The disclosure relates to a network node of a wireless network, and to a related method of controlling interference generated by at least one white space device controlled by the network node. The method comprises transmitting a request for information regarding channels available for secondary usage to the remote entity, and receiving information from the remote entity, the information indicating a channel available for secondary usage, a critical position associated with said channel, and an interference threshold for the critical position. The method also comprises deriving a constraint for the allocation of said channel to the at least one white space device, based on a position of the at least one white space device, the critical position, and the interference threshold, and allocating said channel and a transmit power to the at least one white space device based on the derived constraint, whereby the interference generated in the critical position by the at least one white space device is kept below the interference threshold.