• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.11
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• pp.4068-4086
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• 2014

Due to the prevalence of powerful mobile terminals and the rapid advancements in wireless communication technologies, the wireless video streaming service has become increasingly more popular. Recent studies show that video streaming services via Transmission Control Protocol (TCP) are becoming more practical. TCP has more advantages than User Diagram Protocol (UDP), including firewall traversal, bandwidth fairness, and reliability. However, each video service shares an equal portion of the limited bandwidth because of the fair sharing characteristics inherent in TCP and this bandwidth fair sharing cannot always guarantee the video quality for each user. To solve this challenging problem, an Adaptive Multiple TCP (AM-TCP) scheme is proposed in this paper to guarantee the video quality for mobile devices in wireless networks. AM-TCP adaptively controls the number of TCP connections according to the video Rate Distortion (RD) characteristics of each stream and network status. The proposed scheme can minimize the total distortion of all participating video streams and maximize the service quality by guaranteeing the quality of each video streaming session. The simulation results show that the proposed scheme can significantly improve the quality of video streaming in wireless networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.1A
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• pp.62-69
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• 2005

Efforts for standardization of medium access control (MAC) protocol in IEEE802.11e have been made to support quality of service (QoS) in IEEE802.11e MAC protocol. Enhanced disoibuted coordination function (EDCF) of 802.11e MAC protocol is modified to support QoS for packets that have differentiated priority. However, EDCF still has the problem of throughput optimization and priority support. Therefore, we have proposed a scheme called adaptive EDCF for both supporting priority of packets and throughput optimization. We have derived the relation between the number of nodes and contention window size for throughput optimization. Based on the analytic results, we have evaluated the performance of the proposed scheme using OPNET simulations. The simulation results show that using the proposed scheme can improve the overall throughput regardless of the number of nodes and the decrement of the throughput with increasing the number of nodes can be alleviated. Additionally, we have shown that the adaptive EDCF can support priority of packets more effectively than existing EDCF.

• Korean small business review
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• v.43 no.4
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• pp.95-115
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• 2021

Quality is an important factor influencing organizational performance, so it should be possible to accurately and effectively measure the quality perceived by members. The Consumer Cooperative can be seen as a retail industry by industry classification, and there are various studies based on the dimension of retail quality, but compared to the general retail industry, few studies have been conducted based on the quality level perceived by members. The purpose of this study is to develop quality dimensions and sub-attributes by analyzing in detail and elaborately how the quality of cooperative is viewed from the perspective of members who are both consumers and owners. To this end, the quality dimension of cooperative quality is needed to be newly developed and quality components are demonstrated based on previous studies on the quality dimension. The quality dimension of the cooperative was developed through prior research to suit the value of the cooperative in product, service, and social responsibility, and a survey was conducted to demonstrate the four major cooperative members in Korea. Through this, sub-dimensions were constructed and the quality dimension of the high-order model was demonstrated through exploratory factor analysis and confirmatory factor analysis. It aims to discover key management elements in terms of quality management and provide practical implications to management.