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A new ultra-low power (ULP) wireless sensor network (WSN) structure is proposed to monitor the vibration properties of civil structures, such as buildings and bridges. The new scheme integrates energy harvesting, data sensing, and wireless communication into a unified process, and it is fundamentally different from all the existing WSNs. In the new WSN, piezoelectric sensors are employed to harvest vibration energy and measure vibration intensity simultaneously, by utilizing the fact that the harvested energy accumulated through time is proportional to the vibration amplitude and frequency. Once the harvested energy reaches a threshold, it is released as an impulse with a wireless transmitter. An estimate of the structure vibration intensity can then be obtained by measuring the intervals between the binary impulses. Such an approach does not require complicated analog-to-digital conversion or signal processing, and it can achieve an ULP performance unrivaled by existing technologies. Optimum and sub-optimum impulse density estimation algorithms are proposed for the FC to take advantage of the spatial correlation among the sensors. Exact analytical expressions of the optimum estimation mean square error (MSE) are derived. Simulation and analytical results demonstrate that the proposed scheme can achieve a MSE of 5× 10-5 at a signal-to-noise-ratio of -8 dB for a 10-node WSN.