Patent Publication Number: US-11646933-B2

Title: Terminal, radio communication method, and base station

Description:
TECHNICAL FIELD 
     The present disclosure relates to a user terminal and a radio communication method in next-generation mobile communication systems. 
     BACKGROUND ART 
     In the UMTS (Universal Mobile Telecommunications System) network, the specifications of Long Term Evolution (LTE) have been drafted for the purpose of further increasing high speed data rates, providing lower latency and so on (see Non-Patent Literature 1). For the purpose of further high capacity, advancement of LTE (LTE Rel. 8, Rel. 9), and so on, the specifications of LTE-A (LTE-Advanced, LTE Rel. 10, Rel. 11, Rel. 12, Rel. 13) have been drafted. 
     Successor systems of LTE (referred to as, for example, “FRA (Future Radio Access),” “5G (5th generation mobile communication system),” “5G+ (plus),” “NR (New Radio),” “NX (New radio access),” “FX (Future generation radio access),” “LTE Rel. 14,” “LTE Rel. 15” (or later versions), and so on) are also under study. 
     In existing LTE systems (for example, LTE Rel. 8 to Rel. 13), a radio base station (for example, eNB (eNode B)) transmits a physical layer control signal (for example, downlink control information (DCI)) to a user terminal (UE (User Equipment)) by using a control channel (for example, PDCCH (Physical Downlink Control Channel). 
     CITATION LIST 
     Non-Patent Literature 
     Non-Patent Literature 1: 3GPP TS 36.300 V8.12.0 “Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 (Release 8),” April, 2010 
     Summary of Invention 
     Technical Problem 
     For future radio communication systems (for example, NR, 5G, 5G+, Rel. 15 or later versions), studies have been conducted to allow a user terminal to monitor (or search) a control resource set (CORESET), which includes allocation candidate regions of a control channel, to detect DCI. 
     For the future radio communication systems, studies have also been conducted on reporting, to a user terminal (UE), of configuration information of the CORESET and included in UE-specific configuration information (for example, configuration information used to configure UE-specific PDCCH parameters (also referred to as UE-specific PDCCH configuration information, PDCCH-Config, or the like). 
     However, with simple transmission of the CORESET configuration information included in the UE-specific PDCCH configuration information (PDCCH-Config), the user terminal may fail to appropriately configure the CORESET. As a result, DCI mapped into the CORESET may fail to be appropriately detected. 
     The present invention has been made in view of the above, and it is an object of the present invention to provide a user terminal and a radio communication method capable of appropriately configuring a CORESET. 
     Solution to Problem 
     A user terminal according to an aspect of the present disclosure includes a receiving section that receives configuration information of a control resource set, included in common configuration information used to configure a cell-specific downlink control channel parameter, and a control section that controls configuration of the control resource set, based on the configuration information. 
     Advantageous Effects of Invention 
     According to an aspect of the present disclosure, the user terminal can appropriately configure a CORESET. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a diagram to show an example of CORESET configuration information; 
         FIG.  2    is a diagram to show an example of PDCCH-ConfigCommon according to the present embodiment; 
         FIG.  3    is a diagram to show an example of a schematic structure of a radio communication system according to the present embodiment; 
         FIG.  4    is a diagram to show an example of an overall structure of a radio base station according to the present embodiment; 
         FIG.  5    is a diagram to show an example of a functional structure of the radio base station according to the present embodiment; 
         FIG.  6    is a diagram to show an example of an overall structure of a user terminal according to the present embodiment; 
         FIG.  7    is a diagram to show an example of a structure of the user terminal according to the present embodiment; and 
         FIG.  8    is a diagram to show an example of a hardware structure of the radio base station and the user terminal according to the present embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     For future radio communication systems (for example, NR, 5G, 5G+, Rel. 15 or later versions), studies have been conducted on utilization of a control resource set (CORESET) for transmission of a physical layer control signal (for example, downlink control information (DCI)) from a radio base station (which may be also referred to, for example, as a “BS (Base Station),” a “transmission/reception point (TRP),” an “eNB (eNodeB),” a “gNB (NR NodeB),” and so on) to a user terminal. 
     The CORESET is an allocation candidate region for a control channel (for example, PDCCH (Physical Downlink Control Channel)). The CORESET may include a certain frequency domain resource and time domain resource (for example, one or two OFDM symbols). The PDCCH (or DCI) is mapped to a certain resource unit in the CORESET. 
     The certain resource unit may be, for example, at least one of a control channel element (CCE), a CCE group including one or more CCEs, a resource element group (REG) including one or more resource elements (REs), one or more REG bundles (REG group), and a physical resource block (PRB). 
     The user terminal monitors (blind decodes) DCI mapped to a certain resource unit in the CORESET (or a search space in the CORESET) to detect DCI for the user terminal. 
     To the user terminal, configuration information of a CORESET (that may also be referred to as CORESET configuration information, CORESET-config, ControlResourceSet information element (IE), ControlResourceSet, or the like) is reported from the radio base station. The user terminal configures one or more CORESETs, based on the CORESET configuration information. For example, the CORESET configuration information may be used to configure at least one of time domain region and frequency domain region (time/frequency domain region) for the CORESET that is searched for DCI. 
       FIG.  1    is a diagram to show an example of the CORESET configuration information. As shown in  FIG.  1   , the CORESET configuration information may include, for example, at least one of the following types of information (parameters).
     Identifier of the CORESET (ControlResourceSetId).   Frequency resources for the CORESET (frequency DomainResources).   Time resources for the CORESET (duration). For example, the duration may be constituted with one or more symbols.   Type of mapping between the CCE and the REG (CCE-REG mapping type (cce-REG-MappingType)). For example, the CCE-REG mapping type may indicate “interleaved” or “noninterleaved.”   Size of the REG bundles (reg-Bundle Size, CORESET-REG-bundle-size)   Size of an interleaver for the CORESET (interleverSize, CORESET-interleaver-size)   Index of a shift amount for interleaving (shift index, shiftIndex, CORESET-shift-index).   Precoder granularity in the frequency domain (precoderGranularity, CORESET-precoder-granularity). The granularity is specified to be the same as the size of the REG bundle or specified as all resource blocks.   State of a transmission configuration indication (TCI) for a PDCCH (TCI state). The TCI state may indicate (include) information related to quasi collocation (QCL) of the PDCCH (also referred to as QCL information, QCL information for the PDCCH, or the like). The QCL information for the PDCCH may be, for example, information related to the QCL between the PDCCH (or a DMRS port for the PDCCH) and a downlink reference signal (DL-RS) in the CORESET, and may include, for example, at least one of information related to a DL-RS having a QCL relationship (DL-RS-related information) and information indicating the above-described QCL type (QCL type information).   Activation/deactivation of a TCI field.   

     Studies have been conducted on reporting, from the radio base station to the user terminal, of the CORESET configuration information included in configuration information specific to the user terminal (UE) (for example, configuration information used to configure a UE-specific PDCCH parameter (also referred to as UE-specific PDCCH configuration information, PDCCH-Config, or the like). The PDCCH-Config may be reported to the user terminal, for example, by higher layer signaling. 
     However, with simple transmission of the CORESET configuration information included in the UE-specific PDCCH configuration information (PDCCH-Config), the user terminal may fail to appropriately detect, during a certain procedure, DCI mapped into the CORESET. Specifically, during at least one of the procedures below, the DCI mapped into the CORESET may fail to be appropriately detected.
     Handover (HO) for switching a radio base station to which a user terminal is connected.   Random access (RA).   Addition of a secondary cell (SCell) in carrier aggregation (CA).   Addition of an SCell in a master cell group (MCG) or a secondary cell group (SCG) in Dual Connectivity (DC). Note that DC may be, for example, EC-DC (E-UTRA NR Dual Connectivity with MCG using E-UTRA and SCG using NR) or DR of an MCG and an SCG using NR.   Addition of a primary secondary cell (PSCell) in an SCG in DC.   Paging.   

     For the future radio communication systems, studies have also been conducted on transmission of configuration information by the radio base station, the configuration information being used to configure cell specific (that is, user terminal (UE)-common) PDCCH parameters (also referred to as common configuration information, UE-common PDCCH configuration information, PDCCH-ConfigCommon, or the like). 
     Thus, the inventors of the present invention come up with an idea to enable appropriate detection of DCI mapped into the CORESET even during a certain procedure (for example, an SCell and/or a PSCell in the above-described HO, RA, CA, and DC (including EN-DC)) by reporting, to the user terminal, of the CORESET configuration information included in the PDCCH-ConfigCommon. 
     The present embodiments will be described in detail with reference to the drawings as follows. 
     In the present embodiment, the user terminal receives CORESET configuration information (configuration information of a control resource set) included in PDCCH-ConfigCommon (common configuration information used to configure a cell-specific downlink control channel parameter). The user terminal controls configuration of the CORESET (control resource set), based on the CORESET configuration information. 
     The user terminal may receive the PDCCH-ConfigCommon including the CORESET configuration information in a system information block (SIB, for example, SIB1). The user terminal may receive, by higher layer signaling, the PDCCH-ConfigCommon including the CORESET configuration information in at least one of the handover procedure, the secondary-cell addition procedure, and the primary-secondary-cell addition procedure. 
       FIG.  2    is a diagram to show an example of the PDCCH-ConfigCommon according to the present embodiment. As shown in  FIG.  2   , the PDCCH-ConfigCommon may include one or more types of CORESET configuration information (ControlResourceSet) (for example, first and second CORESET configuration information described below). Each CORESET configuration information may include at least one of the types of information (parameters) described with respect to  FIG.  1   . 
     For example, the first CORESET configuration information included in the PDCCH-ConfigCommon may be used for a procedure for receiving at least one of SIB1, OSI, and paging. Specifically, the user terminal may configure a CORESET, based on first CORESET configuration information, and receive at least one of SIB1, OSI, and paging, based on the DCI detected in the CORESET. For example, the user terminal may use downlink shared channel (PDSCH (Physical Downlink Shared Channel)) scheduled by the DCI to receive at least one of SIB1, OSI, and paging. 
     Accordingly, the first CORESET configuration information may include at least one of CORESET configuration information for SIB1 (ControlResourceSetSIB1, SIB1-ControlResourceSet), CORESET configuration information for the OSI (ControlResourceSetOtherSystemInformation, OtherSystemInformation-ControlResourceSet), and CORESET configuration information for the paging (ControlResourceSetPagin, Paging-ControlResourceSet). 
     For example, the second CORESET configuration information included in the PDCCH-ConfigCommon may be used for a procedure for the random access. Specifically, the user terminal may configure a CORESET, based on second CORESET configuration information, and receive at least one of a random access response (RAR, also referred to as message 2 or the like) and a contention resolution message (also referred to as message 4), based on the DCI detected in the CORESET. For example, the user terminal may use the PDSCH scheduled by the DCI to receive at least one of messages 2 and 4. 
     Thus, the second CORESET configuration information may include CORESET configuration information for RA (ControlResourseSetRandomAccess or ra-ControlResourceSet). 
     As shown in  FIG.  2   , the PDCCH-ConfigCommon may include at least one of the following types of information (parameters).
     Configuration information (that may be also referred to as search space configuration information, CommonSearchSpace, SearchSpace, SeacrchSpace information element (IE), or the like) of a search space (for example, a search space common to one or more user terminals). The search space configuration information will be described below.   Identifier of a search space (also referred to as a search space ID (Identifier), searchSpaceSIB1, SearchSpaceId, or the like) for DCI used to schedule at least one of SIB1 and RMSI.   Identifier of a search space (also referred to as a search space ID, searchSpaceOtherSystemInformation, osi-SearchSpace, SearchSpaceId, or the like) for DCI used to schedule other system information (for example, SIB2).   Identifier of a search space (also referred to as a search space ID, pagingSearchSpace, paging-SearchSpace, SearchSpaceId, or the like) for DCI used to schedule the paging.   Identifier of a search space (also referred to as a search space ID, RASearchSpace, ra-SearchSpace, SearchSpaceId, or the like) for DCI used to schedule at least one of messages 2 and 4 in the random access procedure.   

     The PDCCH-ConfigCommon configured as described above may be included in system information (for example, SIB1). SIB1 may include information common to user terminals accessing a cell (for example, the position (ssb) of a time domain in which an SSB is transmitted in an SS (Synchronization Signal) burst set (ssb-PositionsisInBurst), a transmission period of SSBs (Synchronization Signal Blocks), a UL/DL configuration in TDD, and so on). The SSB is a block including a synchronization signal and/or a broadcast channel. 
     Note that the PDCCH-ConfigCommon may be included in the system information other than the SIB (for example, an MIB (Master Information Block), RMSI (Remaining Minimum System Information), and OSI (Other System Information)). 
     (Radio Communication System) 
     Hereinafter, a structure of a radio communication system according to the present embodiment of the present disclosure will be described. In this radio communication system, the radio communication method according to each embodiment of the present disclosure described above may be used alone or may be used in combination for communication. 
       FIG.  3    is a diagram to show an example of a schematic structure of the radio communication system according to the present embodiment. A radio communication system  1  can adopt carrier aggregation (CA) and/or dual connectivity (DC) to group a plurality of fundamental frequency blocks (component carriers) into one, where the system bandwidth in an LTE system (for example, 20 MHz) constitutes one unit. 
     Note that the radio communication system  1  may be referred to as “LTE (Long Term Evolution),” “LTE-A (LIE-Advanced),” “LTE-B (LTE-Beyond),” “SUPER 3G,” “IMT-Advanced,” “4G (4th generation mobile communication system),” “5G (5th generation mobile communication system),” “NR (New Radio),” “FRA (Future Radio Access),” “New-RAT (Radio Access Technology),” and so on, or may be referred to as a system implementing these. 
     The radio communication system  1  includes a radio base station  11  that forms a macro cell C 1  of a relatively wide coverage, and radio base stations  12  ( 12   a  to  12   c ) that form small cells C 2 , which are placed within the macro cell C 1  and which are narrower than the macro cell C 1 . Also, user terminals  20  are placed in the macro cell C 1  and in each small cell C 2 . The arrangement, the number, and the like of each cell and user terminal  20  are by no means limited to the aspect shown in the diagram. 
     The user terminals  20  can connect with both the radio base station  11  and the radio base stations  12 . It is assumed that the user terminals  20  use the macro cell C 1  and the small cells C 2  at the same time by means of CA or DC. The user terminals  20  can execute CA or DC by using a plurality of cells (CCs). 
     Between the user terminals  20  and the radio base station  11 , communication can be carried out by using a carrier of a relatively low frequency band (for example, 2 GHz) and a narrow bandwidth (referred to as, for example, an “existing carrier,” a “legacy carrier” and so on). Meanwhile, between the user terminals  20  and the radio base stations  12 , a carrier of a relatively high frequency band (for example, 3.5 GHz, 5 GHz, and so on) and a wide bandwidth may be used, or the same carrier as that used between the user terminals  20  and the radio base station  11  may be used. Note that the structure of the frequency band for use in each radio base station is by no means limited to these. 
     The user terminals  20  can perform communication by using time division duplex (TDD) and/or frequency division duplex (FDD) in each cell. Furthermore, in each cell (carrier), a single numerology may be employed, or a plurality of different numerologies may be employed. 
     Numerologies may be communication parameters applied to transmission and/or reception of a certain signal and/or channel, and for example, may indicate at least one of a subcarrier spacing, a bandwidth, a symbol length, a cyclic prefix length, a subframe length, a TTI length, the number of symbols per TTI, a radio frame structure, a particular filter processing performed by a transceiver in a frequency domain, a particular windowing processing performed by a transceiver in a time domain, and so on. For example, if certain physical channels use different subcarrier spacings of the OFDM symbols constituted and/or different numbers of the OFDM symbols, it may be referred to as that the numerologies are different. 
     A wired connection (for example, means in compliance with the CPRI (Common Public Radio Interface) such as an optical fiber, an X2 interface and so on) or a wireless connection may be established between the radio base station  11  and the radio base stations  12  (or between two radio base stations  12 ). 
     The radio base station  11  and the radio base stations  12  are each connected with a higher station apparatus  30 , and are connected with a core network  40  via the higher station apparatus  30 . Note that the higher station apparatus  30  may be, for example, access gateway apparatus, a radio network controller (RNC), a mobility management entity (MME) and so on, but is by no means limited to these. Also, each radio base station  12  may be connected with the higher station apparatus  30  via the radio base station  11 . 
     Note that the radio base station  11  is a radio base station having a relatively wide coverage, and may be referred to as a “macro base station,” a “central node,” an “eNB (eNodeB),” a “transmitting/receiving point” and so on. The radio base stations  12  are radio base stations having local coverages, and may be referred to as “small base stations,” “micro base stations,” “pico base stations,” “femto base stations,” “HeNBs (Home eNodeBs),” “RRHs (Remote Radio Heads),” “transmitting/receiving points” and so on. Hereinafter, the radio base stations  11  and  12  will be collectively referred to as “radio base stations  10 ,” unless specified otherwise. 
     Each of the user terminals  20  is a terminal that supports various communication schemes such as LTE and LTE-A, and may include not only mobile communication terminals (mobile stations) but stationary communication terminals (fixed stations). 
     In the radio communication system  1 , as radio access schemes, orthogonal frequency division multiple access (OFDMA) is applied to the downlink, and single carrier frequency division multiple access (SC-FDMA) and/or OFDMA is applied to the uplink. 
     OFDMA is a multi-carrier communication scheme to perform communication by dividing a frequency band into a plurality of narrow frequency bands (subcarriers) and mapping data to each subcarrier. SC-FDMA is a single carrier communication scheme to mitigate interference between terminals by dividing the system bandwidth into bands formed with one or continuous resource blocks per terminal, and allowing a plurality of terminals to use mutually different bands. Note that the uplink and downlink radio access schemes are by no means limited to the combinations of these, and other radio access schemes may be used. 
     In the radio communication system  1 , a downlink shared channel (PDSCH (Physical Downlink Shared Channel), which is used by each user terminal  20  on a shared basis, a broadcast channel (PBCH (Physical Broadcast Channel)), downlink L1/L2 control channels and so on, are used as downlink channels. User data, higher layer control information, SIBs (System Information Blocks) and so on are communicated on the PDSCH. The MIBs (Master Information Blocks) are communicated on the PBCH. 
     The downlink L1/L2 control channels include a PDCCH (Physical Downlink Control Channel), an EPDCCH (Enhanced Physical Downlink Control Channel), a PCFICH (Physical Control Format Indicator Channel), a PHICH (Physical Hybrid-ARQ Indicator Channel) and so on. Downlink control information (DCI), including PDSCH and/or PUSCH scheduling information, and so on are communicated on the PDCCH. 
     Note that the scheduling information may be reported by the DCI. For example, the DCI scheduling DL data reception may be referred to as “DL assignment,” and the DCI scheduling UL data transmission may be referred to as “UL grant.” 
     The number of OFDM symbols to use for the PDCCH is communicated on the PCFICH. Delivery confirmation information (for example, also referred to as “retransmission control information,” “HARQ-ACK,” “ACK/NACK,” and so on) of HARQ (Hybrid Automatic Repeat reQuest) to a PUSCH is transmitted on the PHICH. The EPDCCH is frequency-division multiplexed with the PDSCH (downlink shared data channel) and used to communicate DCI and so on, like the PDCCH. 
     In the radio communication system  1 , an uplink shared channel (PUSCH (Physical Uplink Shared Channel)), which is used by each user terminal  20  on a shared basis, an uplink control channel (PUCCH (Physical Uplink Control Channel)), a random access channel (PRACH (Physical Random Access Channel)) and so on are used as uplink channels. User data, higher layer control information and so on are communicated on the PUSCH. In addition, radio quality information (CQI (Channel Quality Indicator)) of the downlink, delivery confirmation information, scheduling request (SR), and so on are transmitted on the PUCCH. By means of the PRACH, random access preambles for establishing connections with cells are communicated. 
     In the radio communication system  1 , a cell-specific reference signal (CRS), a channel state information-reference signal (CSI-RS), a demodulation reference signal (DMRS), a positioning reference signal (PRS), and so on are transmitted as downlink reference signals. In the radio communication system  1 , a measurement reference signal (SRS (Sounding Reference Signal)), a demodulation reference signal (DMRS), and so on are transmitted as uplink reference signals. Note that DMRS may be referred to as a “user terminal specific reference signal (UE-specific Reference Signal).” Transmitted reference signals are by no means limited to these. 
     &lt;Radio Base Station&gt; 
       FIG.  4    is a diagram to show an example of an overall structure of the radio base station according to the present embodiment. A radio base station  10  includes a plurality of transmitting/receiving antennas  101 , amplifying sections  102 , transmitting/receiving sections  103 , a baseband signal processing section  104 , a call processing section  105  and a transmission line interface  106 . Note that the radio base station  10  may be configured to include one or more transmitting/receiving antennas  101 , one or more amplifying sections  102  and one or more transmitting/receiving sections  103 . 
     User data to be transmitted from the radio base station  10  to the user terminal  20  by the downlink is input from the higher station apparatus  30  to the baseband signal processing section  104 , via the transmission line interface  106 . 
     In the baseband signal processing section  104 , the user data is subjected to transmission processes, such as a PDCP (Packet Data Convergence Protocol) layer process, division and coupling of the user data, RLC (Radio Link Control) layer transmission processes such as RLC retransmission control, MAC (Medium Access Control) retransmission control (for example, an HARQ transmission process), scheduling, transport format selection, channel coding, an inverse fast Fourier transform (IFFT) process, and a precoding process, and the result is forwarded to each transmitting/receiving section  103 . Furthermore, downlink control signals are also subjected to transmission processes such as channel coding and inverse fast Fourier transform, and the result is forwarded to each transmitting/receiving section  103 . 
     The transmitting/receiving sections  103  convert baseband signals that are pre-coded and output from the baseband signal processing section  104  on a per antenna basis, to have radio frequency bands and transmit the result. The radio frequency signals having been subjected to frequency conversion in the transmitting/receiving sections  103  are amplified in the amplifying sections  102 , and transmitted from the transmitting/receiving antennas  101 . The transmitting/receiving sections  103  can be constituted with transmitters/receivers, transmitting/receiving circuits or transmitting/receiving apparatus that can be described based on general understanding of the technical field to which the present disclosure pertains. Note that each transmitting/receiving section  103  may be structured as a transmitting/receiving section in one entity, or may be constituted with a transmitting section and a receiving section. 
     Meanwhile, as for uplink signals, radio frequency signals that are received in the transmitting/receiving antennas  101  are amplified in the amplifying sections  102 . The transmitting/receiving sections  103  receive the uplink signals amplified in the amplifying sections  102 . The transmitting/receiving sections  103  convert the received signals into the baseband signal through frequency conversion and outputs to the baseband signal processing section  104 . 
     In the baseband signal processing section  104 , user data that is included in the uplink signals that are input is subjected to a fast Fourier transform (FFT) process, an inverse discrete Fourier transform (IDFT) process, error correction decoding, a MAC retransmission control receiving process, and RLC layer and PDCP layer receiving processes, and forwarded to the higher station apparatus  30  via the transmission line interface  106 . The call processing section  105  performs call processing (setting up, releasing and so on) for communication channels, manages the state of the radio base station  10 , manages the radio resources and so on. 
     The transmission line interface  106  transmits and/or receives signals to and/or from the higher station apparatus  30  via a certain interface. The transmission line interface  106  may transmit and/or receive signals (backhaul signaling) with other radio base stations  10  via an inter-base station interface (for example, an optical fiber in compliance with the CPRI (Common Public Radio Interface) and an X2 interface). 
     The transmitting/receiving sections  103  may transmit downlink control information (for example, DCI) using a control resource set (CORESET) associated with a specific search space. 
     The transmitting/receiving sections  103  may transmit configuration information of a control resource set (CORESET configuration information), the configuration information being included in common configuration information used to configure a cell-specific downlink control channel parameter. The transmitting/receiving sections  103  may receive the common control information included in the system information block (SIB) or transmit, by higher layer signaling, the common configuration information in at least one of the handover procedure, the secondary-cell addition procedure, and the primary-secondary-cell addition procedure. 
       FIG.  5    is a diagram to show an example of a functional structure of the radio base station according to the present embodiment of the present disclosure. Note that, the present example primarily shows functional blocks that pertain to characteristic parts of the present embodiment, and it is assumed that the radio base station  10  may include other functional blocks that are necessary for radio communication as well. 
     The baseband signal processing section  104  at least includes a control section (scheduler)  301 , a transmission signal generation section  302 , a mapping section  303 , a received signal processing section  304 , and a measurement section  305 . Note that these structures may be included in the radio base station  10 , and some or all of the structures do not need to be included in the baseband signal processing section  104 . 
     The control section (scheduler)  301  controls the whole of the radio base station  10 . The control section  301  can be constituted with a controller, a control circuit or control apparatus that can be described based on general understanding of the technical field to which the present disclosure pertains. 
     The control section  301 , for example, controls the generation of signals in the transmission signal generation section  302 , the mapping of signals by the mapping section  303 , and so on. The control section  301  controls the signal receiving processes in the received signal processing section  304 , the measurements of signals in the measurement section  305 , and so on. 
     The control section  301  controls the scheduling (for example, resource assignment) of system information, a downlink data signal (for example, a signal transmitted on the PDSCH), a downlink control signal (for example, a signal transmitted on the PDCCH and/or the EPDCCH. Delivery confirmation information, and so on). Based on the results of determining necessity or not of retransmission control to the uplink data signal, or the like, the control section  301  controls generation of a downlink control signal, a downlink data signal, and so on. 
     The control section  301  controls the scheduling of a synchronization signal (for example, PSS (Primary Synchronization Signal)/SSS (Secondary Synchronization Signal)), a downlink reference signal (for example, CRS, CSI-RS, DMRS), and so on. 
     The control section  301  controls the scheduling of an uplink data signal (for example, a signal transmitted on the PUSCH), an uplink control signal (for example, a signal transmitted on the PUCCH and/or the PUSCH. Delivery confirmation information, and so on), a random access preamble (for example, a signal transmitted on the PRACH), an uplink reference signal, and so on. 
     The control section  301  may perform control of transmitting the DCI by using the CORESET. The control section  301  may perform, in a specific search space, control of generating and transmitting DCI by using a specific DCI format and RNTI corresponding to the format. 
     The transmission signal generation section  302  generates downlink signals (downlink control signals, downlink data signals, downlink reference signals and so on) based on commands from the control section  301  and outputs the downlink signals to the mapping section  303 . The transmission signal generation section  302  can be constituted with a signal generator, a signal generation circuit or signal generation apparatus that can be described based on general understanding of the technical field to which the present disclosure pertains. 
     For example, the transmission signal generation section  302  generates DL assignment to report assignment information of downlink data and/or UL grant to report assignment information of uplink data, based on commands from the control section  301 . The DL assignment and the UL grant are both DCI, and follow the DCI format. For a downlink data signal, encoding processing and modulation processing are performed in accordance with a coding rate, modulation scheme, or the like determined based on channel state information (CSI) from each user terminal  20 . 
     The mapping section  303  maps the downlink signals generated in the transmission signal generation section  302  to certain radio resources, based on commands from the control section  301 , and outputs these to the transmitting/receiving sections  103 . The mapping section  303  can be constituted with a mapper, a mapping circuit or mapping apparatus that can be described based on general understanding of the technical field to which the present disclosure pertains. 
     The received signal processing section  304  performs receiving processes (for example, demapping, demodulation, decoding and so on) of received signals that are input from the transmitting/receiving sections  103 . Here, the received signals are, for example, uplink signals that are transmitted from the user terminals  20  (uplink control signals, uplink data signals, uplink reference signals and so on). The received signal processing section  304  can be constituted with a signal processor, a signal processing circuit or signal processing apparatus that can be described based on general understanding of the technical field to which the present disclosure pertains. 
     The received signal processing section  304  outputs the decoded information acquired through the receiving processes to the control section  301 . For example, if the received signal processing section  304  receives the PUCCH including HARQ-ACK, the received signal processing section  304  outputs the HARQ-ACK to the control section  301 . The received signal processing section  304  outputs the received signals and/or the signals after the receiving processes to the measurement section  305 . 
     The measurement section  305  conducts measurements with respect to the received signals. The measurement section  305  can be constituted with a measurer, a measurement circuit or measurement apparatus that can be described based on general understanding of the technical field to which the present disclosure pertains. 
     For example, the measurement section  305  may perform RRM (Radio Resource Management) measurement, CSI (Channel State Information) measurement, and so on, based on the received signal. The measurement section  305  may measure a received power (for example, RSRP (Reference Signal Received Power)), a received quality (for example, RSRQ (Reference Signal Received Quality), an SINR (Signal to Interference plus Noise Ratio), an SNR (Signal to Noise Ratio)), a signal strength (for example, RSSI (Received Signal Strength Indicator)), channel information (for example, CSI), and so on. The measurement results may be output to the control section  301 . 
     &lt;User Terminal&gt; 
       FIG.  6    is a diagram to show an example of an overall structure of the user terminal according to the present embodiment. A user terminal  20  includes a plurality of transmitting/receiving antennas  201 , amplifying sections  202 , transmitting/receiving sections  203 , a baseband signal processing section  204  and an application section  205 . Note that the user terminal  20  may be configured to include one or more transmitting/receiving antennas  201 , one or more amplifying sections  202  and one or more transmitting/receiving sections  203 . 
     Radio frequency signals that are received in the transmitting/receiving antennas  201  are amplified in the amplifying sections  202 . The transmitting/receiving sections  203  receive the downlink signals amplified in the amplifying sections  202 . The transmitting/receiving sections  203  convert the received signals into baseband signals through frequency conversion, and output the baseband signals to the baseband signal processing section  204 . The transmitting/receiving sections  203  can be constituted with transmitters/receivers, transmitting/receiving circuits or transmitting/receiving apparatus that can be described based on general understanding of the technical field to which the present disclosure pertains. Note that each transmitting/receiving section  203  may be structured as a transmitting/receiving section in one entity, or may be constituted with a transmitting section and a receiving section. 
     The baseband signal processing section  204  performs, on each input baseband signal, an FFT process, error correction decoding, a retransmission control receiving process, and so on. The downlink user data is forwarded to the application section  205 . The application section  205  performs processes related to higher layers above the physical layer and the MAC layer, and so on. In the downlink data, broadcast information may be also forwarded to the application section  205 . 
     Meanwhile, the uplink user data is input from the application section  205  to the baseband signal processing section  204 . The baseband signal processing section  204  performs a retransmission control transmission process (for example, an HARQ transmission process), channel coding, precoding, a discrete Fourier transform (DFT) process, an IFFT process and so on, and the result is forwarded to the transmitting/receiving section  203 . 
     The transmitting/receiving sections  203  convert the baseband signals output from the baseband signal processing section  204  to have radio frequency band and transmit the result. The radio frequency signals having been subjected to frequency conversion in the transmitting/receiving sections  203  are amplified in the amplifying sections  202 , and transmitted from the transmitting/receiving antennas  201 . 
     The transmitting/receiving sections  203  may use a specific search space determined by the control section  401  described below to monitor a control resource set (CORESET). 
     The transmitting/receiving sections  203  may receive configuration information of a control resource set (CORESET configuration information), the configuration information being included in common configuration information used to configure a cell-specific downlink control channel parameter. The transmitting/receiving sections  203  may receive the common control information included in the system information block (SIB) or receive, by higher layer signaling, the common configuration information in at least one of the handover procedure, the secondary-cell addition procedure, and the primary-secondary-cell addition procedure. 
       FIG.  7    is a diagram to show an example of a functional structure of the user terminal according to the present embodiment. Note that, the present example primarily shows functional blocks that pertain to characteristic parts of the present embodiment, and it is assumed that the user terminal  20  may include other functional blocks that are necessary for radio communication as well. 
     The baseband signal processing section  204  provided in the user terminal  20  at least includes a control section  401 , a transmission signal generation section  402 , a mapping section  403 , a received signal processing section  404  and a measurement section  405 . Note that these structures may be included in the user terminal  20 , and some or all of the structures do not need to be included in the baseband signal processing section  204 . 
     The control section  401  controls the whole of the user terminal  20 . The control section  401  can be constituted with a controller, a control circuit or control apparatus that can be described based on general understanding of the technical field to which the present disclosure pertains. 
     The control section  401 , for example, controls the generation of signals in the transmission signal generation section  402 , the mapping of signals by the mapping section  403 , and so on. The control section  401  controls the signal receiving processes in the received signal processing section  404 , the measurements of signals in the measurement section  405 , and so on. 
     The control section  401  acquires a downlink control signal and a downlink data signal transmitted from the radio base station  10 , from the received signal processing section  404 . The control section  401  controls generation of an uplink control signal and/or an uplink data signal, based on the results of determining necessity or not of retransmission control to a downlink control signal and/or a downlink data signal. 
     The control section  401  may control configuration of a control resource set, based on the configuration information of the control resource set included in common configuration information used to configure a cell-specific downlink control channel parameter. 
     The control resource set may be used to search for downlink control information used to schedule at least one of system information block (SIB) 1, other system information (OSI), and paging. 
     The control resource set may be used to search for downlink control information used to schedule messages in the random access procedure. 
     The control section  401  may be configured to inevitably determine at least two types, the type of a search space for detecting a DCI format CRC (Cyclic Redundancy Check) scrambled with a random access RNTI (Radio Network Temporary Identifier) and the type of a user terminal-specific search space (UE-SS), based on one or more search space configurations 
     Here, the type of the UE-SS may indicate the UE-SS. In other words, the UE-SS may not be configured to further include a plurality of types. The search space type information may be information indicating the C-SS or the UE-SS. 
     If the control section  401  acquires a variety of information reported by the radio base station  10  from the received signal processing section  404 , the control section  401  may update parameters to use for control, based on the information. 
     The transmission signal generation section  402  generates uplink signals (uplink control signals, uplink data signals, uplink reference signals and so on) based on commands from the control section  401 , and outputs the uplink signals to the mapping section  403 . The transmission signal generation section  402  can be constituted with a signal generator, a signal generation circuit or signal generation apparatus that can be described based on general understanding of the technical field to which the present disclosure pertains. 
     For example, the transmission signal generation section  402  generates an uplink control signal about delivery confirmation information, the channel state information (CSI), and so on, based on commands from the control section  401 . The transmission signal generation section  402  generates uplink data signals, based on commands from the control section  401 . For example, when a UL grant is included in a downlink control signal that is reported from the radio base station  10 , the control section  401  commands the transmission signal generation section  402  to generate the uplink data signal. 
     The mapping section  403  maps the uplink signals generated in the transmission signal generation section  402  to radio resources, based on commands from the control section  401 , and outputs the result to the transmitting/receiving sections  203 . The mapping section  403  can be constituted with a mapper, a mapping circuit or mapping apparatus that can be described based on general understanding of the technical field to which the present disclosure pertains. 
     The received signal processing section  404  performs receiving processes (for example, demapping, demodulation, decoding and so on) on received signals that are input from the transmitting/receiving sections  203 . Here, the received signals are, for example, downlink signals transmitted from the radio base station  10  (downlink control signals, downlink data signals, downlink reference signals and so on). The received signal processing section  404  can be constituted with a signal processor, a signal processing circuit or signal processing apparatus that can be described based on general understanding of the technical field to which the present disclosure pertains. The received signal processing section  404  can constitute the receiving section according to the present disclosure. 
     The received signal processing section  404  outputs the decoded information acquired through the receiving processes to the control section  401 . The received signal processing section  404  outputs, for example, broadcast information, system information, RRC signaling, DCI and so on, to the control section  401 . The received signal processing section  404  outputs the received signals and/or the signals resulting from the receiving processes to the measurement section  405 . 
     The measurement section  405  conducts measurements with respect to the received signals. The measurement section  405  can be constituted with a measurer, a measurement circuit or measurement apparatus that can be described based on general understanding of the technical field to which the present disclosure pertains. 
     For example, the measurement section  405  may perform RRM measurement, CSI measurement, and so on, based on the received signal. The measurement section  405  may measure a received power (for example, RSRP), a received quality (for example, RSRQ, SINR, SNR), a signal strength (for example, RSSI), channel information (for example, CSI), and so on. The measurement results may be output to the control section  401 . 
     &lt;Hardware Structure&gt; 
     Note that the block diagrams that have been used to describe the above embodiments show blocks in functional units. These functional blocks (components) may be implemented in arbitrary combinations of hardware and/or software. Also, the method for implementing each functional block is not particularly limited. That is, each functional block may be realized by one piece of apparatus that is physically and/or logically aggregated, or may be realized by directly and/or indirectly connecting two or more physically and/or logically separate pieces of apparatus (via wire and/or wireless, for example) and using these plurality of pieces of apparatus. 
     For example, a radio base station, a user terminal, and so on according to the present embodiment of the present disclosure may function as a computer that executes the processes of the radio communication method of the present disclosure.  FIG.  8    is a diagram to show an example of a hardware structure of the radio base station and the user terminal according to the present embodiment. Physically, the above-described radio base station  10  and user terminals  20  may each be formed as computer apparatus that includes a processor  1001 , a memory  1002 , a storage  1003 , a communication apparatus  1004 , an input apparatus  1005 , an output apparatus  1006 , a bus  1007 , and so on. 
     Note that, in the following description, the word “apparatus” may be interpreted as “circuit,” “device,” “unit,” and so on. The hardware structure of the radio base station  10  and the user terminals  20  may be designed to include one or a plurality of apparatuses shown in the drawings, or may be designed not to include part of pieces of apparatus. 
     For example, although only one processor  1001  is shown, a plurality of processors may be provided. Furthermore, processes may be implemented with one processor or may be implemented at the same time, in sequence, or in different manners with one or more processors. Note that the processor  1001  may be implemented with one or more chips. 
     Each function of the radio base station  10  and the user terminals  20  is implemented, for example, by allowing certain software (programs) to be read on hardware such as the processor  1001  and the memory  1002 , and by allowing the processor  1001  to perform calculations to control communication via the communication apparatus  1004  and read and/or write data in the memory  1002  and the storage  1003 . 
     The processor  1001  controls the whole computer by, for example, running an operating system. The processor  1001  may be configured with a central processing unit (CPU), which includes interfaces with peripheral apparatus, control apparatus, computing apparatus, a register, and so on. For example, the above-described baseband signal processing section  104  ( 204 ), call processing section  105 , and so on may be implemented by the processor  1001 . 
     Furthermore, the processor  1001  reads programs (program codes), software modules, data, and so on from the storage  1003  and/or the communication apparatus  1004 , into the memory  1002 , and executes various processes according to these. As for the programs, programs to allow computers to execute at least part of the operations of the above-described embodiments are used. For example, the control section  401  of each user terminal  20  may be implemented by control programs that are stored in the memory  1002  and that operate on the processor  1001 , and other functional blocks may be implemented likewise. 
     The memory  1002  is a computer-readable recording medium, and may be constituted with, for example, at least one of a ROM (Read Only Memory), an EPROM (Erasable Programmable ROM), an EEPROM (Electrically EPROM), a RAM (Random Access Memory), and other appropriate storage media. The memory  1002  may be referred to as a “register,” a “cache,” a “main memory (primary storage apparatus)” and so on. The memory  1002  can store executable programs (program codes), software modules, and/or the like for implementing a radio communication method according to the present embodiment. 
     The storage  1003  is a computer-readable recording medium, and may be constituted with, for example, at least one of a flexible disk, a floppy (registered trademark) disk, a magneto-optical disk (for example, a compact disc (CD-ROM (Compact Disc ROM) and so on), a digital versatile disc, a Blu-ray (registered trademark) disk), a removable disk, a hard disk drive, a smart card, a flash memory device (for example, a card, a stick, and a key drive), a magnetic stripe, a database, a server, and other appropriate storage media. The storage  1003  may be referred to as “secondary storage apparatus.” 
     The communication apparatus  1004  is hardware (transmitting/receiving device) for allowing inter-computer communication via wired and/or wireless networks, and may be referred to as, for example, a “network device,” a “network controller,” a “network card,” a “communication module” and so on. The communication apparatus  1004  may be configured to include a high frequency switch, a duplexer, a filter, a frequency synthesizer, and so on in order to realize, for example, frequency division duplex (FDD) and/or time division duplex (TDD). For example, the above-described transmitting/receiving antennas  101  ( 201 ), amplifying sections  102  ( 202 ), transmitting/receiving sections  103  ( 203 ), transmission line interface  106 , and so on may be implemented by the communication apparatus  1004 . 
     The input apparatus  1005  is an input device that receives input from the outside (for example, a keyboard, a mouse, a microphone, a switch, a button, a sensor, and so on). The output apparatus  1006  is an output device that allows sending output to the outside (for example, a display, a speaker, an LED (Light Emitting Diode) lamp, and so on). Note that the input apparatus  1005  and the output apparatus  1006  may be provided in an integrated structure (for example, a touch panel). 
     Furthermore, these types of apparatus, including the processor  1001 , the memory  1002 , and others, are connected by a bus  1007  for communicating information. The bus  1007  may be formed with a single bus, or may be formed with buses that vary between pieces of apparatus. 
     Also, the radio base station  10  and the user terminals  20  may be structured to include hardware such as a microprocessor, a digital signal processor (DSP), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), an FPGA (Field Programmable Gate Array), and so on, and part or all of the functional blocks may be implemented by the hardware. For example, the processor  1001  may be implemented with at least one of these pieces of hardware. 
     (Variations) 
     Note that the terminology used in this specification and/or the terminology that is needed to understand this specification may be replaced by other terms that convey the same or similar meanings. For example, “channels” and/or “symbols” may be replaced by “signals” (“signaling”). Also, “signals” may be “messages.” A reference signal may be abbreviated as an “RS,” and may be referred to as a “pilot,” a “pilot signal,” and so on, depending on which standard applies. Furthermore, a “component carrier (CC)” may be referred to as a “cell,” a “frequency carrier,” a “carrier frequency” and so on. 
     Furthermore, a radio frame may be constituted of one or a plurality of periods (frames) in the time domain. Each of one or a plurality of periods (frames) constituting a radio frame may be referred to as a “subframe.” Furthermore, a subframe may be constituted of one or a plurality of slots in the time domain. A subframe may have a fixed time length (for example, 1 ms) independent of numerology. 
     Furthermore, a slot may be constituted of one or a plurality of symbols in the time domain (OFDM (Orthogonal Frequency Division Multiplexing) symbols, SC-FDMA (Single Carrier Frequency Division Multiple Access) symbols, and so on). Furthermore, a slot may be a time unit based on numerology. A slot may include a plurality of mini-slots. Each mini-slot may be constituted of one or a plurality of symbols in the time domain. A mini-slot may be referred to as a “sub-slot.” 
     A radio frame, a subframe, a slot, a mini-slot, and a symbol all express time units in signal communication. A radio frame, a subframe, a slot, a mini-slot, and a symbol may each be called by other applicable terms. For example, one subframe may be referred to as a “transmission time interval (TTI),” a plurality of consecutive subframes may be referred to as a “TTI” or one slot or one mini-slot may be referred to as a “TTI.” That is, a subframe and/or a TTI may be a subframe (1 ms) in existing LTE, may be a shorter period than 1 ms (for example, 1 to 13 symbols), or may be a longer period than 1 ms. Note that a unit expressing TTI may be referred to as a “slot,” a “mini-slot,” and so on instead of a “subframe.” 
     Here, a TTI refers to the minimum time unit of scheduling in radio communication, for example. For example, in LTE systems, a radio base station schedules the allocation of radio resources (such as a frequency bandwidth and transmission power that are available for each user terminal) for the user terminal in TTI units. Note that the definition of TTIs is not limited to this. 
     TTIs may be transmission time units for channel-encoded data packets (transport blocks), code blocks, and/or codewords, or may be the unit of processing in scheduling, link adaptation, and so on. Note that, when TTIs are given, the time interval (for example, the number of symbols) to which transport blocks, code blocks and/or codewords are actually mapped may be shorter than the TTIs. 
     Note that, in the case where one slot or one mini-slot is referred to as a TTI, one or more TTIs (that is, one or more slots or one or more mini-slots) may be the minimum time unit of scheduling. Furthermore, the number of slots (the number of mini-slots) constituting the minimum time unit of the scheduling may be controlled. 
     A TTI having a time length of 1 ms may be referred to as a “normal TTI” (TTI in LTE Rel. 8 to Rel. 12), a “long TTI,” a “normal subframe,” a “long subframe” and so on. A TTI that is shorter than a normal TTI may be referred to as a “shortened TTI,” a “short TTI,” a “partial or fractional TTI,” a “shortened subframe,” a “short subframe,” a “mini-slot,” a “sub-slot” and so on. 
     Note that a long TTI (for example, a normal TTI, a subframe, and so on) may be interpreted as a TTI having a time length exceeding 1 ms, and a short TTI (for example, a shortened TTI and so on) may be interpreted as a TTI having a TTI length shorter than the TTI length of a long TTI and equal to or longer than 1 ms. 
     A resource block (RB) is the unit of resource allocation in the time domain and the frequency domain, and may include one or a plurality of consecutive subcarriers in the frequency domain. Also, an RB may include one or a plurality of symbols in the time domain, and may be one slot, one mini-slot, one subframe, or one TTI in length. One TTI and one subframe each may be constituted of one or a plurality of resource blocks. Note that one or a plurality of RBs may be referred to as a “physical resource block (PRB (Physical RB)),” a “sub-carrier group (SCG),” a “resource element group (REG),” a “PRB pair,” an “RB pair” and so on. 
     Furthermore, a resource block may be constituted of one or a plurality of resource elements (REs). For example, one RE may correspond to a radio resource field of one subcarrier and one symbol. 
     Note that the above-described structures of radio frames, subframes, slots, mini-slots, symbols, and so on are merely examples. For example, structures such as the number of subframes included in a radio frame, the number of slots per subframe or radio frame, the number of mini-slots included in a slot, the numbers of symbols and RBs included in a slot or a mini-slot, the number of subcarriers included in an RB, the number of symbols in a TTI, the symbol length, the cyclic prefix (CP) length, and so on can be variously changed. 
     Also, the information, parameters, and so on described in this specification may be represented in absolute values or in relative values with respect to certain values, or may be represented in another corresponding information. For example, radio resources may be specified by certain indices. 
     The names used for parameters and so on in this specification are in no respect limiting. For example, since various channels (PUCCH (Physical Uplink Control Channel), PDCCH (Physical Downlink Control Channel), and so on) and information elements can be identified by any suitable names, the various names assigned to these individual channels and information elements are in no respect limiting. 
     The information, signals, and/or others described in this specification may be represented by using any of a variety of different technologies. For example, data, instructions, commands, information, signals, bits, symbols, chips, and so on, all of which may be referenced throughout the herein-contained description, may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or photons, or any combination of these. 
     Also, information, signals, and so on can be output from higher layers to lower layers and/or from lower layers to higher layers. Information, signals, and so on may be input and/or output via a plurality of network nodes. 
     The information, signals, and so on that are input and/or output may be stored in a specific location (for example, a memory) or may be managed by using a management table. The information, signals, and so on to be input and/or output can be overwritten, updated, or appended. The information, signals, and so on that are output may be deleted. The information, signals, and so on that are input may be transmitted to another apparatus. 
     Reporting of information is by no means limited to the aspects/embodiments described in this specification, and other methods may be used as well. For example, reporting of information may be implemented by using physical layer signaling (for example, downlink control information (DCI), uplink control information (UCI), higher layer signaling (for example, RRC (Radio Resource Control) signaling, broadcast information (master information block (MIB), system information blocks (SIBs), and so on), MAC (Medium Access Control) signaling and so on), and other signals and/or combinations of these. 
     Note that physical layer signaling may be referred to as “L1/L2 (Layer 1/Layer 2) control information (L1/L2 control signals),” “L1 control information (L1 control signal),” and so on. Also, RRC signaling may be referred to as an “RRC message,” and can be, for example, an RRC connection setup (RRCConnectionSetup) message, an RRC connection reconfiguration (RRCConnectionReconfiguration) message, and so on. Also, MAC signaling may be reported using, for example, MAC control elements (MAC CEs). 
     Also, reporting of certain information (for example, reporting of “X holds”) does not necessarily have to be reported explicitly, and can be reported implicitly (by, for example, not reporting this certain information or reporting another piece of information). 
     Determinations may be made in values represented by one bit (0 or 1), may be made in Boolean values that represent true or false, or may be made by comparing numerical values (for example, comparison against a certain value). 
     Software, whether referred to as “software,” “firmware,” “middleware,” “microcode,” or “hardware description language,” or called by other terms, should be interpreted broadly to mean instructions, instruction sets, code, code segments, program codes, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, execution threads, procedures, functions, and so on. 
     Also, software, commands, information, and so on may be transmitted and received via communication media. For example, when software is transmitted from a website, a server, or other remote sources by using wired technologies (coaxial cables, optical fiber cables, twisted-pair cables, digital subscriber lines (DSL), and so on) and/or wireless technologies (infrared radiation, microwaves, and so on), these wired technologies and/or wireless technologies are also included in the definition of communication media. 
     The terms “system” and “network” as used in this specification are used interchangeably. 
     In the present specification, the terms “base station (BS),” “radio base station,” “eNB,” “gNB,” “cell,” “sector,” “cell group,” “carrier,” and “component carrier” may be used interchangeably. A base station may be referred to as a “fixed station,” “NodeB,” “eNodeB (eNB),” “access point,” “transmission point,” “receiving point,” “femto cell,” “small cell” and so on. 
     A base station can accommodate one or a plurality of (for example, three) cells (also referred to as “sectors”). When a base station accommodates a plurality of cells, the entire coverage area of the base station can be partitioned into multiple smaller areas, and each smaller area can provide communication services through base station subsystems (for example, indoor small base stations (RRHs (Remote Radio Heads))). The term “cell” or “sector” refers to part of or the entire coverage area of a base station and/or a base station subsystem that provides communication services within this coverage. 
     In the present specification, the terms “mobile station (MS),” “user terminal,” “user equipment (UE),” and “terminal” may be used interchangeably. 
     A mobile station may be referred to as, by a person skilled in the art, a “subscriber station,” “mobile unit,” “subscriber unit,” “wireless unit,” “remote unit,” “mobile device,” “wireless device,” “wireless communication device,” “remote device,” “mobile subscriber station,” “access terminal,” “mobile terminal,” “wireless terminal,” “remote terminal,” “handset,” “user agent,” “mobile client,” “client,” or some other appropriate terms in some cases. 
     Furthermore, the radio base stations in this specification may be interpreted as user terminals. For example, each aspect/embodiment of the present disclosure may be applied to a configuration in which communication between a radio base station and a user terminal is replaced with communication among a plurality of user terminals (D2D (Device-to-Device)). In this case, the user terminals  20  may have the functions of the radio base stations  10  described above. In addition, wording such as “uplink” and “downlink” may be interpreted as “side.” For example, an uplink channel may be interpreted as a side channel. 
     Likewise, the user terminals in this specification may be interpreted as radio base stations. In this case, the radio base stations  10  may have the functions of the user terminals  20  described above. 
     Actions which have been described in this specification to be performed by a base station may, in some cases, be performed by upper nodes. In a network including one or a plurality of network nodes with base stations, it is clear that various operations that are performed to communicate with terminals can be performed by base stations, one or more network nodes (for example, MMEs (Mobility Management Entities), S-GW (Serving-Gateways), and so on may be possible, but these are not limiting) other than base stations, or combinations of these. 
     The aspects/embodiments illustrated in this specification may be used individually or in combinations, which may be switched depending on the mode of implementation. The order of processes, sequences, flowcharts, and so on that have been used to describe the aspects/embodiments herein may be re-ordered as long as inconsistencies do not arise. For example, although various methods have been illustrated in this specification with various components of steps in exemplary orders, the specific orders that are illustrated herein are by no means limiting. 
     The aspects/embodiments illustrated in this specification may be applied to LTE (Long Term Evolution), LTE-A (LTE-Advanced), LTE-B (LTE-Beyond), SUPER 3G, IMT-Advanced, 4G (4th generation mobile communication system), 5G (5th generation mobile communication system), FRA (Future Radio Access), New-RAT (Radio Access Technology), NR(New Radio), NX (New radio access), FX (Future generation radio access), GSM (registered trademark) (Global System for Mobile communications), CDMA 2000, UMB (Ultra Mobile Broadband), IEEE 802.11 (Wi-Fi (registered trademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE 802.20, UWB (Ultra-WideBand), Bluetooth (registered trademark), systems that use other adequate radio communication methods and/or next-generation systems that are enhanced based on these. 
     The phrase “based on” (or “on the basis of”) as used in this specification does not mean “based only on” (or “only on the basis of”), unless otherwise specified. In other words, the phrase “based on” (or “on the basis of”) means both “based only on” and “based at least on” (“only on the basis of” and “at least on the basis of”). 
     Reference to elements with designations such as “first,” “second” and so on as used herein does not generally limit the quantity or order of these elements. These designations may be used herein only for convenience, as a method for distinguishing between two or more elements. Thus, reference to the first and second elements does not imply that only two elements may be employed, or that the first element must precede the second element in some way. 
     The term “judging (determining)” as used herein may encompass a wide variety of actions. For example, “judging (determining)” may be interpreted to mean making “judgments (determinations)” about calculating, computing, processing, deriving, investigating, looking up (for example, searching a table, a database, or some other data structures), ascertaining, and so on. Furthermore, “judging (determining)” may be interpreted to mean making “judgments (determinations)” about receiving (for example, receiving information), transmitting (for example, transmitting information), input, output, accessing (for example, accessing data in a memory), and so on. In addition, “judging (determining)” as used herein may be interpreted to mean making “judgments (determinations)” about resolving, selecting, choosing, establishing, comparing, and so on. In other words, “judging (determining)” may be interpreted to mean making “judgments (determinations)” about some action. 
     The terms “connected” and “coupled,” or any variation of these terms as used herein mean all direct or indirect connections or coupling between two or more elements, and may include the presence of one or more intermediate elements between two elements that are “connected” or “coupled” to each other. The coupling or connection between the elements may be physical, logical, or a combination thereof. For example, “connection” may be interpreted as “access.” 
     In this specification, when two elements are connected, the two elements may be considered “connected” or “coupled” to each other by using one or more electrical wires, cables and/or printed electrical connections, and, as some non-limiting and non-inclusive examples, by using electromagnetic energy having wavelengths in radio frequency regions, microwave regions, (both visible and invisible) optical regions, or the like. 
     In this specification, the phrase “A and B are different” may mean that “A and B are different from each other.” The terms “separate,” “be coupled” and so on may be interpreted similarly. 
     When terms such as “including,” “comprising,” and variations of these are used in this specification or in claims, these terms are intended to be inclusive, in a manner similar to the way the term “provide” is used. Furthermore, the term “or” as used in this specification or in claims is intended to be not an exclusive disjunction. 
     Now, although the invention according to the present disclosure has been described in detail above, it should be obvious to a person skilled in the art that the invention according to the present disclosure is by no means limited to the embodiments described in this specification. The invention according to the present disclosure can be implemented with various corrections and in various modifications, without departing from the spirit and scope of the invention defined by the recitations of claims. Consequently, the description in this specification is provided only for the purpose of explaining examples, and should by no means be construed to limit the invention according to the present disclosure in any way.