• 한국전자파학회논문지
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• 제11권4호
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• pp.553-564
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• 2000

본 논문에서는 DS-CDMA 시스템의 성능 열화의 주요 원인인 다중 경로 페이딩이 존재하는 이동통신 채널 환경에서 성능 개선 기법으로 MRC 다이버시티 기법과 에러 정정 부호화 기법을 채용한 경우의 MFSK MDPSK/DS-CDMA 시스템의 성능 개선을 수치해석에 의해 정량적으로 분석하였다. 고려한 변조방식은 비동기식 MFSK와 MFSK에 기반한 MDPSK를 이용한 결합주파수 위상변조 방식이다. 결과에 의하면 MFSKM MDPSK/DS-CDMA 시스템과 기존의 MFSK/DS-CDMA와 MDPSK/DS-CDMA 시스댐을 비교하면 MFSK M MDPSK/DS-CDMA 시스댐의 성능이 우수함을 알았다. 또한. 나카가미 페이딩 환경하에서 MFSK-MDPSK/DS-CDMA 시스템은 다이버시티 가지수의 증가와 부호화의 이득에 의해 에러 성능이 향상되었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권10호
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• pp.4957-4976
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• 2016

This paper investigates the error performance of the amplify-and-forward (AF) relaying systems in the context of full-duplex (FD) communication. In addition to the inherent self-interference (SI) due to simultaneous transmission and reception, coexistent FD terminals may cause crosstalk. In this paper, we utilize the information exchange via the crosstalk channel to construct a particular distributed space-time code (DSTC). The residual SI is also considered. Closed-form pairwise error probability (PEP) is first derived. Then we obtain the upper bound of PEP in high transmit power region to provide more insights of diversity and coding gain. The proposed DSTC scheme can attain full cooperative diversity if the variance of SI is not a function of the transmit power. The coding gain can be improved by lengthening the frame and proper power control. Feasibility and efficiency of the proposed DSTC are verified in numerical simulations.

• 한국정보통신학회논문지
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• 제5권4호
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• pp.645-652
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• 2001

본 논문은 근거리 차량간 통신(IVC)에서 첨단차량도로시스템(AVHS)의 플래툰 주행에 적합한 One-Ray Rician 채널 모델을 적용하여 간섭신호에 강한 장점을 지닌 60GHz 밑리미터파에서 패킷 오율 특성을 분석하였다. 차후에 사용자의 욕구 증대에 따른 멀티미디어 서비스를 만족시키기 위해서 Convolution 부호화 기법과 MRC 다이버시티 수신 기법을 동시에 적용하였으며 그에 따른 DS-CDMA/QPSK System의 패킷 오율 특성을 분석하였다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2003년도 추계종합학술대회
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• pp.154-158
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• 2003

본 논문에서는 Rician Fading 환경에서의 BCH부호화 된 DS-CDMA 16 QAM 신호의 선택합성 (SC : Selective Combining) 다이버시티 수신시의 오율 성능을 해석하였다. 첫 번째로 라이시안 페이딩 환경에서의 성능을 해석하고, 두 번째로 선택합성 다이버시티 수신기법을 채용한 경우, 세 번째로 다이버시티와 BCH부호화를 함께 채용하는 경우 성능을 해석하였다. 수치해석 결과 다이버시티와 부호화기법을 함께 채용함으로서 이동 무선데이터 통신채널 환경을 극복할 수 있는 현저한 성능 개선을 보였다.

• Journal of electromagnetic engineering and science
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• 제11권2호
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• pp.133-142
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• 2011

Coded cooperation that integrates channel coding in cooperative transmission has gained a great deal of interest in wireless relay networks. The performance analysis of coded cooperation protocol with multiple relays is investigated in this paper. We show that the diversity order achieved by the coded cooperation in a multi-relay wireless network is not only dependent on the number of cooperating relays but is also dependent on the code-rate of the system. We derive the code-rate bound, which is required to achieve the full diversity gain of the order of cooperating nodes. The code-rate required to achieve full diversity is a linearly decreasing function of the number of available relays in the network. We show that the instantaneous channel state information (CSI)-based relay selection can effectively alleviate this code-rate bound. Analysis shows that the coded cooperation with instantaneous CSI-based relay selection can achieve the full diversity, for an arbitrary number of relays, with a fixed code-rate. Finally, we develop tight upper bounds for the bit error rate (BER) and frame error rate (FER) of the relay selection based on coded cooperation under a Rayleigh fading environment. The analytical upper bounds are verified with simulation results.

• Journal of Communications and Networks
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• 제5권4호
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• pp.374-385
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• 2003

The growing interest towards ultra-wideband (UWB) communications stems from its unique features such as baseband operation, ample multipath diversity, and the potential of enhanced user capacity. But since UWB has to overlay existing narrowband systems, multiple access has to be achieved in the presence of narrowband interference (NBI). However, existing baseband spreading codes for UWB multiple access are not flexible in handling NBI. In this paper, we introduce two novel spreading codes that not only enable baseband UWB multiple access, but also facilitate flexible NBI cancellation. We construct our codes using a single carrier or multiple carriers (SC or MC), which can be implemented with standard discrete-cosine transform (DCT) circuits. With our SC/MC codes, NBI can be avoided by simply nulling undesired digital carriers. Being digital, these SC/MC codes give rise to multiband UWB systems, without invoking analog carriers. In addition, our SC/MC codes enable full multipath diversity, and maximum coding gains. Equally attractive is their capability to reduce the number of interfering users, with simple matched filter operations. Comprehensive simulations are also carried out to corroborate our analysis.

• International Journal of Internet, Broadcasting and Communication
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• 제15권3호
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• pp.14-23
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• 2023

The cooperative communication systems using MIMO(multiple input multiple-output) relay are known as one of the most promising techniques to improve the performance and coverage of wireless communication systems. In this paper, we propose the cooperative communication systems using the relay with multi-antennas and DSTC(distributed space time coding) for decode-and-forward protocol. As using DSTC for DF(decode-and-forward), we can minimize the risk of error propagation at the wireless system using relay system. Also, the MIMO channel cab be formed by multi-antenna and DSTC at the MS(mobile station)-RS(relay station) and at the RS-BS(base station).Therefore, obtaining truly constructive the MIMO diversity and cooperative diversity gain from the proposed approach, the performance of system can be more improved than one of conventional system (relay with single antenna, no relay). The improvement in bit error rate is investigated through numerical analysis of the cooperative communication system with the proposed approach.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(4)
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• pp.41-44
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• 2002

In the communications systems with diversity, we are commonly faced on needing of new source coding technique, error resilient coding. The error resilient coding addresses the coding algorithm that has the robustness to unreliability of communications channel. In recent years, many error resilient coding techniques were proposed such as data partitioning, resynchronization, error detection, concealment, reference picture selection and multiple description coding (MDC). In this paper, we proposed an MDC using whitening transform. The conventional MDC using correlating transform is need additional information to decode the image. But, if an image is transformed using the whitening transform, the additional information is not necessary to transform because the coefficients of whitening transform have uni-variance statistics.

• Journal of electromagnetic engineering and science
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• 제6권4호
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• pp.222-228
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• 2006

In this paper, the performance of a multiuser diversity system combined with a multi-element transmit antenna system is analyzed under the assumption of independent Rayleigh fading. A measure of system .level performance is an average channel capacity as a function of the number of users and antennas. Average channel capacity is obtained from the instantaneous signal-to-noise ratio(SNR) distribution combined by both transmit diversity(TD) at each link and multiuser diversity at system level. Numerical results show that closed-loop antenna techniques provide an additional gain with multiuser diversity system due to array gain, even though space diversity gain reduces multiuser diversity gain. On the other hand, the space-time block coding(STBC) that provides full order space diversity gain only has a destructive influence on multiuser diversity.

• 한국위성정보통신학회논문지
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• 제4권2호
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• pp.28-33
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• 2009

본 논문에서는 위성-지상 통합(hybrid/integrated)망에서 멀티미디어 방송 서비스를 효율적으로 제공하도록 기여할 수 있는 여러 가지 다이버시티 방식에 대한 성능을 비교 분석한다. 시공간 부호는 부가적인 대역폭 요구 사항 없이도 다중경로 환경에서 다이버시티 이득을 얻을 수 있는 효율적인 방식이다. 위성시스템에서 시공간 부호와 오류정정부호를 적절히 결합하여 지상 중계 장치와의 협동 다이버시티 이득 구현이 가능함이 제안되어 왔다. 본 논문에서는 이러한 선행 연구 결과를 바탕으로 하여, 다양한 시공간부호 및 오류정정 부호의 결합 방식에 따른 성능 분석 결과와 장단점등을 제시하여, 향후 시스템 구현에 도움이 될 수 있도록 한다.