Analysis & Simulation of the Deep Sea Acoustic Channel for Sensor Networks

Nearly 70% of our planet is composed of an aquatic environment, however, due to the lack of appropriate scientific tools and also the relative hostility of the acquatic environment, much of it still remains unexplored. With the advent of global climatic changes, a pronounced energy crisis and changing ecological habitats understanding the oceans of our planet is of vital importance. Monitoring the aquatic environment continually and effectively for oceanographic data collection, offshore exploration, efficient navigation, disaster prevention and monitoring, marine bio sciences data collection, power source exploration and maintenance can now be made possible with the deployment of underwater sensor nodes (USNs). As in terrestrial wireless sensor networks (WSNs), usage of USNs deployed across a large area of the ocean in an underwater wireless sensor networks (UWSNs) can greatly enhance the quality of data collected within the aquatic environment. Recent advancements in unmanned underwater vehicles (UUVs) greatly extends the reach and applicability of UWSNs by enabling the integration of autonomous underwater vehicles (AUVs) acting as mobile sensor nodes (MSNs) for the purposes of underwater resource exploration and also multi-vehicle & diver coordinated collaborative exploration missions for conducting complex investigations, while also enabling autonomous navigational and location determination methodologies. However, since radio frequency (RF) transmissions do not work underwater and optical communication is only suitable for short distances, an UWSN consists of a number of mobile and static nodes that usually communicate using the acoustic channel. Using the acoustic channel for communication causes an UWSN to contend with the issues of high transmission power requirements, rapidly changing channel characteristics, multi-path echoes, possible high ambient noise and interference, high and varying propagation delays and natural ocean currents in addition to the challenges posed by simple WSNs. As such, in order to examine the practices used by UWSNs for successful off-shore deep sea deployments this document first analyzes the underwater channel acoustic propagation model and also looks briefly at the characteristics of the underwater transducers along with the unique effect that they pose upon sonar based communication systems. The document then goes on to exploring the state of the art in UWSNs design paradigms followed by an analysis of areas that warrant research and a discussion of the work carried out during this thesis investigation along with a conclusion highlighting the contributions it makes.