• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.10
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• pp.4804-4822
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• 2017

Coverage problem is a research hot spot in directional sensor networks (DSNs). However, the major problem affecting the performance of the current coverage-enhancing strategies is that they just optimize the coverage of networks, but ignore the maximum number of sleep sensors to save more energy. Aiming to find an approximate optimal method that can cover maximum area with minimum number of active sensors, in this paper, a new scheduling algorithm based on learning automata is proposed to enhance area coverage, and shut off redundant sensors as many as possible. To evaluate the performance of the proposed algorithm, several experiments are conducted. Simulation results indicate that the proposed algorithm have effective performance in terms of coverage enhancement and sleeping sensors compared to the existing algorithms.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.70-73
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• 2002

This paper describes the way to embody the grid coverage and the grid coverage processor which can construct pipelines. The pipeline constructed by the developed grid coverages has internal pipelines that have different resolution and it provides the way of access to very large datasets efficiently. Several operations, such as filtering, image enhancement and band operation, are embedded in the developed grid coverage and grid coverage processor COM components. The practical usefulness of the developed grid coverage and grid coverage processor has been proven by applying them in developing an image processing software for very large images.

• Journal of the Korean institute of surface engineering
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• v.47 no.2
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• pp.68-74
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• 2014

The seed step-coverage enhancement process (SSEP) using Pd/Cu/PVP colloids was investigated for the filling of through silicon via (TSV) without void. TEM analysis showed that the Pd/Cu nano-particles were well dispersed in aqueous solution with the average diameter of 6.18 nm. This Pd/Cu nano-particles were uniformly deposited on the substrate of Si/$SiO_2$/Ti wafer using electrophoresis with the high frequency Alternating Current (AC). After electroless Cu deposition on the substrate treated with Pd/Cu/PVP colloids, the adhesive property between deposited Cu layer and substrate was evaluated. The Cu deposit obtained by SSEP with Pd/Cu/PVP colloids showed superior adhesion property to that on Pd ion catalyst-treated substrate. Finally, by implementing the SSEP using Pd/Cu/PVP colloids, we achieved 700% improvement of step coverage of Cu seed layer compared to PVD process, resulting in void-free filling in high aspect ratio TSV.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.987-992
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• 2012

Magnetic nanoparticles (MNPs) treated with phosphoric acid were used to improve sequence coverage in protein identification by matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). Sample solution of tryptic peptides from proteins was mixed with the MNPs, and the MNPs were separated from the supernatant using a magnet. MALDI mass spectra obtained separately from the supernatant and the MNPs were distinctly different and complementary to each other. Combination of the two spectra led to a significantly increased sequence coverage.

• Communications for Statistical Applications and Methods
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• v.15 no.6
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• pp.875-881
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• 2008

This paper first discusses the existing non-homogeneous Poisson process(NHPP) software reliability growth model(SRGM) frameworks with respect to capability of representing software reliability growth phenomenon. As an enhancement of representational capability a new general coverage-based NHPP SRGM framework is developed. Issues associated with application of the new framework are then considered.

• Journal of Communications and Networks
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• v.18 no.5
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• pp.773-783
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• 2016

Both coordinated multi-point transmission and frequency reuse are effective approaches to mitigate inter-cell interference and improve network coverage. The motivation of this work is to explore the manner to effectively utilize the spectrum resource by reasonably combining cooperation and frequency reuse. The $Mat{\acute{e}}rn$ cluster process, which is appropriate to model networks with hot spots, is used to model the spatial distribution of base stations. Two cooperative mechanisms, coherent and non-coherent joint transmission (JT), are analyzed and compared. We also evaluate the effect of multiple antennas and imperfect channel state information. The simulation reveals that the proposed approach to combine cooperation and frequency reuse is effective to improve the network coverage for users located at both the center and the boundary of the cooperative region.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7A
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• pp.611-619
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• 2005

The present paper proposes two different packet scheduling algorithms in the IEEE 802.16e type TDD-OFDMA downlink, which are the weighted fair scheduling(WFS) and the throughput guarantee scheduling(TGS). The performance of proposed scheduling algorithms are compared to some of conventional schedulers such as round robin(RR), proportional fair(PF), fast fair throughput(FFTH), and fair throughput(FH) in terms of service coverage, effective throughput and fairness at 64 kbps and 128 kbps minimum user throughput requirements. For a relatively smaller throughput(64 kbps) requirement, the proposed algorithms provide higher improvement in the number of users per sector within 95$\%$ service coverage while satisfying the lxEV-DV fairness criterion. For a relatively larger throughput(128 kbps) requirement, the proposed algorithms provide higher coverage enhancement while maintaining the same effective aggregate throughput over PF scheduler.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1A
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• pp.18-26
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• 2009

Various relay technologies have been considered in wireless communication systems to enlarge the coverage and to enhance the system throughput. However, the coverage is limited by its modulation levels and additional time slot(s) is required for relaying. In the paper, by applying the hierarchical modulation to two-relay systems, two-hop relaying can be implemented instead of three hops, and both throughput and coverage can be enhanced. Throughout simulation analysis, the coverage extension is evaluated for different modulation levels and the total throughput is increased by up to two times.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.628-631
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• 2014

Recently, the proliferation of new applications, e.g., mobile TV, Internet gaming, large file transfer, and the various of user terminals, e.g., smart phones and notebooks, has dramatically increased user traffic and network load. In order to meet this traffic growth, vendors and cellular operators are working on the development of new technologies and cellular standards. Within them, small cell deployment has been heralded as one of most promising way to increase both coverage and capacity of future cellular network. Small cell technology enables to improve capacity of cellular radio network by tight cooperation between small cell and macro cell in multi-tier network where small cells are densely deployed within macro cell coverage. In this paper, we describe the deployment scenarios for cooperation between macro cell and small cells and state-of-the-art technologies related to dense small cell deployment. Then, we also provide design principles and standardization trends for small cell enhancement in 3GPP.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.9B
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• pp.876-882
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• 2009

In this paper, we propose a sub-cell coverage control algorithm for enhancement of the cell throughput in OFDMA based relay systems. Relay station (RS) is exploited for improved quality of the received signal in cellular communication systems, especially in shadow areas. However, since a RS requires additional radio resource consumption for the link between the base station (BS) and the RS, we have to carefully control the coverage areas if a mobile station (MS) is serviced via the BS or the RS considering the cell throughput. We consider radio resource reuse as well for the sub-cell coverage configuration by applying various reuse patterns between RSs. We also consider a time varying system by adaptively changing the threshold for coverage depending on the MSs' traffic in the cell. We initially determine the sub-cell coverage of the system depending on the ratio of received signal-interference-noise-ratio (SINR) of the MS from the BS and RSs, respectively. Then, the "sub-cell coverage threshold" varies based on the "effective transmitted bits per sub-channel" with time. Simulation result shows that the proposed "time varying coverage control algorithm" leads to throughput improvement compared to the fixed sub-cell coverage configuration.