  In this paper, we propose a hybrid precoding/combining framework for
communication-centric integrated sensing and full-duplex (FD) communication
operating at mmWave bands. The designed precoders and combiners enable
multiuser (MU) FD communication while simultaneously supporting monostatic
sensing in a frequency-selective setting. The joint design of precoders and
combiners involves the mitigation of self-interference (SI) caused by
simultaneous transmission and reception at the FD base station (BS).
Additionally, MU interference needs to be handled by the precoder/combiner
design. The resulting optimization problem involves non-convex constraints
since hybrid analog/digital architectures utilize networks of phase shifters.
To solve the proposed problem, we separate the optimization of each
precoder/combiner, and design each one of them while fixing the others. The
precoders at the FD BS are designed by reformulating the communication and
sensing constraints as signal-to-leakage-plus-noise ratio (SLNR) maximization
problems that consider SI and MU interference as leakage. Furthermore, we
design the frequency-flat analog combiner such that the residual SI at the FD
BS is minimized under communication and sensing gain constraints. Finally, we
design an interference-aware digital combining stage that separates MU signals
and target reflections. The communication performance and sensing results show
that the proposed framework efficiently supports both functionalities
simultaneously.
