• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.11B
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• pp.946-955
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• 2004

It is shown that the do Bruijn graph (dBG) can be used as an architecture for interconnection network and a suitable structure for parallel computation. Recent works have classified dBG based routing algorithms into shortest path routing and fault tolerant routing but investigation into fault free shortest path (FFSP) on dBG has been non-existent. In addition, as the size of the network increase, more faults are to be expected and therefore shortest path dBG algorithms in fault free mode may not be suitable routing algorithms for real interconnection networks, which contain several failures. Furthermore, long fault free path may lead to high traffic, high delay time and low throughput. In this paper we investigate routing algorithms in the condition of existing failure, based on the Bidirectional do Bruijn graph (BdBG). Two FFSP routing algorithms are proposed. Then, the performances of the two algorithms are analyzed in terms of mean path lengths and discrete set mean sizes. Our study shows that the proposed algorithms can be one of the candidates for routing in real interconnection networks based on dBG.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9B
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• pp.751-759
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• 2008

Carrier Ethernet backbone network integrates distributed layer-2 based metro networks. In this networks, Multiple Spanning Tree Protocol (MSTP) has been uscd as a main routing protocol that allows multiple spanning trees in a network. A better routing protocol called IEEE802.1aq - Shortest Path Bridging (SPB) is recently proposed, that generates the shortest spanning tree per a destination node. As SPB provides a routing path per a destination node, there is no way to adapt network traffic at normal condition. If we are free from the principle of "a spanning tree per a destination node", we can achieve adaptive routing. Based on this philosophy, we propose a new spanning tree based protocol - Edge Node Divided Spanning Tree (ENDIST). ENDIST divides an edge node into sub-nodes as many as connecting links from the node and each sub-node generates a single shortest path tree based on SPB. Depending on network or nodal status, ENDIST chooses a better routing path by flow-basis. This added traffic engineering ability contributes to enhanced throughput and reduced delay in backbone networks. The simulation informs us that ENDIST's throughput under heavy load performs about 3.4-5.8 and 1.5-2.0 times compared with STP's and SPB's one respectively. Also, we verified that ENDIST's throughput corresponds to the theoretical upper bound at half of cases we investigated. This means that the proposed ENDIST is a dramatically enhanced and the close-to-perfect spanning tree based routing schemes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.746-754
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• 2016

Smart healthcare systems, a convergent industry based on information and communications technologies (ICT), has emerged from personal health management to remote medical treatment as a distinguished industry. The smart healthcare environment provides technology to deliver vital information, such as pulse rate, body temperature, health status, and so on, from wearable devices to the hospital network where the physician is located. However, since it deals with the patient's personal medical information, there is a security issue for personal information management, and the system may be vulnerable to cyber-attacks in wireless networks. Therefore, this study focuses on a key-development and device-management system to generate keys in the smart environment to safely manage devices. The protocol is designed to provide safe communications with the generated key and to manage the devices, as well as the generated key. The security level is analyzed against attack methods that may occur in a healthcare environment, and it was compared with existing key methods and coding capabilities. In the performance evaluation, we analyze the security against attacks occurring in a smart healthcare environment, and the security and efficiency of the existing key encryption method, and we confirmed an improvement of about 15%, compared to the existing cipher systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.1B
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• pp.42-48
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• 2002

In broadband wireless networks, the effective meeting of the QoS guarantees may strongly depend on the Contention Resolution Algorithm used in the uplink contention period. The time it takes a station to transmit a successful request to the base station, or request delay, must be kept low even during periods of high contention. If a request suffers many collisions, it cannot rely on the preemptive scheduler to receive low access delays. However, the conventional collision resolution algorithm has a problem that all collided stations are treated equally regardless of their delay from previous contention periods. Some requests may have very long request delay caused by continuous collisions. In this paper, we propose an adaptive collision resolution algorithm for fast random access in broadband wireless networks. The design goal is to provide quick access to the request with a high number of collisions. To do this, the proposed algorithm separates the whole contention region into multiple sub regions and permits access through each sub region only to the requests with equal number of collisions. The sub region is adaptively created according to the feedback information of previous random access. By simulation, the proposed algorithm can improve the performance in terms of throughput, random delay and complementary distribution of random delay by its ability to isolate higher priorities from lower ones. We can notice the algorithm provides efficiency and random access delay in random access environment.

• 전기의세계
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• v.43 no.1
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• pp.13-19
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• 1994

전자식 안정기는 최근 에너지 절약 정책과 관련하여 조명기기분야의 관심의 대상이 되었고, 절전 효율이 높은 고품질의 전자식 안정기에 대한 연구 개발 및 보급이 점점 더 확대되고 있는 추세이다. 일반적으로 전자식 안정기는 수십 KHz의 고주파에서 형광등을 구동시킴으로써 빛의 깜박거림과 가청잡음이 없으며, 저주파(60Hz)에서 사용하는 재래식 안정기(choke coil 방식)에 비해 높은 절전 효과를 얻을 수 있다[1-4]. 특히, 빌딩 사무실의 경우 낮에도 창가의 형광등이 켜져 있어서 막대한 전력을 낭비하고 있는 실정이므로, 일조량에 따른 자동 전력 조절이 가능한 전자식 형광등의 출현이 기대되고 있다. 전자식 안정기의 보급 확대를 위해서는 절전 효과 뿐만 아니라, 품질 문제, 수명 문제등을 고려하여야 하는 바, 예를 들면 순간 점등으로 방전초기의 sputtering 현상에 의한 lamp의 수명 단축, 미소 입력전압 변동에 따른 급격한 광출력의 변화로 절전 효과의 상실과 이상동작에 의한 스위칭 소자의 파괴 현상, 고주파 스위칭시 발생되는 전력손실과 noise등에 대한 대책이 요구되고 있다. 이러한 점을 개선하기 위해 추가되는 회로는 전자식 안정기 시스템을 더욱 복잡하게 만들고, 경제적으로 원가 부담을 주기 때문ㅇ 고품질의 전자식 안정기를 보급하는데 어려운 점으로 부각되고 있다. 본 고에서는 이러한 문제를 해결하기 위하여 조광기능을 포함한 다양한 제어회로와 보호회로를 조광기능을 포함한 다양한 제어회로와 보호회로를 1 chip에 수용하는 고품질의 전자식 안정기 제어용 집적회로에 대해서 기술하고자 한다.되어 나아갈 기술의 조류에도 부합하는 형태라 하겠다. 그러나 이 방식은 기 언급한 바와 같이 분산처리를 관장하는 운영체계의 개발에 상당한 고전이 따르리라 보여지며, 또한 보다 상세한 연구가 선행되어야 하겠지만 개발된 상용의 통신 프로토콜로서는 병렬처리의 성능을 극대화 하기에는 여러가지 제약이 있을 것으로 예측된다.기기들이 어떻게 응용되고 있는지 살펴보기로 하자. real informations would be available. Results are compared with those of optimal power flows.기능시험을 완료했으며 실제 line-of-sight(LOS) 시스템 구현에 적용중이다. 시대를 살아 갈 회원들이다. '컨텐츠의 시대'가 개막되는 것이며, 신세기통신과 SK텔레콤은 선의의 경쟁 과 협력을 통해 이동인터넷 서비스의 컨텐츠를 개발해 나가게 될 것이다. 3배가 높았다. 효소 활성에 필수적인 물의 양에 따른 DIAION WA30의 라세미화 효율에 관하여 실험한 결과, 물의 양이 증가할수록 그 효율은 감소하였다. DIAION WA30을 라세미화 촉매로 사용하여 아이소옥탄 내에서 라세믹 나프록센 2,2,2-트리플로로에틸 씨오에스터의 효소적 DKR 반응을 수행해 보았다. 그 결과 DIAION WA30을 사용하지 않은 경우에 비해 반응 전환율과 생성물의 광학 순도는 급격히 향상되었다. 전통적 광학분할 반응의 최대 50%라는 전환율의 제한이 본 연구에서 찾은 DIAION WA30을 첨가함으로써 성공적으로 극복되었다. 또한 고체 염기촉매인 DIAION WA30의 사용은 라세미화 촉매의

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.2
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• pp.1-11
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• 2020

As an important basic building block of the smart grid environment, smart meter provides real-time electricity consumption information to the utility. However, ensuring information security and privacy in the smart meter data aggregation process is a non-trivial task. Even though the secure data aggregation for the smart meter has been a lot of attention from both academic and industry researchers in recent years, most of these studies are not secure against internal attackers or cannot provide data integrity. Besides, their computation costs are not satisfactory because the bilinear pairing operation or the hash-to-point operation is performed at the smart meter system. Recently, blockchains or distributed ledgers are an emerging technology that has drawn considerable interest from energy supply firms, startups, technology developers, financial institutions, national governments and the academic community. In particular, blockchains are identified as having the potential to bring significant benefits and innovation for the electricity consumption network. This study suggests a distributed, privacy-preserving, and simple secure smart meter data aggregation system, backed up by Blockchain technology. Smart meter data are aggregated and verified by a hierarchical Merkle tree, in which the consensus protocol is supported by the practical Byzantine fault tolerance algorithm.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.10
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• pp.37-46
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• 2007

In wireless sensor networks, one of the most important goals of designing protocols is to extend the network lifetime. A node has lots of duplication in sensing and communication range with surrounding nodes after many of nodes are randomly scattered. Such a heavy duplication overhead affects on the network lifetime seriously so usually all nodes need not activated constantly to carry out sensing and communication operation. One of the optimal methods of prolonging the network lifetime is finding the number of surrounding nodes necessary to maintain the network coverage and connectivity. It has been studied till the current date in wireless networks. If the neighbor necessary can be acquired to satisfy the probability using the ideal number of neighbors necessary and the acquired number of neighbors m to guarantee network coverage and connectivity. We use the result that F. Xue et al and S. Song et al derive previously in finding the neighbor necessary to guarantee the network connectivity and cany out the computer simulation to verify the necessary number. We present that our scheme satisfy the network coverage and connectivity. We present the simulation results compared with constant probability scheme through computer simulation.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.9
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• pp.144-155
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• 2013

This paper presents a low-cost remote power-quality-failure monitoring system (RPMS) using Android App and TI MCU (micro-controller unit), which is appliable to a micro-grid. The designed RPMS testbed consists of smart nodes, a server, and Android APPs. Especially, the C2000-series MCU-based RPMS smart node that is low-cost compared to existing monitoring systems has both a signal processing function for power signal processing and a data transmission function for power-quality monitoring data transmission. The signal processing function implements both a wavelet-based power failure detection algorithm including sag, swell, and interruption, and a FFT-based power failure detection algorithm including harmonics such that reliable and real-time power quality monitoring is guaranteed. The data transmission function implements a low-complexity RPMS transmission protocol and defines a simple data format (msg_Diag) for power monitoring message transmission. We may watch the monitoring data in real time both at a server and Android phone Apps connected to the WiFi network (or WAN). We use RS-232 (or Bluetooth) as the wired (or wireless) communication media between a server and nodes. We program the RPMS power-quality-failure monitoring algorithm using C language in the CCS (Code Composer Studio) 3.3 environment.

• The Journal of the Korea Contents Association
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• v.10 no.3
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• pp.44-52
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• 2010

The most popular world wide web traffic in the Internet uses TCP as the transport layer protocol. Since TCP utilizes the single path, it can not communicate with the correspondent host during the link-down. On the other hand, SCTP can still communicate with the other SCTP entity by using alternate path even while the primary path is down. Most of previous studies have conducted the performance comparison research between TCP and SCTP by using typical file transfer. Since web traffic with self-similarity is characterized by the packet inter-arrival times and shape parameter affecting the size of web file in the Pareto distribution, it is necessary to perform the experiments considering these parameters. This paper aims to compare the throughput between TCP and SCTP while varying parameters reflecting the web traffic characteristics in link-down environment. Experimental results for web traffic using NS-2 simulator show that the throughput of SCTP using multi-homing is better than that of TCP. Simulation also shows that TCP is more affected than SCTP by mean inter-arrival and shape parameters with regard to the web traffic. These results can be applied to estimate the performance variation of web traffic due to the duration of link-down.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.7
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• pp.613-621
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• 2016

This research connected network equipment, including CCTV, PAGA, IP-PBX, and Legacy, in order to enable the operation and configuration of internal IP-based network equipment in maritime plants and vessels, both in the field and from remote places, and to allow for the support of remotely controlling such equipment. It also realized an operating program for the integrated network equipment management system to enable the monitoring and control of equipment status, operation condition, and notifications from distant places. By applying the operating program to satellite stations and vessels sailing on the sea, a performance test was conducted to evaluate data loss and transmission/reception delay in the communication section between the land and vessels. As a result, this research verified the normal operation of CCTV control and of real-time monitoring and control of the network equipment, including PAGA, IP-PBX, and Legacy under the FBB and MVSAT environments. It was observed that the transmission of CCTV video images with a large volume of data as well as the transmission and reception of voice data were found to be slightly delayed, indicating the need to develop technology to compress and convert data for real-time transmission and reception.