A Multi-layer Energy-balanced Opportunistic Routing Protocol for Underwater Optical Wireless Sensor Networks

Underwater optical wireless sensor networks (UOWSNs) have exhibited significant importance in monitoring and utilizing marine resources because of their attractive advantages in security, data rates, and transmission latency. However, due to their limitations in divergence angle and communication-range, tactful routing algorithms are highly desired by UOWSNs to guarantee their networking performance. In this paper, we propose a Multi-Layer Energy-balanced Opportunistic Routing (MEOR) protocol for UOWSNs. By adopting the mobile multi-sink network architecture with fixed beam direction to alleviate the impact of hardware adjustment on networking performance, the proposed MEOR algorithm significantly enhances network connectivity and reduces energy consumption. Besides, the proposed MEOR algorithm jointly considers link quality and residual energy in selecting relay nodes, and employs a void-handling mechanism in routing process. In this way, the proposed MEOR algorithm can remarkably improve packet delivery rate (PDR). In addition, an energy-balanced node deployment strategy is introduced by the proposed MEOR algorithm for energy balance to prolong network lifetime. Simulation results show that the proposed MEOR algorithm achieves up to about 45% and 48% improvements in PDR and network lifetime with about 45% reduction in energy tax, when compared to the classical routing algorithms employed in the simulations.