Browsing by Author "Baykas, T."

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A 130 nm CMOS receiver for visible light communication
(IEEE, 2022-06-15) Kısacık, Rıfat; Yagan, M. Y.; Uysal, Murat; Pusane, A. E.; Baykas, T.; Dundar, G.; Yalcinkaya, A. D.; Electrical & Electronics Engineering; UYSAL, Murat; Kısacık, Rıfat
Visible light communication (VLC) is an emerging technology that has been gaining attention over the last few years. Transmission of data at higher rates in a VLC system is mainly limited by the modulation bandwidth of the employed LED. To alleviate this limitation, equalization is frequently employed. This is usually achieved by either using discrete circuit elements or in digital form. In this paper, we present a power-efficient VLC receiver as a system-on-chip, implemented in 130 nm CMOS technology. The proposed receiver supports LEDs with different bandwidths thanks to the switchable equalizer. We tested the proposed receiver using phosphorescent white LEDs with different bandwidths on an experimental VLC link. For each tested LED, around 20 fold improvement in data rate was achieved compared to the original bandwidth of the LED. For the LED with a modulation bandwidth of 1.6 MHz, data rates of 32 Mbps and 50 Mbps at a BER of 102 were obtained at a distance of 2 meters without and with a blue filter, respectively.
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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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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, Yusuf
In 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.
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Characterization of LEDs for visible-light communications
(SPIE, 2021-02) Kısacık, Rıfat; Yalcinkaya, A. D.; Pusane, A. E.; Baykas, T.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Kısacık, Rıfat
Recent advances in solid-state technologies have enabled the development of light-emitting diodes (LEDs) with favorable features such as long life expectancy, low-power consumption, and reduced heat dissipation. Visible-light communication (VLC) is a short-range wireless access technology that deploys LEDs as wireless transmitters in addition to their primary task of illumination. The major limitation for the design of high-speed VLC systems is the electrical (modulation) bandwidth of the LED. In this study, we investigate the electrical characteristics of a number of off-the-shelf LEDs. Specifically, we determine their frequency responses and match them to their small-signal models. The electrical bandwidths of measured LEDs vary from 250 kHz to 20 MHz and depend on the emitted color and internal circuitry. As a verification of our measurements, we use the sample LEDs as a transmitter in a VLC system setup and determine the supported data rates. The equivalent circuit model is utilized to compare with the measured modulation characteristic of the LED. Furthermore, the bias current effect on the modulation bandwidth is presented.
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Comparative performance evaluation of VLC, LTE and WLAN technologies in indoor environments
(IEEE, 2021) Zeshan, A.; Karbalayghareh, M.; Miramirkhani, F.; Uysal, Murat; Baykas, T.; Electrical & Electronics Engineering; UYSAL, Murat
Recent years have seen an exponential rise in the demand for indoor wireless connections that have driven future generation networks to aim for higher data rates with extended coverage and affordable rates. The two most prominent technologies for providing indoor wireless connections, WLAN and LTE, have their limitations and they can not coexist in a single band to form heterogeneous networks (HetNets). Visible light communication (VLC) has seen rapid growth in recent years as it has the capability to seamlessly merge with the existing technologies and provide wireless connections with high data rates. VLC based hybrid indoor network effectively combines the preferences of an end-user with the practicality of implementation. In this work, we investigate specific VLC/WLAN and VLC/LTE hybrid scenarios to perform a detailed analysis on the effect of user mobility on the performance of the system and how the performance of the network (in terms of throughput) can be maximized. The study aims to show how different technologies complement each other in the best and even the worst-case scenarios.
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Distance and power based experimental verification of channel model in visible light communication
(IEEE, 2019) Kısacık, Rıfat; Efe, B. C.; Pusane, A. E.; Uysal, Murat; Baykas, T.; Dündar, G.; Yalcinkaya, A. D.; Electrical & Electronics Engineering; UYSAL, Murat; Kısacık, Rıfat
In this work, a channel model for line-of-sight (LOS) in visible light communication is elaborated. In the proposed channel model, there is no optical component, such as filter or lens, between the transmitting LED and the receiving photodiode. Later, a suitable setup is built for emulation of the mentioned channel model. In the setup, the LED and the photodiode are located in a line-of-sight orientation. The change of the optical power on the photodiode is measured by varying the distance between the LED and photodiode. The measurement result is compared with the channel model. The channel model is in good agreement with the measurement results. Following that, the signal-to-noise ratio (SNR) at the output of the receiver, as a function of the distance, is measured. Measurement results indicate that the SNR value remains below 15 dB after exceeding a distance of 20 cm for the specific LED-Photodiode pair used in the experiment. The optical signal on photodiode drops to the noise level when the distance exceeds 50 cm.
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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 an FPGA-based outdoor VLC broadcasting system
(IEEE, 2023) Bağlıca, İbrahim; Ashfaq, Bismillah Nasir; Ergin, S.; Kebapçı, B.; Baykas, T.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
Visible light communication (VLC) uses light-emitting diodes (LEDs) to transmit data by turning them on and off at very high speeds, too fast for the human eye to perceive. In outdoor environments, LED-based streetlights can be utilized as VLC transmitters. Given the ubiquity of street lights, they are particularly useful for outdoor broadcasting as required in public safety systems. In this paper, we develop an FPGA-based VLC system with on-off keying using a LED-based streetlight. The system is built upon the Eclypse Z7 FPGA platform integrated with opto-electronic transmitter and receiver front-ends. We present error rate performance results up to transmission distances of 8 meters.
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Experimental validation of a novel RLL code for visible light communication
(IEEE, 2020) Yagan, M. Y.; Kısacık, Rıfat; Erkinaci, T.; Pusane, A. E.; Uysal, Murat; Baykas, T.; Dundar, G.; Yalcinkaya, A. D.; Electrical & Electronics Engineering; Herencsar, N.; UYSAL, Murat; Kısacık, Rıfat
Flicker arising in visible light communication (VLC) system is typically mitigated by run-length-limited (RLL) codes. The IEEE 802.15.7 standard proposes RLL codes according to the modulation type and data rate. In this paper, we propose a new RLL code and present the encoding and decoding operations for use in VLC systems. We provide experimental results for bit error rate (BER) for transmission of uncoded, 8B10B-coded and proposed code at different data rates in a VLC setup. We experimentally demonstrate that the proposed code performs close to the 8B10B code. The proposed code achieves a BER of 10(-5) at 50 Mbps where transmitting the uncoded data at the same rate results in the BER of 10(-3).
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 802.11BB reference channel models for light communications
(IEEE, 2023-12-01) Miramirkhani, F.; Baykas, T.; Elamassie, Mohammed; Uysal, Murat; Electrical & Electronics Engineering; ELAMASSIE, Mohammed; UYSAL, Murat
Increasing industrial attention to visible light communications (VLC) technology led the IEEE 802.11 to establish the task group 802.11bb 'Light Communications' (LC) for the development of a VLC standard. As a part of the standard development process, the development of realistic channel models according to possible use cases is of critical importance for physical layer system design. This article presents the reference channel models for the mandatory usage models adopted by IEEE 802.11bb for the evaluation of system proposals. The use cases include industrial, medical, enterprise, and residential scenarios. Channel impulse responses and corresponding frequency responses are obtained for each use case using a ray tracing approach based on realistic specifications for transmitters and receivers, and optical characterization of the environment.
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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.
Open Access
Link adaptation for MIMO OFDM visible light communication systems
(IEEE, 2017-11-10) Narmanlıoğlu, Ömer; Kizilirmak, R. C.; Baykas, T.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Narmanlıoğlu, Ömer
In this paper, we investigate link adaptation for an orthogonal frequency division multiplexing (OFDM)-based multiple-input multiple-output (MIMO) visible light communication (VLC) system. The proposed adaptive OFDM VLC system supports both repetition coding (RC) and spatial multiplexing (SM) as MIMO modes and allows spatial mode switching based on channel conditions. Regarding to the instantaneous signal-to-noise ratio for both RC and SM modes, the maximum constellation size that can be supported for each MIMO mode on each subcarrier is determined. The MIMO mode that gives the highest spectral efficiency (SE) is then selected. The proposed joint MIMO mode selection and bit loading scheme maximizes the SE while satisfying a target bit error rate. Our numerical results reveal that a peak data rate up to 18.3 Gb/sec can be achieved in a 16 × 16 MIMO setting using light emitting diodes with cut-off frequency of 10 MHz in typical indoor environments.
Open Access
TG7r1 channel model document for high rate PD communications
(2015-09-10) Uysal, Murat; Baykas, T.; Miramirkhani, Farshad; Serafimovski, N.; Jungnickel, V.; 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 contained herein.