According to certain embodiments, a method in a network node, is disclosed. The method comprises selecting a sub set from a predetermined set of P CSI-RS ports for receiving channel information. The network node comprises an antenna array with controllable polarization. Each CSI-RS port corresponds to a combination of a set of resource elements and an antenna port of said antenna array. The predetermined set comprises a first number P1 of CSI-RS ports with a first polarization state and a second number P2 of CSI-RS ports with a second polarization state. The first and second polarization states are distinct. The method further comprises populating the subset with Q CSI-RS pons in such mariner that the ratio of CSI-RS pons respectively having the first and second polarization states is equal to the ratio of the first and second numbers.
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