Terminal device, base station device, control method, and program for using frequency band suitable for movement state of terminal device

Abstract

To promote the use of appropriate frequency bands according to the mobility of a terminal device.SOLUTION: A terminal device that communicates in accordance with the cellular communication standard of the Third Generation Partnership Project receives, from a connected base station device, signal quality or signal strength offset values corresponding to one or more events related to a handover of the terminal device from a cell of a first frequency band to a cell of a second frequency band different from the first frequency band, or dual connectivity that adds a cell of the first frequency band or the second frequency band, the offset values for each movement state of the terminal device, identifies the movement state of the terminal device, and makes a determination on the one or more events using the offset value corresponding to the movement state of the terminal device.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a technique for promoting the use of frequency bands suited to the mobility state of terminal devices. [Background technology]

[0002] The cellular communication standard of the Third Generation Partnership Project (3GPP (registered trademark)) has a provision for setting cell reselection and handover processing based on the moving speed of a terminal device (see Non-Patent Documents 1 and 2). According to this provision, the faster the moving speed of a terminal device, the more quickly the terminal device moves across cells, and therefore it is possible to control so as to shorten the time until cell reselection or handover is executed. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] 3GPP(registered trademark) TS36.304 [Non-patent document 2] 3GPP(registered trademark) TS38.304 Summary of the Invention [Problem to be solved by the invention]

[0004] A cellular communication system is configured to be able to use multiple frequency bands, and a terminal device connects to one of the multiple frequency bands. Among the multiple frequency bands, high-frequency bands are characterized by their relatively difficult coverage area and susceptibility to Doppler shift, but by their wide bandwidth and suitability for high-speed communications. Therefore, high-frequency bands are not suitable for use by terminal devices moving at high speeds. On the other hand, low-frequency bands are characterized by their relatively difficult bandwidth, but by their easy coverage area and their resistance to Doppler shift. Therefore, when a terminal device moving at low speeds or not moving uses a low-frequency band, it may not be able to achieve sufficient communication performance due to the bandwidth limitations. [Means for solving the problem]

[0005] The present invention provides a technique for promoting the use of appropriate frequency bands according to the movement status of terminal devices.

[0006] A terminal device according to one embodiment of the present invention is a terminal device that communicates in accordance with the cellular communication standard of the 3rd Generation Partnership Project, and has: a receiving means that receives, from a connected base station device, signal quality or signal strength offset values ​​corresponding to each of one or more events related to a handover of the terminal device from a cell of a first frequency band to a cell of a second frequency band different from the first frequency band, or dual connectivity that adds a cell of the first frequency band or the second frequency band, the offset values ​​for each movement state of the terminal device; an identification means that identifies the movement state of the terminal device; and a determination means that determines the one or more events using the offset value corresponding to the movement state of the terminal device.

[0007] A base station device according to one embodiment of the present invention is a base station device that communicates in accordance with the cellular communication standard of the 3rd Generation Partnership Project, and has a notification means for notifying a terminal device to which the base station device is connected of signal quality or signal strength offset values ​​corresponding to each of one or more events related to handover of the terminal device from a cell of a first frequency band to a cell of a second frequency band different from the first frequency band, or dual connectivity that adds a cell of the first frequency band or the second frequency band, the offset values ​​being for each movement state of the terminal device. [Effects of the Invention]

[0008] According to the present invention, the use of an appropriate frequency band according to the movement state of a terminal device is promoted. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a wireless communication system. [Figure 2] FIG. 10 is a diagram illustrating an example of offset values ​​according to a moving state. [Figure 3] FIG. 2 is a diagram illustrating an example of the hardware configuration of a base station device and a terminal device. [Figure 4] FIG. 2 is a diagram illustrating an example of a functional configuration of a terminal device. [Figure 5] FIG. 2 is a diagram illustrating an example of a functional configuration of a base station device. [Figure 6] FIG. 1 is a diagram illustrating an example of a flow of processing executed in a wireless communication system. 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] 1 shows an example of the configuration of a wireless communication system according to this embodiment. This wireless communication system is a cellular communication system that complies with cellular communication standards such as Long Term Evolution (LTE) or fifth generation (5G) of the Third Generation Partnership Project (3GPP (registered trademark)) or their successor standards, and is configured to include base station devices (base station device 101 and base station devices 111 to 116) and terminal devices (terminal device 121). Here, it is assumed that base station device 101 configures a cell using a relatively low first frequency band, and base station devices 111 to 116 configure cells using a relatively high second frequency band (at least higher than the first frequency band).

[0012] A relatively low frequency band has a relatively narrow usable bandwidth and is not suitable for high-speed communication, but can cover a wide area and is therefore suitable for providing stable communication services to a mobile terminal device. On the other hand, a relatively high frequency band has a relatively narrow usable area and is not suitable for providing stable communication services to a terminal device moving at high speed, but can use a relatively wide bandwidth and is therefore suitable for providing high-speed communication services to a terminal device that is not moving or moving at low speed. Therefore, the terminal device 121 connects to the base station device 101 while moving at high speed and connects to the base station device 111 to the base station device 116 while moving at low speed, thereby being able to receive stable communication services while moving at high speed and high-speed communication services while moving at low speed. This embodiment provides a technology that enables the terminal device 121 to select an appropriate cell to connect to depending on such a moving state.

[0013] 3GPP (registered trademark) provides a standard called Mobility State as an index indicating the mobility state of a terminal device. The Mobility State of a terminal device is specified by one of a high-speed mobility state (sf-High / High-mobility state), a medium-speed mobility state (sf-Medium / Medium-mobility state), and a normal mobility state (sf-Normal / Normal-mobility state) such as a stationary state or a low-speed mobility state. For example, the terminal device is in the high-speed mobility state when the number of captured cells within a certain period of time is greater than a first predetermined number, in the medium-speed mobility state when the number of captured cells is less than the first predetermined number and exceeds a second predetermined number that is smaller than the first predetermined number, and in the normal mobility state in other cases. A reference value (such as the first predetermined number / second predetermined number) for determining this mobility state is notified to the terminal device from a base station device by a system information block (SIB) or a message of a radio resource control (RRC) layer such as an RRCConnectionReconfiguration message in LTE / RRC Reconfiguration message in 5G. Then, the terminal device identifies its own Mobility State based on this reference value.

[0014] In this embodiment, using this Mobility State, a base station device notifies a terminal device of information for performing a handover to a lower frequency band during high-speed movement or for adding a cell using a lower frequency band in dual connectivity. Specifically, an offset value for the signal quality or signal strength of a radio signal from a currently connected cell, a handover destination cell, or a candidate cell to be added, which corresponds to one or more events related to handover or the addition of a cell in dual connectivity, as defined in 3GPP (registered trademark), is notified to the terminal device. The base station device notifies the currently connected terminal device of this offset value using, for example, an RRCConnectionReconfiguration message for LTE / an RRC Reconfiguration message for 5G. In one example, this message includes reportConfig, which is configuration information related to reporting measurement results, and this offset value is stored in this configuration information and transmitted to the terminal device. Note that the offset value can be defined separately for each of one or more events. Below, this offset value will be described for several events using examples shown in FIG. 2.

[0015] <Example 1: Event A1> Event A1 is an event determined to have occurred when the signal quality or signal strength of the serving cell to which the terminal device is connected exceeds a predetermined threshold. When this event occurs, it is assumed that the radio quality of the current serving cell is sufficiently good, and therefore the terminal device may stop measuring other cells across frequency bands in response to the occurrence of this event. On the other hand, when the terminal device is connected to a high frequency band, its radio quality is expected to deteriorate rapidly, particularly when moving at high speed. Therefore, in this embodiment, when the terminal device is connected to a high frequency band, the higher the moving speed, the higher the predetermined threshold used to determine Event A1. That is, in a high-speed moving state, the terminal device continues measuring the radio quality across frequency bands unless the signal quality or signal strength of the serving cell becomes very high, thereby enabling a smooth handover to a low frequency band. On the other hand, in a low-speed moving state, the terminal device determines this event using a relatively low predetermined threshold, and therefore does not measure other frequency bands in an environment where sufficient radio quality can be obtained. Furthermore, when the terminal device is connected to a low frequency band, the terminal device can determine whether an event has occurred in the same manner as in the past, regardless of its state of movement.

[0016] A terminal device in a normal moving state may determine that Event A1 has occurred when the reference signal received power (RSRP) exceeds −110 dBm. In contrast, in the example of FIG. 2 , the offset value corresponding to the medium-speed moving state (sf-Medium of sf-MeasOffset) is set to “10,” and the offset value corresponding to the high-speed moving state (sf-High of sf-MeasOffset) is set to “20.” Here, it is assumed that the unit of the offset value is 1 dB. In this case, in the medium-speed moving state, Event A1 is determined to have occurred when RSRP exceeds −110 + 10 = −100 dBm. Furthermore, in the high-speed moving state, Event A1 is determined to have occurred when RSRP exceeds −110 + 20 = −90 dBm. In this way, the faster the moving speed of the terminal device, the higher the RSRP value required to generate Event A1, making it less likely that Event A1 will occur. The offset value associated with Event A1 as shown in FIG. 2 may be applied only when the terminal device is connected to a cell using a high frequency band. That is, a terminal device connected to a cell in a low frequency band can determine that Event A1 has occurred when it obtains an RSRP in the serving cell that exceeds the same predetermined threshold (e.g., −110 dBm) as in a low speed moving state, even when moving at high speed. In this way, a terminal device connected to a high frequency band in a high speed moving state can continue to measure radio signals in other frequency bands, such as the low frequency band, and can immediately initiate handover when the quality of the serving cell deteriorates to a level below a predetermined level.

[0017] <Example 2:Event A2> Event A2 is an event determined to have occurred when the signal quality or signal strength of the serving cell to which the terminal device is connected falls below a predetermined threshold. In response to the occurrence of this event, the terminal device may, for example, start measuring other cells across frequency bands. That is, this event may be used to resume (start) the measurement in response to a deterioration in the radio quality of the serving cell after the measurement of the radio quality of other frequency bands has been stopped due to the occurrence of Event A1. When the terminal device is connected to a high frequency band, its radio quality is expected to deteriorate rapidly, particularly when the terminal device is moving at high speed. That is, if a terminal device moving at high speed uses the same predetermined threshold as when moving at low speed, the grace period from the start of measurement of other cells until the radio quality deteriorates to the point where communication with the serving cell becomes impossible is shortened. In particular, when the frequency band of the cell to which the terminal device is connected is a high frequency band, the cell range is narrow, and the grace period is short, which increases the probability of a radio link failure (RLF) occurring. For this reason, in this embodiment, when a terminal device is connected to a high frequency band, the higher the moving speed, the higher the predetermined threshold value used to determine Event A2. That is, even if a relatively high quality is obtained in a high-speed moving state, the terminal device starts measuring other cells. This makes it possible to ensure a grace period before radio quality deteriorates to the point where communication in the serving cell becomes impossible, even when the terminal device is in a high-speed moving state, and to prevent the occurrence of RLF.

[0018] An example of an offset value for Event A2 will now be described with reference to FIG. 2. A terminal device in a normal moving state may determine that Event A2 has occurred when the reference signal received power (RSRP) falls below −114 dBm. In contrast, in the example of FIG. 2, the offset value corresponding to the medium-speed moving state (sf-Medium of sf-MeasOffset) is set to “10,” and the offset value corresponding to the high-speed moving state (sf-High of sf-MeasOffset) is set to “20.” Here, it is assumed that the unit of the offset value is 1 dB. In this case, in the medium-speed moving state, Event A2 is determined to have occurred when RSRP falls below −114+10=−104 dBm. In addition, in the high-speed moving state, Event A2 is determined to have occurred when RSRP falls below −114+20=−94 dBm. In this way, the faster the moving speed of the terminal device, the more likely Event A2 is to occur, even in a state where a higher RSRP value is obtained. 2 can be applied only when the terminal device is connected to a cell in a high frequency band. That is, a terminal device connected to a cell in a low frequency band can determine that Event A2 has occurred even when the terminal device is moving at high speed if the RSRP in the serving cell falls below the same predetermined threshold (e.g., −114 dBm) as in the low speed moving state. In this way, a terminal device moving at high speed and connected to a high frequency band can start measuring radio signals in other frequency bands, such as the low frequency band, early when radio quality begins to deteriorate, and can immediately initiate handover when the quality of the serving cell deteriorates to a level below a predetermined level.

[0019] <Example 3:Event A3> Event A3 is an event that is determined to have occurred when the signal quality of a neighboring cell exceeds a value obtained by adding a predetermined value to the signal quality of the serving cell to which the terminal device is connected, or when the signal strength of a neighboring cell exceeds a value obtained by adding a predetermined value to the signal strength of the serving cell. That is, this event can be used as a trigger for executing a handover to a neighboring cell when the wireless quality of the serving cell deteriorates and the wireless quality of the neighboring cell becomes sufficiently good. Here, when a terminal device connected to a cell using a high frequency band is in a high-speed moving state, it is assumed that the wireless quality of the serving cell will deteriorate sharply. In this case, if the above-mentioned predetermined value is set to the same as in a low-speed moving state, the terminal device will wait until the neighboring cell's quality improves sufficiently in the high-speed moving state. As a result, handover will be delayed and the probability of RLF occurring will increase. Therefore, in this embodiment, when a terminal device is connected to a high frequency band, the predetermined value used to determine Event A3 is set to be lower as the moving speed increases. That is, the terminal device is configured to initiate handover even when the difference between the wireless quality of the neighboring cell and the wireless quality of the serving cell is small when the terminal device is in a high-speed moving state. This allows the timing of starting handover to be advanced when the terminal device is in a high-speed moving state, thereby making it possible to prevent the occurrence of RLF.

[0020] An example of an offset value for Event A3 will now be described with reference to FIG. 2. When a terminal device in a normal moving state has a reference signal received power (RSRP) of a neighboring cell that is 3 dB higher than the RSRP of the serving cell, the terminal device changes the connection destination cell to the neighboring cell by handover. In contrast, in the example of FIG. 2, the offset value (sf-High of sf-MeasOffset) corresponding to the high-speed moving state is set to "-6." Assume that the unit of the offset value here is 0.5 dB. In this case, in the high-speed moving state, the above-mentioned predetermined value is 3 + (-6 / 2) = 0 dB, and it is determined that Event A3 has occurred when the RSRP of the neighboring cell is equivalent to the RSRP of the serving cell. Note that in the example of FIG. 3, the offset value (sf-Medium of sf-MeasOffset) corresponding to the medium-speed moving state is set to "0," indicating that the same predetermined value as in the normal moving state is used. However, this is merely an example, and the offset value may also be set so that the predetermined value is lower in the medium-speed moving state. In this way, the faster the moving speed of the terminal device, the more likely it is that a handover to another cell will be promoted. In particular, by applying such an offset value only to cells in a high frequency band, handovers are more likely to occur in terminal devices moving at high speeds using a high frequency band, thereby increasing opportunities for movement to cells in a low frequency band. On the other hand, in a low frequency band, handovers are made to occur according to the same criteria as in normal moving states, even when the terminal device is moving at high speeds, so that a terminal device moving at high speeds can remain in a cell in a low frequency band. This makes it possible to promote connection of terminal devices moving at high speeds to cells in a low frequency band.

[0021] <Example 4:Event A4> Event A4 is an event determined to have occurred when the signal quality or signal strength of a neighboring cell exceeds a predetermined threshold. This event can be used to initiate a handover to a neighboring cell regardless of the wireless quality of the serving cell. In this embodiment, the predetermined threshold for a high-frequency band cell can be increased so that a terminal device connected to a low-frequency band cell does not unnecessarily attempt to connect to a high-frequency band cell when moving at high speed. That is, an offset value is provided for a high-frequency band cell to promote handover in a normal moving state and to prevent handover as the terminal device's moving speed increases. This can prevent, for example, a terminal device moving at high speed from attempting handover to a high-frequency band cell in response to a momentary improvement in the wireless quality of the high-frequency band cell, resulting in a connection failure due to a decrease in the wireless quality of the cell during connection processing. Furthermore, even if a handover to a high-frequency band cell is successful, if the terminal device is moving at high speed, it is expected that the terminal device will leave the range of the high-frequency band cell within a short period of time, which could result in a high probability of a second handover. During handover processing, there is a period during which user data communication is not possible, and if handovers occur frequently, communication efficiency will decrease. In contrast, by using the offset value described above, a terminal device moving at high speed will no longer attempt handover to a cell using a high frequency band, and this can prevent a decrease in communication efficiency.

[0022] An example of an offset value for Event A4 will be described with reference to FIG. 2. Here, it is assumed that a terminal device is connected to a cell using a low frequency band. For example, a terminal device in a normal moving state attempts handover to a cell using a high frequency band when the reference signal reception quality (RSRQ) of the cell using a high frequency band exceeds −16 dB. This prompts a handover of the terminal device in a normal moving state to a cell using a high frequency band. In contrast, in the example of FIG. 2, the offset value corresponding to the medium moving speed state (sf-Medium of sf-MeasOffset) is set to “4”, and the offset value corresponding to the high moving speed state (sf-High of sf-MeasOffset) is set to “16”. Here, it is assumed that the unit of the offset value is 0.5 dB. In this case, in the medium moving speed state, it is determined that Event A4 has occurred when the RSRQ exceeds −16 + (4 / 2) = −14 dB. Furthermore, in the high moving speed state, it is determined that Event A4 has occurred when the RSRQ exceeds −16 + (16 / 2) = −8 dB. In this way, the faster a terminal device connected to a low frequency band cell is moving, the less likely it is to initiate a handover to a high frequency band cell unless it observes high radio quality for the high frequency band cell.

[0023] <Example 5:Event A5> Event A5 is an event that is determined to have occurred when the signal quality or signal strength of the serving cell falls below a first predetermined threshold and the signal quality or signal strength of a neighboring cell exceeds a second predetermined threshold. This event can be used to trigger a handover to a neighboring cell when the radio quality of the serving cell deteriorates and the radio quality of the neighboring cell is good. In this embodiment, the first predetermined threshold for the cell in the low frequency band can be lowered, or the second predetermined threshold for the cell in the high frequency band can be raised, or both, so that a terminal device connected to a cell in the low frequency band does not unnecessarily attempt to connect to a cell in the high frequency band in a high-speed moving state. That is, as described in relation to Event A4, an offset value is provided for the cell in the high frequency band to promote handover in a normal moving state and to suppress handover as the moving speed of the terminal device increases.

[0024] An example of the offset value for Event A5 will be described with reference to FIG. 2. Here, it is assumed that the terminal device is connected to a cell of a low frequency band. For example, if the RSRQ of the cell of a low frequency band is below -3 dB and the RSRQ of the cell of a high frequency band is above -16 dB, the terminal device in a normal moving state attempts a handover to the cell of the high frequency band. This prompts the terminal device in a normal moving state to handover to the cell of the high frequency band. In contrast, in the example of FIG. 2, the offset values ​​corresponding to the medium moving speed state (sf-Medium of sf-MeasOffset) are set to "0" and "4" for the cell of the low frequency band and the cell of the high frequency band, respectively, and the offset values ​​corresponding to the high moving speed state (sf-High of sf-MeasOffset) are set to "0" and "16" for the cell of the low frequency band and the cell of the high frequency band, respectively. Here, it is assumed that the unit of the offset value is 0.5 dB. In this case, in the medium-speed moving state, it is determined that Event A5 has occurred when the RSRQ of the cell in the low frequency band falls below -3 dB and the RSRQ of the cell in the high frequency band exceeds -16 + (4 / 2) = -14 dB. Also, in the high-speed moving state, it is determined that Event A5 has occurred when the RSRQ of the cell in the low frequency band falls below -3 dB and the RSRQ of the cell in the high frequency band exceeds -16 + (16 / 2) = -8 dB. In this way, the faster the moving speed of the terminal device connected to the cell in the low frequency band, the less likely it is to initiate handover to the cell in the high frequency band unless it observes high radio quality for the cell in the high frequency band. Note that, in the example of FIG. 2, an example is shown in which only the second predetermined threshold for the RSRQ of the cell in the high frequency band is changed by the offset value. However, instead of or in addition to this, the offset value may be set so that the first predetermined threshold for the RSRQ of the cell in the low frequency band is lowered. In other words, by reducing the probability that a terminal device connected to a low frequency band cell will experience a wireless quality in that cell that falls below a predetermined threshold, it may be possible to make it less likely that a handover from that cell to another cell will occur when moving at high speed.

[0025] <Example 6:Event B1> Event B1 is an event that is determined to have occurred when the signal quality or signal strength of a neighboring cell of a different RAT exceeds a predetermined threshold. This event is used for handover between RATs, addition of a cell for dual connectivity, and the like. In this embodiment, an example will be described in which Event B1 is used when a terminal device is connected to a cell conforming to a first cellular communication standard such as LTE and a cell conforming to a second cellular communication standard such as 5G is added as a secondary cell for dual connectivity. In one example, when the terminal device of this embodiment is in a high-speed moving state, an offset value is set so that, among cells that are candidates for a secondary cell conforming to the second cellular communication standard, a cell in a high frequency band is less likely to be added and a cell in a low frequency band is more likely to be added. That is, an offset value that increases the first predetermined threshold for a cell in a high frequency band, or an offset value that decreases the second predetermined threshold for a cell in a low frequency band, or both of these offset values ​​may be prepared. This makes it possible to make it easier for a terminal device moving at high speed to select a cell in a low frequency band as the secondary cell, and harder for a cell in a high frequency band to be selected.

[0026] An example of offset values ​​related to Event B1 will be described with reference to FIG. 2. Here, it is assumed that a terminal device is connected to a cell (base station device) conforming to a first cellular communication standard, and the values ​​shown in FIG. 2 are values ​​related to a cell conforming to a second cellular communication standard. A terminal device in a normal moving state may add a cell conforming to the second cellular communication standard, either a low frequency band cell or a high frequency band cell, as a secondary cell if the RSRP exceeds −116 dBm in that cell. Meanwhile, in the example of FIG. 2, the offset values ​​corresponding to a medium moving speed state (sf-Medium of sf-MeasOffset) are set to “0” and “10” for the low frequency band cell and the high frequency band cell, respectively, and the offset values ​​corresponding to a high moving speed state (sf-High of sf-MeasOffset) are set to “0” and “56” for the low frequency band cell and the high frequency band cell, respectively. Here, it is assumed that the unit of the offset value is 1 dB. In this case, in the medium-speed moving state, it is determined that Event B1 has occurred when the RSRP of the cell in the low frequency band exceeds -116 dBm or the RSRQ of the cell in the high frequency band exceeds -116 + 10 = -106 dBm. Also, in the high-speed moving state, it is determined that Event B1 has occurred when the RSRP of the cell in the low frequency band exceeds -116 dBm or the RSRP of the cell in the high frequency band exceeds -116 + 56 = -60 dBm. As described above, the faster the moving speed of the terminal device, the more difficult it becomes to satisfy the radio quality conditions of the cell in the high frequency band, and the less likely such a cell in the high frequency band is to be selected as a secondary cell. Note that, in the example of FIG. 2, an example is shown in which only the predetermined threshold for the RSRP of the cell in the high frequency band is changed by the offset value. However, instead of or in addition to this, the offset value may be set so that the predetermined threshold for the RSRP of the cell in the low frequency band is lowered. In other words, when a terminal device moving at high speed adds a cell conforming to the second cellular communication standard as a secondary cell, an offset value may be provided that relaxes the conditions so that a cell in a low frequency band is more likely to be selected.

[0027] FIG. 3 shows an example of the hardware configuration of a base station device (base station device 101, base station devices 111 to 116) and a terminal device (terminal device 121) according to this embodiment. In one example, the base station device and the terminal device are configured to 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 configured to include one or more processing circuits, such as a general-purpose CPU (Central Processing Unit) or an ASIC (Application Specific Integrated Circuit), and performs the overall processing of the device and each of the above-mentioned processes by reading and executing programs stored in the ROM 302 or 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 device and the terminal device. The RAM 303 functions as a workspace when the processor 301 executes a program, and is also 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 configured by a circuit for wireless communication of, for example, LTE, 5G, or a successor standard. Although FIG. 3 illustrates one communication circuit 305, the base station apparatus and the terminal apparatus may have multiple communication circuits. For example, the base station apparatus and the terminal apparatus may have wireless communication circuits for 5G and a successor standard, respectively, and a common antenna for these circuits. The base station apparatus and the terminal apparatus may also have separate antennas suitable for each standard. 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 conforming to a wireless communication standard other than the cellular communication standard, such as a wireless local area network (LAN) or Bluetooth (registered trademark). The base station apparatus and the terminal apparatus may have separate communication circuits 305 for each of multiple available frequency bands, or may have a common communication circuit 305 for at least some of these frequency bands.

[0028] FIG. 4 shows an example of the functional configuration of a terminal device. The terminal device includes, for example, an offset value acquisition unit 401, a moving state identification unit 402, and an event determination unit 403. Note that FIG. 4 only shows functions particularly related to this embodiment, and does not illustrate various other functions that the terminal device may have. For example, the terminal device naturally has other functions that terminal devices conforming to LTE, 5G, or subsequent standards generally have. The functional blocks in FIG. 4 are shown schematically, and the respective functional blocks may be realized as an integrated unit or may be further subdivided. Furthermore, the functions 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 may be realized, for example, by a processor present within the communication circuit 305 executing predetermined software.

[0029] The offset value acquisition unit 401 acquires, from a connected base station device (for example, the base station device 101, or any of the base station devices 111 to 116), information on offset values ​​of signal quality or signal strength corresponding to one or more events such as handover or dual connectivity cell addition, as described above. The offset value acquisition unit 401 acquires this offset value information, for example, via an RRC message. The offset value information is information for each movement state and each frequency band of the terminal device, and is a value used to suppress connection to a cell in a high frequency band when the terminal device is in a high-speed movement state, as described above. The movement state determination unit 402 determines the movement state of the terminal device itself. The movement state determination unit 402 determines the movement state of the terminal device itself in the same way as in conventional mobility state determination. Note that in this embodiment, processing based on a mobility state defined in a cellular communication standard has been described, but the present invention is not limited to this, and the movement state determination unit 402 may determine which of the movement states of the terminal device for which each offset value is defined is in question. The event determination unit 403 determines whether an event has occurred based on the movement state of the terminal device itself. The details of this determination are as described above, and will not be repeated here.

[0030] FIG. 5 shows an example of the functional configuration of a base station device. The base station device includes, for example, a setting information notification unit 501. Note that FIG. 5 only shows 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 base station devices conforming to LTE, 5G, and subsequent standards generally have. The functional blocks in FIG. 5 are shown schematically, and each functional block may be realized as an integrated unit or may be further subdivided. Furthermore, 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, for example, by a processor present in the communication circuit 305 executing predetermined software.

[0031] The setting information notification unit 501 notifies the connected terminal device of information on offset values ​​of signal quality or signal strength corresponding to one or more events such as handover or addition of a cell for dual connectivity, as described above. The setting information notification unit 501 can notify the information on the offset values ​​using, for example, an RRC message. The setting information notification unit 501 also notifies information on conditions for the terminal device to determine its mobility state, etc.

[0032] FIG. 6 is a diagram showing an example of the flow of processing executed in the wireless communication system according to this embodiment.

[0033] The base station device first determines an offset value that reduces the probability that a terminal device in a high-speed moving state, such as the above, will connect to a cell in a high frequency band and makes it easier for a terminal device in a low-speed moving state to connect to a cell in a high frequency band (S601). The base station device then transmits configuration information including the offset value to the terminal device (S602). This configuration information may include, for example, information on criteria for the terminal device to identify its moving state. However, this is not limited to this, and the criteria information may be transmitted via a message separate from the offset value. When control based on the Mobility State in a cellular communication standard is performed, the base station device notifies the terminal device of the criteria for identifying the state. However, when the moving state is identified by other criteria, the base station device does not need to notify the terminal device of the criteria information. The terminal device identifies its own moving state based on the criteria information received from the base station device (S603), and observes a predetermined signal, such as a reference signal transmitted in a candidate cell other than the serving cell to which it is connected, to identify signal quality or signal strength (S604). 6 shows an example in which the connection candidate cell is provided by a base station device different from the currently connected serving cell, but the connection candidate cell and the serving cell may be provided by a common base station device.The terminal device then identifies an offset value to be applied in determining whether an event has occurred based on the movement state of the terminal device itself and the frequency band used in the connection candidate cell (S605), and determines whether an event has occurred based on the offset value and the measurement result of the reference signal (S606).

[0034] As described above, in this embodiment, by providing offset values ​​associated with one or more events that can be used for handover, adding a cell for dual connectivity, and the like, the probability that a terminal device in a high-speed moving state will newly connect to or continue to connect to a cell in a high-frequency band can be reduced. Also, the probability that a terminal device in a low-speed moving state will connect to a cell in a high-frequency band can be improved. As a result, it is possible to provide stable communication services to terminal devices in a high-speed moving state, and high-speed communication services to terminal devices in a low-speed moving state. Therefore, it is 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."

[0035] 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 that performs communication in accordance with the cellular communication standard of the Third Generation Partnership Project, a receiving means for receiving, from a connected base station device, an offset value of signal quality or signal strength corresponding to each of one or more events related to a handover of the terminal device from a cell of a first frequency band to a cell of a second frequency band different from the first frequency band, or to dual connectivity that adds a cell of the first frequency band or the second frequency band, the offset value for each movement state of the terminal device; a determination means for determining the movement state of the terminal device; a determination means for determining the one or more events using the offset value corresponding to the moving state of the terminal device; A terminal device comprising:

2. the first frequency band is a higher frequency band than the second frequency band, the one or more events include Event A1, which is determined to have occurred when a signal quality or a signal strength of a serving cell of the first frequency band exceeds a predetermined threshold; the offset value includes an offset value for increasing the predetermined threshold value related to the Event A1 to the extent that the movement state indicates that the terminal device is moving at a high speed; 2. The terminal device according to claim 1, wherein:

3. the first frequency band is a higher frequency band than the second frequency band, the one or more events include Event A2, which is determined to have occurred when a signal quality or a signal strength of a serving cell in the first frequency band falls below a predetermined threshold; the offset value includes an offset value for increasing the predetermined threshold value related to the Event A2 to the extent that the movement state indicates that the terminal device is moving at a high speed; 2. The terminal device according to claim 1, wherein:

4. the first frequency band is a higher frequency band than the second frequency band, the one or more events include Event A3 that is determined to have occurred when a signal quality of a cell in the second frequency band exceeds a value obtained by adding a predetermined value to the signal quality of a serving cell in the first frequency band or when a signal strength of a cell in the second frequency band exceeds a value obtained by adding a predetermined value to the signal strength of the serving cell in the first frequency band; The offset value includes an offset value for lowering the predetermined value related to the Event A3 to the extent that the movement state indicates that the terminal device is moving at a high speed.

2. The terminal device according to claim 1, wherein:

5. the first frequency band is a frequency band lower than the second frequency band, The one or more events include Event A4, which is determined to have occurred when a signal quality or a signal strength of a cell of the second frequency band exceeds a predetermined threshold while the terminal device is connected to a cell of the first frequency band; the offset value includes an offset value for increasing the predetermined threshold value related to the Event A4 to the extent that the movement state indicates that the terminal device is moving at a high speed.

2. The terminal device according to claim 1, wherein:

6. the first frequency band is a frequency band lower than the second frequency band, the one or more events include Event A5, which is determined to have occurred when a signal quality or a signal strength of a serving cell in the first frequency band falls below a first predetermined threshold and a signal quality or a signal strength of a cell in the second frequency band exceeds a second predetermined threshold; the offset value includes an offset value for lowering the first predetermined threshold value associated with the Event A5 or raising the second predetermined threshold value to the extent that the movement state indicates that the terminal device is moving at high speed; 2. The terminal device according to claim 1, wherein:

7. the terminal device is connected to the base station device conforming to a first cellular communication standard, the first frequency band is a higher frequency band than the second frequency band, the one or more events include Event B1 that is determined to have occurred when, among cells conforming to a second cellular communication standard different from the first cellular communication standard, a signal quality or a signal strength of a cell in the first frequency band exceeds a first predetermined threshold or when a signal quality or a signal strength of a cell in the second frequency band exceeds a second predetermined threshold; the offset value includes an offset value for increasing the first predetermined threshold value or decreasing the second predetermined threshold value associated with the Event B1 to the extent that the movement state indicates that the terminal device is moving at a high speed; 2. The terminal device according to claim 1, wherein:

8. 8. The terminal device according to claim 1, wherein the receiving means receives the offset value via a radio resource control (RRC) message.

9. A base station device that performs communication in accordance with the cellular communication standard of the Third Generation Partnership Project, A base station device characterized by having a notification means for notifying a terminal device to which the base station device is connected of signal quality or signal strength offset values ​​corresponding to each of one or more events related to handover of the terminal device from a cell of a first frequency band to a cell of a second frequency band different from the first frequency band, or dual connectivity that adds a cell of the first frequency band or the second frequency band, the offset values ​​being for each movement state of the terminal device.

10. the first frequency band is a higher frequency band than the second frequency band, the one or more events include Event A1, which is provided by the base station device in the first frequency band and is determined to have occurred when a signal quality or signal strength of a cell to which the terminal device is connected exceeds a predetermined threshold; the offset value includes an offset value for increasing the predetermined threshold value related to the Event A1 to the extent that the movement state indicates that the terminal device is moving at a high speed; 10. The base station device according to claim 9,

11. the first frequency band is a higher frequency band than the second frequency band, the one or more events include Event A2, which is provided by the base station device in the first frequency band and is determined to have occurred when signal quality or signal strength of a cell to which the terminal device is connected falls below a predetermined threshold; the offset value includes an offset value for increasing the predetermined threshold value related to the Event A2 to the extent that the movement state indicates that the terminal device is moving at a high speed; 10. The base station device according to claim 9,

12. the first frequency band is a higher frequency band than the second frequency band, The one or more events include Event A3, which is determined to have occurred when the signal quality of a second cell in the second frequency band exceeds a value obtained by adding a predetermined value to the signal quality of a first cell that is provided by the base station device in the first frequency band and to which the terminal device is connected, or when the signal strength of the second cell exceeds a value obtained by adding a predetermined value to the signal strength of the first cell; The offset value includes an offset value for lowering the predetermined value related to the Event A3 to the extent that the movement state indicates that the terminal device is moving at a high speed.

10. The base station device according to claim 9,

13. the first frequency band is a frequency band lower than the second frequency band, the one or more events include Event A4, which is determined to have occurred when a signal quality or a signal strength of a cell in the second frequency band exceeds a predetermined threshold while the terminal device is connected to a cell provided by the base station device in the first frequency band; the offset value includes an offset value for increasing the predetermined threshold value related to the Event A4 to the extent that the movement state indicates that the terminal device is moving at a high speed.

10. The base station device according to claim 9,

14. the first frequency band is a frequency band lower than the second frequency band, the one or more events include Event A5 that is determined to have occurred when a signal quality or a signal strength of a cell that is provided by the base station device in the first frequency band and to which the terminal device is connected falls below a first predetermined threshold, and a signal quality or a signal strength of a cell in the second frequency band exceeds a second predetermined threshold; the offset value includes an offset value for lowering the first predetermined threshold value associated with the Event A5 or raising the second predetermined threshold value to the extent that the movement state indicates that the terminal device is moving at high speed; 10. The base station device according to claim 9,

15. the base station device conforms to a first cellular communication standard, the first frequency band is a higher frequency band than the second frequency band, the one or more events include Event B1 that is determined to have occurred when, among cells conforming to a second cellular communication standard different from the first cellular communication standard, a signal quality or a signal strength of a cell in the first frequency band exceeds a first predetermined threshold or when a signal quality or a signal strength of a cell in the second frequency band exceeds a second predetermined threshold; the offset value includes an offset value for increasing the first predetermined threshold value or decreasing the second predetermined threshold value associated with the Event B1 to the extent that the movement state indicates that the terminal device is moving at a high speed; 10. The base station device according to claim 9,

16. 16. The base station apparatus according to claim 9, wherein the notification means transmits a radio resource control (RRC) message including the offset value to the terminal apparatus.

17. A control method executed by a terminal device that performs communication in accordance with a cellular communication standard of the Third Generation Partnership Project, comprising: receiving, from a connected base station device, an offset value of signal quality or signal strength corresponding to each of one or more events related to a handover of the terminal device from a cell of a first frequency band to a cell of a second frequency band different from the first frequency band, or a dual connectivity that adds a cell of the first frequency band or the second frequency band, the offset value for each movement state of the terminal device; Identifying the movement state of the terminal device; determining the one or more events using the offset value corresponding to the movement state of the terminal device; A control method comprising:

18. A control method executed by a base station device that performs communication in accordance with a cellular communication standard of the Third Generation Partnership Project, comprising: A control method characterized by including notifying a terminal device connected to the base station device of signal quality or signal strength offset values ​​corresponding to each of one or more events related to handover of the terminal device from a cell of a first frequency band to a cell of a second frequency band different from the first frequency band, or dual connectivity that adds a cell of the first frequency band or the second frequency band, the offset values ​​being for each movement state of the terminal device.

19. A program for causing a computer provided in a terminal device that performs communication in compliance with the cellular communication standard of the Third Generation Partnership Project to execute the control method according to claim 17.

20. A program for causing a computer provided in a base station device that performs communication in compliance with the cellular communication standard of the Third Generation Partnership Project to execute the control method according to claim 18.

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