Patent ID: 7113480

Claim:
A mobile communication system which includes a mobile unit, a radio base station, and a radio controller, wherein the radio controller comprises: first and second user plane processing means for performing processing to control transfer of user data in relation to the mobile unit; and control plane processing means for processing to control transfer of signaling having a control signal, the control plane processing means being physically separated from the first and second user plane processing means, and when detecting a congestion state of processing, the first user plane processing means transfers a first part of the processing to the second user plane processing means while maintaining a second part of the processing at the first user plane processing means, wherein said first user plane processing means comprises: a Layer 2 processing unit; an ATM/IP interface unit that is configured to convert ATM packets input thereto from an external node to IP packets and to transfer the IP packets to either said Layer 2 processing unit or to a router, said ATM/IP interface unit also configured to convert IP packets input thereto from said Layer 2 processing unit or from said router into ATM packets and to transfer said ATM packets to said external node; and an APL unit that is configured to provide control information to said ATM/IP interface unit to direct transfer of said ATM packets and said IP packets to either said Layer 2 processing unit or said router, wherein said APL unit comprises: a lower protocol management part; a congestion detection part that detects a state of congestion; a congestion state control part that performs control during the state of congestion as detected by said congestion detection part; a control unit for controlling said lower protocol management part, said congestion detection part, and said congestion state control part; and a bus that communicatively connects said lower protocol management part, said congestion detection part, and said congestion state control part.