Leveraging the Near-Far Effect for Improved Spatial-Reuse Scheduling in Underwater Acoustic Networks

Abstract

We present a spatial reuse resource allocation for underwater acoustic networks that organizes communications so as to avoid destructive collisions. One prime source of collisions in underwater acoustic networks is the so called near-far effect, where a node located farther from the receiver is jammed by a closer node. While common practice considers such situation as a challenge, in this paper we consider it as a resource, and use it to increase network throughput of spatial reuse time-division multiple access. Our algorithm services two types of communications: 1) contention-free and 2) opportunistic. Our objective is to miximize the time slot allocation while guaranteeing a minimum per-node packet transmission rate. The result is an increase in number of contention-free packets received and a decrease in the scheduling delay of opportunistic packets. Numerical results show that, at a slight cost in terms of fairness, our scheduling solutions achieve higher throughput and lower transmission delay than benchmark spatial-reuse scheduling protocols. The results are verified in a field experiment conducted in the Garda Lake, Italy, where we demonstrated our solution using off-the-shelf acoustic modems. To allow the reproducibility of our results, we publish the implementation of our proposed algorithm.