Design and Performance Evaluation of a Relay-Assisted Hybrid LoRa/Optical Wireless Communication System for IoUT

Long-range wide-area network (LoRaWAN) offers reliable connectivity for terrestrial applications, but its use in underwater wireless communication faces challenges, particularly because of the effects of the air–water interface and signal attenuation in water. To address this issue, we design a hybrid LoRa/optical relay node (LoOp) suitable for LoRaWAN. This design utilizes optical wireless communication and LoRa technology for energy-efficient, real-time, and reliable underwater communication. Depending on the situation, either the LoRa side or optical side of LoOp can serve as a transmitter or receiver. For each design phase, we conducted experimental and theoretical investigations to explore the challenges associated with underwater LoRa applications. Based on the experimental results, we developed a link performance calibration strategy to ensure efficient connectivity. To accommodate the integrated nature of LoOp, we introduced a mechanism for data rate flow control. We compared LoOp with another type of relay node to evaluate its performance in terms of delay and energy consumption. The experimental results show LoOp’s capabilities for underwater applications.