JP2017028415A - User device and communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide techniques that avoid radio resources to be wasted when uplink data pertaining to a split bearer is transmitted.SOLUTION: There is provided a user device that communicates with a first base station and a second base station in a wireless communication system supporting uplink carrier aggregation. The user device includes: a determination unit that determines whether an amount of uplink data accumulated in a buffer exceeds a first threshold or not and further determines whether a given condition is met or not; and a communication unit that performs uplink communication with the first base station and the second base station using a split bearer for uplink while it is determined that an amount of uplink data accumulated in the buffer exceeds the first threshold and that the given condition is met.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a user apparatus and a communication method.

  The LTE (Long Term Evolution) system employs carrier aggregation (CA) that performs communication using a plurality of carriers simultaneously with a predetermined bandwidth (maximum 20 MHz) as a basic unit. A carrier that is a basic unit in carrier aggregation is called a component carrier (CC).

  When CA is performed, a PCell (Primary Cell) that is a reliable cell that secures connectivity and a SCell (Secondary Cell) that is an ancillary cell are provided to the user equipment. Is set. First, the user apparatus can connect to the PCell and add an SCell as necessary. The PCell is a cell similar to a single cell that supports RLM (Radio Link Monitoring), SPS (Semi-Persistent Scheduling), and the like.

  The SCell is a cell that is added to the PCell and set for the user apparatus. The addition and deletion of the SCell is performed by RRC (Radio Resource Control) signaling. The SCell is a cell that is in an inactive state (deactivate state) immediately after being set for the user apparatus, and is thus capable of communication (schedulable) only after being activated.

  As shown in FIG. 1, LTE Rel-10 CA uses a plurality of CCs under the same base station.

  On the other hand, in Rel-12, dual connectivity has been proposed in which simultaneous communication is performed using CCs under different base stations to achieve high throughput. That is, in dual connectivity, the user apparatus performs communication using radio resources of two physically different base stations at the same time.

  Dual connectivity is a type of CA, also called Inter eNB CA (inter-base station carrier aggregation), and introduces Master-eNB (MeNB) and Secondary-eNB (SeNB). FIG. 4 shows an example of dual connectivity. In the example of FIG. 2, the dual connectivity (hereinafter, DC) is realized when the MeNB communicates with the user apparatus at CC # 1 and the SeNB communicates with the user apparatus at CC # 2.

  In DC, a cell group composed of cells (one or more) under the MeNB is defined as MCG (Master Cell Group), and a cell group composed of cells (one or a plurality) under the SeNB is defined as SCG ( Secondary Cell Group). A UL CC is set in at least one SCell of the SCGs, and a PUCCH is set in one of them. This SCell is called PSCell (primary SCell).

  Moreover, in DC, the bearer called a split bearer (Split bearer) is prescribed | regulated.

  FIG. 3 is a diagram for explaining a bearer and protocol architecture used in DC. In DC, the same bearer as the conventional MCG bearer and SCG bearer, and split bearer are defined. FIG. 3A shows the protocol architecture of the MCG bearer and the SCG bearer, and FIG. 3B shows the architecture of the split bearer.

  As shown in FIG. 3B, the split bearer is a layer (RLC (Radio Link Control) layer, MAC (Media Access Control) layer, and physical (PHY: Physical)) lower than the PDCP (Packet Data Control Protocol) layer. In the layer, it is a bearer capable of transferring uplink data (PDCP PDU) to the user apparatus using radio resources of both the MeNB and SeNB.Data transmitted to the user apparatus by using the split bearer Throughput can be improved.

3GPP TS 36.300 V12.5.0 (2015-03)

In the Rel-12 split bearer, only the downlink can transmit U-plane data (user's IP packet) using both MeNB and SeNB radio resources, and the uplink U-plane data is MeNB. Or it was necessary to transmit using only one of the radio resources of SeNB. On the other hand, in Rel-13, it is discussed that U-plane data can be transmitted using both radio resources of MeNB and SeNB for uplink (UL). As a specific implementation method, in Rel-13, it is discussed that the user apparatus behaves as follows.
(1): When the data retention amount in the UL PDCP buffer exceeds a predetermined threshold (or when it is equal to or higher than the predetermined threshold), the user apparatus transmits (triggers) a BSR (Buffer Status Report) to both the MeNB and SeNB. .
(2): When the data retention amount in the UL PDCP buffer is below a predetermined threshold (or below the predetermined threshold), the user apparatus transmits (triggers) a BSR to either MeNB or SeNB.

Furthermore, in the case of (2), it is discussed that the user apparatus behaves as follows.
(3): The user apparatus transmits (triggers) the BSR only to the base station (one of MeNB and SeNB) instructed from the network in advance. Further, when transmitting the uplink data, the user apparatus transmits the uplink data only to the instructed base station.

  Here, when the data retention amount in the UL PDCP buffer exceeds a predetermined threshold and the user apparatus transmits a BSR to both the MeNB and SeNB, the transmission timing of the UL grant (UL grant) transmitted from the MeNB and SeNB If they are different, UL grant and uplink radio resources transmitted later may be wasted.

  FIG. 4 is a diagram for explaining the problem. In FIG. 4, when the data retention amount in the UL PDCP buffer is below a predetermined threshold (or below a predetermined threshold), the user apparatus is instructed in advance by the network to transmit BSR and uplink data to the MeNB. Assuming that The data amount shown in FIG. 4 indicates the data retention amount in the UL PDCP buffer in the user apparatus (hereinafter simply referred to as “data retention amount” in FIG. 4). In FIG. 4, it is assumed that the predetermined threshold is 100 bytes. First, uplink data to be transmitted to the base station is generated, and 120-byte data is accumulated in the UL PDCP buffer (S1). Next, since the data retention amount in the UL PDCP buffer exceeds a predetermined threshold, the user apparatus transmits a BSR to the MeNB and SeNB according to (1) described above (S2). Note that 120 bytes are set for each BSR transmitted to the MeNB and SeNB.

  Subsequently, a UL grant indicating a 30-byte radio resource is notified from the MeNB (S3). The user apparatus transmits 30-byte uplink data to the MeNB using PUSCH (Physical Uplink Shared Channel) (S4). At this time, the data retention amount in the UL PDCP buffer is 90 bytes (120 bytes-30 bytes).

  Then, UL grant is notified from SeNB (S5). It is assumed that 90 bytes of radio resources are allocated to the UL grant.

  Here, the data retention amount in the UL PDCP buffer is 90 bytes. That is, the data retention amount in the UL PDCP buffer is below a predetermined threshold (100 bytes). Therefore, according to the above (3), the user apparatus determines that the uplink data should be transmitted only to the MeNB, and uses padding data (particularly meaningless data) instead of the data in the UL PDCP buffer using the PUSCH. (S6).

  That is, when the data retention amount in the UL PDCP buffer slightly exceeds a predetermined threshold, if the UL grant reception timing transmitted from the MeNB and SeNB is different, the UL grant and uplink transmitted to the user apparatus later Wireless resources may be wasted.

  The disclosed technology has been made in view of the above, and an object of the present invention is to provide a technology capable of avoiding wasteful radio resources when uplink data related to a split bearer is transmitted. To do.

  A user apparatus according to the disclosed technique is a user apparatus that communicates with a first base station and a second base station in a wireless communication system that supports uplink carrier aggregation, and is configured to store uplink data stored in a buffer. In addition to determining whether or not the amount exceeds the first threshold, a determination unit that determines whether or not a specific condition is further satisfied, and the amount of uplink data stored in the buffer is the first threshold Communication in which uplink communication is performed between the first base station and the second base station by applying a bearer split to the uplink while it is determined that a specific condition is satisfied. Part.

  According to the disclosed technique, there is provided a technique capable of avoiding waste of radio resources when uplink data related to a split bearer is transmitted.

It is a figure for demonstrating CA of Rel-10 LTE. It is a figure which shows the example of DC introduced by Rel-12. It is a figure for demonstrating the bearer and protocol architecture which are used by DC. It is a figure for demonstrating a subject. It is a figure which shows an example of a structure of the radio | wireless communications system in embodiment. It is a figure for demonstrating an example of the flow of the uplink data in case a split bearer is used. It is a flowchart which shows the switching method (the 1) of a bearer split state. It is a flowchart which shows the switching method (the 2) of a bearer split state. It is a flowchart which shows the switching method (the 3) of a bearer split state. It is a figure for demonstrating a mode that a bearer split state switches according to the change of the retention amount of data. It is a flowchart which shows the switching method (the 4) of a bearer split state. It is a flowchart which shows the switching method (the 5) of a bearer split state. It is a flowchart which shows the switching method (the 6) of a bearer split state. It is a figure for demonstrating a mode that a bearer split state switches according to the change of the retention amount of data. It is a figure which shows an example of a function structure of the user apparatus which concerns on embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. The embodiment described below is only an example, and the embodiment to which the present invention is applied is not limited to the following embodiment. For example, although the wireless communication system according to the present embodiment assumes a system based on LTE, the present invention is not limited to LTE and can be applied to other systems. In addition, in this specification and claims, “LTE” corresponds to not only a communication method corresponding to Release 8 or 9 of 3GPP but also Release 10, 11, 12, 13, or Release 14 or later of 3GPP. It is used in a broad sense including the fifth generation communication system.

<Overview>
FIG. 5 is a diagram illustrating an example of a configuration of the wireless communication system according to the embodiment. As illustrated in FIG. 5, the radio communication system in the present embodiment is a radio communication system including a base station MeNB, a base station SeNB, and a user apparatus UE. Moreover, the user apparatus UE can perform CA communication using DC between the base station MeNB and the base station SeNB. In FIG. 5, one user apparatus UE is shown, but this is for convenience of illustration, and a plurality of user apparatuses UE may exist. In the following description, an arbitrary base station among the base station MeNB and the base station SeNB is represented as “base station eNB”. In the following description, UP PDCP buffer means a buffer included in an uplink PDCP entity related to a split bearer unless otherwise specified.

(Basic operation example)
FIG. 6 is a diagram for explaining an example of the flow of uplink data when a split bearer is used. When uplink data related to the split bearer is transmitted using both MeNB and SeNB radio resources, the uplink data stored in the UL PDCP buffer (B1) related to the split bearer is divided in the order shown in the solid and dotted lines. Is transferred and finally reaches the PDCP buffer (B2) of the MeNB.

  On the other hand, when the uplink U-plane data related to the uplink split bearer is transmitted using only the MeNB resource, the uplink data accumulated in the UL PDCP buffer (B1) is transferred in the order shown in the solid line, It reaches the PDCP buffer of the base station MeNB.

  As described with reference to FIG. 4, in the user apparatus UE, in order to avoid a problem caused by simply determining whether or not the amount of data accumulated in the UL PDCP buffer exceeds a predetermined threshold. In this embodiment, the user apparatus UE determines whether or not the retention amount of data accumulated in the UL PDCP buffer exceeds the predetermined threshold, and further determines whether or not a specific condition is satisfied. . More specifically, while the data retention amount exceeds a predetermined threshold and further satisfies a specific condition, the user apparatus UE uses the radio resources of both the MeNB and SeNB to increase the uplink data in order to improve the throughput. And the uplink bearer split state managed in the user apparatus UE is switched to the valid (ON) state. In addition, when the data retention amount falls below a predetermined threshold, or when a specific condition is not satisfied (when it is no longer satisfied), the user apparatus UE can receive uplink data without using both the MeNB and SeNB radio resources. It is determined that transmission is possible, and the uplink bearer split state is switched to an invalid (OFF) state.

  Here, the state where the uplink bearer split state is valid (ON) means that the BSR is transmitted (triggered) to both the base station MeNB and the base station SeNB, and the UL grant is received from both the base station MeNB and the base station SeNB. Is received, the uplink data related to the split bearer can be transmitted to both the base station MeNB and the base station SeNB.

  Note that the state where the uplink bearer split state is valid (ON) is defined to include a state in which a scheduling request (SR) can be transmitted (triggered) to both the base station MeNB and the base station SeNB. Good. In addition, the state where the uplink bearer split state is valid (ON) includes that the PDCP entity notifies the two MAC entities (two MAC entities included in the user apparatus UE) of the data amount. May be defined.

  Similarly, when the uplink bearer split state is invalid (OFF), the base station MeNB and the base station SeNB transmit (trigger) the BSR to the base station eNB designated in advance from the network, and the split bearer. Is a state in which uplink data according to is transmitted to a base station eNB (MeNB or SeNB) designated in advance from the network. The uplink data related to the split bearer may not include a control signal such as PDCP control PDU.

  The state where the uplink bearer split state is invalid (OFF) includes a state in which a scheduling request can be transmitted (triggered) to a base station eNB designated in advance from the network among the base station MeNB and the base station SeNB. May be defined. The uplink bearer split state is invalid (OFF) when the split bearer is included in the buffer status report transmitted from the base station MeNB and the base station SeNB to the base station eNB designated in advance from the network. May be defined as a state that takes into account the amount of transmission data for In addition, the state where the uplink bearer split state is invalid (OFF) is defined to include that the PDCP entity notifies the MAC entity corresponding to the base station eNB designated in advance from the network of the data amount. May be.

  The state where the uplink bearer split state is valid (ON) may be referred to as “validate uplink bearer split” or as “apply bearer split to uplink”. It may be. Also, the state where the uplink bearer split state is invalid (OFF) may be referred to as “invalidate uplink bearer split (Bearer Split)” or “do not apply bearer split to the uplink. May be called. Further, switching the uplink bearer split state from the invalid (OFF) state to the valid (ON) state may be referred to as “starting application of the uplink bearer split”, or the uplink. The switching of the bearer split state from the valid (ON) state to the invalid (OFF) state may be referred to as “stopping the application of the uplink bearer split”.

  In the embodiment, “the amount of data accumulated in the UL PDCP buffer” may mean the data amount of a PDCP SDU (Service Data Unit) in the PDCP buffer, or the data in the PDCP buffer. And the amount of data in the RLC buffer combined, or the amount of PDCP SDU or / and PDCP PDU not transmitted from the PDCP buffer to the RLC entity, or the base station eNB This may mean the amount of data of PDCP SDUs and / or PDCP PDUs that have not been transmitted to.

<Processing procedure>
(Bearer split state switching method (1))
First, the bearer split state switching method (part 1) will be described. In the switching method (part 1), the user apparatus UE notifies (instructs) the threshold value X and a predetermined period (TTT: Time To Trigger) from the base station eNB in advance using, for example, an RRC message or broadcast information (SIB). ), May be predetermined in the wireless communication system, or may be determined (selected) according to the system band or the UE category. In addition, the predetermined period (TTT) and the threshold value X are instructed from the base station eNB in units of bearers (units of PDCP entities), units of user apparatuses UE, and units of bearers (or logical channels) obtained by grouping bearers (or logical channels). You may do it.

  FIG. 7 is a flowchart showing a bearer split state switching method (part 1).

  In step S11, the user apparatus UE determines whether or not the retention amount of data accumulated in the UL PDCP buffer exceeds the threshold value X (or is equal to or more than the threshold value X). If it is determined that the threshold value X is exceeded (or greater than or equal to the threshold value X), the process proceeds to step S12. If it is determined that the threshold value X is less than or equal to the threshold value X (or less than the threshold value X), the process proceeds to step S14.

  In step S12, the user apparatus UE determines whether or not the state in which the amount of data accumulated in the UL PDCP buffer exceeds the threshold value X (or is equal to or greater than the threshold value X) continues for a predetermined period (TTT). Determine. When it is determined that the predetermined period (TTT) continues, the process proceeds to step S13, and when it is determined that the predetermined period (TTT) does not continue, the process ends.

  The user apparatus UE starts the timer when it is determined in step S11 that the amount of data accumulated in the UL PDCP buffer exceeds the threshold value X (or is equal to or greater than the threshold value X), and the timer expires. Whether or not the amount of data accumulated in the UL PDCP buffer has continuously exceeded the threshold value X (or was greater than or equal to the threshold value X) until the specified period (until the predetermined period (TTT) elapses) It may be made to perform the processing procedure of Step S12 by judging.

  In step S13, the user apparatus UE switches the uplink bearer split state to a valid state, and ends the process.

  In step S14, the user apparatus UE determines whether or not the uplink bearer split state is valid. If the uplink bearer split state is valid, the process proceeds to step S15. If the uplink bearer split state is invalid, the process ends.

  In step S15, the user apparatus UE switches the uplink bearer split state to an invalid state, and ends the process.

  Note that the user apparatus UE repeatedly switches the uplink bearer split state according to the amount of data accumulated in the UL PDCP buffer by repeatedly performing the processing procedure of steps S11 to S15.

  Also, when DC is performed using three or more base stations eNB, the user apparatus UE transmits uplink data related to the split bearer using radio resources of one base station eNB, or two base stations It is assumed that it is possible to select whether to transmit using radio resources of the eNB or to transmit using all radio resources of three or more base stations eNB. In this case, a plurality of different “predetermined periods (TTT)” and / or “threshold values X” may be set corresponding to the number of base stations eNB that transmit uplink data related to the split bearer. For example, “predetermined period (TTT)” and / or “threshold X” used when switching between transmission using radio resources of one or two base stations eNB and radio of two or three base stations eNB Different values may be set for the “predetermined period (TTT)” and / or the “threshold value X” used when switching between transmission using resources.

  According to the bearer split state switching method (part 1) described above, even if the data retention amount in the UL PDCP buffer slightly exceeds a predetermined threshold value, It is possible to prevent the invalidation from being frequently switched.

(Bearer split state switching method (2))
Next, the bearer split state switching method (part 2) will be described. In the switching method (part 2), the user apparatus UE may notify (instruct) the threshold value X and the threshold value Y from the base station eNB in advance by, for example, an RRC message or broadcast information (SIB). Alternatively, it may be determined in advance in the wireless communication system, or may be determined (selected) according to the system band or the UE category. Further, the threshold value X and the threshold value Y may be instructed from the base station eNB in units of bearers (in units of PDCP entities). Further, the threshold value Y may be expressed as “threshold value X + hysteresis”, and conversely, the threshold value X may be expressed as “threshold value Y−hysteresis”. In the switching method (part 2), threshold value Y> threshold value X.

  FIG. 8 is a flowchart showing a bearer split state switching method (part 2).

  In step S21, the user apparatus UE determines whether or not the retention amount of data accumulated in the UL PDCP buffer exceeds the threshold value X (or is equal to or more than the threshold value X). If it is determined that the threshold value X is exceeded (or greater than or equal to the threshold value X), the process proceeds to step S22. If it is determined that the threshold value X is less than or equal to the threshold value X (or less than the threshold value X), the process proceeds to step S24.

  In step S22, the user apparatus UE determines whether or not the amount of data accumulated in the UL PDCP buffer exceeds the threshold Y (or is greater than or equal to the threshold Y). If it is determined that the threshold value Y is exceeded (or greater than or equal to the threshold value Y), the process proceeds to step S23. If it is determined that the threshold value Y is less than or equal to the threshold value Y (or less than the threshold value Y), the process ends.

  In step S23, the user apparatus UE switches the uplink bearer split state to a valid state, and ends the process.

  In step S24, the user apparatus UE determines whether or not the uplink bearer split state is valid. When the uplink bearer split state is valid, the process proceeds to step S25, and when the uplink bearer split state is invalid, the process ends.

  In step S25, the user apparatus UE switches the uplink bearer split state to an invalid state, and ends the process.

  Note that the user apparatus UE repeatedly switches the uplink bearer split state according to the amount of data accumulated in the UL PDCP buffer by repeatedly performing the processing procedure of steps S21 to S25.

  In addition, when DC is performed using three or more base stations eNB, a plurality of different “threshold X” and / or “threshold Y” corresponding to the number of base stations eNB transmitting uplink data related to the split bearer. May be set.

  According to the bearer split state switching method (part 2) described above, the uplink bearer split state can be activated immediately when the data retention amount in the UL PDCP buffer increases to some extent. Link throughput can be improved.

(Bearer split state switching method (3))
Next, the bearer split state switching method (part 3) will be described. The switching method (part 3) is a combination of the bearer split state switching method (part 1) and the bearer split state switching method (part 2). The points not particularly mentioned may be the same as the bearer split state switching method (part 1) and the bearer split state switching method (part 2).

  FIG. 9 is a flowchart showing a bearer split state switching method (part 3).

  In step S31, the user apparatus UE determines whether or not the retention amount of data accumulated in the UL PDCP buffer exceeds the threshold value X (or is equal to or more than the threshold value X). If it is determined that the threshold value X is exceeded (or greater than or equal to the threshold value X), the process proceeds to step S32. If it is determined that the threshold value X is less than or equal to the threshold value X (or less than the threshold value X), the process proceeds to step S35.

  In step S32, the user apparatus UE determines whether or not the amount of data accumulated in the UL PDCP buffer exceeds the threshold Y (or is greater than or equal to the threshold Y). If it is determined that the threshold value Y is exceeded (or greater than or equal to the threshold value Y), the process proceeds to step S33. If it is determined that the threshold value Y is less than or equal to the threshold value Y (or less than the threshold value Y), the process ends.

  In step S33, the user apparatus UE determines whether or not the state in which the amount of data accumulated in the UL PDCP buffer exceeds the threshold Y (or is greater than or equal to the threshold Y) continues for a predetermined period (TTT). Determine whether. When it is determined that the predetermined period (TTT) continues, the process proceeds to step S34, and when it is determined that the predetermined period (TTT) does not continue, the process ends.

  Note that the user apparatus UE activates the timer when it is determined in step S32 that the amount of data accumulated in the UL PDCP buffer exceeds the threshold Y (or is greater than or equal to the threshold Y), and the timer expires. Whether or not the amount of data accumulated in the UL PDCP buffer has continuously exceeded the threshold Y (or more than the threshold X) until the specified period (until the predetermined period (TTT) elapses) By determining the above, the processing procedure of step S33 may be performed.

  In step S34, the user apparatus UE switches the uplink bearer split state to a valid state, and ends the process.

  In step S35, the user apparatus UE determines whether or not the uplink bearer split state is valid. When the uplink bearer split state is valid, the process proceeds to step S36, and when the uplink bearer split state is invalid, the process ends.

  In step S36, the user apparatus UE switches the uplink bearer split state to an invalid state, and ends the process.

  According to the bearer split state switching method (part 3) described above, even if the data retention amount in the UL PDCP buffer slightly exceeds a predetermined threshold value, It is possible to prevent the invalidation from being frequently switched.

(Summary of switching methods (1 to 3))
Regarding the bearer split state switching method (Nos. 1 to 3) described above, FIG. 10 shows a specific example of how the bearer split state is switched according to the change in the retention amount of the data accumulated in the UL PDCP buffer.

  In FIG. 10, it is assumed that threshold value X = 100 bytes, threshold value Y = 150 bytes, and predetermined period (TTT) = 100 ms. In the graph, the vertical axis indicates the amount of data accumulated in the UL PDCP buffer, and the horizontal axis indicates time.

  As shown in FIG. 10, it can be seen that the bearer split state switching method (Nos. 1 to 3) is controlled so that the bearer split state is not frequently switched as compared with the conventional switching method.

  Further, in the bearer split state switching method (part 2), when the data retention amount increases abruptly (when the threshold Y is exceeded), the bearer split state switching method is faster than the bearer split state switch method (part 1). It turns out that it controls so that it may switch to effective (ON).

  Next, for example, when the operation of the bearer split state switching method (parts 1 to 3) is applied to FIG. 4, it will be described that the problem described in FIG. 4 is solved. It is assumed that the threshold value X = 100 bytes and a predetermined period (TTT) = 100 ms.

  In FIG. 4, data to be transmitted to the base station eNB is generated, and 120-byte data is accumulated in the UL PDCP buffer (S1). Next, the user apparatus UE transmits a BSR to the base station eNB. When the switching methods 1 and 3 are applied, the data retention amount in the UL PDCP buffer exceeds the threshold value X, but the predetermined period (TTT) has not elapsed. A BSR will be transmitted. Similarly, when the switching method 2 is applied, since the data retention amount in the UL PDCP buffer does not exceed the threshold Y, the user apparatus UE transmits the BSR only to the base station MeNB.

  As illustrated in FIG. 4, according to the conventional technique, the user apparatus transmits the BSR to both the base station MeNB and the base station SeNB, and as a result, the UL grant (S5) and PUSCH radio transmitted by the base station SeNB. The resource (S6) was wasted. On the other hand, as described above, the user apparatus UE in the embodiment transmits the BSR only to the base station MeNB. That is, since the process of step S5 in FIG. 4 is not performed, it is possible to avoid wasting radio resources of the base station SeNB.

(Bearer split state switching method (4))
Next, the bearer split state switching method (part 4) will be described. In the switching method (part 4), the user apparatus UE is notified (instructed) in advance of the threshold value X and the predetermined period (TTT) from the base station eNB, for example, by an RRC message, broadcast information (SIB), or the like. Alternatively, it may be determined in advance in the wireless communication system, or may be determined (selected) according to the system band or the UE category. In addition, the predetermined period (TTT) and the threshold value X are instructed from the base station eNB in units of bearers (units of PDCP entities), units of user apparatuses UE, and units of bearers (or logical channels) obtained by grouping bearers (or logical channels). You may do it.

  FIG. 11 is a flowchart showing a bearer split state switching method (part 4).

  In step S41, the user apparatus UE determines whether or not the amount of data accumulated in the UL PDCP buffer exceeds the threshold value X (or is equal to or more than the threshold value X). If it is determined that the threshold value X is exceeded (or greater than or equal to the threshold value X), the process proceeds to step S42. If it is determined that the threshold value X is less than or equal to (or less than the threshold value X), the process proceeds to step S43.

  In step S42, the user apparatus UE switches the uplink bearer split state to a valid state, and ends the process.

  In step S43, the user apparatus UE determines whether or not the uplink bearer split state is valid. If the uplink bearer split state is valid, the process proceeds to step S44. If the uplink bearer split state is invalid, the process ends.

  In step S44, the user apparatus UE determines whether or not the state in which the amount of data accumulated in the UL PDCP buffer is equal to or less than the threshold value X (or less than the threshold value X) continues for a predetermined period (TTT). judge. When it is determined that the predetermined period (TTT) continues, the process proceeds to step S45, and when it is determined that the predetermined period (TTT) does not continue, the process ends.

  Note that the user apparatus UE starts the timer when it is determined in step S41 that the amount of data accumulated in the UL PDCP buffer is equal to or less than the threshold value X (or less than the threshold value X), and the timer expires. Whether or not the amount of data accumulated in the UL PDCP buffer is continuously less than or equal to the threshold value X (or less than the threshold value X) until the predetermined period (TTT) elapses) By determining, the processing procedure of step S44 may be performed.

  In step S45, the user apparatus UE switches the uplink bearer split state to an invalid state, and ends the process.

  Note that the user apparatus UE repeatedly switches the uplink bearer split state according to the amount of data accumulated in the UL PDCP buffer by repeatedly performing the processing procedure of steps S41 to S45.

  Also, when DC is performed using three or more base stations eNB, a plurality of different “predetermined periods (TTT)” and / or corresponding to the number of base stations eNB transmitting uplink data related to the split bearer and / or Alternatively, “threshold X” may be set.

  According to the bearer split state switching method (part 4) described above, it is frequently switched between enabling / disabling of the uplink bearer split state due to the fluctuation of the data retention amount in the UL PDCP buffer. Can be prevented.

(Bearer split state switching method (5))
Next, the bearer split state switching method (part 5) will be described. In the switching method (part 5), the user apparatus UE may be notified (instructed) in advance of the threshold value X and the threshold value Z from the base station eNB, for example, by an RRC message, broadcast information (SIB), or the like. Alternatively, it may be determined in advance in the wireless communication system, or may be determined (selected) according to the system band or the UE category. Further, the threshold value X and the threshold value Z may be instructed from the base station eNB in bearer units (PDCP entity units). Further, the threshold value Z may be expressed as “threshold value X−hysteresis”, and conversely, the threshold value X may be expressed as “threshold value Z + hysteresis”. In the switching method (part 5), the threshold value X> the threshold value Z.

  FIG. 12 is a flowchart showing a bearer split state switching method (part 5).

  In step S51, the user apparatus UE determines whether or not the retention amount of data accumulated in the UL PDCP buffer exceeds the threshold value X (or is equal to or more than the threshold value X). If it is determined that the threshold value X is exceeded (or greater than or equal to the threshold value X), the process proceeds to step S52. If it is determined that the threshold value X is less than or equal to the threshold value X (or less than the threshold value X), the process proceeds to step S53.

  In step S52, the user apparatus UE switches the uplink bearer split state to a valid state, and ends the process.

  In step S53, the user apparatus UE determines whether or not the uplink bearer split state is valid. When the uplink bearer split state is valid, the process proceeds to step S54, and when the uplink bearer split state is invalid, the process ends.

In step S54, the user apparatus UE determines whether or not the amount of data accumulated in the UL PDCP buffer is below the threshold Z (or is below the threshold Z). When it is determined that the threshold value Z is below (or below the threshold value Z), the process proceeds to step S55, and when it is determined that the threshold value Z is above the threshold value Z (or above the threshold value Z), the process is terminated. In S55, the user apparatus UE switches the uplink bearer split state to an invalid state, and ends the process.

  Note that the user apparatus UE repeatedly switches the uplink bearer split state according to the amount of data accumulated in the UL PDCP buffer by repeatedly performing the processing procedure of steps S51 to S55.

  In addition, when DC is performed using three or more base stations eNB, a plurality of different “threshold X” and / or “threshold Z” corresponding to the number of base stations eNB transmitting uplink data related to the split bearer. May be set.

  According to the bearer split state switching method (part 5) described above, the uplink bearer split state validation / invalidation is frequently switched due to fluctuations in the amount of data accumulated in the UL PDCP buffer. Can be prevented. Also, the uplink bearer split state can be invalidated immediately when the data retention amount in the UL PDCP buffer becomes small to some extent, and the load on the user apparatus UE can be reduced.

(Bearer split state switching method (6))
Next, the bearer split state switching method (No. 6) will be described. The switching method (part 6) is a combination of the bearer split state switching method (part 4) and the bearer split state switching method (part 5). The points not particularly mentioned may be the same as the bearer split state switching method (part 4) and the bearer split state switching method (part 5).

  FIG. 13 is a flowchart showing a bearer split state switching method (No. 6).

  In step S61, the user apparatus UE determines whether or not the amount of data accumulated in the UL PDCP buffer exceeds the threshold value X (or is equal to or greater than the threshold value X). If it is determined that the threshold value X is exceeded (or greater than or equal to the threshold value X), the process proceeds to step S62. If it is determined that the threshold value X is less than or equal to the threshold value X (or less than the threshold value X), the process proceeds to step S63.

  In step S62, the user apparatus UE switches the uplink bearer split state to a valid state, and ends the process.

  In step S63, the user apparatus UE determines whether or not the uplink bearer split state is valid. When the uplink bearer split state is valid, the process proceeds to step S64, and when the uplink bearer split state is invalid, the process ends.

  In step S64, the user apparatus UE determines whether or not the amount of data accumulated in the UL PDCP buffer is below the threshold value Z (or is equal to or less than the threshold value Z). If it is determined that the value is below the threshold value Z (or less than or equal to the threshold value Z), the process proceeds to step S65. If it is determined that the value is greater than or equal to the threshold value Z (or exceeds the threshold value Z), the process ends.

  In step S65, the user apparatus UE determines whether or not the state in which the amount of data accumulated in the UL PDCP buffer is lower than the threshold value Z (or less than or equal to the threshold value Z) continues for a predetermined period (TTT). Determine. When it is determined that the predetermined period (TTT) continues, the process proceeds to step S66, and when it is determined that the predetermined period (TTT) does not continue, the process ends.

  Note that the user apparatus UE starts the timer when it is determined in step S64 that the amount of data accumulated in the UL PDCP buffer is below the threshold value Z (or less than the threshold value Z), and the timer expires. Whether the accumulated amount of data accumulated in the UL PDCP buffer is continuously below the threshold value Z (or less than the threshold value Z) until the predetermined period (until the predetermined period (TTT) elapses) By determining the above, the processing procedure of step S65 may be performed.

  In step S66, the user apparatus UE switches the uplink bearer split state to an invalid state, and ends the process.

  Note that the user apparatus UE repeatedly switches the uplink bearer split state according to the amount of data accumulated in the UL PDCP buffer by repeatedly performing the processing procedure of steps S61 to S66.

  According to the bearer split state switching method (Part 6) described above, the activation / invalidation of the uplink bearer split state is frequently switched due to the fluctuation of the data retention amount in the UL PDCP buffer. Can be prevented.

(Summary of switching methods (4 to 6))
FIG. 14 shows a specific example of how the bearer split state is switched according to the change in the retention amount of the data accumulated in the UL PDCP buffer for the bearer split state switching method (parts 4 to 6) described above.

  In FIG. 14, it is assumed that threshold value X = 100 bytes, threshold value Z = 50 bytes, and predetermined period (TTT) = 100 ms. In the graph, the vertical axis indicates the amount of data accumulated in the UL PDCP buffer, and the horizontal axis indicates time.

  As shown in FIG. 14, it can be seen that the bearer split state switching method (Nos. 4 to 6) is controlled so that the bearer split state is not frequently switched as compared with the conventional switching method.

  In addition, the bearer split state switching method (part 5) is faster than the bearer split state switching method (part 4) when the data retention amount is drastically decreased (below the threshold value Z). It can be seen that control is performed so as to switch to invalid (OFF).

  Next, for example, when the operation of the bearer split state switching method (parts 4 to 6) is applied to FIG. 4, it will be described that the problem described in FIG. 4 is solved. It is assumed that the threshold value X = 100 bytes and a predetermined period (TTT) = 100 ms.

  In FIG. 4, data to be transmitted to the base station eNB is generated, and 120-byte data is accumulated in the UL PDCP buffer (S1). Moreover, the user apparatus UE validates a bearer split state. Subsequently, since the data retention amount in the UL PDCP buffer exceeds the threshold value X, the user apparatus UE transmits a BSR to the MeNB and SeNB (S2). 120 bytes are set in each of the BSRs transmitted to the base station MeNB and the base station SeNB. Subsequently, a UL grant indicating a 30-byte radio resource is notified from the base station MeNB (S3). The user apparatus UE transmits 30-byte data to the base station MeNB using PUSCH (S4). In this state, the data retention amount in the UL PDCP buffer is 90 bytes. When switching methods 4 and 6 are applied, the data retention amount in the UL PDCP buffer is below the threshold value X, but the predetermined period (TTT) has not elapsed, so the bearer split state remains valid. is there. Then, UL grant is notified from base station SeNB (S5). It is assumed that 90 bytes of radio resources are allocated to the UL grant.

  Here, although the data retention amount in the UL PDCP buffer is below the threshold, the bearer split state is effective as described above. Therefore, the user apparatus UE determines that data can be transmitted to the base station SeNB, and transmits 90-byte data to the base station SeNB using the PDSCH (S6).

  As illustrated in FIG. 4, according to the conventional technique, the user apparatus UE transmits padding data to the base station SeNB because the data retention amount in the UL PDCP buffer is below the threshold, and as a result, the base station The UL grant (S5) and PUSCH radio resources (S6) transmitted by the station SeNB were wasted. On the other hand, as described above, the user apparatus UE in the embodiment can transmit uplink data to the base station SeNB even when the data retention amount in the UL PDCP buffer falls below the threshold. That is, it is possible to avoid wasting radio resources of the base station SeNB.

(Modification of switching method (1 to 6))
The user apparatus UE may transmit (trigger) the BSR to the base station eNB when determining that the retention amount of the data stored in the UL PDCP buffer satisfies a specific condition.

  For example, when the data retention amount in the UL PDCP buffer exceeds the threshold value X, threshold value Y, or threshold value Z (when the threshold value X, threshold value Y, or threshold value Z is greater than or equal to), or the data retention amount in the UL PDCP buffer However, when it falls below the threshold value X, threshold value Y, or threshold value Z (when the threshold value X, threshold value Y, or threshold value Z is less than or equal to), the user apparatus UE transmits (triggers) the BSR to the base station eNB. Also good. Further, the user apparatus UE may transmit (trigger) the BSR to the base station eNB at the timing when the bearer split state is switched.

  The BSR may be a regular BSR (Regular BSR). Moreover, when the uplink radio resource is not allocated, the user apparatus UE may not perform the BSR transmission. That is, the BSR may be a regular BSR not accompanied by a scheduling request (SR).

<Functional configuration>
FIG. 15 shows a functional configuration diagram of the user apparatus according to the present embodiment capable of executing the processing described so far. As illustrated in FIG. 15, the user apparatus UE includes a signal reception unit 101, a signal transmission unit 102, a UL signal generation unit 103, a determination unit 104, and a management unit 105. FIG. 15 shows only functional units particularly related to the embodiment of the present invention in the UE, and also has a function (not shown) for performing an operation based on LTE at least. The functional configuration shown in FIG. 15 is only an example. As long as the operation according to the present embodiment can be performed, the function classification and the name of the function unit may be anything.

  The signal receiving unit 101 includes a function of wirelessly receiving various signals from the base station eNB and acquiring higher layer signals from the received physical layer signals. The signal transmission unit 102 includes a function of wirelessly transmitting various physical layer signals. Each of the signal reception unit 101 and the signal transmission unit 102 includes a function of bundling a plurality of CCs to perform CA communication. Moreover, the signal receiving part 101 and the signal transmission part 102 respectively include the function to perform CA communication by DC between the base station MeNB and the base station SeNB.

  In addition, the signal transmission unit 102 has a UL PDCP buffer, and accumulates the uplink data generated by the UL signal generation unit 103 in the UL PDCP buffer. Further, when the signal reception unit 101 receives the UL grant, the signal transmission unit 102 transmits the uplink data to the base station eNB using the uplink radio resource allocated by the UL grant.

  Further, the signal transmission unit 102 transmits the BSR and uplink data to the base station MeNB or the base station SeNB depending on whether the bearer split state is valid (ON) or invalid (OFF). Select whether or not.

  The UL signal generation unit 103 has a function of generating uplink data to be transmitted to the base station eNB. The UL signal generation unit 103 is, for example, various applications included in the user apparatus UE. Uplink data generated by the UL signal generation unit 103 is passed to the signal transmission unit 102.

  The determination unit 104 is a function for executing any one of the determination processes (the processing procedures in FIGS. 7 to 9 and FIGS. 11 to 13) described in the bearer split state switching method (Nos. 1 to 6). Or a function for executing a plurality of processes, or a function for executing all determination processes. Note that the determination unit 104 may appropriately switch which determination process is used among these determination processes. Further, which determination process is used may be notified (instructed) in advance by, for example, an RRC message or broadcast information (SIB), or may be predetermined in the wireless communication system. However, it may be determined (selected) according to the system band or the UE category.

  The management unit 105 has a function of managing whether the bearer split state is valid (ON) or invalid (OFF). Further, the management unit 105 has a function of switching the bearer split state according to an instruction from the determination unit 104.

  The UL signal generation unit 103, the determination unit 104, and the management unit 105 may be included in the signal transmission unit 102.

<Summary>
According to the embodiment described above, in a wireless communication system that supports uplink carrier aggregation, the user apparatus communicates with the first base station and the second base station, and is stored in the buffer. In addition to determining whether or not the amount of uplink data exceeds the first threshold value, a determination unit that determines whether or not a specific condition is further satisfied, and the amount of uplink data stored in the buffer is the first When it is determined that the threshold value is exceeded and it is determined that a specific condition is satisfied, uplink communication is performed between the first base station and the second base station by applying a bearer split to the uplink. And a communication device for performing a user device. A technique capable of avoiding wasteful radio resources when uplink data related to the split bearer is transmitted by the user apparatus UE is provided.

  In addition, the determination unit determines whether or not the state in which the amount of uplink data stored in the buffer exceeds the first threshold continues for a predetermined period, and the communication unit includes the buffer When it is determined that the state in which the amount of uplink data stored therein exceeds the first threshold value continues for a predetermined period, bearer split may be applied to the uplink.

  This prevents frequent activation / invalidation of the uplink bearer split state even when the data retention amount in the UL PDCP buffer slightly exceeds a predetermined threshold. Can do.

  Further, the determination unit determines whether or not the amount of uplink data stored in the buffer exceeds a second threshold value that is larger than the first threshold value, and the communication unit stores the buffer in the buffer. If it is determined that the amount of stored uplink data exceeds the second threshold, bearer splitting may be applied to the uplink.

  As a result, the uplink bearer split state can be validated immediately when the data retention amount in the UL PDCP buffer increases to some extent, so that the uplink throughput related to the split bearer can be improved.

  Further, the determination unit determines whether or not the state in which the amount of uplink data accumulated in the buffer exceeds a second threshold value that is greater than the first threshold value continues for a predetermined period of time, The communication unit applies a bearer split to the uplink when it is determined that the state in which the amount of uplink data accumulated in the buffer exceeds the second threshold value continues for a predetermined period of time. It may be.

  This prevents frequent activation / invalidation of the uplink bearer split state even when the data retention amount in the UL PDCP buffer slightly exceeds a predetermined threshold. Can do.

  In addition, the determination unit is stored in the buffer when uplink communication is performed between the first base station and the second base station by applying bearer split to the uplink. The communication unit determines whether or not the state in which the amount of uplink data is below the first threshold has continued for a predetermined period, and the communication unit applies bearer split to the uplink and the first base station and the first When uplink communication is performed with a second base station, when it is determined that a state in which the amount of uplink data stored in the buffer is below the first threshold has continued for a predetermined period The application of the uplink bearer split may be stopped.

  As a result, it is possible to prevent the activation / invalidation of the uplink bearer split state from being frequently switched due to the fluctuation of the data retention amount in the UL PDCP buffer.

  In addition, the determination unit is stored in the buffer when uplink communication is performed between the first base station and the second base station by applying bearer split to the uplink. It is determined whether the amount of uplink data falls below a second threshold value that is smaller than the first threshold value, and the communication unit applies the bearer split to the uplink to apply the first base station and the second base In the case of performing uplink communication with a station, if it is determined that the amount of uplink data stored in the buffer has fallen below the second threshold, the application of uplink bearer split is stopped. It may be.

  As a result, it is possible to prevent the activation / invalidation of the uplink bearer split state from being frequently switched due to the fluctuation of the data retention amount in the UL PDCP buffer. Also, the uplink bearer split state can be invalidated immediately when the data retention amount in the UL PDCP buffer becomes small to some extent, and the load on the user apparatus UE can be reduced.

  In addition, the determination unit is stored in the buffer when uplink communication is performed between the first base station and the second base station by applying bearer split to the uplink. The communication unit determines whether or not an uplink data amount has fallen below a second threshold value that is smaller than the first threshold value for a predetermined period, and the communication unit applies bearer split to the uplink and transmits the first base station and the first threshold value. When uplink communication is performed with a second base station, if it is determined that the amount of uplink data stored in the buffer has fallen below the second threshold for a predetermined period, an uplink bearer split May be stopped.

  As a result, it is possible to prevent the activation / invalidation of the uplink bearer split state from being frequently switched due to the fluctuation of the data retention amount in the UL PDCP buffer.

  Further, the communication unit determines that the amount of uplink data stored in the buffer exceeds the first threshold, or the amount of uplink data stored in the buffer satisfies the specific condition. When it is determined that the condition is satisfied, a BSR may be transmitted to at least one of the first base station and the second base station.

  Thereby, the user apparatus UE can more accurately convey the uplink data amount stored in its own buffer to the base station MeNB and the base station SeNB. Thereby, the base station MeNB and the base station SeNB can more appropriately perform uplink scheduling for the user apparatus UE.

  Further, according to the embodiment described above, in a radio communication system supporting uplink carrier aggregation, a communication method performed by a user apparatus that communicates with a first base station and a second base station, In addition to determining whether or not the amount of uplink data stored in the buffer exceeds a first threshold, and further determining whether or not a specific condition is satisfied, and the uplink data stored in the buffer While it is determined that the amount of data exceeds the first threshold and it is determined that the specific condition is satisfied, the bearer split is applied to the uplink, and the first base station and the second base station And performing a communication between them. This communication method provides a technique capable of avoiding waste of radio resources when uplink data related to a split bearer is transmitted.

<Supplement of embodiment>
In the above description, it is assumed that the user apparatus UE communicates with a plurality of different base stations eNB, but in the present embodiment, carrier aggregation is performed between different processing units in the same base station eNB. It may also be applied.

  You may make it combine arbitrarily the switching method (the 1-6) of the bearer split state demonstrated above.

  As described above, the configuration of each device (user device UE / base station eNB) described in the embodiment of the present invention is realized by executing the program by the CPU (processor) in the device including the CPU and the memory. It may be a configuration, may be a configuration realized by hardware such as a hardware circuit provided with processing logic described in the present embodiment, or may be a mixture of programs and hardware Good.

  Although the embodiments of the present invention have been described above, the disclosed invention is not limited to such embodiments, and those skilled in the art will understand various variations, modifications, alternatives, substitutions, and the like. I will. Although specific numerical examples have been described in order to facilitate understanding of the invention, these numerical values are merely examples and any appropriate values may be used unless otherwise specified. The classification of items in the above description is not essential to the present invention, and the items described in two or more items may be used in combination as necessary, or the items described in one item may be used in different items. It may be applied to the matters described in (if not inconsistent). The boundaries between functional units or processing units in the functional block diagram do not necessarily correspond to physical component boundaries. The operations of a plurality of functional units may be physically performed by one component, or the operations of one functional unit may be physically performed by a plurality of components. The order of the sequences and flowcharts described in the embodiments may be changed as long as there is no contradiction. For convenience of processing description, the user apparatus UE / base station eNB has been described using a functional block diagram, but such an apparatus may be realized by hardware, software, or a combination thereof. The software operated by the processor of the user apparatus UE according to the embodiment of the present invention and the software operated by the processor of the base station eNB according to the embodiment of the present invention are random access memory (RAM), flash memory, and read-only, respectively. The data may be stored in a memory (ROM), EPROM, EEPROM, register, hard disk (HDD), removable disk, CD-ROM, database, server, or any other suitable storage medium.

  In the embodiment, the threshold value X is an example of a first threshold value. The threshold value Y or the threshold value Z is an example of a second threshold value. The signal reception unit 101 and the signal transmission unit 102 are an example of a communication unit. TTT is an example of a predetermined period.

MeNB Base station SeNB Base station UE User apparatus 101 Signal reception unit 102 Signal transmission unit 103 UL signal generation unit 104 Determination unit 105 Management unit

Claims (9)

In a wireless communication system that supports uplink carrier aggregation, a user apparatus that communicates with a first base station and a second base station,
A determination unit that determines whether or not a specific condition is satisfied, in addition to determining whether or not the amount of uplink data accumulated in the buffer exceeds a first threshold;
While determining that the amount of uplink data stored in the buffer exceeds a first threshold and determining that a specific condition is satisfied, the first base station applies a bearer split to the uplink. And a communication unit that performs uplink communication between the second base station and the second base station;
A user device. The determination unit determines whether or not a state in which the amount of uplink data accumulated in the buffer exceeds the first threshold continues for a predetermined period;
The communication unit applies a bearer split to the uplink when it is determined that the state in which the amount of uplink data accumulated in the buffer exceeds the first threshold continues for a predetermined period. The user device according to claim 1. The determination unit determines whether the amount of uplink data stored in the buffer exceeds a second threshold value that is greater than the first threshold value,
The user apparatus according to claim 1, wherein the communication unit applies bearer split to the uplink when it is determined that the amount of uplink data stored in the buffer exceeds the second threshold. The determination unit determines whether or not the state in which the amount of uplink data accumulated in the buffer exceeds a second threshold value that is greater than the first threshold value continues for a predetermined period of time,
The communication unit applies a bearer split to the uplink when it is determined that the state in which the amount of uplink data accumulated in the buffer exceeds the second threshold continues for a predetermined period of time, The user device according to claim 1. The determination unit applies uplink bearer split to the uplink and performs uplink communication between the first base station and the second base station, and uplink data stored in the buffer Determining whether the amount has fallen below the first threshold for a predetermined period of time;
When the communication unit performs uplink communication between the first base station and the second base station by applying bearer split to the uplink, the uplink data stored in the buffer The user apparatus according to claim 1, wherein when it is determined that the state where the amount is below the first threshold value has continued for a predetermined period, application of the uplink bearer split is stopped. The determination unit applies uplink bearer split to the uplink and performs uplink communication between the first base station and the second base station, and uplink data stored in the buffer Determining whether the amount has fallen below a second threshold that is less than the first threshold;
When the communication unit performs uplink communication between the first base station and the second base station by applying bearer split to the uplink, the uplink data stored in the buffer The user equipment according to claim 1, wherein when it is determined that the amount falls below the second threshold, the application of the uplink bearer split is stopped. The determination unit applies uplink bearer split to the uplink and performs uplink communication between the first base station and the second base station, and uplink data stored in the buffer Determining whether the amount has fallen below a second threshold value less than the first threshold value for a predetermined period of time;
When the communication unit performs uplink communication between the first base station and the second base station by applying bearer split to the uplink, the uplink data stored in the buffer The user equipment according to claim 1, wherein when it is determined that the amount has fallen below the second threshold for a predetermined period, application of the uplink bearer split is stopped.   The communication unit determines that the amount of uplink data stored in the buffer exceeds the first threshold, or the amount of uplink data stored in the buffer satisfies the specific condition The user apparatus according to any one of claims 1 to 7, wherein a BSR is transmitted to at least one of the first base station and the second base station when it is determined. In a wireless communication system supporting uplink carrier aggregation, a communication method performed by a user apparatus that communicates with a first base station and a second base station,
In addition to determining whether the amount of upstream data stored in the buffer has exceeded a first threshold value, further determining whether or not a specific condition is satisfied;
While determining that the amount of uplink data stored in the buffer exceeds a first threshold and determining that a specific condition is satisfied, the first base station applies a bearer split to the uplink. Performing uplink communication between the second base station and the second base station;
A communication method comprising:

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