  Rate-Splitting Multiple Access (RSMA), relying on multi-antenna
Rate-Splitting (RS) techniques, has emerged as a powerful strategy for
multi-user multi-antenna systems. In this paper, RSMA is introduced as a
unified multiple access for multi-antenna radar-communication (RadCom) system,
where the base station has a dual communication and radar capability to
simultaneously communicate with downlink users and probe detection signals to
azimuth angles of interests. Using RS, messages are split into common and
private parts, then encoded into common and private streams before being
precoded and transmitted. We design the message split and the precoders for
this RadCom system such that the Weighted Sum Rate (WSR) is maximized and the
transmit beampattern is approximated to the desired radar beampattern under an
average transmit power constraint at each antenna. We then propose a framework
based on Alternating Direction Method of Multipliers (ADMM) to solve the
complicated non-convex optimization problem. Results highlight the benefits of
RSMA to unify RadCom transmissions and to manage the interference among radar
and communications, over the conventional Space-Division Multiple Access (SDMA)
technique.
