• Journal of the Korea Society of Computer and Information
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• v.27 no.12
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• pp.17-27
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• 2022

In this paper, ED-H algorithm, an optimal real-time scheduling algorithm dealing with the characteristics of the integrated energy harvester system with a capacitor, is extended to satisfy the time constraint under the blackout state which is a deliberate power-off state by an intelligent power management unit adopted in the system. If the power supply system does not have enough energy, it temporarily shuts off the power supply to protect the circuit and capacitor and resumes the supply again when the capacitor is fully charged, which may delay the task execution during these blackout states by calculating the time according to the occurrence of the events. To mitigate the problem, even if task execution is delayed by the original ED-H algorithm, the remaining time of the subsequent time units no longer can afford to delay the execution of the task is predicted in the extended algorithm and the task is forced to be scheduled to meet the time deadline. According to the simulation results, it is confirmed that the algorithm proposed in this paper has a high scheduling performance increase of 0.4% to 7.7% depending on the characteristics of the set of tasks compared to the ED-H.

• The KIPS Transactions:PartA
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• v.16A no.6
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• pp.463-472
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• 2009

Real-time operating systems must have satisfying various conditions such as effective scheduling policies, minimized interrupt delay, resolved priority inversion problems, and its applications to be completed within desired deadline. The real-time operating systems, therefore, should be designed and developed to be optimal for these requirements. MicroC/OS-II, a kind of Real-time operating systems, uses the basic priority inheritance with a mutex to solve priority inversion problems. For the implementation of mutex, the kernel in an operating system should provide supports for numerous tasks with same priority. However, MicroC/OS-II does not provide this support for the numerous tasks of same priority. To solve this problem, MicroC/OS-II cannot but using priority reservation, which leads to the waste of unnecessary resources. In this study, we have dealt with new design a protocol, so called TPSP(Temporary Priority Swap Protocol), by an effective solution for above-mentioned problem, eventually enabling embedded systems with constrained resources environments to run applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.8
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• pp.1567-1576
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• 2015

This paper proposes a reliable real-time data dissemination protocol for mitigating transmission failure of real-time data in WSNs. The re-transmission is well-known for recovery of transmission failure, but this may violate the real-time requirement by transmission delay. To solve this problem, the proposed protocol exploits broadcasting nature and temporal opportunity allocation. In a radio-range of sending node, there may be neighbors satisfying the real-time requirement. The neighbors of specific node could receive data simultaneously by broadcasting, and decide their priority using temporal opportunity allocation method. The method uses time slot and tolerable time. The time slot specifies the priority and transmission deadline for each neighbors, and the tolerable time is the real-time requirement at the sending node. By giving the priority to the node with shorter tolerable time in each slot, we may get more opportunities to forward toward the destination. In other words, even if a node have the longer tolerable time, it still has a chance to forward with the real-time requirement. Simulation results show that the proposed protocol is superior to the existing protocols.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.5
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• pp.281-290
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• 2014

The real-time data dissemination schemes exploit the spatiotemporal commuication approach which forwards data at the delivery speed calculated with the desired time deadline and the end-to-end distance in wireless sensor networks (WSNs). In practical environments, however, the performance of the real-time data dissemination might be degraded by additional and inevitable delay due to some holes. Namely, the holes lengthen the data delivery path and the spatiotemporal approach could not estimate a distance of the data delivery path. To deal with this, we propose A Hole Self-Organization Real-time Routing Protocol for Irregular Wireless Sensor Networks. In proposed protocol, nodes around holes could detect them at deploying phase. A hole is represented as a circle with center point and radius. This hole information is processed and provided as a form of location service. When a source queries a destination location, location provider replies certain points for avoiding holes as well as destination location. Thus, the source could set desired speed toward the destination via the points. Performance evaluation shows that provides better real-time service in practical environments.

• Journal of KIISE:Information Networking
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• v.30 no.4
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• pp.535-544
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• 2003

Integrated services networks should guarantee end-to-end delay bounds for real-time applications to provide high quality services. A real-time scheduler is installed on all the output ports to provide such guaranteed service. However, scheduling algorithms studied so far have problems with either network utilization or scalability. Here, network utilization indicates how many real-time sessions can be admitted. In this paper, we propose service curve allocation schemes that result in both high network utilization and scalability in a service curve algorithm. In service curve algorithm, an adopted service curve allocation scheme determines both network utilization and scalability. Contrary to the common belief, we have proved that only a part of a service curve is used to compute deadlines, not the entire curve. From this fact, we propose service curve allocation schemes that result in a constant time for computing deadlines. We through a simulation study that our proposed schemes can achieve better network utilizations than Generalized processor Sharing (GPS) algorithms including the multirate algorithm. To our knowledge, the service curve algorithm adopting our schemes can achieve the widest network utilization among existing scheduling algorithms that have the same scalability.