Terminal device, 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 terminal device decodes system information transmitted from a second base station apparatus that provides a second cell adjacent to a first cell offered by a currently connected first base station apparatus, acquires restriction information concerning connection restrictions in the second cell, and provides this restriction information to the first base station apparatus.SELECTED DRAWING: Figure 6

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 that cell can perform such a restriction, for example, for preventing or alleviating congestion of a backhaul line or the base station device itself. Such restrictions include, for example, Barred in which the connection of all terminal devices is restricted, and Reserved in which the connection of terminal devices is restricted except for those that transmit data of a specific access class. Also, for example, a throughput 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 a terminal device in an unconnected state connects to any cell, the terminal device does not connect to, for example, a cell in the Barred state, and does not connect to a cell in the Reserved state if the access class of the data transmitted by the device itself is not a specific access class. Also, the terminal device can determine whether to attempt a connection to a cell with a set throughput according to the throughput.

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 providing 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 cell for the handover destination 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 cell for the handover destination. In that case, the base station device that provides the cell for the handover destination may reject the handover request. In this case, for example, by handing over the terminal device to another cell where the regulation is not performed, the connection of the terminal device can be maintained, but the time until the terminal device finally completes the handover may be prolonged. Also, if the handover request is accepted in the cell where the regulation is performed, it may not be 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 technology that enables appropriate execution of handover of a terminal device in an environment where there is a cell subject to regulation.

[0005] A terminal device according to an aspect of the present invention includes communication means for communicating with a first base station device during connection, acquisition means for decoding system information transmitted from a second base station device that provides a second cell adjacent to a first cell provided by the first base station device and acquiring regulation information regarding connection regulation in the second cell, and provision means for providing the regulation information to the first base station device via the communication means.

[0006] A base station device according to an aspect of the present invention is a base station device that provides a first cell, and includes communication means for connecting to a terminal device in the first cell and performing communication, and obtaining means for obtaining, from the terminal device, regulation information regarding connection regulation in a second cell included in system information transmitted from another base station device that provides the second cell adjacent to the first cell, and control means for controlling handover of the terminal device to the second cell based on the regulation information.

Advantages of the Invention

[0007] According to the present invention, it becomes possible to appropriately execute handover of a terminal device in an environment where there is a cell in which regulation is performed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

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 to 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 redundant descriptions are omitted.

[0010] (System Configuration) FIG. 1 shows a configuration example of a wireless communication system according to this 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 is configured to include base station devices 101 to 103 and terminal devices 121 to 122. Here, base station device 101 provides cell 111, base station device 102 provides cell 112, and base station device 103 provides cell 113. Also, terminal device 121 has established a connection with cell 111 (base station device 101) and is assumed to move in the directions of cell 112 and cell 113. Terminal device 122 is assumed to be staying 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 apparatus 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 apparatus 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, for example, when the AC of the communication target data is a predetermined AC, the terminal device 122 requests a connection to the cell 112, and when the AC of the communication target data is other than the predetermined AC, the terminal device 122 does not request a connection to the cell 112. 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), a terminal device 122 in an unconnected state that is not connected to any base station apparatus 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 the probability is q (0 < q < 1), a terminal device 122 in an unconnected state that is not connected to any base station apparatus 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, for signaling, a regulation of 5% (throughput rate 95%) can be performed, and for data, a regulation of 40% (throughput rate 60%) can be performed.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 a plurality of regulations are set according to each AC or each type of terminal device, different regulation times may be set for each of the plurality of 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. Therefore, 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 result 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 cause the terminal device 121 to hand over to the cell 113, for example, 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 restrictions are imposed on a handover destination candidate. In one example, even while the terminal device 121 is connected to the base station device 101, the terminal device 121 can acquire information on restrictions in a cell of a handover destination candidate (for example, cell 112). For example, the base station device 101 makes settings so that the terminal device 121 can receive 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 system information (such as MIB, SIB1, and SIB2) transmitted from the base station device 102. The terminal device 121 acquires the restriction state 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 restrictions are imposed 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 if 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 if the AC of that data is the 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 stipulated 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 becomes significantly higher than that of cell 111. For this reason, the base station device 101 can set the predetermined level to the maximum value for cell 112 in the Barred state. Similarly, by increasing the second predetermined value of Event A5, handover will not be performed unless the radio quality of cell 112 becomes extremely high. For this reason, the base station device 101 can set the second predetermined value to the maximum value for cell 112 in the Barred state. Incidentally, hereinafter, the above-mentioned predetermined level and the second predetermined value may be referred to as Cell Individual Offset (CIO). Further, the base station device 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 will not perform measurement (report) on the cells registered in the black cell list, so that handover to that cell 112 will not be performed. Further, the base station device 101 provides the terminal device 121 with throughput information, 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 device 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 device 101. By these controls, the base station device 101 can greatly suppress the probability of causing the terminal device 121 to hand over to cell 112 where restrictions are in place.In addition, the base station apparatus 101 controls to preferentially execute handover of the terminal apparatus 121 to another cell where no regulation such as cell 113 is performed, thereby suppressing the probability of occurrence of transmission and rejection of handover requests, etc., and making it possible to suppress the occurrence of a period during which the communication of the terminal apparatus 121 is interrupted.

[0016] In addition, the base station apparatus 101 may determine whether to perform handover based on the measurement report from the terminal apparatus 121, without using a special CIO or 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 apparatus 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 apparatus 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 apparatus 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 apparatus 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 an X2 interface or an 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 performed to the base station device 101. Further, in a state where an X2 interface or an 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 setting, the restriction information may be notified to the base station device 101 using a message indicating an update of the setting 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 an 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. In response to receiving the information, 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. Note that the external device may provide the restriction information in each cell as a response to an inquiry received from each base station device. The base station device may, for example, periodically request the external device to provide restriction information and acquire the restriction information in 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 regulation 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 regulation is being performed as described above. Note that the term "adjacent" in the present embodiment and the claims may be interpreted as the 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 being adjacent, and even if the specific cell and the list included in the list actually cover non - continuous geographical areas, these cells are treated as being adjacent. By the above - described operation, a handover request to a cell where regulation is being performed is subject to the same regulation as a new connection to that cell by a terminal device in an unconnected state, so that the effect of the regulation 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 work space 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. Also, 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 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 information indicating, for example, 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 measure the wireless quality and decode 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 connected base station device. 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 connected base station device, 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 connected base station device. 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 connected base station device. 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 device, 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 device. Thereafter, 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 device, executes a random access procedure with the base station device 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 device of the handover destination from the connected base station device, 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 device, 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 not to perform radio quality measurement for cells registered in the black cell list.

[0025] Figure 4 shows an example of the functional configuration of a base station device. The base station device 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 functional blocks shown in FIG. 4 may be implemented integrally with other functional blocks, or one functional block may be divided into a plurality of functional blocks. Also, some functions may be omitted, or additional functions may be added. For example, in FIG. 4, only the functions particularly related to the present embodiment among the functions of the base station device are shown, and the base station device naturally has the functions of a base station device 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, for example, 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 there is no need to cause the connected terminal device to decode the system information in the adjacent cell (for example, when regulation information can be received from the base station device or external device in the adjacent cell), the measurement control unit 402 performs control so that measurements related to conventional handover are performed. Also, when causing the connected terminal device to decode the system information in the adjacent cell to collect regulation 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 regulation 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 another base station device that provides an adjacent cell, for example, when establishing the X2 or Xn interface with the other base station device. 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 another base station device. 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 another base station device that provides an adjacent cell for which the X2 or Xn interface has been established, using a message indicating an update of the settings of the base station device or the like. In this case, for example, the regulation information is included and transmitted in the eNB Configuration Update message transmitted using the X2 interface from another base station device or the NG-RAN Node Configuration Update message transmitted using the Xn interface from another base station device. Also, the regulation information may be transmitted in the EN-DC Configuration Update message indicating an update of the 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 an external device.In addition, 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 the 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 black cell list and notifies the terminal device so that the handover to the adjacent cell is regulated. Further, 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 satisfies a predetermined condition in the terminal device. That is, even when the radio quality of the adjacent cell satisfies a predetermined condition in the terminal device, the handover control unit 404 does not transmit a handover request to the base station device providing the adjacent cell, for example, when the adjacent cell is in the Barred state. Also, even when the radio quality of the adjacent cell satisfies a predetermined condition in the terminal device, the handover control unit 404 does not transmit a handover request to the base station device providing the adjacent cell, 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. 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, when the processor 201 executes programs stored in the ROM 202 and the 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 identifying 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 (Automatic Neighbor Relation (ANR)) that automatically discovers adjacent cells. Then, the base station device can provide information indicating the recognized adjacent cells as information identifying the cell to which the regulation information is to be provided to an external device. 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, the request message may include information indicating which cell's regulation information is requested, and the regulation information providing unit 502 may provide the regulation information on the requested cell to the requesting base station device as a response. Also, the regulation information providing unit 502 may extract the regulation information on all 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. 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. Note that 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, setting information for the measurement of other cells to the terminal device (S601). This setting information may include, for example, setting 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 setting of the MG and the setting of 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 the adjacent cells from the system information transmitted from other base station devices together with or separately from this setting information. The terminal device may operate so as not to collect the regulation information of the adjacent cells unless it receives an instruction from the base station device. According to this, by making the collection of the regulation information of the adjacent cells be performed only in a specific terminal device, it is possible to avoid the base station device from obtaining the same information from an unnecessarily large number of terminal devices. Further, the terminal device may collect the regulation information of the 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 setting information, it returns an RRC Connection Reconfiguration Complete message to the base station device (S602).

[0034] After that, the terminal device executes measurement of radio quality, decoding of system information, etc. For example, the terminal device measures a radio signal transmitted in another cell using a frequency band different from the frequency band used in the currently connected cell during the period of the MG specified by the setting information. Also, the terminal device measures a radio signal transmitted in another cell using the frequency band used in the currently connected cell at a timing 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 the regulation information indicating the regulations being performed in the 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). Note that, 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 specific regulations are being performed and there is no other regulation information or it is uniquely specified, the decoding process for specifying information on other regulations may be omitted. When the terminal device acquires 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 status 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 controls the execution of subsequent measurements and reports. 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 an 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 regulation information of the adjacent cells measured by the terminal device is aggregated in the base station device. As a result, the base station device can collect the regulation information in the adjacent cells adjacent to the cell provided by the device itself, and based on the regulation information, can appropriately control the handover of the connected terminal device. Note that, in the above-described embodiment, an example is shown in which the terminal device provides the regulation information of the adjacent cells to the base station device during connection, but this information may not necessarily be provided. That is, when the terminal device acquires the regulation information of the adjacent cells, the terminal device may perform control so that handover to the adjacent cells is not performed based on the regulation information. For example, when regulation is performed in an adjacent cell, the terminal device may autonomously perform control so as not to transmit MR for the adjacent cell. Since MR is not transmitted, handover to the adjacent 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 adjacent cell is not made either. Therefore, even by such autonomous control in the terminal device, the handover of the terminal device can be appropriately performed based on the regulation information.

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

[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 of a handover and a candidate base station apparatus of a handover destination (S701). In the examples of FIGS. 7 and 8, although an example is shown in which regulation is not performed in a cell provided by the source base station apparatus of the handover and regulatory information is provided only from the candidate base station apparatus of the handover destination, this is merely an example, and regulatory information may also be provided from the source base station apparatus of the handover. In one example, the source base station apparatus of the handover may include regulatory information in the cell provided by its own apparatus in an X2 SETUP RESPONSE message (S702) and provide it to the candidate base station apparatus of the handover destination. Further, for example, the source base station apparatus of the handover may transmit an X2 SETUP REQUEST message not including regulatory information to the candidate base station apparatus of the handover destination, and the candidate base station apparatus of the handover destination may transmit the regulatory information included in the X2 SETUP RESPONSE message to the source base station apparatus of the handover. Note that similar information exchange may be performed in a message when establishing an 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 of a handover destination after the X2 / Xn interface is established. In this case, regulatory information is notified from the candidate base station apparatus of the handover destination as information on updating the settings of the base station apparatus to a base station apparatus (for example, the source base station apparatus of the handover) that provides an adjacent cell adjacent to the cell provided by the base station apparatus (S801). When receiving the notification of this information, the source base station apparatus of the handover transmits a response message (S802). Note that FIG. 8 shows an example in which the X2 interface is established, but similar information exchange may be performed in a message when the Xn interface is established.

[0040] The base station apparatus of the handover source can obtain the restriction information in each of one or more adjacent cells adjacent to the cell provided by the apparatus itself from other base station apparatuses that are the providers of the one or more adjacent cells, by the processes as shown in FIG. 7 or FIG. 8. Then, as described above with reference to FIG. 6, the base station apparatus of 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 device different from the base station apparatus of the handover source and the candidate base station apparatus of the handover destination (S901), and the restriction information is notified from the external device to the base station apparatus that provides 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 an external device. Note that each base station apparatus provides the restriction information to the external device, 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 device together with information that can identify adjacent cells for the cell where the restriction is being performed. Then, the external device provides the restriction information to each base station apparatus that provides adjacent cells for the cell for which the restriction information was provided. Note that this is an example, and each base station apparatus may transmit a message requesting the restriction information by designating adjacent cells to the external device. In this case, the external device may respond to the message to indicate whether there is restriction information for the designated cell, and if so, provide the restriction information to the base station apparatus that requested the restriction information.

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

[0043] As described above, in the present embodiment, in the base station device that provides the cell to which the terminal device is connected, the restriction information about the 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 will be subject to the same restrictions as in the case of 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 the handover request and the response message rejecting the request is suppressed. Also, for the base station device that provides the restricted cell, the handover to a non-restricted cell is performed without transmitting a handover request that is likely to be rejected, so that the cell to which the terminal device is connected can be smoothly switched. As a result, the probability of the communication of the terminal device being 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 terminal device, comprising: communication means for communicating with a first base station device in connection; acquisition means for decoding system information transmitted from a second base station device that provides a second cell adjacent to a first cell provided by the first base station device, and acquiring regulation information regarding connection regulation in the second cell; providing means for providing the regulation information to the first base station device via the communication means; A terminal device characterized by comprising the above.

2. The regulation information is information indicating that another terminal device not connected to any base station device is in a Barred state where it does not request connection to the second cell regardless of access class (AC), or a Reserved state where only the other terminal device of a specific AC requests connection to the second cell, or traffic rate information indicating the probability that the other terminal device requests connection to the second cell. The terminal device according to Claim 1, characterized by including this.

3. The communication means receives from the first base station device at least one setting of a Measurement Gap corresponding to the timing of the system information of the second cell and an Active period and an Inactive period of Connected Discontinuous Reception. The terminal device according to Claim 1, characterized by this.

4. When an instruction to acquire the regulation information is received from the first base station device by the communication means, the acquisition means decodes the system information for acquiring the regulation information of the second cell, and when the instruction is not received, does not decode the system information for acquiring the regulation information of the second cell. The terminal device according to Claim 1, characterized by this.

5. A base station device that provides a first cell, comprising: communication means for connecting to and communicating with a terminal device in the first cell; acquisition means for acquiring regulation information regarding connection regulation in a second cell included in system information transmitted from another base station device that provides a second cell adjacent to the first cell from the terminal device; control means for controlling handover of the terminal device to the second cell based on the regulation information; A base station device characterized by comprising the above.

6. The restriction information indicates that another terminal device not connected to any base station device is in a Barred state where it does not request connection to the second 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 second cell, or includes traffic rate information indicating the probability that the other terminal device requests connection to the second cell. The base station device according to claim 5, characterized in that.

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 traffic rate is set, a handover request is transmitted to the other base station device with a probability corresponding to the traffic rate. The base station device according to claim 6, characterized in that it performs at least one of the above controls.

8. The control means notifies the terminal device of a Cell Individual Offset (CIO) set to a value that reduces the probability of handover to the second cell for the second cell subject to the restriction, or includes the second cell in a black cell list that is a list of cells for which transmission of measurement reports by the terminal device is not performed, and notifies the terminal device of the black cell list. The base station device according to claim 5, characterized in that.

9. The communication means transmits to the terminal device at least one of a setting of a Measurement Gap corresponding to the timing of the system information of the second cell and an Active period and an Inactive period of Connected Discontinuous Reception. The base station device according to claim 5, characterized in that.

10. The base station apparatus according to claim 5, wherein the acquisition means acquires the restriction information from the terminal device by transmitting an instruction to acquire the restriction information to the terminal device by the communication means.

11. A control method executed by a terminal device, decoding system information transmitted from a second base station device that provides a second cell adjacent to a first cell provided by a first base station device during connection, and acquiring restriction information regarding restriction of connection in the second cell; providing the restriction information to the first base station device; A control method characterized by including the above.

12. A control method executed by a base station device that provides a first cell, acquiring, from a terminal device connected in the first cell, restriction information regarding restriction of connection in a second cell included in system information transmitted from another base station device that provides the second cell adjacent to the first cell; controlling handover of the terminal device to the second cell based on the restriction information; A control method characterized by including the above.

13. A program for causing a computer to function as each means included in the terminal device according to any one of claims 1 to 4.

14. A program for causing a computer to function as each means included in the base station device according to any one of claims 5 to 10.

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