• The KIPS Transactions:PartA
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• v.14A no.2
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• pp.99-106
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• 2007

Grid computing, a mechanism which uses heterogeneous systems that are geographically distributed, draws attention as a new paradigm for the next generation operation of parallel and distributed computing. The importance of grid computing concerning communication cost is very huge because grid computing furnishes uses with integrated virtual computing service, in which a number of computer systems are connected by a high-speed network. Therefore, to reduce the execution time, the scheduling algorithm in grid environment should take communication cost into consideration as well as computing ability of resources. However, most scheduling algorithms have not only ignored the communication cost by assuming that all tasks were dealt in one cluster, but also did not consider the overhead of communication cost when the tasks were processed in a number of clusters. In this paper, the functions of original scheduling algorithms are analyzed. More importantly, the functions of algorithms are compared and analyzed with consideration of communication cost within the co allocation environment, in which a task is performed separately in many clusters.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.750-757
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• 2017

Recently, mobile internet traffic has rapidly increased as the huge increase of the smart phone and mobile devices. D2D get attention, because D2D is known that it reduce the traffic load of the base station and also improves the reliability of the network performance. However, D2D has a problem that the efficiency decreases as interference is increased. In this paper, we propose a resource allocation scheme to use the resources efficiently when the D2D link share the cellular resources in the cellular network based the uplink. D2D communication utilizes the location information for allocating resources when the eNB know the location of all devices. The proposed scheme select some cellular user using location informations in order to ensure performance of the D2D communication. and D2D link choose cellular user that performs resource allocation using only selected cellular user. Simulation results show optimal value of resource selection in order to ensure most performance of the D2D communication.

• Journal of the Korean Society for Railway
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• v.15 no.5
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• pp.524-530
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• 2012

Recently, open access policy to railway operation has been widely discussed. Compared to the case of Korea, European countries have dealt with this topic over a few decades. The competition on railway slots incurs an important technological problem about how to optimally allocate railway slots requested from RUs to them. In other words, the authority should be able to coordinate the timetables requested from RUs in the non-discriminatory manner. Related with the coordination, compared to the other European countries, which have done many studies and experiments especially on auction mechanisms, Korean railway has paid less attention to this topic and there have not been any related studies. Our study analyses the state-of-the-arts about the railway slot allocation especially focusing on the auction mechanisms and the associated optimization problems. And we suggest a new railway slot allocation mechanism and related optimization model reflecting the adjustment within the tolerance and the operational policies between railway undertakings.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.4
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• pp.515-521
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• 2020

Recently, data traffic has exploded due to development of various industries, which causes problems about losing of efficiency and overloaded existing networks. To solve these problems, network slicing, which uses a virtualization technology and provides a network optimized for various services, has received a lot of attention. In this paper, we propose a resource allocation method using credit value. In the method using the clustering technology, an operation for selecting a cluster is performed whenever an allocation request for various services occurs. On the other hand, in the proposed method, the credit value is set by using the residual capacity and balancing so that the slice request can be processed without performing the operation required for cluster selection. To prove proposed method, we perform processing time and balancing simulation. As a result, the processing time and the error factor of the proposed method are reduced by about 13.72% and about 7.96% compared with the clustering method.

• Journal of the Korea Society of Computer and Information
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• v.25 no.12
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• pp.83-91
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• 2020

This study aims to identify research topics and examine the trend of Covid19-related papers on DBpia. Applying latent Dirichlet allocation (LDA), we have extracted seven research topics, each of which concerns "International Dynamics", "Technology & Security", "Psychological Impact", "Biomedical-Related", "Economic Impact", "Online Education", and "Religion-Related". In addition, we used the multinomial logistic model to examine the trend of research topics. We found that the papers mainly cover topics related to "International Dynamics" and "Biomedical-Related" before June 2020, but the topics have become diverse since then. In particular, topics regarding "Economic Impact", "Online Education" and "Psychological Impact" has drawn increased attention of researchers. The findings would provide a guideline for collaboration in Covid19-related research, and could serve as a reference work for active research.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.5B
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• pp.449-455
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• 2006

Due to advance in multimedia applications and integrated Internet services, the optical access networks have been actively studied. In particular, Ethernet passive optical network (EPON) has received much attention due to high bandwidth provision with low cost. In EPON system, the data transmission is carried out in two directions: downstream (from OLT to ONU) and upstream (from ONU to OLT). The downstream data is broadcasted to every ONUs, while the upstream data is point-to-point transmitted between each ONU and OLT, where the uplink is shared by all ONUs in the form of TDMA. The bandwidth allocation algorithm is required to efficiently manage the bandwidth on the uplink. The limited algorithm was proposed to enhance the capability of dynamic bandwidth allocation. In this paper, we propose the adaptive limited algorithm to enhance the shortcomings of limited algorithm. The adaptive limited algorithm enhances the dynamics on bandwidth allocation, and at the same time controls the fairness on packet delay. Through the computer simulations, it is shown that the adaptive limited algorithm achieves high dynamic on bandwidth allocation, maintains a good fairness on packet delay between ONUs, and keeps the fairness on the bandwidth on the demand basis.

• IE interfaces
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• v.13 no.3
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• pp.424-430
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• 2000

Supply chain management (SCM) is an area that has recently received a great deal of attention in the business community. While SCM is relatively new, the idea of coordinated planning is not. During the last decades, many researchers have investigated multi-stage inventory problems. However, only a few papers address the problem of cost-optimal coordination of multi-stage inventory control with respect to service measures. Even published approaches have a shortcoming in dealing with a delivery lead time consisted of a shipping time and a waiting time. Assumed that there is no waiting time, or that the delivery lead time is implicitly compounded of a shipping time and a waiting time, the problem is often simplified into a multi-stage buffer allocation and a single-stage stochastic buffer sizing problem at all installations. This paper presents a simulation-based heuristic algorithm and a comparison with others for the problem that cannot be decomposed into a multi-stage buffer allocation and a single-stage stochastic buffer sizing problem because the waiting time ties together all stages. The comparison shows that the simulation-based heuristic algorithm performs better than other approaches in saving average inventory cost for both Poisson and Normal demands.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.12
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• pp.1352-1361
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• 2014

The Federal Communications Commission (FCC), which regulates interstate and international communications in the United States, has established a plan to allocate high demand spectrum to the usage of mobile communication by inducing voluntary relinquishment from broadcasters. This plan was introduced by the National Broadband Plan as an incentive auction in 2010. The FCC suggested the Notice of Proposed Rulemaking (NPRM) in 2012 and issued Report and Order (R&O) on May 2014 regarding the overall rules of incentive auctions expected to be implemented in mid-2015. The incentive auction attracts the attention of many countries because this policy suggests a novel approach regarding the alteration of use from an inefficient usage to an efficient usage in limited spectrum resources. In this paper, we define the key issues in order for implementation of incentive auction. Since the incentive auction is a highly complicated process compared to previous allocation procedures, a careful review of the incentive auction regarding whether this spectrum policy can be introduced is required. In this paper, we describe the detailed procedure of the incentive auction and present policy considerations for the introduction of the incentive auction.

• Journal of Labour Economics
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• v.33 no.2
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• pp.27-52
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• 2010

This study, using Korean Time Use Survey 1999, analyzes how opportunity costs of maternal time affects the ways in which mothers allocate their time to market work/housework/child care/leisure. Opportunity costs include two kinds: hourly child care costs and log hourly wage rates. Results show that a unit increase in child care costs reduces market work but increases housework, child care, and leisure. The effects of log wage rates are opposite those of child care costs. The result that a unit increase in the log wage rates decreases child care lime is not consistent with a previous study for the United Stales. These results differed by mother's educational attainments. This study suggests that policy-makers should pay careful attention to the effects of various types of mother's opportunity costs on non-market time in promoting maternal employment.

• International journal of advanced smart convergence
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• v.9 no.2
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• pp.68-75
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• 2020

Non-orthogonal multiple access (NOMA) has gained the significant attention in the fifth generation (5G) mobile communication, which enables the advanced smart convergence of the artificial intelligence (AI), the internet of things (IoT), and many of the state-of-the-art technologies. Recently, correlated superposition coding (SC) has been proposed in NOMA, to achieve the near-perfect successive interference cancellation (SIC) bit-error rate (BER) performance for the stronger channel users, and to mitigate the severe BER performance degradation for the weaker channel users. In the correlated SC NOMA scheme, the stronger channel user BER performance is even better than the perfect SIC BER performance, for some range of the power allocation factor. However, such excessively good BER performance is not good for the user-fairness, i.e., the more power to the weaker channel user and the less power to the stronger channel user, because the excessively good BER performance of the stronger channel user results in the worse BER performance of the weaker channel user. Therefore, in this paper, we propose the power splitting to establish the user-fairness between both users. First, we derive a closed-form expression for the power splitting factor. Then it is shown that in terms of BER performance, the user-fairness is established between the two users. In result, the power splitting scheme could be considered in correlated SC NOMA for the user-fairness.