Browsing by Author "Elamassie, Mohammed"

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Adaptive DCO-OFDM for underwater visible light communications
(IEEE, 2019-04) Elamassie, Mohammed; Karbalayghareh, Mehdi; Miramirkhani, Farshad; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Elamassie, Mohammed; Karbalayghareh, Mehdi; Miramirkhani, Farshad
Visible light communication (VLC) has been introduced as a complementary technology to acoustic communications for underwater applications. Underwater VLC can achieve much higher data rates sufficiently high for real-time image and video transmission. Such high data rates over underwater channels with frequency-selectivity necessitate the use of efficient multi-carrier techniques such as orthogonal frequency division multiplexing. In this paper, we consider an adaptive DC-biased optical OFDM (DCO-OFDM) underwater VLC system. The design of adaptive algorithm is formulated to maximize the throughput under error rate performance constraints. The receiver first calculates the signal-to-noise ratio (SNR) per each subcarrier. Then, based on SNR information, it determines which subcarrier should be loaded first and selects the maximum constellation size for each subcarrier while satisfying a predefined targeted bit error rate (BER). Our simulation results demonstrated that significant improvements in throughput can be obtained through link adaptation.
Open Access
Adaptive OFDM-based acoustic underwater transmission: system design and experimental verification
(IEEE, 2017) Sadeghi, Mohammad; Elamassie, Mohammed; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Sadeghi, Mohammad; Elamassie, Mohammed
In this paper, we present the design and implementation of a software defined orthogonal frequency division multiplexing (OFDM)-based underwater acoustic (UWA) communication system with link adaptation. Our system implementation is based on the customized versions of National Instruments Universal Software Radio Peripheral (USRP). The modified USRPs are interfaced with hydrophone front-ends for acoustic transmission. We investigate the performance of various adaptive algorithms where both modulation order/type and power on each subcarrier are selected based on channel conditions in order to maximize throughput. The experimental in-pool test results verify the superiority of adaptive transmission.
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Aerosol attenuation model for high altitude UAV-based FSO links
(IEEE, 2022) Elamassie, Mohammed; Uysal, Murat; Electrical & Electronics Engineering; ELAMASSIE, Mohammed; UYSAL, Murat
Free space optical (FSO) communication is well positioned to address connectivity needs in ground-UAV, inter-UAV and UAV-ground links. An accurate performance analysis of airborne FSO links requires the use of proper path loss models. While earlier studies have successfully modeled attenuation arising from rain, drizzle, fog, and snow, aerosols have received less attention. Aerosols are tiny particles suspended in the atmosphere. They can be found drifting in Earth's atmosphere from the stratosphere to the troposphere to the Earth's surface. In this paper, we conduct extensive simulations in MODTRAN to determine the extinction coefficient values for aerosol over the wavelength from 350 nm to 1550 nm including typical wavelengths (e.g., 690 nm, 780nm, 850nm, and 1550 nm) used in commercial FSO systems. Non-linear curve fitting is then used to obtain new closed-form expressions for extinction coefficients.
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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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Asymptotic performance of generalized transmit laser selection over lognormal turbulence channels
(IEEE, 2020-08) Elamassie, Mohammed; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Elamassie, Mohammed
In free space optical communication systems, transmit laser selection (TLS) has been proposed as an efficient fading-mitigation technique over turbulence channels. In TLS, the transmitter is equipped with a number of laser sources and the best laser source is selected for transmission. In practice, feedback error or outdated selection due to temporal changes in the channel may result in selecting another source rather than the best one. In this letter, we consider a FSOC system with generalized TLS (GTLS) where the nth best laser is selected among the available N lasers. Under the assumption of lognormal turbulence channels in addition to pointing errors, we derive a closed-form expression for asymptotic bit error rate. We use our derived closed-form expression to determine the diversity gains. We finally present simulation results to corroborate our analytical findings.
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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.
Open Access
Capacity analysis of NOMA-enabled underwater VLC networks
(IEEE, 2021) Elamassie, Mohammed; Bariah, L.; Uysal, Murat; Muhaidat, S.; Sofotasios, P. C.; Electrical & Electronics Engineering; ELAMASSIE, Mohammed; UYSAL, Murat
Visible light communication (VLC) has recently emerged as an enabling technology for high capacity underwater wireless sensor networks. Non-orthogonal multiple access (NOMA) has been also proven capable of handling a massive number of sensor nodes while increasing the sum capacity. In this paper, we consider a VLC-based underwater sensor network where a clusterhead communicates with several underwater sensor nodes based on NOMA. We derive a closed-form expression for the NOMA system capacity over underwater turbulence channels modeled by lognormal distribution. NOMA sum capacity in the absence of underwater optical turbulence is also considered as a benchmark. Our results reveal that the overall capacity of NOMA-enabled Underwater VLC networks is significantly affected by the propagation distance in underwater environments. As a result, effective wireless transmission at high and moderate spectral efficiency levels can be practically achieved in underwater environments only in the context of local area networks. Moreover, we compare the achievable capacity of NOMA system with its counterpart, i.e., orthogonal frequency division multiple access (OFDMA). Our results reveal that NOMA system is not only characterized by achieving higher sum capacity than the sum capacity of its counterpart, OFDMA system. It is also shown that the distances between sensor nodes and the clusterhead for achieving the highest sum capacity in these two multiple access systems are different.
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Channel modeling and performance characterization of underwater visible light communications
(IEEE, 2018-07-03) Elamassie, Mohammed; Miramirkhani, Farshad; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Elamassie, Mohammed; Miramirkhani, Farshad
Underwater visible light communication (UVLC) has emerged as an attractive complementary solution to long-range acoustic communication and is able to achieve much higher data speeds. In this paper, we investigate the transmission range limits of UVLC systems. We first develop a closed-form path loss expression as a function of transceiver parameters and the water type. We then utilize this new expression to determine the maximum achievable link distance for UVLC systems while satisfying a specified bit error rate. Finally, we provide extensive numerical results to demonstrate the achievable distances in pure sea, clear ocean, coastal water and harbor water.
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Characterization of orbital angular momentum-multiplexed FSO channel in the presence of pointing errors
(IEEE, 2023) Elamassie, Mohammed; Tadayyoni, Hamed; Uysal, Murat; Electrical & Electronics Engineering; ELAMASSIE, Mohammed; UYSAL, Murat; Tadayyoni, Hamed
Free space optical communication (FSO) uses laser transmitters at near-infrared wavelengths for line-of-sight wireless communication. Through the use of advanced laser beams instead of the conventional Gaussian-shaped beam, orbital angular momentum (OAM) allows taking advantage of higher degrees of freedom in the FSO link design. OAM enables the simultaneous transmission of multiple data streams due to the orthogonality between beams of different spatial modes. However, in practice, atmospheric turbulence and pointing errors may destroy the orthogonality. Pointing errors may result in crosstalk between modes and power disparities as a result of shifting the received beam. In this paper, we consider Laguerre-Gaussian beams and investigate the effect of random pointing errors on crosstalk coefficients.
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Diversity gain analysis of underwater vertical MIMO VLC links in the presence of turbulence
(IEEE, 2019) Yılmaz, Anıl; Elamassie, Mohammed; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Yılmaz, Anıl; Elamassie, Mohammed
To satisfy the demands of high data rate underwater applications such as image and real-time video transmission, underwater visible light communication (UVLC) has emerged as an alternative to acoustic signaling. One of the major impairments in UVLC systems is turbulence-induced fading as a result of temporal variations in temperature and salinity. Furthermore, unlike the horizontal links modeled with fixed turbulence strength, vertical links experience varying turbulence strength based on the depth-dependent temperature and salinity profiles. In this paper, we consider a multiple-input multiple-output (MIMO) UVLC link over a vertical turbulence channel which is modeled as the concatenation of multiple non-mixing layers. Under the assumption of cascaded log-normal channel model, we derive the outage probability of vertical MIMO UVLC links and quantify the diversity gain in terms of the number of transmitter/receivers.
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Drizzle attenuation model for visible and infrared wavelengths
(IEEE, 2022) Elamassie, Mohammed; Uysal, Murat; Electrical & Electronics Engineering; ELAMASSIE, Mohammed; UYSAL, Murat
In an outdoor environment, the transmitted optical signal is affected by the atmospheric particles that may scatter or absorb light such as drizzle, rain, snow, fog, and aerosols. Various earlier studies have attempted to provide models that accurately describe the attenuation caused by the propagation of light waves through different atmospheric conditions. While the rain attenuation models have received significant research efforts, the modeling of drizzle attenuation was not yet fully studied. In this paper, we conduct extensive simulations in MODTRAN to model drizzle attenuation over the wavelength from 350 nm to 1550 nm. Based on data fitting to simulation results, we further propose a closed-form expression for the drizzle extinction coefficient.
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Effect of eddy diffusivity ratio on underwater optical scintillation index
(The Optical Society, 2017-10-11) Elamassie, Mohammed; Uysal, Murat; Baykal, Y.; Abdallah, M.; Qaraqe, K.; Electrical & Electronics Engineering; UYSAL, Murat; Elamassie, Mohammed
The performance of underwater optical wireless communication systems is severely affected by the turbulence that occurs due to the fluctuations in the index of refraction. Most previous studies assume a simplifying, yet inaccurate, assumption in the turbulence spectrum model that the eddy diffusivity ratio is equal to unity. It is, however, well known that the eddy diffusivities of temperature and salt are different from each other in most underwater environments. In this paper, we obtain a simplified spatial power spectrum model of turbulent fluctuations of the seawater refraction index as an explicit function of eddy diffusivity ratio. Using the derived model, we obtain the scintillation index of optical plane and spherical waves and investigate the effect of the eddy diffusivity ratio.
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Effect of fog and rain on the performance of vehicular visible light communications
(IEEE, 2018-07-20) Elamassie, Mohammed; Karbalayghareh, Mehdi; Miramirkhani, Farshad; Kızılırmak, R. Ç.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Elamassie, Mohammed; Karbalayghareh, Mehdi; Miramirkhani, Farshad
In Intelligent Transportation Systems, visible light communication (VLC) has emerged as a powerful candidate to enable wireless connectivity in vehicle-to-vehicle (V2V) and vehicle-to- infrastructure (V2I) links. While VLC has been studied intensively in the context of indoor communications, its application to vehicular networking is relatively new. In this paper, we carry out a comprehensive channel modeling study to quantify the effect of rain and fog on a V2V link with a high-beam headlamp acting as the transmitter. Taking advantage of advanced ray tracing features, we first develop a path loss model for V2V link as a function of distance under different weather conditions. Then, we use this expression to determine the maximum achievable distance to ensure a given bit error rate. We further investigate the deployment of relay- assisted systems to extend transmission ranges. Extensive numerical results are presented to corroborate our findings.
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Effect of sea waves on vertical underwater visible light communication links
(IEEE, 2023-04) Elamassie, Mohammed; Sait, S. M.; Uysal, Murat; Electrical & Electronics Engineering; ELAMASSIE, Mohammed; UYSAL, Murat
Underwater visible light communication (VLC) has been proposed to deal with emerging high bandwidth underwater applications. Initial research works on underwater VLC are based on the assumption that both transmitter and receiver are submerged, creating a horizontal link. In most of the vertical communication links, one of the transceiver nodes takes the form of a buoy and requires taking into the effect of the sea surface, which is inherently unsteady due to wind and waves. In this article, we consider a vertical underwater VLC link where the transmitter is in the form of a buoy at the sea surface, and the receiver is a submerged node at a certain depth. We assume sinusoidal waves and consider the fact that the buoy will fluctuate and oscillate, during drifting up and down, around its vertical axis. This effectively results in a 3-D displacement at the suspended transmitter. Building upon these assumptions of practical relevance, we propose an aggregate channel model, which includes a random path loss due to periodic changes of the transmission distance and a fading term induced by pointing errors with periodic changes of relative movement. Based on the proposed statistical model, we derive closed-form expressions for the exact and asymptotic bit error ratio and investigate the achievable diversity orders. We further present numerical results to confirm the analytical findings.
Open Access
Evaluation of wind power for electrical energy generation in the mediterranean coast of Palestine for 14 years
(Institute of Advanced Engineering and Science, 2019-08) Badawi, A. S. A.; Hasbullaha, N. F.; Yusoff, Y.; Khan, S.; Hashim, A.; Zyoud, A.; Elamassie, Mohammed; Elamassie, Mohammed
The generation, distributionand transmission of electricity in Palestine have recently emerged as major issues. This study comprehensively assesses the production of wind energy and the estimation of wind energy potential in Palestine’s south coastal plain. The goal is to evaluate Palestine’s wind energy production by studying wind data and calculating energy and power. This study analyses two actual time series datasets. Findings are elaborated to determine the wind energy conversion per 1 m2. The wind speed data from January 1996 to December 2006 in Gaza and from January 2012 to December 2015 in Ashqelon are selected as the data sample. This study is crucial given the need for clean and renewable energy, the power shortage in the Gaza Strip and the limited number of wind energy studies conducted in the south coastal plain of Palestine, especially Gaza Strip. This study estimates the wind energy potential of the Gaza Strip to determine the wind potential. The annual mean wind speed and power are 4.11 ms-1 and 903.4 Wm-2, respectively. Moreover, the study clarifies the electrical energy generation in the Gaza Strip using small-scale turbines and offers a feasible alternative to existing schemes.
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Experimental characterization of multi-hop vehicular VLC systems
(IEEE, 2021) Mohamed, Bassam Aly Abdelrahman; Elamassie, Mohammed; Uysal, Murat; Electrical & Electronics Engineering; ELAMASSIE, Mohammed; Mohamed, Bassam Aly Abdelrahman
In vehicular visible light communication (VLC), the reliable communication distance may be relatively short due to its dependence on many factors including the weather condition. This necessitates the use of relay-assisted systems to extend the transmission range. In this paper, we investigate experimentally the performance of vehicular multi-hop VLC systems in outdoor environments. Particularly, we first examine the effect of ambient noise on signal-to-noise ratio (SNR) during a whole day. Then, we conduct two multi-hop experiments, i.e., one at daytime and one at nighttime. We measure the bit error rate (BER) for each individual hop and then obtain the overall performance of the multi-hop system. We further compare experimental BER with theoretical BER to confirm our results.
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Experimental evaluation of a software defined visible light communication system
(IEEE, 2020) Mohamed, Bassam Aly Abdelrahman; Elamassie, Mohammed; Kebapçı, Burak; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Mohamed, Bassam Aly Abdelrahman; Kebapçı, Burak
Visible light communication (VLC) allows the dual use of light-emitting diodes (LEDs) for illumination and communication purposes. With its large bandwidth and immunity to electromagnetic interference, VLC can be used as complementary and/or alternative to radio communications. In this paper, we present a comprehensive experimental evaluation of a software-defined VLC system with on-off keying for both line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios. The experimental set-up is based on a pair of modified National Instruments USRPs coupled with a custom design front-end. In the measurement campaign, we vary the distance between 1 to 3 meters with a step size of 0.5 m. For each point in this LOS scenario, we measure signal-to-noise ratio (SNR) and bit error rate (BER) with and without a lens. We also evaluate the effect of the reception angle (i.e, no strict alignment) on system performance. We further evaluate the SNR performance for NLOS scenarios and demonstrate a robust performance due to the wide field-of-view of the front-end.
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Experimental evaluation of unipolar OFDM VLC system on software defined platform
(IEEE, 2019) Mohamed, Bassam Aly Abdelrahman; Elamassie, Mohammed; Uysal, Murat; Kınav, E.; Electrical & Electronics Engineering; UYSAL, Murat; Mohamed, Bassam Aly Abdelrahman; Elamassie, Mohammed
With unique features and advantages, visible light communication (VLC) is considered as a powerful complementary wireless access technology to radio frequency solutions such as WiFi. To handle the frequency-selectivity of VLC channels particularly at high speeds, multi-carrier signaling in the form of orthogonal frequency division multiplexing (OFDM) is typically preferred. Among various variants of optical OFDM, unipolar OFDM (U-OFDM) stands outs with its better error rate performance. In this paper, we present the experimental evaluation of the bit error rate (BER) performance of a U-OFDM-based VLC system. In our experimental set-up, we use the popular software defined platform USRP (Universal software radio peripheral) from National Instruments customized with baseband cards and integrated with VLC front-ends. We first characterize the frequency-selective VLC channel. Then, we present BER performance against the estimated signal-to-noise-ratio and confirm it through comparison with theoretical results.
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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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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.