  We present efficient algorithms for the sum-spectral efficiency (SE)
maximization of the multi-user reconfigurable intelligent surface (RIS)-aided
multiple-input multiple-output (MIMO) broadcast channel based on a zero-forcing
approach. These methods conduct a user allocation for which the computation is
independent of the number of elements at the RIS, that is usually large.
Specifically, two algorithms are given that exploit the line-of-sight (LOS)
structure between the base station (BS) and the RIS. Simulations show superior
SE performance compared to other linear precoding algorithms but with lower
complexity.
