[Claim 1] A communication system comprising:
a master base station that is a base station that operates as a master node of dual connectivity
in which a communication terminal simultaneously connects to two base stations; and
5 a secondary base station that is a base station that operates as a secondary node of the dual
connectivity, wherein
in a case where a second connection destination change process is required while executing a
first connection destination change process that is a process in which a communication terminal
changes a master node as a connection destination or a process in which a communication
10 terminal changes a secondary node as a connection destination, the second connection
destination change process being a process not falling under the first connection destination
change process out of a process in which the master node is changed and a process in which the
secondary node is changed, the second connection destination change process is started and the
first connection destination change process is canceled.
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[Claim 2] The communication system according to claim 1, wherein
the first connection destination change process is a process in which a communication terminal
changes a master node as a connection destination, and the second connection destination
change process is a process in which a communication terminal changes a secondary node as a
20 connection destination.
[Claim 3] The communication system according to claim 1, wherein
the first connection destination change process is a process in which a communication terminal
changes a secondary node as a connection destination, and the second connection destination
25 change process is a process in which a communication terminal changes a master node as a
connection destination.
[Claim 4] A communication system comprising:
a master base station that is a base station that operates as a master node of dual connectivity
30 in which a communication terminal simultaneously connects to two base stations;
a secondary base station that is a base station that operates as a secondary node of the dual
connectivity; and
a communication terminal capable of simultaneously connecting to the master base station and
the secondary base station, wherein
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in a case where both a process in which the communication terminal changes a master node as
a connection destination and a process in which the communication terminal changes a
secondary node as a connection destination are required in a state where the communication
terminal is connected to the master base station and the secondary base station,
5 in a case where the communication terminal selects a new master node as a connection
destination prior to a new secondary node as a connection destination, the communication
terminal selects the new secondary node as a connection destination on a basis of a selection
result of the new master node as a connection destination and a predetermined condition, and in
a case where the communication terminal selects a new secondary node as a connection
10 destination prior to a new master node as a connection destination, the communication terminal
selects the new master node as a connection destination on a basis of a selection result of the
new secondary node as a connection destination and a predetermined condition.
[Claim 5] The communication system according to any one of claims 1 to 4, wherein
15 the process in which a communication terminal changes a master node as a connection
destination is conditional handover.
[Claim 6] The communication system according to any one of claims 1 to 4, wherein
the process in which a communication terminal changes a master node as a connection
20 destination is make-before-break handover.
[Claim 7] The communication system according to claim 6, wherein
in a case where MBB handover that is the make-before-break handover is executed, the master
base station transmits make-before-break information necessary for executing the MBB
25 handover to a communication terminal that executes the MBB handover.
[Claim 8] The communication system according to any one of claims 1 to 4, wherein
the process in which a communication terminal changes a master node as a connection
destination is random access channel-less handover.
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[Claim 9] The communication system according to claim 8, wherein
in a case where RACH-less handover that is the random access channel-less handover is
executed, the master base station transmits RACH-less handover information necessary for the
RACH-less handover to a communication terminal that executes the RACH-less handover.
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[Claim 10] A communication system comprising:
a base station; and
a communication terminal capable of simultaneously connecting to a plurality of base stations,
5 wherein
in a case where the number of base stations being connected is three or more, the
communication terminal notifies, among the base stations being connected, one or more base
stations satisfying a predetermined condition of data amount information of transmission data
held by the communication terminal, and
10 the one or more base stations perform uplink scheduling for the communication terminal on a
basis of the data amount information that the communication terminal has notified the base
stations of