• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.7B
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• pp.477-487
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• 2008

Congestion control of the TCP reduces transmission rate when it detects packet loss because packet loss origines from congestion in the wired network. In the wireless network, packet loss comes from channel errors. Wired TCP degrades performance when there are wireless losses because it does not classify type of loss. These day, there are many researches which classify type of loss between congestion loss and wireless loss for wired-wireless hybrid network. For wireless TCP, many of existing algorithms are based on the estimated bandwidth or variations of packet arrival time. In this paper, we propose a new TCP scheme to distinguish the wireless packet losses from the congestion packet losses using MIB of the IEEE 802.11 MAC. We perform excessive simulations using the NS-2 network simulator and analyze the simulation results to compare the performance of the proposed algorithm to other well-known algorithms. From simulation results, we know that proposed algorithm improves performance about 12% and 32% compared with Spike algorithm and mBiaz algorithm, respectively.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.59-60
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• 2006

TCP applied to the wireless-wired integrated network is the one that was applied to the existing wired network. In the wireless-wired integrated network, both wireless and congestion loss can occur. When wireless packet losses occur, the congestion control of TCP causes performance degradation by reducing its transmission rate. In this paper, we propose the algorithm to distinguish the wireless packet loss from congestion packet loss using MIB of the 802.11 MAC which has been generally used recently in wireless links.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4B
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• pp.391-398
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• 2011

In this paper, we propose a MAC protocol for visible light wireless LAN using LED light. The proposed MAC protocol has a function of automatic direction optimization for LED transceiver. There is periodical time slot for broadcasting and registration in the proposed MAC protocol. We used polling method for data transfer in the protocol since visible light is hard to detect carrier and collision by other mobile stations; thus we cannot use CSMA/CD method in visible light LAN. We also amended the MAC frame of IEEE 802.11 to propose a revised version for visible light wireless LAN using LED light. We investigate the performance of the proposed MAC protocol. When the bit rate of physical layer is 100 Mb/s, the net data throughput using the proposed MAC protocol is estimated to 94.386 Mb/s.

• The Journal of the Korea Contents Association
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• v.9 no.12
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• pp.515-527
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• 2009

IEEE 802.11n is an ongoing next-generation WLAN(Wireless Local Area Network) standard that supports a very high-speed connection with more than 100Mb/s data throughput measured at the MAC(Medium Access Control) layer. Study trends of IEEE 802.11n show two aspects, enhanced data throughput using aggregation among packets in MAC layer, and better data rates adapting MIMO(Multiple-Input Multiple-Output) in PHY(Physical) layer. But, the former doesn't consider wireless channel and the latter doesn't consider aggregation among packets for reality. Therefore, this paper analyzes data throughput for IEEE 802.11n considering MAC and PHY connection. A-MPDU(Aggregation-MAC Protocol Data Unit) and A-MSDU(Aggregation-MAC Service Unit) is adapted considering multi-service in MAC layer, WLAN MIMO TGn channel using SVD(Singular Value Decomposition) is adapted considering MIMO and wireless channel in PHY layer. Consequently, Simulation results shows throughput between A-MPDU and A-MSDU. Also, We use Ns-2(Network simulator-2) for reality.

• Korea Information Processing Society Review
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• v.16 no.3
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• pp.18-24
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• 2009

• The Transactions of the Korea Information Processing Society
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• v.2 no.4
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• pp.581-591
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• 1995

An MIB is the heart of a network management system and it stores all information that is necessary for network management. To operate networks safely, it is essential to control accesses to managed objects. This paper provides three-level architecture of managers so as to perform network management more efficiently in large networks. Moreover, mandatory access control(MAC) policy and role-based access control policy are adopted to ensure the secure access to the MIB. These policies are modeled by using the active object-oriented data model, which makes easy to map these access control models into the active object-oriented database.

• TTA Journal
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• s.110
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• pp.61-68
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• 2007

UWB는 2002년부터 FCC에서 상용을 허용한 이후 IEEE802.15.3a에서 DS-CDMA 방식과 MB-OFDM 방식을 논의해 왔으나 표준안 도출에 실패한 후 지금은 WiMedia Alliance와 UWB Forum에서 각기 표준화 진행중이다. Intel, Microsoft, HP 등이 주축인 WiMdeia Alliance는‘PAN 환경에서 장치간의 무선 멀티미디어 연결과 상호운용성’을 위하여 구성되었으며, 2003년 MBOA와 합병하여 MBOA 기술을 기반으로 하는 물리계층 및 MAC 계층 기능 규격을 ECMA 등에 표준으로 등록하였고, 그 외 표준화 단체에 표준안 채택을 위한 노력을 계속하고 있다. 또한 USB Forum, Bluetooth, IEEE1394 등에 MBOA 기반 응용이 사용될 수 있도록 노력하고 있으며, 2005년 MBOA 기반의 Certified Wireless USB 규격으로 UWB 시장을 선점하기 시작하였으며, Bluetooth 및 IEEE1394에서도 MBOA 기반 표준이 진행되고 있다. 본 고는 WiMedia Alliance의 최근 표준 활동과 WiMedia 규격을 활용한 국내.외 기술동향에 대하여 살펴보고자 한다.

• Information and Communications Magazine
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• v.24 no.9
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• pp.104-110
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• 2007

UWB는 2002년부터 FCC에서 상용을 허용한 이후 IEEE802.15.3a에서 DS-CDMA 방식과 MB-OFDM 방식을 논의해 왔으나 표준안 도출에 실패한 후 지금은 WiMedia Alliance와 UWB Forum에서 각기 표준화 진행중이다. Intel, Microsoft, HP 등이 주축인 WiMdeia Alliance는 "PAN 환경에서 장치간의 무선 멀티미디어 연결과 상호 운용성"을 위하여 구성되었으며, 2003년 MBOA와 합병하여 MBOA 기술을 기반으로 하는 물리계층 및 MAC 계층 기능 규격을 ECMA 등에 표준으로 등록하였고, 그 외 표준화 단체에 표준안 채택을 위한 노력을 계속하고 있다. 또한 USB Forum, Bluetooth, IEEE1394 등에 MBOA 기반 응용이 사용될 수 있도록 노력하고 있으며, 2005년 MBOA 기반의 Certified Wireless USB 규격으로 UWB 시장을 선점하기 시작하였으며, Bluetooth 및 IEEE1394에서도 MBOA 기반 표준이 진행되고 있다. 본 고는 WiMedia Alliance의 최근 표준 활동과 WiMedia 규격을 활용한 국내 외 기술동향에 대하여 살펴보고자 한다.

• Macromolecular Research
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• v.8 no.5
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• pp.231-237
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• 2000

The polymerization of 3-ethynylphenol, phenylacetylene having hydroxy functionality, was carried out by tungsten and molybdenum-based transition metal catalysts. The polymerization proceeded to give a moderate yield of polymer. The effects on the mole ratio of monomer to catalyst (M/C), initial monomer concentration ((Mb), and the polymerization temperature for the polymerization of 3-ethynylphenol were investigated. The catalytic activity of W-based catalysts was found to be greater than that of Mo-based catalysts. The resulting polymers were brown or black powders and mostly insoluble in organic solvents. Structural analysis of the polymer by instrumental methods revealed the conjugated polymer backbone structure carrying hydroxyphenyl moieties. Thermal and morphological properties of the resulting poly(3-ethynylphenol) were also discussed.