Terminal device, base station device, control method, and program for realizing power saving in communication systems

Abstract

To provide a base station device, a terminal device, a control method, and a program that efficiently operate a power-saving function by stopping transmission of SSB and SIB1.SOLUTION: In a wireless communication network in which a communication service is provided to a terminal device using at least one of a plurality of cells, a first base station device notifies the terminal device existing in a cell provided by the first base station device of information about a second cell (anchor cell) to which system information is transmitted that has been suspended in a first cell (power-saving cell) when transmission of system information is suspended in the first cell (power saving cell) of the plurality of cells.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a control technique for realizing wireless communication with low power consumption. [Background technology]

[0002] In the Third Generation Partnership Project (3GPP (registered trademark)), reducing network power consumption is being discussed as an important issue. Non-Patent Document 1 proposes that power saving be achieved by stopping the transmission of at least a portion of a Synchronization Signal / Physical Broadcast Channel block (SSB) and System Information Block Type 1 (SIB1), which have conventionally been always transmitted for each component carrier (CC), in some CCs. Non-Patent Document 1 also proposes that information for connecting to a CC for which transmission of at least a portion of SSB and SIB1 has been stopped be transmitted in another CC. Note that throughout this embodiment, "CC" may be read as "cell." [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] 3GPP contribution, R1-2203173 Summary of the Invention [Problem to be solved by the invention]

[0004] At present, it is not clear how to operate the power saving function described above, and technology for operating it efficiently is required. [Means for solving the problem]

[0005] The present invention provides a technology for efficiently operating a power saving function by stopping transmission of SSBs and SIB1s in some cells.

[0006] According to one aspect of the present invention Terminal The device is In a wireless communication network in which a communication service is provided to a terminal device using at least one of a plurality of cells, the terminal device comprises: an acquisition means for acquiring information on whether a power saving function for stopping transmission of system information is enabled for each of neighboring cells adjacent to a serving cell in which the terminal device is located; and a transmission means for transmitting a request message to a base station device that provides the power saving cell, requesting the suspension of the power saving function, when the wireless quality of a signal transmitted in the power saving cell in which the power saving function is enabled satisfies a movement condition of the serving cell. .

[0007] According to one aspect of the present invention base station The device is A base station device in a wireless communication network in which a communication service is provided to a terminal device using at least one of a plurality of cells, the base station device comprising: an acquisition means for acquiring information from one or more neighboring base stations that respectively provide one or more neighboring cells adjacent to a cell provided by the base station device, as to whether a power saving function for stopping transmission of system information is enabled in the neighboring base stations; and a notification means for notifying a terminal device located in the cell provided by the base station device of the information acquired by the acquisition means as to whether the power saving function is enabled in the neighboring base stations. . [Effects of the Invention]

[0008] According to the present invention, it is possible to efficiently operate the power saving function by stopping the transmission of SSB and SIB1. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a wireless communication network. [Figure 2] FIG. 10 is a diagram illustrating an example of information notified to a terminal device. [Figure 3] FIG. 2 illustrates an example of a hardware configuration of the apparatus. [Figure 4] FIG. 2 is a diagram illustrating an example of a functional configuration of a base station device. [Figure 5] FIG. 2 is a diagram illustrating an example of a functional configuration of a terminal device. [Figure 6] FIG. 1 is a diagram illustrating an example of a flow of processing executed in a wireless communication network. [Figure 7] FIG. 1 is a diagram illustrating an example of a flow of processing executed in a wireless communication network. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention as claimed, and not all combinations of features described in the embodiments are necessarily essential to the invention. Two or more of the features described in the embodiments may be combined in any desired manner. Furthermore, the same reference numerals are used to designate identical or similar components, and redundant descriptions will be omitted.

[0011] (Network configuration) FIG. 1 shows an example of the configuration of a wireless communication network according to this embodiment. This wireless communication network is, for example, a cellular communication system that complies with the cellular communication standard of the Third Generation Partnership Project (3GPP (registered trademark)). The wireless communication network is configured to include, for example, base station devices 101 to 103 and a terminal device 121, and one of the plurality of base station devices establishes a connection with the terminal device 121 to provide a wireless communication service. Here, for example, it is assumed that the base station device 101 provides a first cell 111, the base station device 102 provides a second cell 112, and the base station device 103 provides a third cell 113. Note that the "cell" here may be interpreted as a component carrier (CC). Here, the first cell 111 to the third cell 113 may be provided using different frequencies (CCs) or may be provided using the same CC. Note that, for simplicity of explanation, FIG. 1 shows only three base station devices and one terminal device, but it goes without saying that there may be many base station devices and many terminal devices. Furthermore, one base station device can provide multiple cells (multiple CCs). Also, one base station device may provide multiple cells (CCs) using radio transceivers located at different locations. Note that multiple base station devices may be configured to communicate with each other to exchange control information via, for example, an Xn interface or an S1 interface.

[0012] Conventionally, the base station devices 101 to 103 are configured to transmit a Synchronization Signal / Physical Broadcast Channel block (SSB) and a System Information Block Type 1 (SIB1) in each of a plurality of cells (CC). That is, in each cell, the SSB and SIB1 are transmitted periodically without fail. Therefore, the base station devices 101 to 103 consume power to transmit the SSB and SIB1.

[0013] In response to this, as described in Non-Patent Document 1, by not transmitting SSB or SIB1 in the second cell (CC) but transmitting connection information for the second cell (for example, Master Information Block (MIB) or SIB1) in a first cell different from the second cell, it is possible to reduce power consumption in the second cell. On the other hand, in this case, when searching for a connection destination in the second cell, the terminal device 121 does not transmit MIB, SIB1, etc. in the second cell, and therefore, if only the radio signal of this second cell is observed, it is not possible to perform standby in the second cell or establish a connection. In other words, unless the terminal device 121 performs an observation process in the first cell from which the MIB and SIB1 of the second cell are transmitted, it is not possible to acquire information about the second cell and is not possible to perform standby in the second cell or establish a connection.

[0014] Here, for example, it is assumed that the base station device 102 has stopped transmitting system information such as MIB and SIB1 in the second cell 112. In this case, the terminal device 121 may need to observe radio signals transmitted in a large number of cells in order to identify other cells transmitting MIB and SIB1 for the second cell 112. For this reason, if a large number of cells are provided around the terminal device 121, it may take a long time for the terminal device 121 to acquire information on the second cell 112. For example, in FIG. 1, if the terminal device 121 does not know in which of the first cell 111 and the third cell 113 the system information whose transmission has been stopped in the second cell 112 is being transmitted, it needs to observe radio signals transmitted from the base station device in each cell.

[0015] In view of such circumstances, in this embodiment, the terminal device 121 is notified of information about a cell transmitting system information, the transmission of which has been stopped in the second cell 112, in the cell in which the terminal device 121 is camped. For example, it is assumed that the terminal device 121 is in the first cell 111, and that system information (MIB or SIB1) for the second cell 112 is being transmitted in the third cell 113. At this time, information is provided in the first cell 111 that enables the terminal device 121 to identify that the system information for the second cell is being transmitted in the third cell 113. This information may include, for example, information indicating a cell having a power saving function that stops the transmission of system information. This information may be provided as information in which, for example, information for identifying a cell, such as a physical cell identity or a cell identity, is associated with information indicating the presence or absence of a power saving function. In the example of FIG. 1 , the identifier of the second cell 112 and information indicating that the second cell 112 has a power saving function are associated with each other and notified to the terminal device 121 in the first cell 111. This information may also include, for example, information indicating whether the function is enabled in a cell that has such a power saving function. For example, in one example, it may be assumed that the first cell 111 has a power saving function but has not enabled the power saving function. In this case, information associating the identification information of the first cell 111, the fact that the first cell 111 has the power saving function, and the fact that the power saving function is disabled may be notified to the terminal device 121 from the first cell 111.

[0016] Furthermore, this information includes information indicating a cell that provides system information when transmission is stopped by the power saving function. This information may be, for example, frequency information. In one example, system information of a cell in which the power saving function is enabled may be provided in all cells of a specific frequency. In this case, information indicating the specific frequency may be provided as information indicating a cell that provides system information when transmission is stopped by the power saving function. In this case, identification information of the specific cell may not be included. For example, information on the frequency at which the third cell 113 provides may be notified in the second cell 112 as information indicating the third cell 113 that provides system information whose transmission is stopped. The information indicating the frequency may be an ARFCN (Absolute Radio Frequency Channel Number). In addition to or instead of the frequency information, identification information that identifies an individual cell may be provided as information indicating a cell that provides system information whose transmission is stopped. Note that there may be multiple cells that provide system information whose transmission is stopped, and only frequency information may be notified in some of the cells, and cell identification information may be notified in other of the cells. Note that the third cell 113 may also provide the information notified by the first cell 111 as described above. That is, the third cell 113 is also notified that the second cell 112 has a power saving function, the function is enabled in the second cell 112, and the system information whose transmission has been stopped in the second cell 112 will be provided in the third cell 113.

[0017] FIG. 2 shows an example of information to be provided. Note that, hereinafter, a cell that provides system information whose transmission has been stopped may be referred to as an "anchor cell." In the example of FIG. 2, the first cell 111 has a power saving function but is not shown to have the power saving function enabled. Also, when the power saving function is enabled in the first cell 111 and transmission of system information is stopped, the system information is provided in the cell of ARFCN0. Here, the cell of ARFCN0 (not shown) is provided with system information in the case where transmission has been stopped in all cells included in the area in which this information is provided. As the first anchor cell, only frequency information may be notified. Therefore, information identifying a specific cell may not be included. Furthermore, as the system information, for example, identification information of the third cell 113 of ARFCN1 may be notified as the second anchor cell. In one example, it may be assumed that the system information whose transmission has been stopped is not provided in cells other than the third cell 113 of ARFCN1 in the cell of ARFCN1. In this case, cell identification information may be notified as anchor cell information. Note that only cell identification information may be notified, and frequency information may not be notified. Note that, because the power saving function is not enabled, the system information of the first cell 111 is transmitted in the first cell 111 and is not usually transmitted in the anchor cell. However, this is just an example, and the system information may be provided in the anchor cell even if the power saving function is not enabled. Also, in the example of FIG. 2, it is shown that the second cell 112 has a power saving function and that the power saving function is enabled. It is also shown that the anchor cell of the second cell 112 is the same as the anchor cell of the first cell 111. Since the power saving function is enabled in the second cell 112, the system information is provided in the anchor cell. In the example of FIG. 2, it is shown that the third cell 113 does not have a power saving function. Therefore, the power saving function is not enabled in the third cell 113, and an anchor cell is not set.

[0018] Note that, for example, in the first cell 111, information excluding information about the first cell 111 may be notified to the terminal device 121. Similarly, in the third cell 113, information excluding information about the third cell 113 may be notified to surrounding terminal devices. Naturally, information including information about the first cell 111 may be notified in the first cell 111, and information including information about the third cell 113 may be notified in the third cell 113. Note that, although FIG. 2 shows information about only three cells, this is not limiting. That is, the information notified to the terminal device in each cell includes information about surrounding cells of that cell (and information about those cells as necessary). Therefore, when there are many surrounding cells, information about those many cells is notified. Note that the surrounding cells may be only neighboring cells, or may include cells other than neighboring cells within a certain distance range.

[0019] When the terminal device receives this information, it acquires the information in the anchor cell when acquiring system information for which transmission is stopped for the second cell 112. In one example, if the cell in which the terminal device is located is the anchor cell, the terminal device receives the information in that cell. On the other hand, if the cell in which the terminal device is not located is the anchor cell, the terminal device may move to the anchor cell and receive the information in the anchor cell.

[0020] Here, a method will be described for a terminal device to acquire system information whose transmission has been stopped in another cell (hereinafter referred to as a "power-saving cell") that has a power-saving function and in which the power-saving function is enabled, when the cell in which the terminal device is located is an anchor cell. The anchor cell may, for example, periodically transmit the system information whose transmission has been stopped by broadcast. In this case, the anchor cell may transmit the cell identifier of the power-saving cell in association with the system information whose transmission has been stopped, such as the MIB and SIB1 of the power-saving cell. Note that the anchor cell may transmit part or all of SIBx (x≧2) other than SIB1 in addition to the MIB and SIB1. The anchor cell may also transmit scheduling information (SI-SchedulingInfo) of the SIB of the power-saving cell. The terminal device can recognize which of the MIB, SIB1, or SIBx (x≧2) of the power-saving cell is to be broadcast, using the schedulingInfoList included in the SI-SchedulingInfo provided together with the identification information of the power-saving cell. Then, the terminal device can receive the transport block in which each piece of information is transmitted and receive the MIB or SIB as needed. Note that the base station device of the anchor cell broadcasts the MIB or SIB of the power-saving cell set to "Broadcasting" in the schedulingInfoList. On the other hand, the base station device of the anchor cell does not broadcast the MIB or SIB of the power-saving cell set to "notBroadcasting" in the schedulingInfoList.

[0021] When the base station device of the anchor cell receives a request signal from a terminal device for MIBs and SIBs of a power-saving cell that have been set to "notBroadcasting" in the schedulingInfoList, the base station device of the anchor cell can provide the information to the terminal device. The request signal can be, for example, an RRCSystemInfoRequest message, which is a message of the radio resource control (RRC) layer. The terminal device can request the base station device to acquire system information that has been set to "notBroadcasting" in the schedulingInfoList, using the RRCSystemInfoRequest message. The base station device of the anchor cell may not broadcast all of the MIBs and SIBs of the power-saving cell. In this case, when the terminal device acquires the identification information of the power-saving cell and a schedulingInfoList in which all of the MIBs and SIBs are set to "notBroadcasting," it can receive the MIBs and SIBs by transmitting a request signal specifying the system information that the terminal device should request to receive.

[0022] Furthermore, when establishing a connection with a terminal device, the base station device of the anchor cell may provide the terminal device with system information about the energy-saving cells that has not been transmitted. For example, when the terminal device transitions from the RRC_Idle state to the RRC_Connected state in the anchor cell, the base station device of the anchor cell may provide the terminal device with system information about the energy-saving cells that has not been transmitted, for example, by an individual RRC message. The terminal device may request the anchor cell to provide system information that is indicated to be not broadcast in the SI-SchedulingInfo (set to "notBroadcasting") by transmitting a UEInformationRequest. The base station device of the anchor cell may provide the system information about the energy-saving cells that has not been broadcast, using dedicatedSIB1-Delivery and dedicatedSystemInformationDelivery included in the UEInformationResponse. Note that the anchor cell may function as an anchor cell for multiple energy-saving cells. In this case, the terminal device may acquire system information that has not been transmitted in the multiple energy-saving cells from the base station device of the anchor cell. For example, the terminal device may request the anchor cell for each of the plurality of power-saving cells by an individual RRC message such as UEInformationRequest. The terminal device may obtain the necessary information by transmitting, for example, a request signal that associates the identification information of the power-saving cell with the type of system information to be requested to the base station device of the anchor cell.

[0023] As described above, when a cell in which the terminal device is not located is an anchor cell, the terminal device can move to the anchor cell and receive information from the anchor cell. Here, the terminal device may, for example, move to the anchor cell to acquire information before determining to perform cell reselection to the power-saving cell, or may move to the anchor cell to acquire information after determining to perform cell reselection to the power-saving cell.

[0024] For example, it is assumed that the terminal device 121 recognizes, based on a signal received in the serving cell 111, that the second cell 112 has a power saving function and has enabled the function, and that the anchor cell of the second cell 112 is the third cell 113. In this case, even if the measurement result of the radio signal of the second cell 112, which is the power saving cell, does not satisfy a predetermined condition such as a condition for cell selection or cell reselection, the terminal device may measure the radio quality of the SSB and SIB of the third cell 113, which is the anchor cell. Then, when the measurement result of the SSB and SIB of the third cell 113 satisfies a predetermined condition (for example, when the radio quality is sufficiently good), the terminal device may decode the SSB and SIB of the third cell 113 and acquire system information of the second cell 112. Furthermore, when multiple anchor cells are designated, the terminal device may identify one anchor cell among the anchor cells that satisfies a certain condition, and decode the SSB and SIB transmitted by that cell. Here, the first cell 111 may notify the terminal device of the timing of receiving information transmitted by the third cell 113, which is the anchor cell. The terminal device receives a signal transmitted by the third cell 113 while remaining within the coverage area of ​​the first cell 111. Note that the terminal device stops receiving signals in the first cell 111 and performs reception processing for information transmitted by the third cell 113 at the reception timing notified by the first cell 111. For this reason, the first cell 111 may instruct the reception timing so that the terminal device receives information from the anchor cell at a timing other than when the terminal device transmits a paging signal. Furthermore, when the terminal device receives an instruction to receive information from the anchor cell at the timing when the terminal device transmits a paging signal, the terminal device may determine whether to receive a paging signal or receive information from the anchor cell.

[0025] Note that the terminal device 121 is configured to receive a value indicating the priority of cell selection from the first cell 111 in which it is located, as in the past. When the radio quality of the first cell 111 in which it is located deteriorates below a predetermined reference level, the terminal device 121 measures the radio quality of a neighboring cell that has a lower priority than the first cell 111 in which it is located. Here, for example, depending on the relationship between the priority of the second cell 112 in a power saving state and the priority of the third cell 113 that is the anchor cell, a situation may arise in which only the radio signal of the second cell 112 in a power saving state is measured, and the radio signal of the third cell 113 that is the anchor cell is not measured. For example, if the priority of the second cell 112 is equal to or higher than the priority of the first cell 111 and the priority of the third cell 113 is lower than the priority of the first cell 111, and the radio quality of the first cell 111 is not equal to or lower than a predetermined value, the second cell 112 is measured, but the third cell 113 is not measured. In this case, the terminal device 121 can measure some signals transmitted from the second cell 112, but does not measure the third cell 113. Therefore, it can be assumed that the terminal device 121 cannot obtain system information for which transmission has been stopped in the second cell 112. For this reason, in this embodiment, for example, the terminal device may be configured to measure the anchor cell when starting measurement of the power-saving cell, regardless of the priority of the anchor cell. Also, the terminal device may change the priority of the anchor cell instructed by the base station device to the priority of the power-saving cell. This makes it possible to ensure that the terminal device can obtain system information about the power-saving cell when measurement of the power-saving cell is performed. Note that priority information is notified to the terminal device by SIB2, SIB3, SIB4, or cellReselectionPriority specified in an RRC Release message.

[0026] The terminal device may decode the SSBs and SIBs of the anchor cell regardless of the radio quality of the synchronization signal and SSBs of the anchor cell. In one example, the terminal device may start decoding the SSBs and SIBs of the anchor cell when the radio quality of the power-saving cell satisfies a criterion for cell reselection. If the terminal device attempts to decode the SSBs and SIBs regardless of the radio quality of the anchor cell and fails to decode the information, the terminal device may re-acquire and decode the information after a certain period of time has elapsed. Furthermore, if the terminal device fails to complete the reception process of the system information of the power-saving cell in the anchor cell a certain number of times consecutively or over a certain period of time, the terminal device may exclude the power-saving cell associated with the anchor cell from the targets for cell selection and cell reselection. The certain number of times or the certain period of time may be notified to the terminal device by the first cell 111 in which the terminal device is located. If there are multiple anchor cells, the terminal device may use another anchor cell other than the anchor cell whose information decoding failed as the anchor cell for the power-saving cell.

[0027] Furthermore, the terminal device may attempt to decode SSBs and SIBs of the third cell 113, which is the anchor cell, when a measurement result of a radio signal of the second cell 112, which is a power-saving cell, satisfies a predetermined condition such as a condition for cell selection or cell reselection. That is, when the terminal device determines the second cell 112 as a destination cell by cell selection or cell reselection, the terminal device may attempt to decode SSBs and SIBs in the third cell 113. Note that the measurement result of the radio signal of the second cell 112 satisfies a predetermined condition, but the terminal device may attempt to decode SSBs and SIBs in the third cell 113 before determining the second cell 112 as a destination cell by cell selection or cell reselection. Furthermore, the terminal device may decode SSBs and SIBs of the third cell 113 when both the measurement result of the radio signal of the second cell 112, which is a power-saving cell, and the measurement result of the radio signal of the third cell 113, which is the anchor cell, satisfy a predetermined condition. For example, the terminal device may decode the SSBs and SIBs of the third cell 113 when the second cell 112 meets the conditions for cell selection or cell reselection and the radio quality is sufficiently good to enable decoding of the SSBs and SIBs of the third cell.

[0028] In one example, the terminal device measures the radio quality of the second cell 112 in a power saving state, and may further measure the radio quality of the third cell 113, which is the anchor cell of the second cell 112, regardless of the radio quality. Then, when the second cell 112 satisfies the cell change condition, if the radio quality of the third cell 113 is equal to or greater than a predetermined threshold, the terminal device decodes the SSBs and SIBs of the third cell 113. On the other hand, when the radio quality of the radio signal of the third cell 113 is equal to or less than the predetermined threshold, the terminal device does not decode the SSBs and SIBs of the third cell 113. Thereafter, when the radio quality of the radio signal of the third cell 113 becomes equal to or greater than a predetermined threshold while the second cell 112 still satisfies the cell change condition, the terminal device may decode the SSBs and SIBs of the third cell 113. Note that the predetermined threshold here may be notified to the terminal device by the first cell 111 in which the terminal device is located. This makes it possible to prevent the terminal device from wasting power by performing unnecessary decoding processes in situations where the radio quality of the third cell 113 is poor and there is a high probability of failure in decoding SSBs or SIBs of the third cell 113.

[0029] The terminal device may not decode the SSBs and SIBs of the third cell 113, which is the anchor cell, before the second cell 112, which is the power-saving cell, meets the criteria for cell selection or cell reselection. That is, the terminal device may start receiving the SSBs of the third cell 113, which is the anchor cell, and decode the SIBs, in response to the radio quality of the second cell 112 meeting the criteria for cell selection or cell reselection. The terminal device attempts to decode the SSBs and SIBs of the third cell 113, on the condition that the second cell 112 meets the moving conditions of the serving cell. If a predetermined period of time has elapsed without the terminal device successfully decoding the SSBs and SIBs of the third cell 113, the terminal device may decide not to select the second cell 112 as the moving destination cell for cell selection or cell reselection. Furthermore, even before the predetermined period has elapsed, if the second cell 112 becomes a state in which the movement conditions of the serving cell are not satisfied (for example, the radio quality does not satisfy a standard) before the terminal device has successfully decoded the SSBs and SIBs of the third cell 113, the terminal device may decide not to select the second cell 112 as a destination cell for cell selection or cell reselection. In this case, the terminal device stops the reception process of the system information of the second cell 112 in response to a change in the state of the second cell 112 after starting the reception process of the system information of the second cell 112. Furthermore, the terminal device may decide not to select the second cell 112 as a destination cell for cell selection or cell reselection if the number of attempts to decode the SSBs or SSBs of the third cell 113 reaches a predetermined number without successful decoding, or if the second cell 112 changes to a state in which the movement conditions of the serving cell are not satisfied before the number of attempts to decode reaches the predetermined number. The predetermined period or the predetermined number of times can be notified to the terminal device from the base station device of the first cell 111, for example.

[0030] The condition for moving a serving cell due to cell selection or cell reselection is that there is a cell among neighboring cells whose wireless quality is equal to or greater than a certain value within a certain period of time, and the terminal device recognizes a cell that satisfies this condition as a candidate cell for cell reselection. Triggered by measurements of neighboring cells or serving cells, the terminal device ranks cells that satisfy the cell moving condition based on the priority of cell selection and wireless quality such as reference signal received power (RSRP). The higher the priority and the higher the wireless quality, the higher the rank is set. The terminal device then starts cell reselection to the cell with the highest rank. The terminal device acquires the above-mentioned certain period as Treselection and the above-mentioned certain value as Thresh from the serving cell.

[0031] In addition, if the terminal device does not retain information about the power-saving cell for which the power-saving cell has stopped transmission, such as when the serving cell is not an anchor cell, the terminal device may request the network to disable the power-saving function in the power-saving cell in order to obtain necessary information directly from the power-saving cell rather than the anchor cell. For example, if the wireless quality of a signal transmitted from the power-saving cell satisfies the movement condition of the serving cell, the terminal device transmits a message to the base station device of the serving cell requesting that the power-saving function in the power-saving cell be disabled. Upon receiving the message, the base station device of the serving cell transmits a message to the base station device providing the power-saving cell requesting that the power-saving function be disabled. Here, the terminal device generally starts measuring the wireless quality of a cell with a lower cell selection priority than the serving cell when a certain level of quality degradation is confirmed in the serving cell. At this time, if the cell selection priority of the power-saving cell is specified to be lower than that of the serving cell, the terminal device may request that the power-saving function of the power-saving cell be disabled when it confirms degradation in the wireless quality of the serving cell and starts measuring the wireless quality of the power-saving cell. If the terminal device has previously stored information for transmitting an uplink signal to the energy-saving cell, the terminal device may transmit a request message to the energy-saving cell instead of to the serving cell. Also, the terminal device may collectively request the suspension of the energy-saving functions of multiple energy-saving cells by using one uplink signal (for example, one RRC message such as RRCSystemInfoRequest).

[0032] When the base station device of the power-saving cell receives the request to stop the power-saving function, it determines whether to resume transmission of system information such as MIB and SIB1 that it had stopped transmitting. If it determines to resume transmission of the system information, it notifies the base station device of the neighboring cell that the power-saving function has been stopped. Note that the neighboring cell here may be the cell in which the terminal device that transmitted the request to stop the power-saving function is located. The neighboring cell here may also include, for example, an anchor cell. However, this is not limited thereto, and the base station device may notify all base station devices that have notified the terminal device that the power-saving function is enabled or that indicate the anchor cell (information such as that shown in FIG. 2) that the power-saving function has been stopped. When the base station device of the serving cell receives the notification to stop the power-saving function from the power-saving cell, it changes the information on the enabled state of the power-saving function of the power-saving cell in the information such as that shown in FIG. 2 and starts transmitting the changed information. By receiving this information, the terminal device can identify that the power-saving cell has stopped the power-saving function and started operating as a normal cell. Furthermore, a notification indicating that the power-saving cell has stopped its power-saving function may be separately transmitted to the terminal device. The terminal device can receive system information for the cell from the cell whose power-saving function has been stopped. Meanwhile, the base station device of the anchor cell may stop distributing the system information for the power-saving cell. However, this is not limited thereto, and the base station device of the anchor cell may continue distributing the system information for the power-saving cell.

[0033] If the base station device of the power-saving cell determines not to resume transmission of system information, the base station device of the serving cell of the terminal device that transmitted the request signal may transmit, for example, information that can specify that the request will be rejected or that the power-saving function will be maintained in an enabled state to the base station device of the serving cell of the terminal device that transmitted the request signal or the terminal device. In this case, the terminal device may acquire system information of the power-saving cell from the anchor cell as described above. The terminal device may also determine not to make the power-saving cell a target for cell selection or cell reselection. In this case, the terminal device may exclude the power-saving cell from targets for cell selection or cell reselection for a predetermined period of time. If the terminal device does not receive a notification that the system information transmission will be resumed for a predetermined period of time after transmitting the above-mentioned request signal, the terminal device may determine that the power-saving function has been maintained and acquire system information of the power-saving cell from the anchor cell. That is, if the terminal device does not receive a notification that the system information transmission will be resumed for a predetermined period of time after transmitting the above-mentioned request signal, the terminal device may perform the same processing as when it has received information that can specify that the request will be rejected or that the power-saving function will be maintained in an enabled state.

[0034] In addition, the base station device of the power-saving cell may determine to stop the power-saving function and resume transmission of system information when it receives a predetermined number of requests to stop the power-saving function from multiple terminal devices within a predetermined period. However, this is just one example, and the decision on whether to stop the power-saving function may be made based on other criteria. For example, the base station device of the power-saving cell may determine not to stop the power-saving function when the percentage of the period during which the power-saving function was enabled within the predetermined period is equal to or less than a predetermined value.

[0035] Furthermore, when a terminal device moves to a cell that has transitioned from a power-saving cell to a normal cell (by performing cell reselection to that cell) and has completed receiving necessary broadcast information in that cell, the terminal device may request the base station device of that cell to enable the power saving function. In this case, upon receiving the request to enable the power saving function, the base station device of that cell determines whether to enable the power saving function. If the base station device of that cell determines to enable the power saving function, it enables the power saving function and stops transmitting at least part of the system information that it had been transmitting. The base station device of that cell also notifies the base station device of a neighboring cell, such as the cell in which the terminal device was located before cell reselection, that the power saving function has been enabled. Based on the received information, the base station device of the neighboring cell updates the information, as shown in FIG. 2, that is to be notified to the terminal device, to indicate that the power saving function has been enabled in the cell that transmitted the information, and transmits the updated signal. In this way, the terminal device can efficiently acquire system information of each cell while achieving power saving throughout the system.

[0036] The information shown in FIG. 2 may be transmitted, for example, in each cell in which a power saving function is not being executed, using any one of System Information Block Type 2 (SIB2), System Information Block Type 3 (SIB3), or System Information Block Type 4 (SIB4). Conventionally, a terminal device receives SIB2 to SIB4 transmitted from a base station device in a cell in which the terminal device is located to acquire information about neighboring cells. This neighboring cell information may be used to notify the presence or absence of the power saving function, the activation status of the function, anchor cell information, and the like. Upon acquiring this neighboring cell information, the terminal device measures the wireless quality of the neighboring cell based on the information. For example, the neighboring cell information may include information about cell selection priority, and the terminal device may periodically measure the wireless quality of neighboring cells with a higher cell selection priority than the serving cell, and may measure the wireless quality of neighboring cells with a lower cell selection priority than the serving cell only when the wireless quality of the serving cell has deteriorated to a threshold or lower.

[0037] (Device configuration) An example of the hardware configuration of a base station apparatus and a terminal apparatus will be described using FIG. 3. In one example, the base station apparatus and the terminal apparatus include a processor 301, a ROM 302, a RAM 303, a storage device 304, and a communication circuit 305. The processor 301 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 executes the overall processing of the apparatus and each of the above-mentioned processes by reading and executing programs stored in the ROM 302 and the storage device 304. The ROM 302 is a read-only memory that stores information such as programs and various parameters related to the processing executed by the base station apparatus and the terminal apparatus. The RAM 303 functions as a workspace when the processor 301 executes the program and is a random access memory that stores temporary information. The storage device 304 is, for example, a removable external storage device. The communication circuit 305 is, for example, a circuit for LTE or 5G wireless communication. Although FIG. 3 illustrates one communication circuit 305, the base station apparatus and the terminal apparatus may have multiple communication circuits. For example, a base station apparatus and a terminal apparatus may have a common antenna as well as wireless communication circuits for LTE and 5G. The base station apparatus and the terminal apparatus may also have separate antennas for LTE and 5G. The base station apparatus may also have a wired communication circuit used when communicating with other base station apparatuses or nodes in the core network. The terminal apparatus may also have a communication circuit for other wireless communication networks, such as a wireless LAN. The base station apparatus and the terminal apparatus may have separate communication circuits 305 for each of a plurality of available frequency bands, or may have a common communication circuit 305 for at least some of these frequency bands.

[0038] FIG. 4 is a diagram illustrating an example of the functional configuration of a base station device. The base station device includes, for example, a cell information acquisition unit 401, a cell information notification unit 402, and a system information provision unit 403. Note that FIG. 4 illustrates only functions particularly related to this embodiment, and does not illustrate various other functions that the base station device may have. For example, the base station device naturally has other functions that LTE and 5G base station devices generally have. The functional blocks in FIG. 4 are illustrated schematically, and each functional block may be integrated or further subdivided. Each function in FIG. 4 may be realized, for example, by the processor 301 executing a program stored in the ROM 302 or the storage device 304, or by a processor within the communication circuit 305 executing predetermined software. The details of the processes performed by each functional unit will not be described here, and only their general functions will be outlined.

[0039] The cell information acquisition unit 401 exchanges with neighboring cells information on whether the base station device itself supports a power saving function, whether the power saving function is enabled if the power saving function is supported, and information on the anchor cell when the power saving function is enabled. For example, the base station device of the first cell 111 acquires information from the base station device of the second cell 112 that the power saving function is supported and enabled in the second cell 112, and that the anchor cell is the third cell 113. The base station device of the first cell 111 may also receive a notification from the base station device of the third cell 113 that the third cell 113 does not support the power saving function. The base station device of the first cell 111 may also notify the base station devices of the second cell 112 and the third cell 113 of information that the first cell 111 supports but does not enable the power saving function, and that the anchor cell when the power saving function is enabled is the third cell 113. Note that at least some of this information may be acquired by each base station device by, for example, being preset by a telecommunications carrier, rather than by information exchange between base station devices. In one example, information indicating whether the power saving function is supported and information about the anchor cell may be preset, and only information indicating whether the power saving function is enabled may be exchanged between base station devices. The preset setting by the telecommunications carrier may be notified to each base station device via a network, for example, from a predetermined control device (not shown).

[0040] The cell information notification unit 402 aggregates the information acquired by the cell information acquisition unit 401 and notifies the terminal device of the aggregated information. The information notified here is, for example, information as shown in Fig. 2. Furthermore, the cell information notification unit 402 can further notify information indicating the priority of each neighboring cell for the terminal device to perform cell selection / cell reselection, as in the conventional case.

[0041] The system information providing unit 403 not only provides information such as the MIB and SIB of the cell provided by the own device, but also provides system information such as the MIB and SIB whose transmission has been stopped in the power-saving cell when the cell provided by the own device serves as an anchor cell for other cells. Note that the system information providing unit 403 may transmit only the system information of the cell provided by the own device when the system information providing unit 403 is not functioning as an anchor cell for the power-saving cell. Furthermore, when the power-saving function is used in the own device, the system information providing unit 403 may stop transmission of some system information and transmit only some signals, such as synchronization signals.

[0042] FIG. 5 is a diagram illustrating an example of the functional configuration of a terminal device. The terminal device includes, for example, an information acquisition unit 501 and a cell selection processing unit 502. Note that FIG. 5 illustrates only functions particularly related to this embodiment, and various other functions that the terminal device may have are omitted from the illustration. For example, the terminal device naturally has other functions that LTE and 5G terminal devices generally have. The functional blocks in FIG. 5 are illustrated schematically, and each functional block may be integrated or further subdivided. Each function in FIG. 5 may be realized, for example, by the processor 301 executing a program stored in the ROM 302 or the storage device 304, or may be realized by a processor within the communication circuit 305 executing predetermined software. Details of the processes performed by each functional unit will not be described here, and only their general functions will be outlined.

[0043] The information acquisition unit 501 acquires various information such as system information from surrounding base station devices. The information acquisition unit 501 acquires, for example, system information transmitted from a base station device of a serving cell. The information acquisition unit 501 also acquires system information of cells adjacent to the serving cell. Here, the information acquisition unit 501 acquires, for example, from the base station device of the serving cell, information indicating whether one or more neighboring cells have a power saving function, whether the power saving function is enabled if the neighboring cells have the power saving function, and information that can identify an anchor cell to which system information is transmitted if the power saving function is enabled. Then, when acquiring system information for a power saving cell that has a power saving function and has the power saving function enabled, the information acquisition unit 501 acquires the system information from the anchor cell. The cell selection processing unit 502 performs cell selection or cell reselection based on measurement results of radio signals from surrounding base station devices. For example, the cell selection processing unit 502 may determine whether or not to make a power-saving cell a target for cell selection / cell reselection based on whether or not system information on which transmission has been stopped can be acquired from the anchor cell. Furthermore, in order to acquire the system information of the power-saving cell, the cell selection processing unit 502 may perform processing to make the cell a target for measurement regardless of the cell selection priority of the anchor cell. Furthermore, when the first priority of cell selection of the anchor cell is lower than the second priority of cell selection of the power-saving cell, the cell selection processing unit 502 may treat the first priority as the same as the second priority and make the cell a target for measurement. Furthermore, the cell selection processing unit 502 may determine whether or not to make a power-saving cell a target for cell selection / cell reselection based on whether or not the power-saving function has been stopped in response to a stop request for the function in the power-saving cell.

[0044] (Processing flow) Next, an example of the flow of processing executed in the wireless communication system of this embodiment will be described with reference to FIG. 6. Note that, here, an example will be described in which the cell in which the terminal device is located and the anchor cell of the power-saving cell are different, and the terminal device receives system information whose transmission is suspended in the power-saving cell from the anchor cell. First, the terminal device acquires information about neighboring cells from the base station device of the cell in which the terminal device is located (S601). As described above, the information here includes, for each neighboring cell, a cell identifier, whether the cell supports a power-saving function, whether the power-saving function is enabled if the cell supports the power-saving function, and information about the anchor cell from which system information whose transmission is suspended when the power-saving function is enabled is transmitted. The terminal device measures radio signals transmitted from the base station device of the power-saving cell, and can acquire, for example, only part of the system information whose transmission is not suspended (S602). Note that the base station device of the power-saving cell does not need to transmit all of the system information, and the terminal device may only measure the radio quality of the power-saving cell. Thereafter, the terminal device acquires, based on the information acquired in S601, system information for which transmission has been stopped in the power-saving cell from the base station device of the anchor cell (S603).

[0045] FIG. 7 shows an example of a processing flow when a terminal device transmits a message requesting the base station device of a power-saving cell to disable the power-saving function. Similar to S601, the terminal device acquires information about neighboring cells from the cell in which it is located (S701). Then, when the terminal device needs to acquire system information about the power-saving cell, it transmits a message requesting the power-saving function to be disabled to the power-saving cell (S702). While FIG. 7 shows a processing example in which the message is transmitted directly to the power-saving cell, the message may be transmitted from the terminal device to the base station device of the cell in which it is located and then forwarded from the base station device of the cell in which it is located to the base station device of the power-saving cell. Upon receiving the message, the base station device of the power-saving cell determines whether to disable the power-saving function. If the base station device of the power-saving cell does not disable the power-saving function, the terminal device can acquire information about the power-saving cell from the anchor cell by the processing shown in FIG. 6. On the other hand, if the base station device of the power-saving cell disables the power-saving function (S703), the terminal device can acquire system information for the cell from the base station device (S704).

[0046] By acquiring such system information, the terminal device can perform cell reselection and become located in the power-saving cell.

[0047] In this way, by stopping the transmission of system information from some cells, it is possible to save power while still allowing terminal devices to be present in those cells, enabling the system to be operated efficiently. This will contribute to Goal 9 of the United Nations' Sustainable Development Goals (SDGs), which is to "Develop resilient infrastructure, promote sustainable industrialization and foster innovation."

[0048] The invention is not limited to the above-described embodiment, and various modifications and variations are possible within the scope of the gist of the invention.

Claims

1. A terminal device in a wireless communication network in which a communication service is provided to the terminal device using at least one of a plurality of cells, an acquisition means for acquiring information on whether a power saving function for stopping transmission of system information is enabled for each of neighboring cells adjacent to a serving cell in which the terminal device is located; a transmitting means for transmitting a request message to a base station device that provides the power-saving cell, when a wireless quality of a signal transmitted in the power-saving cell in which the power-saving function is enabled satisfies a movement condition of a serving cell, to request the base station device to stop the power-saving function; A terminal device comprising:

2. The terminal device described in Claim 1, characterized in that the transmitting means transmits the request message when the radio quality of the signal transmitted in the power-saving cell in which the power-saving function is enabled satisfies the movement conditions of the serving cell and when information for transmitting an uplink signal to the power-saving cell is previously stored.

3. A terminal device as described in claim 1, characterized in that it has a means for performing cell selection or cell reselection excluding the power-saving cell from the targets when no notification of resuming transmission of system information is received within a predetermined period after sending the request message.

4. A terminal device as described in claim 1, characterized in that it has a means for excluding the power-saving cell from the target and performing cell selection or cell reselection when the reception processing of system information of the power-saving cell is not completed within a predetermined period of time.

5. A terminal device as described in Claim 4, characterized in that it has a means for obtaining information indicating the specified period from a base station device that provides the serving cell.

6. A terminal device as described in Claim 1, characterized in that it has a means for obtaining information regarding the scheduling of system information whose transmission has been stopped in the power-saving cell from a base station device that provides the serving cell.

7. A base station device in a wireless communication network in which a communication service is provided to a terminal device using at least one of a plurality of cells, an acquisition means for acquiring information on whether a power saving function for stopping transmission of system information is enabled in each of one or more neighboring base stations that respectively provide one or more neighboring cells that are adjacent to a cell provided by the base station device; a notification means for notifying a terminal device located in a cell provided by the base station device of information on whether the power saving function is enabled in the neighboring base station, the information being acquired by the acquisition means; A base station device comprising:

8. The base station device described in Claim 7, characterized in that the notification means notifies the terminal device of information regarding the scheduling of system information that has been stopped in an adjacent base station in which the power saving function is enabled.

9. A receiving means for receiving a request message from the terminal device to request that the power saving function be stopped when the power saving function is enabled in the base station device; a control means for resuming transmission of the system information in response to the request message; 8. The base station apparatus according to claim 7, further comprising:

10. A base station device as described in Claim 7, characterized in that it further has a means for notifying the adjacent base station of information as to whether or not the power saving function is enabled in the base station device.

11. A control method executed by a terminal device in a wireless communication network in which a communication service is provided to the terminal device using at least one of a plurality of cells, comprising: an acquisition step of acquiring information on whether a power saving function for stopping transmission of system information is enabled for each neighboring cell adjacent to a serving cell in which the terminal device is located; a transmission step of transmitting a request message to a base station device that provides the power-saving cell, when a wireless quality of a signal transmitted in the power-saving cell in which the power-saving function is enabled satisfies a movement condition of a serving cell, to request the base station device to stop the power-saving function; A control method comprising:

12. A control method executed by a base station device in a wireless communication network in which communication services are provided to a terminal device using at least one of a plurality of cells, comprising: an acquisition step of acquiring information on whether a power saving function for stopping transmission of system information is enabled in each of one or more neighboring base stations that respectively provide one or more neighboring cells that are adjacent to a cell provided by the base station device; a notification step of notifying a terminal device located in a cell provided by the base station device of information on whether the power saving function is enabled in the neighboring base station, the information being acquired in the acquisition step; A control method comprising:

13. A program for causing a computer provided in a terminal device in a wireless communication network in which communication services are provided to the terminal device using at least one of a plurality of cells to execute the control method described in claim 11.

14. A program for causing a computer provided in a base station device in a wireless communication network in which communication services are provided to a terminal device using at least one of a plurality of cells to execute the control method described in claim 12.

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