• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.14 no.3
• /
• pp.33-42
• /
• 2014

In this paper, we summarize and analyze recent VLC based transmission systems and application technologies by identifying the main issues and challenges and by using several performance parameters. First, we explain the main characteristics of VLC as well as the comparisons of VLC with other technologies. Second, we describe the current issues for VLC technology. Third, we classify and explain the several technologies among VLC based transmission systems in the state of arts in the view points of features, advantages and disadvantages. Fourth, we make a quantitative comparison table for the selected current VLC based transmission systems. Finally, we explain the main application technologies of VLC.This paper.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.22 no.1
• /
• pp.140-146
• /
• 2018

Recently, VLC(Visible Light Communication) fusing with LED(Light Emitting Diode) used in indoor lighting and wireless communication technology has attracted attention. However, the VLC can communicate only within the coverage to measure the optical signal and the communication disconnection phenomenon is occur in the NLoS(Non-Line-of-Sight) area. In this paper, we propose VLC relay module to extend the coverage of VLC and improve the communication disconnection phenomenon in NLoS area. The proposed VLC relay module transmits the packet received from the transmitter to the VLC relay module and receiver. The experiment was carried out by installing one VLC transmitter and three VLC relay modules, communication coverage expansion and the improvement of communication disconnection phenomenon in the NLoS were confirmed by the increase of the VLC relay module. Also, we confirmed that the optical signal measurement performance is improved 2.4 times by using the dual sampling method.

• Journal of Satellite, Information and Communications
• /
• v.10 no.3
• /
• pp.44-47
• /
• 2015

In this paper, P2P VLC Sound Transmission Technology between Underwater Object of 5cm Distance. It proposed a P2P VLC sound transmission technology, and developed a P2P VLC sound transmission technology between LED transmitter and PD(Photo Detector) receiver of 15cm distance. Under the assumption that the underwater environment, it performs a P2P VLC sound transmission experiment between LED transmitter and PD receiver for sound transmission, and demonstrated the usefulness of the proposed technology. In this paper, P2P VLC Sound Transmission Technology between Underwater Object of 5cm Distance, and proposed technology is expected to be widely used in various fields because it can use P2P VLC sound transmission technology between underwater object in the underwater environment.

• Journal of IKEEE
• /
• v.22 no.3
• /
• pp.742-746
• /
• 2018

In this paper, we implemented a VLC(Visible Light Communication) system capable of transmitting/receiving data on a 30MHz clock based on On/Off keying modulation/demodulation. The data rate of the implemented system can be verified by functional verification of VLC channel composed of LED/photodiode driver and VLC transmitting/receiving signal of Tx/Rx platform. But, In the experimental results with the VLC transmitting/receiving for combined module, the maximum transmission rate was measured at 15 MHz. Therefore, we describe the problems that can occur when implement the VLC system using the LED module with output power of 15W or more and propose ways to improve it.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.48 no.5
• /
• pp.1-6
• /
• 2011

LED(Light Emitting Diode) components have advantages of longer lifetime, lower power consumption and easy-to-control, compare to normal lamp and fluorescent light, according to the development of recent technologies. Thus, lots of illuminations which utilize LED components could be used. Recently, Visible Light Communication(VLC) which is a part of communication technologies, utilizing high speed response characteristic of LED components, started receiving public attention. In case of VLC, there is no need of frequency allocation due to no use of radio, but also no interference exists during data transmission, much different in ISM((Industrial Scientific Medical band). This is the reason why a lot of research results about VLC are becoming issued. In this paper, a survey of feasibility for using VLC utilizing an original LED illumination for underwater applications has been done and a primitive possibility of its application has been examined.

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

• Current Optics and Photonics
• /
• v.2 no.6
• /
• pp.532-539
• /
• 2018

Multiple LED arrays can be utilized in visible-light communication (VLC) to improve communication efficiency, while maintaining smart illumination functionality through dimming control. This paper proposes a modulation scheme called "Spatial Intensity Modulation" (SIM), where the effective number of turned-on LEDs is employed for data modulation and dimming control in VLC systems. Unlike the conventional pulse-amplitude modulation (PAM), symbol intensity levels are not determined by the amplitude levels of a VLC signal from each LED, but by counting the number of turned-on LEDs, illuminating with a single amplitude level. Because the intensity of a SIM symbol and the target dimming level are determined solely in the spatial domain, the problems of conventional PAM-based VLC and related MIMO VLC schemes, such as unstable dimming control, non uniform illumination functionality, and burdens of channel prediction, can be solved. By varying the number and formation of turned-on LEDs around the target dimming level in time, the proposed SIM scheme guarantees homogeneous illumination over a target area. An analysis of the dimming capacity, which is the achievable communication rate under the target dimming level in VLC, is provided by deriving the turn-on probability to maximize the entropy of the SIM-based VLC system. In addition, a practical design of dimmable SIM scheme applying the multilevel inverse source coding (MISC) method is proposed. The simulation results under a range of parameters provide baseline data to verify the performance of the proposed dimmable SIM scheme and applications in real systems.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2014.05a
• /
• pp.483-486
• /
• 2014

A Visual Light Communication(VLC) system is a concept of converging illumination with communication. Design of the VLC system aims mainly at minimizing flicker for the illumination and maximizing transmission distance for the communication. This paper proposes an effective detection scheme of the transmitted signal by attenuating noises which may be included in the signal, and then presents implementation results. Inserting designated low and high pass filters in first and second implementations, the receiver became to improve the perception rate of transmitted signals. This verified a relatively higher possibility of receiving data in a dim light, so that the communication distance can be expanded in the visual light communication system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2021.10a
• /
• pp.469-471
• /
• 2021

As wireless communication technology advances to ensure high accuracy and safety at high speeds, research and development of Visible Light Communication (VLC) technology has been accelerated as an alternative to traditional radio frequency (RF) technology. As the radio spectrum of RF communication becomes more congested and demand for bandwidth continues to increase, VLCs that can use unlicensed frequency band are proposed as a solution. However, VLC channels have broadcasting characteristics that make them easily exposed to eavesdropping and jamming attacks, and are vulnerable to MITM (Man-In-The-Middle) due to their line of sight (LOS) propagation characteristics. These attacks on VLC channels compromise the confidentiality, integrity, and availability of communications links and data, resulting in higher data retransmission rates, reducing throughput and increasing power consumption, resulting in lower data transmission efficiency. In this work, we model vulnerable VLC channels to analyze the impact of attacks and communications vulnerabilities by malicious jammers.

• Proceedings of the IEEK Conference
• /
• 2005.11a
• /
• pp.39-42
• /
• 2005

H.264, a recently proposed international video coding standard, has adopted context-based adaptive variable length coding (CAVLC) as the entropy coding tool in the baseline profile. By combining an adaptive variable length coding technique with context modeling, we can achieve a high degree of redundancy reduction. However, CAVLC in H.264 has weakness that the correct prediction rate of the variable length coding (VLC) table is low in a complex area, such as the boundary of an object. In this paper, we propose a VLC table prediction scheme considering multiple reference blocks; the same position block of the previous frame and the neighboring blocks of the current frame. The proposed algorithm obtains the new weighting values considering correctness of the VLC table for each reference block. Using this method, we can enhance the prediction rate of the VLC table and reduce the bit-rate.