• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.3
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• pp.146-154
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• 2016

Visible light communication using LED is a technique for transmitting digital data using the light of the LED. Recently, high-speed data rate plays an important role. Therefore, many scholars have researched the MIMO-VLC which is able to increase data rate using a lot of LED transmitters. However, it has problems such as light interference and flicker when transmitting different bit. Many researcher have focused on reduce interference. However it is not considered about flicker problem. Flicker is defined unstable brightness. It occurred the tired of human eyes, lowers eyesight and also decreases concentration. In order to solve this flicker problem in MIMO-VLC, we propose the PFM(Parallel Flicker Mitigation) code. PFM code using combinatorial theory can maintain constant brightness the whole bit duration. Therefore, it is possible to assure the brightness by confirm simulation results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.10
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• pp.987-994
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• 2011

This paper presents An efficient method of antenna placement considering EMI(Electromagnetic Interference) between equipments which are mounted on the UAV(Unmanned Air Vehicle). The analysis is accomplished for voice communication radio, control datalink, TCAS(Traffic Alert Collision & Avoidance System) and GPS(Global Positioning System) which are vulnerable to EMI because the frequencies are close to each other. There are two steps for analysis procedure : The first one is selecting antenna position on the UAV by monitoring return loss and pattern variation of each antenna. The second one is analyzing EMI via antennas between equipments. In the EMI analysis, spurious level of each transmitter, coupling level between antennas and system noise property are considered. This procedure can be used to predict EMI between equipments in development stage.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.12
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• pp.1125-1134
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• 2013

Small cells such as pico or femto cells are promising as a solution to cope with higher traffic explosion and the large number of users. However, the users within small cells are likely to suffer severe inter-cell interference (ICI) from neighboring base stations (BSs). To tackle this, several papers suggest BS transmit power on/off control algorithms which increase edge user throughput. However, these algorithms require centralized coordinator and have high computational complexity. This paper makes a contribution towards presenting fully distributed and low complex joint BS on/off control and user scheduling algorithm (FDA) by selecting on/off pattern of BSs. Throughput the extensive simulations, we verify the performance of our algorithm as follows: (i) Our FDA provides better throughput performance of cell edge users by 170% than the algorithm without the ICI management. (ii) Our FDA catches up with the performance of optimal algorithm by 88-96% in geometric average throughput and sufficiently small gap in edge user throughput.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.2
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• pp.122-127
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• 2001

The high stability of the interference pattern is very important in the case of measuring interference when a phase noise like a vibration occurs in the measuring environment. In this paper, we proposed the method of phase noise filtering by BaTiO$_3$ with the characteristic of SPPCM. Also, a beam with a shape of an ellipse was incident into BaTiO$_3$ by using the tilted lens so as to improve the reflectivity and the response time. And we confirmed the result by optical experiment.

• Journal of IKEEE
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• v.17 no.3
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• pp.260-266
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• 2013

The open bit line is vulnerable to noise compared to the folded bit line when read/write for the DRAM. According to the increasing DRAM densities, the core circuit operating conditions is exacerbated by the noise when it comes to the open bit line 6F2(F : Feature Size) structure. In this paper, the interference effects were analyzed by the data patterns between the bit line by experiments. It was beyond the scope of existing research. 68nm Tech. 1Gb DDR2, Advan Tester used in the experiments. The noise effects appears the degrade of internal operation margin of DRAM. This paper investigates sense amplifier power line splits by experiments. The noise can be improved by 0.2ns(1.3%)~1.9ns(12.7%), when the sense amplifier power lines split. It was simulated by 68nm Technology 1Gb DDR2 modeling.

• Korean Journal of Optics and Photonics
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• v.12 no.1
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• pp.17-24
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• 2001

Two-dimensional binary-phase diffraction gratings which can be employed to fabricate two- and three-dimensional periodic structures are designed and analyzed using rigorous coupled-wave analysis. These gratings serve as phase-masks which generate several diffracted waves from a normally incident beam and thus can produce a periodic interference pattern in space via nearfield holography. The properties of the diffracted beams can be controlled by varying the polarization and wavelength of the incident beam, surface-profile, groove depth and duty cycle of the mask. For the two-dimensional structure, optimum results can be obtained when the diffraction efficiency of the zero-order beam is minimized while that of the first-order maximized. On the other hand, when the diffraction efficiency of the zero-order is appreciable or even greater than other orders, we can obtain a variety of three-dimensional interference patterns which may be used to fabricate photonic crystals of tetragonal-body-centered and hexagonal structures in a submicron scale. scale.

• Journal of the Institute of Convergence Signal Processing
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• v.17 no.1
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• pp.1-9
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• 2016

In this paper, for the improvement of quality of service(QoS) performance of heterogeneous networks, multi-cell scheduling is proposed. In order to implement the proposed algorithm, for the recognition of the impact on the throughput performance of users, macro-pico-cells that form distributed architecture were proposed. In operating heterogeneous networks, considering the centralized structure, a macro-RRH(Remote Radio Head) deployment scenario was proposed. For interference mitigation of the proposed system, by applying the optional sub-frame, through CQI(Channel Quality Indicator) measurement for each sub-frame period, constraint conditions were measured according to system situations. For the simplification, the pattern of the same ABS muting was assumed. In the above two multi-cell environments, the algorithm of high-speed load balancing maintenance was proposed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.12A
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• pp.1276-1285
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• 2007

Since the TD-SCDMA (Time Division-Synchronous Code Division Multiple Access) system is based on TDD (Time Division Duplexing), the uplink and downlink can be allocated asymmetrically according to the traffic e.g. Web browsing. Although this asymmetric allocation can increase the frequency utilization, it may cause time slot opposing, which implies the time slot is assigned in opposing direction between cells. The time slot opposing can generate significant interference between cells, which results in severe performance degradation. In the paper, a novel dynamic channel allocation (DCA) is proposed in the TD-SCDMA system, to mitigate the impact of time slot opposing considering smart antenna. When the smart antenna is applied in the system, the inter-cell interference is largely affected by beam pattern and beam direction between neighboring cells. Therefore, the time slot opposing and smart antenna should be considered together in the DCA. The intensive simulations show that the proposed scheme can improve the system capacity compared to the conventional DCA schemes.

• Journal of Communications and Networks
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• v.15 no.4
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• pp.383-397
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• 2013

In this paper, the sensitivity of massive antenna arrays and digital beamforming to radio frequency (RF) chain in-phase quadrature-phase (I/Q) imbalance is studied and analyzed. The analysis shows that massive antenna arrays are increasingly sensitive to such RF chain imperfections, corrupting heavily the radiation pattern and beamforming capabilities. Motivated by this, novel RF-aware digital beamforming methods are then developed for automatically suppressing the unwanted effects of the RF I/Q imbalance without separate calibration loops in all individual receiver branches. More specifically, the paper covers closed-form analysis for signal processing properties as well as the associated radiation and beamforming properties of massive antenna arrays under both systematic and random RF I/Q imbalances. All analysis and derivations in this paper assume ideal signals to be circular. The well-known minimum variance distortionless response (MVDR) beamformer and a widely-linear (WL) extension of it, called WL-MVDR, are analyzed in detail from the RF imperfection perspective, in terms of interference attenuation and beamsteering. The optimum RF-aware WL-MVDR beamforming solution is formulated and shown to efficiently suppress the RF imperfections. Based on the obtained results, the developed solutions and in particular the RF-aware WL-MVDR method can provide efficient beamsteering and interference suppressing characteristics, despite of the imperfections in the RF circuits. This is seen critical especially in the massive antenna array context where the cost-efficiency of individual RF chains is emphasized.

• Genomics & Informatics
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• v.3 no.4
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• pp.154-158
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• 2005

Germ-line mutations of the BRCA1 gene confer an increased risk for breast and ovarian cancers. BRCA1 in female cells is directly related with the maintenance of the inactive X chromosome (Xi). The effect by the loss of the BRCA1 function on the X chromosome gene expression remains unclear in cancer cells. We attempted to investigate the expression pattern of the X-linked genes by performing BRCA1 knockdown via RNA interference in the MCF7 breast cancer cell line. The transcriptional and translational levels of BRCA1 were decreased over 95% in the MCF7 cells after BRCA1 knockdown. The expression patterns of one hundred ninety X-linked genes were profiled by the X chromosome-specific cDNA arrays. A total of seven percent of the X-linked genes (14/190) were aberrantly expressed by over 2-fold in the MCF7-BRCA1 knockdown cells, which contained two up-regulated genes (2/190, 1 %) and 12 down-regulated genes (12/190, 6.3%). It is interesting that 72% of the aberrantly expressed X-linked genes were located on the Xq (10/14,) region. Our data suggests that BRCA1 may not be important to maintain X chromosome inactivation in cancer because the BRCA1 knockdown did increase the expression of the only one percent of X-linked genes in the human breast cancer cells.