• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5B
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• pp.480-488
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• 2009

A mobile ad-hoc network is an autonomous collection of wireless mobile nodes that organizes a temporary network without any network infrastructure. Due to node mobility, it is a challenging task to maintain the network topology. In this paper, we propose a stable clustering algorithm that uses node mobility for cluster formation. In the proposed algorithm, the node mobility is measured by counting the number of nodes entering into/leaving from its transmission range. The node having the lowest mobility is selected as a cluster head. For topology maintenance with reduced control overhead, the cluster head adaptively controls the broadcasting period of hello message to the measured node mobility. Through computer simulations, it is verified that the proposed algorithm outperforms previous clustering algorithms in terms of control overhead, the rate of node mobility changes and the number of cluster head changes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.9
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• pp.620-628
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• 2014

Various on-demand manner routing protocols have been proposed for efficient energy consumption in mobile ad-hoc networks. Some of the protocols tried to extend the network lifetime by periodically rerouting paths according to the energy consumption rate of nodes. However, those protocols suffer from frequent flooding and high overhead. This paper proposed a new routing protocol called ALPMR (Adaptive Local Path Modification Routing) that extends the network lifetime by using local path rerouting. The proposed ALPMR protocol performs local rerouting around nodes with little remaining energy as well as data congestion, thus reduces flooding and routing overhead and can extend the network lifetime. The performance of ALPMR protocol is observed using ns-2 simulator.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.11
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• pp.1192-1200
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• 2014

This paper proposes a cooperative spectrum sensing algorithm in a maritime cognitive radio network and evaluates the performance of proposed algorithm. In the proposed algorithm, the secondary ships decide whether to transmit the feedback information or not on the basis of the threshold when the number of available feedback information of the ships is limited. The fusion ship detects whether the channel is available or not on the basis of the feedback information. This paper evaluates the proposed algorithm in terms of the detection probability and the number of secondary ships that are fed back in the maritime cognitive radio network. The simulation results show the proposed algorithm significantly reduces the feedback overhead even though the detection probability is somewhat declined.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.4
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• pp.371-380
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• 2013

D2D (Device-to-Device) communication on an underlying cellular infrastructure which exploits the same spectrum has several advantages such as increased resource utilization and improved cellular coverage. However, D2D communication system needs to cope with ICI (Inter-Cell Interference) and interference between cellular and D2D links. As a result, macro UEs (User Equipments), especially those located near cell edge, will suffer from serious link performance degradation. We propose a novel interference avoidance mechanism assisted by SRN (Shared Relay Node) in this paper. SRN not only performs data re-transmission as a usual Type II relay but also has several features newly defined to avoid interference between cellular and D2D links. In particular, we suggest resource allocation methods based on the SRN for effective interference avoidance, and evaluate their performance through computer simulations.

• Journal of the Korean Home Economics Association
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• v.36 no.3
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• pp.173-190
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• 1998

This study reviewed both consumer movement and consumer policy of government in Japan. Their evolution since the Second World War will be reviewed and compared multiple periods, after the Second World war till the late 1960s, the period of the 1970s, the period after 1980s. In addition, firms' consumer satisfaction policies were briefly reviewed in order to fully understand consumer protection activities in japan. This study found four major characteristics of consumer protection activities led by both voluntary consumer organizations and government. First, consumer protection policy of government in Japan after the late 1960s was more active than that of consumer movement by consumer organizations. Second, major concerns for consumer protection were variant over time. The major goal in the first stage of period(during the 1960s) was to protect consumer safety from defective and dangerous goods and services, whereas the goal after the late 1970s was extended to cover various areas concerning the quality of life. Those areas refer to the quality of services, the way of sales and marketing, pollution of environment, and the quality of consuming life. Third, this study found that computer networks, aiming at collecting and analyzing the very useful to improve the consuming life of Japanese by providing sufficient consumer information to encourge rational choices of consumers. Forth, a close cooperation between the central and local administrations was crucial for the successful outcome In Japan This paper gives us useful guideline regarding how to improve consumer movement and govemments' policies for protecting consumer in Korea. In addition, other lessons on successful consumer satisfaction policies of Japanese firms may enable Korean firms to shape effective consumer policies of enhancing their competitiveness.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.3
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• pp.177-183
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• 2020

Steganography uses digital images as a medium for sending secret messages over insecure networks. There is also a least significant bit(LSB) that is a popular method of embedding secret messages in digital images. The goal of steganography is to securely and flawlessly transmit secret messages using stego media over a communication channel. There is a need for a method to improve resistance to reduce the risk of exposure to third parties. To safely hide secret messages, I propose new algorithms that go through crossing, encryption, chaos and concealment steps. After separating Hangul syllables into choseong, jungseong and jongseong, the bitwised message information is encrypted. After applying the logistic map, bitwised information is reconstructed using the position of the chaotic sequence. The secret message is inserted into the randomly selected RGB channel. PSNR and SSIM were used to confirm the effectiveness of the applied results. It was confirmed as 44.392(dB) and 0.9884, respectively.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.4
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• pp.283-292
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• 2020

Artificial intelligence, which is one of the representative images of the 4th industrial revolution, has been highly recognized since 2016. This paper analyzed domestic paper trends for 'Artificial Intelligence', 'Machine Learning', and 'Deep Learning' among the domestic papers provided by the Korea Academic Education and Information Service. There are approximately 10,000 searched papers, and word count analysis, topic modeling and semantic network is used to analyze paper's trends. As a result of analyzing the extracted papers, compared to 2015, in 2016, it increased 600% in the field of artificial intelligence, 176% in machine learning, and 316% in the field of deep learning. In machine learning, a support vector machine model has been studied, and in deep learning, convolutional neural networks using TensorFlow are widely used in deep learning. This paper can provide help in setting future research directions in the fields of 'artificial intelligence', 'machine learning', and 'deep learning'.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.11
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• pp.2664-2669
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• 2014

Recently, many research efforts have paid attention to spectrum pooling meshanism that provides efficient way to manage transient spectrum requests of secondary users in cognitive radio networks. Spectrum pooling is maintained by WSP (wireless service provider). WSP leases the spectrums stored in her spectrum pool to secondary users with being paid for it. It is natural that WSP tries to get profits as much as possible, which implies the WSP tries to minimize the cost required for maintaining her spectrum pool. In this paper, we model the spectrum pool into a probabilistic inventory model. Assuming secondary users' spectrum requests follow normal distribution, we give a strategic way that minimizes the maintenance cost of the spectrum pool. By a series of simulations, we show that WSP can reduce the total maintenance cost through our inventory model-based spectrum pooling than maintaining fixed inventory level.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.10
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• pp.550-560
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• 2002

External sort on cluster computers requires not only fast internal sorting computation but also careful scheduling of disk input and output and interprocessor communication through networks. This is because the overall time for the execution is determined by reflecting the times for all the jobs involved, and the portion for interprocessor communication and disk I/O operations is significant. In this paper, we improve the sorting performance (sorting throughput) on a cluster of PCs with a low-speed network by developing a new algorithm that enables even distribution of load among processors, and optimizes the disk read and write operations with other computation/communication activities during the sort. Experimental results support the effectiveness of the algorithm. We observe the algorithm reduces the sort time by 45% compared to the previous NOW-sort[1], and provides more scalability in the expansion of the computing nodes of the cluster as well.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4B
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• pp.245-256
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• 2003

2-D OCDMA is considered to be a viable technical solution for optical LANs, and a considerable amount of research effort has been devoted to various 2-D OCDMA techniques. In this paper, we propose two new interference model for 2-D OCDMA LANs employing unipolar random codes, and derive maximum-likelihood detectors based on these interference models. The BER performance of the maximum likelihood detectors and that of other existing detectors are compared through extensive computer simulation. In addition, the complexity of high-speed implementation of the detectors is assessed, and as a result, we found that the AND detector and the maximum-likelihood detectors for the pulse-binomial and the pulse-Poisson model offer the best trade-off between the BER performance and the facility of high-speed implementation.