• Journal of Computing Science and Engineering
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• 제11권2호
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• pp.49-57
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• 2017

This paper proposes a new IPv6 networking paradigm as a counter answer to the rationale for locator/identifier separation. Instead of involving separate number spaces each for node identifiers and locators, the context of the IP address as a node identifier alone is utilized and no additional locators are incorporated. That is, there are only node addresses and no locators, and location information is indirectly derived from neighbor relations between nodes. In order to accomplish this, no subnet IDs are utilized; the ID value is set to zero for all subnets. The paper details how to construct this paradigm through novel choice of operational policies in various IPv6 protocols and some trivial modifications. Especially, inherent provision of intra-domain node- as well as subnet-mobility by use of standard link-state intra-domain routing protocols is discussed. A number of important advantages of this paradigm over the canonical IPv6 networking and various known solutions of locator/identifier separation are discussed. Tailoring for multi-area domains and IPv4 is left for further study.

• 한국멀티미디어학회논문지
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• 제13권6호
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• pp.911-923
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• 2010

In wireless sensor networks (WSNs), cluster based data routing protocols have the advantages of reducing energy consumption and link maintenance cost. Unfortunately, most of clustering protocols have been designed for uniformly distributed sensor networks. However, some urgent situations do not allow thousands of sensor nodes being deployed uniformly. For example, air vehicles or balloons may take the responsibility for deploying sensor nodes hence leading a normally distributed topology. In order to improve energy efficiency in such sensor networks, in this paper, we propose a new cluster formation algorithm named DAEEC (Density Aware Energy-Efficient Clustering). In this algorithm, we define two kinds of clusters: Low Density (LD) clusters and High Density (HD) clusters. They are determined by the number of nodes participated in one cluster. During the data routing period, the HD clusters help the neighbor LD clusters to forward the sensed data to the central base station. Thus, DAEEC can distribute the energy dissipation evenly among all sensor nodes by considering the deployment density to improve network lifetime and average energy savings. Moreover, because the HD clusters are densely deployed they can work in a manner of our former algorithm EEVAR (Energy Efficient Variable Area Routing Protocol) to save energy. According to the performance analysis result, DAEEC outperforms the conventional data routing schemes in terms of energy consumption and network lifetime.

• 정보관리학회지
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• 제30권4호
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• pp.241-264
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• 2013

이 연구에서는 공개된 가중 네트워크 분석용 소프트웨어인 Opsahl의 tnet과 이재윤의 WNET에서 지원하는 가중 네트워크 중심성 지수를 비교 분석해보았다. tnet은 가중 연결정도중심성, 가중 근접중심성, 가중 매개중심성을 지원하고, WNET은 최근접이웃중심성, 평균연관성, 평균프로파일연관성, 삼각매개중심성을 지원한다. 가상 데이터를 대상으로 한 분석에서 tnet의 중심성 지수는 링크 가중치의 선형변화에 민감한 반면 WNET의 중심성 지수는 선형 변화에 영향을 받지 않았다. 실제 네트워크 6종을 대상으로 가중 네트워크 중심성을 측정하고 결과를 비교하여 두 소프트웨어의 가중 네트워크 중심성지수들의 특징을 파악하고 중심성 지수 간 관계를 살펴보았다.

• 디지털융복합연구
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• 제12권12호
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• pp.323-328
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• 2014

융합망에 사용되는 D-MAC 프로토콜은 사물간 무선링크를 연결하기 위해 설계된 프로토콜이다. 이 프로토콜은 이웃 노드 가운데 로컬 데이터 교환과 수집을 위해 제공되고, 싱크로부터 센서 노드로 제어패킷과 관심 패킷이 분배된다. 본 논문에서는 융합망의 D-MAC 보안 인증 적용 여부에 따른 전력소모 효율성에 대해 분석하였다. 인증기법이 MAC 통신에 적용될 경우, 인증처리 유무에 따라 프리앰블의 에너지 소비 여부가 연관이 된다. 인증이 적용될 경우 서비스 공격에 대응하여 에너지 소비가 감소된다. 향후 보안 인증기법에 관련한 연구를 수행할 계획이다.

• 한국통신학회논문지
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• 제34권4A호
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• pp.309-315
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• 2009

무선 Ad-hoc 네트워크는 이동 노드로 구성되는 동적 네트워크이다. 일반적으로 Ad-hoc 네트워크에서 노드는 랩탑, PDA, 모바일 폰 등과 같은 장치로 블루투스나 IEEE 802.11(위피) 네트워크 인터페이스의 특징을 가지고 분산방식으로 통신을 한다. 이러한 Ad-hoc 네트워크의 특성에 기인한 이동성은 라우팅 프로토콜 디자인에 중요한 특징적 요소가 된다. 본 논문에서는 토폴로지 변화에 잘 적응하는 향상된 경로 관리 기법을 제안한다. 제안된 알고리즘에 주된 특징은 경로 실패를 방지하기 위해서 링크 단절 전에 다음-홉 노드를 대체 이웃 노드에 스위칭 하는 방식이다. NS2를 이용한 무선 Ad-hoc 네트워크의 다양한 환경에서 시뮬레이션을 수행한 결과 제안된 알고리즘 성능이 기존의 AODV 프로토콜에 비교하여 향상되었음을 보인다.

• 한국통신학회논문지
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• 제37A권10호
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• pp.834-840
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• 2012

The use of ranging sensors on automobiles is becoming common with the desire of traffic safety by providing drivers the information of the relative distance between the vehicles. In this paper, the LED visible light ranging system different from the conventional ranging systems using the RF signal is investigated. For such a system, we propose a novel ranging algorithm which combines the time-of-flight (TOF) with the CDMA technology. Via the CDMA technology, the TOF ranging system can accurately distinguish the desired ranging signal from the visible light interferences of the neighbor vehicles. In addition, the proposed system can also overcome the light noise from other luminaries, i.e. sun-light, traffic-light, and so on. The simulation results show that the CDMA-based LED ranging system has a significant improvement for the ranging accuracy compared with the case without employing the CDMA.

• 한국전자통신학회논문지
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• 제4권1호
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• pp.14-19
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• 2009

노드의 이동성과 한정된 배터리 용량으로 무선애드혹 네트워크에서는 종종 경로 단절이나 패킷 손실이 발생한다. 본 논문에서는 수신 신호 세기의 변화를 측정함으로써 경로 단절 확률과 패킷손실을 줄일 수 있는 AODV (Ad hoc On-demand Distance Vector routing)에 기반을 둔 향상된 라우팅 프로토콜을 제안한다. 라우팅을 결정하기 위해 노드 이동성과 경로의 홉으로 이루어진 새로운 측정 함수를 사용하고, 데이터 전송 중 노드의 움직임에 의한 경로의 단절을 방지하기 위해 새로운 경로 관리 기법을 소개한다. 이웃 노드의 움직임을 감지되면, 경로가 단절되기 전에 라우팅 에이전트는 다음 홉 노드를 이웃노드로 변경한다. 시뮬레이션 결과를 통해 제안한 라우팅 기법의 성능이 기존의 AODV 방식보다 우수함을 보인다.

• Journal of Communications and Networks
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• 제16권4호
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• pp.371-377
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• 2014

Localized topology control is attractive for obtaining reduced network graphs with desirable features such as sparser connectivity and reduced transmit powers. In this paper, we focus on studying how to prolong network lifetime in the context of localized topology control for wireless multi-hop networks. For this purpose, we propose an energy efficient localized topology control algorithm. In our algorithm, each node is required to maintain its one-hop neighborhood topology. In order to achieve long network lifetime, we introduce a new metric for characterizing the energy criticality status of each link in the network. Each node independently builds a local energy-efficient spanning tree for finding a reduced neighbor set while maximally avoiding using energy-critical links in its neighborhood for the local spanning tree construction. We present the detailed design description of our algorithm. The computational complexity of the proposed algorithm is deduced to be O(mlog n), where m and n represent the number of links and nodes in a node's one-hop neighborhood, respectively. Simulation results show that our algorithm significantly outperforms existing work in terms of network lifetime.

• Bulletin of the Korean Chemical Society
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• 제30권7호
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• pp.1603-1606
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• 2009

A new 1D oxalato bridged compound Ni(en)(ox)-2$H_2$O, (ox = oxalate; en = ethylenediamine) has been hydrothermally synthesized and characterized by single crystal X-ray diffraction, IR spectrum, TG analysis, and magnetic measurements. In the structure the Ni atoms are coordinated with four oxygen atoms in two oxalate ions and two nitrogen atoms in one ethylenediamine molecule. The oxalate anion acts as a bis-bidentate ligand bridging Ni atoms in cis-configuration. This completes the infinite zigzag neutral chain, [Ni(en)(ox)]. The interchain space is filled by water molecules that link the chains through a network of hydrogen bonds. Thermal variance of the magnetic susceptibility shows a broad maximum around 50 K characteristic of one-dimensional antiferromagnetic coupling. The theoretical fit of the data for T > 20 K led to the nearest neighbor spin interaction J = -43 K and g = 2.25. The rapid decrease in susceptibility below 20 K indicate this compound to be a likely Haldane gap candidate material with S = 1.

• Journal of Information Processing Systems
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• 제14권6호
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• pp.1347-1360
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• 2018

Owing to limited energy in wireless devices power saving is very critical to prolong the lifetime of the networks. In this regard, we designed a cross-layer optimization mechanism based on power control in which source node broadcasts a Route Request Packet (RREQ) containing information such as node id, image size, end to end bit error rate (BER) and residual battery energy to its neighbor nodes to initiate a multimedia session. Each intermediate node appends its remaining battery energy, link gain, node id and average noise power to the RREQ packet. Upon receiving the RREQ packets, the sink node finds node disjoint paths and calculates the optimal power vectors for each disjoint path using cross layer optimization algorithm. Sink based cross-layer maximal minimal residual energy (MMRE) algorithm finds the number of image packets that can be sent on each path and sends the Route Reply Packet (RREP) to the source on each disjoint path which contains the information such as optimal power vector, remaining battery energy vector and number of packets that can be sent on the path by the source. Simulation results indicate that considerable energy saving can be accomplished with the proposed cross layer power control algorithm.