• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.12 no.1
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• pp.66-74
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• 2013

This paper introduces the improvement of QoS to compensate the decreasing LED performance by temperature characteristic in the LED-ID communication system. LED does not only use as a lighting device, but also uses as a communication device. The conventional system is transmitted by RGB of LED following the mixture color ratio, which determined the color of lighting, and the BER performance of each RGB signals. However, when the LED used consistently, it has occurred the heat temperature. As a result, LED is degraded the performance by increased temperature each device. To solve this problem, we proposed the adaptive modulation and coding scheme by temperature of device to improve the performance of system and satisfied the QoS in the LED-ID system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.4
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• pp.411-417
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• 2014

In this paper, we propose an efficient OFDM(Orthogonal Frequency Division Multiplexing) frame synchronization scheme for LED-ID(Identification) systems. A frame synchronization is an essential procedure for normal operations of OFDM systems. Bernoulli-Gaussian noise is considered in LED-ID systems' environments. In order to enhance the OFDM frame synchronization performance, we add a ROGS(Repeated Orthogonal Gold Sequence) to OFDM signals in the time domain. The power level of a ROGS does not affect a normal operation of the LED-ID systems. Frame synchronization can be achieved successfully over LED-ID channels interfered by impulsive noise owing to good auto and cross-correlation properties of the ROGS.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.4
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• pp.43-51
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• 2010

In this paper, we studied line coding technology tendency for high speed data communication at LED-ID (Identification) communication system in indoor environment. A LED-ID technology is a communication using visible ray (RGB) that come out in LED device. It is energy curtailment effect and possible in ubiquitous network service applications. The LED-ID system has the above advantages about that the communication throughout the whole room is enabled by high power lighting and lighting equipment with white colored LED which are easy to install and have good outward appearance. Therefore, the transmission by light waves is more suitable for wireless networks than by radio waves. We compared with the NRZ, AMI, 4B5B, HDB3, 8B10B line coding for efficient in error detection and serves data transmission of high speed.

• Journal of Digital Convergence
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• v.13 no.10
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• pp.319-325
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• 2015

We proposed the blocking channel to reduce the performance decrease using the low correlation with cyclic delay scheme in LED-ID system. LED-ID is based on the visible light to transmit the data. However, It is occurred the block channel by structure or environment of indoor for light of straightness. LED-ID system is degraded the performance by the block channel as loss of data, and burst error. To solve the block channel, the proposed system is overcome the burst error by low correlation among data, which is able to obtain the maximize time diversity gain to improve the performance of BER by cyclic delay scheme. The BER performance is evaluated by computer simulation according to channel parameter. The simulation results shows that proposed system gives much better performance than conventional system and constant cyclic delay scheme system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.4
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• pp.169-176
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• 2010

We propose a Z-HBT line coding for a LED-ID system. Z-HBT line coding is defined as follows. First, we apply half bit transition to one bit. Second, we decode encoded bits using difference of bit transition level in one bit duration. As a result, we obtain advantages about synchronization problem and noise effect mitigation at the receiver. We set up outdoor the LED-ID simulation environment. At simulation results, we show 2-3dB gain as compared with existing line coding schemes. The results of the paper can be applied to design and implementation of LED-ID systems for indoor wireless multimedia services.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.12 no.1
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• pp.75-80
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• 2013

In this paper, We proposed a Optical Correlation for indoor positioning based LED-ID. The proposed Optical Correlation has a advantage to low-interference between spread code number sequences and LED-ID. it is applied a spread code to reduce the interference with additional information based LED-ID. The additional information is enable to detect in transmitted signal using auto correlation. Also we designed and implemented the Optical Correlation for clearly detecting the additional information. Simulations were performed to confirm the performance of BER and the power of additional information. Optical Correlation simulator to indoor positioning based LED-ID was implemented to prove a usefulness.

• Journal of Satellite, Information and Communications
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• v.5 no.2
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• pp.69-74
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• 2010

In this paper, we present an indoor positioning system based on light emitting diode (LED). Because LED is a semiconductor light emitting device, we can easily switch and modulate electrical signals into lightwave signals at high speed using LEDs. We assigned unique 8-bit ID address to each LED lights. Photo diode receives data from 16-LED lights and takes correlation coefficient beteween received data and each LED-ID. Using correlation coefficient, proposed positioning system shows resolution of 50 cm in dimensions of $4\;m\;{\times}\;4\;m\;{\times}\;2\;m$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.10B
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• pp.1258-1267
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• 2011

In this paper, using the indoor LED-ID communication system have researched for how to transmit video signals. In LED-ID communications use the LEDs for lighting features at the same time communication is an effective way to implement. This proposed system using Visible light(RGB) as way to transmit signals, depends on the mixture RGB, which decided the color of light, moreover, each things determined their performance. However, if the video signal were fixed allocated RGB to transmit such as the original system, the importance of the each signals a different occur the limit on the quality of the video than SVC signals. In order to solve this problem in this paper, according to the RGB mixture ratios analyze the performance for the White LED, which analyzed based on allocating the SVC signal by transmitting to improve the quality of the video was about how researched.

• Journal of Digital Contents Society
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• v.15 no.1
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• pp.129-136
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• 2014

Wi-Fi fingerprinting system is a very popular positioning method used in indoor spaces. The system depends on Wi-Fi Received Signal Strength (RSS) from Access Points (APs). However, the Wi-Fi RSS is changeable by multipath fading effect and interference due to walls, obstacles and people. Therefore, the Wi-Fi fingerprinting system produces low position accuracy. Also, Wi-Fi signals pass through walls. For this reason, the existing system cannot distinguish users' floor. To solve these problems, this paper proposes a LED fingerprinting system for accurate indoor positioning. The proposed system uses a received optical power from LEDs and LED-Identification (LED-ID) instead of the Wi-Fi RSS. In training phase, we record LED fingerprints in database at each place. In serving phase, we adopt a K-Nearest Neighbor (K-NN) algorithm for comparing existing data and new received data of users. We show that our technique performs in terms of CDF by computer simulation results. From simulation results, the proposed system shows that a positioning accuracy is improved by 8.6 % on average.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.6
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• pp.275-280
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• 2010

Recently, This paper suggests that LED-ID technique applying positioning method for LED light. also, Authors in this paper has launched this investigation earnestly. However, there are various interferences such as MPI(Multi Path Interference) by reflected waves of the surface and interfere factors by their correlation properties of the ID in LED-ID wireless channel. Therefore, in this paper, we propose a novel OOK(On-Off Keying)-CDMA(Code Division Multiple Access) system using unipolar ZCD(Zero Correlation Duration) spreading code and verify the availability of the proposed system via the evaluation performance simulation.