• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.1
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• pp.41-47
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• 2006

This paper presents harmonic evaluation of an IAT(Intra Airport Transit) system in Incheon International Airport. It will be used for electric vehicles with 80[kW] per car produced by Mitsubishi Heavy Industries Ltd, and which is constructed with SIV(Static Inverter), VVVF controller and two induction motor. The vehicles operated in the IAT system can be treated as rapidly changing DC loat and at a feeding substation, 3-phase electric power is transferred to DC 750[V] by rectifier. Since vehicles are changing continuously, the voltages for the load fluctuate in the IAT system, and moreover, the voltage fluctuation generates high-order harmonics. It results the difficulty in maintaining power quality in KEPCO systems' side. The power quality of the IAT system in Incheon International Airport is evaluated using PSCAD/EMTDC simulator in the paper. The THD(Total Harmonic Distortion) of voltages and TDD(Total Demand Distortion) of currents, indices are calculated for the IAT system using the results of PSCAD/EMTDC dynamic simulation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.717-720
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• 2007

This paper presents a novel scheme that quickly searches for the optimal direction of multiple directional antennas, and locks on to it for high-speed millimeter wavelength transmissions, when communications to another antenna directional are disconnected. The proposed method utilizes a modified genetic algorithm, which selects a superior initial group through preprocessing in order to solve the local solution in genetic algorithm. TDD (Time Division Duplex) is utilized as the transfer method and data controller for the antenna. Once the initial communication is completed for the specific number of individuals, no longer antenna's data will be transmitted nil each station processes GA in order to produce the next generation. After reproduction, individuals of the next generation become the data, and communication between each station is made again. In order to verify the effectiveness of the proposed system, simulation results of 1:1, 1:2, 1:5 directional antennas and experiment results of 1:1 directionalantennas confirmed the efficiency of the proposed method. The 16bit split is 8bit, but it has similar performance as 16bit gene.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.9A
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• pp.717-727
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• 2003

The HIPERLAN/2(HIgh PERformance Local Area Network Type2) is one of the wireless LAN standards for providing raw data rates of up to 54 Mbps. The MAC protocol of HIPERLAN/2 is based on TDMA/TDD, and resources in one MAC frame can be allocated dynamically by Access Point(AP). The random channel(RCH) is defined for the purpose of giving a mobile terminal the opportunity to request transmission resources in the uplink MAC frames. It is desirable that the number of RCHs is dynamically adapted by the AP depending on the current traffic situation. Allocation of excessive RCHs may waste radio resources and insufficient RCHs compared to traffic loads may result in many collisions in access attempts. We propose an RCH allocation scheme based on split algorithm in HIPERLAN/2. The simulation and analytic results show that the proposed scheme achieves a higher channel throughput, lower access delay and delay jitter than previously proposed RCH allocation schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6A
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• pp.455-464
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• 2005

In this paper, we implement resource allocation algorithm based on the WiBro system which including OFDMA, TDD, and we propose the algorithm in order to increase bandwidth efficiency. In this algorithm, data is allocated from the subchannel which has large channel gain to the subchannel which has small channel gain with maximum modulation order. The moment total power is more than available power, the modulation order of the latest subchannel is adjusted. The problem of decreasing of throughput in large channel attenuation environment is solved by allocating additional power. Still, this algorithm has large bandwidth efficiency.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.2 s.314
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• pp.39-45
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• 2007

This paper presents a novel scheme that quickly searches for the sweet spot of multiple array antennas, and locks on to it for high-speed millimeter wavelength transmissions, when communications to another antenna array are disconnected. The proposed method utilizes a modified genetic algorithm, which selects a superior initial group through preprocessing in order to solve the local solution in agenetic algorithm. TDD (Time Division Duplex) is utilized as the transfer method and data controller for the antenna. Once the initial communication is completed for the specific number of individuals, no longer antenna's data will be transmitted until each station processes GA in order to produce the next generation. After reproduction, individuals of the next generation become the data, and communication between each station is made again. Simulation results of 1:1, 1:2, 1:5 array antennas confirmed the efficiency of the proposed method. The 16bit split is 8bit, but it has similar performance as 16bit gene.

• KIISE Transactions on Computing Practices
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• v.21 no.2
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• pp.115-120
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• 2015

The Testing Frontier Capability Assessment Model (TCAM) is based on ISO/IEC 9126, TMMi and TPI. Since ISO/IEC 9126, TMMi and TPI were made over 10 years ago, TCAM faces the problem that it can not assess and analyze the capability of small businesses that employ new software development methods or processes, for example Agile, TDD(Test Driven Development), App software, and Web Software. In this paper, a method to improve the problem is proposed. The paper is composed of the following sections: 1) ISO/IEC 9126, ISO/IEC 25010 and ISO/IEC/IEEE 29119 part 2 review 2) TCAM review 3) software product quality perspective comparison, and analysis between ISO/IEC 9126, ISO/IEC 25010 and TCAM 4) comparison, and analysis between ISO/IEC/IEEE 29119 part2 and TCAM and 5) proposal for the improvement of TCAM.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.5A
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• pp.496-503
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• 2010

The implementation of a RF transceiver for WRAN(Wireless Regional Area Network) system based on IEEE 802.22 standard using Cognitive Radio technology is presented in this paper. A CMOS RF transceiver IC for WRAN system operates in VHF/UHF(54~862MHz) broadband, and employs dual-path direct-conversion configuration and the in-band harmonic distortions are effectively suppressed by exploiting the dual-path direct conversion architecture. For 64QAM(3/4 coding rate) OFDM signal, an EVM of <-31.4dB(2.7%) has been achieved at 10dBm off-chip PA output power and the total chip area with pads is 12.95 mm2. The experimental results show that the proposed CMOS RF transceiver IC has perfect performance for WRAN system based on TDD(Time Division Duplex) mode.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5C
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• pp.398-405
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• 2005

The multiuser detection (MUD) based wireless receiver requires more accurate channel estimation than the single user detection (SUD) schemes such as Rake receiver, and hence the post processing is required for MUD to clean up the estimated channel coefficients by eliminating the noise only coefficients. The adaptive post processing method is proposed in order to provide more accurate channel responses and the power level of the background noise and interferences at the cost of the negligible processing delay compared to the conventional method based on the threshold test with the threshold value relative to the noise variance. The simulations are performed in 3GPP-TDD mode environment. The results show that the noise estimation error of the proposed method is maximum $10\%$, which is much smaller than $50\%$ maximum error of the conventional method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.10
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• pp.885-894
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• 2012

Currently, Demand of data traffic has rapidly increased by popular of smart device. It is very difficult to accommodate demand of data traffic by limited resource of base station (BS). To solve this problem, method has proposed that the Device-to-Device (D2D) reduce frequency overload of the BS and all of the user equipment (UE) inside the BS and neighbor BS don't allow communicating directly to BS. However, in LTE-Advance system cellular link and sharing radio resources of D2D link, the strong interference of the cellular network is still high. So we need to eliminate or mitigate the interference. In this paper, we use the transmission power control method and Soft Frequency Reuse (SFR) resource allocation method to mitigate the interference of the cellular link and D2D link. Simulation results show that the proposed scheme has high performance in terms of Signal to Noise Ratio (SINR) and system average throughput.

• 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.