## 2 Literature Review  
In the context of OCC within the IoT, cameras play a crucial role in facilitating efficient data collection from a variety of devices and sensors. This OCC system is responsible for processing data received from multiple sources, and then transmitting it to a gateway via wired or wireless networks. Once the data arrives at the gateway, it is then routed to a backhaul network, such as 5G or satellite, and ultimately stored on a server or in the cloud, providing support for various IoT applications [23]. Several studies on OCC in the field of IoT include:  
Ref. [24] proposed a new approach for OCC using side-emitting fiber transmitters and accomplished an increased communication distance two times that of previous research [25; 26]. The proposed OCC-fiber link successfully fulfills the Fuel and Missions Calculator (FEC), Version 3.8 limit for Bit Error Rate (BER) \(10^{-3}\) on distances of 35 m (BER = \(3.35\cdot 10^{-3}\)) and 40 m (BER = \(1.13\cdot 10^{-3}\)) using fiber with diameters of 2 and 3 mm, respectively. The results show that the frequencies using on-off keying are 3.54 and 5.28 kHz each, which creates potential applications in IoT-based indoor and outdoor environments where OCC uses distributed fiber. However, there are some weaknesses related to the fiber, which has a limited radiation angle coverage compared with a conventional light transmitter. This possibly results in a more limited signal recipient zone, a restricted coverage area that can be reached by the OCC system. Furthermore, fiber usage limits flexibility, and it is possible to increase the implementation cost. Another study proposed a hybrid wireless communication system [27] that combines OWC with direct modulation on LED chips. This system is designed for multipurpose indoor IoT using a single LED as a transmitter and a combination of photodiodes with the camera as the receiver. The experiment shows that the system can reach a throughput of up to 100 Mb/s for visible light communication (VLC) link and data transmission without fault for the OCC link. The result is reached using direct modulation with various amplitude levels, and optimization of the received optical power can significantly enhance the performance of the link. This research also explored various LED colors and sophisticated modulation techniques (direct modulation). Based on the results of the experiments conducted in this research, the obtained results pave the way for implementation in real-world IoT scenarios. Another hybrid research [28] proposed the use of OCC in IoT systems to overcome RF spectrum density. This work proposed an IoT application with an \(8\times 8\) LED matrix to transmit temperature and humidity data through 2 packets/s with a packet error rate (PER) of less than 3% over a 2-m distance. The main problem of this implementation is the noise and interference possibility due to LED usage with different bandwidths from the VLC link. The results of the development of the SIMO hybrid VLC system can provide versatile indoor services for IoT. This is because the system can address RF spectrum density issues and successfully reduce interference and noise in the VLC link with an \(8\times 8\) LED matrix. In Ref. [29], a similar method, which is hybrid SIMO for optical IoT system, uses an LED-based transmitter and photodetector and Image Sensors (IS) based receiver for high and low data rate transmission simultaneously. Photodetector-based VLC is used to download large-sized data, internet browsing, and online streaming, whereas IS-based VLC is used to transmit short messages, identification information, and signal control. This hybrid modulation scheme with Rb-High up to 60 Mb/s and Rb-Low up to 5 kb/s is intended to increase the performance, and the experimental results are as desired. This scheme can be developed by adding a color LED for lighting, equalization technique implementation, and different modulation formats to increase the data reception success rate and BER performance.