Hierarchical underwater acoustic sensor networks with (virtual) transmit/receive arrays

We consider a hierarchical underwater acoustic sensor network architecture in which the sensors and the collector stations operate in distinct layers. The hierarchical architecture is motivated by the property of the acoustic underwater transmission medium that for each transmission distance there exists an operating frequency for which the narrow-band signal- to-noise ratio is maximized. The sensors and collector stations are consequently allocated different operating frequencies. We assume a uniform distribution of both sensors and collector stations over the finite area of the sensing field. The sensors are organized into clusters forming virtual transmit/receive arrays. The collector stations on the other hand are equipped with co-located transmit/receive arrays. We adopt a communication theoretic approach and study the interdependence of the sustainable number of hops through the network, end-to-end frame error probability, power and bandwidth allocation. The analysis is performed under the assumption of Ricean fading and interference from other nodes within the same layer of the hierarchy. We present numerical examples that illustrate the network performance and demonstrate that there are preferred operating frequencies which ensure network operation without any cross-interference between the collector network and the sensor network.