• 한국안전학회지
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• 제32권1호
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• pp.21-26
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• 2017

An IoT-based particulate matter (PM2.5) sensing device (PSD) is developed. The PSD consists of a PM2.5 sensor, signal processing circuit, and wi-fi enabled-microprocessor along with temperature and humidity sensors. The PSD estimates PM2.5 density by measuring light scattered by PM2.5. To gauge performance of the PSD, PM2.5 density of open air was measured with the PSD and compared with that of the collocated-government-certified measuring station. Measurements were taken at a sampling frequency of 100 Hz and moving-averaged to remove measurement noise. When compared to the result of the measuring station, average percentile error of PM2.5 density from the PSD is found to be 31%. A correlation coefficient is found to be 0.72 which indicates a strong correlation. Instantaneous variation, however, may far exceed average errors, leading to a conclusion that the PSD is more suitable for estimating average trend of PM2.5 density variations than estimating instantaneous PM2.5 density.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권6호
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• pp.3029-3045
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• 2017

The main processes of a cognitive radio system include spectrum sensing, spectrum decision, spectrum sharing, and spectrum conversion. Experimental results show that these stages introduce a time delay that affects the spectrum sensing accuracy, reducing its efficiency. To reduce the time delay, the frequency spectrum prediction was proposed to alleviate the burden on the spectrum sensing. In this paper, the deep recurrent neural network (DRNN) was proposed to predict the spectrum of multiple time slots, since the existing methods only predict the spectrum of one time slot. The continuous state of a channel is divided into a many time slots, forming a time series of the channel state. Since there are more hidden layers in the DRNN than in the RNN, the DRNN has fading memory in its bottom layer as well as in the past input. In addition, the extended Kalman filter was used to train the DRNN, which overcomes the problem of slow convergence and the vanishing gradient of the gradient descent method. The spectrum prediction based on the DRNN was verified with a WiFi signal, and the error of the prediction was analyzed. The simulation results proved that the multiple slot spectrum prediction improved the spectrum efficiency and reduced the energy consumption of spectrum sensing.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권6호
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• pp.2811-2830
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• 2017

In this paper, we study the problem of mobile data offloading for a network that contains multiple mobile network operators (MNOs), multiple WiFi or femtocell access points (APs) and multiple mobile users (MUs). MNOs offload their subscribed MUs' data traffic by leasing the unused Internet connection bandwidth of third party APs. We propose a combinatorial auction-based two-stage matching mechanism comprised of MU-AP matching and AP-MNO matching. The MU-AP matching is designed to match the MUs to APs in order to maximize the total offloading data traffic and achieve better MU satisfaction. Conversely, for AP-MNO matching, MNOs compete for APs' service using the Nash bargaining solution (NBS) and the Vickrey auction theories and, in turn, APs will receive monetary compensation. We demonstrated that the proposed mechanism converges to a distributed stable matching result. Numerical results demonstrate that the proposed algorithm well capture the tradeoff among the total data traffic, social welfare and the QoS of MUs compared to other schemes. Moreover, the proposed mechanism can considerably offload the total data traffic and improve the network social welfare with less computation complexity and communication overhead.

• 디지털산업정보학회논문지
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• 제11권3호
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• pp.53-62
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• 2015

Recently, number of tablet or Smartphone users increased significantly in domestic and around the world. But violation of personal information such as leakage, misuse and abuse are constantly occurring by using mobile devices which is very useful in our society. Therefore, in this paper it will talk about the problems in the network environment of the mobile environment such as tablet and Smartphone, Mobile Malware, hacking of the public key certificate, which could be potential threat to mobile environment. This thesis will research for people to use their mobile devices more reliable and safer in mobile environment from invasion and leakage of personal information. In order to use Smartphone safely, users have to use Wi-Fi and Bluetooth carefully in the public area. This paper will research how to use App safely and characteristic of risk of worm and Malware spreading. Because of security vulnerabilities of the public key certificate, it will suggest new type of security certification. In order to prevent from the information leakage and infect from Malware in mobile environment without knowing, this thesis will analyze the improved way to manage and use the mobile device.

• 디지털산업정보학회논문지
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• 제11권3호
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• pp.1-9
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• 2015

In this paper, we implemented the computer vision platform design with MEAN Stack through Raspberry PI 2 model which is an open source platform. we experimented the face recognition, temperature and humidity sensor data logging with WiFi communication under Raspberry Pi 2 model. Especially we directly made the shape of platform with 3D printing design. In this paper, we used the face recognition algorithm with OpenCV software through haarcascade feature extraction machine learning algorithm, and extended the functionality of wireless communication function ability with Bluetooth technology for the purpose of making Android Mobile devices interface. And therefore we implemented the functions of the vision platform for identifying the face recognition characteristics of scanning with PI camera with gathering the temperature and humidity sensor data under IoT environment. and made the vision platform with 3D printing technology. Especially we used MongoDB for developing the performance of vision platform because the MongoDB is more akin to working with objects in a programming language than what we know of as a database. Afterwards, we would enhance the performance of vision platform for clouding functionalities.

• 디지털산업정보학회논문지
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• 제11권3호
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• pp.91-98
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• 2015

There is a new evolution in technological advancement taking place called the Internet of Things (IoT), The IoT enables physical world objects in our surrounding to be connected to the Internet. ISM (Industrial Scientific Medical) band that is 2.4GHz band authorized free of charge is being widely used for smart devices. Accordingly studies have been continuously conducted on the possibility of coexistence among nodes using ISM band. In particular, the interference of IEEE 802.11b based Wi-Fi devices using overlapping channel during communication among IEEE 802.15.4 based wireless sensor nodes suitable for low-power, low-speed communication using ISM band. Because serious network performance deterioration of wireless sensor networks. In this paper, we will propose an algorithm that identifies the possibility of using more accurate channels by mixing utilization of interference signal and RSSI (Received Signal Strength Indicator) Min/Max/Activity of Interference signal by wireless sensor nodes. In addition, it will verify our algorithm by using OPNET Network verification simulator.

• TTA 저널
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• 통권132호
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• pp.28-33
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• 2010

지난 10년 동안 인터넷은 우리 생활에 가히 혁명적인 영향을 끼쳐 왔습니다. 그러나 지난 10년이 인터넷 혁명의 시대였다고 한다면 향후 10년간은 모바일 혁명의 시대가 될 것이라고들 이야기합니다. 모바일 혁명 시대의 핵심에는 스마트폰이 자리하고 있습니다. 작년 이맘때쯤 국내에 아이폰이 도입되면서 국내에도 불붙기 시작한 스마트폰 광풍은 모든 비즈니스와 우리 생활에서 혁명을 예고하고 있습니다. 스마트폰 플랫폼 개발업체, 이동통신업체, 단말 기업체, 콘텐츠 개발자 등 다양한 플레이어들이 모바일 생태계 속에서 새로운 비즈니스 모델들을 탄생시키고 있고, 개인들의 생활속에서도 스마트폰은 깊숙이 자리매김하고 있습니다. 이처럼 우리 산업 전반과 삶에 새로운 변화를 일으키고 있는 스마트폰은 과연 안전한 것일까요? 스마트폰은 다양한 앱이 구동될 수 있는 개방형 플랫폼을 가지고 있고, 앱스토어를 통해 누구나 앱 사용자이자 제공자도 될 수 있습니다. 또한, 3G뿐만 아니라 Wi-Fi, Bluetooth, PC Sync 등 다양한 네트워킹 기능을 제공해 줍니다. 이러한 개방성을 바탕으로 스마트폰은 급격하게 성장하고 있지만 개방성은 악성코드 감염, 해킹, 프라이버시 침해 등 역기능이 발생할 수 있는 여건도 마련해 주고 있습니다. 실제로 스마트폰 해킹 사고는 국내외에서 빈번하게 발생되고 있고 그 피해가 증가하고 있는 추세입니다. 올 4월에 국내에서도 첫 스마트폰용 악성코드가 발견되었고, 전 세계적으로 524건의 모바일 악성코드가 발견되었습니다. 이처럼 스마트폰 해킹은 현실화되어 우리를 위협하고 있습니다. 본 특집에서는 스마트폰 보안과 관련한 정부의 정책방향, 보안위협과 사례, 프라이버시 이슈, 보안시장 전망, 국내외 표준화 동향, 전문인력 양성계획 등을 살펴보도록 하겠습니다.

• 한국융합학회논문지
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• 제2권4호
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• pp.9-14
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• 2011

피싱(Phishing)은 사용자 또는 기기를 가장하여 사용자 신분을 도용하는 공격이다. 최근 스마트폰 및 메신저 프로그램 보급에 따라 그 피해가 급증하고 있다. 스마트폰은 음성 통화, SMS와 같은 고유 기능 외에 무선네트워크 기반의 다양한 응용 프로그램을 구동할 수 있다. 일반적으로 카카오톡, 네이트온과 같은 메신저 프로그램은 클라이언트-서버 구조로 구성되며 안전한 통신을 위해서 상호 인증이 필수적이다. 본 논문에서는 스마트폰 피싱 공격에 안전한 메신저 인증 프로토콜을 제안한다. 제안한 기법은 사용자들 간의 대화를 보호하기 위하여 메시지 암호화 기능과 인증 기능을 제공한다.

• 한국멀티미디어학회논문지
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• 제17권2호
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• pp.160-169
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• 2014

생활 주변의 사물들이 인터넷에 접속되어 사물들과의 통신이 가능한 "사물 인터넷" 시대의 흐름에 맞춰 본 논문에서는 스마트 전력 관리 시스템을 제안한다. 제안된 시스템은 와이파이 기능을 내장한 파워 콘센트와 전력 소비량을 모니터링하고 제어할 수 있는 웹서버로 구성되어 있다. 또한, 사용자가 쉽게 전력 소비 상태를 체크하고 콘센트의 전원 상태를 조작할 수 있는 스마트폰용 웹페이지도 함께 개발하였다. 본 시스템은 방화벽 또는 컴퓨터의 환경 설정 문제가 없도록 고안되어 사용의 편리성을 보장하였다.

• 한국멀티미디어학회논문지
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• 제19권5호
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• pp.901-909
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• 2016

Unprecedented attention is being given to Smart Grid, Micro Grid and Internet of Things (IoT) in the Republic of Korea recently but such systems' effect is not well experienced by the market since they require additional and costly reforms for the existing household electrical system where adaptive communication platforms are needed. As such platforms, both wireless and wire communication technologies are being considered at the moment. Usually, they include WiFi, Zigbee technologies and the latter, LAN technology. However, communication speed decline due to signal attenuation and interference during wireless communications are considered to be the major problem and the extra works involving time and costs for the LAN system construction can be another demerit. Therefore, in this paper, we have introduced a Power Line Communication-based Smart Outlet System Expandable at Home to complement these disadvantages. Proposed IoT system involves Power Line Communication (PLC) technology which is essential to constructing a Smart Grid.