Delay-Sensitive Opportunistic Routing for Underwater Sensor Networks

Acoustic transmission, inherent to aquatic environments and used in underwater sensor networks (UWSNs), presents its own challenges in terms of energy consumption, long propagation delay, and available bandwidth. These UWSN challenges make it difficult to directly adapt ideas which have already been proven reliable in open-air networks. End-to-end latency is one of the key elements for delay-sensitive UWSN applications. In this paper, we apply the idea of opportunistic-based routing (OR) for maximizing goodput while meeting end-to-end latency requirements for delay-sensitive UWSN applications. In doing so, we introduce a new metric called EEL|success(Fi), which is the expected end-to-end latency from node i to the destination when at least one forwarder of Fi successfully receives a packet; we then formulate this UWSN OR routing problem as a nonlinear optimization model. To effectively solve this problem, we propose a two-step heuristic algorithm, which is composed of per-node forwarding set determination and packet forwarding prioritization. The results of a performance study show that our scheme outperforms other existing works in terms of network goodput and energy costs.