A method in a Serving Access Node (SAN) for coordinating with a number of other SANs within a terminal device-specific serving cluster to which the SAN belongs. The method comprises determining an assignment of a communication direction to a timeslot. The assignment of the communication direction to the timeslot is common to all SANs in the serving cluster. The method further comprises transmitting or receiving at least one test beam in the communication direction during the timeslot. Correspondingly, a SAN is disclosed in which the method is implemented.