Center for Embedded Network Sensing

Research in the field of underwater sensor networks exists from the need for scientific data collection, pollution monitoring, offshore oil exploration, tsunami warnings, ocean mapping, and tactical surveillance without human assistance. Aided with acoustic communication systems, autonomous underwater vehicles (AUVs) can work along with fixed nodes to enhance the capablities of sensor networks. With channel estimation algorithms, AUVs can detect connectivity loss and position sensors to self-configure for optimal network efficiency. However, one of the biggest challenges to underwater networks is multipath fading, where the reflection and scattering from the bottom and surface of the ocean result in severe intersymbol interference (ISI) of transmitted signals. Secondly, sound absorption loss increases with the increase in frequency, dramatically limiting the bandwidth available. Orthogonal frequency division multiplexing (OFDM) is proposed as a possible method of communication, by transmitting signals over multiple subcarriers simultaneously.