Wireless sensor network technologies have attracted a lot of attention in recent years. In this paper, we propose an energy-efficient data gathering mechanism using traveling wave and spatial interpolation for wireless sensor networks. In our proposed mechanism, sensor nodes schedule their message transmission timing in a fully-distributed manner such that they can gather sensor data over a whole wireless sensor network and transmit that data to a sink node while switching between a sleep state and an active state. In addition, each sensor node determines the redundancy of its sensor data according to received messages so that only necessary sensor data are gathered and transmitted to the sink node. Our proposed mechanism does not require additional control messages and enables both data traffic and control traffic to be drastically reduced. Through simulation experiments, we confirmed that with our proposed mechanism, the number of message transmissions can be reduced by up to 77% and the amount of transmitted data can be reduced by up to 13% compared to a conventional mechanism.

We proposed self-organizing transmission scheduling mechanisms for periodically gathering sensor data at a base station in wireless sensor networks. In the proposed mechanisms, sensor nodes self-organize message transmissionand sleep timings. To achieve self-organizing control of sensor networks, we apply phase-locking and anti-phase synchronization in a pulse-coupled oscillator model. Simulation experiments confirm that our mechanism significantly improves the data gathering ratio and energy-efficiency in comparison with the conventional mechanism.

Wireless sensor networks have attracted a great deal of attention. The performance of wireless sensor networks is greatly influenced by the initial physical placement of the sensor nodes. In this research, we proposed a novel deployment method for sensor nodes, when a large number of nodes is distributed from the air in a monitoring region that is inaccessible from the ground. In our deployment method, each sensor node is equipped with a parachute and a device to switch between its two falling behaviors in the air. After being dropped from midair, sensor nodes stochastically coordinate their falling behavior in order to distribute themselves uniformly in the monitoring region. Through simulation evaluations, we confirmed that our proposal can achieve a high uniformity in the placement of the nodes.

Recently, sensor devices are being ubiquitously deployed. These devices send and receive a large amount of sensor data over the network. Due to these advances of sensor and network technologies, various services that make use of those 'ubiquitous network contents' are expected to be widely developed. We studied on techniques to collect, manage, discover, and analyze those massive sensor data.