标题： 考虑多普勒效应的可重构智能表面辅助无线通信信道估计 显示英文标题

标题： Channel Estimation for Reconfigurable Intelligent Surface-Assisted Wireless Communications Considering Doppler Effect

摘要： 在由可重构智能表面（RIS）辅助的无线系统中，信道状态信息在实现RIS的性能增益中起着关键作用。 移动性由于多普勒效应使得精确的信道估计（CE）更具挑战性。 在本文中，我们分别提出了两种实用的宽带CE方案，结合多径和单径传播环境中的多普勒频移调整（DSA），用于具有被动反射元件的RIS辅助通信。 对于多径场景，首先假设准静态信道执行普通的CE，然后通过联合RIS反射模式选择和频域与时域之间的转换实现DSA。 与原始CE所需的符号数相比，所提出的CE仅需要一个额外的符号，产生的额外开销可以忽略不计。 对于特别适用于毫米波和太赫兹系统的单径情况，设计了一种新的低复杂度CE方法，利用了RIS处阵列因子的形式。 仿真结果表明，所提出的算法在低复杂度下实现了高CE精度和可实现速率，并优于代表性基准方案。 显示英文摘要

摘要： In wireless systems aided by reconfigurable intelligent surfaces (RISs), channel state information plays a pivotal role in achieving the performance gain of RISs. Mobility renders accurate channel estimation (CE) more challenging due to the Doppler effect. In this letter, we propose two practical wideband CE schemes incorporating Doppler shift adjustment (DSA) for multi-path and single-path propagation environments, respectively, for RIS-assisted communication with passive reflecting elements. For the multi-path scenario, ordinary CE is first executed assuming quasi-static channels, followed by DSA realized via joint RIS reflection pattern selection and transformations between frequency and time domains. The proposed CE necessitates only one more symbol incurring negligible extra overhead compared with the number of symbols required for the original CE. For the single-path case which is especially applicable to millimeter-wave and terahertz systems, a novel low-complexity CE method is devised capitalizing on the form of the array factors at the RIS. Simulation results demonstrate that the proposed algorithms yield high CE accuracy and achievable rate with low complexity, and outperform representative benchmark schemes.