1. A communication system comprising a communication terminal device
(71), a base station device (72) configured to perform radio communication with the
communication terminal device (71), and a host node device (73, 74) that is adapted
to restrict the connection between the communication terminal device (71) and the
base station device (72), wherein
the base station device (72) provides a plurality of cells formed of component carriers having different frequencies, the base station device (72) aggregating two or more cells of the plurality of cells and transmitting and receiving component carriers of the aggregated cells in parallel to perform radio communication with the communication terminal device (71),
the plurality of cells include a cell for specific subscribers that specifies a connectable communication terminal device (71),
upon establishment of radio connection between any one of the plurality of cells and the communication terminal device (71), the connected cell configures any of other cells as an aggregable cell that is allowed to be aggregated with the own cell, the connected cell being a cell in which radio connection with the communication terminal device (71) has been established, and
upon the aggregable cell being configured by the connected cell:
the host node device (73, 74) stops an operation of restricting access to the aggregable cell; and
the communication terminal device (71) stops an operation of restricting access to the aggregable cell based on cell information being the information related to the cell for specific subscribers held in advance.
2. The communication system as claimed in claim 1, wherein the connected cell configures, as the aggregable cell, a cell belonging to the same group of cells for specific subscribers as that of the own cell among the other cells.
3. The communication system as claimed in claim 2, wherein the plurality of cells are configured to belong to the same group of cells for specific subscribers.

4. The communication system as claimed in claim 1, wherein the connected cell configures, as the aggregable cell, the remaining cells except for the cell for specific subscribers among the other cells.
5. A communication system comprising a communication terminal device (71), a base station device (72) configured to perform radio communication with the communication terminal device (71), and a host node device (73, 74) that is adapted to restrict the connection between the communication terminal device (71) and the base station device (72), wherein
the base station device (72) provides a plurality of cells formed of component carriers having different frequencies, the base station device (72) aggregating two or more cells of the plurality of cells and transmitting and receiving component carriers of the aggregated cells in parallel to perform radio communication with the communication terminal device (71),
the plurality of cells include a cell for specific subscribers that specifies a connectable communication terminal device (71),
upon establishment of radio connection between any one of the plurality of cells and the communication terminal device (71), the connected cell is adapted to select any one of the other cells as a candidate cell being a candidate for aggregable cell that is allowed to be aggregated with the own cell and to notify the communication terminal device (71) of information related to the selected candidate cell, the connected cell being a cell in which radio connection with the communication terminal device (71) has been established,
upon notification of the information related to the candidate cell from the connected cell, the communication terminal device (71) is adapted to judge whether or not access to the candidate cell is allowed based on cell information related to the cell for specific subscribers held in advance and to notify the connected cell of the judgment results,
when judging that access to the candidate cell is allowed based on the judgment results notified from the communication terminal device (71), the connected cell configures the candidate cell as the aggregable cell, and

upon the aggregable cell being configured by the connected cell, the host node device (73, 74) stops an operation of restricting access to the aggregable cell.
6. The communication system as claimed in claim 5, wherein the connected cell configures the candidate cell as the aggregable cell based on a situation in which the communication terminal device (71) is allowed access to the candidate cell.