  Full-duplex (FD) communication is a promising candidate to address the data
rate limitations in underwater acoustic (UWA) channels. Because of transmission
at the same time and on the same frequency band, the signal from the local
transmitter creates self-interference (SI) that contaminates the signal from
the remote transmitter. At the local receiver, channel state information for
both the SI and remote channels is required to remove the SI and equalize the
SI-free signal, respectively. However, because of the rapid time-variations of
the UWA environment, real-time tracking of the channels is necessary. In this
paper, we propose a receiver for UWA-FD communication in which the variations
of the SI and remote channels are jointly tracked by using a recursive least
squares (RLS) algorithm fed by feedback from the previously detected data
symbols. Because of the joint channel estimation, SI cancellation is more
successful compared to UWA-FD receivers with separate channel estimators. In
addition, due to providing a real-time channel tracking without the need for
frequent training sequences, the bandwidth efficiency is preserved in the
proposed receiver.
