• Structural Engineering and Mechanics
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• 제46권4호
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• pp.459-486
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• 2013

A novel damage classification method based on wavelet packet transform and statistical analysis is developed in this study for structural health monitoring. The response signal of a structure under an impact load is normalized and then decomposed into wavelet packet components. Energies of these wavelet packet components are then calculated to obtain the energy distribution. Statistical similarity comparison based on an F-test is used to classify the structure from changes in the wavelet packet energy distribution. A statistical indicator is developed to describe the damage extent of the structure. This approach is applied to the test results from simply supported reinforced concrete beams in the laboratory. Cases with single and two damages are created from static loading, and accelerations of the structure from under impact loads are analyzed. Results show that the method can be used with no reference baseline measurement and model for the damage monitoring and assessment of the structure with alarms at a specified significance level.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.767-772
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• 2005

The Internet is a packet switched network which offers best-effort service, but current IP network provide enhanced services such Quality of Services, Virtual Private Network (VPN) services, Distribute Firewall and IP Security Gateways. All such services need packet classification for determining the flow. The problem is performing scalable packet classification at wire speeds even as rule databases increase in size. Therefore, this research offer packet classification algorithm that increase classifier performance when working with enlarge rules database by rearrange rule structure into Bitmap Intersection Lookup (BIL) tables. It will use packet's header field for looking up BIL tables and take the result with intersection operation by logical AND. This approach will use simple algorithm and rule structure, it make classifier have high search speed and fast updates.

• Smart Structures and Systems
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• 제1권1호
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• pp.29-46
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• 2005

In this study, a wavelet packet based method is proposed for identifying damage occurrence and damage location for beam-like structures. This method assumes that the displacement or the acceleration response time histories at various locations along a beam-like structure both before and after damage are available for damage assessment. These responses are processed through a proper level of wavelet packet decomposition. The wavelet packet signature (WPS) that consists of wavelet packet component signal energies is calculated. The change of the WPS curvature between the baseline state and the current state is then used to identify the locations of possible damage in the structure. Two numerical studies, one on a 15-storey shear-beam building frame and another on a simply-supported steel beam, and an experimental study on a simply-supported reinforced concrete beam are performed to validate the proposed method. Results show the WPS curvature change can be used to locate both single and sparsely-distributed multiple damages that exist in the structure. Also the accuracy of assessment does not seem to be affected by the presence of 20-15dB measurement noise. One advantage of the proposed method is that it does not require any mathematical model for the structure being monitored and hence can potentially be used for practical application.

• 한국시뮬레이션학회논문지
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• 제3권1호
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• pp.75-88
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• 1994

Discrete event modeling is finding ever more application to anlysis and design of complex manufacturing, communication, computer systems, etc. This paper shows how packet network systems may be advantageously represented as DEVS (Discrete Event System Specification) models by employing System Entity structure / Model base (SES/MB) framework developed by Zeigler. DEVS models and network structure representations support a strong basis for performance analysis of packet network systems. This approach is illustated in a typical packet network example with several routing strategies.

• 대한전자공학회논문지SD
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• 제49권7호
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• pp.30-38
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• 2012

본 논문은 mmWave OFDM-기반 WPAN 시스템을 위한 패킷 검출과 주파수 옵셋 추정 및 보정 구조를 제안하고 성능 분석 결과를 보여준다. 패킷 검출 블록은 반복된 훈련 심볼의 자기상관 관계를 이용하고 상관된 값이 일정 문턱 값을 넘을 때 패킷 시작점을 검출하는데 사용된다. 적용한 자기상관 알고리즘 구조는 기존의 패킷검출에 사용한 알고리즘에 비해 간단하게 하드웨어를 구현 할 수 있다. 주파수 옵셋 추정 구조는 기존구조와는 다른 위상 천이 처리 블록, 하드웨어 사이즈를 줄여주는 내부비트 줄임 블록 및 look-up table의 사이즈를 줄인 주파수 옵셋 조정 블록을 설계하였다. 추정된 주파수 옵셋 값은 설계한 보정 블록을 통해 수신 신호를 보정함으로써 주파수 옵셋에 대한 영향을 줄일 수 있다. 설계 검증툴을 이용한 성능 분석 결과 제안된 구조는 하드웨어 구현복잡도가 감소함을 보여 주었고 기존구조에 비하여 게이트수가 감소함을 보였다. 따라서 제안된 구조는 OFDM-기반 WPAN 시스템의 초기 동기화 과정에 적용 될 수 있고 고속 저전력 WPAN칩에 사용 될 수 있다.

• 한국통신학회논문지
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• 제13권2호
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• pp.171-181
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• 1988

본 논문에서는 packet-switched network에서 음성을 서비스하는데 있어서 고려해야 할 여러가지 점들을 살펴보고, 실제로 음성과 데이터를 동시에 서비스하는 packet voice/data terminal을 구현하였으며 그 성능 분석을 시도하였다. PVDT의 software는 OSI 7 layer architecture에 맞추어 설계하였으며 음성과 데이터를 link level부터 구별하여 서비스하였다. 또한 음성 packet의 전송 delay를 작게 하기 위해 데이터보다 음성을 우선적으로 서비스하도록 하였으며 간략화된 protocol로 재전송에 의한 overhead를 없앴다. PVDT의 hardware의 구성은 기능별로 master control module, speech processing module, speech activity detection module, telelphone interface module, input/output inteface module로 나누어진다. Packet음성통신망에 대한 해석으로는 음성 packet의 전송 delay의 variance에 의한 영향을 줄이기 위한 최적 재생지연시간을 전송 delay의 분포를 통해 계산하였다.

• 한국산학기술학회논문지
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• 제15권4호
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• pp.2382-2392
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• 2014

본 논문에서는 초고속 광인터넷 구축을 위한 광링액세스네트워크(ORAN: Optical Ring Access Network)의 구조에서 파장 라우팅을 위한 새로운 데이터 프레임 구조를 설계하고 각 필드의 기능을 정의하였다. 또한 IP 패킷의 전송을 위하여 필요한 네트워크의 계층별 구조에 대응하는 프로토콜 스택의 구조를 새로이 제시하여 네트워크 프로토콜을 설계하였다. ORAN의 데이터 전송 및 파장 라우팅에 관한 프로토콜 검증을 위하여 서브망 내의 IP 패킷 전송, 서브망 내의 브로드캐스팅 패킷 전송 그리고 다른 서브망으로의 IP 패킷 전달 과정을 예시를 통하여 보여 주었다. 이 과정에서 라우팅을 위한 파장정보가 인캡슐레이션 되는 프레이밍 과정을 기술하였고 각 단계에서 이루어지는 패킷 스위칭 및 패킷의 전달 과정을 자세히 묘사하였다. 이어서 ORAN의 가입자 노드와 두 링의 제어노드에 대하여 데이터 전송 프로토콜의 송/수신 모듈 구조를 자세히 보여주었다. 링 형태의 광액세스 네트워크 프로토콜은 아직 연구되지 않은 분야이다. 본 논문에서는 파장을 이용한 라우팅이 이루어지도록 ORAN의 패킷 전송 프로토콜을 디자인하였다. 그리고 데모 시나리오를 구성한 망에서의 장시간 전송 테스트에서도 안정적으로 파장 라우팅을 통한 패킷 전송이 이루어졌음을 확인하였다. 따라서 이러한 프로토콜의 검증을 통하여 초고속 인터넷 액세스망 구축 설계의 새로운 해법을 제시하였다.

• ETRI Journal
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• 제26권5호
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• pp.391-396
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• 2004

In this paper, we propose a packet scheduling discipline called packet loss fair scheduling, in which the packet loss of each user from different real-time traffic is fairly distributed according to the quality of service requirements. We consider an orthogonal frequency division multiple access (OFDMA) system. The basic frame structure of the system is for the downlink in a cellular packet network, where the time axis is divided into a finite number of slots within a frame, and the frequency axis is segmented into subchannels that consist of multiple subcarriers. In addition, to compensate for fast and slow channel variation, we employ a link adaptation technique such as adaptive modulation and coding. From the simulation results, our proposed packet scheduling scheme can support QoS differentiations while guaranteeing short-term fairness as well as long-term fairness for various real-time traffic.

• 대한임베디드공학회논문지
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• 제13권2호
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• pp.93-100
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• 2018

In this paper, we present a novel scheme of data transmission for logistics vehicles connected with 3G mobile communication networks. The proposed method enhances the efficiency of data transmission by varying the packet transmission period according to the vehicle speed and by reducing the amount of transmitted data using a reduced packet structure. The main contribution is to present the experimental verification in which the proposed method is applied to commercial logistics vehicles that operate with networked data transmission modules. Being compared with the existing method, the proposed scheme shows superior performance in terms of data reduction and transmission speed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.619-624
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• 2004

In this research, the structural health monitoring method using wavelet packet analysis and artificial neural network (ANN) is developed. Wavelet packet Transform (WPT) is applied to the response acceleration of a 3 element-cantilever beam which is subjected to impulse load and Gaussian random load to decompose the response signal, then the energy of each component is calculated. The first ten largest components in magnitude among the decomposed components are selected as input to an ANN to identify the damage location and severity. This method successfully predicted the amount of damage in the structure when the structure is subjected to impulse load. However, when the beam is subjected to Gaussian random load which can be considered as ambient vibration it did not yield satisfactory results. This method is applicable to structures such as machinery gears that are subjected to repetitive loads.