Base station device, terminal device, and control method for communicating early reporting of channel state information

Abstract

According to the present invention, when a base station device that communicates with terminal devices on the basis of 3rd Generation Partnership Project (3GPP) cellular communication standards is transitioning a terminal device that is connected to the base station device from the connected state to a not-connected state, the base station device gives the terminal device a notification that includes information that indicates a first wireless resource for transmission of a reference signal that is for the terminal device as in the not-connected state to measure reception quality from the base station device, and during a prescribed procedure in which the terminal device as in the not-connected state is transitioned to the connected state, the base station device receives a report that includes a measurement value for reception quality that has been measured using the reference signal from the terminal device and controls communication with the terminal device on the basis of the reception quality.

Description

Base station apparatus, terminal apparatus, and control method for communicating early reporting of channel state information

[0001] The present invention relates to a technology for communicating channel state information in a mobile communication system.

[0002] In a mobile communication system conforming to the cellular communication standard of the 3rd Generation Partnership Project (3GPP (registered trademark)), information on a channel state between a base station and a terminal (channel state information) is communicated, and communication control is performed based on the channel state information. For example, between a connected base station and a terminal, one of the communication devices, either the base station or the terminal, transmits a reference signal, and the other communication device measures the channel state based on the received reference signal. The base station performs communication control based on the measured channel state. For example, the base station can perform selection of beams for the base station itself or the terminal device, transmission power control, MCS determination, radio resource allocation, and the like. MCS is an abbreviation for Modulation and Coding Scheme.

[0003] If the base station does not know the channel state with the terminal, it may not be able to appropriately perform communication control. For example, the base station may not know the channel state with the terminal during the period from when the procedure for establishing connection with the terminal is started to when the connection with the terminal is established and channel state measurement based on reference information is performed. Patent Document 1 describes Early CSI Reporting (ECR), in which a terminal measures the channel state and reports it to the base station while executing a procedure for establishing connection with the base station. CSI is an abbreviation for Channel State Information.

[0004] International Publication No. WO 2021 / 059239

[0005] In the ECR described in Patent Document 1, while the terminal is performing the procedure to establish a connection with the base station, the radio resource to which a reference signal for measuring the channel state is transmitted is notified, and the results measured using that reference signal are reported. Therefore, it takes time from when the terminal starts the procedure to establish a connection with the base station until the connection is established. The present invention provides a technology for completing the establishment of a connection, including the communication of channel state information, in a mobile communication system at an earlier stage.

[0006] A base station device according to one aspect of the present invention is a base station device that communicates with a terminal device based on the cellular communication standard of the Third Generation Partnership Project (3GPP), and comprises: notification means that, when transitioning the terminal device connected to the base station device from a connected state to a disconnected state, notifies the terminal device of information indicating a first radio resource from which a reference signal is transmitted for measuring the reception quality from the base station device when the terminal device has become disconnected; receiving means that, in a predetermined procedure for the terminal device that has become disconnected to transition to the connected state, receives a report from the terminal device including a measurement value of the reception quality measured using the reference signal; and control means that controls communication with the terminal device based on the reception quality.

[0007] A terminal device according to one aspect of the present invention is a terminal device that communicates with a base station device based on the cellular communication standard of the Third Generation Partnership Project (3GPP), and includes: a receiving means that, when transitioning from a connected state to a disconnected state, receives from the base station device a notification from the base station device that includes information indicating a first radio resource from which a reference signal is transmitted for measuring the reception quality from the base station device; a measuring means that performs the measurement using the reference signal in the disconnected state; and a transmitting means that, in a predetermined procedure for the disconnected terminal device to transition to the connected state, transmits to the base station device a report including the measured value of the reception quality measured using the reference signal.

[0008] According to the present invention, in a mobile communication system, the establishment of a connection, including the communication of channel status information, can be completed at an early stage.

[0009] Other features and advantages of this disclosure will become apparent from the following description with reference to the accompanying drawings. In the accompanying drawings, the same or similar components are given the same reference numeral.

[0010] The attached drawings are included in the specification and constitute part thereof, illustrating embodiments of the present disclosure and used together with the description to explain the principles of the present disclosure. Figure 1 is a diagram showing an example configuration of a mobile communication system. Figure 2 is a diagram showing an example sequence performed by a base station and a terminal. Figure 3 is a diagram showing an example hardware configuration of a base station and a terminal. Figure 4 is a diagram showing an example functional configuration of a base station. Figure 5 is a diagram showing an example functional configuration of a terminal. Figure 6 is a diagram showing an example sequence performed by a base station and a terminal.

[0011] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims, and not all combinations of features described in the embodiments are essential to the invention. Two or more of the features described in the embodiments may be combined in any way. Furthermore, identical or similar configurations will be given the same reference numeral, and redundant descriptions will be omitted.

[0012] (System Configuration) Figure 1 shows an example of the configuration of a mobile communication system according to this embodiment. The mobile communication system of this embodiment is, for example, a cellular communication system compliant with the cellular communication standard of the Third Generation Partnership Project (3GPP®). However, it is not limited to this, and the following discussion can be applied to a mobile communication system compliant with any wireless communication standard. This mobile communication system is configured to include, for example, a base station 101 and a terminal 111. The base station 101 exchanges wireless signals with the terminal 111 via a wireless medium. The base station 101 includes, for example, gNB (next Generation Node B), eNB (evolved Node B), etc. The base station 101 is connected to a core network (not shown). The core network may be, for example, an Evolved Packet System (EPS) or a 5G Core Network (5GC). Terminal 111 is a terminal used by a user and exchanges radio signals with base station 101 via a wireless medium. Terminal 111 may be called User Equipment (UE). Terminal 111 may also be called by other names such as wireless terminal. Terminal 111 includes, for example, smartphones, mobile phones, personal computers, tablet terminals, wearable devices, IoT (Internet of Things) terminals, etc. Base station 101 constitutes a cell 121. A cell is, for example, a geographical area from which communication with base station 101 providing this cell is possible. Figure 1 shows an example in which there is one base station 101 and one terminal 111, but in a mobile communication system, there may be two or more base stations 101 and two or more terminals 111. In this case, multiple terminals 111 may be connected to one base station 101, and one terminal 111 may be connected to multiple base stations 101.

[0013] Terminal 111 performs a procedure to establish a connection with base station 101 in order to communicate with the core network. For example, terminal 111 connects with base station 101 at the radio level using a random access procedure. Alternatively, terminal 111 connects with base station 101 at the RRC level by exchanging RRC messages with base station 101. RRC is an abbreviation for Radio Resource Control. The state in which terminal 111 has completed a connection with base station 101 at the RRC level is called the RRC Connected state. By entering the RRC Connected state, terminal 111 can request or receive the allocation of radio resources for communication with base station 101. For example, terminal 111 can request the allocation of radio resources for data communication with the core network and use the allocated radio resources to communicate with the core network. Furthermore, the exchange of signals used to control communication between the base station 101 and the terminal 111 will also take place. For example, the transmission and reception of reference signals for measuring wireless quality between the base station 101 and the terminal 111, and the communication of reporting the measurement results using those reference signals may take place. In this embodiment, the state in which the terminal 111 is RRC Connected to the base station 101 may be referred to as the terminal 111 being in a connected state.

[0014] The base station 101 can put a connected terminal 111 into a disconnected state. Disconnected states include, for example, the RRC Idle state and the RRC Inactive state. A terminal 111 in the RRC Idle state can perform power-saving operations. For example, a terminal 111 in the RRC Idle state maintains the operations necessary to receive incoming calls from the network, but does not perform any other operations. As an example, a terminal 111 in the RRC Idle state performs receiving operations at periodic timings indicated by the network, and does not perform receiving operations at other times. A terminal 111 in the RRC Inactive state can perform power-saving operations in the same way as the RRC Idle state. The difference between the RRC Idle state and the RRC Inactive state is, for example, that in the RRC Inactive state, the context information of terminal 111 is maintained by terminal 111 and base station 101, while in the RRC Idle state, the context information of terminal 111 is not maintained. Due to this difference, terminal 111 in the RRC Inactive state can reconnect to the network more quickly than terminal 111 in the RRC Idle state. Base station 101 can, for example, transition terminal 111 from the connected state to the disconnected state by notifying terminal 111 of an RRC message (RRC Release). As an example, base station 101 can transition terminal 111 from the disconnected state based on the fact that there is no more data to be exchanged in communication with terminal 111 in the connected state, or that the reception quality of the signal received from terminal 111 in the connected state has deteriorated. Terminal 111, which has become disconnected, can transition to a connected state based on a predetermined trigger. For example, a predetermined trigger may be an incoming call from the network or the generation of data that should be sent to the network. In such cases, terminal 111, which is currently disconnected, performs a procedure to re-select a cell to connect to and establish a connection to that cell.

[0015] Figure 2 shows an example of the operation of base station 101 and terminal 111 when terminal 111, which is connected to base station 101, transitions to a disconnected state and then transitions back to a connected state. Base station 101 sends an RRC Release message to terminal 111 to transition it from a connected state to a disconnected state (S201). Terminal 111 transitions to a disconnected state based on the receipt of the RRC Release message. Suppose a predetermined trigger occurs while terminal 111 is performing power-saving operations in the disconnected state. For example, suppose terminal 111 generates data that should be sent to the network. In this case, terminal 111 performs cell reselection to select a base station to connect to. For example, suppose base station 101 is selected as the base station to connect to. Terminal 111 performs a random access procedure to base station 101.

[0016] First, terminal 111 sends message 1 (RACH Msg1) containing a random access preamble (S202). When base station 101 receives message 1, it sends message 2 (RACH Msg2) containing a random access response (S203). The random access response contains information that identifies the radio resources for terminal 111 to send message 3 (RACH Msg3). When terminal 111 receives message 2 from base station 101, it sends message 3 using the radio resources identified in message 2 (S204). When base station 101 receives message 3 from terminal 111, it sends message 4 indicating that the random access was successful (S205). This completes the random access procedure.

[0017] Next, terminal 111 exchanges RRC-level messages with base station 101 to configure radio resources and communication parameters. For example, terminal 111 sends an RRCSetupRequest message requesting RRC-level configuration (S206). Base station 101 sends an RRCSetup message to terminal 111 to configure radio resources and communication parameters (S207). After terminal 111 has completed the received configuration, it sends an RRCSetupComplete message (S208). As a result, terminal 111 establishes an RRC-level connection with base station 101 and enters a connected state with base station 101. Base station 101 may exchange signals to control communication with terminal 111. For example, base station 101 sends a reference signal to measure the quality of the radio communication with terminal 111 (S209). The reference signal is, for example, CSI-RS. CSI-RS is an abbreviation for Channel State Information-Reference Signal. Terminal 111 measures the radio quality (received quality) using the received CSI-RS (S210). For example, terminal 111 measures the received power of the CSI-RS. Terminal 111 reports the measurement result to base station 101 (S211). Base station 101 controls the communication based on the reported radio quality. For example, based on the reported radio quality, base station 101 may select the beam of its own device or terminal 111, control the transmit power, determine the MCS, allocate radio resources, etc. MCS is an abbreviation for Modulation and Coding Scheme. The reference signal may also be SRS. SRS is an abbreviation for Sounding Reference Signal. When SRS is used as a reference signal, it is transmitted by terminal 111. In this case, the base station 101 measures the radio quality of the received SRS. The radio resources used to transmit the reference signal and the radio resources that terminal 111 should use to transmit the measurement report may be notified from base station 101 to terminal 111 using RRC messages. In addition, the settings for terminal 111 to perform the measurement and the settings for reporting the measurement results may also be notified from base station 101 to terminal 111 using RRC messages.

[0018] As described above, when terminal 111 is connected, base station 101 can determine the channel status based on the measurement of radio quality between itself and terminal 111. This allows base station 101 to appropriately control communication with terminal 111. On the other hand, if base station 101 does not know the channel status with terminal 111, it may not be able to appropriately control communication. For example, base station 101 does not know the channel status with terminal 111 from the time the procedure for establishing a connection with terminal 111 is started until the connection with terminal 111 is established and the measurement of radio quality is performed. In contrast to this, there is a method called Early CSI Reporting (ECR) in which terminal 111 measures the radio quality and reports it to the base station while it is performing the procedure for establishing a connection with base station 101. In ECR, while terminal 111 is performing the procedure for establishing a connection with base station 101, base station 101 notifies terminal 111 of the radio resources to which a reference signal for measuring the channel status is transmitted. Terminal 111 measures the radio quality using its reference signal and reports the measurement result to base station 101. This allows base station 101 to determine the channel status earlier compared to measuring radio quality after terminal 111 has established a connection. However, since the radio quality measurement is performed after terminal 111 begins the procedure to establish a connection with base station 101, it takes time for the connection to be established. Also, since radio resources are allocated during the connection establishment procedure, the amount of signal communicated between base station 101 and terminal 111 increases. As mentioned above, CSI-RS and SRS are specified as reference signals used for measuring radio quality. When SRS is used for measuring radio quality, unlike the above, terminal 111 transmits the SRS as a reference signal, and base station 101 measures the radio quality using the received SRS. In the following, without distinguishing whether the base station 101 or the terminal 111 transmits the reference signal or performs the measurement, the exchange of information to determine the radio quality during the procedure for establishing a connection between the terminal 111 and the base station 101 will be referred to as Early CSI Triggering (ECT).

[0019] In light of these circumstances, in this embodiment, when the terminal 111 transitions from a connected state to a disconnected state, the base station 101 sends a notification that includes information indicating a first radio resource from which a reference signal is transmitted for the terminal 111 to measure the reception quality from the base station 101. Furthermore, in the procedure for the terminal 111 transitioning from a disconnected state to a connected state, the base station 101 receives a report from the terminal 111 device that includes the measured value of the reception quality measured using the reference signal. On the other hand, in this embodiment, when the terminal 111 receives a notification from the base station 101, it measures the reception quality using the reference signal while in a disconnected state. Furthermore, in the procedure for transitioning to a connected state, the terminal 111 transmits a report to the base station 101 that includes the measured value of the reception quality measured using the reference signal. With this configuration, the reception quality measurement can be performed on the terminal 111 before the procedure for the terminal 111 transitioning from a disconnected state to a connected state begins, thus enabling the establishment of a connection, including the communication of channel status information, to be completed earlier. For example, when a base station 101 and a terminal 111 establish a connection using a random access procedure, the terminal 111 may send a request for the allocation of a second radio resource for reporting measurement results using message 1, which includes a random access preamble. The base station 101 may send information indicating the second radio resource using message 2, which includes a random access response. The terminal 111 may send a message 3, which includes the report, using the radio resource allocated by message 2.

[0020] Base station 101 may send a notification to terminal 111 containing information indicating a first radio resource when certain conditions are met. For example, base station 101 may send a notification to terminal 111 containing information indicating a first radio resource based on the fact that the value indicating the priority of the data being communicated between it and terminal 111 is higher than a predetermined threshold. Also, base station 101 may send a notification to terminal 111 containing information indicating a first radio resource at the time when terminal 111 is transitioned to a disconnected state, based on the fact that the number of communication devices connected to its own device is less than a predetermined threshold. Furthermore, base station 101 may send a notification to terminal 111 containing information indicating a first radio resource when the reception quality from terminal 111 is greater than a predetermined threshold. In this way, by base station 101 sending a notification containing information indicating a first radio resource to terminal 111 that meets the predetermined conditions, terminal 111 that does not require appropriate communication control immediately after establishing a connection with base station 101 will not execute ECT. Therefore, the radio resources used in the random access procedure can be made more efficient. Furthermore, if all terminals 111 execute ECT, delays may occur in the connection procedures and communication of other terminals. By prioritizing the execution of ECT on terminals 111 that need to execute ECT, such delays can be reduced. Below, we will describe an example of the configuration of the base station 101 and terminals 111 operating as described above, as well as examples of the processes executed in each device.

[0021] (Circuit Configuration) An example of the configuration of the base station 101 and terminal 111 will be described. Figure 3 is a diagram showing the hardware configuration of the base station 101 and terminal 111. In one example, the base station 101 and terminal 111 are configured to include a processor 301, ROM 302, RAM 303, storage device 304, and 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 ASIC (Application-Specific Integrated Circuit). The processor 301 performs the overall processing of the device and the above-mentioned processing by reading and executing programs stored in the ROM 302 and storage device 304. The ROM 302 is a read-only memory in which information such as programs and various parameters related to the processing performed by the base station 101 and terminal 111 is recorded. The RAM 303 functions as a workspace when the processor 301 executes programs and is a random access memory in which temporary information is recorded. The storage device 304 is configured, for example, by a removable external storage device. The communication circuit 305 is configured to include, for example, circuits for wired or wireless communication between the base station 101 and the terminal 111. For example, the base station 101 can communicate with the terminal 111 using the LTE or 5G communication circuit 305 and an antenna (not shown). Similarly, the terminal 111 can communicate with the base station 101 using the LTE or 5G communication circuit 305 and an antenna (not shown).

[0022] (Functional Configuration) Figure 4 shows an example of the functional configuration of the base station 101. The base station 101 is configured to include, for example, a wireless resource notification unit 401, a measurement report receiving unit 402, a wireless communication control unit 403, a terminal condition determination unit 404, a wireless resource allocation unit 405, and a connection establishment unit 406. Figure 4 shows the functional configuration of the base station 101 in this embodiment, and the general configuration of the base station 101 is omitted. These functional units can be realized, for example, by the processor 301 executing a program stored in the ROM 302 or storage device 304 and controlling the communication circuit 305 as needed. However, it is not limited to this, and dedicated hardware for realizing each function may be provided, for example.

[0023] The wireless resource notification unit 401 notifies terminal 111 of information indicating the wireless resources allocated for communication with terminal 111. For example, the wireless resource notification unit 401 notifies terminal 111 of wireless resources allocated for transmitting data to terminal 111 and wireless resources allocated for receiving data from terminal 111. The wireless resource notification unit 401 also notifies terminal 111 of a first wireless resource used to transmit a reference signal used for measuring wireless quality to determine the channel status when terminal 111 is disconnected. For example, the wireless resource notification unit 401 may notify terminal 111 of the first wireless resource when terminal 111 is transitioned from a connected state to a disconnected state. Furthermore, the wireless resource notification unit 401 notifies terminal 111 of a second wireless resource used for reporting the wireless quality measurement results to base station 101 during the procedure in which terminal 111 establishes a connection.

[0024] The measurement report receiving unit 402 receives a report of the wireless quality measurement results from the terminal 111. For example, the measurement report receiving unit 402 may receive a report of the wireless quality measurement results from the terminal 111 during the procedure for establishing a connection with the terminal 111. As an example, the measurement report receiving unit 402 may receive the report using message 3 in the random access procedure for establishing a connection with the terminal 111.

[0025] The wireless communication control unit 403 controls communication with the terminal 111. For example, the wireless communication control unit 403 can control the selection of the beam of its own device or the terminal 111 used for communication with the terminal 111, transmit power control, MCS determination, and wireless resource allocation. As an example, the wireless communication control unit 403 can control communication with the terminal 111 based on the wireless quality report received from the terminal 111.

[0026] The terminal condition determination unit 404 determines whether predetermined conditions are met for notifying terminal 111 of information indicating a first radio resource when transitioning terminal 111 to a disconnected state. For example, the terminal condition determination unit 404 determines whether the priority associated with the data that terminal 111 was communicating is higher than a predetermined threshold. The terminal condition determination unit 404 may also determine whether the reception quality from terminal 111 is greater than a predetermined threshold. Furthermore, the terminal condition determination unit 404 may determine whether the number of terminals 111 connected to base station 101 is greater than a predetermined number. The conditions under which the terminal condition determination unit 404 determines whether to notify terminal 111 of information indicating a first radio resource when transitioning terminal 111 to a disconnected state are not limited to these, and any conditions for determining whether to notify a specific terminal 111 of information indicating a first radio resource may be applied.

[0027] The wireless resource allocation unit 405 allocates wireless resources to be used for communication with the terminal 111. For example, the wireless resource allocation unit 405 allocates wireless resources for transmitting data to the terminal 111. The wireless resource allocation unit 405 also allocates wireless resources for receiving data from the terminal 111. Furthermore, the wireless resource allocation unit 405 allocates a first wireless resource for transmitting a reference signal used for measuring wireless quality to determine the channel status of a disconnected terminal 111. The wireless resource allocation unit 405 also allocates a second wireless resource for the terminal 111 to report the wireless quality measurement results to the base station 101 during the procedure for establishing a connection.

[0028] The connection establishment unit 406 performs a procedure to establish a connection with the terminal 111. For example, the connection establishment unit 406 performs a random access procedure. In addition, during the random access procedure, the connection establishment unit 406 may use the wireless resource notification unit 401 to notify the terminal 111 of information indicating a second wireless resource. Furthermore, during the random access procedure, the connection establishment unit 406 may use the measurement report receiving unit 402 to receive measured values ​​of wireless quality measured by the terminal 111.

[0029] Figure 5 shows an example of the functional configuration of terminal 111. Terminal 111 includes, for example, a wireless resource information receiving unit 501, a wireless quality measurement unit 502, a measurement report transmission unit 503, a wireless resource allocation request unit 504, a connection establishment unit 505, and an information holding unit 506 as its functions. Figure 5 shows the functional configuration of terminal 111 in this embodiment, and omits, for example, the general configuration of terminal 111. These functional units can be realized, for example, by the processor 301 executing a program stored in ROM 302 or storage device 304 and controlling the communication circuit 305 as needed. However, it is not limited to this, and for example, dedicated hardware for realizing each function may be provided.

[0030] The wireless resource information receiving unit 501 receives information indicating the wireless resources allocated by the base station 101. For example, the wireless resource information receiving unit 501 receives information indicating the wireless resources for receiving data from the base station 101. The wireless resource information receiving unit 501 also receives information indicating the wireless resources for transmitting data to the base station 101. Furthermore, the wireless resource information receiving unit 501 receives information indicating a first wireless resource from which a reference signal to be used for measuring wireless quality to identify the channel state when disconnected is transmitted. The wireless resource information receiving unit 501 also receives information indicating a second wireless resource for reporting the wireless quality measurement results to the base station 101 during the procedure for establishing a connection with the base station 101.

[0031] The wireless quality measurement unit 502 performs wireless quality measurements to determine the state of the channel between it and the base station 101. For example, the wireless quality measurement unit 502 performs wireless quality measurements using a reference signal received in a first wireless resource notified by the base station 101.

[0032] The measurement report transmission unit 503 reports the measured wireless quality values ​​measured by the wireless quality measurement unit 502 to the base station 101. For example, the measurement report transmission unit 503 may report the measurement using message 3 in a random access procedure.

[0033] The wireless resource allocation request unit 504 requests the allocation of a second wireless resource to report the measured wireless quality values ​​measured by the wireless quality measurement unit 502 to the base station 101. For example, the wireless resource allocation request unit 504 may request the allocation of a second wireless resource using message 1 in the random access procedure.

[0034] The connection establishment unit 505 executes a procedure to establish a connection with the base station 101. For example, the connection establishment unit 505 establishes a connection with the base station 101 using a random access procedure. In the random access procedure, the connection establishment unit 505 uses the radio resource allocation request unit 504 to request radio resources for reporting measured radio quality values. Also, in the random access procedure, the connection establishment unit 505 uses the measurement report transmission unit 503 to report measured radio quality values ​​to the base station 101.

[0035] The information holding unit 506 holds information indicating the first radio resource notified by the base station 101 when transitioning to a disconnected state. If the information holding unit 506 indicates an expiration date for holding the information indicating the first radio resource, it may discard the information indicating the first radio resource when that expiration date has passed.

[0036] (Processing Flow) The operations performed by the base station 101 and the terminal 111 will be described. Figure 6 shows an example of a sequence of messages exchanged between the base station 101 and the terminal 111. In Figure 6, it is assumed that the terminal 111 is connected to the base station 101. Then, the terminal 111 transitions to a disconnected state based on instructions from the base station 101, and then transitions back to a connected state. Although Figure 6 shows communication between the base station 101 and the terminal 111, it is also possible that a network device (NW) connected to the base station 101 communicates with the terminal 111 via the base station 101. First, when the base station 101 decides to transition the connected terminal 111 to a disconnected state, it sends a notification (S601) that includes information indicating a first radio resource from which a reference signal to be used when measuring radio quality in the disconnected state is transmitted. For example, the base station 101 may send this notification using an ECT Config message. For example, the reference signal may be CSI-RS. Furthermore, base station 101 notifies terminal 111 to transition to a disconnected state (S602). For example, base station 101 can do this by sending an RRC Release message. Base station 101 may also include information indicating a first radio resource in the RRC Release message. This allows a single message to transition terminal 111 from a connected state to a disconnected state while simultaneously instructing it to maintain the information indicating the radio resource to which CSI-RS is transmitted, even in the disconnected state. For example, by transitioning from a connected state to a disconnected state, particularly to the RRC Idle state, terminal 111 can discard the settings (config) it used in previous communications. Therefore, by transitioning to a disconnected state, terminal 111 can discard the information indicating the radio resource for receiving the reference signal transmitted by base station 101. In response to this, the base station 101 notifies the terminal 111 to maintain information indicating the radio resources for receiving the reference signal even when transitioning to a disconnected state, thereby enabling the terminal 111 to perform radio quality measurements even in a disconnected state.Furthermore, when communicating with terminal 111, base station 101 may notify terminal 111 to maintain the setting for a radio resource that periodically transmits CSI-RS. This eliminates the need to notify information identifying the first radio resource, thereby reducing the amount of information exchanged between base station 101 and terminal 111.

[0037] Terminal 111 transitions to a disconnected state based on a notification from the base station, while retaining information indicating the first radio resource. Terminal 111 may periodically measure the radio quality using reference information received based on the information indicating the first radio resource while in the disconnected state. Alternatively, terminal 111 may not periodically measure the radio quality while in the disconnected state, but may measure the radio quality based on the occurrence of a predetermined trigger for transitioning to a connected state.

[0038] Terminal 111 performs cell reselection when a predetermined trigger for transitioning to a connected state occurs. Terminal 111 also performs a procedure to establish a connection to the cell selected by cell reselection. For example, when a predetermined trigger for transitioning to a connected state occurs, terminal 111 measures the radio quality using a reference signal received in the first radio resource (S603, S604). Note that if terminal 111 has measured the radio quality periodically in the disconnected state, or before a predetermined trigger for transitioning to a connected state occurs, and has retained the measurement results, it does not need to perform a new radio quality measurement. Alternatively, terminal 111 may receive a reference signal in the first radio resource in parallel with the procedure for establishing a connection with base station 101 after a predetermined trigger for transitioning to a connected state occurs, and measure the radio quality using the received reference signal.

[0039] Terminal 111 may, for example, perform a random access procedure. First, terminal 111 transmits message 1 (RACH Msg1) containing a random access preamble (S605). For example, terminal 111 performs cell synchronization using a synchronization signal transmitted by base station 101 and identifies the radio resource to be used for random access by receiving a system information block transmitted by base station 101. As an example, the synchronization signal is a Synchronization Signal Block (SSB), and the system information block is a System Information Block (SIB). The radio resource to be used for random access may be called a RACH. RACH is an abbreviation for Random Access Channel. Terminal 111 transmits message 1 containing a random access preamble using the identified RACH. When base station 101 receives message 1, it sends message 2 (RACH Msg2) containing a Random Access Response (S606). The Random Access Response contains information identifying the radio resources that terminal 111 can use to send message 3 (RACH Msg3). When terminal 111 receives message 2 from base station 101, it sends message 3 using the radio resources identified in message 2 (S607). When base station 101 receives message 3 from terminal 111, it sends message 4 indicating that the random access was successful (S608). For example, message 4 may contain a temporary network identifier to be assigned to terminal 111. This completes the random access procedure.

[0040] Terminal 111 may report the radio quality measurement results to base station 101 in the random access procedure. For example, if one of several preamble patterns of the random access preamble is associated with a request for the allocation of a second radio resource to report the radio quality measurement results, terminal 111 may request the allocation of a second radio resource from base station 101 by sending message 1 using the random access preamble of this preamble pattern. Based on receiving the random access preamble of the preamble pattern associated with the request for the allocation of a second radio resource, base station 101 may allocate the second radio resource to terminal 111. For example, base station 101 may include information indicating the second radio resource in the random access response contained in message 2. Based on the received message 2, terminal 111 reports the radio quality measurement results on the second radio resource. Furthermore, if any of the multiple RACHs are associated with a request for the allocation of a second radio resource, terminal 111 may request the allocation of a second radio resource from base station 101 by sending message 1 using this RACH. In this case, base station 101 may allocate the second radio resource to terminal 111 based on the receipt of message 1 in this RACH.

[0041] Next, terminal 111 exchanges RRC-level messages with base station 101 to configure radio resources and communication parameters. For example, terminal 111 sends an RRCSetupRequest message requesting RRC-level configuration (S609). Base station 101 sends an RRC Setup message to terminal 111 to configure radio resources and communication parameters (S610). After terminal 111 has completed the received configuration, it sends an RRCSetupComplete message (S611). As a result, terminal 111 establishes an RRC-level connection with base station 101 and enters a connected state with base station 101. Base station 101 controls communication based on the reported radio quality. Base station 101 may also include communication parameters determined based on the radio quality reported by terminal 111 in the RRC Setup message. For example, based on the reported radio quality, the base station 101 can select a beam for its own device or terminal 111, control the transmit power, determine the MCS, allocate radio resources, etc. In this way, when terminal 111 transitions from a connected state to a disconnected state, terminal 111 is notified of a first radio resource that transmits a reference signal to be used to measure radio quality in the disconnected state, enabling terminal 111 to measure radio quality even in the disconnected state. Furthermore, when terminal 111 reconnects, it can quickly report the radio quality measurement results to the base station 101.

[0042] (Modification 1) The base station 101 may notify a specific terminal 111 that it should maintain information indicating the first radio resource. For example, depending on the type of data communicated by the terminal 111, the requirements for the period from the start of the connection establishment procedure to the measurement of radio quality may not be high. As an example, the base station 101 may notify a terminal 111 communicating data with high latency requirements that it should maintain information indicating the first radio resource. By shortening the time it takes for the terminal 111 communicating data with high latency requirements to perform the connection establishment procedure, the communication quality provided to that terminal 111 can be improved. In addition, by shortening the time it takes for control of communication with that terminal 111 to be properly performed, it may become easier to meet the latency requirements. For example, the base station 101 determines whether or not to notify the terminal 111 that it should maintain information indicating the first radio resource based on information indicating the priority of the data being communicated by the connected terminal 111. For example, base station 101 may determine, based on the value indicating data priority exceeding a predetermined threshold, that it should issue a notification indicating that terminal 111 should maintain information indicating the first radio resource when transitioning to a disconnected state. Alternatively, base station 101 may determine, based on the value indicating data priority being below a predetermined threshold, that it should not issue a notification indicating that terminal 111 should maintain information indicating the first radio resource when transitioning to a disconnected state. For example, base station 101 may determine priority based on the 5QI value of the data being communicated. 5QI is an abbreviation for 5G QoS Identifier. 5QI is a quality of service identifier assigned to each QoS flow containing the data being communicated. Each of the 5QI values ​​is associated with priority, latency, error rate, usage, etc. For example, a value of 1 may be associated with a voice packet as a 5QI. A value of 2 may be associated with a bitrate-guaranteed video packet as a 5QI. A value of 5 may be associated with voice control as a 5QI. A value of 8 can be associated with 5QI for video packets with an unguaranteed bitrate. A value of 9 can be associated with 5QI for data communications.If the 5QI value is 1, a priority of 20 and a request delay of 100ms may be associated. If the 5QI value is 2, a priority of 40 and a request delay of 150ms may be associated. If the 5QI value is 5, a priority of 10 and a request delay of 100ms may be associated. If the 5QI value is 8, a priority of 80 and a request delay of 300ms may be associated. If the 5QI value is 9, a priority of 90 and a request delay of 300ms may be associated. A smaller value indicating priority is considered to indicate a higher priority. For example, base station 101 may set a predetermined threshold value of 50 for priority. In this case, a notification may be sent to terminal 111 communicating data included in a QoS flow where the 5QI values ​​are 1, 2, or 5, indicating that it should maintain information indicating the first radio resource. Also, base station 101 may set a predetermined threshold value of 120 for request delay. In this case, a notification may be sent to terminal 111 that communicates data included in a QoS flow where the 5QI value is 1 or 5, indicating that it should maintain information indicating the first wireless resource.

[0043] The base station 101 may determine whether or not to issue a notification indicating that information indicating the first radio resource should be maintained, based on the reception quality from the connected terminal 111. For example, if the base station 101 decides to transition the connected terminal 111 to a disconnected state, it may measure the received power from the terminal 111 and, based on the measurement value being higher than a predetermined threshold, determine to issue a notification indicating that information indicating the first radio resource should be maintained. If the communication parameters used for communication between the base station 101 and the terminal 111 between the start of the procedure for establishing a connection and the measurement of radio quality are less efficient than the communication parameters that should actually be used, the radio quality provided to the terminal 111 may temporarily decrease. By promptly using the communication parameters that should be used for communication with the terminal 111, the decrease in radio quality provided to the terminal 111 can be quickly resolved. Furthermore, if base station 101 decides to transition a connected terminal 111 to a disconnected state, it may measure the reception quality from that terminal 111 and, based on whether the measured value is lower than a predetermined threshold, determine to issue a notification indicating that the information indicating the first radio resource should be maintained. If the reception quality from terminal 111 is low, communication between base station 101 and terminal 101 may become unstable. Base station 101 may perform control to stabilize communication with terminal 111 by identifying the state of the channel between its device and terminal 111 at an early stage.

[0044] The base station 101 may determine whether to send a notification indicating that information indicating a first radio resource should be retained based on the number of terminals 111 connected to the base station 101 itself. For example, when the base station 101 determines to transition a terminal 111 in a connected state to a disconnected state, the base station 101 may determine to send a notification indicating that information indicating a first radio resource should be retained based on that the number of terminals 111 connected to the base station 101 itself does not exceed a predetermined threshold. Furthermore, when the base station 101 determines to transition a terminal 111 in a connected state to a disconnected state, the base station 101 may determine not to send a notification indicating that information indicating a first radio resource should be retained based on that the number of terminals 111 connected to the base station 101 itself exceeds a predetermined threshold. For example, when there are a large number of terminals 111 that retain information indicating a first radio resource, if these terminals 111 all execute a random access procedure simultaneously, there may be a shortage of second radio resources allocated for reporting measurement results of radio quality. The base station 101 can avoid a situation where the second radio resource is insufficient by keeping the number of terminals 111 that are caused to retain information indicating the first radio resource within a range of a predetermined threshold.

[0045] The method by which base station 101 causes a specific terminal 111 to maintain information indicating the first radio resource is not limited to the above. For example, when base station 101 decides to transition a connected terminal 111 to a disconnected state, it may determine that it should notify the terminal 111 that it should maintain information indicating the first radio resource, based on whether the terminal 111 supports ECT. In this case, base station 101 may determine that it should not notify the terminal 111 that it should maintain information indicating the first radio resource if the terminal 111 does not support ECT. Base station 101 can determine whether or not a terminal 111 supports ECT by obtaining capability information from the terminal 111. In the above explanation, base station 101 has used an example where it decides to transition a connected terminal 111 to a disconnected state and notifies the terminal 111 that it should maintain information indicating the first radio resource. However, when base station 101 decides to transition a connected terminal 111 to a disconnected state, it may also notify the terminal 111 of information indicating whether or not it should maintain information indicating the first radio resource. In this case, the base station 101 may notify all terminals 111 that are to be transitioned to a disconnected state.

[0046] (Modification 2) When the base station 101 notifies the terminal 111 to transition to a disconnected state of information indicating a first radio resource, it may also notify the terminal 111 of the deadline for retaining the information indicating the first radio resource. The terminal 111 may retain the information indicating the first radio resource notified by the base station 101 and discard the information indicating the first radio resource based on the expiration of the deadline. If the terminal 111 has information indicating the first radio resource, it will measure the radio quality using the reference signal transmitted in the first radio resource; if it does not have information indicating the first radio resource, it will not measure the radio quality using the reference signal transmitted in the first radio resource. For example, the terminal 111 may select a base station other than the base station 101 when re-selecting during reconnection. As an example, the terminal 111 may select a base station other than the base station 101 if it moves away from the location where the base station 101 is located. In this case, there is a possibility that the reference signal cannot be received in the first radio resource notified to the base station 101. By discarding the information indicating the first wireless resource based on the aforementioned deadline, terminal 111 can avoid attempting the measurement.

[0047] (Modification 3) The signal used by the base station 101 as a reference signal is not limited to CSI-RS. For example, the base station 101 may use SRS as a reference signal to perform radio quality measurement. In this case, when the base station 101 decides to transition the terminal 111 to a disconnected state, it may notify the terminal 111 of a first radio resource from which to transmit SRS. The terminal 111 retains information indicating the first radio resource. Then, when a predetermined trigger for transitioning to a connected state occurs, the terminal 111 starts transmitting SRS using the first radio resource. The terminal 111 also notifies the base station 101 that it is transmitting SRS during the procedure for establishing a connection. For example, the terminal 111 may notify the base station 101 that it is transmitting SRS using message 1 or message 3 of the random access procedure. When the base station 101 identifies that SRS transmission is taking place during the random access procedure with the terminal 111, it receives the SRS on the first radio resource. Then, the base station 101 uses the received SRS to measure the wireless quality with the terminal 111.

[0048] (Modification 4) After shifting the terminal 111 to a disconnected state, the base station 101 may change the radio resource for transmitting a reference signal from the first radio resource notified to the terminal 111 to another radio resource. In this case, the base station 101 needs to notify the terminal 111 in the disconnected state of the changed radio resource. For example, when the terminal 111 performs a periodic reception operation, the base station 101 can notify the changed radio resource. As an example, when performing a power saving operation in the disconnected state, the terminal 111 performs a reception operation in a paging cycle. The terminal 111 monitors a paging channel for each paging cycle. The base station 101 can notify the changed radio resource via the paging channel in accordance with the paging cycle of the terminal 111 that has been shifted to the disconnected state. Further, when the terminal 111 is in an RRC Inactive state, the base station 101 can notify the changed radio resource using SDT. SDT is an abbreviation for Small Data Transmission. For example, when the terminal 111 shifts to the disconnected state, the base station 101 can allocate periodic radio resources for SDT to the terminal 111. The base station 101 can notify the terminal 111 of the changed radio resource using the periodic radio resource. When the terminal 111 is notified of information indicating the changed radio resource from the base station 101, the terminal 111 updates the information indicating the first radio resource with the information indicating the changed radio resource. Accordingly, the terminal 111 can measure radio quality by using the reference signal transmitted on the changed radio resource.

[0049] As described above, according to this embodiment, when transitioning terminal 111 from a connected state to a disconnected state, terminal 111, now in the disconnected state, sends a notification containing information indicating a first radio resource from which a reference signal for measuring the reception quality from base station 101 is transmitted. In the procedure for terminal 111 transitioning from the disconnected state to a connected state, a report containing the measured reception quality value measured using the reference signal is received from terminal 111. On the other hand, upon receiving a notification from base station 101, terminal 111 measures the reception quality using the reference signal while in the disconnected state, and in the procedure for transitioning to a connected state, transmits a report containing the measured reception quality value measured using the reference signal to base station 101. With this configuration, reception quality measurement can be performed in terminal 111 before the procedure for terminal 111 transitioning from a disconnected state to a connected state begins, thus enabling the establishment of a connection, including the communication of channel status information, to be completed early. As a result, even if there is a requirement for a certain level of communication quality in the data communicated by terminal 111, appropriate control can be performed promptly after terminal 111 connects with base station 101, making it easier to satisfy that communication quality requirement. Therefore, it becomes possible to contribute to Goal 9 of the United Nations-led Sustainable Development Goals (SDGs): "Build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0050] The invention is not limited to the embodiments described above, and various modifications and changes are possible within the scope of the gist of the invention.

[0051] This application claims priority based on Japanese Patent Application No. 2025-043432, filed on 18 March 2025, and all of its contents are incorporated herein by reference.

Claims

1. A base station device that communicates with a terminal device based on the cellular communication standard of the Third Generation Partnership Project (3GPP), comprising: notification means for notifying the terminal device, which, when transitioning the terminal device connected to the base station device from a connected state to a disconnected state, provides information indicating a first radio resource from which a reference signal is transmitted for measuring the reception quality from the base station device; receiving means for receiving a report from the terminal device, which includes a measurement value of the reception quality measured using the reference signal, in a predetermined procedure for the terminal device transitioning from a disconnected state to a connected state; and control means for controlling communication with the terminal device based on the reception quality.

2. The base station device according to claim 1, wherein the reference signal is a Channel State Information Reference Signal (CSI-RS).

3. The base station device according to claim 1 or 2, further comprising determination means for determining whether a value indicating the priority of data being communicated between the terminal device and the base station device that transitions from the connected state to the disconnected state is higher than a predetermined threshold, wherein the notification means provides the notification to the terminal device based on the fact that the value indicating the priority is higher than the predetermined threshold.

4. The base station device according to claim 1 or 2, further comprising determination means for determining whether the number of communication devices connected to the base station device is greater than a predetermined threshold at the timing of transitioning the terminal device from the connected state to the disconnected state, wherein the notification means provides the notification to the terminal device based on the fact that the number is less than the predetermined threshold.

5. The base station device according to claim 1 or 2, further comprising determination means for determining whether the reception quality from the terminal device that causes the transition from the connected state to the disconnected state is greater than a predetermined threshold, wherein the notification means provides the notification to the terminal device when the reception quality is greater than the predetermined threshold.

6. The base station device according to any one of claims 1 to 5, wherein the receiving means further receives from the terminal device a request for the allocation of a second radio resource for making the report in the predetermined procedure, and the base station device further has an allocation means for allocating the second radio resource based on the request.

7. The base station device according to claim 6, wherein the predetermined procedure is a four-step random access procedure, the receiving means receives the request using message 1 including a random access preamble, the assigning means assigns the second radio resource using message 2 including a random access response, and the receiving means receives the report using message 3 transmitted using the second radio resource.

8. The base station device according to any one of claims 1 to 7, wherein the notification means provides a notification that further includes information indicating a period of time during which the terminal device transitioning from the connected state to the disconnected state should retain information indicating the first radio resource.

9. A base station device that communicates with a terminal device based on the cellular communication standard of the Third Generation Partnership Project (3GPP), comprising: notification means for notifying the terminal device, which, when transitioning the terminal device connected to the base station device from a connected state to a disconnected state, provides information indicating a first radio resource from which a reference signal should be transmitted for measuring the radio quality between the disconnected terminal device and the base station device; receiving means for receiving a notification from the terminal device indicating that the first radio resource should transmit the reference signal in a predetermined procedure for the disconnected terminal device to transition to the connected state; and control means for controlling communication with the terminal device based on the radio quality measured by the reference signal.

10. A terminal device that communicates with a base station device based on the cellular communication standard of the Third Generation Partnership Project (3GPP), comprising: receiving means for receiving a notification from the base station device that includes information indicating a first radio resource from which a reference signal is transmitted for measuring the reception quality from the base station device when the terminal device transitions from a connected state to a disconnected state; measuring means for performing the measurement using the reference signal in the disconnected state; and transmitting means for transmitting a report to the base station device that includes a measurement value of the reception quality measured using the reference signal in a predetermined procedure for the terminal device transitioning from the disconnected state to the connected state.

11. The terminal device according to claim 10, wherein the reference signal is a Channel State Information Reference Signal (CSI-RS).

12. The terminal device according to claim 10 or 11, wherein the transmitting means further transmits to the base station device a request for the allocation of a second radio resource for making the report in the predetermined procedure, the receiving means further receives information indicating the second radio resource allocated based on the request, and the transmitting means transmits the report using the second radio resource.

13. The terminal device according to claim 12, wherein the predetermined procedure is a four-step random access procedure, the transmitting means transmits the request using message 1 including a random access preamble, the receiving means receives information indicating the second radio resource using message 2 including a random access response, and the transmitting means transmits message 3 including the report using the radio resource allocated by message 2.

14. The terminal device according to any one of claims 10 to 13, wherein the receiving means receives the notification further including information indicating a period for which information indicating the first wireless resource should be retained, the terminal device further has retaining means for retaining information indicating the first wireless resource during the retaining period and discarding the information indicating the first wireless resource based on the expiration of the retaining period, and the measuring means performs the measurement if information indicating the first wireless resource is retained and does not perform the measurement if information indicating the first wireless resource is not retained.

15. A terminal device that communicates with a base station device based on the cellular communication standard of the Third Generation Partnership Project (3GPP), comprising: receiving means for receiving a notification from the base station device that includes information indicating a first radio resource to which a reference signal should be transmitted for measuring the radio quality between the terminal device in the disconnected state and the base station device when transitioning from a connected state to a disconnected state; and transmitting means for transmitting a notification to the base station device indicating that the reference signal should be transmitted at the first radio resource in a predetermined procedure for the terminal device in the disconnected state to transition to the connected state.

16. A control method performed by a base station device that communicates with a terminal device based on the cellular communication standard of the Third Generation Partnership Project (3GPP), comprising: when transitioning the terminal device connected to the base station device from a connected state to a disconnected state, the base station device notifies the terminal device including information indicating a first radio resource from which a reference signal for measuring the reception quality from the base station device is transmitted; in a predetermined procedure for the disconnected terminal device to transition to the connected state, the base station device receives a report from the terminal device including a measurement value of the reception quality measured using the reference signal; and controlling communication with the terminal device based on the reception quality.

17. A control method performed by a terminal device that communicates with a base station device based on the cellular communication standard of the Third Generation Partnership Project (3GPP), comprising: when transitioning from a connected state to a disconnected state, the terminal device in the disconnected state receives a notification from the base station device that includes information indicating a first radio resource from which a reference signal for measuring the reception quality from the base station device is transmitted; a measurement step of performing the measurement using the reference signal in the disconnected state; and in a predetermined procedure for the terminal device in the disconnected state to transition to the connected state, transmitting a report to the base station device that includes a measurement value of the reception quality measured using the reference signal.

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