Communication control method and relay node for relaying data from lower node to upper node

A communication control method using a relay node comprising a first functional unit configured to connect wirelessly to a lower node and a second functional unit configured to connect wirelessly to an upper node, the relay node relaying data from the lower node to the upper node, the communication control method comprising:

• detecting, by the second functional unit, that an event related to resource allocation to the lower node has occurred in the first functional unit;
• transmitting, by the second functional unit, to the upper node, in a case of detecting occurrence of the event, a first buffer state report including size information indicating an amount of data having yet to be transmitted to the upper node, and
• receiving, by the relay node, from the upper node, event configuration information designating a predetermined event,
• wherein the detecting includes
• detecting the occurrence of the event by monitoring an event occurring in the first functional unit, or by receiving, from the first functional unit, a notification indicating that the event has occurred, and
• determining whether the event that has occurred is the predetermined event designated by the event configuration information received from the upper node, and
• the transmitting includes transmitting, to the upper node, the first buffer state report in response to determining that the event that has occurred is the predetermined event designated by the event configuration information received from the upper node.