Design, Modelling and Analysis of Underwater Acoustic Backscatter Communications

Backscattering enables battery-less and perpetually operating Internet-of-Things (IoT) devices to sweep through ambient electromagnetic waves (in terrestrial networks) or acoustic waves (in underwater networks) rather than generate new waves. The emerging underwater acoustic backscatter communication (UABC) has the potential to avoid the need for underwater nodes to actively emit acoustic signals, thus, reducing their energy consumption. However, there is a lack of a clear design, comprehensive modelling or analysis of UABC systems. This paper studies a UABC system where a high-power transceiver transmits acoustic signals and a piezoelectric UABC node modulates and reflects the incident acoustic signals back to the transceiver. Specifically, a detailed new design for UABC nodes is proposed and a circuit model for the nodes is developed to analyze their acoustic impedance under different materials and operating frequencies. Based on the circuit model, a node load design is introduced to maximize the acoustic reflection coefficients; and a comprehensive communication analytical framework is established and is used to analyze how different UABC parameters, such as piezoelectric material properties, operating frequencies of UABC nodes, transmission distances, ambient noise intensities, carrier wave frequencies, and wind speeds, affect the bit error rate of UABC. Simulation results validate the effectiveness of the proposed designs and models as well as identify the key parameters influencing the UABC performance.