• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 A
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• pp.279-282
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• 2003

This paper proposes a medium-access control(MAC) protocol designed for wireless multi-hop sensor networks which is used for connecting physical world and cyber computing space. Wireless multi-hop sensor networks use battery-operated computing and sensing device. We expect sensor networks to be deployed in an ad hoc fashion, with nodes remaining inactive for long time, but becoming suddenly active when specific event is detected. These characteristics of multi-hop sensor networks and applications motivate a MAC that is different from traditional wireless MACs about power conservation scheme, such as IEEE 802.11. Proposed MAC uses a few techniques to reduce energy consumption. Result show that proposed MAC obtains more energy sayings.

• 한국공간정보시스템학회 논문지
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• 제11권2호
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• pp.63-72
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• 2009

Korean Land Spatialization Program (KLSP) is an R&D program of the National GIS Project for developing ubiquitous GIS technologies under the control of the M inistry of Land, Transport and Maritime Affairs (M LTM). The first program of the KLSP, which lasts from 2006 to 2012, initiated with $132 million of national funds and $42 million of private matching funds. Aiming to develop the 'Innovation of GIS technology for ubiquitous Korean land', the KLSP consists of five core research projects and one research coordination project to practically utilize and commercialize the results of core research projects. The Korean Land Spatialization Group (KLSG) is planning the KLSP Test-Bed for testing, integrating, and exhibiting the KLSP's outcomes. About 40% of the outcomes are related products to geo-sensor and wireless sensor network (W SN). Thus, interoperable, scalable and web accessible frameworks like an OGC SWE (Open Geospatial Consortium Sensor Web Enablement) are mandatory because some of the products must be connected to each other in a KLSG Test-Bed. The main objective of this paper is to introduce the KLSP Test-Bed and the SWE SOS (Sensor Observation Service) prototype, which is developed for interoperable geo-sensor networks of the KLSP.

• 정보처리학회논문지C
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• 제16C권3호
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• pp.373-382
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• 2009

본 논문에서는 실시간 유비쿼터스 센서 네트워크에 적합한 MAC(medium access control) 프로토콜을 제안한다. 기존의 DCF 프로토콜은 데이터 전송을 위한 슬롯(slot)을 선택할 때 패킷 충돌로 인한 재전송이 반복될 때 마다 크기가 변하는 경쟁 윈도우(contention window) 내에서 균등 확률 분포(uniform probability distribution)를 이용한 랜덤(random) 선택 기법을 사용하지만 제안한 프로토콜에서는 센서 데이터의 전송 지연을 최대한 감소시키기 위하여 경쟁 윈도우의 크기를 고정시키고, 전송 슬롯을 보다 효율적으로 선택하도록 비 균등(non-uniform) 확률 분포를 사용하여 전송 슬롯을 랜덤하게 선정한다. 제안한 방법의 성능을 입증하기 위하여 256개의 센서가 배치된 센서 네트워크 모델을 기반으로 ns-2를 이용하여 시뮬레이션을 시행하고, 전체 센서에 발생하는 전송 평균 지연 시간이 기존의 802.11 MAC 표준에 비하여 유비쿼터스 센서 네트워크의 최적 지연 한계점(best latency bound)에 가깝게 나타남을 확인한다.

• 한국정밀공학회지
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• 제25권2호
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• pp.115-122
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• 2008

Mostly used sensors have wired powering and two-way cable systems. It is difficult to employ wired sensor network in ubiquitous era because of a number of sensors and cables. Therefore, sensor networks move from wired systems to wireless systems for the future. However, the power source is a critical obstacle for wireless sensornodes. This research represents the new power source which supplies energy sensor node, maintains over 10 years, and thus replaces batteries with limit of lifetime. The system with piezo materials scavenges extra energies such as vibration and acceleration from the environment. Then it converts the scavenged mechanical energy to electrical energy for powering a sensor, a controller and a circuit for regulating voltage and transmitting sensor value. This study explains the properties of piezo material through theoretical analysis and experiments, and demonstrates powering sensor and transmitting data with stored energy (35mJ) for 14 sec. The developed system provides a solution to overcome the critical problem of making up wireless sensor networks.

• 한국멀티미디어학회논문지
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• 제12권12호
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• pp.1778-1786
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• 2009

Many sensor network applications have been developed for smart home, disaster management, and a wide range of other applications. These applications, however, generally assume a fixed base station as well as fixed sensor nodes. Previous research on sensor networks mainly focused on efficient transmission of data from sensors to fixed sink nodes. Recently there has been active research on mobile sink nodes, sink mobility is one of the most comprehensive trends for information gathering in sensor networks, but the research of an environment where both fixed sink nodes and mobile sinks are present at the same time is rather scarce. This paper proposes a scheme for context-aware by ubiquitous devices with the sink functionality added through fixed sinks under a previously-built, cluster-based multi-hop sensor network environment. To this end, clustering of mobile devices were done based on the fixed sinks of a previously-built sensor network, and by using appropriate fixed sinks, context gathering was made possible. By mathematical comparison with TTDD routing protocol, which was proposed for mobile sinks, it was confirmed that performance increases by average 50% in energy with the number of mobile sinks, and with the number of movements by mobile devices.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권12호
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• pp.4856-4871
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• 2015

Backpressure based scheduling has been considered as a promising technique for improving the throughput of a wide range of communication networks. However, this scheduling technique has not been well studied for heterogeneous wireless networks. In this paper, we propose a virtual-queue based backpressure scheduling (VQB) algorithm for heterogeneous multi-hop wireless networks. The VQB algorithm introduces a simple virtual queue for each flow at a node for backpressure scheduling, whose length depends on the cache size of the node. When calculating flow weights and making scheduling decisions, the length of a virtual queue is used instead of the length of a real queue. We theoretically prove that VQB is throughput-optimal. Simulation results show that the VQB algorithm significantly outperforms a classical backpressure scheduling algorithm in heterogeneous multi-hop wireless networks in terms of the packet delivery ratio, packet delivery time, and average sum of the queue lengths of all nodes per timeslot.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.225-227
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• 2004

A sensor networkis composed of a large number of sensor nodes, which are densely deployed either inside the phenomenon or very close to it. One of the most important constraints on sensor nodes is the low power consumption requirement. Sensor nodes carry limited, generally irreplaceable, power sources. Therefore, while traditional networks aim to achieve high quality of service (QoS) provisions, sensor network protocols must focus primarily on power conservation. This paper presents the characteristics of energy consuming, average delay in 802.11 MAC, S-MAC that is specifically designed for wireless sensor networks. We analyze the energy consuming state in the 802.11 MAC in the simulation topology nodes, and measure average delay in 802.11 and S-MAC. Energy efficiency is the primary goal in this protocol design. 802.11 MAC is more efficient than S-MAC in the average delay, throughput. However S-MAC is an energy efficient protocol, a tradeoff between energy efficiency and delay.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.177-178
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• 2006

The real-time tracking system is an essential factor for the development of low cost sensor networks for use in pervasive computing and ubiquitous networking. In this paper, we address the interference problems of the sensor network platform with ultrasonic for location tracking system. Ubiquitous indoor environments often contain substantial amounts of metal and other such reflective materials that affect the propagation of radio frequency signals in non-trivial ways, causing severe multi-path effects, dead-spots, noise, and interference. Especially we present a novel reducing interference location system that is particularly well suited to support context-aware computing. The system called Pharos, aims to combine the advantages of real-time tracking systems that implement distributed environment with regardless of infrastructure or infrastructure-less wireless sensor networks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제3권6호
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• pp.597-611
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• 2009

With the advent of ubiquitous computing society, many advanced technologies have enabled wireless sensor networks which consist of small sensor nodes. However, the sensor nodes have limited computing resources such as small size memory, low battery life, short transmission range, and low computational capabilities. Thus, decreasing energy consumption is one of the most significant issues in wireless sensor networks. In addition, numerous applications for wireless sensor networks are recently spreading to various fields (health-care, surveillance, location tracking, unmanned monitoring, nuclear reactor control, crop harvesting control, u-city, building automation etc.). For many of them, supporting security functionalities is an indispensable feature. Especially in case wireless sensor networks should provide a sufficient variety of security functions, sensor nodes are required to have more powerful performance and more energy demanding features. In other words, simultaneously providing security features and saving energy faces a trade-off problem. This paper presents a novel energy-efficient security architecture in an IEEE 802.15.4-based wireless sensor network called the Hybrid Adaptive Security (HAS) framework in order to resolve the trade off issue between security and energy. Moreover, we present a performance analysis based on the experimental results and a real implementation model in order to verify the proposed approach.

• 지식정보인프라
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• 통권14호
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• pp.26-31
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• 2004