Person: ELAMASSIE, Mohammed
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Mohammed
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ELAMASSIE
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ArticlePublication Open 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, MuratWireless 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.
ArticlePublication Metadata only Non-orthogonal multiple access-based underwater VLC systems in the presence of turbulence(IEEE, 2022-02) Bariah, L.; Elamassie, Mohammed; Muhaidat, S.; Sofotasios, P. C.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; ELAMASSIE, MohammedThe promising potential of underwater applications in visible light communication (VLC) systems has recently gained considerable research attention, as an efficient technology for enabling high data rate, massive connectivity, and ultra-low latency. Different from indoor VLC, underwater wireless communications experience harsh environmental challenges, yielding a degraded performance. Non-orthogonal multiple access (NOMA) was introduced to enhance spectral efficiency and connectivity of underwater VLC communications. In this paper, we develop a mathematical framework to evaluate the performance of NOMA-enabled underwater VLC systems in the presence of turbulence. Specifically, we derive a closed-form expression for the outage probability of NOMA over lognormal channels, while considering the effect of path loss and turbulence. The derived analytical results with the corresponding numerical results demonstrate that the transmission distance between laser diode and sensor nodes (SNs) has a high impact on the outage performance of the SNs, due to the increased turbulence level with increased distance. Moreover, the presented results show the effect of the water type on the outage performance of the SNs and on the optimum values of the power coefficients.ArticlePublication 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, MuratVisible 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.ArticlePublication Metadata only Spatial power spectrum of natural water turbulence with any average temperature, salinity concentration, and light wavelength(The Optical Society, 2020-10-01) Yao, J. R.; Elamassie, Mohammed; Korotkova, O.; Electrical & Electronics Engineering; ELAMASSIE, MohammedThe power spectrum of water optical turbulence is shown to vary with its average temperature < T > and average salinity concentration < S >, as well as with light wavelength lambda. This study explores such variations for < T > is an element of [0 degrees C, 30 degrees C], < S > is an element of [0 ppt, 40 ppt] covering most of the possible natural water conditions within the Earth's boundary layer and for visible electromagnetic spectrum, lambda is an element of [400 nm, 700 nm]. For illustration of the effects of these parameters on propagating light, we apply the developed power spectrum model for estimation of the scintillation index of a plane wave (the Rytov variance) and the threshold between weak and strong turbulence regimes. (C) 2020 Optical Society of America.Conference ObjectPublication Metadata only 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 AbdelrahmanWith 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.Conference ObjectPublication Metadata only Path selection for relay-assisted underwater visible light communication systems(IEEE, 2022) Elamassie, Mohammed; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; ELAMASSIE, MohammedIn this paper, we consider underwater visible light communication (UVLC) system with M parallel relaying paths where each path has N decode-and-forward (DF) relays. One path (not necessarily the best one) out of M paths is selected for transmission. Such a multi-hop system is especially useful since some relay nodes might break down or malfunction and hence single path might not be sufficient. Furthermore, selection of the best path is not always possible due to several reasons such as the effect of noise on the estimation of the best path and feedback error. Under the assumption of lognormal (LN) turbulence channels, we derive a closed-form expression for the outage probability of UVLC system where the mth best path is selected for transmission. We then use our derived closed-form outage probability for investigating the so-called incremental diversity order (IDO).Conference ObjectPublication Metadata only 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, MuratUnderwater 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.Conference ObjectPublication Metadata only Outage performance analysis of vertical underwater VLC links(IEEE, 2022) Elamassie, Mohammed; Uysal, Murat; Electrical & Electronics Engineering; ELAMASSIE, Mohammed; UYSAL, MuratIn 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.Conference ObjectPublication Metadata only 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, YusufIn 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.ArticlePublication Metadata only Feedback-free adaptive modulation selection algorithm for FSO systems(IEEE, 2021-09) Elamassie, Mohammed; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; ELAMASSIE, MohammedFree 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.