Method for controlling handover, user equipment, base station, and radio communication system

1. A method for controlling a handover from a first base station to a second base station by a user equipment that performs radio communication over a communication channel formed by carrier aggregation of a plurality of component carriers, the method comprising:

transmitting, from the first base station to the user equipment, scheduling information of each component carrier of the plurality of component carriers respectively according to a scheduling information transmission method that is a cross scheduling method;

commanding, by the first base station, the user equipment to perform the handover of the communication channel formed by carrier aggregation of the plurality of component carriers;

causing transfer of a first component carrier of the plurality of component carriers in the first base station to a first transferred component carrier in the second base station, the first component carrier being operated according to the cross scheduling method; and

stopping, by the first base station, transmission of the scheduling information of the first component carrier of the plurality of component carriers in the first base station.

2. The method according to claim 1 , further comprising:

receiving, by the first base station, measurement information from the user equipment; and

determining, by the first base station, whether the handover is necessary according to the measurement information transmitted from the user equipment.

3. The method according to claim 1 , further comprising:

causing, after causing the transfer of the first component carrier, transfer of a second component carrier in the first base station to a second transferred component carrier in the second base station, the second component carrier being operated according to the straight scheduling method.

4. The method according to claim 3 , further comprising:

causing, before causing the transfer of the second component carrier, transfer of a third component carrier of the plurality of component carriers in the first base station to a third transferred component carrier in the second base station, the third component carrier being operated according to the cross scheduling method, and

stopping, by the first base station, transmission of the scheduling information of the third component carrier of the plurality of component carriers in the first base station.

5. The method according to claim 1 , thither comprising

transmitting, from the second base station to the user equipment, the scheduling information of the first transferred component carrier in the second base station according to the straight scheduling method after the first component carrier is transferred to the first transferred component carrier in the second base station.

6. A user equipment, comprising:

a radio communication circuit that performs radio communication with a first base station over a communication channel formed by carrier aggregation of a plurality of component carriers;

a control circuit that controls a handover from the first base station to a second base station and

a quality measuring circuit that measures a channel quality of the communication channel between the user equipment and the first base station, wherein

the radio communication circuit is configured to

receive, from the first base station, scheduling information of each component carrier of the plurality of component carriers respectively according to a scheduling information transmission method that is a cross scheduling method, and

receive a command, from the first base station, to perform the handover of the communication channel formed by carrier aggregation of the plurality of component carriers, and

the control circuit is configured to

cause transfer of a first component carrier of the plurality of component carriers in the first base station to a first transferred component carrier in the second base station, the first component carrier being operated according to the cross scheduling method, and

stop reception of the scheduling information of the first component carrier of the plurality of component carriers in the first base station.

7. The user equipment according to claim 6 , wherein the radio communication circuit transmits measurement information of the channel quality measured by the quality measuring circuit to the first base station.

8. The user equipment according to claim 6 , wherein the control circuit is further configured to cause, after causing the transfer of the first component carrier, transfer of a second component carrier in the first base station to a second transferred component carrier in the second base station, the second component carrier being operated according to the straight scheduling method.

9. The user equipment according to claim 6 , wherein the radio communication circuit is further configured to receive the scheduling information of the first transferred component carrier in the second base station according to the straight scheduling method after the first component carrier is transferred to the first transferred component carrier in the second base station.

10. A base station, comprising:

a radio communication circuit that performs radio communication with a user equipment over a communication channel formed by carrier aggregation of a plurality of component carriers; and

a control circuit that controls a handover to another base station by the user equipment, wherein

the radio communication circuit is configured to transmit scheduling information of each component carrier of the plurality of component carriers respectively according to a cross scheduling method,

the control circuit is configured to command the user equipment to perform the handover of the communication channel formed by carrier aggregation of the plurality of component carriers, such that transfer of a first component carrier of the plurality of component carriers in the base station to a first transferred component carrier in the other base station is caused, the first component carrier being operated according to the cross scheduling method, and

the control circuit is further configured to stop transmission of the scheduling information of the first component carrier of the plurality of component carriers in the base station.

11. The base station according to claim 10 , wherein, after the transfer of the first component carrier is caused, transfer of a second component carrier in the base station to a second transferred component carrier in the other base station is caused, the second component carrier being operated according to the straight scheduling method.

12. A method for controlling a handover from a first base station to a second base station by a user equipment that performs radio communication over a communication channel formed by carrier aggregation of a plurality of component carriers, the method comprising:

receiving, by the user equipment from the first base station, scheduling information of each component carrier of the plurality of component carriers respectively according to a scheduling information transmission method that is a cross scheduling method;

measuring, by the user equipment, a channel quality of the communication channel formed by carrier aggregation of the plurality of component carriers;

transmitting, by the user equipment to the first base station, measurement information of the channel quality;

receiving, by the user equipment from the first base station, a command to perform the handover of the communication channel formed by carrier aggregation of the plurality of component carriers;

causing transfer of a first component carrier of the plurality of component carriers in the first base station to a first transferred component carrier in the second base station, the first component carrier being operated according to the cross scheduling method; and

stopping, by the user equipment, reception of the scheduling information of the first component carrier of the plurality of component carriers in the first base station.

13. The method according to claim 12 , further comprising:

causing, after causing the transfer of the first component carrier, transfer of a second component carrier in the first base station to a second transferred component carrier in the second base station, the second component carrier being operated according to the straight scheduling method.