A buffer status reporting scheme for a terminal (10) wishing to transmit data simultaneously in multiple RATs of a wireless communication network, which enables the co-ordination of multiple base stations (12, 14) of different RATs (e.g. LTE eNB, UMTS base station, WiFi access point, etc.) with the assistance of the terminal (10) in order to achieve efficient radio resource scheduling for multi-RAT multi-flow aggregation in uplink. A radio bearer is configured for multi-RAT multi-flow aggregation by the network, and multiple logical channel IDs are assigned to this RB that may be associated with different RATs. Logical channels associated with a certain RAT (or a given set of RATs) may be grouped into one logical channel group for radio resource scheduling reason. The terminal (10) performs buffer status reporting, according to the configuration, on all involved RATs and sends reports/indications to one or more involved base stations (12.14).