In a cellular communication system, for example UMTS using WCDMA, a configuration of radio links is controlled. In a mobile unit, and in a base station, a synchronization counter indicates time codes (CFN) for synchronization of configuration changes across the system. Messages are exchanged between a network controller, the base stations and the mobile units, which messages include a change command (62) for changing a configuration, and a reconfiguration command (61) for changing a current configuration state to a next configuration state at a selected future time code (63). Traditionally a prepared reconfiguration period (67) for such a reconfiguration change was treated as a blocking period for further changes. According to the invention the prepared reconfiguration period is determined, and a prepared reconfiguration period indicator (66) is added to the change command. Hence other configuration changes can be effected during the prepared reconfiguration period.