• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.850-857
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• 2013

The objective of this paper is to provide service continuity based on an efficient subchannel allocation in OFDMA systems. The resource management for handover are necessary to maintain the QoS requirements of different multimedia applications because the service continuity may be defected by some delay and information loss. Therefore we propose two subchannel management schemes applied to OFDMA systems. Firstly, a superposition allocation of interference subchannels is achieved by modifying a frequency reuse scheme, using co-subchannel interference principle. Secondly for handover applications, we suggest a novel subchannel reservation scheme to adjust the number of allocated channels, depending on the different characteristics and diverse quality of mobile multimedia applications. Simulation results show that the total throughput for the proposed method is increased up to 20% at average and peak arrivals and the handover failure rate is decreased to about 25%, as compared to the conventional method.

• Journal of Digital Contents Society
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• v.10 no.1
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• pp.169-175
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• 2009

Grid computing is an application to obtain the most efficient performance from computing resources in terms of cost and convenience. It is also considered as a good method to solve a problem that cannot be settled by conventional computing technologies such as clustering or is requiring supercomputing capability due to its complex and long-running task. In order to run grid computing effectively, it needs to connect high-performance computing resources in real-time which are distributed geographically. Answering to the needs of this grid application, researchers in several universities with Argonne National Laboratory in the USA (ANL) as the main axis have developed Globus. It is noticed, however, that the quality of service (QoS) is not guaranteed when certain jobs are exchanged through networks in the context of Globus. To tackle with this problem, the ANL has invented Globus Architecture for Reservation and Allocation (GARA). The researchers of this paper constructed a testbed for evaluating the ability to reserve resource in the GARA system and implemented the GARA code for it. We analyzed the applied results and discussed future research plans.

• Journal of the Korea Society for Simulation
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• v.14 no.3
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• pp.119-127
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• 2005

Web services and their composition (web processes) are promising technologies to efficiently integrate disparate software components over various types of systems. As many web services are nowadays available on Internet, quality of services (QoS) and performance/cost become increasingly important to differentiating between similar service providers. In this work, we introduce sPAC (Web Services Performance Analysis Centre) and show how customers can benefit from sPAC to consider performance in composing and commercializing web services. sPAC 1) helps users to graphically describe the workflow of web services, 2) invokes web services to test out performance for light load conditions, 3) automatically converts the web services and the flow between them into a simulation model, 4) conducts extensive simulations for heavy load conditions and various usage patterns, and 5) reports analysis results and estimation data for the web services.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.6
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• pp.127-134
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• 2011

Recently, the wireless data communication infrastructure appearing before the footlights crosses the limit in the wire and develop into the fast speed. Particularly, the issue about the u-Healthcare service using this increases. And the investigation of the quality guarantee of the wireless data network is important for the smooth service providing. However, the quality control research about the wireless network is insufficient because the existing research performs the quality control between the termination about the wired network continually. This paper presented the mobile service quality measurement reference considering the radio environment,that is the method for satisfying the quality guarantee of the wireless data network user offered the u-Healthcare service as the research about this and user needs. For this purpose, wireless data quality measurement indicator and standard was selected. The quality measure evaluation plan was presented according to the service. And each service presented the quality index especially.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.2
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• pp.21-28
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• 2009

To provide IPTV service successfully, we have to guarantee quality of service (QoS). However, in IPTV service, when we change channels, channel zapping delay will cause lower subscriber's satisfaction. Also, we can not provide IPTV service efficiently by limited bandwidth problem. In this paper, we propose a new enhanced IPTV transmission scheme to solve the two types problems using RACR (Robust Aggregation Control Router) which can control bandwidth and channel zapping time.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.4
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• pp.26-33
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• 2012

Please WBAN(Wireless Body Area Networks) is wireless communication of within 3 m radius from inside and outside of the body. WBAN is many uses IEEE 802.15.4 MAC protocol for WBAN MAC protocol requirements. IEEE 802.15.4 MAC protocol applies GTS(Guaranteed Time Slot) allocation scheme for guarantee packet delivery of application which requests QoS(Quality of Service). However, GTS allocation scheme of IEEE 802.15.4 MAC protocol uses FIFS(First In First Service) queueing. So it reduces data transmission reliability and has many problems. Therefore, IEEE 802.15.4 applies not WBAN MAC protocol for emergency data transmission. In this paper, we proposes a priority based MAC protocol for emergency data transmission in wireless body area networks. the proposal MAC protocol sets priority the data. So GTS reqeuest throughput of emergency data increasing and GTS allocation delay of emergency data decreasing.

• Journal of the Korea Computer Industry Society
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• v.3 no.1
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• pp.85-94
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• 2002

EMRCA(Explicit Max_min Rate Control Algorithm) switch, which has been proposed in the ATM(Asychronous Transfer Mode) standard, controls the ABR(Available Bit Rate) service traffic in the ATM networks. The ABR service class of ATM networks uses a feedback control mechanism to adapt to varying link capacities. The VS/VD(Virtual Source/Virtual Destination) technique offers the possibility to segment the otherwise end-to-end ABR control loop into separate loops. The improved feedback delay and the control of ABR traffic inside closed segments provide a better performance and QoS(Quality of Service) for ABR connections with respect to throughput, delay, and jitter. This paper is study of an ABR VS/VD flow control method. Linear control theory offers the means to derive correct choices of parameters and to assess performance issues, like stability of the system, during the design phase. The performance goals are a high link utilization, fair bandwidth distribution and robust operation in various environments, which are verified by discrete event simulations. The major contribution of this work is the use of linear control theory to model and design an ABR flow control method tailored for the special layout of a VS/VD switch, the simulation shows that this techniques better than conventional method.

• Journal of Broadcast Engineering
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• v.19 no.3
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• pp.385-395
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• 2014

This study analyzes empirically main factors of willingness-to-pay for mobile IPTV emphasized as a key service in mobile environment. By structure equation analysis, the results shows that service diversity has influence on usefulness and service quality influences both usefulness and ease-to-use. Secondly, usability has positive impact on attitude and satisfaction. Thirdly, attitude and satisfaction influence willingness-to-pay. These result mean that quality assurance(ex, QoS) and improvement of usability are essential for revenue improvement revenue in mobile IPTV. And also this study can give empirical implications for service portfolio, pricing and bundling strategy as a leading study for mobile IPTV.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.7
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• pp.1447-1454
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• 2017

The realtime test data topic means that process for the data efficiently from many kinds of measurement device at the test range. There are many measurement devices in test range. The test range require accurate observation and determine on test object. In this realtime test data slaving framework system, the system can produce variety of test informations and all these data also must be transmitted to test information management or display system in realtime. Using RTI DDS(Data Distribution Service) middle ware Ver 5.2, we can product the efficiency of system usability and QoS(Quality of Service) requirements. So the application user enables to concentrate on applications, not middle ware. As the reason, Complex function is provided by the DDS, not the application such as Visualization Software. In this paper, I suggest the realtime test data topic on slaving framework of realtime test data based on DDS at the test range system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9A
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• pp.1031-1038
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• 2004

The call admission control algorithm of hybrid scheme is proposed to enhance the QoS(quality of service) of attempted multimedia calls. In the initial stage of 3rd generation multimedia services networks, the major limitations include the small sefyice coverage and the limited radio link capacity. Because the initial massive deployment of network elements such as base stations, base station controllers, and mobile switching centers is restricted to populated areas and the other areas should be covered with the fewer network elements, the radio channel resources are hmited and coverage network is supposed to be established. Therefore the QoS of multimedia services is expected to be severely degraded when tentative traffic hot spot occurs frequently. Thus, the blocking probability of attempted calls mcreases when relatively large number of users try to place multimedia calls in a hot spot area of the wireless networks. In this situation, the proposed hybrid scheme can mitigate the degradation of the QoS of multimedia services by using the available radio channels of the neighboring cells.