Covering Underwater Shadow Zones using Acoustic Reconfigurable Intelligent Surfaces

TL;DR

This paper proposes using acoustic Reconfigurable Intelligent Surfaces to actively eliminate underwater shadow zones, significantly improving communication coverage in challenging ocean environments.

Contribution

It introduces a novel application of acoustic RIS for underwater communication, including analytical modeling, deployment strategies, and practical validation.

Findings

Without RIS, coverage is less than 20%.

Optimal RIS deployment achieves nearly 100% coverage.

Validated through pool tests and simulations.

Abstract

To better explore the oceans, seamless communication coverage of the vast 3D underwater space is desired. Unlike terrestrial networks using radio signals, underwater acoustic communications face a unique challenge: nodes in underwater shadow zones cannot connect to the network, even within the line of sight. These shadow zones can extend for tens of kilometers, causing communication nodes to disconnect. Existing efforts focus on passive avoidance of shadow zones, but this strategy cannot ensure seamless coverage in dynamic ocean environments. This paper addresses the shadow zone problem by utilizing acoustic Reconfigurable Intelligent Surfaces (RIS) to actively control the underwater channel. Shadow zones are analytically modeled, and optimal RIS deployment strategies are developed for both deep-sea and shallow-sea environments. The acoustic RIS is redesigned considering practical engineering limitations and validated through pool tests. Bellhop-based simulations show that without RIS deployment, coverage is limited to less than 20%, regardless of source strength. However, with optimal RIS deployment, energy coverage can reach almost 100%.