Browsing by Author "Xu, Z."

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    Emerging optical wireless communications-advances and challenges
    (IEEE, 2015-09) Ghassemlooy, Z.; Arnon, S.; Uysal, Murat; Xu, Z.; Cheng, J.; Electrical & Electronics Engineering; UYSAL, Murat
    New data services and applications are emerging continuously and enhancing the mobile broadband experience. The ability to cope with these varied and sophisticated services and applications will be a key success factor for the highly demanding future network infrastructure. One such technology that could help address the problem would be optical wireless communications (OWC), which presents a growing research interest in the last few years for indoor and outdoor applications. This paper is an overview of the OWC systems focusing on visible light communications, free space optics, transcutaneous OWC, underwater OWC, and optical scattering communications.
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    Guest editorial: Optical wireless communications
    (IEEE, 2015-09) Arnon, S.; Uysal, Murat; Ghassemlooy, Z.; Xu, Z.; Cheng, J.; Electrical & Electronics Engineering; UYSAL, Murat
    Optical wireless communication (OWC) systems provide many advantages over radio frequency (RF) wireless technologies in some scenarios, including significantly higher data rates and a large amount of available license-free frequency spectrum. Recently, OWC has also been proposed in fifth generation 5G standard as a tool to augment capacity due to RF spectrum crunching challenges. Various forms of OWC can be used to augment RF capacity at both access and backhaul/fronthaul levels. Despite the major advantages and various application areas, the widespread deployment of OWC is delayed by several challenges, such as the demand to maintain strict line-of-sight alignment between transmitter and receiver in long range outdoor applications; the need to combat attenuation due to adverse weather conditions such as fog, cloud, and turbulence; to modulate light emitting diodes at high frequencies without distortion at indoor visible light communication (VLC) applications and retaining power levels within the eye safety limits for laser transmitters and comfortable illumination levels for LED transmitters.
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    ArticlePublicationOpen Access
    Hybrid RF/VLC systems: A comprehensive survey on network topologies, performance analyses, applications, and future directions
    (IEEE, 2021) Abuella, H.; Elamassie, Mohammed; Uysal, Murat; Xu, Z.; Serpedin, E.; Qaraqe, K. A.; Ekin, S.; Electrical & Electronics Engineering; ELAMASSIE, Mohammed; UYSAL, Murat
    Wireless communications refer to data transmissions in unguided propagation media through the use of wireless carriers such as radio frequency (RF) and visible light (VL) waves. The rising demand for high data rates, especially, in indoor scenarios, overloads conventional RF technologies. Therefore, technologies such as millimeter waves (mmWave) and cognitive radios have been adopted as possible solutions to overcome the spectrum scarcity and capacity limitations of the conventional RF systems. In parallel, visible light communication (VLC) has been proposed as an alternative solution, where a light source is used for both illumination and data transmission. In comparison to RF links, VLC links present a very high bandwidth that allows much higher data rates. VLC exhibits also immunity to interference from electromagnetic sources, has unlicensed channels, is a very low power consumption system, and has no health hazard. VLC is appealing for a wide range of applications including reliable communications with low latency such as vehicle safety communication. Despite the major advantages of VLC technology and a variety of its applications, its use has been hampered by its cons such as its dependence on a line of sight connectivity. Recently, hybrid RF/VLC systems were proposed to take advantage of the high capacity of VLC links and better connectivity of RF links. Thus, hybrid RF/VLC systems are envisioned as a key enabler to improve the user rates and mobility on one hand and to optimize the capacity, interference and power consumption of the overall network on the other hand. This paper seeks to provide a detailed survey of hybrid RF/VLC systems. This paper represents an overview of the current developments in the hybrid RF/VLC systems, their benefits and limitations for both newcomers and expert researchers.
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    VisDrone-MOT2021: The vision meets drone multiple object tracking challenge results
    (IEEE, 2021) Chen, G.; Wang, W.; He, Z.; Wang, L.; Yuan, Y.; Zhang, D.; Zhang, J.; Zhu, P.; Gool, L. V.; Han, J.; Hoi, S.; Hu, Q.; Liu, M.; Sciarrone, A.; Sun, C.; Garibotto, C.; Tran, D. N. N.; Lavagetto, F.; Haleem, H.; Motorcu, Hakkı; Ateş, H. F.; Jeon, H. J.; Bisio, I.; Jeon, J. W.; Li, J.; Pham, J. H.; Jeon, M.; Feng, Q.; Li, S.; Tran, T. H. P.; Pan, X.; Song, Y. M.; Yao, Y.; Du, Y.; Xu, Z.; Luo, Z.; Motorcu, Hakkı
    Vision Meets Drone: Multiple Object Tracking (VisDrone-MOT2021) challenge - the forth annual activity organized by the VisDrone team - focuses on benchmarking UAV MOT algorithms in realistic challenging environments. It is held in conjunction with ICCV 2021. VisDrone-MOT2021 contains 96 video sequences in total, including 56 sequences (~24K frames) for training, 7 sequences (~3K frames) for validation and 33 sequences (~13K frames) for testing. Bounding-box annotations for novel object categories are provided every frame and temporally consistent instance IDs are also given. Additionally, occlusion ratio and truncation ratio are provided as extra useful annotations. The results of eight state-of-the-art MOT algorithms are reported and discussed. We hope that our VisDrone-MOT2021 challenge will facilitate future research and applications in the field of UAV vision.