• Proceedings of the Korean Information Science Society Conference
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• 2006.10d
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• pp.625-630
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• 2006

Zigbee 센서 네트워크에서는 multihop 전송을 위하여 tree topology와 beacon-enabled 네트워크 구성을 갖는다. 이러한 multihop beaconing 네트워크의 목적은 routing 노드들에게 Sleep할 기회를 주어 파워의 소모를 줄이고자 하는 데 있다. 파워의 소모를 줄이고 beacon 전송시의 충돌을 방지하기 위하여 beacon 전송 스케줄링이 필요한데 본 논문은 multihop을 지원하고 에너지 효율에 효과적인 beacon 전송 스케줄링 알고리즘과 이를 바탕으로 에너지 효율적인 라우팅 기법을 제안한다. 본 제안은 Zigbee coordinator의 beacon interval(BI)이 결정되면 네트워크 내의 beacon을 전송하는 모든 노드들은 Zigbee coordinator의 BI를 알고 모든 노드의 superframe duration(SD)은 동일하다고 가정한다. 이러한 가정하에서 beacon을 전송하는 노드들이 Zigbee coordinator의 BI 구간 중 항상 정해진 시간에 자신의 beacon을 전송한다면 beacon의 충돌을 막을 수 있음을 보여 준다. 또한 노드들이 서로의 beacon 전송 시간을 알 수 있기 때문에 목적지 노드의 beacon을 tracking하지 않고도 목적지 노드가 active 되는 시점에 패킷을 전송하면 에너지 측면에서 좀 더 효율적인 라우팅 기반을 제공한다는 것을 보여 준다.

• Journal of Digital Contents Society
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• v.7 no.1
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• pp.53-58
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• 2006

In this paper, We proposed extraction method using EZW a specific character and then add watermark significant coefficient of image. After wavelet transform in image, the significant coefficient value add to watermark information image. In this method, the locations of nonzero wavelet coefficients are encoded with a tree structure, called zerotree, which can exploit the self-similarity of the pyramid decomposition across different scales. The simulation shows that this method provides a superior performance over conventional method and can be successfully applied to the application areas that requires of progressive transmission and search for image data.

• Journal of architectural history
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• v.2 no.2 s.4
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• pp.89-106
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• 1993

Wherever Buddhism has flourished, there were stupas in the form of monuments which have their origin in the tumulm of prehistoric times. After the death of Buddha, his body was cremated following the Indian funeral custom. His ashes, which long reserved for the remains of nobles and holymen, were enshrined under such artificial hills of earth and brick. The Stupa was in origin a simple burial-mound. The form of the burial-mound was a symbolical or magic reconstruction of the imagined shape of the sky, like a dome covering the earth. The domical form of the earliest tumuli may have been concious replicas of the shape of the Vedic hut. There are relationships which may have originally existed between the stupa and West Asiatic monuments. Buddhist Stupa originally cosisted of an almost hemispherical tumulus(anda) and an altar-like structure (harmika) on its top, surmounted by one or several superimposed honorific umbrellas (hti, catta). This hemispherical form is associated with centralisation, lunar worship, mother earth, and Siva. Anda means a symbol of latent creative power, the harmika symbolizes the sanctuary enthroned aboved the world. The honorific umbrella, as an abstract imitation of the shade-giving tree is one of the chief solar symbols and that of enlightenment.

• Journal of Digital Contents Society
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• v.18 no.5
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• pp.933-942
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• 2017

In this paper, we propose a web crawler service method for collecting information efficiently about college students and job-seeker's external activities, competition, and scholarship. The proposed web crawler service uses Jsoup tree analysis and Json format data transmission method to avoid problems of duplicated crawling while crawling at high speed. After collecting relevant information for 24 hours, we were able to confirm that the web crawler service is running with an accuracy of 100%. It is expected that the web crawler service can be applied to various web sites in the future to improve the web crawler service.

• ETRI Journal
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• v.37 no.3
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• pp.480-490
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• 2015

The reliability of sensor networks is generally dependent on the battery power of the sensor nodes that it employs; hence it is crucial for the sensor nodes to efficiently use their battery resources. This research paper presents a method to increase the reliability of sensor nodes by constructing a connected dominating tree (CDT), which is a subnetwork of wireless sensor networks. It detects the minimum number of dominatees, dominators, forwarder sensor nodes, and aggregates, as well as transmitting data to the sink. A new medium access control (MAC) protocol, called Homogenous Quorum-Based Medium Access Control (HQMAC), is also introduced, which is an adaptive, homogenous, asynchronous quorum-based MAC protocol. In this protocol, certain sensor nodes belonging to a network will be allowed to tune their wake-up and sleep intervals, based on their own traffic load. A new quorum system, named BiQuorum, is used by HQMAC to provide a low duty cycle, low network sensibility, and a high number of rendezvous points when compared with other quorum systems such as grid and dygrid. Both the theoretical results and the simulation results proved that the proposed HQMAC (when applied to a CDT) facilitates low transmission latency, high delivery ratio, and low energy consumption, thus extending the lifetime of the network it serves.

• Convergence Security Journal
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• v.5 no.1
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• pp.85-92
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• 2005

For an efficient role based access control in highly distributed computing environment to reduce management cost, we utilize attribute certificates. Especially highly distributed computing environments such as ubiquitous computing environments which cannot have global or broad control, need another attribute certificate management technique. The techniques for transmission of the attribute certificates and management of the group keys should be considered to reduce management cost. For better performance we structure attribute certificates. We group roles and make the role group relation tree. It results secure and efficient role renewing and distribution. For scalable attribute certificate distribution, multicasting packets are used. We take into account the packet loss and quantifying performance enhancements of structuring attribute certificates.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7B
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• pp.848-857
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• 2011

Due to the advantages of a conveniet, inexpensive installation, flexibility, and scalability, Wireless AMR systems are recently preferred over wired AMR systems. However, a multi-hop supported AMR network, which generally covers large areas, may create energy wastage problem, energy unbalance, and high interference hazard due to a large amount of concurrent-intensive metering data in the network. Therefore in this paper we propose a novel data gathering method which can solve abovementioned problems as well as conserve energy, by reducing the traffic in the network. In addition, the experimental results demonstrate that the proposed scheme shows superior performance to the conventional data transmission method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.3
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• pp.586-597
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• 2004

MAC (Medium Access Control) protocol is necessary for a OLT (Optical Line Termination) to allocate bandwidth to ONUs (Optical Network Units) dynamically in ATM PON (Passive Optical Network) operated in a kind of optical subscriber network having tree topology. The OLT collect information about ONUs and provide all permission with each ONU effectively by means of MAC protocol. Major functions of MAC protocol are composed of the algorism for distributing permission demanded by a ONU dynamically and allocation all permission used in APON properly. Sometimes MAC get to be a element of limiting the whole operation speed and occupy a most frequent operation part of the TC (Transmission Convergence) function module so it have to be designed to guarantee the best quality for each traffic. This paper introduce the way of implementation of a algorism which satisfy all of the upper renditions. This MAC algorism allocate bandwidth according to a number of working ONU and the information of the queue length dynamically and distribute permission for same interval to minimize delay variation of each ONU cell. MAC scheduler for the dynamic bandwidth allocation which is introduced in this paper has look-up table structure that makes programming possible. This structure is very suitable for implementation and operated in high speed because it require very simple and small chip size.

• Journal of KIISE:Information Networking
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• v.30 no.4
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• pp.513-519
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• 2003

In order to deliver multicast traffic efficiently, multicast routing and reliable transmission mechanisms are required. The reliable delivery implies that lost packets must be retransmitted, which in turn requires that transmitted packets be stored in a retransmission buffer. Therefore how to manage a retransmission buffer is important and, in this paper, we try to solve the problem of how many packets should be maintained in the buffer. Our proposed scheme, the timer-based buffer management (TBM), maintains only necessary amount of buffer based on the timer value calculated from the NAKs between the replier and receivers on a multicast tree and can adjust to the dynamic network conditions. By performing simulations, we show that TBM manages the buffer efficiently regardless of the error situation, network size, and so on.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.2
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• pp.269-286
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• 2011

In this paper, we study a problem that is concerning how to construct a delay-constrained multicast tree on a wireless mesh network (WMN) such that the number of serviced clients is maximized. In order to support high-quality and concurrent interference-free transmission streams, multiple radios are implemented in each mesh node in the WMNs. Instead of only orthogonal channels used for the multicast in the previous works, both orthogonal and partially overlapping channels are considered in this study. As a result, the number of links successfully allocated channels can be expected to be much larger than that of the approaches in which only orthogonal channels are considered. The number of serviced subscribers is then increased dramatically. Hence, the goal of this study is to find interference-free and delay-constrained multicast trees that can lead to the maximal number of serviced subscribers. This problem is referred as the MRDCM problem. Two heuristics, load-based greedy algorithm and load-based MCM algorithm, are developed for constructing multicast trees. Furthermore, two load-based channel assignment procedures are provided to allocate interference-free channels to the multicast trees. A set of experiments is designed to do performance, delay and efficiency comparisons for the multicast trees generated by all the approximation algorithms proposed in this study.