  To mitigate the radar and communication frequency overlapping caused by
massive devices access, we propose a novel joint communication and sensing
(JCS) system in this paper, where a micro base station (MiBS) can realize
target sensing and cooperative communication simultaneously. Concretely, the
MiBS, as the sensing equipment, can also serve as a full-duplex (FD)
decode-and-forward (DF) relay to assist the end-to-end communication. To
further improve the spectrum utilization, non-orthogonal multiple access (NOMA)
is adopted such that the communication between the macro base station (MaBS)
and the Internet-of-Things (IoT) devices. To facilitate the performance
evaluation, the exact and asymptotic outage probabilities, ergodic rates,
sensing probability of the system are characterized. Subsequently, two optimal
power allocation (OPA) problems of maximizing the received
signal-to-interference-plus-noise ratio of sensing signal and maximizing the
sum rate for communication are designed that are solved by means of the
Lagrangian method and function monotonicity. The simulation results demonstrate
that: 1) the proposed JCS NOMA system can accomplish both communication
enhancement and sensing function under the premise of the same power
consumption as non-cooperative NOMA; 2) the proposed OPA schemes manifest
superiorities over a random power allocation scheme.
