1. A method, in a transmitter, for selecting steering vectors for simultaneously transmitting one or more streams between the transmitter and a receiver, wherein the receiver has N R receive antennas, wherein the transmitter knows respective channels associated with M receive antennas of the receiver, wherein M is less than N R , and wherein N S is the number of the one or more streams, the method comprising: 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; and when N S is greater than L, (i) selecting the L independent vectors as steering vectors to steer L streams of the one or more of streams; (ii) selecting N S −L orthogonal vectors in a null space of the L independent vectors as steering vectors to steer a remainder of the streams in the one or more streams; and (iii) respectively utilizing the steering vectors for transmitting (a) the L streams of the one or more of streams (N S ), and (b) the remainder of the streams in the one or more streams (N S ).