Communication system providing mobility management internetworking between a C-interface radio system and an overlay mobile radio network

A communication system comprising:

• a mobile radio network including
• at least one radio system comprising a plurality of radio stations for communicating with mobile stations and a radio station controller, a protocol stack in said controller including a first and a second application layer protocols and a relay protocol for adapting the upper layer protocols to a lower layer protocol;
• a service control point SCP for providing mobility management functions, the service control point SCP having access to a common channel signalling network for sending and receiving first application layer protocol messages;
• a switch for transmitting transparently first and second application layer protocol messages between the radio station controller and the service control point SCP;
• at least one network element having access to said common channel signalling network for sending and receiving first application layer protocol messages;
• wherein in said system:
• the service control point SCP includes a relay protocol means for discriminating between the first and the second application layer protocols, and for routing the first application layer protocol messages forward.