• Bulletin of the Korean Mathematical Society
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• v.46 no.4
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• pp.673-689
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• 2009

We analyze $MAP_1,\;MAP_2$/G/1 finite queues with service scheduling function dependent upon queue lengths. The customers are classified into two types. The arrivals of customers are assumed to be the Markovian Arrival Processes (MAPs). The service order of customers in each buffer is determined by a service scheduling function dependent upon queue lengths. Methods of embedded Markov chain and supplementary variable give us information for queue length of two buffers. Finally, the performance measures such as loss probability and mean waiting time are derived. Some numerical examples also are given with applications in telecommunication networks.

• Journal of Communications and Networks
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• v.7 no.4
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• pp.408-416
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• 2005

Quality of service (QoS) provision is an important and indispensable function for multi-service wireless networks. In this paper, we present a new scheduling/admission control frame­work, including an efficient rate-guaranteed opportunistic scheduling (ROS) scheme and a coordinated admission control (ROS­CAC) policy to support statistic QoS guarantee in multi-service wireless networks. Based on our proposed mathematical model, we derive the probability distribution function (PDF) of queue length under ROS and deduce the packet loss rate (PLR) for individual flows. The new admission control policy makes admission decision for a new incoming flow to ensure that the PLR requirements of all flows (including the new flow) are satisfied. The numerical results based on ns-2 simulations demonstrate the effectiveness of the new joint packet scheduling/admission control framework.

• Journal of applied mathematics & informatics
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• v.31 no.1_2
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• pp.147-154
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• 2013

We analyze queueing model with priority scheduling by supplementary variable method. Customers are classified into two types (type-1 and type-2 ) according to their characteristics. Customers of each type arrive by independent Poisson processes, and all customers regardless of type have same general service time. The service order of each type is determined by the queue length of type-1 buffer. If the queue length of type-1 customer exceeds a threshold L, the service priority is given to the type-1 customer. Otherwise, the service priority is given to type-2 customer. Method of supplementary variable by remaining service time gives us information for queue length of two buffers. That is, we derive the differential difference equations for our queueing system. We obtain joint probability generating function for two queue lengths and the remaining service time. Also, the mean queue length of each buffer is derived.

• IE interfaces
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• v.14 no.4
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• pp.341-347
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• 2001

This paper describes a real-time manufacturing scheduling system on Internet using DBR(Drum-Buffer-Rope) scheduling method. We intend to change company-oriented manufacturing scheduling, which has been used at most manufacturing companies, to customer-oriented manufacturing scheduling. Customers can not only choose product kinds, quantities and order due dates, but also evaluate optimum order due date by themselves in real-time through internet and then the results will be converted into practical manufacturing scheduling. If the company cannot meet the customer order due date, it will offer reliable and accurate information to the customers by suggesting the earliest order due date. To evaluate the customer order due date in real time, companies should be able to estimate their accurate production capacity. This research uses Goldratt's DBR scheduling method to realize that function. The DBR scheduling does not recognize the production capacity of the whole company, but only of the constraint resources which have a great effect on the company throughput. Thus, it can improve the customer service level as well as the profit by performing more dynamic and reliable scheduling through Internet.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.8B
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• pp.615-623
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• 2008

Wireless LAN (WLAN) has greatly benefited from the introduction of various technologies, such as MAC protocol and scheduling algorithm. The majority of these technologies focus on fairness or service differentiation. However, it is difficult to use these technologies to provide many benefits to WLAN simultaneously because the current WLAN system only focuses on the provision of a single aspect of QoS. Unfortunately, multimedia applications require both service differentiation and fairness. Therefore, this paper combines Distributed Fair Scheduling (DFS) and Enhanced Distributed Coordinate Function (EDCF), to provide both fairness and service differentiation simultaneously. Furthermore, we show numerical analysis using Markov process. The simulation results demonstrate that F-EDCF outperforms the EDCF, in terms of throughput, fairness, and delay viewpoints.

• Journal of Communications and Networks
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• v.4 no.3
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• pp.199-208
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• 2002

The downlink rate scheduling problem is considered for CDMA networks with multiple users carrying packets of heterogeneous traffic (voice/audio only, bursty data only or mixed traffic), with each type having its own distinct quality of service requirements. Several rate scheduling algorithms are developed, the common factor of which is that part of the decision on which users to serve is based on a function of the deadline of their head-ofline packets. An approach of Andrews et al., in which the basic Earliest-Deadline-First algorithm is studied for similar systems, is extended to result in better performance by considering a more efficient power usage and by allowing service of more than one user per timeslot if the power resources permit it. Finally, the performance of the proposed schemes is compared through simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.7
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• pp.538-545
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• 2014

This paper proposes a coordinated multi-point (CoMP) based dynamic transmission scheme in a downlink multi-ship network, where a central ship selects a ship in order to maximize the utility function. The proposed scheduling scheme dynamically decides to the usage of the coordinated multi transmissions and selects a user to be served for every frame, in order to the utility function on the basis of the throughput and fairness. In particular, the proposed utilify function based scheduling scheme aims to increase the quality of service of ships at the edge of cells. Under the proportional fair scheduling, the simulation results show that the proposed utility function-based scheduling improves the throughput of the ships at the cell edge with the little sacrifice of the system capacity.

• Convergence Security Journal
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• v.16 no.7
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• pp.159-165
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• 2016

Through the NFV (Network Function Virtualization), companies such as network service providers and carriers have sought to dramatically reduce CAPEX / OPEX by improving the speed of new service provisioning and flexibility of network construction through the S/W-based devices provided by NFV. One of the most important considerations for establishing an NFV network to provide dynamic services is to determine how to dynamically allocate resources (VNFs), the basic building blocks of network services, in the right place. In this paper, we analyzed the latest research trends on VNF node, link allocation, and scheduling in nodes that are required to provide arbitrary NS in NFV framework. In this paper, we also propose VNF scheduling problems that should be studied further in RA (Resource Allocation).

• Journal of the Korean Operations Research and Management Science Society
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• v.28 no.2
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• pp.75-89
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• 2003

Media Access Control (MAC) Protocol in IEEE 802.11 Wireless LAN standard supports two types of services, synchronous and asynchronous. Synchronous real-time traffic is served by Point Coordination Function (PCF) that implements polling access method. Asynchronous nonreal-time traffic is provided by Distributed Coordination Function (DCF) based on Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol. Since real-time traffic is sensitive to delay, and nonreal-time traffic to error and throughput, proper traffic scheduling algorithm needs to be designed. But it is known that the standard IEEE 802.11 scheme is insufficient to serve real-time traffic. In this paper, real-time traffic scheduling and admission control algorithm is proposed. To satisfy the deadline violation probability of the real time traffic the downlink traffic is scheduled before the uplink by Earliest Due Date (EDD) rule. Admission of real-time connection is controlled to satisfy the minimum throughput of nonreal-time traffic which is estimated by exponential smoothing. Simulation is performed to have proper system capacity that satisfies the Quality of Service (QoS) requirement. Tradeoff between real-time and nonreal-time stations is demonstrated. The admission control and the EDD with downlink-first scheduling are illustrated to be effective for the real-time traffic in the wireless LAN.

• Journal of Korean Institute of Industrial Engineers
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• v.29 no.2
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• pp.150-156
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• 2003

The IEEE 802.11 MAC (Media Access Control) Protocol supports two modes of operation, a random access mode for nonreal-time data applications processed by Distributed Coordinated Function (DCF), and a polling mode for real-time applications served by Point Coordinated Function (PCF). It is known that the standard IEEE 802.11 is insufficient to serve real-time traffic. To provide Quality of Service (QoS) of real-time traffic, we propose the Downlink-first scheduling with Earliest Due Date (EDD) in Contention Free Period (CFP) with suitable admission control. The capacity and deadline violation probability of the proposed system is analyzed and compared to the standard pair system of downlink and uplink. Analytical and simulation results show that the proposed scheme is remarkably efficient in view of the deadline violation probability.