Showing papers by "Murat Uysal published in 2015"
TL;DR: This paper is an overview of the OWC systems focusing on visible light communications, free space optics, transcutaneous O WC, underwater OWC, and optical scattering communications.
Abstract: 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.
377 citations
TL;DR: This study is based on ray tracing, which allows for an accurate description of the interaction of rays emitted from the lighting source within a specified confined space and is capable of obtaining channel impulse responses for any nonideal sources, as well as specular and mixed specular-diffuse reflections.
Abstract: In this paper, we present a comprehensive channel modeling and characterization study for visible light communications. Our study is based on ray tracing, which allows for an accurate description of the interaction of rays emitted from the lighting source within a specified confined space. Contrary to existing works, which are mainly limited to ideal Lambertian sources and purely diffuse reflections, our approach is capable of obtaining channel impulse responses (CIRs) for any nonideal sources, as well as specular and mixed specular–diffuse reflections. Furthermore, we can precisely reflect the presence of objects (e.g., furniture) and wavelength-dependent reflection characteristics of surface materials (e.g., ceilings, floor, walls, and furniture) in a channel study. As case studies, we consider a number of indoor environments with various dimensions and different surface materials, i.e., plaster, gloss paint, wood, aluminum metal, and glass. We further consider various scenarios with different transmitter specifications (i.e., single versus multiple transmitters and array type) and receiver specifications (i.e., location and rotation). For each environment, we obtain CIRs and present a channel characterization study where channel parameters, such as channel DC gain, root mean square (RMS) delay spread, coherence bandwidth, and mean excess delay, are obtained. We also make one-to-one comparisons between infrared and visible-light CIRs for the same environments to emphasize the differences between two optical bands.
270 citations
TL;DR: Evaluated performance of cameras integrated UAV for geomatic applications by the way of Digital Elevation Model (DEM) generation in a small area shows that the data derived from UAV Photogrammetry have adequate accuracy very much alike to RTK GPS data, so it is possible to use the UAV photogrammetry data as map producing, surveying, and some other engineering applications with the advantages of low-cost, time conservation, and minimum field work.
239 citations
TL;DR: This article presents the performance evaluation of a typical V2V VLC system with realistic automative light sources and demonstrates that depending on the photodetector position above the ground level, a data rate of 50 Mb/s can be achieved at 70 m.
Abstract: 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.
146 citations
01 Sep 2015
TL;DR: Based on a realistic indoor channel conditions, NOMA is applied to indoor VLC channels and demonstrated its superior performance over orthogonal frequency division multiple access (OFDMA).
Abstract: Providing multiple access support to visible light communication (VLC) systems requires new networking architecture. Non-orthogonal multiple access (NOMA) is a proposed multiple access technique for future cellular systems. In this work, based on a realistic indoor channel conditions, we apply NOMA to indoor VLC channels and demonstrate its superior performance over orthogonal frequency division multiple access (OFDMA).
137 citations
TL;DR: A new probability distribution function which accurately describes turbulence-induced fading under a wide range of turbulence conditions is proposed, based on a doubly stochastic theory of scintillation and developed via the product of two generalized gamma distributions.
Abstract: In this paper, we propose a new probability distribution function which accurately describes turbulence-induced fading under a wide range of turbulence conditions. The proposed model, termed double-generalized gamma (double GG), is based on a doubly stochastic theory of scintillation and developed via the product of two generalized gamma distributions. The proposed double GG distribution generalizes many existing turbulence channel models and provides an excellent fit to the published plane and spherical waves simulation data. Using this new statistical channel model, we derive closed form expressions for the outage probability and the average bit error as well as corresponding asymptotic expressions of free-space optical communication systems over turbulence channels. We demonstrate that our derived expressions cover many existing results in the literature earlier reported for gamma–gamma, double-Weibull and K channels as special cases.
107 citations
TL;DR: In this article, the authors present the major challenges of future machine-to-machine (M2M) cellular networks such as spectrum scarcity, and support for a large number of low-power, low-cost devices.
Abstract: In this article we present the major challenges of future machine-to-machine (M2M) cellular networks such as spectrum scarcity, and support for a large number of low-power, lowcost devices. As an integral part of the future Internet-of-Things (IoT), the true vision of M2M communications cannot be reached with conventional solutions that are typically cost inefficient. The cognitive radio concept has emerged to address spectrum under-utilization and scarcity. The heterogeneous network model is another alternative to relax the number of covered users. To this extent, we present a complete fundamental understanding and the engineering details of cognitive radios, the heterogeneous network model, and power and cost challenges in the context of future M2M cellular networks.
104 citations
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TL;DR: The major challenges of future machine-to-machine (M2M) cellular networks such as spectrum scarcity, and support for a large number of low-power, lowcost devices are presented.
Abstract: In this article, we present the major challenges of future machine-to-machine (M2M) cellular networks such as spectrum scarcity problem, support for low-power, low-cost, and numerous number of devices. As being an integral part of the future Internet-of-Things (IoT), the true vision of M2M communications cannot be reached with conventional solutions that are typically cost inefficient. Cognitive radio concept has emerged to significantly tackle the spectrum under-utilization or scarcity problem. Heterogeneous network model is another alternative to relax the number of covered users. To this extent, we present a complete fundamental understanding and engineering knowledge of cognitive radios, heterogeneous network model, and power and cost challenges in the context of future M2M cellular networks.
102 citations
TL;DR: The most popular standards for optical wireless communications are outlined, and a discussion of the recently announced IEEE 802.15.7 standard on visible light communications is discussed.
Abstract: 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.
74 citations
TL;DR: The bit error rate (BER) performance of the relay-assisted VLC system is investigated, comparisons of two relaying techniques under consideration and the effect of clipping noise on the error rate performance are discussed.
Abstract: In this study, we investigate a relay-assisted visible light communication (VLC) system where an intermediate light source cooperates with the main light source. Specifically, we consider two light sources in an office space: one is the information source employed on the ceiling and the other one is a task light. Our system uses dc biased optical orthogonal frequency division multiplexing (DCO-OFDM) where the task light performs relaying to assist the communication and operates in half-duplex mode for both amplify-and-forward and decode-and-forward relaying. We investigate the bit error rate (BER) performance of the relay-assisted VLC system and optimize the performance through optimal ac/dc power allocation under illumination constraints. The dc power allocation is determined by sharing the number of LED chips between the terminals to satisfy a desired luminance ratio. The ac power allocation decides the fraction of the information signal power to be consumed at the terminals in order to minimize the BER. Numerical results reveal that cooperation brings significant performance gains over direct transmission. We further provide comparisons of two relaying techniques under consideration and discuss the effect of clipping noise on the error rate performance.
57 citations
TL;DR: In this study the five different algorithm is used to filter LiDAR point cloud that is collected from two different sites, and the generated DTM is compared with the reference DTM for each site.
TL;DR: In this article, the authors proposed a new probability distribution function which accurately describes turbulence-induced fading under a wide range of turbulence conditions, which is based on a doubly stochastic theory of scintillation and developed via the product of two Generalized Gamma (GG) distributions.
Abstract: In this paper, we propose a new probability distribution function which accurately describes turbulence-induced fading under a wide range of turbulence conditions. The proposed model, termed Double Generalized Gamma (Double GG), is based on a doubly stochastic theory of scintillation and developed via the product of two Generalized Gamma (GG) distributions. The proposed Double GG distribution generalizes many existing turbulence channel models and provides an excellent fit to the published plane and spherical waves simulation data. Using this new statistical channel model, we derive closed form expressions for the outage probability and the average bit error as well as corresponding asymptotic expressions of free-space optical communication systems over turbulence channels. We demonstrate that our derived expressions cover many existing results in the literature earlier reported for Gamma-Gamma, Double-Weibull and K channels as special cases.
Heinrich Hertz Institute1, Özyeğin University2, University of Oxford3, Sant'Anna School of Advanced Studies4, Northumbria University5, University of Warwick6, University of Edinburgh7, University of Bristol8, Carlos III Health Institute9, Technische Universität Ilmenau10, Czech Technical University in Prague11
TL;DR: 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 M bit/s to 10 Gbit/s, and relevant use cases and main features are described that were recently adopted by the IEEE 802.15.7r1 working group.
Abstract: 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.
TL;DR: An investigation is carried out for generating a proper DEM to analyze terrain futures and according to the accuracy assessments, the TIN algorithm is very satisfactory for filtering process and the NN interpolation method is quite effective for DEM generation.
TL;DR: This paper investigates channel modeling for visible light communications (VLC) using non-sequential ray tracing simulation tools and presents CIRs for a number of indoor environments including empty/furnished rectangular rooms with different sizes and wall/object materials.
Abstract: In this paper, we investigate channel modeling for visible light communications (VLC) using non-sequential ray tracing simulation tools. We create three dimensional realistic simulation environments to depict indoor scenarios specifying the geometry of the environment, the objects inside, the reflection characteristics of the surface materials as well as the characteristics of the transmitter and receivers, i.e., LED sources and photodioes. Through ray tracing simulations, we compute the received optical power and the delay of direct/indirect rays which are then used to obtain the channel impulse response (CIR). Following this methodology, we present CIRs for a number of indoor environments including empty/furnished rectangular rooms with different sizes and wall/object materials (e.g., plaster, gloss paint, wood, aluminum metal, glass) assuming deployment of both single and multiple LED transmitters. We further quantify multipath channel parameters such as delay spread and channel DC gain for each configuration and provide insights into the effects of indoor environment parameters (e.g., size, wall/object materials, etc.), transmitter/receiver specifications (e.g., single vs. multiple transmitters, location, rotation etc.) on the channel.
Patent•
25 Dec 2015TL;DR: In this article, a system and method for communication between vehicles within a platoon of vehicles is presented, where each vehicle is equipped with forward and backward directed optical emitters and receivers in operable communication with a controller.
Abstract: A system and method are provided for communication between vehicles within a platoon of vehicles. In one embodiment, each vehicle is equipped with forward and backward directed optical emitters and receivers in operable communication with a controller. In an initialization phase, each vehicle determines its position within the 5 platoon and the identification of all vehicles of the platoon. In a data transmission phase, each vehicle takes part in a token-based data transmission.
TL;DR: The authors' simulation results show that the optimal transmission scheme depends on the location of the VLC users and the desired illumination power, and show the superiority of the performance of the power control scheme over the orthogonal transmission scheme for low interference regions.
Abstract: In this paper, we consider the performance of a visible light communication (VLC) network with coordinated interference management. The VLC transmitters are allowed to coordinate their transmissions using one of two transmission schemes so as to maximize a network utility function. In the first technique, namely, orthogonal transmission, the utility function is maximized by optimally partitioning all resources. In the second technique, namely, power control, the transmitters are allowed to share the full spectrum while being allowed to control their power so as to maximize network performance. In particular, for each transmission technique, we optimize a general network utility function under the constraint of a desired illumination power for each VLC transmitter, taking into consideration the optical signal clipping effect due to the physical limitations of the VLC transmitters. For the power control transmission scheme, we develop a computationally efficient method for finding the optimal power values by deriving a computationally efficient way to obtain the achievable spectral efficiency region. Considering the summation and the proportional fairness utility functions, our simulation results show that the optimal transmission scheme depends on the location of the VLC users and the desired illumination power. Also, we show the superiority of the performance of the power control scheme over the orthogonal transmission scheme for low interference regions.
08 Jun 2015
TL;DR: This paper studies the error rate performance of FSO links with spatial diversity over atmospheric turbulence channels described by the Double Generalized Gamma distribution which is a new generic statistical model covering all turbulence conditions.
Abstract: A major performance degrading factor in free space optical communication (FSO) systems is atmospheric turbulence. Spatial diversity techniques provide a promising approach to mitigate turbulence-induced fading. In this paper, we study the error rate performance of FSO links with spatial diversity over atmospheric turbulence channels described by the Double Generalized Gamma distribution which is a new generic statistical model covering all turbulence conditions. We assume intensity modulation/direct detection with on-off keying and present the BER performance of single-input multiple-output (SIMO), multiple-input single-output (MISO) and multiple-input multiple-output (MIMO) FSO systems over this new channel model.
05 Jul 2015
TL;DR: This paper investigates the performance of relay-assisted visible light communication (VLC) system over multipath channels in an indoor environment where the ceiling light serves as the information source and a desk light helps the source forward the information to the destination.
Abstract: In this paper, we investigate the performance of relay-assisted visible light communication (VLC) system over multipath channels. We consider an indoor environment where the ceiling light serves as the information source and a desk light helps the source forward the information to the destination. The VLC system is built on orthogonal frequency division multiplexing (OFDM) with either amplify-and-forward or decode-and-forward relaying. A realistic channel impulse response of the indoor environment generated through ray tracing is used. Through simulations, we present the bit error rate performance of OFDM-based relay-assisted VLC system over indoor multipath channels and quantify the performance degradation with respect to idealistic single tap channels. We further discuss the impact of imperfect channel estimation on the performance.
TL;DR: This paper develops performance characterizations of each relaying mode in terms of outage probability, diversity gain, coding gain, and diversity-multiplexing tradeoff (DMT) in free-space optical (FSO) communications over Gamma-Gamma fading channels.
Abstract: In this paper, we investigate the information theoretic performance of parallel relaying in free-space optical (FSO) communications over Gamma-Gamma fading channels. We consider an intensity modulation/direct-detection (IM/DD) FSO system with a single relay and a line-of-sight link between the source and the destination. Considering both amplify-and-forward and decode-and-forward relaying, we develop performance characterizations of each relaying mode in terms of outage probability, diversity gain, coding gain, and diversity-multiplexing tradeoff (DMT). Our results demonstrate that parallel relaying improves the performance of FSO systems by bringing diversity advantages. In addition, both relaying modes achieve the same DMT and diversity gain while their coding gains can be different depending on underlying channels' characteristics.
06 Jul 2015
TL;DR: Under the assumption of log-normal turbulence channels, closed-form outage capacity and outage throughput expressions for the FSO communication system are derived and the effect of the outage probability, number of users and average signal-to-noise ratio on the system performance is demonstrated.
Abstract: In this paper, we investigate the performance of free space optical (FSO) systems with a multiuser scheme employing select-max scheduling technique. Specifically, we consider an FSO communication system which employs a central node equipped with N transmit apertures, each of which aimed to any of the users. Under the assumption of log-normal turbulence channels, we derive closed-form outage capacity and outage throughput expressions for the FSO communication system and demonstrate the effect of the outage probability, number of users and average signal-to-noise ratio on the system performance.
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TL;DR: In this paper, the error rate performance of free space optical communication (FSO) links with spatial diversity over atmospheric turbulence channels described by the Double Generalized Gamma distribution is investigated.
Abstract: A major performance degrading factor in free space optical communication (FSO) systems is atmospheric turbulence. Spatial diversity techniques provide a promising approach to mitigate turbulence-induced fading. In this paper, we study the error rate performance of FSO links with spatial diversity over atmospheric turbulence channels described by the Double Generalized Gamma distribution which is a new generic statistical model covering all turbulence conditions. We assume intensity modulation/direct detection with on-off keying and present the BER performance of single-input multiple-output (SIMO), multiple-input single-output (MISO) and multiple-input multiple-output (MIMO) FSO systems over this new channel model.
03 Dec 2015
TL;DR: This paper presents the implementation of an IEEE standard-based Visible Light Communication (VLC) system using software defined radio (SDR) approach, and successfully demonstrates audio streaming through the software defined VLC system, which can transmit and receive data successfully up to 2 meters.
Abstract: This paper presents the implementation of an IEEE standard-based Visible Light Communication (VLC) system using software defined radio (SDR) approach. Based on widely used SDR platform Universal Software Radio Peripheral (USRP) and visual programming language LabVIEW, we present a fully standard compliant implementation of all PHY I modes of the IEEE 802.15.7 standard. Rest of the equipments used in the experimental set-up are low cost and commercial off-the-shelf devices. We successfully demonstrate audio streaming through our software defined VLC system, which can transmit and receive data successfully up to 2 meters. We also present bit error rate results of all PHY I modes of IEEE 802.15.7 running on our VLC system, which operates at a distance of 1 meter.
01 Dec 2015
TL;DR: This paper derives the optimal policy for sharing the RF transmission time between the RF links and shows the effectiveness of the proposed communication architecture and link allocation policy, and their superiority compared to existing schemes which employ only one type of backhaul link.
Abstract: -In this paper, we consider a mixed RF and hybrid RF/FSO system where several mobile users transmit their data over an RF link to a relay node (e.g. a small cell base station) and the relay forwards the information to a destination (e.g. a macro cell base station) over a hybrid RF/FSO backhaul link. The relay and the destination employ multiple antennas for transmission and reception over the RF links while each mobile user has a single antenna. The RF links are orthogonal with respect to the FSO link and half-duplex with respect to each other, i.e., either the user-relay RF link or the relay-destination RF link is active. For this communication setup, we derive the optimal policy for sharing the RF transmission time between the RF links. Our numerical results show the effectiveness of the proposed communication architecture and link allocation policy, and their superiority compared to existing schemes which employ only one type of backhaul link.
03 Dec 2015
TL;DR: It is identified that for a given link distance the end-to-end outage probability is minimized when using a hybrid FSO/RF link between every two successive nodes of the multi-hop system, and this requires the maximum number of FSO and RF links to be deployed.
Abstract: In this paper, five scenarios are considered for the realization of a multi-hop hybrid free-space optical/radio frequency (FSO/RF) communication system with decode-and-forward (DF) relaying, and analytical outage probability expressions are derived. The scenarios have a different number of FSO and RF links. The aim is to identify an optimum scenario to effectively improve the end-to-end reliability of the multi-hop hybrid FSO/RF system. Outage performance is investigated for the scenarios under various weather conditions through numerical examples. It is identified that for a given link distance the end-to-end outage probability is minimized when using a hybrid FSO/RF link between every two successive nodes of the multi-hop system, and this requires the maximum number of FSO and RF links to be deployed.
05 Jul 2015
TL;DR: This paper considers a cooperative diversity system with orthogonal cooperation protocol and use DC-biased optical OFDM as the underlying physical layer and investigates the error rate performance of the proposed relay-assisted OFDM UV system and demonstrates significant performance gains over point-to-point OFDMUV systems.
Abstract: Ultraviolet (UV) communication enables non-line-of-sight (NLOS) outdoor wireless connectivity and is particularly desirable to relax or eliminate pointing and tracking requirements of infrared links. The main two degrading factors in UV links are high path loss and intersymbol interference resulting from the frequency selectivity nature of the channel. In this paper, we propose the powerful combination of relay-assisted (cooperative) transmission and multicarrier architecture based on orthogonal frequency division multiplexing (OFDM) for a superior performance over UV channels. Specifically, we consider a cooperative diversity system with orthogonal cooperation protocol and use DC-biased optical OFDM as the underlying physical layer. We investigate the error rate performance of the proposed relay-assisted OFDM UV system and demonstrate significant performance gains over point-to-point OFDM UV systems.
TL;DR: This paper investigates the performance of a cooperative vehicular network over a doubly selective fading channel using multiple antennas at source and destination vehicles and derives a pairwise error probability (PEP) expression and demonstrates the achievable diversity gains.
Abstract: In this paper, we investigate the performance of a cooperative vehicular network over a doubly selective fading channel using multiple antennas at source and destination vehicles. Under the assumption of amplify-and-forward (AF) relaying with orthogonal cooperation protocol and Alamouti-type space–time block coding (STBC), we derive a pairwise error probability (PEP) expression and demonstrate the achievable diversity gains. Our results demonstrate that, via proper linear constellation precoding and digital phase sweeping (DPS), the cooperative vehicular scheme is able to extract the maximum available diversity in frequency (through multipath diversity), time (through Doppler diversity), and spatial (through antenna and cooperative diversity) dimensions. We further conduct Monte Carlo simulations to confirm the analytical derivations and present the error rate performance of the vehicular scheme under various mobility conditions and scenarios.
TL;DR: Simulation results show that the proposed fast-decodable MIMo HARQ protocols in both classes provide a significant reduction in the decoding complexity as compared with the original MIMO HARQ method.
Abstract: This paper presents a comprehensive study on the problem of decoding complexity in a Multi-Input Multi-Output (MIMO) Hybrid Automatic Repeat reQuest (HARQ) system based on Space-Time Block Codes (STBCs). We show that there exist two classes of fast-decodable MIMO HARQ systems: independent and dependent STBC structures. For the independent class, two types of protocols namely, fixed and adaptive threshold-based are presented and their effectiveness in both computational complexity reduction and spectral efficiency preservation are discussed. For the dependent class, a fast Sphere Decoder (SD) algorithm with a low computational complexity is proposed for decoding process of HARQ rounds. Two new concepts are introduced to leverage the fast-decodable notion in MIMO HARQ systems. Simulation results show that the proposed fast-decodable MIMO HARQ protocols in both classes provide a significant reduction in the decoding complexity as compared with the original MIMO HARQ method.