• Journal of Electrical Engineering and Technology
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• 제10권6호
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• pp.2384-2392
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• 2015

The technical development and practical applications of big-data for health is one hot topic under the banner of big-data. Big-data medical image fusion is one of key problems. A new fusion approach with coding based on Spherical Coordinate Domain (SCD) in Wireless Sensor Network (WSN) for big-data medical image is proposed in this paper. In this approach, the three high-frequency coefficients in wavelet domain of medical image are pre-processed. This pre-processing strategy can reduce the redundant ratio of big-data medical image. Firstly, the high-frequency coefficients are transformed to the spherical coordinate domain to reduce the correlation in the same scale. Then, a multi-scale model product (MSMP) is used to control the shrinkage function so as to make the small wavelet coefficients and some noise removed. The high-frequency parts in spherical coordinate domain are coded by improved SPIHT algorithm. Finally, based on the multi-scale edge of medical image, it can be fused and reconstructed. Experimental results indicate the novel approach is effective and very useful for transmission of big-data medical image(especially, in the wireless environment).

• Journal of Communications and Networks
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• 제12권4호
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• pp.334-345
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• 2010

In this paper, we study optimal tradeoffs of achievable throughput versus consumed power in wireless ad-hoc networks formed by a collection of multiple antenna nodes. Relying on adaptive modulation and/or dynamic channel coding rate allocation techniques for multiple antenna systems, we examine the maximization of throughput under power constraints as well as the minimization of transmission power under throughput constraints. In our examination, we also consider the impacts of enforcing quality of service requirements expressed in the form of channel coding block loss constraints. In order to properly model temporally correlated loss observed in fading wireless channels, we propose the use of finite-state Markov chains. Details of fading statistics of signal-to-interference-noise ratio, an important indicator of transmission quality, are presented. Further, we objectively inspect complexity versus accuracy tradeoff of solving our proposed optimization problems at a global as oppose to a local topology level. Our numerical simulations profile and compare the performance of a variety of scenarios for a number of sample network topologies.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권5호
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• pp.1642-1661
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• 2015

Wireless mesh networks are a special type of broadcast networks which cover the qualifications of both ad-hoc as well as infrastructure mode networks. These networks offer connectivity to the last mile through hop to hop communication and by comparatively reducing the cost of infrastructure in terms of wire and hardware. Channel assignment has always been the focused area for such networks specifically when using non-overlapping channels and sharing radio frequency spectrum while using multiple radios. It has always been a challenge for mesh network on impartial utilization of the resources (channels), with the increase in users. The rational utilization of multiple channels and multiple radios, not only increases the overall throughput, capacity and scalability, but also creates significant complexities for channel assignment methods. For a better understanding of research challenges, this paper discusses heuristic methods, measurements and channel utilization applications and also examines various researches that yield to overcome this problem. Finally, we highlight prospective directions of research.

• ETRI Journal
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• 제37권3호
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• pp.480-490
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• 2015

The reliability of sensor networks is generally dependent on the battery power of the sensor nodes that it employs; hence it is crucial for the sensor nodes to efficiently use their battery resources. This research paper presents a method to increase the reliability of sensor nodes by constructing a connected dominating tree (CDT), which is a subnetwork of wireless sensor networks. It detects the minimum number of dominatees, dominators, forwarder sensor nodes, and aggregates, as well as transmitting data to the sink. A new medium access control (MAC) protocol, called Homogenous Quorum-Based Medium Access Control (HQMAC), is also introduced, which is an adaptive, homogenous, asynchronous quorum-based MAC protocol. In this protocol, certain sensor nodes belonging to a network will be allowed to tune their wake-up and sleep intervals, based on their own traffic load. A new quorum system, named BiQuorum, is used by HQMAC to provide a low duty cycle, low network sensibility, and a high number of rendezvous points when compared with other quorum systems such as grid and dygrid. Both the theoretical results and the simulation results proved that the proposed HQMAC (when applied to a CDT) facilitates low transmission latency, high delivery ratio, and low energy consumption, thus extending the lifetime of the network it serves.

• Journal of Information Processing Systems
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• 제11권4호
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• pp.509-527
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• 2015

Wireless Video Sensor Networks (WVSNs) have become a leading solution in many important applications, such as disaster recovery. By using WVSNs in disaster scenarios, the main goal is achieving a successful immediate response including search, location, and rescue operations. The achievement of such an objective in the presence of obstacles and the risk of sensor damage being caused by disasters is a challenging task. In this paper, we propose a fault tolerance model of WVSN for efficient post-disaster management in order to assist rescue and preparedness operations. To get an overview of the monitored area, we used video sensors with a rotation capability that enables them to switch to the best direction for getting better multimedia coverage of the disaster area, while minimizing the effect of occlusions. By constructing different cover sets based on the field of view redundancy, we can provide a robust fault tolerance to the network. We demonstrate by simulating the benefits of our proposal in terms of reliability and high coverage.

• Journal of Information Processing Systems
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• 제17권3호
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• pp.615-629
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• 2021

With the development of mobile edge computing, how to utilize the computing power of edge computing to effectively and efficiently offload data and to compute offloading is of great research value. This paper studies the computation offloading problem of multi-user and multi-server in mobile edge computing. Firstly, in order to minimize system energy consumption, the problem is modeled by considering the joint optimization of the offloading strategy and the wireless and computing resource allocation in a multi-user and multi-server scenario. Additionally, this paper explores the computation offloading scheme to optimize the overall cost. As the centralized optimization method is an NP problem, the game method is used to achieve effective computation offloading in a distributed manner. The decision problem of distributed computation offloading between the mobile equipment is modeled as a multi-user computation offloading game. There is a Nash equilibrium in this game, and it can be achieved by a limited number of iterations. Then, we propose a distributed computation offloading algorithm, which first calculates offloading weights, and then distributedly iterates by the time slot to update the computation offloading decision. Finally, the algorithm is verified by simulation experiments. Simulation results show that our proposed algorithm can achieve the balance by a limited number of iterations. At the same time, the algorithm outperforms several other advanced computation offloading algorithms in terms of the number of users and overall overheads for beneficial decision-making.

• 한국차세대컴퓨팅학회논문지
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• 제13권6호
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• pp.21-30
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• 2017

피지컬 컴퓨팅은 단순 컴퓨터 입출력이 아닌 현실세계와 상호작용을 통해 이루어지므로 학생들의 컴퓨팅적 사고와 소양을 기르는데 적합하다. 또한 이를 블록형 코딩 개발환경에서 개발한다면 사용자는 훨씬 더 직관적이고 쉽게 개발을 할 수 있을 것이다. 그러나 기존 블록형 코딩 개발환경은 물리기기가 컴퓨터에 지속적으로 연결되어 있어야 한다는 번거로움이 있다. Blockly는 코드 개념을 나타내는 그래픽 블록이 연동되어 웹과 안드로이드 애플리케이션에 시각적 코드 에디터를 추가하는 오픈소스 라이브러리이다. 본 논문에서는 오픈소스 Blockly 기반으로 기존의 블록형 개발환경에 피지컬 컴퓨팅 기능을 추가하고 이를 무선통신으로 동작시킬 수 있는 모바일용 피지컬 컴퓨팅 개발환경의 구축 내용에 대해 기술한다.

• 한국정보처리학회논문지
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• 제6권1호
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• pp.1-10
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• 1999

이동 컴퓨팅 환경은 무선 통신망 기술의 발전에 힘입어 사용자의 이동성을 지원할 수 있는 환경이다. 사용자들은 이동 트랜잭션을 수행함으로써 데이터베이스에 접근하고 원하는 결과를 얻는다. 이러한 이동 트랜잭션의 올바른 수행과 데이터베이스의 일관성을 유지하기 위해서는 트랜잭션들을 스케줄하기 위한 동시성 제어 기법과 캐쉬를 다루는 캐슁 기법, 그리고 고장에 견고한 시스템 구축을 위한 회복 기법이 필요하다. 이동 컴퓨팅 시스템은 기존의 분산 시스템을 기반으로 하고 있으나, 사용자의 이동성이나 무선 매체의 특성으로 인하여 기존의 분산시스템에서 사용하는 회복방법들을 그대로 사용할 수 없다. 따라서 본 논문에서는 고장에 경고한 이동 컴퓨팅 시스템 구출을 위한 회복 기법을 제안하고자 하는데, 특히 이동 컴퓨팅 환경에서 발생할 수 있는 고장의 유형 가운데 서버의 고장에 대한 회복 알고리즘을 개발하고 평가 분석하다.

• 정보보호학회논문지
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• 제21권1호
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• pp.177-186
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• 2011

스마트 폰의 보급이 확장되면서 데스크톱의 성능과 모바일 특성이 적용된 다양한 모바일 서비스가 증가하고 있다. 모바일 서비스는 모바일 단말의 메모리, 컴퓨팅 파워, 저장 공간 부족과 모바일 단말의 플랫폼에 종속되는 한계를 갖는데 이를 극복할 수 있는 클라우드 컴퓨팅 서비스가 적용된 모바일 클라우드 컴퓨팅 서비스가 최근 각광받고 있다. 모바일 클라우드 서비스는 모바일 서비스와 무선네트워크, 클라우드 서비스가 융합된 서비스로 다양하고 확장된 서비스를 제공하지만, 보안 위협요소가 복합적으로 상속되는 위험이 잠재되어 있다. 그러므로 보안위협이 제거된 안전한 서비스를 배포하고 위협 발생 시 적절하게 대응하기 위한 방안이 필요하다. 본 연구에서는 모바일 단말, 무선네트워크, 클라우드 컴퓨팅 서비스의 위협을 분석하여 모바일 클라우드 서비스의 위협과 위협에 대응하기 위한 방안을 정의하였으며, 위협시나리오를 기반으로 잠재된 위협을 예상하고 대응할 수 있는 방안을 제시하였다.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 2005년도 춘계학술논문발표회 논문집
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• pp.189-189
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• 2005