Performance Enhancement via Real-Time Image-Based Beam Tracking for WA-OWC With Dynamic Waves and Mobile Receivers

• Published in: Journal of lightwave technology Vol. 42; no. 19; pp. 6671 - 6678
• Main Authors: Di, Yujie, Xu, Anzi, Chen, Lian-Kuan
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.10.2024; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acoustic beams; Beam tracking; Bit error rate; Communication; Data transmission; Drone aircraft; Error reduction; High speed; Image enhancement; Laser beams; Light beams; Light spots; Misalignment; Movement; Ocean surface; Optical surface waves; Optical transmitters; Real time; Receivers; Surface waves; Tracking; Tracking systems; Underwater communication; visible light communication; water-air optical wireless communication; wave mitigation; Wireless communication; Wireless communications
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2024.3407140

Intensified underwater activities have driven the escalating demand for reliable, flexible, and high data-rate underwater communication links. Optical wireless communication (OWC) emerges as the most promising technology for short- to medium-range communication, facilitating the real-time high-speed transmission of information from undersea to an aerial vehicle which can subsequently relay the information to a terrestrial station. However, establishing a robust water-air link confronts two primary challenges: (i) beam wandering due to the time-varying refraction when the light beam passes through the undulating ocean surface and (ii) the drone's movement when it hovers above the ocean surface. This paper experimentally demonstrated a real-time imaged-based beam tracking system to mitigate beam misalignment due to dynamic waves and receiver movement over a 0.14-m underwater and 1.83-m free-space OWC channel. Experimental results evince a notable reduction in the standard deviation of the received light spot offset from the receiver. Moreover, the tracking system can proficiently accommodate receiver velocities of up to 150 cm/s while maintaining a paltry packet loss rate (PLR) below 10%. By addressing the combined effects of dynamic waves and moving receivers, the proposed beam tracking system successfully enables a 70% reduction in PLR and an order of magnitude decrease in bit error rate (BER). This results in a substantial 17-fold surge in maximum throughput, from 50 Mbit/s to 850 Mbit/s. The experimental results validate the feasibility and effectiveness of the beam tracking system for vanquishing the detrimental effects in the complex water-air OWC (WA-OWC) channel and supporting high-speed data transmission.