• Journal of Digital Contents Society
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• v.3 no.1
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• pp.47-57
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• 2002

Recently, wireless networks have been pursuing multimedia data service as voice, data, image, video and various form of data according to development of information communication technology. It guarantees cell delivery delay of real time data in efficient real time multimedia data transfer. Also, it minimizes cell loss rate of non-real time multimedia data. In the wireless ATM, there are based on Asynchronous Transfer Mode(ATM). It implies that there are various service with difficult transmission rates and qualities in the wireless communication network. As a result, it is important to find out the ways to guarantee the Quality of Service(QoS) for each kind of traffic in wireless network. In this thesis, we propose an improved TCRM scheduling algorithms for transmission real-time multimedia data service in wireless ATM Networks. We appear real time multimedia scheduling policy that apply each different method to uplink and downlik to wireless ATM network. It can guarantee QoS requirements for each real time data and non-real time data. It also deals the fairness problem for sharing the scarce wireless resources. We solve fault of TCRM as inefficient problem of non-real data by using arbitrary transmission speed and RB(Reservation Buffer) through VC(Virtual Control) and BS(Base Station).

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.3
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• pp.1-7
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• 2012

Cognitive radio, a new paradigm for wireless communication, is being recently expected to support various types of multimedia traffics. To guarantee Quality of Service (QoS) from SUs, a static packet priority policy can be considered. However, this approach can easily satisfy Quality of Service of high priority application while that of lower priority applications is being degraded. In the paper, we propose a fuzzy-based dynamic packet scheduling algorithm to support multimedia traffics in which the dynamic packet scheduler modifies priorities of packets according to Fuzzy-rules with the information of priority and delay deadline of each packet, and determines which packet would be transmitted through the channel of the primary user in the next time slot in order to reduce packet loss rate. Our simulation result shows that packet loss rate can be improved through the proposed scheme when overall traffic load is not heavy.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.10
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• pp.2263-2268
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• 2015

This paper describes packet scheduling techniques that can be used to alleviate the impact of interference. The mechanism is consisted of interference estimation and master delay police. Proposed scheduling police is effective in reducing packet loss and delay. Another advantage worth mentioning, are the additional saving s in the transmitter power since packet are not transmitted when channel is bad. This paper gives that scheduling policy works only with data traffic since voice packets need to be sent at fixed intervals. However, if the delay variance is constant and the delay can be limited to a slot, it may be worthwhile to use DM packet for voice.

• Journal of Korea Multimedia Society
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• v.4 no.1
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• pp.13-28
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• 2001

In a VOD(Vide-On-Demand) system, video data are generally stored in magnetic disk array. In order to provide real-time requirement for data retrieval, video streams must be delivered continuously to the clients such that the delivery of continuous media can be guaranteed in a timely fashion. Compared to the increased performance of processors and networks, the performance of magnetic disk systems have improved only modestly. In order to improve the performance of storage system, disk array system is proposed and used. The array system improves I/O performance by placing disks in parallel and retrieving data concurrently. In this paper, two approaches are considered in order to access the video data in a VOD system, which are CTL(Constant Time Length) and CDL(Constant Data Length) access policies. Disk scheduling policies are also classified into the two categories and compared in terms of the maximum allowable video streams with different degrees of disk array synchronization, under the mixed environments in which both data access policy and disk scheduling policy are considered. Among the compared scheduling policies, LOOK was shown to have the best performance. In terms of degree of disk synchronization, more gain was achieved with large degree of synchronization. In comparisons of performance of CTL and CDL, CTL was proved to have a little superior performance in terms of number of maximum allowable streams.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.8
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• pp.1480-1485
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• 2017

A conventional max SNR scheme, which allocates uplink resources to the user with the highest gain of desired signal channel with a serving base station (BS), exhibits excellent performance in low interference environments. On the other hand, max SGIR scheme, which allocates resources by considering both the desired signal chanel gain and users' interference generating to neighboring BSs, outperforms the max SNR in high interference environments. The conventional two scheduling schemes exhibit optimal performance in different interference environments. Thus, we propose an adaptive scheduling scheme in order to overcome disadvantages of the conventional schemes. In the proposed scheme, a user is selected by max SNR and then the user's generating interference is compared with a pre-determined threshold value. If the generating interference is larger than a pre-determined threshold, then a user is re-selected by max SGIR policy. Monte-Carlo simulation results reveals that the proposed scheme outperforms the conventional schemes in various interference environments.

• KEPCO Journal on Electric Power and Energy
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• v.5 no.1
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• pp.25-32
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• 2019

K-BEMS System was introduced to reduce peak load and to save total energy of the 200 buildings that KEPCO headquarter and branch offices use. And K-BEMS system is composed of PV, battery, and hybrid PCS. KEPCO research institute has carried out this K-BEMS research project for 3 years since January 2016. In this paper, the results of the project are shown. 9 modes of test results of K-BEMS system and are operational problems were analyzed. And measures to cure the trouble are also suggested. Batteries are operated more than 20% of SOC, and less than 20% of SOC battery protection switches are automatically shutting down the system and the system no longer respond to EMS, ending the supply of PV, and so therefore to continue the PV power supply it was turn out to be necessary that the EMS should automatically change its policy to change PV only supply mode automatically when the Battery Switch automatically operated. To operate the system continuously and automatically, it is necessary to modify the minimum operational SOC value, and in addition to that the EMS computer must remember the last shut-down SOC and Voltage which interrupted the system and add some margin to reflect the measurement error in the system.

• The Journal of the Korea Contents Association
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• v.17 no.12
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• pp.289-298
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• 2017

This study analyzed the accomplishment of the outsourcing production policy which forces broadcasting companies to schedule and broadcast more than a certain proportion of outsourcing production programs. According to the results from the examination of whether or not the policy increased the diversity of broadcasting programs, it is positive that a rise in the number of production companies resulting from the implementation of the outsourcing production policy increased the diversity of broadcasting program makers, but programs supplied were limited to certain genres, failing to be diverse. According to the results from the examination of whether or not the competitiveness of broadcasting and video contents increased, production conditions had not improved due to the controversy over the ownership of the right of production between terrestrial broadcasting companies and outsourcing production companies. In addition, though there was the positive effect of increasing export of broadcasting programs, the exports were limited to certain genres.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.44 no.3
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• pp.22-32
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• 2021

To meet rapidly changing market demands, manufacturers strive to increase both of productivity and diversity at the same time. As a part of those effort, they are applying flexible manufacturing systems that produce multiple types and/or options of products at a single production line. This paper studies such flexible manufacturing system with multiple types of products, multiple Bernoulli reliability machines and dedicated buffers between them for each of product types. As one of the prevalent control policies, priority based policy is applied at each machines to select the product to be processed. To analyze such system and its performance measures exactly, Markov chain models are applied. Because it is too complex to define all relative transient and its probabilities for each state, an algorithm to update transient state probability are introduced. Based on the steady state probability, some performance measures such as production rate, WIP-based measures, blocking probability and starvation probability are derived. Some system properties are also addressed. There is a property of non-conservation of flow, which means the product ratio at the input flow is not conserved at the succeeding flows. In addition, it is also found that increased buffer capacity does not guarantee improved production rate in this system.

• Management Science and Financial Engineering
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• v.4 no.2
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• pp.43-58
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• 1998

Packet switch is a key component in high speed digital networks. This paper investigates congestion phenomena in the packet switching with input buffers. For large value of switch size N, mathematical models have been developed to analyze asymptotic maximum switch throughput under nonuniform traffic. Simulation study has also been done for small values of finite N. The rapid convergence of the switch performance with finite switch size to asymptotic solutions implies that asymptotic analytical solutions approximate very closely to maximum throughputs for reasonably large but finite N. Numerical examples show that non-uniformity in traffic pattern could result in serious degradation in packet switch performance, while the maximum switch throughput is 0.586 when the traffic load is uniform over the output trunks. Window scheduling policy seems to work only when the traffic is relatively uniformly distributed. As traffic non-uniformity increases, the effect of window size on throughput is getting mediocre.

• The Transactions of the Korea Information Processing Society
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• v.5 no.11
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• pp.2997-3009
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• 1998

독자-필자 문제(readers-writers problem)를 위한 기존의 스케쥴링 정책들은 대부분 독자나 필자 중 어느 한 쪽에 편향된 처리 성향을 가지고 있기 때문에 응답 시간이나 처리량, 둘 중 하나의 성능이 상당히 좋지 않은 특성이 있다. 본 논문에서는 이러한 문제를 개선하고자 새로룬 동적 스케쥴링 정책인 CAP(Counter-based Adaptive Priority)을 제안한다. CAP은 동시에 수행될 수 없는 필자에게 가중치를 주는 기법과 소수의 독자를 무작정 지연시키는 것을 막기 위한 에이징(aging) 기법을 동적으로 결합하여 사용하고 있다. CAP은 기는(starvation) 문제를 가지고 있지 않으며 주어진 상황에 동적으로 대응하는 능력을 가지고 있기 때문에 처리량과 응답 시간 모두 FCFS에 비하여 더 우수하다. 제안된 정책에 대한 효과성을 입증하기 위하여 세마포어 기반의 해법을 제시하고 사건-기반 시뮬레이션을 사용하여 기존의 정책들과 성능을 비교하였다.