• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.4
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• pp.378-386
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• 2013

In this paper, we propose a multi-way relaying system, in which N communicating nodes interchange their information one another by the help of a multiple-antenna non-regenerative relay station (RS). While the conventional multi-way relaying requires 2N transmission phases to complete the data exchange, the proposed system completes the mission with N phases composed of one multiple access phase and N-1 broadcast phases. For effective broadcast transmission, the proposed system pairs users for signal transmission with a new RS beamforming matrix not to interfere with the nodes of different pairs and a self-interference canceler at each node. The performance evaluation in terms of the average sum rate shows that the proposed system outperforms the conventional one with more significant gain when the number of RS antennas is comparable to the number of communicating nodes. The proposed schemes can be applicable to marine communications where the ships need to share their information with extended coverage.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.10
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• pp.989-997
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• 2002

This paper presents a new technique that enhances the performance of the smart antenna system especially in signal environments of wide angular spread by adopting a weight vector obtained from two eigenvectors of theautocovariance matrix of the received data. While the conventional beamformingtechnique employs only one eigenvector corresponding to the largest eigenvalue, the proposed algorithm uses two eigenvectors corresponding to the largest and second largest eigenvalue in such a way that it can be robust enough to the signal environments of wide angular spread. An efficient adaptive procedure is shown to verify that the optimal weight vector consisting of the two eigenvectors is obtained with a reasonable complexity(3.5$N_2$+ 12N) and accuracy. it is also shown in this paper that the numerical results obtained from the proposed adaptive procedure well agree with those obtained from a commercial tool computing the eigen-function of MATLABTM.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.2
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• pp.182-190
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• 2009

GPS receivers can be disrupted by intentional or unintentional jamming, then it is unable to receive GPS signals and it is impossible to get the correct navigation results. Anti-jamming schemes using array antennas are being studied well due to high performance of those, and the efforts to apply them to GPS receiver are also being done. A GPS receiver structure for a multiple beam-forming scheme among those schemes has been proposed in this paper, and the performance is also compared with that using a general GPS receiver structure. For a general GPS receiver structure, each satellite signal which is formed by a beam-forming scheme is summed to be processed in a part of digital signal processing. For a proposed GPS receiver structure, however, each satellite signal is respectively processed by a designated channel in a part of digital signal processing. Finally, it is confirmed that the proposed GPS receiver structure is superior to a general GPS receiver structure in a point of the carrier to noise power ratio and the navigation accuracy using a software platform.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.10A
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• pp.974-983
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• 2007

In this paper, a low complexity subcarrier allocation scheme is proposed for multiuser MIMO-OFDM systems with zero-forcing beamformer (ZFBF) so that the total transmit power can be minimized satisfying given target data rate. Since the optimal method requires very high computational complexity, we propose a low complextiy suboptimal method. Using the fact that the effective channel gain is proportional to the orthogonallity of channels of multiplexed users, a user set with the highest orthogonality of channel among users is assigned to each subcarrier in order to minimize required transmit power. The numerical results show that the proposed suboptimal method can reduce computational complexity with little performance loss.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6A
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• pp.488-496
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• 2012

In this paper, the scheme for designing optimal beamforming matrix for interference control is proposed. The optimal beamforming matrix is found though linear combination of interference alignment conditions and renewal of linear combination coefficient. The proposed scheme has advantages that the complexity is reduced and there is no multiplying operation in matrix calculations even if proposed scheme has the form similar to that of existing least square based scheme. The simulation results show that proposed scheme has about 4bps/Hz higher gain than existing least square scheme. Also there is no additional multiplying calculation and increase of matrix size when the number of transmit and receive antennas is increased.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.1
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• pp.11-17
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• 2009

This paper deals with the estimation performance DoA (Direction of Arrival) using the 3D adaptive array antenna in W-CDMA signal. For this, we proposed the 5 types of 3D array antenna, and appied for the MUSIC in order to the estimation of DoA algorithm for that antenna, commonly, then the DoA estimation error was used for the estimation performance. In the mobile communication and radio positioning service, performing the spatial filtering after the DoA estimation in array antenna, the quality of receiving signal can improve by the nulling or minimization of interfering signal which is from the undesired direction and the forming of beam which is from the desired direction. The result of DoA estimation and the DoA estimation error by varying the signal to noise ration and the number of interfering signal and power of each type antenna was calculated by computer simulation. As a result of simulation, the other propose antenna has good performance excluding the stack 3D antenna in DoA estimation and the Curved-B type antenna has more superior performance when increasing the number of interfering signal and power in the DoA estimation error.

• 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.48 no.8
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• pp.15-26
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• 2011

In this paper, we present a new beamforming scheme for a downlink of multiuser multiple-input multipleoutput (MIMO) communication systems. Recently, a block-diagonalization (BD) algorithm has been proposed for the multiuser MIMO downlink where both a base station and each user have multiple antennas. However, the BD algorithm is not efficient when the number of supported streams per user is smaller than that of receive antennas. Since the BD method utilizes the space based on the channel matrix without considering the receive combining, the degree of freedom for beamforming cannot be fully exploited at the transmitter. In this paper, we optimize the receive beamforming vector under a zero forcing (ZF) constraint, where all inter-user interference is driven to zero. We propose an efficient algorithm to find the optimum receive vector by an iterative procedure. The proposed algorithm requires two phase values feedforward information for the receive combining vector. Also, we present another algorithm which needs only one phase value by using a decomposition of the complex general unitary matrix. Simulation results show that the proposed beamforming scheme outperforms the conventional BD algorithm in terms of error probability and obtains the diversity enhancement by utilizing the degree of freedom at the base station.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.2
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• pp.245-254
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• 2022

In this paper, a design optimization method for anti-jamming GPS antenna is presented. For this purpose, jamming performance analysis criteria and methods are presented. And based on the proposed analysis method, the antenna design elements that can realize the best performance were optimized. The anti-jamming GPS antenna for applying the presented method has a structure in which 7 radiating elements are arranged. Here, six radiating elements were circular arranged, and one element was arranged in the center of the circular arrangement. The optimized antenna design parameter(radius of the circular array) is 0.48 λ. As a result of the simulation, it was confirmed that when the steering angle(theta, phi) of the main lobe was (0°, 0°), the pattern null steering range(based on theta) was 57° to 90°.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.8
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• pp.623-628
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• 2013

The retrodirective array antenna system is operated faster than existing techniques of beamforming due to its less complexity. Therefore, it is effective for beam tracking in the environment of fast vehicle. On the other hand, it also has difficulty in estimating AOA according to multipath environment or multiuser signals. To improve the certainty of estimating AOA), this article proposes hybrid digital retrodirective array antenna systme combined with MUSIC algorithm. In this paper, the digital retrodirective array antenna system is designed according to the number of antenna array by using only one digital PLL which finds angle of delayed phase. And we evaluate the performance of the digital retrodirective array antenna for the high speed tracking application. Performance is studied by simulink when the speed of mobile is 300km/h and the distance between transmitter and receiver is 100m and then we have to confirm the performance of the system in multi path environment. As a result, the mean of AOA (Angle Of Arrival) error is $4.2^{\circ}$ when SNR is 10dB and it is $1.3^{\circ}$ when SNR is 20dB. Consequently, the digital RDA shows very good performance for high speed tracking due to the simple calculation and realization.