• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.9
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• pp.1998-2004
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• 1997

In this paper, we have analyzed the bit error performance ofthe chip-spreading OCDM system proposed in the previous papaer and compared the results, through computer simulations, with those of conventional DS/CDMA system which employs the maximal ration combining method. WE have shown, analytically, that the BER upper bound of the OCDM system coincides with that of the conventional DS/CDMA system and the lower bound exhibits much improved results. From the simulation results, we have confirmed that the BER curves of proposed OCDM system actually lie between the two theoretical bounds and its performance is superior to that of the DS/CDMA system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.8
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• pp.629-637
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• 2013

Chaos communication systems have the characteristics such as non-periodic, wide-band, non-predictability of signals and easy implementation. There have been many studies about chaos communication systems because of these advantages. But, chaos communication systems have low BER(Bit Error Rate) compare to general digital communication system. Existing researches on chaos communication systems only analyze BER performance according to various chaos maps. There are no studies on analysis of BER performance according to PDF(Probability Density Function) of chaos maps. In this paper, we analyze the BER performance according to changing parameter, equation, and initial values of chaos map's PDF. In addition, we propose new chaos map to improve BER performance. Simulation results show that BER performance of CDSK(Correlation Delay Shift Keying) is changed when PDF of chaos map changed. And the proposed chaos map has a better BER performance compare to previous chaos maps such as Tent map, Logistic map, and Henon map.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.5
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• pp.1031-1037
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• 2011

Pilot symbol assisted modulation (PSAM) can be used for the channel estimation in orthogonal frequency division multiplexing (OFDM) transmission systems. However, imperfect channel estimates in PSAM systems degrade the bit error rate (BER) performance. I derive the BER of PSAM OFDM systems over time dispersive fading channels. The BER performance of OFDM systems with SFBC antenna diversity are analyzed, where data is transmitted over time and frequency selective Rayleigh fading channel. The performance of this PSAM SFBC OFDM systems, gauged by the average bit error rate, is analyzed considering the channel estimation error.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.35T no.1
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• pp.105-110
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• 1998

When communication network is designed, total Quantity of lines is decided by expected capacity to be caculated based on busy hour traffic. But this method is wasted many a portion of communication networks because of caculation by busy hour traffic. In this paper, it is proposed the solution that applied CDMA to the wired lines and it is shown changing the volume of networks via BER. In example, when a channel of 13kbps voice was transmitted to El at 2% BER, we can get 120 channels and the higher BER makes the bigger channels. So, it is shown that communication networks is designed by BER instead of busy hour traffic.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.2
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• pp.294-301
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• 2013

OFDM technique uses multiple sub-carriers for the data transmission. Therefore, bit error rate increases because of inter-carrier interference caused by nonlinear high power amplifier and carrier frequency offset. Wireless OFDM transmission over multi path fading channels is characterized by small transmission gain in multiple sub-carrier frequency interval. Therefore bit error rate increases because of burst errors. Inter-leaver and convolution error control coding are effective for the reduction of this burst error. Pilot symbol is used for the channel estimation in OFDM systems. However, imperfect channel estimates in this systems degrade the performance. The performance of this convolution coding OFDM systems using inter-leaver, gauged by the bit error rate, is analyzed considering the nonlinear high power amplifier, carrier frequency offset and channel estimation error.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.04a
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• pp.31-32
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• 2016

최근 소형 임베디드 시스템에서 고사양 컴퓨터 시스템까지 저장매체로 낸드 플래시 메모리를 채택하고 있다. 낸드 플래시는 물리적 성질로 인해 비트 오류가 발생하며 저장매체로써의 신뢰성이 부각되고 있다. 낸드 플래시 연구를 위해 낸드 플래시 하드웨어로 실험 환경을 구성할 경우 다른 종류의 낸드 플래시 하드웨어를 테스트하려면 전체 실험 환경을 수정해야 하는 번거로움이 발생한다. 본 논문은 실제 낸드 플래시의 비트 오류율(Bit Error Rate : BER)을 수집하여 비트 오류 발생 모델을 구축하였고 리눅스 커널의 낸드 플래시 시뮬레이터인 NANDSim에서 가상으로 생성한 낸드 플래시 종류에 따라 비트 오류율을 적용하여 소프트웨어적 실험 환경을 구성하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.8A
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• pp.1367-1377
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• 2001

고전력 증폭기의 비선형성, 수신 주파수 편차 및 심볼 타이밍 편차가 모두 존재하는 실제 IEEE 802.11a 무선 LNA 시스템의 성능을 분석하였다. 이러한 시스템에서 데이터가 OFDM 변조된 후 주파수 선택적 Rayleigh 페이딩 채널을 통하여 전송될 때의 비트 오류율을 구하였다. 증폭기의 최대 출력 전력 대 평균 출력 전력비가 6dB이며 주파수 편차가 0.01이고 심볼 타이밍 편차가 2 샘플링 주기 시간인 경우에, 이 무선 LAN 시스템에서 10-5의 비트 오류율을 얻기 위하여 필요한 $E_{b}$ /$N_{o}$ 의 크기는 대략 20~24dB로 분석되었다. 이와 같은 실제 시스템과 정확한 채널 추정, 선형 증폭기, 정확한 주파수 동기 및 심볼 동기 가정의 이상적인 시스템간의 성능을 비교한 결과, 같은 크기의 비트 오류율을 얻기 위하여 이 실제 시스템에서 대략 1~3dB 정도의 $E_{b}$ /$N_{o}$ 가 더 소요된다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.5
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• pp.983-987
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• 2004

Pilot symbol assisted modulation (PSAM) can be used for the channel estimation. However, imperfect channel estimates degrade the bit error rate (BER) performance. I derive the exact BER of 16-level quadrature amplitude modulated (16-QAM) orthogonal frequency division multiplexing (OFDM) systems with PSAM in time dispersive Rayleigh fading channels. In real system, there is 2.5 dB penalty in $\overline{\gamma_b}$for the same BER relative to ideal system with perfect channel estimation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.3
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• pp.504-509
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• 2005

This paper evaluates the BER performance of MC-DS-CDMA systems in frequency selective Rayleigh fading channel, considering the carrier frequency offset and the nonlinear high power amplifier. In the uplink MC-DS-CDMA, the BER performance is better than in the downlink. This paper presents the required output back-off of the nonlinear amplifier and value of frequency offset for good BER performance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.5
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• pp.798-805
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• 2006

I evaluate the BER performance of downlink OFDMA systems in time variant Rayleigh Doppler fading channel, considering the carrier frequency offset and the nonlinear high power amplifier. I obtain the required output back-off of the nonlinear amplifier and value of frequency offset for good BER performance. And I also analyze the BER degradation upon Doppler fading channel.