A communication system includes a plurality of nodes including a base station; at least one terminal; and at least one relay node through which each terminal can be connected to the base station. An entity in a network higher in layer than each relay node configures the relay node to set a target value for a predetermined parameter reflecting a radio link status of the relay node. The relay node monitors the predetermined parameter to notify an upper-layer node of difference information corresponding to a difference between the target value and a monitored parameter value. The upper-layer node controls a link parameter of a radio link connecting the upper-layer node and the relay node depending on the difference information, resulting in efficient radio resource allocation in a relay network with small signaling overhead.