In this paper, we consider the problem of spread pilot design and effective channel estimation in multiple-input multiple-output Zak-OTFS (MIMO-Zak-OTFS) with superimposed spread pilots, where data and spread pilot signals are superimposed in the same frame. To achieve good estimation performance in a MIMO setting, the spread pilots at different transmit antennas need to be effectively separated at the receiver. Towards this, we propose a spread pilot design that separates the pilot sequences in the cross-ambiguity domain and enables the estimation of the effective channel taps by a simple read-off operation. To further alleviate the effect of pilot-data interference on performance, we carry out turbo iterations between channel estimation and detection. Simulation results for $2\times 2$ and $3\times 3$ MIMO-Zak-OTFS with Gaussian-sinc pulse shaping filter for vehicular-A channel model show that the proposed pilot design and estimation scheme with three turbo iterations can achieve very good estimation/detection performance.

翻译：本文研究了采用叠加扩频导频的多输入多输出Zak-OTFS（MIMO-Zak-OTFS）系统中的扩频导频设计与有效信道估计问题，其中数据信号与扩频导频信号在同一帧内叠加传输。为在MIMO配置下实现良好的估计性能，需要使来自不同发射天线的扩频导频在接收端能够被有效分离。为此，我们提出了一种在交叉模糊域中分离导频序列的扩频导频设计方案，该方案能够通过简单的读取操作实现有效信道抽头的估计。为进一步减轻导频-数据干扰对性能的影响，我们在信道估计与检测之间执行了Turbo迭代。针对采用高斯sinc脉冲成形滤波器的Vehicular-A信道模型，在$2\times 2$与$3\times 3$ MIMO-Zak-OTFS系统中的仿真结果表明，所提出的导频设计方案与经过三次Turbo迭代的估计方案能够实现优异的估计/检测性能。