A method in a first node for adapting a multi-antenna transmission to a second node over a wireless channel is provided. The wireless channel has at least three inputs and at least one output. The first node and the second node are comprised in a wireless communication system. The method includes obtaining at least one symbol stream, determining a precoding matrix having a product structure created by a block diagonal matrix being multiplied from the left with a block diagonalizing unitary matrix, precoding the at least one symbol stream with the determined preceding matrix, and transmitting the precoded at least one symbol stream over a wireless channel to the second node.