Radio communication system, radio station, radio terminal, communication control method, and computer-readable medium

A first radio station configured to operate a first cell, the first radio station comprising:

• a transceiver;
• and
• at least one processor configured to, via the transceiver, communicate with a radio terminal capable of performing Dual Connectivity using either the first cell or a third cell of a third radio station as a primary cell and a second cell of a second radio station as a secondary cell, wherein
• the at least one processor is further configured to, within a procedure changing a radio station operating the primary cell of the radio terminal from the first radio station to the third radio station, transmit a Radio Resource Control (RRC) Connection Reconfiguration message to trigger the radio terminal to:
• release configuration information on the second cell except for Data Radio Bearer (DRB) configuration information corresponding to a DRB established in the second cell;
• and
• re-configure the DRB established in the second cell.

A radio terminal comprising:

• a transceiver;
• and
• at least one processor configured to perform Dual Connectivity using either a first cell of a first radio station or a third cell of a third radio station as a primary cell and a second cell of a second radio station as a secondary cell, wherein
• the at least one processor is further configured to, within a procedure changing the primary cell from the first cell to the third cell:
• receive a Radio Resource Control (RRC) Connection Reconfiguration message from the first radio station;
• release, in response to the RRC Connection Reconfiguration message, configuration information on the second cell except for Data Radio Bearer (DRB) configuration information corresponding to a DRB established in the second cell;
• and
• re-configure the DRB established in the second cell.

A communication control method in a first radio station configured to operate a first cell, the method comprising:

• communicating, via a transceiver of the first radio station, with a radio terminal capable of performing Dual Connectivity using either the first cell or a third cell of a third radio station as a primary cell and a second cell of a second radio station as a secondary cell;
• and
• transmitting, within a procedure changing a radio station operating the primary cell of the radio terminal from the first radio station to the third radio station, a Radio Resource Control (RRC) Connection Reconfiguration message to trigger the radio terminal to:
• release configuration information on the second cell except for Data Radio Bearer (DRB) configuration information corresponding to a DRB established in the second cell;
• and
• re-configure the DRB established in the second cell.

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

• performing Dual Connectivity using either a first cell of a first radio station or a third cell of a third radio station as a primary cell and a second cell of a second radio station as a secondary cell;
• receiving, within a procedure changing the primary cell from the first cell to the third cell, a Radio Resource Control (RRC) Connection Reconfiguration message from the first radio station;
• releasing, in response to the RRC Connection Reconfiguration message, configuration information on the second cell except for Data Radio Bearer (DRB) configuration information corresponding to a DRB established in the second cell;
• and
• re-configuring the DRB established in the second cell.

A non-transitory computer-readable medium storing therein a program for causing a computer to perform a communication control method in a first radio station configured to operate a first cell, wherein the communication control method comprises:

• communicating, via a transceiver of the first radio station, with a radio terminal capable of performing Dual Connectivity using either the first cell or a third cell of a third radio station as a primary cell and a second cell of a second radio station as a secondary cell;
• and
• transmitting, within a procedure changing a radio station operating the primary cell of the radio terminal from the first radio station to the third radio station, a Radio Resource Control (RRC) Connection Reconfiguration message to trigger the radio terminal to:
• release configuration information on the second cell except for Data Radio Bearer (DRB) configuration information corresponding to a DRB established in the second cell;
• and
• re-configure the DRB established in the second cell.

A non-transitory computer-readable medium storing therein a program for causing a computer to perform a communication control method in a radio terminal, wherein the communication control method comprises:

• performing Dual Connectivity using either a first cell of a first radio station or a third cell of a third radio station as a primary cell and a second cell of a second radio station as a secondary cell;
• receiving, within a procedure changing the primary cell from the first cell to the third cell, a Radio Resource Control (RRC) Connection Reconfiguration message from the first radio station;
• releasing, in response to the RRC Connection Reconfiguration message,
• configuration information on the second cell except for Data Radio Bearer (DRB) configuration information corresponding to a DRB established in the second cell;
• and
• re-configuring the DRB established in the second cell.