A Multiple Data Collection Tree Protocol for UWSNs

We propose a new efficient and robust routing protocol for underwater wireless sensor networks (UWSNs) called the Multiple Data Collection Tree (MDCT) protocol. MDCT proactively constructs and maintains multiple node-disjoint shortest-path routing trees connecting the underwater sensor nodes to onshore sink nodes. These trees provide readily available paths for routing data packets from underwater sensor nodes to surface sink nodes. Using multiple trees improves reliability, reduces congestion (especially at near-root nodes), and shortens routing paths. It also balances energy consumption by distributing the packet-forwarding load over a larger number of nodes. MDCT updates the trees continuously in response to changing underwater conditions such as sensor movements (due to underwater currents) and sensor out-of-power failures. We prove formally the correctness and optimality of the constructed trees. We also show how MDCT outperforms other protocols (namely, VBF, ERGR-EMHC and DCTP) in terms of packet delivery ratio, average end-to-end delay and energy consumption via extensive simulation. For example, compared to VBF, MDCT has increased the delivery ratio by over 75%, has reduced the average end-to-end delay by nearly 60%, and has reduced the energy consumption by 25% in some tested scenarios.