• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.249-252
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• 2001

We, for the first time, propose a novel adaptive beamforming algorithm for smart antenna. The algorithm requires neither spatial knowledge nor reference signal. The algorithm is based on gradient method and its merit is in the simplicity of calculation load while maintaining good performance. Computer simulations are presented to verify the performance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.2
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• pp.247-250
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• 2001

We, for the first time, propose a novel adaptive beamforming algorithm for smart antenna. The algorithm requires neither spatial knowledge nor reference signal. The algorithm is based on gradient method and its merit is in the simplicity of calculation load while maintaining good performance. Computer simulations are presented to verify the performance.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.7
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• pp.46-52
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• 1998

This paper presents an experimenal proof for criteria of selecting an optimum adaptive beamforming (ABF) algorithm for a large distorted phased array. A single point target embedded in clutter model is suggested to compare four well-known ABF algorithms. These algorithms are tested to low variance and high variance real data for self-calibrating a large distored phased array. It is shown that these algorithms require at least one dominant scatterer with large radar cross section (RCS) or multiple scatterers with moderate RCS in the field of view. Experimental results are provided to demonstrate the comparisons of the four algorithems in terms of gain loss and image correlaion coefficient, along with corresponding reconstructed cross-range images and range-azimuth images.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.5
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• pp.115-122
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• 2011

Adaptive arrays suffer from severe performance degradation when there are errors in the steering vector. The DCRCB (doubly constrained robust Capon beamformer) overcomes such a problem, introducing a spherical uncertainty set of the steering vector together with a norm constraint. However, in the standard DCRCB, it is a difficult task to determine the bound for the uncertainty, the radius of the spherical set, such that a near best solution is obtained. A novel beamforming method is presented which has no difficulty of the uncertainty bound setting, employing a recursive search for the steering vector. Though the basic idea of recursive search has been known, the conventional recursive method needs to set a parameter for the termination of the search. The proposed method terminates it by using distances to the signal subspace, without the need for parameter setting. Simulation demonstrates that the proposed method has better performance than the conventional recursive method and than the non-recursive standard DCRCB, even the one with the optimum uncertainty bound.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.459-462
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• 2004

간섭신호가 광대역이거나 빠르게 기동할 경우 기존의 협대역 적응 빔형성(NABF: Narrowband Adaptive Beam-forming)기법의 성능이 크게 저하되는 것으로 알려져 있다. 이는 간섭신호가 빠르게 기동할 경우 추정된 빔패턴의 널(null)을 벗어나게 되고 협대역을 가정하여 얻어진 빔패턴의 널은 광대역 신호일 경우 이를 효과적으로 제거할 수 없기 때문이다. 이러한 환경에서 견실한 성능을 얻기 위해 NABF 기법에 미분제한조건을 주어 간섭신호 방향의 널 폭을 넓히는 기법이 알려져 있다. 본 논문에서는 광대역의 기동하는 간섭신호에 보다 견실하게 대처하기 위해 광대역 적응 빔형성 (WABF: Wideband Adaptive Beamforming)기법에 미분제한 조건을 적용하였다. 그리고 빠르게 기동하는 광대역 간섭신호가 존재하는 환경에서 모의실험을 수행하여 제안한 기법과 기존의 NABF기법 성능을 비교한다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.2
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• pp.102-107
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• 2011

In multicell wireless systems with insufficient frequency reuse, user transmission will suffer other-cell interference (OCI). Cell cooperation is an effective way to mitigate OCI and increase the system sum rate. An adaptive scheme for serving one user in each cell was proposed in [1]. In this paper, we generalize that scheme by serving two users in each cell with adaptive zeroforcing beamforming (ZF) strategies. Based on our derived statistics of the signal-to-noise plus interference ratios, we choose the scheme to maximize the total ergodic sum-rate based on user locations. Through the numerical examples, we show that the total system sum rate can be improved by selecting appropriate transmitting strategy adaptively. As a result, our proposed system can explore spatial multiplexing gain without additional power and thus improves total system sum rate significantly.

• Journal of the Korea Society of Computer and Information
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• v.15 no.5
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• pp.75-81
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• 2010

Adaptive array antenna system estimates target signal, as making a null pattern toward the interference signal. However, receiving a coherent interference signal at adaptive array antenna system, as target signal is regarded as interference signal, the performance of system rapidly decreases. The main beam does not direct an incidence direction of target signal due to sensitivity in directivity error. This paper proposes beamforming algorithm which combines high order limit condition and directivity error modify method. And it minimizes degree of freedom and decreases interference signal and directivity error using proposed algorithm. This paper compares and analyzes the performance of proposed algorithm and general algorithm using simulation. In this paper, the proposed algorithm correctly estimates an incident angle, but general algorithm occurs an error of about $0.8^{\circ}$.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.10 s.352
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• pp.18-26
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• 2006

In this paper, we propose new beamforming algorithm which overcomes signal cancellation effect even high cross correlation existing between target and interfering signal. Using the proposed method, we show that direction of arrival (DOA) of interfering signal can be estimated using correlation matrix and the cross-correlation can be eliminated in the correlation matrix of input signal. The proposed method gives high performance enhancement compared with the spatial averaging method in our computer simulation results.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.7
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• pp.80-84
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• 2010

A novel hybrid antenna array system for the code division multiple access (CDMA) using the diversity and beamforming technique has been proposed which is called as a dynamic selection method (DSM). Through the derived outage probability analysis, we have shown that the proposed DSM technique can give benefit over the conventional diversity-only or beamforming-only system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.9
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• pp.1-8
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• 2007

In this paper, the new beamforming is proposed for an orthogonal frequency division multiplexing(OFDM) system with multi-input multi-output(MIMO). Through the proposed Pre-FFT beamforming technique for MIMO-OFDM, the multibeams are formed toward each multi-transmitter antenna of the desired user. The proposed beamforming for MIMO-OFDM can reduce cochannel interference and get diversity gain in the multi-user environment. Therefore, the performance of MIMO-OFDM system is very improved. BER performance improvement of the proposed approach is investigated through computer simulation by applying it to MIMO-OFDM system in the multi-user environment.