human health [4], while RF waves generate electromagnetic interference, which not only reduces the performance of the system but also affects human health. * Visible light waves are more efficient and secure if the channel model achieves line-of-sight (LOS) transmission. With such great potential, companies are extensively funding research on improving this technology. Standards for OWC technologies have been presented in IEEE 802.15 [5]. In [5], the uniqueness of OWC and its wide range of protocol complexity acceptance are also recognized. The purpose of the IEEE 802.15.7m Task Group (TG 7m) is to amend the previous standard, which was classified into four categories:  
* Existing VLC modes available in the IEEE 802.157-2011 standard [6]. * OCC: baseband modulation techniques that use cameras or image sensors to receive signals from a light source. * Light-emitting diode identification (LED-ID): communication techniques that use photodiodes at low speeds, with data rates below 1 Mbps at the physical layer. * High-speed Light Fidelity (Li-Fi): high-rate photodiode modulation techniques with data rates exceeding 1 Mbps at the physical layer. Li-Fi technologies utilize optical orthogonal frequency division multiplexing modulation. Because of improvements in manufacturing technology, LEDs have the potential to become next-generation lighting sources, owing to their advantages in terms of long life, power consumption, and good visibility. Their ability to switch on/off at a fast rate [7; 8] facilitates high-rate transmission in OWC/OOC and VLC systems. As mentioned in [9; 10], RF technologies generate electromagnetic interference (EMI), whereas visible light technology has emerged as a novel EMI-free alternative that could replace RF technologies [11]. A conventional VLC system includes LEDs that transmit data based on fast-switching on/off status and photodiodes (PDs) on the receiver side, which receive power from LEDs and decode data [12]. In [13; 14], the authors implement an ultra-high-speed PD modulation scheme, based on VLC, with extremely effective spectral properties. Multiple-input multiple-output (MIMO) technology, with an ultra-high-speed multichannel for the VLC system, is also presented in [15; 16]. However, the disadvantage of a VLC or Li-Fi system is that it only applies to short transmission distances, so using PDs as detectors limits the VLC or Li-Fi system's suitability to indoor environments only. Unlike VLCIn [13, 23], it propose a mobile environment monitoring system that uses color LEDs to transmit data.