WO2020261460A1

WO2020261460A1 - Terminal

Info

Publication number: WO2020261460A1
Application number: PCT/JP2019/025500
Authority: WO
Inventors: 徹内野; 天楊閔; 高橋　秀明
Original assignee: 株式会社Ｎｔｔドコモ
Priority date: 2019-06-26
Filing date: 2019-06-26
Publication date: 2020-12-30
Also published as: CN114009137A

Abstract

A terminal (UE) transitions to a target wireless base station (gNB) without using a reconnection procedure. If the terminal transitions to the target wireless base station in conjunction with radio link failure, the terminal initiates a random-access procedure with respect to the target wireless base station, at a prescribed timing.

Description

Terminal

The present invention relates to a terminal that executes wireless communication, particularly a terminal that transitions to a target wireless base station without using a reconnection procedure.

The 3rd Generation Partnership Project (3GPP) has specified Long Term Evolution (LTE), and aims to further speed up LTE with LTE-Advanced (hereinafter referred to as LTE including LTE-Advanced), and the 5th generation mobile communication system. Specifications (also called 5G, New Radio (NR) or Next Generation (NG)) are also underway.

For example, in a conventional handover (HO) procedure, a network sets a target radio base station (also called a target cell) based on quality information such as a measurement report transmitted from a terminal (User Equipment, UE). After making a decision and preparing for the handover, the handover command is transmitted to the terminal.

However, if the terminal passes an appropriate handover point while preparing for the handover on the network side, it transitions to the target radio base station without receiving the handover command from the source radio base station (also called the source cell). Therefore, there is a problem that a momentary interruption of the wireless link may occur.

Therefore, in order to solve such a problem, a procedure called Conditional HO is being studied (Non-Patent Document 1). In Conditional HO, the candidate cell for handover and the transition condition to the candidate cell are set in advance for the terminal.

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

As a result, the terminal can transition to the target radio base station without waiting for the handover command from the network. That is, Conditional HO allows the terminal to transition to the target radio base station without using the reconnection procedure at the target radio base station and the radio resource control layer (RRC).

Furthermore, a procedure for early recovery from a wireless link failure (RLF) using a cell transition procedure according to Conditional HO is also being studied (Non-Patent Document 3).

However, if the cell transition procedure according to Conditional HO is applied as it is to the return from RLF, the following problems are considered.

Specifically, as described above, in Conditional HO, the terminal transmits RRC reconfiguration complete to the target radio base station, but for example, the data already transmitted via Signalling Radio Bearer 1 (SRB1) is In certain situations, such as when it exists, the Buffer Status Report (BSR) is not triggered, so there is a problem that the random access procedure for sending a scheduling request (SR) with the target radio base station is not started.

Therefore, the present invention has been made in view of such a situation, and even when transitioning to the target radio base station without using the reconnection procedure as in Conditional HO, the target radio base station and the target radio base station are surely used. The purpose is to provide a terminal that can initiate a random access procedure.

One aspect of the present disclosure includes a control unit (control unit 250) that transitions to the target radio base station without using a reconnection procedure, and the control unit transitions to the target radio base station due to a radio link failure. In this case, it is a terminal that starts a random access procedure with the target radio base station at a specified timing.

One aspect of the present disclosure includes a control unit (control unit 250) that transitions to the target radio base station without using a reconnection procedure, and the control unit transitions to the target radio base station due to a radio link failure. In the case, it is a terminal that determines the destruction of data transmitted via the signaling radio bearer.

FIG. 1 is an overall schematic configuration diagram of the wireless communication system 10. FIG. 2 is a functional block configuration diagram of the UE 200. FIG. 3 is an explanatory diagram of a conventional handover procedure. FIG. 4 is an explanatory diagram of the handover procedure by Conditional HO. FIG. 5 is an explanatory diagram of a procedure for recovering from a handover failure (HOF) using a reconnection procedure in the RRC layer. FIG. 6 is an explanatory diagram of a procedure for recovering 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 communication between layers in the terminal at the time of handover. FIG. 10 is a diagram showing an image of communication 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 transmission enable / disable period of SRB0, SRB1 and SRB2 / DRB and the message transmission / reception timing in RRC. FIG. 12 is a diagram showing an example in which the RA procedure is not activated when Conditional HO is applied to wireless link failure (RLF). FIG. 13 is a diagram showing an example in which the RA procedure is activated when the problem shown in FIG. 12 is solved and Conditional HO is applied to the radio link failure (RLF). FIG. 14 is a diagram showing an example of the hardware configuration of UE200.

Hereinafter, embodiments will be described based on the drawings. The same functions and configurations are designated by the same or similar reference numerals, and the description thereof will be omitted as appropriate.

(1) Overall Schematic Configuration of Wireless Communication System FIG. 1 is an overall schematic configuration diagram of the wireless communication system 10 according to the present embodiment. The wireless communication system 10 is a wireless communication system according to 5G New Radio (NR), and includes a Next Generation-Radio Access Network (NG-RAN) and a user terminal 200 (User Equipment 200, hereinafter, UE200) (not shown).

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

In addition, NG-RAN actually includes multiple NG-RAN Nodes, specifically gNB (or ng-eNB), and is connected to a core network (5GC, not shown) according to 5G. Note that NG-RAN and 5GC may be simply expressed as a network.

GNB100A to gNB100C are radio base stations that comply with 5G, and execute wireless communication according to UE200 and 5G. gNB100A to gNB100C and UE200 are Massive MIMO that generates a beam with higher directivity by controlling radio signals transmitted from multiple antenna elements, and carrier aggregation (CA) that uses multiple component carriers (CC) in a bundle. ), And dual connectivity (DC) that communicates between the UE and multiple NG-RAN Nodes at the same time.

GNB100A to gNB100C each form one or more cells. The UE200 can transition between cells (which may be called radio base stations) formed by gNB100A to gNB100C. “Transition” typically means a handover between cells (radio base stations), but the behavior of the UE 200 (behavior) such that the cell (radio base station) to be connected to is changed, such as cell reselection. ) Can be included.

The transition destination cell (radio base station) to which the UE200 transitions is called the target cell or target radio base station. The transition source cell (radio base station) is called a source cell or a source radio base station.

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

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

(2) Functional block configuration 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 UE200 will be described.

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

The wireless transmitter 210 transmits an uplink signal (UL signal) according to NR. The wireless receiver 220 receives the downlink signal (DL signal) according to the NR.

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

Control channels include PDCCH (Physical Downlink Control Channel), PUCCH (Physical Uplink Control Channel), RACH (Random Access Channel, Random Access Radio Network Temporary Identifier (RA-RNTI), Downlink Control Information (DCI)), and Physical. Broadcast Channel (PBCH) etc. are included.

In addition, the data channels include PDSCH (Physical Downlink Shared Channel) and PUSCH (Physical Downlink Shared Channel).

The RA procedure execution unit 230 executes a random access (RA) procedure with a radio base station, specifically, any of gNB100A to gNB100C. Specifically, the RA procedure execution unit 230 sends and receives a message according to the RA procedure based on the control by the control unit 250.

Note that the RA procedure may include contention-based random access (CBRA) and contention-free random access (CFRA) RA procedure.

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

The RA procedure is executed, for example, in the initial access from the RRC_IDLE state and the procedure for reestablishing the RRC connection. In this embodiment, as will be described later, the target radio base station is accompanied by a radio link failure (RLF). The RA procedure is also executed when transitioning to.

The data destruction unit 240 manages UL data and discards UL data based on the control by the control unit 250. Specifically, the data discarding unit 240 discards UL data held without being transmitted to the buffer (not shown) based on the control by the control unit 250.

Specifically, the data discard unit 240 discards UL data transmitted via the wireless bearer (RB) and untransmitted UL data held in the buffer under the control of the control unit 250. To do.

The wireless bearer includes a signaling wireless bearer (SRB) and a data wireless bearer (DRB). The SRB is for control plane data and the DRB is for user plane data. In addition, SRB0, 1, 2, and 3 can be set for SRB depending on the application.

SRB0 is for RRC messages that use the Common Control Channel (CCCH) logical channel. Specifically, SRB0 is used to send and receive specific RRC messages (RRCSetupRequest, etc.).

SRB1 is for RRC messages (which may include piggybacked Non-Access Stratum (NAS) messages) and NAS messages before the establishment of SRB2 using the Dedicated Control Channel (DCCH) logical channel.

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

SRB3 is for a specific RRC message when UE200 is in E-UTRA-NR Dual Connectivity (EN-DC) and uses a DCCH logical channel.

Also, DRB is for user data.

The control unit 250 controls each functional block constituting the UE 200. In particular, in the present embodiment, the transition (including handover) between gNBs of UE200 is controlled.

Specifically, the control unit 250 transitions to the target radio base station without using the reconnection procedure to the network. More specifically, the control unit 250 uses the cell transition procedure according to the Conditional HO to transition to the target radio base station without using the reconnection procedure in the RRC layer.

Further, when the control unit 250 transitions to the target radio base station due to a radio link failure (RLF), the control unit 250 starts a random access procedure (RA procedure) with the target radio base station at a specified timing.

Specifically, the control unit 250 controls the RA procedure execution unit 230, and the RA is based on a specified timing, for example, an instruction from the RRC layer, or generation or transmission of a predetermined message on the RRC layer. You can start the procedure. The details of the timing will be described later.

Further, the control unit 250 can determine at least the destruction of the data transmitted via the signaling radio bearer (SRB) when transitioning to the target radio base station along with the RLF. Specifically, the control unit 250 controls the data destruction unit 240 to discard data transmitted via SRB0, 1, 2 (if SRB3 is set, SRB3 may be included). Let the data discard unit 240 execute.

Further, 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 considers the data generated thereafter as high-priority data by discarding the data, and causes the RA procedure execution unit 230 to execute the RA procedure based on the normal BSR.

(3) Operation of Wireless Communication System Next, the operation of the wireless communication system 10 will be described. Specifically, after explaining the operation of Conditional HO and the operation of returning from RLF using Conditional HO, the operation that can solve the problem of the operation of returning 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.

As shown in FIG. 3, in the conventional handover procedure, the network (gNB) is based on quality information ((1) in the figure) such as a measurement report (Measurement Report) transmitted from the terminal (User Equipment, UE). Then, the target radio base station (T-gNB) is determined, and the handover command is transmitted to the terminal ((3) in the figure) after the preparation for the handover ((2) in the figure).

However, if the terminal passes an appropriate handover point while preparing for the handover on the network side, it transitions to the target radio base station without receiving the handover command from the source radio base station (S-gNB) ( (4) in the figure) may occur (may be called "too late HO"). Therefore, the terminal cannot recognize the setting related to the target radio base station, and the radio link may be interrupted momentarily.

In order to solve such a problem, a procedure called Conditional HO (may be abbreviated as CHO) is being considered. In Conditional HO, the candidate cell for handover and the transition condition to the candidate cell are set in advance for the terminal. As a result, the terminal can connect to the target radio base station without waiting for an instruction (handover command) from the network, and can avoid a momentary interruption of the radio link.

Specifically, as shown in FIG. 4, preparations for handover are executed in advance between the source radio base station (S-gNB) and the target radio base station (T-gNB) ((1) in the figure). , Conditional HO settings including transition conditions to the target radio base station 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 based on the setting contents of Conditional HO ((3) in the figure).

The "handover command" may be called reconfigurationWithSync in NR and RRC connection reconfiguration (including mobilitycontrolinfo) in LTE.

(3.2) Recovery from radio link failure (RLF) using Conditional HO Next, the procedure for recovery from radio link failure (RLF) using Conditional HO will be described. Specifically, as an example of RLF, a terminal (UE) fails to perform a handover to the initial target cell (cell A) (referred to as a handover failure (HOF)) and performs a handover to another target cell (cell B). The case will be described.

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

In FIGS. 5 and 6, the terminal attempts a handover to cell A ((1) in the figure), but moves into cell B ((2) in the figure) before the handover is completed, and the cell An example of executing the handover to B ((3) in the figure) is shown.

In the case of returning from HOF using the reconnection procedure, when the terminal (UE) detects RLF, it searches for the optimum cell (best cell) as the transition destination (handover destination) at that time. If the best cell can be searched, the terminal activates the reconnection procedure (RRC connection re-establishment) for the cell and executes the connection with the cell (3GPP TS38.331, etc.).

On the other hand, in the case of returning from HOF using Conditional HO (CHO), the procedure according to Conditional HO is executed instead of the reconnection procedure ((3) in the figure). As a result, the momentary interruption time of the wireless link can be reduced.

Below, a more specific explanation will be given. FIG. 7 shows a recovery sequence from a handover failure (HOF) using a reconnection procedure at the RRC layer. Further, FIG. 8 shows a recovery sequence from a handover failure (HOF) using Conditional HO.

As shown in FIGS. 7 and 8, both the return from the HOF using the reconnection procedure and the return from the HOF using the Conditional HO are based on the preparation for handover (HO preparation / CHO preparation). The terminal (UE) is notified of the settings (HO config / CHO config) related to the handover.

As described above, in the case of Conditional HO, information on CHO such as a candidate cell for handover and a transition condition to the candidate cell is set in advance for the terminal.

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

After that, in the case of returning from HOF using the reconnection procedure shown in FIG. 7, the terminal starts the cell B (here, gNB # 2) and RA procedure. In addition, a reconnect procedure at the RRC layer is performed to conduct (establish) the user plane.

On the other hand, in the case of returning from HOF using Conditional HO shown in FIG. 8, the terminal executes the RA procedure with cell B (gNB # 2), and then transmits only RRC reconfiguration complete, so that the user plane becomes conductive ( Establish. In Conditional HO, since the terminal recognizes the candidate cell for handover and the transition condition to the candidate cell, it is not necessary to execute the reconnection procedure in the RRC layer. As a result, the momentary interruption time is shortened as compared with the return from the HOF using the reconnection procedure (FIG. 7).

Note that RRC reconfiguration complete in the case of returning from HOF using Conditional HO may be further omitted. This is because cell B (gNB # 2) can implicitly recognize that the terminal has transitioned by Conditional HO.

In addition, the terminal may operate as follows. Specifically, when RLF occurs, the terminal executes cell selection and attempts CHO if the selected cell is a CHO candidate cell. If not, the terminal performs a reconnect procedure at the RRC layer. In addition, the terminal executes cell selection in the case of legacy HO failure (expiration of T304) or access failure in the CHO candidate cell, and attempts CHO if the selected cell is a CHO candidate cell.

(3.3) Layer 2 control at the time of handover / reconnection Including the control by Conditional HO with respect to the conventional layer 2 control at the time of RLF occurrence as described above, there are the following problems.

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 (that is, send UL data). (Cannot) Situations can occur.

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

Regarding layer 2 control during handover / reconnection, the following can be said from the viewpoint of RA procedure and UL data transmission.

-RA procedure perspective-Conventional HO and reconnection procedures stipulate that the RA procedure be started and synchronization be established for the target cell.-In the medium access control layer (MAC) layer, such The RA procedure is invoked based on the buffer status report (specifically, Regular BSR) due to the occurrence of high priority data (3GPP TS38.321).
In other words, the operation flow inside the terminal is (i) high priority data generation, (ii) Regular BSR is triggered, (iii) scheduling request (SR) is triggered, and (iv) RA procedure is activated. ..

Also, in the case of HO, all SRB1 data is discarded when RLF occurs, and then RRC reconfiguration complete is generated. RRC reconfiguration complete is treated as if "high priority data" has occurred.

Furthermore, when reconnecting to the target radio base station, an RRC Reestablishment Request (transmitted by SRB0 (CCCH)) is generated. RRCReestablishmentRequest is treated as if "high priority data" has occurred.

-UL data perspective-In the case of HO, all radio bearer data can be transmitted after HO-When reconnecting to the target radio base station by RLF, transmission is temporarily suspended at RLF. , After the reconnection is established, it will be resumed (resume) with the following triggers ・ SRB1: When sending RRC Reestablishment Request ・ SRB2 / DRB: After receiving RRC Reconfiguration Fig. 9 and Fig. 10 are terminals related to the activation of RA procedure. Shows an image of the interaction between the inner layers. Specifically, FIG. 9 shows an image of communication between layers in the terminal at the time of handover, and FIG. 10 shows an image of communication between layers in the terminal at the time of reconnection to the target radio base station.

As shown in FIGS. 9 and 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 ( MAC) is provided.

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

PDCP / RLC notifies the MAC of the display of the buffer status (BS). The MAC activates the RA procedure based on the display of the BS.

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

After that, the same as in FIG. 9, PDCP / RLC notifies the MAC of the display of the buffer status (BS). The MAC activates the RA procedure based on the display of the BS.

FIG. 11 shows an image of suspension / resume of the radio bearer in reconnection to the target radio base station. Specifically, FIG. 11 shows the relationship between the period during which data transmission of SRB0, SRB1 and SRB2 / DRB is possible / impossible and the timing of sending and receiving 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 sends an RRC Reestablishment Request, SRB1 is resumed. Furthermore, when the terminal receives RRC Reconfiguration and sends RRC reconfiguration complete, SRB2 / DRB is also restarted. Note that SRB0 is not particularly stopped / restarted, and as a state, data can always be transmitted.

(3.4) Random access procedure As described above, if the control by Conditional HO (CHO) is included in the conventional layer 2 control when RLF occurs, the target radio base station and the random access procedure (RA procedure). There may be no opportunity to start.

More specifically, in CHO, the terminal sends an RRC reconfiguration complete to the target radio base station, but the buffer status report (Regular BSR) is not triggered, so the RA for scheduling request (SR) transmission. There are cases where the procedure is not started.

FIG. 12 shows an example in which the RA procedure is not activated when Conditional HO is applied to wireless link failure (RLF).

Specifically, when there is already data to be transmitted via SRB1, for example, when the RRC reconfiguration complete that was being transmitted at the first HO exists. As shown in FIG. 12, the RRC reconfiguration complete is retained even after RLF.

More specifically, Regular BSR is not triggered even if additional data is generated in the state where (untransmitted) data of the same priority already exists in the terminal (see 3GPP TS38.321). Also, in the normal case, once the Regular BSR is triggered, the Regular BSR can be triggered by the expiration of the Retx BSR-timer, but in the above case, the Retx BSR-timer is stopped by the MAC reset at the time of RLF. It ends up.

Therefore, in the present embodiment, the terminal activates the RA procedure at a predetermined timing. FIG. 13 shows an example in which the RA procedure is activated when the problem shown in FIG. 12 is solved and Conditional HO is applied to wireless link failure (RLF).

Specifically, the terminal can activate the RA procedure by any of the following methods.

-(Method 1): Start the RA procedure directly at a predetermined timing- (Method 2): In the case of discarding the SRB1 data at the time of CHO after RLF (Method 1), the predetermined timing may be any of the following.

-When 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 sent from RRC to a lower layer such as PDCP / RLC Case-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, RRC reconfiguration complete has a different name, for example, CHO completion message. It may be called (the same applies hereinafter). Further, the "predetermined timing" may be either after RLF or after CHO. Alternatively, it may be the timing when the wireless bearer (RB) is stopped or the timing when the MAC reset is transmitted.

In addition, the activation of the RA procedure can be realized by any of the following (instruction from RRC or MAC layer is executed autonomously).

-Trigger the RA procedure directly (may be considered triggered)
-Trigger a scheduling request (SR) (may be considered triggered)
-Trigger Regular BSR (may be considered triggered)
Further, in the case of (Method 2), at least one of the following may be applicable to the destruction of the data.

・ By discarding the data, the RRC reconfiguration complete generated after that is regarded as "high priority data", and the RA procedure based on the conventional Regular BSR is started. Alternatively, it may be considered that there is no data (which can be transmitted) without discarding the data.

-Destroy (timing to consider that there is no data) can be any of the following-When RLF is detected (may be limited to when CHO is set)
-When transitioning to a new cell by CHO-When applying the setting corresponding to the new cell (preset by the CHO setting) -After a predetermined time has passed from any of the above timings-Destroy any of the following・ It is considered that discardOnPDCP (specified for SRB) has been set. ・ The terminal (UE) that executes PDCP data recovery or PDCP re-establishment for SRB1 is notified of discardOnPDCP to PDCP. Then, at least one or both of the transmission data and the reception data accumulated at that time for the SRB are discarded. Further, when the PDCP is notified of the PDCP data recovery or PDCP re-establishment, the terminal discards at least one or both of the transmission data and the reception data to the wireless bearer. As a result, the data is destroyed while using the existing procedure.

(4) Action / Effect According to the above-described embodiment, the following action / effect can be obtained. Specifically, according to UE200 (terminal), it corresponds to Conditional HO that transitions to the target radio base station without using the reconnection procedure in the RRC layer, and UE200 corresponds to radio link failure (RLF). , When transitioning to the target radio base station according to the Conditional HO without using the reconnection procedure, the random access procedure (RA procedure) with the target radio base station can be started at the specified timing.

The UE200 also decides to discard the data transmitted via the signaling radio bearer when transitioning to the target radio base station according to Conditional HO without using the reconnection procedure due to a radio link failure (RLF). Can be done.

Specifically, after discarding the data, the UE200 starts the RA procedure with the target radio base station based on the buffer status report (BSR).

In ConditionalHO, the UE200 sends an RRC reconfiguration complete to the target radio base station, but in certain situations, for example, if there is already data to be sent via SRB1, the buffer status report (BSR) Is not triggered, so the RA procedure for sending a scheduling request (SR) to the target radio base station may not be started, but even in such a case, the RA procedure with the target radio base station is surely performed. Can start.

As a result, by including the control by Conditional HO (CHO) in addition to the conventional control of layer 2 when RLF occurs, for example, communication by not starting the RA procedure while shortening the instantaneous interruption time at the time of HOF. Delays can be avoided.

(5) Other Embodiments Although the contents of the present invention have been described above with reference to Examples, the present invention is not limited to these descriptions, and various modifications and improvements are possible. It is obvious to the trader.

For example, in the above-described embodiment, NR has been described as an example, but Conditional HO is also applicable to LTE, and the same operation may be executed in LTE as well. It may also be applied to the addition / change of the Primary SCell (PSCell) of the Multi-RAT Dual Connectivity (MR-DC).

Further, in the above-described embodiment, Conditional HO has been described as an example, but if it is a transition procedure for transitioning to the target radio base station without using the reconnection procedure in the RRC layer, another procedure is applied instead of Conditional HO. May be done. For example, it may be generally applied when the terminal autonomously selects a cell and executes a random access procedure, such as when transitioning from the IDLE state or the Inactive state to the 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 the random access procedure may be executed as described above when transitioning from the predetermined state to the target radio base station.

In the above-described embodiment, the destruction of the data transmitted via the SRB1 has been described as an example, but the terminal (UE200) is the data transmitted via the signaling radio bearer other than the SRB1 or the data radio bearer (DRB). May be decided to discard.

Further, the block configuration diagram (FIG. 2) used in the description of the above-described embodiment shows a block for each functional unit. These functional blocks (components) are realized by any combination of at least one of hardware and software. Further, the method of realizing each functional block is not particularly limited. That is, each functional block may be realized using one device that is physically or logically connected, or two or more physically or logically separated devices that are directly or indirectly (eg, for example). , Wired, wireless, etc.) and may be realized using these plurality of devices. The functional block may be realized by combining the software with the one device or the plurality of devices.

Functions include judgment, decision, judgment, calculation, calculation, processing, derivation, investigation, search, confirmation, reception, transmission, output, access, solution, selection, selection, establishment, comparison, assumption, expectation, and assumption. There are broadcasting, notifying, communicating, forwarding, configuring, reconfiguring, allocating, mapping, assigning, etc., but only these. I can't. For example, a functional block (constituent unit) that makes transmission function is called a transmitting unit or a transmitter. As described above, the method of realizing each is not particularly limited.

Further, the UE 200 described above may function as a computer that processes the wireless communication method of the present disclosure. FIG. 14 is a diagram showing an example of the hardware configuration of UE200. As shown in FIG. 14, the UE 200 may be configured as a computer device including a processor 1001, memory 1002, storage 1003, communication device 1004, input device 1005, output device 1006, bus 1007, and the like.

In the following explanation, the word "device" can be read as a circuit, device, unit, etc. The hardware configuration of the device may be configured to include one or more of the devices shown in the figure, or may be configured not to include some of the devices.

Each functional block of UE200 (see FIG. 2) is 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 such that the processor 1001 performs an operation by loading predetermined software (program) on the hardware such as the processor 1001 and the memory 1002 to control the communication by the communication device 1004 and the memory 1002. And by controlling at least one of reading and writing of data in the storage 1003.

Processor 1001 operates, for example, an operating system to control the entire computer. The processor 1001 may be composed of a central processing unit (CPU) including an interface with peripheral devices, a control device, an arithmetic unit, a register, and the like.

Further, the processor 1001 reads a program (program code), a software module, data, etc. from at least one of the storage 1003 and the communication device 1004 into the memory 1002, and executes various processes according to these. As the program, a program that causes a computer to execute at least a part of the operations described in the above-described embodiment is used. Further, 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. Processor 1001 may be implemented by one or more chips. The program may be transmitted from the network via a telecommunication line.

The memory 1002 is a computer-readable recording medium, and is composed of at least one such as ReadOnlyMemory (ROM), ErasableProgrammableROM (EPROM), Electrically ErasableProgrammableROM (EEPROM), and RandomAccessMemory (RAM). May be done. The memory 1002 may be called a register, a cache, a main memory (main storage device), or the like. The memory 1002 can store a program (program code), a software module, or the like that can execute the method according to the embodiment of the present disclosure.

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

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 referred to as, for example, a network device, a network controller, a network card, a communication module, or the like.

Communication device 1004 includes, for example, a high frequency switch, a duplexer, a filter, a frequency synthesizer, etc. in order to realize at least one of frequency division duplex (FDD) and time division duplex (TDD). It may be composed of.

The input device 1005 is an input device (for example, keyboard, mouse, microphone, switch, button, sensor, etc.) that accepts 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 have an integrated configuration (for example, a touch panel).

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

Furthermore, the device includes hardware such as a microprocessor, a digital signal processor (Digital Signal Processor: DSP), ApplicationSpecific IntegratedCircuit (ASIC), ProgrammableLogicDevice (PLD), and FieldProgrammableGateArray (FPGA). The hardware may implement some or all of each functional block. For example, processor 1001 may be implemented using at least one of these hardware.

Further, the notification of information is not limited to the mode / embodiment described in the present disclosure, and may be performed by using another method. For example, information notification includes physical layer signaling (for example, Downlink Control Information (DCI), Uplink Control Information (UCI), upper layer signaling (eg, RRC signaling, Medium Access Control (MAC) signaling, broadcast information (Master Information Block)). (MIB), System Information Block (SIB)), other signals or combinations thereof. RRC signaling may also be referred to as an RRC message, for example, RRC Connection Setup. ) Message, RRC Connection Reconfiguration message, etc. may be used.

Each aspect / embodiment described in the present disclosure includes LongTermEvolution (LTE), LTE-Advanced (LTE-A), SUPER3G, IMT-Advanced, 4th generation mobile communication system (4G), 5th generation mobile communication system ( 5G), FutureRadioAccess (FRA), NewRadio (NR), W-CDMA (registered trademark), GSM (registered trademark), CDMA2000, UltraMobile Broadband (UMB), IEEE802.11 (Wi-Fi (registered trademark)) , IEEE802.16 (WiMAX®), IEEE802.20, Ultra-WideBand (UWB), Bluetooth®, and other systems that utilize appropriate systems and at least one of the next generation systems extended based on them. It may be applied to one. Also, a plurality of systems may be applied in combination (for example, a combination of at least one of LTE and LTE-A and 5G).

The order of the processing procedures, sequences, flowcharts, etc. of each aspect / embodiment described in the present disclosure may be changed as long as there is no contradiction. For example, the methods described in the present disclosure present elements of various steps using exemplary order, and are not limited to the particular order presented.

In some cases, the specific operation performed by the base station in the present disclosure may be performed by its upper node (upper node). In a network consisting of one or more network nodes having a base station, various operations performed for communication with the terminal are performed by the base station and other network nodes other than the base station (for example, MME or). It is clear that it can be done by at least one of (but not limited to, S-GW, etc.). Although the case where there is one network node other than the base station is illustrated above, it may be a combination of a plurality of other network nodes (for example, MME and S-GW).

Information and signals (information, etc.) can be output from the upper layer (or lower layer) to the lower layer (or upper layer). Input / output may be performed via a plurality of network nodes.

The input / output information may be stored in a specific location (for example, memory) or may be managed using a management table. The input / output information can be overwritten, updated, or added. The output information may be deleted. The input information may be transmitted to another device.

The determination may be made by a value represented by 1 bit (0 or 1), by a boolean value (Boolean: true or false), or by comparing numerical values (for example, a predetermined value). It may be done by comparison with the value).

Each aspect / embodiment described in the present disclosure may be used alone, in combination, or switched with execution. Further, the notification of predetermined information (for example, the notification of "being X") is not limited to the explicit one, but is performed implicitly (for example, the notification of the predetermined information is not performed). May be good.

Software is an instruction, instruction set, code, code segment, program code, program, subprogram, software module, whether called software, firmware, middleware, microcode, hardware description language, or another name. , Applications, software applications, software packages, routines, subroutines, objects, executable files, execution threads, procedures, features, etc. should be broadly interpreted to mean.

In addition, software, instructions, information, etc. may be transmitted and received via a transmission medium. For example, a website, where the software uses at least one of wired technology (coaxial cable, fiber optic cable, twist pair, Digital Subscriber Line (DSL), etc.) and wireless technology (infrared, microwave, etc.). When transmitted from a server, or other remote source, 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 be represented using any of a variety of different techniques. For example, data, instructions, commands, information, signals, bits, symbols, chips, etc. that may be referred to throughout the above description are voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, light fields or photons, or any of these. It may be represented by a combination of.

Note that the terms explained in the present disclosure and the terms necessary for understanding the present disclosure may be replaced with terms having the same or similar meanings. For example, at least one of a channel and a symbol may be a signal (signaling). Also, the signal may be a message. Further, the component carrier (CC) may be referred to as a carrier frequency, a cell, a frequency carrier, or the like.

The terms "system" and "network" used in this disclosure are used interchangeably.

Further, the information, parameters, etc. described in the present disclosure may be expressed using absolute values, relative values from predetermined values, or using other corresponding information. It may be represented. For example, the radio resource may be one indicated by an index.

The names used for the above parameters are not limited in any respect. Further, mathematical formulas and the like using these parameters may differ from those explicitly disclosed in this disclosure. Since the various channels (eg PUCCH, PDCCH, etc.) and information elements can be identified by any suitable name, the various names assigned to these various channels and information elements are in any respect limited names. is not.

In this disclosure, "Base Station (BS)", "Wireless Base Station", "Fixed Station", "NodeB", "eNodeB (eNB)", "gNodeB (gNB)", " "Access point", "transmission point", "reception point", "transmission / reception point", "cell", "sector", "cell group", "cell group" Terms such as "carrier" and "component carrier" can be used interchangeably. Base stations are sometimes referred to by terms such as macrocells, small cells, femtocells, and picocells.

The base station can accommodate one or more (for example, three) cells (also called sectors). When a base station accommodates multiple cells, the entire coverage area of the base station can be divided into multiple smaller areas, each smaller area being a base station subsystem (eg, a small indoor base station (Remote Radio)). Communication services can also be provided by Head: RRH).

The term "cell" or "sector" refers to a base station that provides communication services in this coverage, and part or all of the coverage area of at least one of the base station subsystems.

In the present disclosure, terms such as "mobile station (MS)", "user terminal", "user equipment (UE)", and "terminal" may be used interchangeably. ..

Mobile stations can be subscriber stations, mobile units, subscriber units, wireless units, remote units, mobile devices, wireless devices, wireless communication devices, remote devices, mobile subscriber stations, access terminals, mobile terminals, wireless, depending on the trader. It may also be referred to as a terminal, remote terminal, handset, user agent, mobile client, client, or some other suitable term.

At least one of the base station and the mobile station may be called a transmitting device, a receiving device, a communication device, or the like. At least one of the base station and the mobile station may be a device mounted on the mobile body, the mobile body itself, or the like. The moving body may be a vehicle (eg, car, airplane, etc.), an unmanned moving body (eg, drone, self-driving car, etc.), or a robot (manned or unmanned). ) May be. It should be noted that at least one of the base station and the mobile station includes a device that does not necessarily move during communication operation. For example, at least one of a base station and a mobile station may be an Internet of Things (IoT) device such as a sensor.

Further, the base station in the present disclosure may be read as a mobile station (user terminal, the same applies hereinafter). For example, communication between a base station and a mobile station has been replaced with communication between a plurality of mobile stations (for example, it may be called Device-to-Device (D2D), Vehicle-to-Everything (V2X), etc.). Each aspect / embodiment of the present disclosure may be applied to the configuration. In this case, the mobile station may have the function of the base station. In addition, words such as "up" and "down" may be read as words corresponding to communication between terminals (for example, "side"). For example, the uplink, downlink, and the like may be read as side channels.

Similarly, the mobile station in the present disclosure may be read as a base station. In this case, the base station may have the functions of the mobile station.
The radio frame may be composed of one or more frames in the time domain. Each one or more frames in the time domain may be referred to as a subframe.
Subframes may further consist of one or more slots in the time domain. The subframe may have a fixed time length (eg, 1 ms) that is independent of numerology.

The numerology may be a communication parameter that applies to at least one of the transmission and reception of a signal or channel. Numerology includes, for example, SubCarrier Spacing (SCS), bandwidth, symbol length, cyclic prefix length, transmission time interval (TTI), number of symbols per TTI, wireless frame configuration, transmission / reception. At least one of a specific filtering process performed by the machine in the frequency domain, a specific windowing process performed by the transmitter / receiver in the time domain, and the like may be indicated.

The slot may be composed of one or more symbols (Orthogonal Frequency Division Multiple Access (OFDM) symbol, Single Carrier Frequency Division Multiple Access (SC-FDMA) symbol, etc.) in the time domain. Slots may be unit of time based on numerology.

The slot may include a plurality of mini slots. Each minislot may consist of one or more symbols in the time domain. Further, the mini slot may be called a sub slot. A minislot may consist of a smaller number of symbols than the slot. PDSCH (or PUSCH) transmitted in time units larger than the minislot may be referred to as PDSCH (or PUSCH) mapping type A. PDSCH (or PUSCH) transmitted using the minislot may be referred to as PDSCH (or PUSCH) mapping type B.

The wireless frame, subframe, slot, mini slot and symbol all represent the time unit when transmitting a signal. The radio frame, subframe, slot, minislot and symbol may have different names corresponding to each.

For example, one subframe may be referred to as a transmission time interval (TTI), a plurality of consecutive subframes may be referred to as TTI, and one slot or one minislot may be referred to as TTI. That is, at least one of the subframe and TTI may be a subframe (1ms) in existing LTE, a period shorter than 1ms (eg, 1-13 symbols), or a period longer than 1ms. It may be. The unit representing TTI may be called a slot, a mini slot, or the like instead of a subframe.

Here, TTI refers to, for example, the minimum time unit of scheduling in wireless communication. For example, in the LTE system, the base station schedules each user terminal to allocate wireless resources (frequency bandwidth that can be used in each user terminal, transmission power, etc.) in TTI units. The definition of TTI is not limited to this.

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

When one slot or one mini slot is called TTI, one or more TTIs (that is, one or more slots or one or more mini slots) may be the minimum time unit for scheduling. Further, the number of slots (number of mini-slots) constituting the minimum time unit of the scheduling may be controlled.

A TTI having a time length of 1 ms may be called a normal TTI (TTI in LTE Rel.8-12), a normal TTI, a long TTI, a normal subframe, a normal subframe, a long subframe, a slot, or the like. TTIs shorter than normal TTIs may also be referred to as shortened TTIs, short TTIs, partial TTIs (partial or fractional TTIs), shortened subframes, short subframes, minislots, subslots, slots, and the like.

Note that long TTIs (eg, normal TTIs, subframes, etc.) may be read as TTIs with a time length of more than 1 ms, and short TTIs (eg, shortened TTIs, etc.) are less than the TTI length of long TTIs and 1 ms. It may be read as a TTI having the above TTI length.

A resource block (RB) is a resource allocation unit in the time domain and the frequency domain, and may include one or a plurality of continuous subcarriers in the frequency domain. The number of subcarriers contained in RB may be the same regardless of numerology, and may be, for example, 12. The number of subcarriers contained in the RB may be determined based on numerology.

Further, the time domain of RB may include one or more symbols, and may have a length of 1 slot, 1 mini slot, 1 subframe, or 1 TTI. Each 1TTI, 1 subframe, etc. may be composed of one or a plurality of resource blocks.

One or more RBs include a physical resource block (Physical RB: PRB), a sub-carrier group (Sub-Carrier Group: SCG), a resource element group (Resource Element Group: REG), a PRB pair, an RB pair, etc. May be called.

Further, the resource block may be composed of one or a plurality of resource elements (ResourceElement: RE). For example, 1RE may be a radio resource area of 1 subcarrier and 1 symbol.

Bandwidth Part (BWP) (which may also be called partial bandwidth, etc.) may represent a subset of consecutive common resource blocks (RBs) for a neurology in a carrier. Good. Here, the common RB may be specified by the index of the RB with respect to the common reference point of the carrier. PRBs may be defined in a BWP and numbered within that BWP.

BWP may include BWP for UL (UL BWP) and BWP for DL (DL BWP). One or more BWPs may be set in one carrier for the UE.

At least one of the configured BWPs may be active, and the UE may not expect to send or receive a given signal / channel outside the active BWP. In addition, "cell", "carrier" and the like in this disclosure may be read as "BWP".

The above-mentioned structures such as wireless frames, subframes, slots, mini slots and symbols are merely examples. For example, the number of subframes contained in a wireless frame, the number of slots per subframe or wireless frame, the number of minislots contained within a slot, the number of symbols and RBs contained in a slot or minislot, included in RB. The number of subcarriers, the number of symbols in the TTI, the symbol length, the cyclic prefix (CP) length, and other configurations can be changed in various ways.

The terms "connected", "coupled", or any variation thereof, mean any direct or indirect connection or connection between two or more elements, and each other. It can include the presence of one or more intermediate elements between two "connected" or "combined" elements. The connection or connection between the elements may be physical, logical, or a combination thereof. For example, "connection" may be read as "access". As used in the present disclosure, the two elements use at least one of one or more wires, cables and printed electrical connections, and, as some non-limiting and non-comprehensive examples, the radio frequency domain. , Electromagnetic energies with wavelengths in the microwave and light (both visible and invisible) regions, etc., can be considered to be "connected" or "coupled" to each other.

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

The phrase "based on" as used in this disclosure does not mean "based on" unless otherwise stated. In other words, the statement "based on" means both "based only" and "at least based on".

The "means" in the configuration of each of the above devices may be replaced with "part", "circuit", "device" and the like.

Any reference to elements using designations such as "first", "second" as used in this disclosure does not generally limit the quantity or order of those elements. These designations can be used in the present disclosure as a convenient way to distinguish between two or more elements. Thus, references to the first and second elements do not mean that only two elements can be adopted there, or that the first element must somehow precede the second element.

When "include", "including" and variations thereof are used in the present disclosure, these terms are as comprehensive as the term "comprising". Is intended. Moreover, the term "or" used in the present disclosure is intended not to be an exclusive OR.

In the present disclosure, if articles are added by translation, for example, a, an and the in English, the disclosure may include that the nouns following these articles are in the plural.

The terms "determining" and "determining" used in this disclosure may include a wide variety of actions. "Judgment" and "decision" are, for example, judgment (judging), calculation (calculating), calculation (computing), processing (processing), derivation (deriving), investigation (investigating), search (looking up, search, inquiry). (For example, searching in a table, database or another data structure), ascertaining may be regarded as "judgment" or "decision". Also, "judgment" and "decision" are receiving (for example, receiving information), transmitting (for example, transmitting information), input (input), output (output), and access. (Accessing) (for example, accessing data in memory) may be regarded as "judgment" or "decision". In addition, "judgment" and "decision" mean that "resolving", "selecting", "choosing", "establishing", "comparing", etc. are regarded as "judgment" and "decision". Can include. That is, "judgment" and "decision" may include that some action is regarded as "judgment" and "decision". Further, "judgment (decision)" may be read as "assuming", "expecting", "considering" and the like.

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

Although the present disclosure has been described in detail above, it is clear to those skilled in the art that the present disclosure is not limited to the embodiments described in the present disclosure. The present disclosure may be implemented as an amendment or modification without departing from the purpose and scope of the present disclosure, which is determined by the description of the scope of claims. Therefore, the description of the present disclosure is for the purpose of exemplary explanation and does not have any limiting meaning to the present disclosure.

10 Wireless communication system 100A-100C gNB
200 UE
210 Wireless transmitter 220 Wireless receiver 230 RA Procedure execution unit 240 Data discard unit 250 Control unit 1001 Processor 1002 Memory 1003 Storage 1004 Communication device 1005 Input device 1006 Output device 1007 Bus

Claims

Equipped with a control unit that transitions to the target radio base station without using the reconnection procedure
The control unit is a terminal that starts a random access procedure with the target radio base station at a specified timing when transitioning to the target radio base station due to a radio link failure.
Equipped with a control unit that transitions to the target radio base station without using the reconnection procedure
The control unit is a terminal that determines the destruction of data transmitted via a signaling radio bearer when transitioning to the target radio base station due to a radio link failure.
The terminal according to claim 2, wherein the control unit starts a random access procedure with the target radio base station based on the buffer state report after discarding the data.