• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.10C
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• pp.984-994
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• 2003

This paper proposes a novel blind adaptive algorithm for computing the weight vector of an antenna array system. The new technique utilizes a Generalized On-Off algorithm to obtain the weight vector maximizing the SINR(Signal to Interference plus Noise Ratio) of the received signal. It is observed that the proposed algorithm generates a suboptimal weight vector with a linear computational load(O(6N+8)). From the various simulations, it is confirmed that, when the signal environment becomes adverse, e.g., low Processing Gain, and/or wide angular spread. the proposed algorithm outperforms the conventional one in terms of the communication capacity by about 3 times. Applying the proposed algorithm to satellite tracking systems as well as IS2000 1X mobile communication system, we have found that both communication capacity and communication quality are significantly improved.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.8
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• pp.975-980
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• 2019

In this paper, we propose a deep learning-based scheduling scheme for user selection in multi-user multi-antenna networks which is considered one of key technologies for the next generation mobile communication systems. We obtained 90,000 data samples from the conventional optimal scheme to train the proposed neural network and verified the trained neural network to check if the trained neural network is over-fitted. Although the proposed neural network-based scheduling algorithm requires considerable complexity and time for training in the initial stage, it does not cause any extra complexity once it has been trained successfully. On the other hand, the conventional optimal scheme continuously requires the same complexity of computations for every scheduling. According to extensive computer-simulations, the proposed deep learning-based scheduling algorithm yields about 88~96% average sum-rates of the conventional scheme for SNRs lower than 10dB, while it can achieve optimal average sum-rates for SNRs higher than 10dB.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1402-1405
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• 2016

In this paper, we develop an interference neutralization (IN) method based on a set of multi-antenna relays for K-user interference channel. The feasibility condition for IN is fully characterized. We further provide a relaxed IN method for the cases in which there are not enough relays to satisfy the feasibility condition.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.3
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• pp.459-464
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• 2001

We propose a transmit beamforming algerian for array antenna in FDD (Frequency Division Duplex) environments. The proposed method estimates the directions and spectra of the users, and constructs the spatial covariance matrix of the interferences at the downlink frequency. The weights are computed by that covariance matrix and desired user's direction vector Simulations are performed under Rayleigh fading environments. The proposed method don't need the data feedback, has the enhanced performance in BER (Bit Error Rate).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.4
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• pp.530-536
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• 1993

In adaptive antenna, recently Gooch suggested a new adaptive system using equation error method, but the system demands inverse model about the pole part and thus does not guarantee stability. In this paper, algorithm is proposed that has a basis on Popov's extra-stability theory. And system is developed of output error method. In addition, the result obtained by applying proposed algorithm to system of output error method is compared with that of Gooch model.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5A
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• pp.347-354
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• 2009

In this paper, we propose a new transmit diversity technique for multiple-input multiple-output (MIMO) systems to improve the link level performance of open-loop systems. By cyclically applying a predetermined set of preceding weight vectors, artificially induced fluctuation is created to achieve additional diversity gain in flat fading channels. To design the set of the precoding vectors, we exploit the knowledge on the distribution of near optimum Preceding vectors observed in a beamforming scheme based on the rotation transformations. Simulation results demonstrate that the proposed open-loop diversity scheme with an arbitrary number of transmit antennas achieves a full diversity gain with computational complexity comparable to a single-input single-output (SISO) system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.12
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• pp.5015-5027
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• 2015

Transceiver optimization in multiple input multiple output (MIMO) cognitive systems is studied in this paper. The joint transceiver beamformer design is introduced to minimize the transmit power at secondary base station (SBS) while simultaneously controlling the interference to primary users (PUs) and satisfying the secondary users (SUs) signal-to-interference-plus-noise ratio (SINR) based on the convex optimization method. Due to the limited cooperation between SBS and PUs, the channel state information (CSI) usually cannot be obtained perfectly at the SBS in cognitive system. In this study, both perfect and imperfect CSI scenarios are considered in the beamformer design, and the proposed method is robust to CSI error. Numerical results validate the effectiveness of the proposed algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.5
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• pp.1028-1048
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• 2011

The relation of multicast transmission and directional antennas is an open problem that has been debated for a long period of time. In this paper, we propose a group-aware multicast scheme of efficient multicast communication using the directional antennas for 60GHz millimeter wave wireless networks. For this purpose, we first derive the relation among beamwidth, distance between devices and most suitable data rate in the 60GHz frequency-based wireless network. In addition, for the dynamic beamforming of multicast communication, the x and y coordinates of any point with sender device at the center is generated, and a best-chosen group is deduced based on the Euclidean distance. Then the most suitable data rate for the group is obtained using the law of cosine. Using the Standard IEEE 802.11ad MAC protocol as an example, extensive simulation results demonstrate that the proposed scheme outperforms the existing multicast communication schemes with directional antennas under different situations.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.07a
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• pp.185-187
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• 2012

단일주파수방송망을 이용하여 지상파 3D-HDTV 전송 시 단일주파수방송망에서 발생하는 다중경로채널은 지상파 3D-HDTV 수신성능을 열화시킨다. 최대 다중경로채널의 길이는 단일주파수방송망 내 송신기간 거리에 의해 결정되며, 최소 다중경로 개수는 수신기에 근접한 송신기 개수에 의해 결정된다. 이에 본 논문에서는 다중경로채널의 각 경로 입사각을 추정하기 위한 스마트안테나기반 수신기를 설계하고, beamforming과 nulling 기법 적용 시 지상파 3D-HDTV 수신성능을 분석하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.3B
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• pp.212-219
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• 2002

In this paper, how to perform beamforming and power control for the systems with smart antennas is introduced in consideration of macro-diversity, and cell capacity of the systems is analyzed. In the result, as the number of the base stations linked to mobiles increases, capacity increases in the reverse link. On the other hand, macro diversity causes capacity loss in forward link. It is expected that the result of this work may be used in designing the next generation mobile communication systems for high quality services such as multi media data and wireless internet etc.