The increasing demand for high-speed, reliable communication in underwater environments has sparked significant interest in underwater optical multiple-input multiple-output (MIMO) systems. This paper investigates the potential of MIMO technology to substantially enhance data transmission rates for underwater optical wireless communication (UWOC) networks, specifically in the context of the internet of underwater things (IoUT) applications. We conduct a comprehensive comparative analysis of a 4 × 4 MIMO system against Single-Input Single-Output (SISO) and single-input multiple-output configurations (1 × 1 and 1 × 4, respectively) across various modulation schemes, including On–Off Keying (OOK), 32-Phase Shift Keying (32-PSK), and 64-quadrature amplitude modulation (64-QAM), in two water types: pure seawater and clear ocean water. Our system employs a laser diode (LD) operating at a wavelength of 450 nm, which is particularly effective in these aquatic environments. By leveraging spatial diversity, we address challenges related to optical turbulence, scattering, and attenuation in underwater communication. Extensive simulations were conducted to evaluate performance metrics such as bit error rate (BER), signal-to-noise ratio (SNR), channel capacity, received power, and data throughput. The proposed optical MIMO (4 × 4) system demonstrates superior data rates, enhanced communication range, and improved reliability compared to conventional single-beam approaches. At a BER of 10−5, the required transmitted power per bit for OOK in pure seawater decreases significantly from 16.67 dB in SISO to 4.85 dB in MIMO, representing a 70.9% reduction. Similarly, the link range for OOK in pure seawater increases from 2.02 m in SISO to 36.87 m in MIMO, achieving an 18-fold improvement. Furthermore, the channel capacity at an SNR of 10 dB for 64-QAM in pure seawater improves from 20.44 bits/sec/Hz in SISO to 43.64 bits/sec/Hz in MIMO, more than doubling the capacity. These results emphasize the advantages of MIMO configurations and higher-order modulation in UOWC systems, particularly in optical turbulence. The study illustrates MIMO's ability to enhance communication range, link reliability, and data throughput, making it suitable for critical IoUT applications such as environmental monitoring, underwater exploration, and maritime security. Thus, MIMO stands out as a robust solution for addressing underwater communication challenges in turbulent and high-attenuation environments.

Underwater optical MIMO for high data-rate IoUT

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发表日期：

2025年2月15日

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M. Mokhtar Zayed,
Mona Shokair,
Salah Elagooz

摘要

The increasing demand for high-speed, reliable communication in underwater environments has sparked significant interest in underwater optical multiple-input multiple-output (MIMO) systems. This paper investigates the potential of MIMO technology to substantially enhance data transmission rates for underwater optical wireless communication (UWOC) networks, specifically in the context of the internet of underwater things (IoUT) applications. We conduct a comprehensive comparative analysis of a 4 × 4 MIMO system against Single-Input Single-Output (SISO) and single-input multiple-output configurations (1 × 1 and 1 × 4, respectively) across various modulation schemes, including On–Off Keying (OOK), 32-Phase Shift Keying (32-PSK), and 64-quadrature amplitude modulation (64-QAM), in two water types: pure seawater and clear ocean water. Our system employs a laser diode (LD) operating at a wavelength of 450 nm, which is particularly effective in these aquatic environments. By leveraging spatial diversity, we address challenges related to optical turbulence, scattering, and attenuation in underwater communication. Extensive simulations were conducted to evaluate performance metrics such as bit error rate (BER), signal-to-noise ratio (SNR), channel capacity, received power, and data throughput. The proposed optical MIMO (4 × 4) system demonstrates superior data rates, enhanced communication range, and improved reliability compared to conventional single-beam approaches. At a BER of 10⁻⁵, the required transmitted power per bit for OOK in pure seawater decreases significantly from 16.67 dB in SISO to 4.85 dB in MIMO, representing a 70.9% reduction. Similarly, the link range for OOK in pure seawater increases from 2.02 m in SISO to 36.87 m in MIMO, achieving an 18-fold improvement. Furthermore, the channel capacity at an SNR of 10 dB for 64-QAM in pure seawater improves from 20.44 bits/sec/Hz in SISO to 43.64 bits/sec/Hz in MIMO, more than doubling the capacity. These results emphasize the advantages of MIMO configurations and higher-order modulation in UOWC systems, particularly in optical turbulence. The study illustrates MIMO's ability to enhance communication range, link reliability, and data throughput, making it suitable for critical IoUT applications such as environmental monitoring, underwater exploration, and maritime security. Thus, MIMO stands out as a robust solution for addressing underwater communication challenges in turbulent and high-attenuation environments.