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In opportunistic networking, it is hard to predict when a node gets and how long it keeps in contact with another. The persistent probing for prompt neighbor discovery consumes too much energy for battery-operated devices to afford. The most important issue is to carefully manage the power states at all stages of network operations. For the problem(More)
Topology management protocols aim to minimize the number of nodes in densely distributed sensor networks that constitute the topology. Most protocols construct the topology with a fixed transmission range (i.e. maximum transmission power). However, in data transmission , it is more efficient to communicate with shorter transmission range, even with(More)
Underwater acoustic sensor networks (UWASN) is being actively researched for its broad spectrum of potential applications. Submarine or whale tracking can also be greatly leveraged by UWASN. These applications require localization of sensor nodes. We propose a novel scheme that minimizes the influence of node mobility inherent to underwater environment. We(More)
In opportunistic networks, it is difficult to predict when a node encounters others and how long it keeps in contact with another. Nodes continually attempt to explore neighbor nodes in the vicinity to transmit data. In battery-operated devices, this persistent exploration consumes a great deal of energy. In this paper, we propose an optimal(More)
—In opportunistic networking, networks are sparse and nodes are moving around, so it is hard to predict when a node gets and how long it keeps in contact with another. For prompt neighbor discovery, a node is assumed to broadcast continuously probing messages to discover another in its vicinity. This kind of persistent probing consumes too much energy for(More)
Various routing structures have been proposed for the data gathering in wireless sensor networks, which are supposed to be efficient in terms of energy consumption and delivery delay. Unfortunately, most of these structures assume not only a static and stable network environment but also the network-wide information such as global topology. These(More)