• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.2
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• pp.60-67
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• 2010

In the ubiquitous age, applications of wireless personal area network (WPAN) technology using LEDs are in progress. However, visible light communications (VLC) using the LEDs have weakness which deteriorate performance of communication because of multi-path fading that occurs propagation delay by interior walls or other things in indoor environments. In this paper, orthogonal frequency division multiplexing (OFDM) scheme is adapted to decrease multi-path fading and multi-path dispersion and to provide high speed data transmission. Besides, to reduce information losses caused by optical noise (incandescent lamps, fluorescent lamps, sunbeam etc.) also proposed channel coding using turbo codes. The encoding and decoding of the proposed system is described, and simulation results are analyzed. We can know that performance of proposed system is increased about 4 [dB] through the simulation results. Also, when the system take doppler effect, the system performance worsened.

• Journal of Satellite, Information and Communications
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• v.12 no.3
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• pp.15-21
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• 2017

Following the successful launch of KOMPSAT-3 in May 2012, KOMPSAT-5 in August 2013, and KOMPSAT-3A in March 2015 have succeeded in launching the integrated operation of optical, radar and thermal infrared sensors in Korea. We have established a foundation to utilize the characteristics of each sensors. In order to overcome limitations in the range of application and accuracy of the application of a single sensor, multi-sensor image fusion techniques have been developed which take advantage of multiple sensors and complement each other. In this paper, we introduce the development of software (InFusion) for multi-sensor image fusion and valued-added product generation using KOMPSAT series. First, we describe the characteristics of each sensor and the necessity of fusion software development, and describe the entire development process. It aims to increase the data utilization of KOMPSAT series and to inform the superiority of domestic software through creation of high value-added products.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.11
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• pp.755-762
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• 2014

In recent year, along with the rapid development of LED technology, many applications using LEDs with Visible Light Communication(VLC) have been researched. Since it is easy to provide LOS communication environment along with cheap deployment cost, the indoor positioning system based on VLC has been actively studied. In this paper, we propose an accurate indoor positioning algorithm using a stereo image sensor and white-light LEDs with the visible light communication. Indoor white-light LEDs are located at the ceiling of a room and broadcast their position information by VLC technology. Mobile receiver with stereo image sensor receives LED position information by VLC and estimates its position and angle information. Simulation results are given to show the efficiency of proposed indoor positioning algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6C
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• pp.604-610
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• 2009

This paper propose a digital watermarking method for digital contents which satisfies both the invisibility and the robustness to attacks to prohibit counterfeiting, modification, illegal usage and illegal re-production of video contents. This watermarking algorithm insert a watermark(digital hologram) by generated using Fresnel transform which improve the robustness. The inserting positions of the watermark choose by considering the frequency property of an image and a watermark. Also the amount of watermarking for watermark bit decide by considering the level of 2DDWT. This algorithm was implemented by C++ and experimented for invisibility and robustness with optical system. The experiment results showed that the method satisfied enough the invisibility of the inserted watermark and robustness against attacks. For the general attacks, the error rate of the extracted watermark was less than 15%, which is enough in robustness against the attacks.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.493-496
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• 2005

The PMU (Payload Management Unit) in MSC (Multi-Spectral Camera) is the main subsystem for the management, control and power supply of the MSC payload operation. The PMU shall handle the communication with the BUS (Spacecraft) OBC (On Board Computer) for the command, the telemetry and the communications with the various MSC units. The PMU will perform that distributes power to the various MSC units, collects the telemetry reports from MSC units, performs thermal control of the EOS (Electro-Optical Subsystem), performs the NUC (Non-Uniformity Correction) function of the raw imagery data, and rearranges the pixel data and output it to the DCSU (Data Compression and Storage Unit). The BUS provides high voltage to the MSC. The PMU is connected to primary and redundant BUS power and distributes the high unregulated primary voltages for all MSC sub-units. The PSM (Power Supply Module) is an assembly in the PMU implements the interface between several channels on the input. The bus switches are used to prevent a single point system failure. Such a failure could need the PSS (Power Supply System) requirement to combine the two PSM boards' bus outputs in a wired-OR configuration. In such a configuration if one of the boards' output gets shorted to ground then the entire bus could fail thereby causing the entire MSC to fail. To prevent such a short from pulling down the system, the switch could be opened and disconnect the short from the bus. This switch operation is controlled by the BUS.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3C
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• pp.77-82
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• 2005

Partial response maximum likelihood (PRML) detection using the Viterbi algorithm involves the calculation of likelihood metrics that determine the most likely sequence of decoded data. In general, it is assumed that branches at each node in the trellis diagram have same probabilities. If modulation code with minimum and maximum run-length constraints is used, the occurrence ratio (Ro) of each particular pattern is different, and therefore the assumption is not true. We present a calculation scheme of the likelihood metrics for the PRML detection using the occurrence ratio. In simulation, we have tested the two (1,7) run-length-limited codes and calculated the occurrence ratios as the orders of PR targets are changed. We can identify that the PRML detections using the occurrence ratio provide more than about 0.5dB gain compared to conventional PRML detections at 10/sup -5/ BER in high-density magnetic recording and optical recording channels.

• Journal of Satellite, Information and Communications
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• v.10 no.2
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• pp.90-94
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• 2015

We stuidied liauid crystal alignment treatment using solution process for making thin oxide layer in liquid crystal display. It is the one of very effient and popular process in making thin oxide layer in electronical industrial fields. Particularly, this process has highly potential value in liquid crystal display industrial fields because it cause automatically induced alignment process without tranditional alignment process in liquid crystal alignment process. We made several different kinds of mol density solutions using strontium oxide solution. And those solutions were treated for solidification layers using annealing process for 2 hours. And we stuided pretilt angle properties of these alignment layers of strontium oxide for clarifying the relationship of liquid crystal molecules and thin strontium oxide layer. And we also tested the existence of strontium oxide thin layer on substrate using XPS measurement. We expected the hig gain of electro-optical properties in liquid crystal display using strontium oxide thin layer because it has high K property material than the other metal-based oxide layers. In this results, we measured 1.447 to 1.613 thresholds volts as 0.1 mol to 0.4 mol density in 0.1 mol density steps. This is significant better characteristics than conventional liquid crystal display as higher than 1.85 thresholds volts. And it make possible to making next-generation liquid crystal display which present low-power consumption and wide gray scale in liquid crystal display.

• Journal of Satellite, Information and Communications
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• v.12 no.1
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• pp.6-12
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• 2017

Recently, the demand for SAR imaging is growing to monitor natural disasters or military sites to foresee topographic changes, where optical sensing is not easily available. High-resolution SAR images are useful in exploring topography and monitoring artificial land objects in all weather conditions. In this paper,high resolution SAR images acquired from KOMPSAT-5 are exploited for the applications of change detection and classification. In order to detect change areas, amplitude change detection (ACD) and coherence change detection (CCD) algorithms are employed and their performances are compared in practical applications. For enhanced performance, the potential of small scaled change detection is explored by combining multi-temporary SAR images. The k-means and SVM methods are applied for land classifications and their performances are compared by applying to the real spaceborne SAR images.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1B
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• pp.71-82
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• 2007

Recent advances in optical-network technologies have led to the advent of broadband networks reaching 10 Gbps. The increase of available network bandwidth envisions wide-spread use of broadband applications such as uncompressed Internet HDTV, which would be a cutting-edge application for networked collaborations. Despite of breakthroughs in high-performance systems and networks, expensiveness blocks wide-range deployments of uncompressed Internet HDTV systems. In this paper, we propose a low-cost uncompressed Internet HDTV system and discuss its software architecture in depth. We conducted several network-based experiments utilizing a research network test-bed to evaluate the performance of the proposed system.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.7
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• pp.52-58
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• 2013

This paper proposes an adaptive algorithm based on a method of dynamic error signal generation suitable for signal state by examining the equalizer output signal in blind equalization. In the proposed method, it estimates the error signals using single modulus and multiple modulus each effective to the early stage of equalization or steady-state, and it generates a new error signal from the two error estimates. Two equalizer structures are implemented and their performances are compared: 1-equalizer structure that generates a new error signal by combining the two error estimates weightedly and updates the equalizer using this, and 2-equalizer structure that updates two equalizers respectively depending on the weights of the two error signals. In the proposed method, as the error signals were generated optimally before and after the initial convergence respectively, it was confirmed by computer simulations that the equalizer was updated effectively.