Certain aspects of the present disclosure provide techniques and apparatus for efficiently managing groups of stations (STAs) receiving simultaneous transmissions in a multiuser multiple-input multiple-output (MU-MIMO) scheme. One example method generally includes; for a first apparatus in a number of groups of apparatuses, allocating a first spatial stream position for each of at least one first group in the number of the groups; and transmitting a first unicast message to the first apparatus, wherein the first unicast message comprises an indication of the allocated spatial stream position for each of the at least one first group and, for each group in the number of the groups, an indication of a membership status, in the group, of the first apparatus.