Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8651
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Article Citation - WoS: 20Citation - Scopus: 22Analysis of Optical Wireless Mimo Communication in Underwater Medium(Ieee-inst Electrical Electronics Engineers inc, 2024) Ata, Yalcin; Baykal, Yahya; Gokce, Muhsin CanerLeveraging on the multiple-input-multiple-output (MIMO) application for enabling high data rates and ensuring reliable communication between underwater platforms connected to underwater sensor network, this article presents a comprehensive analysis of the performance of optical wireless MIMO communication systems depending on the various phenomena. The outage performance of an underwater optical wireless communication (UOWC) is obtained in analytical form using the Meijer-G function. Aysmptotic expression of outage probability is also derived for high signal-to-noise ratio (SNR) regime. Results show that the destructive combined effect of the underwater turbulence, pointing error, attenuation, and angle of arrival (AOA) on the outage performance can be reduced by applying the MIMO spatial diversity technique.Article Citation - WoS: 12Citation - Scopus: 15Intelligent Reflecting Surface Aided Vehicular Optical Wireless Communication Systems Using Higher-Order Mode in Underwater Channel(Ieee-inst Electrical Electronics Engineers inc, 2024) Ata, Yalcin; Gokce, Muhsin Caner; Baykal, YahyaInstead of traditional acoustic communication, optical wireless communication (OWC) remains as a prominent solution in terms of ensuring high data rates for underwater sensor network (USN) including autonomous underwater vehicles (AUVs), remotely operated vehicles (ROVs), submarines, and other underwater platforms. This study is devoted to the performance analysis of underwater optical wireless communication (UOWC) systems using higher-order mode optical beam source and performance improvement with the application of intelligent reflecting surface (IRS) by using realistic parameters. To make the study as comprehensive as possible, the effects of beam misalignment, attenuation (absorption- and scattering-induced), and underwater turbulence are included. The analytical expressions are obtained for probability density function (PDF), cumulative distribution function (CDF) and outage probability (OP) of UOWC channel. The benefit of IRS application is observed to attain at significant levels for UOWC.Article Citation - WoS: 81Citation - Scopus: 98Underwater Turbulence, Its Effects on Optical Wireless Communication and Imaging: a Review(Elsevier Sci Ltd, 2022) Baykal, Yahya; Ata, Yalcin; Gokce, Muhsin C.Theory of optical turbulence in underwater medium and the effects of underwater turbulence on various ap-plications done in underwater or under ocean are reviewed. A detailed survey of underwater turbulence studies in literature is reported. Underwater physics covering salinity, temperature and dissipation rates, various power spectra such as Hill, Nikishov and Nikishov, Li, new form and the oceanic turbulence optical power spectrum (OTOPS) spectra are explained. Wave and phase structure functions, related coherence length, anisotropy, in-tensity, field correlations in underwater turbulence are elaborated. Scintillation indices of spherical, plane, Gaussian, and other types of optical beams are mentioned. Bit-error-rate (BER), signal-to-noise-ratio (SNR) performances of optical wireless communication systems operating in underwater, and the effects of modulation types of these systems on the performances are reported. Channel capacity of underwater optical wireless communication systems when the channel experiences log-normal, gamma-gamma, Weibull, and negative exponential statistics are reflected. Underwater imaging and the related modulation transfer function, under-water turbulence mitigation techniques in the form of aperture averaging, adaptive optics, receiver, transmitter and multiple-input, multiple-output (MIMO) spatial diversity techniques are revised.Article Citation - WoS: 6Citation - Scopus: 6Mitigation of Atmospheric Turbulence on Up and Downlink Optical Communication Systems Using Receiver Diversity and Adaptive Optics(Springer, 2022) Gokce, Muhsin Caner; Baykal, Yahya; Ata, YalcinImprovement in the performance of uplink and downlink optical communication systems by means of receive diversity and adaptive optics correction is investigated. We develop a communication system model using adaptive optics correction in the transmitter and maximum ratio combining diversity technique in the receiver. The effect of adaptive optics correction modes, receive diversity, zenith angle, link length, wind speed and the height of transmitter/receiver on the ground are evaluated. Performance improvement is observed with both adaptive optics correction and the receive diversity. It is aimed to provide researchers an option to determine the method they will use to reduce the effect of turbulence. As the numerical values of the main results, we report that adaptive optics correction with 5 mode Zernike removal reduces BER from 10(-8) to 10(-10) for one receiver. When the number of receivers is 6, BER is found to reduce from 10(-6) to 10(-12). The results obtained in this study can be beneficial to optimize the design of the slant path uplink and downlink optical communication links between the ground and low-orbit satellites that are exposed to atmospheric turbulence.Article Citation - WoS: 9Citation - Scopus: 13Fiber-Coupling Efficiency of Laser Array Beam From Turbulent Atmosphere To Fiber Link(Ieee-inst Electrical Electronics Engineers inc, 2023) Baykal, Yahya; Ata, Yalcin; Gokce, Muhsin CanerFree-space optical communication (FSOC) systems are nowadays integrated with fiber optical components developed for fiber-optic communications. In such integrated systems, the collected portion of the incident beam on the receiver lens is coupled into a single-mode fiber. The process of coupling, however, is mostly affected by the atmospheric turbulence which distorts the coherency of the propagating beam i.e., it results in speckle over the coupling lens causing a reduction in the coupling efficiency. In this article, we aimed at investigating the fiber coupling efficiency of laser array beams propagating in a turbulent atmosphere. For this purpose, using the Huygens-Fresnel principle, mutual coherence function (MCF) for a laser array beam incidence is formulated. In this way, the average power coupled into the fiber and the average received power on the coupling lens are derived for a laser array beam incidence. It is found that the fiber coupling efficiency clearly increases with the increase in ring radius and the number of Gaussian beams in the array and rapidly decreases with increasing structure constant of atmosphere, link distance, and the number of speckles over the receiver aperture. We also demonstrate the effect of various FSOC system parameters on the coupling efficiency.Article Citation - WoS: 17Citation - Scopus: 16Transmittance of Multi Gaussian Optical Beams for Uplink Applications in Atmospheric Turbulence(Ieee-inst Electrical Electronics Engineers inc, 2015) Ata, Yalcin; Baykal, YahyaOn-axis slant path uplink transmittance (used in short as transmittance throughout the text) for multi Gaussian optical beam in Kolmogorov atmospheric turbulent medium is investigated. It is observed that for both the flat-topped and the annular beams, as the propagation distance, wind speed and the zenith angle increase, the transmittance decreases. The transmittance of flat-topped beams increases when the number of beams, source size or the wavelength increases. For the annular beam, when the outer/inner beam size ratio is kept constant, larger source sizes yield larger transmittance values. Transmittance of the thicker annular beams is found to be larger than the transmittance of the thinner annular beams.