Integrated sensing and communication (ISAC) is considered as the potential key technology of the future mobile communication systems. The signal design is fundamental for the ISAC system. The reference signals in mobile communication systems have good detection performance, which is worth further research. Existing studies applied the single reference signal to radar sensing. In this paper, a multiple reference signals collaborative sensing scheme is designed. Specifically, we jointly apply channel state information reference signal (CSI-RS), positioning reference signal (PRS) and demodulation reference signal (DMRS) in radar sensing, which improve the performance of radar sensing via obtaining continuous time-frequency resource mapping. Cr\'amer-Rao lower bound (CRLB) of the joint reference signal for distance and velocity estimation is derived. The impacts of carrier frequency and subcarrier spacing on the performance of distance and velocity estimation are revealed. The results of simulation experiments show that compared with the single reference signal sensing scheme, the multiple reference signals collaborative sensing scheme effectively improves the sensing accuracy. Moreover, because of the discontinuous OFDM symbols, the accuracy of velocity estimation could be further improved via compressed sensing (CS). This paper has verified that multiple reference signals, instead of single reference signal, have much more superior performance on radar sensing, which is a practical and efficient approach in designing ISAC signal.

翻译：集成感知与通信（ISAC）被视为未来移动通信系统的潜在关键技术。信号设计是ISAC系统的基础。移动通信系统中的参考信号具有良好的检测性能，值得进一步研究。现有研究将单一参考信号应用于雷达感知。本文设计了一种多参考信号协作感知方案。具体而言，我们联合应用信道状态信息参考信号（CSI-RS）、定位参考信号（PRS）和解调参考信号（DMRS）进行雷达感知，通过获取连续的时频资源映射来提升雷达感知性能。推导了联合参考信号的距离与速度估计的克拉美-罗下界（CRLB），揭示了载波频率和子载波间隔对距离与速度估计性能的影响。仿真实验结果表明，与单一参考信号感知方案相比，多参考信号协作感知方案有效提升了感知精度。此外，由于非连续OFDM符号的存在，可通过压缩感知（CS）进一步提升速度估计精度。本文验证了多参考信号（而非单一参考信号）在雷达感知中具有更优越的性能，是设计ISAC信号的实用且高效的方法。