• 전자공학회논문지 IE
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• 제45권3호
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• pp.50-55
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• 2008

CDMA 시스템에서는 각 기지국이 수신하는 총 간섭량에 따라 각 셀에서 동시에 통화할 수 있는 이동 가입자들이 수가 영향을 받는다. 본 연구에서는 다중 셀 CDMA 시스템에서 등가대역 개념을 이용한 호 수락 제어 방법을 사용하며, 신규 호의 차단률 및 핸드오프 호의 절단률에 따라 각 셀의 대역폭을 가변시켜 신규 호와 핸드오프 호를 처리하고 핸드오프 호를 위해서는 자원을 예약해 둔다. 모의실험을 통하여 핸드오프 호를 위해서 자원을 예약해 둠에 따른 시스템의 성능을 분석한다. 예약자원이 많을수록 핸드오프 호의 절단율을 감소함을 알 수 있다.

• Journal of Power Electronics
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• 제13권1호
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• pp.170-176
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• 2013

Power converters produce a vast range of harmonics, subharmonics and interharmonics. Harmonics analyzing tools based on the Fast Fourier Transform (FFT) assume that only harmonics are present and the periodicity intervals are fixed, while these periodicity intervals are variable and long in the presence of interharmonics. Using FFT may lead to invalid and undesired results due to the above mentioned issues. They can also lead to problems such as frequency blending, spectral leakage and the picket-fence effect. In this paper, the group-harmonic weighting (GHW) approach has been presented to identify the interharmonics in a power system. Afterwards, a modified GHW has been introduced to calculate the proper bandwidth for analyzing the various values of interharmonics. Modifying this method leads to more precise results in the FFT of a waveform containing inter harmonics especially in power systems with a fundamental frequency drift or frequency interference. Numerical simulations have been performed to prove the efficiency of the presented algorithm in interharmonics detection and to increase the accuracy of the FFT and the GWH methods.

• 한국통신학회논문지
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• 제22권5호
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• pp.939-948
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• 1997

본 논문에서는 ATM 네트워크에서의 접속된 ABR 서비스에 대해 공정한 대역폭을 할당하는 새로운 비율 기반 전송률 제어 알고려즘을 제안한다. 기존 ABR 서비스에서는 일정률로 전송률을 증가, 감소를 하면서 대역폭을 할당하나 제안된 알고리즘에서는 이용 가능한 대역폭을 퍼지 추론을 하여 접속된 호에 대해 전송률을 공평하게 분할하는 기법이다. 퍼지 추론은 입력 변수로 버퍼 상태, 버퍼 변화율을 사용하고 출력 변수로 전체 전송률을 사용한다. 이 추론된 결과값은 동작 중에 있는 ABR 서비스 호에 공평하게 분배되어 진다. 모의 실험 결과 기존의 E EPRCA 방식보다 제안된 방식이 링크 효율면에서 RIF, RDF가 1일 경우 0.17%, 1/4 경우 6%, 1/16 경우 38.6%, 1/32 경우 82.4%의 향상을 보였다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권2호
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• pp.189-195
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• 2005

This paper presents a new velocity estimation strategy for a non-salient permanent magnet synchronous motor drive without high frequency signal injection or special PWM pattern. This approach is based on the d-axis current regulator output voltage of the drive system, which contains the rotor position error information. The rotor velocity can be estimated through a rotor position tracking PI controller that controls the position error at zero. For zero and low speed operation, the PI gain of the rotor position tracking controller has a variable structure according to the estimated rotor velocity. Then, at zero speed, the rotor position and velocity have sluggish dynamics because the varying gains are very low in this region. In order to boost the bandwidth of the PI controller during zero speed, the loop recovery technique is applied to the control system. The PI tuning formulas are also derived by analyzing this control system by frequency domain specifications such as phase margin and bandwidth assignment.

• 한국인터넷방송통신학회논문지
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• 제10권5호
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• pp.259-264
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• 2010

본 논문에서는 기존에 근거리전용통신 방식보다 다양한 서비스를 제공하고, 위치정보와 무선통신망을 이용한 브랜드 콜, 화물차 및 관용차 등의 서비스에 적용이 가능할 뿐 아니라 긴급 구난 정보제공, 무선인터넷, 영화 및 게임 등 멀티미디어 서비스를 제공하기 위한 경쟁력 있는 차량용 무선 이동시스템을 설계하여 이를 바탕으로 와이브로 기반의 무선 텔레매틱스 단말시스템을 구현하고자 한다. 이동 차량 내 유비쿼터스 환경 구축을 위한 와이브로 기반의 무선 텔레매틱스 단말 시스템을 구현한다. 모의실험을 통하여 텔레매틱스 시스템의 고정대역과 가변대역에 대한 시스템 분석을 하였다.

• 한국통신학회논문지
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• 제21권12호
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• pp.3132-3143
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• 1996

In the evaluation of Broadband-ISDN, the main issue is to interconnect existing LANs and MANs to B-ISDN based on Asynchrous Transfer Mode. However, LANs provide connectionless services, whereas the ATM network provides connection-oriented services. So some problem arises from accessing ATM switchs to transparently transmit connectionless data via B-ISDN. Two methods then were recommended by ITU-TS to support the connectionaless services. In the paper, we do the numerical analysis, using the stochastic fluid flow method, of dynamic bandwidth allocation sheme with two class traffics in the virtual path established between Interworking Units(JWUS) interconnecting LANs to an ATM network and Connectionless Servers(CLSs). The loss mechanism of each traffic is controlled by the contents of buffer. The vandwidth which the IWU requests the CLS is estimated by the number of On-Off sources in the On state. We use the stochsastic fluide flow method which is to find the steady-state joint probability in each level of the IWU buffer. The length of the IWU buffer as the real random variable is changed by traffics entering the IWU.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 추계종합학술대회 논문집
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• pp.97-100
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• 1999

Mobile network applications are growing and this requires a fast and efficient transport method between the BS(Base Station) and the MSC(Mobile Switching Center). One possible solution is to use ATM and a voice CODEC standard which compresses 64kbps voice data to less than 8kbps. The low bit tate and small-sized packets made by the voice CODEC imply that significant amount of link bandwidth would be wasted, if this small-sized packet is carried by one ATM cell. The cell assembly delay increases if one ATM cell is fully filled with the small-sized packets. For the bandwidth-efficient transmission of low-rate, short, and variable length packets in delay sensitive applications, AAL-2 was standardized. This paper evaluates performance of AAL-2 by using voice CODEC standard.

• International Journal of Automotive Technology
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• 제3권3호
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• pp.123-128
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• 2002

This paper presents the design of an active roll control system for a ground vehicle and an experimental study using an devised electric-actuating roll control system. Based on a three degree of freedom linear vehicle model, the controller is designed using lateral acceleration and rollrate feedback. In order to investigate the feasibility of an active control system, experimental work is carried out using a hardware-in-the-loop (Hil) setup which has been constructed by the devised electric-actuating system and the full vehicle model including tire characteristics. The performance is evaluated by an experiment using the Hil setup with limited bandwidth. Finally, in order to enhance the control performance in the transient region, a hybrid control strategy is proposed and evaluated.

• 한국군사과학기술학회지
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• 제13권1호
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• pp.133-139
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• 2010

GNSS receiver which uses the weak satellite signal is very vulnerable to the intentional jamming or non-intentional electromagnetic interference. It is a very simple method among the use method of GNSS receiver to vary tracking loop bandwidth of satellite signal appropriately as the jamming signal level. In this paper, this anti-jamming performance is experimented and analyzed in the laboratory and the anechoic chamber by the GNSS simulator to generate the satellite signal and the jamming signal generator to generate the jamming signal.

• 대한전기학회논문지
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• 제39권1호
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• pp.49-56
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• 1990

An induction motor position control system based on the sliding mode control is presented. In the sliding mode control, control function is discontinuous on the hyperplane, which causes harmful effects such a s current harmonics and acoustic noise in the motor drive application. In this study, a low pass filter is introduced between the sliding mode controller output and the motor controller input to reduce these effects. The filter, however, makes the torque response slggish and the system performance may become poor in cost of chattering reduction. To overcome these problems, the bandwidth of the filer is varied according to the error function. It is shown that the proposed sliding mode control with variable-bandwidth filter shows good performance, which is confirmed through experiments.