## 2 Related Work  
This section highlights previous work carried out in the domain of OCC, specifically about its challenges in adopting Li-Fi Systems, modulation techniques, and thresholding mechanisms. In paper [9], the author has provided a performance analysis of OOK modulation based on different camera parameters such as frame rate, focal length, rolling rate, and shutter speed. It was observed that the pixel intensity was higher for closer distances, resulting in a high Signal-to-Noise Ratio(SNR) and thus better data decoding. Paper [10] shows the effects of ISO exposure values on the Bit Error Rate. The experimental results demonstrated that the system observed an increase in noise, directly proportional to the camera's sensitivity concerning ISO values and shutter speeds. In paper [11], the difference between rolling shutter vs. global shutter is discussed. Issues such as mixed symbol frames, stripe width estimation, and image pre-processing are addressed by their proposed \"Rolling Lights\" System. These works provided sufficient insight into the relation between camera parameters and their impact on information reconstruction. It also helped  
Figure 1: VLC enabled Lamp. to understand the \"Rolling Shutter\" phenomenon and techniques used for its adaptation in OCC. In a camera-based VLC System, the captured video/images must be processed to decode the encoded data from the light blink pattern. Matlab-based digital image processing methods such as gray-scaling, histogram equalization, and high pass filters were discussed to improve signal quality in OCC System [12]. [PERSON] et al. [13] provided an overview and performance evaluation of three thresholding methods, namely as Background Subtraction, Polynomial Regression, and Moving Average. The Background Subtraction method, includes masking of reference frame over current frame to identify difference in intensities. Whereas, Polynomial Regression and Moving Average thresholding method directly calculates raw intensity values. It was observed that the Background Subtraction method out performed other two techniques in terms of computational speed. These works highlighted various image processing and thresholding techniques used under OCC which inspired our proposed work. The modulation technique is crucial in providing efficient bandwidth and data rate. Various existing modulation techniques, such as OOK, FSK, and Color Shift Keying(CSK), are modified to serve OCC-based Li-Fi systems. Thus, in a simple OOK Modulation, logic 0 means light is Off, and logic 1 means light is On. These changes in the On-Off cycle produce black and white stripes in the captured image/video under tuned conditions [14]. However, in OCC, direct encoding data in OOK is complex due to the low frame rate of cameras and the flickering frequency of source light. Thus, the most common way to achieve OOK without flickering is to encode data bits in terms of frequencies. In paper [15] a frequency shift-based OOK Modulation technique is implemented and evaluated. It also provides a sub-carrier frequency design based on the relationship between bit interval and sampling interval and between Sub-carrier frequencies and flickering mitigation conditions. A binary frequency shift-based OOK (BPSOOK) [16] modulation is proposed, and experimental analysis is provided for the relation between distance and detectable stripes. The proposed system mapped each binary bit to a pair of frequencies separated by the guard band frequency, enabling the detection of data bits from the frame. In paper [17] the OOK frequencies logic 1 and 0 are selected such that when under-sampled by a low frame rate camera, these frequencies align to low pass frequencies that can then be further decoded to the original bit values. Modulation based on the color changes is unique to VLC and Li-Fi Systems. There are different color constellations such as 4-CSK, 8-CSK, 16-CSK depending upon the number of bits mapped to a color.