A method and a control node for supporting transmissions of reference signals in spatially differentiated beams from a first network node of a wireless network. A sequence of beams to be used for transmitting the reference signals is determined based on ability information indicating radio resources which the first network node is able to use for beam transmissions during a predefined time period. The control node then instructs the first network node to transmit reference signals in at least one beam at a time according to the determined sequence of beams. Thereby, it can be avoided that the first network node is instructed to transmit a reference signal in a beam on a radio resource that the first network node is unable to use.