Self-interference characterization for in-band full duplex underwater acoustic communications

In-band full duplex (IBFD) communications attracts increasing attention in the underwater acoustic communication community due to its potential to increase spectral efficiency. The suppression of the self-interference remains the main obstacle to achieve IBFD in the ocean. Limited work in the literature has been done to characterize the self-interference in underwater acoustics. Here we analyze the characteristics of the self-interference based on the fieldwork, where self-interference measurements have been collected for multiple acoustic frequencies ranging from 20 to 180 kHz. The interference cancellation (IC) gain, as the performance metric of the digital self-interference suppression, is found to decrease when the acoustic carrier frequency increases. We propose to use the channel variation ratio (CVR) to characterize channel variability. Experimental results show that the CVR is larger at higher acoustic frequencies and high CVRs lead to the performance degradation in the self-interference suppression. Computer simulations have also been conducted to explain the experimental observations.