Communication device, base station, and communication method

Abstract

A communication device (100) according to an embodiment comprises: a reception unit (112) that receives, from a base station (200), both updated system information indicating a change in a period of a physical random access channel (PRACH) opportunity, and control information that is information indicating a change in the period of the PRACH opportunity and is carried by signaling of a lower layer than a radio resource control (RRC) layer; and a control unit (120) that prioritizes one of the updated system information and the control information, according to priority information received from the base station or a prescribed rule, and changes the period of the PRACH on the basis of the prioritized information.

Description

Communication device, base station, and communication method CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on and claims the benefit of priority from Patent Application No. 2023-174676, filed October 6, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a communication device, a base station, and a communication method.

[0003] 3GPP (Third Generation Partnership Project, a registered trademark; the same applies hereinafter), a standardization project for mobile communication systems, is discussing network energy saving (NES). As one NES technique, dynamic adaptation, which dynamically changes the duration of a physical random access channel (PRACH) opportunity (hereinafter referred to as PRACH period), has been proposed (see, for example, Non-Patent Document 1).

[0004] Dynamic adaptation of PRACH opportunities, e.g., by changing the PRACH period via downlink control information (DCI), allows the PRACH period to be changed at shorter intervals compared to changing the PRACH period via, e.g., system information block updates, resulting in energy savings for the network.

[0005] "RWS-230156" (On NW Energy Savings for Rel-19)

[0006] A communication device according to a first aspect includes a receiver that receives from a base station both updated system information indicating a change in a duration of a physical random access channel (PRACH) opportunity and control information indicating the change in a duration of the PRACH opportunity, the control information being carried by signaling in a layer lower than a radio resource control (RRC) layer; and a controller that prioritizes one of the updated system information and the control information according to priority information received from the base station or a predefined rule, and changes the duration of the PRACH based on the prioritized information.

[0007] A base station according to a second aspect includes a transmitter configured to transmit, to a communication device, both updated system information for modifying a duration of a Physical Random Access Channel (PRACH) opportunity and control information for modifying the duration of the PRACH opportunity, the control information being carried by signaling in a layer lower than a Radio Resource Control (RRC) layer. The transmitter transmits, to the communication device, priority information for the communication device to determine which of the updated system information and the control information should be prioritized.

[0008] A communication method according to a third aspect is a method executed by a communication device, the method comprising: receiving, from a base station, both updated system information indicating a change in a duration of a Physical Random Access Channel (PRACH) opportunity and control information indicating the change in a duration of the PRACH opportunity, the control information being carried by signaling in a layer lower than a Radio Resource Control (RRC) layer; prioritizing one of the updated system information and the control information according to priority information received from the base station or a predefined rule, and modifying the PRACH duration based on the prioritized information.

[0009] Objects, features, advantages, etc. of the present disclosure will become clearer from the following detailed description with reference to the accompanying drawings. FIG. 1 is a diagram illustrating a configuration of a mobile communication system according to an embodiment. FIG. 2 is a diagram illustrating an example configuration of a protocol stack according to an embodiment. FIG. 3 is a diagram illustrating a configuration of a UE according to an embodiment. FIG. 4 is a diagram illustrating a configuration of a base station according to an embodiment. FIG. 5 is a sequence diagram illustrating a first operation example according to an embodiment. FIG. 6 is a flowchart illustrating the first operation example according to an embodiment. FIG. 7 is a diagram (part 1) illustrating the first operation example according to an embodiment. FIG. 8 is a diagram (part 2) illustrating the first operation example according to an embodiment. FIG. 9 is a diagram (part 3) illustrating the first operation example according to an embodiment. FIG. 10 is a sequence diagram illustrating a second operation example according to an embodiment. FIG. 11 is a diagram illustrating the second operation example according to an embodiment.

[0010] A mobile communication system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0011] However, specific operations related to dynamic adaptation of PRACH opportunities are not defined, which raises concerns that communication devices may not be able to properly perform dynamic adaptation of PRACH opportunities.

[0012] Therefore, one object of the present disclosure is to provide a communication device, a base station, and a communication method that are capable of appropriately performing dynamic adaptation of PRACH opportunities.

[0013] (System Configuration) First, the configuration of a mobile communication system 1 according to this embodiment will be described with reference to Fig. 1. The mobile communication system 1 is, for example, a system that complies with the 3GPP Technical Specification (TS). In the following, the mobile communication system 1 will be described using as an example a 5th Generation System (5G system) of the 3GPP standard, i.e., a mobile communication system based on NR (NR (New Radio) radio access).

[0014] The mobile communication system 1 includes a network 10 and a user equipment (UE) 100 that communicates with the network 10. The network 10 includes a next generation radio access network (NG-RAN) 20, which is a 5G radio access network, and a 5G core network (5GC) 30, which is a 5G core network.

[0015] The UE 100 is a communication device that communicates via the base station 200. The UE 100 may be a device used by a user. The UE 100 may be a mobile device such as a mobile phone terminal such as a smartphone, a tablet terminal, a laptop PC, a communication module, or a communication card. The UE 100 may be a vehicle (e.g., a car, a train, etc.) or a device provided therein (e.g., a Vehicle UE). The UE 100 may be a transport vehicle other than a vehicle (e.g., a ship, an airplane, etc.) or a device provided therein (e.g., an Aerial UE). The UE 100 may be a sensor or a device provided therein. Note that the UE 100 may be referred to by other names such as a terminal, a terminal device, a mobile station, a mobile terminal, a mobile device, a mobile unit, a subscriber station, a subscriber terminal, a subscriber device, a subscriber unit, a wireless station, a wireless terminal, a wireless device, a wireless unit, a remote station, a remote terminal, a remote device, or a remote unit. Furthermore, the UE 100 is an example of a terminal, and the terminal may include factory equipment or the like.

[0016] The NG-RAN 20 includes multiple base stations 200. Each base station 200 manages at least one cell. One or more base stations 200 may correspond to one or more cells. A base station 200 may be replaced with a cell, or a cell may be replaced with a base station 200. A cell constitutes the smallest unit of a communication area. One cell belongs to one frequency (carrier frequency). The term "cell" may refer to wireless communication resources or to a communication target of the UE 100. Each base station 200 can perform wireless communication with the UE 100 located in its own cell. The base station 200 communicates with the UE 100 using a RAN protocol stack. Details of the protocol stack will be described later. Furthermore, the base station 200 is connected to other base stations 200 (which may be referred to as neighbor base stations) via an Xn interface. The base station 200 communicates with the neighbor base stations via the Xn interface. In addition, the base station 200 provides NR user plane and control plane protocol termination for the UE 100 and is connected to the 5GC 30 via an NG interface. Such an NR base station 200 is sometimes referred to as a gNodeB (gNB).

[0017] The 5GC 30 includes a core network device 300. The core network device 300 includes, for example, an AMF (Access and Mobility Management Function) and / or a UPF (User Plane Function). The AMF performs mobility management for the UE 100. The UPF provides functions specialized for U-plane processing. The AMF and the UPF are connected to the base station 200 via an NG interface.

[0018] (Configuration Example of Protocol Stack) Next, a configuration example of a protocol stack according to this embodiment will be described with reference to FIG.

[0019] The protocol of the wireless section between UE 100 and base station 200 includes a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, and a radio resource control (RRC) layer.

[0020] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of the UE 100 and the PHY layer of the base station 200 via a physical channel.

[0021] The MAC layer performs data priority control, retransmission processing using Hybrid ARQ (HARQ), random access procedures, etc. Data and control information are transmitted between the MAC layer of UE 100 and the MAC layer of base station 200 via a transport channel. The MAC layer of base station 200 includes a scheduler. The scheduler determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the resources to be allocated to UE 100.

[0022] The RLC layer transmits data to the RLC layer on the receiving side using the functions of the MAC layer and the PHY layer. Data and control information are transmitted between the RLC layer of the UE 100 and the RLC layer of the base station 200 via logical channels.

[0023] The PDCP layer performs header compression / decompression and encryption / decryption.

[0024] A Service Data Adaptation Protocol (SDAP) layer may be provided as an upper layer above the PDCP layer. The SDAP layer maps IP flows, which are units for Quality of Service (QoS) control by the core network, to radio bearers, which are units for QoS control by an Access Stratum (AS).

[0025] The RRC layer controls logical channels, transport channels, and physical channels according to the establishment, re-establishment, and release of radio bearers. RRC signaling for various settings is transmitted between the RRC layer of the UE 100 and the RRC layer of the base station 200. When an RRC connection exists between the RRC of the UE 100 and the RRC of the base station 200, the UE 100 is in an RRC connected state. When there is no RRC connection between the RRC of the UE 100 and the RRC of the base station 200, the UE 100 is in an RRC idle state. When the RRC connection between the RRC of the UE 100 and the RRC of the base station 200 is suspended, the UE 100 is in an RRC inactive state.

[0026] The NAS layer, which is located above the RRC layer in the UE 100, performs session management and mobility management for the UE 100. NAS signaling is transmitted between the NAS layer of the UE 100 and the NAS layer of the core network device 300.

[0027] The UE 100 has an application layer and the like in addition to the radio interface protocol.

[0028] (Radio Frame Configuration) In a 5G system, downlink transmission and uplink transmission are configured within a radio frame having a duration of 10 ms. For example, a radio frame is represented by a system frame number (SFN) ranging from 0 to 1023. For example, a radio frame is configured with 10 subframes. For example, one subframe may be 1 ms. Furthermore, one subframe may be configured with one or more slots. For example, the number of symbols that make up one slot is 14 for a normal CP (Cyclic Prefix) and 12 for an extended CP. Furthermore, the number of slots that make up one subframe varies depending on the set subcarrier spacing. For example, for a normal CP, if the subcarrier spacing is set to 15 kHz, the number of slots per subframe is 1 (i.e., 14 symbols); if the subcarrier spacing is set to 30 kHz, the number of slots per subframe is 2 (i.e., 28 symbols); if the subcarrier spacing is set to 60 kHz, the number of slots per subframe is 4 (i.e., 56 symbols); and if the subcarrier spacing is set to 120 kHz, the number of slots per subframe is 8 (i.e., 112 symbols). Furthermore, if the subcarrier spacing is set to 60 kHz for an extended CP, the number of slots per subframe is 4 (i.e., 48 symbols). That is, the number of slots constituting one subframe is determined based on the subcarrier spacing set by the base station 200. Furthermore, the number of symbols constituting one subframe is determined based on the subcarrier spacing set by the base station 200. That is, the number of symbols constituting a 1 ms subframe is determined based on the subcarrier spacing set by the base station 200, and the length of each symbol (length in the time direction) changes.

[0029] (Determination of PRACH Transmission Opportunity) The determination of a PRACH transmission opportunity will be described. For example, when performing a random access (RA) procedure, the UE 100 determines a PRACH opportunity (or referred to as a PRACH transmission opportunity).

[0030] The UE 100 may receive, for example, (a) initial access from an RRC idle state, (b) an RRC Connection Re-establishment procedure, (c) arrival of downlink data or uplink data during an RRC connected state when the uplink synchronization status is “asynchronous”, (d) arrival of uplink data when there are no physical uplink control channel (PUCCH) resources for a scheduling request (SR) available, (e) an SR failure, (f) a request by the RRC at synchronization reconfiguration (e.g., handover), (g) an RRC connection resume procedure from an RRC inactive state, (h) a request to establish timing adjustment of a secondary timing advance group (TAG), (i) other system information (OTHER The RA procedure may be performed if it is triggered by any of the following events: (i) a request for SI, (j) beam failure recovery, (k) consistent uplink listen-before-talk (UL LBT) failure in the SpCell, (l) small data transmission (SDT) in the RRC inactive state, (m) positioning purposes during the RRC connected state that require an RA procedure (e.g., when a timing advance is required for UE positioning), etc.

[0031] In the RA procedure, the UE 100 determines resources for PRACH transmission (i.e., PRACH opportunities) using, for example, a plurality of predefined random access configurations and random access (RA) parameters included in a system information block type 1 (SIB1).

[0032] The random access (RA) configuration is defined by a table (RA configuration table) that indicates associations between PRACH preamble formats, time domain allocation configurations of PRACH opportunities, and PRACH configuration indexes. The UE 100 stores the table in advance.

[0033] The RA parameters are specified, for example, by RACH configuration common information (e.g., RACH-ConfigCommon, RACH-ConfigCommonTwoStepRA) used to specify random access parameters. "RACH-ConfigCommon" may be information used to specify cell-specific random-access parameters. "RACH-ConfigCommonTwoStepRA" may be information used to specify cell-specific two-step random access type parameters.

[0034] The RACH configuration common information may include, for example, a PRACH configuration index (e.g., prach-ConfigurationIndex, msgA-PRACH-ConfigurationIndex(-r16)), information on the number of PRACH transmission opportunities (e.g., msg1-FDM, msgA-RO-FDM(-r16)), etc. "msg1-FDM" may indicate the number of PRACH transmission opportunities that are FDM-multiplexed in one instance. "msgA-RO-FDM" may indicate the number of msgA PRACH transmission opportunities that are Frequency-Division Multiplexed in one instance. The PRACH configuration index indicates which PRACH opportunity of an RA configuration is to be used in PRACH transmission from among a plurality of RA configurations defined in the RA configuration table. The UE 100 determines the PRACH opportunity using the RA configuration indicated by the PRACH configuration index.

[0035] In addition, the UE 100 maps a synchronization signal (SS) and a physical broadcast channel (PBCH) block (SSB) index (hereinafter, sometimes referred to as an SSB index) to a PRACH opportunity.

[0036] The SSB indexes are mapped to valid PRACH opportunities using parameters (e.g., the number of SSBs associated with one PRACH occasion, the number of contention-based preambles per SSB per valid PRACH opportunity) provided by the RACH configuration common information (e.g., ssb-perRACH-OccasionAndCB-PreamblesPerSSB included in RACH-ConfigCommon and / or msgA-SSB-PerRACH-OccasionAndCB-PreamblesPerSSB included in RACH-ConfigCommonTwoStepRA), for example in the following order: First, ascending order of preamble index within a single PRACH opportunity. Second, ascending order of frequency resource index for frequency multiplexed PRACH occasions. Third, ascending order of time resource for time multiplexed PRACH occasions within a PRACH slot. Fourth, ascending order of index for PRACH slots.

[0037] The association period when the UE 100 performs this mapping is specified. The association period is the smallest value in a set determined by the PRACH configuration period. The association period starts from frame 0. Within the association period, a predetermined number of SSB indices are mapped to a PRACH opportunity at least once. The UE 100 obtains the predetermined number from information (e.g., ssb-PositionsInBurst) in SIB1 or serving cell configuration common information (e.g., ServingCellConfigCommon). Note that in the set determined by the PRACH configuration period, the PRACH configuration period (ms) and the association period (the number of PRACH configuration periods) are associated in this table.

[0038] If there is a PRACH opportunity or a set of PRACH preambles that is not mapped to a predetermined number of SSB indices after an integer number of SSB indices to PRACH opportunity mapping cycles within an association period, then the SSB index is not mapped to that PRACH opportunity or set of PRACH preambles.

[0039] An association pattern period includes one or more association periods. The association pattern period is determined such that the pattern between PRACH opportunities and SSB indices repeats every 160 msec. PRACH opportunities that are not associated with an SSB index after an integer number of association periods are not used for PRACH transmission.

[0040] (SI Modification) The SI modification will be described.

[0041] When the network 10 changes (a part of) the system information, the network 10 first notifies the UE 100 of the change. The network 10 may transmit a change notification to the UE 100 in a certain modification period (hereinafter, sometimes referred to as a first modification period). Note that the change notification may be transmitted multiple times throughout the first modification period. The network 10 transmits updated system information (i.e., changed system information) in a modification period (hereinafter, sometimes referred to as a second modification period) following the first modification period.

[0042] An outline of the operation of the UE 100 when the SI is changed will be specifically described. The UE 100 receives DCI including a short message. The DCI may be DCI to which a CRC (also referred to as a CRC parity bit) scrambled with a paging radio network temporary identifier (P-RNTI) is added. This instructs the UE 100 that the system information will be updated (changed) from the modification period (second modification period) next to the first modification period in which the DCI was received.

[0043] The modification period is determined based on parameters (e.g., modificationPeriodCoeff, defaultPagingCycle) included in the SIB1 message. For example, the modification period (modification period m) is determined by the following formula: The modification period is expressed in number of radio frames.

[0044] modification period m = modificationPeriodCoeff * defaultPagingCycle, where "modificationPeriodCoeff" indicates a value for calculating the actual modification period. "defaultPagingCycle" is the default paging cycle. The value of the default paging cycle corresponds to the number of radio frames (e.g., 32, 64, 128, 256). The boundaries of the modification period are defined by SFN values ​​such that SFN mod m = 0.

[0045] The UE 100 acquires new system information (i.e., updated system information) from the start of the second modification period based on the reception of the change notification in the first modification period. The UE 100 applies the previously acquired system information until the new system information is acquired.

[0046] (Assumed Scenario) In the 3GPP, a standardization project for mobile communication systems, Network Energy Saving (NES) is being discussed. As one of the NES measures, dynamic adaptation, which dynamically changes the duration of a Physical Random Access Channel (PRACH) opportunity (hereinafter referred to as PRACH period), has been proposed.

[0047] Dynamic adaptation of PRACH opportunities, e.g., by changing the PRACH period via downlink control information (DCI), allows the PRACH period to be changed at shorter intervals compared to changing the PRACH period via, e.g., system information block updates, resulting in energy savings for the network.

[0048] However, specific operations related to dynamic adaptation of PRACH opportunities are not specified. Therefore, there is a concern that the UE 100 may not be able to properly perform dynamic adaptation of PRACH opportunities. Therefore, later, an operation for enabling proper dynamic adaptation of PRACH opportunities to be performed will be described.

[0049] For example, there is a concern that UE 100 may or may not perform dynamic adaptation without knowing whether the (re)selected cell supports dynamic adaptation. Also, for example, even if UE 100 attempts to change the PRACH period using DCI, it may not be able to determine how to change the PRACH period (for example, it may not be able to determine which RA configuration to use as the RA setting after the change), which may result in a failure of PRACH transmission and reception between UE 100 and base station 200 (cell). Therefore, later, an operation for enabling dynamic adaptation of PRACH opportunities to be appropriately performed will be described.

[0050] Furthermore, when a mechanism for changing the periodicity of PRACH opportunities by updating system information (system information block) and a mechanism for changing the periodicity of PRACH opportunities by DCI coexist, the two mechanisms may conflict with each other. In this case, it becomes unclear which mechanism UE 100 should follow to change the periodicity of PRACH opportunities, and there is a concern that an unexpected error may occur. Therefore, when UE 100 performs PRACH transmission, it may not be possible to appropriately determine which change to apply to PRACH transmission, and there is a concern that PRACH transmission and reception between UE 100 and base station 200 (cell) may fail. Therefore, an operation for enabling appropriate dynamic adaptation of PRACH opportunities will be described below.

[0051] (Configuration of User Equipment) The configuration of the UE 100 according to the embodiment will be described with reference to Fig. 4. The UE 100 includes a communication unit 110 and a control unit 120.

[0052] The communication unit 110 performs wireless communication with the base station 200 by transmitting and receiving radio signals to and from the base station 200. The communication unit 110 has at least one transmission unit 111 and at least one reception unit 112. The transmission unit 111 and the reception unit 112 may be configured to include multiple antennas and RF (Radio Frequency) circuits. The antenna converts a signal into radio waves and radiates the radio waves into space. The antenna also receives radio waves in space and converts the radio waves into a signal. The RF circuit performs analog processing of the signal transmitted and received via the antenna. The RF circuit may include a high-frequency filter, an amplifier, a modulator, a low-pass filter, etc.

[0053] The control unit 120 performs various controls in the UE 100. The control unit 120 controls communication with the base station 200 via the communication unit 110. The operations of the UE 100 described above and below may be operations controlled by the control unit 120. The control unit 120 may include at least one processor capable of executing a program and a memory that stores the program. The processor may execute the program to perform the operations of the control unit 120. The control unit 120 may include a digital signal processor that performs digital processing of signals transmitted and received via the antenna and the RF circuit. The digital processing includes processing of a RAN protocol stack. The memory stores the program executed by the processor, parameters related to the program, and data related to the program. The memory may include at least one of read-only memory (ROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), random access memory (RAM), and flash memory. All or a portion of the memory may be contained within the processor.

[0054] In the UE 100 configured in this manner, the receiver 112 receives from the base station 200 both updated system information indicating a change in the duration of the PRACH opportunity and control information indicating a change in the duration of the PRACH opportunity, the control information being carried by signaling in a layer lower than the RRC layer. The controller 120 prioritizes one of the updated system information and the control information according to priority information received from the base station 200 or a predefined rule, and changes the PRACH duration based on the prioritized information. This allows the UE 100 to appropriately determine which change to apply to the PRACH transmission when performing PRACH transmission according to the priority information received from the base station 200 or a predefined rule. The changes to be applied can be shared between the UE 100 and the base station 200 (cell), thereby preventing PRACH transmission / reception failures. As a result, dynamic adaptation can be appropriately performed. The priority information is information for determining which of the updated system information and the control information should be prioritized. The predefined rules are rules for determining which of the updated system information and the updated control information should be given priority.

[0055] (Configuration of Base Station) The configuration of the base station 200 according to this embodiment will be described with reference to Fig. 5. The base station 200 includes a communication unit 210, a network communication unit 220, and a control unit 230.

[0056] The communication unit 210 receives, for example, a radio signal from the UE 100 and transmits the radio signal to the UE 100. The communication unit 210 has at least one transmission unit 211 and at least one reception unit 212. The transmission unit 211 and the reception unit 212 may be configured to include an RF circuit. The RF circuit performs analog processing of signals transmitted and received via an antenna. The RF circuit may include a high-frequency filter, an amplifier, a modulator, a low-pass filter, etc.

[0057] The network communication unit 220 transmits and receives signals to and from the network. For example, the network communication unit 220 receives signals from adjacent base stations connected via an Xn interface, which is an interface between base stations, and transmits the signals to the adjacent base stations. The network communication unit 220 also receives signals from the core network device 300 connected via an NG interface, and transmits the signals to the core network device 300.

[0058] The control unit 230 performs various controls in the base station 200. The control unit 230 controls, for example, communication with the UE 100 via the communication unit 210. The control unit 230 also controls, for example, communication with a node (e.g., a neighboring base station, the core network device 300) via the network communication unit 220. The operations of the base station 200 described above and below may be controlled by the control unit 230. The control unit 230 may include at least one processor capable of executing a program and a memory that stores the program. The processor may execute the program to perform the operations of the control unit 230. The control unit 230 may include a digital signal processor that performs digital processing of signals transmitted and received via the antenna and the RF circuit. The digital processing includes processing of a RAN protocol stack. The memory stores programs executed by the processor, parameters related to the programs, and data related to the programs. All or a part of the memory may be included in the processor.

[0059] In the base station 200 configured in this manner, the transmitter 211 transmits to the UE 100 both updated system information indicating a change in the duration of the PRACH opportunity and control information indicating a change in the duration of the PRACH opportunity, the control information being carried by signaling in a layer lower than the RRC layer. The transmitter 211 transmits to the UE 100 priority information that enables the UE 100 to determine which of the updated system information and the control information should be prioritized. This allows the UE 100 to appropriately determine which change to apply to the PRACH transmission in accordance with the priority information received from the base station 200 when performing PRACH transmission. The changes to be applied can be shared between the UE 100 and the base station 200 (cell), thereby preventing PRACH transmission / reception from failing. As a result, dynamic adaptation can be appropriately performed.

[0060] (First Operation Example) A first operation example will be described with reference to Fig. 5 to Fig. 9. Previously described explanations may be omitted.

[0061] The UE 100 may be in an RRC idle state or an RRC inactive state with a cell managed by the base station 200. The UE 100 may also be in an RRC connected state with the cell. The cell may be a cell on which the UE 100 is camped, or may be a cell that the UE 100 has (re)selected. The cell may also be a cell to which the UE 100 has established an RRC connection. In this operation example, the description will proceed assuming that the UE 100 is in an RRC idle state.

[0062] Note that, for UE 100, communication with base station 200 may be communication with a cell. Therefore, for UE 100, receiving information / messages, etc. from base station 200 may be receiving information / messages, etc. from a cell, and transmitting information / messages, etc. to base station 200 may be transmitting information / messages, etc. to a cell.

[0063] Step S101: The transmitter 211 of the base station 200 transmits a system information block type 1 (SIB1) message to the UE 100. The transmitter 211 of the base station 200 transmits the SIB1 by broadcast. The receiver 112 of the UE 100 receives the SIB1 message from the base station 200 (cell).

[0064] The SIB1 message includes information relevant to the UE 100 when evaluating whether access to the cell is permitted. The SIB1 message may include support information regarding support for dynamic adaptation of the cell. The control unit 230 of the base station 200 may control whether to include the support information in the SIB1 message based on whether the cell supports dynamic adaptation.

[0065] The support information may indicate whether the cell supports dynamic adaptation. If the cell supports dynamic adaptation, the support information may indicate that the cell supports dynamic adaptation. On the other hand, if the cell does not support dynamic adaptation, the support information may indicate that the cell does not support dynamic adaptation. The support information may also indicate whether the cell supports dynamic adaptation depending on whether the support information is included in the SIB1 message.

[0066] The control unit 230 of the base station 200 may control whether or not to include support information in the SIB1 message based on whether or not the cell of the base station 200 supports dynamic adaptation. For example, if the cell supports dynamic adaptation, the control unit 230 of the base station 200 may (always) include support information indicating that the cell supports dynamic adaptation (e.g., "true") in the SIB1 message. Alternatively, the control unit 230 may not include support information indicating that the cell does not support dynamic adaptation in the SIB1 message. In this case, the control unit 120 of the UE 100 may determine that the cell supports dynamic adaptation by not including the support information in the SIB1 message.

[0067] Furthermore, if the cell does not support dynamic adaptation, the control unit 230 of the base station 200 may (always) include support information indicating that the cell does not support dynamic adaptation (for example, "false") in the SIB1 message. Alternatively, the control unit 230 may not include support information indicating that the cell supports dynamic adaptation in the SIB1 message. In this case, the control unit 120 of the UE 100 may determine that the cell does not support dynamic adaptation by the fact that the support information is not included in the SIB1 message.

[0068] The support information may be information indicating whether dynamic adaptation is enabled or disabled. The support information may be information indicating whether dynamic adaptation (execution of dynamic adaptation) is permitted in a cell.

[0069] Here, dynamic adaptation may be referred to as dynamic RACH adaptation, for example. Dynamic adaptation may be, for example, at least any of the following operations (or definitions): UE 100 switches RA configuration by signaling of a layer lower than the RRC layer UE 100 supports multiple PRACH configurations Multiple PRACH configurations are configured in UE 100 for one cell Multiple PRACH configurations are configured in UE 100 for one bandwidth portion (BWP) Multiple PRACH configurations are configured in UE 100 for one subcarrier spacing Multiple PRACH configurations are configured in UE 100 for one component carrier Changing configurations and / or parameters for PRACH transmission

[0070] The settings and / or parameters for PRACH transmission may be, for example, at least any of a PRACH preamble index, a preamble SCS (Subcarrier Spacing), a PRACH resource (time resource, frequency resource), and / or a period (cycle) of a PRACH opportunity.

[0071] Note that the base station 200 may include configuration information related to dynamic adaptation (hereinafter referred to as DA configuration information) in the SIB1 message, separate from the support information.

[0072] Furthermore, when the cell supports dynamic adaptation, the transmission unit 211 of the base station 200 may transmit, to the UE 100, a dedicated PDCCH configuration for monitoring a PDCCH (or DCI) that triggers a change in the RA configuration. The reception unit 112 of the UE 100 may receive the dedicated PDCCH configuration from the base station 200.

[0073] The control unit 230 of the base station 200 may, for example, include a dedicated PDCCH configuration in a system information block (e.g., SIBx). The base station 200 may include a dedicated PDCCH configuration in an individual RRC message. The dedicated PDCCH configuration may be information for configuring a search space (common search space) dedicated to dynamic adaptation and / or a CORESET.

[0074] Furthermore, when the cell supports dynamic adaptation, the transmission unit 211 of the base station 200 may transmit, to the UE 100, configuration information for configuring, in the UE 100, multiple RA configurations for determining PRACH opportunities. The UE 100 receives the configuration information. The control unit 230 of the UE 100 may perform control so that multiple RA configurations are configured in the UE 100, based on the configuration information.

[0075] The multiple RA configurations may be configured with (only) a general RA configuration that is not a dedicated RA configuration, or may be configured with (only) a dedicated RA configuration described later, or may be configured with a combination of a general RA configuration and a dedicated RA configuration. The general RA configuration may be, for example, a configuration that can be configured even in a UE 100 (which may be referred to as a legacy UE) that does not support dynamic adaptation (i.e., does not have the capability of dynamic adaptation). The general RA configuration may be, for example, an RA configuration specified in a technical specification of a release earlier than the technical specification of a release in which dynamic adaptation is supported.

[0076] Step S102: The control unit 120 of the UE 100 performs a support determination. Specifically, the control unit 120 determines whether the cell supports dynamic adaptation. For example, as described above, the control unit 120 may determine whether the cell supports dynamic adaptation based on the support information. The control unit 120 may determine whether the cell supports dynamic adaptation based on whether the SIB1 message includes the support information.

[0077] 6 , for example, in step S121, if the SIB1 message includes support information indicating that the cell supports dynamic adaptation, the control unit 120 may perform the process of step S122. On the other hand, if the SIB1 message does not include support information indicating that the cell supports dynamic adaptation, the control unit 120 may perform the process of step S123.

[0078] In step S122, the control unit 120 determines that the cell supports dynamic adaptation. If the control unit 120 determines that the cell supports dynamic adaptation, the control unit 120 may perform dynamic adaptation.

[0079] In step S123, the control unit 120 determines that the cell does not support dynamic adaptation. If the control unit 120 determines that the cell does not support dynamic adaptation, the control unit 120 does not need to perform dynamic adaptation.

[0080] Step S103: The transmitter 211 of the base station 200 transmits signaling of a layer lower than the RRC layer to the UE 100. The receiver 112 of the UE 100 receives the signaling of the lower layer from the base station 200. The signaling of the lower layer may be DCI. The signaling of the lower layer may be a PDCCH carrying DCI. The signaling of the lower layer may be signaling in the MAC layer (e.g., MAC CE). In this operation example, the description will proceed assuming that the signaling of the lower layer is DCI.

[0081] If the cell of base station 200 supports dynamic adaptation, control unit 230 of base station 200 may transmit a DCI (hereinafter, sometimes referred to as a specific DCI) that includes a specific field (or has a specific field set) for changing the duration of a PRACH opportunity. On the other hand, if the cell of base station 200 does not support dynamic adaptation, control unit 230 may transmit a DCI (hereinafter, sometimes referred to as a normal DCI) that does not include a specific field (or has a specific field not set).

[0082] The specific field may be a field for changing the duration of a PRACH opportunity. Furthermore, the specific field may be, for example, a field for changing a random access setting. The specific field may include specific information. The specific information may be information for changing the duration of a PRACH opportunity. Furthermore, the specific information may be information for changing a random access setting. Details of the specific information will be described later.

[0083] When a dedicated PDCCH configuration is configured for UE 100, transmitter 211 of base station 200 may transmit the specific DCI in a search space and / or CORESET dedicated for dynamic adaptation. Note that transmitter 211 may transmit the normal DCI in a search space and / or CORESET configured by a normal PDCCH configuration.

[0084] The specific DCI may be a DCI to which a CRC (also referred to as a CRC parity bit) scrambled with a predetermined Radio Network Temporary Identifier (RNTI) is added. The specific DCI may be information that triggers a change in RA configuration. A PDCCH including the specific DCI may be referred to as a PDCCH with a predetermined RNTI or as a PDCCH addressed to a predetermined RNTI. The predetermined RNTI may be an SI-RNTI, a P-RNTI, an RA-RNTI, and / or an RNTI dedicated to dynamic adaptation.

[0085] Note that the search space and CORESET for monitoring a specific DCI may be configured for each of one or more DL BWPs in the UE 100. In this case, the control unit 120 of the UE 100 may perform control to perform dynamic adaptation (PRACH transmission based on the dynamic adaptation) in an uplink bandwidth portion (UL BWP) corresponding to the DL BWP in which the DCI is received.

[0086] Step S104: The control unit 120 of the UE 100 may perform DCI determination. Specifically, the control unit 120 may determine whether the received DCI is a normal DCI or a specific DCI. Note that, when the control unit 120 receives predetermined signaling in a layer lower than the RRC layer, the control unit 120 may determine whether the predetermined signaling includes a specific field.

[0087] When the control unit 120 receives predetermined signaling (e.g., DCI) from a cell, the control unit 120 may determine, based on the support information, whether or not the received predetermined signaling (e.g., DCI) includes a specific field. When the control unit 120 determines, based on the support information, that the cell supports dynamic adaptation, the control unit 120 may determine that the predetermined signaling includes a specific field. The control unit 230 may determine that the received DCI is a specific DCI. On the other hand, when the control unit 120 determines, based on the support information, that the cell does not support dynamic adaptation, the control unit 230 may determine that the predetermined signaling does not include a specific field. The control unit 230 may determine that the received DCI is a normal DCI.

[0088] Furthermore, when the control unit 120 successfully decodes a PDCCH using a predetermined RNTI (for example, an RNTI dedicated to dynamic adaptation), the control unit 120 may determine that the DCI included (carried) in the PDCCH is a specific DCI.

[0089] Furthermore, when the control unit 120 receives specific field information from a cell, the control unit 120 may determine, based on the specific field information, whether or not the received predetermined signaling (e.g., DCI) includes a specific field.

[0090] The specific field information may be information indicating whether or not a specific field is included in a predetermined signaling (e.g., DCI). The specific field information may indicate that a specific field is included in the predetermined signaling (e.g., DCI). In this case, the control unit 120 determines that the specific field is included in the predetermined signaling (e.g., DCI). Therefore, the control unit 120 may determine that the received DCI is a specific DCI. On the other hand, the specific field information may indicate that the specific field is not included in the predetermined signaling (e.g., DCI). In this case, the control unit 120 determines that the specific field is not included in the predetermined signaling (e.g., DCI). Therefore, the control unit 120 may determine that the received DCI is a normal DCI.

[0091] The transmitter 211 of the base station 200 may transmit the specific field information to the UE 100. The transmitter 211 may include the specific field information in a radio resource control (RRC) message, for example. The controller 230 of the base station 200 may include the specific field information in a radio resource control (RRC) message (for example, an RRC reconfiguration message) dedicated to the UE 100, for example. The controller 230 may include the specific field information in a system information block (SIB) transmitted by broadcast.

[0092] When a dedicated PDCCH configuration is configured, the control unit 120 of the UE 100 may determine that DCI received in a search space and / or CORESET dedicated to dynamic adaptation is a specific DCI. Note that the control unit 120 may determine that DCI received in a search space and / or CORESET configured by a normal PDCCH configuration is a normal DCI.

[0093] Note that the control unit 120 may make the above determination before receiving the DCI. The control unit 120 may determine whether the received DCI is a normal DCI or a specific DCI based on the determination result. The control unit 120 may make the determination at the timing when support information is received. The control unit 120 may make the determination at the timing when specific field information is received.

[0094] In this operation example, the explanation will proceed on the assumption that the UE 100 determines that the received DCI is a specific DCI.

[0095] Step S105: The control unit 120 of the UE 100 determines a PRACH opportunity. The control unit 120 may also specify a duration of the PRACH opportunity. For example, if the cell supports dynamic adaptation, the control unit 120 may perform at least one of the following methods.

[0096] In a first method, the control unit 120 may change the RA configuration used to determine PRACH opportunities based on lower layer signaling (e.g., DCI). The control unit 120 may specify the duration of the changed PRACH opportunities based on the changed RA configuration. The control unit 120 may specify the duration of the changed PRACH opportunities based on specific information included in a specific field.

[0097] The specific information may include, for example, an index (e.g., PRACH config index) indicating an RA configuration related to the period of the PRACH opportunity after the change. The control unit 120 may change to the RA configuration indicated by the index. When multiple RA configurations are configured in the UE 100, the control unit 230 of the UE 100 may change to the RA configuration indicated by the index among the multiple configured RA configurations.

[0098] Furthermore, the specific information may include information specifying a dedicated RA configuration that is a configuration dedicated to dynamic adaptation and includes a configuration related to the duration of a PRACH opportunity. The information may indicate, for example, the dedicated RA configuration. The control unit 120 may change to the dedicated RA configuration indicated by the index. The control unit 120 may identify the duration of a PRACH opportunity after the change based on the dedicated RA configuration.

[0099] The dedicated RA configuration is specified by, for example, a table (e.g., a dedicated RA configuration table) indicating a link between a PRACH preamble format and a time domain allocation configuration of a PRACH opportunity, and a dedicated PRACH configuration index. The UE 100 may store the dedicated RA configuration table in advance. When a dedicated RA configuration is indicated by the index, the UE 100 may determine the dedicated RA configuration based on the dedicated RA configuration table instead of the RA configuration table. When multiple RA configurations are configured in the UE 100, the control unit 230 of the UE 100 may change the RA configuration to a designated dedicated RA configuration from among the multiple configured RA configurations.

[0100] When multiple RA configurations are configured in the UE 100, the control unit 120 of the UE 100 may determine the number of bits of a specific field based on the number of multiple RA configurations. For example, when two or less RA configurations are configured in the UE 100, the number of bits of the specific field may be 1. When four or less RA configurations are configured in the UE 100, the number of bits of the specific field may be 2. When eight or less RA configurations are configured in the UE 100, the number of bits of the specific field may be 3. The control unit 120 may indicate one RA configuration after the change by specific information included in a specific field represented by one or more bit numbers.

[0101] 7A, 7B, and 8, it is assumed that the control unit 120 applies (or uses or configures) an RA configuration associated with a PRACH configuration index indicating, for example, 34. In this RA configuration, it is assumed that the PRACH configuration period is 40 ms. The control unit 120 determines a radio frame to which a PRACH opportunity is allocated within the PRACH configuration period. From the determined radio frame, the control unit 120 determines a slot to which a PRACH opportunity is allocated and a symbol from the slot to which the PRACH opportunity is allocated.

[0102] Thereafter, for example, when specific information in a specific field included in the received specific DCI indicates an index of 38, the control unit 120 changes (applies) the RA setting to be applied to the RA setting associated with the PRACH setting index indicating 38. Therefore, (the specific information within) the specific DCI may be an instruction to change the PRACH setting index applied by the UE 100 from 34 to 38. In the RA setting after the change, the PRACH setting period is assumed to be 20 ms. In the same manner as described above, the control unit 120 determines the radio frame to which the PRACH opportunity is allocated, the slot to which the PRACH opportunity is allocated, and the symbol to which the PRACH opportunity is allocated.

[0103] In a second method, the control unit 120 may identify the changed duration of the PRACH opportunity based on a setting value for adjusting the duration of the PRACH opportunity.

[0104] For example, the control unit 120 may calculate a different PRACH opportunity duration based on a setting value for a PRACH opportunity duration based on an already set RA configuration. The control unit 120 may identify the calculated PRACH opportunity duration as the changed PRACH opportunity duration. Furthermore, the control unit 120 may calculate a different PRACH opportunity duration based on a setting value for a PRACH opportunity duration based on an RA configuration (or a dedicated RA configuration) determined by the first method.

[0105] The configuration value may be a scaling factor for changing the periodicity. The scaling factor may be a scaling factor that extends the periodicity of the baseline RA configuration (or a dedicated RA configuration). The control unit 230 of the base station 200 may include the configuration value in a specific DCI, for example. The receiving unit 112 of the UE 100 may receive the configuration value from the base station 200.

[0106] The control unit 120 of the UE 100 may determine the timing to change the RA setting. That is, the control unit 120 may determine the timing to apply the changed RA setting. The control unit 120 may determine the timing to change the duration of the PRACH opportunity. The control unit 120 may change the RA setting by, for example, at least one of the following methods.

[0107] In a first method, the control unit 120 may change the RA setting (or determine the timing to change the RA setting) based on a change period (hereinafter, sometimes referred to as a DA change period) related to a change in the duration of a PRACH opportunity based on dynamic adaptation. For example, as shown in FIGS. 7A and 9 , DA change periods may be repeated periodically. The control unit 120 may change the RA setting at or after the boundary between a certain DA change period (e.g., a first DA change period MP1) and the next DA change period (e.g., a second DA change period MP2). If the control unit 120 receives a specific DCI in the first DA change period MP1, the control unit 120 may change the RA setting in the second DA change period MP2. Therefore, the control unit 120 determines to change the RA setting in the second DA change period MP2.

[0108] The DA modification period may be defined or set based on the PRACH configuration period, association period, and / or association pattern period. The DA modification period may be, for example, an integer (natural number) multiple of the PRACH configuration period, association period, and / or association pattern period. The control unit 120 may determine the DA modification period based on the PRACH configuration period, association period, and / or association pattern period. The second DA modification period MP2 may be defined or set based on the PRACH configuration period, association period, and / or association pattern period in the changed RA configuration and / or dedicated RA configuration.

[0109] In a second method, the control unit 120 may change the RA setting after a minimum period has elapsed since the reception of the specific DCI. Thus, the control unit 120 determines to change the RA setting after a minimum period has elapsed since the reception of the specific DCI.

[0110] The minimum period is a minimum period during which the UE 100 is not expected to change the RA setting after receiving the lower layer signaling (specific DCI). The minimum period may be defined based on, for example, the time required for the UE 100 to change the RA setting. The minimum period may also be defined based on, for example, the time (system frame number, subframe, slot, and / or symbol) at which the lower layer signaling (specific DCI) is received, a cell-specific scheduling offset (cellSpecificKoffset), a UL BWP for PRACH transmission, and / or an SCS configuration (preamble SCS) for PRACH transmission. Note that the "cellSpecificKoffset" may be a scheduling offset used for a timing relationship modified for a Non-Terrestrial Network (NTN).

[0111] Furthermore, the control unit 120 may determine valid PRACH opportunities and / or invalid PRACH opportunities in dynamic adaptation, for example, in accordance with predefined information (for example, rules defined in a technical specification).

[0112] A valid PRACH opportunity is a PRACH opportunity where PRACH transmission is valid. An invalid PRACH opportunity is a PRACH opportunity where PRACH transmission is invalid. Therefore, the UE 100 cannot transmit the PRACH on an invalid PRACH opportunity. The UE 100 may be able to perform PRACH transmission only on a valid PRACH opportunity.

[0113] The receiver 112 of the UE 100 may receive information indicating valid PRACH opportunities and / or invalid PRACH opportunities from the base station 200. For example, the information may be included in the DA configuration information, may be included in an individual RRC message to the UE 100, or may be included in specific information (i.e., a specific field).

[0114] The control unit 120 may determine valid PRACH opportunities and / or invalid PRACH opportunities based on the information. The information may specify valid PRACH opportunities and / or invalid PRACH opportunities. The information may include, for example, a PRACH mask index. The control unit 120 may set the PRACH opportunity indicated by the index as an invalid PRACH opportunity.

[0115] Furthermore, the control unit 120 may determine, among one or more PRACH opportunities determined by changing the duration of a PRACH opportunity, a PRACH opportunity with the same timing as a PRACH opportunity determined based on the duration of the PRACH opportunity before the change as an invalid PRACH opportunity. Therefore, the control unit 120 may determine, among one or more PRACH opportunities determined by changing the duration of a PRACH opportunity, a PRACH opportunity with a different timing from the PRACH opportunity determined based on the duration of the PRACH opportunity before the change as a valid PRACH opportunity. The control unit 120 may determine whether the PRACH opportunity with the same timing as described above is a valid PRACH opportunity or an invalid PRACH opportunity based on information indicating a valid PRACH opportunity and / or an invalid PRACH opportunity.

[0116] As shown in Fig. 8, in the RA configuration before the change, it is assumed that the fourth radio frame is determined as the radio frame to which a PRACH opportunity is allocated. Next, it is assumed that the control unit 120 determines the second and fourth radio frames as the radio frames to which a PRACH opportunity is allocated in the RA configuration after the change. In this case, since a PRACH opportunity is allocated to the fourth radio frame before and after the change of the RA configuration, the control unit 120 determines that the PRACH opportunity allocated to the fourth radio frame is an invalid PRACH opportunity. As a result, the fourth radio frame may be secured as a PRACH opportunity for the conventional UE 100 and the UE 100 that does not perform dynamic adaptation.

[0117] As described above, the control unit 120 of the UE 100 may specify the period of the PRACH opportunity after the change, for example, based on the RA configuration after the change. The period of the PRACH opportunity may be any of the PRACH configuration period, the association period, and / or the association pattern period. The period of the PRACH opportunity may be the DA change period.

[0118] When the received DCI is a normal DCI, the control unit 120 of the UE 100 may determine the PRACH opportunity based on the RA setting that has already been set. The control unit 120 does not need to change the RA setting and does not need to change the duration of the PRACH opportunity.

[0119] Furthermore, when changing the RA configuration (or the duration of a PRACH opportunity), the control unit 120 of the UE 100 may remap the SSB (SSB index) to the PRACH opportunity. The control unit 120 may map the SSB (SSB index) to the PRACH opportunity taking into account the duration of the PRACH opportunity, the PRACH configuration period, the association period, and / or the association pattern period.

[0120] The SSB may be a cell-defining SSB (CD-SSB) and / or a non-cell defining SSB (NCD). The UE 100 may always perform dynamic adaptation based on the CD-SSB. The control unit 120 of the UE 100 may include information for setting the subcarrier spacing for the SSB in the serving cell and / or the downlink bandwidth portion (DL BWP) in the SIB or in an RRC message.

[0121] Furthermore, information for setting subcarrier spacing for the PRACH may be included in RACH configuration information (e.g., RACH-config common). This information may be included in predetermined configuration information (e.g., BWP-UplinkCommon) within the RACH configuration information. "BWP-UplinkCommon" may be information used to set common parameters for uplink BWPs. The subcarrier spacing may be set for each of one or more DL BWPs (e.g., initial DL BWP and / or dedicated DL BWP) and one or more UL BWPs (e.g., initial UL BWP and / or dedicated UL BWP).

[0122] In addition, if information for setting up the SSB is not included (absent) in the SIB (or RRC message), the control unit 120 of the UE 100 may perform dynamic adaptation based on the SSB settings predefined by the technical specifications.

[0123] Step S106: The transmitter 111 of the UE 100 performs PRACH transmission at the determined PRACH opportunity. The receiver 212 of the base station 200 receives the PRACH from the UE 100.

[0124] Here, a validity period may be set in the RA configuration after the change. A case will be described in which the control unit 120 of the UE 100 changes the RA configuration from a first RA configuration to a second RA configuration, for example.

[0125] 9, when a specific DCI is received in a first DA modification period MP1, the control unit 120 applies a second RA configuration in a second DA modification period MP2. The control unit 120 determines the duration of a PRACH opportunity according to the second RA configuration.

[0126] Thereafter, the control unit 120 applies the first RA configuration in the third DA change period MP3. Therefore, the control unit 120 determines the (period of) PRACH opportunities in accordance with the first RA configuration. That is, when a predetermined validity period has elapsed since the change to the second RA configuration, the control unit 120 changes from the second RA configuration to the first RA configuration. The control unit 120 executes control to return to the RA configuration before the change.

[0127] The validity period may be defined or set based on the PRACH configuration period, the association period, and / or the association pattern period. For example, the validity period may be an integer (natural number) multiple of the PRACH configuration period, the association period, and / or the association pattern period. The control unit 120 may determine the validity period based on the PRACH configuration period, the association period, and / or the association pattern period. In FIG. 9 , the predetermined validity period may be 1 time (1 cycle) the PRACH configuration period.

[0128] The receiver 112 of the UE 100 may receive information specifying the validity period from the base station 200. For example, the information specifying the validity period may be included in the DA configuration information, may be included in an individual RRC message to the UE 100, or may be included in specific information (i.e., a specific field).

[0129] The control unit 120 of the UE 100 may set the validity period when receiving information specifying the validity period. That is, the control unit 120 may execute control based on the validity period. Alternatively, when the control unit 120 receives information specifying the validity period and instruction information for setting the validity period from the base station 200, the control unit 120 may execute control based on the validity period. The instruction information may be included in a specific field, for example.

[0130] Also, a default value for the validity period may be defined in advance. Alternatively, the information specifying the validity period may include a default value in addition to a specific value indicating the validity period. The control unit 120 of the UE 100 may store a default value for the validity period in advance. When the control unit 120 does not receive information specifying the validity period, the control unit 120 may set the default value as the validity period. Alternatively, when the control unit 120 does not receive instruction information, the control unit 120 may set the default value as the validity period.

[0131] Note that the control unit 120 of the UE 100 controls the change of the RA setting (i.e., the period of the PRACH opportunity) based on the validity period, but is not limited to this. The UE 100 may change the RA setting (or restore the RA setting) in response to a direct instruction from the base station 200, for example.

[0132] The transmitter 211 of the base station 200 may transmit lower layer signaling (e.g., DCI) to the UE 100 instructing the UE 100 to change to (or revert to) the default RA configuration. The control unit 120 of the UE 100 may change to the default RA configuration based on the received signaling (e.g., DCI). The DCI may be a specific DCI. For example, a specific field of the specific DCI may include information instructing the UE 100 to revert to the default RA configuration. The control unit 120 may change to the default RA configuration based on the information. Alternatively, the DCI may be a normal DCI. The control unit 120 may change to the default RA configuration based on receiving the normal DCI.

[0133] The default RA setting may be, for example, a general RA setting. Therefore, the default RA setting may be included in the SIB1 message. Alternatively, the default RA setting may be a dedicated default RA setting. Furthermore, the default RA setting may be predefined in, for example, a technical specification. The control unit 120 may store the default RA setting. When the default RA setting is not set in the UE 100 by the base station 200, the control unit 120 may change the UE 100 to a predefined default RA setting.

[0134] As described above, the transmitter 211 of the base station 200 transmits the SIB1 message to the UE 100. The control unit 230 controls whether to include support information indicating whether the cell supports dynamic adaptation in the SIB1 message, based on whether the cell supports dynamic adaptation, which changes the duration of PRACH opportunities through signaling in layers lower than the RRC layer. The receiver 112 of the UE 100 receives, from the cell, the SIB1 message, which includes information relevant to when the UE 100 evaluates whether access to the cell is permitted. The control unit 120 controls dynamic adaptation, which changes the duration of PRACH opportunities through signaling in layers lower than the RRC layer. When the support information indicating that the cell supports dynamic adaptation is included in the SIB1 message, the control unit 120 determines that the cell supports dynamic adaptation based on the support information. This allows the UE 100 to determine that the cell supports dynamic adaptation. As a result, the UE 100 can appropriately perform dynamic adaptation in a cell that supports dynamic adaptation.

[0135] Furthermore, when the cell supports dynamic adaptation, the control unit 120 may change the RA setting used to determine the PRACH opportunity based on lower layer signaling. The control unit 120 may identify a changed PRACH opportunity based on the changed RA setting. This allows the base station 200 to change the duration of the PRACH opportunity by changing the RA setting, thereby enabling appropriate control of dynamic adaptation.

[0136] Furthermore, the receiver 112 may receive DCI including a specific field for changing the duration of the PRACH opportunity as lower layer signaling. The controller 120 may specify the changed duration of the PRACH opportunity based on specific information included in the specific field. This allows the base station 200 to appropriately control dynamic adaptation using the DCI.

[0137] Furthermore, the specific information may include an index indicating an RA configuration related to the period of the PRACH opportunity after the change. The control unit 120 may change the RA configuration to the RA configuration indicated by the index. This allows the UE 100 to know the RA configuration to be changed by dynamic adaptation. This allows the UE 100 to appropriately control the dynamic adaptation.

[0138] Furthermore, the specific information may include information specifying a dedicated RA configuration that is a configuration dedicated to dynamic adaptation and includes a configuration related to a duration of a PRACH opportunity. The control unit 120 may specify the duration of the PRACH opportunity after the change based on the dedicated RA configuration. This allows the UE 100 to appropriately control dynamic adaptation by using the dedicated RA configuration.

[0139] Furthermore, if the cell supports dynamic adaptation, the receiver 112 may receive a configuration value for adjusting the duration of the PRACH opportunity through lower layer signaling. The controller 120 may identify the duration of the PRACH opportunity after the change based on the configuration value. This allows the UE 100 to change the duration of the PRACH opportunity even if the RA setting is not changed.

[0140] Furthermore, when the cell supports dynamic adaptation, the receiver 112 may receive a dedicated PDCCH configuration for monitoring DCI that triggers a change in RA configuration. The receiver 112 may receive DCI as lower layer signaling based on the dedicated PDCCH configuration. This allows the UE 100 to determine that the received DCI is a specific DCI. The UE 100 can distinguish between normal DCI and specific DCI and appropriately control dynamic adaptation.

[0141] Furthermore, a change period for changing the duration of a PRACH opportunity based on dynamic adaptation may be periodically repeated. The control unit 120 may change the RA setting in a change period following the change period for which lower layer signaling was received. This allows the base station 200, when configuring dynamic adaptation for multiple UEs 100, to change the RA setting of each UE 100 simultaneously, rather than changing the RA setting at the timing of each UE 100 individually. As a result, the control load of the base station 200 can be reduced.

[0142] Furthermore, the control unit 120 may change the RA setting after a minimum period has elapsed since receiving the lower layer signaling, which is a period during which the UE 100 is not expected to change the RA setting. This makes it possible to prevent PRACH transmission / reception from failing due to differences in the RA settings applied between the UE 100 and the base station 200, which are caused by the UE 100 being unable to immediately set the RA setting depending on its capability.

[0143] Furthermore, the control unit 120 may determine, among one or more PRACH opportunities determined by changing the duration of the PRACH opportunity, a PRACH opportunity with the same timing as a PRACH opportunity determined based on the duration of the PRACH opportunity before the change as a PRACH opportunity in which PRACH transmission is disabled. This makes it possible to differentiate the PRACH opportunities between the UE 100 that performs dynamic adaptation, the conventional UE 100, and the UE 100 that does not perform dynamic adaptation. As a result, it becomes difficult for the UEs 100 that perform PRACH transmission on a specific PRACH opportunity to concentrate, the RACH load of the cell does not increase, and the PRACH success rate can be increased.

[0144] Furthermore, the control unit 120 may change the RA setting from the first RA setting to the second RA setting. When a predetermined validity period has elapsed since the change to the second RA setting, the control unit 120 may change from the second RA setting to the first RA setting. This allows the base station 200 to restore the RA setting of the UE 100 to its original state without issuing an instruction to do so.

[0145] Furthermore, when the control unit 120 receives predetermined signaling of a layer lower than the RRC layer from a cell, the control unit 120 may determine, based on the support information, whether or not the received predetermined signaling includes a specific field for changing the duration of the PRACH opportunity. This allows the UE 100 to determine, based on the SIB1 message, whether or not the specific field is included.

[0146] Furthermore, the receiving unit 112 may receive, from the cell, specific field information indicating whether or not a specific field for changing the duration of a PRACH opportunity is included in specific signaling in a layer lower than the RRC layer. When the control unit 120 receives the specific signaling from the cell, the control unit 120 may determine, based on the specific field information, whether or not the received specific signaling includes the specific field. This allows the UE 100 and the base station 200 to control, based on the specific field information, whether or not to include the specific field in the specific signaling even when the cell supports dynamic adaptation. This allows the base station 200 to flexibly control dynamic adaptation.

[0147] Furthermore, the receiving unit 112 may receive, from the cell, configuration information for configuring a plurality of RA configurations for determining a PRACH opportunity in the UE 100. The control unit 120 may determine the number of bits of a specific field based on the number of the plurality of RA configurations configured by the configuration information. As a result, the UE 100 can grasp the number of bits of the specific field by receiving the configuration information.

[0148] (Second Operation Example) A second operation example will be described with reference to Fig. 10 and Fig. 11. The previous description may be omitted. In this operation example, the UE 100 determines which information to prioritize between updated system information and control information (specific DCI).

[0149] 11 , the base station 200 transmits system information (SI) to the UE 100 in a certain modification period (first modification period). The UE 100 performs communication with the base station 200 (the cell thereof) by applying, for example, information included in the system information received from the base station 200.

[0150] Step S201: The transmitting unit 211 of the base station 200 may transmit priority information to the UE 100. The receiving unit 112 of the UE 100 may receive the priority information from the base station 200.

[0151] The priority information may be included in, for example, system information, an SIB1 message, DA configuration information related to dynamic adaptation, or an individual RRC message to the UE 100.

[0152] The priority information may indicate whether the updated system information is to be prioritized over control information that changes the duration of the PRACH opportunity and is carried by signaling in a layer lower than the RRC layer. The control information may be, for example, a specific DCI. In the following description, the control information is referred to as the specific DCI.

[0153] The priority information may indicate, for example, that the updated system information takes priority over a specific DCI. The priority information may indicate that the updated system information does not take priority over a specific DCI.

[0154] That the updated system information has priority over a specific DCI may be indicated by the presence or absence of priority information in a field where priority information can be set in the information received from base station 200. Also, that the updated system information does not have priority over a specific DCI may be indicated by the presence or absence of priority information in a field where priority information can be set in the information received from base station 200. The control unit 120 may determine whether the updated system information has priority over a specific DCI based on the presence or absence of priority information in a field where priority information can be set in the information received from base station 200.

[0155] Step S202: The transmitter 211 of the base station 200 transmits DCI including the short message to the UE 100 via the PDCCH. The receiver 112 of the UE 100 receives the DCI from the base station 200 via the PDCCH.

[0156] When updating (changing) system information (SI), the control unit 230 of the base station 200 may transmit the DCI to the UE 100. When changing information included in a system information block type 1 message, for example, the control unit 230 may transmit the DCI to the UE 100.

[0157] The control unit 120 of the UE 100 attempts to decode the PDCCH using, for example, the P-RNTI. If the P-RNTI set for the UE 100 is equal to the P-RNTI scrambled in the CRC added to the DCI transmitted from the base station 200, the UE 100 can decode the PDCCH. This allows the control unit 120 to successfully receive the DCI, i.e., the short message.

[0158] Based on the reception of the short message, the control unit 120 determines to attempt to acquire updated system information in a modification period (i.e., a second modification period in FIG. 11 ) following the modification period in which the DCI was received (i.e., the first modification period in FIG. 11 ). The control unit 120 of the UE 100 attempts to acquire updated system information after the boundary between the first modification period and the second modification period.

[0159] Step S203: The transmitter 211 of the base station 200 transmits the updated system information. The receiver 112 of the UE 100 receives the updated system information from the base station 200. The updated system information may indicate a change in the duration of the PRACH opportunity.

[0160] Step S204: The transmitter 211 of the base station 200 transmits the specific DCI. The receiver 112 of the UE 100 receives the specific DCI from the base station 200.

[0161] The specific DCI may include priority information, and the control unit 120 may prioritize the priority information included in the specific DCI over priority information included in other messages and / or a predefined rule.

[0162] Since the control unit 120 of the UE 100 has received the updated system information and the specific DCI from the base station 200, the control unit 120 may execute the process of step S205.

[0163] The control unit 120 may execute the process of step S205 in at least one of the following cases.

[0164] - When the timing of receiving the specific DCI is the same as the timing of receiving the DCI containing a short message or within a predetermined time from that timing. - When the timing of receiving the specific DCI is the same as the boundary of the modification period in which the specific DCI was received (i.e., the end of the modification period) or within a predetermined time from that timing. - When the timing of receiving the specific DCI is the same as the timing of acquiring updated system information or within a predetermined time from that timing. - When the timing of receiving the specific DCI is the same as the timing of changing the periodicity of PRACH opportunities based on the updated system information (e.g., applying the modified RA settings) or within a predetermined time from that timing. - When the timing of changing the periodicity of PRACH opportunities based on the specific DCI (e.g., applying the modified RA settings) (hereinafter may be referred to as the timing of change based on the specific DCI) is the same as the timing of receiving the DCI containing a short message or within a predetermined time from that timing. - When the timing of change based on the specific DCI is the same as the boundary of the modification period in which the specific DCI was received (i.e., the end of the modification period) or within a predetermined time from that timing. - When the change timing based on the specific DCI is the same as the timing when updated system information is acquired or within a predetermined time from that timing - When the change timing based on the specific DCI is the same as the timing when the periodicity of PRACH opportunities is changed based on the updated system information (for example, when the changed RA configuration is applied) or within a predetermined time from that timing Note that the receiving unit 112 of the UE 100 may receive information indicating the value of the predetermined time from the base station 200. The control unit 120 of the UE 100 may determine whether to perform the process of step S205, based on a timer in which the value of the predetermined time based on the information is set.

[0165] Furthermore, the control unit 120 may ignore the specific DCI in at least one of the following cases: In this case, the control unit 120 may skip the process of step S205.

[0166] - When the timing at which the specific DCI is received is after the boundary at which transmission of updated system information begins (hereinafter sometimes referred to as the boundary of the change period); - When the timing of the change based on the specific DCI is after the boundary of the change period. If the control unit 120 ignores the specific DCI, it applies the settings based on the acquired updated system information.

[0167] Furthermore, when ignoring a specific DCI, the control unit 120 may ignore specific information in a specific field included in the specific DCI. The control unit 120 may execute control based on information outside the specific field included in the specific DCI.

[0168] Step S205: The control unit 120 executes a priority determination. Specifically, the control unit 120 determines which information is to be prioritized: the updated system information or the control information (i.e., the specific DCI). The control unit 120 may make this determination based on at least one of the following methods:

[0169] In the first method, the control unit 120 determines which information is to be prioritized, the updated system information or the specific DCI, according to a predetermined rule.

[0170] The control unit 120 stores a predefined rule. The predefined rule may be, for example, a rule described in a 3GPP technical specification. The predefined rule may be, for example, that updated system information is given priority over a specific DCI, or that updated system information is not given priority over a specific DCI.

[0171] When it is specified that the updated system information is given priority over the specific DCI, the control unit 120 determines that the updated system information is given priority over the specific DCI. On the other hand, when it is specified that the updated system information is not given priority over the specific DCI, the control unit 120 determines that the specific DCI is given priority over the updated system information.

[0172] Note that the control unit 120 may perform priority determination based on the first method when priority information has not been received from the base station 200. The control unit 120 may perform priority determination based on the following second method when priority information has been received from the base station 200. Therefore, the control unit 120 may prioritize the determination result of the second method over the determination result of the first method.

[0173] In the second method, the control unit 120 determines, in accordance with the priority information, which of the updated system information and the specific DCI should be given priority.

[0174] When the priority information indicates that the updated system information has priority over the specific DCI, the control unit 120 determines that the updated system information has priority over the specific DCI. On the other hand, when the priority information indicates that the updated system information does not have priority over the specific DCI, the control unit 120 determines that the specific DCI has priority over the updated system information.

[0175] Furthermore, the control unit 120 determines that the updated system information takes priority over the specific DCI when the presence or absence of priority information in a field where priority information can be set in the information received from the base station 200 indicates that the updated system information takes priority over the specific DCI. On the other hand, the control unit 120 determines that the specific DCI takes priority over the updated system information when the presence or absence of priority information in a field where priority information can be set in the information received from the base station 200 indicates that the updated system information does not take priority over the specific DCI.

[0176] In the third method, the control unit 120 determines which information to prioritize, the updated system information or the specific DCI, based on the timing of receiving the specific DCI. The control unit 120 may perform the following determination, for example.

[0177] (a1) The control unit 120 may determine that a specific DCI is prioritized when a specific DCI is received before a DCI including a short message is received. (b1) The control unit 120 may determine that a specific DCI is prioritized when a specific DCI is received after a DCI including a short message is received and before the boundary of the modification period in which the DCI was received is reached. (c1) The control unit 120 may determine that a specific DCI is prioritized when a specific DCI is received after the boundary of the modification period in which the DCI including a short message was received is reached and before updated system information is acquired. (d1) The control unit 120 may determine that the updated system information is prioritized when a specific DCI is received after updated system information is acquired. (e1) The control unit 120 may determine that a specific DCI is prioritized when a specific DCI is received after a certain period has elapsed since the updated system information was acquired. The receiving unit 112 of the UE 100 may receive information indicating the value of the certain period from the base station 200. The control unit 120 of the UE 100 may determine whether or not to execute the process of step S205 based on a timer to which a value of a certain period based on the information is set.

[0178] Note that, when the control unit 120 executes the determinations (a1) to (c1) above, the control unit 120 may apply the RA configuration based on the specific DCI, for example, until updated system information is acquired. When the control unit 120 acquires the updated system information, the control unit 120 may apply the RA configuration based on the updated system information.

[0179] The control unit 120 may perform priority determination based on the third method when priority information is not received from the base station 200. The control unit 120 may prioritize the determination result of the second method over the determination result of the third method.

[0180] In the fourth method, the control unit 120 determines which information, the updated system information or the specific DCI, to prioritize based on the timing (change timing based on the specific DCI) of changing the periodicity of the PRACH opportunity based on the specific DCI (for example, applying the changed RA configuration). The control unit 120 may perform the following determination, for example.

[0181] (a2) The control unit 120 may determine to prioritize the specific DCI if the timing for change based on the specific DCI occurs before receiving a DCI including a short message. (b2) The control unit 120 may determine to prioritize the specific DCI if the timing for change based on the specific DCI occurs after receiving a DCI including a short message and before reaching the boundary of the change period in which the DCI was received. (c2) The control unit 120 may determine to prioritize the specific DCI if the timing for change based on the specific DCI occurs after reaching the boundary of the change period in which the DCI including a short message was received and before acquiring updated system information. Alternatively, the control unit 120 may determine to prioritize the updated system information if the timing for change based on the specific DCI occurs after reaching the boundary of the change period in which the DCI including a short message was received and before acquiring updated system information. (d2) The control unit 120 may determine to prioritize the updated system information if the timing for change based on the specific DCI occurs after acquiring updated system information. (e2) When a timing for change based on the specific DCI arrives after a certain period of time has elapsed since the updated system information was acquired, the control unit 120 may determine that the specific DCI is to be prioritized. The receiving unit 112 of the UE 100 may receive information indicating the certain period of time from the base station 200.

[0182] Note that, when the control unit 120 executes the determinations (a2) to (c2) above, the control unit 120 may apply the RA configuration based on the specific DCI until, for example, updated system information is acquired. When the control unit 120 acquires the updated system information, the control unit 120 may apply the RA configuration based on the updated system information.

[0183] The control unit 120 may perform priority determination based on the fourth method when priority information is not received from the base station 200. The control unit 120 may prioritize the determination result of the second method over the determination result of the fourth method.

[0184] In the fifth method, the control unit 120 determines which information to prioritize, the updated system information or the specific DCI, based on the content of the updated system information. Specifically, the control unit 120 may determine which information to prioritize based on whether the information for setting the duration of the PRACH opportunity has been updated.

[0185] For example, the control unit 120 may determine that the updated system information is prioritized when information for setting the period of the PRACH opportunity has been updated, that is, when the updated system information indicates a change in the period of the PRACH opportunity set to the UE 100. For example, the control unit 120 may determine that the updated system information is prioritized when the RA setting specified (indicated) by the updated system information differs from the RA setting already set to the UE 100.

[0186] On the other hand, the control unit 120 may determine that a specific DCI is prioritized, for example, when the information for setting the period of the PRACH opportunity has not been updated, i.e., when the updated system information does not indicate a change in the period of the PRACH opportunity set for the UE 100.

[0187] Note that even when the control unit 120 determines that a specific DCI is to be prioritized, it applies the contents of the updated system information other than the information for changing the duration of the PRACH opportunity.

[0188] Step S206: The control unit 120 determines a PRACH opportunity based on the prioritized information, which allows the control unit 120 to change the duration of the PRACH opportunity.

[0189] When the updated system information is prioritized, the control unit 120 determines a PRACH opportunity based on the updated system information. The control unit 120, for example, changes the RA configuration to the RA configuration included in the updated system information. The control unit 120 determines a PRACH opportunity based on the changed RA configuration. As a result, the control unit 120 changes the period of the PRACH opportunity.

[0190] On the other hand, when a specific DCI is prioritized, the control unit 120 determines a PRACH opportunity based on the specific DCI. The control unit 120 may determine a PRACH opportunity and a period of the PRACH opportunity, similar to the first operation example. As a result, the control unit 120 changes the period of the PRACH opportunity.

[0191] Step S207: The transmitter 111 of the UE 100 performs PRACH transmission at the determined PRACH opportunity, similar to step S106. The receiver 212 of the base station 200 receives the PRACH from the UE 100.

[0192] As described above, the receiver 112 of the UE 100 receives from the base station 200 both updated system information indicating a change in the duration of the PRACH opportunity and control information (i.e., specific DCI) indicating a change in the duration of the PRACH opportunity and carried by signaling in a layer lower than the RRC layer. The controller 120 prioritizes one of the updated system information and the specific DCI according to the priority information received from the base station 200 or a predefined rule, and changes the PRACH duration based on the prioritized information. This allows the UE 100 to appropriately determine which change to apply to the PRACH transmission when performing PRACH transmission according to the priority information received from the base station 200 or a predefined rule. The changes to be applied can be shared between the UE 100 and the base station 200 (cell), thereby preventing PRACH transmission / reception failures. As a result, dynamic adaptation can be appropriately performed.

[0193] Furthermore, the transmitting unit 211 of the base station 200 transmits both updated system information indicating a change in the duration of the PRACH opportunity and specific DCI, which is information indicating a change in the duration of the PRACH opportunity and is carried by signaling in a layer lower than the RRC layer, to the UE 100. The transmitting unit 211 transmits priority information to the UE 100 to enable the UE 100 to determine which information, the updated system information or the specific DCI, should be prioritized. As a result, similar to the above, the changes to be applied can be shared between the UE 100 and the base station 200 (cell), and failures in PRACH transmission and reception can be suppressed.

[0194] In addition, the priority information may indicate that the updated system information is prioritized over the specific DCI. Since the system information generally includes basic settings for communication with the base station 200, by prioritizing the updated system information first, it is possible to suppress the occurrence of a problem in communication between the UE 100 and the base station 200.

[0195] Furthermore, the updated system information may include priority information, which enables the UE 100 to acquire the priority information even when the UE 100 is not in an RRC connected state.

[0196] Furthermore, the specific DCI may include priority information. As a result, since the specific DCI is carried by signaling of a lower layer, it is possible to transmit the priority information to the UE 100 earlier than the higher layer. As a result, the network 10 can flexibly control the priority determination of the UE 100.

[0197] Furthermore, the receiving unit 112 may receive an individual RRC message for the UE 100 from the base station 200. The individual RRC message may include priority information. This allows the network 10 to change the content of the priority information for each UE 100. As a result, the network 10 can flexibly control priority determination for the UE 100.

[0198] Furthermore, the control unit 120 may prioritize the updated system information according to a rule indicating that the updated system information is prioritized over a specific DCI. This allows the UE 100 to make a decision without signaling regarding priority information between the UE 100 and the base station 200, thereby enabling radio resources to be saved.

[0199] Furthermore, when the timing for changing the duration of the PRACH opportunity based on the specific DCI is later than the boundary at which the transmission of the updated system information starts, the control unit 120 may ignore the specific DCI. This allows the UE 100 to reliably apply the updated system information when it needs to acquire the updated system information.

[0200] Furthermore, the control unit changes the PRACH period based on the specific DCI when receiving updated system information that does not indicate a change in the period of the PRACH opportunity set for the UE 100. This allows the network 10 to change the period of the PRACH opportunity for each UE 100, even when the network 10 does not change the period of the PRACH opportunity according to the system information.

[0201] (Other Embodiments) In the above-described embodiment, the control unit 120 of the UE 100 determines whether or not the cell supports dynamic adaptation based on the support information, but this is not limited to this. The control unit 120 may determine whether or not the cell supports dynamic adaptation based on, for example, DA configuration information. For example, the control unit 120 may determine that the cell supports dynamic adaptation when the DA configuration information is included in the system information (for example, an SIB1 message). On the other hand, the control unit 120 may determine that the cell does not support dynamic adaptation when the DA configuration information is not included in the system information.

[0202] If the cell of the base station 200 supports dynamic adaptation, the control unit 230 of the base station 200 may include DA setting information in the system information. The transmission unit 211 of the base station 200 may transmit system information including the DA setting information for the cell. On the other hand, if the cell of the base station 200 does not support dynamic adaptation, the control unit 230 may not include the DA setting information in the system information. The transmission unit 211 of the base station 200 may transmit system information not including the DA setting information for the cell.

[0203] In the above-described embodiment, the period of the PRACH opportunity is changed by dynamic adaptation, but this is not limited to this. For example, by changing the RA setting by dynamic adaptation, other parameters related to PRACH transmission may be changed without changing the period of the PRACH opportunity. That is, the UE 100 may change parameters other than the period of the PRACH opportunity by signaling of a lower layer.

[0204] In the above-described embodiment, a case where a validity period is set in the changed RA configuration has been described as an example, but this is not limiting. The validity period may not be set. The base station 200 may control the UE 100 to change the periodicity of PRACH opportunities or the RA configuration using a specific DCI, regardless of the validity period (i.e., regardless of whether the validity period is set). The UE 100 may change the periodicity of PRACH opportunities or the RA configuration using a specific DCI received from the base station 200, regardless of the validity period (i.e., regardless of whether the validity period is set).

[0205] In the above-described embodiment, the order of the steps may be changed. For example, the process of step S203 may be performed after step S204.

[0206] In the above-described embodiment, the "change" of the RA configuration or the period of the PRACH opportunity may be replaced with "update." Note that the "period" of the PRACH opportunity may also be referred to as a "cycle."

[0207] In the above-described embodiment, an NR-based mobile communication system has been described as an example of the mobile communication system 1. However, the mobile communication system 1 is not limited to this example. The mobile communication system 1 may be a system compliant with the TS of either LTE (Long Term Evolution) or another generation system (e.g., 6th generation) of the 3GPP standard. The base station 200 may be an eNB that provides E-UTRA user plane and control plane protocol termination toward the UE 100 in LTE. The mobile communication system 1 may be a system compliant with the TS of a standard other than the 3GPP standard. The base station 200 may be an IAB (Integrated Access and Backhaul) donor or an IAB node.

[0208] In the above-described embodiment, an NR-based mobile communication system has been described as an example of the mobile communication system 1. However, the mobile communication system 1 is not limited to this example. The mobile communication system 1 may be a system conforming to the TS of either LTE or another generation system (e.g., 6th generation) of the 3GPP standard. The base station 200 may be an eNB that provides E-UTRA user plane and control plane protocol termination for the UE 100 in LTE. The mobile communication system 1 may be a system conforming to the TS of a standard other than the 3GPP standard.

[0209] The steps in the operations of the above-described embodiments do not necessarily have to be executed in chronological order according to the order depicted in the flow diagrams or sequence diagrams. For example, the steps in the operations may be executed in an order different from that depicted in the flow diagrams or sequence diagrams, or may be executed in parallel. Some of the steps in the operations may be deleted, or additional steps may be added to the process. Furthermore, the above-described operational flows are not limited to being executed independently, but may be executed by combining two or more operational flows. For example, some steps of one operational flow may be added to another operational flow, or some steps of one operational flow may be replaced with some steps of another operational flow.

[0210] A program may be provided that causes a computer to execute each process performed by the UE 100 or the base station 200. The program may be recorded on a computer-readable medium. Using the computer-readable medium, the program can be installed on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM (Compact Disk Read Only Memory) or a DVD-ROM (Digital Versatile Disc Read Only Memory). Furthermore, circuits that execute each process performed by the UE 100 or the base station 200 may be integrated, and at least a part of the UE 100 or the base station 200 may be configured as a semiconductor integrated circuit (chip set, SoC (System On Chip)).

[0211] In the above-described embodiments, "transmit" may mean performing processing at least one layer in a protocol stack used for transmission, or may mean physically transmitting a signal wirelessly or via a wired connection. Alternatively, "transmit" may mean a combination of performing processing at least one layer and physically transmitting a signal wirelessly or via a wired connection. Similarly, "receive" may mean performing processing at least one layer in a protocol stack used for reception, or may mean physically receiving a signal wirelessly or via a wired connection. Alternatively, "receive" may mean a combination of processing at least one layer and physically receiving a signal wirelessly or via a wired connection. Similarly, "obtain / acquire" may mean obtaining information from stored information, obtaining information from information received from another node, or obtaining information by generating the information. Similarly, the terms "based on" and "depending on / in response to" do not mean "based only on" or "depending only on," unless expressly stated otherwise. The term "based on" means both "based only on" and "based at least in part on." Similarly, the term "depending on" means both "depending only on" and "depending at least in part on." Similarly, "include" and "comprise" do not mean including only the listed items, but may mean including only the listed items or may include additional items in addition to the listed items. Similarly, in this disclosure, "or" does not mean an exclusive or, but rather a logical or. Furthermore, any reference to elements using designations such as "first," "second," etc., as used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used in this disclosure as a convenient method of distinguishing between two or more elements.Thus, a reference to a first and a second element does not imply that only two elements may be employed therein or that the first element must precede the second element in some way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall include the plural unless the context clearly indicates otherwise.

[0212] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

[0213] (Additional Notes) Additional notes will be given regarding the features of the above-described embodiment.

[0214] (Supplementary Note 1) A communication device comprising: a receiver that receives from a base station both updated system information indicating a change in a duration of a physical random access channel (PRACH) opportunity and control information indicating a change in a duration of the PRACH opportunity, the control information being carried by signaling in a layer lower than a radio resource control (RRC) layer; and a controller that prioritizes one of the updated system information and the control information in accordance with priority information received from the base station or a predefined rule, and changes the duration of the PRACH based on the prioritized information.

[0215] (Supplementary Note 2) The communication device according to Supplementary Note 1, wherein the priority information indicates that the updated system information has priority over the control information.

[0216] (Supplementary Note 3) The communication device according to Supplementary Note 1 or 2, wherein the updated system information includes the priority information.

[0217] (Supplementary Note 4) The communication device according to any one of Supplementary Notes 1 to 3, wherein the control information includes the priority information.

[0218] (Supplementary Note 5) The communication device according to any one of Supplementary Notes 1 to 4, wherein the receiving unit receives an RRC message dedicated to the communication device from the base station, and the dedicated RRC message includes the priority information.

[0219] (Supplementary Note 6) The communication device according to any one of Supplementary Notes 1 to 5, wherein the control unit prioritizes the updated system information in accordance with the rule indicating that the updated system information is prioritized over the control information.

[0220] (Supplementary Note 7) The communication device according to any one of Supplementary Notes 1 to 6, wherein the controller ignores the control information when a timing at which a period of the PRACH opportunity is changed based on the control information is after a boundary at which transmission of the updated system information starts.

[0221] (Supplementary Note 8) The communication device according to any one of Supplementary Notes 1 to 7, wherein the controller changes the PRACH period based on the control information when updated system information is received that does not indicate a change in the PRACH opportunity period set for the communication device.

[0222] (Supplementary Note 9) A base station comprising: a transmitter that transmits, to a communication device, both updated system information that changes a duration of a physical random access channel (PRACH) opportunity and control information that changes the duration of the PRACH opportunity and that is carried by signaling in a layer lower than a radio resource control (RRC) layer; and the transmitter that transmits, to the communication device, priority information that enables the communication device to determine which of the updated system information and the control information to prioritize.

[0223] (Supplementary Note 10) A method executed by a communication device, comprising: receiving from a base station both updated system information indicating a change in a duration of a Physical Random Access Channel (PRACH) opportunity and control information indicating a change in a duration of the PRACH opportunity, the control information being carried by signaling in a layer lower than a Radio Resource Control (RRC) layer; and prioritizing one of the updated system information and the control information in accordance with priority information received from the base station or a predefined rule, and modifying the duration of the PRACH based on the prioritized information.

Claims

1. A communications device (100) comprising: a receiver (112) that receives from a base station (200) both updated system information indicating a change in a duration of a physical random access channel (PRACH) opportunity and control information indicating a change in the duration of the PRACH opportunity, the control information being carried by signaling of a layer lower than a radio resource control (RRC) layer; and a control unit (120) that prioritizes one of the updated system information and the control information in accordance with priority information received from the base station or a predefined rule, and changes the duration of the PRACH based on the prioritized information.

2. The communication device according to claim 1, wherein the priority information indicates that the updated system information is to be prioritized over the control information.

3. The communication device according to claim 1 or 2, wherein the updated system information includes the priority information.

4. The communication device according to claim 1 or 2, wherein the control information includes the priority information.

5. The communication device according to claim 1 or 2, wherein the receiving unit receives an individual RRC message for the communication device from the base station, and the individual RRC message includes the priority information.

6. The communication device according to claim 1, wherein the control unit prioritizes the updated system information according to the rule indicating that the updated system information is to be prioritized over the control information.

7. The communication device according to claim 1 or 2, wherein the control unit ignores the control information when the timing for changing the period of the PRACH opportunity based on the control information is after the boundary at which transmission of the updated system information starts.

8. The communication device according to claim 1 or 2, wherein the control unit changes the PRACH period based on the control information when updated system information is received that does not indicate a change in the period of the PRACH opportunity set in the communication device.

9. A base station (200), comprising: a transmission unit (211) that transmits to a communication device (100) both updated system information that changes a duration of a physical random access channel (PRACH) opportunity and control information that changes the duration of the PRACH opportunity and is carried by signaling of a layer lower than a radio resource control (RRC) layer, wherein the transmission unit transmits priority information to the communication device for the communication device to determine which of the updated system information and the control information should be prioritized.

10. A method executed by a communication device (100), comprising: a step of receiving from a base station (200) both updated system information indicating a change in a duration of a physical random access channel (PRACH) opportunity and control information indicating a change in the duration of the PRACH opportunity, the control information being carried by signaling of a layer lower than a radio resource control (RRC) layer; and a step of prioritizing one of the updated system information and the control information in accordance with priority information received from the base station or a predefined rule, and changing the duration of the PRACH based on the prioritized information.

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