• Journal of Broadcast Engineering
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• v.14 no.4
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• pp.475-487
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• 2009

We propose a visible light road-to-vehicle communication system at intersection as one of ITS technique. In this system, the communication between vehicle and a LED traffic light is approached using LED traffic light as a transmitter, and on-vehicle high-speed camera as a receiver. The LEDs in the transmitter are emitted in 500Hz and those emitting LEDs are captured by a high-speed camera for making communication. Here, the luminance value of each LED in the transmitter should be found for consecutive frames to achieve effective communication. For this purpose, first the transmitter should be identified, then it should be tracked for consecutive frames while the vehicle is moving, by processing the images from the high-speed camera. In our previous work, the transmitter was identified by getting the subtraction of two consecutive frames. In this paper, we mainly introduce an algorithm to track the identified transmitter in consecutive frames. Experimental results using appropriate images showed the effectiveness of the proposal.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.9
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• pp.787-794
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• 2012

The visible light communication is considered as a next generation communication technology, when utilizes LED and PD for communication. Since it is easy to provide LOS communication environment along with cheap deployment cost, the positioning system based on VLC has been actively studied. However, the existing positioning system using VLC requires a complex computation and an additional deployment cost due to sensors for example. In this paper, we propose a new positioning system based on VLC which does not require additional complexity and the cost. In addition, the procedure for operating LED panels for positioning and the recognition schemes of pilot signal are proposed. The performance of recognition schemes of pilot signal is analyzed through the computer simulations.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.1
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• pp.23-30
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• 2014

Recently, Light Emitting Diode(LED) light is changing the light equipment, which was considered just as a power-controlled device in home-network, into a IT convergence device by combining illumination function with wireless communication. As a result, Visible Light Communication(VLC) becomes a more practical solution to ubiquitous networks due to the more spread of LED light. One of representative applications using VLC is a VLC-based indoor navigation system which can provide high-accuracy indoor localization. In this paper, we model and implement a VLC based-indoor navigation system in which a fluorescent light type of LED lamp, which is normally used in large buildings, and smart devices, which are usually used by users, are utilized as main components for indoor navigation. Subsequently, it is expected that the paper can contribute to make VLC applications be more active.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.6
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• pp.476-481
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• 2014

In this paper, we design the pre-equalizer of transmitter circuit in order to enhancement modulation bandwidth of white LED which is light source of VLC (Visible Light Communication). Also, we eliminate yellow light component by optical filtering which mitigate frequency response of white LED. Power loss by optical filtering is overcome by using convex lens. By applying proposed system, 3 dB bandwidth deciding modulation bandwidth of white LED increases from 3 MHz to more than 25 MHz and the transmission distance increases by optical design which secure additional signal power. We optically modulate NRZ-OOK signal to LED and receive light signal using APD. We analyze received data using CSA and RFSA. As a result, we experimently demonstrate the possibility that transmits NRZ-OOK signal up to 30 Mbps in 4.5 m, 50 Mbps in 1.5 m through the pre-equalizer and optical design.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.10
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• pp.3-10
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• 2012

The visible light communication takes advantages of LED and PD for communication and is considered as a next generation wireless communication technology. It can support variety indoor applications. Especially, Visible LAN service has drawn much attention due to high data rate and no interference with existing WPAN system as well as high efficiency in illumination. However, existing MAC protocol occurs a high communication delay due to uplink collision and backoff time. In this paper, to reduce packet delay, we propose an enhanced MAC protocol based on FDD where the time difference between uplink frame and downlink frame transmission is utilized. Through computer simulations, we verified that the proposed MAC protocol outperforms the existing MAC protocol in terms of average packet delay.

• Journal of the Optical Society of Korea
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• v.19 no.6
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• pp.586-591
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• 2015

In recent years, along with the rapid development of LED technology, indoor positioning systems based on visible light communication (VLC) have been researched. In this paper, we propose an accurate indoor positioning method using white-light LEDs and a dual image sensor. Indoor LED lights are located at the ceiling in a room and broadcast information on their positions using VLC technology. A mobile device with a dual image sensor receives LED position information by VLC and estimates its position and azimuth angle. Simulation and experimental results are given to show the performance of the proposed indoor positioning system.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.1
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• pp.79-85
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• 2016

Recently, visible light communication(VLC) is being actively researched as green wireless communication services are drawing attention. Currently, VLC mostly uses LED for transmission and PD(Photo Diode) for receiving. However, this kind of system has limited applications. Therefore, we design and propose in this paper, a LED-to-LED two way VLC system that doesn't use PD(Photo Diode). This system has the following features and contributions. First, this system uses just LED at both transmitter and receiver with analog switch, Second, this system support both one-way communication and two way communication together. One way communication can support multi-hop communication. The performance evaluation of the proposed system is conducted at a place with standard light. We test the success or failure of one way communication by changing distance and baud rate while test the success and failure of two way communication by changing distance. We expect that the proposed LED-to-LED system in this paper can be applied for various application fields.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.226-229
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• 2010

LED(Light Emitting Diode) is an emitting device which energy is same to the bandgap of p-type and n-type semiconductor junction. Recently high brightness LED is used in fish-luring light and traffic signal light alternative of normal light bulb, and widely used in the area of display pannel. Moreover nowadays LED has been used as a back light of LCD display. Recently, visible light communication(VLC) using LED, that allow two-way serial data communication between LEDs over a distance of sveral centimeters or meters, has been widely studied in the area of digital information transmission along with illumination and display. In this paper, we present LED communication system and their applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.9
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• pp.784-790
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• 2012

In this paper, we propose a upstream transmission method to extend coverage in visible light communication (VLC) systems. We extend transmission distance by using focused infrared(IR) light emitting diodes(LEDs). Since the focused light covers just limited area, it might have a difficulty in transmitting data if the transmitter and receiver are not properly aligned. To solve this problem, we arrange multiple IR-LEDs in different direction and select a single best performing IR-LED among multiple IR-LEDs. Also, the transmission performance is periodically checked and another IR-LED is reselected to support the required quality of service (QoS) and to minimize battery consumption required by a mobile terminal.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.2
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• pp.309-314
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• 2012

In this paper, we present surface-to-underwater visible light communication systems using white LEDs. Pulse position modulation (PPM)-based analogue data communications and on-off keying-based digital data communications systems are developed. Inexpensive and commercial power-LEDs and photo-diodes are used to construct two types of systems. We report the experimental results obtained from the prototype systems to show the possibility of an optical underwater visible light transceiver as a basis for short range underwater wireless network. Their performance deteriorates more than the atmosphere's one because of attenuation and scattering of the light in water, but these results are promising for the potential to create more robust network interface that improve medium performance such as a LED modulation and a photo-detector demodulation.