Chapter 11: Array-Fed RIS

Learning Objectives

• State the array-fed RIS architecture: small active array illuminating a large passive RIS
• Derive the eigenmode decomposition of the BS-RIS near-field channel $\mathbf{H}_1$
• Explain how the number of users is bounded by the rank of $\mathbf{H}_1$
• Compute the multi-user multiplexing capacity gain of array-fed RIS
• Identify when array-fed RIS dominates over conventional RIS + massive MIMO