• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.6
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• pp.1066-1072
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• 2001

ALOHA Multi-Carrier DS-CDMA systems in the multipath Rayleigh fading channel. The throughput of two systems are compared according to the length of a packet in the fast Rayleigh and the slow Rayleigh multipath fading. As a result, we have known that Multi-Carrier DS-CDMA system has less capacity than wideband DS-CDMA system in the same bandwidth, but throughput of Multi-Carrier DS-CDMA system is higher than that of wideband DS-CDMA system. And in Multi-Carrier DS-CDMA systems, higher throughput can be obtained through shortening the length of packet in the fast Rayleigh fading, and it is efficient to control the length of a packet adequately or increase the system capacity of Multi-Carrier DS-CDMA system in the slow Rayleigh fading.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.675-679
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• 2001

In this paper, throughput is derived for slotted ALOHA wideband DS-CDMA and slotted ALOHA Multi-Carrier DS-CDMA systems in the multipath Rayleigh fading channel. The throughput of two systems are compared according to the length of a packet in the fast Rayleigh and the slow Rayleigh multipath fading. As a result, we have known that Multi-Carrier DS-CDMA system has less capacity than wideband DS-CDMA system in the same bandwidth, but throughput of Multi-Carrier DS-CDMA system is higher than that of wideband DS-CDMA system. And in Multi-Carrier DS-CDMA systems, higher throughput can be obtained through shortening the length of packet in the fast Rayleigh fading and it is efficient to control the length of a packet adequately or increase the system capacity of Multi-Carrier DS-CDMA system in the slow Rayleigh fading.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.3
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• pp.643-652
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• 2000

In this paper, we analyze the BER performance of OFDM/QPSK system in frequency selective Rayleigh fading channel with impulsive noise and improve its performance by adopting convolutional coding. When the channel delay time is shorter than the guard band, the OFDM/QPSK system shows a good BER performance while, when the channel delay time becomes longer than the guard band, its BER performance is abruptly degraded. Moreover, when the transmitted signal is contaminated by a strong impulsive noise in the channel, the BER performance falls to about $10^{-1}$. Also, without channel coding technique, the system doesn't meet even the voice service requirement while it meets the data service requirement with convolutional coding in frequency selective Rayleigh fading channel with impulsive noise.

• Journal of the Korea Society of Computer and Information
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• v.16 no.10
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• pp.137-145
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• 2011

In this paper, we modeled digital M/W transmission channel by frequency non-selective fading channel and analyzed the power spectrum magnitude of digital M/W transmission systems adopting OFDM modulation scheme through simulation. From the simulation results, it was found that deep does not appear in the specified fixed bandwidth under the AWGN environment. Also, lower power spectrum magnitude was shown in frequency non-selective fading channel than that in AWGN channel. Futhermore, the power spectrum magnitude value became more lowered when carrier frequency and vehicle speed became higher.

• ETRI Journal
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• v.8 no.4
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• pp.95-102
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• 1986

본 연구에서는 이동통신 시스팀에서 채널 모델의 시뮬레이션을 수행하는데 사용 가능한 알고리즘을 개발하였으며 이동체 속도에 따라 그 특성을 분석하였다. 이동통신 채널에서는 다중 경로에 의하여 레일리 페이딩 채널이 구성되어 지는데 이의 알고리즘 개발을 위하여 실제 제작 구현이 용이한 위상 변조신호 합성 방법과 shaping 필터를 이용하는 방법을 채택하였다. 개발 알고리즘을 분석한 결과 제시한 두 모델 모두가 채널 시뮬레이션을 위하여 사용가능함을 확인하였으며 특히 레일리 분포 특성에서는 위상변조 신호 합성방식이 이론치와 더욱 유사됨을 알 수 있었다.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.5 no.3
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• pp.3-13
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• 1994

In the environments with interference and Rayleigh fading the bit error probability equation of FH / MFSK signal has been derived and the error rate has been evaluated. And the results are shown in graphs and discussed. The degree of improvement of error rate performance has been found out in space diversity technique. From the results, we know that maximal ratio combining is very effective for Rayleigh fading and interference.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.311-314
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• 2001

본 논문에서는 다중 경로 레일리 페이딩 채널에서 MC (Multi-Carrier) CDMA 시스템의 BER 성능을 분석하였고, 최근에 가장 강력한 부호화 기법으로 급부상하고 있는 터보 코드를 MC CDMA 시스템에 적용하여 성능 개선 정도를 평가하였다. 성능 해석 결과, 레일리 페이딩 채널에서는 강력한 성능 개선 기법을 적용하지 않는 한 사용자수와 E$_{b}$/N$_{o}$ 값에 관계없이 음성 서비스를 지원하지 못함을 알 수 있었다. 한편, 터보 코드를 성능 개선 기법으로 적용하면 BER 성능이 매우 개선되고, 사용자 수와 E$_{b}$/N$_{o}$ 값에 관계없이 음성 서비스를 충분히 지원할 수 있음을 알 수 있었다. 예를 들어 E$_{b}$/N$_{o}$ 가 10 dB이고 사용자 수가 10명인 경우, 터보 코드를 적용함에 의해 BER 성능이 약 5$\times$$10^{-3}$ 정도 개선됨을 알 수 있었다.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.292-296
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• 2000

본 논문에서는 임펄스 잡음과 다중경로 레일리 페이딩이 함께 존재하는 최악의 채널 환경에서 비동기 DS/CDMA BPSK 시스템의 오율식을 유도하고 수치계산 하여 BER 성능을 분석하였다. 그 결과, 비교적 낮은 신호 대 잡음 전력비 영역에서 시스템의 BER 성능은 임펄스 잡음의 영향으로 크게 열화되지만 페이딩의 영향은 거의 없다. 그러나, 임펄스 잡음의 영향이 작아지는 높은 신호 대 잡음 전력비에서는 페이딩에 의해서 BER 성능이 결정된다. 다중사용자의 간섭도 낮은 신호 대 잡음 전력비 영역에서는 BER 성능에 거의 영향을 미치지 못하지만 높은 신호 대 잡음 전력비 영역에서는 BER 성능을 좌우한다 그러나, 실제 이동통신 시스템에서는 비교적 낮은 신호 전력을 사용하므로, 임펄스 환경에서 페이딩을 경감하기 위한 방법이나, 다중사용자 간섭을 줄이기 위한 기법을 적용하더라도 성능 개선이 거의 되지 않는다.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.6 no.2
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• pp.45-53
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• 1995

In mobile communication, the performance of QAM technique is poor under deep fading even though Rayleigh channel characteristics are estimated and compensated. In this paper, we analyze the performance of 3/4 Trellis coded 16QAM in Rayleigh channel where burst errors are randomized by bit reversal block interleaver, and TCM coder is designed by computer search to be adequate for Rayleigh channel. The simulation results show that the interleaver has 2dB gain, the modified Viterbi decoder has 2.5dB, and diversity has 9dB gain at $P_{b}b/=10^{-3}$. This indicates that the 3/4 TC 16QAM is applicable to digital mobile communication with good performance.

• Journal of Digital Contents Society
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• v.1 no.1
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• pp.39-52
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• 2000

In this paper, we derive the BER performance of an asynchronous DS/CDMA system and analyze the improvement of BER performance through turbo coding and RAKE receiver in multipath Rayleigh fading and impulsive noise environments. As a result, impulsive noise affects the performance of the system more than multipath fading in lower $E_b/N_o$ than a certain threshold. However, in higher $E_b/N_o$, multipath fading are more dominant than impulsive noise. It is found that in lower $E_b/N_o$, turbo code improves the performance of the system against impulsive noise, and in higher $E_b/N_o$, RAKE receiver improves the performance of the system against multipath fading. Therefore, great improvement can be obtained by employing turbo code and RAKE receiver in multipath Rayleigh fading and impulsive noise environments.