• Journal of Communications and Networks
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• 제12권3호
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• pp.209-215
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• 2010

In an asymmetrical speed channel environment like asymmetric digital subscriber line, the up-link bandwidth is normally smaller than the down-link bandwidth, which will lead to extremely low utilization of down-link bandwidth when current P2P video transmission is applied. To overcome this, a new fast P2P video transmission method applied in an asymmetrical speed channel environment is proposed in this paper. On the basis of the many-to-one concept, the proposed method uses a new multipeer aggregation technique to enhance the utilization of down-link bandwidth. In addition, an adaptive peer assignment algorithm is also introduced in order to minimize the overall transmission time. Experimental results show that by using our proposed method, the utilization of down-link bandwidth is significantly improved, and the overall transmission time is greatly reduced.

• ETRI Journal
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• 제26권2호
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• pp.92-100
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• 2004

In this paper, we propose an efficient method to broadcast digital television signals using single frequency networks (SFNs) within the Advanced Television Systems Committee (ATSC) transmission systems. In implementing the SFNs of an 8-vestigial side band (8-VSB) Digital Television (DTV) system, the ambiguity problem of the trellis coder is unavoidable in a conventional ATSC transmission system. We propose a memory initialization of the trellis coder to resolve this ambiguity problem. Since the proposed scheme to synchronize multiple transmitters minimizes the changes from the conventional ATSC system, the hardware complexity for these changes is very low. Our simulation results show that the proposed scheme makes a less than 0.1 dB degradation at the threshold of visibility with a bit error rate of $3{\times}10^{-6}$ in the additive white Gaussian noise (AWGN) channel. It is possible to reduce the performance degradation by increasing the initialization period of the proposed scheme.

• 방송공학회논문지
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• 제20권1호
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• pp.122-139
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• 2015

지상파 TV의 디지털 전환이 완료되었지만 지상파 라디오는 전송방식을 결정하지 못해 아날로그 방송을 유지하며 표류하고 있는 상태이다. 본 연구에서는 지상파 방송사의 종사자를 대상으로 상호지향성 모델을 토대로 디지털 라디오 전송방식을 결정하는 중요 요인에 대한 인식차이를 살펴보고 쟁점 요인을 도출하였다. 연구결과, 지상파 방송 3사는 디지털 라디오가 점유할 주파수 대역 선택에서 가장 큰 인식의 차이가 있으며 제작과 송출의 병행 여부, 주파수 이용 효율성, 방송 품질과 서비스 정도는 서로 의견의 차이가 없는 것으로 나타났다. 그리고 디지털 라디오 방송의 전환에 있어 가장 큰 쟁점 요인은 FM 라디오방송이 사용하는 주파수대역(88-108 MHz)과 지상파 DMB방송 주파수대역(VHF Ch7~13), FM 라디오방송 인접대역(76~88MHz: VHF Ch5~6) 중 어떤 주파수 대역을 디지털 라디오용으로 선택하는지의 문제, 즉 DAB+, HD-Radio, DRM+ 가운데 특정 전송방식을 선택하는 문제로 귀결되었다. 이에 본 연구에서는 제작 송출 병행이 가능하고 송 중계소 1-2개로 송신 효율을 높일 수 있고 신규 사업자 진입이 가능한 방식을 채택함으로써 라디오방송서비스의 품질과 이용자의 만족도를 높일 것을 제안하고자 한다.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2004년도 High Temperature Superconductivity Vol.XIV
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• pp.50-50
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• 2004

• 디지털콘텐츠학회 논문지
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• 제14권4호
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• pp.521-528
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• 2013

최근 날로 증가하는 자동차와 교통체증으로 인하여 대기 오염이 갈수록 심화되고 있으며, 인구가 밀집된 대도시에서의 대기 오염은 심각한 질병을 유발시키기도 한다. 본 연구에서는 이러한 대기 오염을 감소시키기 위하여, 대기 오염 정보를 효과적으로 전송하고 이를 이용하여 대기 오염이 한계치에 도달한 특정지역으로의 자동차 유입 억제 등에 활용할 수 있는 대기오염 정보 및 교통류 제어정보 전송 방안을 제안한다. 특히 대기오염 정보 및 교통류 제어 정보를 전송하는 방법으로 교통 및 여행정보 전송을 위한 국제표준기술인 TPEG이 적용되었다.

• 한국정밀공학회지
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• 제12권7호
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• pp.148-157
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• 1995

This study deals with controlling the speed of Hydrostatic Transmission (HST) system throuth the control of pumping stroke of positive displacement pump using high-speed solenoid valve controlled by digital closed loop PWM method. The method which was done in this study is as follows: First, we modified original positive displacement pump and designed pumping stroke control system of HST by using the high-speed solenoid valve. Second, after experimenting static and dynamic characteristics on each signal flow, we identified system parameter of approximated model. Finally, to control the speed of HST, we controlled the angle of the swash plate of positive displacement pump by controlling the pressure in the control cylinder chamber. Test which was carried out in the laboratory shows that transient and steady state response could be improved by PID controller.

• 전기학회논문지P
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• 제56권1호
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• pp.56-62
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• 2007

In this paper, design method for power tower hazard diagnosis/predition system based on UsN was proposed. The proposed method used multi-hybrid sensors to measure rotation, displacement, and inclination state of power tower, and made decision/prediction of hazard of power tower. System design was made with requirement analysis of monitoring for transmission power facility and use of MEMS and optic fiber sensors. For hazard decision, analysis of correlation was made using sensor output. LN based on IEC61850,international standard for digital substation, was also proposed. For transmission facility monitoring, digital substation and power tower were considered as parts of power facility networks.

• ETRI Journal
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• 제30권4호
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• pp.495-505
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• 2008

This paper presents a parallel processing searcher structure for the initial synchronization of a direct sequence ultra-wideband (DS-UWB) system, which is suitable for the digital implementation of baseband functionalities with a 1.32 Gsample/s chip rate analog-to-digital converter. An initial timing acquisition algorithm and a data demodulation method are also studied. The proposed searcher effectively acquires initial symbol and frame timing during the preamble transmission period. A hardware efficient receiver structure using 24 parallel digital correlators for binary phase-shift keying DS-UWB transmission is presented. The proposed correlator structure operating at 55 MHz is shared for correlation operations in a searcher, a channel estimator, and the demodulator of a RAKE receiver. We also present a pseudo-random noise sequence generated with a primitive polynomial, $1+x^2+x^5$, for packet detection, automatic gain control, and initial timing acquisition. Simulation results show that the performance of the proposed parallel processing searcher employing the presented pseudo-random noise sequence outperforms that employing a preamble sequence in the IEEE 802.15.3a DS-UWB proposal.

• 디지털산업정보학회논문지
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• 제11권3호
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• pp.69-77
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• 2015

MANET is composed of only the mobile nodes have a limited transmission range. The dynamic topology by the frequent movement of nodes makes routing difficult and is also cause exposed to security vulnerabilities. In this paper, we propose the security routing technique consisted of mechanism of two steps in order to respond effectively to attack by the modification of the routing information and transmit secure data. The hierarchical structure is used and the authentication node that issues the key of the nodes within each cluster is elected in this proposed method. The authentication node manages key issues and issued information for encrypting the routing information from the source node. The reliability value for each node is managed to routing trust table in order to secure data transmission. In the first step, the route discovery is performed using this after the routing information is encrypted using the key issued by the authentication node. In the second step, the average reliability value of the node in the found path is calculated. And the safety of the data transmission is improved after the average reliability value selects the highest path. The improved performance of the proposed method in this paper was confirmed through comparative experiments with CBSR and SEER. It was confirmed a better performance in the transmission delay, the amount of the control packet, and the packet transmission success ratio.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 추계학술대회 논문집 학회본부
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• pp.95-97
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• 1988

A method of digital transmission line protection using travelling wave is presented. It is shown that the fault current appears as a difference of two quantities associated with the travelling wave at each terminal. The phasor of these quantities are extracted and transmitted to the other end via communication channel to detect the line fault.