COMMUNICATION DEVICE, BASE STATION, AND COMMUNICATION METHOD

Abstract

To provide user equipment, a base station, and a communication method that are used in a mobile communication system, and allow radio link monitoring in units of cells and beam failure detection in units of TRPs to appropriately coexist when a cell is operated with a plurality of TRPs.SOLUTION: UE 100 that performs wireless communication with a base station that manages a cell having N (N≥2) TRPs includes: a communication unit 110 that receives, from the base station, an RRC message containing a radio link monitoring setting for setting radio link monitoring in units of cells and a beam failure detection setting list for setting N beam failure detection resource sets; and a control unit 120 that detects a radio link failure in units of cells based on the radio link monitoring setting, and individually detects a beam failure for each of the N beam failure detection resource sets based on the beam failure detection setting list.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a user equipment, a base station, and a communication method for use in a mobile communication system. [Background technology]

[0002] In recent years, the 3GPP (3rd Generation Partnership Project), a standardization project for mobile communication systems, has been considering the introduction of multiple transmission / reception point (TRP) transmission as an extension of MIMO (multi-input multi-output) (see Non-Patent Document 1). In such multiple TRP transmission, one cell is formed by multiple TRPs that are distributed and these multiple TRPs are used simultaneously to perform wireless communication with a user device, thereby achieving efficient transmission. Note that the TRP is sometimes called a panel or an antenna panel.

[0003] In the case of cell operation using multiple TRPs, it has been proposed to perform beam fault detection and recovery on a TRP basis, which was previously performed on a cell basis (see Non-Patent Documents 2 and 3). Specifically, a counter timer specific to the TRP is introduced to detect beam faults, and in the user equipment, a counter counts beam fault events (beam fault instance indicators) notified from the physical layer to the medium access control (MAC) layer, and if the count value reaches a specified number of times before the timer expires, beam fault is detected. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] 3GPP contribution RP-202803 “Summary for WI: Enhancement on MIMO for NR” [Non-Patent Document 2] 3GPP contribution R2-2105870 “Beam failure with mTRP” [Non-Patent Document 3] 3GPP contribution R2-2105341 “Discussion on RAN2 specification impacts of TRP-specific BFR” Summary of the Invention [Problem to be solved by the invention]

[0005] In order to perform beam fault detection and recovery on a TRP-by-TRP basis when operating a cell using multiple TRPs, it is considered necessary to configure a beam fault detection resource set including reference signal resources for detecting beam faults in the user equipment individually for each TRP.

[0006] However, existing radio link monitoring (i.e., detection of radio link failure and detection of beam failure) is performed on a cell-by-cell basis. Therefore, it is desirable to appropriately coexist such existing technology with beam failure detection on a TRP-by-TRP basis.

[0007] Therefore, the present invention aims to provide a user equipment, a base station, and a communication method that enable radio link monitoring on a cell-by-cell basis and beam fault detection on a TRP-by-TRP basis to coexist appropriately when a cell is operated using multiple TRPs. [Means for solving the problem]

[0008] A user device according to a first aspect is a user device (100) that performs wireless communication with a base station (200) that manages a cell (250) having N (N≧2) transmitting / receiving points (201#0, 201#1), and is equipped with a communication unit (110) that receives a radio resource control (RRC) message from the base station (200) including a radio link monitoring setting (510) that sets radio link monitoring on a cell-by-cell (250) basis and a beam fault detection setting list (520) that sets N beam fault detection resource sets (521#0, 521#1), and a control unit (120) that detects radio link faults on a cell-by-cell basis based on the radio link monitoring setting (510) and individually detects beam faults for each of the N beam fault detection resource sets (521#0, 521#1) based on the beam fault detection setting list (520).

[0009] A base station according to the second aspect is a base station (200) that manages a cell (250) having N (N≧2) transmitting / receiving points (201#0, 201#1) and performs wireless communication with a user device (100), and is equipped with a control unit (230) that generates a radio resource control (RRC) message including a radio link monitoring setting (510) that sets radio link monitoring on a cell (250) basis and a beam fault detection setting list (520) that sets N beam fault detection resource sets (521#0, 521#1), and a communication unit (210) that transmits the RRC message to the user device (100), wherein the radio link monitoring setting (510) includes information that sets a reference signal resource and a use of the reference signal resource, and when the control unit (230) sets the beam fault detection setting list (520) to the user device (100), the control unit (230) sets the detection of radio link fault as the use without setting the detection of the beam fault.

[0010] A communication method according to a third aspect is a communication method executed by a user equipment (100) that performs wireless communication with a base station (200) that manages a cell (250) having N (N≧2) transmitting / receiving points (201#0, 201#1), and includes the steps of receiving a radio resource control (RRC) message from the base station (200) including a radio link monitoring setting (510) that sets radio link monitoring on a cell-by-cell (250) basis and a beam fault detection setting list (520) that sets N beam fault detection resource sets (521#0, 521#1), detecting a radio link fault on a cell-by-cell basis based on the radio link monitoring setting (510), and individually detecting beam fault for each of the N beam fault detection resource sets (521#0, 521#1) based on the beam fault detection setting list (520). Effect of the Invention

[0011] According to one aspect of the present invention, a user equipment, a base station, and a communication method can be provided that enable radio link monitoring on a cell-by-cell basis and beam failure detection on a TRP-by-TRP basis to coexist appropriately when a cell is operated using multiple TRPs. [Brief description of the drawings]

[0012] [Figure 1] 1 is a diagram showing a configuration of a mobile communication system according to an embodiment; [Diagram 2] FIG. 2 is a diagram illustrating an example of the configuration of a protocol stack in a mobile communication system according to an embodiment. [Diagram 3] FIG. 11 is a diagram illustrating an example of an operation when a beam failure is detected in a secondary cell (SCell) during cell operation using a single TRP. [Figure 4] FIG. 11 is a diagram showing an example of operation when a beam failure is detected in a special cell (SpCell) during cell operation using a single TRP. [Diagram 5] FIG. 1 is a diagram illustrating an overview of multi-TRP transmission according to one embodiment. [Figure 6]A diagram showing the configuration of a UE according to one embodiment. [Figure 7] FIG. 2 is a diagram illustrating a configuration of a base station according to an embodiment. [Figure 8] A diagram illustrating BFD operation on a per-TRP basis according to one embodiment. [Figure 9] FIG. 2 is a diagram illustrating an example of the configuration of an RRC message according to an embodiment. [Figure 10] A diagram illustrating BFD operation on a per-TRP basis according to one embodiment. [Figure 11] FIG. 1 is a diagram illustrating a configuration example of a BWP setting (BWP-DownlinkDedecated) according to an embodiment. [Figure 12] A diagram showing an example configuration of a BFD configuration list (BFD-ConfigurationList) according to one embodiment. [Figure 13] FIG. 1 illustrates an operation in a UE according to an embodiment. [Figure 14] A diagram to explain the operation when a reference signal resource for BFD is not provided in one embodiment. [Figure 15] A diagram to explain the operation when a reference signal resource for BFD is not provided in one embodiment. [Figure 16] A diagram to explain the operation when a reference signal resource for BFD is not provided in one embodiment. [Figure 17] FIG. 13 is a diagram for explaining coexistence with existing radio link monitoring according to an embodiment. [Figure 18] FIG. 2 is a diagram illustrating an example of the configuration of an RRC message according to an embodiment. [Figure 19] FIG. 11 is a diagram illustrating an example of the configuration of a radio link monitoring setting (RadioLinkMonitoringConfig) according to an embodiment. [Figure 20] FIG. 13 is a diagram illustrating a comparative example of BFD·BFR operation in an SpCell according to an embodiment. [Figure 21] FIG. 1 is a diagram illustrating BFD·BFR operations in an SpCell according to an embodiment. [Figure 22]FIG. 1 is a diagram illustrating BFD·BFR operations in an SpCell according to an embodiment. [Figure 23] A diagram showing a specific example of the operation of a MAC entity in a UE according to one embodiment. [Figure 24] A diagram showing a specific example of the operation of a MAC entity in a UE according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] A mobile communication system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0014] (Mobile communication system) First, a configuration of a mobile communication system 1 according to an embodiment will be described with reference to Fig. 1. The mobile communication system 1 is, for example, a system that complies with the 3GPP Technical Specification (TS). In the following, the mobile communication system 1 will be described by taking as an example a 5th Generation System (5GS) of the 3GPP standard, that is, a mobile communication system based on NR (New Radio).

[0015] The mobile communication system 1 includes a network 10 and a user equipment (UE) 100 that communicates with the network 10. The network 10 includes a Next Generation Radio Access Network (NG-RAN) 20 that is a 5G radio access network, and a 5G Core Network (5GC) 30 that is a 5G core network.

[0016] The UE 100 is a device used by a user. The UE 100 is a mobile device such as a mobile phone terminal such as a smartphone, a tablet terminal, a notebook PC, a communication module, or a communication card. The UE 100 may be a vehicle (e.g., a car, a train, etc.) or a device provided therein. The UE 100 may be a transport body other than a vehicle (e.g., a ship, an airplane, etc.) or a device provided therein. The UE 100 may be a sensor or a device provided therein. The UE 100 may be called by another name such as a mobile station, a mobile terminal, a mobile device, a mobile unit, a subscriber station, a subscriber terminal, a subscriber device, a subscriber unit, a wireless station, a wireless terminal, a wireless device, a wireless unit, a remote station, a remote terminal, a remote device, or a remote unit.

[0017] The NG-RAN 20 includes a plurality of base stations 200. Each base station 200 manages at least one cell. A cell constitutes the smallest unit of a communication area. One cell belongs to one frequency (carrier frequency) and is composed of one component carrier. The term "cell" may represent a wireless communication resource, and may represent a communication target of the UE 100. Each base station 200 can perform wireless communication with the UE 100 located in its own cell. The base station 200 communicates with the UE 100 using a protocol stack of the RAN. The base station 200 provides NR user plane and control plane protocol terminations toward the UE 100, and is connected to the 5GC 30 via an NG interface. Such an NR base station 200 may be referred to as a gNodeB (gNB).

[0018] The 5GC 30 includes a core network device 300. The core network device 300 includes, for example, an Access and Mobility Management Function (AMF) and / or a User Plane Function (UPF). The AMF performs mobility management of the UE 100. The UPF provides a function specialized for user plane processing. The AMF and the UPF are connected to the base station 200 via an NG interface.

[0019] Next, with reference to FIG. 2, a configuration example of a protocol stack in the mobile communication system 1 according to the embodiment will be described.

[0020] The protocol for the wireless section between UE 100 and base station 200 includes a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, and a radio resource control (RRC) layer.

[0021] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of the UE 100 and the PHY layer of the base station 200 via a physical channel.

[0022] A physical channel is composed of multiple OFDM symbols in the time domain and multiple subcarriers in the frequency domain. One subframe is composed of multiple OFDM symbols in the time domain. A resource block is a resource allocation unit and is composed of multiple OFDM symbols and multiple subcarriers. A frame can be composed of 10 ms and can include 10 subframes, each composed of 1 ms. A subframe can include a number of slots according to the subcarrier interval.

[0023] Among the physical channels, the Physical Downlink Control Channel (PDCCH) plays a central role for purposes such as downlink scheduling assignments, uplink scheduling grants, and transmission power control.

[0024] In NR, the UE 100 can use a bandwidth narrower than the system bandwidth (i.e., the bandwidth of the cell). The base station 200 configures the UE 100 with a bandwidth portion (BWP) consisting of consecutive PRBs. The UE 100 transmits and receives data and control signals in the active BWP. For example, up to four BWPs can be configured for the UE 100. Each BWP may have a different subcarrier interval, and may overlap with each other in frequency. When multiple BWPs are configured for the UE 100, the base station 200 can specify which BWP to activate by control in the downlink. This allows the base station 200 to dynamically adjust the UE bandwidth according to the amount of data traffic of the UE 100, etc., and can reduce UE power consumption.

[0025] The base station 200 can configure, for example, up to three control resource sets (CORESETs) for each of up to four BWPs on the serving cell. The CORESET is a radio resource for control information to be received by the UE 100. Up to 12 CORESETs can be configured for the UE 100 on the serving cell. Each CORESET has an index of 0 to 11. For example, the CORESET is composed of six resource blocks (PRBs) and one, two, or three consecutive OFDM symbols in the time domain.

[0026] The MAC layer performs data priority control, retransmission processing using hybrid ARQ (HARQ), random access procedures, etc. Data and control information are transmitted between the MAC layer of the UE 100 and the MAC layer of the base station 200 via a transport channel. The MAC layer of the base station 200 includes a scheduler. The scheduler determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the resources to be allocated to the UE 100.

[0027] The RLC layer transmits data to the RLC layer on the receiving side by using the functions of the MAC layer and the PHY layer. Data and control information are transmitted between the RLC layer of the UE 100 and the RLC layer of the base station 200 via logical channels.

[0028] The PDCP layer performs header compression / decompression and encryption / decryption.

[0029] A Service Data Adaptation Protocol (SDAP) layer may be provided above the PDCP layer. The Service Data Adaptation Protocol (SDAP) layer maps IP flows, which are units for QoS control by the core network, to radio bearers, which are units for QoS control by the access stratum (AS).

[0030] The RRC layer controls logical channels, transport channels, and physical channels in response to establishment, re-establishment, and release of radio bearers. RRC signaling for various settings is transmitted between the RRC layer of the UE 100 and the RRC layer of the base station 200. layer and the RRC of the base station 200 layer When there is an RRC connection between the UE 100 and the RRC layer and the RRC of the base station 200 layer When there is no RRC connection between the UE 100 and the RRC layer and the RRC of the base station 200 layer When the RRC connection between the UE 100 and the UE 100 is suspended, the UE 100 is in the RRC inactive state.

[0031] The NAS layer located above the RRC layer performs session management and mobility management for the UE 100. NAS signaling is transmitted between the NAS layer of the UE 100 and the NAS layer of the core network device 300 (AMF). The UE 100 has an application layer and the like in addition to the protocol of the radio interface.

[0032] (Beam failure detection and recovery overview) Next, an overview of beam failure detection and restoration will be described with reference to FIGS.

[0033] Compared with LTE (Long Term Evolution), which is a fourth-generation wireless access technology, NR is capable of wideband transmission using high frequency bands such as the millimeter wave band or the terahertz wave band. In order to compensate for radio wave attenuation in such high frequency bands, NR obtains high beam gain by using highly directional beamforming using multiple antennas between the base station 200 and the UE 100. In NR, a beam control technology is introduced for establishing and maintaining a beam pair between the base station 200 and the UE 100. Beam failure detection and recovery technology is one such beam control technology.

[0034] Regarding beam failure detection (BFD), the base station 200 configures the UE 100 with a downlink reference signal resource for detecting a beam failure. Such a reference signal resource is either an SSB (SS / PBCH Block) or a CSI-RS (Channel State Information Reference Signal). The SSB includes a Primary Synchronization Signal (PSS), a Secondary Synchronization Signal (SSS), a PBCH (Physical Broadcast Channel), and a Demodulation Reference Signal (DMRS). For example, the SSB may be composed of four consecutive OFDM symbols in the time domain. The SSB may also be composed of 240 consecutive subcarriers (i.e., 20 resource blocks) in the frequency domain. The PBCH is a physical channel that carries a master information block (MIB). The CSI-RS is a reference signal transmitted so that the UE 100 can measure the state of a wireless channel.

[0035] If the SSB is within the downlink BWP band, the UE 100 can detect beam failure using the SSB. If the SSB is not within the downlink BWP band, the UE 100 can detect beam failure using the CSI-RS set by the base station 200.

[0036] In the UE 100, the MAC layer counts beam failure events (beam failure instance indicators) notified from the physical layer using a counter, and detects (declares) beam failure if the count value reaches or exceeds a prescribed number of times before the timer expires.

[0037] FIG. 3 shows an example of an operation when a beam failure is detected in a secondary cell (SCell) during cell operation using a single TRP.

[0038] 3 shows an example in which base station 200 manages SCell 250B configured by one TRP 201. Base station 200 (TRP 201) forms a total of three beams, beam #0 to beam #2. UE 100 detects beam failure in SCell 250B during communication using beam #0.

[0039] In this case, UE 100 triggers beam failure recovery (BFR) by starting transmission of a beam failure recovery MAC control element (BFR MAC CE). Here, UE 100 selects a beam (e.g., beam #1) suitable for the SCell and indicates the selected beam information together with information about the beam failure by the BFR MAC CE. When UE 100 receives a PDCCH indicating an uplink grant for a new transmission of the HARQ process used for transmitting the BFR MAC CE, recovery from beam failure of SCell 250B is completed.

[0040] 4 shows an example of an operation when a beam failure is detected in a special cell (SpCell) during cell operation using a single TRP. The SpCell may be referred to as a primary cell (PCell).

[0041] 4 shows an example in which the base station 200 manages the SpCell 250A configured by one TRP 201. The base station 200 (TRP 201) forms a total of three beams, beam #0 to beam #2. The UE 100 detects a beam failure in the SpCell 250A during communication using beam #0.

[0042] In this case, the UE 100 triggers the BFR by initiating a random access procedure to the SpCell 250A. Here, the UE 100 selects an appropriate beam (e.g., beam #1) to perform the BFR. When the random access procedure is completed, the BFR is completed.

[0043] (Overview of multiple TRP transmission) Next, an overview of multi-TRP transmission according to the embodiment will be described with reference to FIG.

[0044] In multiple TRP transmission, the base station 200 configures one cell 250 with multiple TRPs 201 that are distributed. In FIG. 5, two TRPs (TRP201#0 and TRP201#0) are illustrated as multiple TRPs 201. However, the base station 200 may configure one cell 250 with three or more TRPs 201. In the following, the case where the number of TRPs 201 that configure one cell 250 is two will be mainly described.

[0045] In multiple TRP transmission, it is possible to transmit different data from multiple TRPs 201 for spatial multiplexing to increase the data rate, or to transmit the same data from multiple TRPs 201 for diversity to improve the reliability and robustness of the transmission.

[0046] There are two types of multiple TRP transmission: a single PDCCH scheme and a multiple PDCCH scheme. In the single PDCCH-based scheme, one TRP 201 transmits a PDCCH (Downlink Control Information (DCI)) and schedules a set of PDSCH layers for each TRP 201. In contrast, in the multiple PDCCH scheme, each TRP 201 schedules its own PDSCH individually. In the following, the multiple PDCCH scheme is mainly considered.

[0047] In a scheme using multiple PDCCHs, it is possible to use a different CORESET for each TRP 201. Specifically, the TRP 201 and the CORESET pool index are in one-to-one correspondence. When the base station 200 configures a CORESET in the UE 100, the base station 200 notifies the UE 100 of the CORESET pool index to which the CORESET belongs. Therefore, the CORESET pool index can be considered as an index that identifies the TRP 201.

[0048] In the embodiment, in the case of cell operation using such a plurality of TRPs 201, it is assumed that BFD / BFR, which was conventionally performed in units of cells 250, is performed in units of TRPs 201. Specifically, a counter / timer specific to the TRPs 201 for detecting beam failure is introduced, and in the UE 100, a counter counts beam failure instance indicators notified from the physical layer to the MAC layer, and if the count value reaches or exceeds a specified number of times before the timer expires, beam failure is detected.

[0049] In order to perform BFD·BFR on a TRP201 basis, it is considered necessary to configure a beam fault detection resource set (hereinafter referred to as a "BFD resource set") including a reference signal resource for detecting a beam fault in the UE 100 for each TRP201. However, in the existing 3GPP technical specifications, there is no mechanism for configuring a BFD resource set for each TRP201 in the UE 100. In one embodiment, it is possible to perform BFD·BFR on a TRP201 basis.

[0050] Furthermore, if it is mandatory to set a reference signal resource for BFD in the UE 100 individually for each TRP 201, there is a concern that the amount of signaling for BFD·BFR may increase. In one embodiment, a mechanism is realized that enables BFD·BFR even for a BFD resource set / TRP 201 for which a reference signal resource for BFD is not provided.

[0051] In addition, existing radio link monitoring (i.e., detection of radio link failure (RLF) and detection of beam failure) is performed on a cell 250 basis, not on a TRP 201 basis. In one embodiment, it is possible to appropriately coexist such existing technology with BFD on a TRP 201 basis.

[0052] In addition, even if the UE 100 detects beam failure for all TRPs 201, if any of the TRPs 201 has recovered from the beam failure, communication (data transmission / reception) can be performed. If a random access procedure for recovery from a beam failure is started without considering whether the beam failure has been recovered, data transmission / reception cannot be performed during the execution of the random access procedure, and communication will be interrupted. In one embodiment, such communication interruption can be suppressed.

[0053] (Configuration of user device) Next, a configuration of the UE 100 according to an embodiment will be described with reference to Fig. 6. The UE 100 includes a communication unit 110 and a control unit 120.

[0054] The communication unit 110 performs wireless communication with the base station 200 by transmitting and receiving radio signals to and from the base station 200. The communication unit 110 has at least one transmission unit 111 and at least one reception unit 112. The transmission unit 111 and the reception unit 112 may be configured to include multiple antennas and RF circuits. The antenna converts a signal into radio waves and radiates the radio waves into space. The antenna also receives radio waves in space and converts the radio waves into a signal. The RF circuit performs analog processing of the signal transmitted and received via the antenna. The RF circuit may include a high-frequency filter, an amplifier, a modulator, a low-pass filter, and the like.

[0055] The control unit 120 performs various controls in the UE 100. The control unit 120 controls communication with the base station 200 via the communication unit 110. The above-mentioned and below-mentioned operations of the UE 100 may be operations controlled by the control unit 120. The control unit 120 may include at least one processor capable of executing a program and a memory that stores the program. The processor may execute a program to perform the operation of the control unit 120. The control unit 120 may include a digital signal processor that performs digital processing of signals transmitted and received via the antenna and the RF circuit. The digital processing includes processing of a protocol stack of the RAN. The memory stores a program executed by the processor, parameters related to the program, and data related to the program. The memory may include at least one of a read only memory (ROM), an erasable programmable read only memory (EPROM), an electrically erasable programmable read only memory (EEPROM), a random access memory (RAM), and a flash memory. All or a part of the memory may be included in the processor.

[0056] In the UE 100 according to an embodiment, the communication unit 110 performs wireless communication with the base station 200 that manages the cell 250 having N (N≧2) TRPs 201. The communication unit 110 receives an RRC message from the base station 200, which includes a beam failure detection configuration list (hereinafter, referred to as a "BFD configuration list") that is a list for configuring N BFD resource sets and is associated with a downlink BWP that is a part of the bandwidth of the cell 250. The control unit 120 detects beam failure for each of the N BFD resource sets individually based on the BFD configuration list in wireless communication using the downlink BWP. This makes it possible to configure the BFD resource set for each TRP 201 in the UE 100 in the RRC layer during operation of the cell 250 using multiple TRPs 201, thereby making it possible to perform BFD·BFR on a TRP 201 basis. As a result, even if a failure occurs in one TRP 201, communication can be continued in the other TRP 201, thereby improving the fault tolerance of communication.

[0057] Also, in the UE 100 according to one embodiment, when there is a BFD resource set that does not provide a reference signal resource for detecting a beam failure, the control unit 120 detects a beam failure for the BFD resource set by using a predetermined reference signal resource instead of the reference signal resource. For example, the control unit 120 identifies an active Transmission Configuration Indicator (TCI) state for PDCCH based on a CORESET pool index associated with the BFD resource set, and detects a beam failure for the BFD resource set by using the reference signal resource indicated by the active TCI state as a predetermined reference signal resource. This makes it possible to perform BFD·BFR even for TRPs that do not provide reference signal resources when a cell 250 using multiple TRPs 201 is operated. As a result, it becomes possible to reduce the amount of signaling.

[0058] Also, in the UE 100 according to an embodiment, the communication unit 110 receives an RRC message from the base station 200, including a radio link monitoring configuration for setting radio link monitoring in units of the cell 250 and a BFD configuration list for setting N BFD resource sets. The control unit 120 detects RLF in units of the cell 250 based on the radio link monitoring configuration, and detects beam failures individually for each of the N BFD resource sets 521#0 and 521#1 based on the BFD configuration list 520. This makes it possible to appropriately coexist radio link monitoring in units of the cell 250 and BFD in units of the TRP 201 when the cell 250 is operated using a plurality of TRPs 201. As a result, it is possible to realize two-stage failure detection and recovery by RLF detection and recovery in units of the cell 250 and BFD and BFR in units of the TRP 201, thereby improving the fault tolerance of communication.

[0059] Furthermore, in the UE 100 according to one embodiment, when the control unit 120 detects beam failure for all of the N BFD resource sets, the control unit 120 determines whether or not to start a random access procedure for the cell 250 (specifically, the SpCell) based on the status of recovery from the beam failure. For example, the control unit 120 that detects beam failure for one BFD resource set detects beam failure for other BFD resource sets and starts the random access procedure for the cell 250 only when none of the BFD resource sets have recovered from the beam failure. This allows the BFR status to be reflected in the start condition of the random access procedure, thereby allowing communication to continue as long as possible.

[0060] (Base station configuration) Next, a configuration of the base station 200 according to an embodiment will be described with reference to Fig. 7. The base station 200 includes N TRPs 201 (TRPs 201#0 and TRPs 201#1 in the example of Fig. 7), a communication unit 210, a network interface 220, and a control unit 230.

[0061] Each TRP 201 includes multiple antennas and is configured to be capable of beamforming. The TRP 201 may be referred to as a panel or an antenna panel. The antenna converts a signal into radio waves and radiates the radio waves into space. The antenna also receives radio waves in space and converts the radio waves into signals. Each TRP 201 is distributed and arranged to form one cell 250. When the base station 200 manages multiple cells, the base station 200 may have N TRPs 201 for each cell.

[0062] The communication unit 210 receives, for example, a radio signal from the UE 100 and transmits a radio signal to the UE 100. The communication unit 210 has at least one transmission unit 211 and at least one reception unit 212. The transmission unit 211 and the reception unit 212 may be configured to include an RF circuit. The RF circuit performs analog processing of a signal transmitted and received via an antenna. The RF circuit may include a high-frequency filter, an amplifier, a modulator, a low-pass filter, and the like.

[0063] The network interface 220 transmits and receives signals to and from the network. For example, the network interface 220 receives signals from adjacent base stations connected via an Xn interface, which is an interface between base stations, and transmits signals to the adjacent base stations. The network interface 220 also receives signals from the core network device 300 connected via an NG interface, and transmits signals to the core network device 300.

[0064] The control unit 230 performs various controls in the base station 200. For example, the control unit 230 controls communication with the UE 100 via the communication unit 210. The control unit 230 also controls communication with a node (for example, an adjacent base station, the core network device 300) via the network interface 220. The operations of the base station 200 described above and below may be operations under the control of the control unit 230. The control unit 230 may include at least one processor capable of executing a program and a memory that stores the program. The processor may execute a program to perform the operation of the control unit 230. The control unit 230 may include a digital signal processor that performs digital processing of signals transmitted and received via the antenna and the RF circuit. The digital processing includes processing of a protocol stack of the RAN. The memory stores the program executed by the processor, parameters related to the program, and data related to the program. All or a part of the memory may be included in the processor.

[0065] The base station 200 according to an embodiment manages a cell 250 having N TRPs 201 and performs wireless communication with the UE 100. The communication unit 210 transmits an RRC message including a BFD configuration list, which is a list for configuring N BFD resource sets and is associated with a downlink BWP that is a part of the bandwidth of the cell 250, to the UE 100. The BFD configuration list is used by the UE 100 to individually detect beam failure for each of the N BFD resource sets in wireless communication using the downlink BWP. This makes it possible to configure a BFD resource set for each TRP 201 in the UE 100 in the RRC layer during operation of the cell 250 using multiple TRPs 201, and therefore makes it possible for the UE 100 to perform BFD·BFR on a TRP 201 basis. As a result, even if a failure occurs in one TRP 201, the UE 100 can continue communication using the other TRP 201, thereby improving the fault tolerance of communication.

[0066] Also, in the base station 200 according to an embodiment, the control unit 230 generates an RRC message including a radio link monitoring configuration for setting radio link monitoring in units of cells 250 and a BFD configuration list for setting N BFD resource sets. The communication unit 210 transmits the RRC message to the UE 100. The radio link monitoring configuration includes information indicating a reference signal resource and information indicating a use of the reference signal resource. When the control unit 120 sets the BFD configuration list to the UE 100, the control unit 120 sets RLF detection without setting beam fault detection as a use of the reference signal resource in the radio link monitoring configuration. This makes it possible to appropriately coexist radio link monitoring in units of cells 250 and BFD in units of TRPs 201 during operation of the cells 250 using multiple TRPs 201. As a result, the UE 100 can realize two-stage fault detection and recovery by RLF detection and recovery in units of cells 250 and BFD and BFR in units of TRPs 201, thereby improving the fault tolerance of communication.

[0067] (Beam obstruction detection operation on a TRP basis) Next, with reference to Figures 8 to 10, a BFD operation on a TRP 201 basis according to one embodiment will be described.

[0068] As shown in Fig. 8, in step S101, the base station 200 (communication unit 210) that manages the cell 250 having N TRPs 201 transmits an RRC message including a BFD configuration list that is a list for configuring N BFD resource sets and is associated with a downlink BWP that is a part of the bandwidth of the cell 250, to the UE 100. The UE 100 (communication unit 110) receives the RRC message. Note that the RRC message is a UE-specific RRC message, and may be, for example, an RRC Reconfiguration message.

[0069] In this way, by associating the downlink BWP with the BFD configuration list, the BFD configuration list can be configured individually for each downlink BWP. Therefore, it is possible to configure the optimal BFD configuration list according to the requirements for the downlink BWP.

[0070] In step S102, the UE 100 (control unit 120) detects beam failures individually (beam monitoring) for each of the N BFD resource sets in the wireless communication using the downlink BWP, based on the BFD configuration list set by the base station 200. When the UE 100 (control unit 120) detects beam failure for any of the BFD resource sets, the UE 100 (control unit 120) starts (triggers) a BFR procedure for recovering from the detected beam failure.

[0071] As shown in FIG. 9 , the RRC message according to an embodiment includes a BWP configuration (BWP- DownlinkDedicated ) 500. BWP setting (BWP- DownlinkDedicated ) 500 is an information element for configuring UE-specific parameters of the downlink BWP. DownlinkDedicated The BWP configuration (BWP- DownlinkDedicated By including the BFD configuration list (BFD-ConfigurationList) 520 in the BFD configuration list (BFD-ConfigurationList) 500, it becomes possible to set the BFD configuration list (BFD-ConfigurationList) 520 for each downlink BWP to be set in the UE 100. DownlinkDedicatedWhen the downlink BWP configured in BFD-ConfigurationList 500 is used for wireless communication, i.e., when the downlink BWP is an active BWP, beam monitoring is performed using the BFD configuration list (BFD-ConfigurationList) 520 associated with the downlink BWP.

[0072] Here, the BFD configuration list (BFD-ConfigurationList) 520 is an information element different from the radio link monitoring configuration (RadioLinkMonitoringConfig) 510. Specifically, the radio link monitoring configuration (RadioLinkMonitoringConfig) 510 is an information element defined in an existing technical specification, and the BFD configuration list (BFD-ConfigurationList) 520 is a new information element not defined in an existing technical specification. In this way, by introducing a new information element for BFD on a TRP201 basis, BFD on a TRP201 basis becomes possible, and coexistence with existing radio link monitoring becomes possible.

[0073] The BFD configuration list (BFD-ConfigurationList) 520 includes N BFD resource sets (BFD Resource Sets) 521. For example, when N=2, the BFD configuration list (BFD-ConfigurationList) 520 includes two BFD resource sets (BFD Resource Sets) 521#0 and 521#1. Each BFD resource set (BFD Resource Set) 521 includes a reference signal resource in the downlink. The reference signal resource is either SSB or CSI-RS. Here, the reference signal resource in the BFD resource set (BFD Resource Set) 521 is set as a reference signal resource intended for detecting a beam failure. In other words, the reference signal resource in the BFD resource set (BFD Resource Set) 521 is not set as a reference signal resource intended for detecting an RLF. Details will be described later, but in one embodiment, RLF detection is performed on a cell 250 basis using a radio link monitoring configuration (RadioLinkMonitoringConfig) 510, and beam fault detection is performed on a TRP 201 basis using a BFD configuration list (BFD-ConfigurationList) 520.

[0074] In one embodiment, N BFD resource sets 521 are associated one-to-one with N TRPs 201. For example, BFD resource set 521#0 is associated with TRP 201#0, and BFD resource set 521#1 is associated with TRP 201#1. This enables BFD on a TRP 201 basis.

[0075] Also, in one embodiment, each BFD resource set (BFD Resource Set) 521 includes one or more reference signal resources, and each of the one or more reference signal resources may be associated with a beam on a one-to-one basis. For example, as shown in FIG. 10, it is assumed that TRP201#0 forms three beams #0 to #2, and TRP201#1 forms three beams #0 to #2. In such a case, the base station 200 (control unit 230) configures the BFD resource set (BFD Resource Set) 521#0 associated with the TRP201#0 and the BFD resource set (BFD Resource Set) 521#1 associated with the TRP201#1 in the UE 100 by an RRC message. Then, the base station 200 (control unit 230) configures three reference signal resources associated with the three beams #0 to #2 on a one-to-one basis in the BFD resource set (BFD Resource Set) 521#0. In addition, the base station 200 (control unit 230) configures three reference signal resources in one-to-one correspondence with the three beams #0 to #2 in the BFD resource set 521#1. This enables the UE 100 (control unit 120) to detect beam failure for each TRP 201 and for each beam.

[0076] Next, a specific example of an RRC message according to an embodiment will be described with reference to Fig. 11 and Fig. 12. Fig. 11 and Fig. 12 show a description example in the technical specification (TS38.331) of the RRC layer of 3GPP.

[0077] As shown in FIG. 11, a BWP setting (BWP- DownlinkDedicated) 500 can include a radio link monitoring configuration (RadioLinkMonitoringConfig) 510 that sets radio link monitoring in units of cells 250, and a BFD configuration list (BFD-ConfigurationList-r17) 520 that sets N BFD resource sets. Here, "-r17" means that this is an information element introduced in Release 17 of the 3GPP standard, but may be introduced in Release 18 or later. In the following, the notation "-r17" will be omitted as appropriate.

[0078] The BFD configuration list (BFD-ConfigurationList) 520 configured in the UE 100 can be released by a release instruction from the base station 200. For example, when changing from a cell operation using multiple TRPs to a cell operation using a single TRP, the base station 200 transmits to the UE 100 a release instruction to release the BFD configuration list (BFD-ConfigurationList) 520 configured in the UE 100. In response to receiving the release instruction, the UE 100 releases the configured BFD configuration list (BFD-ConfigurationList) 520.

[0079] As shown in FIG. 12, the BFD configuration list (BFD-ConfigurationList) 520 includes up to maxNrOfBFD-ResourceSets BFD resource sets (BFD Resource Sets) 521.

[0080] Each BFD resource set (BFD Resource Set) 521 may include a BFD resource set identifier (bfd-ResourceSetId) that identifies the BFD resource set, an add / modify list (bfd-ResourcesToAddModList) that adds / modifies one or more reference signal resources, a release list (bfd-ResourcesToReleaseList) that releases one or more reference signal resources, a maximum count value of beam failure instance indicators from the physical layer (beamFailureInstanceMaxCountPerRS), and a timer value for detecting beam failure (beamFailureDetectionTimerPerRS).

[0081] The BFD resource set identifier (bfd-ResourceSetId) is an identifier that identifies a BFD resource set. The BFD resource set identifier (bfd-ResourceSetId) can be considered to be an identifier that identifies the corresponding TRP 201. The BFD resource set identifier (bfd-ResourceSetId) may correspond one-to-one with the CORESET pool index (coresetPoolIndex). For example, the "0" of the BFD resource set identifier (bfd-ResourceSetId) corresponds to the "0" of the CORESET pool index (coresetPoolIndex), and the "1" of the BFD resource set identifier (bfd-ResourceSetId) corresponds to the "1" of the CORESET pool index (coresetPoolIndex).

[0082] The add / modify list (bfd-ResourcesToAddModList) is a list of one or more reference signal resources (BeamFailureDetectionRS) to be added / modified. Specifically, the add / modify list (bfd-ResourcesToAddModList) is a list of reference signals for detecting beam failure, and the restrictions on reference signals that the network (base station 200) can set are specified in a technical specification (e.g., Table 5-1 of TS38.213). The network (base station 200) sets a maximum predetermined number of reference signal resources for each resource set. As will be described in detail later, for each BFD resource set (BFD Resource Set) 521, if a reference signal is not provided for BFD purposes, the UE 100 performs beam monitoring based on the active TCI state for the PDCCH associated with the corresponding CORESET pool index (coresetPoolIndex).

[0083] The set reference signal resource (BeamFailureDetectionRS) includes a reference signal resource identifier (beamFailureDetectionRS-Id) for identifying the reference signal resource, and a reference signal resource (detectionResource) that is a reference signal to be used for BFD by the UE 100. In the reference signal resource (detectionResource), an SSB index (ssb-Index) or a CSI-RS index (csi-RS-Index) is set.

[0084] The release list (bfd-ResourcesToReleaseList) is a list of reference signal resource identifiers (beamFailureDetectionRS-Id) of reference signal resources to be released.

[0085] The maximum count value (beamFailureInstanceMaxCountPerRS) indicates the number of beam failure events (i.e., the number of beam failure instance indicators from the physical layer) at which the UE 100 triggers a BFR procedure. For example, the value "n1" corresponds to one beam failure instance indicator, and the value "n2" corresponds to two beam failure instances. The timer value (beamFailureDetectionTimerPerRS) is a timer for BFD.

[0086] As described above, the MAC layer of the UE 100 (control unit 120) detects a beam failure when a beam failure event (beam failure instance indicator) is notified from the physical layer a specified number of times within a specified time. Each BFD Resource Set 521 includes information for setting the specified time and the specified number of times independently of other BFD Resource Sets. A maximum count value (beamFailureInstanceMaxCountPerRS) indicating the specified number of times and a timer (beamFailureDetectionTimerPerRS) indicating the specified time are set for each BFD Resource Set 521, i.e., for each TRP 201. This makes it possible to optimize the conditions for detecting a beam failure for each TRP 201.

[0087] As shown in FIG. 13, in the UE 100, the physical (PHY) layer evaluates the radio link quality for each configured BFD resource set. The radio link quality may be a block error rate (BLER) of the PDCCH. For example, when the radio link quality of all reference signal resources in a BFD resource set is worse than a threshold, the physical layer periodically outputs a beam failure instance indicator to the MAC layer together with the BFD resource set identifier (bfd-ResourceSetId) of the BFD resource set. This period is set to, for example, the period of the smallest reference signal in the BFD resource set or 2 ms, whichever is larger. Note that the BFD resource set identifier (bfd-ResourceSetId) may be used as the beam failure instance indicator.

[0088] Each BFD Resource Set 521 may include information for setting a threshold value to be compared with the radio link quality measured in the physical layer independently of other BFD Resource Sets. When the radio link quality in any BFD Resource Set 521 is worse than the threshold value associated with the BFD Resource Set 521, the physical layer notifies the MAC layer of a beam failure event (beam failure instance indicator) indicating the BFD Resource Set 521. This allows the threshold value to be compared with the radio link quality to be individually set for each BFD Resource Set 521, i.e., for each TRP 201, so that the condition for detecting a beam failure event can be optimized for each TRP 201.

[0089] The MAC layer manages a timer and a counter for each configured BFD resource set, and performs BFD-BFR for each BFD resource set. Figure 13 shows an example in which there are two BFD resource sets, and the MAC layer manages a timer #0 and a counter #0 for BFD resource set #0, and a timer #1 and a counter #1 for BFD resource set #1.

[0090] When the MAC layer receives a beam failure instance indicator together with the BFD resource set identifier (bfd-ResourceSetId) from the physical layer, it starts a timer corresponding to the BFD resource set identifier (bfd-ResourceSetId) and increments (i.e., adds 1) a counter corresponding to the BFD resource set identifier (bfd-ResourceSetId). If the count value of the counter reaches or exceeds a prescribed number of times before the timer expires, the MAC layer detects a beam failure for the BFD resource set corresponding to the counter. Details of such an operation will be described later.

[0091] (Operation when reference signal resources for beam fault detection are not provided) Next, with reference to Figures 14 to 16, an operation in a case where a reference signal resource for BFD according to one embodiment is not provided will be described.

[0092] There is a concern that the amount of signaling for BFD may increase if it is mandatory to set the reference signal resource for BFD (BeamFailureDetectionRS) in the UE 100 for each TRP 201. In one embodiment, a mechanism is realized that enables BFD·BFR even for a BFD resource set (BFD Resource Set) or a TRP 201 in which the reference signal resource for BFD (BeamFailureDetectionRS) is not provided.

[0093] Here, beamforming in NR will be described. In order to perform multi-beam operation of PDCCH, NR supports TCI state setting, which is a higher layer setting for beamforming, for each CORESET. When UE100 monitors a PDCCH search space associated with CORESET, UE100 receives PDCCH in CORESET based on the TCI state setting set for CORESET. Beam information for PDCCH reception is implicitly recognized by UE100 by a quasi-co-location (QCL) relationship between a downlink reference signal (particularly, CSI-RS associated with a beam) and a demodulation reference signal (DMRS) of PDCCH. The DMRS of PDCCH is in a quasi-co-location relationship with the downlink reference signal by QCL-TypeA and / or QCL-TypeD. QCL-TypeA corresponds to channel statistical properties observed on the UE100 side, such as Doppler shift, Doppler spread, average delay, and delay spread. QCL-TypeD corresponds to reception beam information on the UE100 side. In the case of QCL-TypeD, it may be assumed that the spatial parameters of the downlink reference signal and the DMRS of the PDCCH are the same. If the DMRS of the PDCCH is in a quasi-co-location relationship with the downlink reference signal of QCL-TypeD, the UE 100 can receive the PDCCH using the same spatial reception parameters that it uses to receive the downlink reference signal by beamforming.

[0094] As shown in FIG. 14, base station 200 can explicitly set the QCL relationship to UE 100 by RRC signaling. UE 100 is configured with multiple TCI states for CORESET to receive PDCCH. Each TCI state includes parameters related to downlink reference signal resources and QCL relationships between DMRS ports of downlink reference signals and PDCCH for QCL-TypeA and QCL-TypeD. UE 100 uses only one beam to receive one PDCCH. Therefore, when multiple TCI states are configured in CORESET, base station 200 activates one of the TCI states used for CORESET using an activation command by MAC CE.

[0095] In one embodiment, a UE 100 that performs wireless communication with a base station 200 that manages a cell 250 having N TRPs 201 includes a communication unit 110 that receives a BFD configuration list (BFD-ConfigurationList) 520 that configures N BFD resource sets (BFD Resource Sets) 521 from the base station 200, and a control unit 120 that individually detects beam failure for each of the N BFD resource sets (BFD Resource Sets) 521 based on the BFD configuration list 520. When there is a BFD resource set (BFD Resource Set) 521 that does not provide a reference signal resource (BeamFailureDetectionRS) for BFD, the control unit 120 detects beam failure for the BFD resource set (BFD Resource Set) 521 by using a predetermined reference signal resource instead of the reference signal resource (BeamFailureDetectionRS).

[0096] As shown in FIG. 15, when there is a BFD resource set (BFD Resource Set) 521 (here, BFD resource set 521#0) that does not provide a reference signal resource (BeamFailureDetectionRS), the UE 100 (control unit 120) identifies an active TCI state for PDCCH based on a CORESET pool index #0 associated with the BFD resource set (BFD Resource Set) 521#0, and detects a beam failure for the BFD resource set (BFD Resource Set) 521#0 by using a reference signal resource indicated by the active TCI state as a predetermined reference signal resource. For example, the UE 100 (control unit 120) determines a downlink reference signal (e.g., CSI-RS) indicated by an active TCI state among TCI states (i.e., TCI states for PDCCH) set for a CORESET belonging to the CORESET pool index #0 as a reference signal resource for BFD (BeamFailureDetectionRS). This makes it possible to perform BFD using the downlink reference signal indicated by the active TCI state for the PDCCH even if the BFD resource set (BFD Resource Set) 521 does not provide a reference signal resource (BeamFailureDetectionRS).

[0097] A specific example of such an operation is shown in Fig. 16. Note that Fig. 16 shows an example of description in the 3GPP physical layer technical specification (TS38.213).

[0098] As shown in FIG. 16, when a UE 100 is configured with a BFD configuration list (bfd-ConfigurationList) 520 for the BWP of the serving cell, an add and modify list (bfd-ResourcesToAddModList) provides a periodic set of CSI-RS resource configuration indexes q0 for each BFD Resource Set (BFD Resource Set) 521 identified by a BFD resource set identifier (bfd-ResourceSetId).

[0099] If the UE 100 is not provided with set q0 by the addition and modification list (bfd-ResourcesToAddModList) for the BFD resource set (BFD Resource Set) 521, the UE 100 determines to include in set q0 a periodic CSI-RS resource configuration index having the same value as the reference signal index of the downlink reference signal set indicated by the TCI state of each CORESET belonging to the CORESET pool index associated with the BFD resource set identifier (bfd-ResourceSetId) used for monitoring the PDCCH. If there are two reference signal indexes in the TCI state, the reference signal index with the qcl-Type of the corresponding TCI state set to "typeD" is included in set q0.

[0100] (Coexistence with existing wireless link monitoring) Next, coexistence with existing radio link monitoring will be described with reference to Figures 17 to 19. Note that Figure 19 shows an example of description in the technical specification (TS38.331) of the RRC layer of 3GPP.

[0101] As described above, existing radio link monitoring (i.e., detection of RLF and detection of beam obstruction) is performed on a cell 250 basis, not on a TRP 201 basis.

[0102] In one embodiment, detection of beam failure is performed on a TRP 201 basis, not on a cell 250 basis. Detection of RLF on a cell 250 basis in existing radio link monitoring can coexist with BFD on a TRP 201 basis, so detection of RLF on a cell 250 basis can be set in UE 100. On the other hand, detection of beam failure on a cell 250 basis in existing radio link monitoring conflicts with detection of beam failure on a TRP 201 basis, so detection of beam failure on a cell 250 basis cannot be set in UE 100.

[0103] As shown in Fig. 17, in step S301, the base station 200 (control unit 230) that manages the cell 250 having N TRPs 201 generates an RRC message including a radio link monitoring configuration (RadioLinkMonitoringConfig) that sets radio link monitoring in units of the cell 250, and a BFD configuration list (BFD-ConfigurationList) that sets N BFD resource sets (BFD Resource Set). The base station 200 (communication unit 210) transmits the generated RRC message to the UE 100. The UE 100 (communication unit 110) receives the RRC message.

[0104] In step S302, the UE 100 (control unit 120) performs radio link monitoring to detect RLF on a cell 250 basis based on a radio link monitoring configuration (RadioLinkMonitoringConfig). Also, the UE 100 (control unit 120) performs beam monitoring to individually detect beam failure for each of the N BFD resource sets based on a BFD configuration list (BFD-ConfigurationList). That is, the UE 100 (control unit 120) performs beam monitoring on a TRP 201 basis.

[0105] When UE100 (control unit 120) detects a beam failure for any BFD resource set by beam monitoring based on the BFD configuration list (BFD-ConfigurationList), it performs a process for recovering from the detected beam failure, for example, a BFR MAC CE transmission process. Also, when UE100 (control unit 120) detects an RLF for cell 250 by radio link monitoring based on the radio link monitoring configuration (RadioLinkMonitoringConfig), it performs a process for recovering from the detected RLF, for example, an RRC re-establishment process. Such two-stage failure detection and recovery makes it possible to improve the fault tolerance of communication.

[0106] As shown in FIG. 18 and FIG. 19, in the RRC message, BWP setup (BWP- DownlinkDedicated Radio link monitoring configuration (RadioLinkMonitoringConfig) 510 included in BFD-ConfigurationList 500 includes, as configuration information, reference signal resources for radio link monitoring (RS for RLM) 511 and purpose 512 of the reference signal resources (RS for RLM) 511. When setting BFD configuration list (BFD-ConfigurationList) 520 in UE 100, base station 200 (control unit 230) sets RLF (rlf) detection as purpose 512 without setting beam failure detection.

[0107] Specifically, in the technical specifications, there are three options for the purpose 512 of the reference signal resource (RS for RLM) 511: "beam failure", "RLF (rlf)", and "both". However, when the BFD configuration list (BFD-ConfigurationList) 520 is configured in the UE 100, a restriction is stipulated that only RLF (rlf) can be configured as the purpose 512 of the reference signal resource (RS for RLM) 511. Therefore, when the BFD configuration list (BFD-ConfigurationList) 520 is configured, the UE 100 (control unit 120) detects RLF on a cell 250 basis without detecting beam failure based on the radio link monitoring configuration (RadioLinkMonitoringConfig) 510. This makes it possible to appropriately coexist the existing radio link monitoring and the detection of beam failure on a TRP 201 basis.

[0108] Note that even when the BFD configuration list (BFD-ConfigurationList) 520 is configured, it may be assumed that the base station 200 sets beam failure (beamfailure) or both (both) as the purpose (512) of the reference signal resource (RS for RLM) 511 due to an unexpected error. Therefore, when the BFD configuration list (BFD-ConfigurationList) 520 is configured and beam failure (beamfailure) or both (both) is set as the purpose (512) of the reference signal resource (RS for RLM) 511, the UE 100 (control unit 120) may interpret the purpose (512) of the reference signal resource (RS for RLM) 511 as RLF (rlf).

[0109] (Beam failure detection and recovery operations in SpCell) Next, the BFD-BFR operation in an SpCell according to one embodiment will be described with reference to Fig. 20 to Fig. 22. Here, it is assumed that the UE 100 performs radio communication with a cell 250 (specifically, an SpCell) having two TRPs 201 #0 and #1. However, one cell 250 may be configured with three or more TRPs 201. It is also assumed that a BFD resource set 521 for each TRP 201 has already been set in the UE 100.

[0110] Before describing the BFD·BFR operation in the SpCell according to an embodiment, a comparative example will be described with reference to FIG.

[0111] In step S401, the UE 100 (control unit 120) detects a beam failure for the BFD resource set 521#0 associated with the TRP 201#0, and starts (triggers) a BFR involving the transmission of a BFR MAC CE.

[0112] In step S402, the UE 100 (control unit 120) detects a beam failure for the BFD resource set 521#1 associated with the TRP 201#1. In response to detecting the beam failure for both the BFD resource sets 521#0 and #1 (i.e., both the TRPs 201#0 and #1), the UE 100 (control unit 120) decides to start a random access procedure for the cell 250 (SpCell).

[0113] In step S403, the UE 100 (control unit 120) successfully completes BFR for the BFD resource set 521#0 associated with the TRP201#0, and becomes capable of transmitting and receiving data to and from the TRP201#0.

[0114] In step S404, the UE 100 (control unit 120) starts a random access procedure for the cell 250 (SpCell). The UE 100 (control unit 120) cannot transmit or receive data to or from the cell 250 (SpCell) during the execution of the random access procedure.

[0115] In step S405, although the UE 100 (control unit 120) is in a state in which data transmission and reception with the TRP 201#0 is possible, the UE 100 is unable to communicate (transmit and receive data) with the cell 250 (SpCell) due to the random access procedure.

[0116] In this way, even if the UE 100 detects beam failures for the TRP 201 #0 and #1, if the beam failure for the TRP 201 #0 is recovered, communication with the cell 250 (SpCell) is possible. However, if the random access procedure is started (step S404) without considering whether the beam failure has been recovered, data cannot be transmitted or received during the execution of the random access procedure, and communication is interrupted.

[0117] Therefore, when the UE 100 (control unit 120) according to one embodiment detects beam failure for all of the N BFD resource sets 521 associated with the N TRPs 201, the UE 100 (control unit 120) determines whether or not to start a random access procedure for the cell 250 (SpCell) based on the state of recovery from the beam failure. For example, when the UE 100 (control unit 120) detects beam failure for one of the N BFD resource sets 521, and detects beam failure for the other BFD resource sets 521, and none of the BFD resource sets 521 has recovered from the beam failure, the UE 100 (control unit 120) starts the random access procedure for the cell 250 (SpCell). This makes it possible to prevent communication with the cell 250 (SpCell) from being disabled due to the random access procedure.

[0118] A first example of the BFD·BFR operation in an SpCell according to an embodiment will be described with reference to FIG.

[0119] In step S431, the UE 100 (control unit 120) detects a beam failure for the BFD resource set 521#0 associated with the TRP 201#0, and starts BFR involving the transmission of a BFR MAC CE.

[0120] In step S432, the UE 100 (control unit 120) detects a beam failure for the BFD resource set 521#1 associated with the TRP 201#1.

[0121] In step S433, the UE 100 (control unit 120) successfully completes BFR for the BFD resource set 521#0 associated with the TRP201#0, and becomes capable of transmitting and receiving data to and from the TRP201#0.

[0122] In step S434, the UE 100 (control unit 120) decides not to initiate a random access procedure for the cell 250 (SpCell) in response to successful completion of BFR for the BFD resource set 521#0 associated with the TRP201#0.

[0123] In step S435, the UE 100 (control unit 120) is in a state in which communication (data transmission / reception) with the cell 250 (SpCell) is possible, and communicates with the cell 250 (SpCell). Note that the UE 100 (control unit 120) may start BFR involving transmission of BFR MAC CE for the BFD resource set 521#1 associated with the TRP201#1.

[0124] Thus, in one embodiment, the UE 100 (control unit 120) that detects a beam failure for the BFD resource set 521#1 detects a beam failure for the BFD resource set 521#0, and when the BFD resource set 521#0 is recovered from the beam failure, determines not to start a random access procedure for the cell 250 (SpCell). This makes it possible to prevent communication with the cell 250 (SpCell) from becoming impossible due to the random access procedure. In addition, the UE 100 (control unit 120) may determine not to start a random access procedure for the cell 250 (SpCell) and start a BFR procedure (i.e., a transmission process of a BFR MAC CE) for recovering from the beam failure for the BFD resource set 521#1. This makes it possible to attempt to recover communication with the TRP 201#1.

[0125] With reference to FIG. 22, a second example of the BFD·BFR operation in the SpCell according to one embodiment will be described.

[0126] In step S451, the UE 100 (control unit 120) detects a beam failure for the BFD resource set 521#0 associated with the TRP 201#0, and starts BFR involving the transmission of a BFR MAC CE.

[0127] In step S452, the UE 100 (control unit 120) detects a beam failure for the BFD resource set 521#1 associated with the TRP 201#1, and starts BFR involving the transmission of a BFR MAC CE.

[0128] In step S453, the UE 100 (control unit 120) has not yet completed (has not succeeded) BFR for the BFD resource set 521#0 associated with the TRP201#0.

[0129] In step S454, the UE 100 (control unit 120) has not yet completed (has not succeeded) BFR for the BFD resource set 521#1 associated with the TRP201#1.

[0130] In step S455, UE 100 (control unit 120) detects beam failure for all N BFD resource sets 521 and initiates a random access procedure for cell 250 (SpCell) in response to the fact that none of the BFD resource sets 521 have recovered from beam failure.

[0131] (Specific example of operation of MAC entity in user equipment) Next, a specific example of the operation of a MAC entity (i.e., an entity of a MAC layer) in the UE 100 according to an embodiment will be described with reference to Fig. 23 and Fig. 24. The operation of the MAC entity may be a part of the operation of the control unit 120 of the UE 100. Note that Fig. 23 and Fig. 24 show an example of the operation as described in the 3GPP technical specification for the MAC layer (TS38.321).

[0132] As shown in FIG. 23, when one or more BFD resource sets 521 are configured for each serving cell in which BFD is configured (step S501), the MAC entity performs operations of steps S502 to S521.

[0133] When the MAC entity receives a beam failure instance indicator from a lower layer (i.e., a physical layer) for a BFD resource set (BFD Resource Set) 521 identified by a BFD resource set identifier (bfd-ResourceSetId) (step S502), the MAC entity performs the operations of steps S503 to S510.

[0134] In step S503, the MAC entity starts or restarts a timer (beamFailureDetectionTimerPerRS) configured for the BFD resource set (BFD Resource Set) 521 identified by the BFD resource set identifier (bfd-ResourceSetId).

[0135] In step S504, the MAC entity increments the count value (BFI_COUNTER_BFD_RS) set for the BFD resource set (BFD Resource Set) 521 identified by the BFD resource set identifier (bfd-ResourceSetId), that is, adds "1." Note that the initial value of the count value (BFI_COUNTER_BFD_RS) is "0."

[0136] The MAC entity performs the operations of steps S506 to S510 when the count value (BFI_COUNTER_BFD_RS) becomes equal to or greater than the maximum count value (beamFailureInstanceMaxCountPerRS) set for the BFD resource set (BFD Resource Set) 521 identified by the BFD resource set identifier (bfd-ResourceSetId).

[0137] Here, if the serving cell is an SpCell (step S506) and a beam failure is detected in another BFD Resource Set 521 and has not yet been restored by the beam restoration procedure (step S507), the MAC entity initiates a random access procedure on the SpCell for beam restoration in step S508.

[0138] On the other hand, if the serving cell is not an SpCell or if another BFD Resource Set 521 has been restored by a beam restoration procedure (step S509), the MAC entity triggers a BFR for the BFD Resource Set 521 in step S510.

[0139] When the corresponding timer (beamFailureDetectionTimerPerRS) for each BFD Resource Set 521 expires (step S511), the MAC entity sets (resets) the count value (BFI_COUNTER_BFD_RS) to zero in step S513.

[0140] The MAC entity also sets a BFD resource set 521 and associated timers (beamFailureDetectionTimerPerRS), a maximum count value (beamFailureInstanceMaxCountPerRS), and reference signal resources for BFD (reference signal resource When any of the count values ​​(BFI_COUNTER_BFD_RS) used for beam failure detection is reconfigured by a higher layer (i.e., the RRC layer) (step S512), the count value (BFI_COUNTER_BFD_RS) is set (reset) to zero in step S513.

[0141] If the serving cell is an SpCell and the random access procedure for BFR of the SpCell is successfully completed (step S514), the MAC entity performs the operations of steps S515 to S517.

[0142] In step S515, the MAC entity sets (resets) the count value (BFI_COUNTER_BFD_RS) to zero.

[0143] In step S516, the MAC entity stops the timer (beamFailureDetectionTimerPerRS) if the timer (beamFailureDetectionTimerPerRS) is set.

[0144] In step S517, the MAC entity determines that the BFR has been completed successfully.

[0145] On the other hand, when the serving cell is an SCell and the MAC entity receives a PDCCH addressed to a C-RNTI indicating an uplink grant for new transmission for the HARQ process used for transmitting the BFR MAC MAC including the BFR information of the BFD Resource Set 521 (step S518), or when the SCell is deactivated (step S519), the MAC entity executes the operations of steps S520 and S521. CE and Truncated BFR MAC CE.

[0146] In step S520, the MAC entity sets (resets) the count value (BFI_COUNTER_BFD_RS) to zero.

[0147] In step S521, the MAC entity determines that the BFR has been completed successfully and cancels all BFRs triggered for the BFD Resource Set 521.

[0148] As shown in FIG. 24, if the MAC entity determines in the BFR procedure that at least one BFR has been triggered and not canceled for an SCell or BFD Resource Set 521 for which candidate beams are being evaluated in accordance with the requirements specified in TS38.133, the MAC entity performs the operations of steps S532 to S537.

[0149] If uplink shared channel (UL-SCH) resources are available for a new transmission and the UL-SCH resources can accommodate the BFR MAC CE and its subheader as a result of logical channel prioritization (LCP) (step S532), in step S533 the MAC entity instructs the multiplexing and assembly procedure to generate the BFR MAC CE.

[0150] On the other hand, if the UL-SCH resources are available for a new transmission and can accommodate the Truncated BFR MAC CE and its subheader as a result of the LCP (step S534), in step S535, the MAC entity instructs the multiplexing and assembly procedure to generate a Truncated BFR MAC CE.

[0151] On the other hand, if neither of the conditions in steps S532 and S534 are satisfied (step S536), in step S537, the MAC entity triggers a Scheduling Request (SR) for BFR of the SCell for each SCell or BFD Resource Set 521 for which candidate beams have been evaluated and BFR has been triggered and not cancelled according to the requirements specified in TS38.133.

[0152] When a MAC PDU is transmitted and the PDU includes a BFR MAC CE or a Truncated BFR MAC CE including beam failure information for the SCell or the BFD Resource Set 521, the MAC entity cancels all BFRs triggered for the SCell or the BFD Resource Set 521 (step S538).

[0153] In this way, the user device 100 that performs radio communication with the base station 200 that manages the cell 250 having N transmission / reception points 201 includes a communication unit 110 that receives a message for setting N BFD resource sets 521 from the base station 200, and a control unit 120 that detects beam failures individually for each of the N BFD resource sets 521. The control unit 120 triggers BFR for one BFD resource set in which a beam failure is detected. The communication unit 110 transmits a BFR MAC MAC including information on the detected beam failure, or an SR requesting resources for transmitting the BFR MAC CE. When a MAC protocol data unit PDU including a BFR MAC MAC is transmitted, the control unit 120 cancels all BFRs triggered for the one BFD resource set. This makes it possible to appropriately perform BFR on a TRP201 basis.

[0154] In the UE 100, the control unit 120 detects a beam failure in response to a beam failure event being notified a specified number of times within a specified time for each of the N BFD resource sets 521. As described above, each of the N BFD resource sets 521 includes information for setting a timer (beamFailureDetectionTimerPerRS) indicating the specified time and a maximum count value (beamFailureInstanceMaxCountPerRS) indicating the specified number of times independently of other BFD resource sets.

[0155] In the UE 100, when a beam failure event is notified from the physical layer for the one BFD resource set (BFD Resource Set) 521, the control unit 120 starts or restarts a timer (beamFailureDetectionTimerPerRS) associated with the one BFD resource set (BFD Resource Set) 521, and increments a count value (BFI_COUNTER_BFD_RS) associated with the one BFD resource set (BFD Resource Set) 521. This makes it possible to appropriately perform BFD on a TRP 201 basis.

[0156] In the UE 100, when a timer (beamFailureDetectionTimerPerRS) associated with the one BFD resource set (BFD Resource Set) 521 expires, the control unit 120 resets a count value (BFI_COUNTER_BFD_RS) associated with the one BFD resource set (BFD Resource Set) 521. This makes it possible to appropriately perform BFD on a TRP 201 basis.

[0157] In the UE 100, the control unit 120 sets a timer (beamFailureDetectionTimerPerRS), a maximum count value (beamFailureInstanceMaxCountPerRS), and a reference signal resource for BFD (reference signal resource When any of the BFD resource sets (used for beam failure detection) is reconfigured by the base station 200, the count value (BFI_COUNTER_BFD_RS) associated with the BFD resource set (BFD Resource Set) 521 is reset. This makes it possible to appropriately perform BFD on a TRP 201 basis.

[0158] In the UE 100, after transmitting the BFR MAC MAC, the communication unit 110 receives a PDCCH indicating an uplink grant for the HARQ process used in transmitting the BFR MAC MAC for the one BFD Resource Set 521 when the cell 250 is an SCell. In response to receiving the PDCCH, the control unit 120 resets a count value (BFI_COUNTER_BFD_RS) associated with the one BFD Resource Set 521, and considers the BFR to be successful, canceling all BFRs triggered for the one BFD Resource Set 521. This makes it possible to appropriately perform BFD on a TRP 201 basis.

[0159] (Other embodiments) The operation sequences (and operation flows) in the above-mentioned embodiments do not necessarily have to be executed in chronological order according to the order described in the flow diagram or sequence diagram. For example, the steps in the operations may be executed in an order different from that described in the flow diagram or sequence diagram, or may be executed in parallel. Some of the steps in the operations may be deleted, and additional steps may be added to the process. The operation sequences (and operation flows) in the above-mentioned embodiments may be executed separately and independently, or two or more operation sequences (and operation flows) may be executed in combination. For example, some steps of one operation flow may be added to another operation flow, or some steps of one operation flow may be replaced with some steps of another operation flow.

[0160] In the above embodiment, the base station 200 may include a plurality of units. The plurality of units may include a first unit hosting a higher layer included in a protocol stack and a second unit hosting a lower layer included in the protocol stack. The higher layer may include an RRC layer, an SDAP layer, and a PDCP layer, and the lower layer may include an RLC layer, a MAC layer, and a PHY layer. The first unit may be a central unit (CU), and the second unit may be a distributed unit (DU). The plurality of units may include a third unit performing processing below the PHY layer. The second unit may perform processing above the PHY layer. The third unit may be a radio unit (RU). The base station 200 may be one of the plurality of units, and may be connected to other units of the plurality of units. The base station 200 may also be an integrated access and backhaul (IAB) donor or an IAB node.

[0161] In the above-described embodiment, an NR-based mobile communication system has been described as an example of the mobile communication system 1. However, the mobile communication system 1 is not limited to this example. The mobile communication system 1 may be a system that complies with a TS of any of LTE or other generation systems (e.g., 6th generation) of the 3GPP standard. The base station 200 may be an eNB that provides E-UTRA user plane and control plane protocol termination toward the UE 100 in LTE. The mobile communication system 1 may be a system that complies with a TS of a standard other than the 3GPP standard.

[0162] A program may be provided that causes a computer to execute each process performed by the UE 100 or the base station 200. The program may be recorded in a computer-readable medium. Using the computer-readable medium, it is possible to install the program in the computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM. In addition, a circuit that executes each process performed by the UE 100 or the base station 200 may be integrated, and at least a part of the UE 100 or the base station 200 may be configured as a semiconductor integrated circuit (chip set, SoC).

[0163] In the above-mentioned embodiment, "transmit" may mean performing processing of at least one layer in a protocol stack used for transmission, or may mean physically transmitting a signal wirelessly or wired. Alternatively, "transmit" may mean a combination of performing processing of at least one layer and physically transmitting a signal wirelessly or wired. Similarly, "receive" may mean performing processing of at least one layer in a protocol stack used for reception, or may mean physically receiving a signal wirelessly or wired. Alternatively, "receive" may mean a combination of performing processing of at least one layer and physically receiving a signal wirelessly or wired. Similarly, "obtain / acquire" may mean obtaining information from stored information, obtaining information from information received from another node, or obtaining the information by generating the information. Similarly, "include" and "comprise" do not mean including only the items listed, but may mean including only the items listed, or may include additional items in addition to the items listed. Similarly, in this disclosure, "or" does not mean an exclusive or, but rather a logical or.

[0164] The above describes the embodiments in detail with reference to the drawings, but the specific configuration is not limited to that described above, and various design changes, etc. are possible without departing from the spirit of the invention. [Explanation of symbols]

[0165] 1: Mobile communication systems 10: Network 100: UE (user equipment) 110: Communications Department 111: Transmitter 112: Receiving unit 120: Control section 200:Base station 201: TRP (transmission / reception point) 210: Communications Department 211: Transmission unit 212: Receiving unit 220: Network interface 230: Control section 250: Cell 300: Core network equipment 520: BFD configuration list 521: BFD resource set

Claims

1. A communication device (100) that performs wireless communication with a base station (200) that manages a cell having N (N≧2) transmission / reception points, A communication unit (110) that receives a radio resource control (RRC) message from the base station (200), the radio resource control message including a radio link monitoring configuration that configures radio link monitoring and a beam failure detection configuration that configures N beam failure detection resource sets; A control unit (120) that performs radio link monitoring based on the radio link monitoring configuration and detects beam failures individually for each of the N beam failure detection resource sets based on the beam failure detection configuration; The radio link monitoring configuration includes information indicating a reference signal resource for radio link monitoring and information indicating a use of the reference signal resource; As the above-mentioned applications, three applications are defined: beam failure, radio link failure (RLF), and both of them. When the beam obstruction detection setting is set, only the RLF is set as the use. A communication device (100).

2. When the beam failure detection setting is set, the control unit (120) detects the RLF based on the radio link monitoring setting. The communication device (100) of claim 1.

3. When the beam obstruction detection setting is set, the beam obstruction is not set and the RLF is set as the use. A communication device (100) according to claim 1 or 2.

4. The RRC message includes BWP-DownlinkDedicated, which is an information element for setting communication device-specific parameters of a downlink bandwidth portion; The BWP-DownlinkDedicated includes the radio link monitoring setting and the beam failure detection setting. A communication device (100) according to any one of claims 1 to 3.

5. Each of the N beam failure detection resource sets includes an addition / change list for adding and / or changing one or more reference signal resources. A communication device (100) according to any one of claims 1 to 4.

6. A cell having N (N≧2) transmission / reception points is managed, and a communication device (100 A base station (200) for wireless communication with a A control unit (230); A communication unit (210) that transmits a radio resource control (RRC) message including a radio link monitoring setting for setting radio link monitoring and a beam failure detection setting for setting N beam failure detection resource sets to the communication device (100), The radio link monitoring configuration includes information indicating a reference signal resource for radio link monitoring and information indicating a use of the reference signal resource; As the above-mentioned applications, three applications are defined: beam failure, radio link failure (RLF), and both of them. The control unit (230) When setting the beam obstruction detection setting, set only the RLF as the purpose. Base station (200).

7. The control unit (230) When the beam obstruction detection setting is set, the RLF is set without setting the beam obstruction as the purpose. The base station (200) of claim 6.

8. The RRC message includes BWP-DownlinkDedicated, which is an information element for setting communication device-specific parameters of a downlink bandwidth portion; The BWP-DownlinkDedicated includes the radio link monitoring setting and the beam failure detection setting. The base station (200) of claim 7.

9. Each of the N beam failure detection resource sets includes an addition / change list for adding and / or changing one or more reference signal resources. A base station (200) according to any of claims 7 to 8.

10. A communication method implemented by a communication device (100) that performs wireless communication with a base station (200) that manages a cell (250) having N (N≧2) transmission / reception points, comprising: receiving a radio resource control (RRC) message from the base station (200), the radio link monitoring configuration including a radio link monitoring configuration and a beam failure detection configuration including a beam failure detection resource set of N beam failure detection resources; performing radio link monitoring based on the radio link monitoring configuration; Detecting beam failures for each of the N beam failure detection resource sets individually based on the beam failure detection configuration; The radio link monitoring configuration includes information indicating a reference signal resource for radio link monitoring and information indicating a use of the reference signal resource; As the above-mentioned applications, three applications are defined: beam failure, radio link failure (RLF), and both of them. When the beam obstruction detection setting is set, only RLF is set as the use. Communication methods.

11. When the beam failure detection setting is set, the RLF is detected based on the radio link monitoring setting. The communication method according to claim 10.

12. When the beam obstruction detection setting is set, the beam obstruction is not set and the RLF is set as the use. The communication method according to claim 11.

13. The RRC message includes BWP-DownlinkDedicated, which is an information element for setting communication device-specific parameters of a downlink bandwidth portion; The BWP-DownlinkDedicated includes the radio link monitoring setting and the beam failure detection setting. A communication method according to any one of claims 11 to 12.

14. Each of the N beam failure detection resource sets includes an addition / change list for adding and / or changing one or more reference signal resources. A communication method according to any one of claims 11 to 13.

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