The joint communication and sensing (JCS) system can provide higher spectrum efficiency and load-saving for 6G machine-type communication (MTC) applications by merging necessary communication and sensing abilities with unified spectrum and transceivers. In order to suppress the mutual interference between the communication and radar sensing signals to improve the communication reliability and radar sensing accuracy, we propose a novel code-division orthogonal frequency division multiplex (CD-OFDM) JCS MTC system, where MTC users can simultaneously and continuously conduct communication and sensing with each other. {\color{black} We propose a novel CD-OFDM JCS signal and corresponding successive-interference-cancellation (SIC) based signal processing technique that obtains code-division multiplex (CDM) gain, which is compatible with the prevalent orthogonal frequency division multiplex (OFDM) communication system.} To model the unified JCS signal transmission and reception process, we propose a novel unified JCS channel model. Finally, the simulation and numerical results are shown to verify the feasibility of the CD-OFDM JCS MTC system {\color{black} and the error propagation performance}. We show that the CD-OFDM JCS MTC system can achieve not only more reliable communication but also comparably robust radar sensing compared with the precedent OFDM JCS system, especially in low signal-to-interference-and-noise ratio (SINR) regime.

翻译：联合通信与感知（JCS）系统通过统一频谱与收发器融合必要的通信与感知能力，可为6G机器类通信（MTC）应用提供更高的频谱效率和负载节省。为抑制通信与雷达感知信号之间的相互干扰，提升通信可靠性与雷达感知精度，我们提出一种新型码分正交频分复用（CD-OFDM）JCS MTC系统，其中MTC用户可同时且持续地进行相互通信与感知。我们提出一种新型CD-OFDM JCS信号及相应的基于连续干扰消除（SIC）的信号处理技术，该技术可获得码分复用（CDM）增益，且与主流正交频分复用（OFDM）通信系统兼容。为建模统一的JCS信号收发过程，我们提出一种新型统一JCS信道模型。最后，通过仿真与数值结果验证了CD-OFDM JCS MTC系统及其错误传播性能的可行性。研究表明，相较于先前的OFDM JCS系统，CD-OFDM JCS MTC系统不仅能实现更可靠的通信，还能在低信干噪比（SINR）条件下保持同等鲁棒的雷达感知性能。