• Information and Communications Magazine
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• v.26 no.5
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• pp.30-35
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• 2009

본고에서는 무선 가시광 통신을 위한 Medium Access Control (MAC) 프로토콜의 설계에 관해 기술한다. 조명등을 이용한 가시광 무선랜 네트워크는 고정된 상태의 Access Point (AP)에 의한 인프라를 Mobile Node (MN)를 상대로 구성하고 인터넷과 같은 기존의 인프라와 연결되는 구조적 특징을 가진다. 이러한 네트워크에 사용되는 무선 가시광 통신 채널의 특성을 이해하고 MAC프로토콜의 기능에 대한 요구조건을 도출하였다. 주어진 가시광 통신 채널을 효율적으로 사용할 수 있도록 시 분할다중 접속 방식과Full duplex를 도입하는 Frame 구조를 구성하였고 가시성을 이용한 접속 절차를 제안하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5A
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• pp.417-425
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• 2005

KOINONIA is high-rate Wireless Personal Area Network (WPAN) technology, and is developed for multimedia traffic transmission in personal area. A KOINONIA piconet is a collection of one or more associated slaves under a single master. Efficient scheduling of a master for the traffic of slaves is essential to use channel effectively and to guarantee QoS of multimedia traffic. We propose a new scheduling algorithm to allocate channel time at desired intervals regardless of superframe length, and a Connection Admission Control(CAC) algorithm to regulate the number of traffics in a piconet. Our proposed algorithms have been shown to save channel time and to meet QoS requirements compared to the conventional weighted round-robin algorithm.

• Journal of Broadcast Engineering
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• v.16 no.6
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• pp.962-968
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• 2011

The conventional lossless compression of color images is to apply a compression method to each of color components separately, without considering the channel correlation. There had been several methods that consider the channel correlation, but they were confined to the compression of satellite or aerial images only, and the performance of these algorithms to general photos is not satisfactory. This paper proposes a new lossless color image compression method that exploits the correlation between the color components. Specifically, asymmetric sampling is applied to transform an image into mosaic image and the rest, which are compressed separately. By using the information from the compressed mosaic image, the rest images are predicted for further reducing the information to be compressed. Experimental results show that the proposed method improves the compression performance by 35% over the conventional separate compression methods and 10% over the existing methods that exploit the channel correlation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.11
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• pp.2543-2551
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• 1997

This paper proposes a compression technique of image data, a variable length PN code and channel models which are required in CDMA communication system. It also analyzes their performances. Original images is compressed by 2-D DCT and its coefficients are quantized by optimal quantizer at compression rate 0.84bit/pel. Channel model 1 and 2 which are composed of 5 and 4 channels respectively are employed to be used in CDMA. Such a situation forces us to empoly variable length PN code, such as Chebyshev map for spread spectrum system. When average PN code length of model 1 and 2 is 44.4 and 26.7 chips respectively, the received image through these models under Gaussian noise with variance 1.75 is visually of the same quality as the transmitting image. Thus, the model 2 appears to be better in channel efficiency, comparing with channel model 1 and channel model which uses fixed length PN code.

• Journal of Digital Convergence
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• v.15 no.10
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• pp.183-191
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• 2017

This study tries to explain the relationships among omni-channel service characteristics, utilitarian/hedonic shopping value, and reuse intention. We derive instant connectivity, localization, consistency, integration, privacy risk as omni-channel service characteristics from previous studies and collect data from 190 omni-channel service users. The major findings are as follows. First, localization, consistency, and privacy risk have a significant effect on utilitarian shopping value but no significant effect on hedonic shopping value. Second, instant connectivity and integration have a positive effect on both utilitarian and hedonic value. Third, utilitarian and hedonic shopping value have a positive effect on reuse intention. This study extends the scope of omni-channel consumer behaviors by focusing on multi-dimensionality of shopping value. The results of this research can provide useful implications for practitioners to build successful strategies on omni-channel service.

• The Journal of the Korea Contents Association
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• v.11 no.8
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• pp.59-67
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• 2011

Digital Contents have been considered as major parts in the areas, such as design, cartoon, video and etc. A number of Digital Contents are made with the works of popular computer program, Photoshop, and used in some courses of making works. Channel is obviously regarded as a high-level function among others in using Photoshop, even though it hinder a lot of users in understanding the way and the principle to use. Channel and Displacement Map have something in common, because they share the infoshade of channel. The infoshade is the information of 256 levels which consists of black and achromatic colors between white and black color. The infoshade of Channel is used as a concept of movement in Displacement Map. Displacement Map analyzes infoshade in 'Displacement map images' and transfer the pixels of original images under the application of displacement map. This means that the infoshade of Channel can be made for the application with characteristic of movement. This study was carried out to analyze the principle of application of infoshade in 'Displacement Map' with Photoshop. Thus, the central aim of this study is not so much studying engineering algorithm as studying and analyzing the principle of Channel's infoshade through studying how the infoshade of channel is applied in the work.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.11
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• pp.135-143
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• 1990

A new over-the-cell routing system is proposed in this paper. The proposed system efficiently reduces not only the channel density but also the routing density in cell region. Generally, the over-the-cell system consists of three phases. Namely, over-the-cell routing, terminal selection and channel routing. In this paper, to select the nets to be routed over the cells, weights are assigned on the intersection graph considering both the channel density and the intersection relations among other nets. When selected nets are blocked by feedthroughs or metal layers for internal logic, they are routed by maze algorithm. Also, in order to reduce channel density, the terminals to be routed in a channel are selected using the minimum weight spanning tree. Channel routing is carried out with a channel router of HAN-LACAD_G. The effectiveness of the over-the-cell routing system is shown by the experiments with benchmark data and its application to the gate array layout system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.9
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• pp.47-54
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• 2004

The previous works for WLAN system based on OFDM is mainly individual study for independent frequency offset or symbol synchronization. In this paper, the performance of IEEE 802.11a WLAN(Wireless Local Area Network) system in the realistic indoor multipath channel models is analyzed with frequency offset compensation and channel estimation methods. For the performance analysis of the WLAN system indoor Rayleigh multipath channels are adopted, and the BER(Bit Error Rate) of WLAN system is calculated with y2 code-rate 16-QAM based on standard specification. From the simulation results, the difference of required Eb/No for BER of 10-3 is 1-2dB between the channel estimation and frequency offset compensation, and perfect channel estimation and no frequency offset.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.11
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• pp.2158-2165
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• 2007

In this paper, a Modified Fuzzy C-Means algorithm with Gaussian Weights(MFCM_GW) is presented for nonlinear blind channel equalization. The proposed algorithm searches the optimal channel output states of a nonlinear channel from the received symbols, based on the Bayesian likelihood fitness function and Gaussian weighted partition matrix instead of a conventional Euclidean distance measure. Next, the desired channel states of a nonlinear channel are constructed with the elements of estimated channel output states, and placed at the center of a Radial Basis Function(RBF) equalizer to reconstruct transmitted symbols. In the simulations, binary signals are generated at random with Gaussian noise. The performance of the proposed method is compared with those of a simplex genetic algorithm(GA), a hybrid genetic algorithm(GA merged with simulated annealing(SA): GASA), and a previously developed version of MFCM. It is shown that a relatively high accuracy and fast search speed has been achieved.

• The Journal of the Acoustical Society of Korea
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• v.38 no.5
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• pp.494-510
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• 2019

Underwater acoustic communication channel parameters consist of impulse response, delay spreading, scattering function, coherence bandwidth, frequency selective fading, coherence time and time variant magnitude fading statistics on which communication system modem and channel coding are designed. These parameters are influenced by sound velocity profile, platform motion and sea surface roughness in given acoustical oceanography condition. In this paper, channel model based on phasor, channel simulator, measurement and analysis method of channel parameters are given in a fixed source-to-receiver system and the parameters are analyzed using shallow water experimental data. For two different source-to-receiver ranges of 300 m and 600 m, the parameters are characterized by three multipaths such as a direct, a surface reflection path with time variant scattering and a bottom reflection path. The results present a channel modelling method of a fixed source source-to-receiver system, channel parameters measurement and analysis methods and a system design and performance assessment method in shallow water.