Feasibility Study of Underwater Acoustic Communications Between Buried and Bottom-Mounted Sensor Network Nodes

This paper presents a feasibility study of underwater communications between buried sensor network nodes. To investigate this problem, two experiments have been conducted: where some sensor nodes are buried in the sediment, and where all sensor nodes are buried in the sediment. The orthogonal frequency-division multiplexing (OFDM) communications have been chosen to test underwater communications because of its unique strength in handling transmissions over long dispersive channels. Since the existing OFDM schemes for underwater communications are designed to achieve high data rate communications within the water column and are not adequate for communications between sensors placed on the ocean floor, a new low-complexity OFDM receiver has been proposed. The proposed receiver performs frame-by-frame channel estimation, residual phase tracking, diversity combining, and data demodulation. This approach is adopted because of its effectiveness in applications with very fast varying channels and a large number of propagation paths. It is demonstrated that the error-free performance can be achieved between buried sensors using the proposed OFDM receiver.