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.

翻译：联合感知与通信系统未来极具前景的波形候选是正交频分复用（OFDM）。对于此类系统，支持多发射天线需要采用复用方法生成正交发射信号，其中等间隔子载波交织（ESI）是最常用的复用方法。本研究分析了一种称为多普勒分复用（DDM）的复用方法。该方法通过对不同OFDM符号间施加相位偏移，使不同发射天线发射的信号在距离-多普勒图的速率轴上实现分离。尽管本文分析了DDM在雷达感知任务中的通用特性，但其主要关注点在于DDM对通信任务的影响。研究证明，采用DDM时通信接收机观测到的信道具有强时变性，若未对此加以应对，将导致数据传输失去实际意义。本文提出了一种针对这些时变信道设计的通信系统，包含数据估计、同步及信道估计等方法。误码率（BER）仿真结果表明，该通信系统的性能优于采用ESI的系统。