• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.4
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• pp.726-747
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• 2013

In order to support a large number of mobile stations (MSs) with statistical multiplexing in cellular networks, a random access scheme is widely used for uplink (UL) bandwidth request (BR). In the design of a random access based BR scheme, there are two important requirements: short connection delay and diverse Quality of Services (QoSs) support. Such requirements are crucial for IMT-Advanced systems like IEEE 802.16m to provide various types of fourth generation (4G) data services. IEEE 802.16m provides advanced UL BR schemes for non-real time polling service (nrtPS) and best-effort (BE) service to meet the requirements of short connection time and multiple QoS level support. In order to provide short connection time and multiple QoS support, three-step and differentiated BR procedures are adopted. In this paper, a novel modelling of IEEE 802.16m contention based BR scheme is proposed that uses a 2-dimensional discrete time Markov chain. Both the short access delay three-step BR procedures and normal five-step BR procedure are considered in the model. Our proposed model also incorporates the IEEE 802.16m differentiated BR procedure. With the proposed model, we extensively evaluate the performance of IEEE 802.16m BR for two different service classes by changing QoS parameters, such as backoff window size and BR timer. Computer simulations are performed to corroborate the accuracy of the proposed model for various operation scenarios. With the proposed model, accurate QoS parameter values can be derived for the IEEE 802.16m contention-based BR scheme.

• Bulletin of the Korean Mathematical Society
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• v.43 no.2
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• pp.277-292
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• 2006

We consider a single-server queue with service time distribution of phase type where positive customers, negative customers and disasters arrive according to a Markovian arrival process with marked transitions (MMAP). We derive simple formulae for the stationary queue length distributions. The Laplace-Stieltjes transforms (LST's) of the sojourn time distributions under the combinations of removal policies and service disciplines are also obtained by using the absorption time distribution of a Markov chain.

• Communications of the Korean Mathematical Society
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• v.14 no.3
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• pp.611-625
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• 1999

We consider ΜΑΡ/G/ 1 finite capacity queue with mul-tiple thresholds on buffer. The arrival of customers follows a Markov-ian arrival process(MAP). The service time of a customer depends on the queue length at service initiation of the customer. By using the embeded Markov chain method and the supplementary variable method, we obtain the queue length distribution ar departure epochs and at arbitrary epochs. This gives the loss probability and the mean waiting time by Little's law. We also give a simple numerical examples to apply the overload control in packetized networks.

• Communications of the Korean Mathematical Society
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• v.14 no.4
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• pp.805-814
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• 1999

We consider an MMPP/G/1/K finite queue with two-level threshold overload control. This model has frequently arisen in the design of the integrated communication systems which support a wide range applications having various Quality of Service(QoS) requirements. Through the supplementary variable method, se derive the queue length distribution.

• Journal of Korean Society for Quality Management
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• v.32 no.4
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• pp.30-47
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• 2004

The tremendous growth of the Internet, particularly world wide web, has resulted in significant changes in commerce environments. Internet has brought significant changes in the economics of marketing channels and has led to a redefinition of industry value chain. E-commerce has become so important that countries and firms unprepared for this new trend would lose competitive advantages in the coming century of digital economy. The purpose of this study is to identify logistic!; service quality elements about internet shopping mall customers and examine the relationship among e-commerce logistics service quality, customer satisfaction, relationship quality and repurchase intentions in the area of internet shopping mall. To do so, prior studies on logistics service quality, customer satisfaction, relationship qualify and repurchase intentions were broadly reviewed and the relationship among those four concepts was empirically tested.

• Journal of Information Technology Services
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• v.3 no.1
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• pp.89-99
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• 2004

Mobile service, which is related to all stages of supply chain, can enhance the efficiency of perception and response of the participants. The advantage of mobile service is ubiquity, speed, traceability, positioning, personalization and safety. The purpose of this paper is to propose an overall framework utilizing mobile service in SCM. In the areas of inventory management, remote diagnostics, communications with field workers, and order fulfillment, customer-centric mobile supply web is proposed and implemented for the wireless warehousing and replenishment system.

• Journal of the Korea Safety Management & Science
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• v.9 no.1
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• pp.85-93
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• 2007

Recently, RFID technology is being widely embraced in the supply chain, by manufacturers, retailers, and logistics firms. This study shows the RFID system to provide location based service for commercial vehicle by integrating tracking function of GPS with Mobile service. For this, we configured PC-based terminal for vehicle and developed application consisted of RFID and GPS manager program. In web service module which uses mobile service, commodity information acquired from each vehicle at real-time is added at database and it is analyzed in various aspects to support management decision through the Legacy system.

• ETRI Journal
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• v.41 no.2
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• pp.207-223
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• 2019

Network function virtualization can significantly improve the flexibility and effectiveness of network appliances via a mapping process called service function chaining. However, the failure of any single virtualized network function causes the breakdown of the entire chain, which results in resource wastage, delays, and significant data loss. Redundancy can be used to protect network appliances; however, when failures occur, it may significantly degrade network efficiency. In addition, it is difficult to efficiently map the primary and backups to optimize the management cost and service reliability without violating the capacity, delay, and reliability constraints, which is referred to as the reliability-aware service chaining mapping problem. In this paper, a mixed integer linear programming formulation is provided to address this problem along with a novel online algorithm that adopts the joint protection redundancy model and novel backup selection scheme. The results show that the proposed algorithm can significantly improve the request acceptance ratio and reduce the consumption of physical resources compared to existing backup algorithms.

• Proceedings of the Korean Society of Computer Information Conference
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• 2020.01a
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• pp.109-110
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• 2020

Today, the tourism industry, unlike the past, is fused with various fields and is closely related to various fields, not just one field. In the case of the tourism industry, it leads to an increase in product sales through not only national import but also enhancing national image, forming a positive virtuous chain. As mentioned in order to verify the hypothesis presented in this study, pilot tests were conducted on about 50 copies of the data, and as a result, in-flight service (H1), flight service (H2), compensation service (H3), and reservation service (H4) It has been shown to have a positive effect on customer satisfaction, and when customer satisfaction is achieved, it naturally leads to reuse.

• Journal of Information Technology Services
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• v.11 no.2
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• pp.107-118
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• 2012

Recently, as the clouding computing begins to receive a great attention from people all over the world, it became the most popular buzz word in recent IT magazines or journal and heard it in many different services or different fields. However, a notion of the cloud service is defined vaguely compared to increasing attentions from others. Generally the cloud service could be understood as a specific service model base on the clouding computing, but the cloud, the cloud computing, the cloud computing service and cloud service, these four all terms are often used without any distinction of its notions and characteristics so that it's difficult to define the exact nature of the cloud service. To explore and analyze the cloud service systematically, an accurate conception and scope have to be preceded. Therefore this study is to firstly clarify its definition by Delpi method using expert group and then tries to provide the foundation needed to enable relative research such as establishing business model or value chain and policies for its activation to set off. For the Delpi, 16 experts participated in several surveys from different fields such industry, academy and research sector. As a result of the research, Characteristics of the Cloud Service are followings : Pay per use, Scalability, Internet centric Virtualization. And the scope as defined including Grid Computing, Utility Computing, Server Based Computing, Network Computing.