Seong-Yong Choi

Vacant technology forecasting using new Bayesian patent clustering

Vacant technology forecasting (VTF) is a technology forecasting approach to find technological needs for given industrial field in the future. It is important to know the future trend of developing technology for the R&D planning of a company and a country. In this paper, we propose a new Bayesian model for patent clustering. This is a VTF methodology based on patent data analysis. Our method is composed of Bayesian learning and ensemble method to construct the VTF model. To illustrate the practical way of the proposed methodology, we perform a case study of given technology domain using retrieved patent documents from patent databases in the world.

Alternative Cluster Head Selection Protocol for Energy Efficiency in Wireless Sensor Networks

The traditional cluster routing method is a typical method for enhancing an energy efficiency, which selects cluster head in order to send the aggregated data arriving from the nodes in cluster to a base station. However the major challenges are the equal distribution of each cluster over the whole sensor network and the energy dissipation caused by the frequent information exchange between selected cluster head and nodes in the cluster in every setup phase of cluster formation.In this study, in order to configure the optimum distribution of cluster throughout the sensor network, cluster head is alternatively selected using the information such as direction information obtained from upper level cluster head, distance among nodes in the cluster, residual energy and density. In addition, this study suggests the modified cluster head selection scheme which uses the conserved energy in the steady-state phase by reducing unnecessary communications of unchanged nodes between selected cluster head and previous cluster head in the setup phase, and thus prolongs the network lifetime and provides equal opportunity for being cluster head.

REDM: Robust and Energy Efficient Dynamic Routing for a Mobile Sink in a Multi Hop Sensor Network

An energy efficient multi hop sensor network cannot avoid the energy hole problem, which is the rapid decrease in the energy of nodes around the sink. Also as a sensor network has a limited node resources and unexpected changes of external environment, its nodes should show energy efficiency, reliable data transmission, and topological adaptation to the change of external environment. This study proposes Robust and Energy efficient Dynamic routing for a Mobile sink (REDM), a routing mechanism that satisfies the above-mentioned conditions at the same time using a dynamic single path and sink mobility in a multi hop sensor network. And we also suggest power aware heuristic (PAH) algorithm in which the sink determines its move by itself in consideration of the energy of nodes within a specific number of hops from the sink. According to the result of simulation, compared to the algorithms with other multi hop routing, REDM proposed in this study extended network lifetime by improving the energy efficiency of the nodes while maintaining the same reliability, and REDM based on the PAH algorithm showed a longer network lifetime than stationary REDM and random REDM.

Dynamic routing for mitigating the energy hole based on heuristic mobile sink in wireless sensor networks

Because the nodes of a sensor network have limited node resources and are easily exposed to harsh external environment, they should be able to use energy efficiently, send data reliably, and cope with changes in external environment properly. Furthermore, the lifetime of networks adopting the multi hop routing is shortened by the energy hole, which is the rapid decrease of energy in the nodes surrounding the sink. This study proposes Dynamic Routing that solves the above-mentioned conditions at the same time by using a dynamic single path, monitoring its own transmission process, and moving the sink heuristically in response to change in surrounding environment. According to the results of our experiment, the proposed method increased network lifetime, and mitigated the energy hole and enhanced its adaptability to topological changes.

Dynamic Single Path Routing Mechanism for Reliability and Energy-Efficiency in a Multi Hop Sensor Network

What are important in wireless sensor networks are reliable data transmission, energy efficiency of each node, and the maximization of network life through the distribution of load among the nodes. The present study proposed DSPR, a dynamic unique path routing machanism that considered these requirements in wireless sensor networks. In DSPR, data is transmitted through a dynamic unique path, which has the least cost calculated with the number of hops from each node to the sink, and the average remaining energy. At that time, each node monitors its transmission process and if a node detects route damage it changes the route dynamically, referring to the cost table, and by doing so, it enhances the reliability of the network and distributes energy consumption evenly among the nodes. In addition, when the network topology is changed, only the part related to the change is restructured dynamically instead of restructuring the entire network, and the life of the network is extended by inhibiting unnecessary energy consumption in each node as much as possible. In the results of our experiment, the proposed DSPR increased network life by minimizing energy consumption of the nodes and improved the reliability and energy efficiency of the network.

Dynamic Routing Algorithm for Reliability and Energy Efficiency in Wireless Sensor Networks

What are important in wireless sensor networks are energy efficiency, reliable data transmission, and topological adaptation to the change of external environment. This study proposes dynamic routing algorithm that satisfies the above-mentioned conditions at the same time using a dynamic single path in wireless sensor networks. In our proposed algorithm, each node transmits data through the optimal single path using hop count to the sink and node average energy according to the change of external environment. For reliable data transmission, each node monitors its own transmission process. If a node detects a damaged path, it switches from the damaged path to the optimal path and, by doing so, enhances network reliability. In case of a topological change, only the changed part is reconstructed instead of the whole network, and this enhances the energy efficiency of the network.

Cluster Head Selection Protocol Using Modified Setup Phase

Traditional cluster-based routing method is a representative method for increasing the energy efficiencies. In these cluster-based routing methods, the selected cluster head collect/aggregate the information and send the aggregated information to the base station. But they have to solve the unnecessary energy dissipation of frequent information exchange between the cluster head and whole member nodes in cluster. In this paper, we minimize the frequency of the information exchange for reducing the unnecessary transmit/receive frequencies as calculate the overlapped area or number of overlapped member nodes between the selected cluster head and previous cluster head in the setup phase. So, we propose the modified cluster selection protocol method that optimizes the energy dissipation in the setup phase and reuses the saved energy in the steady-state phase efficiently that prolongs the whole wireless sensor network lifetime by uniformly selecting the cluster head.

A Fault-Tolerant and Energy Efficient Routing in a Dense and Large Scale Wireless Sensor Network

In a wireless sensor network, a large number of small-size cheap sensor nodes are scattered, and have limited resources such as battery power, data processing capability and memory capacity. They should show fault-tolerance, energy efficiency, and topological adaptation to the change of external environment, therefore, an effective routing algorithm is essential. In general, if a network is large in scale, multi-hop transmission is more energy efficient than direct transmission. In case a large number of nodes are deployed densely within a fixed 1-hop communication range, however, many nodes participate in data transmission, multi-hop transmission consumes much more energy in such a case. Thus, this study proposes a routing algorithm that solves above problems at the same time in a dense and large scale sensor network. The result of experiment showed that routing algorithm proposed in this study has reasonable fault-tolerance, energy efficiency, and offers its adaptability to topological changes in a dense and large scale sensor network.

REDS: Robust and Energy Efficient Dynamic Single Path Routing in a Multi Hop Sensor Network

As a sensor network has a limited node resources and unexpected changes of external environment, its nodes should show energy efficiency, reliable data transmission, and topological adaptation to the change of external environment. However, it is not easy to satisfy these requirements at the same time. This study proposes Robust and Energy efficient Dynamic Single path routing (REDS), a routing mechanism that satisfies the above-mentioned conditions at the same time using a dynamic single path in a multi hop sensor network. In REDS, each node transmits data through the optimal single path using hop count to the sink and average residual energy according to the change of external environment. For reliable data transmission, each node monitors its own transmission process. In case of a topological change, only the changed part is reconstructed instead of the whole network, and this enhances the energy efficiency of the network. The results of experiment showed that REDS proposed in this study is superior in energy efficiency and provide its adaptability to topological changes.

Secure and Energy Efficient Key Management Scheme Using Authentication in Cluster Based Routing Protocol

Previous key management methods are not adequate for secure data communication through cluster-based routing. Because the cluster head is changed at each round in cluster-based routing, it has to take the step of authentication or shared key setting with each member node. In addition, because most of previous key management mechanisms do not assign mobility to all nodes in the sensor network, there happens a large overhead for secure communication when the mobility of nodes are considered. Accordingly, this study proposes a secure and efficient key management mechanism suitable for cluster-based routing even when the nodes are mobile and new nodes are inserted frequently.