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A wireless sensor network for condition monitoring and its corresponding sensor node powered by a vibration energy harvester producing about 100 \muW are presented. The sensor network utilizes an asynchronous beacon-detection based duty cycle control architecture to reduce power consumption and support ID-based TDMA while avoiding the need for timing synchronization between nodes. It also provides FDMA and fixed-time slot TDMA for further network flexibility. The sensor node transceiver includes a duty-cycle timing control unit to minimize power consumption; an LO-less, TDMA-capable, addressable beacon receiver; an FDMA-capable transmitter; and a low-power, universal sensor interface. The proposed sensor node, implemented in 0.13-\mum CMOS technology, achieves low power consumption and a high degree of flexibility without requiring calibration or the use of BAW or SAW filters. The sensor node is experimentally demonstrated to operate autonomously from the power provided by a piezoelectric vibration energy harvester with dimensions of 27\,\times\,23\,\times\,6.5 mm^3 excited by 4.5-m/s^2 acceleration at 40.8 Hz. The WSN condition monitoring behavior is measured with a capacitive temperature sensor, and achieves an effective temperature resolution of 0.36^\circC. [ABSTRACT FROM PUBLISHER]