• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.6
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• pp.567-574
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• 2003

It is important to design and evaluate the chip waveform with the minimum MAI under the bandwidth constraint in the interference-limited DS-CDMA system. In this paper, by approximation we present the analytical chip waveforms that are proposed and optimized in the reference. Their performances are compared with performances of three conventional chip waveforms: rectangular, half-sine and raised-cosine. Waveform 1 of the proposed chip waveform outperforms the conventional ones. BER and throughput performance are evaluated in the Rayleigh and Nakagami-m fading channels when DPSK modulation is used. When the required BER is 10$\^$-3/ in two fading channels, the capacity of the waveform 1 is improved about 20 % rather than raised-cosine one. When the offered traffic is 30 and the number of packet per bit(N$\sub$d/) is 14, maximum throughput of the waveform 1 is better than raised-cosine chip waveform about 18 % in two fading channels.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.14 no.3
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• pp.280-292
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• 1989

In this paper, the error rate equations of digitally modulated signals transmitted through the channel which is not only Gaussian/Impulsive noise but also multi-path fading have been derived. Using the derived equations for the error probabilities of ASK, QAM, CPSK, DPSK, FSK, and MSK signals, the error rate performances of digital modulation systems have been evaluated and represented in the graphs as the functions of CNR, Impulsive indes, the ratio of Gaussian noise power component to Impulsive noise power component, and fading figures. The results show that, in the deep fading environment, the error is occurred more frequency by Gaussian noise than Impulsive noise. And the comparison of various systems certifies that PSK is superior to the ohter systems in the deep fading or shallow fading environment.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.429-432
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• 2000

수중에서 AUV신호나 화상데이터의 정확한 고속 전송 등을 위해 수중 데이터 통신에 대한 많은 연구가 진행되어 왔다. 수중 데이터 통신에서 잔향과 배경 잡음 등의 해양 환경 특성을 극복하는 것은 신뢰성 있는 통신 환경을 이룩하는데 중요하다. 특히 해면과 해저로 이루어진 천해 환경에서 해면과 해저 반사파에 의한 영향은 수중 데이터 통신의 성능을 좌우하는 중요한 요소 중의 하나로 알려져 있다. 이러한 환경적 영향을 최소화하여 높은 성능의 통신 환경을 제공하기 위해 다중경로의 영향을 적게 받는 변조방식을 선택하는 것이다. 수중 데이터 통신에서 일반적으로 사용되는 변조방식은 FSK, PSK, DPSK 등이 있다. 본 연구에서는 해면$\cdot$해저로 이루어진 해양 통신 채널에서 세 가지 변조방식의 성능을 수치모의실험을 통하여 비교$\cdot$분석하였다. 수치모의실험에서 해면 해저로 이루어진 천해의 해양 통신 채널은 음원 영상법을 적용하여 구성하였으며 각 변조방식의 성능은 BER(Bit Error Ratio)로 나타내었다.

• Journal of Satellite, Information and Communications
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• v.9 no.3
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• pp.1-4
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• 2014

A radio communication system has interference caused by other radio transmitters operated in co-channel or adjacent channels. Therefore technical specifications are made by considering and investigating the effects of interference between the new system and present systems when the new system will be started to serve in the near future. FTS is used for preventing an abnormal mission and guaranteeing public protection. Recently the next generation FTS's are researched to reinforce the security and to increase the operating capability of simultaneous use. EFTS known as one of the next generation FTS's is suitable for such purposes. In this paper the effects of interference signals on the performance of EFTS are investigated. Noncoherent DPSK and noncoherent CPFSK are considered for the modulation method of EFTS and a FMCW and a pulse RADAR considered as a interferer. The power of FMCW is 20.3dB lower than the power of EFTS and the power of pulse RADAR is 19.1dB lower than that of EFTS. Simulation results show that FMCW interferer reduce $E_b/N_o$ of about 1dB and $E_b/N_o$ of EFTS deteriorates about 0.5dB due to interference signals generated from pulse RADAR.

• ETRI Journal
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• v.34 no.6
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• pp.800-806
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• 2012

Transmission performances of direct detection-based 100-Gb/s modulation formats are investigated and compared for metro area optical networks. The effects of optical signal-to-noise ratio sensitivity, chromatic dispersion, cross-channel nonlinearity, and transmission distance on the performance of differential 8-ary phase-shift keying (D8PSK), differential phase-shift keying plus three-level amplitude-shift keying (DPSK+3ASK), and dual-carrier differential quaternary phase-shift keying (DC-DQPSK) are evaluated. The performance of coherent dual-polarization quadrature phase-shift keying (DP-QPSK) with block phase estimation and coherent DP-QPSK with digital differential detection are also presented for reference. According to our analysis, all three direct detection modulation formats could transmit a 100-Gb/s signal over several hundred kilometers of a single-mode fiber link. The results also show that DC-DQPSK outperforms D8PSK and DPSK+3ASK, and the performance of DC-DQPSK is comparable to that of coherent DP-QPSK with digital differential detection. The maximum transmission distance of DC-DQPSK is over 1,000 km, which is enough distance for metro applications.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.2
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• pp.208-216
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• 2001

Signal Fading due to multipath propagation severely impairs the performance of high-speed mobile communication systems. Effective diversity scheme for fading channel is STTD (Space Time Transmitter Diversity) method. This scheme is very simple and using 2 transmit antennas and 1 receive antenna provides a diversity order of two[1],[2]. In this paper, we derive the new probability density function of the envelope of the received signal over correlated Rayleigh fading channel. Using the new pdf of the envelope we analyze the performance of noncoherent M-ary FSK, DPSK and ASKSTTD (Space Time Transmitter Diversity) a system on correlated Rayleigh fading channel.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.4
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• pp.699-705
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• 2001

It is considered DPSK modulation and the channel is modeled as multipath Nakagami fading type which has been recently taken as a general model in the communication environments in this paper. Most paper assumed that Nakagami fading index(m) of each branch of Rake receiver was fixed the same value in recent years. However, Nakagami fading index(m) of each branch of Rake receiver takes several value through communication environments. In this case, the branch ,which takes a small Nakagami fading index(m), exclude. So we can improve performance. We are considered phase error and analyzed wideband DS/CDMA cellular system. When nakagami fading index(m) takes voluntary value, we analyze BER of wideband DS/CDMA cellular system. Finally, When the branch, which takes a small Nakagami fading index(m), exclude, we analyze BER of wideband DS/CDMA cellular system.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1987.04a
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• pp.223-229
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• 1987

The error rate eqations of digital modulated signals transmitted through the fading cdannel have been derived in the Gaussian/Impulsive noise environments Whing the derived equations for the error drobadillties of ASK, QAM, FSK, MSK, PSK, and DPSK signais, the error tate performance of digital modulation systems have been evaluated and represented in the graghes as parameters of carrier to \ulcornernoise power ratio (CNR) and fading figures The results show that in the fading environenet the error is occurred more frequently by gaussian noise in the deep fading Howerer in the shallow fading lmpulsive noise is more domiant than gaussian nosie in occurring the error

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.745-748
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• 2001

본 논문에서는 무선 홈네트워킹 시스템으로 대두되고 있는 Wireless LAN(802.11b), HomeRF, Bluetooth 성능을 간섭이 고려되지 않는 경우의 실내 무선 환경하에서 시스템의 변조 방식만을 비교 분석하였다. 무선 홈네트워킹 시스템의 채널 수 및 주파수 대역은 동일하며 실내 무선 환경을 라이시안 페이딩 환경으로 고려하였을 경우, 직접파 대 반사파 전력비(K)가 6[dB]인 라이시안 페이딩 환경하에서 오율 $10^{-3}$을 기준으로 비교하여 보면, DPSK 방식이 4FSK와 GFSK 보다 4[dB], DQPSK와는 11[dB] 그리고 2FSK 보다 28[dB] 정도 우수하였다. 또한 GFSK와 4FSK가 0.4[dB] 차이를 두고 일정하게 분포함을 알 수 있었다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.693-696
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• 2001

본 논문에서는 무선 홈네트워킹 시스템으로 대두되고 있는 Wireless LAN(802.11), HomeRF, Bluetooth 성능을 간섭이 고려되지 않는 경우의 실내 무선 환경하에서 시스템의 변조 방식만을 고려하였으며 실내환경에서 발생되는 에러에 대한 제어 기술로 Truncated Type-B Hybrid ARQ를 적용하였다. 무선 홈네트워킹 시스템의 채널 수 및 주파수 대역은 동일하며 실내 무선 환경을 라이시안 페이딩 환경으로 고려하였을 경우, 직직접파 대 반사파 전력비(K)가 6[dB]인 라이시안 페이딩 환경하에서 오율 $10^{-3}$을 기준으로 할 때 2FSK가 DQPSK보다는 E$_{b}$ /N$_{o}$ 가 약 3[dB] 정도 우수하며 오율 $10^{-6}$을 기준으로 비교하여 보면, DPSK 방식이 4FSK 보다 약 E$_{b}$ /N$_{o}$ 가 5[dB] 우수하였다. 또한 K=6인 라이시안 환경하에서 변조 방식만을 고려한 경우보다 성능 개선 기법을 채용한 무선 홈네트워킹 시스템의 E$_{b}$ /N$_{o}$ 가 더 우수함을 알 수 있었다.