• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.8
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• pp.1004-1010
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• 2019

In the EH-WSN (Energy harvesting wireless sensor network), a MAC (medium access control) protocol is required to select a relay node considering the power status of a node. Existing EH-WSN studies emphasize the power aspect, so it does not consider the QoS like the urgency of the sensed data. The required power and transmission delay must be changed according to the urgency so that the medium access control according to the data QoS can be performed. In case of relay node, relaying data without consideration of data urgency and node power may cause delay due to power shortage in case of urgent data. In this paper, we designed a MAC protocol that minimizes the power shortage that can occur during emergency data generation. For this, relay node requirements are set differently according to the urgency of data. The performance was analyzed through simulation. Simulation results show the reduced latency and improved reliability of urgent data transmission.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.7
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• pp.1026-1031
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• 2022

Cognitive Radio Ad-Hoc Networks (CRAHNs) enable to overcome the shortage of frequency resources due to the increase of radio services. In order to avoid interference with the primary user in CRANH, channel sensing to check the idle channel is required, and when the primary user appears, the time delay due to handover should be minimized through fast idle channel selection. In this paper, throughput was improved by reducing the number of channel sensing and preferentially sensing a channel with a high probability of being idle, using reinforcement learning. In addition, we proposed a multi-channel MAC (Medium Access Control) protocol that can minimize the possibility of collision with the primary user by sensing the channel at the time of data transmission without performing periodic sensing. The performance was compared and analyzed through computer simulation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.464-467
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• 2001

There nay be fierce debate over the nature of the medium that will herald the brave new world copper, fiber, wireless or satellite there is little doubt that future networks will be broadband in their capabilities. The Republic of Korea is a significant exception and leads the world, at present, in terms of number of subscribers with broadband access via ADSL. In order to further drive the growth in the broadband Internet access market, the government is scheduled to implement open access for ISPs and unbundling of the local loops of incumbent public telecom operators during the course of 2001. By the Way, Should incumbent telecommunication operators be obliged to provide unbundled access to the local loop\ulcorner

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.3 s.345
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• pp.84-94
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• 2006

In this paper, we propose the algorithm to reduce guard time of UWB MAC time slot for throughput gain. In the proposed draft by multiband ofdm alliance (MBOA), Guard time of each medium access slot (MAS) is composed of shortest inter-frame space (SIFS) and MaxDrift which is the time caused by maximum frequency offset among devices. In this paper, to reduceguard time means that we nearly eliminate MaxDrift term from guard time. Each device of a piconet computes relative frequency offset from the device initiating piconet using periodically consecutive transferred beacon frames. Each device add or subtract the calculated relative frequency offset to the estimated each MAS starting point in order to synchronize with calculated MAS starting point of the device initiating piconet. According to verification of simulations, if the frequency offset estimator is implemented with 8 decimal bit, the ratio of the wasted time to Superframe is always less than 0.0001.

• The Journal of the Acoustical Society of Korea
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• v.36 no.3
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• pp.211-217
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• 2017

In this paper, we propose a bidirectional full duplex MAC (Medium Access Control) protocol for underwater acoustic networks. An underwater sensor node can set a back-off timer according to the priority of transmission. When the back-off timer expires, the underwater sensor node acquires a transmission opportunity. If a source node wants to send data to a destination node, it broadcasts RTS (Request-To-Send) including ID of the destination node to neighbor nodes. The destination node receiving RTS sends CTS (Clear-To-Send) to the source node to inform the bidirectional full duplex communication. After the source node receives CTS, the source node and the destination node can send the data to each other. In the underwater environment, the existing MAC protocol may take a lot of time for successful transmission of data due to long underwater propagation delay. On the other hand, the proposed bidirectional full duplex MAC protocol improves the throughput by shortening the time for successful transmission of data. In this paper, we analyze the throughput of the proposed bidirectional full duplex MAC protocol. In addition, we show that the proposed bidirectional full duplex MAC protocol has better performance in the presence of the long underwater propagation delay compared with existing MAC protocols for underwater environments.

• Journal of information and communication convergence engineering
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• v.1 no.4
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• pp.213-216
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• 2003

A VPN is widely used in a communications environment which access is controlled to permit peer connections only within a defined community of interest. It is constructed through some form of partitioning of a common underlying communication medium, where this underlying communications medium provides services to the network on a non-exclusive basis. In this paper, we have analyzed a variety of architecture to implement Giga bps VPN system. The proposed architecture will satisfy the needs of clients who adopt Giga bps VPN system in the various environments.

• Proceedings of the IEEK Conference
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• summer
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• pp.321-324
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• 2004

A VPN is widely used in a communications environment which access is controlled to permit peer connections only within a defined community of interest. It is constructed through some form of partitioning of a common underlying communication medium, where this underlying communications medium provides services to the network on a non-exclusive basis. In this paper, we have analyzed a variety of architecture to implement Giga bps VPN system. The proposed architecture will satisfy the needs of clients who adopt Giga bps VPN system in the various environments.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.1 s.343
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• pp.111-120
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• 2006

In this paper, a node architecture of WDM metro network for connecting broadband access networks to converge wire/wireless networks. In consideration of the proposed node architecture and network requirements we proposed and evaluated medium access control protocols. We review WDM related technologies of sub-carrier multiplexing and optical components in order to resolve the bottleneck between optical backbone networks md access networks, and a access node architecture sharing common wavelength is introduced. Source-stripping (SS) MAC protocol Is evaluated under the proposed functional node architecture. DS+IS (Destination-Stripping and Source-Stripping) and DS+IS (Destination-Stripping and Intermediate-Stripping) MAC protocols are described to increase the slot-reuse factor which is low on SS MAC protocol. The key function of new MAC protocols regards the optical switch module of proposed node architecture and helps intermediate or source access nodes for dropping slots to destinations of different wavelength group. Thus, slot-reuse factor increases as the MAC protocols reduce the unnecessary ring-rotation of transferred slots. We use a numerical analysis to expect bandwidth efficiency and maximum throughput by slot-reuse factor Throughput network simulation, the verification of throughput, queuing delay, and transmission fairness are compared among MAC protocols.

• Journal of Information Technology Applications and Management
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• v.10 no.3
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• pp.109-120
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• 2003

This paper proposes an e-business maturity model for small and medium-sized enterprises. The model consists of five maturity levels, which are on-line access, on-line business, matured on-line business, and full on-line business from least matured level to most matured level. The model can be used to assess e-business maturity level of individual enterprises. individual enterprise's maturity level can be assessed by examining sample check lists. Additionally, this paper summarizes the results of an application of the proposed model to a couple of small and medium-sized enterprises. This model can also be used to suggest what individual enterprises need to be upgraded towards higher maturity level.

• East Asian Journal of Business Economics (EAJBE)
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• v.4 no.4
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• pp.24-32
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• 2016

There hardly have been support policies for small wholesale vendors or any materials such as proper statistical standards and figures compared to diversity of support policies and size of budget for small and medium manufacturing business. The biggest concern coming from it is that there have never been any policies for small and medium wholesale vendors. This study proposes some ways to improve support policies through investigating the current status of those vendors as their true values haven't been properly recognized, while diverse support systems have been devised for manufacturing business thanks to the traditional industrial development process. According to the study on support policies for domestic and international small and medium wholesale vendors, I realized that those vendors need a policy to ensure them to be promptly adjusted to the rapidly changing distribution environment and to be competitive to access to the global distribution market to finally become hidden champions through systematical operations of small and medium wholesale vendors and implementing educational business through sales management. Therefore, I propose five ways to improve support policies for small and medium wholesale vendors by considering social and economic value, systematizing small wholesalers and scaling small and medium wholesale vendors, reinforcing support for wholesalers, support policies for new online market opening and offline market opening.