Underwater Sensor Networks: A New Challenge for Opportunistic Routing Protocols

Opportunistic routing (OR) is a promising paradigm that selects the next-hop forwarder on the fly. OR has gained a lot of attention from the research community for its ability to increase the performance of wireless networks. In OR a potential group of nodes (candidates) is selected to help as the next-hop forwarder. Each candidate that receives the packet can continue forwarding the packet. In OR, by using a dynamic relay node to forward the packet, the transmission reliability and network throughput are increased. Underwater sensor networks (UWSNs) collect data from the environment and transfer them to the sonobuoys on the surface to send them to a center for further processing. Because of the acoustic channels common to UWSNs, they have low bandwidth, high error probability, and longer propagation delay compared to radio channels. These properties of UWSNs make them good potential candidates for using OR concepts to deliver packets to the destination. This article reviews and compares different OR protocols proposed for UWSNs. We classify the existing approaches in different categories, discuss representative examples for each class of protocols, and uncover the requirements considered by the different protocols, as well as the design requirements and limitations under which they operate. Finally, we discuss potential future research directions for UWSNs using the OR paradigm.