Leveraging the Near––Far Effect for Improved Spatial-Reuse Reuse Scheduling in Underwater Acoustic Networks
Abstract: We present a spatial reuse resource allocation scheme 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 nearnear far effect, where a node located farther from the receiver is jammed by a closer node. While common practice considers such a situation a challenge challenge, in this paper we consider it a resource, and use it to increase the network throughput of spatial-reuse time-division division multiple access. Our algorithm serves two types of communications: (1) contention-free contention free and (2) opportunistic. Our objective is to maximize ze the time slot allocation, while guaranteeing a minimum per-node per packet transmission rate. The result is an increase in the number of contentioncontention free packets received, and a decrease in the scheduling delay of opportunistic packets. Numerical results show show that, at a slight cost in terms of fairness, our scheduling solutions achieve higher throughput and lower transmission delay than benchmark spatial-reuse reuse scheduling protocols. These results are verified in a field experiment conducted in the Garda Lake, Italy, where we demonstrated our solution using off-the-shelf shelf acoustic modems. To allow the reproducibility of our results, we publish the implementation of our proposed algorithm.