• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12C
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• pp.1177-1183
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• 2009

In this paper, support vector machines (SVM) are applied to multi-user detector (MUD) for direct sequence (DS)-CDMA system. This work shows an analytical performance of SVM based multi-user detector with some of kernel functions, such as linear, sigmoid, and Gaussian. The basic idea in SVM based training is to select the proper number of support vectors by maximizing the margin between two different classes. In simulation studies, the performance of SVM based MUD with different kernel functions is compared in terms of the number of selected support vectors, their corresponding decision boundary, and finally the bit error rate. It was found that controlling parameter, in SVM training have an effect, in some degree, to SVM based MUD with both sigmoid and Gaussian kernel. It is shown that SVM based MUD with Gaussian kernels outperforms those with other kernels.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.3A
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• pp.172-178
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• 2012

This paper studies the application of a fuzzy-ARTMAP (FAM) neural network to multi-user detector (MUD) for direct sequence (DS)-code division multiple access (CDMA) system. This method shows new solution for solving the problems, such as complexity and long training, which is found when implementing the previously developed neural-basis MUDs. The proposed FAM based MUD is fast and easy to train and includes capabilities not found in other neural network approaches; a small number of parameters, no requirements for the choice of initial weights, automatic increase of hidden units, no risk of getting trapped in local minima, and the capabilities of adding new data without retraining previously trained data. In simulation studies, binary signals were generated at random in a linear channel with Gaussian noise. The performance of FAM based MUD is compared with other neural net based MUDs in terms of the bit error rate.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.7
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• pp.693-701
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• 2002

In this paper, we analyze the coverage of asynchronous IMT(International Mobile Telecommunication)-2000 reverse link with a MUD(Multi-User Detector) system. The MUD system is utilized to increase the coverage of reverse link. Also we have considered a propagation loss model and an interference effect. Because it is very difficult that we have calculated the interference accurately, so a fractional cell loading factor(F) is used in this paper. We make use of a MUD efficiency($\beta$) to analyze the performance; this efficiency is presented the MAI of reduction. A simulation utilizes Hata's model, we calculated the coverage according to voice and data services. In this paper, we have assumed that the frequency of carrier has 800 MHz or 1.9 GHz, and a bandwidth is decided 3.84 MHz. We have predicted the performance of actual system by the analysis of capacity and coverage.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.2
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• pp.221-227
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• 2002

In this paper, in order to know the effect of the interference, we have analyzed the BER (Bit Error Rate) performance of the MUD(Multi-User Detector) employing HIC(Hybrid Interference Cancellation) scheme for the asynchronous WCDMA system based on 3GPP(3rd Generation Partnership Project) Spec. through the In this paper, in order to know the effect of the interference, we have analyzed the BER (Bit Error Rate) performance of the MUD(Multi-User Detector) employing HIC(Hybrid Interference Cancellation) scheme for the asynchronous WCDMA system based on 3GPP(3rd Generation Partnership Project) Spec. through the computer simulation. we have assumed Rayleigh fading channel. And we have compared its BER performance with SIC's(Successive Interference Cancellation) and with PIC's(Parallel Interference Cancellation), which are the representative schemes in the subtractive interference cancellation. From the results, it is shown that PlC or HIC is effective for high data-rate users and SIC of HIC for low data-rate users to eliminate the interference. Regardless of the data rate, it is reasonable to use the HIC structure for WCDMA system to satisfy all of users' services. The reason is that the SIC scheme in front of HIC can guarantee the performance of low power users to cancel the serious interference caused by the high power users, while PIC in the rear of it can guarantee the performance of high power users to cancel the interference caused by the low power users.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.11C
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• pp.1085-1091
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• 2006

The major goal of this paper is to develop a practically implemental radial basis function (RBF) neural network based multi-user detector (MUD) for direct sequence (DS)-CDMA system. This work is expected to provide an efficient solution for RBF based MUD by quickly setting up the proper number of RBF centers and their locations required in training. The basic idea in this research is to estimate all the possible RBF centers by using supervised ${\kappa-means$ clustering technique, and select the only centers which locate near seemingly decision boundary between centers, and reduce further by grouping the some of centers adjacent each other. Therefore, it reduces the computational burden for finding the proper number of RBF centers and their locations in the existing RBF based MUD, and ultimately, make its implementation practical.

• 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 IEEK Conference
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• 2001.06a
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• pp.17-20
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• 2001

This paper studies the channel estimation schemes of Time Division Duplex (TDD) Code Division Multiple Access (CDMA) system with a parallel interference cancellation (PIC) scheme in the multi-Path fading channel. Also, the effective interpolation scheme which maintains the merits of WCDMA TDD mode is proposed. By Monte Carlo simulations, it is shown that the proposed interpolation method can be used in order to obtain the proper performance of a multi-stage PIC and in order to reduce the required Eb/No in the second stage at a BER= 10$^{-2}$

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.6A
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• pp.885-892
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• 2000

A multi-used detector(MUD) using a radial basis function(RBF) network is proposed in a multicarrier-code division multiple access (MC-CDMA) system. In the proposed scheme, a RBF network is connected to the frequency domain in order to effectively utilize the frequency diversity. Simulations have been performed over the frequency selective and multipath fading channel. From these simulations, the proposed receiver is verified to be used for making the performance improvement in combating near-far effects and increasing the number of active users. The system capacity is increaed about 1.8 times at a BER of $10^{-3}$ under a single cell when the proposed scheme is compared with MUD using a parallel interference canceller(PIC).