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[IEEE 2019 International Conference on Advances in Computing and Communication Engineering (ICACCE) - Sathyamangalam, Tamil Nadu, India (2019.4.4-2019.4.6)] 2019 International Conference on Advances in Computing and Communication Engineering (ICACCE) - Estimation of maximum range for underwater optical communication using PIN and avalanche photodetectors
摘要： This paper presents an estimate of underwater optical communication (UWOC) range, using PIN and avalanche photodetectors (APDs). In this simulation-based study, the maximum range while transmitting high-quality video at 6Mbps speed is estimated as 520m in Pure Sea water, 65m in Clear Ocean and 44m in Coastal waters, when using a 100mW laser and APD. The channel here is modeled to include the effect of attenuation and noise. This work quantifies the benefits of using an adaptive system where the wavelength (blue, blue-green and green) of transmission and modulation scheme is changed based on water transmission. Wavelength adaptation according to varying water transmission was found to provide 16 to 40dB advantage in SNR, compared to a system with fixed wavelength, in different waters. A recommendation for wavelength adaptable transmitter design is made based on this. This study assumes the current state of the art in commercially available components.
关键词： Laser,photodetector,underwater communication,range,attenuation
更新于2025-11-14 15:24:45
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Underwater Imaging Based on LF and Polarization
摘要： The underwater image restoration based on polarization information has achieved good results in improving the image quality in scattering media. However, the previous methods are difficult to obtain the true distribution of degree of polarization in the scene. In this paper, we combine synthetic aperture imaging with polarimetric imaging, and propose a method for retrieving radiation of object based on the degree of polarization and intensity of backscattering at the multi-view image. In addition, compared with the previous methods, the proposed method can achieve simultaneous acquisition of 4D light field information and polarization information, effectively increasing the information dimension obtained by single imaging. In order to verify the effectiveness and superiority of the proposed method, we have established a relevant experimental platform and compared with the experimental results of the previous methods, and obtained the expected experimental results.
关键词： synthetic aperture imaging,polarimetric imaging,underwater image restoration
更新于2025-09-23 15:23:52
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[IEEE 2018 OCEANS - MTS/IEEE Kobe Techno-Ocean (OTO) - Kobe, Japan (2018.5.28-2018.5.31)] 2018 OCEANS - MTS/IEEE Kobe Techno-Oceans (OTO) - A Novel Approach to Underwater De-Scattering Based on Sparse and Low-Rank Matrix Decomposition
摘要： The images captured in turbid water suffer from severe visual degradation due to the dramatic scattering effects caused by abundant large suspended particles. This paper propose a novel underwater image de-scattering approach with low complexity, which can separate the scattering component from the image by using the sparse and low-rank matrix decomposition. The experimental results show that the proposed approach can enhance the global image contrast effectively. Additionally, this approach does not require specialized hardware or prior knowledge about the underwater environment; it is suitable for the underwater imaging system in real time.
关键词： turbid water,low-rank matrix decomposition,de-scattering,underwater image
更新于2025-09-23 15:23:52
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Underwater optical wireless sensor networks using resource allocation
摘要： Optical wireless communications is an energy efficient and cost-effective solution for high speed and high secure wireless connections. In this paper, we propose an underwater optical wireless sensor network using multiple input multiple output technique and power allocation algorithm for supporting multiple users with the impacts of underwater channel uncertainty interferences. In proposed power allocation algorithm, all the LED nodes in are coordinated and controlled by a central controller; each LED node supports all the users within its field of view. To separate users, optical code division multiple access is used; cyclic optical orthogonal code working as CDMA code is employed. At the receiver, a minimal mean squared error (MMSE) filter is uniquely designed for each user. The MMSE filters and the assigned power can be jointly optimized to improve the overall throughput and signal to noise ratio. Since the system performance may be impacted by the underwater channel uncertainty, the proposed power allocation can use the predicted channel uncertainty variance to reduce the interference of the channel uncertainty and improve the signal to noise ratio. Compared to the equal power allocation algorithm, the proposed algorithm can support longer transmission distance, higher bit rate and lower bit error rate.
关键词： Multiple access interference,Underwater communications,Wireless sensor networks,Channel uncertainty,MIMO system,CDMA,Optical wireless communications,Resource allocation
更新于2025-09-23 15:23:52
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Enhanced performance of odd order square geometrical shaping QAM constellation in underwater and free space VLC system
摘要： Visible light communication(VLC) employing light-emitting diodes(LED) as light source has become a promising field for underwater wireless communication. However, due to the complex underwater environment and scattering, absorption and diffusion effects during optical transmission in water, the underwater VLC system will suffer from poor SNR and highly nonlinear distortion. In this paper, we proposed and experimentally demonstrated a novel Square Geometrical Shaping(SGS) odd order QAM discrete multitone(DMT) and carrier-less amplitude phase(CAP) modulation based VLC system. Unlike to traditional odd order QAM constellation aiming at the minimum Euclidean distance but without Gray coding at edge constellation points, the new SGS constellation boasts acceptable Euclidean distance and thoroughly Gray coding for every constellation point. Therefore, the system performance can be effectively enhanced by SGS constellation for low SNR and high nonlinearity cases. Both numerical and experimental results verify that SGS 32QAM and 128QAM constellations can outperform traditional QAM constellation by mitigating nonlinearity in a blue LED based underwater and free space VLC system using DMT modulation or CAP modulation. By employing SGS 128QAM, we successfully demonstrate 2.534Gb/s 1.2meter underwater transmission at the driving voltage of 1.1Vpp.
关键词： SGS constellation,nonlinearity,CAP,VLC underwater system,QAM-DMT
更新于2025-09-23 15:23:52
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An 82-m 9 Gb/s PAM4 FSO-POF-UWOC Convergent System
摘要： With the increasing demands in free-space/underwater environmental monitoring, disaster precaution, and manufacturing industry applications, free-space optical (FSO)-plastic optical fiber (POF)-underwater wireless optical communication (UWOC) convergence is designed to be a promising framework for providing long-haul free-space with underwater links. An 82-m 9 Gb/s four-level pulse amplitude modulation (PAM4) system employing a 405-nm blue-light injection-locked laser diode (LD) is thereby offered and practically demonstrated. Results reveal that a 1.8-GHz 405-nm blue-light injection-locked LD can be effectively applied for a 9 Gb/s PAM4 signal transmission over 50 m FSO link, 30 m graded-index (GI)-POF transportation, and 2 m clear ocean underwater channel. To the authors’ understanding, this study is the first to practically build an 82-m 9 Gb/s PAM4 FSO-POF-UWOC convergent system that effectively constructs a long-haul optical wireless-wired-wireless link using doublet lenses, GI-POF, and optical beam reducer. The performances of the proposed convergent systems are analyzed by bit error rate and non-return-to-zero eye diagram in real-time over an 82-m transport. This framework is the leading one to establish a long-haul FSO-POF-UWOC convergent system with qualified transmission performances. It guides a promising way to facilitate wide applications in the convergence of FSO, POF and UWOC.
关键词： Graded-index plastic optical fiber,Underwater wireless optical communication,Four-level pulse amplitude modulation,Free-space optical
更新于2025-09-23 15:23:52
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Positioning Method for an AUV in Arctic Seawater Based on Polarization
摘要： In this paper, a positioning method for an autonomous underwater vehicle (AUV) in the Arctic that uses an electromagnetic direction-of-arrival (DOA) based on the polarization of the near field of three positioning nodes is studied. The positioning nodes each transmit a monochromatic wave with a different frequency. The AUV can obtain the polarized field and then estimate its position through comparison of the different components of the field. The positioning error caused by the measurement error of the different components of the field has been analyzed, and numerical simulations are in agreement with the analysis. The positioning error caused by the fluctuation of the sea surface has also been analyzed. The results show that triangulation with polarization-based DOA (PDOA) can be used for the positioning of an AUV in Arctic seawater.
关键词： DOA,AUV,positioning,underwater
更新于2025-09-23 15:23:52
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Offshore Underwater Image Restoration Using Reflection-Decomposition-Based Transmission Map Estimation
摘要： A new restoration model for underwater images is presented, based on the dark channel reflection-illumination decomposition and local backscattering lighting estimation, to promote the clarity of edge detail and the colorfulness of the output image. For turbid offshore environments, a novel underwater image restoration method is further introduced by applying a statistical prior to the offshore attenuation coefficients. It is shown that the estimated transmission map with lighting-reflection decomposition, rather than dividing the dark channel by the maximal backscattering light as the other methods do, provides better clarity and color restoration. Detailed qualitative and quantitative analysis on hundreds of underwater images is performed, which demonstrates that the proposed method outperforms the state-of-the-art algorithms on the images taken in offshore water characterized by a heavy concentration of colored dissolved organic matter and total suspended matter, and is suitable for fast underwater processing.
关键词： underwater image restoration,underwater imaging,Offshore,underwater optical model
更新于2025-09-23 15:22:29
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Encyclopedia of Robotics || Vision for the Marine Environment
摘要： Vision for the Marine Environment refers to underwater imaging hardware and algorithms that enable the perception of the subsea environment for marine science applications, inspection and intervention. For a long time, optical cameras have been used in ROVs to provide the user with visual feedback of the operational scene. Conversely, AUVs have been traditionally equipped with sonar imaging systems, for two main reasons. First, the range of acoustic imaging is significantly higher, and second, as a consequence, they can work at a safer altitude, while the AUV follows the bottom profile. Nevertheless, during the last decades, vision systems have become smaller and more power-efficient, and the robot hardware has become more powerful and capable of storing the images onboard. Nowadays, commercial AUVs may be equipped with vision systems able to provide high-resolution seafloor imagery in clear waters. A single AUV survey may provide many thousands of images making it tedious to analyze the results. Image processing techniques may significantly improve the quality of the images and combine them into maps enabling faster interpretation. While the role of vision in commercial off-the-shelf robots is mostly passive (they gather data that is later processed after the mission), there have been research contributions aimed at incorporating computer vision algorithms to make the robot more autonomous, adapting its behavior online depending on the sensed situation. Algorithms for pipe/cable tracking, visual odometry, station-keeping, or target-tracking among others are paving the way toward an enhanced breed of autonomous robot, exploiting vision as a primary sensor modality.
关键词： Underwater computer vision,Underwater optical sensing and processing
更新于2025-09-23 15:22:29
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[IEEE 2018 OCEANS - MTS/IEEE Kobe Techno-Ocean (OTO) - Kobe, Japan (2018.5.28-2018.5.31)] 2018 OCEANS - MTS/IEEE Kobe Techno-Oceans (OTO) - Multi-Scale Gradient Domain Underwater Image Enhancement
摘要： Underwater images often suffer from low visibility, due to the attenuation and scattering of the propagated light, which are caused by the dense and non-uniform medium. Based on the observation that degradation of underwater images occurs both in contrast and color, this paper aims at compensating the contrast and color saturation of the image respectively. To achieve this, we first white balance the degraded image to remove the color casts while producing a natural appearance of the underwater image. Then propose a multi-scale gradient domain contrast enhancement strategy to increase the visibility, and compensate the attenuation of color saturation according to the estimated transmission. Both qualitative and quantitative results demonstrate the effectiveness of the proposed method. Our method yields accurate results with significantly enhanced contrast and superior color, even better than other state-of-the-art methods.
关键词： Underwater image,Gradient Domain,Contrast enhancement,Edge-preserving image decomposition,Color correction
更新于2025-09-23 15:22:29