  A promising waveform candidate for future joint sensing and communication
systems is orthogonal frequencydivision multiplexing (OFDM). For such systems,
supporting multiple transmit antennas requires multiplexing methods for the
generation of orthogonal transmit signals, where equidistant subcarrier
interleaving (ESI) is the most popular multiplexing method. In this work, we
analyze a multiplexing method called Doppler-division multiplexing (DDM). This
method applies a phase shift from OFDM symbol to OFDM symbol to separate
signals transmitted by different Tx antennas along the velocity axis of the
range-Doppler map. While general properties of DDM for the task of radar
sensing are analyzed in this work, the main focus lies on the implications of
DDM on the communication task. It will be shown that for DDM, the channels
observed in the communication receiver are heavily timevarying, preventing any
meaningful transmission of data when not taken into account. In this work, a
communication system designed to combat these time-varying channels is
proposed, which includes methods for data estimation, synchronization, and
channel estimation. Bit error ratio (BER) simulations demonstrate the
superiority of this communications system compared to a system utilizing ESI.
