• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 통신소사이어티 추계학술대회논문집
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• pp.216-219
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• 2003

In this paper, we present performance analysis of an IEEE P802.15.3a high rate wireless personal area network transceiver. This physical layer standard uses QOSK as its sub-channel modulation scheme and orthogonal frequency domain modulation (OFDM) for sub-bands. OFDM is used for each sub-band so that multi-path effects are absorbed by equalizer and guard, and fading can be approximately modeled as additive white Gaussian noise. In multi-band ultra-wideband system, DAC quantization error is important noise source since high resolution conversion cannot be used due to high power consumption. Simulation result shows that, to get 640-Mbps throughput, at least 5-bits precision is necessary to maintain bit-error rate under 10$\^$-2/, which can be lowered, with channel coding, to 10$\^$-6/ that is the bit-error rate required by IEEE 802.15 upper protocol layer, in 4-meter LOS fading channel.

• Journal of Communications and Networks
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• 제18권3호
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• pp.288-298
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• 2016

Proactive relay selection in cognitive radio networks has recently received considerable attention. However, its outage probability analysis is limited to partially-identical fading distributions, uncorrelation among received signal-to-noise ratios (SNRs), and no direct channel. This paper completes this literature deficiency by generalizing the existing analysis for non-identical fading distributions, correlation among received SNRs, and with direct channel. Numerous results demonstrate that relay selection with a direct channel achieves a higher diversity order and superior performance than that without a direct channel at virtually no cost of power and bandwidth. Further, proactive relay selection suffers an error floor at either a large maximum transmit power or large maximum interference power; however, the error floor level can be significantly remedied with an increase in the number of relays.

• Journal of Electrical Engineering and information Science
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• 제1권1호
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• pp.10-16
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• 1996

In this paper, we have analyzed the error performance of the optimum threshold detection(OTD) of 16 QAM signal in the Rician fading channel with and without the maximal ratio combining(MRC) diversity technique in the presence of cochannel Rayleigh interference. An also the error performance of OTD is compared to that of conventional threshold detection(CTD) in the Rician fading channel in the presence of cochannel Rayleigh interference. With the result of analysis, it is found that there exists a synergistic effect due to both MRC diversity and optimum threshold detection in the Rician fading channel in the presence of cochannel Rayleigh interference.

• Journal of electromagnetic engineering and science
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• 제4권4호
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• pp.175-182
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• 2004

When the M-ary signal experiences the Rayleigh fading, the diversity schemes can reduce the effect of fading since the probability that all the signals components will fade simultaneously is reduced considerably. The symbol error probabilities for various M-ary signals, such as MDPSK(M-ary DPSK) and MPSK(M-ary PSK), are mathematically derived for the Selection Combining 2(SC-2) and Selection Combining 3(SC-3) demodulation system which requires a less complex receiver than Maximum Ratio Combining(MRC). The propagation model used in this paper is the frequency-nonselective slow Rayleigh fading channel corrupted by the Additive White Gaussian Noise(AWGN). The numerical results presented in this paper are expected to provide information for the design of radio system using M-ary modulation method for above mentioned channel environment.

• Journal of electromagnetic engineering and science
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• 제7권4호
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• pp.183-189
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• 2007

When the M-ary signal experiences the Rayleigh fading, the diversity schemes can reduce the effect of fading since the probability that all the signals components will fade simultaneously is reduced considerably. The symbol error probabilities for various M-ary signals, such as MDPSK(M-ary DPSK) and MPSK(M-ary PSK), are mathematically derived for the Selection Combining 2(SC-2) and Selection Combining 3(SC-3) demodulation system which requires a less complex receiver than maximum ratio combining(MRC). The propagation model used in this paper is the frequency-nonselective slow Rayleigh fading channel corrupted by the additive white gaussian noise(AWGN). The numerical results presented in this paper are expected to provide information for the design of radio system using M-ary modulation method for above mentioned channel environment.

• Journal of Communications and Networks
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• 제6권3호
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• pp.203-208
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• 2004

A combined precoding and turbo decoding strategy for multi-path frequency-selective fading channels is presented. The precoder and multi-path fading channel are jointly modeled as a finite-state probabilistic channel to provide the multi-stage turbo decoder with its statistics information. Both a priori and a posteriori probabilities are used in the metric computation to improve the system performance. Structures of the combined turbo-encoder, interleaver, and precoder in the transmitter and two-stage turbo decoder in the receiver are described. Performance of the proposed scheme in fixed, Rician and Rayleigh multi-path fading channels are evaluated by simulation. The results indicate that the combined precoding and two-stage turbo decoding strategy provides a considerable performance improvement while maintaining the same inner structure of a conventional turbo decoder.

• 한국정보통신학회논문지
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• 제4권3호
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• pp.643-652
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• 2000

본 논문에서는 임펄스 잡음과 주파수 선택성 레일리 페이딩이 공존하는 통신로에서 OFDM/ QPSK 시스템의 오율 성능을 해석하고, 성능 개선 기법으로 컨벌루션 부호화 기법을 적용하여 성능 개선을 도모하였다. 임펄스 잡음과 주파수 선택성 레일리 페이딩이 공존하는 채널에서는 보호 구간 길이보다 채널 지연 시간이 짧은 경우에 좋은 오율 성능을 나타내고, 보호 구간 길이를 벗어나면 오율 성능이 현격히 떨어짐을 알 수 있었다. 그리고 채널 상에서 존재하는 강한 임펄스 잡음의 영향을 받으면 오율 성능이 약 $10^{-1}$ 정도로 떨어짐을 알 수 있었다. 또한 임펄스 잡음과 주파수 선택성 레일리 페이딩이 공존하는 통신로에서는 부호화기법을 적용하지 않으면 음성 서비스조차 지원할 수 없는 반면에, 컨벌루션 부호화 기법을 적용하면 데이터 서비스까지 지원할 수 있음을 알 수 있었다.

• Journal of Communications and Networks
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• 제16권2호
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• pp.217-226
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• 2014

In this research, we study the problem of opportunistic spectrum access (OSA) in a time-varying environment with fading channels, where the channel state is characterized by both channel quality and the occupancy of primary users (PUs). First, a finite-state Markov channel model is introduced to represent a fading channel. Second, by probing channel quality and exploring the activities of PUs jointly, a two-dimensional partially observable Markov decision process framework is proposed for OSA. In addition, a greedy strategy is designed, where a secondary user selects a channel that has the best-expected data transmission rate to maximize the instantaneous reward in the current slot. Compared with the optimal strategy that considers future reward, the greedy strategy brings low complexity and relatively ideal performance. Meanwhile, the spectrum sensing error that causes the collision between a PU and a secondary user (SU) is also discussed. Furthermore, we analyze the multiuser situation in which the proposed single-user strategy is adopted by every SU compared with the previous one. By observing the simulation results, the proposed strategy attains a larger throughput than the previous works under various parameter configurations.

• Journal of the Optical Society of Korea
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• 제17권6호
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• pp.494-499
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• 2013

In this paper, we present an optical encryption and information authentication of 3D objects considering wireless channel characteristics. Using the optical encryption such as double random phase encryption (DRPE) and 3D integral imaging, a 3D scene with encryption can be transmitted. However, the wireless channel causes the noise and fading effects of the 3D transmitted encryption data. When the 3D encrypted data is transmitted via wireless channel, the information may be lost or distorted because there are a lot of factors such as channel noise, propagation fading, and so on. Thus, using digital modulation and maximum likelihood (ML) detection, the noise and fading effects are mitigated, and the encrypted data is estimated well at the receiver. In addition, using computational volumetric reconstruction of integral imaging and advanced correlation filters, the noise effects may be remedied and 3D information may be authenticated. To prove our method, we carry out an optical experiment for sensing 3D information and simulation for optical encryption with DRPE and authentication with a nonlinear correlation filter. To the best of our knowledge, this is the first report on optical encryption and information authentication of 3D objects considering the wireless channel characteristics.

• 한국통신학회논문지
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• 제25권3A호
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• pp.362-374
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• 2000

In this paper, trellis coded 16 QAM Multi-Carrior CDMA system is proposed, Using the equivalent signal-to-noise plus interference Power ratio (SNIR) of Multi-Carrier CDMA system in the reverse link, capacity and BER performance of trellis coded 16 QAM Multi-Carrier CDMA system are analyzed taking into account the number of multi-carrier, the number of multiple access user, the number of SC/MRC diversity branch, and Rician fading parameter in multiuser interference and Rician fading channel. And the capacity and the BER performance of trellis coded 16 QAM Multi-Carrier CDMA system using selection combining (SC) and maximal ratio cabining (MRC) diversity are numerically compared. Obtained results show that the capacity of proposed system depends on the number of multi-carrier. ti is found that the trellis coded 16 QAM Multi-Carrier CDMA system with SC/MRC antenna diversity scheme is efficient to combat multipath fading and to increase the maximum number of users in high speed data communication. With the results of analysis. MRC diversity technique provides the performance fro high speed data communications. Finally, we present a numerical approach to derive the capacity and the BER performance and to find the maximum number of multiple access user for Multi-Carrier system in multiuser interference and Rician fading channel.