• 산업기술연구
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• 제24권B호
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• pp.143-148
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• 2004

We present a fast algorithm for CDMA (code division multiple access) multiuser detection using the gradient guided search. The fast algorithm calculates the maximum likelihood (ML) metric so efficiently that it needs only O(K) additions in the presence of K users once some initialization is completed. The computational advantages of the fast algorithm over the conventional method are more noticeable as more iterations are required to obtain a suboptimal solution as in the initialization with matched filters.

• ETRI Journal
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• 제32권3호
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• pp.479-481
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• 2010

An optimal multiuser detection algorithm with a computational complexity of O(K log K) is proposed for the class of linear multiple-access systems which have constant cross-correlation values. Here the optimal multiuser detection is implemented by searching for a monotone sequence with maximum likelihood, under the ranking of sufficient statistics. The proposed algorithm is intuitive and concise. It is carried out in just two steps, and at each step only one kind of operation is performed. Also, the proposed algorithm can be extended to more complex systems having more than a single cross-correlation value.

• Journal of Communications and Networks
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• 제9권2호
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• pp.185-191
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• 2007

Alpha stable distribution is better for modeling impulsive noises than Gaussian distribution in signal processing. This class of process has no closed form of probability density function and finite second order moments. In general, Wiener filter theory is not meaningful in S$\alpha$SG environments because the expectations may be unbounded. We proposed a new adaptive recursive least p-norm Kalman filtering algorithm based on least p-norm of innovation process with infinite variances, and a new robust multiuser detection method based on least p-norm Kalman filtering. The simulation experiments show that the proposed new algorithm is more robust than the conventional Kalman filtering multiuser detection algorithm.

• 한국통신학회논문지
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• 제35권2C호
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• pp.229-237
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• 2010

기존 SM MIMO 시스템을 위한 신호검출 기법인 OSIC 계열의 기법과 준최적 신호검출 기법인 QRD-M 기법을 협력적 공간다중화 기반 상향링크 다중사용자 시스템에 적용할 경우 사용자별 신호의 검출성능에 차이가 발생한다. 본 논문에서는 협력적 공간다중화 기반 상향링크 다중사용자 시스템을 위한 사용자간별 검출성능 차이가 발생하지 않으면서 최적 신호검출 기법과 유사한 성능을 보이는 신호검출 기법을 제안한다. 제안된 신호검출 기법의 연산복잡도는 QPSK 변조에서는 QRD-M과 유사하지만, 16-QAM, 64-QAM과 같이 높은 차수의 변조방식의 시스템에서는 QRD-M에 비해 매우 낮은 연산복잡도를 가진다.

• 한국통신학회논문지
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• 제27권3B호
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• pp.188-195
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• 2002

본 논문에서는 멀티 레이트 부호분할 다중접속(Code Division Multiple Access: CDMA) 방식에서의 효과적인 다중 사용자 검출 기술을 제안한다. 최적 다중 사용자 검출 기술이 최적의 비트 오류 확률(Bit Error Rate: BER) 성능을 보이긴 하지만, 실제 구현을 위해서는 계산상의 복잡도 측면에서의 문제가 있다. 따라서, 본 논문에서는 멀티 레이트 CDMA 환경에서 비교적 낮은 계산상의 복잡도를 갖는 준칙적의 다중 사용자 검출기 구조를 제안하며, 기존의 정합필터(matched filter)와 멀티 레이트 환경에서 제안된 다른 다중 사용자 검출기와의 성능 비교를 수행한다. 레일리 페이딩 환경에서의 컴퓨터 시뮬레이션을 통해 제안된 홉필em(Hopfield) 신경망(neural network) 알고리즘을 이용한 다중 사용자 검출기법의 성능이 우수함을 검증한다.

• 한국통신학회논문지
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• 제31권2C호
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• pp.184-190
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• 2006

본 논문에서는 다중 사용자 간섭과 원근 효과에 대한 견실한 블라인드 다중 사용자 검출기를 제안하였다. 제안된 검출기는 부분 간섭 제거기와 블라인드 최소 출력 에너지 다중 사용자 검출기가 결합된 형태이다. 부분 간섭 제거기는 수신된 신호로부터 간섭 성분을 부분적으로 제거한 후 다중 사용자 검출기의 입력으로 사용한다. 모의실험 결과, 원근 효과와 다중 사용자가 존재하는 경우, 기존 MOE 다중 사용자 검출기의 성능이 급격히 열화 되는 반면 제안된 검출기는 두 성분에 대하여 견실한 특성을 지니고 있음을 보여 주고 있다. 따라서, 제안된 부분 간섭 블라인드 다중 사용자 검출 기술이 기존 MOE 보다 더 나은 성능을 지님을 알 수 있었다.

• ETRI Journal
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• 제45권6호
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• pp.929-938
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• 2023

The detection of all the symbols transmitted simultaneously in multiuser systems using limited wireless resources is challenging. Traditional model-based methods show high performance with perfect channel state information (CSI); however, severe performance degradation will occur if perfect CSI cannot be acquired. In contrast, data-driven methods perform slightly worse than model-based methods in terms of symbol error ratio performance in perfect CSI states; however, they are also able to overcome extreme performance degradation in imperfect CSI states. This study proposes a novel deep learning-based method by improving a state-of-the-art data-driven technique called deep soft interference cancellation (DSIC). The enhanced DSIC (EDSIC) method detects multiuser symbols in a fully sequential manner and uses an efficient neural network structure to ensure high performance. Additionally, error-propagation mitigation techniques are used to ensure robustness against channel uncertainty. The EDSIC guarantees a performance that is very close to the optimal performance of the existing model-based methods in perfect CSI environments and the best performance in imperfect CSI environments.

• Journal of information and communication convergence engineering
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• 제4권4호
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• pp.151-154
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• 2006

In this work, a novel optimal multiuser detection (MUD) approach, which not only achieves the optimal maximum-likelihood (ML)-like performance but also has reasonably low computational complexity, for Space-time coded OFDM (ST-OFDM) systems is presented. In the proposed detection scheme, the signal model is firstly re-expressed into linearly equivalent one. Then, with the linearly equivalent signal model, a new jointly MUD algorithm is proposed to detect signals. The ML-like bit-error-rate (BER) performance and reasonably low complexity of the proposed detection are verified by computer simulations.

• 한국통신학회논문지
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• 제23권4호
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• pp.865-872
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• 1998

This paper proposes a multiuse detection system in a multi-cell M-ary Frequency Shift Keying(MFSK)/frequency hopping(FH)-Code Division Multiple Access(CDMA) environment, in which the channel model is an OR-channel and in the reverse link. We have proposed a multiuse detection system in a single cell. However, this sitye is not adequate to detect multiuser in a multi-cell environment. Therefore, we propose a multiuser detection system based on 3 level OR decision with two threholds. The proposed detection system can delete interference as well as intra-cell interference, receive the weakened desired signal and reject the false alarm. computer simulation shows the performance improvement.

• 한국통신학회논문지
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• 제25권9A호
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• pp.1273-1281
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• 2000

In this paper we studied for multi-user detection system, which hold the merit of CDMA system and can enhance the system capacity. We designed actually realizable quasi-optimal multiuser detection system by use of linear equalizer on the concept that multiuser detection algorithm can be reduced by combining TDMA with CDMA. we call this the hybrid TDMA/CDMA system. And we proposed multiuser detection system, which can use PSAD and MSDD channel estimation method. As a result of performance analysis we acquired equal or much better performance by use of linear multichannel equalizer in the case of not so many user. And on the occasion of many user within cell we can also acquired much better performance in comparison with conventional single user detection system by use of hybrid TDMA/CDMA system.