Abstract: In mobile radio systems, it may be necessary to support multiple radio interfaces within a single mobile radio network. To support these multiple radio interfaces, it may be necessary to support even multiple signalling protocols within a single interface between a base station controller and a mobile switch, when base stations supporting different radio interfaces are connected via a common base station controller to the mobile switch. The mobile switch and the base station controller must be capable of recognizing to which signalling protocol a message transfer in the single interface belongs to. The messages transferred in the single interface are provided with a discrimination parameter which can be used to discriminate between the messages belonging to different radio interfaces and signalling protocols.