Base station device, control method, and program for properly controlling handover between cells including regulated cells

Abstract

To properly execute handover of a terminal device in an environment where cells subject to regulation exist.SOLUTION: A base station apparatus acquires restriction information regarding connection limitations in a second cell, which is provided by another base station apparatus offering the second cell adjacent to a first cell provided by the base station apparatus. On the basis of this restriction information, it controls the handover of a terminal device currently connected via the first cell to the second cell.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a control technique related to handover between cells including restricted cells.

Background Art

[0002] In a cellular communication system, due to various factors, the connection of a terminal device to a specific cell may be restricted. The base station device providing the cell can perform such restrictions, for example, to prevent or relieve congestion of a backhaul line or the base station device itself. Such restrictions include, for example, Barred in which connections in all terminal devices are restricted, and Reserved in which connections of terminal devices are restricted except for those that transmit data of a specific access class. Also, for example, a throughput rate setting for establishing a connection with a certain probability according to the type of call (e.g., signaling / data distinction) can be performed as such a restriction. Information on these restrictions is notified to the terminal device using system information sent from the base station device. When an unconnected terminal device connects to any cell, the terminal device, for example, does not connect to a Barred cell, and does not connect to a Reserved cell when the access class of the data transmitted by the device is not a specific access class. Also, the terminal device can determine whether to attempt a connection to a cell with a set throughput rate according to the throughput rate.

Summary of the Invention

Problems to be Solved by the Invention

[0003] When a terminal device connected to any cell performs a handover, the terminal device measures the radio quality of a synchronization signal transmitted from a cell that is a candidate for the handover destination. The terminal device notifies the base station device that provides the cell in which it is connected of the measurement result of the radio quality for the cell that is a candidate for the handover destination. The base station device determines the handover destination cell based on the notification and transmits a handover request to another base station device that provides the cell. However, there may be a case where the above-described regulation is performed in the handover destination cell. In this case, the base station device that provides the handover destination cell may reject the handover request. In this case, for example, the connection of the terminal device can be maintained by handing over the terminal device to another cell where the regulation is not performed, but the time until the terminal device finally completes the handover may be prolonged. Also, if a handover request is accepted in a cell where the regulation is performed, it is not possible to achieve prevention or alleviation of congestion in the backhaul line or in that cell, and the effect of the regulation may be diminished.

Means for Solving the Problem

[0004] The present invention provides a technique that enables appropriate execution of handover of a terminal device in an environment where there is a cell subject to regulation.

[0005] A base station device according to an aspect of the present invention includes an acquisition unit that acquires regulation information regarding connection regulation in a second cell provided by another base station device that provides a second cell adjacent to a first cell provided by the base station device, and a control unit that controls handover of a terminal device connected via the first cell to the second cell based on the regulation information.

[0006] Another base station device according to an aspect of the present invention includes a provision unit that provides regulation information regarding connection regulation in a first cell provided by the base station device to another base station device that provides a second cell adjacent to the first cell.

Effect of the Invention

[0007] According to the present invention, it is possible to appropriately execute handover of a terminal device in an environment where there are cells subject to regulation.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

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Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims, and not all combinations of the features described in the embodiments are essential for the invention. Two or more of the features described in the embodiments may be arbitrarily combined. Also, the same or similar configurations are given the same reference numerals, and duplicate descriptions are omitted.

[0010] (System Configuration) Fig. 1 shows a configuration example of the wireless communication system according to the present embodiment. The wireless communication system in Fig. 1 is, for example, a cellular wireless communication system compliant with the fifth generation (5G) standard of the 3rd Generation Partnership Project (3GPP (registered trademark)) or its successor standard, and includes base station devices 101 to 103 and terminal devices 121 to 122. Here, the base station device 101 provides cell 111, the base station device 102 provides cell 112, and the base station device 103 provides cell 113. Also, it is assumed that the terminal device 121 has established a connection with cell 111 (base station device 101) and moves in the directions of cell 112 and cell 113. It is assumed that the terminal device 122 stays within the range of cell 112.

[0011] Here, it is assumed that the cell 112 is in a regulated state, such as a Barred state, a Reserved state, or a state where a throughput rate is set. This regulation information is transmitted as system information, for example, from the base station device 102. Here, the system information can be, for example, a Master Information Block (MIB) or a System Information Block (SIB) Type 1 (SIB1) or SIB Type 2 (SIB2). The terminal device 122 can receive the MIB or SIB transmitted from the base station device 102 and identify that the cell 112 is in a regulated state. When the cell 112 is in the Barred state, the terminal device 122 does not request a connection to the cell 112 regardless of the access class (AC) of the data that the device itself attempts to communicate (transmit or receive). Also, when the cell 112 is in the Reserved state, the terminal device 122 requests a connection to the cell 112, for example, when the AC of the communication target data is a predetermined AC, and does not request a connection to the cell 112 when the AC of the communication target data is other than that AC. The throughput rate can be, for example, the probability of actually requesting a connection when the terminal device 122 should request a connection. When the throughput rate is p (0 < p < 1), the terminal device 122 in an unconnected state that is not connected to any base station device can generate a random number in the range from 0 to 1 and operate so as not to request a connection when the random number exceeds the value of the throughput rate. Also, the throughput rate may be expressed by the probability of not requesting a connection. When that probability is q (0 < q < 1), the terminal device 122 in an unconnected state that is not connected to any base station device can generate a random number in the range from 0 to 1 and operate so as not to request a connection when the random number is less than the value of the throughput rate. Also, the throughput rate may be set for each AC. In one example, different throughput rates can be set for, for example, the transmission of a data signal and the transmission of signaling (such as location registration). For example, 5% regulation (throughput rate 95%) can be performed for signaling, and 40% regulation (throughput rate 60%) can be performed for data.In one example, regulations may not be imposed on the data of a specific AC (throughput rate: 100%), and regulations may be imposed only on the data of other ACs. Also, the setting of regulations may include a regulation time, which is the length of time for which regulations are imposed. At this time, when multiple regulations are set according to each AC or each type of terminal device, different regulation times may be set for each of the multiple regulations.

[0012] In cell 112, due to such regulations, a connection request by a terminal device (e.g., terminal device 122) that is not connected to any base station device is suppressed, so that congestion of the cell or the backhaul line can be prevented or reduced. Note that when the terminal device 122 does not request a connection to the cell 112 due to regulations, it may request a connection to, for example, the cell 113 where no regulations are being imposed.

[0013] On the one hand, since the terminal device 121 is connected to the cell 111 (base station device 101), it does not receive the system information transmitted from the base station device 102 and does not recognize that restrictions are imposed in the cell 112. For this reason, for example, when the terminal device 121 moves in the direction of the cell 112, the handover process of the terminal device 121 may be attempted without considering the restriction state of the cell 112. That is, when the terminal device 121 enters the range of the cell 112, for example, it measures the reference signal received power (RSRP) or the reference signal received quality (RSRQ) based on the synchronization signal (Primary Synchronization Signal (SS) / Secondary SS (PSS / SSS)) transmitted from the base station device 102. Also, the terminal device 121 identifies the physical cell identifier (PCI) of the cell 112 from the PSS / SSS. The terminal device 121 notifies the base station device 101 of the identified PCI and the measurement results of the RSRP or RSRQ. Then, the base station device 101 can transmit a handover request to the base station device 102 regardless of the restriction state in the cell 112 according to the values of the RSRP and RSRQ. On the other hand, the base station device 102 can reject the handover request based on the restrictions being imposed in the cell 112. In this case, the base station device 101 can, for example, cause the terminal device 121 to hand over to the cell 113 based on the RSRP, RSRQ, etc. of the cell 113 measured at the terminal device 121. However, due to the handover request made regardless of whether restrictions are imposed in the cell 112, the time until the terminal device 121 completes the handover may be prolonged. Also, since the handover request and the response rejecting the request are transmitted in the backhaul line, the effect of preventing or reducing the congestion of the backhaul line due to the restrictions in the cell 112 may be reduced.

[0014] In this embodiment, in view of such circumstances, a technique is provided that enables the base station device 101 to which the terminal device 121 is connected to identify whether there are restrictions in the handover destination candidates. In one example, even while the terminal device 121 is connected to the base station device 101, the terminal device 121 can obtain information on the restrictions in the handover destination candidate cell (for example, cell 112). For example, the base station device 101 makes settings so that the terminal device 121 can receive the system information transmitted from the base station device 102. Then, while being connected to the base station device 101, the terminal device 121 operates to decode not only the PSS / SSS but also the system information (such as MIB, SIB1, SIB2, etc.) transmitted from the base station device 102. The terminal device 121 obtains the restriction status in cell 112 from the system information and notifies the base station device 101. Based on the information received from the terminal device 121, the base station device 101 identifies whether there are restrictions in cell 112 and, if so, the type thereof. Then, based on the restriction information in that cell 112, the base station device 101 determines whether to hand over the terminal device 121 to cell 112, and if it determines not to perform the handover, it executes control therefor. For example, when cell 112 is in the Barred state, the base station device 101 prevents the handover of the terminal device 121 to cell 112. Also, when cell 112 is in the Reserved state, the base station device 101 prevents the handover to cell 112 when the AC of the data to be communicated by the terminal device 121 is not a specific AC, and controls so that the handover to cell 112 can be performed when the AC of that data is a specific AC. Further, when a throughput rate is set in cell 112, the base station device 101 controls so that a handover request is transmitted with a probability corresponding to that throughput rate.

[0015] In one example, as events in which handover is performed, it is defined that the radio quality of cell 112 is higher than that of cell 111, which the terminal device 121 is currently connected to, by a predetermined level or more (Event A3), and that the radio quality of cell 111 falls below a first predetermined value and the radio quality of cell 112 exceeds a second predetermined value (Event A5). At this time, by increasing the predetermined level of Event A3, handover will not be performed unless the radio quality of cell 112 is significantly higher than that of cell 111. Therefore, for cell 112 in the Barred state, the base station apparatus 101 can set the predetermined level to the maximum value. Similarly, by increasing the second predetermined value of Event A5, handover will not be performed unless the radio quality of cell 112 becomes very high. Therefore, for cell 112 in the Barred state, the base station apparatus 101 can set the second predetermined value to the maximum value. Hereinafter, the above-mentioned predetermined level and second predetermined value may be referred to as Cell Individual Offset (CIO). In addition, the base station apparatus 101 may register cell 112 in the Barred state in the black cell list in order to exclude it from the measurement targets in the terminal device 121. The black cell list is notified to the terminal device 121, and the terminal device 121 does not perform measurement (report) on the cells registered in the black cell list, so handover to that cell 112 will not be performed. In addition, the base station apparatus 101 provides throughput information to the terminal device 121, and the terminal device 121 generates a random number when the radio quality of adjacent cells satisfies a predetermined condition, and based on the relationship between the throughput and the random number, determines whether to transmit a measurement report to the base station apparatus 101. When the terminal device 121 does not transmit a measurement report due to the value of the random number, it waits for a predetermined period notified together with the throughput information, then generates a random number again, and based on the relationship between the throughput and the random number, can determine again whether to transmit a measurement report to the base station apparatus 101. By these controls, the base station apparatus 101 can greatly suppress the probability of causing the terminal device 121 to hand over to cell 112 where regulation is being performed.Further, the base station apparatus 101 controls to preferentially execute handover of the terminal device 121 to another cell where no regulation is performed, such as cell 113, thereby suppressing the probability of occurrence of transmission and rejection of handover requests and the like, and suppressing the occurrence of a period during which the communication of the terminal device 121 is interrupted.

[0016] Further, the base station apparatus 101 may determine whether to perform handover based on the measurement report from the terminal device 121 without using a special CIO or a black cell list for suppressing handover, based on the regulation state in cell 112. For example, when the base station apparatus 101 receives a measurement report from the terminal device 121 corresponding to the satisfaction of handover conditions for a cell in the Barred state, the base station apparatus 101 does not transmit a handover request to that cell. Also, when the base station apparatus 101 receives a measurement report from the terminal device 121 communicating data of a specific AC corresponding to the satisfaction of handover conditions for a cell in the Reserved state that permits connection of that specific AC, the base station apparatus 101 may transmit a handover request to that cell. On the other hand, even if the base station apparatus 101 receives a measurement report from the terminal device 121 communicating data of an AC different from the specific AC corresponding to the satisfaction of handover conditions for that cell, the base station apparatus 101 may refrain from transmitting a handover request to that cell. Further, when the base station apparatus 101 receives a measurement report from the terminal device 121 corresponding to the satisfaction of handover conditions for a cell with a throughput rate set, the base station apparatus 101 may generate a random number and determine whether to transmit a handover request to that cell based on the generated random number and the throughput rate. For example, the base station apparatus 101 may generate a random number in the range from 0 to 1, transmit a handover request to the target cell when the random number is less than or equal to the throughput rate, and refrain from transmitting a handover request when the random number exceeds the throughput rate.

[0017] In the above example, the terminal device 121 acquires the restriction information in the cell 112 and notifies the base station device 101. However, the present invention is not limited to this. For example, the base station device 102 that provides the cell 112 may notify the base station device 101 of the restriction information. For example, when the X2 interface or the Xn interface is established between the base station device 101 and the base station device 102, the restriction information may be notified from the base station device 102 where the restriction is being performed to the base station device 101. Also, in a state where the X2 interface or the Xn interface is established between the base station device 101 and the base station device 102, when the base station device 102 starts the restriction or updates the restriction settings, the restriction information may be notified to the base station device 101 using a message indicating an update of the settings of the base station device or the like. Note that the base station device 102 may similarly notify the base station device 101 of the restriction information when ending the restriction.

[0018] In addition, an external device such as a server other than the base station device may be prepared so that information on whether or not a restriction is being performed in each cell and the content of the restriction is aggregated in the external device. For example, the base station device 102 may notify the external device that a restriction is being performed in the cell 112, and the base station device 101 may acquire the restriction information in the cell 112 from the external device. In one example, the base station device 102 provides the external device with information on adjacent cells adjacent to the cell 112 provided by the own device and restriction information in the cell 112 provided by the own device. The external device may provide the restriction information of the cell 112 to the base station device that provides each cell specified by the information on the adjacent cells in response to receiving the information. Note that the external device may provide the restriction information in each cell as a response to an inquiry from each base station device when receiving the inquiry. The base station device may, for example, periodically request the external device to provide the restriction information and acquire the restriction information in the adjacent cells of the cell provided by the own device. In this case, each base station device may provide information to the external device each time the restriction state of the cell provided by the own device is changed.

[0019] In addition, when each base station device receives information on the restriction of an adjacent cell from another base station device or an external device that provides the adjacent cell, it restricts handover to the cell where the restriction is being performed as described above. Note that the term "adjacent" in the present embodiment and the claims may be interpreted as an adjacent relationship in the adjacent cell list defined in the cellular communication standard, and the cells may not actually be adjacent or partially overlapping. That is, in a specific cell, the cells included in the adjacent cell list are treated as adjacent, and even if a specific cell and the list included in the list actually cover non-continuous geographical areas, these cells are treated as adjacent. By operating as described above, a handover request to a cell where a restriction is being performed is subject to the same restriction as a new connection to that cell by a terminal device in an unconnected state, so that the effect of the restriction can be sufficiently obtained, and the generation of transmission and reception of a handover request and a response message rejecting the request is suppressed.

[0020] (Device Configuration) FIG. 2 shows an example of the hardware configuration of each device according to this embodiment. In one example, each device includes a processor 201, a ROM 202, a RAM 203, a storage device 204, and a communication circuit 205. The processor 201 is a computer including one or more processing circuits such as a general-purpose CPU (central processing unit) or an ASIC (application-specific integrated circuit), and reads and executes programs stored in the ROM 202 and the storage device 204 to execute the overall processing of the device and each of the above-described processes. The ROM 202 is a read-only memory that stores information such as programs and various parameters related to the processes executed by each device. The RAM 203 functions as a workspace when the processor 201 executes a program, and is a random access memory that stores temporary information. The storage device 204 is configured by, for example, a removable external storage device or the like. The communication circuit 205 is configured by, for example, a circuit capable of communicating with other devices. For example, the communication circuit 205 of the terminal device and the base station device includes a baseband circuit, a radio frequency (RF) circuit, an antenna, etc. for providing a wireless interface capable of wireless communication compliant with a cellular communication standard. In addition, the communication circuit 205 of the base station device includes a circuit for wired or wireless communication that enables communication with other base station devices, network nodes, external devices, etc. Further, the communication circuit 205 of the external device includes a circuit for wired or wireless communication that enables communication with the base station device. Note that in FIG. 2, one communication circuit 205 is illustrated, but each device may have a plurality of communication circuits.

[0021] Figure 3 shows an example of the functional configuration of a terminal device. The terminal device includes, for example, a communication processing unit 301, a measurement unit 302, a reporting unit 303, and a handover processing unit 304. Note that these functions can be implemented, for example, by a processor 201 executing programs stored in a ROM 202 or a storage device 204. However, this is just an example, and the functions in Figure 3 may be realized by other configurations. Also, the functions shown in Figure 3 are just an example, and the function blocks shown in Figure 3 may be implemented integrally with other function blocks, or one function block may be divided into multiple function blocks. Further, some functions may be omitted, or additional functions may be added. For example, in Figure 3, only the functions particularly related to this embodiment among the functions of the terminal device are shown, and the terminal device naturally has the functions of a terminal device in a normal cellular communication system that are not shown in Figure 3.

[0022] The communication processing unit 301 performs processing for establishing a connection with any base station device and executing communication. The communication processing unit 301 performs communication settings based on the setting information notified from the connected base station device, and performs wireless communication with that base station device based on the settings. In one example, the setting information may include a setting for causing the terminal device to measure a wireless signal transmitted from another base station device (for example, in a frequency band different from the frequency band used in the communication with the currently connected base station device) in response to the electric field strength or wireless quality of the wireless signal transmitted from the connected base station device falling below a predetermined value. This setting may include, for example, information indicating a measurement period and a cycle (Measurement Gap (MG)). Also, this setting may include settings for the Active period and Inactive period of Connected Discontinuous Reception (CDRX). For example, the base station device can set the Active period and Inactive period of CDRX when establishing a connection with the terminal device, but when the above-mentioned electric field strength or wireless quality falls below a predetermined value, the Inactive period can be reset so that the terminal device can perform measurement of the wireless quality and decoding of system information for candidate cells (adjacent cells) of the handover destination, and the terminal device can be notified.

[0023] Based on the configuration information received by the communication processing unit 301, the measurement unit 302 measures a radio signal transmitted from another base station device different from the base station device currently connected. For example, the measurement unit 302 measures the RSRP or RSRQ based on the synchronization signal (PSS / SSS) transmitted from another base station device. Also, for example, when the measurement unit 302 receives a predetermined instruction from the base station device currently connected, it decodes the system information (such as MIB, SIB1, SIB2) in another base station device to obtain the regulation information. By decoding the system information, the measurement unit 302 can obtain the regulation information in the cell provided by another base station device. When the measurement unit 302 is not connected to any base station device, it can measure the synchronization signal transmitted in each cell and determine the cell to establish a connection by decoding the system information. The reporting unit 303 reports the measured radio quality to the base station device currently connected. Also, when the system information is obtained by the measurement unit 302, the reporting unit 303 reports the regulation information included in the system information to the base station device currently connected. These reports are transmitted to the base station device as a Measurement Report (MR). In one example, the regulation information may be reported in a message separate from the MR.

[0024] When the handover processing unit 304 receives the above-mentioned CIO from the connected base station apparatus, it determines whether or not the measurement result of the radio quality in the measurement unit 302 satisfies the conditions of the event based on the CIO. Then, in response to the conditions of the event being satisfied, the handover processing unit 304 controls the reporting unit 303 to transmit the MR to the base station apparatus. After that, the handover processing unit 304 transmits the MR by the reporting unit 303, and in response to receiving a handover instruction from the base station apparatus, executes a random access procedure with the base station apparatus of the handover destination to perform the handover. Note that this is an example. For example, the handover processing unit 304 may previously acquire setting information for connecting to a candidate base station apparatus of the handover destination from the connected base station apparatus, and perform the handover without transmitting the MR when the conditions of the event are satisfied. Note that when the handover processing unit 304 has acquired a black cell list from the connected base station apparatus, it performs processing so as not to execute a handover to a cell registered in the black cell list. For example, the handover processing unit 304 may control the measurement unit 302 so as not to measure the radio quality for cells registered in the black cell list.

[0025] FIG. 4 shows an example of the functional configuration of a base station apparatus. The base station apparatus includes, for example, a communication control unit 401, a measurement control unit 402, a regulation information acquisition unit 403, a handover control unit 404, and a regulation information notification unit 405. Note that these functions can be implemented, for example, by the processor 201 executing programs stored in the ROM 202 and the storage device 204. However, this is an example, and the functions in FIG. 4 may be realized by other configurations. Also, the functions shown in FIG. 4 are an example, and the function blocks shown in FIG. 4 may be implemented integrally with other function blocks, or one function block may be divided into a plurality of function blocks. Also, some functions may be omitted, or additional functions may be added. For example, in FIG. 4, only the functions particularly related to this embodiment among the functions of the base station apparatus are shown, and the base station apparatus naturally has the functions of a base station apparatus in a normal cellular communication system that are not shown in FIG. 4.

[0026] The communication control unit 401 controls communication with the terminal device. When connecting to the terminal device, the communication control unit 401 notifies the terminal device of the setting information to be used during communication, and communicates with the terminal device based on the setting information. In one example, the communication control unit 401 allocates radio resources to the terminal device during the period outside the MG period set for the terminal device and during the Active period of CDRX, and communicates using the allocated radio resources. The measurement control unit 402 performs control to cause the terminal device to perform measurements for handover, for example, on a terminal device whose radio field strength or radio quality from its own device has fallen below a predetermined level. For example, the measurement control unit 402 can control the communication control unit 401 to set at least one of the Active period and the Inactive period of MG and CDRX for the terminal device to enable at least one of the measurement of the radio signal transmitted from the base station device that is a candidate for the handover destination and the decoding of the system information transmitted from that base station device. Note that when it is not necessary to cause the connected terminal device to decode the system information in the adjacent cell (for example, when the connected terminal device can receive restriction information from the base station device or an external device in the adjacent cell), the measurement control unit 402 performs control so that the measurements related to the conventional handover are performed. Also, when causing the connected terminal device to decode the system information in the adjacent cell to collect restriction information, the measurement control unit 402 controls the communication control unit 401 to perform control such as instructing the terminal device to acquire (decode the system information) the restriction information.

[0027] The regulation information acquisition unit 403 collects information indicating the regulation status in each cell that is a candidate for the handover destination of the terminal device. For example, the regulation information acquisition unit 403 can collect the regulation information of adjacent cells by causing the terminal device to decode the system information of the adjacent cells to obtain the regulation information and then notifying the terminal device of the regulation information. In this case, the regulation information acquisition unit 403 controls, for example, the measurement control unit 402 to instruct the terminal device to acquire the regulation information. Then, the regulation information acquisition unit 403 can extract the regulation information from the radio signal received from the terminal device via the communication control unit 401. Also, the regulation information acquisition unit 403 can receive the regulation information from other base station devices that provide adjacent cells, for example, when establishing the X2 or Xn interface with other base station devices. In this case, for example, the regulation information is included and transmitted in the X2 SETUP REQUEST message or Xn SETUP REQUEST message transmitted from other base station devices. Then, the regulation information acquisition unit 403 can obtain the regulation information by receiving this message. Also, the regulation information acquisition unit 403 can receive the regulation information from other base station devices that provide adjacent cells with which the X2 or Xn interface has been established, using a message indicating an update of settings such as the base station device. In this case, for example, the regulation information is included and transmitted in the eNB Configuration Update message transmitted using the X2 interface from other base station devices or the NG-RAN Node Configuration Update message transmitted using the Xn interface. Also, the regulation information may be transmitted in the EN-DC Configuration Update message indicating an update of settings related to dual connectivity transmitted via the X2 interface. Then, the regulation information acquisition unit 403 can obtain the regulation information by receiving this message. Also, the regulation information acquisition unit 403 can obtain the regulation information of adjacent cells from an external device. For example, the regulation information acquisition unit 403 can obtain the regulation information about adjacent cells by receiving information periodically provided from the external device.Further, the regulation information acquisition unit 403 can, for example, request information from an external device and acquire regulation information about adjacent cells in response to the request.

[0028] The handover control unit 404 controls handover by the terminal device. For example, based on the regulation information of the adjacent cell acquired by the regulation information acquisition unit 403, the handover control unit 404 sets the CIO and the black cell list and notifies the terminal device so that the handover to the adjacent cell is regulated. Also, for example, based on the regulation information of the adjacent cell, the handover control unit 404 may determine whether to hand over the terminal device to the adjacent cell when the radio quality of the adjacent cell in the terminal device satisfies a predetermined condition. That is, even when the radio quality of the adjacent cell in the terminal device satisfies a predetermined condition, for example, when the adjacent cell is in the Barred state, the handover control unit 404 does not transmit a handover request to the base station device providing the adjacent cell. Also, even when the radio quality of the adjacent cell in the terminal device satisfies a predetermined condition, for example, when the AC of the data that the terminal device attempts to communicate is not a specific AC and the adjacent cell is in the Reserved state that allows connection only for the specific AC, the handover control unit 404 does not transmit a handover request to the base station device providing the adjacent cell. Further, the handover control unit 404 can transmit a handover request to the base station device providing the adjacent cell only in some cases where a specific condition is satisfied so that a certain throughput indicated by the regulation information is achieved.

[0029] When the regulation information notification unit 405 exchanges regulation information between base station apparatuses of adjacent cells and sets regulations for the cells provided by its own apparatus, it notifies the base station apparatus of the adjacent cell or an external apparatus of the regulation information indicating the content of the regulation. For example, when starting, changing, or ending a regulation, if the X2 or Xn interface is not established with another base station apparatus providing an adjacent cell, the regulation information notification unit 405 transmits the regulation information to the other base station apparatus using a message for establishing the interface. Also, when starting, changing, or ending a regulation, if the X2 or Xn interface is established with another base station apparatus providing an adjacent cell, the regulation information notification unit 405 may transmit the regulation information to the other base station apparatus using a message for updating the setting of the interface. Further, the regulation information notification unit 405 can provide regulation information to an external apparatus when starting, changing, or ending a regulation, or periodically. Note that when the regulation information of an adjacent cell is collected by a report from a terminal apparatus, the regulation information notification unit 405 may be omitted.

[0030] FIG. 5 shows a functional configuration example of an external apparatus used for exchanging regulation information between base station apparatuses. The external apparatus includes, for example, a regulation information collection unit 501 and a regulation information providing unit 502. Note that these functions can be implemented, for example, by a processor 201 executing programs stored in a ROM 202 and a storage device 204. However, this is just an example, and the functions in FIG. 5 may be realized by other configurations. Also, the functions shown in FIG. 5 are just an example, and the functional blocks shown in FIG. 5 may be implemented integrally with other functional blocks, or one functional block may be divided into a plurality of functional blocks. Further, some functions may be omitted, or additional functions may be added. The external apparatus can be implemented using a general-purpose server in one example.

[0031] The regulation information collection unit 501 collects regulation information in the cells provided by each base station device. This regulation information can be provided from each base station device, for example, periodically or when the regulation in each cell starts, changes, or ends. Note that the regulation information can be provided together with information specifying the cell (or the base station device providing the cell) to which the regulation information is to be provided. That is, each base station device can recognize information on adjacent cells adjacent to the cells provided by the device itself either by the operation of the network operator or by using a function for automatically discovering adjacent cells (Automatic Neighbor Relation (ANR)). Then, the base station device can provide information indicating the recognized adjacent cells to an external device as information specifying the cell to which the regulation information is to be provided. The regulation information providing unit 502 provides the regulation information collected by the regulation information collection unit 501 to the base station device that provides the adjacent cells associated with the regulation information. Note that the regulation information providing unit 502 may provide the regulation information to the base station device when a request from the base station device is received. In this case, information indicating which cell's regulation information is requested may be included in the request message, and the regulation information providing unit 502 may provide the regulation information about the requested cell to the requesting base station device as a response. Also, the regulation information providing unit 502 may extract the regulation information about all the cells having the cell provided by the requesting base station device as an adjacent cell, and provide the extracted regulation information to the requesting base station device.

[0032] (Flow of processing) Next, an example of the processing flow executed in the wireless communication system according to the present embodiment will be described. FIG. 6 shows an example of the processing flow when the terminal device receives system information including restriction information in an adjacent cell adjacent to the cell to which the terminal device is connected, and the restriction information is notified to the base station device that provides the cell to which the terminal device is connected from the terminal device. FIGS. 7 and 8 show examples of the processing flow when restriction information is transmitted and received between the base station device that provides the cell to which the terminal device is connected and the base station device that provides an adjacent cell adjacent to the cell. Further, FIG. 9 shows an example of the processing flow when the base station device that provides the cell to which the terminal device is connected acquires the restriction information of the base station device that provides an adjacent cell adjacent to the cell via an external device. In these processes, the terminal device is connected to one of the base station devices. For example, when the electric field strength or radio quality in the connected base station device falls below a predetermined level, the connected base station device instructs the terminal device to measure other cells. Here, in FIGS. 6 to 9, the connected base station device is shown as the source base station device for handover, and the base station device that provides an adjacent cell adjacent to the cell provided by the base station device is shown as the target candidate base station device for handover. In addition, each message in the following description uses, as an example, the name of a message used in a Long Term Evolution (LTE) and a core network that accommodates LTE. However, it can be naturally replaced with a similar message in a network after the fifth generation (5G). For example, the RRC Connection Reconfiguration message and the RRC Connection Reconfiguration Complete message described later can be replaced with the RRC Reconfiguration message and the RRC Reconfiguration Complete message in a 5G network, respectively. Also, the E-UTRAN Cell Global Identifier (ECGI) can be replaced with the NR Cell Global Identifier (NCGI) in a 5G network.

[0033] The source base station device that provides the cell to which the terminal device is connected transmits, using the RRC Connection Reconfiguration message, configuration information for measurements of other cells to the terminal device (S601). This configuration information may include, for example, configuration information on the length and period of the MG, and information indicating the active period and inactive period of the reconfigured CDRX. At this time, the base station device performs the configuration of the MG and the CDRX so that the terminal device can collect the regulation information in other base station devices. Further, the base station device may instruct the terminal device to collect the regulation information of adjacent cells from the system information transmitted from other base station devices, together with or separately from this configuration information. The terminal device may operate so as not to collect the regulation information of adjacent cells unless it receives an instruction from the base station device. According to this, by enabling the collection of the regulation information of adjacent cells only in a specific terminal device, it is possible to avoid the base station device obtaining the same information from an unnecessarily large number of terminal devices. Also, the terminal device may collect the regulation information of adjacent cells without receiving an explicit instruction from the base station device. According to this, the base station device can control the handover based on accurate regulation information at the time of handover of each terminal device. When the terminal device receives the configuration information, it returns an RRC Connection Reconfiguration Complete message to the base station device (S602).

[0034] Thereafter, the terminal device performs measurements of radio quality, decoding of system information, etc. For example, during the MG period specified by the configuration information, the terminal device measures radio signals transmitted in other cells using a frequency band different from the frequency band used in the currently connected cell. Also, the terminal device measures radio signals transmitted in other cells using the frequency band used in the currently connected cell at times when no communication is being performed. For example, the terminal device measures the synchronization signal (PSS / SSS) (S603). By this measurement, the terminal device can identify the radio quality and electric field strength of the synchronization signal, and further identify the physical cell identifier (PCI) by detecting the sequence used in the synchronization signal. The terminal device can further obtain the system information of an adjacent cell, for example, when the Inactive period of CDRX is set during the period when the system information of the adjacent cell is transmitted. Here, when the conventional ANR is used, the terminal device can measure the E-UTRAN cell global identifier (ECGI) of SIB1. In the present embodiment, the terminal device can obtain not only the ECGI but also regulation information indicating the regulations being performed in that cell from the system information (MIB, SIB1, SIB2, etc.). In the example of FIG. 6, the terminal device can check whether the adjacent cell is in the Barred state or the Reserved state by decoding the SIB1 transmitted from the base station device of the adjacent cell (handover destination candidate base station device) (S604). Also, the terminal device can obtain the throughput information set in the adjacent cell by decoding the SIB2 transmitted by the base station device of the adjacent cell (S605). In one example, when the terminal device confirms that the adjacent cell is in the Barred state, it may not need to check further system information. That is, when a specific regulation is being performed and other regulation information does not exist or is uniquely specified, the decoding process for specifying information regarding other regulations may be omitted. When the terminal device obtains the regulation information, it transmits the MR including the regulation information to the currently connected base station device (S606). Note that the regulation information may be notified to the currently connected base station device separately from the MR.The base station device can collect regulation information of adjacent cells adjacent to the cell provided by the device itself by receiving notifications from one or more terminal devices. In one example, the base station device may list and hold the regulation information in each of the adjacent cells, and sequentially update the list based on reports from the terminal devices to identify the regulation state in each adjacent cell in real time.

[0035] Then, the base station device controls the handover of the terminal device based on the collected regulation information. For example, the base station device sets the CIO and the black cell list so that handover to an adjacent cell where regulation is being performed does not occur, and notifies the terminal device (S607). For example, the base station device may transmit an RRC Connection Reconfiguration message including the CIO and the black cell list to the terminal device. When the terminal device receives the setting information, it transmits an RRC Connection Reconfiguration Complete message to the base station device (S608), and performs execution control of subsequent measurement and reporting. In one example, the base station device may transmit the CIO set to the maximum value in association with the PCI to the terminal device. Thereby, the terminal device will not transmit an MR that triggers a handover to the adjacent cell unless the radio quality of the adjacent cell corresponding to the PCI is extremely high compared to the radio quality of the currently connected cell, or unless the radio quality of the currently connected cell falls below a predetermined level and the radio quality of the adjacent cell corresponding to the PCI is not extremely high. Also, when the terminal device is notified that the PCI of the adjacent cell is registered in the black cell list, the terminal device will not transmit an MR for the cell corresponding to the PCI. Thereby, it is possible to prevent the terminal device from handing over to the cell corresponding to the PCI. Note that the base station device may set a CIO regardless of whether regulation is being performed in the adjacent cell and notify the terminal device. In this case, an MR for the adjacent cell is transmitted from the terminal device to the base station device, but when the base station device receives this MR, it may determine whether to transmit a handover request to the base station device of the adjacent cell based on the regulation information. Also, the base station device may notify the terminal device of throughput information, and the terminal device may transmit an MR with a probability corresponding to the throughput.

[0036] As described above, in the example of FIG. 6, the restriction information of the neighboring cells measured by the terminal device is aggregated by the base station device. As a result, the base station device can collect the restriction information in the neighboring cells adjacent to the cell provided by the device itself, and based on the restriction information, it can appropriately control the handover of the connected terminal device. In the above-described embodiment, an example is shown in which the terminal device provides the restriction information of the neighboring cell to the connected base station device. However, the provision of this information does not necessarily have to be performed. That is, when the terminal device acquires the restriction information of the neighboring cell, it may perform control so that a handover to the neighboring cell is not performed based on the restriction information. For example, when restrictions are imposed in a neighboring cell, the terminal device may autonomously control not to transmit the MR for that neighboring cell. Since the MR is not transmitted, the handover to the neighboring cell is not performed, and a handover request from the base station device to which the terminal device is connected to the base station device of the neighboring cell is not made either. Therefore, even by such autonomous control in the terminal device, the handover of the terminal device can be appropriately controlled based on the restriction information.

[0037] FIGS. 7 and 8 show an example in which, between two base station devices whose provided cells are adjacent to each other, the restriction information in those cells is exchanged via the X2 / Xn interface.

[0038] FIG. 7 shows an example in which regulatory information is exchanged in an X2 SETUP REQUEST message when establishing an X2 interface between a source base station apparatus for handover and a candidate base station apparatus for the handover destination (S701). In the examples of FIGS. 7 and 8, regulation is not performed in the cell provided by the source base station apparatus for handover, and an example is shown in which regulatory information is provided only from the candidate base station apparatus for the handover destination. However, this is just an example, and regulatory information may also be provided from the source base station apparatus for handover. In one example, the source base station apparatus for handover may include, in an X2 SETUP RESPONSE message (S702), regulatory information in the cell provided by the own apparatus and provide it to the candidate base station apparatus for the handover destination. Further, for example, the source base station apparatus for handover may transmit an X2 SETUP REQUEST message not including regulatory information to the candidate base station apparatus for the handover destination, and the candidate base station apparatus for the handover destination may transmit the regulatory information included in the X2 SETUP RESPONSE message to the source base station apparatus for handover. Note that similar information exchange may be performed in the message when establishing the Xn interface.

[0039] FIG. 8 shows an example of a processing flow when start, change, or end of regulation occurs in a candidate base station apparatus for the handover destination after the X2 / Xn interface is established. In this case, regulatory information is notified as information on update of the setting of the base station apparatus from the candidate base station apparatus for the handover destination to a base station apparatus (for example, the source base station apparatus for handover) that provides an adjacent cell adjacent to the cell provided by the base station apparatus (S801). When receiving this information notification, the source base station apparatus for handover transmits a response message (S802). Note that FIG. 8 shows an example in the case where the X2 interface is established, but similar information exchange may be performed in the message in the case where the Xn interface is established.

[0040] The base station apparatus at the handover source can obtain the restriction information in each of one or more adjacent cells adjacent to the cell provided by the own apparatus from other base station apparatuses that are the providers of the one or more adjacent cells, by means of the processing as shown in FIG. 7 or FIG. 8. Then, as described above with reference to FIG. 6, the base station apparatus at the handover source can control the handover of the terminal apparatus based on the restriction information.

[0041] FIG. 9 shows that the restriction information is aggregated in an external apparatus different from the base station apparatus at the handover source and the candidate base station apparatuses at the handover destination (S901), and the restriction information is notified from the external apparatus to the base station apparatuses that provide adjacent cells for the cell where the restriction is being performed (S902). In FIGS. 7 and 8, the base station apparatus directly provides the restriction information to other base station apparatuses, whereas in FIG. 9, the restriction information is provided via the external apparatus. Note that each base station apparatus provides the restriction information to the external apparatus, for example, in response to the start, change, or end of the restriction for the cell it provides. Further, the restriction information is provided to the external apparatus together with information capable of specifying adjacent cells for the cell where the restriction is being performed. Then, the external apparatus provides the restriction information to each base station apparatus that provides adjacent cells for the cell for which the restriction information has been provided. Note that this is an example, and each base station apparatus may transmit a message for requesting the restriction information by designating adjacent cells to the external apparatus. In this case, the external apparatus may respond to the message to provide whether or not there is restriction information for the designated cell, and if so, the restriction information, to the base station apparatus that is the requester of the restriction information.

[0042] Thereby, the base station apparatus at the handover source can obtain the restriction information in each of one or more adjacent cells adjacent to the cell provided by the own apparatus via the external apparatus. Note that by using the external apparatus as shown in FIG. 9, it becomes possible to exchange restriction information even between base station apparatuses between which the X2 / Xn interface is not established. Then, as described above with reference to FIG. 6, the base station apparatus at the handover source can control the handover of the terminal apparatus based on the restriction information.

[0043] As described above, in this embodiment, in the base station device that provides the cell to which the terminal device is connected, restriction information about adjacent cells adjacent to the cell is collected, and considering the restrictions of the adjacent cells, the handover of the terminal device can be controlled. As a result, a handover request to a restricted cell is subject to the same restrictions as a new connection to that cell by a terminal device in an unconnected state, so that the effect of the restriction can be sufficiently obtained, and the generation of transmission and reception of a handover request and a response message rejecting the request is suppressed. Also, a handover to a non-restricted cell is performed without transmitting a handover request that is likely to be rejected to the base station device that provides the restricted cell, so that the cell to which the terminal device is connected can be smoothly switched. As a result, the probability that the communication of the terminal device is interrupted can be reduced. Therefore, it becomes possible to contribute to Goal 9 of the Sustainable Development Goals (SDGs) led by the United Nations, "Build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0044] The invention is not limited to the above-described embodiment, and various modifications and changes are possible within the scope of the gist of the invention.

Claims

1. A base station apparatus, comprising: an acquisition means for acquiring regulation information regarding regulation of connection in a second cell provided by another base station apparatus that provides a second cell adjacent to a first cell provided by the base station apparatus; a control means for controlling handover of a terminal apparatus being connected via the first cell to the second cell based on the regulation information; The base station apparatus characterized by comprising the above.

2. The regulation information is provided from the other base station apparatus to an external apparatus different from the base station apparatus and the other base station apparatus, and the acquisition means acquires the regulation information from the external apparatus. The base station apparatus according to claim 1, characterized by the above.

3. The regulation information is provided by the other base station apparatus to the external apparatus together with information on an adjacent cell adjacent to the second cell, and the acquisition means acquires the regulation information transmitted from the external apparatus to the base station apparatus based on the information on the adjacent cell. The base station apparatus according to claim 2, characterized by the above.

4. The acquisition means directly acquires the regulation information from the other base station apparatus. The base station apparatus according to claim 1, characterized by the above.

5. When an X2 interface or an Xn interface is not established between the acquisition means and the other base station apparatus, in a message received from the other base station apparatus when establishing the X2 interface or the Xn interface, or when the X2 interface or the Xn interface is established between the acquisition means and the other base station apparatus, in a message indicating updating of settings of the other base station apparatus via the X2 interface or the Xn interface, the acquisition means acquires the regulation information. The base station apparatus according to claim 4, characterized by the above.

6. The regulation information is information indicating that another terminal apparatus not connected to any base station apparatus is in a Barred state where it does not request connection to the second cell regardless of an access class (AC) or a Reserved state where only the other terminal apparatus communicating data of a specific AC requests connection to the second cell, or includes traffic rate information indicating a probability that the other terminal apparatus requests connection to the second cell. The base station apparatus according to claim 1, characterized by the above.

7. The control means, For the second cell in the Barred state, the other terminal device does not transmit a handover request to the other base station device regardless of the AC of the data transmitted by the other terminal device. For the second cell in the Reserved state, when the data communicated by the other terminal device is the specific AC, a handover request is transmitted to the other base station device, and when the data communicated by the other terminal device is not the specific AC, a handover request is not transmitted to the other base station device. For the second cell, when the throughput rate is set, a handover request is transmitted to the other base station device with a probability corresponding to the throughput rate. The base station device according to claim 6, wherein at least any one of the above controls is performed.

8. The control means notifies the terminal device of a Cell Individual Offset (CIO) set to a value at which the probability of handover to the second cell for which the regulation is performed is low, or includes the second cell in a black cell list that is a list of cells for which transmission of a measurement report by the terminal device is not performed, and notifies the terminal device of the black cell list. The base station device according to claim 1, characterized in that.

9. A base station device, A base station device, characterized by having a providing means for providing regulation information regarding connection regulation in a first cell provided by the base station device to another base station device that provides a second cell adjacent to the first cell.

10. The providing means provides the regulation information to an external device different from the base station device and the other base station device. The regulation information is provided from the external device to the other base station device. The base station device according to claim 9, characterized in that.

11. The providing means provides information on adjacent cells adjacent to the first cell to the external device together with the regulation information. The regulation information is provided from the external device to the other base station device based on the information on the adjacent cells. The base station device according to claim 10, characterized in that.

12. The providing means directly provides the regulation information to the other base station device. The base station device according to claim 9, characterized in that.

13. The base station apparatus according to claim 12, wherein the providing means provides the restriction information in a message transmitted to the other base station apparatus when establishing an X2 interface or an Xn interface when the X2 interface and the Xn interface are not established with the other base station apparatus, or in a message indicating updating the settings of the base station apparatus via the X2 interface or the Xn interface when the X2 interface or the Xn interface is established with the other base station apparatus.

14. The base station apparatus according to claim 9, wherein the restriction information is information indicating that another terminal device not connected to any base station apparatus is in a Barred state where it does not request connection to the first cell regardless of the access class (AC), or a Reserved state where only the other terminal device communicating data of a specific AC requests connection to the first cell, or includes traffic rate information indicating the probability that the other terminal device requests connection to the first cell.

15. The base station apparatus according to claim 9, wherein the providing means provides the restriction information to the other base station apparatus when starting the restriction, when the restriction is changed, and when ending the restriction in the first cell.

16. A control method executed by a base station apparatus, comprising: obtaining restriction information regarding connection restriction in a second cell provided by another base station apparatus that provides the second cell adjacent to the first cell provided by the base station apparatus; controlling handover of a terminal device connected via the first cell to the second cell based on the restriction information; A control method characterized by comprising the above.

17. A control method executed by a base station apparatus, comprising: providing restriction information regarding connection restriction in the first cell provided by the base station apparatus to another base station apparatus that provides the second cell adjacent to the first cell.

18. A program for causing a computer to function as each means of the base station apparatus according to any one of claims 1 to 15.

Images