In tree-based wireless sensor networks (WSNs), multihop sensor nodes require a longer time frame to send sensed data to a sink node as the number of hops increases. The time taken for delivery of sensed data becomes a critical issue when a large WSN is deployed. This paper proposes a new data collection scheme with rapid data delivery that utilizes the so-called mobile agent technique. The proposed scheme achieves high data collection efficiency while not relying on route optimization unlike conventional data collection techniques. Simulation results show that the larger the size or the maximum hops of the network, the more effective the proposed scheme becomes. Effectiveness of the proposed scheme is also confirmed through field experiments with actual sensor devices.

Currently, there are various routing methods that consider the energy in a wireless sensor environment. The algorithm we consider is a low-rate wireless personal area network, viz., 802.15.4, and ZigBee routing network. Considering, the overall organization of the network energy efficiency, we suggest a logical position exchange (LPE) algorithm between specified nodes. Logical positioning means connecting high sub-networks and low sub-networks based on the neighbor nodes information of the address ID, and depth in the ZigBee tree topology network. When one of the nodes of the tree topology network, which is responsible for connecting multiple low sub-networks and high sub-networks, has difficulty performing its important roles in the network, because of energy exhaustion, it exchanges essential information and entrusts logical positioning to another node that is capable of it. A partial change in the logical topology enhances the energy efficiency in the network.

This paper presents a Maximum Likelihood Location Estimation (MLLE) algorithm for the home network environments. We propose a deployment of cluster-tree topology in the ZigBee networks and derive the MLE under the log-normal models for the Received Signal Strength (RSS) measurements. Experiments are also conducted to validate the effectiveness of the proposed algorithm.