6 sonuçlar
Arama Sonuçları
Listeleniyor 1 - 6 / 6
Yayın Channel modelling for indoor visible light communications(Royal Society Publishing, 2020-04-17) Miramirkhani, Farshad; Uysal, MuratVisible light communication (VLC) allows the dual use of light-emitting diodes (LEDs) for wireless communication purposes in addition to their primary purpose of illumination. As in any other communication system, realistic channel modelling is a key for VLC system design, analysis and testing. In this paper, we present a comprehensive survey of indoor VLC channel models. In order to set the background, we start with an overview of infrared (IR) channel modelling, which has received much attention in the past, and highlight the differences between visible and IR optical bands. In the light of these, we present a comparative discussion of existing VLC channel modelling studies and point out the relevant advantages and disadvantages. Then, we provide a detailed description of a site-specific channel modelling approach based on non-sequential ray tracing that precisely captures the optical propagation characteristics of a given indoor environment. We further present channel models for representative deployment scenarios developed through this approach that were adopted by the Institute of Electrical and Electronics Engineering (IEEE) as reference channel models. Finally, we consider mobile VLC scenarios and investigate the effect of receiver location and rotation for a mobile indoor user. This article is part of the theme issue ‘Optical wireless communication’.Yayın ViLDAR-Visible light sensing-based speed estimation using vehicle headlamps(IEEE, 2019-11) Abuella, Hisham; Miramirkhani, Farshad; Ekin, Sabit; Uysal, Murat; Ahmed, SamirThe introduction of light emitting diodes (LED) in automotive exterior lighting systems provides opportunities to develop viable alternatives to conventional communication and sensing technologies. Most of the advanced driver-assist and autonomous vehicle technologies are based on Radio Detection and Ranging (RADAR) or Light Detection and Ranging (LiDAR) systems that use radio frequency or laser signals, respectively. While reliable and real-time information on vehicle speeds is critical for traffic operations management and autonomous vehicles safety, RADAR or LiDAR systems have some deficiencies especially in curved road scenarios where the incidence angle is rapidly varying. In this paper, we propose a novel speed estimation system so-called the Visible Light Detection and Ranging (ViLDAR) that builds upon sensing visible light variation of the vehicle's headlamp. We determine the accuracy of the proposed speed estimator in straight and curved road scenarios. We further present how the algorithm design parameters and the channel noise level affect the speed estimation accuracy. For wide incidence angles, the simulation results show that the ViLDAR outperforms RADAR/LiDAR systems in both straight and curved road scenarios.Yayın A path loss model for vehicle-to-vehicle visible light communications(Institute of Electrical and Electronics Engineers Inc., 2019-07) Eldeeb, Hossien Badr; Miramirkhani, Farshad; Uysal, MuratThe increasing adoption of LEDs in exterior automotive lighting makes visible light communication (VLC) a natural solution for vehicular networking. In this paper, we consider a vehicle-to-vehicle link and propose a path loss expression as a function of distance and different weather conditions. We conduct ray tracing simulations and verify the accuracy of proposed expression. We further use this expression to derive the achievable transmission distance for a targeted data rate while satisfying a given value of bit error rate. Numerical results are presented to demonstrate the achievable distances for single and dual photodetector deployment cases.Yayın Low complexity least minimum symbol error rate based post-distortion for vehicular VLC(Institute of Electrical and Electronics Engineers Inc., 2020-10-22) Mitra, Rangeet; Miramirkhani, Farshad; Bhatia, Vimal; Uysal, MuratVehicular visible light communications (VLC) has emerged as a viable supplement for high speed next-generation vehicle to vehicle (V2V) communication systems. However, performance of a V2V-VLC link is impaired due to nonlinear transfer-characteristics of light emitting diodes (LEDs), and inter-symbol interference (ISI). In this article, a low-complexity least-squares based post-distortion algorithm is formulated over reproducing kernel Hilbert space (RKHS) for a multi-hop V2V-VLC link. The impairments encountered in V2V-VLC channels are mitigated in RKHS by a minimum symbol error-rate post-distorter using a low dimensional approximation of random Fourier features (RFF) (which is a soft approximation of the feature-map to RKHS), that facilitates computationally simple post-distortion under finite memory-budget. The convergence and the BER-performance of the proposed post-distorter is analyzed over realistic V2V VLC channels obtained via ray-tracing. From the analysis, and the presented computer-simulations, the proposed post-distorter is found to exhibit equivalent convergence characteristics and error-rate over reasonable distances, with much lower computational complexity.Yayın Channel modelling and performance limits of vehicular visible light communication systems(IEEE-INST Electrical Electronics Engineers Inc, 2020-07) Karbalayghareh, Mehdi; Miramirkhani, Farshad; Eldeeb, Hossien Badr; Kızılırmak, Refik Çağlar; Sait, Sadiq Q.; Uysal, MuratVisible light communication (VLC) has been proposed as an alternative or complementary technology to radio frequency vehicular communications. Front and back vehicle lights can serve as wireless transmitters making VLC a natural vehicular connectivity solution. In this paper, we evaluate the performance limits of vehicular VLC systems. First, we use non-sequential ray tracing to obtain the channel impulse responses (CIRs) for vehicle-to-vehicle (V2V) link in various weather conditions. Based on these CIRs, we present a closed-form path loss expression which builds upon the summation of geometrical loss and attenuation loss and takes into account asymmetrical patterns of vehicle light sources and geometry of V2V transmission. The proposed expression is an explicit function of link distance, lateral shift between two vehicles, weather type (quantified by the extinction coefficient), transmitter beam divergence angle and receiver aperture diameter. Then, we utilize this expression to determine the maximum achievable link distance of V2V systems for clear, rainy and foggy weather conditions while ensuring a targeted bit error rate.Yayın Visible light communication with solar cell receiver for indoor IoT applications(Institute of Electrical and Electronics Engineers Inc., 2024) Bonakdar, Roozbeh; Edemen, Çağatay; Akbulut, Muhammed Emin; Keskin, Onur; Kaya, Onur; Uysal, MuratThe rapid increase of Internet of Things (IoT) devices has ushered in a new era of connectivity, with an increasing reliance on efficient communication models. In this context, Optical Wireless Communications (OWC) presents a promising avenue for transmitting data at the speed of light, utilizing the optical spectrum to alleviate congestion in urban environments. Leveraging Light Emitting Diodes (LEDs) as transmitters and solar cells as receivers, this paper explores the feasibility of indoor OWC systems. Moreover, we present an experimental setup focusing on bandwidth measurement, data transmission, and energy harvesting. Our results indicate a maximum data rate of 19.2 Kbps using On-Off Keying (OOK) modulation at a 15 cm link distance. Notably, by avoiding the utilization of external circuitry for performance enhancement of the solar cell, we tried to maintain the system's suitability for IoT applications. Our findings contribute to understanding solar cell-based data reception from LEDs, offering simulation results for practical implementation and performance considerations for indoor IoT communication systems.
