Communication device, master node, and communication control method

Abstract

To provide a user device, a master base station, and a communication control method that appropriately transmit data to the MCG side.SOLUTION: In a mobile communication system, user equipment (UE) connected to a master base station and a secondary base station using a dual connectivity method includes a wireless communication unit that transmits first data belonging to a split bearer to the master base station and transmits second data belonging to the split bearer to the secondary base station, and a control unit having a PDCP entity and a first RLC entity associated with the master base station and a second RLC entity associated with the secondary base station, and when a secondary cell group managed by the secondary base station is in an inactive state, the PDCP entity outputs a PDCP data amount indicating the amount of data available for transmission in the PDCP entity to the first RLC entity and outputs a message that the PDCP data amount is 0 to the second RLC entity.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a user equipment, a master base station, and a communication control method used in a mobile communication system. [Background technology]

[0002] 2. Description of the Related Art In 3GPP (Third Generation Partnership Project, registered trademark; the same applies hereinafter), a standardization project for mobile communication systems, a dual connectivity method (DC) has been introduced.

[0003] In the dual connectivity scheme, only one base station (hereinafter referred to as a "master base station" or "master node") among multiple base stations establishes an RRC (Radio Resource Control) connection with a user equipment (UE (User Equipment)). On the other hand, other base stations (hereinafter referred to as "secondary base stations" or "secondary nodes") among the multiple base stations other than the master base station do not establish an RRC connection with the user equipment, but provide additional radio resources to the user equipment.

[0004] In the dual connectivity scheme, a user equipment (UE) transmits and receives user data using the radio resources of the master node and the radio resources of the secondary node, thereby improving throughput.

[0005] 3GPP has introduced MR-DC (Multi-Radio DC), which is a dual connectivity method between LTE (Long Term Evolution) nodes and NR (New Radio) nodes, or a dual connectivity method between NR nodes.

[0006] On the other hand, the power consumption of a user device performing wireless communication using the dual connectivity method is higher than when performing wireless communication with one base station.

[0007] Therefore, 3GPP is studying a technique for deactivating a secondary cell group (SCG) managed by a secondary node depending on the situation.

[0008] Regarding the deactivation of an SCG, the 3GPP has agreed on the following points: Only the master node can generate an RRC message related to the activation or deactivation of an SCG, and the user equipment can instruct the master node that it wants to deactivate the SCG.

[0009] Also, currently, the following is proposed in 3GPP: while the SCG is deactivated, if the user equipment has uplink data to transmit on a split bearer, the user equipment transmits the uplink data on a master cell group (MCG) leg regardless of the primary path. [Prior art documents] [Non-patent literature]

[0010] [Non-Patent Document 1] 3GPP TS 37.340 V16.5.0 [Non-patent document 2] 3GPP contribution: R2-2104315 [Non-patent document 3] 3GPP contribution: R2-2103977 [Non-patent document 4] 3GPP contribution: R2-2103979 Summary of the Invention [Problem to be solved by the invention]

[0011] Regarding the above proposals, 3GPP has not yet agreed on how to implement how the user equipment transmits uplink data to the MCG side.

[0012] Therefore, when a split bearer capable of transmitting uplink data to both the MCG and the SCG is configured in a user equipment, if the SCG is deactivated, the user equipment may not be able to properly transmit uplink data to the MCG side.

[0013] Therefore, one aspect of the present invention aims to provide a user equipment, a master base station, and a communication control method that are capable of appropriately transmitting data to the MCG side. [Means for solving the problem]

[0014] A user equipment according to one embodiment of the present disclosure is a user equipment connected to a master base station and a secondary base station using a dual connectivity scheme. The user equipment includes a radio communication unit configured to transmit first data belonging to a split bearer to the master base station and to transmit second data belonging to the split bearer to the secondary base station. The user equipment also includes a control unit having a Packet Data Convergence Protocol (PDCP) entity, a first Radio Link Control (RLC) entity associated with the master base station, and a second RLC entity (134) associated with the secondary base station. When a secondary cell group managed by the secondary base station is in an inactive state, the PDCP entity outputs a PDCP data amount indicating an amount of data available for transmission in the PDCP entity to the first RLC entity and outputs a signal indicating that the PDCP data amount is "0" to the second RLC entity.

[0015] A master base station according to one embodiment of the present disclosure is a master base station that connects to a user equipment (UE) together with a secondary base station using a dual connectivity scheme. The master base station has a radio communication unit that receives first data belonging to a split bearer from the UE and receives second data belonging to the split bearer from the UE via the secondary base station. The master base station also has a control unit that, when a secondary cell group managed by the secondary base station is in an inactive state, configures the UE to switch the primary path of the UE from the secondary cell group to a master cell group managed by the master base station.

[0016] According to one aspect of the present disclosure, there is provided a communication control method for a user equipment (UE), the user equipment (UE) including: a radio communication unit connected to a master base station and a secondary base station using a dual connectivity scheme, configured to transmit first data belonging to a split bearer to the master base station and to transmit second data belonging to the split bearer to the secondary base station; and a control unit having a Packet Data Convergence Protocol (PDCP) entity, a first Radio Link Control (RLC) entity associated with the master base station, and a second RLC entity associated with the secondary base station. The communication control method includes, when a secondary cell group managed by the secondary base station is in an inactive state, the PDCP entity outputting, to the first RLC entity, a PDCP data amount indicating an amount of data available for transmission in the PDCP entity, and outputting, to the second RLC entity, a message indicating that the PDCP data amount is "0." [Effects of the Invention]

[0017] According to one aspect, it is possible to provide a user equipment, a master base station, and a communication control method that are capable of appropriately transmitting data to the MCG side. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a mobile communication system according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a diagram illustrating an example of the configuration of a protocol stack according to an embodiment of the present disclosure. [Figure 3] FIG. 3 is a diagram illustrating an example of the configuration of a protocol stack according to an embodiment of the present disclosure. [Figure 4] FIG. 4 is a diagram illustrating an example configuration of a UE according to an embodiment of the present disclosure. [Figure 5] FIG. 5 is a diagram illustrating a configuration example of a base station according to an embodiment of the present disclosure. [Figure 6] FIG. 6 is a diagram illustrating an example of a split bearer according to an embodiment of the present disclosure. [Figure 7] FIG. 7 is a diagram illustrating an example of operation according to an embodiment of the present disclosure. [Figure 8] FIG. 8 is a diagram illustrating an example of operation according to specifications according to an embodiment of the present disclosure. [Figure 9] FIG. 9 is a diagram illustrating an example of operation according to specifications according to an embodiment of the present disclosure. [Figure 10] FIG. 10 is a diagram illustrating an example of a split bearer according to an embodiment of the present disclosure. [Figure 11] FIG. 11 is a diagram illustrating an example of operation according to an embodiment of the present disclosure. [Figure 12] FIG. 12 is a diagram illustrating an example of information included in a message according to an embodiment of the present disclosure. [Figure 13] FIG. 13 is a diagram illustrating an example of information included in a message according to an embodiment of the present disclosure. [Figure 14] FIG. 14 is a diagram illustrating an example of information included in a message according to an embodiment of the present disclosure. [Figure 15] FIG. 15 is a diagram illustrating an example of information included in a message according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In this specification and the drawings, elements that can be similarly described may be designated as identical or similar, and redundant description may be omitted.

[0020] [First embodiment] (1.1) Example of a mobile communication system configuration FIG. 1 illustrates a configuration example of a mobile communication system 1 according to an embodiment of the present disclosure. The mobile communication system 1 is, for example, a 3GPP 5G (5th Generation) system. The mobile communication system 1 may be a mixture of an LTE system and a 5G system. The mobile communication system 1 may also be a mixture of a 5G system and a system of another generation (for example, a sixth generation). The mobile communication system 1 may also include a system conforming to a standard other than 3GPP.

[0021] As shown in FIG. 1, the mobile communication system 1 includes a radio access network (hereinafter, sometimes referred to as "NG-RAN" (Next Generation Radio Access Network)) 20, a core network (hereinafter, sometimes referred to as "5GC" (5G Core Network)) 30, and a user equipment (hereinafter, sometimes referred to as "UE" (User Equipment)) 100.

[0022] The NG-RAN 20 includes a base station (gNB) 200, which is a node of the radio access network.

[0023] The base station 200 is a wireless communication device that performs wireless communication with the UE 100. The base station 200 manages one or more cells. The base station 200 performs wireless communication with the UE 100 that has established an RRC connection in its own cell. The base station 200 has a radio resource management function, a routing function for user data (hereinafter sometimes referred to as "data"), a measurement control function for mobility control and scheduling, and the like.

[0024] The term "cell" is used as a term indicating the smallest unit of a wireless communication area. The term "cell" may be used as a term indicating a function for performing wireless communication with the UE 100, or as a term indicating a resource. One cell belongs to one carrier frequency. In FIG. 1, the base station 200-1 manages the cell C1, and the base station 200-2 manages the cell C2.

[0025] The 5GC30 includes a core network device 300.

[0026] The core network device 300 includes a device corresponding to the control plane. In this case, the core network device 300 can perform various mobility controls on the UE 100 by communicating with the UE 100 using NAS (Non-Access Stratum) signaling. The core network device 300 may be an AMF (Access Management Function) or an MME (Mobility Management Entity).

[0027] Furthermore, the core network device 300 includes a device corresponding to the user plane. In this case, the core network device 300 controls the transfer of data of the UE 100. The core network device 300 may be a UPF (User Plane Function) or an S-GW (Serving Gateway).

[0028] 1, the base stations 200-1 and 200-2 are connected to each other via an interface called an NG interface and the 5GC 30. The base stations 200-1 and 200-2 are also connected to each other via an interface called an Xn interface.

[0029] The UE 100 is a mobile wireless communication device such as a smartphone, a tablet terminal, a personal computer, a communication module, or a communication card. The UE 100 may be a vehicle (e.g., a car, a train, etc.) or a device installed in a vehicle. The UE 100 may also be a transport body (e.g., a ship, an airplane, etc.) or a device installed in a transport body. The UE 100 may also be a sensor or a device installed in a sensor. The UE 100 may also be referred to as a mobile station, a mobile terminal, a mobile device, a mobile unit, a subscriber station, a subscriber terminal, a subscriber device, a remote station, a remote terminal, a remote device, or a remote unit.

[0030] FIG. 1 shows an example in which UE 100 is present in both cell C1 managed by base station 200-1 and cell C2 managed by base station 200-2.

[0031] (1.2) Protocol stack configuration example Fig. 2 is a diagram illustrating an example of the configuration of a protocol stack related to a control plane according to an embodiment of the present disclosure.

[0032] 2, as protocols related to the control plane, a PHY (Physical) layer, a MAC (Media Access Control) layer, an RLC (Radio Frequency Control) layer, a PDCP (Packet Data Convergence Protocol) layer, and an RRC layer are included in the UE 100 and the base station 200. Furthermore, a NAS layer is included in the UE 100 and the core network device 300.

[0033] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of the UE 100 and the PHY layer of the base station 200 via a physical channel.

[0034] The MAC layer performs data priority control, retransmission processing using Hybrid ARQ (HARQ), random access procedures, etc. Data and control information are transmitted between the MAC layer of the UE 100 and the MAC layer of the base station 200 via a transport channel. The MAC layer of the base station 200 includes a scheduler, which determines the transport format (transport block size, modulation and coding scheme) and allocated resource blocks for the uplink and downlink.

[0035] The RLC layer transmits data to the RLC layer on the receiving side using the functions of the MAC layer and PHY layer. Data and control information are transmitted between the RLC layer of the UE 100 and the RLC layer of the base station 200 via logical channels.

[0036] The PDCP layer performs header compression / decompression, and encryption / decryption. Data and control information are transmitted between the PDCP layer of the UE 100 and the PDCP layer of the base station 200 via a radio bearer.

[0037] The RRC layer controls logical channels, transport channels, and physical channels according to the establishment, re-establishment, and release of radio bearers. RRC signaling for various settings is transmitted between the RRC layer of the UE 100 and the RRC layer of the base station 200. When there is an RRC connection with the base station 200, the UE 100 is in an RRC connected state. When there is no RRC connection with the base station 200, the UE 100 is in an RRC idle state.

[0038] The NAS layer performs session management, mobility management, etc. NAS signaling is transmitted between the NAS layer of the UE 100 and the NAS layer of the core network device 300.

[0039] Fig. 3 is a diagram illustrating an example of the configuration of a protocol stack related to a user plane according to an embodiment of the present disclosure.

[0040] As shown in FIG. 3, the UE 100 and the base station 200 include a PHY layer, a MAC layer, an RLC layer, a PDCP layer, and an SDAP (Service Data Protocol) layer as protocols related to the user plane.

[0041] The SDAP layer maps Quality of Service (QoS) flows to data radio bearers and assigns QoS flow identification (ID) for both uplink (UL) and downlink (DL). Note that the SDAP layer does not necessarily exist in the LTE system.

[0042] (1.3) Dual connection method The UE 100 can utilize resources provided by two different nodes connected by a non-ideal backhaul. In this case, one node is a master node (MN) that manages a master cell group (hereinafter, sometimes referred to as "MCG"). The other node is a secondary node (SN) that manages a secondary cell group (hereinafter, sometimes referred to as "SCG"). The master node and the secondary node are connected via a network interface (Xn interface). At least the master node is connected to the core network.

[0043] The master node provides a single control plane for the core network (e.g., 5GC 30). The master node may be referred to as a master eNB (evolved Node B), a master ng-eNB (new generation -eNB), or a master gNB.

[0044] The secondary node does not have a control plane connection to the core network and provides additional radio resources to the UE 100. The secondary node may be referred to as an en-gNB, a secondary ng-eNB, or a secondary gNB.

[0045] Here, the master node and the secondary node are logical entities. In this embodiment, the following description will be given assuming that the master node corresponds to base station 200-1 and the secondary node corresponds to base station 200-2.

[0046] An MCG is a cell group of serving cells associated with a master node. An MCG has a primary cell (Sp cell or P cell) and optionally one or more secondary cells (S cells).

[0047] An SCG is a group of serving cells associated with a secondary node. An SCG has a primary cell (Sp cell or PS cell) and optionally one or more secondary cells (S cells). An Sp cell is the primary cell in the MCG and also the primary cell in the SCG.

[0048] The UE 100 can connect to a master node that manages the MCG and a secondary node that manages the SCG. In this case, the UE 100 connects to each node simultaneously and performs wireless communication.

[0049] The dual connectivity method is configured by the master node sending a predetermined message (e.g., an SN Addition Request message) to the secondary node, and then the master node sending an RRC message (e.g., an RRC Reconfiguration message) to UE 100.

[0050] Hereinafter, the base station 200-1 may be referred to as the master node 200-1 or the master base station 200-1. Also, hereinafter, the base station 200-2 may be referred to as the secondary node 200-2 or the secondary base station 200-2.

[0051] (1.4) Deactivating the SCG Next, we will explain the deactivation of the SCG.

[0052] In 3GPP, deactivation of SCG is being considered in order to reduce the power consumption of UE 100. When UE 100 deactivates an SCG, it deactivates all cells (PSCell and SCell) belonging to the SCG. For cells belonging to the deactivated SCG, UE 100 does not report CSI (Channel Status Information) for the cells, nor does it monitor PDCCH. Furthermore, UE 100 does not transmit RACH (Random Access CHannel), SRS (Sounding Reference Signal), UL-SCH (UL-Shared CHannel), or the like to the cells. This reduces the power consumption of UE 100.

[0053] The UE 100 deactivates the SCG in one of the following ways:

[0054] Method 1: The UE 100 deactivates the SCG in response to receiving an instruction to deactivate the SCG from the master node (base station 200-1). The instruction is transmitted by RRC layer signaling (RRC message), MAC layer signaling (MAC CE), or PHY layer signaling (PDCCH).

[0055] Method 2: The UE 100 deactivates the SCG in response to the expiration of a timer for deactivating the SCG.

[0056] (1.5) Split Bearer In MR-DC, from the viewpoint of UE 100, there are three bearer types: MCG bearer, SCG bearer, and split bearer. The MCG bearer is a bearer established between UE 100 and the master node 200-1. The SCG bearer is a bearer established between UE 100 and the secondary node 200-2. The split bearer is established between UE 100 and the master node 200-1 and so as to be transmitted from UE 100 to the master node 200-1 via the secondary node 200-2. In MR-DC, the split bearer is a radio bearer having both an MCG RLC and an SCG RLC.

[0057] Fig. 6 is a diagram illustrating an example of a split bearer for UL data. As will be described in detail later, when the split bearer is set up, as shown in Fig. 6, the PDCP entity 131 of the UE 100 is associated with two RLC entities, a first RLC entity 132 and a second RLC entity 134.

[0058] With respect to UL data, the PDCP entity 131 outputs a first PDCP PDU (Protocol Data Unit) (or a PDCP PDU corresponding to the first data) to the first RLC entity 132 corresponding to the master node 200-1. The PDCP entity 131 also outputs a second PDCP PDU (or a PDCP PDU corresponding to the second data) to the second RLC entity 134 corresponding to the secondary node 200-2.

[0059] The first data is then output to the PDCP entity 233 via the first RLC entity 132, the first MAC entity 133, the MAC entity 231 of the master node 200-1, and the RLC entity 232. On the other hand, the second data is output to the PDCP entity 233 via the second RLC entity 134, the second MAC entity 135, the MAC entity 234 of the secondary node 200-2, and the RLC entity 235.

[0060] In this way, the split bearer sets two branched logical data paths for the UE 100, and the UE 100 can transmit data to the master node 200-1 and the secondary node 200-2 using the two bearers. Specifically, when the total amount of the PDCP data volume and the amount of RLC data pending initial transmission is equal to or greater than a threshold (ul-DataSplitTheshold), the PDCP entity 233 outputs the PDCP PDU to either the primary RLC entity (e.g., the first RLC entity 132) or the split secondary RLC entity (e.g., the second RLC entity 134).

[0061] Here, the PDCP data volume refers to the amount of data available for transmission in the PDCP entity 131.

[0062] The split bearer setting is performed between the master node 200-1 and the secondary node 200 By negotiating with master node 200-1 and master node 200-2, it becomes possible to set up a split bearer in each of nodes 200-1 and 200-2. Furthermore, by master node 200-1 transmitting an RRC message or the like to UE 100, it becomes possible to set up a split bearer in UE 100.

[0063] (1.6) Primary Path The master node 200-1 can set a primary path for the UE 100 by using an RRC message. The primary path is a path indicated by the cell group ID and LCID (Logical Channel ID) of a primary RLC entity capable of responding to split bearer operation. The master node 200-1 can use an RRC message to indicate the cell group ID and LCID of the primary RLC entity, thereby allowing the UE 100 to set the primary RLC entity side as the primary path. The example of FIG. 6 shows an example in which the second RLC entity 134 is set as the primary RLC entity and the primary path is set on the SCG side. In this way, the master node 200-1 can set the primary path on the SCG side.

[0064] Furthermore, the master node 200-1 can also use an RRC message to set a split secondary path other than the primary path for the UE 100. A split secondary path is a path indicated by the LCID of a split secondary RLC entity, which is an RLC entity other than the primary RLC entity. A path other than the primary path can be a split secondary path. The master node 200-1 can use an RRC message to indicate the LCID of the split secondary RLC entity, thereby allowing the UE 100 to set the side of the split secondary RLC entity as the split secondary path. The example of FIG. 6 shows an example in which the first RLC entity 132 is set as the split secondary RLC entity, and a split secondary path is set on the MCG side. In this way, the master node 200-1 can set a split secondary path on the MCG side.

[0065] For example, when the amount of data is less than a threshold, PDCP entity 131 of UE 100 outputs a PDCP PDU to the primary RLC entity set as the primary path (second RLC entity 134 in the example of FIG. 6). When the amount of data exceeds the threshold, PDCP entity 131 outputs a PDCP PDU to a path other than the primary path, i.e., to the split secondary RLC entity set as the split secondary path (first RLC entity 132 in the example of FIG. 6).

[0066] (1.7) UE configuration example 4 is a diagram illustrating an example of the configuration of UE 100. As illustrated in FIG. 4, UE 100 includes antenna 101, radio communication unit 120, control unit 130, and memory 140.

[0067] The antenna 101 receives a radio signal transmitted from the base station 200 and outputs the received radio signal to the radio communication unit 120. The antenna 101 also transmits the radio signal output from the radio communication unit 120 to the base station 200.

[0068] The wireless communication unit 120 performs wireless communication with the base station 200 via the antenna 101 under the control of the control unit 130. For example, the wireless communication unit 120 converts (down-converts) a wireless signal output from the antenna 101 into a baseband signal (received signal) and outputs the converted baseband signal to the control unit 130. Furthermore, for example, the wireless communication unit 120 converts (up-converts) a baseband signal (transmitted signal) output from the control unit 130 into a wireless signal and outputs the converted wireless signal to the antenna 101.

[0069] The control unit 130 performs various controls in the UE 100. The control unit 130 controls, for example, wireless communication with the base station 200 or wireless communication with other UEs via the wireless communication unit 120 or the like. The control unit 130 may perform various operations by processing a received signal output from the wireless communication unit 120. The control unit 130 may also perform various operations and output a transmission signal to the wireless communication unit 120. The operation of the UE 100 described below may be an operation performed by the control unit 130.

[0070] The memory 140 stores various types of information under the control of the control unit 130. The memory 140 may function as a working memory for the control unit 130. The memory 140 may also store a program. In this case, the control unit 130 reads out and executes the program from the memory 140 to realize the operation of the UE 100. The memory 140 may be a read-only memory (ROM), a random access memory (RAM), or the like.

[0071] (1.8) Example of base station configuration 5 is a diagram illustrating an example of the configuration of base station 200. As shown in FIG. 5, base station 200 includes antenna 201, wireless communication unit 220, control unit 230, memory 240, and network communication unit 250.

[0072] The antenna 201 receives a radio signal transmitted from the UE 100, and outputs the received radio signal to the radio communication unit 220. The antenna 201 also transmits the radio signal output from the radio communication unit 220 to the UE 100.

[0073] The radio communication unit 220 performs radio communication with the UE 100 via the antenna 201 under the control of the control unit 230. For example, the radio communication unit 220 converts (down-converts) a radio signal output from the antenna 201 into a baseband signal (reception signal) and outputs the converted baseband signal to the control unit 230. Furthermore, for example, the radio communication unit 220 converts (up-converts) a baseband signal output from the control unit 230 into a transmission signal and outputs the converted radio signal to the antenna 201.

[0074] The control unit 230 performs various controls in the base station 200. The control unit 230 controls wireless communication with the UE 100, for example, via the wireless communication unit 220 or the like. The control unit 230 may perform various operations by processing a received signal output from the wireless communication unit 220. Furthermore, the control unit 230 may perform various operations and output a transmission signal to the wireless communication unit 220.

[0075] Furthermore, the control unit 230 controls communication with the core network device 300 or other base stations via the network communication unit 250. The control unit 230 receives messages and the like transmitted from the core network device 300 or other base stations via the network communication unit 250, and performs various operations. Furthermore, the control unit 230 performs various operations and instructs the network communication unit 250 to generate and transmit messages, thereby enabling the network communication unit 250 to transmit various messages to the core network device 300 or other base stations.

[0076] The operation of the base station 200 described below may be an operation performed by the control unit 230.

[0077] The memory 240 stores various types of information under the control of the control unit 230. The memory 240 may function as a working memory for the control unit 230. The memory 240 may also store a program. In this case, the control unit 230 reads and executes the program from the memory 240 to realize the operation of the base station 200. The memory 240 may be a read-only memory (ROM), a random access memory (RAM), or the like.

[0078] The network communication unit 250 is capable of communicating with other base stations. In this case, the network communication unit 250 communicates with other base stations using messages on the Xn interface. The network communication unit 250 is also capable of communicating with each node of the core network 30. In this case, the network communication unit 250 communicates with each node of the core network 30 using messages on the NG interface.

[0079] In the first embodiment, UE 100 is connected to master base station 200-1 and secondary base station 200-2 using a dual connectivity scheme. UE 100 includes radio communication unit 120 configured to transmit first data belonging to a split bearer to master base station 200-1 and to transmit second data belonging to the split bearer to secondary base station 200-2. UE 100 also includes control unit 130 having PDCP entity 131, first RLC entity 132 associated with master base station 200-1, and second RLC entity 134 associated with secondary base station 200-2. When the secondary cell group managed by secondary base station 200-2 is in an inactive state, PDCP entity 131 outputs a PDCP data amount indicating the amount of data available for transmission in PDCP entity 131 to first RLC entity 132 and outputs a message indicating that the PDCP data amount is "0" to second RLC entity 134. This allows the UE 100 to properly transmit data to the MCG side when the SCG is deactivated while the split bearer is set in the UE 100. Details will be described in the following first and second operation examples.

[0080] (2) Example of operation (2-1) First operation example 6 is a diagram illustrating an example of setting a split bearer according to an embodiment of the present disclosure. In the example of FIG. 6, it is assumed that a dual connectivity mode is set for the UE 100.

[0081] 6, the UE 100 includes a PDCP entity 131, a first RLC entity 132, a first MAC entity 133, a second RLC entity 134, and a second MAC entity 135. These entities are included in the control unit 130 of the UE 100, for example.

[0082] Master base station 200-1 includes MAC entity 231, RLC entity 232, and PDCP entity 233. These entities are included in control unit 230 of master base station 200-1, for example.

[0083] The secondary base station 200-2 includes a MAC entity 234 and an RLC entity 235. These entities are included in, for example, the control unit 230 of the secondary base station 200-2.

[0084] Here, the path from PDCP entity 131 to PDCP entity 224 of master base station 200-1 via first RLC entity 132 is set as an MCG. Also, in the example of Fig. 6, the path from PDCP entity 131 to RLC entity 235 of secondary base station 200-2 via second RLC entity 134 to PDCP entity 233 is set as an SCG.

[0085] A split bearer is also set. Therefore, the UE 100 can transmit first data belonging to the split bearer to the master base station 200-1 via the MCG. Furthermore, the UE 100 can transmit second data belonging to the split bearer to the secondary base station 200-2 via the SCG.

[0086] Furthermore, as shown in FIG. 6, the primary path is set on the SCG side.

[0087] In the first operation example, when the SCG becomes inactive in this state, the PDCP entity 131 outputs the PDCP data volume to the first RLC entity 132 while maintaining the primary path setting, and outputs a message indicating that the PDCP data volume is "0" to the second RLC entity 134. Specifically, the PDCP entity 131 outputs the PDCP data volume to the first RLC entity 132, which is not suspended, and outputs a message indicating that the PDCP data volume is "0" to the second RLC entity 134, which is suspended because the SCG has become inactive.

[0088] The PDCP data volume output from PDCP entity 131 is output from first RLC entity 132 to first MAC entity 133. First MAC entity 133 generates a BSR (Buffer Status Report) based on the PDCP data volume. First MAC entity 133 transmits the BSR to master base station 200-1. MAC entity 231 of master base station 200-1 transmits a UL grant to UE 100 based on the BSR through scheduling. First MAC entity 133 can transmit data to master base station 200-1 using radio resources allocated by master base station 200-1 based on the UL grant.

[0089] On the other hand, when the second RLC entity 134 receives the notification that the PDCP data volume is "0", because the SCG is in an inactive state, it does not output the PDCP data volume to the second MAC entity 135. Therefore, the SCG side does not receive a UL grant from the secondary base station 200-2, and the UE 100 cannot transmit data using the SCG.

[0090] In the first operation example, the PDCP entity 131 outputs a PDCP PDU (Protocol Data Unit) to the first RLC entity 132, but does not output a PDCP PDU to the second RLC entity .

[0091] First RLC entity 132 converts the PDCP PDU output from PDCP entity 131 into an RLC PDU and outputs it to first MAC entity 133. First MAC entity 133 converts the RLC PDU into a MAC PDU and outputs it to the PHY layer. The PHY layer converts the MAC PDU into a radio signal and transmits the radio signal to master base station 200-1 using radio resources granted by the UL. This enables UE 100 to transmit UL data to master base station 200-1.

[0092] On the other hand, since the PDCP PDU is not output to the second RLC entity 134, the UE 100 can prevent the UL data from being transmitted to the secondary base station 200-2.

[0093] 7 is a diagram illustrating an example of operation according to an embodiment of the present disclosure. It is assumed that the dual connectivity mode is set in the UE 100 and the split bearer is also set in the UE 100 before the process of FIG.

[0094] As shown in FIG. 7, in step S10, the mobile communication system 1 starts the process.

[0095] In step S11, control unit 230 of master base station 200-1 sets the primary path to the SCG side. Control unit 230 can set UE 100 to use the SCG side as the primary path by transmitting an RRC message to UE 100.

[0096] In step S12, the SCG becomes inactive (deactivate state). For example, control unit 230 of master base station 200-1 detects that the SCG has become inactive, and transmits an RRC message to UE 100, thereby notifying UE 100 that the SCG has become inactive.

[0097] In step S13, the PDCP entity 131 of the UE 100 outputs the PDCP data volume to the non-suspended first RLC entity 132. The PDCP entity 131 also outputs a notification to the suspended second RLC entity 134 indicating that the PDCP data volume is "0".

[0098] In step S14, the PDCP entity 131 of the UE 100 submits the PDCP PDU to the first RLC entity 132 that is not suspended. In addition, the PDCP entity 131 does not output the PDCP PDU to the second RLC entity 134 that is suspended.

[0099] Then, in step S15, the mobile communication system 1 ends the series of processes.

[0100] Thus, in the first operation example, in the mobile communication system 1, when a dual connectivity method is set, a split bearer is set, and the primary path is set to the SCG, if the SCG becomes inactive, the PDCP entity 131 performs a predetermined operation.

[0101] That is, the PDCP entity 131 outputs the PDCP data volume to the first RLC entity 132 that is not suspended, and outputs a notification to the suspended second RLC entity 134 that the PDCP data volume is "0".

[0102] Furthermore, the PDCP entity 131 outputs PDCP PDUs to the first RLC entity 132 that is not suspended, and does not output PDCP PDUs to the second RLC entity 134 that is suspended.

[0103] This allows the UE 100 to properly transmit data to the MCG side when the SCG is deactivated while the split bearer is set in the UE 100.

[0104] 8 and 9 show examples of operation according to the specifications, with Fig. 8 showing an example of PDCP PDU transmission.

[0105] As shown in (X) of FIG. 8, if neither the primary RLC entity nor the split secondary RLC entity is suspended, the PDCP PDU is output to either the primary RLC entity or the split secondary RLC entity.

[0106] Furthermore, as shown in (Y) of FIG. 8, when either the primary RLC entity or the split secondary RLC entity is suspended, the PDCP PDU is output to the RLC entity that is not suspended.

[0107] In the first operation example, a case has been described in which the primary RLC entity is the second RLC entity 134 and the split secondary RLC entity is the first RLC entity 132 due to the setting of the primary path.

[0108] 9 is a diagram showing an example of transmission of the PDCP data volume. As shown in (X) of FIG. 9, if neither the primary RLC entity nor the split secondary RLC entity is suspended, the PDCP data volume is output to either the primary RLC entity or the split secondary RLC entity.

[0109] Furthermore, as shown in (Y) of Figure 9, when either the primary RLC entity or the split secondary RLC entity is suspended, the PDCP data volume is output to the non-suspended RLC entity, and a message indicating that the PDCP data volume is "0" is output to the suspended RLC entity.

[0110] In the first operation example, data is transmitted to the MCG when the SCG becomes inactive without changing the RRC setting. Specifically, the example in which the primary path setting is not changed is described. As a result, in the first operation example, processing for changing the RRC setting is not performed, and it is possible to reduce processing in the mobile communication system 1 and reduce processing delays.

[0111] On the other hand, a second operation example described below is an example of changing the RRC setting, specifically, changing the setting of the primary path.

[0112] (2-2) Second operation example FIG. 10 is a diagram illustrating an example of setting up a split bearer according to an embodiment of the present disclosure.

[0113] 10, similarly to the first operation example, a dual connectivity mode is configured in mobile communication system 1. Therefore, a path from PDCP entity 131 to PDCP entity 233 of master base station 200-1 via first RLC entity 132 is configured as an MCG. On the other hand, a path from PDCP entity 131 of UE 100 to PDCP entity 233 of master base station 200-1 via second RLC entity 134 and secondary base station 200-2 is configured as an SCG.

[0114] A split bearer is also set up in the mobile communication system 1. Furthermore, in the mobile communication system 1, a primary path is set up on the SCG side.

[0115] In the second operation example, if the SCG becomes inactive in this state, the master base station 200-1 sets (changes) the primary path from the SCG to the MCG.

[0116] Specifically, master base station 200-1 is a master base station that connects to UE 100 together with secondary base station 200-2 using the dual connectivity scheme. Master base station 200-1 has a radio communication unit 220 that receives first data belonging to a split bearer from UE 100 and receives second data belonging to the split bearer from UE 100 via secondary base station 200-2. Master base station 200-1 also has a control unit 230 that, when the secondary cell group managed by secondary base station 200-2 is in an inactive state, performs a setting on UE 100 to switch the primary path of UE 100 from the secondary cell group to the master cell group managed by master base station 200-1.

[0117] On the other hand, when the secondary cell group is in an inactive state, control unit 130 of UE 100 switches the primary path from the secondary cell group to the master cell group managed by master base station 200-1. Then, PDCP entity 131 of UE 100 outputs the amount of PDCP data to first RLC entity 132, which is the primary RLC entity, and outputs a signal indicating that the amount of PDCP data is "0" to second RLC entity 134, which is the split secondary RLC entity.

[0118] Furthermore, the PDCP entity 131 outputs PDCP PDUs to the first RLC entity 132, which is the primary RLC entity, but does not output PDCP PDUs to the second RLC entity 134, which is the split secondary RLC entity.

[0119] 11 is a diagram illustrating an example of operation according to an embodiment of the present disclosure. It is assumed that the dual connectivity mode is set in the UE 100 and the split bearer is also set in the UE 100 before the process of FIG.

[0120] In step S20, the mobile communication system 1 starts the process.

[0121] In step S21, master base station 200-1 sets the primary path on the SCG side. For example, control unit 230 of master base station 200-1 transmits to UE 100 an RRC message indicating that the primary path is to be set on the SCG side.

[0122] Fig. 14 is a diagram illustrating an example of information included in a message according to an embodiment of the present disclosure. Fig. 14 illustrates an example of a "PDCP-Config Information element" included in an RRC message. As shown in (X) of Fig. 14, the information element includes a "PrimaryPath" as an information element.

[0123] Fig. 15 is an explanatory diagram of "PrimaryPath". As described in the first sentence of Fig. 15, "PrimaryPath" represents an information element that indicates a primary RLC entity among multiple RLC entities. Control unit 230 of master base station 200-1 can set an SCG that includes second RLC entity 134 as the primary path by specifying the cell group ID and LCID of second RLC entity 134 as the primary RLC entity in "PrimaryPath".

[0124] In the second operation example, furthermore, as shown in (X) of Figure 15, when the SCG becomes inactive, UE100 can include information in the "PrimaryPath" that sets the cell group ID corresponding to the MCG.

[0125] That is, master base station 200-1 transmits an RRC message further including a "PDCP-Config Information element" including such a "PrimaryPath" to UE 100. Then, when the SCG becomes inactive, UE 100 becomes able to set the primary path to the SCG in accordance with the setting indicated in "PrimaryPath".

[0126] By setting "PrimaryPath", the control unit 130 of the UE 100 changes the first RLC entity 132 from a split secondary RLC entity to a primary RLC entity. On the other hand, by setting "PrimaryPath", the control unit 130 changes the second RLC entity 134 from a primary RLC entity to a split secondary RLC entity.

[0127] Returning to FIG. 11, in step S22, the SCG becomes inactive.

[0128] In step S23, control unit 130 of UE 100 sets the primary path to the MCG side. As described above, MCG is set as the primary path in accordance with the setting of "PrimaryPath" included in the information element "PDCP-Config Information element" received in step S21.

[0129] In step S24, PDCP entity 131 of UE 100 outputs the PDCP data volume to the primary RLC entity (first RLC entity 132). PDCP entity 131 also outputs to the split secondary RLC entity (second RLC entity 134) a message indicating that the PDCP data volume is "0." As a result, in the second operation example as well, as in the first operation example, master base station 200-1 transmits a UL grant only to the MCG side of UE 100.

[0130] In step S25, the PDCP entity 131 outputs the PDCP PDU to the primary RLC entity (first RLC entity 132), and does not output the PDCP PDU to the split secondary RLC entity (second RLC entity 134).

[0131] Then, in step S26, the mobile communication system 1 ends the series of processes.

[0132] In this way, in the second operation example, as in the first operation example, when a split bearer is set in UE100 and the SCG is deactivated, UE100 can properly transmit data to the MCG side.

[0133] 12 and 13 are diagrams showing examples of operation according to the specifications, with Fig. 12 showing an example of PDCP PDU transmission.

[0134] As shown in (X) of Figure 12, when a split secondary RLC entity (e.g., second RLC entity 134) is suspended due to SCG deactivation, the PDCP PDU is submitted to an unsuspended primary RLC entity (e.g., first RLC entity 132). On the other hand, when the split secondary RLC entity is not suspended, the PDCP PDU is submitted to either the primary RLC entity or the split secondary RLC entity.

[0135] Figure 13 shows an example of PDCP data volume transmission. As shown in (X) in Figure 13, when a split secondary RLC entity is suspended due to SCG deactivation, the PDCP data volume is indicated to the MAC entity associated with the primary RLC entity. On the other hand, the PDCP data volume is indicated to the MAC entity associated with an RLC entity other than the primary RLC entity (or a split secondary RLC entity) that the PDCP data volume is "0".

[0136] Furthermore, if the split secondary RLC entity is not suspended and the PDCP data volume and the total amount of RLC data whose initial transmission is suspended are equal to or greater than a threshold, the PDCP data volume is output to both the primary RLC entity and the split secondary RLC entity.

[0137] [Other embodiments] The above-described operational examples are not limited to being implemented independently, but may be implemented by appropriately combining the operational examples. Furthermore, for example, the steps in the processes described herein do not necessarily have to be executed in chronological order according to the order shown in the flowcharts or sequence diagrams. For example, the steps in the processes may be executed in an order different from that shown in the flowcharts or sequence diagrams, or may be executed in parallel. Furthermore, some of the steps in the processes may be deleted, or additional steps may be added to the processes.

[0138] Also, for example, a method including the operation of one or more components of the apparatus described in this specification may be provided, or a program for causing a computer to execute the operation of the above components may be provided. The program may be recorded on a computer-readable medium. The computer-readable medium can be used to install the program on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM. An example of such a recording medium is the memory 140, 240 described above.

[0139] Furthermore, circuits for executing the processes performed by the UE 100 or the base station 200 may be integrated, and at least a part of the UE 100 or the base station 200 may be configured as a semiconductor integrated circuit (chip set, SoC).

[0140] Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to the above, and various design changes can be made without departing from the scope of the invention. Furthermore, it is also possible to combine all or part of each embodiment within a consistent range. [Explanation of symbols]

[0141] 1: Mobile communication system 20: Wireless Access Network 30: Core network 100: User equipment (UE) 101: Antenna 120: Wireless communication unit 130: Control unit 131:PDCP Entity 132: First RLC entity 133: First MAC entity 134: Second RLC entity 135: Second MAC entity 140: Memory 200:Base station 200-1: Master base station 200-2: Secondary base station 201: Antenna 220: Radio Communication Department 230: Control unit 231,234: MAC entities 232,235 : RLC entities 233:PDCP Entity 240: Memory 250: Network Communication Department

Claims

1. A communication device (100) that is connected to a master node (200-1) associated with a master cell group (MCG) and to a secondary node (200-2) associated with a secondary cell group (SCG) using a dual connectivity method, a control unit (130) including a primary RLC (Radio Link Control) entity (132) and a secondary RLC entity (134) associated with the split bearer; a receiving unit (120) for receiving, using an RRC (radio resource control) message, an ID of a cell group associated with a Packet Data Convergence Protocol (PDCP) entity (131), which is included in a PDCP configuration information element, as a primary path for uplink data when the SCG is deactivated and the PDCP entity (131) is associated with the primary RLC entity (132) and the secondary RLC entity (134); A communication device (100), wherein the ID of the cell group associated with the primary RLC entity (132) corresponds to the MCG.

2. The receiving unit (120) receives the RRC message including information indicating the deactivation of the SCG. The communication device (100) of claim 1.

3. A master node (200-1) connected to a secondary node (200-2) associated with a secondary cell group (SCG) and a communication device (100) using a dual connectivity method, and associated with a master cell group (MCG), a control unit (230) including a primary RLC (Radio Link Control) entity (232) and a secondary RLC entity (235) associated with the split bearer; a transmitter (220) for transmitting, when the SCG is deactivated, to the communication device (100) an ID of a cell group associated with the primary RLC (Packet Data Convergence Protocol) entity (232), the ID being included in a PDCP configuration information element, as a primary path for uplink data when the PDCP (Packet Data Convergence Protocol) entity (233) is associated with the primary RLC entity (232) and the secondary RLC entity (235); The ID of the cell group associated with the primary RLC entity (232) corresponds to the MCG. Master node (200-1).

4. The transmitting unit (220) transmits the RRC message including information indicating the deactivation of the SCG to the communication device (100). The master node (200-1) according to claim 3.

5. Using a dual connectivity scheme, the node is connected to a master node (200-1) associated with a master cell group (MCG) and is also connected to a secondary node (200-2) associated with a secondary cell group (SCG); A communication control method in a communication device (100) including a primary RLC (Radio Link Control) entity (132) and a secondary RLC entity (134) associated with a split bearer, comprising: When the SCG is deactivated, the method includes receiving, using an RRC (Radio Resource Control) message, an ID of a cell group associated with the primary RLC (Packet Data Convergence Protocol) entity (131), the ID being included in a PDCP configuration information element, as a primary path for uplink data when the PDCP entity (131) is associated with the primary RLC entity (132) and the secondary RLC entity (134); The ID of the cell group associated with the primary RLC entity (132) corresponds to the MCG. Communication control method.

6. receiving the RRC message including information indicating deactivation of the SCG. The communication control method according to claim 5.

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