• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.3B
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• pp.188-195
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• 2002

In this paper, we consider efficient multiuser receiver structures using Hopfield neural network algorithm focused to construct a synchronous multi-rate code division multiple access (CDMA) system. Although the optimum receiver for multiuser detection can be realized attaining the best BER performance, it is too complex for practical implementation. Therefore, we propose near-optimal receivers of relatively low computationally complex multiuser detection structures for realizing multi-rate CDMA system and their performances are compared with conventional matched filter and other prominent multi-rate multiuser detectors, Computer simulations show that the Hopfield neural network based multiuser receiver achieves substantially better BER performance in Rayleigh fading environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.8A
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• pp.1099-1106
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• 1999

In this paper, the bit error ratio(BER) performance of multi-carrier CDMA system in multi-user/multi-path environment is analytically derived, and effect of interferences due to multi-user, multi-carrier, multi-path is analyzed. A multi-carrier/multi-user/multi-path joint detection scheme incorporating a decorrelating detector is proposed, and its performance as well as the enhancement of noise due to decorrelating process are analyzed. BER of the proposed joint detection scheme is only slightly degraded compared to the ideal case of single user environment.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2001.06a
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• pp.1-4
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• 2001

In this paper, we develop a blind adaptive multiuser detector for synchronous CDMA with a noise-whitened filter. To Improve the symbol error probability performance, Decision-Feedback Blind Adaptive Multiuser Detector(DFBD) is proposed and compared with Blind Adaptive Multiuser Detector(BD). The proposed DFBD is slightly improved.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3C
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• pp.153-157
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• 2005

Frequency selective fading occurs due to the Doppler Effect in mobile communication systems. The performances of the systems are rapidly reduced due to effect of multiuser interference under frequency selective channels at DS-CDMA systems. To overcome these problems, we adopted the multi-carrier modulation techniques, and it is able to solve the frequency selective channel effects by means of these modulation techniques, and interference problems due to multiuser access are solved by means of multiuser detection techniques. In this paper, we proposed the blind MOE/PIC multiuser detection method which is composed of both the blind multiuser detection technique and parallel interference canceller. Thus, simulation results show that the proposed method performs better than conventional methods.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.8
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• pp.26-32
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• 2002

In this paper, we propose a suboptimal receiver combining adaptive array antenna and orthogonal decision-feedback detector in DS/CDMA system. Adaptive way antenna can cancel out undesired signal using beamforming scheme. However, if there are interfering signals from undesired users with the same incident angle as that of a desired user, an adaptive array antenna cannot suppress them. The proposed receiver can cancel out remaining interference from users having nearly the same beam pattern. And we employ Orthogonal Decision-Feedback Detector (ODFD) as Multiuser detection. The ODFD performs as good as the decorrelating decision -feedback detector (DDFD) with much less complexity. Simulation results show that the proposed system provides a significantly enhanced performance.

• Journal of Satellite, Information and Communications
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• v.12 no.1
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• pp.1-5
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• 2017

In this paper, multiuser detector (MUD) based on radial basis function (RBF) is proposed and simulated for a multicode direct sequence/code division multiple access (DS/CDMA) system in a multipath fading channel. The performance of RBF-based MUD is compared with that of many suboptimal multiuser detectors in terms of bit error probability. From the simulation results, it is confirmed that the RBF-based MUD outperforms decorrelating detector, and achieves near-optimum performance under various environments. The results in this paper can be applied to design of MUD for a multicode DS/CDMA system.

• Journal of Korea Multimedia Society
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• v.5 no.5
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• pp.582-589
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• 2002

In this paper, we propose a new method that combines antenna array, which employs any beamforming algorithm, and successive interference cancelling multiuser detector which improves the performance of the receiver and analyse its performance. Antenna away receivers can improve the performance by spatially discriminating among the users and reducing the multiple access interference. But the performance of the receivers degrades when the difference of the direction of arrival of the users are too small. Many interference cancelling multiuser detectors have been suggested for DS/CDMA systems which have low complexity for their performance. In this paper, we show how to mitigate such a degradation by combining successive interference cancelling multiuser detector.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9C
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• pp.882-888
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• 2006

Multiuser detection can significantly increase system capacity and improve service quality compared with the existing matched filter. In this paper, we introduce an method which efficiently calculates the maximum likelihood (ML) metric based on the gradient search (GS). The ML detection needs user powers as well as their spreading codes. A method is also proposed that allows us to detect data bits with the estimation of user powers when they are unknown. Computer simulation shows that the proposed method can nearly achieve the same performance as the GS with perfectly hewn user powers.

• Journal of Korea Society of Industrial Information Systems
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• v.11 no.4
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• pp.40-46
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• 2006

The performance of iterative multiuser detector and turbo decoder is presented to provide high quality multimedia services in WCDMA (wideband code division multiple access) system in this paper. Especially the relationship between the local iteration of turbo decoder and the global iteration of multiuser detector including the turbo decoder is analyzed. As a result, three local iterations and three global iterations are considered to be sufficient to provide satisfactory error performance with resonable complexity. The interference cancellation capability of global iteration is improved when the number of users is increased.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.142-146
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• 2002

직접 대역 확산 통신 방식에서 처리 이득에 비해 강한 협대역 간섭 신호가 존재 할 때 성능 향상을 위하여 다중 사용자 탐지 기술(MUD)을 사용하여 간섭 신호 제고를 위한 신호 검출을 하였으며, 적응 접속 채널 배열 응답과 다중 사용자 검출을 하기 위하여 BISP 알고리즘을 제안하였다. 또한 CDMA 채널에서 MAI와 ISI 검출에 BISP 알고리즘 신호 흐름 형태를 파악하여, 신호대 간섭 비율(SIR)과 신호대 잡음비율(SNR)에서 시간에 따른 비트율를 평가 하였다. 제안한 BISP 알고리즘은 방사 특성에 시간 지연 효율이 절반 이상 차이가 나지만 채널 특성 따라서 입력 신호를 조정 할 수 있다. 그리고 매치 필터를 통과하면서 각 채널간의 간섭을 억제하고, 사용자 검출을 용이하게 처리할 수 있다.