On Spatial Multiplexing Using Reconfigurable Intelligent Surfaces

We consider an uplink multi-user scenario and investigate the use of reconfigurable intelligent surfaces (RIS) to optimize spatial multiplexing performance when a linear receiver is used. study two different formulations problem, namely maximizing effective rank minimum singular value RIS-augmented channel. employ gradient-based optimization solve problems compare solutions in terms sum-rate achievable Our results show that proposed criteria can be used RIS obtain channels with favorable properties drastically improve even propagation through contributes small fraction received power.