# The Utilization of Artificial Neural Network Equalizer in Optical Camera Communications +
## 1 Introduction  
Optical camera communication (OCC) systems, which are part of the optical wireless communications (OWC), leverage the use of off-the-shelf conventional, complementary metal-oxide-semiconductor (CMOS) image sensors (ISs) and standard light-emitting diodes (LEDs) as the receiver (Rx) and the transmitter (Tx), respectively. The camera-based Ross can capture intensity-modulated light signals from a range of LED light sources (i.e., traffic lights, advertising boards, signage, display screens, vehicle head, and taillights, streetlights, etc.). The OCC technology together with the visible and infrared light transmission could be used in different low data rate \(R_{\text{b}}\) applications, such as the Internet of Things (IoT) (e.g., as part of the fifth-generation wireless and beyond), motion capturing [1], intelligent transportation systems [2], indoor localization, security, virtual reality, and advertising [3]. OOC comprises a plurality of pixels (i.e., photodetectors (PDs)), where the signal strength of each pixel depends on the intensity of incident light [4]. Each pixel can detect signals at different wavelengths over the visible range, e.g., red, green,and blue (RGB), hence offering parallel detection capabilities and an adaptive field of view (FoV) feature. In addition, the transmitted information from many light sources, different directions, and locations via the line-of-sight (LOS) [5; 6], non-LOS, and/or a combination of both paths [7] can be captured using a single-pixel or a pixel-array IS-based Rx. Thus resulting in a higher signal-to-noise ratio, improved mobility, and flexibility over a linkspan up to hundreds of meters [8]. On the contrary, the IS requires a higher sampling duration and lower number of quantization levels compared with the PDs due to the light integration time (known as the exposure time \(T_{\text{exp}}\)), and the built-in analog to digital converter circuit [9]. The sequential-readout nature of CMOS IS-based Rx allows each pixel-row to capture the incident light at a different time, thus resulting in the so-called rolling shutter (RS) effect [9]. Note that, the performance of VLC with IS-based Rx is limited mainly by the camera capabilities, i.e., the frame rate \(R_{p}\), \(T_{\text{exp}}\), and FoV. As a result, in OCC, the transmission bandwidth is rather low and limited to a few tens of kHz compared to the PD-based VLC systems. Although, low data should not be seen as a problem considering that there are many applications where low \(R_{b}\) is not critical at all (i.e., IoT, etc.). However, in OCC, lower \(R_{b}\) may result in the flickering effect at the Tx [10; 11]. In IEEE 802.15.7m standard [12], different schemes have been proposed for OCC to mitigate flickering and to increase \(R_{b}\)[13]. For example, in [14], an optical orthogonal frequency division multiplexing VLC with a special IS-based Rx with a built-in PD-array was used to achieve a very high \(R_{b}\) of 55 Mbps. However, the fabrication process of the IS was too complex and, therefore, not commercially available. In [15; 16], under-sampled frequency and phase shift on-off keying (OOK) modulation schemes were proposed to mitigate flickering in OCC with low \(R_{b}\). In [17], Manchester coding was proposed to alleviate flickering in the RS mode, where it was shown that link performance in terms of \(R_{b}\) deteriorated with the transmission range [8; 17]. Moreover, an OCC link with the under-sampled pulse amplitude modulation (PAM) with subcarriers was experimentally demonstrated with the increase \(R_{b}\) to 250 bps [18; 19]. In addition, a multilevel-intensity modulation scheme for RS-based OCC with the frame rate \(R_{f}\) of 30 fps was proposed in [20] with \(R_{b}\) of 10 kbps over a link range of up to 2 m. Furthermore, a parallel transmission VLC system with color-shift-keying (i.e., different colors RGB-LEDs) was reported in [21] with an overall \(R_{b}\) of 5.2 kbps. In [22], the concept of parallel transmission was demonstrated over a range of up to 60 m and with \(R_{b}\) of 150 bps.