Low-PAPR and Low-Complexity Transmission Schemes for DHT-Based Underwater Optical Wireless Systems

This paper presents a low-complexity, low-peak-to-average power ratio (PAPR) transmission scheme for discrete Hartley transform (DHT)-based underwater optical wireless communication (UOWC) systems, termed LPC-DHT-OFDM. The proposed scheme reduces transmitter complexity and mitigates nonlinear distortion by separately processing the real and imaginary parts of the modulated symbols. The real part is generated using multiply-accumulate and anti-symmetric operations, while the imaginary part is produced through a repetition-based method, thereby eliminating conventional DHT/IDHT operations. Non-negative signals are obtained through zero-level clipping and DC biasing and are transmitted simultaneously via two LEDs. As a member of the DHT-spread OFDM family, LPC-DHT-OFDM achieves substantial reductions in both PAPR and computational complexity, making it a promising candidate for practical UOWC applications. In addition, this paper provides the numerical analysis of its spectral efficiency, electrical and optical power requirements, PAPR, bit error rate, and computational complexity.