• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2008.11a
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• pp.91-94
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• 2008

본 논문에서는 준 정적(quasi-static) 레일레이 페이딩(Rayleigh fading) 채널에서 상향링크 다중 사용자 MIMO-OFDM 시스템을 위한 최소평균제곱오차-순차간섭제거(MMSE-SIC: Minimum mean square error-successive interference cancellation) 수신기에 대해 연구한다. 송신 안테나가 하나인 사용자와 수신 안테나가 다수인 기지국에서 MMSE-SIC 수신기를 기반으로 신호를 검출하는 시스템에서는 하나의 부대역 내에서 동시에 전송 가능한 사용자의 수가 기지국에서의 수신안테나 수보다 작아야 하는 제한 조건을 가지고 있다. 따라서 사용자간 공정성을 보장하고 시스템의 효율성을 높이기 위해 낮은 복잡도를 가지는 비례 공정(Proportional fair) 스케줄링 알고리즘을 제안한다. 제안된 비례 공정 스케줄링 알고리즘에서는 부대역 내에서 다중 사용자 채널 행렬을 기반으로 동시에 전송하는 사용자들의 집합을 찾는다. 평균 채널 이득이 사용자마다 다른 환경에서의 모의실험을 통해 제안된 비례 공정 스케줄링 기법의 성능을 알아본다. 제안된 비례 공정 스케줄링 기법은 기존의 공정성을 기반으로 하는 스케줄링 알고리즘보다 더 큰 일반 비례 공정(General proportional fair) 기준과 더 높은 셀 수율(Cell throughput)을 가지는 것을 보이고 있다.

• Journal of Advanced Navigation Technology
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• v.14 no.1
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• pp.49-56
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• 2010

Severe energy constraints and the low power consumption require the significance of the energy efficient error control mechanisms in wireless sensor network (WSN). In this paper, an automatic repeat request (ARQ) methodology for the analysis of error control schemes in WSN is presented such that the effects of packet length, the modulation scheme and the interference effect of the wireless channel are investigated. Moreover, an analyis of ARQ error control is provided by considering two major architectures for wireless sensor network, i.e., Mica2 and MicaZ sensor nodes. And the throughput performance of WSN with asynchronous FSK signal and DSSS-OQPSK signal with selective repeat ARQ scheme are analyzed in multiple interference environment, and the probability of receiving a correct bit and packet from target node to sink node is evaluated as a function of the channel parameter, the number of wireless sensor node, and the spreading factor.

• Proceedings of the KAIS Fall Conference
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• 2009.12a
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• pp.953-956
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• 2009

무선 센서 네트워크에서 이동하는 표적의 위치를 추정하기 위한 연구는 센서 노드의 에너지가 제한 되어 있어 센서 노드 상호간의 협력적인 신호처리 기법이 필수적이다. 기존의 무선 센서 네트워크에서 이동 표적의 위치를 추정하는 방법은 각 센서 노드에서 이동 표적으로부터 수신된 신호를 이용해 수신신호강도, 잡음제거, 압축 등의 신호처리를 수행하고 기지국으로 전송하는 형태이다. 이런 기존의 기법은 애드 호크 방법의 무선 센서 네트워크에는 적용이 어렵고, 각 센서 노드에서 신호처리 및 통신에 의한 에너지 소모가 크기 때문에 무선 센서 네트워크의 생존 시간이 짧아지게 된다. 본 논문에서는 웨이블릿 기반의 무선 센서 네트워크의 협력적 신호 처리 방법을 제안한다. 제안된 방법은 웨이블릿 변환을 이용한 센서노드에서의 에너지 효율적 특징추출을 수행하고 각 센서 노드간의 특징 전송을 통해 표적의 위치를 추정한다.

• The Journal of the Acoustical Society of Korea
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• v.30 no.8
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• pp.474-481
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• 2011

Conventional beamforming is ineffective in producing directional information in system with sparse degree of the freedom such as DIFAR (DIrectional Frequency Analysis and Recording) sonobuoy and in the presence of high directional noise. In this paper, Adaptive beamforming techniques are applied to produce directional spectra from a small number of sensors in highly directional noise environment. Conventional method as well as minimum variance and eigenvectors as adaptive method are evaluated via numerical test and real data.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.2
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• pp.348-354
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• 2005

These days, Electronic mail is being used in everyday's life. And on the other hand, we are facing spam mails' problems. Spam mails are widely used by means of marketing in e-Commerce. To block these spam mails, we are using filtering or pricing systems. But these solutions are raising other problems such as impediment in reception or availability caused by false positive or payment resistance. To solve these problems, we propose an Indirect Model on Electronic Mail Control System(IMEMCS) which controls an unsolicited electronic mail and prevents an useful electronic mail from discarding. We design and implement the IMEMCS to enhance the usefulness and the availability. Being tested the IMEMCS to verify the usability and the efficiency, it gave us a very successful result.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.2
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• pp.3-9
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• 2014

We propose energy efficient transmit and receive strategies for nomadic M2M devices. Recently, communication applications consume more and more battery. Hence, the efficient battery management is becoming increasingly important. Turbo code as a channel coding is being widely used in many communication areas. Accordingly, the efficient energy management in using turbo code is an important issue. In this paper, we optimize joint transmit and receive energy for M2M devices pair. We first model the transmit energy and receive energy. Then, we develop the energy efficient transmit and receive strategies.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4B
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• pp.329-337
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• 2009

In wireless networks, maximizing throughput and minimizing energy consumption are two conflicting objectives. For elastic traffic, it is important to enhance the throughput since it directly affects the quality-of-service(QoS) of users. At the same time, the energy consumption should be minimized in order to prolong the battery lifetime of the mobile station. In this paper, we propose an energy efficient sleep scheme that considers throughput and energy saving simultaneously. The proposed scheme is designed for an efficient tradeoff between throughput and energy saving when receiving elastic traffic. Through extensive simulations, we compare the proposed scheme with the conventional scheme. Our proposed scheme outperforms the conventional one in terms of utility, i.e., user satisfaction, which is defined as inversely proportional to the weighted multiplication of service completion time and energy consumption.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.1
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• pp.69-76
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• 2004

Recently, The development of DTV receiver and the need of its additional services have been increased vastly. In this paper, we implement new closed caption engine for the deaf and hard of hearing person and languages studying on DTV receiver, The specification of domestic closed caption is almost adopted that of EIA-608A. In this paper, with fully following the specification, we will present how to implement functions of closed caption with new algorithm. the function includes paint-on, Pop-on, roll-up/down, etc. experimental results show that the proposed technique provides satisfactory performance on DTV receiver.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.862-865
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• 2007

Rx and Tx signal use same band in RFID. Then RFID system is not used duplexer and used coupler. RFID system have problem about Rx part to Tx leakage signal because that Rx signal port is Tx signal port's Isolation port. We proposal using phase shifter Tx leakage signal decrease than other RFID system. It is same signal Tx signal port's coupling port and isolation port signal except amplitude and phase. So if make coupling signal and isolation signal is in all same signal. We cancel Tx leakage signal used coupling port. And verification about ADS2006.

• The Journal of the Korea Contents Association
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• v.6 no.2
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• pp.65-74
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• 2006

The MPEG-2 video compressed bitstream is very sensitive to transmission errors due to the complex coding structure of the MPEG-2 video coding standard. If one packet is lost or received with errors, not only the current frame will be corrupted, but also errors will propagate to succeeding frames within a group of pictures. Therefore, we employ various error resilient coding/decoding techniques to protect and reduce the transmission error effects. Error concealment technique is one of them. Error concealment technique exploits spatial and temporal redundancies of the correctly received video data to conceal the corrupted video data. Motion vector recovery and compensation with the estimated motion vector is good approach to conceal the corrupted data. In this paper, we propose various error concealment algorithms based on motion vector recovery, and compare their performance to those of conventional error concealment methods.