Abstract: The present invention provides a method implemented in a base station having a plurality of antennas. The method includes associating a plurality of users with a plurality of first pre-coding matrices based on information provided by the plurality of users. The method also includes determining whether at least one of the plurality of first pre-coding matrices is incomplete and associating users with at least one second pre-coding matrix when at least one first pre-coding matrix is incomplete. The users are associated with the incomplete first pre-coding matrix and the second pre-coding matrix is formed based on the incomplete first pre-coding matrix.