• IEIE Transactions on Smart Processing and Computing
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• v.5 no.5
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• pp.346-348
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• 2016

Coordinated multi-point transmission is a candidate technique for next-generation cellular communications systems. We consider a system with multiple cells in which base stations coordinate with each other by sharing user channel state information, which mitigates inter-cell interference (ICI), especially for users located at the cell edge. We introduce a new user scheduling method that considers both ICI and intra-cell orthogonality. Due to the influence of ICI cancellation and the loss reduction of effective channel gain during the beamforming process, the proposed method improves the system sum rate, when compared to the conventional method, by an average of 0.55bps/Hz for different numbers of total users per cell.

• Electronics and Telecommunications Trends
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• v.21 no.2 s.98
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• pp.170-183
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• 2006

모뎀 진단/감시 장치(DM)는 기지국 DM 데이터 수집부와 단말 DM 데이터 수집부로각각 구분되어 DM 장치 내에서 기지국/단말 모뎀 플랫폼을 수용한다. 기지국 변조기, 기지국 동기, 기지국 채널 디코더, 기지국 복조기의 데이터는 기지국 DM 데이터 수집부에서 수집하고, 단말 변조기, 단말 동기, 단말 채널 디코더, 단말 복조기의 데이터는 단말 DM 데이터 수집부에서 수집하여 각각 수집된 데이터를 호스트 PC에서 분석하여 물리 계층 송수신 데이터 및 각종 통계 정보를 사용자 및 운용자가 확인할 수 있도록GUI로 화면에 표시해 준다. 모뎀 진단/감시 장치(DM)는 무선 전송 시스템(HM20)MIMO 구조 기지국/단말 모뎀의 물리 계층에 대한 상태 진단 및 감시 기능을 수행하여 모뎀 개발 과정에서 개발자에게 디버깅을 쉽게 하기 위한 장치로 사용된다. 또한 기지국 모뎀과 단말 모뎀의 유지 보수시 오류 발견을 위한 장치로 사용하기 위함이다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.1
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• pp.110-116
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• 2012

This paper proposes a new diversity antenna which is the base of MIMO, tunable and reconfigurable antennas. The antenna has a small size and high inter-antenna isolation resulting from the compact radiating element comprising a meandered line and an open-loop combined in one limited uniplanar space and a modified T-shaped decoupling structure, respectively. In a WiMAX band, the radiating element and the entire antenna are $0.092{\lambda}$ and $0.2216{\lambda}$ in size, which shows effective size-reduction and the gain and efficiency of the proposed antenna attached to the ground of a handheld device are 3.7dBi and 56% acceptable to the industrial standard.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.533-534
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• 2013

This paper is concerned with the active vibration control of rectangular plate equipped with MFC actuators. To this end, the dynamic model of the rectangular plate bonded with MFC sensors and actuators was derived by means of the Rayleigh-Ritz method. The MFC actuator and sensor were modeled based on the pin-force assumption. The theoretical model was then validated experimentally. The multiinput and multi-output (MIMO) Positive Position Feedback (PPF) controller was designed based on the natural mode shapes and implemented using dSpace system and Simulink. The proposed control algorithm was applied to the cantilever plate having two MFC wafers having both sensor and actuator. Numerical and experimental investigations were carried out. Both theoretical and experimental result shows that the proposed control algorithm can effectively suppress vibrations of cantilever plate.

• ETRI Journal
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• v.44 no.1
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• pp.117-124
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• 2022

In this paper, the performance of precoding-aided differential spatial modulation (PDSM) systems with optimal transmit antenna subset (TAS) selection is examined analytically. The average bit error rate (ABER) performance of the optimal TAS selection-based PDSM systems using a zero-forcing (ZF) precoder is evaluated using theoretical upper bound and Monte Carlo simulations. Simulation results validate the analysis and demonstrate a performance penalty < 2.6 dB compared with precoding-aided spatial modulation (PSM) with optimal TAS selection. The performance analysis reveals a transmit diversity gain of (N_T-N_R+1) for the ZF-based PDSM (ZF-PDSM) systems that employ TAS selection with N_T transmit antennas, N_S selected transmit antennas, and N_R receive antennas. It is also shown that reducing the number of activated transmit antennas via optimal TAS selection in the ZF-PDSM systems degrades ABER performance. In addition, the impacts of channel estimation errors on the performance of the ZF-PDSM system with TAS selection are evaluated, and the performance of this system is compared with that of ZF-based PSM with TAS selection.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7A
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• pp.568-577
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• 2005

In this paper, we propose the transmission scheme for the space-time block coded spatial multiplexing systems that have adaptive rate and power allocation per each transmit antenna through the use of feedback information related to channel state. Simulation results show that the adaptive power and rate transmission scheme gain more than 4.5 dB over conventional equal-power and rate transmission scheme.

• Journal of Korea Society of Industrial Information Systems
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• v.16 no.4
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• pp.19-26
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• 2011

Relay-assisted multiple input multiple output (MIMO) technique has become a promising candidate for next generation broadband wireless communications. In this paper, we propose maximum ratio combining (MRC) minimum mean-square-error (MMSE) equalization for single carrier-frequency domain equalizer (SC-FDE) in amplify-and-forward (AF) relaying networks. The performance of SC-FDE system can be improved considerably by achieving both the diversity gain and the MMSE equalization gain when the signals from source-destination (S->D) and source-relay-destination (S->R->D) are combined and equalized by means of the MMSE criteria. We find the weighting coefficients of MRC combining and the tap coefficients of MMSE equalizer for SC-FDE in AF relaying networks. Simulation results show that the proposed relay-based system considerably outperforms the conventional SC-FDE system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7C
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• pp.644-651
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• 2007

In multiple antenna systems, vertical Bell Labs Layered Space-Time (V-BLAST) systems enable very high throughput by nulling and cancelling at each layer detection. In this paper, we propose a V-BLAST system which combines with signal space diversity technique. The benefit of the signal space diversity is that we can obtain an additional gain without extra bandwidth and power expansion by applying inphase/quadrature interleaving and the constellation rotation. Through simulation results, it is shown that the performance of the proposed system is less than 0.5dB away from the ideal upper bound.

• JSTS:Journal of Semiconductor Technology and Science
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• v.11 no.4
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• pp.295-301
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• 2011

A triple-band transceiver module for 2.3/2.5/3.5 GHz mobile WiMAX, IEEE 802.16e, applications is introduced. The suggested transceiver module consists of RFIC, reconfigurable/multi-resonance MIMO antenna, embedded PCB, mobile WiMAX base band, memory and channel selection front-end module. The RFIC is fabricated in $0.13{\mu}m$ RF CMOS process and has 3.5 dB noise figure(NF) of receiver and 1 dBm maximum power of transmitter with 68-pin QFN package, $8{\times}8\;mm^2$ area. The area reduction of transceiver module is achieved by using embedded PCB which decreases area by 9% of the area of transceiver module with normal PCB. The developed triple-band mobile WiMAX transceiver module is tested by performing radio conformance test(RCT) and measuring carrier to interference plus noise ratio (CINR) and received signal strength indication (RSSI) in each 2.3/2.5/3.5 GHz frequency.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.5
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• pp.383-388
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• 2018

This paper presents a 1.8 GHz six-port-based impedance modulator using CMOS technology, which can select an arbitrary load impedance with switch control. The proposed 1.8-GHz impedance modulator comprises a Wilkinson power divider, three quadrature hybrid couplers, and four SP3T switches for each load impedance selection. The measured insertion loss of -13 dB and the input/output return losses of >10 dB are achieved in the range of 1.4~2.2 GHz. The low drop output regulator for a stable 3.3 V DC power and the serial peripheral interface(SPI) for an easy digital control are integrated. The chip size, including the pads, is $1.7{\times}1.8mm^2$.