Routing in multi-modal underwater networks: A throughput-optimal approach

While acoustic signals are still the main communication means under water, other technologies are being developed, e.g., based on optical and radio-frequency electro-magnetic waves. Each technology has its own advantages and drawbacks to trade off, e.g., communication range vs. bit rate. Recently, new approaches are emerging to leverage the advantages of several underwater technologies by incorporating them in a multi-modal communication system. In this paper, we address a fundamental part of these multi-modal systems by proposing a novel routing protocol for networks of multi-modal nodes. Our protocol makes distributed optimal and fair decisions about the per-link flow, prevents bottlenecks, and allows simultaneous transmissions using multiple technologies in order to advance a packet towards its destination. We analyze the performance of our protocol via model-based simulations and compare it to benchmark results. Our results show that our protocol successfully leverages all technologies to deliver data, even in the presence of imperfect topology information.