• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권11호
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• pp.4644-4661
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• 2015

Wireless sensor networks are often organized in the form of clusters leading to the new framework of WSN called cluster or hierarchical WSN where each cluster head is responsible for its own cluster and its members. These hierarchical WSN are prone to various routing layer attacks such as Black hole, Gray hole, Sybil, Wormhole, Flooding etc. These routing layer attacks try to spoof, falsify or drop the packets during the packet routing process. They may even flood the network with unwanted data packets. If one cluster head is captured and made malicious, the entire cluster member nodes beneath the cluster get affected. On the other hand if the cluster member nodes are malicious, due to the broadcast wireless communication between all the source nodes it can disrupt the entire cluster functions. Thereby a scheme which can detect both the malicious cluster member and cluster head is the current need. Abnormal energy consumption of nodes is used to identify the malicious activity. To serve this purpose a learning based energy prediction algorithm is proposed. Thus a two level energy prediction based intrusion detection scheme to detect the malicious cluster head and cluster member is proposed and simulations were carried out using NS2-Mannasim framework. Simulation results achieved good detection ratio and less false positive.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 춘계학술대회
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• pp.781-783
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• 2014

유동성을 가진 노드들로 구성된 모바일 애드 혹 네트워크(Mobile Ad hoc Network)는 토폴로지의 변화에 따른 오버헤드를 발생한다. 오버헤드를 줄이기 위해, 클러스터를 형성하여 클러스터 헤드노드를 통해 통신하는 계층적 네트워크연구가 진행되어 왔다. 클러스터 헤드노드가 트래픽의 집중에 의해 트래픽이 증가하면, 클러스터 멤버노드는 목적지 노드에게 메시지를 전달하지 못하는 상황이 발생한다. 이를 해결하기 위해 본 논문에서는 Step Parent 알고리즘을 제안한다. 본 논문에서 제안하는 알고리즘은 클러스터 멤버노드는 통신 반경 안에 있는 클러스터 헤드노드들의 경로를 통해, 클러스터 멤버노드가 속한 클러스터 헤드노드의 트래픽을 파악한다. 클러스터 헤드노드가 트래픽이 집중되어 있을 경우, 클러스터 멤버노드는 타 클러스터 헤드노드의 경로 정보를 이용하여, 새로운 라우팅 경로를 생성하고 메시지를 전달함으로써, 네트워크 전달성이 증가한다.

• 한국정보통신학회논문지
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• 제19권4호
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• pp.1001-1008
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• 2015

모바일 애드 혹 네트워크(Mobile Ad hoc Network)는 유동성을 가진 노드들로 구성된 네트워크로써 각 노드들은 라우팅의 역할을 하여 통신기반 시설이 없어도 스스로 네트워크를 구축하는 기능을 가진다. 이러한 모바일 애드 혹 네트워크에서는 노드의 유동성에 의한 토폴로지의 변화가 빈번하며, 토폴로지의 변화를 줄이기 위해 계층적 네트워크에 대한 연구가 진행되었다. 계층적 네트워크에서 클러스터 멤버노드는 클러스터 헤드노드를 통해 통신하며, 클러스터 헤드노드의 패킷 저장 공간에 비해 수신 받은 패킷의 양이 초과하였을 경우, 소속된 클러스터 멤버노드는 패킷을 베이스스테이션에게 전송할 수 없다. 이러한 문제를 해결하기 위해 본 논문에서는 로드밸런싱을 이용하여 분산노드를 선정하는 Load Tolerance(LT)알고리즘을 제안한다. 본 논문에서 제안하는 알고리즘은 클러스터 멤버노드가 로드밸런싱이 집중되어 있는 클러스터 헤드노드에 의해 통신을 할 수 없는 경우, 선정된 LT노드를 통해 지속적인 통신을 하는 알고리즘이다. 모의실험 결과, 클러스터가 형성된 계층적 네트워크에서 제안된 알고리즘의 전송률이 향상됨을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권6호
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• pp.2513-2533
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• 2018

In cognitive radio technology, the overall efficiency of communications systems can be improved without allocating additional bands by allowing a secondary system to utilize the licensed band when the primary system, which has the right to use the band, does not use it. In this paper, we propose a fast and reliable common channel initialization protocol without any exchange of initialization messages between the cluster head and the member nodes in cognitive ad-hoc networks. In the proposed method, the cluster and member nodes perform channel-based spectrum sensing. After sensing, the cluster head transmits a system activation signal through its available channels with a predetermined angle difference pattern. To detect the cluster head's transmission channels and to join the cluster, each member node implements fast Fourier transform (FFT) and computes autocorrelation for the angle difference sequence of the received signal patterns. This is compared to the predetermined reference angle difference pattern. The join-request and channel-decision procedures are presented in this paper. Performance evaluation of the proposed method is presented in the simulation results.

• 디지털산업정보학회논문지
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• 제10권2호
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• pp.75-82
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• 2014

MANET has various types of attacks. In particular, routing attacks using characteristics of movement of nodes and wireless communication is the most threatening because all nodes which configure network perform a function of router which forwards packets. Therefore, mechanisms that detect routing attacks and defense must be applied. In this paper, we proposed hierarchical structure attack detection techniques in order to improve the detection ability against routing attacks. Black hole detection is performed using PIT for monitoring about control packets within cluster and packet information management on the cluster head. Flooding attack prevention is performed using cooperation-based distributed detection technique by member nodes. For this, member node uses NTT for information management of neighbor nodes and threshold whether attack or not receives from cluster head. The performance of attack detection could be further improved by calculating at regular intervals threshold considering the total traffic within cluster in the cluster head.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권10호
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• pp.4223-4249
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• 2015

A novel jamming detection technique to detect the presence of jamming in the downstream direction for cluster based wireless sensor networks is proposed in this paper. The proposed technique is deployed in base station and in cluster heads. The proposed technique is novel in two aspects: Firstly, whenever a cluster head receives a packet it verifies whether the source node is legitimate node or new node. Secondly if a source node is declared as new node in the first step, then this technique observes the behavior of the new node to find whether the new node is legitimate node or jammed node. In order to monitor the behavior of the existing node and new node, the second step uses two metrics namely packet delivery ratio (PDR) and received signal strength indicator (RSSI). The rationality of using PDR and RSSI is presented by performing statistical test. PDR and RSSI of every member in the cluster is measured and assessed by the cluster head. And finally the cluster head determines whether the members of the cluster are jammed or not. The CH can detect the presence of jamming in the cluster at member level. The base station can detect the presence of jamming in the wireless sensor network at CH level. The simulation result shows that the proposed technique performs extremely well and achieves jamming detection rate as high as 99.85%.

• 천문학회보
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• 제43권2호
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• pp.37.2-37.2
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• 2018

We present the results from a spectroscopic survey of the nearby galaxy cluster Abell 2107 at z=0.04 that has been known as a rotating cluster. By combining 978 new redshifts from the MMT/Hectospec observations with the data in the literature, we construct a large sample of 1968 galaxies with measured redshifts at R<60', which results in high (80%) and spatially uniform completeness at $m_{r,Petro,0}<19.1$. We use this sample to study the global rotation of the cluster and its connection to the large-scale structures in the universe. We first apply the caustic method to the sample and identify 285 member galaxies in Abell 2107 at R<60'. We then measure the rotation amplitude and the position angle of rotation axis. The member galaxies show strong global rotation at R<20' ($V/{\sigma}{\sim}0.60-0.70$) with a significance of >3.8 ${\sigma}$, which is confirmed by two independent methods. The rotation becomes weaker in outer regions. We find at least four filamentary structures at $R<30h^{-1}Mpc$ smoothly connected to the cluster galaxies, which can suggest that the global rotation of the cluster is induced by the inflow of galaxies from the surrounding large-scale structures in the universe.

• 한국지구과학회지
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• 제36권5호
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• pp.427-436
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• 2015

We classified Abell clusters using the magnitude differences between two or three bright member galaxies and investigated how such classification was correlated with the properties of brightest cluster galaxies (BCGs). S-type BCGs being clearly brighter than the rest of the member galaxies were likely to be red, luminous, and evolved as early type galaxies. On the other hand, T-type BCGs being not dominant at all were less luminous than early type galaxies. A small fraction of BCGs was currently forming stars, and all of the star-forming BCGs were T-type BCGs. Active galactic nuclei were most frequent for S-type BCGs. Through these quantitative analyses of the BCG properties, we discussed the possible scenario of BCG formation and the differences between S-type and T-type of BCGs.

• 천문학회지
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• 제29권spc1호
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• pp.55-56
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• 1996

In order to investigate the spatial orientation of the spin vectors of galaxies in the Virgo cluster, we carried out a detailed identification of all the certain and possible member disk galaxies with four UK Schmidt Telescope (UKST) III a-j direct plates digitized by the Automated Plate Measuring System (APM). As a result, a relatively large and complete database with no selection effect of the member galaxies has been established. We provide the APM measured values of the position angle (P.A.) and diameters at the isophotal level of 24.5 $m_j / arcsec^2$. Based on this newly generated database, an initial study on the spatial orientation of the spin vectors of galaxies in the Virgo cluster is shown.

• 디지털산업정보학회논문지
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• 제9권1호
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• pp.87-93
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• 2013

MANET has the advantage of having the flexibility to build easily a network in a difficult situation that builds a wired network. But, data transmission errors by movement of nodes and eavesdropping by wireless communications have become a problem of security. Authentication service is the most essential in order to overcome these problems and operate network stably. In this paper, we propose 3-tiers authentication structure to exclude of malicious node and operate stable network through more systematic and thorough node authentication. After network is composed into a cluster, cluster head which play CA role is elected. Among these, the highest-CA is elected. The highest-CA receives certificates to cluster head and the cluster head evaluates trust value of their member nodes. Authentication technique which issues member node key is used. We compared PSS and experimented to evaluate performance of proposed scheme in this paper and efficiency of the proposed technique through experience was confirmed.