To support extremely high data rates, reconfigurable intelligent surface (RIS)-assisted terahertz (THz) communication is considered to be a promising technology for future sixth-generation networks. However, due to the typical employment of hybrid beamforming architecture in THz systems, as well as the passive nature of RIS which lacks the capability to process pilot signals, obtaining channel state information (CSI) is facing significant challenges. To accurately estimate the cascaded channel, we propose a novel low-complexity channel estimation scheme, which includes three steps. Specifically, we first estimate full CSI within a small subset of subcarriers (SCs). Then, we acquire angular information at base station and RIS based on the full CSI. Finally, we derive spatial directions and recover full-CSI for the remaining SCs. Theoretical analysis and simulation results demonstrate that the proposed scheme can achieve superior performance in terms of normalized mean-square-error and exhibit a lower computational complexity compared with the existing algorithms.

翻译：为支持极高数据传输速率，可重构智能表面辅助太赫兹通信被认为是未来第六代网络的一项有前景的技术。然而，由于太赫兹系统通常采用混合波束赋形架构，且RIS具有无法处理导频信号的被动特性，获取信道状态信息面临重大挑战。为精确估计级联信道，我们提出了一种新颖的低复杂度信道估计方案，该方案包含三个步骤。具体而言，我们首先在小子载波子集上估计完整CSI；然后基于完整CSI获取基站和RIS处的角度信息；最后推导空间方向并恢复剩余子载波的完整CSI。理论分析与仿真结果表明，与现有算法相比，所提方案在归一化均方误差方面能实现优越性能，且计算复杂度更低。