• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12A
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• pp.1214-1222
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• 2006

In this paper, an efficient direction-r)f-arrival based adaptive beamforming algorithm for orthogonal frequency-division multiple-access smart antenna systems is proposed. The proposed algorithm provides a high performance by steering main beams to the directions of a desired signal, whereas steering nulls to the directions of the interference, using the estimated directions. The beamforming outputs obtained by steering the main beams to the distinct directions of resolvable multipath signals are combined in a maximal ratio manner to exploit angular diversity gain. The performance elf the proposed algorithm is finally evaluated in cellular mobile environments to verify its efficiency and is compared with that of least-squares beamforming algorithm, by taking the WiBro system as a target system.

• ETRI Journal
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• v.40 no.1
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• pp.26-38
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• 2018

To overcome considerable path loss in millimeter-wave propagation, high-gain directional beamforming is considered to be a key enabling technology for outdoor 5G mobile networks. Associated with beamforming, this paper investigates propagation power loss characteristics in two aspects. The first is beamwidth effects. Owing to the multipath receiving nature of mobile environments, it is expected that a narrower beamwidth antenna will capture fewer multipath signals, while increasing directivity gain. If we normalize the directivity gain, this narrow-beamwidth reception incurs an additional power loss compared to omnidirectional-antenna power reception. With measurement data collected in an urban area at 28 GHz and 38 GHz, we illustrate the amount of these additional propagation losses as a function of the half-power beamwidth. Secondly, we investigate power losses due to steering beam misalignment, as well as the measurement data. The results show that a small angle misalignment can cause a large power loss. Considering that most standard documents provide omnidirectional antenna path loss characteristics, these results are expected to contribute to mmWave mobile system designs.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.1
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• pp.43-52
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• 2010

In this paper, the mobile-WiMAX (m-WiMAX) using the Smart antenna technique is implemented. Experiments are performed to compare Smart antenna system with conventional single antenna system. To implement the m-WiMAX smart antenna system there are many considerations, key issues of which are symbol time acquisition, beamforming, calibration. In the paper, symbol time acquisition, beamforming, calibration are implemented in WiMAX Smart antenna system and we verified that Smart antenna system is superior to single antenna system. The experimental results show 5.5 dB performance enhancement of implemented Smart antenna system in throughput compared with a single antenna system. The experimental result is almost same as theoretical result of 6 dB.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.1
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• pp.11-17
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• 2017

In this paper, an 8-direction switched beamforming antenna system at 28GHz frequency band is described for 5th generation wireless communication. This system is composed of an $8{\times}8$ Butler matrix and an 8-element patch array antenna. The antenna system switches beams in 8-direction in the wide range of ${\pm}40^{\circ}$. The antenna spacing is $0.65{\lambda}$ to achieve ${\pm}40^{\circ}$ steering range. Designed results show that the 8-direction beams are placed at ${\pm}6^{\circ}$, ${\pm}17^{\circ}$, ${\pm}28^{\circ}$, ${\pm}40^{\circ}$ offset from the center. Parasitic radiation effect from the large dimension Butler matrix need to be suppressed by employing a stripline structure.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.3
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• pp.1-5
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• 2011

In this thesis, we have developed novel geometrical analysis method for the double constraints linear constraint minimum variance (LCMV) beamforming algorithm. The proposed analysis method was matched well with the computer simulation result.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.4
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• pp.643-650
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• 2020

The phased array antenna has an advantage enabling rapid beam aim without the mechanical rotation of the antenna, because it arranges multiple elements in a linear or planer (grid or circular) and electronically controls the phase for each element. The planar array antenna is generally used a grid array and a circular array, and the circular form has the higher resolution comparing to the grid form due to the its structural characteristics. However, a concentric circular array (CCA) or a concentric ring array (CRA) with multiple circular arrays which each has different radius is used in the limited area, because the entire radius should be increased for the circular array with a number of elements. In this paper, we introduce the angle-of-arrival (AOA) estimator for an adaptive beamforming satellite system based on CRA and provide the simulation results for performance evaluation. In addition, simulation results are compared and analyzed to the case for the circular array antenna.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.249-254
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• 2002

In this paper, we propose an adaptive Beamforming Algorithm, called MC-LMS, for adaptive antenna applied to an MC-CDMA system. New method for updating the weight vector based on the MSE criterion is derived. Computer simulations show that MC-LMS algorithm is capable of rejecting co-channel interference that affects the MC-CDMA system. Thus, the BER performance of the MC-CDMA system is much higher than that of the MC-CDMA system without using adaptive antenna and that of the DS-CDMA system with adaptive antenna in multi-path Rayleigh fading channel.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.311-316
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• 2002

In this paper, an adaptive beamforming algorithm, based on the Minimum Mean Squared Error (MMSE) criterion, is devised fer adaptive antenna applied to an MC-CDMA system. A new method for updating the weight vector is derived. Computer simulations show that proposed algorithm is capable of rejecting co-channel interference that affects the MC-CDMA system. Thus, the BER performance of the MC-CDMA system is improved compared with that of the MC-CDMA system without using adaptive antenna and that of the DS-CDMA system with adaptive antenna in multi-path Ricean fading channel.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.409-413
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• 2008

In this paper, we introduce a platform of advanced multiple antenna system based on orthogonal frequency-division multiplexing (OFDM). The advanced multiple antennas have beamforming gain using array antenna. In array antenna systems, received signal has phase delay caused distance of each antennas, therefore it should compensate with optimum weight vector which calculated by Lagrange algorithm. To implement the presented above procedures using Digital Signal Processor (DSP), we should fixed-point design. The performance of implemented platform is verified through MATLAB$^{(R)}$ simulations with various signal environments.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.10
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• pp.5049-5062
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• 2016

This paper analyzes the secrecy performance of an amplify-and-forward (AF) relay network, where a multi-antenna eavesdropper attempts to overhear the transmitted message from a multi-antenna source to a multi-antenna destination with a single antenna relay. Firstly, we derive the approximate analytical expressions for the secrecy outage probability (SOP) and average secrecy rate (ASR) of the relay network. Then, asymptotic expressions of SOP and ASR at high main-to-eavesdropper ratio (MER) are also provided to reveal the diversity gain of the secure communication. Finally, numerical results are given to verify the theoretical analysis and show the effect of the number of antennas in the considered relay network.