A method in a transmitter for selecting steering vectors for simultaneously transmitting a plurality of streams (NS) between the transmitter and a receiver, where the receiver has NR receive antennas, where the transmitter knows respective channels associated with M receive antennas of the receiver, and where M is less than NR, includes constructing a partial channel matrix that describes a multiple input, multiple output (MIMO) channel between the transmitter and the M receive antennas, generating L independent vectors using the partial channel matrix, wherein L is a rank of the partial channel matrix, selecting a respective steering vector for each of the plurality of streams to be transmitted to the receiver, including, if NS is less than or equal to L, selecting NS of the L independent vectors as the steering vectors, and, if NS is greater than L, (i) selecting the L independent vectors as steering vectors to steer L of the plurality of streams; and (ii) selecting NS−L orthogonal vectors in a null space of the L independent vectors.