Patent Description:
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 <NUM>). In addition, the specifications of LTE-A (LTE advanced and LTE Rel. <NUM>, <NUM>, <NUM> and <NUM>) have also been drafted for the purpose of achieving increased capacity and enhancement beyond LTE (LTE Rel. <NUM> and <NUM>).

Successor systems of LTE are also under study (for example, referred to as "FRA (Future Radio Access)," "<NUM> (5th Generation mobile communication system)," "<NUM>+ (plus)," "NR (New Radio)," "NX (New radio access)," "FX (Future generation radio access)," "LTE Rel. <NUM> or <NUM> and later versions," etc.).

In existing LTE systems (LTE Rel. <NUM> to <NUM>), the quality of a radio link is subject to monitoring (RLM (Radio Link Monitoring)). When a radio link failure (RLF) is detected based on RLM, a user terminal (UE (User Equipment)) is required to re-establish the RRC (Radio Resource Control) connection.

Non-Patent Literature <NUM>: <NPL>ET AL, "Beam recovery procedure", 3GPP DRAFT.

Furthermore, future radio communication systems (for example, LTE Rel. <NUM> or later versions, NR or <NUM> etc.) are under study to allow communication using beamforming (BF).

Also, in order to prevent occurrence of radio link failures (RLFs) in future radio communication systems, studies are underway to perform a procedure for detecting beam failures and switching to other beams (which may be referred to as "beam recovery (BR) procedure," and the like). The question lies in how to control the beam recovery procedure based on beam failure detection results.

It is therefore an object of the present disclosure to provide a user terminal and a radio communication method, whereby recovery from beam failures can be controlled properly.

Further examples not falling within the scope of the claims are not part of the invention, but are provided for facilitating the understanding of the invention. In accordance with one example of the present disclosure, a user terminal has a control section that increments a beam failure instance counter based on a beam failure instance indication received from a physical layer, in a higher layer, and a transmission section that transmits a random access preamble based on a transmission command from the higher layer when the beam failure instance counter reaches or exceeds a given threshold.

According to one aspect of the present disclosure, recovery from beam failures can be controlled properly.

For example, beams that are used by a user terminal and/or a radio base station (for example, a gNB (gNodeB)) may include beams that are used to transmit signals (also referred to as "transmitting beams," "Tx beams," etc.), beams that are used to receive signals (also referred to as "receiving beams," "Rx beams," etc.) and so forth. A pair of a transmitting beam from the transmitting end and a receiving beam from the receiving end may be referred to as a "beam pair link (BPL).

To select BPLs, the base station and the use terminal may select beams that are favorable for both, autonomously, or may exchange information that can identify combinations that are suitable for both, via RRC, MAC CE, L1 signaling, etc., and select beam based on this information.

Between different BPLs, either transmission or receipt, or both, may use different antenna devices for transmission and receipt (for example, antenna panels, antenna element sets, transmitting/receiving points ("TRPs (Transmission and Reception Points)," "TxRPs (Transmitter and Reception Points)," "TRxPs (Transmission and Receiver Points)," etc.). In this case, quasi-co-location (QCL), which shows the statistical properties of channels, also varies between different BPLs. Therefore, QCL may be the same or different between different BPLs, and information as to whether QCLs is the same or different may be recognized by the transmitter/receiver, by way of signaling or measurements.

In an environment to use BF, radio link is more susceptible to the impact of blockage from obstacles, and so the quality of a radio link is more likely to deteriorate. There is a danger that, if the quality of a radio link deteriorates, radio link failures (RLFs) might occur frequently. When an RLF occurs, it is necessary to re-connect with cells, so that, frequent occurrence of RLFs may lead to a decline in system throughput.

For this reason, the method of radio link monitoring (RLM) for future radio communication systems is being discussed. For example, envisaging future radio communication systems, research is underway to support one or more downlink signals (also referred to as "DL-RSs (Reference Signals)" and the like) for RLM.

Resources for DL-RSs (DL-RS resources) may be associated with resources and/or ports for synchronization signal blocks (SSBs) or channel state measurement RSs (CSI-RSs (Channel State Information RSs)). Note that SSBs may be referred to as "SS/PBCH (Physical Broadcast CHannel) blocks" and the like.

The DL-RS may be at least one of a primary synchronization signal (PSS), a secondary synchronization signal (SSS), a mobility reference signal (MRS), a CSI-RS, a demodulation reference signal (DMRS), a beam-specific signal and so forth, or may be a signal formed by enhancing and/or changing these (for example, a signal formed by changing the density and/or cycle).

A user terminal may be configured, by higher layer signaling, to perform measurements using DL-RS resources. In this case, the assumption is that the user terminal, where such measurements are configured, determines whether the radio link is in a synchronous state (IS (In-Sync)) or in an asynchronous state (OOS (Out-Of-Sync)), based on measurement results in DL-RS resources. In the event no DL-RS resources are configured from the radio base station, default DL-RS resources to allow the user terminal to conduct RLM may be set forth in the specification.

If the quality of a radio link that is estimated (or "measured") based at least on <NUM> DL-RS resource configured exceeds a given threshold Qin, the user terminal may judge that the radio link is in IS.

If the quality of a radio link that is estimated based at least on <NUM> DL-RS resource configured falls below a given threshold Qout, the user terminal may judge that the radio link is in OOS. Note that this radio link quality may correspond to, for example, the block error rate (BLER) of a hypothetical PDCCH.

In existing LTE systems (LTE Rel. <NUM> to <NUM>), IS and/or OOS (IS/OOS) are reported (indicated) from the physical layer to higher layers (for example, MAC layer, RRC layer, etc.) in a user terminal, and RLF is detected based on reports of IS/OOS.

To be more specific, when a user terminal receives an OOS report associated with a given cell (for example, the primary cell) N310 times, the user terminal will activate (start) a timer T310. When the user terminal receives an IS report associated with the given cell N311 times while the timer T310 is running, the user terminal will stop the timer T310. When the timer T310 expires, the user terminal judges that RLF has been detected with respect to this given cell.

Note that the names "N310," "N311," "T310" and others are by no means limiting. T310 may be referred to as a "timer for RLF detection" or the like. N310 may be referred to as "the number of times OOS is reported before timer T310 is activated" or the like. N311 may be referred to as "the number of times IS is reported before the timer T310 is stopped" or the like.

<FIG> is a schematic diagram in which RLF is detected based on IS/OOS. This drawing assumes that N310=N311=<NUM>. T310 shows the period from the activation of timer T310 to its expiration, but does not show a timer counter.

The upper part of <FIG> shows <NUM> cases (case <NUM> and case <NUM>) in which the estimated quality of a radio link changes. The lower part of <FIG> shows IS/OOS reports corresponding to the above <NUM> cases.

In case <NUM>, first, OOS occurs N310 times, and the timer T310 starts. After that, if T310 expires while the radio link quality does not exceed the threshold Qin, RLF is detected.

Referring to case <NUM>, although the timer T310 starts as in case <NUM>, following this, the radio link quality exceeds the threshold Qin and IS occurs N311 times, and T310 stops.

Now, envisaging future radio communication systems (for example, LTE Rel. <NUM> or later version, NR, <NUM>, etc.), research is being conducted on executing a procedure for switching to another beam (which may be referred to as "beam recovery (BR)," "beam failure recovery (BFR)," "L1/L2 beam recovery," etc.) when the quality of a particular beam deteriorates in order to prevent the occurrence of RLF. RLF, as mentioned earlier, is detected by controlling RS measurements in the physical layer and the activation and expiration of timers in higher layers, and recovery from RLF should follow the same procedure as that of random access, but in switching to other beams (BR, L1/L2 beam recovery), it is expected that the procedures in at least some layers will be more simplified than recovery from RLF.

<FIG> is a diagram to show an example of the beam recovery procedure. The number of beams and the like are examples and not limiting. In the initial state shown in <FIG> (step S101), a user terminal receives a downlink control channel (PDCCH (Physical Downlink Control CHannel)), which is transmitted from a radio base station using <NUM> beams.

In step S102, when the radio wave from the radio base station is blocked, the user terminal cannot detect the PDCCH. Such blocking might take place, for example, due to the impacts of obstacles between the user terminal and the radio base station, fading, interference and so forth.

The user terminal detects beam failures when a given condition is satisfied. The radio base station may judge that the user terminal has detected a beam failure when no report arrives from the user terminal, or the radio base station may judge that a beam failure has been detected when a given signal (beam recovery request in step S104) is received from the user terminal.

In step S103, the user terminal starts a search for new candidate beams to use for communication, for beam recovery. To be more specific, upon detecting a beam failure, the user terminal performs measurements based on pre-configured DL-RS resources, and identifies one or more new candidate beams that are desirable (that have good quality, for example). In the case of this example, <NUM> beam is identified as a new candidate beam.

In step S104, the user terminal, having identified a new candidate beam, transmits a beam recovery request. The beam recovery request may be transmitted, for example, by using at least one of an uplink control channel (PUCCH (Physical Uplink Control CHannel)), a random access channel (PRACH (Physical Random Access CHannel)), and a UL grant-free PUSCH (Physical Uplink Shared CHannel). The beam recovery request may be referred to as a "beam recovery request signal," a "beam failure recovery request signal," and the like.

The beam recovery request may include information about the new candidate beam identified in step S103. The resource for the beam recovery request may be associated with the new candidate beam. Information about the beam may be reported by using, for example, a beam index (BI)), a given reference signal's port and/or resource index (for example, CSI-RS resource indicator (CRI)), and so forth.

In step S105, the radio base station, having detected the beam recovery request, transmits a response signal in response to the beam recovery request from the user terminal. The response signal may include reconfiguration information (for example, configuration information of DL-RS resource) associated with one or more beams. The response signal may be transmitted, for example, in a user terminal-common search space in PDCCH. The user terminal may determine which transmitting beam and/or receiving beam to use based on beam reconfiguration information.

In step S106, the user terminal may transmit, to the radio base station, a message indicating that beam reconfiguration has been completed. The message may be transmitted by using the PUCCH, for example.

A successful beam recovery (BR success) may represent, for example, the case in which step S106 is reached. On the other hand, failure of beam recovery (BR failure) may represent, for example, a case where no candidate beam can be identified in step S103.

Note that the index numbers of these steps are just numbers for illustrative purposes, and several steps may be put together, or re-ordered.

The present inventors have come up with a control method that is suitable for steps S102 to S104 in the beam recovery procedure described above. To be more specific, a control method that is suitable for interaction between the physical layer (which may be referred to as, for example, the "PHY (PHYsical) layer," "layer <NUM>," etc.) and higher layers (which may be referred to as, for example, the "MAC (Medium Access Control) layer," "layer <NUM>," etc.).

Now, embodiments of this disclosure will be described below in detail with reference to the accompanying drawings. Higher layer as used in the following description will refer to the MAC layer, but this is by no means limiting.

In one example of the present disclosure, when UE detects a beam failure, the UE sends a beam failure-related report from the PHY layer to the MAC layer.

The occurrence of beam failure may be referred to as a "beam failure instance" and the like. The above-noted beam failure-related report may be referred to as a "beam failure instance indication," "information about a beam failure," "information about whether a beam failure is present or not" and the like. A beam failure instance may cover any number of beam failures (for example, <NUM> times, <NUM> time, multiple times, etc.) or cover beam failures detected in a given period.

The beam failure instance indication may contain, for example, information to report at least one of the following states.

That is, the beam failure instance indication may include information to indicate whether a beam failure (or beam failure instance) has occurred or not, and/or whether there is a new candidate beam or not.

When the PHY layer of the UE does not detect a beam failure in the beam recovery procedure, the PHY layer may transmit a beam failure instance indication to show state <NUM> to the MAC layer. Note that when it is mentioned that no beam failure is detected, this can mean that there is at least <NUM> beam where no beam failure is detected. Also, a beam failure instance indication to show state <NUM> may be referred to as a "non-beam failure instance indication.

When the PHY layer of the UE does detects a beam failure in the beam recovery procedure, the PHY layer may transmit a beam failure instance indication to show state <NUM> or state <NUM>, to the MAC layer.

After detecting a beam failure, if a new candidate beam is found, the PHY layer of the UE may transmit a beam failure instance indication to show state <NUM>, to the MAC layer. At this time, information (for example, a beam index) related to the new candidate beam that is found may be reported to the MAC layer together with or instead of the beam failure instance indication. If multiple new candidate beams are found, information about one or more new candidate beams may be reported to the MAC layer.

After detecting a beam failure, the PHY layer of the UE may transmit a beam failure instance indication to show state <NUM>, to the MAC layer, if a new candidate beam is not found.

The MAC layer counts beam failure instances based on beam failure instance indications. Beam failure instances may be counted using a beam failure instance counter. This counter may be used for the MAC layer. This counter may start from a given value (for example, <NUM>).

The MAC layer may increment the beam failure instance counter by a given value (for example, +<NUM>) when receiving a beam failure instance indication to show state <NUM> or <NUM>, from the PHY layer.

When the MAC layer receives a non-beam-failure instance indication from the PHY layer, the MAC layer may stop or reset the beam failure instance counter, or perform a specific operation (for example, set the timer value to <NUM>, -<NUM>, etc.). Resetting the beam failure instance counter upon receipt of a non-beam-failure instance indication is equivalent to the MAC layer's counting of consecutive beam failure instances.

Note that, when it is mentioned that a non-beam-failure instance indication is received from the PHY layer, this may be interpreted as meaning that a beam failure instance indication has not been received for a certain period of time, and the like.

The MAC layer may trigger the transmission of a beam recovery request when the beam failure instance counter reaches or exceeds a given threshold. In this case, the MAC layer may report a beam recovery request transmission command (trigger information) to the PHY layer. The MAC layer may select information about one or more new candidate beams (for example, beam index) to include in the beam recovery request, and report this to the PHY layer.

Note that a timer for beam failure instances (also referred to as a "beam failure instance timer") may be used with or instead of the beam failure instance counter. If the beam failure instance timer is not activated when a beam failure instance indication is received, the MAC layer of the UE may start the timer. The MAC layer may trigger a beam recovery request when the timer expires or when no non-beam-failure instance indication is received before the timer expires.

The MAC layer may decrement the beam failure instance timer by a given value when receiving a beam failure instance indication to show state <NUM> or <NUM>, from the PHY layer.

When the MAC layer receives a non-beam failure instance indication from the PHY layer, the MAC layer may stop the beam failure instance timer, reset the beam failure instance timer to the initial value, or perform a specific operation (for example, increment the timer by a given value).

Note that information regarding the beam failure instance counter or the beam failure instance timer (for example, the above-mentioned given threshold, timer duration, etc.) may be reported by using higher layer signaling, physical layer signaling, or a combination of these.

Here, higher layer signaling may be, for example, any of RRC (Radio Resource Control) signaling, MAC (Medium Access Control) signaling, broadcast information, etc., or a combination of these.

For example, a MAC control element (MAC CE (Control Element)), a MAC PDU (Protocol Data Unit), etc. may be used for MAC signaling. The broadcast information may be, for example, the master information block (MIB), a system information block (SIB), minimum system information (RMSI (Remaining Minimum System Information)) and the like.

Physical layer signaling may be, for example, downlink control information (DCI).

The PHY layer transmits a beam recovery request based on the above trigger. Note that the MAC layer may decide which channel is used to transmit the beam recovery request from the PHY layer, and send an indication thereof to the PHY layer. For example, the MAC layer may choose whether to use a contention-based PRACH (CBRA (Contention-Based PRACH)) or use a non-contention-based PRACH (CFRA (Contention-Free PRACH)) to transmit a beam recovery request from the PHY layer.

The beam recovery request may include information related to one or more new candidate beams, and this information may be selected by the PHY layer (based on, for example, the measured quality of the new candidate beams), or may be selected based on a report from the MAC layer.

For example, the MAC layer may command the PHY layer to include, in a beam recovery request, a new candidate beam that corresponds to a BI that has been reported a greater number of times than other BIs by beam failure instance indications.

If the new candidate beam selected for the beam recovery request is associated with a given CFRA (given CFRA configuration), the MAC layer may decide to transmit the beam recovery request using that CFRA otherwise, the MAC layer may decide to transmit a beam recovery request using CBRA.

Note that information about the association between new candidate beam and the CFRA may be reported using higher layer signaling, physical layer signaling, or a combination of these.

<FIG> is a diagram to show an example of the beam recovery procedure using beam failure instance indications, according to the present embodiment. <FIG> is a schematic diagram of contents of beam failure instance indications corresponding to times T1 to T9 and operations related to each layer (L1 and L2) in the beam recovery procedure.

In this example, L1 of the UE detects a beam failure at time T1, searches for new candidate beams, and, as a result of this, discovers the beam of BI #<NUM>. L1 transmits a beam failure instance indication to show state <NUM> and BI #<NUM>, to L2. L2 receives the report and increments the count on the beam failure instance counter.

Similarly, at time T2, L1 discovers the beam of BI #<NUM> and transmits a beam failure instance indication for state <NUM>. At time T3, L1 discovers the beam of BI #<NUM> and transmits a beam failure instance indication for state <NUM>.

At time T4, no beam failure is detected, so that L1 does not have to transmit a beam failure instance indication, or L1 may transmit a beam failure instance indication for state <NUM>. In this case, L2 may stop the beam failure instance counter.

At time T5, L1 discovers the beam of BI #<NUM> and transmits a beam failure instance indication for state <NUM>. At time T6, L1 cannot find a new candidate beam, and therefore transmits a beam failure instance indication for state <NUM>. Times T7 and T8 may be the same as times T2 and T3, respectively, and therefore their description will be omitted.

At time T9, L1 discovers the beam of BI #<NUM> and transmits a beam failure instance indication for state <NUM>. L2 increments the count on the beam failure instance counter according to this indication, and transmits (triggers) a BFR request to L1 when the value on the counter reaches or exceeds a given threshold (in this example, <NUM>), and L1 transmits a BFR request.

According to one embodiment of the present disclosure, it is possible to unify the contents reported between the PHY layer and the MAC layer for beam recovery, and avoid redundant mutual interaction. Also, the method (such as the channel) for transmitting beam recovery requests can be selected properly by the MAC layer.

Referring back to the process of step S105 described above with reference to <FIG>, a period to allow the UE to monitor for a response from the base station (for example, a gNB) in response to the beam recovery request may be provided. This period may be referred to as, for example, "gNB response window," "gNB window," "beam recovery request response window" or the like.

The UE may retransmit the beam recovery request when there is no gNB response detected in the window period.

Also, a period for performing a beam recovery procedure may be provided. The period may be referred to as "beam recovery timer. " When this period expires, the UE may terminate or cancel the beam recovery procedure. The beam recovery timer may start with detecting beam failures and stop when a gNB response is received.

After having transmitted the beam recovery request, the UE may periodically transmit, or stop transmitting, beam failure instance indications, from the PHY layer to the MAC layer. The UE may control the retransmission of beam recovery requests from the MAC layer to the PHY layer based on beam failure instance indications.

As for the gNB response window, the PHY layer and the MAC layer may share the same gNB response window, or have different gNB response windows. These windows may be measured by, for example, the timer of the MAC layer and/or the PHY layer.

The gNB response window may be provided in the PHY layer alone. In this case, after transmitting a beam recovery request, the PHY layer may report to the MAC layer whether a gNB response has been received successfully.

For example, if a gNB response is received in a gNB window, the PHY layer may transmit a report to indicate that "a gNB response has been received (gNB response received)," to the MAC layer, or, otherwise, the PHY layer may transmit a report to indicate that "no gNB response has been received (gNB response not received)," to the MAC layer.

Note that, if no report to the effect "a gNB response has been received" arrives in a given period, the MAC layer may judge that an indication to the effect that "no gNB response has been received" has arrived. If no report to the effect "no gNB response has been received" arrives in a given period, the MAC layer may judge that an indication to the effect that "a gNB response has been received" has arrived.

If the MAC layer receives a report to indicate that "a gNB response has been received," the MAC layer may reset the beam failure instance counter, set the beam failure instance counter to a particular value, or perform a particular operation.

If the MAC layer receives a report to indicate that "no gNB response has been received," the MAC layer may trigger the transmission of a beam recovery request, again, to the PHY layer.

Now, the structure of a radio communication system according to the present embodiment will be described below. In this radio communication system, communication is performed using at least one of the above examples or a combination of these.

<FIG> is a diagram to show an exemplary schematic structure of a radio communication system according to the present embodiment. A radio communication system <NUM> can adopt carrier aggregation (CA) and/or dual connectivity (DC) to group a plurality of fundamental frequency blocks (component carriers) into one, where the LTE system bandwidth (for example, <NUM>) constitutes <NUM> unit.

Note that the radio communication system <NUM> may be referred to as "LTE (Long Term Evolution)," "LTE-A (LTE-Advanced)," "LTE-B (LTE-Beyond)," "SUPER <NUM>," "IMT-Advanced," "<NUM> (4th generation mobile communication system)," "<NUM> (5th generation mobile communication system)," "NR (New Radio)," "FRA (Future Radio Access)," "New-RAT (Radio Access Technology)," and so on, or may be seen as a system to implement these.

The radio communication system <NUM> includes a radio base station <NUM> that forms a macro cell C1, and radio base stations <NUM> (12a to 12c) that are placed within the macro cell C1 and that form small cells C2, which are narrower than the macro cell C1. Also, user terminals <NUM> are placed in the macro cell C1 and in each small cell C2. The arrangement and number of cells and user terminals <NUM> are not limited to those illustrated in the drawing.

The user terminals <NUM> can connect with both the radio base station <NUM> and the radio base stations <NUM>. The user terminals <NUM> may use the macro cell C1 and the small cells C2 at the same time by means of CA or DC. Furthermore, the user terminals <NUM> may apply CA or DC using a plurality of cells (CCs) (for example, five or fewer CCs or six or more CCs).

Furthermore, the user terminals <NUM> can communicate by using time division duplexing (TDD) and/or frequency division duplexing (FDD), in each cell. Furthermore, in each cell (carrier), a single numerology may be used, or a plurality of different numerologies may be used.

A numerology may refer to communication parameters that are applied to transmission and/or receipt of a given signal and/or channel, and represent at least one of the subcarrier spacing, the bandwidth, the duration of symbols, the length of cyclic prefixes, the duration of subframes, the length of TTIs, the number of symbols per TTI, the radio frame configuration, the filtering process, the windowing process and so on.

The radio base station <NUM> and a radio base station <NUM> (or <NUM> radio base stations <NUM>) may be connected with each other by cables (for example, by optical fiber, which is in compliance with the CPRI (Common Public Radio Interface), the X2 interface and so on), or by radio.

OFDMA is a multi-carrier communication scheme to perform communication by dividing a frequency bandwidth into a plurality of narrow frequency bandwidths (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 not limited to these combinations, and other radio access schemes may be used as well.

In the radio communication system <NUM>, a downlink shared channel (PDSCH (Physical Downlink Shared CHannel)), which is used by each user terminal <NUM> 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 in the PDSCH. Also, the MIB (Master Information Blocks) is communicated in the PBCH.

The L1/L2 control channels include at least one of DL control channels (such as PDCCH (Physical Downlink Control CHannel), and/or an EPDCCH (Enhanced Physical Downlink Control CHannel), etc.), a PCFICH (Physical Control Format Indicator CHannel), a PHICH (Physical Hybrid-ARQ Indicator CHannel) and so on. Downlink control information (DCI), which includes PDSCH and/or PUSCH scheduling information, is communicated by the PDCCH.

Note that scheduling information may be reported in DCI. For example, DCI to schedule receipt of DL data may be referred to as a "DL assignment," and DCI to schedule UL data transmission may also be referred to as a "UL grant.

The number of OFDM symbols to use for the PDCCH is communicated by the PCFICH. HARQ (Hybrid Automatic Repeat reQuest) delivery acknowledgment information (also referred to as, for example, "retransmission control information," "HARQ-ACKs," "ACK/NACKs," etc.) in response to the PUSCH is transmitted by 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 <NUM>, an uplink shared channel (PUSCH (Physical Uplink Shared CHannel)), which is used by each user terminal <NUM> 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 by the PUSCH. Also, in the PUCCH, downlink radio quality information (CQI (Channel Quality Indicator)), delivery acknowledgment information, scheduling requests (SRs) and so on are communicated. By means of the PRACH, random access preambles for establishing connections with cells are communicated.

In the radio communication system <NUM>, cell-specific reference signals (CRSs), channel state information reference signals (CSI-RSs), demodulation reference signals (DMRSs), positioning reference signals (PRSs) and so on are communicated as downlink reference signals. Also, in the radio communication system <NUM>, measurement reference signals (SRSs (Sounding Reference Signals)), demodulation reference signals (DMRSs) and so on are communicated as uplink reference signals. Note that the DMRSs may be referred to as "user terminal-specific reference signals (UE-specific reference signals). " Also, the reference signals to be communicated are by no means limited to these.

<FIG> is a diagram to show an exemplary overall structure of a radio base station according to the present embodiment. A radio base station <NUM> has a plurality of transmitting/receiving antennas <NUM>, amplifying sections <NUM>, transmitting/receiving sections <NUM>, a baseband signal processing section <NUM>, a call processing section <NUM> and a communication path interface <NUM>. Note that one or more transmitting/receiving antennas <NUM>, amplifying sections <NUM> and transmitting/receiving sections <NUM> may be provided.

In the baseband signal processing section <NUM>, the user data is subjected to transmission processes, including a PDCP (Packet Data Convergence Protocol) layer process, user data division and coupling, RLC (Radio Link Control) layer transmission processes such as RLC retransmission control, MAC (Medium Access Control) retransmission control (for example, an HARQ (Hybrid Automatic Repeat reQuest) 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 <NUM>. Furthermore, downlink control signals are also subjected to transmission processes such as channel coding and an inverse fast Fourier transform, and forwarded to each transmitting/receiving section <NUM>.

Baseband signals that are pre-coded and output from the baseband signal processing section <NUM> on a per antenna basis are converted into a radio frequency band in the transmitting/receiving sections <NUM>, and then transmitted. The radio frequency signals having been subjected to frequency conversion in the transmitting/receiving sections <NUM> are amplified in the amplifying sections <NUM>, and transmitted from the transmitting/receiving antennas <NUM>. The transmitting/receiving sections <NUM> can be constituted by transmitters/receivers, transmitting/receiving circuits or transmitting/receiving apparatus that can be described based on general understanding of the technical field to which this disclosure pertains. Note that a transmitting/receiving section <NUM> may be structured as a transmitting/receiving section in one entity, or may be constituted by a transmitting section and a receiving section.

In the baseband signal processing section <NUM>, 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 <NUM> via the communication path interface <NUM>. The call processing section <NUM> performs call processing (such as setting up and releasing communication channels), manages the state of the radio base stations <NUM> and manages the radio resources.

The communication path interface section <NUM> transmits and receives signals to and from the higher station apparatus <NUM> via a given interface. Also, the communication path interface <NUM> may transmit and receive signals (backhaul signaling) with other radio base stations <NUM> via an inter-base station interface (which is, for example, optical fiber that is in compliance with the CPRI (Common Public Radio Interface), the X2 interface, etc.).

Note that the transmitting/receiving sections <NUM> may furthermore have an analog beamforming section that forms analog beams. The analog beamforming section may be constituted by an analog beamforming circuit (for example, a phase shifter, a phase shifting circuit, etc.) or analog beamforming apparatus (for example, a phase shifting device) that can be described based on general understanding of the technical field to which this disclosure pertains. Furthermore, the transmitting/receiving antennas <NUM> may be constituted by, for example, array antennas. Also, the transmitting/receiving sections <NUM> are configured to be able to adopt single-BF and multi-BF.

The transmitting/receiving sections <NUM> may transmit signals using transmitting beams, or receive signals using receiving beams. The transmitting/receiving sections <NUM> may transmit and/or receive signals using given beams determined by the control section <NUM>.

The transmitting/receiving sections <NUM> may receive various pieces of information described in each example above from the user terminal <NUM>, or transmit these to the user terminal <NUM>.

<FIG> is a diagram to show an exemplary functional structure of a radio base station according to the present embodiment. Note that, although this example primarily shows functional blocks that pertain to characteristic parts of present embodiment, the radio base station <NUM> has other functional blocks that are necessary for radio communication as well.

The baseband signal processing section <NUM> has a control section (scheduler) <NUM>, a transmission signal generation section <NUM>, a mapping section <NUM>, a received signal processing section <NUM> and a measurement section <NUM>. Note that these configurations have only to be included in the radio base station <NUM>, and some or all of these configurations may not be included in the baseband signal processing section <NUM>.

The control section <NUM> can be constituted by a controller, a control circuit or control apparatus that can be described based on general understanding of the technical field to which this disclosure pertains.

The control section <NUM> controls, for example, generation of signals in the transmission signal generation section <NUM>, allocation of signals in the mapping section <NUM>, and so on. Furthermore, the control section <NUM> controls signal receiving processes in the received signal processing section <NUM>, measurements of signals in the measurement section <NUM>, and so on.

The control section <NUM> controls the scheduling (for example, resource allocation) of system information, downlink data signals (for example, signals transmitted in the PDSCH) and downlink control signals (for example, signals communicated in the PDSCH and/or the EPDCCH). Also, the control section <NUM> controls the generation of downlink control signals, downlink data signals and so on based on the results of deciding whether or not retransmission control is necessary in response to uplink data signals and so on.

The control section <NUM> controls scheduling of synchronization signals (for example, PSS/SSS), downlink reference signals (for example, CRS, CSI-RS, DMRS, etc.) and the like.

The control section <NUM> may exert control so that transmitting beams and/or receiving beams are formed by using digital BF (for example, precoding) in the baseband signal processing section <NUM> and/or analog BF (for example, phase rotation) in the transmitting/receiving sections <NUM>.

The control section <NUM> may control the configuration of RLF and/or BR based on configuration information related to radio link failure (RLF) and/or beam recovery (BR).

The control section <NUM> may control radio link monitoring (RLM) and/or beam recovery (BR) for the user terminal <NUM>. The control section <NUM> may exerts control so that a response signal in response to the beam recovery request is transmitted to the user terminal <NUM>.

The transmission signal generation section <NUM> generates downlink signals (downlink control signals, downlink data signals, downlink reference signals and so on) based on commands from the control section <NUM>, and outputs these signals to the mapping section <NUM>. The transmission signal generation section <NUM> can be constituted by a signal generator, a signal generating circuit or signal generating apparatus that can be described based on general understanding of the technical field to which this disclosure pertains.

For example, the transmission signal generation section <NUM> generates DL assignments, which report downlink data allocation information, and/or UL grants, which report uplink data allocation information, based on commands from the control section <NUM>. DL assignments and UL grants are both DCI, in compliance with DCI format. Also, the downlink data signals are subjected to the coding process, the modulation process and so on, by using coding rates and modulation schemes that are determined based on, for example, channel state information (CSI) from each user terminal <NUM>.

The mapping section <NUM> maps the downlink signals generated in the transmission signal generation section <NUM> to given radio resources based on commands from the control section <NUM>, and outputs these to the transmitting/receiving sections <NUM>. The mapping section <NUM> can be constituted by a mapper, a mapping circuit or mapping apparatus that can be described based on general understanding of the technical field to which this disclosure pertains.

The received signal processing section <NUM> performs receiving processes (for example, demapping, demodulation, decoding and so on) of received signals that are input from the transmitting/receiving sections <NUM>. Here, the received signals include, for example, uplink signals transmitted from the user terminal <NUM> (uplink control signals, uplink data signals, uplink reference signals, etc.). For the received signal processing section <NUM>, 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 this disclosure pertains can be used.

The received signal processing section <NUM> outputs the decoded information acquired through the receiving processes, to the control section <NUM>. For example, when a PUCCH to contain an HARQ-ACK is received, the received signal processing section <NUM> outputs this HARQ-ACK to the control section <NUM>. Also, the received signal processing section <NUM> outputs the received signals and/or the signals after the receiving processes to the measurement section <NUM>.

The measurement section <NUM> can be constituted by a measurer, a measurement circuit or measurement apparatus that can be described based on general understanding of the technical field to which this disclosure pertains.

For example, the measurement section <NUM> may perform RRM (Radio Resource Management) measurements, CSI (Channel State Information) measurements and so on, based on the received signals. The measurement section <NUM> may measure the received power (for example, RSRP (Reference Signal Received Power)), the received quality (for example, RSRQ (Reference Signal Received Quality), SINR (Signal to Interference plus Noise Ratio), etc.), SNR (Signal to Noise Ratio), the signal strength (for example, RSSI (Received Signal Strength Indicator)), transmission path information (for example, CSI), and so on. The measurement results may be output to the control section <NUM>.

<FIG> is a diagram to show an exemplary overall structure of a user terminal according to the present embodiment. A user terminal <NUM> has a plurality of transmitting/receiving antennas <NUM>, amplifying sections <NUM>, transmitting/receiving sections <NUM>, a baseband signal processing section <NUM> and an application section <NUM>. Note that one or more transmitting/receiving antennas <NUM>, amplifying sections <NUM> and transmitting/receiving sections <NUM> may be provided.

Radio frequency signals that are received in the transmitting/receiving antennas <NUM> are amplified in the amplifying sections <NUM>. The transmitting/receiving sections <NUM> receive the downlink signals amplified in the amplifying sections <NUM>. The received signals are subjected to frequency conversion and converted into the baseband signal in the transmitting/receiving sections <NUM>, and output to the baseband signal processing section <NUM>. A transmitting/receiving section <NUM> can be constituted by a transmitters/receiver, a transmitting/receiving circuit or transmitting/receiving apparatus that can be described based on general understanding of the technical field to which this disclosure pertains. Note that a transmitting/receiving section <NUM> may be structured as a transmitting/receiving section in one entity, or may be constituted by a transmitting section and a receiving section.

The baseband signal processing section <NUM> performs receiving processes for the baseband signal that is input, including an FFT process, error correction decoding, a retransmission control receiving process and so on. Downlink user data is forwarded to the application section <NUM>. The application section <NUM> performs processes related to higher layers above the physical layer and the MAC layer, and so on. In the downlink data, the broadcast information can be also forwarded to the application section <NUM>.

Meanwhile, uplink user data is input from the application section <NUM> to the baseband signal processing section <NUM>. The baseband signal processing section <NUM> 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 sections <NUM>.

The baseband signal that is output from the baseband signal processing section <NUM> is converted into a radio frequency band in the transmitting/receiving sections <NUM>. The radio frequency signals that are subjected to frequency conversion in the transmitting/receiving sections <NUM> are amplified in the amplifying sections <NUM>, and transmitted from the transmitting/receiving antennas <NUM>.

The transmitting/receiving sections <NUM> may receive various pieces of information described in each example above from the user terminal <NUM>, or transmit these to the user terminal <NUM>. For example, the transmitting/receiving sections <NUM> may transmit a beam recovery request to the radio base station <NUM>.

<FIG> is a diagram to show an exemplary functional structure of a user terminal according to the present embodiment. Note that, although this example primarily shows functional blocks that pertain to characteristic parts of present embodiment, the user terminal <NUM> has other functional blocks that are necessary for radio communication as well.

For the control section <NUM>, a controller, a control circuit or control apparatus that can be described based on general understanding of the technical field to which this disclosure pertains can be used.

The control section <NUM> may exert control so that transmitting beams and/or receiving beams are formed using digital BF (for example, precoding) in the baseband signal processing section <NUM> and/or analog BF (for example, phase rotation) in the transmitting/receiving sections <NUM>.

The control section <NUM> may control radio link monitoring (RLM) and/or beam recovery (BR) based on the measurement results of the measurement section <NUM>.

The control section <NUM> may include a MAC layer processing section and a PHY layer processing section. Note that, the MAC layer processing section and/or the PHY layer processing section may be realized by any of the control section <NUM>, the transmission signal generation section <NUM>, the mapping section <NUM>, the received signal processing section <NUM>, and the measurement section <NUM>, or a combination of these.

The MAC layer processing section performs MAC layer processing, and the PHY layer processing section performs PHY layer processing. For example, downlink user data and broadcast information input from the PHY layer processing section may be output to a higher layer processing section that performs RLC layer processing, PDCP layer processing, etc. through processing in the MAC processing section.

The PHY layer processing section may detect beam failures. The PHY layer processing section may report information about detected beam failures to the MAC layer processing section.

The MAC layer processing section may trigger the transmission of beam recovery requests in the PHY layer processing section. For example, the MAC layer processing section may trigger transmission of a beam recovery request based on information about beam failures reported from the PHY layer processing section.

The MAC layer processing section may increment the count on a given counter (beam failure instance counter) based on the information about beam failures reported from the PHY layer processing section above, and trigger the transmission of the beam recovery request from the PHY layer processing section when the value on the counter reaches or exceeds a given threshold.

Also, when various pieces of information reported from the radio base station <NUM> are acquired from the received signal processing section <NUM>, the control section <NUM> may update the parameters used in the control based on these pieces of information.

The transmission signal generation section <NUM> generates uplink signals (uplink control signals, uplink data signals, uplink reference signals, etc.) based on commands from the control section <NUM>, and outputs these signals to the mapping section <NUM>. The transmission signal generation section <NUM> can be constituted by a signal generator, a signal generating circuit or signal generation apparatus that can be described based on general understanding of the technical field to which this disclosure pertains.

For example, the transmission information generation section <NUM> generates uplink control signals such as delivery acknowledgment information, channel state information (CSI) and so on, based on commands from the control section <NUM>. Also, the transmission signal generation section <NUM> generates uplink data signals based on commands from the control section <NUM>. For example, when a UL grant is included in a downlink control signal that is reported from the radio base station <NUM>, the control section <NUM> commands the transmission signal generation section <NUM> to generate an uplink data signal.

The mapping section <NUM> maps the uplink signals generated in the transmission signal generation section <NUM> to radio resources based on commands from the control section <NUM>, and output the result to the transmitting/receiving sections <NUM>. The mapping section <NUM> can be constituted by a mapper, a mapping circuit or mapping apparatus that can be described based on general understanding of the technical field to which this disclosure pertains.

The received signal processing section <NUM> performs receiving processes (for example, demapping, demodulation, decoding and so on) of received signals that are input from the transmitting/receiving sections <NUM>. Here, the received signals include, for example, downlink signals (downlink control signals, downlink data signals, downlink reference signals and so on) that are transmitted from the radio base station <NUM>. The received signal processing section <NUM> can be constituted by 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 this disclosure pertains. Also, the received signal processing section <NUM> can constitute the receiving section according to this disclosure.

The received signal processing section <NUM> outputs the decoded information acquired through the receiving processes, to the control section <NUM>. The received signal processing section <NUM> outputs, for example, broadcast information, system information, RRC signaling, DCI and so on, to the control section <NUM>. Also, the received signal processing section <NUM> outputs the received signals and/or the signals after the receiving processes to the measurement section <NUM>.

For example, the measurement section <NUM> may perform RRM measurements, CSI measurements, and so on, based on the received signals. The measurement section <NUM> may measure the received power (for example, RSRP), the received quality (for example, RSRQ, SINR, SNR, etc.), the signal strength (for example, RSSI), transmission path information (for example, CSI) and so on. The measurement results may be output to the control section <NUM>.

Note that the block diagrams that have been used to describe the present embodiment 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 <NUM> 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 or wireless, for example) and using these multiple pieces of apparatus.

For example, the radio base station, user terminals and so on according to the present embodiment may function as a computer that executes the processes of each example of the present embodiment. <FIG> is a diagram to show an exemplary hardware structure of a radio base station and a user terminal according to the present embodiment. Physically, the above-described radio base stations <NUM> and user terminals <NUM> may be formed as a computer apparatus that includes a processor <NUM>, a memory <NUM>, a storage <NUM>, communication apparatus <NUM>, input apparatus <NUM>, output apparatus <NUM> and a bus <NUM>.

For example, although only <NUM> processor <NUM> is shown, a plurality of processors may be provided. Furthermore, processes may be implemented with <NUM> processor, or processes may be implemented in sequence, or in different manners, on one or more processors.

The functions of the radio base station <NUM> and the user terminal <NUM> are implemented by allowing hardware such as the processor <NUM> and the memory <NUM> to read given software (programs), thereby allowing the processor <NUM> to do calculations, the communication apparatus <NUM> to communicate, and the memory <NUM> and the storage <NUM> to read and/or write data.

The processor <NUM> may control the whole computer by, for example, running an operating system. The processor <NUM> 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 <NUM> (<NUM>), call processing section <NUM> and so on may be implemented by the processor <NUM>.

The memory <NUM> is a computer-readable recording medium, and may be constituted by, 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/or other appropriate storage media. The memory <NUM> may be referred to as a "register," a "cache," a "main memory" (primary storage apparatus) and so on. The memory <NUM> can store executable programs (program codes), software modules and so on for implementing the radio communication methods according to the present embodiment.

The communication apparatus <NUM> is hardware (transmitting/receiving apparatus) for allowing inter-computer communication by using 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 <NUM> 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 <NUM> (<NUM>), amplifying sections <NUM> (<NUM>), transmitting/receiving sections <NUM> (<NUM>), communication path interface <NUM> and so on may be implemented by the communication apparatus <NUM>.

Note that the terminology used in this specification and 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" (or "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 comprised of one or more periods (frames) in the time domain. Each of one or more periods (frames) constituting a radio frame may be referred to as a "subframe. " Furthermore, a subframe may be comprised of one or multiple slots in the time domain. A subframe may be a fixed time duration (for example, <NUM>) not dependent on the numerology.

Furthermore, a slot may be comprised of one or more symbols in the time domain (OFDM (Orthogonal Frequency Division Multiplexing) symbols, SC-FDMA (Single Carrier Frequency Division Multiple Access) symbols, and so on). Also, a slot may be a time unit based on numerology. Also, a slot may include a plurality of mini-slots. Each mini-slot may be comprised of one or more symbols in the time domain. Also, a mini-slot may be referred to as a "subslot.

A radio frame, a subframe, a slot, a mini-slot and a symbol all represent the time unit in signal communication. A radio frame, a subframe, a slot, a mini-slot and a symbol may be each called by other applicable names. For example, <NUM> subframe may be referred to as a "transmission time interval (TTI)," or a plurality of consecutive subframes may be referred to as a "TTI," or <NUM> slot or mini-slot may be referred to as a "TTI. " That is, a subframe and/or a TTI may be a subframe (<NUM>) in existing LTE, may be a shorter period than <NUM> (for example, <NUM> to <NUM> symbols), or may be a longer period of time than <NUM>. Note that the unit to represent the TTI may be referred to as a "slot," a "mini slot" and so on, instead of a "subframe.

For example, in LTE systems, a radio base station schedules the radio resources (such as the frequency bandwidth and transmission power that can be used in each user terminal) to allocate to each user terminal in TTI units.

The TTI may be the transmission time unit of 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 a TTI is given, the period of time (for example, the number of symbols) in which transport blocks, code blocks and/or codewords are actually mapped may be shorter than the TTI.

Note that, when <NUM> slot or <NUM> mini-slot is referred to as a "TTI," one or more TTIs (that is, one or multiple slots or one or more mini-slots) may be the minimum time unit of scheduling. Also, the number of slots (the number of mini-slots) to constitute this minimum time unit of scheduling may be controlled.

A TTI having a time duration of <NUM> may be referred to as a "normal TTI" (TTI in LTE Rel. <NUM> to <NUM>), 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 TTI" (or a "fractional TTI"), a "shortened subframe," a "short subframe," a "mini-slot," a "sub-slot" and so on.

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 more symbols in the time domain, and may be <NUM> slot, <NUM> mini-slot, <NUM> subframe or <NUM> TTI in length. <NUM> TTI and <NUM> subframe each may be comprised of one or more resource blocks. Note that one or more RBs may be referred to as a "physical resource block (PRB (Physical RB))," a "subcarrier group (SCG)," a "resource element group (REG)," a "PRB pair," an "RB pair" and so on.

For example, <NUM> RE may be a radio resource field of <NUM> subcarrier and <NUM> symbol.

Note that the structures of radio frames, subframes, slots, mini-slots, symbols and so on described above are merely examples. For example, configurations pertaining to the number of subframes included in a radio frame, the number of slots included per subframe or radio frame, the number of mini-slots included in a slot, the number 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 duration, the length of cyclic prefixes (CPs) and so on can be variously changed.

Also, the information and parameters described in this specification may be represented in absolute values or in relative values with respect to given values, or may be represented using other applicable information. For example, a radio resource may be specified by a given index.

The information, signals and so on that are input and/or output may be stored in a specific location (for example, in a memory), or may be managed in a control 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 other pieces of apparatus.

Reporting of information is by no means limited to the examples/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 (the 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.

Also, reporting of given information (for example, reporting of information to the effect that "X holds") does not necessarily have to be sent explicitly, and can be sent in an implicit way (for example, by not reporting this piece of information, by reporting another piece of information, and so on).

Decisions may be made in values represented by <NUM> bit (<NUM> or <NUM>), may be made in Boolean values that represent true or false, or may be made by comparing numerical values (for example, comparison against a given value).

As used herein, 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 can accommodate one or more (for example, <NUM>) 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 or all of the coverage area of a base station and/or a base station subsystem that provides communication services within this coverage.

Furthermore, the radio base stations in this specification may be interpreted as user terminals. For example, each example/embodiment of this 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, user terminals <NUM> may have the functions of the radio base stations <NUM> described above. In addition, terms such as "uplink" and "downlink" may be interpreted as "side. " For example, an "uplink channel" may be interpreted as a "side channel.

Certain actions which have been described in this specification to be performed by base stations may, in some cases, be performed by their upper nodes. In a network comprised of one or more network nodes with base stations, it is clear that various operations that are performed so as to communicate with terminals can be performed by base stations, one or more network nodes (for example, MMEs (Mobility Management Entities), S-GWs (Serving-Gateways) and so on may be possible, but these are not limiting) other than base stations, or combinations of these.

The examples/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 examples/embodiments herein may be re-ordered as long as inconsistencies do not arise.

The examples/embodiments illustrated in this specification may be applied to systems that use LTE (Long Term Evolution), LTE-A (LTE-Advanced), LTE-B (LTE-Beyond), SUPER <NUM>, IMT-Advanced, <NUM> (4th generation mobile communication system), <NUM> (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 <NUM>, UMB (Ultra Mobile Broadband), IEEE <NUM> (Wi-Fi (registered trademark)), IEEE <NUM> (WiMAX (registered trademark)), IEEE <NUM>, UWB (Ultra-WideBand), Bluetooth (registered trademark) and other adequate radio communication methods, and/or next-generation systems that are enhanced based on these.

Reference to elements with designations such as "first," "second" and so on as used herein does not generally limit the number/quantity or order of these elements. These designations are used herein only for convenience, as a method for distinguishing between two or more elements. In this way, reference to the first and second elements does not imply that only <NUM> elements may be employed, or that the first element must precede the second element in some way.

As used herein, the terms "connected" and "coupled," or any variation of these terms, 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 <NUM> elements that are "connected" or "coupled" to each other. The coupling or connection between the elements may be physical, logical or a combination of these.

As used herein, when <NUM> elements are connected, these 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 a number of non-limiting and non-inclusive examples, by using electromagnetic energy, such as electromagnetic energy having wavelengths in the radio frequency, microwave and optical (both visible and invisible) regions.

In the present specification, the phrase "A and B are different" may mean "A and B are different from each other. " The terms such as "leave" "coupled" and the like may be interpreted as well.

Now, supplementary ideas about the present disclosure will be provided below for additional explanation.

RAN (Radio Access Network) <NUM> has agreed on the following:.

Note that the counter may be replaced by a timer.

Proposal <NUM>: For beam failure detection in the beam failure recovery procedure, the number of consecutive beam failure instances is counted in the MAC layer.

Claim 1:
A terminal (<NUM>) comprising:
a control section (<NUM>) configured to increment a beam failure instance counter, in a higher layer, based on a beam failure instance indication received from a physical layer; and
a transmission section (<NUM>) configured to, when the beam failure instance counter is greater than or equal to a given threshold, transmit a beam recovery request using a random access preamble based on a transmission instruction from the higher layer, characterized in that if there is no response for the random access preamble within a given response window period, the control section is configured to perform a control to retransmit the random access preamble, and
the control section (<NUM>) is configured to notify the transmission instruction from the higher layer to the physical layer, which is used for instructing the transmission of the random access preamble using a Physical Random Access Channel, PRACH, wherein the random access preamble corresponds to a Synchronization Signal Block, SSB, or a Channel State Information Reference Signal, CSI-RS, associated with a candidate beam.