A
wireless base station device, connected to a higher-level
station device via a wired line, comprises
baseband processors 11, one for each
virtual link 21 to which user data flows belong. In the
baseband processor 11, a congestion monitor 51 monitors the reception bandwidth usage rate of a
virtual link allocated to each
cell for detecting congestion and, upon detecting congestion, sends a notification to a flow controller 57. A user traffic
distributor 52 distributes a received user traffic into the
traffic flow of each user and, at the same time, extracts, for each user data flow, the buffer holding amount in the higher-level
station device where user data flows are multiplexed and sends a notification to the flow controller 57. The flow controller 57 manages the data flow of each user and, in response to a congestion notification from the congestion monitor 51, requests the higher-level
station device to reduce the rate of a user data flow in descending order of rates beginning with a data flow with a highest rate.