• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.11
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• pp.5323-5343
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• 2018

Mobile applications and social networks tend to enhance the need for high-quality content access. To address the rapid growing demand for data services in mobile networks, it is necessary to develop efficient content caching and distribution techniques, aiming at significantly reduction of redundant content transmission and thus improve content delivery efficiency. In this article, we develop optimal cooperative content cache and distribution policy, where a geographical cluster model is designed for content retrieval across the collaborative small cell base stations (SBSs) and replacement of cache framework. Furthermore, we divide the SBS storage space into two equal parts: the first is local, the other is global content cache. We propose an algorithm to minimize the content caching delay, transmission cost and backhaul bottleneck at the edge of networks. Simulation results indicates that the proposed neighbor SBSs cooperative caching scheme brings a substantial improvement regarding content availability and cache storage capacity at the edge of networks in comparison with the current conventional cache placement approaches.

• ETRI Journal
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• v.44 no.6
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• pp.915-924
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• 2022

In this paper, we present a two-stage scalable channel estimator (TSCE), a deep learning (DL)-based scalable, and robust channel estimator for wireless cellular networks, which is made up of two DL networks to efficiently support different resource allocation sizes and reference signal configurations. Both networks use the transformer, one of cutting-edge neural network architecture, as a backbone for accurate estimation. For computation-efficient global feature extractions, we propose using window and window averaging-based self-attentions. Our results show that TSCE learns wireless propagation channels correctly and outperforms both traditional estimators and baseline DL-based estimators. Additionally, scalability and robustness evaluations are performed, revealing that TSCE is more robust in various environments than the baseline DL-based estimators.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.53 no.1
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• pp.22-31
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• 2004

This paper deals with the dynamic hand gesture recognition based on computer vision using neural networks. This paper proposes a global search method and a local search method to recognize the hand gesture. The global search recognizes a hand among the hand candidates through the entire image search, and the local search recognizes and tracks only the hand through the block search. Dynamic hand gesture recognition method is based on the skin-color and shape analysis with the invariant moment and direction information. Starting point and ending point of the dynamic hand gesture are obtained from hand shape. Experiments have been conducted for hand extraction, hand recognition and dynamic hand gesture recognition. Experimental results show the validity of the proposed method.

• Journal of Communications and Networks
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• v.3 no.4
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• pp.334-341
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• 2001

The provision of QoS control is a key of the successful deployment of multimedia networks. Buffer management plays an important role in QoS control. Therefore, this paper proposes a novel QoS buffer management algorithm named GREEN (Global Random Early Estimation for Nipping), which extends the concepts of ERD (early random drop) and RED (random early detection). Specifically, GREEN enhances the concept of "Random" to "Global Random" by globally considering the random probability function. It also enhances the concept of "Early" to "Early Esti mation" by early estimating the network status. For performance evaluation, except compared with RED, extensive simulation cases are performed to probe the characteristics of GREEN.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.560-562
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• 2005

The electronic transmission of VLBI data(dubbed e-VLBI) presents a special challenge to the use of high-speed global network. with long-term requirements for simultaneous or near-simultaneous Gbps data streams from antennas worldwide converging in a single processing center, e-VLBI is both a useful and highly synergetic application for global high-speed networksAs broband access to high speed research and education networks has become increasingly available to radio telescopes around the world the use of e-VLBI has also increased. High bandwidth e-VLBI experiments have been achieved across wide areas e-VLBI has also been used for the transfer of data from "production"exoeriments

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.12
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• pp.4799-4818
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• 2015

In this paper, we investigate the problem of achieving global optimization for distributed carrier aggregation (CA) in small cell networks, using a game theoretic solution. To cope with the local interference and the distinct cost of intra-band and inter-band CA, we propose a non-cooperation game which is proved as an exact potential game. Furthermore, we propose a spatial adaptive play learning algorithm with heterogeneous learning parameters to converge towards NE of the game. In this algorithm, heterogeneous learning parameters are introduced to accelerate the convergence speed. It is shown that with the proposed game-theoretic approach, global optimization is achieved with local information exchange. Simulation results validate the effectivity of the proposed game-theoretic CA approach.

• Journal of the Korean Regional Science Association
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• v.11 no.1
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• pp.93-111
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• 1995

This study investigated the nature of spatial concentration and dispersion of corporate control within an international system of decision-making centers. It introduces a simplified model of the global evolution of quaternary places. Linked to the national quaternary place model, the proposed model is useful for examinations involving real world situations associated with international corporations. This five stage model emphasizes the importance of the organizational structure of large corporations, industrial networks and the development of information technology. It suggests the dispersion of international quaternary places along with the diversification of corporate control linkages among quaternary centers. A case study for 1974-1991 uses information statistics to identify the current stage of the international quaternary system. The result is in general agreement with major elements of the stage model. This theoretical concept and empirical research contribute to the expansion of quaternary place theory to the global scale in particular, and to the development of location analysis in general.

• Journal of Communications and Networks
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• v.17 no.3
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• pp.241-246
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• 2015

In this paper, we consider a relaying system which employs a single relay in a wireless network with distributed sources and destinations. Here, all source, destination, and relay nodes are equipped with multiple antennas. For amplify-and-forward relay systems, we confirm the achievable sum rate through a joint multiple source precoders and a single relay filter design. To this end, we propose a new linear processing scheme in terms of maximizing the sum rate performance by applying a blockwise relaying method combined with geometric programming techniques. By allowing the global channel knowledge at the source nodes, we show that this joint design problem is formulated as a standard geometric program, which can guarantees a global optimal value under the modified sum rate criterion. Simulation results show that the proposed blockwise relaying scheme with the joint power allocation method provides substantial sum rate gain compared to the conventional schemes.

• Journal of Communications and Networks
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• v.9 no.4
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• pp.356-367
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• 2007

In large networks, maintaining precise global network state information is impossible. The imprecise network state information has significant impacts on Quality-of-Service(QoS) routing and path establishment. In this paper, we develop analytical models for investigating the QoS routing schemes that are designed to tolerate imprecise network state information, and study the performance of various QoS routing schemes, including randomized routing, multi-path routing, and probability based routing, using both the models and simulations. We further propose a new mechanism, called local rerouting, that improves the effectiveness of QoS path establishment in the presence of imprecise global network state information. Local rerouting is orthogonal to existing schemes for dealing with imprecise state information and can be used in conjunction with them to alleviate the impacts of the imprecise information. The results of our performance study indicate that local rerouting is robust and effective.

• Journal of the Optical Society of Korea
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• v.13 no.1
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• pp.2-7
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• 2009

This paper reviews evolution of the research networks on intense laser science under international and Asian frameworks during 2000 to 2008. The OECD Global Science Forum Steering Committee on Compact, High-Intensity Short-Pulse Lasers led to the establishment of the International Union of Pure and Applied Physics (IUPAP) Working Group: International Committee on Ultrahigh Intensity Lasers (ICUIL) and the Asian Intense Laser Network (AILN) in 2004. Through various activities under AILN such as the Asian Symposium on Intense Laser Science (ASILS), the Asian Summer School on Laser Plasma Acceleration and Radiation, and the High-Order Harmonics Workshops, closer relations are being formed among the scientists and also among the young generations working in intense laser science in the Asian regions.