Hyunchong Cho

Vehicle location service scheme based on road map in Vehicular Sensor Networks

Abstract Vehicular Sensor Networks (VSNs) are merging for supporting communications between roadside sensor nodes and vehicles on for notifying environment events on roads to drivers and passengers. Geographic routing has been considered as an efficient and scalable approach to send sensing data from sensor nodes to vehicles. Fundamentally, geographic routing requires sensor nodes to be aware of the location information of vehicles. Since sensor nodes are deployed around roads and vehicles move on the roads, this field property of VSNs brings about a challenging issue to provide location service of vehicles. In this paper, we propose a quorum-based location service scheme to provide sensor nodes with the location information of vehicles in VSNs. For providing the location service, the proposed scheme exploits a crossing point between a quadrangular path quorum of a location update and a line path quorum of a location query by using the road map information. Then, the proposed scheme is extended to accommodate several considerations such as voids, multiple vehicles and sources, and energy depletion. The effectiveness of the proposed scheme is analyzed and validated by extensive numerical and simulation results.

Sink Mobility Support Scheme for Continuous Object Tracking in Wireless Sensor Networks

In wireless sensor networks, one of the most important application is tracking diffusive and large-scale phenomena, called continuous object. A number of sources from the large size of a continuous object bring huge communication overhead that former studies have to deal with. Meanwhile, recent application scenarios, such as forest fire suppression by firefighters, require sink mobility support. Most sink mobility support schemes have proposed for individual object tracking. They provide one-to-one connection between a mobile sink and a source. That is, too many connections resulting excess energy consumption are built if continuous object tracking directly adopts them. In this paper, we propose a solution to the problem with building a one-to-many connection between a sink and sources detecting a continuous object. The proposed scheme gradually extends the initial connection between a sink and the first source according to the spread of the continuous object. Our simulation results show that the proposed scheme is superior to existing schemes in terms of energy consumption.

A flexible real-time multicasting protocol in multi-hop industrial cyber physical system

The adoption of multi-hop wireless networks has received attention from industrial cyber-physical system. In industrial applications, real-time multicasting is widely used for controlling and monitoring machines. In multi-hop wireless networks, the end-to-end delay depends on the end-to-end distance. Existing real-time multicasting studies use a fixed distance limitation to achieving real-time transmission without complexity from time factor. However, when given time factor changes, existing protocols might lead to real-time fails and inefficient multicasting because of the difference between the fixed distance limitation and the maximum transmittable distance under the given time. To solve the problems, in this paper, we propose a flexible real-time multicasting protocol based on given time factor. We first introduce a scheme for obtaining a maximum transmittable distance under a given time. Then we provide a real-time multicasting protocol based on the maximum transmittable distance. Our simulation results show that the proposed protocol achieves higher real-time delivery success ratio and energy efficiency than existing protocols.

Low-Cost Multipath Routing Protocol by Adapting Opportunistic Routing in Wireless Sensor Networks

The wireless sensor networks (WSNs) are special network which has purpose of gathering information in certain area. The reliability is an important factor in the WSNs for transferring the information to the destination. However, the reliability is decreased while multi-hop transmission of the information because a node which composes the WSNs has limited communication range. Also, the transmission process may suffer from the various factors including the faulty nodes and network congestion. To solve this, the multipath routing protocols, which transfer the information through a multipath to the destination at the same time, have been proposed for improving the reliability. In the existing multipath routing protocols, however, the network scale should be sufficient for constructing multipath to guarantee of the disjoint path and the energy is consumed for multipath construction#x002F;maintenance consistently. The energy consumption leads to the reduction of networks lifetime and the restricted network scale may not even ensure the enough reliability. Thus, we proposed Low-Cost Multipath Routing Protocol by Adapting Opportunistic Routing which can reduce consistent energy consumption and less affected by network scale. The proposed protocol exploits the opportunistic routing that improves the single-hop reliability in order to improve the reliability in each path. It reduces the number of paths, which constructed for ensuring the enough reliability. Also, a fewer path reduces the energy consumption and alleviates the restriction of network scale. Simulation results show that the proposed protocol provides the more reliable performance than the existing protocols in the network, which restricted scale, and consumes the less energy.

Energy-efficient lookahead face routing using coverage range in wireless networks

In geographical network systems, face routing is the unique recovery solution for local minimum problem. A node in local minimum could not choose its neighbor node closer to the destination. Since the face routing is based on novel graph named planar graph, the nodes search a link between adjacent nodes in the graph and send their data via the link. During the planarization of the topology, many links become hidden although the links are available for communication. Due to the hidden links, the graph leads too many number of data transmission in the face routing. With this reason, face routing leads lots of node energy and shortens the lifetime of sensor networks. This paper proposes the novel face routing which is able to reduce the data transmission. The proposed scheme searches the hidden links which are able to select the farthest neighbors at first. When the proposed scheme finds those neighbor links, it stops the searching behavior and transmits the data packets to them directly in order to reduce the data transmission. The simulation compares the proposed scheme with the previous face routing and shows that the proposed scheme is more energy efficiency.

Multipath-based opportunistic routing scheme for large-scale wireless sensor network

Opportunistic routing (OR) has been emerged as a promising routing strategy to improve transmission reliability for wireless networks. By taking broadcast nature of wireless medium, a set of forwarding candidate nodes receive a data packet simultaneously, so one of them can relay it unless they all fail to receive. This strategy can dramatically improve one-hop reliability even in unreliable wireless links, however, it cannot be directly applied into large-scale wireless multi-hop networks since multi-hop communication significantly decreases end-to-end reliability. In this letter, we propose a novel opportunistic routing scheme for large-scale wireless multi-hop networks, which adopts multipath based routing in order to improve end-to-end reliability. While taking advantages of opportunistic routing, each intermediate node can determine whether it branches into multiple paths or not without any network topology information, so that a desired delivery ratio from a source to a destination given by application demands can be achieved in a fully localized manner.

Moving Object Tracking using Query Relaying in Wireless Sensor Networks

In wireless sensor networks, two methods have been generally used to track continuously moving object: a user query-based method and a periodic report-based method. Although the former method generates more overhead as a result of the user queries, the former one is also an energy-efficient method that does not transfer unnecessary information. For the user query-based method, a virtual tree that consist of sensor nodes is used to perform the user query and the sensor reporting. The tree stores the information of the mobile objects, and the stored information triggers a report b the user query. However, in case of a fast-moving object, the tracking accuracy decreases as a result of the time delay of the end-to-end repeated query. In order to solve this problem, we propose a query-relay method that reduces the time delay for mobile object tracking. In the proposed method, the nodes in the tree relay the query to adjacent nodes according to the movement of mobile object that is tracked. When the query messages are relayed. The end-to-end querying time delay is reduced. and a simulation shows that our method is superior to existing ones in terms of tracking accuracy.

An Energy-Efficient Location Update Scheme for Mobile Sinks in Continuous Object Detection Using Wireless Sensor Networks

A continuous object is large phenomenon diffusing continuously. Therefore, a large number of sources is a major problem in researches for continuous object. Existing studies for continuous object detecting focus on reducing communication cost generated by the sources. But, they only deal with the static sink located in fixed position. In this paper, we propose the location update scheme for mobile sinks in continuous object detecting. Generally, to receive data, a mobile sink should notice its current location to sources. Previous studies for location update of mobile sinks consider individual object. So they need a lot of energy for location update when a mobile sink notices its current location toward many sources of a continuous object independently. Proposed scheme exploits regional locality of the sources involved one continuous object. The regional locality makes the location update of mobile sinks efficient. Our simulation results show that the proposed scheme superior to existing schemes in terms of energy efficiency.