In this paper we describe the design and implementation of ATEMU, a fine grained sensor network simulator. ATEMU is intended to bridge the gap between actual sensor network deployments and sensor network simulations. We adopt a hybrid strategy, where the operation of individual sensor nodes is emulated in an instruction by instruction manner, and their interactions with each other via wireless transmissions are simulated in a realistic manner. A unique feature of ATEMU is its ability to simulate a heterogeneous sensor network. Using ATEMU it is possible to not only accurately simulate the operation of different application on the MICA2 platform but also a complete sensor network where the sensor nodes themselves maybe based on different hardware platforms. In addition we also describe our implementation of XATDB, our front-end debugger/GUI for ATEMU. XATDB provides an excellent educational tool for people to start learning about the operation of sensor nodes and sensor networks, without requiring the purchase of actual sensor node hardware. The accuracy and emulation capabilities provided by ATEMU ensure that when and if actual hardware is used, the software will already have undergone rigorous testing and debugging on an accurate platform. This would provide the sensor network deployment community with a much more accurate estimate of the performance of various algorithms and protocols in realistic scenarios and platforms.

We investigate GHz metamaterial resonator arrays that respond to only the electric field with the goal of reducing the resonator size in comparison to the excitation wavelength. By exploiting capactive coupling between the "electrodes" of adjacent resonators, we achieve a large effective capacitance and strong coupling to the applied electric field. By adding meander lines to connect the electrodes, we are able to lower the resonant frequency to obtain a ratio of wavelength to resonator size of about 30. In contrast to other low-frequency designs, our designs do not require vias and maintain strong coupling to the applied field.

The design, fabrication, and characterization of a hybrid energy scavenger system, combining simultaneous piezoelectric and electrostatic energy conversion, is reported.A piezoelectric resonator beam (PZT) is integrated with an electrostatic scavenger whose variable capacitor (C VAR ) doubles as the proof mass as shown in Fig. 1. This paper focuses on the piezoelectric component, which provides an inherent displacement feedback signal and a rectified 3.3V DC rail with a 2.68mW/cm 3 power density to operate signal conditioning, and initial electrostatic charge control circuits. The system is mechanically robust with no change in operation after 30 million cycles at 2.5m/s 2 of 120Hz sinusoidal excitation.

No abstract