The capacity of the single-user MIMO system can be achieve by unitary precoding at the transmitter. In particular, static random unitary matrix and adaptive SVD precoding must be used to achieve the open-loop and closed-loop MIMO capacities, respectively. The precoding vectors for a single user MIMO system are generally determined based on the downlink channel of one corresponding user, while the precoding vectors for a multiuser MIMO system are generally determined based on the downlink channels of a set of candidate users.
==Static random unitary precoding==
Random unitary precoding including identity transformation matrix can achieve the open-loop MIMO capacity where no signaling burden in the reverse link is required.
==Adaptive SVD precoding==
SVD precoding has been proven to achieve the (real) channel capacity of MIMO systems at the cost of closed-loop signaling burden<ref>E. Telatar (June 1995.). "Capacity of multiantenna gaussian channels". AT&T Bell Laboratories, Tech. Memo.</ref>.