Lightwave Power Transfer-Enabled Underwater Optical ISAC Systems under Ship Attitude Variation

TL;DR

This work tackles the challenge of enabling high-bandwidth underwater links while maintaining sensing capabilities in the presence of ship-induced attitude variation. It proposes a lightwave power transfer-enabled underwater O-ISAC system where a sea-surface AP transmits downlink signals to a seabed energy-harvesting sensor and to a sensing target observed by a pinhole-camera array, with the ship's roll, pitch, and yaw modeled as Gaussian. The authors derive closed-form approximations for the average sensing MSE $\overline{\text{MSE}}$ and the average uplink rate $R_{UL}^E$, validating them against simulations and revealing a fundamental communications–sensing tradeoff governed by the frame time split $\alpha$ and camera geometry. The results provide practical design insights, including optimal camera placement and a harvest-use ratio around $0.55$, and demonstrate that increasing the number of cameras mitigates the attitude-induced performance degradation, enabling robust LPT-enabled underwater O-ISAC deployments. These findings advance autonomous underwater networks by enabling energy-sustainable sensing and high-rate uplink communication under realistic ship motion conditions, with implications for ocean monitoring and offshore operations.

Abstract

In this paper, we propose a lightwave power transfer-enabled underwater optical integrated sensing and communication (O-ISAC) system, where an access point (AP) mounted on a seasurface ship transmits lightwave signals to two nodes, namely ($i$) a seabed sensor that harvests energy and transmits uplink information to the AP, and ($ii$) a sensing target whose position is estimated by the AP using an array of pinhole cameras. To capture practical deployment conditions, the ship attitude variation is modeled through its roll, pitch, and yaw angles, each following a Gaussian distribution under low-to-moderate sea states. Closed-form approximations are derived for the mean squared error (MSE) of target localization and the achievable uplink data rate. Analytical and simulation results demonstrate excellent agreement, validating the proposed models and derived expressions, while revealing the fundamental communication-sensing tradeoff in the O-ISAC system. The results further provide valuable design insights, including the optimal camera placement on the ship to minimize localization error, achieving a minimum MSE of $10^{-2}$ $\text{m}^2$ with multiple cameras under roll, pitch, and yaw angle variation of $10^{\circ}$, and the optimal harvest-use ratio of $0.55$ for the considered setup.

Figures (4)

• Figure 1: LPT-enabled O-ISAC system consisting of a sea-surface AP as well as an EH sensor, and a sensing target at the seabed.
• Figure 2: Average sensing MSE versus downlink transmit power $P_{DL}$.
• Figure 3: Average sensing MSE versus distance between pinhole cameras.
• Figure 4: Average sensing MSE and achievable rate versus time allocation parameter $\alpha$.