Routing TCP Flows in Underwater Mesh Networks

Due to the growing importance of coastline surveillance and protection, underwater communication is playing an increasingly important role in military networks. As compared to terrestrial networks, large propagation delays and low data rates are fundamental characteristics of underwater communication. Furthermore, due to some key differences in the factors causing fluctuations in the quality of the underwater channels, the corresponding communication links experience more prolonged data rate changes as compared to those in terrestrial networks. Large propagation delays and prolonged link data rate deteriorations severely degrade the end-to-end performance of Transmission Control Protocol (TCP) based applications. Since military applications often require the reliable data delivery provided by TCP, it is important to devise solutions to alleviate this problem. In this paper, we propose a new routing scheme called Linear Coded Digraph Routing (LCDR) to enhance the end-to-end throughput of TCP based packet flows in underwater mesh networks. LCDR is a fully distributed scheme designed to locally respond to changes in the link data rates. In LCDR, each ingress node forwards packets after network coding. Each intermediate node adaptively uses network coding before forwarding the packets to the outgoing links. Each terrestrial gateway decodes the network coded packets before forwarding them to terrestrial networks. Each node adapts its packet forwarding rate based on the available bandwidth on the outgoing links, such that the terrestrial gateway can successfully receive packets with higher probability without significantly affecting cross-traffic. The effectiveness of the proposed scheme is evaluated using simulation. The simulation results show that the proposed scheme uses the spare bandwidth on each link efficiently and it significantly improves end-to-end throughput of TCP flows.