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In the last few years the continuous demand of energy saving has brought continuous research on low-power devices, energy storage and new sources of energy. Energy harvesting is an interesting solution that captures the energy from the environment that would otherwise be wasted. This work presents an electric-mechanical model of a piezoelectric transducer in a cantilever configuration. The model has been characterized measuring the acceleration and the open circuit voltage of a piezoelectric cantilever subjected to a sinusoidal force with different values frequency and subject to an impulsive force. The model has been used to identify the optimal position in which the piezoelectric cantilever has to be placed on a shoe in order to obtain the maximum energy while walking or running. As a second step we designed the DC-DC converter with an hysteresis comparator. The circuit is able to give energy to switch on a microprocessor for the amount of time long enough to capture and store the information required. The complete system has been implemented, installed on a shoe and used in a 10 Km running competition.

In the emerging context of wireless (mobile) ad-hoc networks, cross-layer design has been proposed in recent years to pursue joint optimization at various layers. Modifications to the OSI reference model have been envisaged in order to allow description of cross-layer solutions. Nevertheless, it can be also observed that a sound and reference methodology does not yet exist to support optimization, and this might severely restrict effective adoption and deployment of cross-layer solutions [1].In this work we propose some conjectures about exploitation of OSI-like layered approach to model and design cross-layer solutions. Specifically, we apply our method to the modelling and analysis of a particular class of cross-layer solutions, namely energy-aware routing protocols. We analyze two proposals available in the literature according to a layered structure. The applied method drives the definition of a novel energy-aware solution that, compared to the previous ones, shows better performance and provides interesting and clear insights on the role that each layer does play in the overall optimization process.

In the last few years the increased development of wireless technologies led to the development of micropower devices with power management and real time power control, aimed to maximize the battery life time. 1 The main and simplest method to estimate residual battery life time is by voltage measurement. This kind of measurement is simple but is useless in many cases, especially when long term Lithium-Thionyl chloride batteries are used, since its voltage is flat for more than 90% of the battery discharge. In this case, a current control should be used. However, these kinds of devices have various problems as a limited range of measurement and not negligible quiescent current that may distort the measurements.In this work we developed a micropower supervisor for wireless sensor nodes with a charge battery monitor, whose features are aimed at solving the problems just described. The current measured by a sense resistor, is filtered by a super-capacitor, amplified by a current sense amplifier and then fed to a voltage to pulse frequency modulator. In this way, the charge consumption can be estimated without the saturation of the current sense amplifier, even if the wireless node consumes time limited high current spikes, for example during transmission.

The factors which affect the choice of the LuckyNet radio link design, involving data rates on the order of 2.5 Gb/s, are discussed. The specific design of the 2.5 Gb/s radio link for the 23mile path between the Murray Hill and CrawfordHill locations of AT&T Bell Laboratories is described, along with preliminary performance results. The propagation factors which have the dominant effect on link availability are fading due to rain, water vapor and multipath. Less than lo-" BER is achieved with an estimated availability of about 95% per year. The link provides 2.5 bits per-second-per-Hz of bandwidth by using dual polarization and QPSK modulation. I. KEY FEATURES OF THE RADIO LINKThe radio link between the Crawford Hill (HOH) and Murray Hill (MH) locations of AT&T Bell Laboratories is a line-of-sight path, part of which is over Raritan Bay in central New Jersey. The path length is 22.8 miles long and has been extensively measured at microwave and optical frequencies for its propagation properties [I-31. Figure 1 shows a map and profile of the transmission path between HOH and MH. The previous measurements showed that the specular reflection point is normally not on Raritan Bay and is therefore reduced about 14 dB relative to the direct ray. During about 1% of the year, reflections will occur from the bay because of abnormal atmospheric bending, and at a strength nearly equal to that of the direct ray. Under these conditions the discrimination against the reflected ray may be as low as 10dB. However, multipath through the atmosphere can also occur during these times, so this 1% of the year was assumed to be unavailable in our estimates. Furthermore, the antenna beamwidth was chosen to place a null near the specular reflection direction while the antenna boresight is directed almost exactly along the direct ray. It is expected that a net discrimination of about 25 dB will normally be maintained between direct ray and reflected ray. This is important because the reflected ray has about 3.5 nanoseconds of delay relative to the direct ray, which could be a cause of significant intersymbol interferenee (ISI) at the data rates of interest.The overall data rate will be 2.488 Gbps, corresponding to the SONET OC-48 rate, and the goal is to transmit it in a bandwidth of 1 GHz, to remain within our experimental license bandwidth allocation. By planning for a spectrally efficient radio, prospects for FCC approval are enhanced. At the same time, a simple design is needed to expedite completion of the experimental link. A good compromise for this purpose is to use coherent QPSK transmission on two orthogonal polarizations. This approach provides readily for a spectral efficiency of 2.5 bpsmz. In addition, coherent QPSK is robust in the presence of impairments, and QPSK modulators and demodulators suitable for this link [4], already exist.The experimental link will not require the extremely high availabilities normally quoted for commercial systems. In fact, an availability of 95% should be sufficient for our purposes (as opposed t...