Diversity-enhanced multicarrier transmission for secure, band-limited, and turbulent UOWC systems

Low-pass band limitation and turbulence are two critical issues faced by practical underwater optical wireless communication (UOWC) systems. In this Letter, we propose an orthogonal frequency division multiplexing (OFDM)-based diversity-enhanced multicarrier (D-MC) scheme for joint mitigation of low-pass band limitation and turbulence issues in UOWC systems. The OFDM-based D-MC scheme is realized by performing diversity transmission in both the frequency and time domains during OFDM modulation. Moreover, to enhance the security of OFDM-based D-MC transmission, a two-stage chaotic encryption scheme is further proposed which includes chaotic phase rotation and chaotic scrambling. Experimental results show that OFDM-based D-MC with 2D diversity can achieve a substantial 69.9% usable bandwidth extension compared with the conventional scheme without diversity.