Synchronization, Identification, and Signal Detection for Underwater Photon-Counting Communications With Input-Dependent Shot Noise

TL;DR

This paper introduces a novel iterative detection method for underwater photon-counting optical wireless communications, addressing signal-dependent shot noise and multi-user interference to improve detection accuracy.

Contribution

It proposes a new synchronization and multi-user detection algorithm tailored for grant-free underwater PhC OWC systems with shot noise, reducing complexity and latency.

Findings

Achieves bit error rates comparable to perfect synchronization scenarios.

Effective user identification and delay estimation in multi-user environments.

Improved detection performance under signal-dependent shot noise.

Abstract

Photon counting (PhC) is an effective detection technology for underwater optical wireless communication (OWC) systems. The presence of signal-dependent Poisson shot noise and asynchronous multi-user interference (MUI) complicates the processing of received data signals, hindering the effective signal detection of PhC OWC systems. This paper proposes a novel iterative signal detection method in grant-free, multi-user, underwater PhC OWC systems with signal-dependent Poisson shot noise. We first introduce a new synchronization algorithm with a unique frame structure design.The algorithm performs active user identification and transmission delay estimation. Specifically, the estimation is performed first on a user group basis and then at the individual user level with reduced complexity and latency.We also develop a nonlinear iterative multi-user detection (MUD) algorithm that utilizes a detection window for each user to identify interfering symbols and estimate MUI on a slot-by-slot basis, followed by maximum \textit{a-posteriori} probability detection of user signals.Simulations demonstrate that our scheme achieves bit error rates comparable to scenarios with transmission delays known and signal detection perfectly synchronized.