FD-UWA: Full-Duplex Underwater Acoustic Comms via Self-Interference Cancellation in Space

Traditionally, underwater acoustic communications is half duplex, i.e., the hydrophones and transducers operate in non-overlapping time-slots/frequency-bands in one direction at a time or frequency. To double the spectral efficiency and allow simultaneous transmission and reception in Full-Duplex mode (FD), a Self-Interference Cancellation (SIC) technique in space is introduced and deployed. Specifically, a novel underwater acoustic system is proposed to perform FD-SIC efficiently via an integrated design combining underwater Acoustic Vector Sensor (AVS) and Phased Array Transducer (PAT) to realize spatial SIC. The energy focusing function of the Beamformer (BF) helps PAT avoid self and mutual spatial interference. The AVS keeps updating the direction of arrival information to let BF adjust the steering angle via an adaptive protocol. The proposal is evaluated and verified via simulations in realistic underwater acoustic channels and is able to achieve 59 dB SIC at 80 kHz steering angle at -5 ° and at least 37 dB within the steering angle region before the input of digital SIC. This indicates that the design is a promising solution for the chosen angle region to perform spatial SIC as well as to prevent the grating lobe interference. The design is being experimentally validated using the data collected from an underwater testbed and implemented on an Field Programmable Gate Array (FPGA) board that provides energy efficiency and real-time processing capabilities.