On Using the Raspberry Pi Camera to Receive 8-PAM Signals in Optical Camera Communication

Optical Camera Communication (OCC) has emerged as a way of implementing Optical Wireless Communication (OWC) without the need of adding an additional interface to smart devices equipped with cameras, and is suitable for applications in Internet of Things (IoT), secure communications, indoor positioning and electromagnetic interference sensitive scenarios. Given the fact that a camera consists of an array of photodetectors connected to analog-to-digital converters, we can leverage this fact to implement not only binary signal reception, but also a multi-level Pulse Amplitude Modulation (PAM) receiver. In this paper, we explore the usage of the Raspberry Pi Camera V2.1 as a receiver for implementing 8-PAM OCC, focusing on the technical characteristics of this camera and identifying the limitations that arise from its low cost. A decoder algorithm is proposed, aimed at circumventing the identified limitations with signal processing solutions. The proposed algorithm was experimentally validated in an indoor scenario and a Symbol Error Rate (SER) was measured for up to 1.8m, remaining under 1.3%.