  Joint communication and radar sensing (JCR) represents an emerging research
field aiming to integrate the above two functionalities into a single system,
sharing a majority of hardware and signal processing modules and, in a typical
case, sharing a single transmitted signal. It is recognised as a key approach
in significantly improving spectrum efficiency, reducing device size, cost and
power consumption, and improving performance thanks to potential close
cooperation of the two functions. Advanced signal processing techniques are
critical for making the integration efficient, from transmission signal design
to receiver processing. This paper provides a comprehensive overview of JCR
systems from the signal processing perspective, with a focus on
state-of-the-art. A balanced coverage on both transmitter and receiver is
provided for three types of JCR systems, communication-centric, radar-centric,
and joint design and optimization.
