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Gürbilek, Gökhan

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Gökhan

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Gürbilek

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2018 - 201952020 - 20234

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Researcher Of Publications: search.filters.isAuthorOfPublication.175a0b65-15fe-4073-aba1-523f77fa7066

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Now showing 1 - 9 of 9
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    Vehicular networks for combating a worldwide pandemic: preventing the spread of COVID-19
    (Elsevier, 2022) Elbir, Ahmet M.; Papazafeiropoulos, Anastasios K.; Kourtessis, Pandelis; Department of Electrical and Electronics Engineering; N/A; N/A; Department of Electrical and Electronics Engineering; Ergen, Sinem Çöleri; Gürbilek, Gökhan; Soner, Burak; Faculty Member; PhD Student; PhD Student; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; 7211; N/A; N/A
    As a worldwide pandemic, the coronavirus disease-19 (COVID-19) has caused serious restrictions in people's social life, along with the loss of lives, the collapse of economies and the disruption of humanitarian aids. Despite the advance of technological developments, we, as researchers, have witnessed that several issues need further investigation for a better response to a pandemic outbreak. Therefore, researchers recently started developing ideas to stop or at least reduce the spread of the pandemic. While there have been some prior works on wireless networks for combating a pandemic scenario, vehicular networks and their potential bottlenecks have not yet been fully examined. Furthermore, the vehicular scenarios can be identified as the locations, where the social distancing is mostly violated. With this motivation, this article provides an extensive discussion on vehicular networking for combating a pandemic. We provide the major applications of vehicular networking for combating COVID-19 in public transportation, in-vehicle diagnosis, border patrol and social distance monitoring. Next, we identify the unique characteristics of the collected data in terms of privacy, flexibility and coverage, then highlight corresponding future directions in privacy preservation, resource allocation, data caching and data routing. We believe that this work paves the way for the development of new products and algorithms that can facilitate the social life and help controlling the spread of the pandemic.
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    Location-aware adaptive physical layer design for vehicular visible light communication
    (IEEE, 2019) Department of Electrical and Electronics Engineering; N/A; N/A; N/A; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Gürbilek, Gökhan; Koca, Mertkan; Uyrus, Ali; Soner, Burak; Başar, Ertuğrul; Ergen, Sinem Çöleri; Researcher; Master Student; PhD Student; PhD Student; Faculty Member; Faculty Member; College of Sciences; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; N/A; N/A; N/A; 149116; 7211
    Vehicular visible light communication (V2LC) is expected to complement radio frequency (RF) technologies for higher reliability in vehicular connectivity. Since high mobility makes the line-of-sight V2LC channel very dynamic, an adaptive physical layer (PHY) design is required for realizing a rate-optimal and reliable V2LC system. Existing studies on adaptive PHY designs have mostly considered indoor scenarios with low mobility and require a feedback channel for both reporting the received signal-to-noise ratio (SNR) to the transmitter and channel equalization (CE), which increases system complexity and introduces overhead. This paper presents a novel low-complexity adaptive PHY design that provides rate-optimal and reliable V2LC without a feedback channel. The proposed design utilizes a priori measurements of the BER with respect to SNR, which are static for V2LC on the road. SNR is predicted in real-time based on the relative locations of the transmitting (TX) and receiving (RX) vehicles using a path loss model based on a priori measurements of the SNR-distance relationship and the polar beam pattern for a given TX/RX pair, in a given setting. The proposed design is validated via night-time experiments with On-Off-Keying (OOK), 4-Pulse-Position Modulation (4-PPM) and Direct Current-Biased Optical OFDM (DCO-OFDM). The proposed location-aware adaptive PHY design can be expanded for general reliable rate-optimal V2LC use by updating the path loss model with additional measurements for different settings.
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    mmWave channel model for intra-vehicular wireless sensor networks
    (Elsevier, 2022) N/A; N/A; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Koca, Mertkan; Gürbilek, Gökhan; Ergen, Sinem Çöleri; Master Student; Researcher; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; N/A; 7211
    Intra-vehicular wireless sensor networks (IVWSNs) have significant potential to reduce part, manufacturing and repair costs, facilitate the integration of new nodes and provide more freedom for the sensor placement in previously impossible locations by obviating the need for wiring harness. mmWave stands up as a promising candidate to fulfill the high reliability, security and low latency requirements of IVWSNs, exploiting the availability of large bandwidth at high frequencies and high nominal gains with directional antennas while attenuating through the car body significantly. This work focuses on building a mmWave channel model for IVWSNs. The model is built for the engine compartment, passenger compartment and beneath the chassis of a vehicle by conducting vast number of measurements for 14 x 14, 13 x 13 and 15 x 15 transmitter and receiver links in a Fiat Linea, respectively. The path loss exponent is approximately 3, showing almost no variation within different compartments. The power variation around the path loss model has a Generalized Extreme Value (GEV) distribution with zero mean for all compartments and 5 dB standard deviation for the engine compartment and approximately 7.6 dB standard deviation for the other two compartments. A modified Saleh-Valenzuela (SV) model is used to represent the clustering of power delay profiles (PDPs). Log-normal distribution is used to model the inter-arrival times of clusters, while the dependencies of cluster amplitude and ray decay rate on the cluster arrival times are represented by a dual slope linear fit model with breakpoints 1.2 ns and 5.6 ns for engine compartment, respectively, and 1.6 ns and 2.6 ns for the other two compartments, respectively. The experimental PDPs vary around the SV model and these variations are represented by a normal distribution with zero mean and 5.8 dB standard deviation, which is independent of both the delay bins and the compartment of the vehicle. All these findings are used to build a simulation model for each compartment of the vehicle. The simulation model is validated by comparing the distributions of the received powers and Root Mean Square (RMS) delay spreads of the experimental and simulated PDPs.
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    Empirical feasibility analysis for energy harvesting intravehicular wireless sensor networks
    (Ieee-Inst Electrical Electronics Engineers Inc, 2021) N/A; N/A; Department of Electrical and Electronics Engineering; N/A; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Koca, Mertkan; Gürbilek, Gökhan; Soner, Burak; Ergen, Sinem Çöleri; Master Student; Researcher; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; 7211
    Vehicle systems currently utilize wired networks for power delivery and communication between nodes. Wired networks cannot practically accommodate nodes in moving parts and with the increasing functional complexity in vehicles, they require kilometer-long harnesses, significantly increasing fuel consumption, manufacturing, and design costs. Alternatively, energy harvesting intravehicular wireless sensor networks (IVWSNs) can accommodate nodes in all locations and they obviate the need for wiring, significantly lowering costs. This article empirically analyzes the feasibility of such an IVWSN framework via extensive in-vehicle measurements for communications at 2.4 GHz, ultrawideband (UWB), and millimeter-wave (mmWave) together with radio frequency (RF), thermal, and vibration energy harvesting. Our analyses indicate mmWave performs best for short Line-of-Sight (LoS) links in the engine compartment with performance close to UWB for LoS links in the chassis and passenger compartments considering worst case signal-to-interference-and-noise ratio (SINR). For non-LoS links, which appear mostly in the engine compartment and chassis, UWB provides the highest security and reliability. 2.4 GHz suffers heavily from interference in all compartments while UWB utilizes narrowband suppression techniques at the cost of lower bandwidth; mmWave inherently experiences very low interference due to its propagation characteristics. On the other hand, RF energy harvesting provides up to 1 mW of power in all compartments. Vibration and thermal energy harvesters can supply nodes consuming <10 mW in the engine compartment and <5 mW nodes in the chassis. In the passenger compartment, thermal harvesting is not available due to low temperature gradients, but vibration and RF sources can supply <1 mW nodes.
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    Poster: vehicular VLC experimental modulation performance comparison
    (Ieee, 2018) Department of Electrical and Electronics Engineering; N/A; N/A; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Gürbilek, Gökhan; Koca, Mertkan; Turan, Buğra; Ergen, Sinem Çöleri; Researcher; Master Student; PhD Student; Faculty Member; College of Sciences; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; 7211
    Vehicular visible light communication (V2LC) has recently gained popularity as a complementary technology to radio frequency (RF) based vehicular communication schemes due to light emitting diode (LED) s' readily availability on vehicles with its secure and RF-interference free nature. However, vehicular visible light communication (V2LC) system performance mainly depends on LED characteristics. Investigating various LED bulbs for their frequency response and optical OFDM (O-OFDM) based modulation performances, it has been observed that LED and DC-bias voltage selection is key for the V2LC system modulation performance. Experimental results indicate that, on contrary to simulation results in the literature, asymmetrically clipped optical OFDM (ACO-OFDM) is observed to perform better than unipolar OFDM (U-OFDM) as it inherits lower peak-to-average power ratio (PAPR) with lower clipping noise which is crucial for LEDs under consideration with limited linear working region.
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    Vehicular VLC frequency domain channel sounding and characterization
    (IEEE, 2018) N/A; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Turan, Buğra; Gürbilek, Gökhan; Uyrus, Ali; Ergen, Sinem Çöleri; PhD Student; Researcher; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; 7211
    Vehicular visible light communication (V2LC) has recently gained popularity as a complementary technology to radio frequency (RF) based vehicular communication schemes due to its low-cost, secure and RF-interference free nature. In this paper, we propose outdoor vehicular visible light communication (V2LC) frequency domain channel sounding based channel model characterization under night, sunset and sun conditions with the usage of vector network analyzer (VNA) and commercial off-the-shelf (COTS) automotive light emitting diode (LED) light. We further bring forward a new practical system bandwidth criterion named as effective usable bandwidth (EUB) for an end-to-end V2LC system with respect to the real world measurements. We demonstrate outdoor static V2LC channel measurement results, taking into account vehicle light emitting diode (LED) response, road reflections from nearby vehicles and various daylight conditions with respect to varying inter-vehicular distances. Measurement results indicate that, sunlight decreases system effective usable bandwidth due to the limited dynamic range of avalanche photodiode (APD), nearby vehicles cause constructive interference whereas road reflections change time dispersion characteristics of the V2LC channel.
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    Blind channel estimation for DCO-OFDM based vehicular visible light communication
    (Elsevier B.V., 2023) Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; N/A; Department of Electrical and Electronics Engineering; Ergen, Sinem Çöleri; Gürbilek, Gökhan; Koca, Mertkan; Faculty Member; Researcher; Master Student; College of Engineering; College of Engineering; Graduate School of Sciences and Engineering; 7211; N/A; N/A
    Blind channel estimation (CE) methods for OFDM based RF communication provide high-rate transmission by eliminating pilot overhead in conventional pilot-based methods, at the cost of lower accuracy. However, there is no work on the blind CE for OFDM based visible light communication (VLC) systems. In this paper, we propose a novel blind CE method for vehicular VLC with the goal of improving CE accuracy based on the exploitation of the channel statistics derived, by utilizing extensive amount of data collected for different communication angles, distances, and ambient light conditions. First, the normalized channel frequency response (CFR) of the V2LC channel is demonstrated to be invariant of inter-vehicular distance, relative transmitter/receiver zenith angle and ambient light. Then, this channel characteristic is exploited in the blind CE to improve its accuracy with two-step estimation of normalization factor. Extensive simulations at different vehicle speeds show that the proposed method outperforms the pilot-based and superimposed training-based CE methods in terms of spectral efficiency both for all modulation schemes and at all relative speeds. The proposed blind channel estimation (CE) method provides 9.77% increase in the spectral efficiency, compared to the second best method, superimposed training-based CE, at 20 dB signal-to-noise ratio (SNR) and 160 km/h relative speed, for 64-Quadrature Amplitude Modulation (QAM) Direct Current-Biased Optical Orthogonal Frequency Division Multiplexing (DCO-OFDM). Moreover, the real-time performance of the proposed blind CE is demonstrated for a realistic vehicle mobility scenario extracted from SUMO. © 2022 Elsevier B.V.
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    PublicationOpen Access
    Location-aware adaptive physical layer design for vehicular visible light communication
    (Institute of Electrical and Electronics Engineers (IEEE), 2019) Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Gürbilek, Gökhan; Koca, Mertkan; Uyrus, Ali; Soner, Burak; Ergen, Sinem Çöleri; Başar, Ertuğrul; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; N/A; 7211; 149116
    Vehicular visible light communication (V2LC) is expected to complement radio frequency (RF) technologies for higher reliability in vehicular connectivity. Since high mobility makes the line-of-sight V2LC channel very dynamic, an adaptive physical layer (PHY) design is required for realizing a rate-optimal and reliable V2LC system. Existing studies on adaptive PHY designs have mostly considered indoor scenarios with low mobility and require a feedback channel for both reporting the received signal-to-noise ratio (SNR) to the transmitter and channel equalization (CE), which increases system complexity and introduces overhead. This paper presents a novel low-complexity adaptive PHY design that provides rate-optimal and reliable V2LC without a feedback channel. The proposed design utilizes a priori measurements of the BER with respect to SNR, which are static for V2LC on the road. SNR is predicted in real-time based on the relative locations of the transmitting (TX) and receiving (RX) vehicles using a path loss model based on a priori measurements of the SNR-distance relationship and the polar beam pattern for a given TX/RX pair, in a given setting. The proposed design is validated via night-time experiments with On-Off-Keying (OOK), 4-Pulse-Position Modulation (4-PPM) and Direct Current-Biased Optical OFDM (DCO-OFDM). The proposed location-aware adaptive PHY design can be expanded for general reliable rate-optimal V2LC use by updating the path loss model with additional measurements for different settings.
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    PublicationOpen Access
    Vehicular VLC frequency domain channel sounding and characterization
    (Institute of Electrical and Electronics Engineers (IEEE), 2018) Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Ergen, Sinem Çöleri; Turan, Buğra; Uyrus, Ali; Gürbilek, Gökhan; Faculty Member; Other; PhD Student; Graduate School of Sciences and Engineering; 7211; N/A; N/A; N/A
    Vehicular visible light communication (V2LC) has recently gained popularity as a complementary technology to radio frequency (RF) based vehicular communication schemes due to its low-cost, secure and RF-interference free nature. In this paper, we propose outdoor vehicular visible light communication (V2LC) frequency domain channel sounding based channel model characterization under night, sunset and sun conditions with the usage of vector network analyzer (VNA) and commercial off-the-shelf (COTS) automotive light emitting diode (LED) light. We further bring forward a new practical system bandwidth criterion named as effective usable bandwidth (EUB) for an end-to-end V2LC system with respect to the real world measurements. We demonstrate outdoor static V2LC channel measurement results, taking into account vehicle light emitting diode (LED) response, road reflections from nearby vehicles and various daylight conditions with respect to varying inter-vehicular distances. Measurement results indicate that, sunlight decreases system effective usable bandwidth due to the limited dynamic range of avalanche photodiode (APD), nearby vehicles cause constructive interference whereas road reflections change time dispersion characteristics of the V2LC channel.