• Journal of Advanced Navigation Technology
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• v.12 no.6
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• pp.619-626
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• 2008

In this paper, we proposed a RSS based cooperative localization algorithm using VRN for wireless sensor networks, which can estimate the BN position. The proposed localization system monitoring all nodes estimates a position of BN, and calculates an intersection area with cooperative localization. From the results, we confirm that BN intersection area is reduced as the number of RN is increased. In addition, the fewer RN exists, the more iteration needs at least 4 times. Moreover, the propose algorithm using 4 RNs is improved 71.6% estimation performance than conventional method. Therefore, the cooperative localization algorithm with VRN provides higher localization accuracy than RSS based conventional method.

• The KIPS Transactions:PartC
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• v.14C no.1 s.111
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• pp.87-94
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• 2007

In mobile ad hoc networks the most popular on demand routing protocols are the Dynamic Source Routing (DSR) protocol and the Ad hoc On demand Distance Vector (AODV) routing protocol. These and other representative standard routing protocols are designed to find and maintain only a single path. Whenever there is a link break on the active route, source node has to invoke a route discovery process from the beginning and it causes a lot of overhead. Multipath routing protocols, which can alleviate these problems by establishing multiple alternative paths between a source and a destination, are widely studied. In this paper we propose a node disjoint multipath discovery technique based on AODV local route discovery. This technique can find and build completely separated node disjoint multi paths from a source to a destination as many as possible. It will make routing more robust and stable.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.4
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• pp.39-46
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• 2013

Cooperative spectrum sensing can improve sensing reliability, compared with single node spectrum sensing. In addition, Eigenvalue-based spectrum sensing has also drawn a great attention due to its performance improvement over the energy detection method in which the more smoothing factor, the better performance is achieved. However, the more smoothing factor in Eignevalue-based spectrum sensing requires the more sensing time. Furthermore, more reporting time in cooperative sensing will be required as the number of nodes increases. Subsequently, we in this paper propose an Eigenvalue and superposition-based spectrum sensing where the reporting time is utilized so as to increase the number of smoothing factors for autocorrelation calculation. Simulation result demonstrates that the proposed scheme has better detection probability in both local as well as global detection while requiring less sensing time as compared with conventional Eigenvalue-based detection scheme.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10b
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• pp.191-193
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• 1998

지금까지 제시된 최근접 질의 알고리즘은다소간의 cklms 있으나 기본적으로 질의 점과 MBR간의 최소거리에 기반한 분기와 한정 기법을 이용하고 있다. 그러나 차원이 증가함에 따라 질의 구와 겹치는 노드가 급속히 증가하기 때문에 최근접 질의 알고리즘의 성능은 매우 비효율적이다. 이러한 문제를 해결하기 위해서 MBR 간의 중첩을 줄이고 MBR 내에 가급적 많은 점을 포함할 수 있는 다양한 다차원 색인 구조가 제시도 되었다. 그러나 우리의 실험에 의하면 이러한 방법이 근본적인 해결책이 되지 못함을 알 수 있다. 고차원 백터 공간 모델이 가지는 문제로써 임의의 질의 점으로부터 모든 데이터 점들까지의 거리가 차원이 올라감에 따라 유사해지는 현상 때문에 비효율적인 성능이 나옴을 본 논문에서 지적한다.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.12
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• pp.56-63
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• 2012

The WBAN technology means a short distance wireless network which provides each device interactive communication by connecting devices inside and outside of body. Standardization on the physical layer, data link layer, network layer and application layer is in progress by IEEE 802.15.6 TG BAN. Wireless body area network is usually configured in energy efficient using sensor and zigbee device due to the power limitation and the characteristics of human body. Wireless sensor network consist of sensor field and sink node. Sensor field are composed a lot of sensor node and sink node collect sensing data. Wireless sensor network has capacity of the self constitution by protocol where placed in large area without fixed position. Mobile sink node distribute energy consumption therefore network life time was increased than fixed sink node. The energy efficient is important matter in wireless body area network because energy resource was limited on sensor node. In this paper we proposed cluster topology algorithm for efficient data transmission in wireless body area network based mobile sink. The proposed algorithm show good performance under the advantage of grid routing protocol and TDMA scheduling that minimized overlap area on cluster and reduced amount of data on cluster header in error prone wireless sensor network based on mobile sink.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.3
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• pp.441-450
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• 2015

Nowadays, many WLAN access points (APs) are deployed in hotspot areas such as shopping malls and stations. As the number of WLAN APs deployed increases, how to manage densely deployed APs in an efficient manner becomes one of the most important issues in WLANs. In this environment, uncoordinated multicast services can lead to frequent collisions due to simultaneous transmissions among APs. In this paper, we propose a multicast scheduling algorithm that can exploit simultaneous transmissions in multiple sectors and avoid redundant transmissions in dense networks. Simulation results demonstrate that the proposed scheme can reduce the multicast transmission latency compared to comparison scheduling schemes.

• Journal of Korea Multimedia Society
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• v.12 no.11
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• pp.1609-1622
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• 2009

In wireless sensor networks, a clustering protocol is an efficient method to prolong network lifetime. In general, it results in more energy consumption at the cluster-head node. Hence, such a protocol must changes the cluster formation and cluster-head node in each round to prolong the network lifetime. But, this method also causes large amount of energy consumption during the set-up process of cluster formation. In order to improve energy efficiency, in this paper, we propose a new clustering algorithm. In this algorithm, we exclude duplicated data of adjacent nodes and transmits the threshold value. We define a group as the sensor nodes within close proximity of each other. In a group, a node senses and transmits data at a time on the round-robin basis. In a view of whole network, group is treated as one node. During the setup phase of a round, intra clusters are formed first and then they are re-clustered(network cluster) by choosing cluster-heads(group). In the group with a cluster-head, every member node plays the role of cluster-head on the round-robin basis. Hence, we can lengthen periodic round by a factor of group size. As a result of analysis and comparison, our scheme reduces energy consumption of nodes, and improve the efficiency of communications in sensor networks compared with current clustering methods.

• The Journal of Korean Association of Computer Education
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• v.10 no.5
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• pp.81-88
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• 2007

To support the movement of a mobile network consisting of several mobile nodes, the IETF NEMO working group proposed NEMO basic support protocol using bi-directional tunneling between the home agent and the mobile router. Since NEMO basic support protocol is based on bi-directional tunneling, all communications to and from mobile nodes are suffer from inefficient routing all the cases. To solve the routing inefficiency problem, several proposals are proposed. However, those proposals results in new problems, such as binding update storm and changes in existing protocol. Especially, binding update storm problem may cause the delay in binding update, this subsequently causes the difficulty for a real time service and the handoff delay on the movement of mobile network. In this paper, we propose a new binding update scheme which reduces binding update latency and the handoff delay through the distribution of the transmission time of binding update messages. The performance of the proposed scheme is also evaluated to demonstrate its efficiency. Simulation results show that the proposed scheme can efficiently reduce the binding update latency.

• The Journal of the Korea Contents Association
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• v.12 no.4
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• pp.60-68
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• 2012

In recent years, the requirements on the high quality environment monitoring by using the sensor nodes which can handle the multimedia data in WSN have been increased. However, because the volume of multimedia data is tremendous, the limited bandwidth of a wireless channel may incur the bottleneck of a system. To solve such a problem, most of the existing distributed multi-path routing protocols based on multimedia data just focused on overcoming the limited bandwidth in order to enhance the energy efficiency and the transmission rate. However, because the existing methods can not apply a key-based technique to encrypt the multimedia data, they are very weak for the security. In this paper, we propose a secure disjointed multipath routing scheme for multimedia data transmission. Since our proposed scheme divides multimedia data(eg. image) into pixels and sends them through disjointed multipath routing, it can provide security to the whole network without using the key-based method. Our experimental results show that our proposed scheme reduces about 10% the amount of the energy consumption and about 65% the amount of the missed data packets caused by malicious nodes over the existing methods on average.

• The Transactions of the Korea Information Processing Society
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• v.7 no.11
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• pp.3323-3332
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• 2000

본 논문에서는 PML-트리라는 공간색인구조를 제안한다. PML-트리는 object distribution heuristics를 사용하여 공간 데이터 객체를 여러 개의 데이터 공간에 균일하게 배치함으로써 질의처리 속도를 향상시킨다. 두 가지의 object distribution heuristics(absolute crowd index와 relative crowd index)가 제안이 된다. PML-트리는 공간 객체를 분배함으로써 R+-트리의 말단 노드 내에 존재하는 데이터의 중복을 제거하면서, R-트리의 단점인 색인 사각형들 사이에 중첩을 허용치 않는다. PML-트리의 성능은 여러 타입의 테스트 데이터를 사용하여 MXR-트리와 비교된다. PML-트리는 MXR-트리에 비해 높은 공간활용도와 빠른 질의 반응시간을 보임으로써 공간 데이터베이스를 위한 효율적인 색인구조로 사용이 될 것으로 기대된다.