Radio base station

A terminal comprising:

• a receiving unit that receives, from a source radio base station, a message which has a list including plural pieces of information on candidate cells and transition conditions associated with the candidate cells,
• a first transaction ID being included in a piece of information on each candidate cell, and
• a second transaction ID being included in the message;
• a control unit that performs, when one transaction condition included in the list in the message is satisfied, a synchronization with one candidate cell associated with the one transaction condition, and performs a transition to a target radio base station which configures one piece of information of the one candidate cell, without receiving a handover command;
• and
• a transmitting unit that transmits, to the source radio base station, a first complete message in which the second transaction ID is included, before a start of the synchronization, and transmits, to the target radio base station, a second complete message in which the first transaction ID is included, after the start of the synchronization.

A radio communication system comprising:

• a source radio base station and a terminal,
• wherein the source radio base station includes:
• a receiving unit that receives plural pieces of information on candidate cells;
• and
• a transmitting unit that transmits, to the terminal, a message which has a list including the plural pieces of information on the candidate cells and transition conditions associated with the candidate cells,
• a first transaction ID being included in a piece of information on each candidate cell, and
• a second transaction ID being included in the message, and
• the terminal includes:
• a receiving unit that receives the message;
• a control unit that performs, when one transaction condition included in the list in the message is satisfied, a synchronization with one candidate cell associated with the one transaction condition, and performs a transition to a target radio base station which configures one piece of information of the one candidate cell, without receiving a handover command;
• and
• a transmitting unit that transmits, to the source radio base station, a first complete message in which the second transaction ID is included, before a start of the synchronization, and transmits, to the target radio base station, a second complete message in which the first transaction ID is included, after the start of the synchronization.

A radio communication method comprising:

• a step of receiving, by a source radio base station, plural pieces of information on candidate cells;
• a step of transmitting to a terminal, by the source radio base station, a message which has a list including the plural pieces of information on the candidate cells and transition conditions associated with the candidate cells,
• a first transaction ID being included in a piece of information on each candidate cell, and
• a second transaction ID being included in the message;
• a step of receiving, by the terminal, the message;
• a step of transmitting to the source radio base station, by the terminal, a first complete message in which the second transaction ID is included;
• a step of performing, by the terminal, a synchronization with one candidate cell associated with one transaction condition, which is included in the list in the message, when the one transaction condition is satisfied, and performing, by the terminal, a transition to a target radio base station which configures one piece of information of the one candidate cell, without receiving a handover command;
• and
• a step of transmitting to the target radio base station, by the terminal, a second complete message in which the first transaction ID is included.