Several underwater network characteristics, including long propagation delays and a bandwidth dependent on distance, provide unique challenges to protocol designers. In this paper we present STUMP-WR, a distributed routing and channel scheduling protocol, designed for heavily loaded underwater networks. STUMP-WR selects and schedules links using a distributed algorithm to overlap communications by leveraging the long propagation delays. Through simulation we show that STUMP-WR outperforms previously proposed channel access protocols for underwater networks by achieving higher throughput and lower energy consumption per bit delivered at nearly all traffic rates. We also determine the effect of using CDMA on protocol operation.

In this paper, we propose the Staggered TDMA Underwater MAC Protocol (STUMP), a scheduled, collision free TDMA-based MAC protocol that leverages node position diversity and the low propagation speed of the underwater channel. STUMP uses propagation delay information to overlap node communication and increase channel utilization. Our work yields several important conclusions. First, leveraging node position diversity through scheduling yields large improvements in channel utilization. Second, STUMP does not require tight node synchronization to achieve high channel utilization, allowing nodes to use simple or more energy efficient synchronization protocols. Finally, we briefly present and evaluate algorithms that derive STUMP schedules.