Precoding, also known as digital beamforming, consists in using an antenna array to transmit one or multiple spatially directive signals simultaneously. Every antenna of the transmit array emits a different signal, designed in the digital domain according to some optimization criteria. Thus, precoding is particularly desirable for spatial multiplexing, where we want to transmit a superposition of signals, each with a separate directivity (i.e., each directed to a different receiver, […]