• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.5
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• pp.17-26
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• 2013

ISO/IEC 29157 originally developed in the Republic of Korea and is based on commercially available PicoCast v1.0. ISO/IEC JTC1 SC6 was registered by the international standard on May 2010. A single platform for a variety of applications and media formats to support development objectives were. ISO/IEC 29157 based wireless networks, ie, Pico-net to master node periodically transmit sync signal is synchronized to the number of slave nodes have the communications structure. Pico-net also supports a variety of network topologies and direct communication between nodes(single-hop communication) and QoS is guaranteed. But Pico-net network structure has the following problems. Loss of communication problems due to mobile nodes, resulting in limitations of node mobility and wireless network operation range of conventional wireless networks operating range less than 1/4 was reduced to the problem. In this paper, a possible solution to the problems mentioned is proposed, using multi-hop communication technology and sync signal transmission technology between nodes.

• Journal of KIISE:Information Networking
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• v.30 no.4
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• pp.474-483
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• 2003

The secret sharing is the basic concept of the threshold cryptosystem and has an important position in the modern cryptography. At 1995, Jarecki proposed the proactive secret sharing to be a solution of existing the mobile adversary and also proposed the share renewal scheme for (k, n) threshold scheme. For n participants in the protocol, his method needs O($n^2$) modular exponentiation per one participant. It is very high computational cost and is not fit for the scalable cryptosystem. In this paper, we propose the efficient share renewal scheme that need only O(n) modular exponentiation per participant. And we prove our scheme is secure if less that ${\frac}\frac{1}{2}n-1$ adversaries exist and they static adversary.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.8
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• pp.34-42
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• 2009

Mobile communication traffic is changing from voice to data/internet, e.g. wireless internet access, SMS/MMS. more and more. Therefore many data services are coming out over 3G, Mobile WiMAX(WIBRO), LTE etc. Wireless internet market is growing and MIPv6 is more important and many protocols being studied and developed from MIPv6 to Fast MIPv6, Hierachical MIPv6, Proxy MIPv6, etc. The significant factor over MIPv6 is Hand-over latency and Packet-loss PMIPv6 is efficient for reducing mobility related messages and hand-over latency, but it considers single LMA domain. If mobile node is moving inter-LMAs, hand-over delay time affects the real-time communications. To overcome this hand-over delay, we propose present and new enhanced schemes and analize the performance and show the results.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.4
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• pp.68-76
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• 2011

In this paper, we propose a method for joining mobile nodes in wireless sensor networks using hysteresis features. It is possible to use static hysteresis, whereby joining and withdrawal are carried out repeatedly when a mobile node is located at boundary points. The energy consumption of the nodes can be effectively managed by a decrease in the response packets of the neighbors under the joining requests of the mobile nodes. However, static hysteresis causes a decrease in the joining rate. In order to increase the joining rate, dynamic hysteresis is used. To evaluate the performance of the proposed technique, the joining rate is investigated and analyzed. Simulation results show that the proposed method enables efficient joining according to the mobility of nodes in wireless sensor networks.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.225-234
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• 2012

In Wireless Sensor Networks (WSNs) where deployed sensors are not stationary, the most important demand of is to design a cost effective and reliable network. This paper proposes an energy aware network construction and routing scheme, which is based on the hierarchical approach to distribute the task in some sensors in order to prolong the network lifetime. It aims to make even the energy consumption on constitute nodes. With the node hierarchy, the sink initiates the construction by electing gateway nodes in the network and the elected gateway nodes participate to form logical clusters by electing a cluster head in each cluster. Then, the cluster heads aggregate data from the sensing sensors and transmit the data to the sink through the gateway. Our simulation result illustrates that the proposed scheme provides a basement to reduce the source of energy dissipation in network construction, and as well as in data routing.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.2
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• pp.87-95
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• 2010

A Vehicular Ad-Hoc Network (VANET) is form of the Mobile Ad-hoc Network (MANET) to provide temporary communication among vehicles via wireless links. In VANET, the vehicle is one of the nodes in networks and communicates with each other. However, the wireless links disconnect very frequently, because vehicles have mobility and move freely. The reason why data accessibility degrades is that disconnection occurs frequently. To improve data accessibility, data replica allocation methods that made group to allocate data replica have proposed in MANET. However, those are not suitable because it is difficult to maintain stable links among the nodes moving fast by centralized group. In this paper, we proposed TBG (Tree Based Grouping) to allocate data replica with the distributed grouping method. Each node has own TBG and allocates data replica based on stability of links to improve data accessibility. The experiment demonstrates that the proposed method outperforms traditional methods in term of data accessibility.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.3
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• pp.181-188
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• 2011

With the rapid proliferation of wireless networks and mobile computing applications, the landscape of the network security has greatly changed recently. Especially, Vehicular Ad Hoc Networks maintaining network topology with vehicle nodes of high mobility are self-organizing Peer-to-Peer networks that typically have short-lasting and unstable communication links. VANETs are formed with neither fixed infrastructure, centralized administration, nor dedicated routing equipment, and vehicle nodes are moving, joining and leaving the network with very high speed over time. So, VANET-security is very vulnerable for the intrusion of malicious and misbehaving nodes in the network, since VANETs are mostly open networks, allowing everyone connection without centralized control. In this paper, we propose a weighted intrusion detection method using rough set that can identify malicious behavior of vehicle node's activity and detect intrusions efficiently in VANETs. The performance of the proposed scheme is evaluated by a simulation study in terms of intrusion detection rate and false alarm rate for the threshold of deviation number ${\epsilon}$.

• Journal of Intelligence and Information Systems
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• v.23 no.2
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• pp.89-105
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• 2017

As the advances of technology in mobile networking and the popularity of online social networks (OSNs), the mobile social networks (MSNs) provide opportunities for marketing strategy. Therefore, understanding the information diffusion in the emerging MSNs is a critical issue. The information diffusion address a problem of how to find the proper initial nodes who can effectively propagate as widely as possible in the minimum amount of time. We propose a new diffusion scheme, called Hotspot DBC, which is to find k influential nodes considering each node's mobility behavior in the hotspot zones. Our experiments were conducted in the Opportunistic Network Environment (ONE) using real GPS trace, to show that the proposed scheme results. In addition, we demonstrate that our proposed scheme outperforms other existing algorithms.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.776-785
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• 2006

Ship builder's requirement for a higher power output rating has lead to the development of super large two stroke low speed diesel engines. Usually a large-sized bore ranging from 8-14 cylinders, this engine group is capable of delivering power output of more than 100,000 bhp at maximum continuous rating. Other positive aspects of this engine type include higher thermal efficiency, reliability, durability and mobility. This all playa vital role in meeting the propulsion requirement of vessels, specifically for large container ships, of which speed is a primary concern to become more competitive. Consequently, this also resulted in the modification of engine parameters and new component designs to meet the consequential higher mean effective pressure and higher maximum combustion pressure. Even though the fundamental excitation mechanism unchanged, torsional vibration stresses in the propulsion shafting are subsequently perceived to be higher. As such, one important viewpoint in the initial engine design is the resulting vibration characteristic expected to prevail on the propulsion shafting system(PSS). This paper investigated the torsional vibration characteristics of these super large engines. For the two node torsional vibration with a nodal point on the crankshaft, a tuning damper is necessary to reduce the torsional stresses on the crankshaft. Hence, the tuning torsional vibration damper design and compatibility to the shafting system was similarly reviewed and analyzed.

• The KIPS Transactions:PartC
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• v.14C no.3 s.113
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• pp.267-276
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• 2007

In OSPF, the larger and more unstable the area, the greater the likelihood for performance problems associated with routing protocol recalculation. Generally, an area should have no more than 50 routers. Areas with unstable links should be smaller. Military tactical data network is used for military operations during war-time. It consists of wireless network for mobility of node. Thus, it has low-bandwidth and unstable property. In addition, it is expected that many kinds of router-failure, Link-failure and recovery at emergency period. However, Military tactical data network is designed with about one and half times the number of recommendation. This paper proves that the traffic is limited by the increase of re-calculation of area.