Base station, mobile station, communication system, and communication method

Abstract

Optimize cell selection and reselection. [Solution] In one aspect, the base station is a base station capable of transmitting a synchronization signal at multiple periods with a predetermined transmission interval, and has a transmitting unit that can continuously transmit the synchronization signal in multiple radio signals, and a control unit that can control radio measurements of a mobile station connected to the base station so that the mobile station detects the synchronization signal under conditions corresponding to second information scaled using first information.

Description

[Technical Field]

[0001] The present invention relates to a base station, a mobile station, a communication system, and a communication method. [Background technology]

[0002] In current networks, traffic from mobile devices (smartphones and feature phones) accounts for the majority of network resources. Furthermore, the traffic used by mobile devices is expected to continue to expand. Meanwhile, with the development of IoT (Internet of Things) services (e.g., transportation systems, smart meters, and equipment monitoring systems), there is a need to support services with diverse requirements. Therefore, in addition to the standard technologies of fourth-generation mobile communications (4G), the fifth-generation mobile communications (5G) standard requires technologies that achieve even higher data rates, larger capacity, and lower latency. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application 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

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[0005] However, in communication systems based on the 5th generation mobile communication standards, cell selection and reselection may not be performed appropriately depending on the measurement method of the mobile station.

[0006] The disclosed technology has been made in view of the above, and aims to provide a base station, a mobile station, a communication system, and a communication method that can optimize cell selection and reselection. [Means for solving the problem]

[0007] In one aspect, the base station disclosed in the present application is a base station capable of transmitting a synchronization signal at multiple periods with a predetermined transmission interval, and includes a transmitter unit capable of continuously transmitting the synchronization signal in multiple radio signals, and a controller unit capable of controlling radio measurements of a mobile station connected to the base station so that the mobile station detects the synchronization signal under conditions according to second information scaled using first information. [Effects of the Invention]

[0008] According to one aspect of the wireless device disclosed in the present application, cell selection and reselection can be optimized. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a communication system according to a first embodiment. [Figure 2] FIG. 2 is a diagram illustrating a relationship between the transmission interval of a synchronization signal group from a base station and second information (first measurement period, second measurement period) in a mobile station according to the second embodiment. [Figure 3] FIG. 3 is a diagram illustrating continuous transmission (beam sweeping) of a plurality of radio signals from a base station in the second embodiment. [Figure 4] FIG. 4 is a diagram illustrating a configuration of a base station according to the second embodiment. [Figure 5] FIG. 5 is a diagram illustrating a configuration of a mobile station according to the second embodiment. [Figure 6] FIG. 6 is a sequence diagram illustrating an operation of the communication system according to the second embodiment. [Figure 7] FIG. 7 is a diagram illustrating conversion information used to generate the first information in the second embodiment. [Figure 8] FIG. 8 is a diagram illustrating conversion information used for scaling the second information in the second embodiment. [Figure 9] FIG. 9 is a diagram illustrating an improvement in the own cell capture rate in the second embodiment. [Figure 10] FIG. 10 is a sequence diagram illustrating an operation of the communication system according to the third embodiment. [Figure 11] FIG. 11 is a diagram illustrating an example of the hardware configuration of a wireless device used in each embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the communication system disclosed in the present application will be described in detail with reference to the drawings. Note that the disclosed technology is not limited to this embodiment. Furthermore, components having the same functions in the embodiments will be assigned the same reference numerals, and duplicated descriptions will be omitted. [Example]

[0011] A communication system CS using a radio access network is configured, for example, as shown in FIG. 1. FIG. 1 is a diagram showing the configuration of the communication system CS. The communication system CS has a plurality of base stations CU-1 and CU-2, and is provided with a plurality of cells CL-1 and CL-2 corresponding to the plurality of base stations CU-1 and CU-2. Hereinafter, when the plurality of base stations CU-1 and CU-2 are not distinguished from one another, they will be simply referred to as base stations CU. When the plurality of cells CL-1 and CL-2 are not distinguished from one another, they will be simply referred to as cells CL. Note that the mobile station UE can also be referred to as, for example, a communication device, a terminal, etc.

[0012] Each base station CU can transmit information to a mobile station UE present in a cell CL via a radio link, and can receive information from the mobile station UE via a radio link.

[0013] For example, each base station CU can broadcast system information within a cell CL. The mobile station UE measures (radio measurement) a reference signal (e.g., a synchronization signal) included in the system information, and, according to the result of the radio measurement, can select a cell CL suitable for wireless communication from among multiple cells CL-1 and CL-2 as its own cell and connect to it (cell selection). Furthermore, when the cell CL suitable for wireless communication from among multiple cells CL-1 and CL-2 changes from its own cell to another cell according to the result of the radio measurement, the mobile station UE can reselect and connect to the other cell (e.g., cell CL-2) (cell reselection).

[0014] At this time, each base station CU can broadcast within the cell CL, first information included in the system information, which can control the conditions for radio measurement (for example, to perform cell selection and reselection appropriately). As a result, the mobile station UE generates second information controlled using the first information, and detects a synchronization signal under conditions according to the second information. If the first information is information that allows cell selection and reselection to be performed appropriately, the second information controlled using the first information can also be a condition that allows cell selection and reselection to be performed appropriately. As a result, the base station CU can control the mobile station UE that receives the system information to perform cell selection and reselection appropriately. In other words, the mobile station UE can perform cell selection and reselection appropriately.

[0015] For example, even if the UE temporarily enters a radio wave dead zone (e.g., a dead zone due to radio wave blocking or diffraction caused by buildings, etc.), it can remain in its own cell within an acceptable range (e.g., a range determined by the selection conditions according to the second condition) without immediately starting measurements of other cells.

[0016] The contents described in the first embodiment can be proposed as a technical standard and implemented. For example, the operation of measuring the radio quality of a mobile station and the operation of cell selection / reselection can be included in the standard specifications. [Example]

[0017] In the first embodiment, a method for optimally performing cell reselection is described. In the second embodiment, a case will be described in which the base station CU controls the radio measurement period of the mobile station UE so that the mobile station UE appropriately performs cell selection and reselection. Note that the same symbols are used for the same configurations as in the first embodiment.

[0018] For example, each base station CU can transmit synchronization signals required for cell selection at predetermined transmission intervals in multiple cycles as shown in Fig. 2. Fig. 2 is a diagram illustrating the relationship between the transmission intervals of synchronization signals from the base station CU and second information (first measurement cycle, second measurement cycle) in the mobile station UE in the second embodiment.

[0019] In order to select its own cell, the mobile station UE performs radio measurement to measure the reception quality from the base station CU of its own cell during a measurement period MP indicated by diagonal hatching. The mobile station UE repeatedly performs this radio measurement of its own cell every first measurement period Tm1. If the first measurement period Tm1 is considered to be one period, the mobile station UE performs cell measurement determination every N periods (N is an integer equal to or greater than 2), i.e., every second measurement period Tm2 (=Tm1×N). For cell measurement determination, for example, the mobile station UE determines whether a criterion for the reception quality of its own cell is met (for example, the reception strength of a reference signal is equal to or greater than a threshold), and selects its own cell if the criterion is met, and performs radio measurement to measure the reception quality from the base station CU of another cell if the criterion is not met. The mobile station UE determines whether the reception quality of the other cell meets the criterion, and reselects the other cell if the criterion is met.

[0020] In each measurement period MP, a transmission window (transmission interval) WD indicated by cross hatching is repeated n times (n is an integer equal to or greater than 2) every transmission period ΔTss (e.g., 20 ms) (MP = ΔTss × n). In each transmission window WD (e.g., 5 ms), a synchronization signal is transmitted within the own cell by beam sweeping. Each transmission window WD includes multiple synchronization signal blocks SSB-1 to SSB-8 corresponding to multiple 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 a radio beam.

[0021] For example, the base station CU can perform beam sweeping as shown in Fig. 3. Fig. 3 is a diagram showing continuous transmission (beam sweeping) of a plurality of radio signals from the base station.

[0022] The base station CU can form directional radio beams using beamforming, but when broadcasting a synchronization signal required for cell selection within a cell CL, multiple beams are transmitted to transmit in all possible directions. Because it is difficult to form multiple beams simultaneously, the base station CU sequentially forms multiple beams BM-1 to BM-8 and transmits them while changing the direction. This allows the base station CU to transmit beams in all directions by having multiple beams BM-1 to BM-8 travel around the cell CL once within the transmission window WD.

[0023] Note that Figures 2 and 3 illustrate an example in which the beam sweeping number, which is the number of beams used for beam sweeping, is eight, but the beam sweeping number is not limited to eight and can be changed to cover all possible directions.

[0024] Here, a case will be described in which an obstacle OBS (see FIG. 9) is present in a region corresponding to beam BM-2 of multiple beams BM-1 to BM-8 used for beam sweeping within a cell CL. In this case, if the mobile station UE is moving at a low speed, even if the mobile station UE is present in a region corresponding to beam BM-1 and can detect a synchronization signal from the base station CU during a certain measurement period MP, the mobile station UE may move to a region corresponding to beam BM-2 during a subsequent measurement period MP, making it difficult to detect the synchronization signal from the base station CU. This possibility tends to become more pronounced when the first measurement period Tm1 and the second measurement period Tm2 have fixed lengths.

[0025] Therefore, in the second embodiment, the base station CU generates broadcast information including the first information and transmits it to the mobile station UE together with a synchronization signal so that the mobile station UE scales the second information related to the measurement period of the radio measurement in accordance with the first information, thereby optimizing the measurement period of the radio measurement in the mobile station.

[0026] Specifically, the base station CU may be configured as shown in Fig. 4. 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 radio receiving unit 3 receives measurement information measured by the mobile station UE (for example, speed information related to the moving speed, information on measured radio quality, etc.) from the mobile station UE and supplies the measurement information to the first generating unit 4a. Note that the radio receiving unit 3 may not receive the measurement information depending on the state of the mobile station UE. For example, when the RRC state of the mobile station UE is in connected mode, the radio receiving unit 3 receives the measurement information transmitted from the mobile station UE, but when the RRC state of the mobile station UE is in idle mode or inactive mode, the measurement information is not transmitted from the mobile station UE and therefore is not received.

[0028] The first generator 4a generates first information and supplies it to the second generator 4b. For example, the first generator 4a generates the first information with a parameter of a first value in response to the fact that the moving speed of the mobile station UE is a first speed. The first generator 4a generates the first information with a parameter of a second value in response to the fact that the moving speed of the mobile station UE is a second speed. Also, for example, the second speed is slower than the first speed. The second value is a value greater than the first value. The first generator 4a supplies the generated first information to the second generator 4b. Alternatively, for example, the first generator 4a generates parameters assuming that the mobile station UE will move at a speed within a predetermined range (for example, assuming a first range, and parameters corresponding to the speed within that range) as the first information. Note that when parameters are generated based on an assumption, it is preferable to generate a plurality of parameters (for example, a parameter of a first value corresponding to the speed within the first range and a parameter of a second value corresponding to the speed within the second range). As explained, each parameter may correspond to a speed range or to a speed.

[0029] The second generator 4b generates broadcast information including the first information so that the mobile station UE scales second information related to a measurement period for radio measurement according to the first information when the mobile station UE selects its own cell. If the first information includes multiple parameters, the second generator 4b generates second information for each parameter. The second information includes a first measurement period Tm1 during which the mobile station UE measures the reception quality of its own cell and a second measurement period Tm2 during which the mobile station UE measures the reception quality of another cell. The first measurement period Tm1 is scaled to a first length when the first information is a parameter with a first value, and to a second length longer than the first length when the first information is a parameter with a second value. The second measurement period Tm2 is scaled to a third length when the first information is a parameter with a first value, and to a fourth length longer than the third length when the first information is a parameter with a second value. The second generator 4b supplies the generated broadcast information to the radio transmitter 2.

[0030] The radio transmitter 2 periodically transmits a synchronization signal and broadcast information within its own cell by beam sweeping.

[0031] Moreover, the mobile station UE may be configured as shown in Fig. 5. Fig. 5 is a diagram showing the configuration of the mobile station UE. The mobile station UE has a radio communication unit 11, a control unit 14, a storage unit 15, and a radio communication unit 17. The radio communication unit 11 is a radio interface used for communication with a base station CU, and has a radio transmission unit 12 and a radio reception unit 13. The radio communication unit 17 is a radio interface for a side link (D2D link), and has a radio transmission unit 18 and a radio reception unit 19.

[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 radio transmission unit 12. The radio transmission unit 12 transmits the speed information to the base station CU. Note that the radio transmission unit 12 may not transmit the speed information depending on the state of the mobile station UE. For example, when the RRC state of the mobile station UE is in connected mode, the mobile station UE transmits the speed information, but when the RRC state of the mobile station UE is in idle mode or inactive mode, the mobile station UE does not receive the speed information because the state does not allow transmission from the mobile station UE.

[0033] The radio receiving unit 13 receives broadcast information from the base station. The broadcast information may include a synchronization signal and first information. When the mobile station UE selects its own cell, the control unit 14 scales the second information according to the first information included in the broadcast information, and performs radio measurement at a measurement period according to the scaled second information.

[0034] At this time, if the first information is a parameter of a first value, the control unit 14 scales the first measurement period Tm1 to a first length, and if the first information is a parameter of a second value, the control unit 14 scales the first measurement period Tm1 to a second length longer than the first length. If the first information is a parameter of the first value, the control unit 14 scales the second measurement period Tm2 to a third length, and if the first information is a parameter of the second value, the control unit 14 scales the second measurement period Tm2 to a fourth length longer than the third length. The control unit 14 performs radio measurement in accordance with the scaled first measurement period Tm1 and the scaled second measurement period Tm2.

[0035] The control unit 14 supplies the results of the radio measurement to the radio transmission unit 12. The radio transmission unit 12 transmits the results of the radio measurement to the base station CU.

[0036] Next, the operation of the communication system CS will be described with reference to Fig. 6 to Fig. 8. Fig. 6 is a sequence diagram showing the operation of the communication system CS according to a first application example of the embodiment. Fig. 7 is a diagram showing conversion information used to generate first information in the first application example of the embodiment. Fig. 8 is a diagram showing conversion information used to scale second information in the first application example 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 the speed information and transmits it to the base station CU (S2). Upon receiving the report information including the speed information, the base station CU generates first information (for example, a parameter Ps) according to the moving speed of the mobile station UE indicated by the speed information (S3).

[0038] It is noted that the generation of speed information (S1) and the transmission of report information including the speed information do not have to be performed. In particular, when the RRC state of the mobile station UE is idle or inactive, it is preferable that the mobile station UE not perform transmission in consideration of power consumption. In order for the mobile station UE to transmit report information including speed information, the mobile station UE needs to be in the RRC state of the connected mode. Therefore, in order to transmit when the RRC state of the mobile station UE is idle or inactive, it is necessary to transition to the connected mode, which increases power consumption.

[0039] Furthermore, when no report information is transmitted from the mobile station UE, the first information is generated as parameters assuming that the mobile station UE will be at a speed for each predetermined range (for example, assuming a first range, parameters corresponding to the speed in that range).

[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), and can refer to the conversion information 51. In the conversion information 51, for example, the moving speed of the mobile station UE is associated with the value of first information (for example, parameter Ps). In the example of Fig. 7, when the moving speed is V2~ (V2 or more), the value of the first information is Ps3, when the moving speed is V1 to V2 (V1 or more and less than V2), the value of the first information is Ps2 (>Ps3), and when the moving speed is 0 to V1 (0 or more and less than V1), the value of the first information is Ps1 (>Ps2).

[0041] For example, if the representative value of "V2~ (V2 or more)" is 90 km / h, Ps3 = 1 can be set. If the representative value of "V1~V2" is 30 km / h, Ps2 = 3 can be set. If the representative value of "0~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] Furthermore, when the base station CU has not received speed information, the base station CU generates information on an assumed speed range (for example, Ps1, Ps2, and 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 Master Information Block (MIB) or a System Information Block (SIB). The base station CU transmits the synchronization signal and the broadcast information within 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, it scales the second information (e.g., the first measurement period Tm1 and the second measurement period Tm2) according to the first information (e.g., the parameter Ps) included in the broadcast information (S6).

[0046] If the broadcast information includes a plurality of parameters (for example, Ps1, Ps2, and Ps3), the mobile station UE selects, for example, a parameter according to the current moving speed in the control unit 14.

[0047] Furthermore, 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), and can refer to the conversion information 151. In the conversion information 151, the value of first information (for example, parameter Ps) is associated with the value of second information (for example, first measurement period Tm1 and second measurement period Tm2). In the example of Fig. 8, when the value of the first information is Ps3, the value of the first measurement period Tm1 is Td x Ps3 (Td: reference time length), and the value of the second measurement period Tm2 is Td x N x Ps3. When the value of the first information is Ps2, the value of the first measurement period Tm1 is Td x Ps2, and the value of the second measurement period Tm2 is Td x N x Ps2. When the value of the first information is Ps1, the value of the first measurement period Tm1 is Td×Ps1, and the value of the second measurement period Tm2 is Td×N×Ps1.

[0048] For example, if one standard period for own cell measurement is 320 ms and cell measurement determination is performed every four periods, Td=320 ms and N=4 can be set.

[0049] The base station CU can refer to the conversion information 151 and determine the value of the second information (e.g., the first measurement period Tm1 and the second measurement period Tm2) corresponding to the value of the first information included in the broadcast information.

[0050] 6, the mobile station UE performs radio measurement of its own cell during the first measurement period MP (S7). When the measurement period MP ends, the mobile station UE generates report information including the results of the radio measurement and transmits it to the base station CU (S8).

[0051] Note that the mobile station UE does not need to transmit report information including the results of radio measurement when the RRC state is idle or inactive or when the mobile station UE is operating in a low power consumption mode. In other words, the transmission of report information including the results of radio measurement in Fig. 6 (S8) does not need to be performed.

[0052] Thereafter, the mobile station UE repeatedly performs the processes of S7 and S8 for each first measurement period Tm1.

[0053] The mobile station UE performs radio measurement of its own cell during the Nth measurement period MP (S9), and then performs cell measurement determination in response to reaching the second measurement period Tm2 (S10). In the cell measurement determination, the mobile station UE determines whether the reception quality of its own cell satisfies a criterion (for example, the reception strength of a reference signal is equal to or greater than a threshold), and if the criterion is satisfied, selects its own cell, and if the criterion is not satisfied, performs radio measurement 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 satisfies the criterion, and if the criterion is satisfied, reselects the other cell.

[0054] The mobile station UE generates report information including the results of radio measurement (that is, the measurement results of its own cell and the results 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 a mobile station UE traveling at low to medium speeds can be extended, thereby improving the own cell capture rate. FIG. 9 is a diagram illustrating an improvement in the own cell capture rate in a first application example of the embodiment. For example, as shown in FIG. 9(a), when an obstacle OBS is present in the area corresponding to beam BM-2, the base station CU detects a synchronization signal in the synchronization transmission block SSB-1 corresponding to beam BM-1 during a predetermined measurement period MP. Then, as shown in FIG. 9(b), when the mobile station UE moves into the area corresponding to beam BM-2, the mobile station UE has not yet reached the measurement period MP next to the predetermined measurement period MP. Therefore, the mobile station UE does not perform radio measurement. Thereafter, as shown in FIG. 9(c), when the mobile station UE moves into the area corresponding to beam BM-3, the mobile station UE reaches the next measurement period MP and detects a synchronization signal in the synchronization transmission block SSB-3 corresponding to beam BM-3.

[0056] That is, the base station CU can control the measurement period of the radio measurement of the mobile station UE so that the mobile station UE detects synchronization signals in the synchronization transmission block SSB-1 corresponding to the beam BM-1 and the synchronization transmission block SSB-3 corresponding to the beam BM-3. This allows the mobile station UE to reduce power consumption due to operations (measurement of other cells) following a failure in cell selection. Furthermore, the mobile station UE can also perform cell selection efficiently.

[0057] The contents described in the second embodiment can be proposed as a technical standard and implemented. For example, the first information can be included in the specifications for MIBs, SIBs, etc., such as TS36.331 and TS38.331. [Example]

[0058] In the second embodiment, an example is shown in which cell selection is performed efficiently by controlling the measurement period of radio measurements of a terminal. In the third embodiment, a method for controlling other cell measurements of a mobile station UE by a base station CU is described. Note that the same reference numerals are used for components similar to those in the other embodiments.

[0059] When the radio receiving unit 13 of the base station CU receives a measurement result of the reception quality of its own cell from the mobile station UE, the radio receiving unit 13 supplies the measurement result of the reception quality of its own cell to the second generating unit 4b. The second generating unit 4b generates a measurement instruction that enables the mobile station UE to measure other cells without waiting for the scaled second measurement period Tm2 when the reception quality of the own cell does not satisfy a criterion, according to the measurement result of the reception quality of the own cell. Note that the mobile station UE measures other cells, for example, when it detects that the speed of the mobile station UE is in a state below a predetermined value (for example, a state where it is not moving). The second generating unit 4b supplies the measurement instruction to the radio transmitting unit 2. The radio transmitting 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, it supplies the measurement instruction to the control unit 14. In accordance with the measurement instruction, the control unit 14 can measure other cells without waiting for the second measurement period Tm2 to expire.

[0061] Note that the mobile station UE may not measure other cells even if it receives a measurement instruction, for example, when the moving speed of the mobile station UE is higher than a predetermined value. This is because, when the moving speed is higher than the predetermined value, the mobile station UE is likely to quickly leave a radio wave dead zone (for example, a dead zone due to radio wave blocking or diffraction by a building, etc.) even if it temporarily stays in such a zone.

[0062] In the third embodiment, the operation of the communication system CS is as shown in Fig. 10. Note that some of the operations can be omitted (processing not executed) as explained in Fig. 6.

[0063] After the processes of S1 to S8 are performed in the same manner as in the first application example, the base station CU determines whether the reception quality of its own cell satisfies a standard (for example, the reception strength exceeds a threshold) based on the measurement result of the reception quality of its own cell included in the report information (S21), and waits if the standard is satisfied (S22).

[0064] After that, for each first measurement period Tm1, the processing of S7 and S8 by the mobile station UE and the processing of S21 by the base station CU are repeatedly performed.

[0065] During the measurement period MP of the K-th cycle (K < N, K is an integer), the mobile station UE performs radio measurements on its own cell (S23). When the measurement period MP ends, the mobile station UE generates report information including the results of the radio measurements and transmits it to the base station CU (S24).

[0066] Based on the measurement results of the reception quality of its own cell included in the report information, the base station CU determines whether the reception quality of its own cell meets the standard (for example, the reception strength exceeds the threshold) (S25). If it does not meet the standard, it generates a measurement instruction (S26). The measurement instruction includes instructions for the mobile station UE to perform measurements on other cells without waiting for the scaled second measurement period Tm2. The base station CU transmits the measurement instruction to the mobile station UE (S27).

[0067] When the mobile station UE receives the measurement instruction from the base station CU, it performs measurements on other cells without waiting for the second measurement period Tm2 according to the measurement instruction (S28). The mobile station UE generates report information including the results of the radio measurements (i.e., the results of the measurements on other cells) and transmits it to the base station CU (S29).

[0068] Regarding the processing steps S21 to S25, although it has been described on the premise of receiving measurement information from the mobile station UE, the mobile station UE may not transmit report information when the RRC state is idle or inactive, or when the mobile station UE is operating in a low-power consumption mode. For example, when the RRC state of the mobile station UE is idle or inactive and it needs to transmit measurement information, the RRC state of the mobile station UE needs to be transitioned to the connected mode, which increases power consumption. Therefore, from the perspective of power saving, it is preferable not to transmit (not to transition to connected).

[0069] In this case, for example, the measurement instruction is transmitted using a periodically transmitted synchronization signal or broadcast information. In other words, the information of processing step S27 is also transmitted in processing step S5. Alternatively, the base station CU may transmit the measurement instruction information to the mobile station UE in advance as RRC setting information, by including it in an RRC message.

[0070] When the mobile station UE receives the measurement instruction, it can measure other cells (S28) if a predetermined condition is met. The predetermined condition may be, for example, the moving speed of the mobile station UE, the state of radio quality (for example, when the communication quality is below a predetermined value N times consecutively), etc.

[0071] This allows for quick guidance to another cell without being bound by the second measurement period Tm2 when the reception quality of the own cell does not satisfy the standard, thereby suppressing deterioration of communication quality due to delays in measuring other cells.

[0072] The measurement instruction described in the third embodiment can be included in the specifications of, for example, an RRC message such as TS36.331 or TS38.331, an MIB, an SIB, or the like.

[0073] As described above, in the third embodiment, the base station CU transmits information including first information that can control the conditions of radio measurement to the base station CU, thereby controlling radio measurement to be performed in the mobile station UE under conditions according to the second information controlled by the first information. This allows the base station CU to control the conditions of radio measurement in the mobile station UE to conditions that allow appropriate cell selection and reselection. Cell selection and reselection by the mobile station UE can be made appropriate. [Example]

[0074] It should be noted that the first to third embodiments can be appropriately combined within a range that does not contradict each other. For example, in the second and third embodiments, it is possible to control the other cell measurement to be accelerated or delayed depending on the state of the mobile station UE by using both the relationship between the first information and the moving speed defined in the second embodiment and the measurement instruction defined in the third embodiment.

[0075] The components of each unit illustrated in the examples do not necessarily have to be physically configured as illustrated. In other words, the specific form of distribution and integration of each unit is not limited to that illustrated, and all or part of them can be functionally or physically distributed and integrated in any unit depending on various loads, usage conditions, etc.

[0076] Furthermore, the various processing functions performed by each device may be executed in whole or in part on a CPU (Central Processing Unit) (or a microcomputer such as an MPU (Micro Processing Unit) or MCU (Micro Controller Unit)). Also, the various processing functions may be executed in whole or in part on a program analyzed and executed by a CPU (or a microcomputer such as an MPU or MCU), or on hardware using wired logic.

[0077] The radio devices of the embodiment (that is, the aggregation nodes CU-CP and CU-UP, the distributed nodes DU, and the terminals UE) can be realized, for example, by the following hardware configuration.

[0078] Fig. 11 is a diagram showing an example of the hardware configuration of a wireless device. As shown in Fig. 11, the wireless device 100 has a processor 101, a memory 102, a current sensor 103, a power supply circuit 104, and an RF circuit 105. Examples of the processor 101 include a CPU, a DSP (Digital Signal Processor), and an FPGA (Field Programmable Gate Array). Examples of the memory 102 include a RAM (Random Access Memory) such as an SDRAM (Synchronous Dynamic Random Access Memory), a ROM (Read Only Memory), and a flash memory.

[0079] The various processing functions performed by the wireless device of the embodiment may be realized by a processor executing programs stored in various memories such as non-volatile storage media. That is, a program corresponding to each process may be recorded in memory 102, and each program may be executed by processor 101. The communication I / F may be realized by RF circuit 105. [Explanation of symbols]

[0080] 1. Wireless Communication Unit 2. Radio transmitter 3. Radio receiver 4. Control section 5 Storage section 6. Communications Department 11. Wireless Communication Section 12 Radio transmitter 13 Radio receiving unit 14 Control Unit 15 Storage section 17. Radio Communication Department 18 Radio transmitter 19 Radio receiving unit CL, CL-1, CL-2 cells CS communication system CU, CU-1, CU-2 base station UE mobile station

Claims

1. A base station capable of transmitting a synchronization signal at a predetermined transmission interval in a plurality of periods, a transmitter capable of transmitting the synchronization signal by a plurality of wireless signals; a control unit that is controlled using first information that can control conditions of radio measurement in a mobile station connected to the base station, and that can control the mobile station to detect the synchronization signal under conditions according to second information related to radio measurement of the mobile station; Equipped with the first information is a parameter corresponding to a moving speed of the mobile station and is information included in a System Information Block (SIB) transmitted from the transmitter to the mobile station; the second information is information corresponding to a measurement interval of the radio measurement in the mobile station; the measurement interval corresponding to the second information is determined in accordance with the first information and is an interval that is N times (N is an integer) the length of a reference time; the control unit controls the measurement interval corresponding to the second information of the mobile station to be a first interval when the moving speed of the mobile station corresponds to a first speed, and controls the measurement interval corresponding to the second information of the mobile station to be a second interval longer than the first interval when the moving speed of the mobile station corresponds to a second speed slower than the first speed; The control unit can control the mobile station to select either a first cell to which the mobile station is connected or a second cell different from the first cell by causing the mobile station to perform cell measurement determination for each measurement interval. Base station.

2. The control unit can control radio measurement of the mobile station so that the mobile station detects the synchronization signal in a first interval corresponding to a first radio signal among the plurality of radio signals and in a second interval corresponding to a second radio signal different from the first radio signal. The base station of claim 1 .

3. The control unit a first generating unit that generates the first information; a second generation unit that generates broadcast information including the first information such that, when the mobile station selects its own cell, the mobile station scales second information related to a measurement period of radio measurement in accordance with the first information; have The base station of claim 1 .

4. The transmitter periodically transmits the synchronization signal and the broadcast information within its own cell by beam sweeping or beam spanning. The base station according to claim 3 .

5. a receiving unit that receives speed information relating to a moving speed of the mobile station from the mobile station, The first generation unit generates the first information in response to the received speed information. The base station according to claim 3 .

6. The first generation unit generates the first information with a parameter of a first value in response to a moving speed of the mobile station being a first speed, and generates the first information with a parameter of a second value larger than the first value in response to a moving speed of the mobile station being a second speed slower than the first speed. The base station of claim 5.

7. a receiving unit that receives speed information relating to a moving speed of the mobile station from the mobile station, the first generation unit generates the first information in response to the received speed information; The second information includes a first measurement period in which the mobile station measures the reception quality of its own cell and a second measurement period in which the mobile station measures the reception quality of another cell. The base station according to claim 3 .

8. the first generation unit generates the first information with a parameter of a first value in response to a moving speed of the mobile station being a first speed, and generates the first information with a parameter of a second value larger than the first value in response to a moving speed of the mobile station being a second speed slower than the first speed; the first measurement period is scaled to a first length when the first information is a parameter of the first value, and to a second length longer than the first length when the first information is a parameter of the second value; The second measurement period is scaled to a third length when the first information is a parameter of the first value, and is scaled to a fourth length longer than the third length when the first information is a parameter of the second value. The base station of claim 7.

9. the receiving unit receives a measurement result of reception quality of the mobile station's own cell from the mobile station; the second generation unit generates an instruction for the mobile station to measure another cell without waiting for the scaled second measurement period when the mobile station has selected its own cell and the reception quality of the own cell does not satisfy a standard; The transmitter transmits the generated instruction to the mobile station. The base station of claim 8.

10. A mobile station capable of receiving a synchronization signal transmitted from a base station at a predetermined transmission interval in a plurality of cycles, a receiving unit capable of receiving the synchronization signal; a control unit that is controlled using first information that can control conditions of radio measurement and that can control to detect the synchronization signal under conditions according to second information related to radio measurement of the mobile station; Equipped with the first information is a parameter corresponding to a moving speed of the mobile station and is information included in a System Information Block (SIB) received by the receiving unit; the second information is information corresponding to a measurement interval of the radio measurement in the mobile station; the measurement interval corresponding to the second information is determined in accordance with the first information and is an interval that is N times (N is an integer) the length of a reference time; the control unit controls the measurement interval corresponding to the second information of the mobile station to be a first interval when the moving speed of the mobile station corresponds to a first speed, and controls the measurement interval corresponding to the second information of the mobile station to be a second interval longer than the first interval when the moving speed of the mobile station corresponds to a second speed slower than the first speed; The control unit can control the mobile station to select either a first cell to which the mobile station is connected or a second cell different from the first cell by causing the mobile station to perform cell measurement determination for each measurement interval. Mobile station.

11. the receiving unit receives the synchronization signal and broadcast information including the first information from the base station; the control unit scales the second information according to first information included in the broadcast information when the mobile station selects its own cell, and performs radio measurement at a measurement period according to the scaled second information; The mobile station further includes a transmitter that transmits the results of the radio measurement to the base station. The mobile station of claim 10.

12. a base station capable of transmitting a synchronization signal at predetermined transmission intervals in a plurality of cycles; a mobile station connected to the base station; Equipped with The base station a transmitter capable of transmitting the synchronization signal by a plurality of wireless signals; a control unit that controls a measurement interval of the radio measurement of the mobile station so that the synchronization signal is detected under a condition according to second information related to the radio measurement of the mobile station, the second information being controlled using first information that can control a condition of the radio measurement of the mobile station connected to the base station; and the first information is a parameter corresponding to a moving speed of the mobile station and is information included in a System Information Block (SIB) transmitted from the transmitter to the mobile station; the second information is information corresponding to a measurement interval of the radio measurement in the mobile station; the measurement interval corresponding to the second information is determined in accordance with the first information and is an interval that is N times (N is an integer) the length of a reference time; the control unit controls the measurement interval corresponding to the second information of the mobile station to be a first interval when the moving speed of the mobile station corresponds to a first speed, and controls the measurement interval corresponding to the second information of the mobile station to be a second interval longer than the first interval when the moving speed of the mobile station corresponds to a second speed slower than the first speed; The control unit can control the mobile station to select either a first cell to which the mobile station is connected or a second cell different from the first cell by causing the mobile station to perform cell measurement determination for each measurement interval. Communication system.

13. A communication method in a communication system having a base station capable of transmitting a synchronization signal at a predetermined transmission interval in a plurality of cycles, and a mobile station connected to the base station, comprising: transmitting said synchronization signal over a plurality of wireless signals; a step of controlling a measurement interval of the radio measurement of the mobile station so as to detect the synchronization signal under a condition according to second information related to the radio measurement of the mobile station, the second information being controlled using first information capable of controlling a condition of the radio measurement of the mobile station connected to the base station; Equipped with the first information is a parameter corresponding to a moving speed of the mobile station and is information included in a System Information Block (SIB) transmitted from the base station to the mobile station; the second information is information corresponding to a measurement interval of the radio measurement in the mobile station; the measurement interval corresponding to the second information is determined in accordance with the first information and is an interval that is N times (N is an integer) the length of a reference time; The step of controlling the measurement interval of the radio measurement of the mobile station includes controlling the measurement interval corresponding to the second information of the mobile station to be a first interval when the moving speed of the mobile station corresponds to a first speed, and controlling the measurement interval corresponding to the second information of the mobile station to be a second interval longer than the first interval when the moving speed of the mobile station corresponds to a second speed slower than the first speed; The step of controlling the measurement interval of the radio measurement of the mobile station can control the mobile station to select either a first cell to which the mobile station is connected or a second cell different from the first cell by making the mobile station perform cell measurement determination for each measurement interval. Communication method.

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