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

Abstract

To optimize cell selection / reselection.SOLUTION: A base station according to an embodiment capable of transmitting synchronization signals in a plurality of cycles at predetermined transmission intervals includes a transmitting unit capable of continuously transmitting the synchronization signals in a plurality of radio signals, and a control unit capable of controlling radio measurement of a mobile station such that the mobile station connected to the base station detects the synchronization signal under a condition corresponding to second information scaled using first information.SELECTED DRAWING: Figure 6

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 in the future. Meanwhile, with the development of IoT (Internet of Things) services (for example, transportation systems, smart meters, and monitoring systems for devices), there is a need to support services with diverse requirements. For this reason, in addition to the standard technologies of fourth-generation mobile communications (4G), the communication standards for fifth-generation mobile communications (5G) require technologies that achieve even higher data rates, larger capacities, and lower latency. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-212733 A [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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Non-licensed literature 9

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[0005] However, in a communication system based on the fifth generation mobile communication standard, depending on the measurement method of a mobile station, cell selection and reselection may not be performed appropriately.

[0006] The disclosed technology has been made in consideration of the above, and has an object to provide a base station, a mobile station, a communication system, and a communication method that are capable of optimizing 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 has a transmitting unit capable of continuously transmitting the synchronization signal in multiple radio signals, and a control unit capable of controlling radio measurement 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. Effect 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 description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a communication system according to a first embodiment. [Diagram 2] FIG. 2 is a diagram illustrating a relationship between a transmission interval of a synchronization signal group from a base station and second information (first measurement period, second measurement period) in a mobile station in the second embodiment. [Diagram 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 in the second embodiment. [Diagram 5] FIG. 5 is a diagram illustrating a configuration of a mobile station in 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 of an operation of the communication system according to the third embodiment. [Figure 11] FIG. 11 is a diagram illustrating an example of a hardware configuration of a wireless device used in each embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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. In addition, in the embodiments, components having the same functions are given the same reference numerals, and duplicated descriptions are omitted. EXAMPLES

[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, CU-2, and is provided with a plurality of cells CL-1, CL-2 corresponding to the plurality of base stations CU-1, CU-2. In the following, when the plurality of base stations CU-1, CU-2 are not distinguished from each other, they will be simply referred to as base stations CU. When the plurality of cells CL-1, CL-2 are not distinguished from each other, they will be simply referred to as cells CL. Note that the mobile station UE can also be referred to, for example, as 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 can measure (radio measurement) a reference signal (e.g., a synchronization signal) included in the system information, and select a cell CL suitable for wireless communication from among the multiple cells CL-1 and CL-2 as its own cell and connect to it (cell selection) according to the result of the radio measurement. Furthermore, when the cell CL suitable for wireless communication from among the 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, in the cell CL, first information that can control the conditions of radio measurement (for example, cell selection / reselection can be performed appropriately) by including it in the system information. 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 / reselection to be performed appropriately, the second information controlled using the first information can also be a condition that allows cell selection / 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 / reselection appropriately. That is, the mobile station UE can perform cell selection / 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 a building, etc.), it can remain in its own cell within an acceptable range (e.g., a range determined by a selection condition according to the second condition) without immediately starting measurement 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 provisions of the standard specifications. EXAMPLES

[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 a base station CU controls a radio measurement period of a mobile station UE so that the mobile station UE appropriately performs cell selection and reselection. Note that the same symbols are used for configurations similar to those in the first embodiment.

[0018] For example, each base station CU can transmit a synchronization signal required for cell selection at a predetermined transmission interval in a plurality of periods as shown in Fig. 2. Fig. 2 is a diagram showing a relationship between the transmission interval of a group of synchronization signals from a base station CU and second information (first measurement period, second measurement period) in a mobile station UE in a 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 hatching with diagonal lines. 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 regarded as one period, the mobile station UE performs cell measurement determination every N periods (N is an integer equal to or greater than 2), that is, every second measurement period Tm2 (=Tm1×N). In the cell measurement determination, for example, the mobile station UE determines whether a criterion for the reception quality of its own cell (for example, the reception strength of a reference signal is equal to or greater than a threshold) is satisfied, and if the criterion is satisfied, the mobile station UE 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 another cell satisfies a criterion, and if the criterion is satisfied, reselects the other cell.

[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 successive transmission (beam sweeping) of a plurality of radio signals from the base station.

[0022] The base station CU can form directional radio beams by beamforming, but when broadcasting a synchronization signal required for cell selection within a cell CL, multiple beams are transmitted in order to transmit in all possible directions. Since 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 in the transmission window WD.

[0023] Note that Figures 2 and 3 show 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) exists in an area corresponding to beam BM-2 among multiple beams BM-1 to BM-8 used in beam sweeping in a cell CL. In this case, if the mobile station UE is moving at a low speed, even if the mobile station UE exists in an area corresponding to beam BM-1 in a certain measurement period MP and is able to detect a synchronization signal from the base station CU, the mobile station UE may move to an area corresponding to beam BM-2 in the subsequent measurement period MP, making it difficult to detect the synchronization signal from the base station CU. This possibility tends to be prominent 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 the broadcast information together with a synchronization signal to the mobile station UE so that the mobile station UE scales second information related to the measurement period of the radio measurements in accordance with the first information, thereby optimizing the measurement period of the radio measurements 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 receiver 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 it to the first generator 4a. Note that the radio receiver 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 the connected mode, the radio receiver 3 receives the measurement information transmitted from the mobile station UE, but when the RRC state of the mobile station UE is the idle mode or the inactive mode, the radio receiver 3 does not receive the measurement information because it is not transmitted from the mobile station UE.

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

[0029] The second generating unit 4b generates broadcast information including the first information so that the mobile station UE scales second information related to a measurement period of radio measurement according to the first information when the mobile station UE selects its own cell. In addition, when a plurality of parameters are included in the first information, the second generating unit 4b generates second information for each parameter. The second information includes a first measurement period Tm1 in which the mobile station UE measures the reception quality of its own cell and a second measurement period Tm2 in 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 of a first value, and is scaled to a second length longer than the first length when the first information is a parameter of a second value. The second measurement period Tm2 is scaled to a third length when the first information is a parameter of a first value, and is scaled to a fourth length longer than the third length when the first information is a parameter of a second value. The second generating unit 4b supplies the generated broadcast information to the radio transmitting unit 2.

[0030] The radio transmitting unit 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 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 a 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 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 it 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 it is not transmitted 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, the control unit 14 scales the first measurement period Tm1 to a first length when the first information is a parameter of a first value, and scales the first measurement period Tm1 to a second length longer than the first length when the first information is a parameter of a second value. The control unit 14 scales the second measurement period Tm2 to a third length when the first information is a parameter of a first value, and scales the second measurement period Tm2 to a fourth length longer than the third length when the first information is a parameter of a second value. The control unit 14 performs radio measurement according to the scaled first measurement period Tm1 and the scaled second measurement period Tm2.

[0035] The control unit 14 supplies the result of the radio measurement to the radio transmitting unit 12. The radio transmitting 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 Fig. 6 to Fig. 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 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 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 RRC state of the mobile station UE in 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] In addition, when no report information is transmitted from the mobile station UE, parameters assuming that the mobile station UE will have a speed for each predetermined range (for example, assuming a first range, parameters corresponding to the speed in that range) are 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), 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 the 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~V2 (V1 or more and less than V2), the value of the first information is Ps2 (>Ps3), and when the moving speed is 0~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 90km / h, Ps3=1 can be set. If the representative value of "V1~V2" is 30km / h, Ps2=3 can be set. If the representative value of "0~V1" is 3km / 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 MIB (Master Information Block) or a SIB (System Information Block). 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] When 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] Also, 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 the first information (for example, parameter Ps) is associated with the value of the 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 a standard period for own cell measurement is 320 ms and cell measurement determination is performed every four periods, then 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 in 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 in the Nth measurement period MP (S9), and 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 selects its own cell if the criterion is satisfied, and performs radio measurement to measure the reception quality from the base station CU of another cell if the criterion is not satisfied. The mobile station UE determines whether the reception quality of the other cell satisfies a criterion, and reselects the other cell if the criterion is satisfied.

[0054] The mobile station UE generates report information including the results of radio measurement (that is, the measurement results of the own cell and the cell measurement decision results) and transmits the report information to the base station CU (S11).

[0055] As a result, as shown in FIG. 9, the cell selection time of a low-medium speed mobile station UE can be extended, and the own cell capture rate can be improved. FIG. 9 is a diagram showing 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 exists in an area corresponding to beam BM-2, the base station CU detects a synchronization signal in a synchronization transmission block SSB-1 corresponding to beam BM-1 in a predetermined measurement period MP. Then, as shown in FIG. 9(b), when the mobile station UE moves to an area corresponding to beam BM-2, the mobile station UE has not yet reached the next measurement period MP of the predetermined measurement period MP. Therefore, the mobile station UE does not perform radio measurement. After that, as shown in FIG. 9(c), when the mobile station UE moves to an 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 a synchronization signal 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 an operation (measurement of other cells) associated with a failure in the selection of its own cell. In addition, 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. EXAMPLES

[0058] In the second embodiment, an example of efficiently performing cell selection by controlling the measurement period of the radio measurement of the terminal is described. In the third embodiment, a method of controlling the measurement of other cells of the mobile station UE by the base station CU is described. Note that the same reference numerals are given to the same components as in the other embodiments.

[0059] When the radio receiver 13 of the base station CU receives the measurement result of the reception quality of its own cell from the mobile station UE, the radio receiver 13 supplies the measurement result of the reception quality of its own cell to the second generator 4b. The second generator 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 the standard, 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 the mobile station UE is not moving). The second generator 4b supplies the measurement instruction to the radio transmitter 2. The radio transmitter 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 perform measurement of other cells without waiting for the second measurement period Tm2.

[0061] Note that the mobile station UE may not measure other cells even if it receives a measurement instruction when the moving speed of the mobile station UE is greater than a predetermined value, for example. This is because, when the moving speed is greater 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 caused by buildings, 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 operations can be omitted (processing not executed) as described 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 or not the reception quality of its own cell satisfies a criterion (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 criterion is satisfied (S22).

[0064] Thereafter, 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] The base station CU determines whether the reception quality of its own cell meets the standard (for example, the reception strength exceeds the threshold) according to the measurement results of the reception quality of its own cell included in the report information (S25). If the standard is not met, a measurement instruction is generated (S26). The measurement instruction includes content instructing 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] Note that for the processing steps S21 to S25, the description is based on the premise of receiving measurement information from the mobile station UE. However, 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, the communication quality is less than 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 performing measurements on other cells.

[0072] The measurement instruction described in the third embodiment can be included in the provisions 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 the first information capable of controlling 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. EXAMPLES

[0074] In addition, the first to third embodiments can be appropriately combined and used within a range that does not contradict each other. For example, in the second and third embodiments, the relationship between the first information and the moving speed defined in the second embodiment and the measurement instruction defined in the third embodiment can be used to control the other cell measurement to be accelerated or delayed according to the state of the mobile station UE.

[0075] Each component of each unit illustrated in the embodiment does 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 according to 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 an MCU (Micro Controller Unit)). Also, the various processing functions may be executed in whole or in part on a program that is analyzed and executed by a CPU (or a microcomputer such as an MPU or an MCU), or on hardware using wired logic.

[0077] The wireless devices of the embodiment (that is, the aggregation node CU-CP, aggregation node CU-UP, distributed node DU, and terminal 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, a 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] Various processing functions performed by the wireless device of the embodiment may be realized by executing programs stored in various memories such as non-volatile storage media by the processor. That is, a program corresponding to each process may be recorded in the memory 102, and each program may be executed by the processor 101. Also, the communication I / F may be realized by the RF circuit 105. [Explanation of symbols]

[0080] 1 Wireless communication section 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 section 14 Control section 15 Storage section 17 Wireless Communication Section 18 Radio transmitter 19 Radio receiving section CL, CL-1, CL-2 cells CS Communication System CU, CU-1, CU-2 base station UE mobile station

Claims

1. A base station that can transmit a synchronization signal at a predetermined transmission interval and forms a first cell, A transmitting unit that can transmit the synchronization signal via the first cell, A control unit that can control a mobile station connected to the base station to detect the synchronization signal under conditions corresponding to second information related to radio measurement of the mobile station, which is controlled using first information, It has, The control unit can cause the mobile station to select or re-select a cell according to the reception quality conditions for the first cell. The measurement period for the wireless measurement is N times the reference measurement period (where N is an integer). Base station.

2. The first information is a parameter corresponding to the mobile station's speed and is included in the System Information Block (SIB) transmitted from the transmitter. The second piece of information is information corresponding to the measurement interval of the wireless measurement, The measurement interval is determined according to the first information and is an interval that is N times the length of the reference time (where N is an integer). The control unit can, when the mobile station's speed corresponds to a first speed, control the measurement interval corresponding to the second information of the mobile station to be the first interval, and when the mobile station's speed corresponds to a second speed that is slower than the first speed, control the measurement interval corresponding to the second information of the mobile station to be the second interval that is longer than the first interval. The control unit can cause the mobile station to measure the reception quality at each measurement interval. The base station according to claim 1.

3. The control unit controls the transmission unit to transmit measurement instruction information that enables measurement of the second cell, thereby causing the mobile station to select or re-select the cell. The base station according to claim 1.

4. The selection or re-selection of the cell includes the process by which the mobile station measures the signal of a second cell different from the first cell. The base station according to claim 1.

5. The selection or re-selection of the cell includes a process in which the mobile station measures the signal of a second cell different from the first cell at a timing different from the timing corresponding to the measurement cycle. The base station according to claim 4.

6. The transmitting unit can periodically transmit the synchronization signal and broadcast information in the first cell using beam sweep or beam spanning. The base station according to claim 1.

7. The control unit generates the first information and generates notification information including the first information so as to scale the second information according to the first information when the mobile station selects the first cell. The base station according to claim 1.

8. A mobile station capable of receiving a synchronization signal transmitted at a predetermined transmission interval from a base station forming a first cell, A receiving unit capable of receiving the aforementioned synchronization signal, A control unit that can control the detection of the synchronization signal under conditions corresponding to second information related to wireless measurement, which is controlled using first information, and can perform cell selection or re-selection according to the reception quality conditions for the first cell, It has, The measurement period for the wireless measurement is N times the reference measurement period (where N is an integer). Mobile station.

9. The first information is a parameter corresponding to the mobile station's speed and is included in the System Information Block (SIB) transmitted from the base station. The second piece of information is information corresponding to the measurement interval of the wireless measurement, The measurement interval is determined according to the first information and is an interval that is N times the length of the reference time (where N is an integer). The control unit can, when the mobile station's speed corresponds to a first speed, control the measurement interval corresponding to the second information to be the first interval, and when the mobile station's speed corresponds to a second speed that is slower than the first speed, control the measurement interval corresponding to the second information to be longer than the first interval. The control unit can control the mobile station to measure the reception quality at each measurement interval. The mobile station according to claim 8.

10. The control unit can perform the selection or re-selection of the cell when the receiving unit receives measurement instruction information that enables the measurement of the second cell. The mobile station according to claim 8.

11. The selection or re-selection of the cell includes the process by which the control unit measures the signal of a second cell different from the first cell. The mobile station according to claim 8.

12. The selection or re-selection of the cell includes a process in which the mobile station measures the signal of a second cell different from the first cell at a timing different from the timing corresponding to the measurement cycle. The mobile station according to claim 8.

13. A base station that forms a first cell and transmits a synchronization signal at a predetermined transmission interval, A mobile station capable of receiving the aforementioned synchronization signal, It has, The mobile station is controlled to detect the synchronization signal under conditions corresponding to second information related to the radio measurement of the mobile station, which is controlled using first information. The mobile station can be instructed to select or re-select a cell according to the reception quality conditions for the first cell. The measurement period for the wireless measurement is N times the reference measurement period (where N is an integer). Communication system.

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