CN114009137A - Terminal device - Google Patents

Abstract

The terminal (UE) migrates to the target radio base station (gNB) without using the reconnection procedure. When the terminal migrates to the target radio base station due to a radio link failure, the terminal starts a random access procedure with the target radio base station at a predetermined timing.

Description

terminal

technical field

The present invention relates to a terminal performing wireless communication, and more particularly, to a terminal that migrates to a target wireless base station without using a reconnection procedure.

Background technique

Long Term Evolution (LTE) is standardized in the 3rd Generation Partnership Project (3GPP), and LTE-Advanced (hereinafter, including LTE- Advanced (also called LTE) has been standardized, and it has also promoted the standardization of the fifth generation mobile communication system (5th generation mobile communication system, also known as 5G, New Radio (NR) or Next Generation (NG)).

For example, in a conventional handover (HO) process, the network determines a target radio base station (also referred to as a target cell) based on quality information such as a measurement report (Measurement Report) sent from a terminal (User Equipment, UE). A handover command is sent to the terminal after the handover is ready.

However, when the terminal passes an appropriate handover point during the preparation for handover on the network side, it directly migrates to the target wireless base station because it does not receive a handover command from the source wireless base station (also referred to as the source cell). , so there is a problem of instantaneous interruption of the wireless link.

Therefore, in order to solve such a problem, a procedure called Conditional HO (Conditional Handover) has been studied (Non-Patent Document 1). In Conditional HO, a candidate destination cell for handover and transition conditions for the candidate destination cell are preset for the terminal.

Furthermore, in Conditional HO, it is agreed that the terminal transmits RRC reconfiguration complete (RRC reconfiguration complete) to the target radio base station (Non-Patent Document 2).

Thereby, the terminal can migrate to the target radio base station without waiting for a handover command from the network. That is, according to Conditional HO, the terminal can migrate to the target radio base station without using a reconnection procedure in the radio resource control layer (RRC) with the target radio base station.

In addition, a procedure for early recovery from a radio link failure (RLF) using a cell relocation procedure according to Conditional HO has also been studied (Non-Patent Document 3).

prior art literature

Non-patent literature

Non-patent document 1: "New WID: NR mobility enhancements", RP-190489, 3GPP TSG RANMeeting #83, 3GPP, March 2019

Non-patent document 2: "Running CR for the introduction of NR mobilityenhancement", R2-1906284, 3GPP TSG-RAN WG2 Meeting#106, 3GPP, May 2019

Non-Patent Document 3: "Summary of mobility robustness agreements from LTEmobility", R2-1908417, 3GPP TSG RAN WG2 Meeting#106, 3GPP, May 2019

SUMMARY OF THE INVENTION

However, if the cell relocation procedure according to Conditional HO is directly applied to recovery from RLF, it is considered that there are problems as described below.

Specifically, as described above, in Conditional HO, although the terminal transmits RRC reconfiguration complete to the target radio base station (RRC reconfiguration complete), for example, there is already a signal transmitted via Signalling Radio Bearer 1 (SRB1) In certain situations such as the case of data, since a buffer status report (BSR) is not triggered, there is a problem that a random access procedure for transmitting a scheduling request (SR) is not started with the target radio base station.

Accordingly, the present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a method that can reliably start with a target wireless base station even when migrating to a target wireless base station without using a reconnection procedure as in Conditional HO terminal for random access procedure.

According to one aspect of the present disclosure, there is provided a terminal having a control unit (control unit 250 ) that migrates to a target radio base station without using a reconnection procedure, the control unit being associated with a radio link In the case of transitioning to the target radio base station due to a failure, a random access procedure with the target radio base station is started at a predetermined timing.

According to one aspect of the present disclosure, there is provided a terminal having a control unit (control unit 250 ) that migrates to a target radio base station without using a reconnection procedure, the control unit being associated with a radio link In the case of migrating to the target radio base station due to a failure, it is decided to discard the data sent via the signaling radio bearer.

Description of drawings

FIG. 1 is an overall schematic configuration diagram of a wireless communication system 10 .

FIG. 2 is a functional block diagram of UE200.

FIG. 3 is an explanatory diagram of a conventional handover process.

FIG. 4 is an explanatory diagram of a handover procedure based on Conditional HO (Conditional HO).

FIG. 5 is an explanatory diagram of a recovery process from a handover failure (HOF) using a reconnection process in the RRC layer.

FIG. 6 is an explanatory diagram of a recovery procedure from a handover failure (HOF) using Conditional HO.

FIG. 7 is a diagram showing a recovery sequence from a handover failure (HOF) using a reconnection procedure in the RRC layer.

FIG. 8 is a diagram showing a recovery sequence from a handover failure (HOF) using Conditional HO.

FIG. 9 is a diagram showing an image of interaction between layers within a terminal at the time of switching.

FIG. 10 is a diagram showing an image of interaction between layers in the terminal at the time of reconnection to the target radio base station.

FIG. 11 is a diagram showing the relationship between the data-transmittable/non-transmittable periods of SRB0 , SRB1 , and SRB2/DRB and the transmission/reception timing of messages in RRC.

FIG. 12 is a diagram showing an example in which the RA procedure is not started in the case where Conditional HO is applied to Radio Link Failure (RLF).

FIG. 13 is a diagram showing an example in which an RA procedure is initiated in a case where the problem shown in FIG. 12 is eliminated and Conditional HO is applied to Radio Link Failure (RLF).

FIG. 14 is a diagram showing an example of the hardware configuration of the UE 200 .

Detailed ways

Hereinafter, embodiments will be described based on the drawings. In addition, the same or similar code|symbol is attached|subjected to the same function and structure, and the description is abbreviate|omitted suitably.

(1) Overall schematic configuration of a wireless communication system

FIG. 1 is an overall schematic configuration diagram of a wireless communication system 10 according to the embodiment. The wireless communication system 10 is a wireless communication system based on 5G New Radio (New Radio), and includes a not-shown Next Generation-Radio Access Network (NG-RAN), and user terminals 200 (User Equipment 200, hereinafter referred to as UE200).

The NG-RAN includes a radio base station 100A (hereinafter referred to as gNB100A) to a radio base station 100C (hereinafter referred to as gNB100C). In addition, the specific structure of the wireless communication system 10 including the number of gNBs and UEs is not limited to the example shown in FIG. 1 .

Furthermore, the NG-RAN actually includes a plurality of NG-RAN Nodes (NG-RAN Nodes), specifically gNBs (or ng-eNBs), which are connected to a 5G-compliant core network (5GC, not shown). In addition, NG-RAN20 and 5GC can also be simply expressed as "network".

gNB100A to gNB100C are 5G-compliant wireless base stations, and perform 5G-compliant wireless communication with UE 200 . gNB100A to gNB100C and UE200 support Massive MIMO in which beams with higher directivity are generated by controlling radio signals transmitted from a plurality of antenna elements, carrier aggregation (CA) using a plurality of component carriers (CCs), and A dual connection (DC), etc., in which CCs are simultaneously transmitted between the NG-RAN node and the terminal.

gNB100A to gNB100C respectively form one or more cells. The UE 200 can migrate between cells (which may also be referred to as radio base stations) formed by the gNB 100A to the gNB 100C. "Relocation" typically refers to handover between cells (radio base stations), but may also include behavior (behavior) of the UE 200 such that the cell (radio base station) to which the connection is to be connected is changed, such as cell reselection. .

The cell (radio base station) to which the UE 200 is relocated is referred to as a target cell or a target radio base station. In addition, the cell (radio base station) of the migration source is referred to as a source cell or a source radio base station.

In the radio communication system 10, Conditional HO is used, that is, a process in which the UE 200 migrates to a target radio base station without using a reconnection process in the radio resource control layer (RRC). In addition, in the wireless communication system 10, a procedure of early recovery from a radio link failure (RLF) using a cell relocation procedure according to Conditional HO is also employed.

Details of the Conditional HO and the procedure for early recovery from RLF using the cell relocation procedure according to the Conditional HO will be described later.

(2) Functional block structure of the wireless communication system

Next, the functional block configuration of the wireless communication system 10 will be described. Specifically, the functional block configuration of the UE 200 will be described.

FIG. 2 is a functional block diagram of UE200. As shown in FIG. 2 , the UE 200 includes a radio transmission unit 210 , a radio reception unit 220 , an RA procedure execution unit 230 , a data discarding unit 240 , and a control unit 250 .

The radio transmission unit 210 transmits an uplink signal (UL signal) according to NR. The radio reception unit 220 receives a downlink signal (DL signal) according to NR.

Specifically, the wireless transmission unit 210 and the wireless reception unit 220 perform wireless communication via a control channel or a data channel.

Control channels include PDCCH (Physical Downlink Control Channel: Physical Downlink Control Channel), PUCCH (Physical Uplink Control Channel: Physical Uplink Control Channel), RACH (Random Access Channel: Random Access Channel, including RA-RNTI (Random Access Channel) Radio Network TemporaryIdentifier: DCI (Downlink Control Information: Downlink Control Information) of random access wireless network temporary identifier), PBCH (Physical Broadcast Channel: Physical Broadcast Channel), and the like.

In addition, the data channel includes PDSCH (Physical Downlink Shared Channel: Physical Downlink Shared Channel), PUSCH (Physical Uplink Shared Channel: Physical Uplink Shared Channel), and the like.

The RA procedure execution unit 230 executes a random access (RA) procedure with the radio base station (specifically, any one of gNB100A to gNB100C). Specifically, the RA procedure execution unit 230 transmits and receives messages according to the RA procedure under the control of the control unit 250 .

In addition, the RA procedures may include contention based random access (CBRA) and non-contention based random access (CFRA) RA procedures.

In the case of CBRA, the RA procedure execution unit 230 transmits a random access preamble (Msg. 1) to the gNB of the connection request destination, and receives a random access preamble (Random Access Preamble) from the gNB. The response is the Random Access Response (Msg.2). After that, the RA procedure execution unit 230 transmits Scheduled Transmission (Msg.3) to the gNB, and receives Contention Resolution (Msg.4) from the gNB.

The RA procedure is performed, for example, in the initial access from the RRC_IDLE state and the RRC connection re-establishment procedure. In the case of the base station, the RA procedure is also performed.

The data discarding unit 240 manages the UL data, and discards the UL data according to the control by the control unit 250 . Specifically, the data discarding unit 240 discards the UL data held without being transmitted to a buffer (not shown) under the control of the control unit 250 .

Specifically, the data discarding unit 240 discards the UL data transmitted via the radio bearer (RB), that is, discards the untransmitted UL data held in the buffer according to the control performed by the control unit 250 .

In addition, the radio bearers include a signaling radio bearer (SRB) and a data radio bearer (DRB). SRB is used for control plane data, and DRB is used for user plane data. In addition, SRB0 , SRB1 , SRB2 , and SRB3 can be set in the SRB according to the application.

SRB0 is used for RRC messages using the CCCH (Common Control Channel: Common Control Channel) logical channel. Specifically, SRB0 is used for transmission and reception of specific RRC messages (RRC Setup Request (RRC Setup Request), etc.).

SRB1 uses a DCCH (Dedicated Control Channel: Dedicated Control Channel) logical channel for RRC messages (which may include non-access stratum (Non-Access Stratum, NAS) messages) and NAS messages before the establishment of SRB2.

SRB2 is used for NAS messages, using the DCCH logical channel. SRB2 has a lower priority than SRB1 and can be set by the network after AS security is activated.

SRB3 is used for a specific RRC message when the UE 200 is in E-UTRA-NR Dual Connectivity (EN-DC) and uses the DCCH logical channel.

Also, DRB is used for user data.

The control unit 250 controls each functional block constituting the UE 200 . In particular, in this embodiment, the transition (including handover) of the UE 200 between gNBs is controlled.

Specifically, the control unit 250 migrates to the target radio base station without using the reconnection procedure to the network. More specifically, the control unit 250 uses the cell relocation procedure according to Conditional HO and does not use the reconnection procedure in the RRC layer to relocate to the target radio base station.

In addition, the control unit 250 starts a random access procedure (RA procedure) with the target radio base station at a predetermined timing when transitioning to the target radio base station due to a radio link failure (RLF).

Specifically, the control unit 250 can control the RA procedure execution unit 230 to start the RA procedure according to a predetermined timing, for example, an instruction from the RRC layer, or generation and/or transmission of a predetermined message in the RRC layer. Note that the details of this timing will be described later.

In addition, the control unit 250 can decide to discard at least data transmitted via a signaling radio bearer (SRB) when the RLF transitions to the target radio base station. Specifically, the control unit 250 controls the data discarding unit 240 to cause the data discarding unit 240 to perform discarding of data transmitted via SRB0, SRB1, and SRB2 (if SRB3 is set, SRB3 may be included).

In addition, after discarding the data, the control unit 250 starts the RA procedure with the target radio base station based on the buffer status report (BSR). Specifically, the control unit 250 discards the data, and treats the data generated later as high-priority data, and causes the RA procedure execution unit 230 to execute the RA procedure based on the normal BSR.

(3) Operation of the wireless communication system

Next, the operation of the wireless communication system 10 will be described. Specifically, after describing the operation of Conditional HO and the operation of recovery from RLF using Conditional HO, an operation that can eliminate the problem of recovery operation from RLF using Conditional HO will be described.

(3.1) Conditional HO

FIG. 3 is an explanatory diagram of a conventional handover procedure, and FIG. 4 is an explanatory diagram of a handover procedure by Conditional HO (Conditional HO).

As shown in FIG. 3 , in the conventional handover process, the network (gNB) determines the target wireless network based on the quality information ((1) in the figure) such as the measurement report (Measurement Report) sent from the terminal (User Equipment, UE). The base station (T-gNB), after preparing for handover ((2) in the figure), sends a handover command to the terminal ((3) in the figure).

However, when the terminal passes an appropriate handover point in the preparation for handover in the network side, it sometimes does not receive a handover command from the source radio base station (S-gNB) and directly transfers to the target radio base station (S-gNB). (4)) in the figure (also known as "too late HO"). Therefore, the terminal cannot recognize the setting related to the target radio base station, and a momentary interruption of the radio link occurs.

To solve this problem, a process called Conditional HO (which can also be omitted as CHO) has been studied. In Conditional HO, a candidate destination cell for handover and a transition condition for the candidate destination cell are preset for the terminal. Thereby, the terminal can connect to the target radio base station without waiting for an instruction (handover command) from the network, and it is possible to avoid instantaneous interruption of the radio link.

Specifically, as shown in FIG. 4 , preparations for handover ((1) in the figure) are performed in advance between the source radio base station (S-gNB) and the target radio base station (T-gNB), including the The setting contents of Conditional HO such as transition conditions are notified to the terminal ((2) in the figure). When the terminal decides to connect to the target radio base station by moving or the like, it starts the RA procedure with the target radio base station according to the setting content of Conditional HO ((3) in the figure).

In addition, the "handover command" may be called reconfigurationWithSync in NR, and may be called RRC connection reconfiguration (including mobilitycontrolinfo) in LTE.

(3.2) Recovery from Radio Link Failure (RLF) using Conditional HO

Next, a recovery procedure from a radio link failure (RLF) using the above-mentioned Conditional HO will be described. Specifically, as an example of RLF, a case where the terminal (UE) fails to handover to the original target cell (cell A) (referred to as handover failure (HOF)) and is handed over to another target cell (cell B) will be described. .

FIG. 5 is an explanatory diagram of a recovery procedure from a handover failure (HOF) using a reconnection procedure in the RRC layer, and FIG. 6 is an explanatory diagram of a recovery procedure from a handover failure (HOF) using Conditional HO.

5 and 6 show that the terminal attempts to handover to cell A ((1) in the figure), but moves into cell B ((2) in the figure) before the handover is completed and executes the handover to cell B An example of switching ((3) in the figure).

In the case of recovery from HOF using the reconnection procedure, when a terminal (UE) detects RLF, it searches for an optimal cell (best cell) as a migration destination (handover destination) at that time. . If the optimal cell can be searched, the terminal starts a reconnection procedure (RRC connection re-establishment) for the cell, and performs connection with the cell (3GPP TS38.331, etc.).

On the other hand, in the case of recovery from HOF using Conditional HO (CHO), instead of the reconnection procedure, a procedure according to Conditional HO ((3) in the figure) is performed. Thereby, the instantaneous interruption time of the wireless link can be reduced.

Hereinafter, further specific description will be given. FIG. 7 shows a recovery sequence from a handover failure (HOF) using the reconnection procedure in the RRC layer. Furthermore, FIG. 8 shows a recovery sequence from a handover failure (HOF) using Conditional HO.

As shown in FIGS. 7 and 8 , in either the recovery from the HOF using the reconnection procedure or the recovery from the HOF using the Conditional HO, according to the preparation for handover (HO preparation/CHOpreparation), the same The handover-related settings (HO config (HO configuration)/CHO config (CHO configuration)) are notified to the terminal (UE).

In addition, as described above, in the case of Conditional HO, a candidate cell for handover and information related to CHO such as a transition condition for the candidate cell are preset for the terminal.

The terminal transmits a random access preamble (Random Access (RA) Preamble) to the target cell (cell A, see FIGS. 5 and 6 ), but because it moves to cell B, the RA process fails and HOF is determined.

After that, in the case of recovery from the HOF using the reconnection procedure shown in FIG. 7 , the terminal and the cell B (herein, expressed as gNB#2) start the RA procedure. In addition, the reconnection procedure in the RRC layer is performed, and the user plane is turned on (established).

On the other hand, in the case of recovery from HOF using Conditional HO shown in FIG. 8 , after performing the RA procedure with cell B (gNB#2), the terminal transmits only RRC reconfiguration complete (RRC reconfiguration complete) , so that the user plane is turned on (established). In Conditional HO, since the terminal recognizes the candidate destination cell for handover and the migration conditions for the candidate destination cell, the reconnection procedure in the RRC layer does not need to be performed. Thereby, the momentary interruption time is shortened compared to the recovery from the HOF using the reconnection procedure (FIG. 7).

In addition, RRC reconfigurationcomplete (RRC reconfiguration complete) in the case of recovery from HOF using Conditional HO may be omitted. This is because cell B (gNB#2) can implicitly recognize that the terminal has relocated due to Conditional HO.

In addition, the terminal can operate as follows. Specifically, when RLF occurs, the terminal performs cell selection, and attempts CHO when the selected cell is a CHO candidate cell. Otherwise, the terminal performs a reconnection procedure in the RRC layer. In addition, the terminal performs cell selection when conventional HO fails (expiration of T304) or access to a CHO candidate cell fails, and attempts CHO when the selected cell is a CHO candidate cell.

(3.3) Layer 2 control at the time of handover and reconnection

When the control of layer 2 at the time of occurrence of the conventional RLF as described above includes control by Conditional HO, the following problems exist.

Specifically, (i) there is no opportunity to start a random access procedure (RA procedure) with the target radio base station, and (ii) there is no opportunity to resume the radio bearer (ie, UL data cannot be transmitted). condition.

Therefore, it is desirable to specify the restart opportunity of the radio bearer after the occurrence of the HOF, and the Layer 2 control for the start of the RA procedure.

Layer 2 control at the time of handover and reconnection can be performed as follows from the viewpoint of the RA procedure and UL data transmission.

· RA process perspective

In the past HO and reconnection process, it is specified to start the RA process for the target cell and establish synchronization

In the medium access control layer (MAC) layer, the initiation of such RA procedure is performed according to the buffer status report (specifically, Regular BSR) based on the occurrence of high priority data (3GPP TS38.321)

That is, the operation flow inside the terminal is (i) high-priority data generation, (ii) regular BSR triggering, (iii) scheduling request (SR) triggering, and (iv) RA procedure activation.

Also, in the case of HO, when RLF occurs, all data of SRB1 is discarded, and after that, RRC reconfiguration complete (RRC reconfiguration complete) is generated. RRC reconfiguration complete (RRC reconfiguration complete) is handled as the occurrence of "high priority data".

In addition, at the time of reconnection with the target radio base station, an RRC Reestablishment Request is generated (transmitted by SRB0 (CCCH)). The RRC Reestablishment Request is processed as the occurrence of "high priority data".

· UL data point of view

In the case of HO, all data of the radio bearer can be sent after the HO

When reconnection with the target radio base station is performed by RLF, once transmission is suspended (suspend) at the time of RLF, after reconnection is established, it resumes (resume) with the following triggers

SRB1: When sending an RRC Reestablishment Request

SRB2/DRB: After receiving processing of RRC Reconfiguration

9 and 10 show images of interactions between layers within a terminal related to initiation of an RA procedure. Specifically, FIG. 9 shows an image of interaction between layers in a terminal at the time of handover, and FIG. 10 shows an image of interaction between layers in a terminal at the time of reconnection to the target radio base station.

As shown in FIG. 9 and FIG. 10 , the terminal (UE200) has a radio resource control layer (RRC), a packet data convergence protocol layer (PDCP), a radio link control layer (RLC), and a medium access control layer. layer (MAC).

As shown in FIG. 9 , in the case of HO, when the terminal (RRC) receives the handover command, it requests a reset (Reset) to the MAC, and requests a re-establishment (re-est) to the PDCP/RLC. In addition, RRC notifies PDCP/RLC of RRC reconfiguration complete (RRC reconfiguration complete).

The PDCP/RLC informs the MAC of the display of the Buffer Status (BS). The MAC initiates the RA procedure according to the display of the BS.

On the other hand, as shown in FIG. 10 , in the case of performing reconnection to the target radio base station, when the terminal (RRC) detects RLF, it suspends (suspends) all radio bearers except SRB0. In addition, RRC requests MAC reset, and notifies PDCP/RLC of RRC Reestablishment Request (RRC Reestablishment Request).

Hereinafter, the PDCP/RLC notifies the MAC of the display of the buffer status (BS) in the same manner as in FIG. 9 . The MAC initiates the RA procedure according to the display of the BS.

FIG. 11 shows an image of suspend/resume of the radio bearer in the reconnection process to the target radio base station. Specifically, FIG. 11 shows the relationship between the data transmission/data transmission non-transmittable periods of SRB0, SRB1, and SRB2/DRB and the transmission/reception timing of messages in RRC.

As shown in FIG. 11 , when the terminal detects RLF and starts the RA procedure, SRB1 and SRB2/DRB are suspended.

After that, when the terminal transmits an RRC Reestablishment Request (RRC Reestablishment Request), the SRB1 is resumed. In addition, when the terminal receives RRC Reconfiguration (RRC Reconfiguration) and sends RRCreconfiguration complete (RRC Reconfiguration Complete), SRB2/DRB is also restarted. In addition, SRB0 is not particularly stopped and restarted, and as a state, data transmission can always be performed.

(3.4) Random access procedure

As described above, when the conventional layer 2 control at the occurrence of RLF includes control by Conditional HO (CHO), there may be no opportunity to start the random access procedure (RA procedure) with the target radio base station.

More specifically, in CHO, the terminal sends RRC reconfigurationcomplete (RRC reconfiguration complete) to the target radio base station, but since the buffer status report (Regular BSR) is not triggered, there is an RA for scheduling request (SR) transmission. When the process is not started.

FIG. 12 shows an example in which the RA procedure is not initiated in the case of applying Conditional HO to Radio Link Failure (RLF).

Specifically, when there is data already transmitted by SRB1, for example, there may be an RRC reconfiguration complete (RRC reconfiguration complete) transmitted by the first HO. As shown in FIG. 12 , the RRC reconfiguration complete (RRC reconfiguration complete) is maintained after the RLF.

More specifically, in the terminal, in a state where data of the same priority already exists (not transmitted), even if additional data occurs, the Regular BSR is not triggered (refer to 3GPP TS38.321). In addition, in general, once the Regular BSR is triggered, the Regular BSR can be triggered later due to the expiration of the RetxBSR-timer, but in the above case, the RetxBSR-timer is stopped due to the MAC reset during RLF.

Thus, in the present embodiment, the terminal starts the RA procedure at a predetermined timing. FIG. 13 is an example showing that the RA procedure is initiated in the case where the problem shown in FIG. 12 is eliminated and Conditional HO is applied to Radio Link Failure (RLF).

Specifically, the terminal can start the RA process through any of the following methods.

(Method 1): Directly start the RA process at a predetermined timing

(Method 2): Discard the data of SRB1 at the time of CHO after RLF

In the case of (Method 1), the predetermined timing may be any timing described below.

Timing at which a layer such as PDCP/RLC receives an instruction from the RRC layer

- When a specific message (for example, RRC reconfiguration complete) is generated in the RRC layer, or when it is sent from RRC to a lower layer such as PDCP/RLC

When a specific message arrives in the PDCP/RLC buffer, or when a PDCP PDU, RLC PDU or MAC subPDU is generated based on the message

In addition, about RRC reconfiguration complete (RRC reconfiguration complete), it can be called by other names, for example, it can be called CHO completion message (CHO completion information), etc. (the same below). Also, the "predetermined timing" may be any timing after RLF or after CHO. Alternatively, it may be the timing at which the radio bearer (RB) is stopped or the timing at which the MAC reset is transmitted.

Furthermore, the initiation of the RA procedure can be achieved by any of the methods described below (indication from the RRC or autonomously performed by the MAC layer).

Directly trigger the RA process (can also be considered triggered)

Trigger a scheduling request (SR) (can also be considered triggered)

Trigger Regular BSR (can also be considered triggered)

In addition, in the case of (Method 2), the discarding of the data may be at least any one of the following.

· By discarding this data, the RRC reconfiguration complete generated later is regarded as "high-priority data", and the RA process based on the conventional Regular BSR is started. Alternatively, the data may not be discarded and it may be considered that there is no (transmittable) data.

・Discard (the timing when there is no data) can be any of the following cases

· RLF detection (can be limited to the case where CHO is set)

· CHO-based migration to a new cell

・When the setting corresponding to the new cell (preset by the setting of CHO) is applied

· After a predetermined time has elapsed from any of the above-mentioned timings

· Discard can be achieved by any of the following methods

・It is considered that discardOnPDCP is set (specified for SRB)

Perform PDCP data recovery or PDCP re-establishment on SRB1

When the PDCP is notified of discardOnPDCP, the terminal (UE) discards at least one or both of the transmission data and the reception data that have been held up at that time with respect to the SRB. In addition, when PDCP data recovery or PDCP re-establishment is notified to PDCP, the terminal discards at least one or both of transmission data and reception data with respect to the radio bearer. Thus, the discarding of the data is performed while using the existing procedure.

(4) Action and effect

According to the above-described embodiment, the following effects can be obtained. Specifically, according to the UE 200 (terminal), Conditional HO of "move to the target radio base station without using the reconnection procedure in the RRC layer" is supported. In the case of HO transition to the target radio base station, UE 200 can start a random access procedure (RA procedure) with the target radio base station at a predetermined timing.

In addition, in the case of migrating to the target radio base station according to Conditional HO without using a reconnection procedure due to a radio link failure (RLF), the UE 200 can decide to discard the data transmitted via the signaling radio bearer.

Specifically, after discarding the data, the UE 200 starts the RA procedure with the target radio base station according to the Buffer Status Report (BSR).

In Conditional HO, UE 200 transmits RRC reconfiguration complete (RRC reconfiguration complete) to the target radio base station. However, in certain cases such as the case where data transmitted via SRB1 already exists, since buffer status report (BSR) is not triggered, there is In the case where the RA procedure for transmitting the scheduling request (SR) with the radio base station is not started, even in this case, the RA procedure can be reliably started with the target radio base station.

Therefore, by including control based on Conditional HO (CHO) in the control of layer 2 when the conventional RLF occurs, it is possible to shorten the momentary interruption time at the time of HOF, for example, and avoid the communication delay caused by the RA process not being started.

(5) Other Embodiments

As mentioned above, although the content of this invention was demonstrated based on an Example, this invention is not limited to these descriptions, It is clear for those skilled in the art that various deformation|transformation and improvement are possible.

For example, in the above-described embodiments, NR has been described as an example, but Conditional HO can also be applied to LTE, and the same operation can be performed in LTE. In addition, it is also applicable to addition and change of the primary SCell (Primary SCell, PSCell) of Multi-RAT Dual Connectivity (MR-DC).

In addition, in the above-mentioned embodiments, the Conditional HO is used as an example for description, but as long as it is a migration process for migrating to the target radio base station without using the reconnection process in the RRC layer, other than the Conditional HO, other methods may be applied. process. For example, it is generally applicable to a case where a terminal autonomously selects a cell and performs a random access procedure, such as a transition from an IDLE state (idle state) or an inactive state (inactive state) to a connected state (connected state). That is, it is not necessarily limited to the case of transitioning to the target radio base station without using the reconnection procedure, and in the case of transitioning to the target radio base station from a predetermined state, the random access procedure may be performed as described above.

In the above-mentioned embodiment, the description is given by taking the example of discarding the data transmitted via SRB1, but the terminal (UE 200) may decide to discard the data transmitted via other signaling radio bearers than SRB1, or the data transmitted via the data radio bearer (DRB). data.

In addition, the block diagram ( FIG. 2 ) used in the description of the above-described embodiment shows blocks in units of functions. These functional blocks (structural parts) are realized by any combination of at least one of hardware and software. In addition, the realization method of each functional block is not specifically limited. That is, each functional block may be implemented by one device that is physically or logically combined, or two or more physically or logically separated devices may be connected directly or indirectly (for example, using wired, wireless, etc.) , using these multiple devices to achieve. The functional blocks can also be realized by combining software with the above-mentioned one means or a plurality of the above-mentioned means.

Judging, deciding, judging, calculating, calculating, processing, exporting, investigating, searching, confirming, receiving, sending, outputting, accessing, resolving, selecting, selecting, establishing, comparing, envisioning, expecting, viewing , broadcasting, notifying, communicating, forwarding, configuring, reconfiguring, allocating, mapping, assigning, etc., but not limited to these. For example, a functional block (configuration unit) that functions for transmission is called a transmitting unit or a transmitter. In short, as described above, the implementation method is not particularly limited.

In addition, the above-described UE 200 may also function as a computer that performs processing of the wireless communication method of the present disclosure. FIG. 14 is a diagram showing an example of the hardware configuration of the UE 200 . As shown in FIG. 14 , the UE 200 may be configured as a computer device including a processor 1001 , a memory 1002 (memory), a memory 1003 (storage), a communication device 1004 , an input device 1005 , an output device 1006 , a bus 1007 , and the like.

In addition, in the following description, the wording of "means" may be replaced by "circuit", "device", "unit" and the like. The hardware structure of the device may be configured to include one or more of the respective devices shown in the drawings, or may be configured to not include a part of the devices.

Each functional block (see FIG. 2 ) of the UE 200 can be realized by any hardware element of the computer device or a combination of the hardware elements.

In addition, each function in the UE 200 is realized by the following methods: reading predetermined software (programs) on hardware such as the processor 1001 and the memory 1002, so that the processor 1001 performs operations, and controls the communication of the communication device 1004 or controls the memory 1002 and the memory 1002. At least one of reading and writing of data in the memory 1003 .

The processor 1001 operates, for example, an operating system to control the entire computer. The processor 1001 may be constituted by a central processing unit (CPU: Central Processing Unit) including an interface with peripheral devices, a control device, an arithmetic device, a register, and the like.

Further, the processor 1001 reads out programs (program codes), software modules, data, etc. from at least one of the memory 1003 and the communication device 1004 to the memory 1002, and executes various processes accordingly. As the program, a program for causing the computer to execute at least a part of the operations described in the above-described embodiments is used. In addition, regarding the above-described various processes, the above-described various processes may be executed by one processor 1001 , or the above-described various processes may be executed by two or more processors 1001 simultaneously or sequentially. The processor 1001 may also be mounted on more than one chip. In addition, the program may also be sent from the network via a telecommunication line.

The memory 1002 is a computer-readable recording medium, and may be composed of, for example, ROM (Read Only Memory), EPROM (Erasable Programmable ROM: Erasable Programmable ROM), EEPROM (Electrically Erasable Programmable ROM: Electrically Erasable ROM) At least one of programmable ROM), RAM (Random Access Memory: random access memory), etc. is constituted. Memory 1002 may also be referred to as registers, cache, main memory (main storage), and the like. The memory 1002 can store a program (program code), a software module, and the like capable of executing the method according to an embodiment of the present disclosure.

The memory 1003 is a computer-readable recording medium, for example, an optical disk such as a CD-ROM (Compact Disc ROM), a hard disk drive, a floppy disk, a magneto-optical disk (for example, a compact disk, a digital versatile disk, Blu-ray (registered trademark) At least one of a disk, smart card, flash memory (eg, card, stick, Key drive), Floppy (registered trademark) disk, magnetic stripe, etc. is constituted. The memory 1003 may also be referred to as an auxiliary storage device. The above-mentioned storage The medium may be, for example, a database including at least one of the memory 1002 and the storage 1003, a server, or other appropriate medium.

The communication device 1004 is hardware (transmitting device) for communicating between computers via at least one of a wired network and a wireless network, and may also be referred to as a network device, a network controller, a network card, a communication module, or the like, for example.

The communication device 1004 may be configured to include a high-frequency switch, a duplexer, a filter, a frequency division duplex, a frequency division duplex (FDD), a frequency division duplex (TDD), and a frequency division duplex (TDD), for example. synthesizer, etc.

The input device 1005 is an input device (eg, a keyboard, a mouse, a microphone, a switch, a key, a sensor, etc.) that accepts input from the outside. The output device 1006 is an output device (eg, a display, a speaker, an LED lamp, etc.) that implements output to the outside. In addition, the input device 1005 and the output device 1006 may be formed integrally (for example, a touch panel).

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 for each device.

In addition, the device may be configured to include a microprocessor, a digital signal processor (DSP: Digital Signal Processor), an ASIC (Application Specific Integrated Circuit: an application specific integrated circuit), a PLD (Programmable Logic Device: programmable logic device), an FPGA (Field Programmable GateArray: Field Programmable Gate Array) and other hardware, a part or all of each functional block can also be realized by the hardware. For example, the processor 1001 may also be installed using at least one of these hardwares.

Furthermore, the notification of information is not limited to the form/implementation described in this disclosure, and other methods may be used. For example, the notification of information may be performed through physical layer signaling (eg, DCI (Downlink Control Information: downlink control information), UCI (Uplink Control Information: uplink control information)), higher layer signaling (eg, RRC (Radio Resource Control: Radio Resource Control) signaling, MAC (Medium Access Control: Medium Access Control) signaling, broadcast information (MIB (Master Information Block: Master Information Block), SIB (System Information Block: System Information Block)), others Signals or their combinations are implemented. In addition, RRC signaling may also be called RRC messages, for example, may also be RRC connection setup (RRC Connection Setup) messages, RRC connection reconfiguration (RRC Connection Reconfiguration) messages, and the like.

The various forms/embodiments described in this disclosure can also be applied to Long Term Evolution (LTE), LTE-Advanced (LTE-A), SUPER 3G, IMT-Advanced, and 4th generation mobile communication systems (4th generation mobile communication systems). communication system: 4G), 5th generation mobile communication system (5G), Future Radio Access (FRA), New Radio (NR), W-CDMA (registered trademark), GSM (registered trademark), CDMA 2000, Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi (registered trademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE 802.20, UWB (Ultra-WideBand) ), Bluetooth (registered trademark), systems using other suitable systems, and next-generation systems extended accordingly. Furthermore, a combination of a plurality of systems (for example, a combination of at least one of LTE and LTE-A and 5G, etc.) may be used.

Regarding the processing procedures, sequences, and flows of the various forms/embodiments described in the present disclosure, the order may be changed unless they are inconsistent. For example, for the methods described in this disclosure, elements of the various steps are presented using the illustrated order, but are not limited to the particular order presented.

In the present disclosure, the specific operation performed by the base station may be performed by its upper node depending on the situation. In a network consisting of one or more network nodes with base stations, various actions for communicating with terminals may be performed by the base station and other network nodes other than the base station (for example, consider MME or S- GW, etc., but not limited to at least one of these), it is obvious. In the above, the case where the other network node other than the base station is one is exemplified, but the other network node may be a combination of a plurality of other network nodes (for example, MME and S-GW).

Information, signals (information), and the like can be output from a higher layer (or a lower layer) to a lower layer (or a higher layer). It is also possible to input or output via multiple network nodes.

Input or output information and the like can be stored in a specific location (eg, memory), or managed using a management table. Input or output information, etc. can be rewritten, updated or written down. The output information and the like can also be deleted. The input information and the like can also be transmitted to other devices.

The determination can be performed by a value (0 or 1) represented by 1 bit, by a Boolean value (Boolean: true or false), or by a comparison of numerical values (for example, a comparison with a predetermined value).

Each aspect/embodiment described in the present disclosure may be used alone or in combination, and may be switched and used according to execution. In addition, the notification of the reservation information is not limited to be performed explicitly (eg, notification of "Yes X"), and may be performed implicitly (eg, without notification of the reservation information).

Software, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise, should be construed broadly to mean commands, command sets, codes, code segments, program code, programs (program), subprogram, software module, application, software application, software package, routine, subroutine, object, executable, thread of execution, procedure, function, etc.

Also, software, commands, information, and the like can be transceived via a transmission medium. For example, using at least one of wired technology (coaxial cable, optical fiber cable, twisted pair, Digital Subscriber Line (DSL), etc.) and wireless technology (infrared, microwave, etc.) or other remote sources sending software, at least one of these wired and wireless technologies is included within the definition of transmission medium.

The information, signals, etc. described in this disclosure may also be represented using any of a variety of different technologies. For example, data, commands, commands, information, signals, bits, codes that may be referred to in the foregoing description as a whole may be represented by voltages, currents, electromagnetic waves, magnetic or magnetic particles, optical fields or photons, or any combination of these Element (symbol), chip (chip), etc.

Further, terms described in the present disclosure and terms necessary for understanding the present disclosure may be replaced with terms having the same or similar meanings. For example, at least one of the channel and the symbol may be a signal (signaling). In addition, a signal can also be a message. In addition, a component carrier (CC: Component Carrier) may be referred to as a carrier frequency, a cell, a frequency carrier, or the like.

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

In addition, the information, parameters, and the like described in the present disclosure may be expressed using absolute values, may also be expressed using relative values with predetermined values, and may also be expressed using corresponding other information. For example, radio resources can also be indicated by an index.

The names used for the above parameters are in no way limiting. Furthermore, the numerical expression etc. using these parameters may differ from the content expressly shown in this indication. Various channels (eg, PUCCH, PDCCH, etc.) and information elements can be identified by appropriate names, so the various names assigned to these various channels and information elements are in any way irrelevant. restrictive.

In the present disclosure, "base station (BS: Base Station)", "radio base station", "fixed station", "NodeB", "eNodeB (eNB)", "gNodeB (gNB)", "access point" (access point)", "transmission point", "reception point", "transmission/reception point", "cell", "sector", "cell group", " The terms "carrier", "component carrier" and the like are used interchangeably. Base stations are also sometimes referred to as macro cells, small cells, femto cells, pico cells, and the like.

A base station can accommodate one or more (eg, 3) cells. When the 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 also pass through the base station subsystem (for example, an indoor small base station (RRH: Remote Radio Head). (Remote Wireless Head)) to provide communication services.

The term "cell" or "sector" refers to a part or the whole of the coverage area of at least one of a base station and a base station subsystem that perform communication services within the coverage area.

In the present disclosure, terms such as "Mobile Station (MS)", "user terminal", "User Equipment (UE: User Equipment)", "terminal" and the like may be used interchangeably.

For mobile stations, those skilled in the art also sometimes use the following terms: subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless device, wireless communication device, remote device, mobile Subscriber station, access terminal, mobile terminal, wireless terminal, remote terminal, handset, user agent, mobile client, client, or some other appropriate term.

At least one of the base station and the mobile station may also be referred to as a transmission device, a reception device, a communication device, or the like. In addition, at least one of the base station and the mobile station may be a device mounted on a mobile body, the mobile body itself, or the like. The moving body may be a vehicle (eg, a car, an airplane, etc.), a moving body (eg, an unmanned aerial vehicle, an autonomous vehicle, etc.) that moves in an unmanned manner, or a robot (human or unmanned) human type). In addition, at least one of the base station and the mobile station also includes a device that does not necessarily move during a communication operation. For example, at least one of the base station and the mobile station may be an IoT (Internet of Things) device such as a sensor.

In addition, the base station in the present disclosure may also be replaced by a mobile station (user terminal, the same applies hereinafter). For example, the communication between the base station and the mobile station is replaced by the communication between a plurality of mobile stations (for example, it can also be referred to as D2D (Device-to-Device: device-to-device), V2X (Vehicle-to-Everything: It is also possible to apply the various forms/embodiments of the present disclosure to the structure from the vehicle to any system, etc. In this case, the mobile station may have a structure that has the functions of the base station. In addition, "uplink" and "downlink" etc. may also be replaced with words corresponding to inter-terminal communication (eg, "side"). For example, an uplink channel, a downlink channel, etc. may also be replaced by a side channel.

Likewise, mobile stations in the present disclosure may be replaced by base stations. In this case, the base station may be configured to have functions that the mobile station has.

A radio frame may consist of one or more frames in the time domain. One or more of each frame may also be referred to as a subframe in the time domain. A subframe may also consist of one or more time slots in the time domain. A subframe may be a fixed length of time (eg, 1 ms) independent of a parameter set (numerology).

The parameter set may also be a communication parameter applied to at least one of transmission and reception of a certain signal or channel. The parameter set can represent, for example, subcarrier spacing (SCS: SubCarrier Spacing), bandwidth, symbol length, cyclic prefix length, transmission time interval (TTI: Transmission Time Interval), number of symbols per TTI, radio frame structure, transceiver in At least one of a specific filtering process performed in the frequency domain, a specific windowing process performed by the transceiver in the time domain, and the like.

In the time domain, a time slot may be composed of one or more symbols (Orthogonal Frequency Division Multiplexing) (OFDM) symbols, SC-FDMA (Single Carrier Frequency Division Multiple Access) symbols etc.) composition. A time slot may be a unit of time based on a parameter set.

A slot can also contain multiple mini-slots. Each mini-slot may consist of one or more symbols in the time domain. In addition, mini-slots may also be referred to as sub-slots. A mini-slot may also be composed of a smaller number of symbols than a slot. A PDSCH (or PUSCH) transmitted in a time unit larger than a mini-slot may also be referred to as PDSCH (or PUSCH) mapping type A. PDSCH (or PUSCH) transmitted using mini-slots may also be referred to as PDSCH (or PUSCH) mapping type B.

Radio frames, subframes, slots, mini-slots, and symbols all represent time units when a signal is transmitted. Radio frames, subframes, time slots, mini-slots, and symbols may also use other names corresponding to them.

For example, 1 subframe may also be referred to as a transmission time interval (TTI: Transmission Time Interval), multiple consecutive subframes may also be referred to as TTI, and 1 slot or 1 mini-slot may also be referred to as TTI. That is, at least one of the subframe and the TTI may be a subframe (1ms) in the conventional LTE, a period shorter than 1ms (for example, 1-13 symbols), or a period longer than 1ms . In addition, the unit representing the TTI may not be a subframe, but may be called a slot, a mini-slot, or the like.

Here, the TTI refers to, for example, the smallest time unit of scheduling in wireless communication. For example, in the LTE system, the base station performs scheduling for allocating radio resources (frequency bandwidth, transmission power, etc. that can be used by each user terminal) in units of TTIs for each user terminal. In addition, the definition of TTI is not limited to this.

TTI may be a transmission time unit of channel-coded data packets (transport blocks), code blocks, code words, etc., or may be a processing unit such as scheduling and link adaptation. In addition, when a TTI is given, the time interval (for example, the number of symbols) in which transport blocks, code blocks, code words, etc. are actually mapped may be shorter than the TTI.

In addition, when 1 slot or 1 minislot is called a TTI, one or more TTIs (ie, one or more slots or one or more minislots) may also constitute the minimum time unit for scheduling . In addition, the number of time slots (the number of mini-slots) constituting the smallest time unit of the schedule may be controlled.

A TTI having a time length of 1 ms may be referred to as a normal TTI (TTI in LTE Rel. 8-12), a normal TTI, a long TTI, a normal subframe, a normal subframe, a long subframe, a slot, or the like. A TTI shorter than a normal TTI may be referred to as a shortened TTI, a short TTI, a partial TTI (partial or fractional TTI), a shortened subframe, a short subframe, a minislot, a subslot, a time slot, or the like.

In addition, long TTIs (eg, normal TTIs, subframes, etc.) can be replaced with TTIs having a time length exceeding 1 ms, and short TTIs (eg, shortened TTIs, etc.) can also be replaced with TTIs having a TTI length smaller than the long TTI and more than 1 ms TTI of TTI length.

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

In addition, the time domain of the RB may include one or more symbols, and may also have a length of 1 slot, 1 mini-slot, 1 subframe, or 1 TTI. 1 TTI, 1 subframe, etc. may be respectively constituted by one or more resource blocks.

In addition, one or more RBs may also be referred to as a physical resource block (PRB: Physical RB), a sub-carrier group (SCG: Sub-Carrier Group), a resource element group (REG: Resource Element Group), a PRB pair, and an RB pair. Wait.

In addition, the resource block may be composed of one or more resource elements (RE: Resource Element). For example, 1 RE may be a radio resource region of 1 subcarrier and 1 symbol.

Bandwidth Part (BWP: Bandwidth Part) (may also be referred to as partial bandwidth, etc.) in a certain carrier may also represent a subset of continuous common resource blocks (common resource blocks) for a certain parameter set. Here, the common RB may also be determined by the index of the RB based on the common reference point of the carrier. PRBs can also be defined by a BWP and numbered within that BWP.

The BWP may include BWP for UL (UL BWP) and BWP for DL (DL BWP). For the UE, one or more BWPs may be configured in one carrier.

At least one of the set BWPs may be activated, and the UE may not be expected to transmit and receive predetermined signals/channels other than the activated BWPs. In addition, "cell", "carrier", etc. in the present disclosure may also be replaced with "BWP".

The above-mentioned structures of radio frames, subframes, slots, mini-slots, symbols, etc. are only examples. For example, the number of subframes contained in a radio frame, the number of slots per subframe or radio frame, the number of minislots contained in a slot, the symbols contained in a slot or minislot, and The number of RBs, the number of subcarriers included in the RB, the number of symbols in the TTI, the symbol length, and the cyclic prefix (CP: Cyclic Prefix) length can be variously changed.

The terms "connected", "coupled" or all variations of these terms are intended to mean any direct or indirect connection or combination between two or more elements, which may be included in the mutual " A case where there are one or more intervening elements between two elements that are "connected" or "joined". The combination or connection between elements may be a physical combination or connection, a logical combination or connection, or a combination of these. For example, "connection" may be replaced by "access". As used in the present disclosure, for two elements, it may be considered that by using at least one of one or more wires, cables, and printed electrical connections, and as some non-limiting and non-inclusive examples by using having Electromagnetic energy such as electromagnetic energy of wavelengths in the radio frequency domain, microwave domain, and light (both visible and invisible) domains to "connect" or "combine" with each other.

The reference signal may be referred to as RS (Reference Signal) for short, and may also be referred to as pilot (Pilot) according to the applied standard.

The description of "based on" used in the present disclosure does not mean "only based on" unless it is clearly stated otherwise. In other words, the description of "based on" means both "based only on" and "based on at least".

The "unit" in the structure of each device described above may be replaced by a "section", a "circuit", a "device", or the like.

Any reference to an element using the terms "first", "second", etc. used in this disclosure is not intended to limit the number and order of those elements. These terms are used in this disclosure as a convenient way of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements can be taken here or that the first element must precede the second element in any form.

Where "include," "including," and variations thereof are used in this disclosure, these terms are meant to be inclusive as well as the term "comprising." Also, the term "or" used in this disclosure means not an exclusive-or.

In the present disclosure, for example, such as a, an, and the in English, when articles are added by translation, the present disclosure also includes the case where the nouns following these articles are plural.

Terms such as "determining" and "determining" used in the present disclosure may include various operations. "Judging" and "determining" may include, for example, that judging, calculating, computing, processing, deriving, investigating, looking up (for example, , searches in tables, databases, or other data structures), matters of confirmation (ascertaining) are deemed to have been "judged", "determined", etc. In addition, "judging" and "determining" may include receiving (eg, receiving information), transmitting (eg, sending information), input (input), output (output), accessing (accessing) ) (for example, accessing data in memory) is regarded as a matter of "judgment" and "decision". In addition, "judgment" and "determination" may include considering matters that have been resolved, selected, chosen, established, compared, etc. as "judgment", "determined", and the like " matter. That is, "judgment" and "determination" may include "judgment" and "determination" of any action. In addition, "judgment (decision)" can also be replaced by "assuming", "expecting", "considering", etc.

In the present disclosure, the phrase "A and B are different" may also mean "A and B are different from each other". In addition, this term may also mean that "A and B are different from C, respectively." Terms such as "separate" and "combined" can also be similarly interpreted as "different".

The present disclosure has been described in detail above, but it should be 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 as modified and changed modes without departing from the spirit and scope of the present disclosure defined by the claims. Therefore, the description of the present disclosure is for the purpose of illustration and does not have any limiting meaning to the present disclosure.

Label description:

10 Wireless Communication Systems

100A～100C gNB

200UE

210 Wireless Transmitter

220 Wireless Receiver

230 RA Process Executive

240 Data Discard Section

250 Control Department

1001 processor

1002 memory

1003 memory

1004 Communication device

1005 Input device

1006 Output device

1007 bus

Claims (3)

1. A terminal, wherein,

the terminal has a control section that migrates to a target radio base station without using a reconnection procedure,

the control unit starts a random access procedure with the target radio base station at a predetermined timing when the radio link failure occurs and the radio base station moves to the target radio base station.

2. A terminal, wherein,

the terminal has a control section that migrates to a target radio base station without using a reconnection procedure,

the control unit determines to discard data transmitted via a signaling radio bearer when the radio link failure occurs and the radio link is transferred to the target radio base station.

3. The terminal of claim 2, wherein,

the control unit starts a random access procedure with the target radio base station based on the buffer status report after discarding the data.

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