• Journal of Korean Institute of Industrial Engineers
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• v.29 no.2
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• pp.135-144
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• 2003

Traffic performance in a microcellular system is much more affected by cell dwell time and channel holding time in each cell. Cell dwell time of a call is characterized by its mobility pattern, i.e., stochastic changes of moving speed and direction. Cell dwell time provides important information for other analyses on traffic performance such as channel holding time, handover rate, and the average number of handovers per call. In the next generation mobile communication system, the cell size is expected to be much smaller than that of current one to accommodate the increase of user demand and to achieve high bandwidth utilization. As the cell size gets small, traffic performance is much more affected by variable mobility of users, especially by that of pedestrians. In previous work, analytical models are based on simple probability models. They provide sufficient accuracy in a simple second-generation cellular system. However, the role of them is becoming invalid in a picocellular environment where there are rapid change of network traffic conditions and highly random mobility of pedestrians. Unlike in previous work, we propose an improved probability model evolved from so-called Random walk model in order to mathematically formulate variable mobility of pedestrians and analyze the traffic performance. With our model, we can figure out variable characteristics of pedestrian mobility with stochastic correlation. The above-mentioned traffic performance measures are analyzed using our model.

• International journal of advanced smart convergence
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• v.4 no.1
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• pp.1-10
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• 2015

Automotive Theft has been an obstinate problem around the world. Design and manufacture of anti-theft systems have become more and more complex due to the rise in complexity of theft in the system. Most of the anti-theft systems available in the market, are the alarm types which audibly deter some thieves away but do not prevent one's car from being stolen and even are not good enough to meet the growing complexity of theft in the country. This paper presents a simple and an efficient anti-theft system which provides improved security by the use of efficient access mechanisms and immobilization systems. This security system can immobilise an automobile and its key auto systems through remote control when it is stolen. It hence deters thieves from committing the theft. It also effectively prevents stealing of key auto systems for reselling by introducing four layers of security features written in the form of firmware and embedded on the Electronic Control Units (ECUs). The particulars of system design and operation are defined in the paper. The experimental outcomes show that this system is practicable and the owner can steadily control his vehicle within a few seconds.

• Korean Journal of Optics and Photonics
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• v.23 no.6
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• pp.264-268
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• 2012

In this paper, we propose a new method for broadcasting in a WDM-PON system which has the merits of a simple and cost effective structure. It can be constructed using only an ASE (Amplified Spontaneous Emission) light source and a PI-RSOA (Polarization Independent - Reflective Semiconductor Optical Amplifier). Error-free broadcast signal transmission over 30 Km for 24 channels at 1.25 Gb/s has been successfully demonstrated.

• Journal of Digital Convergence
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• v.10 no.6
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• pp.197-203
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• 2012

In this paper, researching for the video quality estimation of IPTV in the situation that increase the broadcasting network traffic on the IPTV multicasting service using the ETSI TR 101 290 that is the European digital video quality standard estimating method and present the experiment result. Proving that the intimate relation is between IPTV video quality and ETSI TR 101 290 estimation, also ETSI TR 101 290 can detect the video quality factors which can't be detected by the exist video estimation methods.

• International journal of advanced smart convergence
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• v.6 no.4
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• pp.33-40
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• 2017

In this paper, complex quadruplet zeros of microwave filter systems are investigated. For the cascaded systems the chain matrices are most conveniently used to derive the voltage transfer function of Laplace transform with cascaded two-port subsystems. The convenient relations of transfer function and chain matrix are used in order to find the transmission zeros. Starting from a ladder network, we introduced a crossed-coupled lumped element, in order to show the improved response of bandpass filter. By solving the transmission zero characteristic equation derived from the cascaded subsystems, we found the zeros of filter system with externally cross-coupled lumped elements. With the cross-coupled elements of capacitors, the numerator polynomial of system transfer function is used to locate the quadruplet zeros in complex plane. When the two pairs of double are on the zeros -axis, with the perturbed values of element, we learned that the transition band of lowpass filter is improved. By solving the characteristic equation of cascaded transfer function, we can obtain the zeros of the cross-coupled filter system, as a result of perturbed values on lumped element.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2014.06a
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• pp.126-128
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• 2014

디지털 방송기술의 비약적인 발전으로 기존 HD(High Definition) 화질의 4~16배까지 지원 가능한 UHD(Ultra High Definition) 방송 서비스가 제공되는 새로운 시대를 맞이하게 되었다. UHD 방송은 초고선명 비디오와 22.2 채널 오디오 서비스가 가능한 차세대 실감방송 기술이다. 이러한 UHD 서비스를 제공하기 위해서는 고압축 영상 코덱 기술인 HEVC(High Efficiency Video Coding), OFDM(Othogonal Frequency Division Multiplexing) 기반 대용량 전송기술과 다양한 멀티미디어 부가서비스 가능한 전송 프로토콜이 필수적으로 요구된다. 최근 UHD 방송 전송 프로토콜로 표준화 추진 중인 MMT(MPEG Media Transport)는 이기종망에서 적용할 수 있으며, 양방향 전환이 가능하여 시청자의 요구사항을 실시간으로 반영할 수 있다는 장점을 지닌다. 한편, 지상파 UHD 방송 서비스를 빠르고 효과적으로 수신하기 위해 필요한 정보인 NIT(Network Information Table), RRT(Rating Region Table) 및 SDT(Service Description Table)가 MMT 시그널링 프로토콜에서는 포함되어 있지 않다. 따라서 본 논문에서는 지상파 UHD 방송 서비스의 효과적 수신이 가능한 MMT 기반 지상파 UHD 방송을 위해 NIT, RRT 및 SDT 정보가 포함된 서비스 시그널링 구조을 제안한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.12
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• pp.3622-3625
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• 2009

This study develops a variable structure controller using the time-varying nonlinear sliding surface instead of the fixed sliding surface, which has been the robustness against parameter variations and extraneous disturbance during the reaching phase. By appling TS algorithm to the regulation of the rionlinear sliding surface, the reaching time of the system trajectory is faster than the fixed method. This proposed scheme has better performance than the conventional method in reaching time, parameter variation and extraneous disturbance. The effectiveness of the proposed control scheme is verified by simulation results.

• Journal of Internet Computing and Services
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• v.11 no.5
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• pp.9-17
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• 2010

During the last decade, Internet protocol television(IPTV), broadcasting of multimedia services using well understood Internet technologies, is a fast spreading technology for distributing multimedia content to consumers. As IPTV services advance, an increasing user demand and tremendous content volume of multimedia content cause some difficulties in network resource management. In this paper, we propose an improved load balancing algorithm for video-on-demand(VoD) service. Unlike existing algorithms, the proposed algorithm considers user's behaviors for VoD service, and determines the most efficient allocation of VoD requests by estimating expected server load and expected user waiting time.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2013.06a
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• pp.85-86
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• 2013

AT-DMB의 향상계층은 DQPSK 신호에 BPSK 또는 QPSK 신호를 더하여 변조하는 계층변조 방식을 사용하였기 때문에 수신기에서 채널 왜곡을 보상해야 신호의 복조가 가능하다. 다중 경로가 많은 지역에서는 주파수 선택적 페이딩이 발생하기 때문에 페이딩을 정확하게 추정하지 못하면 AT-DMB 향상계층 수신 성능이 저하되게 된다. 채널왜곡 추정을 위하여 AT-DMB 수신기에서는 채널추정 값을 스무딩하는 대역제한 필터를 사용한다. AT-DMB의 향상 계층 성능은 이 스무딩 필터의 대역폭에 따라 결정이 되며 적절한 필터 대역을 채널의 지연에 따라 설정해야 한다. 특히 SFN 환경에서는 수신 전력이 큰 둘 이상의 서로 다른 지연시간을 가지면서 수신이 되기 때문에 고정 대역폭 스무딩 필터를 사용한 채널왜곡 추정은 성능의 저하를 가져올 수 있다. 본 논문에서는 채널 지연 값을 추정하고 필터의 대역폭을 가변적으로 결정하는 방법에 대하여 설명하고 실험 결과를 보여준다.

• The Journal of the Korea Contents Association
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• v.9 no.2
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• pp.60-66
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• 2009

In this paper, implementation of an ensemble transport interface (ETI) adapter for multimedia services based on terrestrial-digital multimedia broadcasting (T-DMB) is introduced. In general, ETI adapter should manipulate three functions: receiving packets packing multimedia data from service providers, configuring an ETI frame (G.703) from these data, and transmitting these frames to T-DMB multiplexer. To achieve these roles, the proposed ETI adapter consists of the network management module for data transmission and flow control between service providers and this adapter, the ETI configuration module for gathering data and then making ETI frames, and the hardware board for pushing ETI frames in real-time. The proposed adapter yielded faithful results without data lose on transmitting ETI frames to T-DMB multiplexer in the range of $64{\sim}1,153kbps$ specified in ETSI EN 300 401 after packing multimedia data received via Internet.