• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.5
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• pp.917-926
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• 2019

At present, TICN has been developed and distributed for military command control. TICN is known as the 3.5G mobile communication technology based on WiBro, which shows technical limitation in the field operation situation. Accordingly, the drone-type base station platform is attracting attention as an alternative to overcome technical limitations such as difficulty in securing communication LoS and limiting expeditious network configuration. In this study, we performed simulation performance evaluation of drone-type base station operation in 28 GHz that is considered most suitable for cellular communication within mmWave frequency band. Specifically, we analyzed the changes in throughput and fairness performance according to radio resource management policies such as frequency reuse and scheduling in multi-cell topology. Through this, we tried to provide insights on the operation philosophy on drone-type base station.

• Journal of the Korea Society for Simulation
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• v.19 no.1
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• pp.1-11
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• 2010

K company produces semiconductor package products under the make-to-order policy to supply for domestic and foreign semiconductor manufacturing companies. Its production process is a machine-paced assembly line type, which consists of die sawing, assembly, and test. This paper suggests three plans to increase process throughput based on the process analysis of K company and evaluates them via a simulation model using a real data collected. The three plans are line balancing by adding machines to the bottleneck process, product group scheduling, and reallocation of the operators in non-bottleneck processes. The evaluation result shows the highest daily throughput increase of 17.3% with an effect of 2.8% reduction of due date violation when the three plans are applied together. Payback period for the mixed application of the three plans is obtained as 1.37 years.

• Journal of Digital Convergence
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• v.18 no.10
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• pp.225-232
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• 2020

The underlaying communication scheme in 5G cellular network is a very promising resource sharing scheme, and it is an effective scheme for improving service performance of 5G and reducing communication load between a cellular link and a device to device (D2D) link. This paper proposes the algorithm to minimize the resource interference that occurs when performing 5G-based multi-class service on gNB(gNodeB) and the cooperative priority-based resource allocation scheduling scheme (CPRAS) to maximize 5G communication service according to the analyzed control conditions of interference. The proposed CPRAS optimizes communication resources for each device, and it optimizes resource allocation according to the service request required for 5G communication and the current state of the network. In addition, the proposed scheme provides a function to guarantee giga-class service by minimizing resource interference between a cellular link and a D2D link in gNB. The simulation results show that the proposed scheme is better system performance than the Pure cellular and Force cellular schemes. In particular, the higher the priority and the higher the cooperative relationship between UE(User Equipment), the proposed scheme shows the more effective control of the resource interference.

• Journal of Korea Multimedia Society
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• v.1 no.1
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• pp.67-79
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• 1998

In this paper, we present the design and analyze the transmission rate of a control algorithm for the client buffer on the VOD systems. The design is based on the server's data transmission rate and clients' data consumption rate. The proposed algorithm stabilizes the client's buffer by reducing the oscillation phenomena of the buffer. And it uses the BCT (Buffer Check Time) to reduce the scheduling load of the client system. The client's data consumption rate and the buffer size are calculated on the basis of BCT. In case that the predicted buffer size operates in the overrun or starvation the buffer. As the load fluctuation of the network, the transmission rate control policy cannot stabilize the client's buffer alone. The media scaling policy, therefore, also performs its complementary part in stabilizing the client's buffer, and performance evaluation of the proposed algorithm is provided through simulation.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.31B no.11
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• pp.11-19
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• 1994

Turnaround time of a job performing frequent disk I/O operations is greatly affected by I/O bottleneck which incurs due to the large gap in the speeds of I/O devices and the CPU. This paper proposes to employ a Write Dedicated Buffer(WDB) in disk arrays to improve the response time for read requests and analyzes the scheduling policies and the efficiency of the WDB. Through a series of simulations we show that, among the three policies examined, the partial stripe join(PSJ) policy is the most effective in terms of response time for both read and write requests and that, especially when using a WDB on declustered arrays, improvement of response time for read requests becomes greater as the request rate increases.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.186-195
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• 2006

In real-time control systems, the traditional timing analysis based on worst-case response-time(WCRT) is too conservative for the firm and soft real-time control systems, which permit the maximum utilization factor greater than one. We suggested a probabilistic analysis method possible to apply the firm and soft real-time control systems under considering dependency relationship between tasks. The proposed technique determines the deadline miss probability(DMP) of each task from computing the average response-time distribution under a fixed-priority scheduling policy. The method improves the predictable ability forthe average performance and the temporal behavior of real-time control systems.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.12
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• pp.5712-5728
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• 2017

Recently, there are many studies, that considering green wireless cellular networks, have taken the energy consumption of the base station (BS) into consideration. In this work, we first introduce an energy consumption model of multi-mode sharing BS powered by multiple energy sources including renewable energy, local storage and power grid. Then communication load requests of the BS are transformed to energy demand queues, and battery energy level and worst-case delay constraints are considered into the virtual queue to ensure the network QoS when our objective is to minimize the long term electricity cost of BSs. Lyapunov optimization method is applied to work out the optimization objective without knowing the future information of the communication load, real-time electricity market price and renewable energy availability. Finally, linear programming is used, and the corresponding energy efficient scheduling policy is obtained. The performance analysis of our proposed online algorithm based on real-world traces demonstrates that it can greatly reduce one day's electricity cost of individual BS.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.3
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• pp.446-452
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• 2006

In this paper, I evaluated the throughput of various multimedia traffic by using computer simulation over wireless LAN environment based on 802.11e MAC protocol. The number of mobile terminals which generate various traffic and have different Internet QoS varies to improve the reliability of performance evaluation by simulation. Therefore, we investigate throughput of traffic that each mobile terminal generates. I expect that the result of study will be utilized as a fundamental data to control priorities of various types of traffic in case of formulating a scheduling policy supporting a variety of Internet QoS over wired and wireless networks.

• Journal of Digital Contents Society
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• v.7 no.3
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• pp.207-210
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• 2006

A synchronized multimedia presentation consists of a collection of objects, with each object having one or more rendering intervals within the presentation timeline. These intervals specify the objects' start times and end times relative to the presentation timeline. In this paper we consider the problem of streaming a multimedia presentation from a server to a client over a bandwith-limited communication network. We suppose that each of the static objects is layered-encoded. For a given maximum delay, we consider the problem of finding the optimal number of quality of the presentation. We devise efficient algorithms for determining an optimal policy for several criteria. We also consider the problem of gradual rendering of objects after their start times.

• Journal of the Korean Operations Research and Management Science Society
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• v.20 no.2
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• pp.39-60
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• 1995

In this paper, an integration of stochastic dynamic programming (SDP), integer goal programming (IGP) and analytic hierarchy process (AHP) is proposed to handle multiobjective-multicriteria sequential decision making problems under uncertainty inherent in R & D investment planning. SDP has its capability to handle problems which are sequential and stochastic. In the SDP model, the probabilities of the funding levels in any time period are generated using a subjective model which employs functional relationships among interrelated parameters, scenarios of future budget availability and subjective inputs elicited from a group of decision makers. The SDP model primarily yields an optimal investment planning policy considering the possibility that actual funding received may be less than anticipated one and thus the projects being selected under the anticipated budget would be interrupted. IGP is used to handle the multiobjective issues such as tradoff between economic benefit and technology accumulation level. Other managerial concerns related to the determination of the optimal project portifolio within each stage of the SDP model. including project selection, project scheduling and annual budget allocation are also determined by the IGP. AHP is proposed for generating scenario-based transformation probabilities under budgetary uncertainty and for quantifying the environmental risk to be considered.