Self-Optimizing Wireless Networks on Structures

This brief proposes half-duplex wireless networks that use acoustic guided waves traveling on or through structures for physically-secure long-range power and data telemetry. It also develops a protocol for such networks to optimize their power and data delivery to compensate for slowly-varying factors like temperature and structural damage. Specifically, near-maximum power point tracking (nMPPT) is implemented by searching for the optimal transmission frequency in complex acoustic channels. Binary frequency shift keying (BPSK) modulated on the power waveform is proposed for downlink. A power-efficient fast uplink is achieved by using Non Return to Zero - Inverted (NRZ-I) data encoding. Data security is naturally ensured by the unique channel responses defined by the transceivers' physical locations. Miniature smart sensor nodes with a quiescent power of 4.8 μW and a peak power of ~200 μW have been developed for such sparse networks. The proposed half-duplex telemetry approach is experimentally evaluated on a structural health monitoring (SHM) test bed and achieves a power transfer of ~181.8 μW at 0.5 m and a BER of 10-4for a 80 bps downlink driven at 20 Vpp, and a BER of 10-4for a 2 Mbps uplink driven at ~2 Vpp.