  Dual-function radar-communication (DFRC) systems, which can efficiently
utilize the congested spectrum and costly hardware resources by employing one
common waveform for both sensing and communication (S&C), have attracted
increasing attention. While the orthogonal frequency division multiplexing
(OFDM) technique has been widely adopted to support high-quality
communications, it also has great potentials of improving radar sensing
performance and providing flexible S&C. In this paper, we propose to jointly
design the dual-functional transmit signals occupying several subcarriers to
realize multi-user OFDM communications and detect one moving target in the
presence of clutter. Meanwhile, the signals in other frequency subcarriers can
be optimized in a similar way to perform other tasks. The transmit beamforming
and receive filter are jointly optimized to maximize the radar output
signal-to-interference-plus-noise ratio (SINR), while satisfying the
communication SINR requirement and the power budget. An majorization
minimization (MM) method based algorithm is developed to solve the resulting
non-convex optimization problem. Numerical results reveal the significant
wideband sensing gain brought by jointly designing the transmit signals in
different subcarriers, and demonstrate the advantages of our proposed scheme
and the effectiveness of the developed algorithm.
