Time-Domain Hybrid PAM for Data-Rate and Distance Adaptive UWOC System

TL;DR

This paper introduces a novel time-domain hybrid PAM system for underwater optical wireless communication that adapts transmission rate and distance, optimizing power and capacity based on water properties and distance.

Contribution

It proposes a unique TDHP method for adaptive data-rate and distance optimization in UWOC systems, combining different modulation formats for improved performance.

Findings

Maximum transmission distance varies with PAM type and system configuration.

Numerical simulations demonstrate the effectiveness of the TDHP method.

Power optimization enhances transmission capacity and distance adaptability.

Abstract

The challenge for next-generation underwater optical wireless communication systems is to develop optical transceivers that can operate with low power consumption by maximizing the transmission capacity according to the transmission distance between transmitters and receivers. This study proposes an underwater wireless optical communication (UWOC) system using an optical transceiver with an optimum transmission rate for the deep sea with near-pure water properties. As a method for actualizing an optical transceiver with an optimum transmission rate in a UWOC system, time-domain hybrid pulse amplitude modulation (PAM) (TDHP) using a transmission rate and distance-adaptive intensity modulation/direct detection optical transceiver is considered. In the TDHP method, variable transmission capacity is actualized while changing the generation ratio of two intensity-modulated signals with different noise immunities in the time domain. Three different color laser diodes (LDs), red, blue, and green are used in an underwater channel transmission transceiver that comprises the LD and a photodiode. The maximum transmission distance while changing the incidence of PAM 2 and PAM 4 signals that calibrate the TDHP in a pure transmission line and how the maximum transmission distance changes when the optical transmitter/receiver spatial optical system is altered from the optimum conditions are clarified based on numerical calculation and simulation. To the best knowledge of the authors, there is no other research on data-rate and distance adaptive UWOC system that applies the TDHP signal with power optimization between two modulation formats.