terminal device (21, 21-1, 1021) for use in a communication system using inter-site carrier aggregation comprising: a wireless communication part (102, 122, 142) configured to wirelessly communicate with a primary base station device (1, 1-1, 1-2, 1001-1) configured to act as a PCell, i. e. as a primary cell, and to communicate C-Plane, i. e. control plane, data and with a secondary base station device (2, 2-1, 2-2, 2-3, 1002-1) configured to act as an SCell, i. e. as a secondary cell, and to communicate U-Plane, i. e. user plane, data; wherein the terminal device (21, 21-1, 1021) is configured to carry out communications with the primary base station device (1, 1-1, 1-2 1001-1) and the secondary base station device (2, 2-1, 2-2, 2-3, 1002-1) concurrently in a C/U isolation; a link controller configured to establish a radio link with the primary base station device (1, 1-1, 1-2 1001-1, 2) and with the secondary base station device (2, 2-1, 2-2, 2-3, 1002-1) via the wireless communication part (102, 122, 142); a primary base station link failure detector configured to detect a primary radio link failure with the primary base station device (1, 1-1, 1-2 1001-1) under a primary failure condition which is determined in advance; a primary base station link failure information transmitter (205, 302, 402) configured to wirelessly transmit primary failure information concerning the primary radio link failure with the primary base station device (1, 1-1, 1-2 1001-1) to the secondary base station device (2, 2-1, 2-2, 2-3, 1002-1) via the wireless communication part (102, 122, 142); a secondary base station link failure detector configured to detect a secondary radio link failure with the secondary base station device (2, 2-1, 2-2, 2-3, 1002-1) under a secondary failure condition which is determined in advance; and a secondary base station link failure information transmitter (204, 303, 403) configured to wirelessly transmit secondary failure information concerning the secondary radio link failure with the secondary base station device (2, 2-1, 2-2, 2-3, 1002-1) to the primary base station device (1, 1-1, 1-2 1001-1) via the wireless communication part (102, 122, 142), wherein the primary failure information comprises a C-RNTI, Cell-Radio Network Identifier, of the mobile terminal in the primary base station device, and wherein the secondary failure information comprises the C-RNTI of the mobile terminal in the secondary base station device. a wireless communication part (102, 122, 142) configured to wirelessly communicate with a primary base station device (1, 1-1, 1-2, 1001-1) configured to act as a PCell, i. e. as a primary cell, and to communicate C-Plane, i. e. control plane, data and with a secondary base station device (2, 2-1, 2-2, 2-3, 1002-1) configured to act as an SCell, i. e. as a secondary cell, and to communicate U-Plane, i. e. user plane, data; wherein the terminal device (21, 21-1, 1021) is configured to carry out communications with the primary base station device (1, 1-1, 1-2 1001-1) and the secondary base station device (2, 2-1, 2-2, 2-3, 1002-1) concurrently in a C/U isolation; a link controller configured to establish a radio link with the primary base station device (1, 1-1, 1-2 1001-1, 2) and with the secondary base station device (2, 2-1, 2-2, 2-3, 1002-1) via the wireless communication part (102, 122, 142); a primary base station link failure detector configured to detect a primary radio link failure with the primary base station device (1, 1-1, 1-2 1001-1) under a primary failure condition which is determined in advance; a primary base station link failure information transmitter (205, 302, 402) configured to wirelessly transmit primary failure information concerning the primary radio link failure with the primary base station device (1, 1-1, 1-2 1001-1) to the secondary base station device (2, 2-1, 2-2, 2-3, 1002-1) via the wireless communication part (102, 122, 142); a secondary base station link failure detector configured to detect a secondary radio link failure with the secondary base station device (2, 2-1, 2-2, 2-3, 1002-1) under a secondary failure condition which is determined in advance; and a secondary base station link failure information transmitter (204, 303, 403) configured to wirelessly transmit secondary failure information concerning the secondary radio link failure with the secondary base station device (2, 2-1, 2-2, 2-3, 1002-1) to the primary base station device (1, 1-1, 1-2 1001-1) via the wireless communication part (102, 122, 142), wherein the primary failure information comprises a C-RNTI, Cell-Radio Network Identifier, of the mobile terminal in the primary base station device, and wherein the secondary failure information comprises the C-RNTI of the mobile terminal in the secondary base station device.