• ETRI Journal
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• 제28권3호
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• pp.275-281
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• 2006

A very simple and efficient scheme for jitter reduction is proposed for a carrier frequency recovery loop using phase differential frequency estimation, which estimates the current frequency offset based on the difference of the average phases of two successive intervals. Analytical and numerical results presented in this paper show that by simply overlapping the observation intervals by half for frequency offset estimations, both the steady-state and transient performances can be improved. The proposed scheme does not require any additional hardware circuitry, but results in improved performance even with reduced complexity.

• 기술혁신학회지
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• 제7권3호
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• pp.555-580
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• 2004

We analyzed the effect of 6-month lagged number portability policy and introduction of common number among carriers on Korean mobile market. Our result shows that the policy change contributed to both the increase in number of mobile subscribers and decrease in dominant carrier's market share. We found that unified prefix among mobile operators is more effective than the lagged number portability policy. The carriers' profit, however, decreased a lot due to excessive marketing expenditure. We also estimated market shares of carriers up to year 2005 when full number portability policy is adopted. The results show that dominant carrier's monopolistic power will be recovered by the end of 2005 implying government's number policy itself cannot guarantee the effective competition in Korean mobile market.

• Journal of electromagnetic engineering and science
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• 제12권3호
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• pp.223-225
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• 2012

In this paper, we develop a symbol/frame time and carrier frequency synchronization scheme for multi-carrier signaling in wireless mobile channels. The proposed scheme achieves simultaneous time synchronization and carrier frequency offset estimation. Simulation results show that the frequency offset of multiple sub-carrier spacings can be estimated and that performance is improved with robustness regardless of the cyclic prefix length.

• ETRI Journal
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• 제32권2호
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• pp.255-264
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• 2010

Interference scenarios and methodologies between a terrestrial mobile service (MS) system and mobile-satellite service (MSS) system in a co-channel environment are established. Taking into account a practical deployment situation for both systems, we perform computational simulation of interference in terms of carrier-to-interference ratio (C/I) and interference-to-noise ratio (I/N) to evaluate the cofrequency interference from an MS system into an MSS system, and from an MSS system into an MS system, respectively. The methodology and results can be used as a guide when planning the deployment of MSS and MS systems with no unacceptable interference impact between them.

• 경영과학
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• 제21권2호
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• pp.235-252
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• 2004

Recently domestic mobile carriers have been engaged in heated battles for survival as the market is now rapidly approaching its maturity phase. and the launch of 3G service combined with the introduction of mobile number portability is dramatically reshaping the market landscape. The mobile carriers may have to create and maintain their competitive advantage based on their core capabilities and differentiated strategies. which will lead continuous survival and profits of the firm. This paper investigated competitiveness factors among mobile carriers. and analyzed the relationships of firm capabilities. competitive strategies and competitive advantage. We found that core capabilities and competitive strategies affecting competitive advantage are different from each carrier. Finally. we discussed strategic implications for carriers to increase their competitiveness.

• 대한산업공학회지
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• 제33권1호
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• pp.126-137
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• 2007

This study addresses the analytic models for estimating the capacity and performance of the multi-carrierCDMA system where several carriers would be assigned to a single cell to accommodate the required trafficdemand. Two key features of the multi-carrier CDMA system, carrier selections of new calls and inter-camerhard handoffs, are accommodated in the models, Computation experiments are conducted to show the effectiveness of the proposed model.

• 한국멀티미디어학회논문지
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• 제9권6호
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• pp.728-734
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• 2006

Carrier interferometry code is considered as a promising scheme that provides significant performance improvement via frequency diversity effect. Space-time coding is commonly employed to achieve a performance gain through space diversity. The combination of these techniques and forward error correction coding will lead to enhanced system capacity and performance. This paper presents a low-density parity check (LDPC) coded space-time orthogonal frequency division multiplexing (OFDM) transmission scheme with carrier interferometry code for high-capacity and high-performance mobile multimedia communications. Computer simulations demonstrate that the proposed mobile multimedia transmission system offers a considerable performance improvement of approximately 9dB in terms of Eb/No in the Rayleigh fading channel with relatively low delay spread, in comparison with space-time OFDM. Performance gains are further increased, comparing with traditional OFDM systems.

• 한국통신학회논문지
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• 제35권6C호
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• pp.516-522
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• 2010

본 논문에서는 중국향 휴대이동방송인 CMMB(China multimedia mobile broadcasting)를 위한 소수배 주파수 동기와 정수배 주파수 오차 추정 알고리듬을 제안한다. 제안한 소수배 주파수 동기 알고리듬은 CMMB의 프레임 구조에 가장 적합하도록 전치부호를 활용하여 매 CMMB 심볼마다 추정이 가능하다. 또한 제안된 정수배 주파수 알고리듬은 CMMB 동기 신호를 이용하여 매 프레임마다 추정 한다. 제안 알고리듬은 시간 오프셋이 존재할 때에도 소수배와 정수배 주파수 오프셋을 정확히 추정할 수 있으며 다중 경로 상황에서도 우수한 성능을 보인다.

• 시스템엔지니어링학술지
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• 제11권1호
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• pp.33-39
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• 2015

This paper describes a development of aircraft carrier aviation support system architecture using DoDAF. The aircraft carrier, a warship performing a role of mobile sea air base in offensive and defense mission, is super system that is comprised of carrier itself and carrier-based airwing. Performing critical role in step with aviation operations in carrier-airwing interactions, the aviation support system of aircraft carrier is also system of systems. It requires a complex and integrated approach based on systems engineering in establishing concept of this complex systems. In this view, this study establishes an operational scenario and derives operational requirements by identifying aviation operations environment on deck of aircraft carrier. The study presents the operational architecture of the carrier aviation support system by using DoDAF and CASE tool CORE.

• Transactions on Electrical and Electronic Materials
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• 제18권4호
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• pp.195-198
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• 2017

This research analyzed the electrical characteristics of an 80 V optimal trench power MOSFET (metal oxide field effect transistor) for mobile applications. The power MOSFET is a fast switching device in fields with low voltage(<100 V) such as mobile application. Moreover, the power MOSFET is a major carrier device that is not minor carrier accumulation when the device is turned off. We performed process and device simulation using TCAD tools such as MEDICI and TSUPREM. The electrical characteristics of the proposed trench gate power MOSFET such as breakdown voltage and on resistance were compared with those of the conventional power MOSFET. Consequently, we obtained breakdown voltage of 100 V and low on resistance of $130m{\Omega}$. The proposed power MOSFET will be used as a switch in batteries of mobile phones and note books.