Base station, mobile station, communication system, and communication method for performing cell selection/reselection appropriately

1. A base station that can transmit a synchronization signal at a predetermined transmission interval in a plurality of cycles, the base station comprising:

a processor configured to:

continuously transmit the synchronization signal in a plurality of radio signals; and

control a radio measurement cycle of radio measurement of a mobile station connected to the base station such that the mobile station detects the synchronization signal under a condition in accordance with second information associated with the radio measurement cycle, the second information being controlled by information for configuring the radio measurement included in first information that is transmitted from the base station to the mobile station, wherein

the radio measurement cycle is a cycle obtained by multiplying a measurement cycle as a criterion by N (N is an integer multiple).

2. The base station according to claim 1 , wherein the processor is configured to control the radio measurement of the mobile station such that the mobile station detects the synchronization signal in a first duration corresponding to a first radio signal among the plurality of radio signals and in a second duration corresponding to a second radio signal that is different from the first radio signal.

3. The base station according to claim 1 , wherein

the processor is further configured to:

generate the first information; and

generate notification information including the first information such that, when the mobile station selects an own cell, the mobile station performs scaling on the second information related to a measurement cycle of the radio measurement in accordance with the first information.

4. The base station according to claim 3 , wherein the processor is further configured to receive speed information related to a moving speed of the mobile station from the mobile station, wherein

the processor if further configured to generate the first information in accordance with the received speed information.

5. The base station according to claim 4 , wherein the processor is further configured to generate the first information by a parameter of a first value in accordance with a state in which the moving speed of the mobile station is a first speed and generate the first information by a parameter of a second value that is greater than the first value in accordance with a state in which the moving speed of the mobile station is a second speed that is slower than the first speed.

6. The base station according to claim 3 , wherein the processor is further configured to receive speed information related to a moving speed of the mobile station from the mobile station, wherein

the processor is further configured to generate the first information in accordance with the received speed information, and

the second information includes a first measurement cycle in which the mobile station measures reception quality of the own cell and a second measurement cycle in which the mobile station measures reception quality of another cell.

7. The base station according to claim 6 , wherein

the processor is further configured to generate the first information by a parameter of a first value in accordance with a state in which the moving speed of the mobile station is a first speed and generate the first information by a parameter of a second value that is greater than the first value in accordance with a state in which the moving speed of the mobile station is a second speed that is slower than the first speed,

when the first information is the parameter of the first value, the first measurement cycle is scaled to a first length and, when the first information is the parameter of the second value, the first measurement cycle is scaled to a second length that is longer than the first length, and

when the first information is the parameter of the first value, the second measurement cycle is scaled to a third length and, when the first information is the parameter of the second value, the second measurement cycle is scaled to a fourth length that is longer than the third length.

8. The base station according to claim 7 , wherein

the processor is further configured to receive a measurement result of the reception quality of the own cell from the mobile station,

when the mobile station selects the own cell and the reception quality of the own cell does not meet a criterion, the processor is further configured to generate an instruction that instructs the mobile station to perform measurement of the other cell without waiting for the second measurement cycle that has been scaled, and

the processor is further configured to transmit the generated instruction to the mobile station.

9. The base station according to claim 3 , wherein the processor is further configured to cyclically transmit the synchronization signal and the broadcast information to the own cell by using beam sweeping or beam spanning.

10. A mobile station that can receive a synchronization signal transmitted from a base station at a predetermined transmission interval in a plurality of cycles, the mobile station comprising:

a processor configured to:

continuously receive the synchronization signal; and

detect the synchronization signal under a condition in accordance with second information associated with a radio measurement cycle of radio measurement, the second information being controlled by information for configuring the radio measurement included in first information that is transmitted from the base station to the mobile station, and perform radio measurement, wherein

the radio measurement cycle is a cycle obtained by multiplying a measurement cycle as a criterion by N (N is an integer multiple).

11. The mobile station according to claim 10 , wherein

the processor is further configured to:

receive the synchronization signal and broadcast information that includes the first information from base station, and

when the mobile station selects an own cell, perform scaling on the second information in accordance with the first information included in the broadcast information and perform the radio measurement in a measurement cycle in accordance with the second information that has been scaled, wherein

the processor is further configured to transmit a result of the radio measurement to the base station.

12. A communication system comprising:

a base station that can transmit a synchronization signal at a predetermined transmission interval in a plurality of cycles; and

a mobile station that is connected to the base station, wherein

the base station includes a processor is configured to:

continuously transmit the synchronization signal in a plurality of radio signals; and

control a radio measurement cycle of radio measurement of a mobile station connected to the base station such that the mobile station detects the synchronization signal under a condition in accordance with second information associated with the radio measurement cycle, the second information being controlled by information for configuring the radio measurement included in first information that is transmitted from the base station to the mobile station, wherein

the radio measurement cycle is a cycle obtained by multiplying a measurement cycle as a criterion by N (N is an integer multiple).

13. A communication method used in a communication system that includes a base station that can transmit synchronization information at a predetermined transmission interval in a plurality of cycles and a mobile station that is connected to the base station, the communication method comprising:

transmitting continuously the synchronization information in a plurality of radio signals; and

controlling a radio measurement cycle of radio measurement of the mobile station connected to the base station such that the mobile station detects the synchronization signal under a condition in accordance with second information associated with the radio measurement cycle, the second information being controlled by information for configuring the radio measurement included in first information that is transmitted from the base station to the mobile station, wherein

the radio measurement cycle is a cycle obtained by multiplying a measurement cycle as a criterion by N (N is an integer multiple).