• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.6
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• pp.2095-2110
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• 2015

This paper presents a design for a throughput-efficient online relay selection scheme for dual-hop multi-relay cooperative networks. Problems arise with these networks due to unpredictability of the relaying link quality and high time-consumption to probe the dual-hop link. In this paper, we firstly propose a novel probing and relaying protocol, which greatly reduces the overhead of the dual-hop link estimation by leveraging the wireless broadcasting nature of the network. We then formulate an opportunistic relay selection process for the online decision-making, which uses a tradeoff between obtaining more link information to establish better cooperative relaying and minimizing the time cost for dual-hop link estimation to achieve higher throughput. Dynamic programming is used to construct the throughput-optimal control policy for a typically heterogeneous Rayleigh fading environment, and determines which relay to probe and when to transmit the data. Additionally, we extend the main results to mixed Rayleigh/Rician link scenarios, i.e., where one side of the relaying link experiences Rayleigh fading while the other has Rician distribution. Numerical results validate the effectiveness and superiority of our proposed relaying scheme, e.g., it achieves at least 107% throughput gain compared with the state of the art solution.

• Journal of the Optical Society of Korea
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• v.18 no.4
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• pp.330-334
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• 2014

In this paper, we present an incoherent dual-parallel modulation linearized optical link employing two different optical wavelengths. Comparing with previous dual-parallel modulation, this linearization method prevents the recreation of distortion products and can be readily implemented. Furthermore, a dual-wavelength dual-parallel modulation linearized optical link constructed with the commercially available devices is experimentally demonstrated with a spurious-free dynamic range of $122.5dB.Hz^{4/5}$. More than 25 dB suppression of the intermodulation distortion, 15.6 dB improvement of spurious-free dynamic range and 1.5 dB improvement of compression dynamic range are achieved after linearization.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2008.10a
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• pp.308-311
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• 2008

The ant colony optimization (ACO) is a metaheuristic inspired by the behavior of real ants. Recently, ACO has been widely used to solve the difficult combinatorial optimization problems. In this paper, we propose an ACO algorithm to solve the two disjoint paths problem with dual link cost structure (TDPDCP). We propose a dual pheromone structure and a procedure for solution construction which is appropriate for the TDPDCP. Computational comparisons with the state-of-the-arts algorithms are also provided.

• Korea Journal of Hospital Management
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• v.22 no.4
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• pp.102-112
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• 2017

[purpose] This study was conducted to identify how a hospital's outsourcing workers' QWL influences Turnover Intention and to determine Dual Commitment cause any discrepancies in regards to the link between QWL and Turnover Intention. [Methodology/Approach] The study is based on 254 survey sheets answered by outsourcing employees working at general hospitals with more than 300 beds in Seoul and the methods of analysis used are as follows: reliability analysis, correlation analysis, multiple regression analysis, and hierarchical regressions analysis. [Findings] The study results First, analyzing how different types of QWL (individual, organizational, managemental) influence Turnover Intention, R2 turned out to be 30.7% and organizational factors and managemental factors show a statistically significant difference. In addition, organizational and managemental factors have negative effects on Turnover Intention while that of organization factors has a bigger influence. Second, verifying regulation effects of Dual Commitment in regards to the link between QWL and Turnover Intention, it is learned that Dual Commitment (hiring firm) has no regulation effects on the link. However, it does have a regulation effect on the link between QWL (managemental) and Turnover Intention. Moreover, after verifying regulation effects of Dual Commitment (client's firm), it is learned that it has regulation effect on the link between QWL (organizational and managemental) and Trunover Intention. [Practical Implications] In conclusion, lower Turnover Intention, it is necessary to impose tasks that suit the employees' competence and to encourage efficiency throughout clear communications and accurate directions.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.19-22
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• 2005

In order to achieve high capacity and reliable link quality in user communication, this paper proposes a new concept of virtual cell: the Dual Virtual Cell(DVC), and DVC employment strategy based on DWCS. The proposed system uses two kinds of virtual cell. One is the AVC(Active Virtual Cell) which exists for actual traffic and the other is the CVC(Candidate Virtual Cell) which contains a set of candidate antennas to protect user's link quality from performance degradation or interruption. And also this system aims to reduce MT's overloads and acheive a prompt link change successfuly by introducing DVC structure which makes it possible for network to monitor real-time channel and to conrol communication links. The proposed system constructs DVC by using antenna selection method and improves frame error performance with employing Space-Time Trellis Code(STTC).

• Journal of Power Electronics
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• v.15 no.6
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• pp.1421-1428
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• 2015

The efficiency and reliability of the dual-buck inverter (DBI) were greatly improved by eliminating the shoot-through problem and optimally designing the freewheeling diode. The traditional DBI suffers from large harmonic components with low output voltage and large capacity output filter inductor. To overcome the aforementioned disadvantages, a modified DBI (MBDI) was proposed by adopting a quasi-resonant link and pulse density modulation (PDM). This paper first introduces the working principle of the MBDI and PDM, and then the selection principle of system parameters is presented. Finally, a mathematical model of the MBDIis built, and an experiment prototype is set up. Simulation and experimental results verify the correctness of the theoretical analysis and the feasibility of the scheme.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.3
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• pp.40-47
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• 2012

In dual-hop relaying systems, the conventional partial relay selection is based on the channel information only for the first hop. On the other hand, the efficient partial relay selection is based on the channel information for the hop with the minimum of the average channel powers for the first and second hops at each end-to-end link since the correlation coefficient between the end-to-end link quality and the link quality of the hop with the minimum of the average channel powers for the first and second hops is larger than that between the end-to-end link quality and the link quality of the other hop. In this paper, the outage probability of the conventional partial relay selection and the efficient partial relay selection in dual-hop decode-and-forward relaying systems is analyzed for non-identically distributed Rayleigh fading channels. Through numerical investigation, the outage performance of the efficient partial relay selection is compared with the outage performances of the conventional partial relay selection and the best relay selection based on all the channel information for the first and second hops.

• Journal of Korea Multimedia Society
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• v.21 no.4
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• pp.493-498
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• 2018

In this paper, we provide the performance analyses of a dual-hop amplify-and-forward(AF) relay transmission composed of asymmetric radio-frequence(RF) and free-space optical(FSO) links. In the mixed RF/FSO system, a relay is equipped with two receive antennas for RF signals and one additional transmit antenna for FSO signals. In order to improve a performance of RF link, a switch-and-stay (SSC) diversity technique is applied at the relay which can provide a proper link performance with a low complexity. Specifically, we offer the performance analyses of the proposed system in terms of outage probability and secrecy outage probability. In numerical examples, we compare the system performances with no diversity and selection combining systems and verify our analytical results via computer-based Monte-Carlo simulations.

• The KIPS Transactions:PartA
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• v.12A no.6 s.96
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• pp.557-562
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• 2005

Throughput and latency of interconnection network are important factors of the performance of multiprocessor systems. The dual-link CC-NUMA architecture using point-to-point unidirectional link is one of the popular structures in high-end commercial systems. In terms of optimal path between nodes, several paths exist with the optimal hop count by its native multi-path structure. Furthermore, transaction latency between nodes is affected by congestion of links on the transaction path. Hence the transaction latency may get worse if the transactions make a hot spot on some links. In this paper, I propose a dynamic transaction routing algorithm that maintains the balanced link utilization with the optimal path length, and I compare the performance with the fixed path method on the dual-link CC-NUMA systems. By the proposed method, the link competition is alleviated by the real-time path selection, and consequently, dynamic transaction algorithm shows a better performance. The program-driven simulation results show $1{\~}10\%$ improved fluctuation of link utilization, $1{\~}3\%$ enhanced acquirement of link, and $1{\~}6\%$ improved system performance.

• The KIPS Transactions:PartA
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• v.11A no.3
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• pp.199-206
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• 2004

Under the multiprogrammed situation, the performance of multiprocessor system is affected by the process allocation policy of the operating systems. The lowest communication cost can be achieved when the related processes positioned to the adjacent processors. While the effective allocation is quite difficult to the real situation, and the processing of the allocation policy consumes some computation time. The dual-ring CC-NUMA systems exhibit a quite performance difference according to the process a1location policy due to a lot of unbalanced memory transactions on the interconnection networks. In this paper, I propose a load balanced dual-link CC-NUMA system that does not requires the processes allocation policy. By the program-driven simulation results. the proposed system shows no remarkable difference according to the allocation policy while the dual-ring systems shows 10％ performance improvement by the process allocation. In addition, the proposed system outperforms the dual~ring systems about 1.5 times.