JP7402874B2 - terminal - Google Patents

Description

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

The 3rd Generation Partnership Project (3GPP) has standardized Long Term Evolution (LTE), and has developed LTE-Advanced (hereinafter referred to as LTE including LTE-Advanced) with the aim of further increasing the speed of LTE, and the 5th generation mobile communication system. (also known as 5G, New Radio (NR) or Next Generation (NG)) specifications are also progressing.

For example, in a conventional handover (HO) procedure, a network selects a target radio base station (also called a target cell) based on quality information such as a measurement report sent from a user equipment (UE). After determining and preparing for handover, a handover command is sent to the terminal.

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

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

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

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

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

"New WID: NR mobility enhancements", RP-190489, 3GPP TSG RAN Meeting #83, 3GPP, March 2019 "Running CR for the introduction of NR mobility enhancement", R2-1906284, 3GPP TSG-RAN WG2 Meeting #106, 3GPP, May 2019 "Summary of mobility robustness agreements from LTE mobility", R2-1908417, 3GPP TSG RAN WG2 Meeting #106, 3GPP, May 2019

However, if the cell transition procedure according to Conditional HO is directly applied to return from RLF, the following problems may occur.

Specifically, in the case of the RRC reconnection procedure due to the occurrence of RLF, Signaling Radio Bearer 1 (SRB1) is resumed with the transmission of the RRC Reestablishment Request as a trigger, but in Conditional HO, the RRC Reestablishment Request is Because it is not sent, SRB1 cannot be restarted and RRC Reestablishment Complete is not sent.

That is, there is no opportunity to restart the radio bearer (RB) and there is a problem that uplink (UL) data cannot be transmitted.

Therefore, the present invention was made in view of this situation, and it is possible to reliably restart a radio bearer even when transitioning to a target radio base station without using a reconnection procedure like Conditional HO. The purpose is to provide a terminal that can be used to obtain information.

One aspect of the present disclosure includes a control unit (control unit 250) that makes a transition to the target radio base station without using a reconnection procedure, and the control unit makes a transition to the target radio base station in response to a radio link failure. In this case, the terminal (UE 200) resumes the radio bearer at the specified timing.

FIG. 1 is an overall schematic configuration diagram of a wireless communication system 10. FIG. 2 is a functional block diagram of the UE 200. FIG. 3 is an explanatory diagram of a conventional handover procedure. FIG. 4 is an explanatory diagram of a handover procedure using Conditional HO. FIG. 5 is an explanatory diagram of a recovery procedure from a handover failure (HOF) using a reconnection procedure 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 illustrating an image of interactions between intra-terminal layers during handover. FIG. 10 is a diagram illustrating an image of interactions between layers within a terminal when reconnecting to a target radio base station. FIG. 11 is a diagram showing the relationship between periods in which data transmission of SRB0, SRB1, and SRB2/DRB is enabled/disabled and message transmission/reception timing in RRC. FIG. 12 is a diagram illustrating an example in which a radio bearer is not restarted when Conditional HO is applied to radio link failure (RLF). FIG. 13 is a diagram illustrating an example in which a radio bearer is restarted when the problem shown in FIG. 12 is solved 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.

Hereinafter, embodiments will be described based on the drawings. Note that the same functions and configurations are given the same or similar symbols, 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 a wireless communication system 10 according to the present embodiment. The radio communication system 10 is a radio communication system according to 5G New Radio (NR), and includes a Next Generation-Radio Access Network (NG-RAN) (not shown) and a user terminal 200 (User Equipment 200, hereinafter referred to as UE 200).

NG-RAN includes radio base stations 100A (hereinafter referred to as gNB100A) to radio base stations 100C (hereinafter referred to as gNB100C). Note that 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. 1.

Furthermore, NG-RAN actually includes multiple NG-RAN Nodes, specifically gNBs (or ng-eNBs), and is connected to a 5G-compliant core network (5GC, not shown). Note that NG-RAN and 5GC may also be simply expressed as networks.

gNB100A to gNB100C are 5G-compliant wireless base stations and perform 5G-compliant wireless communication with the UE 200. gNB100A to gNB100C and UE200 use Massive MIMO, which generates a highly directional beam by controlling radio signals transmitted from multiple antenna elements, and Carrier Aggregation (CA), which uses multiple component carriers (CC) in a bundle. ), and dual connectivity (DC) where communication is performed simultaneously between the UE and each of multiple NG-RAN nodes.

gNB100A to gNB100C each form one or more cells. UE 200 can transition between cells (which may also be referred to as radio base stations) formed by gNB 100A to gNB 100C. "Transition" typically means handover between cells (radio base stations), but the behavior of the UE 200 (behavior) such as cell reselection that changes the connected cell (radio base station) ) may be included.

The cell (radio base station) to which the UE 200 transitions is called a target cell or target radio base station. Further, the cell (radio base station) of the transition source is called a source cell or source wireless base station.

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

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

(2) Functional block configuration of wireless communication system Next, the functional block configuration of the wireless communication system 10 will be explained. Specifically, the functional block configuration of UE 200 will be explained.

FIG. 2 is a functional block diagram of the UE 200. As shown in FIG. 2, the UE 200 includes a wireless transmitter 210, a wireless receiver 220, an RA procedure execution unit 230, a data discard unit 240, and a control unit 250.

Radio transmitter 210 transmits an uplink signal (UL signal) according to NR. Radio receiving section 220 receives a downlink signal (DL signal) according to NR.

Specifically, the wireless transmitter 210 and the wireless receiver 220 perform 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, Downlink Control Information (DCI) including Random Access Radio Network Temporary Identifier (RA-RNTI)), and Physical Includes Broadcast Channel (PBCH), etc.

Further, data channels include PDSCH (Physical Downlink Shared Channel), PUSCH (Physical Downlink Shared Channel), and the like.

The RA procedure execution unit 230 executes a random access (RA) procedure with a wireless base station, specifically, with any of gNB 100A to gNB 100C. Specifically, the RA procedure execution unit 230 transmits and receives messages according to the RA procedure under the control of the control unit 250.

Note that the RA procedure may include contention-based random access (CBRA) and contention-free 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 that is the connection request destination, and receives a Random Access Response (Msg.2) that is a response to the Random Access Preamble from the gNB. . 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 executed, for example, during the initial access from the RRC_IDLE state and the RRC connection re-establishment procedure, but in this embodiment, as will be described later, the target radio base station The RA procedure is also executed when transitioning to .

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

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

Note that the radio bearer includes a signaling radio bearer (SRB) and a data radio bearer (DRB). SRB is for control plane data, and DRB is for user plane data. Furthermore, SRB0, 1, 2, and 3 can be set as SRBs depending on the purpose.

SRB0 is for RRC messages using the Common Control Channel (CCCH) logical channel. Specifically, SRB0 is used to send and receive specific RRC messages (such as RRC Setup Request).

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

SRB2 is for NAS messages and uses the DCCH logical channel. SRB2 has lower priority than SRB1 and may be configured by the network after AS security activation.

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

Further, DRB is for user data.

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

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

Furthermore, when transitioning to a target radio base station due to a radio link failure (RLF), the control unit 250 restarts the radio bearer at a specified timing.

Note that radio bearers may include signaling radio bearers (SRBs) and data radio bearers, and SRBs include SRBs 1 and 2 (further may include SRBs 0 and 3).

Specifically, the control unit 250 controls the RA procedure execution unit 230 and performs wireless communication based on prescribed timing, for example, an instruction from the RRC layer, or generation and transmission of a predetermined message in the RRC layer. Bearer can be resumed. Note that the details of the timing will be described further later.

Further, the control unit 250 may restart the radio bearer at different timings for each type of radio bearer. For example, SRB1 and SRB2 may be restarted at different timings, or each radio bearer group (for example, SRB2 and DRB) may be restarted at different timings.

Furthermore, the control unit 250 may restart the radio bearer in response to instructions received from the network. The instruction from the network may be an RRC layer message, or a lower layer message such as MAC-CE (Control Element) may be used. Further, the instruction from the network may be given before, at the time of, or after detecting the RLF, and is not particularly limited, such as when determining the transition to the target radio base station.

(3) Operation of wireless communication system Next, the operation of the wireless communication system 10 will be explained. Specifically, the operation of Conditional HO and the operation of returning from RLF using Conditional HO will be explained, and then the operation that can solve problems in the operation of returning from RLF using Conditional HO will be explained.

(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 using Conditional HO.

As shown in Figure 3, in the conventional handover procedure, the network (gNB) uses quality information ((1) in the figure) such as measurement reports sent from the terminal (User Equipment, UE). After determining the target radio base station (T-gNB) and preparing for handover ((2) in the figure), a handover command is sent to the terminal ((3) in the figure).

However, if the terminal passes through an appropriate handover point while preparing for handover on the network side, it will transition to the target wireless base station (S-gNB) without receiving a handover command from the source wireless base station (S-gNB). (4) in the figure may occur (this may also be called "too late HO"). Therefore, the terminal cannot recognize the settings related to the target radio base station, and a momentary interruption of the radio link may occur.

To solve these problems, a procedure called Conditional HO (may be abbreviated as CHO) is being considered. In Conditional HO, a handover candidate cell and transition conditions to the candidate cell are set in advance for the terminal. Thereby, the terminal can connect to the target wireless base station without waiting for an instruction (handover command) from the network, and can avoid instantaneous interruption of the wireless link.

Specifically, as shown in Figure 4, handover preparations are performed in advance ((1) in the figure) between the source wireless base station (S-gNB) and the target wireless base station (T-gNB). , the Conditional HO settings, including conditions for transition to the target wireless base station, are notified to the terminal ((2) in the figure). When a terminal decides to connect to a target radio base station due to movement or the like, it starts an RA procedure with the target radio base station ((3) in the figure) based on the settings of the Conditional HO.

Note that 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, a procedure for recovering from Radio Link Failure (RLF) using Conditional HO described above will be described. Specifically, as an example of RLF, when a terminal (UE) fails to handover to the original target cell (cell A) (referred to as a handover failure (HOF)), it attempts to handover to another target cell (cell B). Explain the case.

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

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

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

On the other hand, in the case of recovery from HOF using Conditional HO (CHO), the procedure according to Conditional HO is executed ((3) in the figure) instead of the reconnection procedure. This can reduce the momentary interruption time of the wireless link.

This will be explained in more detail below. FIG. 7 shows a recovery sequence from a handover failure (HOF) using a reconnection procedure in 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, in both the return from HOF using the reconnection procedure and the return from HOF using Conditional HO, based on handover preparation (HO preparation/CHO preparation), The settings related to the handover (HO config/CHO config) are notified to the terminal (UE).

Note that, as described above, in the case of Conditional HO, information regarding the CHO, such as a candidate cell for handover and transition conditions to the candidate cell, is set in advance for the terminal.

The terminal transmits 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.

Thereafter, in the case of recovery from HOF using the reconnection procedure shown in FIG. 7, the terminal starts an RA procedure with cell B (here, expressed as gNB#2). Furthermore, a reconnection procedure in the RRC layer is executed, and the user plane is established.

On the other hand, in the case of recovery from HOF using Conditional HO shown in Figure 8, the terminal performs the RA procedure with cell B (gNB#2) and then sends only RRC Reconfiguration Complete to ensure that the user plane is connected ( Establish. In Conditional HO, the terminal knows the handover candidate cell and the transition conditions to the candidate cell, so there is no need to perform a reconnection procedure in the RRC layer. As a result, the instantaneous interruption time is shortened compared to recovery from 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 due to Conditional HO.

Additionally, the terminal may operate as follows. Specifically, when RLF occurs, the terminal performs cell selection and attempts CHO if the selected cell is a CHO candidate cell. Otherwise, the terminal performs a reconnection procedure at the RRC layer. The terminal also performs cell selection in case of legacy HO failure (T304 expiration) or failure to access a 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 In contrast to the conventional layer 2 control at the time of RLF occurrence as described above, when control by Conditional HO is included, the following problems arise.

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, transmit UL data). situations may arise where it is not possible to do so.

Therefore, it is desirable to specify the trigger for restarting 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 perspective of RA procedures and UL data transmission.

・Aspects of RA procedures ・Conventional HO and reconnection procedures stipulate starting RA procedures for the target cell and establishing synchronization. ・The medium access control layer (MAC) layer The activation of the RA procedure is based on the buffer status report (specifically, Regular BSR) due to the occurrence of high priority data (3GPP TS38.321)
In other words, the internal operation flow of the terminal is (i) high-priority data generation, (ii) Regular BSR is triggered, (iii) scheduling request (SR) is triggered, and (iv) RA procedure activation. .

Furthermore, 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 an occurrence of "high priority data".

Furthermore, when reconnecting with the target radio base station, an RRC Reestablishment Request (transmitted using SRB0 (CCCH)) is generated. RRC Reestablishment Request is handled as if "high priority data" has been generated.

- UL data perspective - In the case of HO, all radio bearer data can be transmitted after HO. - When reconnecting with the target radio base station using RLF, transmission is temporarily suspended during RLF. , after re-establishing the connection, it will be resumed by the following triggers:
・SRB1: When sending RRC Reestablishment Request
- SRB2/DRB: After RRC Reconfiguration reception processing Figures 9 and 10 show an image of interaction between layers within the terminal related to activation of the RA procedure. Specifically, FIG. 9 shows an image of interactions between layers within a terminal during handover, and FIG. 10 shows an image of interactions between layers within a terminal when reconnecting to a target radio base station.

As shown in FIGS. 9 and 10, the terminal (UE 200) supports radio resource control layer (RRC), packet data convergence protocol layer (PDCP), radio link control layer (RLC), and medium access control layer ( MAC).

As shown in FIG. 9, in the case of HO, when the terminal (RRC) receives a handover command, it requests a reset from the MAC and a re-est from the PDCP/RLC. Furthermore, RRC notifies PDCP/RLC of RRC Reconfiguration Complete.

PDCP/RLC notifies the MAC of the buffer status (BS) indication. The MAC initiates the RA procedure based on the indication 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. Furthermore, RRC requests the MAC to reset and also notifies PDCP/RLC of an RRC Reestablishment Request.

The subsequent steps are the same as in FIG. 9, and PDCP/RLC notifies the MAC of the buffer status (BS). The MAC initiates the RA procedure based on the indication of the BS.

FIG. 11 shows an image of suspension/resume of a radio bearer in reconnecting to a target radio base station. Specifically, FIG. 11 shows the relationship between the period during which data transmission is possible/impossible for SRB0, SRB1, and SRB2/DRB and the message transmission/reception timing in RRC.

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

Thereafter, 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 or restarted, and data transmission is always possible.

(3.4) Resume of radio bearer As mentioned above, if control by Conditional HO (CHO) is included in the conventional layer 2 control when RLF occurs, there is no opportunity to resume the radio bearer. There are cases.

To explain more specifically, in the conventional RLF detection to RRC layer reconnection procedure, SRB1 is restarted upon transmission of an RRC Reestablishment Request, but recovery from RLF using CHO (Radio Link Recovery ( In RLR)), since no RRC Reestablishment Request is sent, there is no opportunity to restart SRB1, and RRC Reconfiguration Complete cannot be sent.

FIG. 12 shows an example in which a radio bearer is not restarted when Conditional HO is applied to radio link failure (RLF). As shown in FIG. 12, when the terminal (RRC) detects RLF, it stops radio bearers (RB) except SRB0. There is no opportunity to restart the radio bearer that was stopped at this timing.

Therefore, even if the RA procedure is completed after the CHO and data transmission via PUSCH occurs, UL data cannot be transmitted via PUSCH because the stopped radio bearer (for example, DRB) has not been restarted.

Therefore, in this embodiment, the terminal autonomously restarts the radio bearer. FIG. 13 shows an example in which the problem shown in FIG. 12 is solved and a radio bearer is restarted when Conditional HO is applied to radio link failure (RLF).

Specifically, the terminal can resume the radio bearer using any of the following methods.

・(Method 1): The terminal autonomously resumes the radio bearer ・(Method 2): The terminal resumes the radio bearer based on instructions from the network When resuming the radio bearer according to (Method 1), Before and after restart, at least one of any actions that trigger PDCP PDU discard is performed, such as PDCP data recovery, PDCP re-establishment, discardOnPDCP (specified in Release 15 for SRB), or RLC re-establishment. It's fine. Note that which one to apply may be changed for each resource block (RB) or for each RLC bearer (for example, discardOnPDCP is applied to SRB).

Alternatively, it may be specified in advance by the network using CHO config, or PDCP re-establishment may be executed when it is necessary to reconfigure the PDCP SDU, such as when updating a security key.

Further, the radio bearer restart timing may be any of the following.

・When transitioning to a new cell by CHO ・When applying the settings corresponding to the new cell (preset by CHO settings) ・When a layer such as PDCP/RLC receives an instruction from the RRC layer ・Identification When a 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 at the PDCP/RLC buffer, or when the message When a PDCP PDU, RLC PDU or MAC subPDU is generated based on - When the RA procedure is started (any step (Msg.1 to 4) during the execution of the RA procedure is fine)
・When the RA procedure is completed (Msg2 reception for CFRA, Msg4 reception for CBRA or MsgB reception for 2 step RACH)
- After a predetermined period of time has elapsed from any of the above timings In addition, in the case of (method 2), the terminal may restart the radio bearer when it receives any of the following.

- A message that instructs the radio bearer to perform at least one of PDCP data recovery, PDCP re-establishment, or RLC re-establishment - A specific type of RRC message (for example, RRC Reestablishment Request)
Furthermore, (Method 1) and (Method 2) may be different for each type of radio bearer (SRB1, 2, DRB, etc.) or for each combination thereof.

(4) Actions and Effects According to the embodiment described above, the following effects can be obtained. Specifically, according to the UE 200 (terminal), it supports Conditional HO, which transitions to the target radio base station without using the reconnection procedure in the RRC layer, and the UE 200 supports Conditional HO, which transitions to the target radio base station without using the reconnection procedure in the RRC layer. , when transitioning to the target radio base station according to the Conditional HO without using the reconnection procedure, the radio bearer can be restarted at a specified timing.

As mentioned above, when recovering from RLF using CHO (Radio Link Recovery (RLR)), RRC Reestablishment Request is not sent, so there is no opportunity to restart SRB1, and RRC Reconfiguration Complete cannot be sent. Even in such a case, the radio bearer can be reliably restarted.

As a result, by including Conditional HO (CHO) control in addition to the conventional layer 2 control when RLF occurs, for example, it is possible to reduce the momentary interruption time during HOF and improve communication by not restarting the radio bearer. Delays can be avoided.

In this embodiment, the UE 200 can resume the radio bearer in response to instructions received from the network. Therefore, it is possible to specify an appropriate radio bearer restart method and timing that takes into consideration the overall network situation. Thereby, it is possible to more reliably avoid communication delays due to the radio bearer not being restarted.

In this embodiment, the UE 200 can restart the radio bearer at different timings for each type of radio bearer. Therefore, a flexible radio bearer can be resumed depending on the usage status of the radio bearer. Thereby, the radio bearer can be restarted at an appropriate timing for each type of radio bearer, and communication delays can be avoided more reliably.

(5) Other Embodiments Although the content of the present invention has been explained above with reference to Examples, it is understood that the present invention is not limited to these descriptions and that various modifications and improvements are possible. It is self-evident to business operators.

For example, in the embodiment described above, NR was described as an example, but Conditional HO is also applicable to LTE, and similar operations may be performed in LTE as well. Additionally, it may be applied to addition/change of Primary SCell (PSCell) of Multi-RAT Dual Connectivity (MR-DC).

Furthermore, in the above embodiment, Conditional HO was explained as an example, but if it is a transition procedure for transitioning to a target wireless base station without using a reconnection procedure in the RRC layer, other procedures may be applied instead of Conditional HO. may be done. For example, it may be generally applied when a terminal autonomously selects a cell and executes a random access procedure, such as when transitioning from an IDLE state or an Inactive state to a Connected state. In other words, the random access procedure is not necessarily limited to the case where the transition is made to the target radio base station without using the reconnection procedure, but the random access procedure may be executed as described above when the transition is made from the predetermined state to the target radio base station.

Further, the block configuration diagram (FIG. 2) used to explain the embodiment described above shows blocks in functional units. These functional blocks (components) are realized by any combination of at least one of hardware and software. Furthermore, the method for realizing each functional block is not particularly limited. That is, each functional block may be realized using one physically or logically coupled device, or may be realized using two or more physically or logically separated devices directly or indirectly (e.g. , wired, wireless, etc.) and may be realized using a plurality of these devices. The functional block may be realized by combining software with the one device or the plurality of devices.

Functions include judgment, decision, judgment, calculation, calculation, processing, derivation, investigation, exploration, confirmation, reception, transmission, output, access, resolution, selection, selection, establishment, comparison, assumption, expectation, consideration, These include, but are not limited to, broadcasting, notifying, communicating, forwarding, configuring, reconfiguring, allocating, mapping, and assigning. I can't do it. For example, a functional block (configuration unit) that performs transmission is called a transmitting unit or a transmitter. In either case, as described above, the implementation method is not particularly limited.

Furthermore, the UE 200 described above may 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, a storage 1003, 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 word "apparatus" can be read as a circuit, a device, a unit, etc. The hardware configuration of the device may include one or more of the devices shown in the figure, or may not include some of the devices.

Each functional block of the UE 200 (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 implemented by loading predetermined software (programs) onto hardware such as the processor 1001 and the memory 1002, so that the processor 1001 performs calculations, controls communication by the communication device 1004, and controls the memory 1002. This is realized by controlling at least one of reading and writing data in the storage 1003.

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

Furthermore, the processor 1001 reads programs (program codes), software modules, data, and the like from at least one of the storage 1003 and the communication device 1004 to the memory 1002, and executes various processes in accordance with these. As the program, a program that causes a computer to execute at least part of the operations described in the above embodiments is used. Further, the various processes described above may be executed by one processor 1001, or may be executed by two or more processors 1001 simultaneously or sequentially. Processor 1001 may be implemented by one or more chips. Note that the program may be transmitted from a network via a telecommunications line.

The memory 1002 is a computer-readable recording medium, and includes at least one of Read Only Memory (ROM), Erasable Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), Random Access Memory (RAM), etc. may be done. Memory 1002 may be called a register, cache, main memory, or the like. The memory 1002 can store programs (program codes), software modules, etc. that can execute a method according to an embodiment of the present disclosure.

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

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.

The communication device 1004 includes, for example, a high frequency switch, a duplexer, a filter, a frequency synthesizer, etc. 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 (eg, 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 performs output to the outside. Note that the input device 1005 and the output device 1006 may have an integrated configuration (for example, a touch panel).

Further, 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.

Furthermore, the device may include hardware such as a microprocessor, digital signal processor (DSP), application specific integrated circuit (ASIC), programmable logic device (PLD), and field programmable gate array (FPGA). A part or all of each functional block may be realized by the hardware. For example, processor 1001 may be implemented using at least one of these hardwares.

Further, the notification of information is not limited to the aspects/embodiments described in this disclosure, and may be performed using other methods. For example, notification of information may be performed using physical layer signaling (e.g., Downlink Control Information (DCI), Uplink Control Information (UCI)), upper layer signaling (e.g., RRC signaling, Medium Access Control (MAC) signaling, broadcast information (Master Information Block (MIB), System Information Block (SIB)), other signals, or a combination thereof. RRC signaling may also be referred to as RRC messages, such as RRC Connection Setup (RRC Connection Setup). ) message, RRC Connection Reconfiguration message, etc.

Each aspect/embodiment described in this disclosure is applicable to Long Term Evolution (LTE), LTE-Advanced (LTE-A), SUPER 3G, IMT-Advanced, 4th generation mobile communication system (4G), 5th generation mobile communication system ( 5G), Future Radio Access (FRA), New Radio (NR), W-CDMA (registered trademark), GSM (registered trademark), CDMA2000, Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi (registered trademark)) , IEEE 802.16 (WiMAX (registered trademark)), IEEE 802.20, Ultra-WideBand (UWB), Bluetooth (registered trademark), and other suitable systems and next-generation systems enhanced based on these. may be applied to. Moreover, a combination of multiple systems (for example, a combination of at least one of LTE and LTE-A with 5G) may be applied.

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

The specific operations performed by the base station in this disclosure may be performed by its upper node in some cases. In a network consisting of one or more network nodes including a base station, various operations performed for communication with a terminal are performed by the base station and other network nodes other than the base station (e.g., MME or It is clear that this can be done by at least one of the following: (conceivable, 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 multiple other network nodes (for example, MME and S-GW).

Information, signals (information, etc.) may be output from an upper layer (or lower layer) to a lower layer (or upper layer). It may be input/output via multiple network nodes.

The input/output information may be stored in a specific location (for example, memory) or may be managed using a management table. Information that is input and output may be overwritten, updated, or additionally written. The output information may be deleted. The input information may be sent to other devices.

Judgment may be made using a value expressed by 1 bit (0 or 1), a truth value (Boolean: true or false), or a comparison of numerical values (for example, a predetermined value). (comparison with a value).

Each aspect/embodiment described in this disclosure may be used alone, may be used in combination, or may be switched and used in accordance with execution. In addition, notification of prescribed information (for example, notification of "X") is not limited to being done explicitly, but may also be done implicitly (for example, not notifying the prescribed information). Good too.

Software includes instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, whether referred to as software, firmware, middleware, microcode, hardware description language, or by any other name. , should be broadly construed to mean an application, software application, software package, routine, subroutine, object, executable, thread of execution, procedure, function, etc.

Additionally, software, instructions, information, etc. may be sent and received via a transmission medium. For example, if the software uses wired technology (coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL), etc.) and/or wireless technology (infrared, microwave, etc.) to When transmitted from a server or other remote source, these wired and/or wireless technologies are 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 technologies. For example, data, instructions, commands, information, signals, bits, symbols, chips, etc. that may be referred to throughout the above description may refer to voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, light fields or photons, or any of the foregoing. It may also be represented by a combination of

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

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

In addition, the information, parameters, etc. described in this disclosure may be expressed using absolute values, relative values from a predetermined value, or using other corresponding information. may be expressed. For example, radio resources may be indicated by an index.

The names used for the parameters described above are not restrictive in any respect. Furthermore, the mathematical formulas etc. using these parameters may differ from those explicitly disclosed in this disclosure. Since the various channels (e.g. PUCCH, PDCCH, etc.) and information elements can be identified by any suitable designation, the various names assigned to these various channels and information elements are in no way exclusive designations. isn't it.

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", " The terms "carrier", "component carrier", etc. may be used interchangeably. A base station is sometimes referred to by terms such as macrocell, small cell, femtocell, and picocell.

A base station can accommodate one or more (eg, three) cells (also called sectors). If a base station accommodates multiple cells, the overall coverage area of the base station can be partitioned into multiple smaller areas, and each smaller area is divided into base station subsystems (e.g., small indoor base stations (Remote Radio Communication services can also be provided by Head: RRH).

The term "cell" or "sector" refers to part or all of the coverage area of base stations and/or base station subsystems that provide communication services in this coverage.

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

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

At least one of a base station and a mobile station may be called a transmitting device, a receiving device, a communication device, or the like. Note that 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 object may be a vehicle (for example, a car, an airplane, etc.), an unmanned moving object (for example, a drone, a self-driving car, etc.), or a robot (manned or unmanned). ). Note that at least one of the base station and the mobile station includes devices that do not necessarily move during communication operations. For example, at least one of the base station and the mobile station may be an Internet of Things (IoT) device such as a sensor.

Furthermore, the base station in the present disclosure may be read as a mobile station (user terminal, hereinafter the same). For example, communication between a base station and a mobile station is replaced with communication between multiple mobile stations (for example, it may be called Device-to-Device (D2D), Vehicle-to-Everything (V2X), etc.). Regarding the configuration, each aspect/embodiment of the present disclosure may be applied. In this case, the mobile station may have the functions that the base station has. Further, words such as "up" and "down" may be replaced with words corresponding to inter-terminal communication (for example, "side"). For example, uplink channels, downlink channels, etc. may be replaced with 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 that the mobile station has.
A radio frame may be composed of one or more frames in the time domain. Each frame or frames in the time domain may be called a subframe.
A subframe may further be composed of one or more slots in the time domain. A subframe may have a fixed time length (eg, 1 ms) that does not depend on numerology.

Numerology may be a communication parameter applied to the transmission and/or 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, radio frame configuration, transmission and reception. It may also indicate at least one of a specific filtering process performed by the device in the frequency domain, a specific windowing process performed by the transceiver in the time domain, etc.

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

A slot may include multiple minislots. Each minislot may be made up of one or more symbols in the time domain. Furthermore, a mini-slot may also be called a sub-slot. A minislot may be made up of fewer symbols than a slot. PDSCH (or PUSCH) transmitted in time units larger than minislots may be referred to as PDSCH (or PUSCH) mapping type A. PDSCH (or PUSCH) transmitted using minislots may be referred to as PDSCH (or PUSCH) mapping type B.

Radio frames, subframes, slots, minislots, and symbols all represent time units for transmitting signals. Other names may be used for the radio frame, subframe, slot, minislot, and symbol.

For example, one subframe may be referred to as a transmission time interval (TTI), multiple consecutive subframes may be referred to as a TTI, or one slot or minislot may be referred to as a TTI. In other words, at least one of the subframe and TTI may be a subframe (1ms) in existing LTE, a period shorter than 1ms (for example, 1-13 symbols), or a period longer than 1ms. It may be. Note that the unit representing TTI may be called a slot, minislot, etc. instead of a subframe.

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

The TTI may be a transmission time unit of a channel-coded data packet (transport block), a code block, a codeword, etc., or may be a processing unit of scheduling, link adaptation, etc. Note that when a TTI is given, the time interval (for example, the number of symbols) to which transport blocks, code blocks, code words, etc. are actually mapped may be shorter than the TTI.

Note that when one slot or one minislot is called a TTI, one or more TTIs (that is, one or more slots or one or more minislots) may be the minimum time unit for scheduling. Further, the number of slots (minislot number) that constitutes 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), normal TTI, long TTI, normal subframe, normal subframe, long subframe, slot, etc. A TTI that is shorter than the normal TTI may be referred to as a shortened TTI, short TTI, partial or fractional TTI, shortened subframe, short subframe, minislot, subslot, slot, etc.

Note that long TTI (e.g., normal TTI, subframe, etc.) may be read as TTI with a time length exceeding 1ms, and short TTI (e.g., shortened TTI, etc.) may be interpreted as TTI with a time length of less than the long TTI and 1ms. It may also be read as a TTI having a TTI length of the above length.

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

Additionally, the time domain of an RB may include one or more symbols and may be one slot, one minislot, one subframe, or one TTI long. One TTI, one subframe, etc. may each be composed of one or more resource blocks.

Note that one or more RBs are classified into physical resource blocks (Physical RBs: PRBs), sub-carrier groups (SCGs), resource element groups (REGs), PRB pairs, RB pairs, etc. May be called.

Further, a resource block may be configured by one or more resource elements (RE). For example, 1 RE may be a radio resource region of 1 subcarrier and 1 symbol.

Bandwidth Part (BWP) (also called partial bandwidth, etc.) refers to a subset of contiguous common resource blocks (RBs) for a certain numerology in a certain carrier. good. Here, the common RB may be specified by an RB index based on a common reference point of the carrier. PRBs may be defined in a BWP and numbered within that BWP.

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

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

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

The terms "connected", "coupled", or any variations thereof, refer to any connection or coupling, direct or indirect, between two or more elements and to each other. It can include the presence of one or more intermediate elements between two elements that are "connected" or "coupled." The bonds or connections between elements may be physical, logical, or a combination thereof. For example, "connection" may be replaced with "access." As used in this disclosure, two elements may include one or more electrical wires, cables, and/or printed electrical connections, as well as in the radio frequency domain, as some non-limiting and non-inclusive examples. , electromagnetic energy having wavelengths in the microwave and optical (both visible and non-visible) ranges, and the like.

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

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

"Means" in the configurations of each of the above devices may be replaced with "unit", "circuit", "device", etc.

As used in this disclosure, any reference to elements using the designations "first," "second," etc. does not generally limit the amount or order of those elements. These designations may be used in this disclosure as a convenient way to distinguish between two or more elements. Thus, reference to a first and second element does not imply that only two elements may be employed therein or that the first element must precede the second element in any way.

Where "include", "including" and variations thereof are used in this disclosure, these terms, like the term "comprising," are inclusive. It is intended that Furthermore, the term "or" as used in this disclosure is not intended to be exclusive or.

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

As used in this disclosure, the terms "determining" and "determining" may encompass a wide variety of operations. "Judgment" and "decision" include, for example, judging, calculating, computing, processing, deriving, investigating, looking up, search, and inquiry. (e.g., searching in a table, database, or other data structure), and regarding an ascertaining as a "judgment" or "decision." In addition, "judgment" and "decision" refer to receiving (e.g., receiving information), transmitting (e.g., sending information), input, output, and access. (accessing) (e.g., accessing data in memory) may include considering something as a "judgment" or "decision." In addition, "judgment" and "decision" refer to resolving, selecting, choosing, establishing, comparing, etc. as "judgment" and "decision". may be included. In other words, "judgment" and "decision" may include regarding some action as having been "judged" or "determined." Further, "judgment (decision)" may be read as "assuming", "expecting", "considering", etc.

In this disclosure, the term "A and B are different" may mean "A and B are different from each other." Note that the term may also mean that "A and B are each different from C". Terms such as "separate" and "coupled" may also be interpreted similarly to "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 can be implemented as modifications and variations without departing from the spirit and scope of the present disclosure as determined by the claims. Therefore, the description of the present disclosure is for the purpose of illustrative explanation and is not intended to have any limiting meaning on the present disclosure.

10 wireless communication system
100A~100C gNB
200 U.E.
210 Wireless transmitter
220 Wireless receiver
230 RA procedure execution part
240 Data discard section
250 Control section
1001 processor
1002 memory
1003 Storage
1004 Communication equipment
1005 Input device
1006 Output device
1007 bus

Claims (3)

a transmitting unit that performs uplink transmission via a radio bearer;
a control unit that transitions to a target cell without using a reconnection procedure when a wireless link failure occurs;
Equipped with
When the target cell is a CHO candidate cell , the control unit restarts the radio bearer upon application of settings corresponding to the target cell.
terminal. A wireless communication system comprising a base station forming a target cell, and a terminal transitioning to the target cell,
The terminal is
a transmitting unit that performs uplink transmission via a radio bearer;
a control unit that transitions to the target cell without using a reconnection procedure when a wireless link failure occurs;
Equipped with
When the target cell is a CHO candidate cell , the control unit restarts the radio bearer upon application of settings corresponding to the target cell.
Wireless communication system. a transmitting step of performing uplink transmission via the radio bearer;
a transition step of transitioning to a target cell without using a reconnection procedure if a radio link failure occurs;
including;
The transition step includes, when the target cell is a CHO candidate cell , restarting the radio bearer upon application of the settings corresponding to the target cell.
Wireless communication method.

Images