Establishing simultaneous radio connection between a user equipment and two eNodeBs

A communication control method in a second radio station, the method comprising:

• operating a second cell;
• receiving, from a first radio station configured to operate a first cell, a first request for requesting the second radio station to prepare a radio resource for a radio terminal, while an established first radio connection between the first radio station and the radio terminal is maintained on the first cell;
• and
• sending, to the first radio station, radio resource configuration information of the second cell,
• wherein the first radio station is configured to transmit, to the radio terminal, an RRC (Radio Resource Control) Connection Reconfiguration message including the radio resource configuration information of the second cell while the established first radio connection is maintained,
• the first request includes an E-RAB ID (E-UTRAN Radio Access Bearer Identity) which indicates an E-UTRAN radio access bearer, between the radio terminal and an S-GW (Serving Gateway) via the second radio station, to be added, and
• the radio resource configuration information of the second cell includes
• a drb-identity (Data Radio Bearer Identity) which indicates a data radio bearer, between the radio terminal and the second radio station, and
• an eps-Bearerldentity (Evolved Packet System Bearer Identity) which indicates an EPS-bearer mapped on the data radio bearer.

A radio terminal, comprising:

• a memory;
• and
• at least one hardware processor coupled to the memory, the at least one hardware processor configured to:
• establish a first radio connection between a first radio station and the radio terminal on a first cell operated by the first radio station;
• receive an RRC (Radio Resource Control) Connection Reconfiguration message from the first radio station, wherein the RRC Connection Reconfiguration message includes radio resource configuration information of a second cell operated by a second radio station;
• add the second cell as a secondary cell based on the radio resource configuration information of the second cell for aggregating the first cell as a primary cell with the second cell while the first radio connection is maintained on the first cell, wherein
• the radio resource configuration information of the second cell includes a drb-identity (Data Radio Bearer Identity) which indicates a data radio bearer between the radio terminal and the second radio station, and an eps-Bearerldentity (Evolved Packet System Bearer Identity) which indicates an EPS-bearer mapped on the data radio bearer,
• the radio resource configuration information of the second cell is sent from the second radio station to the first radio station in response to a first request from the first station, and
• the first request, for preparing a radio resource by the second radio station for the radio terminal on the second cell, includes an E-RAB ID (E-UTRAN Radio Access Bearer Identity) which indicates an E-UTRAN radio access bearer, between the radio terminal and an S-GW (Serving Gateway) via the second radio station, to be added.

A communication control method in a radio terminal, the method comprising:

• establishing a first radio connection between a first radio station and the radio terminal on a first cell operated by the first radio station;
• receiving an RRC (Radio Resource Control) Connection Reconfiguration message from the first radio station, wherein the RRC Connection Reconfiguration message includes radio resource configuration information of a second cell operated by a second radio station;
• adding the second cell as a secondary cell based on the radio resource configuration information of the second cell for aggregating the first cell as a primary cell with the second cell while the first radio connection is maintained on the first cell, wherein
• the radio resource configuration information of the second cell includes a drb-identity (Data Radio Bearer Identity) which indicates a data radio bearer between at least the radio terminal and the second radio station, and an eps-Bearerldentity (Evolved Packet System Bearer Identity) which indicates an EPS-bearer mapped on the data radio bearer,
• the radio resource configuration information of the second cell is sent from the second radio station to the first radio station in response to a first request from the first station, wherein
• the first request, for preparing a radio resource by the second radio station for the radio terminal on the second cell, includes an E-RAB ID (E-UTRAN Radio Access Bearer Identity) which indicates an E-UTRAN radio access bearer, between the radio terminal and an S-GW (Serving Gateway) via the second radio station, to be added.