• 디지털콘텐츠학회 논문지
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• 제11권4호
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• pp.519-527
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• 2010

유비쿼터스 센서 네트워크(Ubiquitous Sensor Network) 기술은 새로운 컴퓨팅 패러다임인 유비쿼터스 컴퓨팅의 핵심 분야로 센서 네트워크를 이용한 상황정보 모니터링 시스템에 적합한 기술이다. 최근 대학들은 유비쿼터스 컴퓨팅을 기반으로 하는 유비쿼터스 캠퍼스 환경을 구축하기 위해 힘을 기울이고 있다. 본 논문에서는 각종 센서를 통해 상황인식을 위한 컨텍스트 정보를 획득하고, 장애학생의 모바일 기기를 통하여 장애유형별 학사 및 안전서비스를 제공할 수 있는 상황인지 모니터링 시스템을 구축한다. 유비쿼터스 센서 시스템을 기반으로 한 u-캠퍼스 기술은 특히 장애인과 비장애인을 위한 맞춤형 정보 제공에 활용될 수 있다.

• 한국공간정보시스템학회 논문지
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• 제8권3호
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• pp.117-130
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• 2006

유비쿼터스 센서 네트워크 관련 기술의 급속한 발전으로 센서가 여러 응용 분야에서 널리 활용되고 있다. 일반적으로, 유비쿼터스 센서 네트워크에서 각 센서 노드로부터 센싱되는 데이타는 검색의 효율성을 위해 중앙 서버에 저장된다. 이러한 환경에서 센싱된 데이타의 갱신 비용을 줄이기 위한 갱신지연 등으로 인해 중앙 서버에 불확실한 데이타가 저장되며, 이로 인해 질의 처리 시 잘못된 결과를 야기할 수 있다. 본 논문에서는 유비쿼터스 센서 네트워크에서 불확실한 데이타 처리 방법에 대해서 살펴보고, 불확실한 데이타를 효율적으로 처리하기 위한 인덱스를 제시한다. 이 인덱스는 불확실한 데이타가 실제 존재할 가능성이 있는 영역인 불확실성 영역 내에서 갱신을 지연시킴으로써 갱신 비용을 감소시킨다. 특히, 갱신 지연은 특정 갱신 영역 내에서만 수행되도록 제한함으로써 갱신 지연으로 인해 검색의 정확성이 감소되는 문제를 해결한다. 마지막으로, 성능 평가를 통해 이 인덱스의 성능을 분석하여 우수성을 입증한다.

• 한국정보통신학회논문지
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• 제16권9호
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• pp.1939-1946
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• 2012

IEEE 802.15.4 Zigbee 네트워크와 같은 USNs(Ubiquitous Sensor Networks)은 ISM(Industrial, Scientific, and Medical) 주파수 대역을 WiFi 네트워크와 공동으로 사용을 하고 있다. 동일 지역 내에서 두 개의 네트워크가 동작하게 되면 주파수가 겹침으로 인하여 패킷 충돌이 발생 할 수 있다. 이를 확인하기 위해 WiFi와 ZigBee 통신 네트워크을 한 지역에 설치하여 실험을 수행하였다. 실험결과 WiFi 와 ZigBee 간 주파수 간섭으로 인해 데이터 전송률이 저하됨을 확인하였다. 이러한 문제점을 해결하기 위해 주파수 충돌회피 알고리즘을 제안한다. 이 알고리즘에서는 주파수 충돌이 감지되면 각 노드에 다른 주파수를 갖는 새로운 통신 채널을 할당한다. 제안된 주파수 충돌 회피 알고리즘의 성능을 평가하고 결과를 기술하였다.

• Journal of Information Processing Systems
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• 제14권2호
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• pp.286-308
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• 2018

The availability of powerful and sensor-enabled mobile and Internet-connected devices have enabled the advent of the ubiquitous sensor network (USN) paradigm. USN provides various types of solutions to the general public in multiple sectors, including environmental monitoring, entertainment, transportation, security, and healthcare. Here, we explore and compare the features of wireless sensor networks and USN. Based on our extensive study, we classify the security- and privacy-related challenges of USNs. We identify and discuss solutions available to address these challenges. Finally, we briefly discuss open challenges for designing more secure and privacy-preserving approaches in next-generation USNs.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2007년도 춘계종합학술대회
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• pp.379-382
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• 2007

유비쿼터스 센서 네트워크에서는 무선 센서 네트워크 상의 센싱 장치를 통해 주변의 상태 정보를 습득하고 이를 처리한 후 무선 인터페이스를 통해 다른 노드로 전달하게 된다. 이런 과정에서 저전력, 저비용의 제한된 자원을 보다 효율적으로 사용하는 것이 에너지 소비측면에서의 유비쿼터스 네트워크라 하겠다. 본 논문에서는 에너지 소비 측면에서 노드별 에너지 소비량을 n-2 시뮬레이션을 통해 측정 분석 하였다.

• Journal of Information Technology Applications and Management
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• 제14권2호
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• pp.1-10
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• 2007

The ubiquitous computing system is expected to be widely utilized in digital home, logistics control, environment/disaster management, medical/health-care services and other applications. The ubiquitous sensor network (USN) is a key infra-structure of this system. Nodes in the USN are exposed to adverse environments and required to perform their missions with very limited power supply only. Also the sensor network is composed of much more nodes. In case some node consumes up its power capacity under a certain required level, the network topology should change and re-routing/ re-transmission of data is necessitated. Resultantly communication protocols studied for conventional wireless networks or ad-hoc networks are not suitable for the sensor network. Schemes should be devised to control the efficient usage of node power in the sensor network. This paper proposes a routing algorithm to enhance the efficiency of power consumption for USN node and analyzes its performance by simulation.

• Journal of Communications and Networks
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• 제16권4호
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• pp.378-384
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• 2014

Replication routing can greatly improve the data delivery performance by enabling multiple replicas of the same packet to be transmitted towards its destination simultaneously. It has been studied extensively recently and is now a widely accepted routing paradigm in delay tolerant networks (DTNs). However, in this field, the issue of how to maximize the utilization efficiency of limited replication quota in a resource-saving manner and therefore making replication routing to be more efficient in networks with limited resources has not received enough attention. In this paper, we propose a DTN routing protocol with back-pressure based replica distribution. Our protocol models the replica distribution problem from a resource allocation perspective and it utilizes the idea of back-pressure algorithm, which can be used for providing efficient network resource allocation for replication quota assignment among encountered nodes. Simulation results demonstrate that the proposed protocol significantly outperforms existing replication routing protocols in terms of packet delay and delivery ratio.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권4호
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• pp.1415-1435
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• 2018

Resource allocation in device-to-device (D2D) aided cellular systems, in which the proximity users are allowed to communicate directly with each other without relying on the intervention of base stations (BSs), is investigated in this paper. A new uplink resource allocation policy is proposed by exploiting the relationship between D2D-access probability and channel gain among variant devices, such as cellular user equipments (CUEs), D2D user equipments (DUEs) and BSs, etc., under the constraints of their minimum signal to interference-plus-noise ratio (SINR) requirements. Furthermore, the proposed resource-allocation problem can be formulated as the cost function of "maximizing the number of simultaneously activated D2D pairs subject to the SINR constraints at both CUEs and DUEs". Numerical results relying on system-level simulations show that the proposed scheme is capable of substantially improving both the D2D-access probability and the network throughput without sacrificing the performance of conventional CUEs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권4호
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• pp.1611-1629
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• 2016

Recently, deploying WiFi access points (APs) for facilitating indoor localization has attracted increasing attention. However, most existing mechanisms in this aspect are typically simulation based and further they did not consider how to jointly utilize pre-existing APs in target environment and newly deployed APs for achieving high localization performance. In this paper, we propose a measurement-based AP deployment mechanism (MAPD) for placing APs in target indoor environment for assisting fingerprint based indoor localization. In the mechanism design, MAPD takes full consideration of pre-existing APs to assist the selection of good candidate positions for deploying new APs. For this purpose, we first choose a number of candidate positions with low location accuracy on a radio map calibrated using the pre-existing APs and then use over-deployment and on-site measurement to determine the actual positions for AP deployment. MAPD uses minimal mean location error and progressive greedy search for actual AP position selection. Experimental results demonstrate that MAPD can largely reduce the localization error as compared with existing work.

• Journal of information and communication convergence engineering
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• 제9권1호
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• pp.1-5
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• 2011

Everyday, technology is evolved in many different disciplines. Computer and smart devices revolution take part of the evolved technology that continuously promising new features. Moreover, social networks services recently become widely popular, which most people in the world become a social-network-fond. In addition to the revolution of the evolved technology and social networks services, ubiquitousness is taking significant part in our daily lives. Although, there are many e-learning systems already existed, which use Internet technology along with a Web technology to provide education in various ways, in despite of that, there is no such existing system exploits the usefulness of smart devices along with the legacy of the online social networks besides the power of the ubiquitous computing technology. Therefore, we propose a smart device application, which fills the gap that has been missing in the recent contemporary era. It is an application that runs on smart devices particularly Smartphone devices; we call our system “Smart Device based Social E-learning System(SDES)”. We have preliminary implemented our system on Android OS. In this paper, we intentionally propose the system in order to ease the way people learn, to provide interactive accessibility in our system, and to utilize the advanced technology more wisely.