• The Journal of the Acoustical Society of Korea
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• v.19 no.8
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• pp.3-11
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• 2000

This paper considers the performance of a dynamic priority control function (DPCF) of a threshold-based Bernoulli priority jump (TBPJ) scheme. Loss-sensitive and delay-sensitive traffics are applied to a system with a TBPJ scheme that is a general state-dependent Bernoulli scheduling scheme. Loss-sensitive and delay-sensitive traffics represent sound and data, respectively. Under the TBPJ scheme, the first packet of the loss-sensitive traffic buffer goes into the delay-sensitive traffic buffer with Bernoulli probability p according to system states which represent the buffer thresholds and the number of packets waiting for scheduling. Performance analysis shows that TBPJ scheme obtains large performance build-up for the delay-sensitive traffic without performance degradation for the loss-sensitive traffic. TBPJ scheme shows also better performance than that of HOL scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12B
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• pp.1017-1027
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• 2006

Recently, Internet service providers are offering triple play service which combines voice and video services with the existing high speed Internet service under the common network infrastructure of IP protocol, so that they can create more benefit from operating a single network architecture. In line with this movement in the convergence of network and services, in this work we propose a bandwidth dimensioning method for the subscriber network of the IP network at flow level. To that purpose, let us propose a series of bandwidth dimensioning methods: bandwidth for best effort service only, bandwidth dimensioning for premium services, and bandwidth dimensioning schemes for the premium Internet services as well as the best effort service which comprise the TPS. Our link dimensioning method is based on the flow level that incorporates the flow blocking probability as a measure of grade of services(GoS), and investigates the characteristics of the proposed methods via extensive numerical experiments. After that, let us carry out a simulation experiment concerning the delay and loss performance of the packet scheduling for the premium services (QoS) using the bandwidth designed by our proposed method, via which the packet level quality of service (QoS) for the proposed link dimensioning method can be observed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.8B
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• pp.509-520
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• 2007

In this paper, we propose a real-time sensor node platform that guarantees the real-time scheduling of periodic and aperiodic tasks through a multitask-based software decomposition technique. Since existing sensor networking operation systems available in literature are not capable of supporting the real-time scheduling of periodic and aperiodic tasks, the preemption of aperiodic task with high priority can block periodic tasks, and so periodic tasks are likely to miss their deadlines. This paper presents a comprehensive evaluation of how to structure periodic or aperiodic task decomposition in real-time sensor-networking platforms as regard to guaranteeing the deadlines of all the periodic tasks and aiming to providing aperiodic tasks with average good response time. A case study based on real system experiments is conducted to illustrate the application and efficiency of the multitask-based dynamic component execution environment in the sensor node equipped with a low-power 8-bit microcontroller, an IEEE802.15.4 compliant 2.4GHz RF transceiver, and several sensors. It shows that our periodic and aperiodic task decomposition technique yields efficient performance in terms of three significant, objective goals: deadline miss ratio of periodic tasks, average response time of aperiodic tasks, and processor utilization of periodic and aperiodic tasks.

• Journal of KIISE:Computer Systems and Theory
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• v.32 no.5
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• pp.243-254
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• 2005

Soft real-time applications such as multimedia feature highly variable processor requirements and probabilistic guarantees on deadline misses, meaning that each task in the application meets its deadline with a given probability. Thus, for such soft real-time applications, a system designer may want to improve the system utilization by allocating to each task a processor time less than its worst-case requirement, as long as the imposed probabilistic timing constraint is met. In this case, however, we have to address how to schedule jobs of a task that require more than (or, overrun) the allocated processor time to the task. In this paper, to address the overrun problem, we propose an overrun control method, which probabilistically controls the execution of overrunning jobs. The proposed overrun control method probabilistically allows overrunning jobs to complete for better system utilization, and also probabilistically prevents the overrunning jobs from completing so that the required probabilistic timing constraint for each task can be met. In the paper, we show that the proposed method outperforms previous methods proposed in the literature in terms of the overall deadline miss ratio, and that it is possible to synthesize the scheduling parameters of our method so that all tasks can meet the given probabilistic timing constraints.

• Journal of Korea Port Economic Association
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• v.34 no.1
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• pp.111-132
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• 2018

As China continues to evolve as a major economic power and the Free Trade Agreement (FTA) between the Republic of Korea and China was ratified on June 1, 2015, market volume between the two countries is expected to grow more rapidly. This study aims on improving the efficiency of car-ferry lines. We conducted two surveys- for shippers and forwarders of car-ferry companies, and container liners. The study analyzes the decision factors for delivery companies and their importance for shippers and forwarders of car-ferry companies and container liners. Based on analysis of prior studies on the competition for car-ferry companies and liners, three primary variables are selected-promptness, economics, and safety. The promptness variable consists of shipping time, loading/unloading time, and customs clearing time. The economic variable consists of marine transportation cost from a domestic harbor to China, loading/unloading cost in the harbor, and overland transport cost from the harbor to shippers inland. Finally, the safety variable consists of cargo damage rates, safety facilities, such as lashing and shoring, and punctuality of transportation time. The survey and AHP results show that the promptness, safety, and economics factors are 0.549, 0.309, and 0.142 in the shipper groups of car-ferry companies' category, respectively. It indicates that there is considerable difference in the importance of each factor. In contrast, the factors are 0.350, 0.348, and 0.302 in the forwarders category, which suggests that there is little difference in each factor's importance. As for shippers and forwarders of liners, the importance of each factor is found to be in the following order: economics, safety, and promptness.