• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.4
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• pp.740-749
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• 2015

In the visible light (VL) communication based on the conventional LED lights, depending on the increase of the communication range, the signal received at the photodiode of the VL receiver has usually the random distorted and decreased amplitude due to the path loss and fading effects of the VL channel. In order to overcome this problem, we propose, design, and implement the visible light communication circuit based on the comparator threshold voltage, where has a built-in distance compensation function. In addition, the performance of the proposed technique is evaluated and analyzed depending on the distance and communication speed through comparing the proposed VLC system based on the threshold voltage with the conventional one.

• Journal of Sensor Science and Technology
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• v.26 no.3
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• pp.192-198
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• 2017

In this paper, we newly developed a passive transponder for visible light identification (VLID) using ultrasonic wave. The solar cell in the transponder receives the reader light and generates current for supplying power to the transponder circuit. At the same time the solar cell detects the interrogating signal in the visible light from the reader. The transponder recognizes the interrogating signal and generates the responding signal using ultrasonic wave. In experiments, we used 40 kHz ultrasonic wave for the responding signal from the transponder. The maximum read distance was about 3.4 m when the transponder was exposed to the reader light of 24W LED array.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.9B
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• pp.1117-1125
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• 2011

In this paper, as a study of the simple visible light communication(VLC) with LED light, the visible light communication system that are made up with the $3{\times}3$ white LED array for visible light transmission, various photodiodes for visible light reception, and a non-carrier NRZ-OOK modulation scheme is designed and implemented to have a 115.2 kbps data speed at 2.5 m distance between transmitter and receiver. For the performance analysis of the developed VLC system, the maximum distance between VLC transmitter and receiver on the conditions of various transmission speeds, the number of LED array, or the various kind of LED and photodiode is obtained, and various performances are analyzed by experiments.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.6
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• pp.935-941
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• 2017

This paper proposes a method for estimating the distance betweeen vehicles in a moving situation using the image ratio of the distance between the tail lamps of a front vehicle. The actual distance between the tail lamps of a front vehicle was transmitted by LED tail lamps using visible light communication. As the distance between the front vehicle and the rear vehicle changes, it calculates the ratio of the pixel width between the tail lamps of the front vehicle projected on the image. The calculated values are used to derive a distance-mapping function through non-linear regression technique. Then, the distance between vehicles in the moving situation is estimated based on this function.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.6 no.1
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• pp.51-56
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• 2013

In this paper, we had design the module of the LED-based media transmission mechanics visible light communication system. To implement the media transmission system through visible light communication transmitter, receiver module the using high brightness, we proposed visible light communication system to implement communication distance of up to a maximum transmitter-receiver distance using a variable PD sensor to the receiver and 1~12 the LED light-emitting device to the transmitter. It was increased efficiency of approximately 20% by measuring the performance during lens wearing or not wearing on the LED module to improve the efficiency of the media transmission system.

• Transactions on Electrical and Electronic Materials
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• v.11 no.5
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• pp.238-241
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• 2010

The purpose of this study is to solve the problems of radio frequency bandwidth frequency depletion, confusion possibilities, and security that are in current wireless communications systems, and to confirm the possibility of applying those solutions for the next generation network. To solve the problems of the current wireless communications system, a visible light communications system for power line communication (PLC) via 8-bit microcontroller is created and the capacity is analyzed. The exclusive PLC chip APLC-485MA, an 8-bit ATmega16 microcontroller, high brightness 5pi light emitting diodes (LEDs), and the LLS08-A1 visible light-receiving sensor were used for the transmitter and receiver. The performance was analyzed using a designed program and an oscilloscope. The voltage change was measured as a function of distance from 10-50 cm. Blue LEDs showed the best performance among the measured LED types, with 0.47 V of voltage loss, but for a distance over 50 cm, precise data was not easy to obtain due to the weak light. To overcome these types of problems, specific values such as the changing conditions and efficiency value relevant to the light emitting parts and the visible light-receiving sensor should be calculated, and continuous study and improvements should also be realized for better communication conditions.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.11
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• pp.2043-2047
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• 2010

This study is to solve problems of depletion of RF bandwidth frequency, confusion possibility, security that current wireless communications system have and is to confirm possibility of applying next generation network. To solve problems of current wireless communications system, visible light communications system for power line communications using ATmega16 Microcontroller is was realized and receiver property was analyzed. PLC exclusive chip APLC-485MA, Microcontroller ATmega16, 5pi bulb type LED and high flux LED, visible light receiving sensor LLS08-A1 were used for transmitter and receiver. Performance was analyzed by designed program and an oscilloscope. It was showed average 20% improved receiver rate rather than bulb type LED in the case of high flux LED through voltage change rate on communication distance and LED type of distance between 10 to 50 cm. The blue LED showed the best performance among measured LED types with above 10% of voltage decreasing rate. But As it gradually becomes more distant, the precise date was difficult to obtain due to weak light. To overcome these sort of problems, specific values such as changing conditions and efficiency value relevant to light emitting parts and visible light receiving sensor should be calculated and continuous study and improvements should also be accomplished for the better communications condition.

• Imaging Science in Dentistry
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• v.34 no.3
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• pp.123-128
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• 2004

Purpose: To evaluate the reliability of measurements in spiral tomography through assessing the visibility of the alveolar crest and the measurements between the alveolar crest and other anatomic structures. Materials and Methods: 110 spiral tomograms of the jaws were taken by Scanora X-ray unit from the patients. The visibility of the alveolar crests was estimated by 3 observers and classified as clearly visible, questionable visibility, or not visible. 3 observers measured the distance between the alveolar crest and the reference points of anatomic structures. The measurements were repeated 2 weeks later. Results: 52.9% of alveolar crests on upper jaws and 61.5% of alveolar crests on lower jaws were visible. The interobserver and intraobserver agreements on the visibility were low. The mean ranges of the measurements were 1.39 mm (SD = 1.37 mm) on maxilla and 1.03 mm (SD = 1.01 mm) on mandible in the interobserver evaluation. The interobserver variance was greater than the intraobserver variance in the measurements of distance. Conclusion: Spiral tomography showed a relatively low reliability in the visibility and measurements of the alveolar crest.

• Journal of Korean Society for Geospatial Information Science
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• v.17 no.4
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• pp.75-80
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• 2009

The Beacon Mounds play a important role in defence and communication extending from the period of the Three States to the period of Chosun. About the research of beacon mounds have focused on investigation in old literature. This research analyzed geographic factors such as altitude, cross section, distance and visible distance affect in selecting location of beacon mounds. And it was presumed how each beacon mound geographic characteristics was considered in selecting location of beacon mounds. As a result, it is presumed that communicating among beacon mounds and watching the coast were affected by geographic characteristics and selecting location of beacon mounds was considered by several geographic factors.

• Journal of the Optical Society of Korea
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• v.19 no.5
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• pp.514-520
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• 2015

This paper presents a novel shore-to-sea maritime data transmission system based on time-code diversity, using visible light in maritime environments to overcome the limitations of conventional maritime wireless communications. The proposed system is primarily comprised of existing LED-based lighthouses and maritime transceivers (marine beacons, buoys, etc.), and thus is considered cost-effective in terms of implementation. We first analyze maritime visible-light communications on the basis of the unique properties of a maritime environment, i.e. sea states (wave height, wind speed, etc.), plus atmospheric turbulence, using the Pierson-Moskowitz (PM) and JONSWAP (JS) spectrum models. It is found that the JS model outperforms the PM model, and that the coverage distance depends on the LED power and sea states. To combat maritime fading conditions that significantly degrade performance and coverage distance, we propose a time-code diversity (TCD) scheme in which the delayed versions of the original data are retransmitted using orthogonal Walsh codes. This TCD scheme is found to be superior, in that it offers three orders of magnitude in terms of BER performance, compared to a conventional (non-TCD) transmission scheme. The proposed scheme is robust and efficient in overcoming the effect of impairments present in maritime environments with a BER of approximately $10^{-5}$and a data rate of 100 Kbps at a distance of 1 km.