A first radio station (1) requests or instructs a second radio station (2) to prepare for communication with a radio terminal (3) on a second cell (20) while a first radio connection on a first cell (10) with the radio terminal (3) is established. Further, the first radio station (1) instructs the radio terminal (3) or the second radio station (2) to establish a second radio connection on the second cell (20) with the radio terminal (3) while maintaining the radio connection on the first cell (10) with the radio terminal (3). It is thus for example possible to enable a single radio terminal to establish radio connections with cells of a plurality of radio stations, in order to achieve carrier aggregation of cells operated by different radio stations.