A radio network controller assembly arranged to control a plurality of base stations, each base station arranged to control at least one radio cell, the radio network controller assembly comprising: a plurality of unit radio network controllers; wherein each unit radio network controller comprises a set of external interfaces (Iur, Iu, Iub) for interacting with a core network, at least one base station and other radio network controllers; and a set of internal interfaces (20a-c), distinct from the set of external interfaces (Iur, Iu, Iub), for at least interacting with peer unit radio network controllers (12, 12', 12") the radio network controller assembly further comprising: a database arranged to store configuration data comprising mappings of each base station and one respectively associated unit radio network controller of the plurality of unit radio network controllers, wherein the radio network controller assembly is arranged to use the sets of external interfaces for communication with the plurality of base stations, the core network and other radio network controllers external to the radio network controller assembly; wherein the radio network controller assembly comprises external interfaces which are identical to those of an independent radio network controller; and wherein the radio network controller assembly is characterized in that one of the unit radio network controllers is a singleton device which owns a Signalling System #7 interface for the radio network controller assembly which is to be performed by only one unit radio network controller in relation to the core network. a plurality of unit radio network controllers; wherein each unit radio network controller comprises a set of external interfaces (Iur, Iu, Iub) for interacting with a core network, at least one base station and other radio network controllers; and a set of internal interfaces (20a-c), distinct from the set of external interfaces (Iur, Iu, Iub), for at least interacting with peer unit radio network controllers (12, 12', 12") a set of external interfaces (Iur, Iu, Iub) for interacting with a core network, at least one base station and other radio network controllers; and a set of internal interfaces (20a-c), distinct from the set of external interfaces (Iur, Iu, Iub), for at least interacting with peer unit radio network controllers (12, 12', 12") the radio network controller assembly further comprising: a database arranged to store configuration data comprising mappings of each base station and one respectively associated unit radio network controller of the plurality of unit radio network controllers, wherein the radio network controller assembly is arranged to use the sets of external interfaces for communication with the plurality of base stations, the core network and other radio network controllers external to the radio network controller assembly; wherein the radio network controller assembly comprises external interfaces which are identical to those of an independent radio network controller; and wherein the radio network controller assembly is characterized in that one of the unit radio network controllers is a singleton device which owns a Signalling System #7 interface for the radio network controller assembly which is to be performed by only one unit radio network controller in relation to the core network. a database arranged to store configuration data comprising mappings of each base station and one respectively associated unit radio network controller of the plurality of unit radio network controllers, wherein the radio network controller assembly is arranged to use the sets of external interfaces for communication with the plurality of base stations, the core network and other radio network controllers external to the radio network controller assembly; wherein the radio network controller assembly comprises external interfaces which are identical to those of an independent radio network controller; and wherein the radio network controller assembly is characterized in that one of the unit radio network controllers is a singleton device which owns a Signalling System #7 interface for the radio network controller assembly which is to be performed by only one unit radio network controller in relation to the core network. one of the unit radio network controllers is a singleton device which owns a Signalling System #7 interface for the radio network controller assembly which is to be performed by only one unit radio network controller in relation to the core network.