Terminal, base station, wireless communication system, and wireless communication method

Abstract

A terminal according to the present invention comprises: a control unit that executes, in a dual connectivity using a master cell group and a secondary cell group, the connection to a target cell included in the secondary cell group on the basis of a conditional reconfiguration; and a transmission unit that, in a case of failure in the connection to the target cell, transmits a message including failure information of the secondary cell group to a network. The control unit puts, as the type of the failure information of the secondary cell group, information element for identifying the conditional reconfiguration into the message.

Description

[Technical field]

[0001] The present disclosure relates to a terminal that transmits a message including failure information of a second cell group to a network. [Background technology]

[0002] The 3rd Generation Partnership Project (3GPP) has developed specifications for the 5th generation mobile communication system (5G, also known as New Radio (NR) or Next Generation (NG)), and is also developing specifications for the next generation, known as Beyond 5G, 5G Evolution, or 6G.

[0003] 3GPP supports dual connectivity (MR-DC (Multi-RAT Dual Connectivity)) using a first cell group (MCG (Master Cell Group)) and a second cell group (SCG (Secondary Cell Group)). Examples of MR-DC include EN-DC (E-UTRA-NR Dual Connectivity), NE-DC (NR-EUTRA Dual Connectivity), and NR-DC (NR-NR Dual Connectivity).

[0004] 3GPP Release 16 introduces a conditional reconfiguration-based procedure for adding (CPA; Conditional PSCell Addition) or changing (CPC; Conditional PSCell Change) a target cell (target PSCell) to specifications prior to Release 15. CPA and CPC are procedures that realize a connection to a target cell without sending a re-establishment request message to the network for the target cell.

[0005] Furthermore, for purposes such as SON (Self Organizing Network) and MDT (Minimization of Drive Test), Mobility Robustness Optimization (MRO) for SN change failure of a Secondary Node (SN) having an SCG and extended optimization of Random Access Channel (RACH) are being considered (e.g., Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] " New WID on enhancement of data collection for SON / MDT in NR ", RP-201281, 3GPP TSG RAN Meeting #86-e, 3GPP, July 2020 Summary of the Invention

[0007] In the above-mentioned background, the inventors have conducted intensive studies and found that, for the purpose of optimizing the SN change failure and the RACH, it is necessary to distinguish whether or not the SN change failure has occurred due to conditional reconfiguration.

[0008] Therefore, the following disclosure has been made in consideration of such circumstances, and aims to provide a terminal and a base station that enable optimization of SN change failure and RACH.

[0009] One aspect of the present disclosure is a terminal that, in dual connectivity using a first cell group and a second cell group, includes a control unit that performs a connection to a target cell included in the second cell group based on conditional reconfiguration, and a transmission unit that transmits a message including failure information of the second cell group to a network if the connection to the target cell fails, wherein the control unit includes in the message an information element that identifies the conditional reconfiguration as a type of failure information of the second cell group. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing an overall schematic configuration of a wireless communication system 10. As shown in FIG. [Diagram 2] FIG. 2 is a functional block diagram of the UE 200. [Diagram 3] FIG. 3 is a diagram for explaining a usage scene. [Figure 4] FIG. 4 is a sequence diagram showing the first operation example. [Diagram 5] FIG. 5 is a sequence diagram showing the second operation example. [Figure 6] FIG. 6 is a diagram showing an example of SCG Failure Information (ASN.1 format). [Figure 7] FIG. 7 is a diagram showing an example of SCG Failure Information (ASN.1 format). [Figure 8] FIG. 8 is a diagram showing an example of SCG Failure Information (ASN.1 format). [Figure 9] FIG. 9 is a diagram showing an example of SCG Failure Information (ASN.1 format). [Figure 10] FIG. 10 is a diagram showing an example of SCG Failure Information (ASN.1 format). [Figure 11] FIG. 11 is a diagram showing an example of SCG Failure Information (ASN.1 format). [Figure 12] FIG. 12 is a diagram illustrating an example of a hardware configuration of the UE 200. As shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment will be described with reference to the drawings. Note that the same or similar reference numerals are used to designate the same functions or configurations, and the description thereof will be omitted as appropriate.

[0012] (1) Overall configuration of wireless communication system 1 is a schematic diagram of an overall configuration of a wireless communication system 10 according to an embodiment. The wireless communication system 10 is a wireless communication system conforming to Long Term Evolution (LTE) and 5G New Radio (NR). Note that LTE may be called 4G, and NR may be called 5G.

[0013] Also, LTE and NR may be interpreted as radio access technologies (RATs), and in an embodiment, LTE may be referred to as a first radio access technology and NR may be referred to as a second radio access technology.

[0014] The wireless communication system 10 includes an Evolved Universal Terrestrial Radio Access Network 20 (hereinafter, E-UTRAN 20) and a Next Generation-Radio Access Network 30 (hereinafter, NG RAN 30). The wireless communication system 10 also includes a terminal 200 (hereinafter, UE 200, User Equipment).

[0015] The E-UTRAN 20 includes an eNB 100A that is a base station conforming to LTE. The NG RAN 30 includes a gNB 100B that is a base station conforming to 5G (NR).

[0016] The eNB100A, gNB100B and UE200 are capable of supporting carrier aggregation (CA) that uses multiple component carriers (CC) and dual connectivity (DC) that simultaneously communicates between the UE and each of multiple nodes.

[0017] The E-UTRAN 20 is connected to a core network 40 for LTE. Note that the E-UTRAN 20, the NG RAN 30 and the core network 40 may be simply referred to as a network.

[0018] An operation administration and management server 50 (hereinafter, OAM server 50) may be provided in the core network 40. The OAM server 50 may execute processes related to a self-organizing network (SON) and a minimization of drive test (MDT).

[0019] The eNB100A and the gNB100B may form an area (which may be expressed as a cell) in which wireless communication with the UE200 can be performed, specifically, area A1 or area A2.

[0020] Here, the area A1 may be interpreted as an area in which the UE 200 can communicate with the eNB 100A. The area A2 may be interpreted as an area in which the UE 200 can communicate with the gNB 100B. The area A1 and the area A2 may overlap with each other, and in an area in which the area A1 and the area A2 overlap, EN-DC (E-UTRA-NR Dual Connectivity) or NE-DC (NR-EUTRA Dual Connectivity) may be performed in which the UE 200 communicates with the eNB 100A and the gNB 100B simultaneously. Note that, although FIG. 2 illustrates a case in which the base station capable of communicating with the UE 200 in the area A1 is the eNB 100A, the base station capable of communicating with the UE 200 in the area A1 may be the gNB 100B provided in the NG RAN 30. In such a case, NR-DC (NR-NR Dual Connectivity) may be performed in which the UE 200 communicates with two or more gNBs 100B (or cells) simultaneously.

[0021] Here, in the above-mentioned DC, a group of cells capable of performing processes related to the control plane (C-plane) and the user plane (U-plane) may be referred to as a first cell group (Master Cell Group (MCG)). In the above-mentioned DC, a group of cells capable of performing processes related to the user plane (U-plane) may be referred to as a second cell group (Secondary Cell Group (SCG)). For example, in the above-mentioned EN-DC, the eNB100A may be referred to as a Master Node (MN), and the gNB100B may be referred to as a Secondary Node (SN). In the above-mentioned NE-DC, the eNB100A may be referred to as an SN, and the gNB100B may be referred to as an MN.

[0022] In the following, EN-DC, NE-DC and NR-DC may be collectively referred to as MR (Multi-RAT)-DC.

[0023] (2) Functional block configuration of wireless communication system Next, a description will be given of a functional block configuration of the wireless communication system 10. Specifically, a functional block configuration of the UE 200 will be described.

[0024] Fig. 2 is a functional block diagram of the UE 200. As shown in Fig. 2, the UE 200 includes a radio signal transmitting / receiving unit 210, an amplifier unit 220, a modulation / demodulation unit 230, a control signal / reference signal processing unit 240, an encoding / decoding unit 250, a data transmitting / receiving unit 260, and a control unit 270.

[0025] The radio signal transmission / reception unit 210 transmits and receives radio signals conforming to LTE or NR. The radio signal transmission / reception unit 210 supports Massive MIMO, CA and DC that use a bundle of multiple CCs, and the like.

[0026] The amplifier unit 220 is configured by a PA (Power Amplifier) / LNA (Low Noise Amplifier) ​​etc. The amplifier unit 220 amplifies the signal output from the modem unit 230 to a predetermined power level. The amplifier unit 220 also amplifies the RF signal output from the wireless signal transmitting / receiving unit 210.

[0027] The modem unit 230 performs data modulation / demodulation, transmission power setting, resource block allocation, and the like for each predetermined communication destination (eNB100A or gNB100B). The modem unit 230 may apply Cyclic Prefix-Orthogonal Frequency Division Multiplexing (CP-OFDM) / Discrete Fourier Transform - Spread (DFT-S-OFDM). Furthermore, DFT-S-OFDM may be used not only for uplink (UL) but also for downlink (DL).

[0028] The control signal / reference signal processor 240 executes processing related to various control signals transmitted and received by the UE 200, and processing related to various reference signals transmitted and received by the UE 200.

[0029] Specifically, the control signal / reference signal processor 240 receives various control signals, such as radio resource control layer (RRC) control signals, transmitted from the eNB 100A or gNB 100B via a predetermined control channel. The control signal / reference signal processor 240 also transmits various control signals to the eNB 100A or gNB 100B via a predetermined control channel.

[0030] The control signal / reference signal processor 240 executes processing using reference signals (RS) such as a Demodulation Reference Signal (DMRS) and a Phase Tracking Reference Signal (PTRS).

[0031] DMRS is a known reference signal (pilot signal) between a base station and a terminal for estimating a fading channel used for data demodulation. PTRS is a terminal-specific reference signal for estimating phase noise, which is an issue in high frequency bands.

[0032] In addition to the DMRS and PTRS, the reference signals may include a Channel State Information-Reference Signal (CSI-RS), a Sounding Reference Signal (SRS), and a Positioning Reference Signal (PRS) for position information.

[0033] The channels include a control channel and a data channel. The control channels include a PDCCH (Physical Downlink Control Channel), a PUCCH (Physical Uplink Control Channel), a RACH (Random Access Channel), Downlink Control Information (DCI) including a Random Access Radio Network Temporary Identifier (RA-RNTI), and a Physical Broadcast Channel (PBCH).

[0034] The data channel includes a physical downlink shared channel (PDSCH) and a physical uplink shared channel (PUSCH), etc. Data means data transmitted via the data channel. The data channel may be read as a shared channel.

[0035] Here, the control signal and reference signal processor 240 receives downlink control information (DCI). The DCI includes fields for storing DCI Formats, Carrier indicator (CI), BWP indicator, Frequency Domain Resource Allocation (FDRA), Time Domain Resource Allocation (TDRA), Modulation and Coding Scheme (MCS), HARQ Process Number (HPN), New Data Indicator (NDI), Redundancy Version (RV), and the like as existing fields.

[0036] The value stored in the DCI Format field is an information element that specifies the format of the DCI. The value stored in the CI field is an information element that specifies the CC to which the DCI is applied. The value stored in the BWP indicator field is an information element that specifies the BWP to which the DCI is applied. The BWP that can be specified by the BWP indicator is set by an information element (BandWidthPart-Config) included in the RRC message. The value stored in the FDRA field is an information element that specifies the frequency domain resource to which the DCI is applied. The frequency domain resource is identified by the value stored in the FDRA field and an information element (RA Type) included in the RRC message. The value stored in the TDRA field is an information element that specifies the time domain resource to which the DCI is applied. The time domain resource is identified by the value stored in the TDRA field and an information element (pdsch-TimeDomainAllocationList) included in the RRC message. The time domain resource may be identified by the value stored in the TDRA field and a default table. The value stored in the MCS field is an information element that specifies the MCS to which the DCI is applied. The MCS is identified by the value stored in the MCS and an MCS table. The MCS table may be specified by an RRC message or may be specified by RNTI scrambling. The value stored in the HPN field is an information element that specifies the HARQ process to which the DCI is applied. The value stored in the NDI is an information element for specifying whether the data to which the DCI is applied is initial transmission data or not. The value stored in the RV field is an information element that specifies the redundancy of the data to which the DCI is applied.

[0037] In an embodiment, the control signal and reference signal processor 240 configures a transmitter that transmits a message including SCG failure information to the network (MN 300) when a connection to a target cell included in an SCG based on conditional reconfiguration in MR-DC fails. The conditional reconfiguration may include a PSCell addition (CPA; Conditional PSCell Addition) or a PSCell change (CPC; Conditional PSCell Change). The SCG failure information may be referred to as SCG Failure information. Alternatively, the message including the SCG failure information may be referred to as SCG Failure.

[0038] Note that CPA and CPC are procedures for achieving connection to a target cell without transmitting an RRC re-establishment request (a re-establishment request message) to the target cell to the network.

[0039] The encoding / decoding unit 250 performs data division / concatenation and channel coding / decoding for each predetermined communication destination (eNB100A or gNB100B).

[0040] Specifically, the encoding / decoding unit 250 divides the data output from the data transmitting / receiving unit 260 into pieces of a predetermined size, performs channel coding on the divided data, and decodes the data output from the modem unit 230 and concatenates the decoded data.

[0041] The data transmission / reception unit 260 transmits and receives Protocol Data Units (PDUs) and Service Data Units (SDUs). Specifically, the data transmission / reception unit 260 performs assembly / disassembly of PDUs / SDUs in multiple layers (such as a Medium Access Control layer (MAC), a Radio Link Control layer (RLC), and a Packet Data Convergence Protocol layer (PDCP)). In addition, the data transmission / reception unit 260 performs data error correction and retransmission control based on a hybrid automatic repeat request (Hybrid ARQ).

[0042] The control unit 270 controls each functional block constituting the UE 200. In the embodiment, the control unit 270 constitutes a control unit that executes a connection to a target cell included in the SCG based on conditional reconfiguration (CPA or CPC) in the MR-DC. The control unit 270 includes an information element that identifies the conditional reconfiguration in the SCG Failure as a type of failure information of the SCG. The type of failure information of the SCG may be referred to as failure type or failure type-v17xy. The information element that identifies the conditional reconfiguration may be referred to as condSynchReconfigFailureSCG.

[0043] Furthermore, the control unit 270 may include an information element regarding the target cell in a message including the SCG failure information. The information element regarding the target cell may include identification information of the target cell (e.g., FailedPSCellID). The identification information of the target cell may include a Cell Global Identify (CGI) of the target cell that uniquely identifies the cell in the wireless communication system 10. The information element regarding the target cell may include a Physical Cell Identify (PCI) of the target cell that uniquely identifies the cell in the SN 400. The information element regarding the target cell may include an Absolute Radio-Frequency Channel Number (ARFCN) that identifies the frequency of the target cell. The information element regarding the target cell may include a measurement result of the reception quality of the target cell (e.g., measResultFailedPSCell). The measurement result may include Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), or Signal to Interference and Noise Ratio (SINR).

[0044] The control unit 270 may include an information element regarding the source cell in a message including the SCG failure information. The information element regarding the source cell may include identification information of the source cell (e.g., PreviousPSCellID). The identification information of the source cell may include a CGI of the source cell. The identification information of the source cell may include a PCI of the source cell. The identification information of the source cell may include an ARFCN of the source cell. The information element regarding the source cell may include a measurement result of the reception quality of the source cell (e.g., measResultPreviousPSCell). The measurement result may include an RSRP, an RSRQ, or an SINR.

[0045] The control unit 270 may include an information element on a candidate cell of the target cell in a message including the failure information of the SCG. The information element on the candidate cell (e.g., measResultCandidatePSCellInfoList) may include a measurement result of the candidate cell (e.g., measResultCandidatePSCellInfo). The information element on the candidate cell may include the measurement results of two or more candidate cells in a list format. The measurement result of the candidate cell may include identification information of the candidate cell. The identification information of the candidate cell may include the PCI of the candidate cell or the frequency of the candidate cell. The measurement result of the candidate cell may include a measurement result of the reception quality of the candidate cell (e.g., measResult). The measurement result may include RSRP, RSRQ, or SINR. The measurement result of the candidate cell may include an information element (e.g., executionConditionSatisfied) indicating whether the measurement result performed on the candidate cell satisfies the execution condition for conditional reconfiguration. The measurement result of the candidate cell may include an information element (e.g., configuredExecutionConditionEvent) specifying an execution condition event configured for the candidate cell. Such information elements may include two or more execution condition events. The measurement result of the candidate cell may include an information element (e.g., satisfiedTriggeringQuantity) specifying a reception quality that satisfies the execution condition for the conditional reconfiguration. Such information elements may include two or more reception qualities that satisfies the execution condition for the conditional reconfiguration. The measurement result of the candidate cell may include an information element (e.g., satisfiedTriggeringEvent) specifying an execution condition event that satisfies the execution condition for the conditional reconfiguration. Such information elements may include two or more execution condition events that satisfies the execution condition for the conditional reconfiguration.

[0046] For example, the execution condition event may include Event A3 (§5.5.4.4 “Neighbor becomes offset better than SpCell” in TS38.331 V16.1.0) and Event A5 (§5.5.4.6 “SpCell becomes worse than threshold1 and neighbour becomes better than threshold2” in TS38.331 V16.1.0). The execution condition for conditional reconfiguration is a condition defined for each execution condition event. For example, the execution condition for conditional reconfiguration associated with Event A3 may be that the reception quality of the neighbouring cell (candidate cell) is better than the current PSCell by an offset. The execution condition for conditional reconfiguration associated with Event A5 may be that the reception quality of the current PSCell is worse than threshold1 and the reception quality of the neighbouring cell (candidate cell) is better than threshold2.

[0047] The control unit 270 may include an information element regarding a random access procedure to the target cell in the message including the SCG failure information. The information element regarding the random access procedure (e.g., attemptedRAInformation) may include an information element specifying a four-step random access procedure (e.g., fourStepRAInformation) or may include an information element specifying a two-step random access procedure (e.g., twoStepRAInformation). These information elements may include information elements that specify a frequency to be used in the random access procedure (e.g., absoluteFrequencyPoint), information elements that specify the location and frequency band of the BWP (BandWidth Part) to be used in the random access procedure (e.g., locationAndBandwidth), information elements that specify the SCS (SubCarrier Spacing) to be used in the random access procedure (e.g., subcarrierSpacing), and information elements regarding the random access preamble (msg 1 or msg A) (e.g., FrequencyStart, FrequencyStartCFRA, subcarrierSpacing, subcarrierSpacingCFRA, FDM, FDMCFRA, perRAInfoList).

[0048] (3) Application Scenes In the following, application scenes of the embodiment will be described. In the application scene, a case will be described in which a PSCell change is executed in MR-DC in which UE 200 communicates with MN 300 and SN 400. In FIG. 3, MN 300 is exemplified as MN 300, and SN 400A to SN 400D are exemplified as SN 400. MC is exemplified as a cell included in MN 300, and SC 1 to SC 4 are exemplified as cells included in SN 400. For example, the coverage area of ​​SC 1 to SC 4 overlaps with the coverage area of ​​MC. In such a case, MC is a cell that can be used as a PCell (Primary Cell), and SC 1 to SC 4 are cells that can be used as a PSCell.

[0049] Under such a premise, consider a case where a connection to a target cell fails in the addition (CPA) or change (CPC) of a PSCell. Specifically, consider a case where a connection to SC2 fails in a procedure for changing a PSCell from SC1 to SC2 in conditional reconfiguration in a state where MC1 is used as a PCell and SC1 is used as a PSCell. Alternatively, consider a case where a connection to SC2 fails in a procedure for adding SC2 as a PSCell in conditional reconfiguration in a state where MC1 is used as a PCell and SC1 is used as a PSCell. In these cases, SC1 is an example of a source cell included in an SCG, and SC2 is an example of a target cell included in an SCG.

[0050] In such a case, the UE 200 transmits a message (SCG Failure) including SCG failure information to the network (MN 300), and includes in the message an information element (condSynchReconfigFailureSCG) that identifies conditional reconfiguration as the type of SCG failure information (failure type).

[0051] (4) Example of operation An operation example of the embodiment will be described below. In the following, a case where an EN-DC is executed as an MR-DC will be illustrated. That is, a case where an eNB100A included in an E-UTRAN 20 is an MN 300, and a gNB100B included in an NG RAN 30 is an SN 400 will be illustrated. However, the embodiment is not limited to this. The MR-DC may be an NE-DC or an NR-DC.

[0052] (4.1) Example 1 A procedure for adding a target cell as a PSCell based on conditional reconfiguration will be described below. In Fig. 4, T-SN1 (SN 400A) and T-SN2 (SN 400B) are examples of nodes that manage candidate cells for the target cell.

[0053] As shown in Fig. 4, in step S10, the UE 200 transmits a measurement report to the MN 300. The measurement report includes measurement results (RSRP, RSRQ, SINR) of the reception qualities of a current cell (e.g., SC1 shown in Fig. 3) and neighboring cells (e.g., SC2 to SC4 shown in Fig. 3).

[0054] In step S11, the MN 300 decides to add a PSCell by conditional reconfiguration, and determines a candidate cell for a target cell to be added as a PSCell (CPA decision).

[0055] In step S12A, the MN 300 transmits a message (SN Addition Request) to the SN 400A requesting that the gNB 100B be added as an SN. Similarly, in step S12B, the MN 300 transmits a message (SN Addition Request) to the SN 400B requesting that the gNB 100B be added as an SN.

[0056] In step S13A, the SN 400A transmits a response message (SN Addition Request Ack) to the SN Addition Request to the MN 300. Similarly, in step S13B, the SN 400B transmits a response message (SN Addition Request Ack) to the MN 300 to the SN Addition Request.

[0057] In step S14, the MN 300 transmits a message (RRC Reconfiguration) including an information element (e.g., conditionalReconfiguration) instructing conditional reconfiguration to the UE 200. The conditionalReconfiguration includes information elements for identifying the candidate cell and the execution condition configuration. The conditionalReconfiguration may include an information element (condReconfigId) associated with the type of the execution condition event (Event A3, Event A5, etc.).

[0058] In step S15, the UE 200 transmits a response message (RRC Reconfiguration Complete) to the MN 300 in response to the RRC Reconfiguration.

[0059] In step S16, the UE 200 judges whether or not there is a candidate cell that satisfies the execution condition of the CPA. Here, the description will be continued assuming that there is a candidate cell that satisfies the execution condition of the CPA. If there are two or more candidate cells that satisfy the execution condition of the CPA, the UE 200 selects a target cell from among the two or more candidate cells. Here, the description will be continued assuming that the cell managed by the SN 400A is the target cell.

[0060] In step S17, the UE 200 transmits, to the MN 300, a message (RRC Reconfiguration Complete) indicating that a connection to the target cell based on the CPA is to be performed.

[0061] In step S18, the MN 300 transmits a message (SN Reconfiguration Complete) to the SN 400A indicating that the gNB 100B has been added as an SN.

[0062] In step S19, the MN 300 transmits a message (SN Status Transfer) notifying the SN 400A of the status related to the SN.

[0063] In step S20, data transfer is performed between the UPF (User Plane Function) 500, the MN 300, and the SN 400A.

[0064] In step S21, the UE 200 executes a random access procedure between the UE 200 and the SN 400A. The random access procedure may be a four-step random access procedure or a two-step random access procedure. Here, the description will be continued assuming that the UE 200 fails in the random access procedure. In other words, the UE 200 fails to connect to the target cell based on the CPA.

[0065] In step S22, the UE 200 transmits a message (SCG Failure) including SCG failure information to the MN 300. The SCG Failure includes an information element (condSynchReconfigFailureSCG) that identifies conditional reconfiguration as a type of SCG failure information.

[0066] Furthermore, the SCG Failure may include information elements (FailedPSCellID, measResultFailedPSCell) regarding the target cell. The SCG Failure may include information elements (PreviousPSCellID, measResultPreviousPSCell) regarding the source cell. The SCG Failure may include information elements (measResultCandidatePSCellInfoList) regarding the candidate cells of the target cell. The measResultCandidatePSCellInfoList may include candidate cell identification information (PCI, frequency), a measurement result of the reception quality of the candidate cell (measResult), whether the measurement result satisfies the execution condition of CPA (executionConditionSatisfied), an execution condition event (configuredExecutionConditionEvent), a reception quality that satisfies the execution condition (satisfiedTriggeringQuantity), and an execution condition event that satisfies the execution condition (satisfiedTriggeringEvent). The SCG Failure may include information elements (attemptedRAInformation) regarding the random access procedure to the target cell.

[0067] (4.2) Example 2 The procedure for changing the PSCell to a target cell based on conditional reconfiguration will be described below. In Fig. 5, T-SN1 (SN400A) and T-SN2 (SN400B) are examples of nodes that manage candidate cells for the target cell. S-SN (SN400C) is an example of a node that manages a source cell.

[0068] 5, in step S30, the UE 200 transmits a measurement report to the SN 400C. The measurement report includes measurement results (RSRP, RSRQ, SINR) of the reception quality of a current cell (e.g., SC1 shown in FIG. 3) and neighboring cells (e.g., SC2 to SC4 shown in FIG. 3).

[0069] In step S31, the SN400C decides to change the PSCell by conditional reconfiguration, and determines a candidate cell for the target cell to be changed to the PSCell (CPC decision).

[0070] In step S32, the SN 400C transmits to the MN 300 a message (SN change required) requesting a change of the PSCell.

[0071] In step S33A, the MN 300 transmits a message (SN Addition Request) requesting that the gNB 100B be added as an SN to the SN 400A. Similarly, in step S33B, the MN 300 transmits a message (SN Addition Request) requesting that the gNB 100B be added as an SN to the SN 400B.

[0072] In step S34A, the SN 400A transmits a response message (SN Addition Request Ack) to the SN Addition Request to the MN 300. Similarly, in step S34B, the SN 400B transmits a response message (SN Addition Request Ack) to the MN 300 to the SN Addition Request.

[0073] In step S35, the MN 300 transmits a message (RRC Reconfiguration) including an information element (e.g., conditionalReconfiguration) instructing conditional reconfiguration to the UE 200. The conditionalReconfiguration includes information elements for identifying candidate cells and execution condition settings. The conditionalReconfiguration may include an information element (condReconfigId) associated with the type of execution condition event (Event A3, Event A5, etc.).

[0074] In step S36, the UE 200 transmits a response message (RRC Reconfiguration Complete) to the MN 300 in response to the RRC Reconfiguration.

[0075] In step S37, the UE 200 judges whether or not there is a candidate cell that satisfies the execution condition of the CPC. Here, the description will be continued assuming that there is a candidate cell that satisfies the execution condition of the CPC. If there are two or more candidate cells that satisfy the execution condition of the CPC, the UE 200 selects a target cell from among the two or more candidate cells. Here, the description will be continued assuming that the cell managed by the SN 400A is the target cell.

[0076] In step S38, the UE 200 transmits, to the MN 300, a message (RRC Reconfiguration Complete) indicating that a connection to the target cell based on the CPC is to be performed.

[0077] In step S39, the MN 300 transmits a message (SN Reconfiguration Complete) to the SN 400A indicating that the gNB 100B has been added as an SN.

[0078] In step S40, the SN 400C transmits a message (SN Status Transfer) notifying the MN 300 of the status related to the SN, and the MN 300 transmits a message (SN Status Transfer) notifying the SN of the status related to the SN to the SN 400A.

[0079] In step S41, data transfer is performed between the UPF 500, the SN 400C, the MN 300, and the SN 400A.

[0080] In step S42, the UE 200 executes a random access procedure between the UE 200 and the SN 400A. The random access procedure may be a four-step random access procedure or a two-step random access procedure. Here, the description will be continued assuming that the UE 200 fails in the random access procedure. In other words, the UE 200 fails to connect to the target cell based on the CPC.

[0081] In step S43, the UE 200 transmits a message (SCG Failure) including SCG failure information to the MN 200. The MN 300 may transfer the SCG Failure received from the UE 200 to the SN 400. The SCG Failure includes an information element (condSynchReconfigFailureSCG) that identifies conditional reconfiguration as a type of SCG failure information.

[0082] Furthermore, the SCG Failure may include information elements (FailedPSCellID, measResultFailedPSCell) regarding the target cell. The SCG Failure may include information elements (PreviousPSCellID, measResultPreviousPSCell) regarding the source cell. The SCG Failure may include information elements (measResultCandidatePSCellInfoList) regarding the candidate cells of the target cell. The measResultCandidatePSCellInfoList may include candidate cell identification information (PCI, frequency), a measurement result of the reception quality of the candidate cell (measResult), whether the measurement result satisfies the execution condition of CPC (executionConditionSatisfied), an execution condition event (configuredExecutionConditionEvent), a reception quality that satisfies the execution condition (satisfiedTriggeringQuantity), and an execution condition event that satisfies the execution condition (satisfiedTriggeringEvent). The SCG Failure may include information elements (attemptedRAInformation) regarding a random access procedure to the target cell.

[0083] (5) Example of information element configuration Fig. 6 to Fig. 11 are diagrams showing configuration examples of information elements of SCG Failure Information. Fig. 6 to Fig. 8 are diagrams showing SCG Failure Information used in a case where MN 300 is eNB 100A, that is, SCG Failure Information used in E-UTRAN 20. Fig. 9 to Fig. 11 are diagrams showing SCG Failure Information used in a case where MN 300 is gNB 100B, that is, SCG Failure Information used in NG RAN 30.

[0084] As shown in Figures 6 and 9, the SCG Failure Information may include an information element (condSynchReconfigFailureSCG) that identifies conditional reconfiguration as a type of SCG failure information. The SCG Failure Information may include information elements (FailedPSCellID, measResultFailedPSCell) regarding the target cell. The SCG Failure Information may include information elements (PreviousPSCellID, measResultPreviousPSCell) regarding the source cell.

[0085] As shown in Fig. 7 and Fig. 10, the SCG Failure Information may include information elements (measResultCandidatePSCellInfoList) regarding candidate cells of the target cell. The measResultCandidatePSCellInfoList may include candidate cell identification information (PCI, frequency), a measurement result of the reception quality of the candidate cell (measResult), whether the measurement result satisfies the execution condition of CPC (executionConditionSatisfied), an execution condition event (configuredExecutionConditionEvent), a reception quality that satisfies the execution condition (satisfiedTriggeringQuantity), and an execution condition event that satisfies the execution condition (satisfiedTriggeringEvent).

[0086] As shown in Fig. 8 and Fig. 11, the SCG Failure Information may include an information element (attemptedRAInformation) regarding a random access procedure to the target cell. The attemptedRAInformation may include an information element (fourStepRAInformation) specifying a four-step random access procedure, or an information element (twoStepRAInformation) specifying a two-step random access procedure. These information elements may include an information element (e.g., absoluteFrequencyPoint) specifying a frequency used in the random access procedure, an information element (e.g., locationAndBandwidth) specifying a location and frequency band of a BWP (BandWidth Part) used in the random access procedure, an information element (e.g., subcarrierSpacing) specifying a SCS (SubCarrier Spacing) used in the random access procedure, and an information element (e.g., FrequencyStart, FrequencyStartCFRA, subcarrierSpacing, subcarrierSpacingCFRA, FDM, FDMCFRA, perRAInfoList) regarding a random access preamble (msg 1 or msg A).

[0087] (6) Actions and Effects In the embodiment, the UE 200 transmits, to the network, an SCG Failure including an information element identifying conditional reconfiguration as a type of SCG failure information in the CPA or CPC in the MR-DC. With this configuration, it is possible to optimize a decision to add a PSCell (CPA decision) or a decision to change a PSCell (CPC decision). For example, as in the operation example 1, when the CPA decision is made by the MN 300, the MN 300 can optimize the CPA decision by receiving an SCG Failure including an information element identifying conditional reconfiguration. As in the operation example 2, when the CPC decision is made by the SN 400, the SN 400 can optimize the CPC decision by acquiring, from the MN 300, an SCG Failure including an information element identifying conditional reconfiguration.

[0088] The SCG Failure includes information elements about the target cell, information elements about the source cell, and information elements about candidate cells of the target cell. According to this configuration, the decision to add a PSCell (CPA decision) or change a PSCell (CPC decision) can be further optimized.

[0089] The SCG Failure includes an information element related to a random access procedure to the target cell. According to this configuration, it is possible to optimize the random access procedure to the target cell.

[0090] [Other embodiments] Although the embodiment has been described above, it will be apparent to those skilled in the art that the present invention is not limited to the description of the embodiment and that various modifications and improvements are possible.

[0091] In the embodiment, the EN-DC is mainly illustrated as an example of the MR-DC. However, the embodiment is not limited to this. The MR-DC may be the NE-DC or the NR-DC. In the NE-DC, the SRB3 is not set in the UE 200, so the operation example 3 described in the embodiment may not be used.

[0092] In the operation example 1 (FIG. 4), a case where the CPA decision is executed by the MN 300 is illustrated. However, the operation example 1 is not limited to this. The CPA decision may be executed by the SN 400. In such a case, the MN 300 may transfer the SCG Failure received from the UE 200 to the SN 400.

[0093] In the second operation example (FIG. 5), a case where the CPC decision is made by the SN 400 has been illustrated. However, the second operation example is not limited to this. The CPC decision may be made by the MN 300.

[0094] In the embodiment, a case where a connection to a target cell (PSCell) is made based on conditional reconfiguration in MR-DC is illustrated. However, the embodiment is not limited thereto. For example, in MR-DC, the present invention may be applied to PSCell Addition (hereinafter, normal PSCell Addition) in which a PSCell is added without being based on conditional reconfiguration, and PSCell change (hereinafter, normal PSCell Change) in which a PSCell is changed without being based on conditional reconfiguration. For example, in the normal PSCell Addition or normal PSCell Change, when a connection to a target cell (PSCell) fails, the UE 200 may perform the following operation. Specifically, the UE 200 may include information elements (FailedPSCellID, measResultFailedPSCell) related to the target cell in the SCG Failure. The UE 200 may include information elements (PreviousPSCellID, measResultPreviousPSCell) related to the source cell in the SCG Failure. The UE 200 may include an information element (attemptedRAInformation) regarding a random access procedure to the target cell in the SCG Failure.

[0095] Moreover, the block diagram (FIG. 2) used in the description of the above-mentioned embodiment shows functional blocks. These functional blocks (components) are realized by any combination of at least one of hardware and software. Furthermore, the method of realizing each functional block is not particularly limited. That is, each functional block may be realized by using one device that is physically or logically combined, or may be realized by using two or more devices that are physically or logically separated and directly or indirectly connected (for example, by using wires, wirelessly, etc.). The functional block may be realized by combining the one device or the multiple devices with software.

[0096] Functions include, but are not limited to, judgment, determination, judgment, calculation, computation, processing, derivation, investigation, search, confirmation, reception, transmission, output, access, resolution, selection, selection, establishment, comparison, assumption, expectation, consideration, broadcasting, notifying, communicating, forwarding, configuring, reconfiguring, allocating, mapping, and assignment. For example, a functional block (component) that performs the function of transmission is called a transmitting unit or a transmitter. As described above, there is no particular limitation on the method of realization of any of these.

[0097] Furthermore, the above-mentioned UE 200 (the device) may function as a computer that performs processing of the wireless communication method of the present disclosure. Fig. 12 is a diagram showing an example of a hardware configuration of the device. As shown in Fig. 12, the device may be configured as a computer device including a processor 1001, a memory 1002, a storage 1003, a communication device 1004, an input device 1005, an output device 1006, and a bus 1007.

[0098] In the following description, the term "apparatus" may be interpreted as a circuit, a device, a unit, etc. The hardware configuration of the apparatus may be configured to include one or more of the apparatuses shown in the drawings, or may be configured to exclude some of the apparatuses.

[0099] Each functional block of the device (see FIG. 2) is realized by any hardware element of the computer device, or a combination of the hardware elements.

[0100] In addition, each function in the device is realized by loading a specific software (program) onto hardware such as the processor 1001, memory 1002, etc., so that the processor 1001 performs calculations, controls communication by the communication device 1004, and controls at least one of reading and writing of data in the memory 1002 and storage 1003.

[0101] The processor 1001 controls the entire computer by running, for example, an operating system, and may be configured by a central processing unit (CPU) including an interface with peripheral devices, a control unit, an arithmetic unit, a register, and the like.

[0102] Furthermore, the processor 1001 reads out programs (program codes), software modules, data, etc. from at least one of the storage 1003 and the communication device 1004 into the memory 1002, and executes various processes according to these. As the programs, programs that cause a computer to execute at least a part of the operations described in the above-mentioned embodiments are used. Furthermore, the above-mentioned various processes may be executed by one processor 1001, or may be executed simultaneously or sequentially by two or more processors 1001. The processor 1001 may be implemented by one or more chips. The programs may be transmitted from a network via a telecommunications line.

[0103] The memory 1002 is a computer-readable recording medium, and may be configured by at least one of, for example, a Read Only Memory (ROM), an Erasable Programmable ROM (EPROM), an Electrically Erasable Programmable ROM (EEPROM), a Random Access Memory (RAM), etc. The memory 1002 may also be called a register, a cache, a main memory (primary storage device), etc. The memory 1002 can store a program (program code), a software module, etc., capable of executing a method according to an embodiment of the present disclosure.

[0104] Storage 1003 is a computer-readable recording medium, and may be composed of at least one of, for example, an optical disk such as a Compact Disc ROM (CD-ROM), a hard disk drive, a flexible disk, a magneto-optical disk (e.g., a compact disk, a digital versatile disk, a Blu-ray (registered trademark) disk), a smart card, a flash memory (e.g., a card, a stick, a key drive), a floppy (registered trademark) disk, a magnetic strip, and the like. Storage 1003 may be referred to as an auxiliary storage device. The above-mentioned recording medium may be, for example, a database, a server, or other suitable medium including at least one of memory 1002 and storage 1003.

[0105] The communication device 1004 is hardware (transmission / reception device) for performing communication between computers via at least one of a wired network and a wireless network, and is also called, for example, a network device, a network controller, a network card, or a communication module.

[0106] The communication device 1004 may be configured to include a high-frequency switch, a duplexer, a filter, a frequency synthesizer, and the like to realize, for example, at least one of Frequency Division Duplex (FDD) and Time Division Duplex (TDD).

[0107] The input device 1005 is an input device (e.g., a keyboard, a mouse, a microphone, a switch, a button, a sensor, etc.) that accepts input from the outside. The output device 1006 is an output device (e.g., a display, a speaker, an LED lamp, etc.) that performs output to the outside. The input device 1005 and the output device 1006 may be integrated into one device (e.g., a touch panel).

[0108] In addition, each device such as the processor 1001 and the memory 1002 is connected by a bus 1007 for communicating information. The bus 1007 may be configured using a single bus, or may be configured using different buses between each device.

[0109] Furthermore, the device may be configured to include hardware such as a microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a programmable logic device (PLD), a field programmable gate array (FPGA), etc., and some or all of the functional blocks may be realized by the hardware. For example, the processor 1001 may be implemented using at least one of these pieces of hardware.

[0110] Furthermore, the notification of information is not limited to the aspects / embodiments described in the present disclosure, and may be performed using other methods. For example, the notification of information may be performed by physical layer signaling (e.g., Downlink Control Information (DCI), Uplink Control Information (UCI)), higher layer signaling (e.g., RRC signaling, Medium Access Control (MAC) signaling, broadcast information (Master Information Block (MIB), System Information Block (SIB)), other signals, or a combination of these. Furthermore, the RRC signaling may be called an RRC message, and may be, for example, an RRC Connection Setup message, an RRC Connection Reconfiguration message, or the like.

[0111] Each aspect / embodiment described in the present disclosure may be applied to at least one of a system using Long Term Evolution (LTE), LTE-Advanced (LTE-A), SUPER 3G, IMT-Advanced, 4th generation mobile communication system (4G), 5th generation mobile communication system (5G), Future Radio Access (FRA), New Radio (NR), W-CDMA (registered trademark), GSM (registered trademark), CDMA2000, Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi (registered trademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE 802.20, Ultra-WideBand (UWB), Bluetooth (registered trademark), other suitable systems, and next-generation systems extended based on these. In addition, a combination of multiple systems (e.g., a combination of at least one of LTE and LTE-A and 5G, etc.) may be applied.

[0112] The order of the steps, sequences, flow charts, etc. of each aspect / embodiment described in this disclosure may be changed unless inconsistent. For example, the methods described in this disclosure present elements of various steps using an example order, and are not limited to the particular order presented.

[0113] In the present disclosure, a specific operation performed by a base station may be performed by its upper node in some cases. In a network consisting of one or more network nodes having a base station, it is clear that various operations performed for communication with a terminal may be performed by at least one of the base station and other network nodes other than the base station (e.g., MME or S-GW, etc., but are not limited to these). Although the above example illustrates a case in which there is one other network node other than the base station, it may also be a combination of multiple other network nodes (e.g., MME and S-GW).

[0114] Information, signals (information, etc.) may be output from a higher layer (or a lower layer) to a lower layer (or a higher layer), and may be input and output via multiple network nodes.

[0115] The input / output information may be stored in a specific location (e.g., memory) or may be managed using a management table. The input / output information may be overwritten, updated, or appended. The output information may be deleted. The input information may be transmitted to another device.

[0116] The determination may be based on a value represented by a single bit (0 or 1), a Boolean (true or false) value, or a numerical comparison (e.g., comparison with a predetermined value).

[0117] Each aspect / embodiment described in this disclosure may be used alone, in combination, or switched according to execution. In addition, notification of specific information (e.g., notification that "X is the case") is not limited to being done explicitly, but may be done implicitly (e.g., not notifying the specific information).

[0118] Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

[0119] Additionally, software, instructions, information, etc. may be transmitted or received over a transmission medium. For example, if the software is transmitted from a website, server, or other remote source using wired and / or wireless technologies (such as coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL)), and / or wireless technologies (such as infrared, microwave, etc.), then these wired and / or wireless technologies are included within the definition of transmission media.

[0120] The information, signals, etc. described in this disclosure may be represented using any of a variety of different technologies. For example, the data, instructions, commands, information, signals, bits, symbols, chips, etc. that may be referred to throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, optical fields or photons, or any combination thereof.

[0121] In addition, the terms described in this disclosure and the terms necessary for understanding this disclosure may be replaced with terms having the same or similar meanings. For example, at least one of a channel and a symbol may be a signal (signaling). Also, a signal may be a message. Also, a component carrier (CC) may be called a carrier frequency, a cell, a frequency carrier, etc.

[0122] As used in this disclosure, the terms "system" and "network" are used interchangeably.

[0123] In addition, the information, parameters, etc. described in the present disclosure may be represented using absolute values, may be represented using relative values ​​from a predetermined value, or may be represented using other corresponding information. For example, a radio resource may be indicated by an index.

[0124] The names used for the above-mentioned parameters are not limiting in any way. Furthermore, the formulas using these parameters may differ from those explicitly disclosed in this disclosure. The various channels (e.g., PUCCH, PDCCH, etc.) and information elements may be identified by any suitable names, and therefore the various names assigned to these various channels and information elements are not limiting in any way.

[0125] In this disclosure, terms such as "base station (BS)", "radio base station", "fixed station", "NodeB", "eNodeB (eNB)", "gNodeB (gNB)", "access point", "transmission point", "reception point", "transmission / reception point", "cell", "sector", "cell group", "carrier", "component carrier", etc. may be used interchangeably. A base station may also be referred to by terms such as a macro cell, a small cell, a femto cell, a pico cell, etc.

[0126] A base station can accommodate one or more (e.g., three) cells (also called sectors). When a base station accommodates multiple cells, the entire coverage area of ​​the base station can be divided into multiple smaller areas, and each smaller area can also be provided with communication services by a base station subsystem (e.g., a small indoor base station (Remote Radio Head: RRH)).

[0127] 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 that coverage.

[0128] In this disclosure, the terms "Mobile Station (MS)", "user terminal", "User Equipment (UE)", "terminal", etc. may be used interchangeably.

[0129] A mobile station may also be referred to by those skilled in the art as a subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile terminal, wireless terminal, remote terminal, handset, user agent, mobile client, client, or some other suitable terminology.

[0130] At least one of the base station and the mobile station may be called a transmitting device, a receiving device, a communication device, etc. At least one of the base station and the mobile station may be a device mounted on a moving body, the moving body itself, etc. The moving body may be a vehicle (e.g., a car, an airplane, etc.), an unmanned moving body (e.g., a drone, an autonomous vehicle, etc.), or a robot (manned or unmanned). At least one of the base station and the mobile station may include a device that does not necessarily move during communication operation. For example, at least one of the base station and the mobile station may be an Internet of Things (IoT) device such as a sensor.

[0131] Furthermore, a base station in the present disclosure may be read as a mobile station (user terminal, the same applies below). For example, each aspect / embodiment of the present disclosure may be applied to a configuration in which communication between a base station and a mobile station is replaced with communication between multiple mobile stations (which may be called, for example, Device-to-Device (D2D) or Vehicle-to-Everything (V2X)). In this case, the mobile station may be configured to have the functions of a base station. Furthermore, terms such as "uplink" and "downlink" may be read as terms corresponding to communication between terminals (for example, "side"). For example, an uplink channel, a downlink channel, etc. may be read as a side channel.

[0132] Similarly, a mobile station in the present disclosure may be interpreted as a base station, in which case the base station may have the functions of a mobile station. A radio frame may be composed of one or more frames in the time domain. Each of the one or more frames in the time domain may be called a subframe. A subframe may further be composed of one or more slots in the time domain. A subframe may have a fixed time length (e.g., 1 ms) that is independent of numerology.

[0133] Numerology may be a communication parameter that applies to the transmission and / or reception of a signal or channel, and may indicate, for example, at least one of a SubCarrier Spacing (SCS), a bandwidth, a symbol length, a Cyclic Prefix length, a Transmission Time Interval (TTI), a number of symbols per TTI, a radio frame structure, a particular filtering operation that the transceiver performs in the frequency domain, a particular windowing operation that the transceiver performs in the time domain, etc.

[0134] A slot may consist of one or more symbols in the time domain (such as an Orthogonal Frequency Division Multiplexing (OFDM) symbol, a Single Carrier Frequency Division Multiple Access (SC-FDMA) symbol, etc.) A slot may be a numerology-based unit of time.

[0135] A slot may include multiple minislots. Each minislot may be composed of one or more symbols in the time domain. A minislot may also be called a subslot. A minislot may be composed of fewer symbols than a slot. A PDSCH (or PUSCH) transmitted in a time unit larger than a minislot may be called PDSCH (or PUSCH) mapping type A. A PDSCH (or PUSCH) transmitted using a minislot may be called PDSCH (or PUSCH) mapping type B.

[0136] A radio frame, a subframe, a slot, a minislot, and a symbol each represent a time unit for transmitting a signal. The radio frame, the subframe, the slot, the minislot, and the symbol may each be referred to by a different name.

[0137] For example, one subframe may be called a transmission time interval (TTI), multiple consecutive subframes may be called a TTI, or one slot or one minislot may be called a TTI. That is, at least one of the subframe and the TTI may be a subframe (1 ms) in the existing LTE, a period shorter than 1 ms (for example, 1-13 symbols), or a period longer than 1 ms. Note that the unit representing the TTI may be called a slot, minislot, etc., instead of a subframe.

[0138] Here, TTI refers to, for example, the minimum time unit for scheduling in wireless communication. For example, in an LTE system, a base station performs scheduling to allocate radio resources (such as frequency bandwidth and transmission power that can be used by each user terminal) to each user terminal in TTI units. Note that the definition of TTI is not limited to this.

[0139] The TTI may be a transmission time unit for a channel-encoded data packet (transport block), a code block, a code word, etc., or may be a processing unit for scheduling, link adaptation, etc. When a TTI is given, the time interval (e.g., the number of symbols) in which a transport block, a code block, a code word, etc. are actually mapped may be shorter than the TTI.

[0140] In addition, when one slot or one minislot is called TTI, one or more TTIs (i.e., one or more slots or one or more minislots) may be the minimum time unit of scheduling. Also, the number of slots (minislots) constituting the minimum time unit of scheduling may be controlled.

[0141] A TTI having a time length of 1 ms may be called a normal TTI (TTI in LTE Rel. 8-12), a normal TTI, a long TTI, a normal subframe, a normal subframe, a long subframe, a slot, etc. A TTI shorter than a normal TTI may be called a shortened TTI, a short TTI, a partial or fractional TTI, a shortened subframe, a short subframe, a minislot, a subslot, a slot, etc.

[0142] In addition, a long TTI (e.g., a normal TTI, a subframe, etc.) may be interpreted as a TTI having a time length exceeding 1 ms, and a short TTI (e.g., a shortened TTI, etc.) may be interpreted as a TTI having a TTI length shorter than the TTI length of a long TTI and equal to or greater than 1 ms.

[0143] A resource block (RB) is a resource allocation unit in the time domain and the frequency domain, and may include one or more consecutive subcarriers in the frequency domain. The number of subcarriers included in an RB may be the same regardless of the numerology, for example, 12. The number of subcarriers included in an RB may be determined based on the numerology.

[0144] In addition, the time domain of the RB may include one or more symbols and may be one slot, one minislot, one subframe, or one TTI in length. Each of one TTI, one subframe, etc. may be composed of one or more resource blocks.

[0145] One or more RBs may be called a physical resource block (PRB), a sub-carrier group (SCG), a resource element group (REG), a PRB pair, an RB pair, or the like.

[0146] Furthermore, a resource block may be composed of one or more resource elements (REs). For example, one RE may be a radio resource region of one subcarrier and one symbol.

[0147] A Bandwidth Part (BWP), which may also be referred to as a fractional bandwidth, may represent a subset of contiguous common resource blocks (RBs) for a numerology on a carrier, where the common RBs may be identified by the index of the RBs relative to a common reference point of the carrier. PRBs may be defined in a BWP and numbered within the BWP.

[0148] The BWP may include a BWP for UL (UL BWP) and a BWP for DL ​​(DL BWP). One or more BWPs may be configured for a UE within one carrier.

[0149] At least one of the configured BWPs may be active, and the UE may not expect to transmit or receive a given signal / channel outside the active BWP. Note that the terms "cell", "carrier", etc. in this disclosure may be replaced with "BWP".

[0150] The above-mentioned structures of radio frames, subframes, slots, minislots, symbols, etc. are merely examples. For example, the number of subframes included in a radio frame, the number of slots per subframe or radio frame, the number of minislots included in a slot, the number of symbols and RBs included in a slot or minislot, the number of subcarriers included in an RB, the number of symbols in a TTI, the symbol length, the cyclic prefix (CP) length, etc. may be changed in various ways.

[0151] The terms "connected," "coupled," or any variation thereof, refer to any direct or indirect connection or coupling between two or more elements, and may include the presence of one or more intermediate elements between two elements that are "connected" or "coupled" to each other. The coupling or connection between elements may be physical, logical, or a combination thereof. For example, "connected" may be read as "access." As used in this disclosure, two elements may be considered to be "connected" or "coupled" to each other using at least one of one or more wires, cables, and printed electrical connections, as well as electromagnetic energy having wavelengths in the radio frequency range, microwave range, and optical (both visible and invisible) range, as some non-limiting and non-exhaustive examples.

[0152] The reference signal may also be abbreviated as Reference Signal (RS), and may be called a pilot depending on the applicable standard.

[0153] As used in this disclosure, the phrase "based on" does not mean "based only on," unless expressly stated otherwise. In other words, the phrase "based on" means both "based only on" and "based at least on."

[0154] The "means" in the configuration of each of the above devices may be replaced with "part," "circuit," "device," etc.

[0155] Any reference to an element using a designation such as "first," "second," etc., used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used in this disclosure as a convenient way to distinguish between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed therein or that the first element must precede the second element in some way.

[0156] When the terms "include," "including," and variations thereof are used in this disclosure, these terms are intended to be inclusive, as is the term "comprising." Further, as used in this disclosure, the term "or" is not intended to be an exclusive or.

[0157] In this disclosure, where articles have been added due to translation, such as a, an, and the in English, the disclosure may include that the nouns following these articles are in the plural form.

[0158] As used in this disclosure, the terms "determining" and "determining" may encompass a wide variety of actions. "Determining" and "determining" may include, for example, judging, calculating, computing, processing, deriving, investigating, looking up, search, inquiry (e.g., searching in a table, database, or other data structure), ascertaining, and the like. "Determining" and "determining" may also include receiving (e.g., receiving information), transmitting (e.g., sending information), input, output, accessing (e.g., accessing data in a memory), and the like. In addition, "judgment" and "decision" can include considering resolving, selecting, choosing, establishing, comparing, etc., to be a "judgment" or "decision." In other words, "judgment" and "decision" can include considering some action to be a "judgment" or "decision." In addition, "judgment" can be interpreted as "assuming," "expecting," "considering," etc.

[0159] In the present disclosure, the term "A and B are different" may mean "A and B are different from each other." The term may also mean "A and B are each different from C." Terms such as "separate" and "coupled" may also be interpreted in the same way as "different."

[0160] Although the present disclosure has been described in detail above, it is clear to those skilled in the art that the present disclosure is not limited to the embodiments described in the present disclosure. The present disclosure can be implemented in modified and altered forms without departing from the spirit and scope of the present disclosure as defined by the claims. Therefore, the description of the present disclosure is intended to be illustrative and does not have any limiting meaning on the present disclosure. [Explanation of symbols]

[0161] 10. Wireless communication systems 20 E-UTRAN 30 NGRAN 40 Core Network 50 E-SMLC 100A eNB 100B gNB 200UE 210 Radio signal transmitter / receiver 220 Amplifier section 230 Modulation and demodulation section 240 Control signal / reference signal processing unit 250 Encoding / Decoding Unit 260 Data transmission and reception unit 270 Control Unit 300 MN 400SN 500 UPF 1001 Processor 1002 Memory 1003 Storage 1004 Communication equipment 1005 Input Device 1006 Output device 1007 Bus

Claims

1. A control unit that adds a cell to the second cell group based on conditional reconfiguration in dual connectivity using a first cell group and a second cell group; A transmitter that transmits a message including failure information of the second cell group to a network when a connection to a target cell to be added to the second cell group fails in the conditional reconfiguration, The message includes an information element regarding the target cell to which connection failed in the conditional reconfiguration and which is to be added to the second cell group.

2. The terminal of claim 1 , wherein the message includes an information element related to a random access procedure to the target cell.

3. In dual connectivity using a first cell group and a second cell group, a control unit that instructs addition of a cell to the second cell group based on conditional reconfiguration; A receiving unit that receives, when a connection to a target cell to be added to the second cell group fails in the conditional reconfiguration, a message including failure information of the second cell group from a terminal; The message includes information elements regarding the target cell to which connection failed in the conditional reconfiguration and which is to be added to the second cell group, the base station.

4. A terminal and a base station, The base station instructs, in dual connectivity using a first cell group and a second cell group, to add a cell to the second cell group based on conditional reconfiguration; When the terminal fails to connect to a target cell to be added to the second cell group in the conditional reconfiguration, the terminal transmits a message including failure information of the second cell group to a network; A wireless communication system, wherein the message includes information elements regarding the target cell to which connection failed in the conditional reconfiguration and which is to be added to the second cell group.

5. In dual connectivity using a first cell group and a second cell group, a step of adding a cell to the second cell group based on conditional reconfiguration; When a connection to a target cell to be added to the second cell group fails in the conditional reconfiguration, transmitting a message including failure information of the second cell group to a network; A wireless communication method, wherein the message includes an information element regarding the target cell to which connection failed in the conditional reconfiguration and which is to be added to the second cell group.

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