  In order to further exploit the potential of joint multi-antenna
radar-communication (RadCom) system, we propose two transmission techniques
respectively based on separated and shared antenna deployments. Both techniques
are designed to maximize the weighted sum rate (WSR) and the probing power at
target's location under average power constraints at the antennas such that the
system can simultaneously communicate with downlink users and detect the target
within the same frequency band. Based on a Weighted Minimized Mean Square
Errors (WMMSE) method, the separated deployment transmission is designed via
semidefinite programming (SDP) while the shared deployment problem is solved by
majorization-minimization (MM) algorithm. Numerical results show that the
shared deployment outperforms the separated deployment in radar beamforming.
The tradeoffs between WSR and probing power at target are compared among both
proposed transmissions and two practically simpler dual-function
implementations i.e., time division and frequency division. Results show that
although the separated deployment enables spectrum sharing, it experiences a
performance loss compared with frequency division, while the shared deployment
outperforms both and surpasses time division in certain conditions.
