Browsing by Author "Miramirkhani, Farshad"

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15-15-0747-00-007a-tg7r1-cirs-channel-model-document-for-high-rate-pd-communications
(IEEE, 2015-11-14) Uysal, Murat; Baykas, T.; Miramirkhani, Farshad; Serafimovski, N.; Jungnickel, V.; Electrical & Electronics Engineering; UYSAL, Murat; Miramirkhani, Farshad
The LiFi channels developed by Prof. Murat Uysal and Mr. Miramirkhani were selected as the "LiFi Reference Channel Models" by the IEEE 802.15.7r Task Group during the IEEE's latest meeting held in Bangkok, Thailand, in September. Accordingly, all companies, universities and research institutions are required to use these channel models as reference for their performance assessments and comparative analysis in the standardization proposals they will submit over the coming months. The channel models developed by them are the most realistic models available in the literature and pointed out the significance of recognition and adoption of these models by industry.
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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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Channel modeling and characterization for visible light communications
(IEEE, 2015-12) Miramirkhani, Farshad; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Miramirkhani, Farshad
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.
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Channel modeling and characterization for visible light communications: indoor, vehicular and underwater channels
(2018-06) Miramirkhani, Farshad; Uysal, Murat; Tekin, Ahmet; Uğurdağ, Hasan Fatih; Başar, Ertuğrul; Baykaş, Tuncer; Department of Electrical and Electronics Engineering; Miramirkhani, Farshad
Despite the increasing attention on visible light communications (VLC) systems, there is a lack of proper visible light (VL) channel models. This is a serious concern since channel modeling is the very first step for efficient, reliable, and robust VLC system design. This dissertation focuses on channel modeling and characterization study for indoor, vehicular and underwater VLC. Our study is based on Zemax®; a commercial optical and illumination design software. Although the main purpose of such software is optical system design, we take advantage of the ray tracing features of this software which allows an accurate description of the interaction of rays emitted from the lighting source within a specified confined space. The simulation environment is created in Zemax® and enables us to specify the geometry of the environment, the objects within as well as the specifications of the sources (i.e., LEDs) and receivers (i.e., photodiodes). For a given number of rays and the number of reflections, the non-sequential ray tracing tool calculates the detected power and path lengths from source to detector for each ray. These are then imported to Matlab® and processed to yield the channel impulse response (CIR). In contrary to existing works which are mainly limited to ideal Lambertian sources and purely diffuse reflections, our approach is capable to obtain CIRs for any non-ideal sources as well as specular and mixed specular-diffuse reflections. Furthermore, we can precisely reflect the presence of objects and wavelength-dependent reflection characteristics of surface materials in channel study. In the first part of this thesis, we propose a realistic indoor channel modeling approach and carry out a detailed channel characterization study. We also investigate the effect of user mobility and receiver orientation on CIRs. In the second part of this thesis, we present VLC channel models for vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) taking into account the asymmetrical pattern of headlamp and street lights, reflections from road surfaces and weather conditions. We further develop a closed-form path loss expression for V2V VLC channel for different weather conditions. In the last part of this thesis, we carry out a detailed underwater optical channel modeling and characterization study taking into account the reflection characteristics of the sea surface and sea bottom as well as the water characteristics, i.e., extinction coefficient, and scattering phase function of particles. We develop a closed-form path loss expression as an explicit function of water type, beam divergence angle and receiver aperture diameter and validate the accuracy of the proposed expression through Monte Carlo simulation results.
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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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Channel modeling for visible light communications
(Springer Science+Business Media, 2016) Miramirkhani, Farshad; Uysal, Murat; Panayirci, E.; Electrical & Electronics Engineering; UYSAL, Murat; Miramirkhani, Farshad
In this chapter, we present a novel and realistic channel modeling approach for visible light communications that overcomes to the limitations of previous works. In our work, we consider wavelength dependency, effect of realistic light sources as well as different types of reflections such as specular and mixed cases of diffuse and specular. We use non-sequential ray tracing algorithms to calculate the detected power and path lengths from source to detector for each ray. These are then processed to yield the channel impulse responses for various indoor environments. We further present a channel characterization study where channel parameters such as channel DC gain, root mean square delay spread, coherence bandwidth, mean excess delay are calculated for different environments.
Open Access
Channel modelling for indoor visible light communications
(Royal Society Publishing, 2020-04-17) Miramirkhani, Farshad; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Miramirkhani, Farshad
Visible light communication (VLC) allows the dual use of light-emitting diodes (LEDs) for wireless communication purposes in addition to their primary purpose of illumination. As in any other communication system, realistic channel modelling is a key for VLC system design, analysis and testing. In this paper, we present a comprehensive survey of indoor VLC channel models. In order to set the background, we start with an overview of infrared (IR) channel modelling, which has received much attention in the past, and highlight the differences between visible and IR optical bands. In the light of these, we present a comparative discussion of existing VLC channel modelling studies and point out the relevant advantages and disadvantages. Then, we provide a detailed description of a site-specific channel modelling approach based on non-sequential ray tracing that precisely captures the optical propagation characteristics of a given indoor environment. We further present channel models for representative deployment scenarios developed through this approach that were adopted by the Institute of Electrical and Electronics Engineering (IEEE) as reference channel models. Finally, we consider mobile VLC scenarios and investigate the effect of receiver location and rotation for a mobile indoor user.
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Cooperative visible light communications
(Springer Science+Business Media, 2016) Narmanlioglu, Ömer; Caglar Kizilirmak, R.; Miramirkhani, Farshad; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Narmanlioglu, Ömer; Miramirkhani, Farshad
In this chapter, we explore the concept of cooperative transmissions in the context of visible light communications (VLC). An indoor office space is considered with two light sources; the one at the ceiling is connected to the backbone network and provides ambient light to the environment while the other one is mounted on the desk and used for task lighting. The system architecture builds upon DC biased optical orthogonal frequency-division multiplexing (DCO-OFDM). The task light performs relaying operation in either amplify-and-forward (AF) or decode-and-forward (DF) mode. Illumination constraints for task lighting are further considered in order to design a cooperative VLC system that provides satisfactory lighting. The communication performance of the system is optimized through a subcarrier-based power allocation mechanism. Numerical results incorporating practical issues such as band-limited channel process and imperfect channel estimation reveal that cooperative VLC systems can significantly outper-form the conventional point-to-point VLC systems.
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Cooperative visible light communications with full-duplex relaying
(IEEE, 2017-06) Narmanlıoğlu, Ömer; Kizilirmak, R. Ç.; Miramirkhani, Farshad; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Miramirkhani, Farshad; Narmanlıoğlu, Ömer
In this paper, we investigate cooperative visible light communication (VLC) system where an intermediate light source acts as a relay terminal. We assume that relay terminal operates in full-duplex mode. In contrast to radio frequency counterparts, full-duplex VLC terminal is relatively easier to implement due to directive propagation characteristic of light. We first model VLC relay terminal taking into account loop interference channel based on ray tracing simulations. Then, we investigate error rate performance of the relay-assisted VLC system. Our performance evaluations demonstrate the superiority of full-duplex relaying over half-duplex counterpart especially for high modulation sizes.
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A custom-design atmospheric channel emulator for the performance evaluation of free space optical communication systems
(IEEE, 2017) Kebapci, Burak; Miramirkhani, Farshad; Nouri, Hatef; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Kebapci, Burak; Miramirkhani, Farshad; Nouri, Hatef
In this paper, we present our custom design atmospheric channel emulator for free space optical (FSO) system evaluations in a controlled environment. Our emulator is in the form of an atmospheric chamber with dimensions of 60 cm × 40 cm × 300 cm. It is equipped with adjustable heaters, coolers and fans to create the turbulence. It also houses a fog generator and droplet watering system to generate different weather conditions. Using this custom-design emulator, we experimentally investigate the performance of FSO links at different wavelengths in fog conditions.
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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 LED wiring and cabling topologies on visible light communication channels
(IEEE, 2018-01-19) Safaraliev, Sadi; Miramirkhani, Farshad; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Safaraliev, Sadi; Miramirkhani, Farshad
Visible light communication (VLC) is an emerging short-range wireless access technology. It involves the dual use of illumination infrastructure for communication purposes and builds upon the principle of modulating light emitting diodes (LEDs) at very high speeds that are not noticeable to the human eye. Although there has been a growing literature on VLC channel modeling, the existing works mainly overlook the effects of wiring and cabling topologies. Wiring topology refers to how LED chips are connected within the luminaire while cabling topology refers to how the luminaires are connected to the communication access point. In this paper, we adopt ray-tracing based VLC channel modeling approach and consider various cabling/wiring topologies. For each topology, we obtain channel impulse responses (CIRs) and quantify the impact of wiring and cabling delays.
Open Access
Effect of wiring and cabling topologies on the performance of distributed MIMO OFDM VLC systems
(IEEE, 2019) Narmanlıoğlu, Ömer; Kızılırmak, R. Ç.; Miramirkhani, Farshad; Safaraliev, Sadi; Sait, S. M.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Narmanlıoğlu, Ömer; Miramirkhani, Farshad; Safaraliev, Sadi
Since most indoor spaces have multiple luminaires for illumination, for visible light communication (VLC) systems, multiple-input multiple-output (MIMO) communication emerges as a natural solution to improve the data rates and/or the link reliability. The existing works on MIMO VLC systems, however, overlook the characteristics of the lighting infrastructure and the luminaire design, which might have implications for the VLC system design. A luminaire typically consists of multiple LED chips. The wiring topology refers to how the LED chips are connected within the luminaire. The cabling topology, on the other hand, refers to how the luminaires are connected to the communication access point (AP). Based on the type and length of cabling and wiring, significant delays can be introduced, which should be taken into account in channel modeling. In this paper, we adopt the non-sequential ray tracing to model the distributed MIMO VLC channels for various practical wiring and cabling topologies. Based on the developed channel models, we provide a comparative performance analysis of repetition coding (RC), spatial multiplexing (SMUX), and spatial modulation (SMOD) MIMO modes. Our results quantify the effect of wiring/cabling delays and provide insights into the optimized design of lighting infrastructure and luminaires for the support of VLC as an add-on service.
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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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Görünür ışık kanalların modellenmesi ve ACO-OFDM için başarım analizi
(IEEE, 2015) Yeşilkaya, A.; Alsan, H. F.; Miramirkhani, Farshad; Panayırcı, E.; Şenol, H.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Miramirkhani, Farshad
Spectrum scarcity of traditional radio communication has led communication engineers to find new alternatives. Indoor visible light communication is one alternative to solve this problem since its spectrum is not regulated and it has much wider bandwidth then traditional communication systems. This increased the research done in the field of visible light communications. However a proper indoor channel model is lacking and all previous studies assumes that only additive white Gaussian noise (AWGN) is present. Lack of proper channel model has motivated us to model a realistic indoor visible light channel. After modeling the indoor visible light channel, the performance of an asymmetrically clipped optical OFDM (ACOOFDM) system which is suitable for optical communications is investigated and compared to that of the AWGN optical channels.
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Handover in VLC networks with coordinated multipoint transmission
(IEEE, 2018-01-31) Demir, Muhammet Selim; Miramirkhani, Farshad; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Demir, Muhammet Selim; Miramirkhani, Farshad
In this work, we consider a cellular visible light communication (VLC) network where each ceiling luminary serves as an access point (AP). The network is assumed to support coordinated multipoint transmission (CoMP). The user is mainly served by an AP (i.e., luminary) from which he/she gets the strongest signal. When the user moves towards the cell edge, the received signal from the served AP drops. Based on the handover algorithm decision, a handover to another AP can take place or CoMP is initiated. In the case of CoMP, the user is jointly served by two coordinating APs that transmit the same information. We compare the performance of proposed joint transmission-handover algorithm with conventional hard handover and demonstrate significant performance gains in terms of user data rate.
Open Access
IEEE 802.11bb reference channel models for indoor environments
(2018-09-10) Uysal, Murat; Miramirkhani, Farshad; Baykas, T.; Qaraqe, K.; Electrical & Electronics Engineering; UYSAL, Murat; Miramirkhani, Farshad
This contribution proposes 802.11bb reference channel models for indoor environments.
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IEEE 802.15.7r1 reference channel models for visible light communications
(IEEE, 2017) Uysal, Murat; Miramirkhani, Farshad; Narmanlioglu, Ömer; Baykas, T.; Panayirci, E.; Electrical & Electronics Engineering; UYSAL, Murat; Miramirkhani, Farshad; Narmanlioglu, Ömer
The IEEE has established the standardization group 802.15.7r1 “Short Range Optical Wireless Communications”, which is currently in the process of developing a standard for visible light communication (VLC). As with any other communication system, realistic channel models are of critical importance for VLC system design, performance evaluation, and testing. This article presents the reference channel models that were endorsed by the IEEE 802.15.7r1 Task Group for evaluation of VLC system proposals. These were developed for typical indoor environments, including home, office, and manufacturing cells. While highlighting the channel models, we further discuss physical layer techniques potentially considered for IEEE 802.15.7r1.
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LiFi channel models: office, home, manufacturing cell
(IEEE, 2015-09) Uysal, Murat; Miramirkhani, Farshad; Baykas, T.; Serafimovski, N.; Jungnickel, J.; Electrical & Electronics Engineering; UYSAL, Murat; Miramirkhani, Farshad
Purpose Providing channel models which allow a fair comparison of different physical layer (PHY) High Rate PD Communications proposals submitted to TG7r1 in response to the Call for Proposals (CFP). ... Notice This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material.
Restricted
LiFi reference channel models: office, home, hospital
(IEEE, 2015-07) Uysal, Murat; Miramirkhani, Farshad; Electrical & Electronics Engineering; UYSAL, Murat; Miramirkhani, Farshad
Purpose To introduce reference channel models for the evaluation of different PHY proposals. Notice This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material.