Browsing by Author "Ghassemlooy, Z."

Now showing 1 - 16 of 16

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Capacity analysis of free space optical links for a partially coherent gaussian beam over a turbulent channel with pointing errors
(IEEE, 2013) Lee, I. E.; Ghassemlooy, Z.; Ng, W. P.; Khalighi, M. A.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, we investigate the joint effects of beam width and the spatial coherence length in a partially coherent free-space optical (FSO) link from the information theory perspective, taking into account the combined influence of atmospheric turbulence and pointing errors. In addition, the effects of aperture-averaging on the average capacity of FSO links employing partially coherent beams (PCBs) are examined. Results show that PCBs are desirable in the weak-to-moderate turbulence regime, whereas highly coherent laser sources are preferred under strong fluctuations conditions; and there exist optimality in the optical beam parameters for different atmospheric channel conditions. Near-optimal average capacity is best achieved through the introduction of a larger receiver aperture and the joint beam width and spatial coherence length optimization technique, which effectively mitigates the effects of scintillation and pointing errors.
Open Access
Coverage of a shopping mall with flexible OLED-based visible light communications
(The Optical Society, 2020-03-30) Chaleshtori, Z. N.; Zvanovec, S.; Ghassemlooy, Z.; Eldeeb, Hossıen Badr; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; ELDEEB, Hossien Badr Hossien
Visible light communications (VLC) can utilize light-emitting diodes (LEDs) to provide illumination and a safe and low-cost broadcasting network simultaneously. In the past decade, there has been a growing interest in using organic LEDs (OLEDs) for soft lighting and display applications in public places. Organic electronics can be mechanically flexible, thus the potential of curved OLED panels/displays devices. This paper provides unique characteristics of a flexible OLED-based VLC link in a shopping mall. We show that, for curved OLED the radiation pattern displays a symmetry, which is wider than Lambertian. A number of scenarios of VLC system with flexible OLED are analyzed. Numerical models for the delay spread and optical path loss are derived, which followed a 2-term power series model for both empty and furnished rooms. We show that using a full-circular OLED for both empty and furnished rooms offers a uniform distribution of emitted power for the same transmission link spans. The link performance using full and half-circular OLED in an empty room shows that the average optical path losses are lower by 5 and 4 dB, compared with the furnished room.
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Emerging optical wireless communications-advances and challenges
(IEEE, 2015-09) Ghassemlooy, Z.; Arnon, S.; Uysal, Murat; Xu, Z.; Cheng, J.; Electrical & Electronics Engineering; UYSAL, Murat
New data services and applications are emerging continuously and enhancing the mobile broadband experience. The ability to cope with these varied and sophisticated services and applications will be a key success factor for the highly demanding future network infrastructure. One such technology that could help address the problem would be optical wireless communications (OWC), which presents a growing research interest in the last few years for indoor and outdoor applications. This paper is an overview of the OWC systems focusing on visible light communications, free space optics, transcutaneous OWC, underwater OWC, and optical scattering communications.
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A European view on the next generation optical wireless communication standard
(IEEE, 2015) Jungnickel, V.; Uysal, Murat; Serafimovski, N.; Baykas, T.; O’Brien, D.; Ciaramella, E.; Ghassemlooy, Z.; Green, R.; Haas, H.; Haigh, P. A.; Gil Jimenez, V. P.; Miramirkhani, Farshad; Wolf, M.; Zvánovec, S.; Electrical & Electronics Engineering; UYSAL, Murat; Miramirkhani, Farshad
Optical wireless technology uses light for mobile communications. The idea is to simultaneously combine the illumination provided by modern high-power light-emitting diodes (LEDs) with high-speed wireless communications. There have been numerous practical demonstrations of this concept, and the technology is now well matured to be deployed in practice. Independent market analysts forecast a high-volume market for mobile communication devices connected to the ubiquitous lighting infrastructure. This paper aims to make optical and wireless industries aware of the requirement for standardization in this area. The authors present the view of the European COST 1101 research network OPTICWISE towards a next-generation optical wireless standard aiming at data rates from 1 Mbit/s to 10 Gbit/s. Besides key technical insights, relevant use cases and main features are described that were recently adopted by the IEEE 802.15.7r1 working group. Moreover, a channel model is introduced to enable assessment of technical proposals.
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Experimental demonstration of polarisation shift keying in the free space optical turbulence channel
(IEEE, 2012) Tang, X.; Ghassemlooy, Z.; Rajbhandari, S.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, the performance of binary polarisation shift keying (BPOLSK) with the direct detection (DD) scheme is experimentally investigated. BPOLSK scheme is used to mitigate the atmospheric turbulence induced fading in a free space optical (FSO) communication link. For comparison the experimental and analytical results for the non-return-to-zero on-off keying (NRZ-OOK) have also been presented. The experimental Q-factors are verified in conjunction with theoretical values in weak turbulence regime to confirm the validity of the proposed scheme. The results have shown that BPOLSK offers higher Q-factor values compared to NRZ-OOK for the same transmitted optical power and the turbulence variance. For example, when the turbulence variance σ2l is 0.03, the Q-factors are 4.6 and 5 for NRZ-OOK and BPOLSK respectively.
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A flexible OLED VLC system for an office environment
(IEEE, 2020) Chaleshtori, Z. N.; Zvanovec, S.; Ghassemlooy, Z.; Eldeeb, Hossıen Badr; Uysal, Murat; Electrical & Electronics Engineering; ELDEEB, Hossien Badr Hossien; UYSAL, Murat
The potential use of flexible substrate-based organic light emitting diodes (OLEDs) as curved or rolled lighting sources offers news opportunities for the implementation of visible light communications (VLC) in indoor environments. This paper outlines the use of such a system in a furnished office and investigates the impact of the beam pattern of OLED, which is symmetrical and wider than Lambertian, on the VLC system. We present new results of the VLC system performance in terms of the root-mean-square delay spread and the bit error rate (BER) for the link using both flat and half-circular OLEDs. We demonstrate a data rate of 4 Mb/s using both the curved and flat OLEDs for the transmitter's half-angle within the range of ±90° and ±53°, respectively with a BER below the forward error correction BER limit.
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Guest editorial: Optical wireless communications
(IEEE, 2015-09) Arnon, S.; Uysal, Murat; Ghassemlooy, Z.; Xu, Z.; Cheng, J.; Electrical & Electronics Engineering; UYSAL, Murat
Optical wireless communication (OWC) systems provide many advantages over radio frequency (RF) wireless technologies in some scenarios, including significantly higher data rates and a large amount of available license-free frequency spectrum. Recently, OWC has also been proposed in fifth generation 5G standard as a tool to augment capacity due to RF spectrum crunching challenges. Various forms of OWC can be used to augment RF capacity at both access and backhaul/fronthaul levels. Despite the major advantages and various application areas, the widespread deployment of OWC is delayed by several challenges, such as the demand to maintain strict line-of-sight alignment between transmitter and receiver in long range outdoor applications; the need to combat attenuation due to adverse weather conditions such as fog, cloud, and turbulence; to modulate light emitting diodes at high frequencies without distortion at indoor visible light communication (VLC) applications and retaining power levels within the eye safety limits for laser transmitters and comfortable illumination levels for LED transmitters.
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Optimal combiners in optical wireless systems with spatial diversity and pre-amplification
(IEEE, 2016) Yiannopoulos, K.; Sagias, N. C.; Boucouvalas, A. C.; Uysal, Murat; Ghassemlooy, Z.; Electrical & Electronics Engineering; UYSAL, Murat
We present analytical results on the operation of a pre-amplified optical wireless communication (OWC) system that also takes advantage of spatial diversity to improve its outage probability and average bit-error-rate (BER) performance against turbulence induced fading. The paper focuses on the design of an optimal electronic combiner that minimizes the instantaneous BER for any given channel state by properly adjusting the gains that are provided to each receiver output after detection. We demonstrate that the optimal combiner performs in a similar manner to an equal gain combiner for a limited number of receiving elements in moderate turbulence, while its potential can be harvested in systems with high diversity factors or under the strong-to-saturated turbulence regime.
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Outage performance of MIMO free-space optical systems in gamma-gamma fading channels
(IEEE, 2013) Kazemi, Hossein; Mostaani, Zohreh; Uysal, Murat; Ghassemlooy, Z.; Electrical & Electronics Engineering; UYSAL, Murat; Kazemi, Hossein; Mostaani, Zohreh
In this paper, we consider a MIMO Free-Space Optical (FSO) communication system over gamma-gamma turbulence channels and derive a closed-form analytical expression for the outage probability taking into account the effects of both the inner scale size of optical channel and the aperture averaging. Our results demonstrate that by increasing the number of transmit and/or receive apertures, the degrading effect of the inner scale size is effectively reduced by extracting the spatial diversity gain of the MIMO scheme. We further provide Monte Carlo simulation results to confirm the validity of the derived expression.
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Performance analysis of free space optical links over turbulence and misalignment induced fading channels
(IEEE, 2012) Lee, I. E.; Ghassemlooy, Z.; Ng, W. P.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
The performance of free-space optical (FSO) communication system is investigated from the information theory perspective, under the influence of atmospheric loss and channel fading due to the turbulence and pointing error. The outage probability and average channel capacity of the FSO link are evaluated using a combined slow-fading channel model and a Gaussian beam wave model, unlike the limiting Rytov-based scintillation model considered in earlier work. Taking into account various link design criteria, our study reveals that lower outage probability can be achieved with larger receiver aperture due to the aperture averaging effect. Optimization of the capacity metrics is best performed through proper selection of the aperture size and beam width for known laser wavelength, particularly for long-distance links and strong turbulence scenarios. Hence, findings and results from our analysis can be treated as the design benchmark for optimal planning and deployment of optical links.
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Practical implementation and performance study of a hard-switched hybrid FSO/RF link under controlled fog environment
(IEEE, 2014) Lee, I. E.; Ghassemlooy, Z.; Ng, W. P.; Gourdel, V.; Khalighi, M. A.; Zvanovec, S.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
The availability and performance of terrestrial free-space optical (FSO) communication systems are heavily deterred by the fluctuating conditions of the atmospheric channel, particularly in the presence of visibility-limiting fog effects. In this paper, we examine the viability of deploying hybrid FSO and radio frequency (RF) links through an experimental study, which takes advantage of a dedicated laboratory atmospheric chamber to emulate the fog scenarios encountered on outdoor environment. In particular, a root mean square power detector is developed and introduced in the system under study to monitor the signal quality of the primary FSO link. The quasi-linear output voltage characteristics of the power detector device is utilized as a useful decision metric to implement hard switching in a hybrid FSO/RF link based upon the changes in the visibility. Our measurement results reveal that the selection of a desirable threshold voltage is dependent upon the intended data rate and minimum achievable bit error rate, in order to enable effective switching between the FSO and RF links.
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Standards for indoor optical wireless communications
(IEEE, 2015-03) Boucouvalas, A. C.; Chatzimisios, P.; Ghassemlooy, Z.; Uysal, Murat; Yiannopoulos, K.; Electrical & Electronics Engineering; UYSAL, Murat
The application of Optical Wireless Communications (OWC) has grown in recent years that the whole industry would benefit from common standards to which competitive products comply. Standards are essential, particularly when the market expands into high-volume products like home appliances and other consumer goods. This article offers a timely review of standards-writing activity, as OWCs find their way into diverse products varying from TV remote controls to satellite links. This article discusses the most popular standards for optical wireless communications. We outline the IEEE 802.11 standard for optical wireless local area networks, and the ongoing standardization effort by IrDA on personal optical wireless systems. The article concludes with a discussion of the recently announced IEEE 802.15.7 standard on visible light communications.
Open Access
Utilization of an oled-based vlc system in office, corridor, and semi-open corridor environments
(MDPI, 2020-12-01) Chaleshtori, Z. N.; Ghassemlooy, Z.; Eldeeb, Hossıen Badr; Uysal, Murat; Zvanovec, S.; Electrical & Electronics Engineering; UYSAL, Murat; ELDEEB, Hossien Badr Hossien
Organic light emitting diodes (OLEDs) have recently received growing interest for their merits as soft light and large panels at a low cost for the use in public places such as airports, shopping centers, offices, and train or bus stations. Moreover, the flexible substrate-based OLEDs provide an attractive feature of having curved or rolled lighting sources for the use in wearable devices and display panels. This technology can be implemented in visible light communications (VLC) for several applications such as visual display, data communications, and indoor localization. This article aims to investigate the use of flexible OLED-based VLC in indoor environments (i.e., office, corridor and semi-open corridor in shopping malls). We derive a two-term power series model to be match with the root-mean-square delay spread and optical path loss (OPL). We show that, for OLED positioned on outer-wall of shops, the channel gain is enhanced in contrast to them being positioned on the inner-wall. Moreover, the channel gain in empty environments is higher compare with the furnished rooms. We show that, the OPL for a 10 m link span are lower by 4.4 and 6.1 dB for the empty and semi-open corridors compared with the furnished rooms, when OLED is positioned on outer-wall of shops. Moreover, the channel gain in the corridor is higher compared with the semi-open corridor. We also show that, in furnished and semi-open corridors the OPL values are 55.6 and 57.2 dB at the center of corridor increasing to 87.6 and 90.7 dB at 20 m, respectively, when OLED is positioned on outer-wall of shops.
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Vehicular visible light communications: The impact of taillight radiation pattern
(IEEE, 2020-09) Eldeeb, Hossıen Badr; Eso, E.; Uysal, Murat; Ghassemlooy, Z.; Zvanovec, S.; Sathian, J.; Electrical & Electronics Engineering; UYSAL, Murat; ELDEEB, Hossien Badr Hossien
We investigate the path-loss of vehicular visible light communications based on the radiation pattern of a commercial car taillight. The measured pattern is incorporated into a ray-tracing model and simulation results indicate up to 4.2 dB variation in the path-loss compared with the Lambertian model.
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Vehicular VLC: A ray tracing study based on measured radiation patterns of commercial taillights
(IEEE, 2021-08-15) Eldeeb, Hossıen Badr; Eso, E.; Jarchlo, E. A.; Zvanovec, S.; Zvanovec, S.; Uysal, Murat; Ghassemlooy, Z.; Sathian, J.; Electrical & Electronics Engineering; ELDEEB, Hossien Badr Hossien; UYSAL, Murat
In this letter, we investigate the performance of vehicular visible light communications based on the radiation patterns of different commercial taillights (TLs) using non-sequential ray tracing simulations. Our simulation results indicate a significant variation in the path loss compared with Lambertian model. Based on the ray tracing results, we propose a new path loss model as a function of the propagation distance considering the asymmetrical radiation pattern of TLs. We use this model to derive the attainable transmission distance. We further present the delay spread for various vehicular communication scenarios to demonstrate the effect of neighboring vehicles.
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Visible light communication for vehicular networking: performance study of a V2V system using a measured headlamp beam pattern model
(IEEE, 2015-12) Uysal, Murat; Ghassemlooy, Z.; Bekkali, A.; Kadri, A.; Menouar, H.; Electrical & Electronics Engineering; UYSAL, Murat
In this article, we discuss visible light communication (VLC) in the context of vehicular communication networks. With the omnipresence of light-emitting diodes (LEDs) in outdoor and automotive lightings, VLC emerges as a natural candidate for vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications. We first provide an overview of this emerging research area highlighting recent advances and identifying open problems for further research. Then, we present the performance evaluation of a typical V2V VLC system with realistic automative light sources. Our evaluation takes into account the measured headlamp beam pattern and the impact of road reflected light. We demonstrate that depending on the photodetector (PD) position above the ground level, a data rate of 50 Mb/s can be achieved at 70 m.