• Journal of Korea Multimedia Society
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• v.13 no.9
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• pp.1285-1298
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• 2010

Since the TinyOS incorporating a non-preemptive task scheduling policy uses a FIFO (First-In First-Out) queue, a task with the highest priority cannot preempt a task with lower priority before the task with lower priority must run to completion. Therefore, the non-preemptive TinyOS cannot guarantee the completion of real-time user tasks within their deadlines. Additionally, the non-preemptive TinyOS needs to meet the deadlines of user tasks as well as those of TinyOS platform tasks called by user tasks in order to guarantee the deadlines of the real-time services requested by user tasks. In this paper, we present a group-based real-time scheduling technique that makes it possible to guarantee the deadlines of real-time user tasks in the TinyOS incorporating a non-preemptive task scheduling policy. The proposed technique groups together a given user task and TinyOS platform tasks called and activated by the user task, and then schedule them as a virtual big task. A case study shows that the proposed technique yields efficient performance in terms of guaranteeing the completion of user tasks within their deadlines and aiming to provide them with good average response time, while maintaining the compatibility of the existing non-preemptive TinyOS platform.

• The Transactions of the Korea Information Processing Society
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• v.1 no.3
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• pp.367-379
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• 1994

This paper describes scheduling algorithms of the UNIX operating system and shows an analytical approach to approximate the average conditional response time for a process in the UNIX operating system. The average conditional response time is the average time between the submittal of a process requiring a certain amount of the CPU time and the completion of the process. The process scheduling algorithms in thr UNIX system are based on the priority service disciplines. That is, the behavior of a process is governed by the UNIX process schuduling algorithms that (ⅰ) the time-shared computer usage is obtained by allotting each request a quantum until it completes its required CPU time, (ⅱ) the nonpreemptive switching in system mode and the preemptive switching in user mode are applied to determine the quantum, (ⅲ) the first-come-first-serve discipline is applied within the same priority level, and (ⅳ) after completing an allotted quantum the process is placed at the end of either the runnable queue corresponding to its priority or the disk queue where it sleeps. These process scheduling algorithms create the round-robin effect in user mode. Using the round-robin effect and the preemptive switching, we approximate a process delay in user mode. Using the nonpreemptive switching, we approximate a process delay in system mode. We also consider a process delay due to the disk input and output operations. The average conditional response time is then obtained by approximating the total process delay. The results show an excellent response time for the processes requiring system time at the expense of the processes requiring user time.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.1
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• pp.57-67
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• 2013

Because many of the FOB key, anti-collision algorithm for a seamless multi-access is applied to the smart-key system. In this paper, we have designed and implemented improved anti-collision algorithm that dramatically reduces the communication response time required in the user authentication process immediately after by dynamically changing the order in which the request of the user ID as the user ID on immediately before in the smart key system for vehicles that use many of the FOB key. In order to evaluate the performance of the system the improved anti-collision algorithm is applied, we show the behavior of the algorithm implemented in the state actually mounted on the vehicle and verify that communication response time required for many of the FOB key was reduced by about 33% compared to existing algorithms.

• IEMEK Journal of Embedded Systems and Applications
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• v.14 no.2
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• pp.97-102
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• 2019

Multi-queue I/O block layer has been recently employed in Linux kernel to support fast storage devices such as NVMe SSDs, but it lacks differentiated I/O services yet. In this paper, we propose an I/O scheduling scheme that can improve the user responsiveness of foreground processes, which are closely related to user satisfaction. To this end, we redesign the existing multi-queue block layer to classify the I/O requests from foreground processes and schedule them by exploiting the feature of NVMe interface. Experimental results show that latency and launch time of the foreground processes have been significantly improved compared to original Linux kernel.

• The KIPS Transactions:PartA
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• v.11A no.1
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• pp.29-36
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• 2004

As the number of Internet users and the amount of web contents have increased very fast, reducing the load of web servers and providing web services more rapidly have been great issues. A web-cache system, which is located between the user and the web server, has been used by many web service providers as an effective way to reduce the load of web servers and the web service response time. In this paper, we have developed a web-cache system which is based on the Squid cache and has a compression capability. The web-cache system in which compression capability reduces the amount of network traffic and the web service response time by transfering the web contents in the compressed format over the network between the web-cache system and the user. The performance enhancement is greater in the reverse-cache system than in the forward-cache system because in the case of the reverse-cache system, the cache reduces the amount of traffic on the Internet which is the bottleneck in the network path between the user and the web server. The experimentation result shows that the amount of data traffic has reduced from 2 to 8 times depending on the size of the web contents. The web server response time has reduced 37% on the average and when the size of the web content is greater than 10Kbyte, the response time has reduced 87% on the average.

• Journal of the Korea Society for Simulation
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• v.15 no.3
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• pp.11-21
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• 2006

Importance of and need for grid resource management have accelerated in accordance with increasing development of grid computing. However, it is very complex to distribute and utilize resources efficiently in geographically dispersed environments. This is due to the different access policies and constraints of grid resource owners. Users request resources according to their needs. Operators of a grid computing system need to be able to monitor the system states for reflecting these demands. So, a grid computing system needs a resource management policy that monitors states of resources and then allocates resources. This paper proposes a user demand-based grid trade management model that provides an efficient resource management by the trade allocation based on a users' demand and providers' supply strategy. To evaluate performance, this paper measures increasing rate of resource trades, average response time of trades, and processing time utilization. Firstly, the average increasing rates of trade are 585.7% and 322.6% higher than an auction model and a double auction model. Secondly, the average response time of the user demand-based grid trade management model is maintained between 3 and 5 simulation time. Finally, it is found that the processing time utilization is an average of 145.4% and 118.0% higher than an auction model and a double auction model. These empirical results demonstrate the usefulness of the user demand-based grid trade management model.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.1
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• pp.136-141
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• 2006

The IEEE 802.1x can be using various user authentication mechanisms: One-Time Password, Certificate-Based TLS, Challenge/Response and Keberos through EAP(Extended Authentication Protocol). But, IEEE 802.1x also has vulnerabilities about the DoS, the session hijacking and the Man in the Middle attack due to the absence of AP authentication. In this paper, we propose a WLAN secure system which can offer a safety secure communication and a user authentications by intensified the vulnerability of spoofing and DoS attacks. The suppose system offers a safe secure communication because it offers sending message of integrity service and also it prevents DoS attack at authentication initial phase.

• Journal of KIISE:Computer Systems and Theory
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• v.28 no.9
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• pp.434-441
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• 2001

The concept of network memory was introduced for the efficient exploitation of main memory in a cluster. Network memory can be used to speed up applications that frequently access large amount of disk data. In this paper, we present a memory a management algorithm that does not require prior knowledge of access patterns and that is practical to implement under the web server cluster, In addition, our scheme has a good user response time for various access distributions of web documents. Through a detailed simulation, we evaluate the performance of our memory managment algorithms.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.33 no.6
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• pp.1021-1031
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• 2023

State-sponsored cyber attacks are highly impactful because they are carried out to achieve pre-planned goals. As a defender, it is difficult to respond to them because of the large scale of the attack and the possibility that unknown vulnerabilities may be exploited. In addition, overreacting can reduce the availability of users and cause business disruption. Therefore, there is a need for a response policy that can effectively defend against attacks while ensuring user availability. To solve this problem, this paper proposes a method to collect the number of processes and sessions of defense assets in real time and use them for learning. Using this method to learn reinforcement learning-based policies on a cyber attack simulator, the attack duration based on 100 time-steps was reduced by 27.9 time-steps and 3.1 time-steps for two attacker models, respectively, and the number of "restore" actions that impede user availability during the defense process was also reduced, resulting in an overall better policy.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.11 no.2
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• pp.68-74
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• 2015

Time domain response analysis for vibro-impact nonlinear behavior of multi-span tube with loose supports was performed using commercial FEA code and user subroutine. Support geometry of multi-span tube with a finite gap is realistically modeled by analytical rigid surface. Model of hydrodynamic force is based on the Qusai-steady model which accounts for the inclined angle of relative flow velocity and time delay between flow force and resulting tube motion. During tube vibration from flow loading, impact and friction at the support location is simulated using commercial FEA code with master slave contact algorithm. Analysis results has reasonable agreement with those of references and test experience. Plan of further refinement of analysis model and future test verification is briefly introduced.