Multiuser diversity is a form of selection diversity among users, the base station can schedule its transmission to those users with favorable channel fading conditions to improve the system throughput. In order to achieve multiuser diversity and apply zero-forcing precoding, the CSI of all users are required at the base station.
Multiuser diversity utilizes advantageous channel conditions for user transmission scheduling to boost system efficiency. For multiuser diversity and applying zero-forcing precoding, the base station requires the CSI (channel state information) of every user involved.