base stations, mobile stations, communication systems, and communication methods Technical field [0001] 　The present invention relates to base stations, mobile stations, communication systems, and communication methods. Background technology [0002] 　In the current network, the traffic of mobile terminals (smartphones and future phones) occupies most of the network resources. In addition, the traffic used by mobile terminals tends to increase in the future. On the other hand, in line with the development of IoT (Internet of a Things) services (for example, monitoring systems for transportation systems, smart meters, devices, etc.), it is required to support services with various requirements. Therefore, in the communication standard of the 5th generation mobile communication (5G), in addition to the standard technology of the 4th generation mobile communication (4G), there is a technology that realizes a higher data rate, a larger capacity, and a lower delay. It has been demanded. Prior art literature Patent documents [0003] Patent Document 1: Japanese Unexamined Patent Publication No. 2017-212733 Non-patent literature [0004] Non-Patent Document 1: 3GPP TS36.133 V15.1.0 Non-Patent Document 2: 3GPP TS36.300 V15.1.0 Non-Patent Document 3: 3GPP TS36.211 V15.1.0 Non-Patent Document 4: 3GPP TS36. 212 V15.1.0 Non-Patent Document 5: 3GPP TS36.213 V15.1.0 Non-Patent Document 6: 3GPP TS36.214 V15.1.0 Non-Patent Document 7: 3GPP TS36.321 V15.1.0 Non-Patent Document 8: 3GPP TS36.322 V15.0.1 Non-Patent Document 9: 3GPP TS36.323 V14.5.0 Non-Patent Document 10: 3GPP TS36.331 V15.1.0 Non-Patent Document 11: 3GPP TS36.413 V15 .1.0 Non-Patent Document 12: 3GPP TS36.423 V15.1.0 Non-Patent Document 13: 3GPP TS36.425 V15.1.0 Non-Patent Document 14: 3GPP TR36.912 V14.1.0 Non-Patent Document 15 : 3GPP TR38.913 V14.3.0 Non-Patent Document 16: 3GPP TR38.801 V14.0.0 Non-Patent Document 17: 3GPP TR38.802 V14.2.0 Non-Patent Document 18: 3GPP TR38.803 V14.2.0 Non-Patent Document 19: 3GPP TR38.804 V14.0.0 Non-Patent Document 20: 3GPP TR38 . 900 V14.3.1 Non-Patent Document 21: 3GPP TS38.300 V15.1.0 Non-Patent Document 22: 3GPP TS37.340 V15.1.0 Non-Patent Document 23: 3GPP TS38.201 V15.0.0 Non -Patent Document Document 24: 3GPP TS38.202 V15.1.0 Non-Patent Document 25: 3GPP TS38.211 V15.1.0 Non-Patent Document 26: 3GPP TS38.212 V15.1.0 Non-Patent Document 27: 3GPP TS38.213 V15 .1.0 Non-Patent Document 28: 3GPP TS38.214 V15.1.0 Non-Patent Document 29: 3GPP TS38.215 V15.1.0 Non-Patent Document 30: 3GPP TS38.321 V15.1.0 Non-Patent Document 31 : 3GPP TS38.322 V15.1.0 Non-Patent Document 32: 3GPP TS38.323 V15.1.0 Non-Patent Document 33: 3GPP TS37.324 V1.5.0 Non-Patent Document 34: 3GPP TS38.331 V15.1.0 Non-Patent Document 35: 3GPP TS38.401 V15.1.0 Non-Patent Document 36: 3GPP TS38. 410 V0.9.0 Non-Patent Document 37: 3GPP TS38.413 V0.8.0 Non-Patent Document 38: 3GPP TS38.420 V0.8.0 Non-Patent Document 39: 3GPP TS38.423 V0.8.0 Non -Patent Document Document 40: 3GPP TS38.470 V15.1.0 Non-Patent Document 41: 3GPP TS38.473 V15.1.0 Outline of the invention Problems to be solved by the invention [0005] 　However, in a communication system conforming to the communication standard of the 5th generation mobile communication, cell selection / reselection may not be performed properly depending on the measurement method of the mobile station. [0006] 　The disclosed technique has been made in view of the above, and an object of the present invention is to provide a base station, a mobile station, a communication system, and a communication method capable of optimizing cell selection / reselection. Means to solve problems [0007] 　The base station disclosed in the present application is, in one embodiment, a base station capable of transmitting a synchronization signal in a plurality of cycles at predetermined transmission intervals, and can continuously transmit the synchronization signal in a plurality of radio signals. The radio measurement of the mobile station can be controlled so that the transmission unit and the mobile station connected to the base station detect the synchronization signal under the conditions corresponding to the second information scaled using the first information. It has a control unit. Effect of the invention [0008] 　According to one aspect of the wireless device disclosed in the present application, cell selection / reselection can be optimized. A brief description of the drawing [0009] FIG. 1 is a diagram showing a configuration of a communication system according to a first embodiment. FIG. 2 is a diagram showing the relationship between the transmission interval of the synchronization signal group from the base station in the second embodiment and the second information (first measurement cycle, second measurement cycle) in the mobile station. is there. FIG. 3 is a diagram showing continuous transmission (beam sweeping) of a plurality of radio signals from a base station in the second embodiment. FIG. 4 is a diagram showing a configuration of a base station in the second embodiment. FIG. 5 is a diagram showing a configuration of a mobile station in the second embodiment. FIG. 6 is a sequence diagram showing the operation of the communication system according to the second embodiment. FIG. 7 is a diagram showing conversion information used for generating the first information in the second embodiment. FIG. 8 is a diagram showing conversion information used for scaling the second information in the second embodiment. FIG. 9 is a diagram showing an improvement in the self-cell capture rate in the second embodiment. FIG. 10 is a sequence diagram showing the operation of the communication system according to the third embodiment. FIG. 11 is a diagram showing a hardware configuration example of a wireless device used in each embodiment. Mode for carrying out the invention [0010] 　Hereinafter, examples of the communication system disclosed in the present application will be described in detail with reference to the drawings. The disclosed technology is not limited by this embodiment. Further, in the examples, the configurations having the same functions are designated by the same reference numerals, and duplicate description is omitted. Example 1 [0011] 　A communication system CS using a wireless access network is configured as shown in FIG. 1, for example. FIG. 1 is a diagram showing a configuration of a communication system CS. The communication system CS has a plurality of base stations CU-1 and CU-2, and a plurality of cells CL-1 and CL-2 corresponding to the plurality of base stations CU-1 and CU-2 are provided. In the following, when a plurality of base stations CU-1 and CU-2 are not distinguished from each other, they are simply shown as base station CU. When a plurality of cells CL-1 and CL-2 are not distinguished from each other, they are simply shown as cell CL. The mobile station UE can be paraphrased as, for example, a communication device, a terminal, or the like. [0012] 　Each base station CU can transmit information to the mobile station UE existing in the cell CL via the wireless link, and can receive information from the mobile station UE via the wireless link. [0013] 　For example, each base station CU can broadcast system information in the cell CL. The mobile station UE measures (wirelessly measures) a reference signal (for example, a synchronization signal) included in the system information, and depending on the result of the wireless measurement, performs wireless communication among a plurality of cells CL-1 and CL-2. A suitable cell CL can be selected as its own cell and connected (cell selection). Further, when the cell CL suitable for wireless communication among a plurality of cells CL-1 and CL-2 changes from its own cell to another cell, the mobile station UE receives another cell (for example, another cell) according to the result of wireless measurement. Cell CL-2) can be reselected and connected (cell reselected). [0014] 　At this time, each base station CU includes the first information that can control the radio measurement conditions (for example, cell selection / reselection is appropriately performed) in the system information and broadcasts the first information into the cell CL. Can be done. As a result, the mobile station UE generates the second information controlled by using the first information, and detects the synchronization signal under the conditions corresponding to the second information. If the first information is information that allows cell selection / reselection to be performed appropriately, the second information controlled using the first information is also appropriately cell selection / reselection. It can be such a condition. As a result, the base station CU can control the mobile station UE that receives the system information so as to appropriately perform cell selection / reselection. That is, the mobile station UE can appropriately perform cell selection / reselection. [0015] 　For example, even if the UE temporarily enters a radio wave dead zone (for example, a radio wave cutoff by a building or the like, a dead zone due to diffraction, etc.), the measurement of another cell is not started immediately, and an acceptable range (for example, a second You can stay in your own cell within the range determined by the selection conditions according to the conditions. [0016] 　The contents described in the first embodiment can be proposed to the technical standard and implemented. For example, the operation of measuring the radio quality of the mobile station and the operation of cell selection / reselection are included in the standard specifications. It is also possible. Example 2 [0017] 　In Example 1, a method for optimally reselecting cells has been described. In the second embodiment, a case where the cycle of the radio measurement of the mobile station UE by the base station CU is controlled so that the mobile station UE appropriately selects and reselects cells will be described. The same symbols are given to the same configurations as in the first embodiment. [0018] 　For example, as shown in FIG. 2, each base station CU can transmit a synchronization signal required for cell selection in a plurality of cycles at a predetermined transmission interval. FIG. 2 is a diagram showing the relationship between the transmission interval of the synchronization signal group from the base station CU in the second embodiment and the second information (first measurement cycle, second measurement cycle) in the mobile station UE. [0019] 　In order to select the cell of its own cell, the mobile station UE performs wireless measurement for measuring the reception quality from the base station CU of its own cell during the measurement period MP indicated by the hatching of the diagonal line. The mobile station UE repeats the wireless measurement of its own cell every first measurement cycle Tm1. When the first measurement cycle Tm1 is regarded as one cycle, the mobile station UE makes a cell measurement determination every N cycles (N is an integer of 2 or more), that is, every second measurement cycle Tm2 (= Tm1 × N). Do. In the cell measurement determination, for example, the mobile station UE determines whether or not the reception quality standard of the own cell (for example, the reception strength of the reference signal is equal to or higher than the threshold value) is satisfied, and if the standard is satisfied, the own cell is determined. If it is selected and does not meet the criteria, wireless measurement is performed to measure the reception quality from the base station CU of another cell. The mobile station UE determines whether the reception quality of the other cell meets the criteria, and if the criteria are met, reselects the other cell. [0020] 　In each measurement period MP, the transmission window (transmission interval) WD indicated by cross hatching is repeated n times (n is an integer of 2 or more) every transmission cycle ΔTss (for example, 20 ms) (MP = ΔTss × n). In each transmission window WD (for example, 5 ms), a synchronization signal is transmitted in the own cell by beam sweeping. Each transmission window WD includes a plurality of synchronization signal blocks SSB-1 to SSB-8 corresponding to the plurality of beams BM-1 to BM-8. Each synchronization signal block SSB is a period during which beamforming is performed by the base station CU and the synchronization signal is transmitted by the radio beam. [0021] 　For example, the base station CU can perform beam sweeping as shown in FIG. FIG. 3 is a diagram showing continuous transmission (beam sweeping) of a plurality of radio signals from a base station. [0022] 　The base station CU can form a directional radio beam by beamforming, but in order to broadcast the synchronization signal required for cell selection into the cell CL in all possible directions. A large number of beams will be transmitted. Since it is difficult to form a large number of beams at the same time, the base station CU sequentially forms a plurality of beams BM-1 to BM-8 and transmits them while changing the direction. As a result, the base station CU can transmit the beams in all directions by making the plurality of beams BM-1 to BM-8 make one round in the cell CL in the transmission window WD. [0023] 　Although FIGS. 2 and 3 illustrate the case where the number of beam sweeping, which is the number of beams used for beam sweeping, is eight, the number of beam sweeping is not limited to eight, and all possible directions are shown. Can be modified to cover. [0024] 　Here, the case where the obstacle OBS (see FIG. 9) exists in the region corresponding to the beam BM-2 among the plurality of beams BM-1 to BM-8 used for the beam sweeping in the cell CL will be described. To do. In this case, if the mobile station UE is moving at a low speed, the mobile station UE exists in the region corresponding to the beam BM-1 for a certain measurement period MP, and the synchronization signal can be detected from the base station CU. However, in the subsequent measurement period MP, the mobile station UE may move to the region corresponding to the beam BM-2, and it may be difficult to detect the synchronization signal from the base station CU. This possibility tends to be remarkable when the first measurement cycle Tm1 and the second measurement cycle Tm2 have a fixed length. [0025] 　Therefore, in the second embodiment, in the base station CU, the broadcast information including the first information is generated so that the mobile station UE scales the second information regarding the measurement cycle of the radio measurement according to the first information. By transmitting the synchronization signal to the mobile station UE together with the synchronization signal, the measurement cycle of the radio measurement in the mobile station is optimized. [0026] 　Specifically, the base station CU can be configured as shown in FIG. FIG. 4 is a diagram showing the configuration of the base station CU. The base station CU has a wireless communication unit 1, a control unit 4, a storage unit 5, and a communication unit 6. The wireless communication unit 1 has a wireless transmission unit 2 and a wireless reception unit 3. The control unit 4 has a first generation unit 4a and a second generation unit 4b. The communication unit 6 is an interface to the network. [0027] 　For example, the wireless receiving unit 3 receives the measurement information measured by the mobile station UE (for example, speed information regarding the moving speed, information measuring the radio quality, etc.) from the mobile station UE and supplies it to the first generation unit 4a. The wireless receiving unit 3 may not receive the measurement information depending on the state of the mobile station UE. For example, when the RRC status of the mobile station UE is in the connect mode, the measurement information transmitted from the mobile station UE is received, but when the RRC status of the mobile station UE is in the idle mode inactive mode, the measurement information is transmitted from the mobile station UE. Not received because it is not done. [0028] 　The first generation unit 4a generates the first information and supplies it to the second generation unit 4b. The first generation unit 4a generates the first information with the parameter of the first value, for example, according to the movement speed of the mobile station UE being the first speed. The first generation unit 4a generates the first information with the parameter of the second value according to the moving speed of the mobile station UE being the second speed. Also, for example, the second speed is slower than the first speed. The second value is a value larger than the first value. The first generation unit 4a supplies the generated first information to the second generation unit 4b. Alternatively, for example, a parameter assuming that the mobile station UE has a speed for each predetermined range (for example, assuming a first range and a parameter corresponding to the speed in that range) is generated as the first information. When the parameters are generated on the assumption, a plurality of parameters (for example, a parameter having a first value corresponding to the speed in the first range and a parameter having a second value corresponding to the speed in the second range). It is preferable to generate. As explained, each parameter may correspond to a speed range or may correspond to a speed. [0029] 　The second generation unit 4b is such that when the mobile station UE selects its own cell, the mobile station UE scales the second information regarding the measurement cycle of the radio measurement according to the first information. Generates broadcast information including the information of. When a plurality of parameters are included in the first information, the second generation unit 4b generates the second information for each parameter. The second information includes a first measurement cycle Tm1 in which the mobile station UE measures the reception quality of its own cell and a second measurement cycle Tm2 in which the mobile station UE measures the reception quality of another cell. The first measurement cycle Tm1 is scaled to the first length when the first information is a parameter of the first value, and the first when the first information is a parameter of the second value. Try to scale to a second length that is longer than the length. The second measurement cycle Tm2 is scaled to a third length when the first information is a parameter of the first value, and a third when the first information is a parameter of the second value. Try to scale to a fourth length that is longer than the length. The second generation unit 4b supplies the generated notification information to the wireless transmission unit 2. [0030] 　The wireless transmission unit 2 periodically transmits the synchronization signal and the broadcast information into the own cell by beam sweeping. [0031] 　Also, the mobile station UE may be configured as shown in FIG. FIG. 5 is a diagram showing a configuration of a mobile station UE. The mobile station UE has a wireless communication unit 11, a control unit 14, a storage unit 15, and a wireless communication unit 17. The wireless communication unit 11 is a wireless interface used for communication with the base station CU, and has a wireless transmission unit 12 and a wireless reception unit 13. The wireless communication unit 17 is a wireless interface for a side link (D2D link), and has a wireless transmission unit 18 and a wireless reception unit 18. [0032] 　The control unit 14 can detect the moving speed of the mobile station UE via a predetermined sensor, generate speed information indicating the detected moving speed, and supply the speed information to the wireless transmission unit 12. The radio transmission unit 12 transmits the speed information to the base station CU. The wireless transmission unit 12 may not transmit speed information depending on the state of the mobile station UE. For example, when the RRC state of the mobile station UE is the connect mode, the mobile station UE transmits speed information, and when the RRC state of the mobile station UE is the idle mode inactive mode, the mobile station UE does not transmit the speed information. Therefore, it is not received. [0033] 　The radio receiving unit 13 receives the broadcast information from the base station. The broadcast information may include a synchronization signal and the first information. The control unit 14 scales the second information according to the first information included in the broadcast information when the mobile station UE selects its own cell, and measures according to the scaled second information. Wireless measurement is performed periodically. [0034] 　At this time, when the first information is a parameter of the first value, the control unit 14 scales the first measurement cycle Tm1 to the first length, and the first information is of the second value. When it is a parameter, the first measurement cycle Tm1 is scaled to a second length longer than the first length. When the first information is a parameter of the first value, the control unit 14 scales the second measurement cycle Tm2 to the third length, and the first information is the parameter of the second value. In some cases, the second measurement cycle Tm2 is scaled to a fourth length that is longer than the third length. The control unit 14 performs wireless measurement according to the scaled first measurement cycle Tm1 and the scaled second measurement cycle Tm2. [0035] 　The control unit 14 supplies the result of the radio measurement to the radio transmission unit 12. The radio transmission unit 12 transmits the result of the radio measurement to the base station CU. [0036] 　Next, the operation of the communication system CS will be described with reference to FIGS. 6 to 8. FIG. 6 is a sequence diagram showing the operation of the communication system CS according to the first application example of the embodiment. FIG. 7 is a diagram showing conversion information used for generating the first information in the first application example of the embodiment. FIG. 8 is a diagram showing conversion information used for scaling the second information in the first application of the embodiment. [0037] 　The mobile station UE measures the moving speed of the mobile station UE and generates speed information indicating the measured moving speed (S1). The mobile station UE generates report information including speed information and transmits it to the base station CU (S2). When the base station CU receives the report information including the speed information, the base station CU generates the first information (for example, the parameter Ps) according to the moving speed of the mobile station UE indicated by the speed information (S3). [0038] 　It is not necessary to generate the speed information (S1) and transmit the report information including the speed information. In particular, when the RRC state of the mobile station UE is idle or inactive, it is preferable that the mobile station UE does not transmit in consideration of power consumption. In order for the mobile station UE to transmit the report information including the speed information, the mobile station UE needs to be in the connect mode in the RRC state. Therefore, in order to transmit when the RRC state of the mobile station UE is idle or inactive, it is necessary to shift to the connect mode, and the power consumption becomes large. [0039] 　Further, the generation of the first information is a parameter assuming that the speed of the mobile station UE is in a predetermined range when the report information is not transmitted from the mobile station UE (for example, assuming that it is in the first range). The parameter corresponding to the speed in the range) is generated as the first information. [0040] 　For example, the base station CU generates conversion information 51 as shown in FIG. 7 in advance and stores it in the storage unit 5 (see FIG. 4), so that the conversion information 51 can be referred to. In the conversion information 51, for example, the moving speed of the mobile station UE and the value of the first information (for example, the parameter Ps) are associated with each other. In the example of FIG. 7, the value of the first information is Ps3 when the moving speed is V2 to (V2 or more), and the first information is when the moving speed is V1 to V2 (V1 or more and less than V2). The value of is Ps2 (> Ps3), and the value of the first information is Ps1 (> Ps2) when the moving speed is 0 to V1 (0 or more and less than V1). [0041] 　For example, when the representative value of "V2 to (V2 or more)" is 90 km / h, Ps3 = 1 can be set. When the representative value of "V1 to V2" is 30 km / h, Ps2 = 3 can be set. When the representative value of "0 to V1" is 3 km / h, Ps2 = 8 can be set. [0042] 　The base station CU can refer to the conversion information 51 and determine the value of the first information corresponding to the moving speed of the mobile station UE indicated by the speed information. [0043] 　Further, when the base station CU does not receive the speed information, the base station CU generates information on the assumed speed range (for example, Ps1, Ps2, Ps3 shown in FIG. 7) as the first information. In this case, a plurality of pieces of information may be generated. [0044] 　Returning to FIG. 6, the base station CU generates broadcast information including the first information (S4). The broadcast information may be, for example, a MIB (Master Information Block) or a SIB (System Information Block). The base station CU transmits the synchronization signal and the broadcast information into its own cell by beam sweeping (S5). [0045] 　When the mobile station UE receives the synchronization signal and the broadcast information from the base station CU, the mobile station UE receives the second information (for example, the first measurement cycle Tm1) according to the first information (for example, the parameter Ps) included in the broadcast information. And the second measurement cycle Tm2) is scaled (S6). [0046] 　When the mobile station UE includes a plurality of parameters (for example, Ps1, Ps2, Ps3) in the broadcast information, for example, the control unit 14 selects a parameter according to the current moving speed. .. [0047] 　Further, for example, the mobile station UE generates conversion information 151 as shown in FIG. 8 in advance and stores it in the storage unit 15 (see FIG. 5), so that the conversion information 151 can be referred to. In the conversion information 151, the value of the first information (for example, the parameter Ps) and the value of the second information (for example, the first measurement cycle Tm1 and the second measurement cycle Tm2) are associated with each other. In the example of FIG. 8, when the value of the first information is Ps3, the value of the first measurement cycle Tm1 is Td × Ps3 (Td: reference time length), and the value of the second measurement cycle Tm2. Is Td × N × Ps3. When the value of the first information is Ps2, the value of the first measurement cycle Tm1 is Td × Ps2, and the value of the second measurement cycle Tm2 is Td × N × Ps2. When the value of the first information is Ps1, the value of the first measurement cycle Tm1 is Td × Ps1, and the value of the second measurement cycle Tm2 is Td × N × Ps1. [0048] 　For example, when the standard one cycle of own cell measurement is 320 ms and the cell measurement determination is performed in four cycles, Td = 320 ms and N = 4 can be set. [0049] 　The base station CU refers to the conversion information 151, and the value of the second information (for example, the first measurement cycle Tm1 and the second measurement cycle Tm2) corresponding to the value of the first information included in the broadcast information. Can be determined. [0050] 　Returning to FIG. 6, the mobile station UE performs wireless measurement of its own cell in the measurement period MP of the first cycle (S7). When the measurement period MP ends, the mobile station UE generates report information including the result of the radio measurement and transmits it to the base station CU (S8). [0051] 　The mobile station UE does not have to transmit the report information including the result of the radio measurement when the RRC state is idle or inactive or when the mobile station UE is operating in the low power consumption mode. In short, it is not necessary to transmit the report information (S8) including the result of the wireless measurement of FIG. [0052] 　After that, the mobile station UE repeats the processes of S7 and S8 every first measurement cycle Tm1. [0053] 　The mobile station UE performs wireless measurement of its own cell in the measurement period MP of the Nth cycle (S9), and makes a cell measurement determination when the second measurement cycle Tm2 is reached (S10). In the cell measurement determination, the mobile station UE determines whether the reception quality of the own cell satisfies the standard (for example, the reception strength of the reference signal is equal to or higher than the threshold value), and if the standard is satisfied, the mobile station UE selects the own cell. If the standard is not satisfied, wireless measurement is performed to measure the reception quality from the base station CU of another cell. The mobile station UE determines whether the reception quality of the other cell meets the criteria, and if the criteria are met, reselects the other cell. [0054] 　The mobile station UE generates report information including the result of radio measurement (that is, the result of measurement of its own cell and the result of cell measurement determination) and transmits it to the base station CU (S11). [0055] 　As a result, as shown in FIG. 9, the cell selection time of the low to medium speed mobile station UE can be lengthened, and the own cell capture rate can be improved. FIG. 9 is a diagram showing an improvement in the own cell capture rate in the first application example of the embodiment. For example, as shown in FIG. 9A, when an obstacle OBS is present in the region corresponding to the beam BM-2, the base station CU causes the mobile station UE to move to the beam BM-1 during a predetermined measurement period MP. The synchronization signal is detected by the corresponding synchronization transmission block SSB-1. Then, as shown in FIG. 9B, when the mobile station UE moves to the region corresponding to the beam BM-2, the mobile station UE has not reached the next measurement period MP of the predetermined measurement period MP. .. Therefore, the mobile station UE does not perform wireless measurement. After that, as shown in FIG. 9C, the mobile station UE reaches the next measurement period MP when it moves to the region corresponding to the beam BM-3, and the synchronous transmission block SSB- corresponding to the beam BM-3. The synchronization signal is detected at 3. [0056] 　That is, the base station CU is a mobile station so that the mobile station UE detects a synchronization signal in the synchronous transmission block SSB-1 corresponding to the beam BM-1 and the synchronous transmission block SSB-3 corresponding to the beam BM-3. The measurement cycle of wireless measurement of the UE can be controlled. As a result, the mobile station UE can reduce the power consumption due to the operation (measurement of other cells) accompanying the failure of the own cell selection. In addition, the mobile station UE can efficiently select cells. [0057] 　The contents described in the second embodiment can be proposed to the technical standard and implemented. For example, the first information can be referred to, for example, a MIB such as TS36.331 or TS38.331, SIB, or the like. Can be included in the regulations. Example 3 [0058] 　In Example 2, an example was shown in which cell selection was efficiently performed by controlling the measurement cycle of wireless measurement of the terminal. In the third embodiment, a method of controlling the measurement of other cells of the mobile station UE by the base station CU will be described. The same reference numerals are given to the same configuration requirements as those of the other embodiments. [0059] 　When the radio reception unit 13 of the base station CU receives the measurement result of the reception quality of the own cell from the mobile station UE, the radio reception unit 13 supplies the measurement result of the reception quality of the own cell to the second generation unit 4b. The second generation unit 4b sets a second measurement cycle Tm2 in which the mobile station UE is scaled according to the measurement result of the reception quality of the own cell when the reception quality of the own cell does not meet the standard. Generates measurement instructions that allow measurements of other cells to be performed without waiting. The mobile station UE measures another cell when, for example, it detects that the speed of the mobile station UE is less than a predetermined value (for example, a state in which it is not moving). The second generation unit 4b supplies the measurement instruction to the wireless transmission unit 2. The wireless transmission unit 2 transmits the measurement instruction to the mobile station UE. [0060] 　When the radio receiving unit 13 of the mobile station UE receives the measurement instruction from the base station CU, the radio receiving unit 13 supplies the measurement instruction to the control unit 14. The control unit 14 can measure another cell according to the measurement instruction without waiting for the second measurement cycle Tm2. [0061] 　The mobile station UE may not perform measurement of another cell even if it receives a measurement instruction when, for example, the moving speed of the mobile station UE is larger than a predetermined value. This is because if the speed is higher than the specified speed, the moving speed is high, so even if you are temporarily staying in a dead zone of radio waves (for example, a dead zone due to radio wave blocking by a building, diffraction, etc.), there is a possibility that you will immediately exit. Is high. [0062] 　Further, in the third embodiment, the operation of the communication system CS is as shown in FIG. Note that some operations can be omitted (processing is not executed) as described in FIG. [0063] 　After the processing of S1 to S8 is performed in the same manner as in the first application example, the base station CU uses the reception quality of its own cell as a reference according to the measurement result of the reception quality of its own cell included in the report information ( For example, it is determined whether or not the reception intensity exceeds the threshold value) (S21), and if the reference is satisfied, the device waits (S22). [0064] 　After that, the processing of S7 and S8 by the mobile station UE and the processing of S21 by the base station CU are repeatedly performed for each first measurement cycle Tm1. [0065] 　The mobile station UE performs wireless measurement of its own cell in the measurement period MP of the Kth cycle (K