5.Options: , from the remaining users , form a set ; let ; represents the candidate set of the element in ;
6.Determine: If , has only elements. If , the th element in is a member of . If ,, determine the th element in according to (17) and (18);
7.Updateć, by (15), (16), repeat the process until the group is complete;
8.Grouping: Repeat (14)ā(18) to group the remaining users until all users are grouped;
9.Intragrouping Identification: From (19) to (22), ML criterion is used in each group to identify the optimal beam and estimate its beamforming gain;
10. Intergrouping Confirmation: The gain of all candidate optimal beams is compared between each group by (23) to confirm the optimal beamforming vector , BS uses it for downlink transmission.