• 한국통신학회논문지
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• 제33권7B호
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• pp.538-549
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• 2008

최근 IEEE 802.22 WRAN 워킹 그룹에서는 부족해지는 주파수 부족의 해결을 위해 CR (Cognitive Radio)의 기술개발을 진행 중에 있다. 채널을 센싱하는 방법에 따라 기존의 시스템 (IS: Incumbent System)의 보호에 상당한 영향을 미치기 때문에 네트워크 상황에 따른 최적의 센싱 방법을 선택하는 것이 중요하다. 이에 IEEE 802.22에서 fine sensing을 제안하고 있지만 아직까지는 다양한 네트워크에 효율적으로 적용할 수 없다. 따라서 본 논문에서는 네트워크 환경에 따라 효율적인 센싱 방법을 선택하기 위한 무선인지 네트워크에서 정책기반 채널 센싱구조 및 알고리즘 (Policy-based Channel Sensing Architecture and Algorithms for Cognitive Radio Networks)을 제안한다. 본 논문에서는 제안하는 채널 센싱 방법 및 알고리즘의 효율성을 확인하기 위하여 제시한 모의실험 결과는 각 센싱 방법에 따라 차이점을 보였지만 제안하는 채널 센싱 방법이 전체적으로 기존의 시스템 검출 시간 및 QP(Quiet Period)를 줄일 수 있었다. 제안하는 방법 중에 클러스터를 이용한 센싱 방법(Channel division round robin sensing)의 경우 IEEE 802.22에서 제안하는 fine sensing에 비교하여 70%정도 평균 검출시간을 줄일 수 있었다.

• 방송과미디어
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• 제11권1호
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• pp.68-77
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• 2006

The Cognitive Radio (CR) technology is a promising solution for exploiting the limited spectrum resources and providing flexibility of spectrum usage. Future interactive broadcasting service can be realized by utilizing CR concept, since the up-link return channel can be found by the spectrum sensing method, which is core functional block of the CR system. In this paper, the spectrum sensing technologies of CR system is presented. First the system architecture of the CR with spectrum sensing block is presented. The suggested spectrum sensing technique consists of the coarse and the fine spectrum sensing. The coarse spectrum sensing technique adopted the wavelet transform to provide the multi-resolution sensing feature - Multi-Resolution Spectrum Sensing (MRSS). The fine spectrum sensing technique uses the beneficial properties of the autocorrelation function Analog Auto-Correlation (AAC). The simulation results for the proposed sensing technologies are presented for various incumbent signals.

• 제어로봇시스템학회논문지
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• 제14권7호
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• pp.720-725
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• 2008

This paper proposes a system architecture for USN with a service robot to provide more active assisted living services for elderly persons by monitoring their mental and physical well-being with USN environments at home, hospital, or silver town. Sensors embedded in USN are used to detect preventive measures for chronic disease. Logged data are transferred to main controller of a service robot via wireless channel in which the analysis of data is performed. For the purpose of handling emergency situations, it needs real-time processing on gathering variety sensor data, routing algorithms for sensor nodes to a moving sink node and processing of logged data. This paper realized multi-hop sensor network to detect user movements with biometric data transmission and performed algorithms on Xenomai, a real-time embedded Linux. To leverage active sensing, a mobile robot is used of which task was implemented with a priority to process urgent data came from the sink-node. This software architecture is anticipated to integrate sensing, communication and computing with real-time manner. In order to verify the usefulness of a proposed system, the performance of data transferring and processing on a real-time OS with non real-time OS is also evaluated.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.825-827
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• 2003

Multi-Spectral Camera(MSC) is a payload on the KOMPSAT-2 satellite to perform the earth remote sensing. The instrument images the earth using a push-broom motion with a swath width of 15 km and a ground sample distance (GSD) of 1 m over the entire field of view (FOV) at altitude 685 Km. The instrument is designed to have an on-orbit operation duty cycle of 20% over the mission lifetime of 3 years with the functions of programmable gain/ offset and on-board image data compression/storage. The MSC instrument has one(1) channel for panchromatic imaging and four(4) channel for multi-spectral imaging covering the spectral range from 450nm to 900nm using TDI CCD Focal Plane Array (FPA). In this paper, the architecture and function of MSC hardware including electrical interface and the operation concept which have been established based on the mission requirements are described. And the design and the preparation of MSC system operation are analyzed and discussed.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.297-302
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• 2002

The subsystems of two channel correlation radiometer such as RF front-end, IF and LF unit, LO unit, software based I/Q demodulator and complex correlator are characterized and their performance is analyzed in this paper. The limited hardware calibration method and receiver design consideration are discussed. The receiver architecture of 37GHz correlation radiometer is integrated. The designed radiometer employs a single-sideband superheterodyne receiver. The center frequency of the radiometer is 37 GHz and IF center frequency is 1.95 GHz with the equivalent noise bandwidth of 79.6 MHz. The receiver has less than 4.2 dB noise figure which is calculated by the Y-factor method and its gain can be adjusted from 60 dB to 80 dB.

• 한국정보통신학회논문지
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• 제25권7호
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• pp.986-992
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• 2021

무선 기반 제어 시스템에서 안정성을 보장하기 위한 일반적인 설계 방식은 제어기가 무선채널을 통하여 개별 센서 값을 수신한 다음 계산된 제어신호를 액추에이터로 전송한다. 본 논문에서는 플랜트의 모든 센서가 동시에 스케일링된 신호를 액추에이터로 전송한 후, 액추에이터가 수신 된 신호를 추가적으로 스케일링하여 피드백 제어신호를 계산할 수 있는 Over-the-air controller 기법을 제안한다. 이러한 제어신호 컴퓨팅 기법은 기본적으로 Over-the-air computation 기술을 적용하여 무선 제어 시스템의 제어신호를 무선채널을 통하여 계산한다. 일반적인 센서-제어기-액추에이터 통신 방식과 대조적으로, Over-the-air controller는 다중 액세스 무선채널의 중첩 속성을 활용하여 단일통신 자원에서 다수 센싱 신호의 통신 및 컴퓨팅을 완료한다. 따라서 제안된 기법은 전용 제어기가 필요하지 않은 단순한 네트워크 구조로 피드백 지연시간 및 무선 자원 사용률을 개선시킬 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권12호
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• pp.4385-4399
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• 2021

The Internet of Things (IoT) eHealth systems composed by Wireless Body Area Network (WBAN) has emerged recently. Sensor nodes are placed around or in the human body to collect physiological data. WBAN has many different applications, for instance health monitoring. Since the limitation of the size of the battery, besides speed, reliability, and accuracy; design of WBAN protocols should consider the energy efficiency and time delay. To solve these problems, this paper adopt the end-edge-cloud orchestrated network architecture and propose a transmission based on reinforcement algorithm. The priority of sensing data is classified according to certain application. System utility function is modeled according to the channel factors, the energy utility, and successful transmission conditions. The optimization problem is mapped to Q-learning model. Following this online power control protocol, the energy level of both the senor to coordinator, and coordinator to edge server can be modified according to the current channel condition. The network performance is evaluated by simulation. The results show that the proposed power control protocol has higher system energy efficiency, delivery ratio, and throughput.

• Smart Structures and Systems
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• 제22권2호
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• pp.239-247
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• 2018

A magnetic flux leakage (MFL) method was applied to detect and quantify defects in a steel bar. A multi-channel MFL sensor head was fabricated using Hall sensors and magnetization yokes with permanent magnets. The MFL sensor head scanned a damaged specimen with five levels of defects to measure the magnetic flux density. A series of signal processing procedures, including an enveloping process based on the Hilbert transform, was performed to clarify the flux leakage signal. The objective damage detection of the enveloped signals was then analyzed by comparing them to a threshold value. To quantitatively analyze the MFL signal according to the damage level, five kinds of damage indices based on the relationship between the enveloped MFL signal and the threshold value were applied. Using the proposed damage indices and the general damage index for the MFL method, the detected MFL signals were quantified and analyzed relative to the magnitude of the damage increase.

• Journal of Communications and Networks
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• 제18권5호
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• pp.784-795
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• 2016

In this paper, we investigate the resource allocation problem in time-varying heterogeneous wireless networks (HetNet) with multi-homing user equipments (UE). The stochastic optimization model is employed to maximize the network utility, which is defined as the difference between the HetNet's throughput and the total energy consumption cost. In harmony with the hierarchical architecture of HetNet, the problem of stochastic optimization of resource allocation is decomposed into two subproblems by the Lyapunov optimization theory, associated with the flow control in transport layer and the power allocation in physical (PHY) layer, respectively. For avoiding the signaling overhead, outdated dynamic information, and scalability issues, the distributed resource allocation method is developed for solving the two subproblems based on the primal-dual decomposition theory. After that, the adaptive resource allocation algorithm is developed to accommodate the timevarying wireless network only according to the current network state information, i.e. the queue state information (QSI) at radio access networks (RAN) and the channel state information (CSI) of RANs-UE links. The tradeoff between network utility and delay is derived, where the increase of delay is approximately linear in V and the increase of network utility is at the speed of 1/V with a control parameter V. Extensive simulations are presented to show the effectiveness of our proposed scheme.

• 인터넷정보학회논문지
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• 제11권2호
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• pp.41-48
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• 2010

u-헬스 서비스를 제공하는 애플리케이션은 기본적으로 개인용 건강관리 기기 즉, PHD와 통신이 가능하고 데이터를 주고받 을 수 있어야 한다. 그러나 이러한 장비들은 대부분 자체 프로토콜 규격을 사용하고 있어 측정된 데이터를 수집하고 u-헬스 서비스 프로바이더에 전달하기 위한 통합 게이트웨이 개발이 어려운 현실이다. 본 논문에서는 이러한 문제점 해결을 위해 u-헬스 게이트웨이를 위한 동적 관리 디바이스 어댑터 모델을 제안하고 프로토타입을 구현하였다. 제안된 모델의 검증을 위해 OSGi 기반 u-헬스 게이트웨이 프레임워크 상에서 프로토타잎을 구현했으며 1채널 심전도 및 혈압/혈당 기기에 대한 디바이스 어댑터 모듈을 구현하였고 측정 데이터 수집 및 전달의 정확성을 확인하였고 의료정보 표준인 HL7 시스템과의 메시지 연동을 통해 기존 시스템과의 상호운용이 가능함을 보였다. 또한 객체 직렬화 방식의 통신 모델을 적용해 어플리케이션과의 연동 및 기능 확장이 용이한 구조임을 확인할 수 있었다.