• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.97-100
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• 2000

IMT-2000 지상 시스템에서는 순방향 링크의 용량을 증대하기 위하여 다중 전송 안테나를 이용하는 다양한 전송 다이버시티 기법들이 연구되고 있으며, 3GPP를 위한 표준 가운데 하나인 폐쇄루프 전송 다이버시티 기법은 단말기에서 순방향 채널의 상태에 따라 전송 안테나의 가중치를 결정하여 궤환함으로써 여타의 기법에 비해 우수한 성능을 보인다. 하지만 지상 시스템과는 달리 IMT-2000 위성 시스템에서는 현재 전송 다이버시티에 대한 표준이 없는 상황이며 이에 대한 연구 역시 미진하다. 본 논문에서는 폐쇄루프 전송 다이버시티를 IMT-2000 위성 시스템에 적용한 결과를 제시한다. IMT-2000 위성 채널 모델에 대한 모의 실험 결과 2개 안테나를 이용하는 폐쇄루프 전송 다이버시티를 통해 단일 안테나 혹은 2개 안테나 전송 신호의 단순한 다이버시티 결합에 비해 월등한 성능 향상이 가능함을 확인하였다.

• Journal of Internet Computing and Services
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• v.4 no.5
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• pp.1-9
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• 2003

In this paper, we combine AMC (Adaptive Modulation and Coding) with MIMO (Multiple Input Multiple Output) multiplexing to improve the throughput performance of AMC in Next Generation Communication Mobile Systems. In addition, we propose a system that adopts STD (Selection Transmit Diversity) in the combined system. The received SNR (Signal to Noise Ratio) is improved by adopting STD techniques and an improved SNR increases a probability of selecting MCS (Modulation and Coding Scheme) level that supports higher data rate. The computer simulation is performed in flat Rayleigh fading channel. The results show that higher throughput is achieved by AMC-TD schemes. AMC-STTD scheme shows about 250kbps increase in throughput. And AMC-STD with 2 transmit antennas achieves about 420 kbps throughput improvement over the conventional AMC at 9dB SNR.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.2A
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• pp.183-190
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• 2008

The balanced Tx diversity with same data on two antennas can have better or lower performance than STBC Tx diversity, depending on the difference between each phase of two channels when the received signal is processed with MRRC. Therefore, using the feedback information based on the phase estimation in each channels, the better scheme of the balanced Tx diversity and STBC Tx diversity can be selected. However, when the phase condition changes during the transmission as the selected Tx. diversity scheme, the decoded bit can be erroneous because the previously estimated phase and newly estimated phase is different. In this case, the receiver should request the re-transmission of the just received signal to the transmitter part. Through computer simulation, it is shown that the combined scheme of the balanced Tx diversity and STBC Tx. diversity has better performance than STBC Tx diversity.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.613-616
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• 2001

본 논문에서는 3GPP에 규격으로 채택된 전송 다이버 시티 기법들 중에 이상적인 상황에서 가장 우수한 성능을 갖는 폐쇄루프 전송 다이버시티 (CLTD : Closed Loop Transmit Diverstiy) 기법과 선형 사전필터의 조합을 통해 MISO 시스템에서 보다 우수한 성능의 전송 다이버시티 기법을 제안하고 이에 대한 성능을 분석하였다. 또한 사전필터의 최적의 필터 계수 값을 사용하여 다이버시티이득을 최대화하였고 이에 대한 성능을 분석한 결과 CLTD 기법보다 월등히 우수한 성능을 확인하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.250-257
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• 2004

MC-CDMA and OFDM are digital modulation techniques where a single data symbol is transmitted at multiple subcarriers which we orthogonal to each other. With this technique, frequency diversity can be achieved. The performance of multi currier systems is analyzed. when data is transmitted over multi-path Rayleigh fading channel. The performance of this technique, gauged by the average bit error rate, is numerically analyzed for the system with the application of antenna diversity.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.4
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• pp.727-732
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• 2005

OFDM is a digital modulation technique where a single data symbol is transmitted at multiple subcarriers which are orthogonal to each other. With this technique, frequency diversity can be achieved. The performance of OFDM systems with SFBC and STBC antenna diversity are analyzed, where data is transmitted over time and frequency selective Rayleigh fading channel. The performance of this technique, gauged by the average bit error rate, is analyzed for the OFDM systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.4
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• pp.652-657
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• 2003

In this paper, Adaptive Modulation and Coding (AMC) is combined with Multiple Input Multiple Output (MIMO) multiplexing to improve the throughput performance of AMC. In addition, a system that adopts Selection Transmit Diversity (STD) in the AMC-MIMO multiplexing system is proposed. The received SNR is improved by adopting STD techniques. And it increases probability of selecting MCS (Modulation and Coding Scheme) level that supports higher data rate. This leads to an increased throughput of the AMC-MIMO system. STD in our simulation selects 2 transmission antennas from 4 antennas and AMC-MIMO multiplexing process operates with the selected antennas. The computer simulation is performed in flat Rayleigh fading channel. The results show that the proposed system achieves a gain of 1Mbps over the AMC-MIMO multiplexing system with the same number of antennas at 15dB SNR.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.8C
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• pp.1040-1046
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• 2004

The BLAST-OFDM system is an efficient method for high data rate multimedia transmission in futurewireless communication system. In this paper, a linear preceding mechanism and an efficient antenna-subcarrier assignment algorithm are proposed for the conventional BLAST-OFDM system, in order to utilize the full spatial diversity and the interleaved frequency diversity. By computer simulation, the proposed system has proved to achieve 4-5㏈ gain over the conventional BLAST-OFDM system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.3A
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• pp.135-140
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• 2012

This paper proposes a technology for performance enhancement of cyclic delay diversity OFDM system using frequency diversity. The frequency diversity in an OFDM system can be done as repetitive transmission of the same symbol on uncorrelated subcarrier, this makes modulation level larger according to the number of repetitive transmission for the comparison with the traditional transmission system. This technique, like cyclic delay diversity, has a benefit which it does not need any special subsidiary hardware irrespective of the increase of the number of transmitter. For the performance comparison, we simulate the proposed algorithm in multiple input single out channel environment, it shows a better performance enhancement in low dense modulation level in comparison with the traditional cyclic delay diversity OFDM system.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2008.11a
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• pp.103-105
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• 2008

차세대 양방향데이터방송 (BIFS: BInary Format for Scenes) 서비스에서는 하향링크(downlink) 데이터 전송률에 상응하는 높은 상향링크(uplink) 데이터 전송률이 요구되고 있다. 이에 무선 전송 채널의 한정된 자원 환경 속에서 상향링크 전송용량 증대를 위한 주파수 효율성 제고 기술의 필요성이 대두되고 있다. 본 논문에서는 차세대 양방향데이터방송을 위한 다중 모바일(mobile) 사용자의 클러스터(cluster) 기반 상향링크 협동 다이버시티(cooperative diversity) 기법을 제안한다. 제안된 기법은 하나의 단일 안테나(single antenna) 방송 기지국과 다수의 단일 안테나 모바일 사용자가 있는 상향링크 시분할다중접속 (TDMA: Time Division Multiple Access) 시스템에서 데이터 지연허용(delay-tolerant)에 따라 클러스터를 구성하고 제곱 다이버시티 차수(square diversity order)의 협동 프로토콜(cooperative protocol)을 통해 높은 공간다이버시티 이득(spatial diversity gain)을 얻는다. 또한, 비대칭(asymmetric) 무선 채널 환경에서 공정성(fairness)을 보장한다.