  The emerging joint sensing and communication (JSC) technology is expected to
support new applications and services, such as autonomous driving and extended
reality (XR), in the future wireless communication systems. Pilot (or
reference) signals in wireless communications usually have good passive
detection performance, strong anti-noise capability and good auto-correlation
characteristics, hence they bear the potential for applying in radar sensing.
In this paper, we investigate how to apply the positioning reference signal
(PRS) of the 5th generation (5G) mobile communications in radar sensing. This
approach has the unique benefit of compatibility with the most advanced mobile
communication system available so far. Thus, the PRS can be regarded as a
sensing reference signal to simultaneously realize the functions of radar
sensing, communication and positioning in a convenient manner. Firstly, we
propose a PRS based radar sensing scheme and analyze its range and velocity
estimation performance, based on which we propose a method that improves the
accuracy of velocity estimation by using multiple frames. Furthermore, the
Cramer-Rao lower bound (CRLB) of the range and velocity estimation for PRS
based radar sensing and the CRLB of the range estimation for PRS based
positioning are derived. Our analysis and simulation results demonstrate the
feasibility and superiority of PRS over other pilot signals in radar sensing.
Finally, some suggestions for the future 5G-Advanced and 6th generation (6G)
frame structure design containing the sensing reference signal are derived
based on our study.
