• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.1
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• pp.210-216
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• 2005

In many real-time applications, security is another important requirement, since the secure real time database system maintains sensitive information to be shared by multiple users with different levels of security clearance or to be attacked by hackers with ill will. Encryption policies are necessary for the security of secure real-time database systems in addition to the existing security methods, too. However, there has not been much work for the encryption policies in secure real-time database systems, although sensitive information must be safeguarded in real-time systems as well. In this paper, we propose a encryption manager for the purpose of solving the encryption policies of the secure real-time database systems. What is important in the encryption policies of secure real-time database systems is security and timeliness. A significant feature of the proposed encryption manager is the ability to dynamically adapt a encryption algorithm that consider transaction deadline and security level.

• The KIPS Transactions:PartB
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• v.15B no.5
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• pp.413-420
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• 2008

Network bandwidth is one of the major factors that impact the cost of a video service. In this paper we propose approaches to reducing the bandwidth requirement for transporting MPEG-4 video traffic over wireless LANs while guaranteeing a required level of quality of service(QoS). To support high quality video playbacks, video frames must be transported to the client prior to their playback times. A real-time transmission scheduling is used for this purpose, which transmits each frame assigned with a priority according to its importance. It addresses the challenge for a scheduling algorithm that efficiently handles the changing workloads of MPEG-4 video traffic. The goal of our research is to maximize the number of frames that are transported within their deadlines while minimizing the tardiness of frames that missed their deadlines. The performance of the proposed method is compared with that of similar service mechanisms through extensive simulation experiments.

• Journal of KIISE
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• v.43 no.3
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• pp.314-326
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• 2016

Some process algebras were applied to enterprise business modelling for formal specification and verification. ${\pi}$-calculus and mobile ambient can be considered for the distributed and mobile, especially to represent the movements of distributed real-time business processes. However there are some limitations to model the movements: 1) ${\pi}$-calculus passes the name of port for indirect movements, and 2) mobile ambient uses ambient to synchronize asynchronous movements forcefully. As a solution to the limitations, this paper presents a new process algebra, called ${\delta}$-calculus, to specify direct and synchronous movements of business processes over geo-temporal space. Any violation of safety or security of the systems caused by the movements can be indicated by the properties of the movements: synchrony, priority and deadline. A tool, called SAVE, was developed on ADOxx metamodelling platform to demonstrate the concept.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.12
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• pp.630-640
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• 2007

As the range of sensor network's applicability is getting wider, it creates new application areas which is required real-time operation, such as military and detection of radioactivity. However, existing researches are focused on effective management for resources, existing sensor network operating system cannot support to real-time areas. In this paper, we propose the ${\mu}TMO$ model which is lightweight real-time distributed object model TMO. We design the real-time sensor network operation system ${\mu}TMO-NanoQ+$ which is based on ETRI's sensor network operation system Nano-Q+. We modify the Nano-Q+'s timer module to support high resolution and apply Context Switch Threshold, Power Aware scheduling techniques to realize lightweight scheduler which is based on EDF. We also implement channel based communication way ITC-Channel and periodic thread management module WTMT.

• The Journal of the Korea Contents Association
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• v.7 no.1
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• pp.83-93
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• 2007

In this paper, we address a power-aware scheduling algorithm for a mixed real-time system which consists of periodic and sporadic tasks, each of which is characterized by its minimum period, worst-case execution requirement and deadline. We propose a dynamic voltage scaling algorithm called DVSMT(DVS for mixed tasks), which dynamically scales down the supplying voltage(and thus the frequency) using on-line distribution of the borrowed resources when jobs complete while still meeting their deadlines. With this scheme, we could reduce more energy consumption. As the proposed algorithm can be easily incorporated with RTOS(Real-Time Operating System), it is applicable for handhold devices and sensor network nodes that use a limited battery power. Simulation results show that DVSMT saves up 60% more than the existing algorithms both in the periodic-task and mixed-task systems.

• Proceedings of the Korea Contents Association Conference
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• 2004.11a
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• pp.545-553
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• 2004

A researcher, who is a member of an academic society, is required to write a report on his or her research and present it at an academic workshop in order to have the contents of the research recognized by others. In order to do that, the researcher frequently has to look up the web pages of each workshop for information such as the submission deadline, paper information, announcements and news. On the other hand, the academic society mostly relies on e-mail or bulletin board to send information about itself to its members to inform its members about its latest news or developments. A system where the researcher can gain all the information required through just a single click and the academic society can provide its members with the necessary information through a simple step is required for the ease of both side. We will take a look at the domestic status of researches being done on such systems where the RSS standard has been applied and suggest a RSS-based dissemination model where the concept of personalization has been applied to satisfy the needs of the individual user.

• Journal of KIISE:Information Networking
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• v.27 no.2
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• pp.197-205
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• 2000

This paper proposes and evaluates a scheme which enhances real-time performance on the Ethernet-based residential network where cable length is very short and most of traffic passes through a specific device. The scheme aims at enhancing deadline meet ratio of the real-time traffic, for example, video stream by means of applying the functionalities such as queue discrimination and early packet discard as well as maintaining network load properly. The design includes the description on hardware interfaces along with the software modules such as scheduler, device driver and connection manager. The simulation results via SMPL suggest that the proposed network can be used as a cost-effective residential network. We also measure the permissible bandwidth for non-real-time traffic without degrading the performance of real-time traffic.

• Journal of Computing Science and Engineering
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• v.1 no.1
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• pp.56-73
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• 2007

Demands have been growing in safety-critical application fields for producing networked real-time embedded computing (NREC) systems together with acceptable assurances of tight service time bounds (STBs). Here a service time can be defined as the amount of time that the NREC system could take in accepting a request, executing an appropriate service method, and returning a valid result. Enabling systematic composition of large-scale NREC systems with STB certifications has been recognized as a highly desirable goal by the research community for many years. An appealing approach for pursuing such a goal is to establish a hard-real-time (HRT) component model that contains its own STB as an integral part. The TMO (Time-Triggered Message-Triggered Object) programming scheme is one HRT distributed computing (DC) component model established by the first co-author and his collaborators over the past 15 years. The TMO programming scheme has been intended to be an advanced high-level RT DC programming scheme that enables development of NREC systems and validation of tight STBs of such systems with efforts far smaller than those required when any existing lower-level RT DC programming scheme is used. An additional goal is to enable maximum exploitation of concurrency without damaging any major structuring and execution approaches adopted for meeting the first two goals. A number of previously untried program structuring approaches and execution rules were adopted from the early development stage of the TMO scheme. This paper presents new concrete justifications for those approaches and rules, and also discusses new extensions of the TMO scheme intended to enable further exploitation of concurrency in NREC system design and programming.

• Journal of the Korea Computer Industry Society
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• v.3 no.9
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• pp.1167-1176
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• 2002

In a (hard) real-time system, every time-critical task must meet its timing constraint, which is typically specified in terms of its deadline. Many computer systems, such as those for open system environment or multimedia services, need an efficient schedulability test for on-line real-time admission control of new jobs. Although various polynomial time schedulability tests have been proposed, they often fail to decide the schedulability of the system precisely when the system is heavily loaded. Furthermore, the most of previous studies on on-line real-time schedulability tests are concentrated on periodic task applications. Thus, this paper presents an efficient on-line real-time schedulability check algorithm which can be used for imprecise real-time system predictability before dispatching of on-line imprecise real-time task system consisted of aperiodic and preemptive task sets when the system is overloaded.

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.810-815
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• 2009

In recent years, embedded systems such as cellular phones, Portable Multimedia Player, intelligent appliance, automobile engine control are reshaping the way people live, work, and play. Thereby, applications for embedded systems become increasingly sophisticated and complicated, such embedded computing platforms must use real-time operating systems (RTOSs) with time determinism. These RTOSs must not only provide predictable services but must also be efficient and small in size and it's kernel services should also be deterministic by specifying how long each service call will take to execute. Having this information allows the application developers to better plan their real-time application software so as not to miss the deadline of each task. In this paper, we present the complete generalized algorithm using multi-dimensional methodology to determine the highest priority in the ready list with 2r levels of priorities for an arbitrary integer number of r.