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ELAMASSIE, Mohammed

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Mohammed

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ELAMASSIE
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Now showing 1 - 10 of 34
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    Vehicular VLC system with selection combining
    (IEEE, 2022-11) Mohamed, Bassam Aly Abdelrahman; Elamassie, Mohammed; Uysal, Murat; Electrical & Electronics Engineering; ELAMASSIE, Mohammed; UYSAL, Murat; Mohamed, Bassam Aly Abdelrahman
    The availability of LED-based headlights and taillights makes possible the use of visible light communication (VLC) as a wireless access technology for vehicle-to-vehicle (V2V) communications. A critical concern to establish a reliable VLC link between two moving vehicles is the number of photodetectors and their locations on the destination vehicle. In this paper, we experimentally investigate the usage of dual photodetectors for a vehicular VLC system with selection combining to enhance signal reception in mobile conditions. We measure the electrical receive signal-to-noise ratio (SNR) for each individual photodetector as well as at the output of selection combiner in two different tracks involving straight and curved roads. Through data fitting to experimental data, we obtain a probability density function (PDF) to describe the instantaneous SNR. Based on the PDF, we derive a closed-form expression for the average bit error rate (BER) in the form of a finite summation and compare it with the measurements.
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    Vehicular visible light communication with low beam transmitters in the presence of vertical oscillation
    (IEEE, 2023-08) Mohamed, Bassam Aly Abdelrahman; Elamassie, Mohammed; Uysal, Murat; Electrical & Electronics Engineering; ELAMASSIE, Mohammed; UYSAL, Murat; Mohamed, Bassam Aly Abdelrahman
    The availability of light-emitting diodes (LEDs) in vehicle exteriors makes possible the use of visible light communication (VLC) as a vehicle-to-vehicle (V2V) wireless connectivity solution. While there has been a growing literature on vehicular VLC, the existing works inherently assume the deployment of regular passenger vehicles. In this paper, we consider the use of VLC for vehicular connectivity between heavy vehicles such as trucks. We assume that low beam headlights are used as transmitters. Due to the nature and function of vehicular low beam lighting, the upward distribution of lighting is fundamentally different from its downward distribution. Hence, the vertical displacement (i.e., the height difference between transmitter and receiver) and the vertical oscillation experienced by heavy vehicles might significantly impact the VLC link. Based on experimental measurements, we first propose an accurate path loss model that takes into account the effect of vertical displacement and oscillation. Then, we derive a bit error rate (BER) expression for VLC-based truck-to-truck communication system and investigate the effect of several system and channel parameters on the performance. In an attempt to mitigate the degrading effects of the vertical oscillation, we further investigate the proper selection of photodetector location to minimize the error rate performance.
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    An experimental study of underwater visible light communication
    (IEEE, 2022) Yıldız, Samet; Baǧlıca, İbrahim; Kebapçı, B.; Elamassie, Mohammed; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; ELAMASSIE, Mohammed; Yıldız, Samet; Baǧlıca, İbrahim
    Visible light communication (VLC) has emerged as a powerful high-data-rate alternative to conventional underwater acoustic technology for short and medium link distances. In this paper, we develop an experimental underwater VLC platform and present some initial performance results. Our set-up uses prerecorded voltage levels fed in the arbitrary waveform generator (AWG) at the transmitter side while an oscilloscope is used to measure the received electrical signal after photodetection. To speed up debugging and troubleshooting, both transmitter and receiver sides are connected to a controller PC. The test instruments are controlled via Standard Commands for Programmable Instruments (SCPI) commands executed by this controller computer with a Python code. Using this set-up, we demonstrate the successful transmission of 8-PAM symbols over an 8-meter-long underwater tank.
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    Bit-error-rate performance of an underwater wireless optical link under misalignment and turbulence effects
    (IEEE, 2022) Ijeh, I. C.; Khalighi, M. A.; Elamassie, Mohammed; Hranilovic, S.; Uysal, Murat; Electrical & Electronics Engineering; ELAMASSIE, Mohammed; UYSAL, Murat
    Underwater wireless optical communication (UWOC) links are highly susceptible to the degrading effects of oceanic turbulence and beam misalignment. In this paper, considering a silicon photo-multiplier at the receiver, we evaluate the link average bit-error rate (BER) performance, where an analytical expression is derived for its calculation, validated further by means of numerical simulations. We further investigate the impact of different system parameters on the link average BER.
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    Experimental investigation of lens combinations on the performance of vehicular VLC
    (IEEE, 2020) Mohamed, Bassam Aly Abdelrahman; Elamassie, Mohammed; Eldeeb, Hossıen Badr; Uysal, Murat; Electrical & Electronics Engineering; ELAMASSIE, Mohammed; ELDEEB, Hossien Badr Hossien; UYSAL, Murat; Mohamed, Bassam Aly Abdelrahman
    With the increasing adoption of LEDs in outdoor light sources such as traffic lights, street lights and vehicle headlamps, visible light communication (VLC) has the promise to become a major enabler for vehicle-to-vehicle and vehicle-to-infrastructure communications. In this paper, we experimentally investigate the effect of using different lens combinations on vehicular VLC systems in outdoor environments. First, we measure the effective channel coefficient which includes the effect of both front-ends and propagation channel. Then, based on the estimated channel coefficients, we characterize the vehicular system performance in terms of signal-to-noise ratio and quantify improvements from utilizing different lens combinations.
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    Reflector-aided underwater optical channel modeling
    (Optica Publishing Group, 2022-10-15) Yıldız, Samet; Bağlıca, İbrahim; Kebapçı, Burak; Elamassie, Mohammed; Uysal, Murat; Electrical & Electronics Engineering; ELAMASSIE, Mohammed; UYSAL, Murat; Yıldız, Samet; Bağlıca, İbrahim; Kebapçı, Burak
    Underwater visible light communication (UVLC) has been proposed as a high-speed alternative to acoustic signaling. While most UVLC systems are configured to work in line-of-sight (LOS) conditions, it is also possible to exploit reflected signals for performance enhancements. In this Letter, we propose a closed-form expression for the underwater path loss assuming non-LOS (NLOS) transmission through the water surface and man-made reflector (e.g., mirror) in addition to the LOS link. Utilizing the derived expression, we quantify the achievable NLOS gain defined as the ratio between the maximum achievable channel coefficient from reflection and the overall channel coefficient. We validate our findings experimentally by utilizing the water surface and the mirror as the reflecting surfaces in an aquarium. Our results reveal that achievable gains up to around 3 dB can be observed due to reflections.
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    Analysis and optimization of the network throughput in IEEE 802.15.13 based visible light communication networks
    (IEEE, 2021) Bülbül, Yusuf; Elamassie, Mohammed; Baykas, T.; Uysal, Murat; Electrical & Electronics Engineering; ELAMASSIE, Mohammed; UYSAL, Murat; Bülbül, Yusuf
    In line with the growing interest on visible light communication (VLC), IEEE has initiated standardization efforts on this emerging technology. In this work, we consider IEEE 802.15.13 Optical Wireless Personal Area Networks (OWPAN) standard draft. The underlying MAC protocol uses contention free and contention access periods. For a standard-compliant VLC network, we analyze the network load and propose an algorithm to improve the network throughput by proper selection of period lengths. Our suggested algorithm improves the network performance by at least 5% in the case of variable network traffic up to 15 active users.
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    Feedback-free adaptive modulation selection algorithm for FSO systems
    (IEEE, 2021-09) Elamassie, Mohammed; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; ELAMASSIE, Mohammed
    Free space optical (FSO) communication systems experience turbulence-induced fading. As a possible solution to mitigate the effects of fading, adaptive transmission that allows the adjustment of transmission parameters such as transmit power and modulation size can be used. Most of the existing works on adaptive FSO systems assume the presence of full channel state information (CSI) at the transmitter side. In practice, incomplete/outdated CSI may prevent the complete extraction of the theoretical gain expected from adaptive systems. In this letter, to avoid the difficulties associated with feedback, we propose a feedback-free adaptive modulation selection algorithm for FSO systems. We formulate the design as an optimization problem where average throughput is maximized by selecting the largest modulation order under the constraint that the required transmit power for a targeted bit error rate (BER) value does not exceed the maximum transmit power. We further present numerical results to confirm the superiority of the proposed adaptive algorithm.
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    Pilot-aided channel estimation for RIS-assisted wireless systems over time-varying fading channels
    (IEEE, 2023) Azizzadeh, Maryam; Elamassie, Mohammed; Uysal, Murat; Electrical & Electronics Engineering; ELAMASSIE, Mohammed; UYSAL, Murat; Azizzadeh, Maryam
    Reconfigurable intelligent surfaces (RISs) have emerged as a promising technology for improving wireless communication system performance. RISs can adjust signals' phase and amplitude, resulting in improved signal strength. In this paper, we investigate the performance of pilot-aided channel estimation for a RIS-assisted wireless communication system over time-varying fading channels. We present numerical results on the effect of the number of pilots and the percentage of pilots per frame on the bit error rate performance.
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    Outage performance analysis of vertical underwater VLC links
    (IEEE, 2022) Elamassie, Mohammed; Uysal, Murat; Electrical & Electronics Engineering; ELAMASSIE, Mohammed; UYSAL, Murat
    In this paper, we investigate the outage performance of vertical stratified underwater optical links in the presence of moderate/strong turbulence conditions. Specifically, we consider the cascaded Gamma-Gamma turbulence channel model and derive a closed-form expression for outage probability. We then use our derived expression to investigate the achievable diversity order (DO) and asymptotic diversity order (ADO). We further confirm our derivations through Monte Carlo simulations.