• Journal of information and communication convergence engineering
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• 제5권4호
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• pp.333-338
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• 2007

In this paper we propose a new structure of the long code MMSE receiver with pilot channel, which maintians excellent symbol detection capability even in the presence of Rayleigh fading. We explain analytically how the stability of the receiver weight vector, which is critical to the system performance, can be achieved by compensating the error signal as well as received signal vector distorted by fading channel. Computer simulation shows while maintaining better performance than the conventional matched filter receiver, the proposed long code MMSE receiver can extend its period up to $16{\times}T_b$ in a fading environment.

• Journal of Communications and Networks
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• 제11권5호
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• pp.473-479
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• 2009

Conventional frequency domain equalization (FDE) schemes were originally devised for quasi-static channels. Thus, such equalization schemes could suffer from significant performance degradation in fast-fading channels. This paper proposes a frequency domain equalization algorithm to mitigate the effect of fast time-varying fading. First, a mathematical expression is derived to quantify the total interference resulting from the time variation of the channel. Then, the proposed approach attempts to eliminate the effect of time-variations of the channel. This cancellation allows efficient use of the classical FDE structures in fast time-varying fading environments, although they are built upon the quasi-static channel model. Simulation results of bit-error-rate performance are provided to demonstrate the effectiveness of the proposed algorithm.

• 한국전자파학회논문지
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• 제10권7호
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• pp.1033-1043
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• 1999

We consider an improved multicarrier(MC) CDMA system that combines both DS-CDMA with a concatenated orthogonal/PN spreading sequence and MC modulation. This system incorporates the advantages of DS-CDMA with a concatenated sequence to achieve large user capacity and MC modulation technique to combat the effects of a multipath fading channel and intersymbol interference(ISI). Considering voice activity and imperfect sectorization, the system performance is analysed for the maximal ratio combiner(MRC) under a multicell, multiuser, and multipath Rayleigh/Rician fading channels. The performance of the system is improved much more for the single path fading channel compared to the multipath fading channel. Also the system is shown to have the more improved average bit error rate(BER) over the orthogonal MC-CDMA with the conventional PN sequence.

• Journal of information and communication convergence engineering
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• 제8권3호
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• pp.281-288
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• 2010

This paper investigates the performance of IEEE 802.11p wireless access in vehicular environments (WAVE) system in small-scale fading models reported by Georgia Institute of Technology (Georgia Tech). We redesign the small-scale fading models to be applied to the computer simulation and develop the IEEE 802.11p WAVE physical layer simulator to provide the bit error rate and packet error rate performances. Moreover, a new channel estimator using decision directed channel estimation and linear minimum mean square error smoothing is proposed in order to improve the performance of the conventional least square channel estimator using two identical long training symbols. The simulation results are satisfactorily coincident with the scenarios of Georgia Tech report, and the proposed channel estimator significantly outperforms the conventional channel estimator.

• 전자공학회논문지S
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• 제35S권2호
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• pp.10-21
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• 1998

In this paper, we analyze the anynchrous cellular hybrid DS/FH spread spectrum system with diversity on nonselective Nakagami fading channel. Binary Psk scheme is considered and random spreading code sequences and random hopping patterns are used. We compare the performance of system using hard-limiting correlation receiver with diversity and linear corrleation receiver in Nakagami fading channel. We compute the average bit error probabilities with/without diversity according to spreading code sequence and the number of hop-ping frequencies under the same handwith espansion, and analyze near-far effect. The results show that hard-limiting correlation receiver with diversity gives a good performance over severe fading channel.

• International Journal of Contents
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• 제3권2호
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• pp.35-39
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• 2007

The cognitive radio communication is taking the attentions because the development of the technique came to be possible to analyze wireless signals. In the IEEE 802.22 WRAN Systems[1], how to detect a spectrum and signals is continuously studied. In this paper, we propose the efficient signal detection method using SCF (Spectral Correlation Function). It is easy to detect the signal feature when we are using the SCF. Because most modulated signals have the cyclo-stationarity which is unique for each signal. But the fading channel effected serious influence even though it detects the feature of the signal. We applied LMS(Least Mean Square) filter for the compensation of the signal which is effected the serious influence in the fading channel. And we analyze some signal patterns through the SCF. And we show the unique signal feature of each signal through the SCF method. It is robust for low SNR(Signal to Noise Ratio) environment and we can distinguish it in the fading channel using LMS Filter.

• 한국정보통신학회논문지
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• 제6권4호
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• pp.544-551
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• 2002

본 논문에서는 레일리 페이딩 상태, 라이시안 페이딩 상태, 쉐도우 라이시안 페이딩 상태로 구성된 혼합페이딩 채널에서 DS/CDMA-BPSK 시스템의 오율 성능을 분석하였다. 결과로부터 본 논문에서 제시한 혼합 페이딩 채널 모델은 다양한 채널 상태을 표현하는데 적절함을 알 수 있었다. 그리고 혼합페이딩 채널에서는 무선 채널의 점유 확률과 쉐도우 심도가 시스템의 BER 성능에 많은 영향을 준다는 것을 알 수 있었다. 또한 Reed-Solomon 부호를 적용한 DS/CDMA-BPSK 시스템은 동시 사용자 간섭과 혼합 페이딩 채널에 매우 강인함을 알 수 있었다.

• 한국통신학회논문지
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• 제19권8호
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• pp.1493-1502
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• 1994

본 논문에서는 순시 페이딩과 장구간 페이딩의 혼합인 Suzuki 페이딩 정확히 모사하는 새로운 광대역 채널 시뮬레이션 알고리즘을 제안한다. 제안된 알고리즘은 수신된 반사파들을 Suzuki 분포를 갖는 랜덤 신호로 발생시키며, Gaussian 분포로부터 대수정규 분포로의 변환을 이용함으로써 반사파들의 장구간 페이딩 성분들 사이의 상관 관계를 임의로 조정할 수 있다. 제안된 알고리즘은 시스템의 성능을 시뮬레이션하는 데 적용될 수 있다.

• 한국산업정보학회:학술대회논문집
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• 한국산업정보학회 1997년도 추계학술대회 발표논문집:21세기를 향한 정보통신 기술의 전망
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• pp.407-415
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• 1997

In this paper, we apply a digital modulation scheme called Multi-Carrier CDMA (MC-CDMA) to the technique for cochannel interference cancellation using reference correlator, previously proposed. The cancellatoin method will be effective for reducing the interference components which are other users'signal components in a common channel, but fading effect of channel remains as the degrading factor of channel condition. For compensating it, MC-CDMA scheme is introduced to combat agianst the multipath fading. We analize above system and derive the average probability of error in AWGN and Rayleigh fading environment.

• 한국음향학회지
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• 제6권1호
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• pp.5-14
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• 1987

이 논문은 시간 및 주파수 선택성페이딩이 동시에 존재하는 채널에서 대역확산 주파수 도약통신시스템의 전송특성을 제시한다. 수신기는 승적합산기를 포함한 binary noncoherent matched-filter fast FH-SS시스템이다. 이 시스템에서 SNR, 채널 선택도, 전력비 등의 변동에 따른 오차확률은 데이터율을 고려하지 않고 다이버시티 개념을 사용하여 구하였으며, 오차확율에 대한 데이터를 분석한 결과 FH-SS 시스템은 시간 선택성 페이딩 채널에서 전송특성이 우수함을 나타내었다.