Performance analysis and optimization of modulation techniques for underwater optical wireless communication in...

Area of Science:

• Optical Wireless Communication
• Aquatic Technology
• Signal Processing

Background:

• Underwater Optical Wireless Communication (UOWC) faces performance challenges from absorption, scattering, and turbulence.
• Modulation scheme selection is critical for reliable UOWC systems.

Purpose of the Study:

• To comprehensively analyze the performance of six modulation schemes in UOWC systems.
• To evaluate trade-offs between communication range, power, and channel capacity under various underwater conditions.

Main Methods:

• Simulated performance of On-Off Keying (OOK), Pulse Position Modulation (PPM), Quadrature Phase Shift Keying (QPSK), Differential Phase Shift Keying (DPSK), 32-Phase Shift Keying (32-PSK), and 64-Quadrature Amplitude Modulation (64-QAM).
• Utilized LED and LD photo-sources at 520 nm with a Silicon Photomultiplier detector.
• Assessed metrics like Bit Error Rate (BER), Signal-to-Noise Ratio (SNR), channel capacity, and link range across different water types and turbulence intensities.

Main Results:

• On-Off Keying (OOK) achieved the longest link range (123.73 m in pure seawater).
• 64-Quadrature Amplitude Modulation (64-QAM) demonstrated superior channel capacity (53.23 bps/Hz).
• Higher-order modulation schemes require increased power and SNR.

Conclusions:

• A fundamental trade-off exists between communication range and spectral efficiency in UOWC.
• The findings guide the selection of optimal modulation strategies for underwater environmental monitoring, robotics, and defense.