• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.4
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• pp.733-738
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• 2011

As increase of nonlinear loads and renewable energy generators (REGs) being connected to power distribution system via inverters, the concern on harmonic problems have increased. Recently, the harmonics evaluation method considering TDD (Total Demand Distortion) is used to analyze the effect of harmonics from inverters on power distribution quality. Harmonic current sources are typically used for simulation of nonlinear load. Most inverter type for REGs is voltage source inverter (VSI). So, harmonic voltage sources are more suitable to analyze impact of renewable energy generator on harmonics problem in power distribution system. In this paper, we presented the circuit model to analyze interaction between harmonics from nonlinear load and REGs. We verified that the harmonic analysis using the proposed circuit model is more appropriate than the harmonics evaluation method considering TDD through case study using PSCAD/EMTDC.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10b
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• pp.143-146
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• 2007

테스트 주도 개발(TDD)에서는 무엇보다 테스팅의 중요성이 강조되고 있으며, 효율적인 단위 테스트를 통해 소프트웨어를 신속하게 개발할 수 있도록 자동화된 테스트 프레임워크를 지원한다. 본 논문은 소프트웨어를 개발하는 과정에서 소프트웨어의 기능뿐만 아니라 비기능적인 요소(non-functional factor)인 성능도 함께 고려하여 모바일 응용 소프트웨어를 개발하도록 하는 성능 테스트 방안을 제안한다. 본 논문에서는 모바일 응용 소프트웨어 성능 테스트 현황과 이슈를 살펴보고, 모바일 응용 소프트웨어 성능 테스트를 위해 필요한 성능 특성들을 분석하여, 테스트 주도 개발의 특징을 반영한 성능 테스트 방안에 대해 제시하고자 한다.

• ETRI Journal
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• v.41 no.4
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• pp.426-436
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• 2019

In time division duplex (TDD)-based multiuser massive multiple input multiple output (MIMO) systems, the uplink channel is estimated and the results are used in downlink for signal detection. Owing to noisy uplink channel estimation, the downlink channel should also be estimated for accurate signal detection. Therefore, recently, a blind method was developed, which assumes the use of a linear high-power amplifier (HPA) in the base station (BS). In this study, we extend this method to a scenario with a nonlinear HPA in the BS, where the Bussgang decomposition is used for HPA modeling. In the proposed method, the average power of the received signal for each user is a function of channel gain, large-scale fading, and nonlinear distortion variance. Therefore, the channel gain is estimated, which is required for signal detection. The performance of the proposed method is analyzed theoretically. The simulation results show superior performance of the proposed method compared to that of the other methods in the literature.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.11a
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• pp.958-961
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• 2013

최근 스마트폰이 빠르게 보급되면서 모바일 OS 시장에서 안드로이드는 79%의 시장점유율을 보여주고 있다. 이와 같은 안드로이드의 빠른 성장과 마켓 시장의 확대에 따라 수많은 애플리케이션이 개발되고 있다. 하지만 개발자 등록과 애플리케이션 배포 절차가 비교적 간단하기 때문에 충분한 검증절차를 거치지 않은 애플리케이션이 얼마든지 배포될 수 있다. 따라서 안드로이드 애플리케이션 개발단계에서 충분한 테스트 작업이 필요하다. 이에 본 논문에서는 단위테스트와 통합테스트를 통해 안드로이드 애플리케이션의 완성도를 높이기 위한 테스트 자동화 시스템을 설계하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.11a
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• pp.336-339
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• 2007

모바일의 소프트웨어 테스팅은 매우 중요하다. 그러나 모바일 특성상 일반 어플리케이션의 테스팅과 다른 점이 있으며, 짧은 생명주기 등으로 빠른 출시를 목적으로 테스팅을 소홀히 하는 경우가 있다. 이렇게 테스팅을 소홀히 함으로써 추가적인 유지보수등의 비용으로 기업의 손실로 직결될 수 밖에 없다. 하지만 현재 모바일의 단위 테스트 방법 및 테스트 개발 방법이 미미한 실정이다. 본 논문에서는 TDD방법을 적용하여 모바일의 테스트 방법 및 개발 절차에 대하여 제시하고자 한다.

• TTA Journal
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• s.154
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• pp.78-83
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• 2014

• Journal of Internet Computing and Services
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• v.11 no.3
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• pp.43-51
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• 2010

In this paper, we evaluate the system throughput and the method of optimal wireless resource allocation for the access zone (AZ) and relay zone (RZ) in downlink when the cell coverage is extended using the non-transparent Relay Station (RS) in a 2-hop cellular relay system based on IEEE802.16j, which uses the OFDMA-TDD structure. For the analyses, we first introduce the MAC (Media Access Control) frame structure in the non-transparent mode, then we investigate the interfering elements in both AZ and RZ for the network devices such as the Mobile Station (MS) and RS. Through computer simulation, we analyze the cell coverage extension and system throughput in terms of the distance between Base Station (BS) and RS, then we present the amount of the optimal allocation of wireless resource for the AZ and RZ in downlink using our results.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.4
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• pp.450-456
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• 2010

In the high-speed packet service, next generation mobile communication system has emerged as a major feature. If the fire of these high-speed kit services and non-continuous transmission of data due to the symmetrical nature of daeyiteo traffic for D-CDMA system has been actively studied. Small amounts of data moving in the uplink, but the real-time video downlink transmission, such as downloading large files to move data and services to those with asymmetric traffic characteristics, a system that can efficiently handle the data requirements be. Of 3GPP TDD(Time Division Duplex) scheme based on CDMA and TDMA in a way by introducing the concept through the proper allocation of time slots that can handle asymmetric traffic efficiently, has an advantage. TD-CDMA system by considering the characteristics of the frame configuration of transmission methods, such as physical channel structure and channel coding has been investigated. In addition, the HARQ scheme TD-CDMA system performance is analyzed by comparing them.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.1
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• pp.73-78
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• 2010

In this paper, the analysis of the harmonics of distribution power system interconnected with DG(distributed generation) is simulated by using PSCAD/EMTDC and evaluated the harmonics. The modeling system for simulation is similar to the actual distribution system, and solar power system. The simulation analyses are performed at connection points for each sector. Harmonic standards of interconnection with DG (IEEE Std 1547 and IEEE Std 519) are applied to the evaluation algorithm, converted the simulated data through FFT method, evaluated by THD and TDD separately. The harmonic contents in the case of without DG and each sector with DG are evaluated and compared. The results of evaluation showed the effect that the harmonic contents are appropriated at all sector with DG (without DG) in the distribution power systems but the large induction motor(50KW) is increased the harmonic contents.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.12A
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• pp.1172-1176
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• 2008

In this paper, we describe the implementation and performance of a dual-mode Software Define Radio (SDR) smart antenna base station system. SDR technology enables a communication system to be reconfigured through software downloads to the flexible hardware platform that is implemented using programmable devices such as Digital Signal Processors (DSPs), Field Programmable Gate Arrays (FPGAs), and microprocessors. The presented base station channel card comprises the physical layer (pHY) including the baseband modem as well as the beamforming module. This channel card is designed to support TDD High-Speed Downlink Packet Access (HSDPA) as well as Wireless Broadband Portable Internet (WiBro) utilizing the SDR technology. We first describe the operations and functions required in WiBro and TDD HSDPA. Then, we explain the channel card design procedure and hardware implementation. Finally, we evaluate WiBro and TDD HSDPA performance by simulation and actual channel-card-based processing. Our smart antenna base-station dual-mode channel card shows flexibility and tremendous performance gains in terms of communication capacity and cell coverage.