• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.3
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• pp.579-586
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• 1999

In this paper, we have analyzed a performance of fast frequency hopping communication systems when a rayleigh fading caused by envelope variations of a signal received in multipath channel is, but it is not considered that intentional or unintentional jamming can be. The multipath fading channel and rayleigh fading are confirmed by theoretical analysis. In fading or non-fading, the performance of this system is studied. When the path diversity is applied to this system, the performance is shown to be superior to non-diversity systems about 20dB. For modulation methods, BFSK was compared with DPSK.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11A
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• pp.852-861
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• 2009

We propose a complexity reduced Lattice Reduction(LR) scheme for MIMO detection under time varying fading environments. It is found that for successive MIMO transmission instances, the integer matrix P after LR decomposition remains the same or only a few elements of the matrix P are slightly changed. Based on this feature, we perform LR reduction by setting the initial values for P matrix for the decomposition to be the one obtained in the previous instance not starting from the identity matrix. Simulation results reveal that the proposed scheme drastically reduces overall complexity of LR reduction compared to the conventional scheme for various system parameters under time varying channels. We also show that the proposed scheme can be applied to Seysen LR as well as LLL(Lenstra, Lenstra, and Lavasaz)-LR.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.6 no.1
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• pp.66-76
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• 1995

In this paper, the error rate performance of DS/SSMA system in multipath fading channel is calculated by computer simulation. At first, the multipath fading channel is modeled with TDL(Tap Delay Line) model. The characteristics of channels, including multipath fading effects and error pattern, are examined by doppler frequency and signal bandwidth, and time spread variation. Using the multipath fading channel model, the error rateperformance of block code and convolutional code is compared, thus the coding sys- tem is applied to the DS / SSMA system. The BER results of DS / SSMA system show that the proposed receiver gives about 2~3[dB] improve- ment compared with the conventional receiver.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6C
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• pp.523-529
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• 2010

We propose a very low complexity lattice reduction (LR) algorithm for MIMO detection in time varying channels. The proposed scheme reduces the complexity by performing LR in a block-wise manner. The proposed scheme takes advantage of the temporal correlation of the channel matrices in a block and its impact on the unimodular matrices during LR process. From this, the proposed scheme can skip a number of redundant LR processes for consecutive channel matrices and performs a single LR in a block. The simulation results investigated in this letter reveal that the proposed detection scheme requires only 43.4% multiplications and 17.3% divisions of LLL-LR and only 50.2% multiplications and 68.2% divisions of the conventional adaptive LR with almost no performance degradation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.7
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• pp.1202-1207
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• 2006

In this paper we analyze the performance improvement of the M-ary FSK systems for low power and low data rate applications. This contribution presents a unified analysis of its MRC diversity, uncoded and performance in A WGN, m=2, m=3, Rayleigh and one sided Gaussian fading channels using optimum noncoherent demodulation with Reed-Solomon(RS) codes. The results of this paper should be useful as benchmarks of obtainable performance and as a reference for validating the results of simulation studies when slow fading models are applicable.

• Annual Conference of KIPS
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• 2003.05b
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• pp.1497-1500
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• 2003

본 논문에서는 나카가미 페이딩 채널하에서 MC DS/CDMA 방식에 FH 방식을 적용한 FH MC/DS CDMA 시스템의 성능을 분석하였다. 나카가미 페이딩 지수 m과 MRC 다이버시티의 브랜치 수 L이 증가할 때 호핑 횟수 1과 4에 대한 분석결과 약 2.8dB의 성능차이를 보이고 있음을 앞 수 있었다. 호핑 횟수의 증가는 주파수 다이버시티 효과를 가져옴으로써 FH MC DS/CDMA 시스템에서 수신측의 부담을 줄이면서 BER 성능을 향상시킬 수 있음을 의미하며 따라서 호핑 횟수를 증가시킴으로써 부담 MC/DS CDMA 시스템의 성능을 개선할 수 있음을 입증하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.4
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• pp.1019-1026
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• 1996

A modulation type classifier based on statistical moments has been successfully employed to classify PSK signals. Previously, developed Classifiers were analyzed in AWGN channel only. In this paper, a moments-based modulation type classifier to classify BPSK and QPSK signals over Rayleigh fading channel is proposed and analyzed. The moments of received signal are evaluated with the exact distribution of the received signal and a moments-based classifier is proposed. The performance evaluation of the proposed classifier in terms of the misclassification probability for BPSK and QPSK is investigated under Rayleigh fading environment.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2015.07a
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• pp.303-305
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• 2015

본 논문에서는 나카가미-m 페이딩 채널 환경을 가진 무선 중계 네트워크에서 reactive 누적분포함수(cumulative distribution function) 기반 중계기 선택 기법을 제안한다. 제안된 기법은 수신 신호대잡음비(signal-to-noise ratio)의 누적분포함수 값에 따라 중계기를 선택한다. 본 논문에서는 제안한 기법의 불능 확률(outage probability)과 다이버시티 차수(diversity order)를 분석한다. 제안된 기법이 얻을 수 있는 다이버시티 차수는 중계기의 개수와 페이딩 파라미터에 의해 결정되며 최대 다이버시티(full diversity)를 얻음을 볼 수 있다. 그리고 모의 실험에서는 분석된 불능 확률 및 다이버시티 차수가 정확하게 일치하는 것을 확인한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.2
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• pp.252-258
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• 2000

In this paper, we improve error performance for BPSK and QPSK when the carrier recovery signal is not perfect in the multipath Rician fading channel based on DS-CDMA system. In the case, we use the MRC(Maximal Ratio Combining) diversity and convolutional coding technique in order to overcome this carrier phase error and Rician fading. With results of analysis, we know that the appropriate use of MRC diversity and convolutional code reduced considerably performance degradation due to phase error.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.486-488
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• 2004

Rayleigh signal fading phenomena due to multipath propagation in wireless communication can be simulated using the sum-of-sinusoids channel model. Jakes' fading model is very simple simulator based on the sum-of-sinusoids and has been widely used. However, It has some short-comings. Its time correlation properties based on the simulated waveform do not correspond to the statistical ones. In this paper, the difference between statistical and time properties of Jakes' fading channel model is examined and new simulator is proposed.