Low-cost Optical Wireless CDMA Transceiver Design for IoT Applications

In this work, we implement a low-cost optical wireless communication (OWC) system based on code-division multiple access (CDMA). The system can be used in Internet of Things (IoT) applications as it is low-cost and can easily be deployed in small IoT devices. Due to the line-of-sight nature of OWC, the system provides a secure communication means. The framework uses white light LEDs for transmission and an array of 9 photodiodes for reception. Pulsed on-off-keying (OOK) modulation is used with CDMA applied for multiuser scenarios. Each user in a CDMA network is assigned a unique code. Two users modulate their signals using the CDMA codes which are jointly transmitted from a single transmitter to multiple receivers. Many formulations exist for generating these unique codes, however, in this work, we use a very popular set of codes called Walsh codes (also known as Hadamard matrices).