• 한국통신학회논문지
• /
• 제33권2A호
• /
• pp.198-203
• /
• 2008

In this paper, we consider the diffuse type of indoor wireless optical communication (WOC) system. To find the channel characteristics of indoor wireless infrared communication system, we investigate the simulation process to get the impulse response of diffuse type and analyze the scenario of the indoor structure which we have built. The simulation results of the impulse response include power ratio and time delay due to bounce times. We get and discuss the receiving power distribution according to six configurations which have different transmitter and receiver positions and reflection coefficients of the indoor structure assumed. The results of this paper are useful to design the indoor wireless optical communication systems.

• 한국전자파학회논문지
• /
• 제21권3호
• /
• pp.285-291
• /
• 2010

본 논문에서는 조명용 LED와 솔라 셀을 사용하여 실내 무선광 통신이 가능함을 보인다. 조명용 LED를 광원으로 사용하면 조명과 신호의 송신을 겸할 수 있으며, 솔라 셀을 수광 소자로 이용하면 조명광을 수신하여 에너지를 축적하는 동시에 신호를 검출할 수 있기 때문에 별도의 통신 시설을 설치하지 않고 전송이 가능하여 매우 편리하다. 실험에서는 조명용 LED와 솔라 셀을 사용하여 9.6 kbps 속도로 무선광 데이터 전송을 실시하였다.

• Journal of the Optical Society of Korea
• /
• 제19권4호
• /
• pp.351-356
• /
• 2015

Visible light communication (VLC) is considered to be an attractive scheme to realize the broadband wireless communication for an indoor environment. We present a room division multiplexing (RDM) mechanism for an indoor multi-room VLC network, which utilizes the spatial position of the LED lamp in different rooms as a novel dimension of network resource for multiplexing, and thus the network capacity is increased. In such a network, the service interruption caused by user cross-room movement is an important problem, and we propose a double-area-positioning based cross-room switch solution. An experimental platform demonstrates the RDM-deployed VLC network, and validates the performance of the presented switch mechanism.

• 한국정보통신설비학회:학술대회논문집
• /
• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
• /
• pp.7-11
• /
• 2008

Future electric lights will be composed of white LEDs (Light Emitting Diodes). Indoor wireless optical communication systems utilizing white LED lights have been studying about it. Generally, plural lights are installed in room. Therefore, their optical path difference must be considered. In this paper, the influence of an optical path difference has been investigated and two approaches against this problem are introduced. One uses OOK-RZ (On-Off Keying, Return-to-Zero) coding and the other uses optical OFDM (Orthogonal Frequency Division Multiplexing). From the results of computer simulations, we have found that these approaches are feasible for the wireless optical communication systems utilizing white LED lights.

• Current Optics and Photonics
• /
• 제2권4호
• /
• pp.308-314
• /
• 2018

Visible light communication (VLC) is considered a strong future candidate for indoor wireless communication. However, its performance seems to be relatively unsatisfactory when compared to wireless local area network (WLAN) communication using millimeter waves. To improve the performance of VLC, numerous technologies have been proposed so far, in both electrical and optical domains. Among the proposals, optical beamforming (OB) is an optical-domain technology that can concentrate light in a specific direction or on a target spot. It can significantly improve VLC performance and can be widely used, because it does not depend on electrical modulation schemes. Therefore, this review discusses the concept, principle, and types of OB, the structure of a VLC system using OB, performance results of OB, and the combination of OB with electrical signal modulation in VLC. OB is expected to be one of the key techniques in future VLC implementations, similar to radio-frequency beamforming in millimeter-wave communication.

• Journal of Advanced Marine Engineering and Technology
• /
• 제34권6호
• /
• pp.852-857
• /
• 2010

본 논문에서는 조명으로 사용되는 LED를 이용하여 실내 가시광 통신을 할 수 있는 시스템을 제안하고 있다. LED는 디지털 변조가 가능하므로 조명과 더불어 광무선 통신시스템으로 적용할 수 있다는 개념과 연구결과에 기인하여 기초연구를 수행하였다. LED는 고 휘도, 신뢰성, 저 전력 소비, 긴 수명의 장점을 가지므로 고 품질의 통신서비스를 제공하는 통신용 광원으로서도 적합하다. 본 연구에서는 오디오 전송을 위한 단방향 광무선 통신시스템과 텍스트 메시지를 전송하기 위한 양방향 통신시스템을 구현하여 통신 성능을 실험하였다. 이 실험결과는 실내 무선 환경을 지향하는 조명등의 내부회로로 설치될 수 있는 저가형 광통신 트랜시버의 구현이 가능함을 보여준다.

• 한국통신학회논문지
• /
• 제33권12A호
• /
• pp.1251-1260
• /
• 2008

Diffuse wireless optical communication offers more robust optical links in terms of coverage and shadowing than line-of-sight links. However, traditional diffuse wireless infrared (IR) transceiver systems are more susceptible to multi-path distortion and great power decrease, which results in limiting high-speed performance. Multi-beam is an effective technique to compensate for multi-path distortion in a wireless infrared environment. The goal of this paper is to analyze the transmission characteristics by replacing traditional diffuse system (TDS) which contains single wide angle transmitter and single element receiver by system consisting of three-beam transmitter and non-imaging receiver (TNS) attached with compound parabolic concentrator (CPC). In the simulation, we use the recursive model developed by Barry and Kahn and build the scenario based on 10 different cases which have been listed in Table 1. Moreover, we also check the reliability of the TNS diffuse link channel by BER test on the basis of different receiver positions and room sizes. The simulation results not only show the basic transmission characteristics of TNS diffuse link, but also are references to design more efficient and reliable indoor infrared transmission systems.

• 센서학회지
• /
• 제23권1호
• /
• pp.1-6
• /
• 2014

In many medical image devices, dc noise often prevents normal diagnosis. In wireless capsule endoscopy systems, multipath fading through indoor wireless links induces inter-symbol interference (ISI) and indoor electric devices generate impulsive noise in the received signal. Moreover, dc noise, ISI, and impulsive noise are also found in optical fiber communication that can be used in remote medical diagnosis. In this paper, a blind signal processing method based on the biased probability density functions of constant modulus error that is robust to those problems that can cause error propagation in decision feedback (DF) methods is presented. Based on this property of robustness to error propagation, a DF version of the method is proposed. In the simulation for the impulse response of optical fiber channels having slowly varying dc noise and impulsive noise, the proposed DF method yields a performance enhancement of approximately 10 dB in mean squared error over its linear counterpart.

• Journal of the Optical Society of Korea
• /
• 제19권6호
• /
• pp.586-591
• /
• 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 Advanced Marine Engineering and Technology
• /
• 제36권8호
• /
• pp.1111-1116
• /
• 2012

현재 LED 조명을 이용한 실내 광무선 통신 기술은 상당히 폭 넓게 연구되고 있다. 각 가정에 설치된 전력선 인프라를 조명통신에 접목할 경우 홈 네트워크의 광대역 접속에 대한 요구를 충족시 킬 수 있는 매우 유용한 방법으로 주목받고 있다. 본 연구에서는 LED를 실내조명용과 원격제어를 위한 통신용의 두 가지 조건을 만족시키는 시스템을 설계하고, 광무선제어 성능을 검증하기 위하여 모형차를 제작하여 통신조건을 만족시키는 적절한 조도를 제시하였다. 간이 테스트베드를 이용하여 동작실험을 성공적으로 수행하였다. 가시권에서만 통신할 수 있는 제한에도 불구하고 제안된 기술은 원격제어 시스템이 필요한 전자파 장애지역에서 광무선 통신 기술을 적용하는 새로운 응용영역을 개척할 수 있을 것으로 기대된다.