• Journal of KIISE:Computer Systems and Theory
• /
• v.26 no.4
• /
• pp.443-454
• /
• 1999

최소 여유시간 우선(Least-Laxity-First)스케쥴링 알고리즘은 여유시간이 작은 태스트가 높은 우선순위를 갖는 동적 우선순위 스케줄링 방법으로서 단일프로세서 시스템에서 최적임이 증명되었다. 그러나, 이 알고리즘은 최소 여유시간을 가진 태스크가 여러 개 존재하여 여유시간 충돌이 발생한 경우 이 태스크들 간에 빈번한 문맥교환이 발생하게 되는 문제점이 있어 실용적이지 못하다. 본 논문에서 제한하는 최소 여유시간 우선 기반의 최소선점을 갖는 스케줄링 알고리즘(Least-Laxity-First with Minimum Preemption 또는 LLF/MP)은 여유시간이 충돌했을 때에 문맥교환을 최소화함으로써 최소 여유시간 우선 스케줄링 알고리즘의 단점을 해결하였다. LLF/MP 스케줄링 알고리듬은 불필요한 문맥교환을 줄임으로써 시스템 오버헤드로 인한 시스템의 성능 저하를 방지할 수 있고 보다 많은 시스템 자원을 예측 불가능한 비주기적 태스크에게 할당할수 있다.

• The KIPS Transactions:PartC
• /
• v.12C no.5 s.101
• /
• pp.679-686
• /
• 2005

Because EPON access network shares a medium and aggregates the traffic from EPON subscribers, scheduling media access control on EPON bandwidth allocation is very important. Furthermore DBA mechanism of EPON based on TDMA is out of specification and up to implementation. This paper deals with a DBA method to guarantee the QoS of the delay sensitive traffic on the base of best-effort service and delay priority queue management. The proposed method performs virtual scheduling algorithm for the integrated traffic. It uses the same MAC messages and tries to guarantee the QoS of higher priority traffic first with a simple DBA architecture. We evaluate the algorithm for traffic delay according to polling interval and traffic load of upstream and downstream. The results show that the proposed method can guarantee the QoS of the delay sensitive traffic with priority of the service classes.

• The KIPS Transactions:PartB
• /
• v.12B no.2 s.98
• /
• pp.173-180
• /
• 2005

In this paper, we propose an efficient real-time scheduling method of multimedia tasks for decoding frames of MPEG-2 video streams. In our task model, each frame is decoded by a separate multimedia task. The decoding task for each frame is assigned to the priority according to the precedence and importance of frames in a video stream. We use a priority-based scheduling policy in order to effectively allocate the CPU bandwidth to multimedia tasks for MPEG-2 decoding. We show how to dynamically control the fraction of the CPU bandwidth allocated to each multimedia task according to the priority. The primary purpose of our scheduling method is to enhance the real-time performance of the multimedia system by minimizing the number of decoding tasks that have missed their deadlines while reducing the decoding times of these multimedia tasks. The performance of this scheduling method is compared with that of similar mechanisms through simulation experiments.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2014.05a
• /
• pp.469-472
• /
• 2014

S-MAC is hybrids of CSMA and TDMA approaches that use local sleep-wake schedules to coordinate packet exchanges and reduce idle listening. In this method, all the nodes are considered with equal priority which may lead to increased delay during heavy traffic. The method introduced in this paper provides high throughput and small end-to-end delay suitable for applications such as real-time voice streaming and its functionality is independent of underlying synchronization protocol. The novel idea behind our scheme is that it uses the priority concept with (m,k)-firm scheduling in order to achieve its objectives. The performance of our scheme is obtained through simulations for various packet sizes, traffic loads which show significant improvements in packet delivery ratio, and delay compared to existing protocols.

• KIPS Transactions on Computer and Communication Systems
• /
• v.8 no.12
• /
• pp.277-286
• /
• 2019

The Unmanned Aerial Vehicle (UAV) is one of the most precious inventions of Internet of things (IOT). UAV faces the necessity to charge battery or replace battery from the charging stations during or between services. We propose scheduling algorithms for drone power charging (SADPC). The basic idea of algorithm is considering both a deadline (for increasing deadline miss ratio) and a charging time (for decreasing waiting time) to decide priority on charging station among drones. Our simulation results show that our power charging algorithm for drones are efficient in terms of the deadline miss ratio as well as the waiting time in general in compare to other conventional algorithms (EDF or SJF). Also, we can choose proper algorithms for battery charge scheduling and charge ready battery allocation according to system parameters and user requirements based on our simulation.

• The Transactions of the Korea Information Processing Society
• /
• v.3 no.6
• /
• pp.1568-1579
• /
• 1996

Most of the real-time scheduling algorithms assume that all tasks are either preemptive or nonpreemptive. In this paper, we present a real-time scheduling algorithm for the more generalized task model in which each task contains both preemptive and nonpreemptive subtasks in a single processor environment. If the task set is found to be scheduling by the method of Harbour et al, it is also found to be scheduling by the proposed method. A simulation is used ti compare two methods and the result shows the maximum of 45% difference between them in their effectiveness.

• The KIPS Transactions:PartA
• /
• v.11A no.7 s.91
• /
• pp.577-582
• /
• 2004

Double-ended Proirity queues(DEPQ) can be used in applications such as scheduling or sorting. The data structures for DEPQ can be con-structed with or without pointers. The implicit representation without pointers uses less memory space than pointer-based representation. This paper presents a novel fast implicit heap called 4-deapr$\ast$ which utilizes cache memory efficiently. Experimental results show that the 4-deap$\ast$ is faster than symmetric min-max heap as well as deap.

• The Transactions of the Korea Information Processing Society
• /
• v.4 no.1
• /
• pp.246-254
• /
• 1997

This paper proposes an improved scheduling model and algorithm which threads in the fixed-priority policy have faster response time and turnaround time than existing ones in SRT system. Sub run queue is added into the system and is used for the quick execution and aging of threads in the fixed-priority policy. Using simulation two method are compared. The results shows that the new scheduling model gets threads in the fixed-priority policy to run faster than existing ones.

• Proceedings of the Korean Information Science Society Conference
• /
• 1999.10c
• /
• pp.405-407
• /
• 1999

WFQ(Weighted Fair Queuing)은 지연이나 공평성의 특성에 있어서 이상적인 트래픽 스케줄링 알고리즘으로 간주되었다. N세션에 서비스를 제공하는 WFQ 스케줄러의 스케줄링 연산은 각 패킷 전송 시간당 O(n)의 계산 복잡도를 가지며, 구현 또한 복잡하다. Self-Clocked Fair Queuing과 같은 WFQ 알고리즘의 구현을 간단히 하고자 하는 노력은 지연범위나 특성에 영향을 주게 되어 다양한 트래픽이 제공되는 경우 각 트래픽의 공평성을 지원해주지 못한다. 그러므로 지연이나 지연 변이 측면에서 공평성을 지원하고 구현상의 계산 복잡도를 줄인 스케줄링 알고리즘이 필요하게 되었다. ATM 다중화기의 셀 스케줄링 알고리즘 역시, ATM의 특성상 다양한 특성의 서비스를 제공하기 위해서, 다양한 특성의 트래픽에 대한 공평성을 제공하는 새로운 알고리즘의 연구가 필요하다. 이 논문에서는 ATM 스위치 내의 다중화기에서 사용되는 새로운 셀 스케줄링 알고리즘을 제안하고 실험을 통해 이 알고리즘의 성능을 검증하고자 한다. 이 알고리즘은 여러 개의 우선 순위 큐를 갖고, 각 우선순위 큐마다 스케줄링 연산이 O(1)의 계산 복잡도를 갖는 Parallel Priority Queuing 알고리즘이다.

• The Journal of the Korea Contents Association
• /
• v.7 no.12
• /
• pp.238-244
• /
• 2007

Guaranteed Frame Rate(GFR), recently approved by the ATM Forum, expects to become an important service category to efficiently support TCP/IP traffic in ATM networks. The GFR service not only guarantees a minimum service rate at the frame level, but also supports a fair share of available bandwidth. We proposed new scheduling scheme for the GFR service. Proposed scheme provides priority to VCs and high priority to a VC which have more untagged cells in buffer. High priority VCs have much more serviced than low priority. Proposed scheme can provide MCR(minimum cell rate) guarantee and fair sharing to GFR VCs. Computer simulation results show that proposed scheduling scheme provide a much better performance in TCP goodput and fairness than previous scheme.