The present disclosure relates to the management of control information in a multi-user multi-input multi-output system with a base unit and two or more user units, where respective user unit sends an index representing a vector from a user codebook belonging to the user unit. The base unit co-schedules compatible user units to simultaneously share one time-frequency resource by selecting a precoding matrix from a base unit codebook based on the indices received from co-scheduled user units, according to a predefined function. The base unit transmits control information regarding selected precoding matrix to each co-scheduled user unit. The predefined function is known to each user unit and the control information to each user unit only contains information on the index from every other user unit.