• Journal of Communications and Networks
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• v.15 no.3
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• pp.321-328
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• 2013

In this paper, we present a technique for obtaining conflict-free schedules for real-time automation protocol for industrial Ethernet (RAPIEnet) switches. Mathematical model of the switch is obtained using graph theory. Initially network traffic entry and exit parts in a single RAPIEnet switch are identified, so that a bipartite conflict graph can be constructed. The obtained conflict graph is transformed to three kinds of matrices to be used as inputs for our simulation model, and selection of any of the matrix forms is application-specific. A greedy edge-coloring algorithm is used to schedule the network traffic and to solve the minimum coloring problem. After scheduling, empty slots are identified for forwarding the non real-time traffic of asynchronous devices. Finally, an algorithm for synchronizing the schedules of adjacent switches is proposed using edge-contraction and minors. All simulations were carried out using Matlab.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.2B
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• pp.11-20
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• 2005

Strict priority scheduling scheme is a good candidate for the implementation of service differentiation in an Internet because of simplicity in implementation and the capability to guarantee the delay requirement of the highest class of traffic. However, it is also blown that strict priority starves the lower-class traffic at the cost of prioritizing the higher-class traffic. The purpose of this work is to propose an analytic method which can estimate the average delay performance of Diffserv service architecture and shows that strict priority scheme does not sacrifice the lower class traffic over a diverse condition of the load. From the numerical experiments for three-class Diffserv network we validate our argument that strict priority scheme may be applied to a service differentiation scheme for the future Internet.

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

• Journal of Advanced Navigation Technology
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• v.22 no.5
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• pp.367-374
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• 2018

A trajectory-based scheduling system is proposed for air traffic management using next generation aviation data communication link. Based on the service concept of 4-dimensional trajectory data link (4DTRAD) using air traffic serveices (ATS) datalink Baseline 2, a procedure for trajectory-based operation of an en-route flight is established and described in detail. To mitigate air traffic controllers' workload which might be caused by various and complicated data utilization, a prototype of the scheduling system, which predicts the aircraft trajectory based on the flight intents received by air traffic service system and provides advisory information for air traffic control, was developed. The simulation environment for trajectory based operation was built to validate the scheduling functionality of the prototype.

• Journal of the Korean Operations Research and Management Science Society
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• v.26 no.2
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• pp.1-11
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• 2001

This paper considers the scheduling of cell-based handoffs to balance the traffic in a fiber-optic microcelluar system. In the system depending on the order of cell based handoff, periodical balancing of the traffic among microcells can be achieved. The cell based handoff problem is formulated as a dynamic programming and the computational complexity is analyzed. Since the scheduling problem requires real time solution, heuristic algorithms are proposed and the computational results are discussed.

• Journal of Korea Multimedia Society
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• v.7 no.9
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• pp.1273-1281
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• 2004

There have been a number of researches on real-time packet scheduling based on EDF algorithm to support end-to-end delay bound guarantees for real-time traffic transmission. However, EDF-based packet scheduler could not guarantee the real-time requirements of real-time traffic if there exist non-real-time traffic. In this paper, we propose a new admission control algorithm and packet scheduling scheme considering non-real-time traffic in the real -time packet scheduler based on EDF policy. Proposed admission control algorithm has pseudo-polynomial time complexity, but we show through simulation that it can be used with little run-time overhead.

• Journal of Communications and Networks
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• v.18 no.3
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• pp.523-530
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• 2016

We use both theoretical analysis and simulations to study the impact of crosspoint-queued (CQ) buffer size on CQ switch throughput and delay performance under different traffic models, input loads, and scheduling algorithms. In this paper, we present the following. 1) We prove the stability of CQ switch using any work-conserving scheduling algorithm. 2) We present an exact closed-form formula for the CQ switch throughput and a non-closed-form but convergent formula for its delay using static non-work-conserving random scheduling algorithms with any given buffer size under independent Bernoulli traffic. 3) We show that the above results can serve as a conservative guide on deciding the required buffer size in pure CQ switches using work-conserving algorithms such as the random scheduling, under independent Bernoulli traffic. 4) Furthermore, our simulation results under real-trace traffic show that simple round-robin and random work-conserving algorithms can achieve quite good throughput and delay performance with a feasible crosspoint buffer size. Our work reveals the impact of buffer size on the CQ switch performance and provides a theoretical guide on designing the buffer size in pure CQ switch, which is an important step toward building ultra-high-speed switch fabrics.

• ETRI Journal
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• v.24 no.2
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• pp.172-175
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• 2002

This paper considers a packet-scheduling algorithm for a given combined traffic of unicast and multicast data packets and proposes a hybrid router with several dedicated buses for multicast traffic. Our objective is to develop a scheduling algorithm that minimizes schedule length for the given traffic in the hybrid router. We derive a lower bound and develop an optimal solution algorithm for the hybrid router.

• Journal of Communications and Networks
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• v.15 no.1
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• pp.87-101
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• 2013

In industrial applications, sensor networks have to satisfy specified time requirements of exchanged messages. IEEE 802.15.4 defines the communication protocol of the physical and medium access control layers for wireless sensor networks, which support real-time transmission through guaranteed time slots (GTSs). In order to improve the performance of IEEE 802.15.4 in industrial applications, this paper proposes a new traffic scheduling algorithm for GTS. This algorithm concentrates on time-critical industrial periodic messages and determines the values of network and node parameters for GTS. It guarantees real-time requirements of periodic messages for industrial automation systems up to the order of tens to hundreds of milliseconds depending on the traffic condition of the network system. A series of simulation results are obtained to examine the validity of the scheduling algorithm proposed in this study. The simulation results show that this scheduling algorithm not only guarantees real-time requirements for periodic message but also improves the scalability, bandwidth utilization, and energy efficiency of the network with a slight modification of the existing IEEE 802.15.4 protocol.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1B
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• pp.20-26
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• 2010

The downlink scheduling algorithm has a great impact on the performance of mobile telecommunication system. In proportional fairness (PF) scheduling algorithm, the resource is allocated proportionally to the quality of wireless channel. Thus, PF has difficulty in servicing the users having more downlink traffic. One can allocate the resource proportionally to the accumulated queue length. However, this leads to system throughput degradation since the users having low channel quality get more and more resource allocated due to accumulation property of queue. In this paper, we propose a new downlink scheduling algorithm, which extends PF algorithm by incorporating downlink traffic arrival rate. The proposed algorithm can effectively cope with users having more downlink traffic, and maintain high system throughput by eliminating accumulation effect in the algorithm. With computer simulations, it is verified that the proposed algorithm performs better than existing algorithms.