JP7418589B2 - User terminal and wireless communication method - Google Patents

Description

The present invention relates to a user terminal and a wireless communication method.

The 3GPP (Third Generation Partnership Project), an international standardization organization, has developed LTE (Long Term Evolution), a 3.9th generation Radio Access Technology (RAT), and LTE-Advanced, a 4th generation RAT. As a successor, Release 15 of NR (New Radio), which is a fifth generation (5G) RAT, has been specified (for example, Non-Patent Document 1). 3GPP is also considering NR release 16 and later.

NR is being considered to be able to operate in multiple frequency ranges (FR). For example, as FRs in which NR operates, FR1 corresponding to 410 MHz to 7125 MHz and FR2 corresponding to 24250 MHz to 52600 MHz are being considered. Further, each FR includes a plurality of frequency bands.

3GPP TS 38.300 V15.9.0 (2020-03)

In NR, even if the frequency band is supported by a specific user equipment (UE), it is being considered to limit the access of that specific user equipment (UE). In this case, even if the cell has a carrier frequency within the frequency band supported by the specific user terminal, the specific user terminal is denied access to the cell, so the specific user terminal cannot communicate properly. There is a possibility that it may not be possible.

The present invention has been made in view of the above circumstances, and provides a user terminal and a wireless communication method that allow appropriate communication even when access of a specific user terminal is restricted in a specific frequency band. One of the purposes is to do so.

A user terminal according to one aspect of the present invention includes a receiving unit that receives priority information indicating the priority of one or more carrier frequencies and information regarding access restrictions for a specific user terminal in a specific frequency band; a determining unit that determines a priority of a carrier frequency within the specific frequency band based on the priority information and the information regarding the access restriction; and a selection of a cell to camp on based on the determined priority. or a control unit that controls reselection.

A wireless communication method according to another aspect of the present invention includes the step of receiving priority information indicating the priority of one or more carrier frequencies and information regarding access restrictions for a specific user terminal in a specific frequency band; a step of determining a priority of a carrier frequency within the specific frequency band based on the priority information and the information regarding the access restriction; and a step of selecting a cell to camp on based on the determined priority; and controlling reselection.

According to the present invention, communication can be performed appropriately even when access of a specific user terminal is restricted in a specific frequency band.

FIG. 1 is a diagram illustrating an example of an overview of a wireless communication system according to the present embodiment. It is a figure showing an example of the frequency band concerning this embodiment. 1 is a diagram showing an example of the hardware configuration of each device in the wireless communication system according to the present embodiment. FIG. 2 is a diagram illustrating an example of a functional block configuration of a user terminal according to the present embodiment. FIGS. 5A to 5C are diagrams illustrating an example of carrier frequency priority determination according to the present embodiment. FIG. 2 is a diagram illustrating an example of a functional block configuration of a base station according to the present embodiment. It is a figure showing an example of operation of cell selection/reselection concerning this embodiment.

Embodiments of the present invention will be described with reference to the accompanying drawings. In addition, in each figure, those with the same reference numerals may have the same or similar configurations.

(Overview of wireless communication system)
FIG. 1 is a diagram illustrating an example of an overview of a wireless communication system according to the present embodiment. As shown in FIG. 1, the wireless communication system 1 may include a user terminal 10, base stations 20A to 20B, and a core network 30. Note that when the base stations 20A to 20B and the cells C1 to C2 are not distinguished, they are collectively referred to as the base station 20 and cell C, respectively. Further, the numbers of user terminals 10 and base stations 20 shown in FIG. 1 are merely examples, and are not limited to the numbers shown.

The wireless communication system 1 operates with one or more radio access technologies (RATs). For example, the wireless communication system 1 may operate in either LTE, LTE-Advanced, or NR, or may operate in multiple RATs (multi-RAT) including LTE and/or LTE-Advanced and NR. Good too. LTE and/or LTE-Advanced is also called Evolved Universal Terrestrial Radio Access (EUTRA).

As shown in FIG. 1, the user terminal 10 is a predetermined terminal or device, such as a smartphone, a personal computer, a vehicle-mounted terminal, a vehicle-mounted device, or a stationary device. The user terminal 10 may be called user equipment (UE) or the like. The user terminal 10 may be mobile or fixed. The user terminal 10 is configured to be able to communicate using at least one RAT of EUTRA and NR, for example.

The base station 20 forms one or more cells C. The cell C may be referred to as a serving cell, a carrier, a component carrier (CC), a primary cell (PCell), a secondary cell (SCell), a special cell, or the like. Note that in FIG. 1, the base stations 20A and 20B form cells C1 and C2, respectively, but the present invention is not limited to this, and each base station may form one or more cells C. Furthermore, the plurality of base stations 20 may be connected to each other through a predetermined interface (for example, an X2 or Xn interface).

The base station 20 communicates with the user terminal 10 using either EUTRA or NR communication method. The base station 20 includes an eNodeB (eNB), ng-eNB, gNodeB (gNB), en-gNB, Next Generation-Radio Access Network (NG-RAN) node, Donor eNodeB (DeNB), Donor eNodeB (DeNB), Donor node , or Central Unit, low-power node, pico eNB, Home eNB (HeNB), Distributed Unit (DU), gNB-DU, Remote Radio Head (RRH), or Integrated Access and Backhaul/Backhauling (IAB) node, etc.

The core network 30 is, for example, a core network compatible with EUTRA (Evolved Packet Core: EPC) or a core network compatible with NR (5G Core Network: 5GC). Devices on the core network 30 (hereinafter also referred to as "core network devices") perform mobility management such as paging and location registration of the user terminals 10. The core network device may be connected to the base station 20 via a predetermined interface (eg, S1 or NG interface).

The core network device includes, for example, a Mobility Management Entity (MME) that manages the movement of the user terminal 10, an Access and Mobility Management Function (AMF) that manages C-plane information (for example, information related to access and movement management, etc.), and a U It may also include at least one User Plane Function (UPF) that controls transmission of plane information (for example, user data).

In the wireless communication system 1, the user terminal 10 can communicate with one or more base stations 20. For example, in FIG. 1, the user terminal 10 can communicate using dual connectivity (DC) that connects to two cell groups each including one or more cells C. If the two cell groups use different RATs, the DC may be called a multi-RAT DC. Further, the user terminal 10 can also perform communication using carrier aggregation (CA) that integrates a plurality of cells C.

<Channel/Signal>
Next, channels and/or signals (hereinafter also referred to as "channels/signals") used in the wireless communication system 1 will be explained. The downlink channel/signal transmitted from the base station 20 to the user terminal 10 includes, for example, at least one of the following.
・Broadcast channel used to transmit broadcast information (e.g., Physical Broadcast Channel (PBCH))
- Synchronization signal (for example, Primary Synchronization Signal (PSS) and/or Secondary Synchronization Signal (PSS))
・Downlink shared channel used for transmitting downlink data (e.g., Physical Downlink Shared Channel (PDSCH))
・Downlink control channel (for example, Physical Downlink Control Channel (PDCCH)) used for transmitting downlink control information (DCI)
- Downlink reference signal (for example, demodulation reference signal (DMRS) of PDCCH and/or PDSCH, channel state information reference signal (Channel State Information Reference Signal: CSI-RS), etc.).

Further, the uplink channel/signal transmitted from the user terminal 10 to the base station 20 includes at least one of the following.
・Random access channel used for transmitting the random access preamble (for example, Physical Random Access Channel (PRACH)
・Uplink control channel (for example, Physical Uplink Control Channel (PUCCH)) used for transmitting uplink control information (UCI)
・Uplink shared channel used for transmitting uplink data (e.g., Physical Uplink Shared Channel (PUSCH))
・Uplink reference signal (for example, PUCCH and/or PUSCH DMRS, Sounding Reference Signal (SRS), etc.)

Hereinafter, the broadcast channel, downlink shared channel, and downlink control channel included in the downlink channel/signal will be referred to as PBCH, PDSCH, and PDCCH, respectively, but it goes without saying that the names are not limited to these. Further, the random access channel, uplink control channel, and uplink shared channel included in the uplink channel/signal are respectively referred to as PRACH, PUCCH, and PUSCH, but the names are of course not limited to these.

The broadcast information transmitted on the PBCH includes system information. Further, the downlink data transmitted on the PDSCH includes, for example, system information, downlink user data, RRC (Radio Resource Control) layer information (for example, RRC message, RRC Information Element (RRC IE)), At least one piece of MAC (Medium Access Control) layer information (for example, MAC Control Element (MAC CE)) may be included.

System information is transmitted on the PBCH and/or PDSCH as described above. Further, the system information includes a master information block (MIB) and one or more system information blocks (SIB) (for example, SIB1 to SIB9). The user terminal 10 receives the MIB via the PBCH. The user terminal 10 may detect the DCI based on information in the MIB, and may receive SIB1 via the PDSCH based on the DCI. The user terminal 10 may detect the DCI based on the information included in SIB1, and receive other system information (for example, at least one of SIB2 to SIB9) via the PDSCH based on the DCI.

The DCI transmitted on the PDCCH is used for scheduling PDSCH and/or PUSCH, and is also called DCI format, scheduling information, etc. The user terminal 10 monitors PDCCH candidates within the search space, detects DCI, and receives downlink data via the PDSCH or uplink data via the PUSCH based on the detected DCI. Send.

<Frequency band>
Next, frequency bands used in the wireless communication system 1 will be explained. The wireless communication system 1 operates in one or more frequency ranges (FR). For example, the wireless communication system 1 may operate with FR1 corresponding to 410 MHz to 7125 MHz and/or FR2 corresponding to 24250 MHz to 52600 MHz. Each FR includes one or more frequency bands. The frequency band is also called an operating band, band, NR operating band, NR band, etc.

FIG. 2 is a diagram showing an example of frequency bands according to this embodiment. For example, FIG. 2 shows an example of each frequency band in FR1. As shown in FIG. 2, the upstream (UL) frequency band and the downstream (DL) frequency band may be identified by predetermined identifiers (for example, n1, n2, . . . ). Further, a duplex mode may be determined for each frequency band. The duplex mode may be either frequency division duplex (FDD), time division duplex (TDD), or supplementary uplink (SUL).

Each frequency band is associated with a plurality of ARFCNs (Absolute Radio Frequency Channel Numbers). Each frequency band is associated with an uplink ARFCN and/or a downlink ARFCN. ARFCN may identify a frequency (hereinafter referred to as "carrier frequency") at which a carrier is placed within a frequency band. The carrier frequency is also called an RF reference frequency, NR frequency, EUTRA frequency, center frequency, channel raster, simply frequency, etc. In this way, ARFCN and carrier frequency are uniquely associated. Note that the ARFCN of E-UTRA may be referred to as E-UTRAN ARFCN (EARFCN). Also, one carrier frequency may be used in one or more cells C.

Each carrier is assigned one or more frequency bands. Additionally, each carrier is assigned one or more carrier frequencies within each frequency band. Further, a supported frequency band may be determined in advance for the user terminal 10 based on the capabilities of the user terminal 10. The capability is, for example, at least one of the number of receiving antennas included in the user terminal 10, the maximum data rate, and the maximum bandwidth. Note that the receiving antenna can be referred to as a receiving antenna port, a receiving port, or the like.

<User terminal status>
Next, the state of the user terminal 10 will be explained. The states of the user terminal 10 include an idle state, an inactive state, and a connected state. The idle state is a state in which the user terminal 10 has not established an RRC connection with the base station 20, and is also called an RRC_IDLE state, idle mode, or the like.

The user terminal 10 in an idle state camps on a cell C selected by cell selection and/or cell reselection (hereinafter referred to as "cell selection/reselection"), and transmits the system information of the cell C. Receive. "Camp on to cell C" may be rephrased as "reside in cell C." The user terminal 10 may be in the EUTRA RRC_IDLE state when camping on EUTRA cell C, and may be in the NR RRC_IDLE state when camping on NR cell C. When the user terminal 10 in the idle state establishes an RRC connection, it transitions to the connected state.

The inactive state is a state in which the RRC connection of the user terminal 10 is suspended, and is also called an RRC_INACTIVE state, an inactive mode, or the like. The user terminal 10 in the inactive state camps on a cell C selected by cell selection/reselection and receives system information of the cell C. The user terminal 10 may be in the EUTRA RRC_INACTIVE state when camping on cell C of EUTRA, and may be in the NR RRC_INACTIVE state when camping on cell C of NR. When the user terminal 10 in the inactive state resumes the RRC connection, it transitions to the connected state.

The connected state is a state in which the user terminal 10 has established an RRC connection, and is also called an RRC_CONNECTED state, connected mode, or the like. The user terminal 10 in the connected state transitions to an idle state when the RRC connection is released by an RRC release message, and transitions to an inactive state when the RRC connection is temporarily suspended.

<Cell selection/reselection>
Next, cell selection and cell reselection performed by the user terminal 10 in an idle state or inactive state will be described.

Cell selection means selecting a cell C (also referred to as a "suitable cell") that satisfies predetermined criteria. In cell C, a synchronization signal block (SSB) (also called an SS/PBCH block) including a PBCH and/or a synchronization signal is transmitted from the base station 20 at a predetermined period. The user terminal 10 may select a cell C that satisfies the predetermined criteria based on the measurement result of the SSB. The user terminal 10 may camp on the selected cell C.

In cell reselection, the user terminal 10 reselects a cell C to camp on according to predetermined criteria (for example, cell reselection criteria). Cell reselection includes reselection of a cell C with the same carrier frequency as the cell C you are camping on (intra-frequency cell reselection), and reselection of a cell C with a carrier frequency different from the cell C you are camping on. (inter-frequency cell reselection), reselection of a cell C with a carrier frequency of a different RAT from the cell C to camp on (inter-RAT frequency cell reselection) .

Specifically, the user terminal 10 determines the priority of one or more carrier frequencies based on information indicating the priority of one or more carrier frequencies (hereinafter referred to as "priority information"), and sets the determined priority. The reselection of cell C may be controlled based on the degree. The priority information may be included in the system information or RRC release message, or may be inherited from another RAT. The priority information may be, for example, the RRC IE "CellReselectionPriority" and/or "CellReselectionSubPriority".

For example, SIB2 may include priority information about the current carrier frequency (also referred to as "serving frequency"). Further, the SIB4 may include a list (for example, "interFreqCarrierFreqList") of carrier frequencies different from the current carrier frequency (neighboring carrier frequencies), and may include priority information for each carrier frequency. Further, the SIB5 may include a list (eg, "carrierFreqListEUTRA") of carrier frequencies of other RATs (eg, EUTRA), and may include priority information for each carrier frequency of the other RAT.

Further, the priority information may be included in an RRC message (for example, an RRC Release message). The RRC release message is a message requesting release of an RRC connection or suspension of an RRC connection. The RRC release message may include a list of the priority information (eg, "freqPriorityListEUTRA" and/or "freqPriorityListNR") for one or more carrier frequencies. The list may include priority information regarding at least one of the current carrier frequency, surrounding carrier frequencies, and carrier frequencies of other RATs.

<Access restrictions>
By the way, in NR releases 15 and 16, the capabilities of the user terminal 10 to be supported can be determined for each frequency band. For example, in frequency bands n7, n38, n41, n77, n78, and n79 in FIG. 2, the user terminal 10 is required to have four or more receiving antennas. Furthermore, in frequency bands other than frequency bands n7, n38, n41, n77, n78, and n79 in FIG. 2, the user terminal 10 is required to include two or more receiving antennas.

In NR Release 17 and later, from the perspective of reducing the cost of user terminals 10, in specific frequency bands, user terminals 10 with lower capabilities than originally requested (hereinafter referred to as "low-capability terminals") are also supported. This is being considered. For example, in at least one of the frequency bands n7, n38, n41, n77, n78, and n79, supporting user terminals 10 with fewer than four receiving antennas (for example, two receiving antennas) is being considered.

On the other hand, the requirements of whether or not to allow access by low-capability terminals in the above-mentioned specific frequency band vary depending on the communication carrier. For example, when access by low-capability terminals is not allowed, the user terminal 10 is equipped with more receiving antennas than the low-capability terminals, so the downlink coverage is expanded and network capacity is increased. On the other hand, when allowing access by low-capacity terminals, the cost of the user terminal 10 can be reduced because the user terminal 10 does not need to be equipped with the above-mentioned many receiving antennas. Note that access may also be referred to as connect or the like.

For this reason, consideration is being given to allowing communication carriers to restrict access by low-capacity terminals in a specific frequency band by setting the base station 20 that uses the specific frequency band. However, when restricting the access of low-capability terminals in a specific frequency band, even if the carrier frequency is within the frequency band supported by the user terminal 10 subject to the access restriction, There is a possibility that access of the user terminal 10 will be denied. A similar problem is not limited to low-capacity terminals, but may occur when restricting access to specific user terminals.

Therefore, the user terminal 10 receives information regarding the access restriction of a particular user terminal 10 (for example, a low-capacity terminal) in a particular frequency band, and based on the information regarding the access restriction, the user terminal 10 selects a carrier frequency within the particular frequency band. The selection or reselection of cell C to camp on is controlled based on the determined priority. As a result, the cell C to camp on is appropriately selected or reselected, so even if access of a specific user terminal 10 is restricted in a specific frequency band, the user terminal 10 can appropriately communicate. .

(Detailed configuration of wireless communication system)
Next, the detailed configuration of each device of the wireless communication system 1 as described above will be explained. It should be noted that the following configuration is for showing a necessary configuration in the description of this embodiment, and does not exclude that each device is provided with functional blocks other than those shown in the drawings.

<Hardware configuration>
FIG. 3 is a diagram showing an example of the hardware configuration of each device in the wireless communication system according to the present embodiment. Each device in the wireless communication system 1 (for example, each of the user terminal 10 and the base station 20) includes a processor 10a, a memory 10b, a storage device 10c, a communication device 10d that performs wired or wireless communication, and an input device 10e that receives input operations. , has at least an output device 10f that outputs information and one or more antennas A.

The processor 10a is, for example, a CPU (Central Processing Unit), and controls each device within the wireless communication system 1. The processor 10a may constitute a control unit that controls each device.

The memory 10b includes, for example, ROM (Read Only Memory), EPROM (Erasable Programmable ROM), EEPROM (Electrically Erasable Programmable ROM), and/or RAM (Random Access Memory).

The storage device 10c is configured of storage such as, for example, an HDD (Hard Disk Drive), an SSD (Solid State Drive), and/or an eMMC (Embedded Multi Media Card).

The communication device 10d is a device that performs communication via a wired and/or wireless network, and is, for example, a network card, a communication module, or the like. Furthermore, the communication device 10d may include an amplifier, an RF (Radio Frequency) device that performs processing related to wireless signals, and a BB (BaseBand) device that performs baseband signal processing.

The RF device generates a radio signal to be transmitted from antenna A by, for example, performing D/A conversion, modulation, frequency conversion, power amplification, etc. on the digital baseband signal received from the BB device. Further, the RF device generates a digital baseband signal by performing frequency conversion, demodulation, A/D conversion, etc. on the radio signal received from antenna A, and transmits the digital baseband signal to the BB device. The BB device performs a process of converting a digital baseband signal into an IP packet, and a process of converting an IP packet into a digital baseband signal.

The input device 10e is, for example, a keyboard, a touch panel, a mouse, and/or a microphone. The output device 10f is, for example, a display and/or a speaker.

<Functional block configuration>
≪User terminal≫
FIG. 4 is a diagram illustrating an example of a functional block configuration of a user terminal according to this embodiment. As shown in FIG. 4, the user terminal 10 includes a receiving section 11, a storage section 12, a determining section 13, a control section 14, a measuring section 15, and a transmitting section 16.

The receiving unit 11 receives downlink channels/signals. Further, the receiving unit 11 performs processing (for example, demapping, demodulation, decoding, etc.) regarding information and/or data transmitted via the downlink channel/signal.

Specifically, the receiving unit 11 receives priority information indicating the priority of one or more carrier frequencies, and information regarding access restrictions for a specific user terminal in a specific frequency band (hereinafter referred to as "access restriction information"). , receive.

The priority information may indicate the priority of one or more carrier frequencies in the same frequency band and/or a different frequency band as the current carrier frequency. Further, the priority information may indicate the priority of one or more carrier frequencies of the same RAT and/or a different RAT from the current carrier frequency. Note that the current carrier frequency may be the carrier frequency of cell C or suitable cell to camp on.

The priority information may be included in the system information (eg, MIB, at least one of SIBs 1 to 9) and/or the RRC release message. Further, the priority information is, for example, the RRC IE "CellReselectionPriority" and/or "CellReselectionSubPriority", and may be associated with information indicating a carrier frequency (for example, ARFCN). Further, the priority information may indicate the priority using a predetermined value (for example, 0 to 7), and the lower the value, the lower the priority.

Furthermore, the access restriction information may indicate whether access of a specific user terminal 10 is restricted in a specific frequency band. For example, the access restriction information may be one bit, and the bit value may be set to "1" when restricting access. The access restriction information may be included in the system information (eg, MIB, at least one of SIBs 1 to 9) and/or the RRC release message.

In addition, specific user terminals 10 that are subject to access restrictions include user terminals 10 that have a predetermined number (for example, 2) or less of receiving antennas, and user terminals 10 that support a maximum bandwidth that is less than or equal to a predetermined value. , the user terminal 10 or the like may support a maximum data rate of a predetermined value or less. Further, the specific frequency band may be, for example, frequency bands n7, n38, n41, n77, n78, and n79. The access restriction information may be composed of multiple bits in order to apply different access restrictions to each frequency band or to each group of frequency bands.

The storage unit 12 stores the priority information and access restriction information received by the reception unit 11.

The determining unit 13 determines the priority of carrier frequencies within a specific frequency band based on the priority information and access restriction information.

Specifically, when the user terminal 10 is subject to access restriction indicated by the access restriction information, the determining unit 13 determines the priority of the carrier frequency within the specific frequency band, in addition to the priority information indicated by the priority information. may be determined to have a lower priority than the carrier frequency of the frequency band. On the other hand, if the user terminal 10 is not subject to the access restriction indicated by the access restriction information, the determining unit 13 determines the priority of the carrier frequency within the specific frequency band of the carrier frequency indicated by the priority information. The priority may be determined.

5A to 5C are diagrams illustrating an example of determining carrier frequency priorities according to this embodiment. For example, in FIGS. 5A to 5C, the user terminal 10 sets the priority of carrier frequency F _X1 corresponding to ARFCN #X1 of frequency band #X and the _priority of carrier frequency F It is assumed that priority information indicating the degree and degree is received. Further, in the priority information, it is assumed that the priority of the carrier frequency F _X1 is "5" which is higher than the priority of the carrier frequency F _Y1 which is "3". Further, it is assumed that carrier frequencies F _X1 and F _Y1 are used in cells C1 and C2, respectively. Further, it is assumed that the user terminal 10 is in an idle state or an inactive state, and is camped on the cell C1.

For example, in FIG. 5A, access by low-capability terminals is restricted in frequency band #X, but access by low-capability terminals is not restricted in frequency band #Y. The user terminal 10 receives access restriction information indicating that access of low-capacity terminals is restricted in cell C1, and the user terminal 10 has low capability for frequency band #X and is subject to access restriction in frequency band #X. Recognize that.

In FIG. 5A, since the user terminal 10 is subject to access restriction for frequency band #X, the determining unit 13 sets the priority of carrier frequency _FX1 to carrier frequency F of another frequency band #Y indicated by the priority information. The priority is determined to be lower than the priority "3" of _Y1 . For example, in FIG. 5A, the determining unit 13 considers the priority of the carrier frequency F _X1 to be the lowest priority "0" instead of the priority "5" of the carrier frequency F _X1 indicated by the priority information. As a result, the priority level "3" of the carrier frequency F _Y1 of the frequency band #Y becomes higher than the priority level "0" of the carrier frequency F _X1 of the frequency band #X.

In this way, when the user terminal 10 is subject to the access restriction for the frequency band #X, the determining unit 13 determines the priority of the carrier frequency F _X1 in the frequency band #X based on the priority information. Regardless of the indicated priority "5", the lowest priority "0" may be determined.

FIG. 5B differs from FIG. 5A in that access by low-capability terminals is restricted not only in frequency band #X but also in frequency band #Y. The user terminal 10 receives access restriction information indicating that access of low-capability terminals is restricted in frequency bands #X and #Y, and the user terminal 10 has low capability in frequency bands #X and #Y, and Recognize that access is restricted in bands #X and #Y.

In FIG. 5B, the priority information does not include the priorities of carrier frequencies of other frequency bands to which the user terminal 10 is not subject to access restrictions (that is, frequency bands other than frequency bands #X and #Y). Therefore, the determining unit 13 sets the priority of _carrier frequency F _X1 higher than the priority of carrier frequency F _Y1 according to the priorities "5" and " ₃ " of carrier frequencies F You may decide to set it higher.

In this way, the determining unit 13 determines that the user terminal 10 is subject to the access restriction for frequency bands #X and #Y, and the priority information is for carrier frequencies of other frequency bands that are not subject to the access restriction. If the priority is not indicated, the priority of the carrier frequencies F _X1 and F _Y1 may be determined according to the priorities "5" and "3" indicated by the priority information.

Although not shown, in FIG. 5B, if the priority information indicates the priority of the carrier frequency of frequency band #Z that does not restrict access by low-capacity terminals, the carrier frequencies F _X1 and F of frequency bands #X and #Y are The priorities "5" and "3" of F _Y1 may be determined to be lower than the priority of the carrier frequency of the frequency band #Z indicated by the priority information.

5C differs from FIG. 5B in that in frequency band #Y, access by low-capability terminals is restricted, while user terminal 10 is not subject to the access restriction. The user terminal 10 receives access restriction information indicating that access by low-capability terminals is restricted in frequency bands #X and #Y, and based on the access restriction information, determines whether the user terminal is subject to access restriction in frequency band #X. However, it is recognized that it is not subject to access restrictions in frequency band #Y.

In FIG. 5C, since the user terminal 10 is not subject to access restriction for frequency band #Y, the determining unit 13 sets the priority of carrier frequency F _X1 to carrier frequency F _Y1 of frequency band #Y indicated by the priority information. The priority level is set to be lower than the priority level "3". For example, in FIG. 5C, the determining unit 13 considers the priority "5" of the carrier frequency _FX1 indicated by the priority information to be the lowest priority "0". As a result, the _priority of the carrier frequency _F 0".

In this way, the determining unit 13 determines whether the frequency band restricts access by low-capacity terminals and/or whether the own terminal is subject to access restriction to the frequency band. , the priority of the carrier frequency indicated by the priority information may be updated.

Note that in FIGS. 5A to 5C, cells C1 and C2 may be the same RAT (eg, EUTRA or NR) or different RATs (eg, EUTRA and NR).

The control unit 14 controls the selection or reselection of the cell C to camp on based on the priority determined by the determination unit 13. Specifically, the control unit 14 selects or reselects a cell C of a predetermined carrier frequency based on the priority determined by the determination unit 13 and/or the measurement result by the measurement unit 15, and selects or reselects the cell C of a predetermined carrier frequency. You may camp on the selected cell C.

When the control unit 14 detects a predetermined trigger, the control unit 14 performs an access process (for example, a random access procedure) for the cell C to camp on, and establishes an RRC connection. Specifically, the control unit 14 may determine whether the user terminal 10 is denied access to the cell C based on the access restriction information received by the reception unit 11. Thereby, it is possible to prevent failure of access to cell C of a carrier frequency within the frequency band supported by the user terminal 10 due to access restriction of a specific user terminal (for example, a low-capacity terminal).

The measurement unit 15 measures one or more carrier frequencies F based on the priority determined by the determination unit 13. Specifically, the measuring unit 15 may measure the received power and/or received quality of downlink signals/channels transmitted in one or more cells C of each carrier frequency F. The received power may be, for example, Reference Signal Received Power (RSRP) or Synchronization Signal based Reference Signal Received Power (SS-RSRP). The reception quality may be, for example, Reference Signal Received Quality (RSRQ), Synchronization Signal based Reference Signal Received Quality (SS-RSRQ), and/or Synchronization Signal based Signal to Noise and Interference Ratio (SS-SINR).

The transmitter 16 transmits uplink channels/signals. Further, the transmitter 16 performs processing (for example, encoding, modulation, mapping to resources, etc.) regarding information and/or data transmitted via the uplink channel/signal.

Note that the storage unit 12 may be realized by, for example, the storage device 10c. The receiving unit 11, the measuring unit 15, and the transmitting unit 16 may be realized, for example, by the communication device 10d, or may be realized by the processor 10a executing a program stored in the storage device 10c in addition to the communication device 10d. Good too. The control unit 14 may be realized by the processor 10a executing a program stored in the storage device 10c. When executing a program, the program may be stored in a storage medium. The storage medium storing the program may be a non-transitory computer readable medium. The non-temporary storage medium is not particularly limited, and may be, for example, a USB (Universal Serial Bus) memory or a CD-ROM (Compact Disc ROM).

≪Base station≫
FIG. 6 is a diagram showing an example of a functional block configuration of a base station according to this embodiment. As shown in FIG. 6, the base station 20 includes a transmitter 21, a receiver 22, and a controller 23.

The transmitter 21 transmits downlink channels/signals. Further, the transmitter 21 performs processing (for example, encoding, decoding, mapping to resources, etc.) regarding information and/or data transmitted via the downlink channel/signal. Specifically, the transmitter 21 receives the priority information and access restriction information.

The receiving unit 22 receives uplink channels/signals. Further, the receiving unit 22 performs processing (for example, demapping, demodulation, decoding, etc.) regarding information and/or data transmitted via the uplink channel/signal.

The control unit 23 controls the transmission of downlink channels/signals by the transmitting unit 21 and/or the reception of uplink channels/signals by the receiving unit 22. Further, the control unit 23 may control the scheduling of PDSCH and/or PUSCH.

Note that the transmitter 21 and the receiver 22 may be realized, for example, by the communication device 10d, or may be realized by the processor 10a executing a program stored in the storage device 10c in addition to the communication device 10d. . The control unit 23 may be realized by the processor 10a executing a program stored in the storage device 10c.

(Operation of wireless communication system)
Next, the operation of the wireless communication system 1 configured as above will be explained.

FIG. 7 is a diagram illustrating an example of cell selection/reselection operations according to this embodiment. Note that in FIG. 7, it is assumed that the user terminal 10 is in an idle state or an inactive state, and is camped on the cell C1 of the carrier frequency F _X1 of the frequency band #X. Furthermore, in FIG. 7, as described in FIGS. 5A and 5C, it is assumed that access by the user terminal 10 is not restricted in frequency band #Y. Note that FIG. 7 is merely an example, and the steps are not limited to what is shown, and the order of steps and the like can be changed as appropriate.

As shown in FIG. 7, in step S101, the user terminal 10 receives system information from the base station 20A in the cell C1 in which it camps on. The system information may include the priority information and/or access restriction information.

Based on the access restriction information received in step S101, the user terminal 10 restricts access of a specific user terminal (for example, a low-capacity terminal) in frequency band #X that includes carrier frequency _FX1 of cell C1. Recognize that. In this case, even if a predetermined trigger is detected, the user terminal 10 does not need to perform access processing (eg, random access processing) for the cell C1. This can prevent the user terminal 10 from being denied access to the cell C1 of the supported frequency band #X.

In step S102, the user terminal 10 determines the priority of carrier frequency _FX1 in frequency band #X based on the priority information and access restriction information received in step S101. For example, as explained in FIGS. 5A and 5C, if the user terminal 10 is subject to the access restriction for the frequency band #X, the user terminal 10 uses the carrier frequency F _X1 in the frequency band #X. The priority may be determined to be the lowest priority "0" regardless of the priority "5" indicated by the priority information.

In step S103, the user terminal 10 controls the selection or reselection of a cell C to camp on based on the priority determined in step S102. For example, in the case of FIGS. 5A and 5C, cell C2 of carrier frequency F _Y1 of frequency band #Y with no access restrictions for a specific user terminal 10 (for example, a low-capacity terminal) may be selected or reselected. Here, the user terminal 10 changes the cell C to camp on from cell C1 to cell C2.

In step S104, the user terminal 10 receives system information from the base station 20B in the cell C2 in which it newly camps on. The system information may include the priority information and/or access restriction information.

Based on the access restriction information received in step _S104 , the user terminal 10 determines whether the access of a specific user terminal (for example, a low-capacity terminal) is not restricted or Recognize that you are not eligible. In step S105, the user terminal 10 may perform access processing for the cell C1 if a predetermined trigger is detected. This is because access of the user terminal 10 to the cell C2 is not denied.

Specifically, in step S105, when the user terminal 10 detects a predetermined trigger, it starts a random access procedure for the cell C2. The user terminal 10 may establish or restart the RRC connection upon completion of the random access procedure. By establishing or resuming an RRC connection, the user terminal 10 transitions from an idle state or an inactive state to a connected state.

Note that in steps S101 and S104, it is assumed that the priority information and the access restriction information are received at the same timing, but they may be received at a plurality of different timings. Further, priority information and/or access restriction information included in the RRC release message may be used instead of priority information and/or access restriction information in the system information received in step S101. The system information is unique to the cell C1 (common among the user terminals 10 in the cell C1), whereas the RRC release message is unique to the user terminal 10, so the priority information and/or Access restriction information may be given priority.

As described above, according to the wireless communication system 1 according to the present embodiment, the priority of the carrier frequency of a specific frequency band to which the user terminal 10 is subject to access restrictions is such that the user terminal 10 is not subject to access restrictions. Since the priority is set lower than the priority of the carrier frequency of other frequency bands, it becomes difficult for the cell C of the particular frequency band to be selected or reselected. As a result, even if access by a specific user terminal 10 is restricted in a specific frequency band, the user terminal 10 can appropriately communicate.

In addition, since the user terminal 10 determines whether or not to perform access processing for the cell C that it camps on based on the access restriction information transmitted by the cell C, the user terminal 10 Access to cell C can be prevented from being denied.

(Other embodiments)
In the above embodiment, the access restriction information relates to access restriction to a specific frequency band, but the target of access restriction is not limited to a specific frequency band, and may be a specific carrier frequency or a specific cell C. good. Further, the access restriction information may be notified for each frequency band, for each carrier frequency within the frequency band, or for each cell C of the carrier frequency.

The embodiments described above are intended to facilitate understanding of the present invention, and are not intended to be interpreted as limiting the present invention. The flowcharts, sequences, and elements included in the embodiments, as well as their arrangement, materials, conditions, shapes, sizes, etc., described in the embodiments are not limited to those illustrated and can be changed as appropriate. Further, it is possible to partially replace or combine the structures shown in different embodiments.

DESCRIPTION OF SYMBOLS 1... Wireless communication system, 10... User terminal, 20... Base station, 30... Core network, 11... Receiving section, 12... Storage section, 13... Determination section, 14... Control section, 15... Measurement section, 16... Transmission section , 21... Transmission section, 22... Receiving section, 23... Control section, A... Antenna, 10a... Processor, 10b... Memory, 10c... Storage device, 10d... Communication device, 10e... Input device, 10f... Output device

Claims (8)

a receiving unit that receives priority information indicating the priority of one or more carrier frequencies and information regarding access restrictions for a specific user terminal in a specific frequency band;
a determining unit that determines a priority of a carrier frequency within the specific frequency band based on the priority information and the information regarding the access restriction;
a control unit that controls selection or reselection of a cell to camp on based on the determined priority;
A user terminal equipped with. When the user terminal is subject to the access restriction, the determining unit sets the priority of the carrier frequency in the specific frequency band to be higher than the priority of carrier frequencies in other frequency bands indicated by the priority information. also determine low,
The user terminal according to claim 1. When the user terminal is not subject to the access restriction, the determining unit determines the priority of the carrier frequency in the specific frequency band to the priority of the carrier frequency indicated by the priority information.
The user terminal according to claim 1 or claim 2. the specific user terminal is a user terminal with a capability lower than the capability defined for the specific frequency band;
The user terminal according to any one of claims 1 to 3. The one or more carrier frequencies in which the priority information indicates the priority include a carrier frequency of the cell, a carrier frequency different from the carrier frequency of the cell, and a carrier of a radio access technology (RAT) different from the cell. including at least one of the frequencies;
The user terminal according to any one of claims 1 to 4. The information regarding the access restriction and/or the priority information is included in system information or an RRC release message.
The user terminal according to any one of claims 1 to 5. the user terminal is in an idle or inactive state;
The user terminal according to any one of claims 1 to 6. receiving priority information indicating the priority of one or more carrier frequencies and information regarding access restrictions for a particular user terminal in a particular frequency band;
determining the priority of carrier frequencies within the specific frequency band based on the priority information and the information regarding the access restriction;
controlling the selection or reselection of a cell to camp on based on the determined priority;
A wireless communication method having.

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