Browsing by Author "Karbalayghareh, Mehdi"

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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.
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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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Performance characterization of vehicular visible light communications
(2019-07-16) Karbalayghareh, Mehdi; Uysal, Murat; Uysal, Murat; Durak, Kadir; Karakaya, B.; Department of Electrical and Electronics Engineering; Karbalayghareh, Mehdi
In Intelligent Transportation Systems (ITSs), 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. VLC has been proposed as an alternative or complementary technology to radio frequency vehicular communications. While VLC has been studied intensively in the context of indoor communications, its application to vehicular networking is relatively new. Light emitting diodes (LEDs) are increasingly used in automotive exterior lighting. The expected wide availability of LED-based front and back lights makes VLC a natural vehicular connectivity solution. A major challenge in vehicular VLC systems is their relatively poor performance in adverse weather conditions such as severe fog. In this thesis, we evaluate the performance limits of vehicular VLC systems. In the first part of this thesis, we determine the maximum achievable distance to ensure a given bit error rate (BER) assuming positive-intrinsic-negative (PIN) diode as a receiver. We further investigate the deployment of relay-assisted systems to extend transmission ranges. In the second part of this thesis, we propose the use of single-photon avalanche diode (SPAD) for vehicular VLC systems. With their higher sensitivity in comparison to conventional photodetectors, SPADs can be efficiently used to detect weak signals. Under the assumption of on-off keying (OOK), we present the error rate performance of vehicular VLC systems. Since the SPAD output is modelled by Poisson statistics, BER takes the form of a semi-infinite summation. Based on Anscombe transformation, we approximate Poisson noise as Gaussian and derive a closed-form BER expression. Using this expression, we obtain a closed-form expression for maximum achievable link distance to ensure a targeted BER. We further investigate the deployment of relay-assisted systems to extend transmission ranges. In the third part of this thesis, we propose the use of SPAD array receiver for vehicular VLC systems. We obtain the closed-form expression for maximum achievable distance to ensure targeted BER. We present an extensive numerical study to validate our derivations and demonstrate the performance of vehicular VLC systems under different weather conditions.
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Resource allocation for downlink OFDMA in underwater visible light communications
(IEEE, 2019-06) Elamassie, Mohammed; Karbalayghareh, Mehdi; Miramirkhani, Farshad; Uysal, Murat; Abdallah, M.; Qaraqe, K.; Electrical & Electronics Engineering; UYSAL, Murat; Elamassie, Mohammed; Karbalayghareh, Mehdi; Miramirkhani, Farshad
As a wireless connectivity solution with low latency and high capacity, visible light communication (VLC) is particularly attractive for high-speed underwater applications such as image or real-time video transmission. In this paper, we consider the downlink of an underwater sensor network (USN) where the communication between the central command unit and sensor nodes takes place through VLC. The system builds upon DC-biased-optical orthogonal frequency division multiple access (DCO-OFDMA) where subsets of subcarriers are assigned to different nodes. We propose a joint subcarrier allocation and bit loading algorithm in an effort to achieve identical data rate for each node in the USN while satisfying a targeted bit error rate (BER). We further present Monte Carlo simulation results to demonstrate the performance of the proposed adaptive algorithm.
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Simultaneous lightwave information and power transfer in underwater visible light communications
(IEEE, 2019) Ghasvarianjahromi, Sara; Karbalayghareh, Mehdi; Diamantoulakis, P. D.; Karagiannidis, G. K.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Ghasvarianjahromi, Sara; Karbalayghareh, Mehdi
Visible light communication (VLC) has emerged as a high-capacity connectivity solution for underwater sensor networks. Since water is relatively transparent to blue or green light, visible light lasers or LEDs can be used as transmitters for underwater wireless connectivity with data rates up to hundreds of Mbps. In underwater networks, a critical system design issue is the network lifetime which highly depends on the battery capacity. Since recharging in underwater scenarios is typically very costly and impractical, energy harvesting can be considered as a promising alternative. In this paper, we explore simultaneous lightwave information and power transfer (SLIPT) for VLC-based USNs. We adopt time splitting method where the receiver switches in time between the modes of energy harvesting (EH) and information decoding (ID). We derive a closed-form expression for the average harvested energy over log-normal model underwater turbulence channel. Using this expression, we determine the splitting factor between EH and ID operation modes to maximize the harvested energy while satisfying a given bit error rate value.
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Vehicular visible light communications with SPAD receivers
(IEEE, 2019) Karbalayghareh, Mehdi; Miramirkhani, Farshad; Safari, M.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Karbalayghareh, Mehdi; Miramirkhani, Farshad
Light emitting diodes (LEDs) are increasingly used in automotive exterior lighting. The expected wide availability of LED-based front and back lights makes visible light communication (VLC) a natural vehicular connectivity solution. A major challenge in vehicular VLC systems is their relatively poor performance in adverse weather conditions such as severe fog. In this paper, we propose the use of single-photon avalanche diode (SPAD) for vehicular VLC systems. With their higher sensitivity in comparison to conventional photodetectors, SPADs can be efficiently used to detect weak signals. Under the assumption of on-off keying (OOK), we present the error rate performance of vehicular VLC systems. Since the SPAD output is modelled by Poisson statistics, the bit error rate (BER) takes the form of a semi-infinite summation. Based on Anscombe transformation, we approximate Poisson noise as Gaussian and derive a closed-form BER expression. Using this expression, we obtain a closedform expression for maximum achievable link distance to ensure a targeted BER. We present an extensive numerical study to validate our derivations and demonstrate the performance of vehicular VLC system under different weather conditions.