Tomoyuki Miyoshi

Wireless sensor network (WSN) is a promising approach for a variety of applications. Routing protocol for WSNs is very challenging because it should be simple, scalable, energy-efficient, and robust to deal with a very large number of nodes, and also self-configurable to node failures and changes of the network topology dynamically. Recently, many researchers have focused on developing hierarchical protocols for WSNs. However, most protocols in the literatures cannot scale well to large sensor networks and difficult to apply in the real applications. In this paper, we propose a novel adaptive routing protocol for WSNs called ARPEES. The main design features of the proposed method are: energy efficiency, dynamic event clustering, and multi-hop relay considering the trade-off relationship between the residual energy available of relay nodes and distance from the relay node to the base station. With a distributed and light overhead traffic approach, we spread energy consumption required for aggregating data and relaying them to different sensor nodes to prolong the lifetime of the whole network. In this method, we consider energy and distance as the parameters in the proposed function to select relay nodes and finally select the optimal path among cluster heads, relay nodes and the base station. The simulation results show that our routing protocol achieves better performance than other previous routing protocols.

This paper presents the analysis of a simplified model for the design of a module structure that avoids the risk of self-excitedoscillation (SE-Osc). A necessaryand sufficient simplified model that can extract the critical oscillation mode is proposed based on a comparison of several simplifying steps. The differential equation of the simplified model is solved, and the solution is plotted in the frequency domain to analyze the oscillatory conditions. The simplified model is verified via a time-domain full-model simulation modeled by 3-D electromagnetic simulation and solved by finite-element simulation. Measurements of test modules show consistent oscillatory conditions and frequency. SE-Osc modes are eliminated by reducing the inductance connected to the emitter and increasing the inductance connected to the collector. Increasing the ratio of C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CE</sub> to C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GC</sub> increases the risk of self-exciting oscillation. Suppressions of SE-Osc from a common package design with state-ofthe-art Si-insulated gate bipolar transistors (IGBTs) presenting small feedback capacitance, SiC-MOS, and hybrids of state-of-art Si-IGBTs and SiC-Schottky barrier diodes are verified.