Nonlinearity Mitigation Based on Modulus Pruned Look-Up Table for Multi-Bit Delta-Sigma 32-CAP Modulation in Underwater Visible Light Communication System

Abstract

Application of light-emitting diodes (LEDs) based visible light communication (VLC) in underwater wireless communication has become a hot topic. However, on the one hand, the performance of underwater VLC (UVLC) system is limited due to power attenuation in water medium. On the other hand, increasing the driving power will induce nonlinearity from the imperfect optoelectronic components. Particularly at high signal amplitude, nonlinearity will become the dominant bottleneck. In this paper, we focus on nonlinearity mitigation method which preprocesses signal at transmitter-side. Multi-bit delta-sigma modulation combined carrier-less amplitude and phase modulation (DSM-CAP) is proposed to obtain quantized signal with lower peak-to-average power ratio (PAPR). Furthermore, as assuming the quantization noise being additive white noise is not appropriate in nonlinearity, modulus pruned weighted look-up table (MP-WLUT) is employed to modify the signal before DSM quantization to mitigate pattern dependent nonlinear distortion. Experimental results indicate that the DSM-CAP has better nonlinearity mitigating performance than normal CAP. At the data rate of about 1.69Gbp/s, utilizing MP-WLUT pre-distorted DSM-CAP an improvement of 1.44 dB Q-factor is realized compared with normal CAP without WLUT, and the size of MP-WLUT can be reduced to 62.5% of the full-size WLUT.

Spectrally Efficient IR-UWB Pulse Designs Based on Linear Combinations of Gaussian Derivatives

“…The PAPR is an important criterion used to evaluate the pulses performance in presence of nonlinear effects inherent to electronic devices, like power amplifiers or signal converters [54][55][56]. The 4 th -5 th couple and dual 4 th combination show a poor performance in terms of PAPR, while the 6 th -7 th -7 th triplet seems…”

A 400-Gb/s WDM-PAM4 OWC system through the free-space transmission with a water–air–water link

“…Underwater wireless laser transmission (UWLT) system is another type of OWC that transmits optical signals via a laser beam through an underwater link. UWLT has attracted widespread attention in research on the problem of high-speed underwater links 6 – 11 . Given the characteristics of FSO communication and UWLT system, they can provide high transmission rate over a free-space transmission with an underwater link.…”

“…With SLM and angle expander-based beam tracking scheme, the laser beam can be controlled to mitigate its movement due to water flow, and the practical engineering problem can be solved to establish a stable OWC system. Compared with previous OWC systems through the free-space transmission with an air–water–air link 6 – 11 , it presents an excellent system with the advantages of high accumulative transmission rate, long-distance optical wireless transmission, and high reliability.…”

A 400-Gb/s WDM-PAM4 OWC System Through the Free- Space Transmission With a Water-Air-Water Link

“…Underwater wireless laser transmission (UWLT) system is another type of OWC that transmits optical signals via a laser beam through an underwater link. UWLT has attracted widespread attention in research on the problem of high-speed underwater links [6][7][8][9][10][11] . With the rapid progress of FSO communication and UWLT system, FSO-UWLT convergence is therefore developed to provide a high-transmission-rate 12,13 .…”

“…With SLM and angle expander-based beam tracking scheme, the laser beam can be controlled to mitigate its movement due to water flow, and the practical engineering problem can be solved to establish a stable OWC system. Compared with previous OWC systems using free-space transmission and an air-water-air link [6][7][8][9][10][11] , it presents an excellent system with the advantages of a high accumulative transmission rate, long-distance optical wireless transmission, and high reliability.…”