• Journal of the Institute of Electronics Engineers of Korea CI
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• v.44 no.3
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• pp.31-36
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• 2007

This paper proposes Co-MAC (Coexistence MAC), an energy efficient medium access control protocol designed for large-scale sensor networks. In Co-MAC protocol, an overall network is divided into independent subnets, and each subnet orthogonally operates on time line in a temporal fashion. The basic idea of Co-MAC is to evenly distribute sensor nodes in a certain geographic area based on subnets to minimize overhearing which means the reception of unnecessary data packets from neighboring nodes. In our simulation, it was observed that energy efficiency of Co-MAC outperforms conventional MAC protocols under the given conditions.

• Journal of Climate Change Research
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• v.3 no.4
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• pp.259-270
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• 2012

Mobile air conditioning(MAC) systems of light-duty vehicles consume the most energy among auxiliary parts. Vehicle $CO_2$ reduction policies in Korea, US EPA and EU include the strategies to reduce additional $CO_2$ by MAC operation with providing incentive for the high-efficient MAC technologies. It is under development how to estimate MAC $CO_2$ and to differentiate advanced or high-efficient MAC system in US EPA and EU. The additional energy by MAC operation would beaffected by not only driving patterns but also environmental conditions such as temperature and humidity. In this study, we estimated MAC $CO_2$ of Korean light-duty vehicles with various driving cycles and environmental conditions. Test results were corrected to reference conditions for varied temperature and humidity during tests to get the comparable data for test vehicles. The test results showed that high-efficient MAC technologies have potential to reduce MAC $CO_2$ approximately by 50%. Considering the rate of MAC $CO_2$ to vehicle $CO_2$, it is expected that the introduction of high-efficient MAC technologies would considerably reduce vehicle $CO_2$ emission in MAC operation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.11
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• pp.1162-1169
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• 2012

One of the important operational requirements for mission critical Ethernet networked system is having the fault tolerant capability. Such capability can be obtained by equipping multiport Network Interface Card (NIC) in each node in the system. Conventional NIC uses two or more Media Access Controls (MACs) and a co-processor for the MAC switching whenever an active port fails. Since firmware is needed for the co-processor, longer fail-over switching and degraded throughput can be generally expected. Furthermore the system upgrading requiring the firmware revision in each tactical node demands high cost. In this paper we propose a novel single MAC based NIC that does not use a co-processor, but just use general discrete building blocks such as MAC chip and switching chip, which results in better performances than conventional method. Experimental results validate our scheme.

• Journal of the Semiconductor & Display Technology
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• v.13 no.1
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• pp.73-81
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• 2014

In this paper, high-speed Hybrid MAC (Medium Access Control layer) implementation suitable for smart grid applications is researched. MB-OFDM (Multi-Band Orthogonal Frequency Division Multiplexing) is considered for high-speed communication method in smart grid application. In this paper, the MAC adopts the distributed network managing method. Also, the MB-OFDM merit of high-speed transfer rate of up to 480Mbps must be supported. Hence, this paper presents an efficient hardware-software integration (co-design) method in order to realize a high- speed transmission, and a realizing method of distribution network. Finally, MAC performance and reliability based on MB-OFDM PHY (PHYsical layer) are confirmed through simulation and emulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.9
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• pp.1819-1828
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• 2009

Until now, much research on cooperative communications to increase system throughput at Ad Hoc networks has been provided. In this paper, in order to enhance system throughput much more at Ad Hoc networks, a network coding-enabled new MAC protocol, called NC-MAC protocol, is proposed and its performance is evaluated with a mathematical approach. Numerical results show that this scheme provides conspicuously enhanced system throughput compared to DCF scheme, and more increased system throughput by 48% than rDCF and CO-MAC schemes.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.107-110
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• 2004

IEEE 802.15.3 is wireless Medium Access Control(MAC) and Physical Layer(PHY) specification for high rate WPAN (Wireless Personal Area Network). IEEE 802.15.3 MAC Layer provides Qos with three kinds of acknowledgements; No acknowledgement, Immediate acknowledgement, and Delayed acknowledgement. This paper presents how to improve QoS with new acknowledgement method called Delayed Negative acknowledgement. This paper describes the method of using Delayed Negative acknowledgement and presents the calculation of QoS improvement by using Delayed Negative acknowledgement.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.8
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• pp.841-848
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• 2013

In order for unlicensed devices to co-exist on the same frequency band, the frequency interference mitigation policy is necessary. Because the effects of frequency interference between unlicensed devices may vary depending on the analysis layer, exact interference analysis must be proceeded before making any related spectrum policy. In this paper, a frequency interference between WLAN and WPAN systems that operate at 2.4 GHz ISM band were analyzed in the physical layer and MAC layer, respectively. From the results, we confirmed that the interference analysis in MAC layer is closer to the measured results. Based on these investigations, we suggest a new co-existence criterion for unlicensed devices in MAC layer.

• Environmental and Resource Economics Review
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• v.27 no.3
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• pp.399-420
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• 2018

This study has attempted environmental economic analysis on the cost structure of offshore fisheries based on fishery management data published by the Fisheries Research Institute to examine the effect of the environmental policy on the fisheries for the effective implementation of the Paris Convention. Under the assumption that both fisheries and carbon dioxide are simultaneously produced, the cost structure of offshore fisheries were analyzed. Cost function in a translog form was estimated and SUR (Seemingly Unrelated Regression) model was used for the analysis. Here, $CO_2$ emission of offshore fishery was calculated by using National Federation of Fisheries Cooperatives' data on supply of tax exemption oil (2003~2016). The cost function estimation showed that there is a weak disposition between catches and $CO_2$ emissions during the sample period, and the marginal abatement cost (MAC) is estimated at 1,457 won per year. In addition, for the same period, when 1% of $CO_2$ per horsepower is to be reduced MAC increases by 2.2%, and when 1% of $CO_2$ per 1 ton of catch is to be reduced, MAC increases by 1.4%.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.8
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• pp.1877-1884
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• 2014

Because of the limited power resource, we need a reliable low-power media access control technique suitable for unmaned remote sensor operation condition for the unmanned sensor processor to perform the task in the remote wireless network situation. Therefore CSMA/CA and X-MAC is generally considered to effectively transmit the signal in the low-power wireless network. In this paper, we propose the more efficient low-power LP-MAC Technique which consumes the minimum power and transmits the data faster in condition that the mobile nodes' joining to and leaving from the network which consists of the fixed nodes is fluid. The fixed nodes operate in an asynchronous mode to perform the network self-configuration and transmit data faster to the mobile node which is frequently join and leave the network. When the mobile node leaves the network, the network's operation mode will be synchronous mode to achieve the minimum power consumption, thus the minimum power operation becomes possible.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.8
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• pp.1561-1570
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• 2009

Being different from traditional mobile communication networks or wireless LAN with access points, ad hoc network can provide direct communications between homogeneous stations. Thus, it can be considered as a much advanced network. Somehow, many researches have been done to enhance system performance of ad hoc networks up to now, one of which is cooperative communications. In this paper, a cooperative MAC protocol, called CO-MAC protocol, is proposed and its performance is evaluated with a mathematical approach. Numerical results show that this scheme provides more enhanced system throughput especially when frame transmission error probability is high than DCF scheme, which is the key protocol in IEEE 802.11 standard, and rDCF scheme.