• Journal of Communications and Networks
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• v.18 no.3
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• pp.493-501
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• 2016

In-network storage is an effective technique for avoiding network congestion and reducing power consumption in continuous data collection in wireless sensor networks. In recent years, network coding based storage design has been proposed as a means to achieving ubiquitous access that permits any query to be satisfied by a few random (nearby) storage nodes. To maintain data consistency in continuous data collection applications, the readings of a sensor over time must be sent to the same set of storage nodes. In this paper, we present an efficient approach to updating data at storage nodes to maintain data consistency at the storage nodes without decoding out the old data and re-encoding with new data. We studied a transmission strategy that identifies a set of storage nodes for each source sensor that minimizes the transmission cost and achieves ubiquitous access by transmitting sparsely using the sparse matrix theory. We demonstrate that the problem of minimizing the cost of transmission with coding is NP-hard. We present an approximation algorithm based on regarding every storage node with memory size B as B tiny nodes that can store only one packet. We analyzed the approximation ratio of the proposed approximation solution, and compared the performance of the proposed coding approach with other coding schemes presented in the literature. The simulation results confirm that significant performance improvement can be achieved with the proposed transmission strategy.

• Annual Conference of KIPS
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• 2011.04a
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• pp.844-847
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• 2011

Wireless mesh network (WMN) is a type of mobile ad-hoc network consists of wireless router, mobile clients and gateway which connects the network with the Internet. To provide security in the network it is required to encrypt the message sent among the communicating nodes in such way so that only legitimate user can retrieve the original data. Several security mechanisms have been proposed so far to enhance the security of WMN. However, there still exists a need for a comprehensive mechanism to prevent attacks in data communication. Considering the characteristic of mesh network, in this paper we proposed a public key cryptography based security architecture to establish a secure key agreement among communicating nodes in mesh network. The proposed security architecture consists of two major sections: client data protection and network data protection. Client data protection deals with the mutual authentication between the client and the access router and provide client to access router encryption for data confidentiality using standard IEEE 802.11i protocol. On the other hand, network data protection ensures encrypted routing and data transfer in the multi hop backbone network. For the network data protection, we used the pre-distributed public key to form a secure backbone infrastructure.

• Journal of Internet Computing and Services
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• v.5 no.1
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• pp.99-111
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• 2004

Two general security measures in computing networks are secure data transmission and user authentication, These problems are still critical in the wireless LAN environments. Thus security becomes most significant issue in personal network environments and ubiquitous networks based on wireless LANs. We purpose a new authentication system for these kind of environments, and coined it UPMA(Ubiquitous Personal Mutual Authen-tication) model. UPMA supports authenticating configurations which provides personal verification for each system. It guarantees secure communications through the session key setup, and provides mutual authentication by verifying each user and his/her station. UPMA solves security problems in ubiquitous networks without accessing authentication server, Instead it performs mutual authentication between terminals or between systems. It is a global authentication system which enables global roaming service through the Internet or other public networks, It can be used to guarantee safe and convenient access to a company Intranet or to a home network.

• Journal of radiological science and technology
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• v.28 no.4
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• pp.307-315
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• 2005

In the ubiquitous computing environments, ICT industries of current society are developed in enormous growth. Medicine or patients with mobile devices can access at any time, any place. The medical procedures at the patient bedside are out of the scope of current systems, which means that patient record and image data access during the medical visit or the execution, recording and confirmation of the medicine prescriptions, still do not enjoy computerized support. Today, the exchange of medical images and clinical information is well defined by DICOM and HL7 standards. The DICOM independent terminal equipment image access system was developed in which a DICOM Engine acts as the gateway between a PACS DB and user's terminal. Implementation system is compatible with most currently available Integration system models. This paper presents a software technology where the medical and nursing staff will be equipped with any device connected by wire and wireless to a central server that provides access to the electronic patient records and that will actively inform about tasks pending distribution. The prototype described in this article implements a medical images and structured reports server that makes the search and recovery of data stored in the DICOM standard possible.

• Journal of Internet Computing and Services
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• v.14 no.1
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• pp.53-62
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• 2013

It is common among users to have multiple computing devices as well as to access their files or do work at different locations. To achieve file consistency as well as mobility in this scenario, an efficient approach for workspace synchronization should be used. However, file synchronization alone cannot guarantee the mobility of work environment which allows activities to be resumed at any place and time. This paper proposes a ubiquitous synchronization approach which provides cloud-based access to a user's workspace. Efficient synchronization is achieved by combining session monitoring with file system management. Experimental results show that the proposed mechanism outperforms Cloud Master-replica Synchronization in terms of number of I/O operations, CPU utilization, as well as the average and maximum latencies in responding to client requests.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.1
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• pp.19-24
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• 2010

This paper proposes a unified time-domain channel estimator (UTD-CE) for ubiquitous wireless broadband access based on orthogonal frequency division multiplexing (OFDM) systems. As a part of a software radio platform for ubiquitous services, the proposed UTD-CE can be exploited with the simply changeable parameters, pilot symbols and pilot subcarriers allocation, which are usually different according to the system specifications such as IEEE802.11x WiFI, IEEE802.16x WiMAX, DMB, Media FLO, DVB-H, etc. Given the pilot information, the channel frequency responses (CFRs) of data subcarriers will be analogously estimated by Wiener filtering and discrete Fourier transform (DFT)-based interpolation in the UTD-CE. Simulation results indicate that the proposed method significantly outperforms the conventional time-domain channel estimator when the pilot information is changed.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.2
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• pp.253-259
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• 2011

In a ubiquitous society, the world is changing to the place where we can access to network anytime, anywhere, on any device. The mobile internet is leading the ubiquitous world and the most commonly used medium is a cell phone. However, it is uncomfortable to link to cafe, blog, and mini homepage. Because we have to stop wap service in order to upload the mobile contents like photos, videos, sound recordings produced by mobile phones. Also we have to re-access. So, in this paper content management system was designed and implemented which mobile users don't have to stop wap service in order to upload photos, videos, sound recordings produced by mobile phones. Also it supports upload in wap service integrative medicine diagnosis and contents can be managed by category.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11B
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• pp.1200-1206
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• 2009

In this paper, we propose an energy-efficient MAC(Medium Access Control) protocol for processing context information in ubiquitous sensor network environments. CASMAC(Context Aware Sensor MAC) use context information for energy-efficient operation and its operation principle is as follows. First, we make scenarios with possible prediction for CASMAC. And then we save setted context information in server. When event occur at specific sensor node, and then it send three times sample data to server. According to context information, server process sample data. If server process sample data with event, it receive continuous data from event occur node by a transmission request signal. And then server send data transmission stop signal to event occur node when it do not need to data. If server process sample data with no event, it have not reply. Through we make energy consumption tables and an energy consumption model, we simulate analysis of CASMAC performance. In a result, we gains about 5.7 percents energy reduction compared to SMAC.

• Journal of the Korea Society for Simulation
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• v.16 no.1
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• pp.11-19
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• 2007

Under ubiquitous environment, applications can gather and utilize various sensing information. There are many issues such as energy management, protocol standardization, independency on sensor fields, and security to be resolved for the complete ubiquitous computing. Especially, the independent information access in the sensor field is one of the most important issues to maximize the usability of sensors in various sensor fields. However, existing frameworks are not suitable for the ubiquitous computing environment because of data heterogeneity between data elements in sensor fields. Existing applications are dependent to sensor fields and sensors in the existing ubiquitous computing on environment is dependent to the application in the sensor field. In other word, an application can utilize just information from a specific sensor field. To overcome this restriction, many issues from a hardware or software view must be resolved. In this paper, we provide the design and implementation of the Metadata Registry-based framework (UbiMDR) of the Ubiquitous environment. This framework can provides the semantic interoperability among ubiquitous applications or various sensor fields. In addition, we describe comparison evaluation between conventional Ubiquitous computing framework and UbiMDR framework with data accuracy of interoperability.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.3 no.1
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• pp.5-14
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• 2004

"언제, 어디에서, 어떤 형태의 접속"도 가능하게 하는 유비쿼터스 네트워크 환경의 실현을 위해 음성, 데이터의 통합은 우선 지원되어야 할 애플리케이션이다. 블루투스는 음성, 데이터의 동시 처리가 가능한 무선 개인 영역 네트워크(WPAN: Wireless Personal Area Network) 표준이다. 저가, 저전력의 무선 통신을 기반으로 휴대폰, 무전 전화기(Cordless Telephone) 의 음성 통화와 노트북, PDA 등의 정보기기의 인터넷 접속을 가능하게 한다. 본 논문에서는 블루투스의 음성, 데이터 통합처리를 구현한 블루투스 액세스 포인트(Access Point)에 대해 기술한다. 근거리 무선 데이터 통신과 유실 네트워크의 연결을 이루어 노트북, PDA 등 단말기의 인터넷 동시 접속을 지원하며 블루투스 폰의 VoIP 통화를 구현하였다. 개발 완료된 시스템의 테스트 결과 다양한 벤더들의 제품들과 호환성을 이루어 표준안을 만족하였으며 성능 면에서 역시 규격에서 제시한 최대치에 근접한 매우 우수함을 나타내었다.