• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.12
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• pp.116-124
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• 2003

According to the convenience and efficiency, IEEE 802.11 WLAN(Wireless LAN) has became rapidly wide-spread on the market. However, QoS support is needed for various multimedia service. In this paper, we consider both MAC method of IEEE 802.11 and IEEE 802.11e and Traffic Category differentiated service by QoS support method. In addition, we study currently existing back-off algorithms in view of comparative analysis. As a result we propose a new back-off algorithm called Collision Rate Based-EDCF. The proposed back-off algorithm confirms the performance by computer simulations in terms of Throughput, and QoS support.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.578-582
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• 2005

This paper describes MAC schemes for QoS enhancement taking into account the traffic characteristics and network states over IEEE 802.11 wireless networks. Our approach uses AR as a Backoff parameter and to slide IFS adaptively for increasing the medium utilization ratio and throughput, and providing fairness. In addition, we evaluate through simulations using NS-2 the performance of proposed MAC scheme and compare it with other MAC schemes.

• Journal of information and communication convergence engineering
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• v.6 no.2
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• pp.228-232
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• 2008

In recent years, wireless ad hoc networks have become increasingly popular in both military and civilian applications due to their capability of building networks without the need for a pre-existing infrastructure. Recently, IEEE 802.11 Task Group e has been working on a new mechanism, the Enhanced Distributed Coordination Function (EDCF), to enhance the performance of 802.11 DCF. However, EDCF only reduces the internal collisions within a station, and external collisions between stations remain high in ad-hoc networks. In this paper, we propose to adopt an adaptive backoff window control technique, based on a dynamic value of the initial value of the range in which the backoff is chosen, so the backoff timer is randomly chosen in the range (InitRng, CW-1). We use ns-2 simulation to evaluate the throughput of our scheme. Results show that the throughput is improved for our scheme compared to the original DCF due to the reduced the number of collisions.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.573-577
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• 2005

Recently there are increasing needs for Internet and various kinds of contents. These traffics for various contents need more amount of data to provide high-quality information and require various QoS depending on the characteristics of contents. However, current Internet service supports BE (Best Effort) service only, therefore IntServ (Integrated Service) scheme and DiffServ (Differentiated Service) scheme are represented to support QoS in IP layer. Moreover, while wireless Internet is getting popular, MAC(Medium Access Control)is also becoming important. This is due to the fact that wireless access, resource allocation and packet scheduling, which are done in another layers before, are performed in MAC layer in many new wireless systems. This paper describes new scheme that provides QoS taking into account the traffic characteristics over Mobile IPv6 network based on IEEE 802.11e EDCF and evaluates the performance through computer simulation.

• Journal of information and communication convergence engineering
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• v.4 no.4
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• pp.141-146
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• 2006

In these days, wireless data services are becoming ubiquitous in our daily life because they offers several fundamental benefits including user mobility, rapid installation, flexibility, and scalability. Moreover, the requests for various multimedia services and the Quality of Service (QoS) support have been one of key issues in wireless data communications. Therefore the research relative to Medium Access Control (MAC) has been progressing rapidly. Especially a number of QoS-aware MAC schemes have been introduced to extend the legacy IEEE 802.11 MAC protocol which has not guaranteed any service differentiation. However, none of those schemes fulfill both QoS features and channel efficiency although these support the service differentiation based on priority. Therefore this paper studies a novel MAC scheme, referred to as Enhanced Distributed Coordination Function with Network Adaptation (EDCF-NA), for enhancements of both QoS and medium efficiency. It uses a smart factor denoted by ACK rate and Network Load Threshold (TH). In this paper, we study how the value of TH has effect on MAC performance and how the use of optimal TH pair improves the overall MAC performance in terms of the QoS, channel utilization, collision rate, and fairness. In addition, we evaluate and compare both the performance of EDCF-NA depending on several pairs of TH and the achievement of various MAC protocols through simulations by using Network Simulator-2 (NS-2).

• Journal of the Korea Society of Computer and Information
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• v.14 no.5
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• pp.77-83
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• 2009

In this parer, an improved backoff algorithm is proposed by supplementing a multiple of persistence factor for IEEE 802.11 Wireless LAN MAC. This algorithm is proposed to complement the shortcomings of the conventional BEB (Binary Exponential Backoff) algorithm which is used for retransmission to control a new contention window in DCF/EDCF MAC. In channel utilization, collision rate and Goodput viewpoint, we analysis the improved backoff algorithm and compared the result with that of the conventional algorithm In this result, we showed that the performance for PFA backoff algorithm is 10% higher than that for the conventional BEB algorithm when the number of station is 40.

• Journal of Advanced Navigation Technology
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• v.10 no.1
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• pp.63-69
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• 2006

Recently there are increasing needs for Internet and various kinds of contents. These traffics for various contents need more amount of data to provide high-quality information and require various QoS depending on the characteristics of contents. However, current Internet service supports BE (Best Effort) service only, therefore IntServ (Integrated Service) scheme and DiffServ (Differentiated Service) scheme are represented to support QoS in IP layer. Moreover, while wireless Internet is getting popular, MAC(Medium Access Control) is also becoming important. This is due to the fact that wireless access, resource allocation and packet scheduling, which are done in another layers before, are performed in MAC layer in many new wireless systems. This paper describes new scheme that provides QoS taking into account the traffic characteristics over Mobile IPv6 network based on IEEE 802.11e EDCF and evaluates the performance through computer simulation.

• International Area Studies Review
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• v.22 no.2
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• pp.211-218
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• 2018

The evaluation of aid effectiveness at the national level has mostly focused on qualitative evaluation. This paper attempts to quantitatively evaluate EDCF 's support for Vietnam in 1995 ~ 2016 on the economy. First, we compare the strengths and weaknesses of various methodologies that can be used for quantitative assessment: panel analysis based on growth theory, input-output analysis, social account matrix analysis, CGE model, DSGE model, and time series analysis. Using the input-output analysis, we estimate that total output and value added have been generated about $5.9 billion and $1.7 billion in Vietnam, respectively. The increase in income per capita from the support was estimated to have contributed to a 0.21%p reduction in the poverty rate in Vietnam.

• KIEAE Journal
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• v.14 no.6
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• pp.43-52
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• 2014

Hospital design technology of Korea has recently been exported to underdeveloped countries through the EDCF business. This business reflects our high technology of the hospital design and the regional features that reflect the natural environments, the architectural features and the architectural technology of underdeveloped countries. In accordance with the trend of the global environmental-friendly design market, introduction of environmental-friendly design is needed in the project of hospital for underdeveloped countries. A result of examining the Bangladesh case, the hospital design for the underdeveloped countries already contains a lots of environmental-friendly design elements which have lots of effect. In addition, these environmental elements already contains the advantage and efficiency of operation. Thus, for the success of the hospital design project of the international assistance business, it is necessary actively to discover the environmental-friendly design elements of the region, and to survey the environmental-friendly construction of the region and to make the guidelines of environmental-friendly hospital design during the feasibility study phase.

• Journal of the Korean Professional Engineers Association
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• v.43 no.4
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• pp.44-49
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• 2010

Th Rach Gia Bypass Project, to be implemented under EDCF Loan VNM-12, constitutes a strategically important part of the Greater Mekong Sub-region Southern Coastal Corridor Project(the GMS-SCCP). The main goal of the GMS strategy is to promote sustainable economic growth, improve employment, and achieve poverty reduction by tapping the comparative advantages of Vietnam, Cambodia and Thailand. As a project manager who once took a responsible position for the completion of RGBP's detailed design, I would like to briefly introduce what our design team including the local sub-contractors had performed for the D/Design of this Project last year, especially in the field of highway, bridge and soft soil treatment method widely used in Mekong Delta area. With the performance of nearly two Projects due to the V.O. in one year on the prescribed time, it was a hard year but a rewarding one. To expand our horizon more about overseas projects, several recommendations for the brighter future of overseas projects are shown herein this paper.