Is Channel Estimation Necessary to Select Phase-Shifts for RIS-Assisted Massive MIMO?

  title={Is Channel Estimation Necessary to Select Phase-Shifts for RIS-Assisted Massive MIMO?},
  author={Ozlem Tugfe Demir and Emil Bj{\"o}rnson},
Reconfigurable intelligent surfaces (RISs) have attracted great attention as a potential beyond 5G technology. These surfaces consist of many passive elements of metamaterials whose impedance can be controllable to change the characteristics of wireless signals impinging on them. Channel estimation is a critical task when it comes to the control of a large RIS when having a channel with a large number of multipath components. In this paper, we propose novel channel estimation schemes for… 
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