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Sürdürülebilir Kalkınma Amaçları

• 2

• MakaleYalnız künye2026/r/gumushane/13880
  A comprehensive optimization framework for indoor laser-based optical wireless communication using gimbal-steered transmitters

  Başer, Oğuzhan; Küçük, Mehmet Ali; Türk, Kadir

  The growing demand for high-speed wireless communication, driven by data-intensive applications such as high-definition video streaming and augmented reality, has highlighted the limitations of the Radio Frequency (RF) spectrum. Optical Wireless Communication (OWC) has emerged as a promising complementary technology, offering wide bandwidth, license-free operation, high security, and immunity to electromagnetic interference. Among OWC transmitters, Laser Diodes (LDs) provide high modulation bandwidth and narrow divergence angles, enabling data rates of several tens of gigabits per second. However, the narrow beam of LDs requires precise Line-of-Sight (LoS) alignment, making beam steering essential. This study focuses on optimizing the positioning and orientation of gimbal- or galvo-based LD transmitters in indoor OWC systems to minimize outage probability under LoS constraints and physical obstructions. An outage probability model considering room geometry and device field-of-view angles is developed and analyzed for three scenarios within a 7 × 5 m room: an empty environment, a room with a 1 × 1 m column, and a user-occupancy-aware environment. The complex optimization problem is solved using multiple meta-heuristic algorithms, including Particle Swarm Optimization (PSO), L-SHADE, and Stochastic Fractal Search with Fitness-Distance Balance (FDB-SFS). The obtained results are subsequently validated through grid search approach. The proposed approach achieves significant outage reduction, demonstrating that incorporating obstacle and user-distribution information enables efficient coverage with fewer terminals, reaching outage probabilities as low as 0.4%.

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  İncele
• MakaleAçık Erişim2026/r/gumushane/13588
  Enhancing precision of low-cost detectors via machine learning for accurate mass attenuation coefficient estimation

  Düzgün, İ.; Küçük, M.A.; Kaya, S.; Çelik, N.

  Low-cost NaI(Tl) detectors are practical for gamma-ray spectrometry but their limited energy resolution can introduce systematic errors in mass attenuation coefficient measurements when scattered photons are included in the peak region. This study proposes a machine-learning correction framework that maps NaI(Tl)-derived attenuation coefficients to XCOM-based HPGe-equivalent reference values through a dimensionless correction factor. An EGS4/XCOM dataset of 756 model-development configurations, covering 18 atomic numbers, six monoenergetic photon energies, and seven collimator radii, was used to train twelve regression models and evaluate them over 60 randomized train–validation–test cycles. Sodium and Bismuth were withheld for external material-wise validation. Gaussian Process Regression with a Matérn 5/2 kernel provided the best overall testing performance. For the withheld materials, the correction reduced the mean deviation from XCOM references from 3.07% to 0.83%, supporting its use as a practical correction layer for low-cost attenuation measurements.

  İncele
• MakaleYalnız künye2026/r/gumushane/13514
  Blue-Shift Effect-Based Positioning for Multi-Color VLC

  Kucuk, Mehmet Ali; Turk, Kadir

  In this letter, an angle-of-arrival (AoA)-based integrated positioning system is proposed that utilizes the standard optical front-end of multi-color visible light communication (MC-VLC). Unlike traditional AoA methods, which rely on specialized receiver architectures, the proposed approach uses the inherent angular dependence of optical filter transmission responses, known as the blue-shift effect, for directly estimating the angle of incidence from the received signal. In this context, an AoA estimation technique is developed by combining eigenvalue decomposition of the MC-VLC channel with regression analysis. Simulation results show that the proposed system achieves millimeter-level positioning accuracy, enabling robust and high-precision indoor localization without additional hardware complexity or cost.

  İncele
• MakaleAçık Erişim2025/r/gumushane/11734
  Energy-Efficient 8-PAM Optical DAC Design for Visible Light Communication Systems

  Başer, Oğuzhan; Küçük, Mehmet Ali; Albayrak, Cenk; Türk, Kadir

  This paper presents a cost-effective and energy-efficient optical digital-to-analog converter (ODAC) transmitter scheme for visible light communication (VLC) systems. The proposed ODAC transmitter enables data transmission while providing lighting, as desired in VLC systems, unlike existing ODAC structures in the literature, by switching power LEDs at high speeds with a MOSFET-based switching circuit design. This paper also discusses the ODAC design stages and presents the points to be considered in detail. In addition, by implementing the hardware design of an ODAC transmitter with a 3-bit resolution, that is, capable of generating 8-PAM signals, based on the proposed ODAC architecture, experimental studies are conducted for energy efficiency and communication performance results via the established VLC system using the designed ODAC. Experimental results demonstrate that the proposed ODAC transmitter achieves a data transmission rate of 18.75 Mbps with a bit error rate (BER) below the forward error correction (FEC) limit at a communication distance of 4 m, while also exhibiting a high power efficiency of 94%.

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  İncele
• BildiriAçık Erişim2024/r/gumushane/16830
  Experimental Demonstration of an Optic-DAC Based Transmitter Structure

  Baser, Oguzhan; Küçük, Mehmet Ali; Albayrak, Cenk; Türk, Kadir

  In this paper, an optical-DAC (ODAC) based transmitter design is proposed for indoor visible light communication (VLC) applications. The proposed design is practically realized and the communication performance of the experimental VLC system is investigated. In the ODAC transmitter, multilevel communication signal can be generated optically by independently switching light emitting diode (LED) groups with different powers. In this way, multilevel modulation techniques in VLC systems can be realized through a simple transmitter structure that can be digitally driven. In the proposed transmitter design, unlike the existing ODAC-based VLC transmitters in the literature, metal oxide semiconductor field effect transistors (MOSFET) are used as switching elements in order to drive high-power LED for ambient illumination and communication. In the experimental studies, an offline VLC system using the designed ODAC-based transmitter with a power of approximately 10 W is tested at different switching speeds and distances. The results show that by implementing 8 PAM modulation in the proposed transmitter design, a data transmission rate of 6.264 Mbps is successfully achieved.

  İncele
• BildiriAçık Erişim2024/r/gumushane/16809
  Reconfigurable Optical Filter Based Receiver Structure For Visible Light Communication

  Küçük, Mehmet Ali; Albayrak, Cenk; Türk, Kadir

  In this paper, a novel receiver structure is proposed to mitigate the inter-channel interference (ICI) effects that limit the data rate in multi-color visible light communication (MC-VLC) systems. Reconfigurable optical filters (ROFs) are used at the receiver side of MC-VLC systems to enable the separation of color channels. ROFs are optical elements that have the ability to electrically change their transmission spectrum. Utilizing this feature of ROFs, a receiver structure is developed that, unlike traditional receiver structures, can adaptively adjust the transmit spectrum based on channel state information. This adaptive adjustment is aimed at maximizing communication performance by effectively separating color channels in MC-VLC systems. The obtained results demonstrate that the proposed receiver structure achieves higher communication performance compared to traditional receivers.

  İncele
• MakaleAçık Erişim2024/r/gumushane/11467
  Optical Filter Design for Multi-Color VLC in Reflective Environments with Multiple Lighting Sources

  Kucuk, Mehmet A.; Albayrak, Cenk; Turk, Kadir; Yanikomeroglu, Halim

  Multi-color visible light communication (MC-VLC) systems, which aim to transmit data in parallel with multi-color LEDs, use optical filters to separate color channels at the receiver side. However, the relatively wide spectrum of LEDs may cause inter-color interference (ICI). In addition, the passband of the optical filters shifts towards the blue wavelength depending on the angle of incidence (AoI) of the light, which may also increase ICI. In this paper, the problem of designing optical filters for MC-VLC systems in the presence of the blue-shift is investigated. The communication environment is assumed to be a typical room illuminated by multiple fixtures in accordance with lighting standards. Moreover, the walls in the room are reflective, resulting in non-line-of-sight (NLoS) components. The passband edges of the optical filter are optimized to maximize the average signal-to-interference-plus-noise ratio (SINR). The effect of the field-of-view (FOV) of the receiver on the system performance is also analyzed. Finally, a generic optical filter has been designed that can be used in standards-compliant environments for selected LEDs and a given FOV range. The results show that the designed optical filter provides a higher and uniform capacity than those in the literature.

  İncele
• BildiriYalnız künye2023/r/gumushane/12773
  Pedestrian Inertial Navigation with Multi-Head CNN

  Cetin, Gokhan; Kucuk, Mehmet Ali; Koroglu, Muhammed Taha

  Traditional pedestrian dead-reckoning (DR) methods utilizing inertial measurement units (IMU) have been successfully employed in GPS-denied environments over the past two decades. However, despite continuous advancements in wearable IMU technology, the long-term solution still suffers from the issue of drift. In light of this, Deep Learning (DL) has emerged as a potential candidate for inertial navigation solutions, leveraging its powerful non-linear regression capabilities. Recent research has demonstrated that DL models trained on public datasets can effectively serve as end-to-end solutions. Most studies focus on smartphones, where the IMU is typically situated at the torso, and generally work with transformed data represented in the navigation coordinate frame to estimate pedestrian velocity and heading change at rates lower than the IMU sampling rate. In contrast, this study uses raw foot-mounted IMU data as input to a multi-headed structure consisting of independent convolutional neural networks (CNNs) and targets displacement directly and heading change. The proposed model is trained on a publicly available foot-mounted IMU dataset where pseudo ground-truth (GT) data is generated heuristically to provide supervision for the learning process. The results indicate that the Multi-Head CNN (MHCNN) model is capable of producing pedestrian trajectories at the IMU sampling rate, with positioning errors of less than 2m throughout the duration of the walks. The code for the trained network can be accessed in the associated repository, i.e., github.com/mtkoroglu/PIN-MHCNN.

  İncele
• MakaleYalnız künye2021/r/gumushane/14647
  Performance evaluation of IEEE 802.15.7 CSK modulation under blue shift effect of optical receiver filters

  Küçük, Mehmet Ali; Türk, Kadir

  In recent years, the use of light-emitting diodes (LEDs) in lighting, which has higher energy efficiency and longer-lasting environmentally friendly lighting compared to conventional lighting devices, has accelerated the development of a promising new technology for short-range wireless optical transmission called visible light communication (VLC). Besides other applications, VLC switches the LEDs at very high speeds to simultaneously realize indoor lighting and data transmission. But the intensity and color of the lighting may vary because of data transmission. Color shift keying (CSK) modulation defined in the IEEE 802.15.7 VLC standard guarantees constant light intensity and color. The CSK receiver uses a band-pass optical filter to separate the light channels. However, the transition band of optical filters shifts towards the blue wavelength depending on the incidence angle of the light which is called the blue shift effect. In this paper, the performance of the CSK receiver is investigated for the first time under the blue shift effect in the case of single and multiple transmitter LED cells. The numerical results show that the blue shift effect significantly decreases system performance. To eliminate the distorting effect, various methods and an adaptive equalizer-based CSK receiver are proposed. The proposed structures provide notable improvement.

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