Terminal and wireless communication system

Abstract

UE 200 transmits a report about a handover to a target base station. The UE 200 transmits the report when measurement settings have been received, when handover conditions have been satisfied, when a measurement report has been transmitted, or when handover instructions have been received.

Description

[Technical Field]

[0001] The present invention relates to a terminal and a wireless communication system for transmitting a report regarding a handover. [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] For example, extensions to data collection for Self-Organizing Networks (SON) and Minimization of Drive Tests (MDT) are being considered (Non-Patent Document 1).

[0004] Such an extension study includes reports on handover (specifically, Successful Handover Reports) that a terminal (User Equipment, UE) sends to a radio base station to which the terminal is to handover (which may also be called a target base station, target cell, etc.), and then sends them to a radio base station from which the terminal is to handover (which may also be called a source base station, source cell, etc.). [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] "Revised WID on enhancement of data collection for SON / MDT in NR and EN-DC", RP-201281, 3GPP TSG RAN meeting #88-e, 3GPP, July 2020 Summary of the Invention

[0006] However, the content, timing and conditions of Successful Handover Reports have not been clarified, and there is a need for effective transmission of reports on handovers such as Successful Handover Reports.

[0007] The following disclosure has been made in light of the above circumstances, and aims to provide a terminal and a wireless communication system that can realize effective transmission of reports related to handover.

[0008] One aspect of the present disclosure is a terminal (UE200) that includes a transmitter (handover reporting unit 230) that transmits a report regarding handover to a target base station, the transmitter transmitting the report including at least one of an identifier of a cell to which handover is to be performed, settings regarding monitoring of a radio link at a source base station, a result of the monitoring, and settings regarding handover.

[0009] One aspect of the present disclosure is a terminal (UE200) that includes a transmitter (handover reporting unit 230) that transmits a report regarding handover to a target base station, and the transmitter transmits the report when it receives a configuration regarding measurement, satisfies a handover condition, transmits a measurement report, or receives a handover instruction.

[0010] One aspect of the present disclosure is a terminal (UE200) that includes a transmitter (handover reporting unit 230) that transmits a report regarding handover to a target base station, and the transmitter transmits the report when the result of monitoring a radio link, the operation status of a timer, or the radio quality during handover exceeds a specific threshold. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing the overall schematic configuration of a wireless communication system 10. As shown in FIG. [Figure 2] FIG. 2 is a functional block diagram of the UE 200. [Figure 3] Figure 3 is a functional block diagram of gNB100B. [Figure 4] FIG. 4 is a diagram showing an example of a sequence of reports regarding handovers (Successful Handovers Reports). [Figure 5A] FIG. 5A is an example (part 1) of the contents of a Successful Handover Report. [Figure 5B] FIG. 5B is an example (part 2) of the contents of a Successful Handover Report. [Figure 5C] FIG. 5C is an example (part 3) of the contents of a Successful Handover Report. [Figure 6] FIG. 6 is a diagram showing a compilation operation flow of the successful handover report by the UE 200. [Figure 7] FIG. 7 is a diagram showing a flow of an operation of the UE 200 to transmit a Successful Handover Report. [Figure 8] FIG. 8 is an example of a Successful handover report that may be additionally included in the case of a MN / SN initiated PSCell change. [Figure 9] FIG. 9 is a diagram showing an example of the hardware configuration of gNB100A, gNB100B, and UE200. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments 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 descriptions thereof will be omitted as appropriate.

[0013] (1) Overall configuration of wireless communication system 1 is a schematic diagram of the overall configuration of a wireless communication system 10 according to this embodiment. The wireless communication system 10 is a wireless communication system conforming to 5G New Radio (NR), and includes a Next Generation-Radio Access Network 20 (hereinafter, NG-RAN 20) and a user equipment 200 (hereinafter, UE 200).

[0014] The wireless communication system 10 may be a wireless communication system conforming to a system called Beyond 5G, 5G Evolution, or 6G.

[0015] The NG-RAN 20 includes a radio base station 100A (hereinafter, gNB100A) and a radio base station 100B (hereinafter, gNB100B). Note that the specific configuration of the radio communication system 10, including the number of gNBs and UEs, is not limited to the example shown in FIG. 1.

[0016] The NG-RAN 20 actually includes multiple NG-RAN nodes and is connected to a 5G-compliant core network (5GC, not shown). The NG-RAN 20 and the 5GC may be simply referred to as a "network."

[0017] The gNB100A and the gNB100B are radio base stations (which may simply be referred to as base stations) that comply with NR, and perform radio communication that complies with NR with the UE 200. The gNB100A, the gNB100B, and the UE 200 are capable of supporting Massive MIMO, which generates a more directional beam by controlling radio signals transmitted from multiple antenna elements, Carrier Aggregation (CA), which aggregates and uses multiple component carriers (CCs), and Dual Connectivity (DC), which simultaneously communicates between the UE and each of multiple NG-RAN nodes.

[0018] gNB100A, gNB100B and UE200 perform wireless communication via a radio bearer, specifically, an SRB Signalling Radio Bearer (SRB) or a DRB Data Radio Bearer (DRB).

[0019] Furthermore, UE200 can perform handover from gNB100A to gNB100B (or from gNB100B to gNB100A). Handover may be interpreted as a change or addition of a base station or cell accessed by the UE. Handover may also be referred to as cell reselection, cell transition, etc. Furthermore, handover, in a broad sense, may include the addition or change of a cell (primary cell (PCell) or secondary cell (PSCell, SCell)) included in a cell group (e.g., a master cell group (MCG) or a secondary cell group (SCG)).

[0020] Furthermore, the UE 200 can transmit a report regarding the handover to the radio base station. Specifically, the UE 200 can transmit a report regarding a successful handover (which may be called, for example, a Successful Handovers Report) to a radio base station of a handover destination (target base station). Note that the UE 200 may transmit the report regarding the handover to a radio base station of a handover source (source base station) or a network.

[0021] Furthermore, Successful Handovers Reports may be expressed in the singular, such as Successful handover Report, or may be called by another name, for example, simply handover report, and may not be limited to successful handovers.

[0022] (2) Functional block configuration of wireless communication system Next, a description will be given of the functional block configuration of the wireless communication system 10. Specifically, the functional block configurations of the gNB100B and the UE200 will be described.

[0023] (2.1)UE200 2 is a functional block diagram of the UE 200. As shown in FIG. 2, the UE 200 includes a radio communication unit 210, a measurement reporting unit 220, a handover reporting unit 230, and a control unit 240.

[0024] The wireless communication unit 210 transmits and receives wireless signals in accordance with NR. Specifically, the wireless communication unit 210 transmits uplink signals (UL signals) in accordance with NR and receives downlink signals (DL signals) in accordance with NR.

[0025] The wireless communication unit 210 supports Massive MIMO, CA that uses a bundle of multiple CCs, and DC that simultaneously communicates between the UE and each of two NG-RAN nodes.

[0026] The measurement reporting unit 220 can perform measurements on the quality of UL signals and DL signals transmitted and received by the UE 200 and report the results of the measurements.

[0027] In particular, in this embodiment, the measurement reporting unit 220 can obtain measurements based on a Minimization of Drive Test (MDT) that collects Quality of Experience (QoE) (that is, may be called QoE collection) by notifying the network of events related to Quality of Experience (QoE) (for example, wireless disconnection during communication, success or failure of handover, etc.), as well as the quality related to the random access channel (RACH), the result of a random access procedure, etc. The report may be called a Measurement Report.

[0028] The MDT includes logged MDT measurement performed by the UE 200 in an idle state in the radio resource control layer (RRC) and immediate MDT performed by the UE 200 in a connected state, but in this embodiment, logged MDT measurement may be assumed. However, immediate MDT may also be the target.

[0029] Furthermore, measurement reporting section 220 may measure the radio communication quality (reception quality) in the cell in which UE 200 is located (standby) and in neighboring cells, and report the measurement results.

[0030] The handover reporting unit 230 performs a report regarding the handover of the UE 200. Specifically, the handover reporting unit 230 can transmit a report regarding the handover to a target base station such as the gNB 100B. In this embodiment, the handover reporting unit 230 configures a transmission unit.

[0031] The handover reporting unit 230 can transmit the report including at least one of the identifier (cell ID) of the cell to which the handover is made, the settings related to monitoring of the radio link in the source base station, the results of monitoring the radio link, and the settings related to the handover.

[0032] The identifier (cell ID) of the cell to which handover is to be performed may be referred to as the target cell ID.

[0033] The settings related to monitoring of the radio link in the source base station may include a reference signal (RS) for monitoring the radio link, information related to beam failure recovery, loss of synchronization, and synchronization establishment, and the results of the monitoring.

[0034] The handover-related settings may include information about various timers (e.g., T304, T312 (details will be described later)), wireless communication quality (e.g., Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), Signal-to-Interference plus Noise power Ratio (SINR)), and location information of UE200.

[0035] Furthermore, the settings related to handover may include the contents of conditional handover (CHO) and handover using dual active protocol stack (DAPS).

[0036] The details of each item will be described later.

[0037] The handover reporting unit 230 may include such a report on the handover (Successful Handovers Reports) in a message transmitted from the UE 200 to the target base station. For example, the report may be included in a UEInformationResponse.

[0038] As described above, the report may be transmitted to the source base station or the network, and the source base station may relay the report to the target base station upon receiving the report.

[0039] The report regarding the handover may be included in a Measurement Report sent to the source base station or in another message (eg, RRC Reconfiguration Complete) sent to the target base station.

[0040] The handover reporting unit 230 may send a report regarding handover as described above when it receives a measurement related configuration, meets a handover condition, sends a measurement report, or receives a handover instruction.

[0041] The measurement-related settings may refer to measConfig defined in 3GPP TS38.331 etc. However, they are not necessarily limited to measConfig and may also be settings related to MDT.

[0042] The handover condition may be, for example, a condition specified in 3GPP TS38.331 Chapter 5.5.4 (which may also be called a handover trigger condition), but may also be any other condition that can trigger a handover.

[0043] The transmission of a measurement report may mean, for example, the transmission of a Measurement Report, but may also include any measurement at the UE 200, such as the transmission of the results of an MDT.

[0044] Furthermore, the reception of a handover instruction may mean the reception of a Handover command, but may also include any other instruction that directly or indirectly triggers the start of a handover.

[0045] The handover reporting unit 230 may transmit a report regarding handover if the result of monitoring the radio link, the operation status of various timers, or the radio quality during handover exceeds a specific threshold.

[0046] The result of monitoring the radio link may include the radio link between the source base station or the target base station and the UE 200. The result of monitoring the radio link may include the result of monitoring the beam (such as beam obstruction).

[0047] As mentioned above, the various timers may include T304 and T312 (details will be described later).

[0048] The radio quality during handover may include RSRP, RSRQ, and SINR. The thresholds may be predefined in the UE 200 or may be set by an instruction from the network.

[0049] The control unit 240 controls each functional block constituting the UE 200. In particular, in this embodiment, the control unit 240 executes control relating to handover of the UE 200.

[0050] Specifically, the control unit 240 determines whether a handover is necessary based on the measurement result by the measurement reporting unit 220, and executes the handover if the handover conditions are met.

[0051] Furthermore, when a handover is executed, the control unit 240 controls the handover reporting unit 230 to transmit a report regarding the handover to the radio base station. Specifically, the control unit 240 can control the contents of the report, the timing of the report, the conditions for the report, etc.

[0052] In this embodiment, 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 PRACH (Physical Random Access Channel), and a PBCH (Physical Broadcast Channel).

[0053] The data channels include a physical downlink shared channel (PDSCH) and a physical uplink shared channel (PUSCH).

[0054] The reference signal includes a Demodulation Reference Signal (DMRS), a Sounding Reference Signal (SRS), a Phase Tracking Reference Signal (PTRS), and a Channel State Information-Reference Signal (CSI-RS), and the signal includes a channel and a reference signal. Furthermore, the data may refer to data transmitted via a data channel.

[0055] (2.2) gNB100B Figure 3 is a functional block configuration diagram of gNB100B. As shown in Figure 3, gNB100B includes a radio communication unit 110, a handover report processing unit 120, and a control unit 130. Note that gNB100A may also have a functional block configuration similar to that of gNB100B. Here, an example will be described in which gNB100B is the target base station for handover.

[0056] The wireless communication unit 110 transmits and receives wireless signals conforming to NR. Specifically, the wireless communication unit 110 receives uplink signals (UL signals) conforming to NR and transmits downlink signals (DL signals) conforming to NR.

[0057] The handover report processing unit 120 executes processing for reporting regarding the handover of the UE 200. Specifically, the handover report processing unit 120 acquires the content of the report transmitted from the UE 200.

[0058] More specifically, the handover report processing unit 120 can request a report regarding handover from the UE 200. For example, the request may be included in a UEInformationRequest, which is a message of the RRC layer, transmitted to the UE 200. Note that the handover report processing unit 120 may transmit the request when notified by the UE 200 that a report regarding handover can be provided.

[0059] The notification that the UE 200 can provide a report regarding handover may be included in, for example, RRC Reconfiguration Complete.

[0060] The handover report processing unit 120 can acquire a report on handover (Successful Handovers Reports) included in a message of the RRC layer, for example, UEInformationResponse (or RRC Reconfiguration Complete).

[0061] The handover report processing unit 120 may transmit (which may be expressed as relaying, forwarding, or providing) the report to the source base station (gNB100A) based on control by the control unit 130. The content of the report transmitted to the source base station may be a part or all of the content received from the UE200.

[0062] The control unit 130 controls each functional block constituting the gNB100B. In particular, in this embodiment, the control unit 130 cooperates with the gNB100A (source base station) to execute control related to handover of the UE200.

[0063] Specifically, the control unit 130 receives a handover request from the source base station, and if the handover is possible, returns an acknowledgment (Handover request Ack.).

[0064] In addition, the control unit 130 can execute a random access (RA) procedure with the UE 200 and transmit a report regarding handover obtained from the UE 200 to the source base station.

[0065] (3) Operation of the wireless communication system Next, a description will be given of the operation of the wireless communication system 10. Specifically, a description will be given of a reporting operation regarding handover for the purpose of Self-Organizing Networks (SON) / Minimization of Drive Tests (MDT).

[0066] 3GPP Release-17 considers enhancements to data collection for SON / MDT, including support for data collection for SON, including Coverage and Capacity Optimization (CCO), and Successful Handover Reports.

[0067] (3.1) Example of a sequence for reporting handover FIG. 4 shows an example of a sequence of reports on handovers (Successful Handovers Reports).

[0068] Specifically, Figure 4 shows the reporting sequence of Successful Handovers Reports when UE200 performs a handover from gNB100A (source base station) to gNB100B (target base station).

[0069] As shown in Figure 4, after performing a random access procedure via RACH with gNB100B, UE200 can include information indicating that a Successful handover Report is available (Successful handover Report available) in RRC Reconfiguration Complete (step 6).

[0070] Based on the information (Successful handover Report available), gNB100B can include a Successful handover Report request in the UEInformationRequest requesting the transmission of a Successful handover Report (step 7).

[0071] Based on the request (Successful handover Report request), UE 200 can include a Successful handover Report in UEInformationResponse (step 8).

[0072] gNB100B may transmit some or all of the received Successful Handover Report to gNB100A (step 9).

[0073] (3.2) Example of operation Next, an example of the operation of the UE 200 regarding the Successful handover Report will be described. Specifically, the following example of the operation will be described.

[0074] (Example 1): Contents of the Successful handover Report (Example 2): Timing for starting compilation of Successful handover Report (Example 3): Successful handover report trigger

[0075] (3.2.1) Example 1 The Successful Handover Report may include at least one of the following contents: Figures 5A, 5B, and 5C show examples of the contents of the Successful Handover Report.

[0076] Target Cell ID - Monitoring settings and results of wireless links on the source base station side 1. Radio Link Monitoring Reference Signal (radioLinkMonitoringRS) - Synchronization signal block (SSB (SS / PBCH Block) index (SSB index) - CSI-RS index 2. Beam Failure Detection History (BeamFailureDetectionHistory) - Beam Failure Instance MaxCount - BeamFailureDetectionTimer - Number of failure detections (NumberOfFailureDetections) (BFI_COUNTER): Number of beam failures counted per failure detection 3. Beam Failure Recovery History - Beam failure recovery configuration (beamFailureRecoveryConfig (see 3GPP TS38.331)) The information element (IE) BeamFailureRecoveryConfig may be used to configure the UE 200 with RACH resources and candidate beams for beam failure recovery in case of a beam failure being detected (see also 3GPP TS 38.321 chapter 5.1.1).

[0077] - Number of beam failure recoveries (NumberOfFailureRecovery) Number of successful beam failure recovery procedures 4. Out-of-Sync-History - Threshold (Q_out threshold) - Count Number (CountNumberOfN310) - The timer T310 elapsed for each radio failure detection (N310 reach the max value) N310 may be reset when an "in sync" indication is received from the lower layers, when an RRCReconfiguration with reconfigurationWithSync for the cell group is received, or at the start of the connection re-establishment procedure, and may be incremented when an "out of sync (unsynchronized)" indication is received from the lower layers while timer T310 is stopped, and if it reaches its maximum value, timer T310 may be started.

[0078] T310 is started when a physical layer problem of a Special Cell (SpCell) is detected, i.e., when consecutive synchronization indications of N310 are received from the lower layers, and may be stopped when consecutive synchronization indications of N311 are received from the lower layers of the SpCell, when RRCReconfiguration is received with reconfigurationWithSync for the cell group, when MobilityFromNRCommand is received, when rlf-TimersAndConstant is reconfigured, when a connection re-establishment procedure is started, when an MCG fault information procedure is started, and when an SCG is released.

[0079] 5. In-sync-History - Threshold (Q_in threshold) - Count Number (CountNumberOfN311) N311 may be reset when an "out of sync" indication is received from lower layers, when an RRCReconfiguration is received with reconfigurationWithSync for the cell group in question, or at the start of the connection re-establishment procedure, and may be increased when an "in-sync" is received from lower layers while timer T310 is running, and may stop timer T310 if it reaches its maximum value.

[0080] ·Handover related configuration 1.T304 elapsed time (T304 elapsed for the handover) Timer T304 may be started upon receiving an RRCReconfiguration message containing reconfigurationWithSync or upon performing a conditional reconfiguration, i.e., applying a stored RRCReconfiguration message containing reconfigurationWithSync, and may be stopped upon successful completion of random access in the corresponding SpCell.

[0081] 2.eventTriggerConfg - Event ID, trigger threshold, trigger offset, hysteresis, timeToTrigger. 3.measTriggerRSType - SSB - CSI-RS 4. Timer T312 setting (T312 configured or not) - T312 elapsed time (If configured, T312 elapsed for each measurement report while T310 is running before receiving RRC Reconfiguration) T312 is initiated if T312 is configured in the MCG and triggers a measurement report for a measurement ID with "useT312" set to true during the execution of T310 on the PCell; If T312 is configured in the SCG and "useT312" is set to true, it may be started if T312 triggers a measurement report for the configured measurement ID during the execution of T310 of the PSCell.

[0082] In addition, T312 may be stopped when an N311 continuous synchronization indication is received from the lower layer of the SpCell, when an RRCReconfiguration is received with reconfigurationWithSync for the cell group and a connection re-establishment procedure is initiated, when rlf-TimersAndConstant is reconfigured, when an MCG fault information procedure is initiated, and when T310 expires in the corresponding SpCell.

[0083] 5. The radio quality (RSRP / RSRQ / SINR) of the source cell when the measurement report is triggered / sent 6. Radio quality of the source cell when the handover command is received (The radio quality (RSRP / RSRQ / SINR) of the source when the handover command is received before conducting RACH with the target cell) 7. Radio quality of source cell when RA procedure is executed (The radio quality (RSRP / RSRQ / SINR) of source when UE is going to do RACH with target cell (Just before RACH execution)) 8. Radio quality of target cell after RA procedure execution (The radio quality (RSRP / RSRQ / SINR) of target cell when UE successfully performed RACH with target cell. (Just after RACH execution)) The wireless quality may be recorded when it falls below a certain threshold, which may be set in advance by the network.

[0084] 9. Common Location Information - GNSS / WLAN / BT(Bluetooth) / LocationInfo -Sensor-LocationInfo Conditional handover related configuration (the following may be added to the contents shown in Figures 5A, 5B, and 5C) 1.eventTriggerConfig - condExecutionCond - Candidate target cell ID 2. The radio quality (RSRP / RSRQ / SINR) of the source cell when the measurement report is triggered / sent 3. Radio quality of the source cell when the conditional handover command is received (The radio quality (RSRP / RSRQ / SINR) of the source cell when the conditional handover command (ConditionalReconfiguration) is received before the conditional handover execution condition is satisfied) 4. Radio quality of source cell when handover condition is satisfied (The radio quality (RSRP / RSRQ / SINR) of source cell when the execution handover execution condition is satisfied before conducting RACH with target cell) 5. Radio quality of target cell when RA procedure is executed (The radio quality (RSRP / RSRQ / SINR) of target cell when the RACH towards target cell succeeded) The wireless quality may be recorded when it falls below a certain threshold, which may be set in advance by the network.

[0085] DAPS handover related configuration (the following may be added to the contents shown in Figures 5A, 5B, and 5C) 1. The radio quality (RSRP / RSRQ / SINR) of the source cell when the measurement report is triggered / sent 2. The radio quality (RSRP / RSRQ / SINR) of the source cell when the handover command is received before performing RACH towards the target cell 3. Radio quality (RSRP / RSRQ / SINR) of source and target cells while performing RACH towards target cell 4. Radio quality of source and target cells during and after RA procedure (The radio quality (RSRP / RSRQ / SINR) of source and target cells when / after RACH towards target cell succeeded) 5. Radio quality (RSRP / RSRQ / SINR) of source and target cells when UE detaches from source cell The wireless quality may be recorded when it falls below a certain threshold, which may be set in advance by the network.

[0086] (3.2.2) Example 2 Fig. 6 shows a flow of the compilation operation of the Successful Handover Report by the UE 200. As shown in Fig. 6, the UE 200 determines whether or not the compilation conditions for the Successful Handover Report are satisfied (S10).

[0087] Note that compiling may be interpreted as generating, transmitting, and collecting the contents of a Successful Handover Report, or more broadly, as reporting a Successful Handover Report.

[0088] The UE 200 may start compiling a Successful Handover Report when any of the following compilation conditions is satisfied (S20).

[0089] When the UE receives measCondfig from the network When the UE's handover trigger condition is satisfied The handover trigger condition is specified as follows in 3GPP TS38.331, Chapter 5.5.4:

[0090] "if the reportType is set to eventTriggered and if the entry condition applicable for this event, ie the event corresponding with the eventId of the corresponding reportConfig within VarMeasConfig, is fulfilled for one or more applicable cells for all measurements after layer 3 filtering taken during timeToTrigger defined for this event within the VarMeasConfig." When the UE starts compiling a Measurement Report When the UE sends a Measurement Report When the UE receives a Handover command The timing at which the UE 200 actually starts compiling the Successful Handover Report does not necessarily have to be the same as the above-mentioned timing, and a certain degree of delay may be allowed.

[0091] (3.2.3) Example 3 Fig. 7 shows an operational flow of transmitting a Successful Handover Report by the UE 200. As shown in Fig. 7, the UE 200 determines whether or not a trigger condition for transmitting a Successful Handover Report is satisfied (S110).

[0092] The trigger for transmitting a Successful handover report may be interpreted as a trigger for determining whether to transmit a Successful handover report available or whether to transmit the Successful handover report itself.

[0093] The UE 200 may transmit a Successful handover Report when any of the trigger conditions shown below is satisfied (S120). As described above, the RRC Reconfiguration Complete may include a Successful handover Report available, and the UEInformationResponse may include a Successful handover Report, but the Successful handover Report available may also include a Successful handover Report.

[0094] - When the NumberOfFailureDetections (BFI_COUNTER: beamFailureIndication count) exceeds a certain threshold in the wireless link monitoring results. Note that BFI_COUNTER is defined in 3GPP TS 38.321 Chapter 5.17, is provided for each serving cell, and counts the number of detected beam failures.

[0095] - When the NumberOfFailureRecovery (number of successful Beam failure recovery procedures) exceeds a certain threshold in the wireless link monitoring results. - Regarding Out-Of-Sync, when CountNumberOfN310 (N310 count number) exceeds a certain threshold When the T304 elapsed time (the time from receiving RRC Reconfiguration to successful RACH with the target cell) exceeds a certain threshold When a T312 measurement (running) occurs or when the elapsed time of the T312 exceeds a certain threshold - If the radio quality (RSRP / RSRQ / SINR of the source or target cell) falls below a certain threshold during handover The threshold may be set in advance from the network.

[0096] (4) Actions and Effects According to the above-described embodiment, the following advantageous effects can be obtained: Specifically, the UE 200 can transmit a report regarding handover, specifically, a Successful Handover Report, to the target base station, and the Successful Handover Report may include at least one of an identifier of a cell at the handover destination, a setting regarding monitoring of a radio link in the source base station, a result of the monitoring, and a setting regarding handover.

[0097] Therefore, the UE 200 can include events such as failures experienced during the handover process in a Successful Handover Report, which is ultimately fed back to the source base station, thereby enabling the UE 200 to effectively transmit a report regarding the handover.

[0098] Furthermore, the source base station can be expected to improve mobility robustness by adjusting the mobility and radio link setting parameters of the UE 200.

[0099] In this embodiment, the UE 200 can send a Successful Handover Report when it receives a measurement-related configuration, satisfies a handover condition, sends a measurement report, or receives a handover instruction, thereby providing the Successful Handover Report to the network at an appropriate time, which can improve mobility robustness.

[0100] Furthermore, the UE 200 can transmit a Successful Handover Report when the operation status of the timer or the radio quality during handover exceeds a specific threshold as a result of monitoring the radio link, thereby enabling the UE 200 to maintain a good radio communication state.

[0101] (5) Other embodiments The present invention has been described above with reference to the examples, but it will be obvious to those skilled in the art that the present invention is not limited to these examples and that various modifications and improvements are possible.

[0102] For example, the content of the Successful handover report described above may be applied to the MN / SN initiated PSCell addition / change. Specifically, the examples of the content of the Successful handover report shown in Figures 5A, 5B, and 5C may be applied to the MN / SN initiated PSCell addition / change.

[0103] In addition, in the case of an SN initiated PSCell change, the UE 200 may transmit a Successful handover Report to the master node (MN) using a ULInformationTransferMRDC message, and the MN may transmit the Successful handover Report to the secondary node (SN) using an RRC Transfer.

[0104] Furthermore, in the case of an MN / SN initiated PSCell change, in addition to the contents of the Successful Handover Report shown in Figures 5A, 5B, and 5C, the following contents may be included in the Successful Handover Report: Figure 8 is an example of a Successful Handover Report that may be additionally included in the case of an MN / SN initiated PSCell change.

[0105] Monitoring settings and results of wireless links on the source base station side of both MCG and SCG The radio quality (RSRP / RSRQ / SINR) of source PCell and source PSCell when a measurement report is triggered / sent Radio quality of source PCell / source PSCell when RRC Reconfiguration is received (The radio quality (RSRP / RSRQ / SINR) of source PCell and source PSCell when RRC Reconfiguration Msg. is received before conducting RACH with target PSCell) Radio quality of source PCell / source PSCell when RA procedure is executed (The radio quality (RSRP / RSRQ / SINR) of source PCell and source PSCell when UE is going to do RACH with target PSCell. (Just before RACH execution)) Radio quality of source PCell / target PSCell after RA procedure execution (The radio quality (RSRP / RSRQ / SINR) of source PCell and target PSCell when UE successfully performed RACH with target PSCell. (Just after RACH execution)) The wireless quality may be recorded when it falls below a certain threshold, which may be set in advance by the network.

[0106] As described above, the Successful handover Report and the Successful Handovers Reports may be called by other names as long as the reports include information related to the handover of the UE 200.

[0107] Furthermore, the block diagrams (FIGS. 2 and 3) used in the description of the above-described embodiments show 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 using a single device that is physically or logically coupled, or may be realized using two or more physically or logically separated devices that are connected directly or indirectly (for example, by wire, wirelessly, etc.) and these multiple devices. The functional block may also be realized by combining the single device or multiple devices with software.

[0108] Functions include, but are not limited to, judgment, determination, judgment, calculation, computation, processing, derivation, investigation, search, confirmation, reception, transmission, output, access, resolution, selection, election, establishment, comparison, assumption, expectation, consideration, broadcasting, notifying, communicating, forwarding, configuring, reconfiguring, allocating, mapping, and assignment. For example, a functional block (component) that performs transmission is called a transmitting unit or transmitter. As mentioned above, there are no particular limitations on how each is implemented.

[0109] Furthermore, the above-described gNB100A, gNB100B, and UE200 (the devices) may function as a computer that performs processing of the wireless communication method of the present disclosure. Fig. 9 is a diagram showing an example of the hardware configuration of the devices. As shown in Fig. 9, the devices 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, a bus 1007, etc.

[0110] In the following description, the term "apparatus" can 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.

[0111] Each functional block of the device (see FIGS. 2 and 3) is realized by any hardware element of the computer device or a combination of the hardware elements.

[0112] In addition, each function of the device is realized by loading specified software (programs) onto hardware such as processor 1001 and memory 1002, causing processor 1001 to perform calculations, control communication via communication device 1004, and control at least one of reading and writing data in memory 1002 and storage 1003.

[0113] The processor 1001 controls the entire computer by running, for example, an operating system, and may be configured as a central processing unit (CPU) including an interface with peripheral devices, a control unit, an arithmetic unit, a register, and the like.

[0114] The processor 1001 also reads 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 in accordance with these. The programs used are those that cause a computer to execute at least some of the operations described in the above-mentioned embodiments. Furthermore, the various processes described above 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.

[0115] The memory 1002 is a computer-readable recording medium and may be configured by, for example, at least one of 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., that can execute a method according to an embodiment of the present disclosure.

[0116] Storage 1003 is a computer-readable recording medium, and may be, for example, at least one of 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 disc), a smart card, a flash memory (e.g., a card, a stick, a key drive), a floppy disk, a magnetic strip, etc. Storage 1003 may also be referred to as an auxiliary storage device. The above-mentioned recording medium may be, for example, a database, a server, or other appropriate medium including at least one of memory 1002 and storage 1003.

[0117] The communication device 1004 is hardware (transmission / reception device) for communicating 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.

[0118] The communication device 1004 may be configured to include a high-frequency switch, a duplexer, a filter, a frequency synthesizer, etc. to realize, for example, at least one of Frequency Division Duplex (FDD) and Time Division Duplex (TDD).

[0119] The input device 1005 is an input device (for example, a keyboard, a mouse, a microphone, a switch, a button, a sensor, etc.) that receives input from the outside. The output device 1006 is an output device (for example, a display, a speaker, an LED lamp, etc.) that outputs to the outside. The input device 1005 and the output device 1006 may be integrated into one device (for example, a touch panel).

[0120] Furthermore, 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.

[0121] 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), or a field programmable gate array (FPGA), 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.

[0122] 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 thereof. Furthermore, the RRC signaling may be referred to as an RRC message, and may be, for example, an RRC Connection Setup message, an RRC Connection Reconfiguration message, or the like.

[0123] 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, a 4th generation mobile communication system (4G), a 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), or other suitable system, and a next-generation system extended based on these. Furthermore, a combination of multiple systems (e.g., a combination of at least one of LTE and LTE-A and 5G) may also be applied.

[0124] The order of the procedures, sequences, flowcharts, etc. of each aspect / embodiment described in this disclosure may be changed unless it is consistent. 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.

[0125] In the present disclosure, a specific operation described as being performed by a base station may also 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 another network node other than the base station (for example, an MME or an S-GW, etc., but are not limited to these). Although the above example illustrates a case where there is one other network node other than the base station, a combination of multiple other network nodes (for example, an MME and an S-GW) may also be used.

[0126] Information, signals (information, etc.) may be output from a higher layer (or a lower layer) to a lower layer (or a higher layer), or may be input / output via multiple network nodes.

[0127] The input and output information may be stored in a specific location (for example, memory) or may be managed using a management table. The input and output information may be overwritten, updated, or added to. The output information may be deleted. The input information may be sent to another device.

[0128] The determination may be made based on a value represented by one bit (0 or 1), a Boolean value (true or false), or a numerical comparison (e.g., comparison with a predetermined value).

[0129] Each aspect / embodiment described in this disclosure may be used alone, in combination, or switched depending on the implementation. Furthermore, notification of predetermined information (e.g., notification that "X is true") is not limited to being done explicitly, but may be done implicitly (e.g., by not notifying the predetermined information).

[0130] 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.

[0131] Software, instructions, information, etc. may also be transmitted or received over a transmission medium. For example, if software is transmitted from a website, server, or other remote source using wired technologies (such as coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL)), and / or wireless technologies (such as infrared, microwave), then these wired and / or wireless technologies are included within the definition of transmission media.

[0132] The information, signals, etc. described in this disclosure may be represented using any of a variety of different technologies. For example, 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.

[0133] Note that terms explained in this disclosure and 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). Furthermore, a signal may be a message. Furthermore, a component carrier (CC) may be called a carrier frequency, a cell, a frequency carrier, etc.

[0134] As used in this disclosure, the terms "system" and "network" are used interchangeably.

[0135] Furthermore, the information, parameters, etc. described in the present disclosure may be expressed using absolute values, relative values ​​from a predetermined value, or other corresponding information. For example, a radio resource may be indicated by an index.

[0136] The names used for the above-described parameters are not intended to be limiting in any way. Furthermore, the mathematical expressions 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 intended to be limiting in any way.

[0137] 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," and "component carrier" may be used interchangeably. Base stations may also be referred to by terms such as macrocell, small cell, femtocell, and picocell.

[0138] A base station can accommodate one or more (e.g., three) cells (also called sectors). When a base station accommodates multiple cells, the overall coverage area of ​​the base station can be divided into multiple smaller areas, and each smaller area can be provided with communication services by a base station subsystem (e.g., a small indoor base station (Remote Radio Head: RRH)).

[0139] The terms "cell" or "sector" refer to part or all of the coverage area of ​​a base station and / or base station subsystem that provides communication services within that coverage area.

[0140] In this disclosure, the terms "Mobile Station (MS)," "user terminal," "User Equipment (UE)," "terminal," etc. may be used interchangeably.

[0141] 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.

[0142] 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 mobile object, or the mobile object itself. The mobile object may be a vehicle (e.g., a car, an airplane, etc.), an unmanned mobile object (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 also include devices that do not necessarily move during communication operations. 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.

[0143] Furthermore, a base station in the present disclosure may be read as a mobile station (user terminal, the same applies hereinafter). For example, the aspects / embodiments 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, terms such as uplink channel and downlink channel may be read as side channel.

[0144] 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.

[0145] A radio frame may consist of one or more frames in the time domain.

[0146] In the time domain, each of one or more frames may be referred to as a subframe.

[0147] A subframe may further be composed of one or more slots in the time domain, and may have a fixed time length (e.g., 1 ms) that is independent of numerology.

[0148] Numerology may be a communication parameter applied to at least one of transmission and reception of a signal or channel, such as subcarrier spacing (SCS), bandwidth, symbol length, cyclic prefix length, transmission time interval (TTI), number of symbols per TTI, radio frame structure, specific filtering operations performed by a transceiver in the frequency domain, and specific windowing operations performed by a transceiver in the time domain.

[0149] 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 time unit.

[0150] A slot may include multiple minislots. Each minislot may consist of one or more symbols in the time domain. A minislot may also be called a subslot. A minislot may consist 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.

[0151] The radio frame, subframe, slot, minislot, and symbol all represent time units for transmitting signals, and may be referred to by other names corresponding to the radio frame, subframe, slot, minislot, and symbol.

[0152] 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 existing LTE, a period shorter than 1 ms (e.g., 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.

[0153] Here, TTI refers to, for example, the smallest 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. However, the definition of TTI is not limited to this.

[0154] 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) to which a transport block, a code block, a code word, etc. is actually mapped may be shorter than the TTI.

[0155] When one slot or one minislot is called a TTI, one or more TTIs (i.e., one or more slots or one or more minislots) may be the minimum time unit for scheduling. Also, the number of slots (minislots) constituting the minimum time unit for scheduling may be controlled.

[0156] A TTI having a time length of 1 ms may be called a regular TTI (TTI in LTE Rel. 8-12), normal TTI, long TTI, regular subframe, normal subframe, long subframe, slot, etc. A TTI shorter than a regular TTI may be called a shortened TTI, short TTI, partial or fractional TTI, shortened subframe, short subframe, minislot, subslot, slot, etc.

[0157] In addition, a long TTI (e.g., a normal TTI, a subframe, etc.) may be interpreted as a TTI having a time length of more than 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.

[0158] A resource block (RB) is a resource allocation unit in the time domain and frequency domain, and may include one or more consecutive subcarriers in the frequency domain.

[0159] The number of subcarriers included in an RB may be the same regardless of the numerology, and may be, for example, 12. The number of subcarriers included in an RB may also be determined based on the numerology.

[0160] The time domain of an RB may include one or more symbols and may be one slot, one minislot, one subframe, or one TTI in length. Each TTI, subframe, etc. may be composed of one or more resource blocks.

[0161] Note that one or more RBs may also 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.

[0162] 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.

[0163] 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 given numerology on a given carrier, where the common RBs may be identified by their index relative to a common reference point of the carrier. PRBs may be defined in a given BWP and numbered within that BWP.

[0164] 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.

[0165] 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 read as "BWP."

[0166] The above-described structures of the radio frame, subframe, slot, minislot, and symbol 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, and other configurations can be changed in various ways.

[0167] 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 one or more wires, cables, and / or 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.

[0168] The reference signal may also be abbreviated as Reference Signal (RS), and may also be called a pilot depending on the applicable standard.

[0169] 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."

[0170] The "means" in the configuration of each of the above devices may be replaced with "part," "circuit," "device," etc.

[0171] As used in this disclosure, any reference to an element using a designation such as "first," "second," etc. does not generally limit the quantity or order of those elements. These designations may be used in this disclosure as a convenient method of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed therein or that the first element must precede the second element in some way.

[0172] When used in this disclosure, the terms "include," "including," and variations thereof are intended to be inclusive, similar to the term "comprising." Furthermore, when used in this disclosure, the term "or" is not intended to be an exclusive or.

[0173] In this disclosure, where articles are added by translation, such as a, an, and the in English, the disclosure may include that the nouns following these articles are in the plural form.

[0174] 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, searching, inquiring (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 memory), and the like. Furthermore, "judgment" and "decision" can include regarding resolving, selecting, choosing, establishing, comparing, etc. as having been "judged" or "decided." In other words, "judgment" and "decision" can include regarding some action as having been "judged" or "decided." Furthermore, "judgment (decision)" can be interpreted as "assuming," "expecting," "considering," etc.

[0175] In the present disclosure, the term "A and B are different" may mean "A and B are different from each other." Note that 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."

[0176] 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 herein. 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]

[0177] 10. Wireless communication systems 20 NG-RAN 100A, 100B gNB 110 Radio Communication Department 120 Handover report processing unit 130 control section 200 UE 210 Radio Communication Department 220 Measurement report section 230 Handover Reporting Department 240 Control Unit 1001 processor 1002 memory 1003 Storage 1004 Communication equipment 1005 Input Device 1006 Output Device 1007 Bus

Claims

1. a transmitter for transmitting a report to the network regarding the successful handover; a control unit that controls the transmission unit to transmit the report including an identifier of a handover destination cell and location information of a terminal; The control unit causes the terminal to transmit the report when the elapsed time of the timer exceeds a threshold value set by the network, based on the threshold value relating to the elapsed time of the timer.

2. the transmitter transmits a message to the network including information indicating that a report regarding the successful handover is available; The terminal according to claim 1 , wherein the control unit controls the transmission unit to transmit the report based on a message including a request for transmission of the report regarding the successful handover received from the network.

3. A wireless communication system including a terminal and a wireless base station, The terminal a transmitter for transmitting a report about a successful handover to the radio base station; a control unit that controls the transmission unit to transmit the report including an identifier of a handover destination cell and location information of a terminal; the control unit causes the radio base station to transmit the report when the elapsed time of the timer exceeds a threshold value set by the radio base station, The wireless communication system includes a receiving unit for receiving the report, wherein the wireless base station includes a receiving unit for receiving the report.

4. sending a report to the network regarding the successful handover; a step of controlling the transmission of the report including an identifier of a handover destination cell and location information of the terminal; A communication method for a terminal, comprising: a step of causing the terminal to transmit the report when the elapsed time of the timer exceeds a threshold set by the network, based on the threshold relating to the elapsed time of the timer.

Images