A method, apparatus, and computer program for carrying out channel sounding are provided. Said method comprises: causing, by an apparatus, transmission of a request for space-time channel sounding to at least one unassociated access node; receiving, in the apparatus as a multi-antenna transmission and in response to said request, at least one message comprising space-time sounding information from at least one unassociated access node; determining, by the apparatus, at least one parameter describing space-time channel quality from the received space-time sounding information; and causing, by the apparatus, transmission of the at least one determined parameter to an associated access node or causing selection of an unassociated access node for further communication based at least partly on the determined at least one parameter.