Orthogonal time frequency space (OTFS) modulation has the potential to enable robust communications in highly-mobile scenarios. Estimating the channels for OTFS systems, however, is associated with high pilot signaling overhead that scales with the maximum delay and Doppler spreads. This becomes particularly challenging for massive MIMO systems where the overhead also scales with the number of antennas. An important observation however is that the delay, Doppler, and angle of departure/arrival information are directly related to the distance, velocity, and direction information of the mobile user and the various scatterers in the environment. With this motivation, we propose to leverage radar sensing to obtain this information about the mobile users and scatterers in the environment and leverage it to aid the OTFS channel estimation in massive MIMO systems. As one approach to realize our vision, this paper formulates the OTFS channel estimation problem in massive MIMO systems as a sparse recovery problem and utilizes the radar sensing information to determine the support (locations of the non-zero delay-Doppler taps). The proposed radar sensing aided sparse recovery algorithm is evaluated based on an accurate 3D ray-tracing framework with co-existing radar and communication data. The results show that the developed sensing-aided solution consistently outperforms the standard sparse recovery algorithms (that do not leverage radar sensing data) and leads to a significant reduction in the pilot overhead, which highlights a promising direction for OTFS based massive MIMO systems.

中文翻译：

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大规模 MIMO 系统的传感辅助 OTFS 信道估计

正交时频空间 (OTFS) 调制有可能在高度移动的场景中实现稳健的通信。然而，估计 OTFS 系统的信道与高导频信令开销相关，该开销随最大延迟和多普勒扩展而扩展。这对于大规模 MIMO 系统而言尤其具有挑战性，因为其开销也随着天线数量的增加而增加。然而，一个重要的观察结果是延迟、多普勒和出发/到达角度信息与移动用户的距离、速度和方向信息以及环境中的各种散射体直接相关。带着这个动机，我们建议利用雷达传感来获取有关环境中移动用户和散射体的信息，并利用它来帮助大规模 MIMO 系统中的 OTFS 信道估计。作为实现我们愿景的一种方法，本文将大规模 MIMO 系统中的 OTFS 信道估计问题表述为稀疏恢复问题，并利用雷达传感信息来确定支持（非零延迟多普勒抽头的位置）。所提出的雷达传感辅助稀疏恢复算法基于具有共存雷达和通信数据的精确 3D 射线追踪框架进行评估。结果表明，开发的传感辅助解决方案始终优于标准稀疏恢复算法（不利用雷达传感数据），并显着降低了飞行员的开销，