  In this article, we study the joint communication and sensing (JCAS) paradigm
in the context of millimeter-wave (mm-wave) mobile communication networks. We
specifically address the JCAS challenges stemming from the full-duplex
operation and from the co-existence of multiple simultaneous beams for
communications and sensing purposes. To this end, we first formulate and solve
beamforming optimization problems for hybrid beamforming based multiuser
multiple-input and multiple-output JCAS systems. The cost function to be
maximized is the beamformed power at the sensing direction while constraining
the beamformed power at the communications directions, suppressing interuser
interference and cancelling full-duplexing related self-interference (SI). We
then also propose new transmitter and receiver beamforming solutions for purely
analog beamforming based JCAS systems that maximize the beamforming gain at the
sensing direction while controlling the beamformed power at the communications
direction(s), cancelling the SI as well as eliminating the potential reflection
from the communication direction and optimizing the combined radar pattern
(CRP). Both closed-form and numerical optimization based formulations are
provided. We analyze and evaluate the performance through extensive
simulations, and show that substantial gains and benefits in terms of radar
transmit gain, CRP, and SI suppression can be achieved with the proposed
beamforming methods.
