• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.12
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• pp.2852-2859
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• 1997

Video-On-Demand system provides electronic video rental services from remote video servers on a broadband communication networks. Most of proposed VOD systems are typically designed for one-to-one conncetion between a user and video server. Therefore, video server stream services to customers individually by allocating a dedicated transmission channel and a set of video server resources for each customer. However, it is inefficiency and wxpensive way when server support multiple users who access the same video stream with a dedicated video channel. Therefore, to achieve cost-effectiveness, batching have studied method that uses multicast communication to simultaneously service all users requesting the same video with a single video with a single video stream. However, the application of the multicast communication by batching detract from the VCR-like function and on-demand nature of the system. In this paepr, we propose a scheme that can support an interactive VCR for all user requesting the same video stream with batching. To reduce a server I/O and network bandwidth requirement, dynamic buffer is allocated to access node which has variable playout poit. Consequently, it makes possible interactive VCR operation as if customer uses true VOD system. Also, this scheme can just deliver a multicast stream without delay after an initial request or VCR action occurred. The policy can guarantee acceptable services to number of users at minimum cost.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4A
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• pp.451-463
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• 2000

In this paper, we design the radio data link protocols with QoS provisioning for mobile multimedia such as voice, data, and video in CDMA-based ATM networks, and analyze the performance of the data link protocols. To support mobile multimedia traffic, the required QoS parameters and the characteristics are analyzed, and wireless protocol stacks are proposed for integrating the wireless access network and ATM transport networks, and radio data link protocols are designed for provisioning QoS Control. The data link protocols are analyzed assuming that the system is supporting voice and data traffic simultaneously. In case of data traffic, the delay and throughput of SREJ ARQ and Type-1 Hybrid ARQ scheme are compared, and in case of voice traffic, the packet loss rate of BCH coding is analyzed according to the varying data traffic loads. The results indicate that the adaptive radio link protocols are efficient to support QoS requirements while the complexities are increased.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4A
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• pp.464-470
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• 2000

In this paper, we introduce a modified interference cancellation scheme to overcome MAI(Multiple Access Interference) in DS-CDMA. Among ICs(Interference Cancellers), PIC(Parallel Interference Canceller) requires the more stages to have the better BER(Bit Error Rate), and SIC(Successive Interference Canceller) faces the problems of power reordering and large delays. To resolve the problems of them, we propose a modified interference cancellation scheme combining SIC and PIC. The proposed interference canceller has improved the performance through the total received signal applied sorting method is fed into the initial stage. Its structure extracts the good characteristics because of the input signal removed MAI in the initial stage. The characteristics of the proposed system are as follows (1) smaller delay, and the strongest user signal is also reduced to MAI(unlike SIC), (2) it has the good BER performance only using fewer stages (unlike PIC).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4B
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• pp.593-603
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• 2000

In this paper, a dynamic route control scheme to increase speed of data communication over public network is presented. And a new structure of gateway which is suitable for the public network environments is proposed and analyzed. For dynamic allocation of transmission routing resources of the gateway and improvement of call processing ratio of the system, virtual queue is used. As results, route utilization ratio of the proposed scheme can be improved up to 60% as compared to the conventional fixed route control scheme. For the case of limited number of routes, it provides high speed data communication while maintaining delay time as low as possible. In addition, as the allocation period at call access node can be varied with the traffic in the proposed scheme, various traffics can be applied easily. Thus, it can be expected that the presented dynamic route control gateway may be suitable for application in high speed data communication over public network.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.8A
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• pp.1198-1205
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• 2000

In this paper, we introduce a modified interference cancellation scheme to overcome MAI in DS-CDMA. Among ICs(Interference Cancellers), PIC(Parallel IC) requires the more complexity, and SIC(Successive IC) faces the problems of the long delay time. Most of all, the adaptive detector achieves the good BER performance using the adaptive Inter conducted iteration algorithm. So it requires many iterations. To resolve the problems of them, we propose an improved adaptive detector that the received signal removed MAI through the sorting scheme and the cancellation method are fed into the adaptive filter. Because the improved input signal is fed into the adaptive filter, it has the same BER performance only using smaller iterations than the conventional adaptive detector, and the proposed detector having adaptive filter requires less complexity than the other detectors.

• The Transactions of the Korea Information Processing Society
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• v.2 no.6
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• pp.891-902
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• 1995

To integrate both the OSI network and the TCP/IP internet, the application gateway that have the powerful and flexible paradigms has been used, but due to the micro-managements of the gateway produce the high costs and the long delay of communication in the case of emergency. The mechanism that maps the access control policies between two domains using the different security policies is needed. These problems are caused by integrating both domains with the different standards. In this paper, the application gateway that delegating to an agent the powerful and flexible services of the CMIP as well as the management functions were proposed. A proposed algorithm that delegates he management script to an gateway safely by capitalizing on the Diffie-Hellman's distribution method, and presents the security mechanism mediating the security policies for guaranteeing the secure communication between two domains using the different security policies.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7A
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• pp.700-709
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• 2007

The heterogeneous wireless access networks has been envisioned to characterize the future wireless networks. In such environments, TCP(Transmission Control Protocol) has to experience poor end-to-end performance because bandwidth and link delay change suddenly when a mobile node moves over different types of wireless networks, which is called vertical handoff. In this paper, we propose a new TCP which maintains each set of congestion control variables, which we call TCP context, for each type of wireless network. The proposed TCP can switch the TCP context against vertical handoff in order to adjust quickly to a newly arrived network. In simulations, the proposed TCP has higher throughput than TCP SACK(Selective Acknowledgment Options) due to its great features to vertical handoff situations.

• Convergence Security Journal
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• v.8 no.3
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• pp.41-49
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• 2008

Other server based-application and the need of more complex interaction is required with functional strengthening and variational uses of mobile device. And mobile environments make a problem of continuous of web-service by making a problem of instance cutting between web-server and mobile device which acts as a client because of mobility. Therefore, this paper embodies a framework which keeps security and connectivity between HTTP based web-service and mobile device, and is for connection to web-service of mobile device which uses WAP in a standard protocol based mobile environment of mobile web-service for continuous web-service. This paper is analyzed in the same standard condition to compared functional delay which is based on HTTP and WAP access, and data transmission volume. Also it investigates improvement of execution overhead which is brought by interaction process.

• Journal of KIISE:Information Networking
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• v.32 no.4
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• pp.508-514
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• 2005

The research in internetworking between UMTS and WLAN, which is completed with merits and demerits, Is actively progressed to establish global roaming environments. This internetworking is classified into two groups: loosely-coupled and tightly-coupled. h tightly-coupled mechanism demands lots of investment and considerable amountof time to construct, which is directly connoted between UNTS and WLAN via IWU. On the other hand, a tersely-coupled mechanism is more scalable and easier to implement than a tightly-coupled one while it has critical drawbacks of packet loss and blocking of services due to handover delay. To alleviate these drawbacks. this work proposes a handover scheme between UMTS and WLAN, which is based on HMIPv6. The performance of the proposed scheme is evaluated by the simaulation. The proposed internetworking scheme based on HMIPv6 shows hotter performance than those based on MIPv6.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11A
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• pp.912-923
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• 2011

In this paper, we propose a routing protocol for WMNs to provide passengers in public transportation vehicles (e.g., bus and tram) with Internet access service. In order to support end users with a reliable Internet connection despite the mobility of vehicles, we assume that mesh router, called mobile mesh router (MMR), is installed in a vehicle and manages a route to Internet Gateway (IGW). We therefore propose an efficient routing protocol and its routing metric, called ETT-TR, considering trajectory information of vehicle as well as link quality in order to find a route between them. Using NS-2 simulations, we observe that our proposed routing protocol reduces the end-to-end delay and improves throughput performance.