Communication system, user device, and base station

Abstract

To provide a communication system and the like that have achieved high speed, high reliability, and low latency in NR (New Radio).SOLUTION: A communication system (200) includes a user device (202) and a plurality of base stations (203) that wirelessly communicate with the user device (202). The plurality of base stations (203) include a master base station and a secondary base station that configure dual connectivity for the user device (202), and at least one of the plurality of base stations (203) individually sets SCG configuration information and bearer configuration information.SELECTED DRAWING: Figure 19

Description

[Technical Field]

[0001] The present invention relates to a communication system or the like that performs wireless communication between a communication terminal device such as a mobile terminal device and a base station device. [Background technology]

[0002] 3GPP (3rd Generation Partnership Project), a standardization organization for mobile communication systems, is considering a communication method called Long Term Evolution (LTE) for the wireless section and System Architecture Evolution (SAE) for the overall system configuration including the core network and radio access network (hereinafter collectively referred to as the network) (see, for example, Non-Patent Documents 1 to 5). This communication method is also called the 3.9G (3.9 Generation) system.

[0003] LTE uses OFDM (Orthogonal Frequency Division Multiplexing) for downlink and SC-FDMA (Single Carrier Frequency Division Multiple Access) for uplink as its access method. Unlike W-CDMA (Wideband Code Division Multiple Access), LTE does not include circuit switching and is only a packet communication method.

[0004] The decisions made by 3GPP regarding the frame configuration in the LTE system, as described in Non-Patent Document 1 (Chapter 5), will be explained using Figure 1. Figure 1 is an explanatory diagram showing the configuration of a radio frame used in an LTE communication system. In Figure 1, one radio frame is 10 ms. The radio frame is divided into 10 equally sized subframes. The subframe is divided into two equally sized slots. The first and sixth subframes of each radio frame include a downlink synchronization signal. The synchronization signals include a primary synchronization signal (P-SS) and a secondary synchronization signal (S-SS).

[0005] The decisions made by 3GPP regarding the channel configuration in the LTE system are described in Non-Patent Document 1 (Chapter 5). It is assumed that the same channel configuration as that of a non-CSG cell is used in a CSG (Closed Subscriber Group) cell.

[0006] The Physical Broadcast Channel (PBCH) is a channel for downlink transmission from a base station (hereinafter simply referred to as a "base station") to a communication terminal (hereinafter simply referred to as a "communication terminal") such as a mobile terminal (hereinafter simply referred to as a "mobile terminal"). A BCH transport block is mapped to four subframes in a 40 ms interval. There is no explicit signaling of the 40 ms timing.

[0007] The Physical Control Format Indicator Channel (PCFICH) is a channel for downlink transmission from a base station to a communication terminal. The PCFICH notifies the communication terminal of the number of Orthogonal Frequency Division Multiplexing (OFDM) symbols used for PDCCHs. The PCFICH is transmitted every subframe.

[0008] The Physical Downlink Control Channel (PDCCH) is a channel for downlink transmission from a base station to a communication terminal. The PDCCH reports resource allocation information for a Downlink Shared Channel (DL-SCH), which is one of the transport channels described below, resource allocation information for a Paging Channel (PCH), which is also one of the transport channels described below, and Hybrid Automatic Repeat reQuest (HARQ) information for the DL-SCH. The PDCCH carries an uplink scheduling grant. The PDCCH carries Acknowledgement (Ack) / Negative Acknowledgement (Nack), which are response signals to uplink transmissions. The PDCCH is also called an L1 / L2 control signal.

[0009] The Physical Downlink Shared Channel (PDSCH) is a channel for downlink transmission from a base station to a communication terminal. A Downlink Shared Channel (DL-SCH), which is a transport channel, and a PCH, which is also a transport channel, are mapped to the PDSCH.

[0010] A physical multicast channel (PMCH) is a channel for downlink transmission from a base station to communication terminals, and a multicast channel (MCH), which is a transport channel, is mapped to the PMCH.

[0011] The Physical Uplink Control Channel (PUCCH) is a channel for uplink transmission from a communication terminal to a base station. The PUCCH carries Ack / Nack, which are response signals to downlink transmissions. The PUCCH also carries CQI (Channel Quality Indicator) reports. CQI is quality information that indicates the quality of received data or the quality of the communication path. The PUCCH also carries Scheduling Requests (SR).

[0012] The Physical Uplink Shared Channel (PUSCH) is a channel for uplink transmission from a communication terminal to a base station. The Uplink Shared Channel (UL-SCH), which is one of the transport channels, is mapped to the PUSCH.

[0013] The Physical Hybrid ARQ Indicator Channel (PHICH) is a channel for downlink transmission from a base station to a communication terminal. The PHICH carries Ack / Nack, which are response signals to uplink transmission. The Physical Random Access Channel (PRACH) is a channel for uplink transmission from a communication terminal to a base station. The PRACH carries a random access preamble.

[0014] Downlink reference signals (RS) are symbols known in LTE communication systems. The following five types of downlink reference signals are defined: Cell-specific Reference Signal (CRS), MBSFN Reference Signal, UE-specific reference signal Demodulation Reference Signal (DM-RS), Positioning Reference Signal (PRS), and Channel State Information Reference Signal (CSI-RS). Measurement of the physical layer of a communication terminal includes measurement of the reference signal received power (RSRP).

[0015] The transport channels described in Non-Patent Document 1 (Chapter 5) will be explained below. Among the downlink transport channels, a broadcast channel (BCH) is broadcast to the entire coverage of the base station (cell). The BCH is mapped to a physical broadcast channel (PBCH).

[0016] Retransmission control using HARQ (Hybrid ARQ) is applied to the Downlink Shared Channel (DL-SCH). DL-SCH can be broadcast to the entire coverage of a base station (cell). DL-SCH supports dynamic or semi-static resource allocation. Semi-static resource allocation is also called persistent scheduling. DL-SCH supports discontinuous reception (DRX) in communication terminals to reduce power consumption of communication terminals. DL-SCH is mapped to the Physical Downlink Shared Channel (PDSCH).

[0017] The Paging Channel (PCH) supports DRX in communication terminals to enable low power consumption in communication terminals. The PCH is required to broadcast to the entire coverage of the base station (cell). The PCH is mapped to physical resources such as the Physical Downlink Shared Channel (PDSCH) that can be dynamically used for traffic.

[0018] The Multicast Channel (MCH) is used for broadcasting to the entire coverage of a base station (cell). The MCH supports SFN combining of MBMS (Multimedia Broadcast Multicast Service) services (MTCH and MCCH) in multi-cell transmission. The MCH supports semi-static resource allocation. The MCH is mapped to the PMCH.

[0019] Among the uplink transport channels, the Uplink Shared Channel (UL-SCH) is subject to retransmission control using HARQ (Hybrid ARQ). The UL-SCH supports dynamic or semi-static resource allocation. The UL-SCH is mapped to the Physical Uplink Shared Channel (PUSCH).

[0020] The Random Access Channel (RACH) is limited to control information. The RACH is subject to collision risk. The RACH is mapped to the Physical Random Access Channel (PRACH).

[0021] We will explain HARQ. HARQ is a technology that improves the communication quality of a transmission channel by combining Automatic Repeat reQuest (ARQ) and Forward Error Correction. HARQ has the advantage that error correction works effectively through retransmission even on transmission channels where communication quality varies. In particular, by combining the reception results of the initial transmission and the retransmission when retransmitting, it is possible to achieve further quality improvement.

[0022] An example of a retransmission method will be explained below. If the receiving side is unable to decode the received data correctly, in other words, if a CRC (Cyclic Redundancy Check) error occurs (CRC=NG), the receiving side will send a "Nack" to the sending side. The sending side, having received the "Nack," will retransmit the data. If the receiving side is able to decode the received data correctly, in other words, if no CRC error occurs (CRC=OK), the receiving side will send an "Ack" to the sending side. The sending side, having received the "Ack," will send the next data.

[0023] The logical channels described in Non-Patent Document 1 (Chapter 6) will be explained below. The Broadcast Control Channel (BCCH) is a downlink channel for broadcast system control information. The BCCH, which is a logical channel, is mapped to the broadcast channel (BCH) or the downlink shared channel (DL-SCH), which are transport channels.

[0024] The Paging Control Channel (PCCH) is a downlink channel for transmitting paging information and changes to system information. The PCCH is used when the network does not know the cell location of the communication terminal. The PCCH, which is a logical channel, is mapped to the Paging Channel (PCH), which is a transport channel.

[0025] A Common Control Channel (CCCH) is a channel for transmission control information between a communication terminal and a base station. CCCH is used when a communication terminal does not have an RRC connection with the network. In the downlink direction, CCCH is mapped to a Downlink Shared Channel (DL-SCH), which is a transport channel. In the uplink direction, CCCH is mapped to an Uplink Shared Channel (UL-SCH), which is a transport channel.

[0026] The Multicast Control Channel (MCCH) is a downlink channel for point-to-multipoint transmission. The MCCH is used to transmit MBMS control information for one or several MTCHs from the network to communication terminals. The MCCH is used only by communication terminals receiving MBMS. The MCCH is mapped to the Multicast Channel (MCH), which is a transport channel.

[0027] A dedicated control channel (DCCH) is a channel that transmits dedicated control information between a communication terminal and a network on a one-to-one basis. The DCCH is used when the communication terminal is in an RRC connection. The DCCH is mapped to an uplink shared channel (UL-SCH) in the uplink and to a downlink shared channel (DL-SCH) in the downlink.

[0028] A Dedicated Traffic Channel (DTCH) is a one-to-one communication channel for transmitting user information to an individual communication terminal. DTCH exists in both uplink and downlink. In uplink, DTCH is mapped to an uplink shared channel (UL-SCH) and in downlink, it is mapped to a downlink shared channel (DL-SCH).

[0029] The Multicast Traffic Channel (MTCH) is a downlink channel for transmitting traffic data from the network to communication terminals. The MTCH is a channel used only by communication terminals receiving MBMS. The MTCH is mapped to the Multicast Channel (MCH).

[0030] CGI stands for Cell Global Identifier. ECGI stands for E-UTRAN Cell Global Identifier. Closed Subscriber Group (CSG) cells are introduced in LTE, LTE-A (Long Term Evolution Advanced) (described below), and UMTS (Universal Mobile Telecommunication System).

[0031] A CSG (Closed Subscriber Group) cell is a cell for which an operator has identified available subscribers (hereinafter referred to as a "specific subscriber cell"). The identified subscribers are permitted to access one or more cells in a PLMN (Public Land Mobile Network). The one or more cells to which the identified subscribers are permitted to access are called "CSG cell(s)." However, there are access restrictions within the PLMN.

[0032] A CSG cell is a part of a PLMN that broadcasts a unique CSG identity (CSG ID) and broadcasts a CSG indication of "TRUE." Members of a pre-registered and authorized subscriber group access the CSG cell using the CSG ID, which is access permission information.

[0033] The CSG ID is broadcast by a CSG cell or cells. There are multiple CSG IDs in an LTE communication system. The CSG ID is used by a communication terminal (UE) to facilitate access by CSG-related members.

[0034] The location of a communication terminal is tracked in units of an area consisting of one or more cells. Location tracking is performed to track the location of the communication terminal even when it is in standby mode and to enable the communication terminal to be called, in other words, to allow the communication terminal to receive calls. The area used for tracking the location of this communication terminal is called a tracking area.

[0035] 3GPP is studying base stations called Home-NodeB (Home-NB; HNB) and Home-eNodeB (Home-eNB; HeNB). HNB in ​​UTRAN and HeNB in ​​E-UTRAN are base stations for access services for homes, businesses, and businesses, for example. Non-Patent Document 2 discloses three different modes of access to HeNB and HNB. Specifically, it discloses an open access mode, a closed access mode, and a hybrid access mode.

[0036] 3GPP is also working on the development of the Long Term Evolution Advanced (LTE-A) standard as Release 10 (see Non-Patent Documents 3 and 4). LTE-A is based on the LTE wireless communication system, and is configured by adding several new technologies to it.

[0037] In the LTE-A system, carrier aggregation (CA) is being considered, which aggregates two or more component carriers (CCs) (also called "aggregation") to support wider frequency bandwidths (transmission bandwidths) up to 100 MHz. CA is described in Non-Patent Document 1.

[0038] When CA is configured, the UE has only one RRC connection with the network (NW). In the RRC connection, one serving cell provides NAS mobility information and security input. This cell is called the primary cell (PCell). In the downlink, the carrier corresponding to the PCell is the downlink primary component carrier (DL PCC). In the uplink, the carrier corresponding to the PCell is the uplink primary component carrier (UL PCC).

[0039] Depending on the UE's capabilities, a secondary cell (SCell) is configured to form a serving cell set together with the PCell. In the downlink, the carrier corresponding to the SCell is the downlink secondary component carrier (DL SCC). In the uplink, the carrier corresponding to the SCell is the uplink secondary component carrier (UL SCC).

[0040] A set of serving cells, which includes one PCell and one or more SCells, is configured for one UE.

[0041] New technologies for LTE-A include wider bandwidth extension, coordinated multiple point transmission and reception (CoMP), etc. CoMP, which is being considered for LTE-A by 3GPP, is described in Non-Patent Document 1.

[0042] Furthermore, in order to handle future massive traffic volumes, 3GPP is considering using small eNBs (hereinafter sometimes referred to as "small-scale base station devices") that configure small cells. For example, technologies are being considered that aim to increase communication capacity by installing a large number of small eNBs and configuring a large number of small cells to improve frequency utilization efficiency. Specifically, there is dual connectivity (abbreviated as DC), in which a UE connects to two eNBs to communicate. DC is described in Non-Patent Document 1.

[0043] Of the eNBs that perform dual connectivity (DC), one may be referred to as a "master eNB (abbreviated as MeNB)" and the other as a "secondary eNB (abbreviated as SeNB)."

[0044] Mobile network traffic volume is on the rise, and communication speeds are also increasing. Once LTE and LTE-A are fully operational, communication speeds are expected to increase even further.

[0045] Furthermore, in response to the increasing sophistication of mobile communications, fifth-generation (hereinafter sometimes referred to as "5G") wireless access systems are being considered, with the goal of launching services after 2020. For example, in Europe, an organization called METIS has compiled requirements for 5G (see Non-Patent Document 5).

[0046] The requirements for a 5G wireless access system are that it will have 1,000 times the system capacity, 100 times the data transmission speed, one-tenth (1 / 10) the data processing delay, and 100 times the number of simultaneous connections of communication terminals compared to an LTE system, while also achieving further reductions in power consumption and lower equipment costs.

[0047] To meet these demands, 3GPP is currently studying 5G standards as Release 14 (see Non-Patent Documents 6 to 10). 5G wireless technology is called "New Radio Access Technology" ("New Radio" is abbreviated as "NR"), and several new technologies are being studied (see Non-Patent Documents 11 to 14). For example, packet duplication using DC or multi-connectivity (abbreviated as MC), and separation of gNB into CU (Central Unit) and DU (Distributed Unit) are being studied. [Prior art documents] [Non-patent literature]

[0048] [Non-licensed document 1] 3GPP TS 36.300 V14.3.0

Non-licensed Document 2

Non-licensed Document 4

Non-licensed Document 5

Non-licensed Document 6

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Non-licensed literature 9

Non-licensed literature 10

Non-licensed Document 11

Non-licensed Document 12

Non-licensed Document 13

Non-licensed Document 14

Non-licensed Document 15

Non-licensed Document 16

Non-licensed Document 17

[0049] In NR, a packet duplication technique is proposed to achieve high reliability and low latency communications. Two methods for packet duplication are proposed: one using CA and the other using DC. The start and stop of packet duplication is controlled using MAC signaling.

[0050] Furthermore, conventional techniques support MAC signaling for starting / stopping the operation of an SCell used in CA. However, in NR using CA, no disclosure is made regarding the behavior when MAC signaling for packet duplication conflicts with MAC signaling for starting / stopping an SCell. Therefore, when the above-mentioned conflict occurs, the UE does not know how to handle packet duplication, which may result in malfunction. As a result, there is a possibility that highly reliable and low-latency communications cannot be achieved.

[0051] Furthermore, MC has been proposed as a technology for realizing high-speed communication in NR. MC is being discussed as a method for connecting one master base station and multiple secondary base stations to one UE. However, for MC when there are two or more secondary base stations, the architecture including the upper network and the method for configuring MC, such as how to configure multiple secondary base stations, have not been disclosed. Therefore, the master base station and secondary base stations cannot configure the aforementioned MC, and the UE cannot perform high-speed communication.

[0052] In view of the above problems, one of the objects of the present invention is to provide a communication system, etc. that is fast, highly reliable, and has low latency in NR. [Means for solving the problem]

[0053] According to the present invention, for example, a communication system is provided that includes a user device and a plurality of base stations that communicate wirelessly with the user device, wherein the plurality of base stations include a master base station and a secondary base station that form dual connectivity for the user device, and at least one of the plurality of base stations individually sets SCG configuration information and bearer configuration information.

[0054] Furthermore, according to the present invention, there is provided, for example, a user device in a communication system including a user device and a plurality of base stations that communicate wirelessly with the user device, wherein the plurality of base stations include a master base station and a secondary base station that form dual connectivity for the user device, and the user device receives a message from at least one of the plurality of base stations that individually sets SCG configuration information and bearer configuration information.

[0055] Furthermore, according to the present invention, there is provided, for example, a base station in a communication system including a user device and a plurality of base stations that communicate wirelessly with the user device, the plurality of base stations including a master base station and a secondary base station that form dual connectivity for the user device, and that individually sets SCG configuration information and bearer configuration information. [Effects of the Invention]

[0056] According to the present invention, it is possible to provide a communication system, etc., in NR that is high-speed, highly reliable, and has low latency.

[0057] The objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings. [Brief explanation of the drawings]

[0058] [Figure 1] FIG. 1 is an explanatory diagram showing the configuration of a radio frame used in an LTE communication system. [Figure 2] 1 is a block diagram showing the overall configuration of an LTE communication system 200 being discussed in 3GPP. [Figure 3] FIG. 3 is a block diagram showing the configuration of a mobile terminal 202 shown in FIG. 2, which is a communication terminal according to the present invention. [Figure 4] FIG. 3 is a block diagram showing the configuration of a base station 203 shown in FIG. 2, which is a base station according to the present invention. [Figure 5] FIG. 2 is a block diagram showing the configuration of an MME according to the present invention. [Figure 6]1 is a flowchart showing an outline of operations from cell search to standby operation performed by a communication terminal (UE) in an LTE communication system. [Figure 7] FIG. 1 is a diagram illustrating the concept of a cell configuration when macro eNBs and small eNBs are mixed. [Figure 8] FIG. 10 is a sequence diagram illustrating the operation of the first embodiment when MAC signaling for starting packet duplication is received by the UE after the designated timing due to the occurrence of HARQ retransmission. [Figure 9] This figure shows the protocol configuration for packet duplication using CA between a gNB and a UE with CU-DU separation, for variant 1 of embodiment 1. [Figure 10] FIG. 10 is a sequence diagram of packet duplication in the case where a DU determines to start packet duplication, according to the first modification of the first embodiment. [Figure 11] FIG. 11 is a sequence diagram of packet duplication in a case where a CU determines to start packet duplication, according to a first modification of the first embodiment. [Figure 12] FIG. 10 is a sequence diagram illustrating an operation of a first modification of the first embodiment when MAC signaling for starting packet duplication is received by a UE after a specified timing due to the occurrence of HARQ retransmission. [Figure 13] FIG. 11 is a sequence diagram in accordance with the second embodiment when the master base station initiates switching of packet duplication. [Figure 14] FIG. 11 is a sequence diagram in the case where a secondary base station initiates switching of packet duplication according to the second embodiment. [Figure 15] FIG. 13 is a sequence diagram showing small data transmission from a UE to a secondary base station according to the fifth embodiment. [Figure 16] FIG. 20 is a diagram illustrating the architecture of an MC according to the sixth embodiment. [Figure 17] FIG. 23 is a diagram showing an example of a sequence for setting an MC according to the sixth embodiment. [Figure 18] FIG. 23 is a diagram showing an example of a sequence for setting an MC according to the sixth embodiment. [Figure 19] FIG. 23 is a diagram showing an example of a sequence for setting an MC according to the sixth embodiment. [Figure 20] FIG. 23 is a diagram showing an example of a sequence for setting an MC according to the sixth embodiment. [Figure 21] This figure shows the architecture and data flow for variant example 1 of embodiment 6 when the upper network is an NG-CN and the base station is an NR gNB. [Figure 22] FIG. 20 is a diagram illustrating the architecture of an MC according to a first modification of the sixth embodiment. [Figure 23] FIG. 22 is a conceptual diagram showing a data flow when an MC is set for each DRB in accordance with a first modification of the sixth embodiment. [Figure 24] FIG. 20 is a conceptual diagram showing a data flow when an MC is set for each QoS flow, in accordance with a first modification of the sixth embodiment. [Figure 25] FIG. 20 is a conceptual diagram illustrating a data flow in a case where a DRB for mapping a QoS flow that performs MC is additionally set, in accordance with the first modification of the sixth embodiment. [Figure 26] 20 shows an example of a sequence for setting an MC for each QoS flow in accordance with the first modification of the sixth embodiment. [Figure 27] 20 shows an example of a sequence for setting an MC for each QoS flow in accordance with the first modification of the sixth embodiment. [Figure 28] FIG. 20 is a diagram illustrating the architecture of an MC according to the seventh embodiment. [Figure 29] A figure showing an example of a sequence for setting up an MC using an SCG bearer in embodiment 7. [Figure 30] A figure showing an example of a sequence for setting up an MC using an SCG bearer in embodiment 7. [Figure 31] A diagram showing the architecture of an MC using an SCG bearer for a first variant of the seventh embodiment. [Figure 32] A conceptual diagram showing the data flow when an MC using an SCG bearer is set for each DRB, in accordance with variant example 1 of embodiment 7. [Figure 33] FIG. 20 is a diagram showing an example of a sequence for setting up an MC using an SGB bearer when the upper network is an NG-CN, in accordance with a first modification of the seventh embodiment. [Figure 34] FIG. 20 is a diagram showing an example of a sequence for setting up an MC using an SGB bearer when the upper network is an NG-CN, in accordance with a first modification of the seventh embodiment. [Figure 35] FIG. 20 is a diagram showing an example of a sequence for setting up an MC using an SGB bearer when the upper network is an NG-CN, in accordance with a first modification of the seventh embodiment. [Figure 36] FIG. 20 is a conceptual diagram showing a data flow when an MC using an SCG bearer is set for each QoS flow, in accordance with a first variant of the seventh embodiment. [Figure 37] FIG. 20 is a diagram illustrating the architecture of an MC according to the eighth embodiment. [Figure 38] FIG. 20 is a diagram showing an example of a sequence for setting up an MC using an SCG split bearer in accordance with the eighth embodiment. [Figure 39] FIG. 20 is a diagram showing an example of a sequence for setting up an MC using an SCG split bearer in accordance with the eighth embodiment. [Figure 40] FIG. 20 is a diagram showing an example of a sequence for setting up an MC using an SCG split bearer in accordance with the eighth embodiment. [Figure 41] FIG. 20 is a diagram illustrating the architecture of an MC according to a first modification of the eighth embodiment. [Figure 42] A conceptual diagram showing the data flow when an MC using an SCG split bearer is set for each DRB, in accordance with variant example 1 of embodiment 8. [Figure 43] FIG. 20 is a diagram showing an example of a sequence for setting up an MC using an SCG split bearer, in accordance with a first variant of the eighth embodiment. [Figure 44] FIG. 20 is a diagram showing an example of a sequence for setting up an MC using an SCG split bearer, in accordance with a first variant of the eighth embodiment. [Figure 45]FIG. 20 is a diagram showing an example of a sequence for setting up an MC using an SCG split bearer, in accordance with a first variant of the eighth embodiment. [Figure 46] FIG. 20 is a conceptual diagram showing a data flow when an MC using an SCG split bearer is set for each QoS flow, in accordance with a first variant of the eighth embodiment. [Figure 47] FIG. 20 is a diagram illustrating the architecture of an MC according to a ninth embodiment. [Figure 48] FIG. 20 is a diagram illustrating the architecture of an MC according to a first modification of the ninth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0059] Embodiment 1 Fig. 2 is a block diagram showing the overall configuration of an LTE communication system 200 being discussed in 3GPP. Fig. 2 will now be described. The radio access network is called E-UTRAN (Evolved Universal Terrestrial Radio Access Network) 201. A mobile terminal device (hereinafter referred to as "mobile terminal (User Equipment: UE)") 202, which is a communication terminal device, is capable of wireless communication with a base station device (hereinafter referred to as "base station (E-UTRAN NodeB: eNB)") 203, and transmits and receives signals via wireless communication.

[0060] Here, the term "communication terminal device" includes not only mobile terminal devices such as mobile cell phone terminal devices, but also stationary devices such as sensors. In the following description, the term "communication terminal device" may be simply referred to as a "communication terminal."

[0061] If control protocols for mobile terminals 202, such as RRC (Radio Resource Control), and user planes (hereinafter sometimes referred to as U-Planes), such as PDCP (Packet Data Convergence Protocol), RLC (Radio Link Control), MAC (Medium Access Control), and PHY (Physical layer), terminate at base stations 203, E-UTRAN is composed of one or more base stations 203.

[0062] The control protocol RRC (Radio Resource Control) between the mobile terminal 202 and the base station 203 performs broadcasting, paging, RRC connection management, etc. The states of the base station 203 and the mobile terminal 202 in RRC include RRC_IDLE and RRC_CONNECTED.

[0063] In RRC_IDLE, PLMN (Public Land Mobile Network) selection, system information (SI) broadcast, paging, cell reselection, mobility, etc. are performed. In RRC_CONNECTED, the mobile terminal has an RRC connection and can transmit and receive data with the network. In addition, in RRC_CONNECTED, handover (HO), measurement of neighbor cells, etc. are performed.

[0064] The base stations 203 are classified into eNBs 207 and Home-eNBs 206. The communication system 200 includes an eNB group 203-1 including a plurality of eNBs 207, and a Home-eNB group 203-2 including a plurality of Home-eNBs 206. A system configured from an EPC (Evolved Packet Core) core network and an E-UTRAN 201 radio access network is called an EPS (Evolved Packet System). The EPC core network and the E-UTRAN 201 radio access network may be collectively referred to as a "network."

[0065] The eNB 207 is connected to a Mobility Management Entity (MME), or a Serving Gateway (S-GW), or an MME / S-GW unit (hereinafter sometimes referred to as an "MME unit") 204 including an MME and an S-GW via an S1 interface, and control information is communicated between the eNB 207 and the MME unit 204. Multiple MME units 204 may be connected to one eNB 207. The eNBs 207 are connected to each other via an X2 interface, and control information is communicated between the eNBs 207.

[0066] The Home-eNB 206 is connected to the MME unit 204 via an S1 interface, and control information is communicated between the Home-eNB 206 and the MME unit 204. A plurality of Home-eNBs 206 are connected to one MME unit 204. Alternatively, the Home-eNB 206 is connected to the MME unit 204 via a Home-eNB GateWay (HeNBGW) 205. The Home-eNB 206 and the HeNBGW 205 are connected via an S1 interface, and the HeNBGW 205 and the MME unit 204 are connected via the S1 interface.

[0067] One or more Home-eNBs 206 are connected to one HeNBGW 205, and information is communicated through an S1 interface. The HeNBGW 205 is connected to one or more MME units 204, and information is communicated through an S1 interface.

[0068] The MME unit 204 and the HeNBGW 205 are upper devices, specifically upper nodes, and control connections between the eNB 207 and the Home-eNB 206, which are base stations, and the mobile terminal (UE) 202. The MME unit 204 constitutes the EPC, which is a core network. The base station 203 and the HeNBGW 205 constitute the E-UTRAN 201.

[0069] Furthermore, 3GPP is considering the following configuration: The X2 interface between Home-eNBs 206 is supported. That is, Home-eNBs 206 are connected via the X2 interface, and control information is communicated between the Home-eNBs 206. From the MME unit 204, HeNBGW 205 appears as Home-eNB 206. From the Home-eNB 206, HeNBGW 205 appears as MME unit 204.

[0070] In either case where the Home-eNB 206 is connected to the MME unit 204 via the HeNBGW 205 or where the Home-eNB 206 is connected directly to the MME unit 204, the interface between the Home-eNB 206 and the MME unit 204 is the same, that is, the S1 interface.

[0071] Base station 203 may configure one cell or multiple cells. Each cell has a predetermined range as coverage, which is the range within which communication with mobile terminal 202 is possible, and performs wireless communication with mobile terminal 202 within the coverage. When one base station 203 configures multiple cells, each cell is configured to be able to communicate with mobile terminal 202.

[0072] FIG. 3 is a block diagram showing the configuration of mobile terminal 202 shown in FIG. 2, which is a communication terminal according to the present invention. The transmission process of mobile terminal 202 shown in FIG. 3 will be described. First, control data from protocol processing unit 301 and user data from application unit 302 are stored in transmission data buffer unit 303. The data stored in transmission data buffer unit 303 is passed to encoder unit 304, where it undergoes encoding processes such as error correction. Some data may be output directly from transmission data buffer unit 303 to modulation unit 305 without undergoing encoding processes. The data encoded by encoder unit 304 is modulated by modulation unit 305. The modulated data is converted into a baseband signal, and then output to frequency conversion unit 306, where it is converted into a radio transmission frequency. A transmission signal is then transmitted from antenna 307 to base station 203.

[0073] Furthermore, the reception process of the mobile terminal 202 is performed as follows. A radio signal from the base station 203 is received by the antenna 307. The received signal is converted from a radio reception frequency to a baseband signal by the frequency conversion unit 306, and demodulated by the demodulation unit 308. The demodulated data is passed to the decoder unit 309, where decoding processes such as error correction are performed. Of the decoded data, the control data is passed to the protocol processing unit 301, and the user data is passed to the application unit 302. A series of processes of the mobile terminal 202 is controlled by the control unit 310. Therefore, although the control unit 310 is omitted in FIG. 3, it is connected to each of the units 301 to 309.

[0074] Fig. 4 is a block diagram showing the configuration of base station 203 shown in Fig. 2, which is a base station according to the present invention. The transmission processing of base station 203 shown in Fig. 4 will be described. EPC communication unit 401 transmits and receives data between base station 203 and EPC (MME unit 204, etc.), HeNBGW 205, etc. Other base station communication unit 402 transmits and receives data with other base stations. EPC communication unit 401 and other base station communication unit 402 each exchange information with protocol processing unit 403. Control data from protocol processing unit 403, and user data and control data from EPC communication unit 401 and other base station communication unit 402 are stored in transmission data buffer unit 404.

[0075] The data stored in the transmission data buffer unit 404 is passed to the encoder unit 405, where it undergoes encoding processes such as error correction. Some data may be output directly from the transmission data buffer unit 404 to the modulator unit 406 without undergoing encoding processes. The encoded data is modulated by the modulator unit 406. The modulated data is converted into a baseband signal, and then output to the frequency converter 407, where it is converted into a radio transmission frequency. The transmission signal is then transmitted from the antenna 408 to one or more mobile terminals 202.

[0076] The reception process of the base station 203 is performed as follows: A radio signal from one or more mobile terminals 202 is received by an antenna 408. The received signal is converted from a radio reception frequency to a baseband signal by a frequency conversion unit 407, and demodulated by a demodulation unit 409. The demodulated data is passed to a decoder unit 410, where decoding processes such as error correction are performed. Of the decoded data, control data is passed to a protocol processing unit 403 or an EPC communication unit 401 or an other base station communication unit 402, and user data is passed to the EPC communication unit 401 and the other base station communication unit 402. A series of processes of the base station 203 is controlled by a control unit 411. Therefore, although the control unit 411 is omitted in FIG. 4, it is connected to each of the units 401 to 410.

[0077] 5 is a block diagram showing the configuration of an MME according to the present invention. FIG. 5 shows the configuration of an MME 204a included in the MME unit 204 shown in FIG. 2 described above. A PDN GW communication unit 501 transmits and receives data between the MME 204a and a PDN GW. A base station communication unit 502 transmits and receives data via the S1 interface between the MME 204a and a base station 203. If the data received from the PDN GW is user data, the user data is passed from the PDN GW communication unit 501 to the base station communication unit 502 via a user plane communication unit 503, and transmitted to one or more base stations 203. If the data received from the base station 203 is user data, the user data is passed from the base station communication unit 502 to the PDN GW communication unit 501 via the user plane communication unit 503, and transmitted to the PDN GW.

[0078] If the data received from the PDN GW is control data, the control data is passed from the PDN GW communication unit 501 to the control plane control unit 505. If the data received from the base station 203 is control data, the control data is passed from the base station communication unit 502 to the control plane control unit 505.

[0079] The HeNBGW communication unit 504 is provided when a HeNBGW 205 is present, and transmits and receives data via an interface (IF) between the MME 204a and the HeNBGW 205 depending on the information type. Control data received from the HeNBGW communication unit 504 is passed from the HeNBGW communication unit 504 to the control plane control unit 505. The result of processing in the control plane control unit 505 is transmitted to the PDN GW via the PDN GW communication unit 501. In addition, the result of processing in the control plane control unit 505 is transmitted to one or more base stations 203 by the S1 interface via the base station communication unit 502, and is also transmitted to one or more HeNBGWs 205 via the HeNBGW communication unit 504.

[0080] The control plane control unit 505 includes a NAS security unit 505-1, an SAE bearer control unit 505-2, an idle state mobility management unit 505-3, etc., and performs overall processing for the control plane (hereinafter sometimes referred to as the C-Plane). The NAS security unit 505-1 performs security for NAS (Non-Access Stratum) messages, etc. The SAE bearer control unit 505-2 performs management of SAE (System Architecture Evolution) bearers, etc. The idle state mobility management unit 505-3 performs mobility management in the idle state (also referred to as the LTE-IDLE state or simply idle), generation and control of paging signals in the idle state, addition, deletion, update, and search of tracking areas for one or more mobile terminals 202 under its control, tracking area list management, etc.

[0081] The MME 204a distributes paging signals to one or more base stations 203. The MME 204a also performs mobility control in an idle state. The MME 204a manages a tracking area list when the mobile terminal is in an idle state and an active state. The MME 204a initiates a paging protocol by transmitting a paging message to cells belonging to a tracking area in which the UE is registered. The idle state mobility management unit 505-3 may manage the CSG, CSG ID, and whitelist of the Home-eNB 206 connected to the MME 204a.

[0082] Next, an example of a cell search method in a communication system is shown. Fig. 6 is a flowchart showing an outline of the process from cell search to standby operation performed by a communication terminal (UE) in an LTE communication system. When the communication terminal starts a cell search, in step ST601, it synchronizes slot timing and frame timing using a primary synchronization signal (P-SS) and a secondary synchronization signal (S-SS) transmitted from a surrounding base station.

[0083] P-SS and S-SS are collectively called the Synchronization Signal (SS). The Synchronization Signal (SS) is assigned a synchronization code that corresponds one-to-one to the PCI assigned to each cell. 504 different PCIs are being considered. These 504 different PCIs are used to achieve synchronization and to detect (identify) the PCI of the synchronized cell.

[0084] Next, in step ST602, for the synchronized cell, a cell-specific reference signal (CRS), which is a reference signal (RS) transmitted from the base station for each cell, is detected and the RS received power (Reference Signal Received Power: RSRP) is measured. The RS uses a code that has a one-to-one correspondence with the PCI. By correlating with this code, it is possible to separate the cell from other cells. By deriving the code for the RS of the cell from the PCI identified in step ST601, it is possible to detect the RS and measure the RS received power.

[0085] Next, in step ST603, the cell with the best RS reception quality, for example, the cell with the highest RS reception power, that is, the best cell, is selected from one or more cells detected up to step ST602.

[0086] Next, in step ST604, the PBCH of the best cell is received to obtain the BCCH, which is broadcast information. A MIB (Master Information Block), which includes cell configuration information, is mapped to the BCCH on the PBCH. Therefore, the MIB can be obtained by receiving the PBCH and obtaining the BCCH. Examples of MIB information include the DL (downlink) system bandwidth (also called transmission bandwidth configuration: dl-bandwidth), the number of transmitting antennas, and the SFN (System Frame Number).

[0087] Next, in step ST605, the DL-SCH of the cell is received based on the cell configuration information in the MIB, and SIB (System Information Block) 1 is obtained from the broadcast information BCCH. SIB 1 includes information on access to the cell, information on cell selection, and scheduling information for other SIBs (SIBk; k is an integer greater than or equal to 2). SIB 1 also includes a tracking area code (TAC).

[0088] Next, in step ST606, the communication terminal compares the TAC of the SIB1 received in step ST605 with the TAC portion of the tracking area identity (TAI) in the tracking area list that the communication terminal already holds. The tracking area list is also called a TAI list. The TAI is identification information for identifying a tracking area, and is composed of an MCC (Mobile Country Code), an MNC (Mobile Network Code), and a TAC (Tracking Area Code). The MCC is a country code. The MNC is a network code. The TAC is a tracking area code number.

[0089] If the comparison in step ST606 shows that the TAC received in step ST605 is the same as the TAC included in the tracking area list, the communication terminal enters standby mode in the cell. If the comparison shows that the TAC received in step ST605 is not included in the tracking area list, the communication terminal requests a core network (EPC) including an MME, etc., to change the tracking area in order to perform a Tracking Area Update (TAU) through the cell.

[0090] An apparatus constituting a core network (hereinafter sometimes referred to as a "core network side apparatus") updates the tracking area list based on the identification number (e.g., UE-ID) of the communication terminal sent from the communication terminal together with a TAU request signal. The core network side apparatus transmits the updated tracking area list to the communication terminal. The communication terminal rewrites (updates) the TAC list held by the communication terminal based on the received tracking area list. Thereafter, the communication terminal enters standby operation in the cell.

[0091] The widespread use of smartphones and tablet devices has led to an explosive increase in cellular wireless communication traffic, raising concerns about a shortage of wireless resources worldwide. In response to this, efforts are being made to develop small cells and promote spatial separation in order to improve frequency utilization efficiency.

[0092] In a conventional cell configuration, a cell configured by an eNB has a relatively wide coverage area. Conventionally, a cell is configured so that a certain area is covered by the relatively wide coverage areas of multiple cells configured by multiple eNBs.

[0093] In the case of small cell configuration, a cell configured by an eNB has a narrower coverage area than a cell configured by a conventional eNB. Therefore, as in the past, a larger number of small cell configuration eNBs are required to cover a certain area compared to conventional eNBs.

[0094] In the following description, a cell with a relatively large coverage, such as a cell configured by a conventional eNB, is referred to as a "macro cell," and an eNB that configures the macro cell is referred to as a "macro eNB." Also, a cell with a relatively small coverage, such as a cell configured as a small cell, is referred to as a "small cell," and an eNB that configures the small cell is referred to as a "small eNB."

[0095] The macro eNB may be, for example, a "Wide Area Base Station" as described in Non-Patent Document 7.

[0096] The small eNB may be, for example, a low-power node, a local area node, a hotspot, etc. Also, the small eNB may be a pico eNB constituting a pico cell, a femto eNB constituting a femto cell, a HeNB, a remote radio head (RRH), a remote radio unit (RRU), a remote radio equipment (RRE), or a relay node (RN). Also, the small eNB may be a "local area base station" or a "home base station" as described in Non-Patent Document 7.

[0097] 7 is a diagram showing the concept of a cell configuration when macro eNBs and small eNBs are mixed. A macro cell configured by a macro eNB has a relatively wide coverage area 701. A small cell configured by a small eNB has a coverage area 702 that is smaller than the coverage area 701 of the macro eNB (macro cell).

[0098] When multiple eNBs are mixed, the coverage of a cell configured by one eNB may be included in the coverage of a cell configured by another eNB. In the cell configuration shown in Figure 7, as indicated by reference numerals "704" and "705," the coverage 702 of a small cell configured by a small eNB may be included in the coverage 701 of a macro cell configured by a macro eNB.

[0099] Also, as indicated by reference numeral "705," the coverage of multiple, for example, two small cells 702 may be included within the coverage of one macro cell 701. A mobile terminal (UE) 703 is included, for example, within the coverage of a small cell 702 and communicates via the small cell.

[0100] Furthermore, in the cell configuration shown in FIG. 7, there may be cases where coverage 701 of a macro cell configured by a macro eNB and coverage 702 of a small cell configured by a small eNB overlap in a complex manner, as indicated by reference numeral "706."

[0101] Also, as indicated by reference numeral "707," there may be cases where coverage 701 of a macro cell configured by a macro eNB and coverage 702 of a small cell configured by a small eNB do not overlap.

[0102] Furthermore, as indicated by reference numeral "708," there may be cases where the coverage 702 of multiple small cells formed by multiple small eNBs is formed within the coverage 701 of one macro cell formed by one macro eNB.

[0103] One of the services in NR is URLLC (Ultra Reliability, Low Latency Communication), which requires low-latency and high-reliability communication. To simultaneously achieve low latency and high reliability, it was agreed at the 3GPP standardization meeting to support packet duplication in the PDCP layer (see Non-Patent Document 11 (3GPP R2-1700672)). In NR, the packet duplication is performed using a carrier aggregation (CA) configuration (see Non-Patent Document 9 (3GPP TR38.804 v14.0.0)).

[0104] In the above-mentioned packet duplication, it was agreed at the 3GPP meeting that the logical channel through which each duplicated packet passes and the radio carrier used to transmit each packet are associated by setting using RRC signaling (see Non-Patent Document 12 (Draft Report of 3GPP TSG RAN WG2 meeting #98, Hangzhou, China, May 15-19, 2017)). It was also agreed at the 3GPP meeting that the activation / deactivation of packet duplication is controlled using MAC signaling (see Non-Patent Document 12).

[0105] It has been proposed that the MAC signaling that controls the start / stop of packet duplication should include a bearer identifier and a PDCP sequence number that starts / stops packet duplication (see Non-Patent Document 13 (3GPP R2-1704578)). It has also been proposed that the MAC signaling should include a logical channel identifier (see Non-Patent Document 14 (3GPP R2-1704660)).

[0106] Furthermore, conventional LTE supports SCell activation / deactivation (see Non-Patent Document 15 (3GPP TS36.321 v14.3.0)). A base station controls the UE to activate / deactivate the SCell. MAC signaling is used for this control. After receiving the MAC signaling, the UE starts / stops transmission / reception using the SCell at a predetermined timing.

[0107] Regarding packet duplication and SCell control, it has been proposed that packet duplication is not performed by controlling the start of packet duplication while the SCell is stopped, or that packet duplication is performed by starting SCell operation (see Non-Patent Document 16 (3GPP R2-1706867)). It has also been proposed that packet duplication is stopped by implicit SCell deactivation caused by the expiration of the SCell deactivation timer (SCellDeactivationTimer) during packet duplication operation, or that packet duplication is continued by continuing SCell operation (see Non-Patent Document 16).

[0108] However, Non-Patent Document 16 does not disclose details of contention handling for contention between packet duplication and SCell control. Furthermore, it does not disclose operations when MAC signaling for packet duplication and MAC signaling for SCell activation / deactivation conflict. Therefore, when the above-mentioned contention occurs, the UE does not know how to handle packet duplication, which may result in malfunction.

[0109] Furthermore, if a PDCP sequence number is included in the MAC signaling that controls packet duplication, and if the MAC signaling from the base station to the UE fails to arrive and HARQ retransmission is repeated, the following problem may occur: If the UE starts transmitting a PDCP PDU with the PDCP sequence number while HARQ retransmission is being repeated, the UE does not know how to process packet duplication after successfully receiving the MAC signaling, which may cause the UE to malfunction.

[0110] In the first embodiment, a method for solving such a problem will be disclosed.

[0111] Priority is given to packet duplication control and SCell control. A UE may prioritize SCell control over packet duplication control. SCell control may be MAC signaling to deactivate SCell. For example, a UE performing packet duplication may stop packet duplication upon receiving MAC signaling to deactivate SCell. This enables reduction of power consumption in the UE and the base station.

[0112] The above-mentioned stopping of packet duplication may be stopping transmission of the duplicated packet in the wireless section, or canceling the association between the logical channel and the transmission carrier, or a combination of both. The timing of both may be simultaneous or different. The same may be applied hereinafter in the present invention.

[0113] In the present invention, the start of packet duplication may be the start of transmission of the duplicated packet in the wireless section, the start of association of the logical channel with the transmission carrier, or a combination of both. The timing of both may be simultaneous or different.

[0114] The UE may stop packet duplication at the timing of SCell deactivation. This makes it possible to avoid complexity of control in the UE. Alternatively, packet duplication may be stopped when MAC signaling of SCell deactivation is received. The above-mentioned "when MAC signaling is received" may be, for example, immediately after MAC signaling is received. This makes it possible to save resources. Another example of the timing to stop packet duplication is when the entire transmission of the PDCP PDU being transmitted at the time of receiving MAC signaling is completed. This ensures reliability in the PDCP PDU transmission and prevents buffer congestion in the RLC of the base station due to inability to receive the entire PDCP PDU.

[0115] Alternatively, the base station may notify the UE of the timing to stop packet duplication. This allows for flexible operation of packet duplication. The notification may be included in MAC signaling for SCell deactivation, or L1 / L2 signaling may be used.

[0116] The above-mentioned method differs from Non-Patent Document 16 (3GPP R2-1706867) in that it is an explicit SCell deactivation method using MAC signaling, rather than an implicit SCell deactivation method.

[0117] The stop timing may be a PDCP sequence number. This can prevent buffering in the RLC of the base station due to inability to receive the entire PDCP PDU. Alternatively, the stop timing may be physical timing. By directly controlling radio resources, it is possible to prevent unnecessary transmission and reception of radio signals. The physical timing may be, for example, a physical frame number, a subframe number, a slot number, a minislot number, or other information indicating timing. Alternatively, the physical timing may be the time until the stop timing. This allows the base station and the UE to appropriately perform processing associated with stopping packet duplication.

[0118] The UE may retain the state of packet duplication operation / stop. The aforementioned state retention may be performed using, for example, a flag for packet duplication control. The aforementioned state retention may be performed when SCell is deactivated. The UE may use the retained state to activate or stop packet duplication. The aforementioned activation or stop may be performed, for example, when SCell is activated. For example, a UE that has had SCell deactivated during packet duplication operation may resume packet duplication operation when it receives MAC signaling for SCell activation again. This may make it unnecessary to perform MAC signaling used to activate or stop packet duplication at SCell activation, for example, and thus make it possible to reduce the amount of MAC signaling.

[0119] The above-mentioned packet duplication enable / disable state may be assigned an initial value. The initial value may be defined by a standard or may be notified to the UE from the base station. The notification may be performed using RRC signaling, for example, RRC dedicated signaling.

[0120] Regarding the above-mentioned resumption of packet duplication operation, the UE may determine the PDCP SN at the time of resumption of packet duplication. For example, after SCell resumption, packet duplication operation may be resumed from the earliest transmittable PDCP PDU. This facilitates control of packet duplication in the UE. Alternatively, the base station may notify the UE of the timing of resumption of packet duplication. The notification may include a logical channel identifier or a PDCP sequence number. The notification may also be information indicating physical timing. The notification may be included in MAC signaling for SCell initiation (resumption) and transmitted from the base station to the UE.

[0121] The UE may update the packet duplication enable / disable state. The above update may be performed using MAC signaling of packet duplication enable / disable. The above update may be performed while the SCell is active or while the SCell is suspended. This makes it possible to distribute the MAC signaling of SCell enable / disable and packet duplication. Alternatively, the UE may not need to update the packet duplication enable / disable state while the SCell is suspended. This makes it possible to avoid the complexity of controlling packet duplication in the base station and the UE.

[0122] The UE does not need to retain the packet duplication on / off state. This allows for a reduction in UE memory usage. The UE may stop packet duplication when SCell operation starts or resumes. This allows for a reduction in radio resource usage. Alternatively, the UE may start packet duplication when SCell operation starts or resumes. This allows for ensuring communication reliability when SCell operation starts.

[0123] The above-mentioned packet duplication enable / disable state may be set for each bearer, allowing for flexible operation of packet duplication.

[0124] The UE may prioritize packet duplication control over SCell control. SCell control may use MAC signaling of SCell deactivation. For example, a UE in packet duplication operation may continue packet duplication even if it receives MAC signaling of SCell deactivation. This makes it possible to improve the reliability of packet duplication from the UE.

[0125] The UE may notify the base station that SCell deactivation is disabled. The notification may be made using MAC signaling or L1 / L2 signaling. The notification may include a reason for the deactivation. The reason may be, for example, "packet duplication in progress." The notification may also include an identifier of the logical channel in which packet duplication is in progress. The notification may also include an identifier of the bearer in which packet duplication is in progress. This enables the base station to smoothly perform control after SCell deactivation is disabled.

[0126] The above-mentioned priority of packet duplication control and SCell control may be determined using the duplicated packets. The UE may use information about the duplicated packets to determine whether to deactivate the SCell. This enables flexible control based on the duplicated packets.

[0127] As an example of prioritizing using replicated packets, priorities may be determined by classification of SRB and DRB. For example, packet replication may be prioritized for SRB, and SCell control may be prioritized for DRB. This enables flexible control depending on the type of bearer.

[0128] Alternatively, a priority may be determined for each bearer. For example, SRB0 and SRB1 may prioritize packet duplication, while SRB2, SRB3, and DRB may prioritize SCell control. Also, for example, with regard to DRBs, some DRBs may prioritize packet duplication, while other DRBs may prioritize SCell control. This allows for more flexible control for each bearer.

[0129] The above-mentioned priority may be determined by a standard, or may be notified in advance from the base station to the UE by RRC signaling. The above-mentioned priority may also be notified by MAC signaling, which allows for flexible control.

[0130] The UE may notify the base station that SCell suspension is disabled. The notification may be made when a packet for which packet duplication is prioritized is used, for example, when a bearer for which packet duplication is prioritized is using the SCell. The notification method and information included in the notification may be the same as those described above. This allows the base station to smoothly perform control after SCell suspension is disabled.

[0131] Prioritization between packet duplication control and SCell control may be applied when a plurality of packets are communicated using the SCell. The plurality of packets may be, for example, a combination of packets that prioritize packet duplication and packets that prioritize SCell control.

[0132] In the above, packet duplication may be prioritized. For example, while the above-mentioned multiple packets are in packet duplication operation, MAC signaling of SCell deactivation may be disabled. In other words, packet duplication may be continued. This makes it possible to ensure reliability of packets for which packet duplication is prioritized. The UE may notify the base station that SCell deactivation is disabled. The notification method and information included in the notification may be the same as those described above. This enables the base station to smoothly perform control after SCell deactivation is disabled.

[0133] In the above, the UE and the base station may stop packet duplication for some packets. The aforementioned some packets may be, for example, packets for which SCell control is prioritized. Packet duplication for packets for which packet duplication is prioritized may be continued. This facilitates SCell control in the base station.

[0134] Alternatively, the UE and the base station may not need to stop packet duplication for some of the packets, thereby ensuring reliability in packet communication.

[0135] In the above, the UE and the base station may suspend SCells when suspending packet duplication for a packet for which packet duplication is prioritized. This allows for reduction in power consumption. The UE may notify the base station that SCell suspension has been enabled. The notification may include a reason for the enablement. The reason may be, for example, suspension of packet duplication for a packet for which packet duplication is prioritized. The notification may include information about the packet, for example, a bearer identifier.

[0136] Alternatively, the UE and the base station may not need to suspend the SCell even when suspending packet duplication of a packet for which packet duplication is prioritized, which makes it easier to control the SCell.

[0137] As another example of prioritizing between packet duplication control and SCell control when multiple packets are being communicated, SCell control may be prioritized. For example, when the above-mentioned multiple packets are in packet duplication operation, MAC signaling for SCell deactivation may be enabled. In other words, the SCell may be deactivated. This allows for reduction in power consumption.

[0138] As an example of prioritizing between packet duplication control and SCell control, control of packet duplication start may be prioritized over the SCell stopped state. That is, the UE may start packet duplication. It is preferable to start SCell operation. MAC signaling may be used for the control of packet duplication start. This makes it possible to ensure reliability.

[0139] Alternatively, the SCell outage state may take priority over the control of packet duplication initiation, i.e., the UE may keep the SCell outage.

[0140] The UE may notify the base station that packet duplication is disabled. The notification may be made during or at the time of SCell deactivation. The notification may be made using MAC signaling or L1 / L2 signaling. The notification may include a target logical channel identifier. The notification may include a reason why packet duplication is disabled. The reason may be, for example, "SCell deactivation." This enables the base station to appropriately and quickly control packet duplication.

[0141] In the above, a UE whose packet duplication start control has been disabled may start packet duplication using SCell start control. SCell start control may be MAC signaling that instructs SCell start. The above-mentioned packet duplication start may use the above-mentioned packet duplication operation / stop state. For example, the UE may use packet duplication start control, for example, MAC signaling of packet duplication start, to set the state to "operation."

[0142] As another example of prioritizing between packet duplication control and SCell control, packet duplication stop control may be prioritized over the SCell active state. That is, the UE may deactivate the SCell using MAC signaling for packet duplication stop. The above-mentioned SCell deactivation may be performed when there is no other bearer for the UE to communicate with the base station using the SCell. This makes it possible to reduce the power consumption of the UE.

[0143] The base station may include information indicating the timing to start / stop packet duplication in MAC signaling that controls the start / stop of packet duplication. The timing may be physical timing. By directly controlling radio resources, it is possible to prevent unnecessary transmission and reception of radio signals. The physical timing may be, for example, a physical frame number, a subframe number, a slot number, a minislot number, or other information indicating the timing. Alternatively, the physical timing may be the time until the start / stop timing. This allows the base station and the UE to appropriately perform processing associated with stopping packet duplication.

[0144] The UE may start / stop packet duplication at the start / stop timing. Alternatively, the UE may start / stop packet duplication from the earliest PDCP PDU boundary after the start / stop timing. This prevents discontinuity in the UE's transmission operation due to the start / stop of packet duplication. Furthermore, it prevents buffer congestion in the base station's RLC due to the inability to receive the entire PDCP PDU.

[0145] The PDCP sequence number may be used as another information indicating the start / stop timing, which can prevent buffer congestion in the RLC of the base station due to the inability to receive the entire PDCP PDU.

[0146] The base station does not need to include information indicating the timing to start / stop packet replication in the MAC signaling that controls the start / stop of packet replication. The UE may start / stop packet replication immediately after receiving the MAC signaling. For example, the UE may start / stop packet replication from the timing (e.g., subframe, slot, minislot, TTI) immediately after receiving the MAC signaling. The timing to start / stop packet replication may be the next scheduling timing after the UE returns an ACK for the MAC signaling. Alternatively, the timing to start / stop packet replication may be the earliest PDCU PDU boundary after the UE receives the MAC signaling. Alternatively, the UE may start / stop packet replication after a predetermined period has elapsed since receiving the MAC signaling. The predetermined period may be defined in advance by a standard or may be notified to the UE by the base station. The predetermined period may be individually notified to the UE by the base station. The individual notification may be performed using RRC signaling. This makes it possible to reduce the amount of signaling required for the timing to start / stop packet replication.

[0147] The base station may include information for controlling the start / stop of the SCell used for packet duplication in MAC signaling for controlling the start / stop of packet duplication. The UE may use the information to start / stop the SCell. This allows the base station to flexibly control the SCell associated with the control of packet duplication.

[0148] Conversely, MAC signaling for controlling the start / stop of an SCell may include information for controlling the start / stop of packet duplication for communication using the SCell. The UE may use the information to start / stop packet duplication. This allows the base station to flexibly control the SCell in accordance with the control of packet duplication.

[0149] Alternatively, the MAC signaling for controlling the start / stop of packet duplication and the MAC signaling for controlling the start / stop of SCell may be combined into one MAC signaling. The one MAC signaling described above may be provided as a new MAC signaling.

[0150] Alternatively, the base station may simultaneously transmit MAC signaling for controlling packet duplication start / stop and MAC signaling for controlling SCell start / stop. Both MAC signaling may be transmitted in the same transport block or in different transport blocks. As an example of transmission in different transport blocks, transmission may be performed on different carriers. This enables rapid control of both SCell and packet duplication. Alternatively, MAC signaling for controlling packet duplication start / stop and MAC signaling for controlling SCell start / stop may be integrated. This allows the amount of signaling to be reduced.

[0151] As another example of prioritizing between packet duplication control and SCell control, packet duplication start control may be prioritized over SCell operation start control. For example, the UE may start SCell operation at the packet duplication start timing. The UE may also start packet duplication. This can improve the reliability of packet transmission from the UE to the base station.

[0152] Alternatively, control of SCell operation start may be prioritized over control of packet duplication start. For example, the UE may start packet duplication at the SCell start timing. This makes it possible to avoid complexity of SCell control in the base station and the UE.

[0153] The UE may notify the base station that SCell activation is disabled. The notification may be made, for example, when the operation of the SCell cannot be started. The notification may include the reason for the invalidation. The reason may be, for example, a failure of the transceiver for the carrier frequency of the SCell or a resource shortage for the SCell. The base station may use the notification to control the activation / deactivation of other SCells. This allows the base station to smoothly perform control after SCell activation is disabled.

[0154] As another example of prioritizing between packet duplication control and SCell control, packet duplication start control may be prioritized over SCell deactivation control. For example, the UE may start packet duplication. That is, SCell deactivation control may be disabled. The above operation may be performed, for example, when the SCell is active and packet duplication is deactivated. This makes it possible to improve the reliability of packet transmission. The UE may notify the base station that SCell deactivation is disabled. This notification enables the base station to appropriately control radio resources.

[0155] Alternatively, the control of SCell deactivation may be prioritized over the control of packet duplication initiation. For example, the UE may deactivate the SCell. That is, the control of packet duplication initiation may be disabled. This makes it possible to save radio resources. The UE may notify the base station that packet duplication is disabled. This notification enables the base station to appropriately determine the radio resources to be used for transmission and reception with the UE.

[0156] As another example of prioritizing between packet duplication control and SCell control, packet duplication stop control may be prioritized over SCell deactivation control. For example, the UE may stop packet duplication at the packet duplication stop timing. For example, if the SCell deactivation timing precedes the packet deactivation timing indicated in the MAC signaling for packet duplication stop, the UE may wait until the packet duplication stop timing to deactivate the SCell operation. This makes it possible to ensure the reliability of packet transmission.

[0157] Alternatively, control of SCell deactivation may be prioritized over control of packet duplication deactivation. For example, the UE may stop packet duplication at the timing of SCell deactivation. For example, if the timing of SCell deactivation precedes the packet stop timing indicated in MAC signaling for packet duplication deactivation, the UE may stop packet duplication in accordance with the timing of SCell operation deactivation. This makes it possible to ensure the reliability of packet transmission.

[0158] The UE may determine packet duplication operation and SCell operation using MAC signaling for packet duplication start / stop and MAC signaling for SCell start / stop. For example, the UE may determine packet duplication start using MAC signaling for packet duplication start, or may determine packet duplication start using both MAC signaling for packet duplication start and MAC signaling for SCell initiation. The above-mentioned determination using both MAC signalings may be a logical sum, a logical product, or other logical operation of both MAC signalings. Alternatively, for example, the UE may determine SCell initiation using MAC signaling for SCell initiation, or may determine SCell initiation using both MAC signaling for packet duplication start and MAC signaling for SCell initiation. The above-mentioned determination using both MAC signalings may be a logical sum, a logical product, or other logical operation of both MAC signalings. This enables flexible control of packet duplication and SCell operation.

[0159] In the above, instead of MAC signaling for starting / stopping packet duplication and MAC signaling for starting / stopping SCell, a flag related to packet duplication and a flag related to SCell operation may be used. The flag related to packet duplication may, for example, hold the above-mentioned state of operating / stopping packet duplication. The flag related to SCell operation may, for example, be one whose value switches between operating / stopping by MAC signaling for starting / stopping SCell. This makes it possible to flexibly and easily control packet duplication and SCell operation.

[0160] The UE may duplicate PDCP PDUs in the PDCP layer regardless of whether packet duplication is started or stopped. The PDCP layer of the UE may forward the duplicated PDCP PDUs to the RLC layer. The RLC layer may forward the PDCP PDUs to the MAC layer. The UE may perform the duplication and / or forwarding process using RRC signaling from the base station. The RRC signaling may be signaling for associating the logical channels through which each duplicated packet travels with the radio carriers used to transmit each packet. The UE may stop the duplication and / or forwarding using RRC signaling from the base station. The RRC signaling may be signaling for canceling the association between the logical channels through which each duplicated packet travels and the radio carriers used to transmit each packet. This allows the UE to quickly transmit duplicate packets when packet duplication is started, for example.

[0161] The UE may start / stop packet duplication when it correctly receives MAC signaling that controls the start / stop of packet duplication. The above-mentioned timing at which the MAC signaling is correctly received may be after the packet duplication start / stop timing indicated by the MAC signaling. In the above, the case where the timing is after the packet duplication start / stop timing indicated by the MAC signaling may be, for example, when HARQ retransmission is performed. The above-mentioned timing may be specified by, for example, a PDCP sequence number, or may be physical timing. The physical timing may be, for example, a physical frame number, a subframe number, a slot number, or a minislot number.

[0162] The base station may transmit the MAC signaling to the UE in advance using multiple HARQ processes, or may use all HARQ processes, thereby improving the reliability of the MAC signaling transmission and reception.

[0163] The base station may stop transmitting the MAC signaling to the UE. For example, the base station may stop transmitting the MAC signaling when it receives an ACK from the UE for the MAC signaling using another HARQ process. This allows radio resources to be saved.

[0164] The UE may start / stop packet duplication using the MAC signaling it receives first. The MAC signaling may be, for example, the first MAC signaling received among the MAC signaling transmitted in multiple HARQ processes. The UE may ignore or discard the MAC signaling received after the first time. This allows for quick processing by the UE.

[0165] Alternatively, in the above, the UE may start packet duplication retroactively. The UE may start packet duplication retroactively to the packet duplication start timing instructed by the MAC signaling. The UE may start packet duplication using data stored in an L2 layer buffer, for example, a PDCP layer buffer. This makes it possible to ensure the reliability of packet duplication.

[0166] Alternatively, the UE may perform packet duplication as far back as possible. For example, the UE may perform the above-described operation when there is no data remaining up to the packet duplication start timing instructed by the MAC signaling. The UE may perform the above-described operation when there is data remaining up to the packet duplication start timing instructed by the MAC signaling. This makes it possible to ensure the reliability of packet duplication.

[0167] Alternatively, in the above description, the UE may start / stop packet duplication at the timing indicated by the MAC signaling. The above-described timing may be, for example, the timing after the sequence number has cycled. As an example, if the UE receives MAC signaling from the base station to start packet duplication from PDCP PDU sequence number 5 while transmitting a PDCP PDU with PDCP sequence number 7, the UE may start packet duplication from the next PDCP PDU with PDCP PDU sequence number 5 after the PDCP sequence number has cycled. This makes it possible to avoid design complexity in the UE.

[0168] Fig. 8 is a sequence diagram showing the operation when MAC signaling for packet duplication start is received by the UE after the specified timing due to the occurrence of HARQ retransmission. Fig. 8 shows the sequence for packet duplication start, but it may also be applied to packet duplication stop. Also, in Fig. 8, the PDCP sequence number is used as the specified timing, but physical timing may also be used. The physical timing may be the one described above.

[0169] In step ST801 shown in FIG. 8, the base station determines to start packet duplication. In step ST802, the base station notifies the UE of MAC signaling of the start of packet duplication. This signaling includes an uplink PDCP sequence number n at which the UE starts packet duplication. In FIG. 8, the UE fails to correctly receive the MAC signaling of the start of packet duplication in step ST802, and in step ST803, the UE notifies the base station of a NACK. After receiving the NACK in step ST803, the base station retransmits the MAC signaling of step ST802 to the UE in step ST804. In FIG. 8, the UE fails to correctly receive the MAC signaling of the start of packet duplication in step ST804, and in step ST805, the UE again notifies the base station of a NACK.

[0170] In step ST806 shown in Fig. 8, the sequence number of the PDCP PDU that the UE is transmitting reaches n. The UE transmits the PDCP PDU with sequence number n to the base station without performing packet duplication.

[0171] In step ST807 shown in Fig. 8, the base station retransmits the MAC signaling for the second time to the UE. In step ST808, the UE notifies the base station of an ACK in response to step ST807.

[0172] 8, a UE that has correctly received MAC signaling instructing the start of packet duplication in step ST807 starts packet duplication in step ST809. In steps ST810 and ST811, the UE transmits the original packet and the duplicated packets to the base station. In step ST812, the base station detects duplicate packets and deletes one of the packets.

[0173] The base station may configure the RLC layer for the duplicated packets. The configuration may be performed immediately after the base station determines whether to start packet duplication. This allows the base station to quickly start packet duplication even when the time until the designated timing is short.

[0174] The base station may set up the RLC layer for the duplicated packets after receiving an ACK from the UE in response to MAC signaling that notifies the UE of the start of packet duplication. This makes it possible to minimize the memory allocation time required for RLC setup.

[0175] The PDCP layer of the base station may instruct the RLC layer to initialize the RLC layer. The RLC layer may use this instruction to initialize the RLC. For example, this instruction may be issued when the PDCP layer has finished receiving PDCP PDUs up to the PDCP sequence number that indicates the timing for stopping packet duplication. The instruction may include, for example, an identifier of the RLC entity to be initialized, or an identifier of a logical channel that uses the RLC entity. The initialization may be, for example, initialization of a buffer in the RLC PDU, initialization of variables used by the RLC entity as described in Section 7.1 of Non-Patent Document 17 (TS36.322 v14.0.0), or a combination of both. This allows the PDCP layer of the CU to reliably receive PDCP PDUs up to the PDCP sequence number that indicates the timing.

[0176] The method described in the first embodiment may be applied to packet duplication using only SCell. This increases the flexibility of carrier selection in packet duplication. Furthermore, the method described in the first embodiment may be applied to both the C-Plane and the U-Plane. It becomes possible to prevent malfunctions during packet duplication in both the C-Plane and the U-Plane.

[0177] In the first embodiment, the base station may change the carrier associated with the logical channel in the packet duplication of the UE. That is, the base station may change the carrier used for transmitting the logical channel in the packet duplication of the UE. The change may be performed, for example, by the MAC layer of the base station. This makes it possible to improve the resistance to the radio wave environment fluctuation during the packet duplication operation.

[0178] The base station may notify the UE of a change in the carrier used for transmitting the above-mentioned logical channel. The notification may include information combining the logical channel and the carrier to be used. The base station may notify the UE of the change by MAC signaling. This enables quick notification and highly reliable notification by HARQ control. Alternatively, the base station may notify the UE of the change by L1 / L2 signaling. This enables even quicker notification. Alternatively, the base station may notify the UE of the change by RRC signaling. This makes it possible to avoid complexity in the design of the communication system.

[0179] The UE may enable signaling transmitted from the base station to associate logical channels with transmission carriers and / or change the association. The signaling may be RRC signaling, MAC signaling, or L1 / L2 signaling. The UE may enable the signaling when the signaling includes an SCell that is not included in the SCell list used by the UE. The SCell included in the SCell list may be, for example, an SCell included in the SCell addition / modification list in the signaling for RRC connection reconfiguration.

[0180] The UE may add an SCell that is not included in the above-mentioned SCell list to the SCell list. The UE may notify the base station of information about the SCell. The information about the SCell may be, for example, the physical cell identifier (PCI) of the SCell, or an SCell identifier such as an SCellIndex, or a combination of both. The UE may allocate the above-mentioned SCell identifier to the SCell. The SCell identifier may be the same as the SCell identifier allocated by the base station, or may be a temporary identifier. The above-mentioned temporary SCell identifier may be one defined by a standard, or may be one that has been broadcast or individually notified to the UE in advance by the base station. The base station may add the cell to the SCell list used by the UE. The base station may notify the UE of information about the added SCell. The information about the added SCell may include the SCell identifier, the PCI of the SCell, or both. The UE may replace the SCell identifier allocated by itself with the SCell identifier notified by the base station.

[0181] The UE may use RRC signaling to notify the base station of the SCell information. For example, if the signaling transmitted from the base station that associates logical channels with transmission carriers is RRC signaling, the UE may notify the information by RRC signaling. By notifying the signaling and the notification by the same type of signaling, the processing related to SCell control in the base station becomes easier.

[0182] Alternatively, the UE may use MAC signaling to notify the base station of the information on the SCell. For example, if the signaling transmitted from the base station that associates the logical channel with the transmission carrier is MAC signaling, the information may be notified by MAC signaling. In addition to obtaining the same effect as above, quick notification becomes possible.

[0183] Alternatively, the UE may use L1 / L2 signaling to notify the base station of the information about the SCell. For example, if the signaling transmitted from the base station to associate a logical channel with a transmission carrier is L1 / L2 signaling, the information may be notified by L1 / L2 signaling. This allows for more rapid notification.

[0184] The UE may disable signaling transmitted from the base station for associating and / or changing the association between logical channels and transmission carriers. The signaling may be the same as described above. The UE may disable the signaling when the signaling includes an SCell that is not in the SCell list used by the UE. The same as described above may be applied to an SCell that is not in the SCell list.

[0185] The UE may perform packet duplication with the original packet duplication setting. Alternatively, the UE may stop packet duplication. The target of stopping packet duplication may be all packets for which the UE performs packet duplication, or may be packets related to the signaling. Alternatively, the UE may delete the packet duplication setting for packets related to the signaling.

[0186] The UE may notify the base station that the signaling is invalid. The notification may include a reason why the signaling is invalid. The reason may be, for example, that the SCell notified by the signaling does not exist in the list of SCells used by the UE. Furthermore, the signaling may include information about the SCell. The information about the SCell may be, for example, information about an SCell that does not exist in the list of SCells used by the UE, such as the PCI of the SCell. This makes it easier for the base station to control the SCell.

[0187] The UE may use RRC signaling for the notification. For example, if the signaling transmitted from the base station that associates logical channels with transmission carriers is RRC signaling, the UE may perform the notification using RRC signaling. By performing the signaling and the notification using the same type of signaling, processing related to SCell control in the base station becomes easier.

[0188] Alternatively, the UE may use MAC signaling for the notification. For example, if the signaling transmitted from the base station that associates the logical channel with the transmission carrier is MAC signaling, the UE may notify the information by MAC signaling. In addition to obtaining the same effect as above, it becomes possible to notify quickly.

[0189] Alternatively, the UE may use L1 / L2 signaling for the notification. For example, if the signaling transmitted from the base station that associates logical channels with transmission carriers is L1 / L2 signaling, the UE may notify the information by L1 / L2 signaling. This allows for even faster notification.

[0190] The base station may transmit to the UE signaling to add the SCell to the UE's list of used SCells. The base station may transmit to the UE signaling to associate a logical channel with a transmission carrier. Packet duplication using the SCell becomes possible. The base station may transmit both signalings to the UE simultaneously or at different times. Both signalings may be integrated into one signaling.

[0191] According to this embodiment 1, it is possible to prevent the UE from malfunctioning when a conflict occurs between packet duplication and SCell control. It is also possible to prevent the UE from malfunctioning when the UE receives packet duplication start / stop MAC signaling from the base station to the UE after the timing specified by the MAC signaling.

[0192] Variation 1 of Embodiment 1 Packet duplication using CA may be applied to a NR base station (gNB) separated into two units.

[0193] 3GPP has proposed that an NR base station (hereinafter sometimes referred to as a gNB) be separated into two units (see Non-Patent Document 7). These two units are called a CU (Central Unit) and a DU (Distributed Unit). With regard to the division of functions between the CU and DU in the CU-DU separation, the CU has PDCP, and the DU has RLC, MAC, and PHY (see Non-Patent Document 18 (3GPP R3-171412)).

[0194] Figure 9 shows the protocol configuration for packet duplication using CA between a gNB and a UE where CU-DU separation is performed.

[0195] The New AS Layer 1022 in the UE 1014 receives packets from an upper layer, such as an application or RRC, generates PDCP SDUs, and transmits them to the PDCP 1021 .

[0196] The PDCP 1021 generates PDCP PDUs using the PDCP SDUs, duplicates the PDCP PDUs, and transmits each PDCP PDU to the RLC 1019 and the RLC 1020. The RLC 1019 and the RLC 1020 each generate an RLC PDU using each PDCP PDU and transmits it to the MAC 1016.

[0197] The MAC 1016 generates transport channel data using the RLC PDU received from the RLC 1019 and transmits it to the HARQ 1015 for Cell #1. The MAC 1016 generates transport channel data using the RLC PDU received from the RLC 1020 and transmits it to the HARQ 1018 for Cell #2.

[0198] The HARQ 1015 transmits transport channel data generated using the RLC PDU from the RLC 1019 to the PHY 1014. The PHY 1014 performs coding and modulation processing on the transport channel data and transmits the data as a radio signal to the DU 1006 using Cell #1. The HARQ 1018 transmits transport channel data generated using the RLC PDU from the RLC 1020 to the PHY 1017. The PHY 1017 performs coding and modulation processing on the transport channel data and transmits the data as a radio signal to the DU 1006 using Cell #2.

[0199] PHY 1011 in DU 1006 receives the signal from Cell #1, performs demodulation and decoding processing, and transmits the signal to HARQ 1010 as transport channel data. HARQ 1010 transfers the transport channel data to MAC 1009. PHY 1013 receives the signal from Cell #2, performs demodulation and decoding processing, and transmits the signal to HARQ 1012 as transport channel data. HARQ 1012 transfers the transport channel data to MAC 1009.

[0200] The MAC 1009 generates RLC PDUs using the transport channel data from the HARQs 1010 and 1012, and transfers them to the RLC 1007 and RLC 1008, respectively. The RLC 1007 generates PDCP PDUs using the RLC PDUs and transfers them to the PDCP 1003 in the CU 1001 using the CU-DU interface 1004. The RLC 1008 generates PDCP PDUs using the RLC PDUs and transfers them to the PDCP 1003 in the CU 1001 using the CU-DU interface 1004.

[0201] In the CU 1001, the PDCP 1003 performs duplicate detection using each PDCP PDU from the RLCs 1007 and 1008, and deletes duplicate PDCP PDUs. The PDCP 1003 generates a PDCP SDU using the original, i.e., undeleted, PDCP PDUs, and transfers it to the New AS Layer 1002.

[0202] However, in a gNB with CU-DU separation, it is not clear whether the CU or the DU makes the decision to duplicate packets. Furthermore, the signaling between the CU and DU for packet duplication is not specified. Therefore, a problem occurs in that a UE cannot duplicate packets in communication with a gNB with CU-DU separation.

[0203] The present first modification of the first embodiment solves the above-mentioned problem.

[0204] The DU decides when to start replicating a packet. The MAC layer may also decide this.

[0205] The DU may use the measurement results of the uplink signal to determine whether to start packet duplication. For example, the SRS may be used as the uplink signal, or the error rate of the uplink signal, such as BER or BLER, may be used. Alternatively, the uplink transmission data size may be used to determine whether to start packet duplication. For example, the uplink transmission data size may be an uplink grant transmitted from the DU to the UE, or a BSR (Buffer Status Report) received from the UE. Alternatively, the load of each cell may be used to determine whether to start packet duplication. For example, the scheduling status of other UEs may be used as the load of each cell. This enables optimization of communications throughout the system.

[0206] As mentioned above, Non-Patent Document 19 (see R2-1706716) discloses that the measurement results of the uplink signal, the uplink transmission data size, and the load of each cell are used. However, the present invention differs from Non-Patent Document 19 in that it discloses specific examples of the measurement results of the uplink signal, the uplink signal data size, and the load of each cell.

[0207] The DU may send a notification to the CU to notify it of the start of packet duplication. The CU may send a response to the notification to the DU. The response may include information about the timing to start packet duplication. The information about the timing may be a PDCP sequence number, as in the first embodiment, or information about physical timing. The PDCP sequence number may be information about the sequence number of a PDCP PDU received by the PDCP layer of the CU, for example, the largest sequence number among the PDCP PDUs. This makes it possible to quickly notify information about the PDCP sequence number from the CU. Alternatively, the CU may notify the DU of the PDCP sequence number at which the UE starts packet duplication. This makes it possible to reduce the amount of processing in the DU.

[0208] The DU may notify the UE of the start of packet duplication by MAC signaling, which may include information about the timing to start packet duplication, as in the first embodiment.

[0209] The response from the CU to the DU does not need to include information about the timing to start packet duplication, and the MAC signaling from the DU to the UE does not need to include information about the timing.

[0210] The processing in the UE may be the same as in embodiment 1. It is possible to avoid the complexity in packet duplication from the UE to the base station.

[0211] The DU does not need to send a packet duplication start notification to the CU. The DU does not need to send a response to the packet duplication start notification to the CU. This makes it possible to reduce the amount of signaling between the CU and DU.

[0212] Fig. 10 is a sequence diagram of packet duplication when a DU determines to start packet duplication. Fig. 10 shows an example in which PDCP sequence number n is used as the packet duplication start timing.

[0213] In step ST1101 shown in Fig. 10, the DU determines whether to start packet duplication. In step ST1102, the DU notifies the CU of the start of packet duplication. In step ST1103, the CU notifies the DU of its consent to start packet duplication. In step ST1103, information regarding the timing to start packet duplication may also be notified. In the example of Fig. 10, the CU notifies the DU of the PDCP sequence number n as this information.

[0214] 10, the DU does not need to notify the CU of step ST1102. Step ST1103 does not need to include information about the packet duplication start timing. Alternatively, the CU does not need to notify the DU of step ST1103. This makes it possible to reduce the amount of signaling in the CU-DU interface.

[0215] In step ST1104 shown in Fig. 10, the DU notifies the UE of MAC signaling of the start of packet duplication. In step ST1104, information regarding the timing of starting packet duplication may be notified. In the example of Fig. 10, the DU notifies the UE of the PDCP sequence number n as this information. In step ST1105, the UE notifies the DU of an ACK in response to step ST1104.

[0216] In step ST1106 shown in Fig. 10, the UE starts packet duplication. In steps ST1107 and ST1108, the UE transmits the original packet and the duplicated packet to the DU. In steps ST1109 and ST1110, the DU transmits the PDCP PDU received in steps ST1107 and ST1108 to the CU, respectively. In step ST1111, the CU detects duplicate packets and deletes one of the packets.

[0217] In this first modification of the first embodiment, the CU may determine whether to start packet duplication, or the RRC layer or the PDCP layer may make the determination.

[0218] The DU may notify the CU of information necessary for determining whether to start packet duplication. This information may be the information necessary for the DU to determine whether to start packet duplication, as described above. This invention differs from Non-Patent Document 19 (3GPP R2-1706716) in that the information is notified from the DU to the CU.

[0219] The CU may notify the DU whether packet duplication is to be performed. The notification may include information regarding the timing to start packet duplication. The information regarding the timing to start packet duplication may be similar to the information included in the response to the packet duplication start notification sent by the CU to the DU. This reduces the amount of processing required for the UE to determine the timing to start packet duplication.

[0220] The DU may notify the UE of the start of packet duplication by MAC signaling, which may include information about the timing to start packet duplication, as in the first embodiment.

[0221] The response from the CU to the DU does not need to include information about the timing to start packet duplication, and the MAC signaling from the DU to the UE does not need to include information about the timing.

[0222] The processing in the UE may be the same as in embodiment 1. It is possible to avoid the complexity in packet duplication from the UE to the base station.

[0223] Fig. 11 is a sequence diagram of packet duplication when a CU determines to start packet duplication. Fig. 11 shows an example in which PDCP sequence number n is used as the timing to start packet duplication. The sequence shown in Fig. 11 includes the same steps as the sequence shown in Fig. 10, so the same step numbers are used for the same steps and common explanations will be omitted.

[0224] In step ST1201 shown in Fig. 11, the DU notifies the CU of information that the CU uses to determine packet duplication. In step ST1202, the CU determines whether to start packet duplication. In step ST1203, the CU notifies the DU of the start of packet duplication. In step ST1203, the CU may also notify information related to the timing of packet duplication start. In the example of Fig. 11, the CU notifies the DU of the PDCP sequence number n as this information.

[0225] Steps ST1104 to ST1111 shown in FIG. 11 are the same processes as those in FIG. 10, and therefore the description thereof will be omitted.

[0226] As in the first embodiment, the UE may start / stop packet duplication at the timing when MAC signaling that controls the start / stop of packet duplication is correctly received. The timing when the MAC signaling is correctly received may be after the timing when packet duplication is started / stopped as instructed by the MAC signaling. In the above, the timing when packet duplication is started / stopped as instructed by the MAC signaling may be, for example, when HARQ retransmission is performed. The operation of the base station in the first embodiment may be implemented by replacing it with the operation in the DU. The same effects as those in the first embodiment can be obtained.

[0227] In the above, as in the first embodiment, the start of packet duplication by the UE may be performed retroactively, or the start / stop timing of packet duplication by the UE may be the packet duplication timing instructed by MAC signaling that controls the start / stop of packet duplication, for example, the packet duplication start / stop timing after the number has cycled around. The same effects as in the first embodiment can be obtained.

[0228] Figure 12 is a sequence diagram showing the operation when MAC signaling for starting packet duplication is received by the UE after a specified timing due to the occurrence of HARQ retransmission in communication between the UE and a gNB with CU-DU separation. Figure 12 shows an example of a case where the DU determines whether to start packet duplication. The sequence shown in Figure 12 includes the same steps as the sequences shown in Figures 8 and 10, so the same step numbers are used for the same steps and common explanations will be omitted.

[0229] Steps ST1101 to ST1104 shown in FIG. 12 are the same as those in FIG. 10, and therefore the description thereof will be omitted.

[0230] Steps ST1301 to ST1304 shown in Fig. 12 are equivalent to steps ST803 to ST806 shown in Fig. 8, except that the communication destination from the UE is changed from the base station to the DU. In step ST1305, the DU transfers the PDCP PDU with PDCP sequence number n received in step ST1304 to the CU. Steps ST1307 to ST1308 are equivalent to steps ST807 to ST808 shown in Fig. 8, except that the communication destination from the UE is changed from the base station to the DU.

[0231] Steps ST1106 to ST1111 shown in FIG. 12 are the same as those in FIG. 10, and therefore the description thereof will be omitted.

[0232] In this first modification of the first embodiment, the DU may notify the CU of ACK / NACK information of MAC signaling notified from the UE, which indicates the start of packet duplication. This enables the CU to easily perform system control when an irregularity occurs, such as an excess of HARQ retransmissions.

[0233] In the above, the DU may notify only the ACK information received from the UE. This makes it possible to reduce the amount of signaling on the CU-DU interface. Only NACK information may be notified. This makes it possible to quickly implement system control in the CU. Both ACK / NACK information may be notified. This makes it possible for the CU to quickly obtain information on the entire system. Alternatively, the ACK information notified from the DU to the UE may be only the first received ACK. The first received ACK may be used, for example, when the above-mentioned MAC signaling is communicated using multiple HARQ processes. This makes it possible to further reduce the amount of signaling on the CU-DU interface.

[0234] The method shown in Modification 1 of Embodiment 1 may also be used to stop packet duplication. In a base station where CU / DU separation is performed, both start and stop of packet duplication can be performed.

[0235] The DU may configure the RLC layer for the duplicated packets. This configuration may be performed immediately after the DU determines whether to start packet duplication. Alternatively, this configuration may be performed immediately after the CU notifies the DU of the start of packet duplication. This allows the DU to quickly start packet duplication even when the time until the specified timing is short.

[0236] The above-mentioned RLC layer configuration for the duplicated packets in the DU may be performed after receiving an ACK from the UE in response to MAC signaling that notifies the UE of the start of packet duplication, which makes it possible to minimize the memory allocation time for RLC configuration.

[0237] The CU may instruct the DU to initialize the RLC layer. The DU may use this instruction to initialize the RLC layer. The instruction may be issued, for example, when the PDCP layer of the CU has finished receiving PDCP PDUs up to the PDCP sequence number that indicates the timing for stopping packet duplication. The instruction may include, for example, an identifier of the RLC entity to be initialized, or an identifier of a logical channel that uses the RLC entity. The initialization may be, for example, initialization of a buffer in the RLC PDU, initialization of variables used by the RLC entity as described in Section 7.1 of Non-Patent Document 17 (TS36.322 v14.0.0), or a combination of both. This ensures that the PDCP layer of the CU can reliably receive PDCP PDUs up to the PDCP sequence number that indicates the timing for stopping packet duplication.

[0238] As in the first embodiment, in this first modification of the first embodiment, the DU may change the carrier associated with the logical channel in packet duplication by the UE. This change may be performed, for example, by the MAC layer of the DU. This makes it possible to improve resistance to fluctuations in the radio wave environment during packet duplication operations.

[0239] As in the first embodiment, the DU may notify the UE of a change in the carrier used for transmitting the aforementioned logical channel. The notification may include information combining the logical channel and the carrier to be used. The DU may also notify the UE of the change by MAC signaling or by L1 / L2 signaling. This allows for quick notification from the DU to the UE.

[0240] In the above, the DU may notify the CU of a change in the carrier used for transmitting the logical channel. This notification from the DU to the CU may be made before, simultaneously with, or after the notification from the DU to the UE. The information included in this notification may be the same as the information included in the notification from the DU to the UE. The notification from the DU to the CU may be made using a CU-DU interface, for example, the F1 interface. The CU may notify the DU of whether to accept or reject the carrier change. This notification of acceptance or rejection may be made using a CU-DU interface, for example, the F1 interface. The DU may use this notification of acceptance or rejection to notify the UE of the change in the carrier used for transmitting the logical channel. Alternatively, the DU may change to another carrier, return to the original carrier, or perform other processing. This enables the CU to efficiently control the entire communication system.

[0241] The CU may change the carrier associated with the logical channel in the packet duplication described above. The CU may notify the UE of the carrier change by RRC signaling. Alternatively, the CU may notify the DU of the carrier change. The information included in the notification may be the same as the information included in the notification from the DU to the UE described above. The DU may transmit the notification to the UE. The transmission may use MAC signaling or L1 / L2 signaling. This allows the CU to efficiently control the entire communication system.

[0242] As in the first embodiment, the UE may enable signaling transmitted from the base station, which associates logical channels with transmission carriers. The UE may enable the signaling when the signaling includes an SCell that is not in the SCell list used by the UE. The operation of the UE when enabling the signaling may be the same as in the first embodiment. The same effects as in the first embodiment can be obtained.

[0243] As in the first embodiment, the UE may notify the DU of information about an SCell that is not included in the above-mentioned SCell list. The DU may notify the CU of the above-mentioned information. The above-mentioned notification to the CU may be performed using a CU-DU interface. The information included in the above-mentioned notification to the CU may be the same as in the first embodiment.

[0244] As in the first embodiment, the UE may disable signaling that is transmitted from the base station and associates logical channels with transmission carriers. The UE may disable the signaling when the signaling includes an SCell that is not in the SCell list used by the UE. The operation of the UE when the signaling is disabled may be the same as in the first embodiment. The same effects as in the first embodiment can be obtained.

[0245] As in the first embodiment, the UE may notify the DU that the signaling is invalid. The DU may notify the CU of the above information. The above notification to the CU may be performed using the CU-DU interface. The information included in the above notification to the CU may be the same as in the first embodiment.

[0246] This first variant of the first embodiment makes it possible to receive duplicate uplink packets even in a gNB where the CU and DU are separated, thereby improving the reliability of packet transmission.

[0247] Embodiment 2 As another method of packet duplication described in the first embodiment, MC (including DC) can be used (see Non-Patent Document 9 (3GPP TR38.804 v14.0.0)).

[0248] However, there is no disclosure about switching between packet duplication using CA and packet duplication using DC. Therefore, for example, when a UE that has packet duplication using CA set during operation moves to the edge of a cell, it is unable to switch to packet duplication using DC, which causes a problem that communication reliability cannot be ensured.

[0249] In the second embodiment, a method for solving such a problem will be disclosed.

[0250] The base station and the UE are able to switch between packet duplication using CA and packet duplication using DC.

[0251] In the above, the base station and the UE may switch the bearer configuration. The bearer configuration may be switched using the pattern shown in Non-Patent Document 22 (R2-1704001). For example, a switch from an MCG (Master Cell Group) bearer to an MCG split bearer may be performed. A switch from packet duplication using CA to packet duplication using DC may be performed. The reverse pattern may also be used. A switch from packet duplication using DC to packet duplication using CA may be performed.

[0252] As another example, a switch from an SCG (Secondary Cell Group) bearer to an SCG split bearer may be performed. A switch from packet duplication using CA to packet duplication using DC is possible. The reverse pattern may also be used. A switch from packet duplication using DC to packet duplication using CA is possible.

[0253] A pattern not shown in Non-Patent Document 22 may be used. For example, an SCG bearer may be switched to a bearer that splits a certain SCG to another SCG with a certain SCG as the anchor base station (hereinafter, sometimes referred to as an SCG-only split bearer). The opposite pattern may also be used. In packet duplication using DC, it is possible to increase the flexibility of base station selection.

[0254] As another example, the MCG bearer may be switched to an SCG split bearer or an SCG-only split bearer. The reverse pattern may also be used. By simultaneously switching the base station using the PDCP layer, i.e., the anchor base station, and switching the packet duplication configuration, the amount of signaling can be reduced.

[0255] As another example, the MCG split bearer may be switched to the SCG bearer, or the reverse pattern may be used. By simultaneously switching the base station using the PDCP layer, i.e., the anchor base station, and switching the packet duplication configuration, the amount of signaling can be reduced.

[0256] The base station and the UE may switch logical channels. In the above description, for example, the base station and the UE may maintain one of the two logical channels used for packet duplication. The maintained logical channel may be, for example, a logical channel that performs wireless communication with the UE at the same base station even after switching packet duplication from packet duplication using CA to packet duplication using DC. Maintaining one logical channel makes it possible to ensure continuity in communication using that logical channel.

[0257] In the above, the other logical channel may be released, which can reduce memory usage in the base station and the UE. Alternatively, the other logical channel may be maintained. For example, when packet duplication is switched again and packet duplication of the original configuration is resumed, the maintained logical channel may be used. This can reduce the amount of signaling required when packet duplication is switched again.

[0258] As another example, the base station and the UE may release both of the two logical channels used for packet duplication, or may set up a new logical channel, which allows flexible resource configuration when switching between packet duplications.

[0259] Alternatively, the logical channel does not need to be switched. The base station and the UE may maintain two logical channels used for packet duplication. In the above case, one of the logical channels may be used as is by switching the base station. This reduces the amount of signaling.

[0260] In maintaining the logical channel, the base station and the UE may maintain the RLC layer, the MAC layer, or both the RLC layer and the MAC layer. This reduces the amount of signaling involved in packet duplication.

[0261] Alternatively, the RLC layer may be released. Alternatively, the MAC layer may be released. Alternatively, both the RLC layer and the MAC layer may be released. This allows flexible configuration of the RLC and / or MAC.

[0262] In the aforementioned logical channel release, the base station and the UE may release the RLC layer, the MAC layer, or both the RLC layer and the MAC layer, which can reduce memory usage.

[0263] The base station and the UE may release the correspondence between the logical channel and the carrier used in packet duplication. The release may be used to switch from packet duplication using CA to packet duplication using DC. When switching packet duplication from CA to DC, the flexibility of the carrier used can be improved.

[0264] The base station and the UE may specify the correspondence between the logical channel and the carrier used in packet duplication. The release may be used to switch from packet duplication using DC to packet duplication using CA. This allows for smooth switching of packet duplication from DC to CA.

[0265] The base station and the UE may set the packet duplication operation to activated. The packet duplication operation may be the operation immediately before switching the packet duplication. The packet duplication operation may be the operation immediately after switching the packet duplication, or may be the operation both before and after switching the packet duplication. This makes it possible to prevent interruption of transmitted and received data before and after packet duplication.

[0266] The base station and the UE may deactivate the packet duplication operation. The packet duplication operation may be performed immediately before switching the packet duplication. The packet duplication operation may be performed immediately after switching the packet duplication, or may be performed both before and after switching the packet duplication. This makes it possible to save radio resources before and after packet duplication.

[0267] The base station and the UE may maintain the packet duplication active / stopped state. This state may be maintained before and after switching packet duplication. For example, if packet duplication is active before switching packet duplication, packet duplication may be set to active after switching packet duplication. This enables smooth transmission and reception of user data and / or control data.

[0268] The packet duplication operation accompanying the packet duplication switch described above may be defined in advance by a standard. Alternatively, the operation may be notified from the base station to the UE. For the notification, RRC signaling, MAC signaling, or L1 / L2 signaling may be used. The RRC signaling described above may be, for example, the RRC signaling used for switching packet duplication. The MAC signaling described above may be, for example, the MAC signaling for starting / stopping packet duplication described in the first embodiment and the first modification of the first embodiment. This improves operational flexibility when switching packet duplication.

[0269] In this second embodiment, the switching of packet duplication may be initiated by the master base station or the secondary base station. Alternatively, the switching of packet duplication may be initiated by the anchor base station. By initiating the switching of packet duplication by the anchor base station, it becomes possible to apply the switching of packet duplication to the above-mentioned split bearer of only SCG.

[0270] Fig. 13 is a sequence diagram when a master base station initiates packet duplication switching. Fig. 13 shows an example of switching from packet duplication using CA in an SCG bearer to packet duplication using DC in an SCG split bearer. In Fig. 13, MeNB indicates an eNB operating as a master base station, and SgNB indicates a gNB operating as a secondary base station.

[0271] In Step ST2001 shown in FIG. 13, the UE performs packet duplication using CA. In Steps ST2002 and ST2003, the UE transmits the duplicated packets to the SgNB using different carriers. In Step ST2004, the SgNB detects and deletes duplicate packets.

[0272] In step ST2005 shown in FIG. 13, the MeNB transmits an SgNB modification request to the SgNB. The SgNB modification request may include information indicating the type of packet duplication. The information indicating the type of packet duplication may be included in the SgNB modification request in the form of being included in SCG-ConfigInfo, for example.

[0273] In Step ST2006 shown in FIG. 13, the SgNB transmits an SgNB modification request acknowledgement to the MeNB. The SgNB modification request acknowledgement may include information regarding modification of the RRC parameters of the UE. The information regarding modification of the RRC parameters of the UE may be included in the SgNB modification request acknowledgement, for example, in the form of being included in the SCG-Config.

[0274] Although the example in FIG. 13 shows an example of an acceptance response to the SgNB modification request, a rejection response may also be used. For example, the SgNB may transmit an SgNB Modification Request Reject to the MeNB. The SgNB Modification Request Reject may include a reason for the rejection. Alternatively, bearer information, for example, an identifier of the bearer, may be included. The bearer may be a bearer that caused the SgNB to reject the request. The MeNB may use the rejection response to, for example, change configuration parameters and notify the SgNB modification request again. This enables smooth processing by the MeNB, for example, when the SgNB cannot fulfill a request from the MeNB.

[0275] In Step ST2007 shown in FIG. 13, the MeNB notifies the UE of an RRC connection reconfiguration (RRCConnectionReconfiguration). Using Step ST2007, the UE switches packet duplication and changes the RRC parameters accordingly. In Step ST2008, the UE notifies the MeNB of an RRC connection reconfiguration completion (RRCConnectionReconfigurationComplete). In Step ST2009, the MeNB notifies the SgNB of an SgNB reconfiguration completion (SgNB Reconfiguration Complete).

[0276] In step ST2010 shown in FIG. 13, the UE performs packet duplication using DC. In steps ST2011 and ST2012, the UE transmits the duplicated packets to the MeNB and SgNB, respectively. In step ST2013, the MeNB transmits the packet received in step ST2011 to the SgNB. In step ST2014, the SgNB detects and deletes duplicate packets.

[0277] 13 shows an example in which the master base station is an eNB and the secondary base station is a gNB, but the master base station may be a gNB. Also, the secondary base station may be an eNB. Both the master and secondary base stations may be gNBs or eNBs.

[0278] Fig. 14 is a sequence diagram when a secondary base station initiates switching of packet duplication. Fig. 14 shows an example of switching from packet duplication using CA in an SCG bearer to packet duplication using DC in an SCG split bearer. In Fig. 14, MeNB indicates an eNB operating as a master base station, and SgNB indicates a gNB operating as a secondary base station. Since Fig. 14 includes the same steps as the sequence shown in Fig. 13, the same step numbers are assigned to the same steps and common explanations will be omitted.

[0279] In step ST2101 shown in FIG. 14, the SgNB transmits a notification that there is an SgNB modification request (SgNB Modification Required) to the MeNB. The notification may include information indicating a type of packet duplication. The notification may also include information related to an RRC parameter modification of the UE. The information indicating the type of packet duplication and / or the information related to an RRC parameter modification of the UE may be included in the notification, for example, in the form of being included in the SCG-Config.

[0280] Although the example in FIG. 14 shows an example in which the MeNB accepts the SgNB modification request from the SgNB, the MeNB may reject the request. For example, the MeNB may transmit an SgNB modification refuse to the SgNB. The SgNB modification refuse may include a reason for the refusal. Alternatively, bearer information, for example, an identifier of the bearer, may be included. The bearer may be the bearer that caused the MeNB to reject the request. The SgNB may use the rejection response to, for example, change configuration parameters and notify the SgNB of the SgNB modification request again. This enables smooth processing by the SgNB, for example, when the MeNB cannot fulfill a request from the SgNB.

[0281] In Step ST2102 shown in FIG. 14, the MeNB notifies the SgNB of an SgNB modification confirm.

[0282] In Fig. 14, as in Fig. 13, the master base station may be a gNB. Also, the secondary base station may be an eNB. Both the master and secondary base stations may be gNBs or eNBs.

[0283] The SgNB change request transmitted from the master base station to the secondary base station may include information indicating a type of packet duplication. The type of packet duplication may be, for example, packet duplication using CA or packet duplication using DC. The information indicating the type of packet duplication may be information indicating a type of packet duplication after switching.

[0284] The master base station may include information indicating the type of packet duplication in the configuration items of the additional bearer. The configuration items of the additional bearer may correspond to the configuration items of the SCG Bearer and Split Bearer in the E-RABs To Be Added Item in Section 9.1.3.5 of Non-Patent Document 23 (3GPP TS36.423 v14.3.0). By including the information in the configuration items of the additional bearer, it becomes possible to switch from packet duplication using CA to packet duplication using DC in the MCG bearer, for example.

[0285] As another example, the master base station may include information indicating the type of packet duplication in the configuration items of the modified bearer. The configuration items of the modified bearer may correspond to the configuration items of the SCG Bearer and Split Bearer in the E-RABs To Be Modified Item in Section 9.1.3.5 of Non-Patent Document 23 (3GPP TS36.423 v14.3.0). By including the information in the configuration items of the modified bearer, it becomes possible to switch, for example, from packet duplication using CA in the SCG bearer to packet duplication using DC in the SCG split bearer.

[0286] As another example, the master base station may include information indicating the type of packet duplication in the configuration items of the released bearer. The configuration items of the released bearer may correspond to the configuration items of the SCG Bearer and Split Bearer in the E-RABs To Be Released Item in Section 9.1.3.5 of Non-Patent Document 23 (3GPP TS36.423 v14.3.0). By including the information in the configuration items of the released bearer, it becomes possible to switch from packet duplication using DC to packet duplication using CA in the MCG bearer, for example.

[0287] The secondary base station may determine whether packet duplication occurs using information indicating the type of packet duplication. For example, the secondary base station may determine that packet duplication will not occur if the information is not included. Alternatively, the information may include a value indicating that packet duplication will not occur. This allows the presence or absence of packet duplication to be handled collectively, thereby reducing the amount of processing.

[0288] In the above, instead of E-RABs To Be Added Item, a configuration item related to the PDU session to be added may be used, or a configuration item related to the radio bearer to be added may be used. The above-mentioned configuration item related to the additional PDU session and / or the additional radio bearer may be newly added. The same may be done for E-RABs To Be Modified Item and E-RABs To Be Released Item. The method described in the second embodiment can also be applied when the master base station is an MgNB. Furthermore, flexible configuration is possible for each PDU session and each radio bearer.

[0289] In the above, the configuration items for the Split Bearer may be configuration items for the MCG Split Bearer, or may be configuration items for the SCG Split Bearer, or may include both. In the above, the configuration items for the Split Bearer may include information indicating the type of split bearer. The type of split bearer may be an MCG split bearer, an SCG split bearer, or an SCG-only split bearer. This makes it possible to avoid complexity in the design of the interface between base stations.

[0290] Alternatively, the setting items for the Split Bearer described above may be divided into (a) setting items for the MCG split bearer, (b) setting items for the SCG split bearer, and (c) setting items for the SCG-only split bearer. By processing bearers of the same type collectively, the amount of processing can be reduced.

[0291] The SgNB change request transmitted from the master base station to the secondary base station may include a radio bearer identifier. The radio bearer identifier may be included in the configuration items of the additional bearer, the modified bearer, or the released bearer. By allowing the secondary base station to uniquely identify the bearer, it is possible to prevent malfunction.

[0292] The SgNB change request transmitted from the master base station to the secondary base station may include an identifier indicating whether to maintain or release the logical channel, an identifier of the logical channel to be maintained, or an identifier of the logical channel to be released. This makes it possible to flexibly switch packet duplication for each logical channel.

[0293] The SgNB change request transmitted from the master base station to the secondary base station may include a cause for the change. The cause may include information indicating packet duplication. The information indicating packet duplication may be information indicating packet duplication setting start, information indicating packet duplication setting change, or information indicating packet duplication release. The above information may be added to the list of causes shown in section 9.2.6 of non-patent document 23 (3GPP TS36.423 v14.3.0). The destination to which the above information is added may be, for example, the Radio Network Layer in the list of causes, or another location. This enables the secondary base station to smoothly perform processing associated with packet duplication.

[0294] The SgNB change request acknowledgement sent from the secondary base station to the secondary base station may include a bearer identifier, and the bearer identifier may be a bearer related to packet duplication switching.

[0295] As with the SgNB change request described above, the secondary base station may include the bearer identifiers in the configuration items for the additional bearer, modified bearer, and released bearer. The configuration items for the additional bearer, modified bearer, and released bearer may correspond to the configuration items for the SCG Bearer and Split Bearer in the E-RABs Admitted To Be Added Item, E-RABs Admitted To Be Modified Item, and E-RABs Admitted To Be Released Item, respectively, in Section 9.1.3.6 of Non-Patent Document 23 (3GPP TS36.423 v14.3.0). This enables bearer identification during packet duplication switching.

[0296] Alternatively, the secondary base station may include the identifier of the bearer in a list of disallowed bearers. The list of disallowed bearers may correspond to, for example, the E-RABs Not Admitted List in section 9.1.3.6 of non-patent document 23 (3GPP TS36.423 v14.3.0). Instead of the E-RABs Not Admitted List, a list of disallowed PDU sessions or a list of disallowed radio bearers may be used. This allows the master base station to exercise control over disallowed bearers.

[0297] In the above, instead of E-RABs Admitted To Be Added Item, a configuration item related to the PDU session to be added may be used, or a configuration item related to the radio bearer to be added may be used. The above-mentioned configuration item related to the additional PDU session and / or the configuration item related to the additional radio bearer may be newly added. The same may be applied to E-RABs Admitted To Be Modified Item and E-RABs Admitted To Be Released Item. The method described in the second embodiment can also be applied when the master base station is an MgNB. Furthermore, flexible configuration is possible for each PDU session and each radio bearer.

[0298] In the above, the configuration items for the Split Bearer may be configuration items for the MCG Split Bearer, or may be configuration items for the SCG Split Bearer, or may include both. In the above, the configuration items for the Split Bearer may include information indicating the type of split bearer. The type of split bearer may be an MCG split bearer, an SCG split bearer, or an SCG-only split bearer. This makes it possible to avoid complexity in the design of the interface between base stations.

[0299] Alternatively, the setting items for the Split Bearer described above may be divided into (a) setting items for the MCG split bearer, (b) setting items for the SCG split bearer, and (c) setting items for the SCG-only split bearer. By processing bearers of the same type collectively, the amount of processing can be reduced.

[0300] The secondary base station may include information about packet duplication in the SgNB change request acknowledgement. In the above, the information about packet duplication may be included in the same location as the bearer identifier described above, or may be included in a location indicating a setting item for the UE, such as SCG-Config.

[0301] The information regarding packet duplication described above may be information indicating whether packet duplication occurs, information indicating the type of packet duplication, or a combination of both. For example, the information indicating the type of packet duplication may include information indicating that packet duplication is not performed.

[0302] Alternatively, the information about packet duplication may include logical channel information, RLC configuration information, or wireless carrier information, or a combination of two or more of the above information.

[0303] The above-mentioned information on packet duplication may be included in information on radio bearers. For example, information on packet duplication may be included in a section corresponding to a list of bearers added and modified in non-patent document 24 (3GPP TS36.331 v14.3.0), such as DRB-ToAddModListSCG-r12. This section may include a combination of logical channel identifiers and RLC setting information, for example, in the form of packetdupListSCG. Radio carrier information may be included in the above combination. Packet duplication using CA can be realized.

[0304] The aforementioned packetdupListSCG may contain one combination. The combination may include information on a logical channel identifier and RLC settings. The combination may be a setting on the secondary base station side in packet duplication using DC. Alternatively, the packetdupListSCG may contain two combinations. The combination may include information on a logical channel identifier, RLC settings, and radio carrier. The combination may be used for packet duplication using CA in an SCG bearer.

[0305] Alternatively, information about packet duplication may be included in the bearer release list in Non-Patent Document 24 (3GPP TS36.331 v14.3.0), for example, in a section corresponding to DRB-ToReleaseListSCG-r12. For example, packet duplication using DC can be switched to packet duplication using CA in the MCG bearer.

[0306] Alternatively, information regarding the combination of logical channels and radio carriers may be included in a MAC configuration item, for example, a section corresponding to MAC-MainConfig in Non-Patent Document 24 (3GPP TS36.331 v14.3.0), which enables a reduction in the amount of processing in the MAC layer.

[0307] The above-mentioned information about packet duplication may be information about packet duplication in the SRB. For example, the above-mentioned SCG-Config may include information about packet duplication in the SRB. This can improve the reliability of communication in the C-Plane.

[0308] The information included in the notification of the SgNB change request transmitted from the secondary base station to the master base station may be the same as the information included in the SgNB change request acknowledgement. This makes it possible to avoid design complexity related to packet duplication switching.

[0309] The information included in the SgNB reconfiguration completion transmitted from the master base station to the secondary base station may be the same as the information included in the SgNB change request acknowledgement. The SCG-Config in the SgNB change request acknowledgement may be replaced with SCG-ConfigInfo. This makes it possible to avoid design complexity related to packet duplication switching.

[0310] The information included in the notification of SgNB reconfiguration completion transmitted from the master base station to the secondary base station may be the same as the information included in the notification of SgNB reconfiguration completion. This makes it possible to avoid design complexity related to packet duplication switching.

[0311] The above-mentioned RRC connection reconfiguration transmitted from the master base station to the UE may include information regarding packet duplication. The information regarding packet duplication may be the same as the information included in the above-mentioned SgNB change request acknowledgement. The master base station may add RRC configuration regarding communication with the master base station to the above-mentioned information regarding packet duplication. The above-mentioned RRC configuration regarding communication with the master base station may be configuration regarding packet duplication using the master base station.

[0312] The master base station may include information regarding packet duplication as, for example, the aforementioned packetdupListSCG. Two combinations may be included in packetdupListSCG. The combination may include information on a logical channel identifier and RLC settings. The combination may include information on a wireless carrier. By including information on a wireless carrier, packet duplication using CA is realized. Both pieces of information included in the combination may be settings for communication between the UE and the master base station. Packet duplication using CA in an MCG bearer is realized. One piece of information may be settings for communication between the UE and the master base station, and the other piece of information may be settings for communication between the UE and a secondary base station. Packet duplication using DC is realized. Alternatively, both pieces of information may be settings for communication between the UE and a secondary base station. Packet communication using CA in an SCG bearer is realized.

[0313] The packet duplication switching method shown in the second embodiment may be applied to setting up packet duplication or to releasing packet duplication. By standardizing the signaling related to packet duplication, it is possible to avoid design complexity.

[0314] The packet duplication and switching method shown in the second embodiment may be applied to multi-connectivity, which makes it possible to improve the reliability of packet transmission and reception in multi-connectivity.

[0315] In packet duplication in multi-connectivity, a split bearer passing through two base stations may be used. In the above, information regarding packet duplication may be included in the RRC connection reconfiguration notified from the master base station to the UE. The information may include information for identifying the SCG. As the information, a new SCG identifier may be provided, or the identifier of the secondary base station may be used. The UE may identify the SCG from the identifier of a cell belonging to the SCG. The above-mentioned cell identifier may be, for example, the identifier of the PSCell or the identifier of the SCell in the SCG.

[0316] In packet duplication in multi-connectivity, a split bearer passing through three or more base stations may be used. In the above, information regarding packet duplication may be included in the RRC connection reconfiguration notified from the master base station to the UE. The information may include the information for identifying the SCG described above. The information regarding packet duplication may include three or more combinations of logical channel identifiers and RLC configuration information. For example, the packetdupListSCG described above may include three or more combinations. Each combination may be a logical channel and RLC configuration used in each base station.

[0317] In packet duplication in multi-connectivity, the UE may start / stop packet duplication using MAC signaling from any base station. The MAC signaling may include information on the logical channel to be started / stopped. Information on the base station using the logical channel may be used. As the base station information, a base station identifier, for example, a gNB-ID, a PCell or PSCell identifier, an MCG-ID or an SCG-ID may be used. MCG-ID and / or SCG-ID may be newly provided. This makes it easier for the UE to start / control packet duplication.

[0318] Alternatively, in the above-mentioned MAC signaling, the base station that uses each logical channel may individually notify the UE of the start / stop of that logical channel, which makes it possible to reduce the amount of MAC signaling.

[0319] In the second embodiment, it is not necessary to include information about logical channels. For example, when setting packet duplication using DC or when switching to packet duplication using DC, it is not necessary to include information about logical channels. This makes it possible to reduce the size of signaling.

[0320] In the second embodiment, the UE may receive signals from all base stations that make up the DC / MC. The signals may be, for example, MAC signaling. This makes it easier to control packet duplication.

[0321] In the above, the UE may receive signals from all carriers used by the UE in each base station. The signals may be, for example, MAC signaling. This allows for increased flexibility in scheduling in the base station. Alternatively, the UE may receive signals, for example, MAC signaling, from some of the carriers used by the UE in each base station. The some carriers may be, for example, PCell or PSCell. The base station and the UE may transmit and receive the MAC signaling using PCell and / or PSCell. This allows for reduced power consumption in the UE.

[0322] Alternatively, in the second embodiment, the UE may receive a signal, for example, MAC signaling, from the base station that transmits the packet during the packet duplication operation, thereby enabling a reduction in power consumption in the UE.

[0323] In the above, the UE may receive signals, for example, MAC signaling, from all carriers used by the UE in each base station. This allows for increased flexibility in scheduling in the base station. Alternatively, the UE may receive signals, for example, MAC signaling, from some of the carriers used by the UE in each base station. The some carriers may be, for example, a PCell or a PSCell. The base station and the UE may transmit and receive the MAC signaling using the PCell and / or the PSCell. This allows for further reduction in UE power consumption.

[0324] Alternatively, in this second embodiment, the UE may receive a signal, for example, MAC signaling, from the master base station. This allows for a reduction in power consumption in the UE and facilitates control in the master base station.

[0325] In the above, the UE may receive signals, for example, MAC signaling, from all carriers used by the UE in the master base station. This allows for increased flexibility in scheduling in the master base station. Alternatively, the UE may receive signals, for example, MAC signaling, from some of the carriers used by the UE in the master base station. The some carriers may be, for example, the PCell. The base station and the UE may transmit and receive the MAC signaling using the PCell. This allows for further reduction in UE power consumption.

[0326] According to the second embodiment, it is possible to switch between packet duplication using CA and packet duplication using DC, thereby ensuring the reliability of communication when, for example, a UE is moving. Also, it is possible to improve the throughput.

[0327] Embodiment 3 It is proposed that data in the RLC layer be cleared when packet duplication is stopped (see Non-Patent Document 20 (R2-1704836)). It is also proposed that start / stop control from the base station to the UE is not performed for downlink packet duplication (see Non-Patent Document 21 (R2-1702753)).

[0328] In addition, in RLC-AM, the RLC entities on the transmitting side and receiving side are integrated (see Non-Patent Document 17 (TS36.322 v14.0.0)).

[0329] However, in packet duplication using RLC-AM, for example, packet duplication in SRB, a problem occurs in that stopping upstream packet duplication also erases the RLC layer buffer for downstream packet duplication.

[0330] In the third embodiment, a method for solving such a problem will be disclosed.

[0331] The UE clears only the buffers on the RLC-AM transmission side. The base station clears only the buffers on the RLC-AM transmission side. The clearing of the buffers in the UE and / or the base station may be performed when uplink packet duplication is stopped.

[0332] The UE may clear the RLC-AM transmitter variables and transmission window.

[0333] Alternatively, the base station may control both downstream and upstream packet duplication simultaneously. Simultaneous downstream and upstream control may be used for packet duplication using RLC-UM and / or RLC-TM.

[0334] The method shown in the third embodiment makes it possible to prevent the buffer from being cleared when downstream packets are copied by stopping upstream packet copying, thereby ensuring the continuity of data.

[0335] Embodiment 4 In NR, the RRC_INACTIVE state has been newly introduced as a UE state (see Non-Patent Document 9 (3GPP TR38.804 V14.0.0)). Also, in NR, it has been proposed to support small data transmission from a UE in the RRC_INACTIVE state (see Non-Patent Document 9 (3GPP TR38.804 V14.0.0)).

[0336] However, there is no discussion as to whether packet duplication described in the first and second embodiments is supported for small data transmission from a UE in the RRC_INACTIVE state. Therefore, when a UE that performs transmission using packet duplication transitions to the RRC_INACTIVE state, the small data transmission method becomes unclear, and a problem occurs in that the UE cannot transmit the small data to the base station.

[0337] In the fourth embodiment, a method for solving such a problem will be disclosed.

[0338] The UE does not support packet duplication in RRC_INACTIVE state.

[0339] The UE may retain the configuration related to packet duplication. The configuration may be retained when the UE transitions to the RRC_INACTIVE state. The configuration may be related to packet duplication using DC or related to packet duplication using CA. This allows packet duplication to be quickly resumed when the UR transitions to RRC_CONNECTED again.

[0340] The UE may stop packet duplication. The UE may stop packet duplication when the UE transitions to the RRC_INACTIVE state. The UE may autonomously stop the packet duplication, or the base station or the master base station may instruct the UE to do so. The instruction may use the MAC signaling for stopping packet duplication described in the first embodiment. Alternatively, the instruction may be included in an RRC_INACTIVE state transition instruction from the base station or the master base station to the UE.

[0341] The UE may release the settings related to packet duplication. The settings may be released when the UE transitions to the RRC_INACTIVE state. The UE may release the settings autonomously, or the base station or the master base station may instruct the UE to release the settings. The UE may release the settings related to packet duplication together with the release of the DC settings or the CA settings. This makes it possible to reduce the memory usage of the UE in the RRC_INACTIVE state.

[0342] As another example, the base station or the master base station may notify the UE whether to maintain or release the packet duplication setting. The base station or the master base station may include the above-mentioned notification of maintenance / release in an RRC_INACTIVE transition instruction to the UE. For example, the instruction may include an identifier indicating whether to maintain or release the packet duplication setting. This allows the base station or the master base station to flexibly configure the setting according to, for example, the radio channel conditions.

[0343] The base station or the master base station may set the maintenance / release of the packet duplication setting for each bearer, enabling flexible operation of packet duplication for each bearer.

[0344] Four examples (1) to (4) of the method for notifying the UE of the above-mentioned maintenance / release of the packet duplication setting for each bearer from the base station or the master base station will be disclosed below.

[0345] (1) Determined by standards.

[0346] (2) Common signaling.

[0347] (3) Individual signaling.

[0348] (4) A combination of (1) to (3) above.

[0349] In the above (1), for example, maintaining / releasing may be determined for each bearer type. For example, SRB may maintain the packet duplication setting, and DRB may release the packet duplication setting. Alternatively, for example, SRB0 may maintain the packet duplication setting, SRB1 may release it, SRB2 may maintain it, SRB3 may release it, and DRB may release it. This makes it possible to reduce the amount of signaling.

[0350] In the above (2), the base station or the master base station may notify the maintenance / release using system information, which makes it possible to reduce the amount of signaling.

[0351] In the above (3), the base station or the master base station may notify the UE of the maintenance / release using, for example, RRC dedicated signaling. The RRC dedicated signaling may be an RRC_INACTIVE transition instruction to the UE or other RRC dedicated signaling. The RRC dedicated signaling may include an identifier of a bearer for maintaining packet duplication configuration, an identifier of a bearer for releasing packet duplication configuration, or both identifiers. This allows flexible configuration of maintaining / releasing packet duplication for each bearer.

[0352] In the above (3), the maintenance / release of the packet duplication setting may be notified for each bearer type. The maintenance / release of packet duplication for each bearer type may be the same as that shown in the above (1). This allows flexible setting for each bearer type.

[0353] In the above (4), for example, the maintenance / release of the packet duplication setting in each SRB may be defined in the standard. The maintenance / release of the packet duplication setting in each DRB may be notified individually from the base station or the master base station to the UE. This makes it possible to reduce the amount of signaling while increasing the flexibility of the setting for each DRB.

[0354] The UE may perform small data transmission using packet duplication. The small data transmission may be performed after transitioning to the RRC_CONNECTED state. The UE may retain the packet duplication setting. The setting may be retained when the UE transitions to the RRC_INACTIVE state. This facilitates control of the UE regarding data transmission.

[0355] The UE may start a packet duplication operation. The above-mentioned packet duplication operation may be started after the UE transitions to the RRC_CONNECTED state. The UE may autonomously start the packet duplication operation. For example, the UE may start the packet duplication operation using information that holds the packet duplication operation / stop state described in the first embodiment. Alternatively, the UE may start the packet duplication operation using a packet duplication operation start instruction from the base station or the master base station. The above-mentioned packet duplication operation start instruction may be included in an RRC_CONNECTED transition instruction from the base station or the master base station to the UE, or may be notified separately from the RRC_CONNECTED transition instruction. The above-mentioned packet duplication operation start instruction may be notified to the UE from the base station or the master base station using MAC signaling described in the first embodiment.

[0356] The UE may release the packet duplication setting during cell reselection. Alternatively, the UE may release the packet duplication setting when transitioning to the RRC_IDLE state. The UE may release the setting autonomously or in response to an instruction from the base station or the master base station. This can reduce the memory usage of the UE during cell reselection and / or in the RRC_IDLE state.

[0357] According to this fourth embodiment, it is possible to prevent UE from performing erroneous operations regarding small data transmission when inactive.

[0358] Embodiment 5. In transmitting data to a secondary base station in the RRC_INACTIVE state described in the fourth embodiment, it is proposed to perform SCG addition after returning from the RRC_INACTIVE state and transmit data to the secondary base station (see Non-Patent Document 25 (R2-1704425)). As another method, Early SCG bearer configuration is proposed, in which SCG addition is performed in conjunction with returning from the RRC_INACTIVE state (see Non-Patent Document 26 (R2-1704420)).

[0359] However, in the two methods described above, the UE waits for the SCG to be added before transmitting data to the secondary base station, which causes a problem of delay in starting data transmission from the UE to the secondary base station.

[0360] In the fifth embodiment, a method for solving such a problem will be disclosed.

[0361] The UE transmits data to the secondary base station via the master base station. The data may be transmitted using an SCG split bearer. The master base station forwards the data to the secondary base station. The forwarding may be performed using an inter-base station interface, such as an X2 interface.

[0362] In the fifth embodiment, the master base station may switch the SCG bearer to an SCG split bearer. The master base station may notify the secondary base station of a request for the above-mentioned switch. The secondary base station may notify the master base station of a response to the request. The master base station may perform the above-mentioned switch simultaneously with an RRC_INACTIVE state transition instruction to the UE, or may perform the switch separately from the state transition instruction. The master base station may include the above-mentioned switch instruction in the RRC_INACTIVE state transition instruction to the UE. The above-mentioned switch instruction may include an identifier of the SCG bearer. This enables quick data transmission from the UE to the secondary base station for the SCG bearer as well.

[0363] Fig. 15 is a sequence diagram showing small data transmission from a UE in the RRC_INACTIVE state to a secondary base station. Fig. 15 shows an example in which the master base station is an eNB and the secondary base station is a gNB. The master base station may be a gNB. The secondary base station may also be an eNB. Fig. 15 also shows an example in which the UE transitions to the RRC_CONNECTED state after transmitting the small data, but the UE may remain in the RRC_INACTIVE state.

[0364] In Step ST3001 shown in FIG. 15, a UE in an RRC_INACTIVE state starts a random access process with the master base station. In Step ST3001, the UE transmits a random access preamble (RA preamble) to the master base station. In Step ST3002, the master base station transmits a random access response (RA response) to the UE. This response includes an uplink grant to the UE.

[0365] In Step ST3003 shown in FIG. 15, the UE transmits an RRC connection resume request (RRCConnectionResumeRequest) to the master base station.

[0366] In Step ST3005 shown in Fig. 15, the UE transmits uplink data intended for the secondary base station to the master base station. In Step ST3006, the master base station transmits the uplink data to the secondary base station.

[0367] In Step ST3007 shown in FIG. 15, the master base station notifies the UE of RRC connection recovery (RRCConnectionResume). In Step ST3008, the UE notifies the master base station of RRC connection recovery completion (RRCConnectionResumeComplete). In Step ST3008, the UE transitions to the RRC_CONNECTED state.

[0368] By using the method disclosed in this embodiment, the UE can quickly transmit data to the secondary base station in the INACTIVE state.

[0369] Embodiment 6 MC has been proposed as a 5G technology in 3GPP (see Non-Patent Document 27 (R2-167583)). As MC, it is being discussed that one UE is configured to be connected to one master base station and multiple secondary base stations. Also, support for MCG split bearers and SCG bearers has been proposed as MC. Note that a group consisting of cells of an MeNB is called an MCG. A group consisting of cells of an SgNB is called an SCG.

[0370] However, for an MC when there are two or more secondary base stations, the architecture including the upper network device (hereinafter also referred to as upper network) and the method of configuring the MC, for example, how to configure multiple secondary base stations, are not disclosed. In the sixth embodiment, the architecture including the upper network and the method of configuring the MC are disclosed.

[0371] Figure 16 is a diagram showing the architecture of an MC. The upper network is an EPC, the master base station is an LTE base station (eNB), and the secondary base station is an NR base station (gNB). The LTE master base station is called an MeNB, and the NR secondary base station is called an SgNB. The protocol configuration of the eNB consists of PDCP, RLC, MAC, and PHY. The protocol configuration of the gNB consists of a New AS sublayer, PDCP, RLC, MAC, and PHY. A New AS sublayer is provided above PDCP.

[0372] Figure 16 shows the architecture on the base station side, but the architecture on the UE side is similar except for the upper network. In one UE, PDCP is configured, RLC, MAC, and PHY for the MeNB are configured, and RLC, MAC, and PHY for each SeNB set for MC are configured.

[0373] Figure 16 shows the case where an MCG split bearer is used. The upper network is connected to the MeNB, and the SgNB for MC is connected to the MeNB. Downlink data is processed by PDCP in the MeNB. Even if there are multiple SgNBs, PDCP assigns a single consecutive sequence number (SN) to each piece of data. The data assigned an SN is split to the MeNB and each SgNB. The split data is sent to the RLC of the MeNB and each SgNB, processed by the RLC, MAC, and PHY of the MeNB and each SgNB, and then sent to the UE.

[0374] Data received by the UE from the MeNB and each SgNB is processed by the PHY, MAC, and RLC for the MeNB and each SgNB, and then forwarded to the PDCP. PDCP performs reordering based on the SN assigned to the data forwarded from the MeNB and each SgNB, and forwards the data to higher layers.

[0375] For uplink data, the UE processes data from higher layers using PDCP. As with downlink, even if there are multiple SgNBs, PDCP assigns a single consecutive sequence number (SN) to each piece of data for uplink. The data with the SN assigned is split and transferred to the RLC for the MeNB and each SgNB. The transferred data is processed by the RLC, MAC, and PHY for the MeNB and each SgNB, and then sent to the MeNB and each SgNB.

[0376] The data received by the MeNB and each SgNB from the U is processed by the PHY, MAC, and RLC for the MeNB and each SgNB, and then forwarded to the PDCP of each MeNB. The PDCP of the MeNB performs reordering based on the SN assigned to the data and forwards the data to the upper NW.

[0377] A method for configuring multiple SCGs for MC is disclosed. The MeNB configures an SCG for MC for the UE. A radio bearer for MC is configured in the SCG configuration. RRC signaling may be used for this notification.

[0378] SCGs are configured one by one. Multiple SCGs for MC are configured using one SCG configuration. It is recommended to configure one SCG for each SCG for MC. Signaling for SCG configuration is performed from the MeNB to the UE for each SCG configured. In the case of DC, only one SCG is connected, so when connecting another SCG after one SCG has been configured, it was necessary to release the previously configured SCG. In contrast, additional SCGs are configured without releasing the previously configured SCG. In this way, the MeNB can configure multiple SCGs for the UE.

[0379] Information indicating that the SCG has been additionally configured while maintaining the previous SCG configuration may be provided. The MeNB notifies the UE of this information. The information may be included in the SCG configuration and notified. As another method, signaling for additionally configuring the SCG while maintaining the previous SCG configuration may be provided. By providing this separate signaling, when the MeNB has configured one SCG through this signaling, the UE can recognize that the SCG has been additionally configured while maintaining the previous SCG configuration.

[0380] As the RRC signaling, for example, RRCConnectionReconfiguration for setting up an RRC connection may be used. For example, the SCG-ConfigPartSCG in the signaling may include the SCG configuration and the bearer configuration for performing MC. The bearer configuration may include a bearer identifier, a bearer AS setting, etc.

[0381] In the case of DC, only an MCG and one SCG are configured for one bearer. When multiple SCGs are configured in an MC, multiple SCGs may be configured for one bearer. When configuring an SCG configuration for the second or subsequent time, the bearer configured with the previous SCG configuration may be used. The same bearer identifier may also be configured. In this way, the UE can recognize that multiple SCG configurations have been configured for the bearer.

[0382] The bearer configuration may be different for each SCG for MC. When configuring a second or subsequent SCG configuration, if the bearer identifier configured with the previous SCG configuration is configured, one or more parameters of the AS configuration for the bearer of the previously configured bearer identifier may be omitted. If a parameter is omitted, it shall be the parameter of the AS configuration for the bearer of the same bearer identifier.

[0383] An SCG identifier may be provided. The SCG identifier may be included as information on the SCG configuration in the SCG configuration. The SCG identifier may be used to configure an SCG with the same AS parameters for the bearer. For example, the SCG identifier may be included in the bearer configuration. This allows the UE to recognize that the bearer configuration configured in the SCG is the bearer configuration configured in the SCG indicated by the SCG identifier. In this way, it is possible to make the AS parameters for the bearer configured in the SCG the same as the AS parameters for the bearer configured in any SCG.

[0384] By doing so, when the AS parameters for the bearer set in each SCG for MC are the same, it is possible to omit the parameters or set the parameters with a small amount of information, thereby reducing the radio resources required for notification from the MeNB to the UE.

[0385] Although it has been disclosed that an SCG identifier may be provided, an SgNB identifier may also be provided. An identifier indicating an SCG or a set of SgNBs may also be provided. By providing such an identifier, when MC is configured in multiple SgNBs, the UE can recognize the configuration for each SgNB or each set of SgNBs, rather than for each cell. For example, this is effective when changing the configuration for each SgNB or each set of SgNBs. This reduces the information notified from the MeNB to the UE.

[0386] Figures 17 and 18 are diagrams showing an example of a sequence for setting up an MC. Figures 17 and 18 are connected at the position of boundary line BL1718. Figures 17 and 18 show a case where an MeNB and two SgNBs (SgNB1, SgNB2) are used. Figures 17 and 18 show a case where an MCG split bearer is used. In Step ST4201, data communication is performed between the UE and the MeNB. In Step ST4202, the MeNB determines to perform DC for the UE. The method disclosed in Non-Patent Document 1 (TS36.300) may be applied to the DC setting process. Steps ST4203 to ST4213 show the DC setting process.

[0387] In step ST4210, the MeNB routes data between the MeNB itself and the SgNB1 in which DC is configured. Here, since there is only one secondary base station to connect to, data from the upper network is processed by the PDCP of the MeNB, and then split and forwarded to the MeNB itself and the SgNB1, as in the conventional DC. In addition, data received from the UE by the MeNB itself and the SgNB1 is forwarded to the MeNB, processed by the PDCP of the MeNB, and forwarded to the upper network.

[0388] The same is true on the UE side.

[0389] In Step ST4214, the MeNB determines to configure MC for the UE. The MeNB decides to connect the UE to SgNB2 while maintaining the connection to SgNB1. In Step ST4215, the MeNB notifies SgNB2 of a request to add an SgNB. This signaling may be performed in accordance with Step ST4203 in the DC configuration process. The MeNB may set the bearer configuration of the SgNB2 to be added as the same as the bearer configuration of its own eNB (MeNB). Alternatively, the MeNB may determine the bearer configuration of the SgNB2 in consideration of the bearer configuration of its own eNB (MeNB) and the bearer configuration of SgNB1. The bearer for performing MC may be configured so as to satisfy the QoS set by the upper network.

[0390] The SgNB2 determines the AS configuration according to the bearer configuration indicated in the SgNB addition request from the MeNB. In Step ST4216, the SgNB2 notifies the MeNB of the determined AS configuration. In Step ST4217, the MeNB notifies the UE of the MC configuration. As the MC configuration, the MeNB notifies the UE of the SCG configuration of the SgNB2 to be added and the configuration of the bearer for performing MC. As signaling, RRCConnectionReconfiguration for configuring an RRC connection may be used.

[0391] Furthermore, in Step ST4217, the MeNB may notify the UE of information indicating that an SCG additional configuration is being performed while maintaining the SCG configuration of the previously configured SgNB1. By explicitly indicating this information, the UE can clearly recognize that the configuration is to connect to SgNB2 while remaining connected to SgNB1, and the occurrence of malfunction can be reduced.

[0392] The UE that has received the SCG additional configuration of the SgNB2 in Step ST4217 configures MC for the SgNB2 in addition to the MeNB and SgNB1 in accordance with the configuration. In Step ST4218, the UE notifies the MeNB of an RRC connection reconfiguration complete (RRCConnectionReconfiguration Complete) including the MC configuration completion.

[0393] In Step ST4219, the MeNB, which has recognized that the UE has completed the MC configuration, notifies the SgNB2 of the signaling indicating that the additional configuration of the SCG of the SgNB2 has been completed. The SgNB2 recognizes that a connection for MC has been configured with the UE.

[0394] In Step ST4220, the UE starts RA processing with the SgNB2. The settings for RA processing of the SgNB2 are notified in the AS configuration from the SgNB2 in Steps ST4216 and ST4217. Having obtained synchronization through the RA processing, the UE starts data communication with the SgNB2 in Step ST4221.

[0395] It is advisable to provide the MeNB with a routing function to multiple SgNBs. Since only one SgNB is connected in DC, the data split to the SgNB side only needs to be forwarded to that single SgNB. Since the MC is connected to multiple SgNBs, the MeNB needs to determine to which SgNB the data split to the SgNB side should be forwarded. For this reason, the MeNB is provided with a routing function that determines the SgNB to which the data should be forwarded and forwards the data to that SgNB.

[0396] The routing function may also have the function of forwarding data received from the UE at its own MeNB and data received at multiple SgNBs and forwarded to the MeNB to the PDCP of the MeNB.

[0397] The routing function may be provided within the PDCP of the MeNB. The routing function may be provided at the lowest level of the PDCP function. Alternatively, the routing function may be provided separately from the PDCP. Although the routing function is disclosed as being provided separately from the splitting function, as an alternative, the routing function may be provided as part of the splitting function. Instead of splitting and then routing, the function may split between the MeNB and multiple SgNBs.

[0398] The routing function may be performed for each data. Routing is performed to each SgNB for each data. Alternatively, the same routing may be performed for a predetermined period. Data for a predetermined period is routed to the same SgNB. In this way, flexible routing can be implemented. Routing suitable for the communication quality status of each SgNB is possible.

[0399] The same is true on the UE side.

[0400] In Step ST4222, the MeNB routes data between its own MeNB and SgNB1 and SgNB2 for which MC configuration has been performed. Since there are two secondary base stations to connect, the data from the upper NW is processed by the PDCP of the MeNB, and then split and forwarded to its own MeNB and the SgNB side. The data split to the SgNB side is routed and forwarded to SgNB1 and SgNB2 by the routing function.

[0401] In addition, data received from the UE by SgNB1 and SgNB2 is forwarded to the MeNB, and then forwarded to the PDCP of the MeNB by the routing function together with data received by the MeNB. The data forwarded to the PDCP is processed by the PDCP and forwarded to the upper network.

[0402] In this way, it becomes possible to perform MC using multiple SgNBs. The MeNB can configure MC using multiple SgNBs for the UE. The UE can perform MC by connecting to the MeNB and the configured multiple SgNBs.

[0403] When deactivating the SgNB configuration, it is advisable to deactivate the SCG configuration of the SgNB where the MC is configured one by one.

[0404] In this way, by configuring or canceling secondary base stations that perform MC one by one, it becomes possible to configure an appropriate SgNB for the UE depending on the radio wave propagation conditions of the MeNB and each SgNB, thereby providing high throughput to the UE.

[0405] Furthermore, by configuring or canceling secondary base stations that perform MC one by one, even if the additional configuration of an SgNB for MC fails midway, it is possible to maintain the previously successful configuration of the SgNB for MC and perform MC using that SgNB configuration. It is possible to perform the additional configuration of the next SgNB again from the successful configuration of the SgNB for MC. This makes it possible to build a robust and stable system even when the additional configuration of an SgNB fails.

[0406] Another method for configuring multiple SCGs for MC is disclosed. The MeNB configures an SCG for MC for the UE. In the SCG configuration, a radio bearer for MC is configured. RRC signaling may be used for this notification.

[0407] Multiple SCGs are configured. Multiple SCGs for MC are configured in one configuration. The MeNB performs signaling to the UE for multiple SCG configuration. Signaling for multiple SCG configuration may also be provided for MC. In this way, the MeNB can configure multiple SCGs for the UE.

[0408] If DC has been configured before, you may release the previous DC setting and then configure multiple SCGs for MC in one configuration. Also, if MC has been configured before and you want to perform MC using the SCG of a different SgNB next, you may release the previous MC setting and then configure a new MC in one configuration.

[0409] The release of the previous DC or MC configuration may be performed separately from the signaling for the multiple SCG configuration for the MC. Alternatively, the release of the previous DC or MC configuration may be performed using the same signaling as the signaling for the multiple SCG configuration for the MC. This reduces the amount of signaling and the control delay.

[0410] As the RRC signaling, for example, RRCConnectionReconfiguration for configuring an RRC connection may be used. For example, the signaling may include information on multiple SCGs to be configured. A list may be used as the information on multiple SCGs. For example, a list of multiple SCGs to be configured may be provided, and the list may include configuration information for each SCG equal to the number of configured SCGs. The configuration information for each SCG may be set, for example, by the above-mentioned SCG-ConfigPartSCG.

[0411] An identifier may be provided for a set of multiple SCGs to be configured. An identifier may be provided for a set of multiple SgNBs to be configured. For example, when multiple SCG settings for MC are to be released at once, the identifier of the set of SCGs assigned at the time of setup can be included in the signaling for SCG release, thereby reducing the amount of information required for setup.

[0412] The UE may store identifiers of a plurality of SCG sets in association with the SCGs of the SgNBs included in the SCG sets. The UE may discard the stored information when the state with the base station becomes an idle state. The UE may maintain the stored information when the state with the MeNB is a connected state and an inactive state, or when the state with the MeNB is a connected state or an inactive state.

[0413] For example, when multiple SCGs for MC are to be added together after the MC configuration is released, the signaling for the additional configuration includes an identifier of the set of multiple SCGs previously configured. The UE can recognize the SCG configuration of the SgNB included in the set of SCGs from the identifier of the set of multiple SCGs previously notified by the MeNB. This makes it possible to reduce the amount of information required for the additional configuration.

[0414] The information of each of the multiple SCGs configured for MC may include an SCG configuration and a configuration of a bearer for performing MC. The bearer configuration may include a bearer identifier, a bearer AS configuration, etc. The bearer may be configured in the same manner as described above. Also, as described above, each SCG may include SCG identifier information. In this way, the MeNB can configure the SCG configurations of multiple SgNBs for MC for the UE at once.

[0415] 19 and 20 are diagrams showing an example of a sequence for setting up an MC. FIG. 19 and FIG. 20 are connected at the position of boundary line BL1920. FIG. 19 and FIG. 20 show a case where an MeNB and two SgNBs (SgNB1, SgNB2) are used. FIG. 19 and FIG. 20 show a case where an MCG split bearer is used. FIG. 19 and FIG. 20 show a method for setting up SCGs of multiple SgNBs for MC at one time. The sequences shown in FIG. 19 and FIG. 20 include the same steps as the sequences shown in FIG. 17 and FIG. 18, so the same step numbers are assigned to the same steps and common explanations will be omitted.

[0416] In Step ST4301, the MeNB determines whether to perform MC using multiple SgNBs for the UE. Here, the MeNB determines that MC will be performed using SgNB1 and SgNB2. In Steps ST4203 and ST4215, the MeNB notifies SgNB1 and SgNB2 of an SgNB addition request. In Steps ST4204 and ST4216, SgNB1 and SgNB2 notify the MeNB of the AS configuration decided in response to the addition request.

[0417] In Step ST4302, the MeNB notifies the UE of MC configuration. As the MC configuration, the MeNB notifies the UE of the SCG configuration of multiple SgNBs for MC and the configuration of the bearer performing MC. As signaling, RRCConnectionReconfiguration for setting up an RRC connection may be used.

[0418] Furthermore, in Step ST4302, if DC or MC has been configured previously, the MeNB may also notify the UE of the release of the configuration. By making the notification, it becomes possible to collectively configure SCGs for multiple SgNBs for MC. The UE can clearly recognize that the configuration is for connecting to SgNB1 and SgNB2 for MC, which can reduce the occurrence of malfunctions.

[0419] The UE that has received the SCG additional configuration of SgNB1 and SgNB2 in Step ST4302 configures MC for the MeNB, SgNB1, and SgNB2 in accordance with the configuration. In Step ST4303, the UE notifies the MeNB of an RRC connection reconfiguration complete (RRCConnectionReconfiguration Complete) including the MC configuration completion.

[0420] The MeNB, which has recognized that the UE has completed the MC configuration, notifies SgNB1 of signaling indicating that the additional configuration of the SCG of each SgNB has been completed in Step ST4207, and notifies SgNB2 of signaling indicating that the additional configuration of the SCG of each SgNB has been completed in Step ST4219. SgNB1 and SgNB2 recognize that a connection for MC has been configured with the UE.

[0421] In steps ST4208 and ST4220, the UE starts RA processing with SgNB1 and SgNB2. The settings for RA processing of SgNB1 are notified in steps ST4204 and ST4302 as part of the AS configuration from SgNB1. The settings for RA processing of SgNB2 are notified in steps ST4216 and ST4302 as part of the AS configuration from SgNB2. The UE that has achieved synchronization through RA processing starts data communication with SgNB1 and SgNB2 in steps ST4209 and ST4221.

[0422] Steps ST4222 to ST4226 are the same as those in FIGS. 17 and 18, and therefore their explanation will be omitted here.

[0423] In this way, it becomes possible to perform MC using multiple SgNBs. The MeNB can configure MC using multiple SgNBs for the UE. The UE can perform MC by connecting to the MeNB and the configured multiple SgNBs.

[0424] When canceling the SCG configuration of multiple SgNBs, all SCG configurations of the SgNBs where MC is configured are canceled at once. The SCG configurations of multiple SgNBs are canceled with a single signaling from the MeNB to the UE.

[0425] In this way, by simultaneously configuring or canceling secondary base stations that perform MC, the amount of signaling can be reduced. Also, it is possible to control the configuration or cancellation of MC with low latency. This makes it possible to configure an appropriate SgNB for a UE in response to rapid changes in the radio wave propagation conditions of the MeNB and each SgNB. This makes it possible to provide high throughput to the UE.

[0426] As methods for setting or canceling multiple SCGs for an MC, a method for setting or canceling SCGs one by one and a method for setting or canceling multiple SCGs for an MC in a single setting have been disclosed. These methods may be combined as appropriate. For example, instead of setting SCGs one by one, multiple SCGs may be set. Multiple SCGs are set for the same bearer. As a method for setting multiple SCGs, it is preferable to use a method for setting multiple SCGs for an MC in a single setting.

[0427] The information may include information indicating whether the SCG is additionally configured while maintaining the previous SCG configuration. The UE can recognize that the configuration of multiple SCGs for MC performed at one time is additionally configured while maintaining the previous SCG configuration.

[0428] In such a case, information for canceling the configuration for MC and information for canceling the configuration of one or more SCGs may be provided separately. The information for canceling the configuration for MC may be information for canceling the current bearer type. Such information may be used, for example, to cancel an MCG split bearer. The information for canceling the configuration of one or more SCGs may be information for canceling the configuration of the one or more SCGs from MC, i.e., information for excluding them from the SCG of the SgNB performing MC. The SCG may be identified using an SCG identifier.

[0429] The MeNB may use the above information appropriately depending on the situation. The MeNB sets the above information to the UE depending on whether it is to cancel the configuration for MC or to cancel the configuration of one or more SCGs. The UE that receives the above information can determine whether it is to cancel the configuration for MC or to cancel the configuration of one or more SCGs.

[0430] For example, when multiple SCGs are configured and a notification of the release of the configuration for MC is received, the UE releases the configuration for all SCGs and releases the MC configuration. The UE releases the bearer type for which the MC was configured. For example, when multiple SCGs are configured and a notification of the release of one or more SCG configurations is received, the UE releases the configuration for those SCGs. However, the MC configuration is not released. The bearer type for which the MC was configured is not released. The UE continues to perform MC using the remaining SCGs.

[0431] This allows flexible configuration of the SCG for MC. MC using an appropriate SgNB can be flexibly configured depending on the UE's movement speed, the status of the services provided, the location of the base station, changes in the radio wave propagation environment between the UE and the base station, etc. This can improve throughput.

[0432] Another method for configuring multiple SCGs for MC is disclosed. The MeNB configures a radio bearer for MC for the UE. The SCG for MC is configured in the radio bearer configuration. RRC signaling may be used to notify the configuration.

[0433] The MeNB configures the SCG of one or more SgNBs for the radio bearer that performs MC for the UE. If there are many secondary base stations that can be connected for MC of the UE, it is possible to configure many SgNBs' SCGs at once for one or more bearers, which reduces the amount of signaling.

[0434] As the RRC signaling, for example, RRCConnectionReconfiguration for setting up an RRC connection may be used. For example, the signaling may include information on one or more radio bearers to be configured by the MC. A list may be used as the information on one or more radio bearers. For example, a list of one or more radio bearers to be configured by the MC may be provided, and the list may include the SCG configuration for each radio bearer and the bearer configuration for each SCG for the number of radio bearers to be configured by the MC. The SCG configuration and bearer configuration information for each radio bearer may be configured, for example, by the above-mentioned SCG-ConfigPartSCG.

[0435] The information of one or more radio bearers configured in the list may include a radio bearer identifier. In this case, the radio bearer identifier may not be included in the above-mentioned SCG-ConfigPartSCG. Alternatively, the information of one or more radio bearers configured in the list may not include a radio bearer identifier. In this case, it is preferable to include the radio bearer identifier in the above-mentioned SCG-ConfigPartSCG. Providing the radio bearer identifier in this way makes it easier to configure the radio bearer for MC.

[0436] The bearer configuration information for each SCG may include an SCG identifier that makes the bearer configuration the same. If an SCG identifier is included as bearer configuration information notified from the MeNB, the UE can determine that the same configuration as the bearer configuration for the SCG of the SCG identifier is applied. If some bearer configurations are different, only the SCG identifier and information on the different bearer configurations may be included as bearer configuration information. For information on bearer configurations not included in the information, the same information as the bearer configuration information of the SCG identifier may be applied.

[0437] By doing this, it is no longer necessary to include all of the bearer configuration information for each SCG as bearer configuration information notified from the MeNB to the UE, making it possible to reduce the amount of information required for signaling.

[0438] In the above example, the SCG configuration information and bearer configuration information for each radio bearer configured by the MC are configured in SCG-ConfigPartSCG. Alternatively, the SCG configuration information and bearer configuration information may be configured separately. For example, the bearer configuration information in SCG-ConfigPartSCG is configured separately from SCG-ConfigPartSCG. It is advisable to configure the bearer configuration information for one or more radio bearers as a list. The SCG configuration information is configured in SCG-ConfigPartSCG.

[0439] This method may be used when the bearer settings are the same for the SCGs of all SgNBs that configure the MC. In this case, it is possible to omit setting the bearer configuration information for each SCG, thereby reducing the amount of information required for signaling.

[0440] The MeNB can apply the sequence described above to the sequence in which the MeNB configures a radio bearer for MC for the UE and configures an SCG for MC in the radio bearer configuration. For example, in step ST4302 of the sequence shown in Figures 19 and 20, the MeNB transmits a notification to the UE containing information on one or more radio bearers for which MC is configured, instead of configuring an SCG for one or more SgNBs for which MC is configured.

[0441] As information on one or more radio bearers, for example, a list of one or more radio bearers to be configured by the MC is provided, and the SCG configuration for each radio bearer and the bearer configuration for each SCG are included for the number of radio bearers to be configured by the MC. The SCG configuration and bearer configuration information for each radio bearer may be set, for example, by the above-mentioned SCG-ConfigPartSCG. Here, the SCG configuration and bearer configuration information for SgNB1 and SgNB2 are set.

[0442] The UE that has received one or more pieces of radio bearer information in Step ST4302 configures MC for the MeNB, SgNB1, and SgNB2 in accordance with the configuration, and in Step ST4303, the UE notifies the MeNB of RRC connection reconfiguration complete (RRCConnectionReconfigurationComplete) including the MC configuration completion.

[0443] By using this method, the SCG of many SgNBs can be configured at once for one or multiple bearers, thereby reducing the amount of signaling. Furthermore, since the configuration can be performed all at once, MC control can be performed with low latency. Furthermore, since the configuration is per bearer, when changing or modifying the bearer format for each bearer, it is only necessary to change or modify the configuration of the target bearer, thereby avoiding the complexity of control. Furthermore, for example, the amount of processing in the UE can be reduced.

[0444] Data is communicated between the MeNB and each SgNB, and an SgNB identifier may be assigned to the data. Each SgNB may also notify the MeNB of the status of downlink data transmission from the SgNB to the UE. For example, each SgNB may notify the MeNB of the highest PDCP PDU SN that was successfully transmitted to the UE among the PDCP PDUs transferred from the MeNB. For example, each SgNB may notify the MeNB of the buffer capacity of the SgNB for a bearer for which an MC is set. The buffer capacity may be the amount of data required to satisfy the set QoS. Information for each bearer for which an MC is set may also be notified.

[0445] For example, each SgNB notifies the UE for which MC is set of the buffer capacity of its own SgNB. The notified buffer capacity may be the minimum data amount required. For example, each SgNB notifies the MeNB of information on packets lost in its own SgNB among the data transferred from the MeNB. The identifier of its own SgNB may be attached to the downlink data transmission status from its own SgNB to the UE that each SgNB notifies the MeNB.

[0446] In this way, by assigning the SgNB identifier, each SgNB can confirm whether the notification is directed to itself or not, and also can identify from which SgNB the MeNB received the notification. The MeNB may use the downlink data transmission status from each SgNB to determine the setting, modification, change, release, etc. of the SgNB for MC. The MeNB may also use the downlink data transmission status from each SgNB to determine to which SgNB to route the packet. It becomes possible to perform MC setting and routing according to the data transmission status between each SgNB and the UE.

[0447] This paper describes a method for splitting data in uplinks in MC. The MeNB sets multiple thresholds for transmission to the SgNB and notifies the UE of these thresholds. Since multiple SgNBs are configured for MC in MC, multiple thresholds are set according to the number of SgNBs to be configured, rather than being limited to one threshold.

[0448] For example, it is advisable to set a threshold value equal to the number of SgNBs configured for MC. Alternatively, a group consisting of one or more SgNBs may be set, and a threshold value equal to the number of SgNB groups may be set. The MeNB sets the multiple threshold values ​​and notifies the UE. RRC signaling may be used for the notification.

[0449] For example, when configuring three SgNBs for MC, three thresholds are set and notified to the UE. The thresholds are TH1, TH2, and TH3. If the amount of uplink data buffered by the UE is TH1 or less, the UE performs uplink transmission only to the MeNB. If the amount of uplink data buffered by the UE is greater than TH1 and less than TH2, the UE performs uplink transmission to the MeNB and one SgNB. If the amount of uplink data buffered by the UE is greater than TH2 and less than TH3, the UE performs uplink transmission to the MeNB and two SgNBs. If the amount of uplink data buffered by the UE is greater than TH3, the UE performs uplink transmission to the MeNB and three SgNBs.

[0450] In this way, by gradually increasing or decreasing the number of SgNBs used for uplink transmission, it is possible to prevent the UE from transmitting data to many SgNBs even when the amount of uplink data is small, and it is possible to reduce the increase in UE power consumption.

[0451] As a method of setting multiple thresholds, one threshold may be set and the other thresholds may be set to values ​​obtained by multiplying the set threshold by a predetermined number. For example, only TH1 may be set, and TH2 = TH1 × 2 and TH3 = TH1 × 3. As another example, TH2 = TH1 × 1.5 and TH3 = TH1 × 2 may be used. The predetermined numbers may be determined in advance by standards or the like. Alternatively, they may be semi-statically notified to the UE by RRC signaling. In this way, it is possible to reduce the amount of signaling notified to the UE.

[0452] The MeNB may configure to the UE which SgNB to use for uplink transmission when a threshold is exceeded. For example, a priority order may be set for the order in which SgNBs are used. The MeNB notifies the UE of the priority order. For example, when configuring three SgNBs for MC, the priorities are set as SgNB1, SgNB2, and SgNB3 in descending order. The MeNB may associate the identifier of each SgNB with the priority order and notify the UE of the association.

[0453] If the amount of uplink data buffered by the UE is equal to or less than TH1, the UE performs uplink transmission only to the MeNB. If the amount of uplink data buffered by the UE is greater than TH1 and equal to or less than TH2, the UE performs uplink transmission to the MeNB and SgNB1. If the amount of uplink data buffered by the UE is greater than TH2 and equal to or less than TH3, the UE performs uplink transmission to the MeNB, SgNB1, and SgNB2. If the amount of uplink data buffered by the UE is greater than TH3, the UE performs uplink transmission to the MeNB, SgNB1, SgNB2, and SgNB3.

[0454] The priority may be notified together with the threshold value. Alternatively, the priority may be notified separately from the threshold value. The priority of each SgNB may be changed. By changing the priority of each SgNB according to the communication status between each SgNB and the UE, it is possible to improve the throughput of uplink communication.

[0455] In the above example, it was disclosed that when the amount of buffered uplink data in the UE is equal to or less than a predetermined threshold, the UE performs uplink transmission from the MeNB. As another example, it may transmit to the SgNB when the amount is equal to or less than a predetermined threshold, and transmit to the MeNB when the amount is greater than the threshold. The MeNB may configure the UE as to which MeNB or SgNB to perform uplink transmission when the amount is equal to or less than the threshold or when the amount is greater than the threshold. Priorities may be set, including the MeNB, and notified to the UE. Using the SgNB from an early stage can improve the throughput of uplink data.

[0456] When an MeNB is configured with MC using multiple SgNBs, the UE may route data from higher layers between the MeNB and all SgNBs. The routing function may apply the above-mentioned method as appropriate. Alternatively, the above-mentioned uplink data splitting method may be applied to route data between the MeNB or SgNBs used. The SgNBs to be split can be flexibly configured.

[0457] A method for starting transmission of uplink data from a UE to a base station is disclosed. The UE notifies the base station of a scheduling request (SR (Scheduling Request)). The UE may also notify the base station of a buffer status report (BSR (Buffer Status Report)).

[0458] The UE notifies the SgNB that performs uplink transmission of SR and BSR. In this way, SR and BSR can be processed in the lower layer present in each SgNB.

[0459] As another method, the UE may notify the MeNB of an SR or BSR for an SgNB that performs uplink transmission. The notification may include information indicating which SgNB the SR or BSR is for. The information may be an SgNB identifier. Upon receiving an SR or BSR for an SgNB from the UE, the MeNB notifies the SgNB that is the target of the SR or BSR of information indicating that the SR or BSR has been received and information indicating the contents of the SR or BSR. The SgNB that receives this information performs uplink scheduling for the UE using the contents.

[0460] In this way, the MeNB can perform uplink scheduling for the UE corresponding to SR and BSR to each SgNB.

[0461] As another method, the UE may notify the MeNB of the SR or BSR for the uplink transmission of the bearer for which the MC is set. The UE notifies the MeNB of the SR or BSR for the uplink transmission of the bearer for which the MC is set, rather than notifying each SgNB. The MeNB that receives the notification determines which SgNB to cause to perform uplink scheduling using a set threshold. The MeNB may notify the SgNB that is to perform uplink scheduling of an uplink scheduling start request.

[0462] The MeNB may notify the SgNB of the contents of the SR and BSR notified by the UE. Alternatively, the MeNB may derive the data capacity that requires uplink scheduling at the SgNB and notify the SgNB of the derivation result. In this way, the UE does not need to notify the SR and BSR for each SgNB. The UE only needs to notify the MeNB of the SR and BSR for uplink transmission of the bearer for which MC is set. This makes it possible to reduce the power consumption of the UE.

[0463] An eNB, which is an LTE base station, may be used as the secondary base station for MC. An eNB and a gNB may also be used. The method disclosed in the sixth embodiment may be applied as appropriate. In the sixth embodiment, the secondary base station does not use a New AS sublayer, so it is possible to use an eNB.

[0464] By using the method disclosed in the sixth embodiment, it becomes possible to set one UE to be connected to one master base station and multiple secondary base stations. This makes it possible to improve the throughput of communication provided to the UE. Furthermore, by connecting to multiple base stations, it is also possible to improve reliability.

[0465] Variation 1 of Embodiment 6 3GPP is currently discussing the establishment of a new New AS sublayer protocol as a NR protocol (see Non-Patent Document 9 (TR38.804V.14.0.0)). The New AS sublayer protocol is also called SDAP (Service Data Adaptation Protocol). In this specification, the New AS sublayer is sometimes referred to as the New AS layer. The New AS sublayer maps PDU session data to the DRB.

[0466] The following has been proposed as a QoS architecture for NG-CN and NR: One or more DRBs can be mapped to one PDU session. Different PDU sessions are mapped to different DRBs. Multiple QoS flows are configured for one PDU session. One or more QoS flows can be mapped to one DRB.

[0467] The upper device assigns a QoS marker to the data of the PDU session according to the QoS. It has been proposed to use a QoS flow identifier as the QoS marker. The gNB establishes a DRB according to the QoS of the data of the PDU session, and the New AS sublayer performs mapping between the data of the PDU session and the DRB according to the QoS flow identifier.

[0468] Figure 21 shows the architecture and data flow when the upper network is an NG-CN and the base station is an NR gNB. In 3GPP, the 5G core network is called the "Next Generation Core Network" (abbreviated as NG-CN). The NG-CN is configured with an access and mobility management function (AMF), a session management function (SMF), and a user plane (U-Plane) function (User Plane Function: UPF).

[0469] The AMF and gNB are connected via the N2 interface. The UPF and SMF are connected via the N3 interface. The SMF and UPF are connected via the N4 interface. The AMF and SMF may be connected via the N11 interface.

[0470] In addition to PDCP, RLC, MAC, and PHY, the gNB is also provided with a New AS Layer. The gNB's New AS Layer is connected to the upper network for each PDU session. Figure 21 shows the cases where one DRB is configured for one PDU session and where two DRBs are configured for one PDU session.

[0471] Figure 21 illustrates the correspondence relationship between QoS flows when two DRBs are configured for one PDU session. In Figure 21, there are three QoS flows for one PDU session, namely, QoS flow 1, QoS flow 2, and QoS flow 3. The gNB configures DRB1 for QoS flow 1 and QoS flow 2, and maps QoS flow 1 and QoS flow 2 to DRB1 in the new AS layer. The gNB configures DRB2 for QoS flow 3, and maps QoS flow 3 to DRB2 in the new AS layer.

[0472] In the gNB, data for QoS flow 1 and QoS flow 2 is processed using the settings of DRB1, and data for QoS flow 3 is processed using the settings of DRB2.

[0473] DC when a New AS sublayer protocol exists has been discussed (see Non-Patent Document 28 (TS37.340V0.2.0(2017-07) 10.2.2 MR-DC with 5GC)). However, the details of MC when a New AS sublayer protocol exists have not yet been discussed. In this Variation 1 of Embodiment 6, a method for implementing MC when a New AS sublayer protocol exists is disclosed. The case of an MCG split bearer is shown.

[0474] Figure 22 is a diagram showing the architecture of MC. The upper network is NG-CN, the master base station is a base station in NR (gNB), and the secondary base station is a base station in NR (gNB). The NR master base station is called MgNB, and the NR secondary base station is called SgNB. The gNB protocol configuration consists of a New AS sublayer, PDCP, RLC, MAC, and PHY. A New AS sublayer is provided above PDCP.

[0475] In FIG. 22, the master base station is a gNB in ​​NR, but an eNB in ​​which a New AS sublayer is provided in an LTE base station may also be the master base station.

[0476] Figure 22 shows the architecture on the base station side, but the architecture on the UE side is similar, except for the upper network. In one UE, a New AS sublayer and PDCP are configured, as well as RLC, MAC, and PHY for the MgNB, and RLC, MAC, and PHY for each SgNB configured for MC.

[0477] Figure 22 shows the case where an MCG split bearer is used. The upper network is connected to an MgNB, and an SgNB for MC is connected to the MgNB. Downlink data is mapped to a DRB according to the QoS flow identifier in the New AS layer of the MgNB, and processed by PDCP for each mapped DRB. Even if there are multiple SgNBs, PDCP assigns a single consecutive sequence number (SN) to each piece of data. The data assigned an SN is split to the MgNB and each SgNB. The split data is sent to the RLC of the MgNB and each SgNB, processed by the RLC, MAC, and PHY of the MgNB and each SgNB, and then sent to the UE.

[0478] Data received by the UE from the MgNB and each SgNB is processed by the PHY, MAC, and RLC for the MgNB and each SgNB, and then forwarded to the PDCP. PDCP reorders the data based on the SN assigned to the data forwarded from the MeNB and each SgNB, and forwards the data to the New AS sublayer. The New AS sublayer separates the data into QoS flows using the QoS flow identifier and forwards them to the upper layer.

[0479] For uplink data, in the UE, data from higher layers is mapped to a DRB in the New AS sublayer according to the QoS flow identifier, and processed by PDCP for each mapped DRB. As with downlink, for uplink data, even if there are multiple SgNBs, PDCP assigns a single consecutive sequence number (SN) to each piece of data. The data assigned an SN is split and transferred to RLC for the MgNB and each SgNB. The transferred data is processed by RLC, MAC, and PHY for the MgNB and each SgNB, and then transmitted to the MgNB and each SgNB.

[0480] Data received from the UE by the MgNB and each SgNB is processed by the PHY, MAC, and RLC for the MgNB and each SgNB, and then forwarded to the PDCP of each MgNB. The PDCP of the MgNB performs reordering based on the SN assigned to the data and forwards the data to the New AS sublayer. The New AS sublayer separates the data into each QoS flow using the QoS flow identifier and forwards it to the upper network.

[0481] Disclose the MC setting method. Set an MC for each DRB. Set an MC using an MCG split bearer for each DRB.

[0482] 23 is a conceptual diagram showing the data flow when MC is set for each DRB. The DRB for which MC is set is assumed to be DRB1. The QoS flows mapped to DRB1 are assumed to be QoS flow 1 and QoS flow 2. MC is performed using an MCG split bearer for DRB1 using MgNB, SgNB1, SgNB2, and SgNB3.

[0483] The data of QoS Flow 1 and QoS Flow 2 mapped to DRB1 is split and routed to the MgNB and each SgNB by PDCP. As with the downlink, the data of QoS Flow 1 and QoS Flow 2 mapped to DRB1 by the UE is split and routed to the RLC for the MgNB and each SgNB by PDCP for uplink data.

[0484] In the uplink, a default DRB may be used instead of DRB1 configured in the downlink. In such a case, the data of QoS flow 1 and QoS flow 2, for which the default DRB is used in the UE, may be split and routed to the RLC for the MgNB and each SgNB using PDCP. The MgNB performs reordering using SN with PDCP for the data from the MgNB and each SgNB, separates the data for each QoS flow using QoS flow identifiers in the New AS layer, and forwards the separated data to the upper network.

[0485] In this way, by setting MC for each DRB, it is possible to set MC without changing the mapping relationship between DRB and QoS flow that is set when MC is not being performed, and it is possible to avoid the complexity of MC control.

[0486] The sequence disclosed in embodiment 6 can be applied to the sequence when setting an MC for each DRB. For example, in the SgNB addition request in steps ST4203 and ST4215 of the sequences shown in Figs. 19 and 20, the MeNB may notify each SgNB for which an MC is to be set of QoS flow characteristic information.

[0487] Six examples of QoS flow characteristic information are disclosed below.

[0488] (1) Bearer identifier.

[0489] (2) Bearer configuration.

[0490] (3) QoS flow identifier.

[0491] (4) QoS profile of each QoS flow.

[0492] (5) PDU session identifier.

[0493] (6) A combination of (1) to (5).

[0494] The MgNB may notify each SgNB that configures MC of the QoS profile of each QoS flow that is requested from each SgNB. The MgNB may determine a QoS profile setting for each SgNB that configures MC so as to satisfy the QoS profile of the QoS flow that performs MC.

[0495] The MgNB may notify each SgNB that sets up MC of the bearer configuration requested from each SgNB. The MgNB may make the bearer configuration the same as the bearer configuration of its own MgNB. Alternatively, the MgNB may determine the bearer configuration so that the bearer configuration of its own MgNB and the bearer configuration of the SgNB that sets up MC are bearer configurations that satisfy the QoS profile of the QoS flow that performs MC.

[0496] Upon receiving an SgNB addition request from an MgNB, the SgNB determines the AS configuration of the bearer for which the MC is to be set up using the QoS flow characteristic information included in the addition request. Each SgNB notifies the MgNB of the determined AS configuration.

[0497] By doing this, when a New AS sublayer is required, the MgNB can set MC for each DRB for the UE. MC for each bearer can be performed between the MgNB and the UE and between each SgNB and the UE using an MCG split bearer.

[0498] As for the data splitting method in the uplink in MC, the method disclosed in the sixth embodiment may be applied as appropriate.

[0499] The method for starting transmission of uplink data from the UE to the base station may be the method disclosed in embodiment 6. An SR and BSR may be provided for each QoS flow, and notified from the UE to the base station.

[0500] Another method for setting MC is disclosed. MC is set for each QoS flow. MC using MCG split is performed for one or more QoS flows among those mapped to DRB in the New AS sublayer.

[0501] 24 is a conceptual diagram showing data flows when MC is set for each QoS flow. The QoS flow for which MC is performed is defined as QoS flow 1. Only QoS flow 1 in DRB1 is split and routed by the MgNB.

[0502] A method for identifying data to be split is disclosed. The MgNB determines whether to split data based on the QoS flow identifier assigned to the data. Similarly, for uplink data, the UE determines whether to split data based on the QoS flow identifier assigned to the data.

[0503] For example, if the data from PDCP at the MgNB contains an identifier for QoS Flow 1, the MgNB decides to split the data to the SgNBs and performs splitting and routing to each SgNB. The same applies to uplink data. If the data from PDCP at the UE contains an identifier for QoS Flow 1, the MgNB decides to split the data to the RLC for the SgNB and performs splitting and routing to the RLC for each SgNB.

[0504] In this way, it becomes possible to perform MC using MCG split for each QoS flow.

[0505] Alternatively, information indicating whether to split or not may be provided separately. This information may be added to data from the upper network or a higher layer in the New AS layer. Alternatively, this information may be added in the PDCP layer. A QoS flow identifier may also be used. Information indicating splitting is added to data with a QoS flow identifier that is to be split. Information indicating not splitting is added to data with a QoS flow identifier that is not to be split.

[0506] Alternatively, only the information indicating whether or not to split the data may be added to the data, and in this way the splitting or routing function can determine which data to split or route using the information indicating whether or not to split the data added to the data.

[0507] By adding information on whether to split or not in the New AS layer or PDCP layer of the MgNB or UE, the information on whether to split or not can be used within the RAN. This eliminates the need for the splitting or routing function to decipher the QoS flow identifier assigned by the upper network or upper layer, simplifying processing.

[0508] The sequence for setting an MC for each QoS flow can be applied to the sequence for setting an MC for each DRB. The MgNB needs to notify the UE that an MC will be set for each QoS flow. For this reason, for example, in step ST4302 of the sequences shown in Figures 19 and 20, the MgNB notifies the UE of the QoS flow for which an MC is to be set. It is preferable to notify the QoS flow identifier for which an MC is to be set. Note that the notification of the SCG configuration and bearer configuration from the MgNB to the UE can be performed in a similar manner.

[0509] In this way, the MgNB can set MC for each QoS flow for the UE. MC for each QoS flow can be performed using an MCG split bearer between the MgNB and the UE and between each SgNB and the UE.

[0510] Another method for performing MC for each QoS flow is disclosed. An additional DRB is set for the QoS flow for which MC is to be performed. The QoS flow for which MC is to be performed is mapped to the additionally set DRB. By setting the additionally set DRB as MC, it becomes possible to set MC for the QoS flow mapped to the DRB.

[0511] 25 is a conceptual diagram showing a data flow when a DRB for mapping a QoS flow for which MC is performed is additionally set. The QoS flow for which MC is performed is called QoS flow 1.

[0512] The mapping relationship between the QoS flows and the DRBs before the MC is set is as shown in Fig. 21. Before the MC is set, QoS flow 1 and QoS flow 2 are mapped to DRB1.

[0513] As shown in Figure 25, the MgNB configures QoS flow 1 to the MC, and therefore additionally configures DRBX1 for mapping QoS flow 1. The New AS sublayer maps QoS flow 1 to DRBX1. QoS flow 2 is mapped to DRB1 in the same way as before the MC configuration.

[0514] In this way, the QoS flow for which MC is performed is mapped to DRBX1. The MgNB configures MC for DRBX1. As a result, MC is performed for QoS flow 1 mapped to DRBX1. To perform MC for the MCG split bearer, the MgNB may split and route the data of QoS flow 1.

[0515] The DRB configuration to be added should be configured using the QoS profile of the QoS flow to be split. The QoS profile of the QoS flow notified from the upper network can also be used. DRBX1 is added and configured in the MgNB, and the New AS sublayer maps the data of QoS flow 1 to DRBX1. The New AS sublayer determines which DRB to map to depending on the QoS flow identifier assigned to the data in the upper network.

[0516] The MgNB configures an MC using an MCG split bearer for DRBX1, splits the data of QoS flow 1 to the SgNB side used for the MC, and routes it to SgNB1, SgNB2, and SgNB3.

[0517] The MgNB may notify the UE of the DRBX1 configuration additionally configured for MC. For this notification, for example, the method disclosed in the sixth embodiment in which the MgNB notifies the UE of the configuration of the DRB that performs MC may be applied.

[0518] The MgNB may notify the UE of the mapping relationship between the QoS flow and the DRB in the new AS layer. For example, it may notify the DRB identifier, DRB configuration information, QoS flow identifier, QoS profile, etc. in association with each other. Here, it notifies information indicating the mapping relationship with QoS flow 1 to be mapped to DRBX1. This enables the UE to map QoS flow 1 to DRBX1 in the new AS layer.

[0519] In this way, the UE can additionally set a DRB for a QoS flow that performs MC, and can set and perform MC for that DRB. The same applies to uplink data.

[0520] The data of QoS Flow 2 is mapped to DRB1 by the New AS sublayer. There is no need to change the configuration of DRB1. Since the configuration of DRB1 was compatible with QoS Flow 2 before MC was set, it can support QoS Flow 2 without any changes. Since MC is not set for DRB1, MC is not performed on the data of QoS Flow 2, and communication is performed using only the MgNB.

[0521] The MgNB may notify the UE of information about the QoS flow to be mapped to DRB1. By additionally configuring DRBX1, the QoS flow to be mapped to DRB1 is changed from QoS flow 1 and QoS flow 2 before the MC configuration to QoS flow 2. By the MgNB notifying the UE of the change or reconfiguration of the QoS flow, the UE becomes able to recognize the QoS flow to be mapped to DRB1.

[0522] The change or reconfiguration of the QoS flow mapped to the DRB may be notified using RRC signaling, which may be performed within the same signaling as the additional configuration of the DRBX1.

[0523] The MgNB may reconfigure DRB1. For example, it may reconfigure DRB1 so that it has a DRB configuration suitable for QoS flow 2 that is mapped to DRB1 after the MC is configured. It may be configured using the QoS profile of QoS flow 2. DRB1 is reconfigured by the MgNB, and the data of QoS flow 2 is mapped to DRB1 by the New AS sublayer.

[0524] The MgNB may notify the UE of the reconfigured DRB1 configuration. For this notification, for example, the method of notifying the UE of the DRB configuration from the MgNB disclosed in the sixth embodiment may be applied. The UE can then reconfigure the DRB1 configuration. The same applies to uplink data. In this way, it is possible to realize an appropriate DRB configuration according to a change in the QoS flow to be mapped.

[0525] As a method for reconfiguring the DRB to which the QoS flow is mapped, the above-mentioned additional configuration and deletion of the DRB may be applied, which makes it possible to configure the DRB appropriately according to the change in the QoS flow to be mapped.

[0526] Figures 26 and 27 show an example of a sequence for setting MC for each QoS flow. Figures 26 and 27 are connected at the position of boundary line BL2627. Figures 26 and 27 show a case where an MgNB additionally sets up a DRB including a QoS flow for which MC is to be performed. In Step ST4901, data communication is being performed between the UE and the MgNB. In Step ST4902, the MgNB decides to perform MC for each QoS flow for the UE. In Step ST4903, the MgNB decides to additionally set up a DRB to which the QoS flow for which MC is to be performed is mapped. In Step ST4904, the MgNB decides on and adds a DRB configuration for the QoS flow for which MC is to be performed.

[0527] In Step ST4905, the MgNB notifies the UE of the added DRB configuration and the QoS flow identifier to be mapped to the added DRB. The QoS profile of the QoS flow may also be notified. Furthermore, the MgNB may notify the UE of an instruction to stop new data transmission of the QoS flow in the DRB to which the QoS flow was mapped before the additional configuration. The instruction may be notified by RRC signaling. For example, the information may be notified by including it in the RRC connection reconfiguration.

[0528] The UE performs configuration using the information received from the MgNB, and in Step ST4906, notifies the MgNB of configuration completion. The configuration completion may be notified by signaling indicating RRC connection reconfiguration completion, for example.

[0529] In Step ST4907, the UE stops new data transmission of the QoS flow on the DRB to which the QoS flow was mapped before the additional configuration. Furthermore, the UE performs additional configuration using the DRB configuration notified by the MgNB, maps the QoS flow to be mapped to the additional DRB to the additional DRB, and starts data transmission. In Step ST4908, the MgNB maps the QoS flow to be mapped to the additional DRB to the additional DRB, and starts data transmission.

[0530] Note that the DRB before the additional setting is still maintained even if the mapped QoS is no longer available. By maintaining it, it is possible to process the data before the data transmission was stopped. For example, it becomes possible to perform retransmission processing in a lower layer. The UE may insert a marker at the end of the data to be transmitted by the DRB before the additional setting. It may also transmit data as a marker at the end. Such a marker is called an end marker.

[0531] In Step ST4909, data communication of the QoS flow is performed in the DRB that has been additionally set up between the UE and the MgNB. Note that in Step ST4909, data communication of the QoS flow is also performed in the DRB before the additional setting. In Step ST4910, the MgNB judges whether or not data processing in the DRB before the additional setting has ended. It is preferable to make this judgment using an end marker. If not, the MgNB returns to Step ST4909 and performs data processing. If completed, the DRB setting before the additional setting is cancelled in Step ST4911.

[0532] In Step ST4912, the MgNB notifies the UE of the cancellation of the DRB configuration before the additional configuration. The cancellation may be notified by RRC signaling. For example, the cancellation may be notified by being included in the RRC connection reconfiguration. The UE that has received the cancellation of the DRB configuration before the additional configuration cancels the DRB configuration before the additional configuration.

[0533] The MgNB may insert an end marker at the end of the data transmitted in the DRB before the additional setting. If the UE receives the end marker, it cancels the DRB setting. If the UE does not receive the end marker, it may wait to cancel the DRB setting until it is received, and then cancel the DRB setting after receiving the end marker.

[0534] Although an example of canceling a DRB before the additional setting has been disclosed, if there is a QoS mapped to the DRB before the additional setting, the DRB before the additional setting does not need to be canceled. Also, when reconfiguring a DRB before the additional setting, the MgNB may notify the UE of the reconfigured DRB configuration.

[0535] As a protocol stack for inserting an end marker, for example, an end marker may be inserted in the New AS sublayer. One end marker may be inserted for all QoS flows that are mapped to the newly configured DRB. This makes control easier. Alternatively, an end marker may be inserted for each QoS flow. This allows for flexible control for each QoS flow and reduces malfunctions.

[0536] In Step ST4914, the MgNB starts MC configuration of the DRB that has been additionally configured for the QoS flow that performs MC. In Step ST4915, the MgNB, the SgNB1 and SgNB2 used for MC, and the UE perform MC configuration processing among themselves. This MC configuration processing may be performed by applying the method disclosed in the sixth embodiment. Since a radio bearer for the QoS flow that performs MC is configured, it is possible to apply the method of configuring MC for the radio bearer.

[0537] When configuring MC for each QoS flow, we have disclosed a method of configuring an additional DRB for the QoS flow for which MC is configured. In this case, for one QoS flow, data from the DRB before the additional configuration and data from the additionally configured DRB are transferred to the New AS sublayer. In this case, reordering is performed in PDCP for each DRB, but reordering is not performed for subsequent packet data.

[0538] Therefore, if the order of data from the PDCP of the newly configured DRB differs from that of the pre-configuration DRB, the New AS sublayer will be unable to reorder the data, resulting in a problem where the data cannot be kept in sequence.

[0539] We will disclose a solution to this problem. The New AS sublayer adds a sequence number to the data. It is recommended to provide a sequence number for each QoS flow and add it to the data. The New AS sublayer that receives data via PDCP should use this sequence number for reordering.

[0540] Another method is disclosed. It utilizes the end marker mentioned above. After the DRB is added, data from the PDCP of the added DRB is stored until the end marker is received. It is recommended to provide a buffer for storing and storing this data. After processing the data from the DRB before the addition up to the end marker and transferring it to the upper network or upper layer, when the end marker arrives, it is recommended to process the data from the PDCP of the added DRB and transfer it to the upper network or upper layer.

[0541] In this way, it is possible to ensure that the packet data is sent in the correct order.

[0542] A buffer for storing and holding the data may be provided in the New AS sublayer, and the New AS sublayer may perform these processes.

[0543] As for the data splitting method in the uplink in the MC, the method disclosed in the sixth embodiment may be applied as appropriate. This may be applied to the MgNB and the SgNB that sets the MC for each QoS flow.

[0544] The method of starting transmission of uplink data from the UE to the base station may be appropriately applied to the method disclosed in the sixth embodiment. This method may be applied to the MgNB and the SgNB that sets the MC for each QoS flow. An SR and BSR may be provided for each QoS flow, and the UE may notify the base station.

[0545] By using this method, the MgNB can perform MC for each QoS flow for the UE. Since MC can be performed for each QoS flow, MC control can be performed with finer QoS accuracy than MC for each bearer.

[0546] The sixth embodiment discloses that the MgNB is provided with a routing function to each SgNB that sets MC. Providing the MgNB with such a routing function may also be applied to this first modification of the sixth embodiment. Furthermore, a function for routing to a different SgNB for each QoS flow may be provided. When there are multiple QoS flows that perform MC, the MgNB routes each QoS flow to a different SgNB. The MgNB may use a QoS flow identifier to determine which SgNB to route to.

[0547] The MgNB may set a correspondence relationship between the QoS flow and the SgNB that routes the flow. The MgNB may notify the UE of the correspondence relationship. The notification may be performed using RRC signaling. For example, the correspondence relationship may be notified by being included in an RRC connection reconfiguration. The correspondence relationship may also be notified to the UE when an MC is configured. It is also possible to set a correspondence relationship between the QoS flow and the SgNB that transmits data for the UE.

[0548] The UE may set a correspondence relationship between the QoS flow and the SgNB that routes the flow. The UE may notify the MgNB of the correspondence relationship. The notification may be made using RRC signaling. The correspondence relationship may be notified, for example, by being included in the RRC connection reconfiguration completion. It is possible to request the MgNB which SgNB to use for each QoS flow.

[0549] When routing each QoS flow to a different SgNB, the MgNB may notify the SgNB of the QoS profile of the corresponding QoS flow in an additional request. Each SgNB may use a DRB configuration according to the notified QoS profile. Each SgNB notifies the MgNB of the DRB configuration according to the QoS profile. The MgNB may notify the UE of the DRB configuration received from the SgNB as the DRB configuration for MC. The notification from the MgNB to the UE may be made using RRC signaling. For example, the DRB configuration according to the QoS profile may be notified by RRC connection reconfiguration.

[0550] By doing this, it is possible to set the DRB configuration in the SgNB that routes for each QoS flow to be suitable for the QoS of the routed QoS flow. It is possible to set an MC using an SgNB with a DRB configuration suitable for each QoS flow.

[0551] An eNB, which is an LTE base station, may be used as the secondary base station for MC. An eNB and a gNB may also be used. The method disclosed in Modification 1 of Embodiment 6 may be applied as appropriate. In Modification 1, the secondary base station does not use a New AS sublayer, so it is possible to use an eNB.

[0552] By using the method disclosed in the present modification 1 of the sixth embodiment, even when the upper network is an NG-CN, it is possible to configure one UE so that one master base station and multiple secondary base stations are connected to it. This makes it possible to improve the throughput of communications provided to the UE. Furthermore, connecting to multiple base stations can also improve reliability.

[0553] Embodiment 7 As mentioned above, Non-Patent Document 27 (R2-167583) proposes support for MC using SCG bearers. MC using SCG bearers requires architecture and configuration methods that include the upper network, such as a method for connecting to the upper network. For example, when multiple SgNBs are used for MC, issues arise such as what the bearer configuration will be, or how data will be distributed to multiple SgNBs.

[0554] However, it is unclear what architecture and setting method should be used in the disclosure of Non-Patent Document 27 and the prior art. In the seventh embodiment, an architecture and setting method of MC using an SCG bearer will be disclosed.

[0555] Figure 28 is a diagram showing the architecture of MC. The upper network is the EPC, the master base station is an LTE base station (eNB), and the secondary base station is an NR base station (gNB). Figure 28 shows the architecture on the base station side, but the architecture on the UE side is similar except for the upper network. One UE is configured with PDCP, RLC, MAC, and PHY for each SeNB configured for MeNB and MC.

[0556] Figure 28 shows the case where an SCG bearer is used. The upper network is connected to the SgNB for MC. Downstream data is routed and forwarded by the upper network to the SgNB for MC. The downstream data is forwarded to PDCP without passing through the New AS sublayer of the SgNB. Data from the upper network may be input to the New AS sublayer of the SgNB, but the data is passed without being processed by the New AS sublayer.

[0557] Each SgNB processes the data using PDCP, RLC, MAC, and PHY, and then transmits it to the UE.

[0558] Data received by the UE from each SgNB for MC is processed by the PHY, MAC, RLC, and PDCP for each SgNB and then forwarded to higher layers.

[0559] For uplink data, data from higher layers in the UE is routed to each SgNB and forwarded to the PDCP for each SgNB, processed by the PDCP, RLC, MAC, and PHY for each SgNB, and then transmitted to each SgNB.

[0560] It has been disclosed that the upper network routes data to the SgNB for MC. A routing function to each SgNB is provided in the upper network. A routing function may be provided in the S-GW of the U-Plane as the upper network. The routing function may be added as one of the functions of the S-GW. The upper network is connected to multiple SgNBs and performs MC without changing the E-RAB bearer set up between the upper network and the UE.

[0561] The routing function may support both downlink and uplink, and may include a function for adding a sequence number to packet data, and may use the sequence number to perform reordering.

[0562] In Figure 28, it is disclosed that the routing function between the S-GW and multiple SgNBs is provided in the S-GW. As an alternative method, the routing function may be provided in a node other than the S-GW. This eliminates the need to extend the functionality of the S-GW.

[0563] In addition, a routing function between the S-GW and multiple SgNBs may be provided on the base station side. The routing function of one of the SgNBs for MC may be used. Data communication is performed between the S-GW and the routing function of that one SgNB. The routing function of that one SgNB routes data to other SgNBs.

[0564] This eliminates the need to expand the functionality of the S-GW, and only expands the functionality of the base station, making it easier to build the system.

[0565] A method for setting up an MC using an SCG bearer will be disclosed. The method disclosed in the sixth embodiment may be applied to the addition request process from the MeNB to the SgNB used for MC and the MC setting from the MeNB to the UE.

[0566] This paper describes a method for forwarding data from an MeNB to an SgNB. Since multiple SgNBs are configured in an MC, the question arises as to which SgNB data should be forwarded to. To solve this problem, the MeNB may determine the SgNB to which data should be forwarded. The MeNB transfers the SN status of the PDCP PDU to the determined SgNB and starts data forwarding. This enables data forwarding until a path switch is performed from the MeNB to the SgNB used for the MC.

[0567] Sets the SgNB to which data is forwarded. When performing MC with multiple SgNBs, the MeNB sets a specific SgNB. The MeNB transfers the SN state and forwards data to the set SgNB. In the SgNB addition request for MC, the MeNB may notify the set SgNB that it is the SgNB to which data is forwarded. Since the SgNB can recognize that data is being forwarded from the MeNB, the occurrence of malfunctions can be reduced.

[0568] The MeNB may notify the UE of information about a specific SgNB set as the data forwarding destination. The MeNB may notify the UE by including it in the MC setting. The UE recognizes from which SgNB the data forwarded will be sent. The UE may process data from the SgNB and forward it to a higher layer before data for which a routing function has been performed in the upper NW according to the MC setting. This makes it possible to correct the order of packet data.

[0569] Another method of data forwarding is disclosed. The MeNB may determine the SgNB to which data is to be forwarded for each packet data. In this case, the MeNB similarly transfers the SN state of the PDCP PDU and forwards the data to the determined SgNB. For example, assume that the MeNB has transmitted data up to PDCP PDU SN n-1. When forwarding the next packet data to SgNB1, the SN state n and the next packet data are forwarded to SgNB1. SgNB1 performs PDCP processing on the packet data. At this time, n is assigned to the SN in PDCP.

[0570] When forwarding the next packet to SgNB2, the SN state n+1 and the next packet data are forwarded to SgNB2. SgNB2 performs PDCP processing on the packet data. n+1 is assigned to the SN in PDCP. Note that although n is forwarded as the SN state when transmission up to n-1 has been completed, n-1 may also be forwarded. Upon receiving the SN state, the SgNB sets n to the SN of the PDCP PDU. By forwarding the SN for each packet data in this way, it becomes possible to forward data for each packet data to multiple SgNBs. SN continuity in PDCP is maintained.

[0571] Instead of transferring each packet data piece, multiple packet data pieces may be transferred consecutively to the SgNB. The MeNB transfers only the first SN of the multiple consecutive packet data pieces to the SgNB. The MeNB counts the number of packet data pieces transferred to the SgNB and uses the count value to derive the SN of the next packet data piece to be transferred to another SgNB. The MeNB transfers the derived SN state and packet data to the other SgNB. In this way, it is also possible to transfer multiple packet data pieces consecutively to the SgNB. Compared to transferring the SN for each packet, this allows for a reduction in the amount of information communicated between base stations.

[0572] The UE may reorder packet data using the SN of each PDCP. The UE may reorder using the SN of the PDCP of the MeNB and each SgNB and transfer the reordered packet to the upper network. Alternatively, the PDCP of the MeNB and each SgNB may notify the upper network of SN information, and the upper network may reorder the packet data using the SN information. Since a unified SN is added between the MeNB and each SgNB, it is possible to correct the order of packet data.

[0573] This section describes a path switching method from MeNB to SgNB. MeNB notifies MME of path switching information for MC. Eleven examples of MC path switching information are shown below.

[0574] (1) Bearer information to be path switched.

[0575] (2) Identifiers of multiple SgNBs that configure the MC.

[0576] (3) Addresses of multiple SgNBs for which MC is configured.

[0577] (4) Path switch request.

[0578] (5) Identifier of a node having routing functionality.

[0579] (6) The address of the node that has routing capabilities.

[0580] (7) A request to activate the routing function.

[0581] (8) Identifier of the UE for which the MC is to be set.

[0582] (9) Identifier of the own MeNB.

[0583] (10) Address of the local MeNB.

[0584] (11) A combination of (1) to (10).

[0585] Regarding the above (1), information on the E-RAB bearer corresponding to the DRB for which the MC is set may be used as bearer information to be path-switched. The E-RAB bearer information may include an E-RAB bearer identifier. The MME will be able to recognize the E-RAB bearer for which the MC is set.

[0586] Regarding the above (2) and (3), the SgNB of the path switch destination may be used as multiple SgNBs that set up MC. When the S-GW or a node with routing function receives the path switch request of the above (4), it switches the path to the SgNB of the path switch destination.

[0587] The MME notifies the S-GW of the MC path switch information received from the MeNB. The S-GW may notify the MC path switch information to a node with a routing function. If the path switch function is provided in the S-GW, there is no need to notify the MC path switch information. Upon receiving the MC path switch information, the S-GW or a node with a routing function switches the path from the MeNB to multiple SgNBs that set the MC, and starts routing to the multiple SgNBs.

[0588] When the routing function is provided in a specific SgNB, the MeNB may notify the specific SgNB of the MC path switch information directly. This notification may be performed together with the notification of the MC path switch information from the MeNB to the S-GW via the MME. The MC path switch information notified from the MeNB to the S-GW via the MME may include the identifier or address of the node having the routing function of (5) or (6) and the path switch request of (4). In response to the path switch request of (4), the S-GW performs a path switch from the MeNB to the node having the routing function.

[0589] The path switch information notified directly from the MeNB to the predetermined SgNB may include identifiers or addresses of the multiple SgNBs that set the MC in (2) and (3), and a request to activate the routing function in (7). The predetermined SgNB routes the data received by the predetermined SgNB from the S-GW to the multiple SgNBs that set the MC, including the SgNB itself.

[0590] The MC path switch information notified from the MeNB to the MME and from the MME to the S-GW may be included in the E-RAB modification signaling configured by the MC. It is sufficient to extend and use the existing messages, and there is no need to create new messages. This simplifies control.

[0591] As another method, in the path switch setting performed by the MeNB to the MME and the MME to the S-GW, the path switch setting may be performed for each SgNB for MC. In the conventional E-RAB modification signaling, the path switch destination is one SgNB, so this may be used. Conventional messages can be used, simplifying the control.

[0592] When setting a path switch for each SgNB for MC, it is preferable to maintain the SgNB that was the path switch destination of the previous path switch request and additionally set the SgNB set in the new path switch request. As information for the path switch, it is preferable to provide information on whether to maintain the SgNB previously set as the path switch destination. The MeNB can set a path switch for multiple SgNBs by notifying the S-GW of this information via the MME.

[0593] Figures 29 and 30 are diagrams showing an example of a sequence for setting up an MC using an SCG bearer. Figures 29 and 30 are connected at the position of boundary line BL2930. Figures 29 and 30 show a case where an MeNB and two SgNBs (SgNB1, SgNB2) are used. Figures 29 and 30 show a method for setting up SCGs for multiple SgNBs for MC at once. Figures 29 and 30 also show a case where a routing function is provided in an S-GW.

[0594] The sequences shown in FIGS. 29 and 30 include the same steps as the sequences shown in FIGS. 19 and 20, so the same step numbers are used for the same steps and common explanations will be omitted.

[0595] The MeNB, which has sent an SgNB reconfiguration completion notification for MC to SgNB1 and SgNB2 in steps ST4207 and ST4219, transfers the SN state for data forwarding to SgNB1 in step ST5201, and starts forwarding data from the S-GW to SgNB1 in steps ST5202 and ST5203.

[0596] In Figures 29 and 30, data transfer is performed only to SgNB1, but data transfer may also be performed for each data item to SgNB1 and SgNB2 using the method disclosed above.

[0597] In Step ST5204, the MeNB notifies the MME of E-RAB modification signaling. The MeNB notifies the MME by including MC path switch setting information in the E-RAB modification signaling. In Step ST5205, the MME notifies the S-GW of bearer modification signaling including the MC path switch setting information. This enables the S-GW to recognize multiple SgNBs as path switch destinations.

[0598] The MME, which has notified the S-GW of the MC path switch setting information in Step ST5205, notifies the MeNB of E-RAB modification completion signaling. As a result, the MeNB recognizes that a path switch has been set in SgNB1 and SgNB2 for MC.

[0599] In Step ST5206, the S-GW that has received the MC path switch setting information transmits an end marker packet as the last packet data to the MeNB and initiates a path switch. In Step ST5207, the MeNB forwards the end marker to the SgNB1. This allows the SgNB1 to recognize that the data from the MeNB has ended.

[0600] In Step ST5209, the S-GW starts data routing between SgNB1 and SgNB2 for which MC is configured. This enables data communication between the UE and SgNB1 and SgNB2, and between SgNB1 and SgNB2 and the S-GW. MC using an SCG bearer is performed between the UE and multiple SgNBs for MC.

[0601] It has been disclosed that a routing function to multiple SgNBs used for MC is provided. Information for routing may be provided as information for the routing function to determine to which SgNB data should be transmitted. For example, this may be the status of downlink data transmission from the SgNB to the UE, which is notified from each SgNB to the MeNB as disclosed in the sixth embodiment.

[0602] As for the data splitting method in the uplink in the MC, the method disclosed in the sixth embodiment may be applied as appropriate. It may be applied to the SgNB for the MC.

[0603] The method for starting transmission of uplink data from the UE to the base station may be the method disclosed in the sixth embodiment, as appropriate. This method may be applied to an MeNB or an SgNB for MC.

[0604] The MeNB makes routing decisions. Each SgNB notifies the MeNB of information for routing. The MeNB uses this information to derive, for example, the amount of data to be routed to each SgNB. The amount of data may be a data rate. The derived amount of data may be the amount of data to be sent to each SgNB relative to the total amount of data. The MeNB notifies the MME of the amount of data to be routed to each SgNB. The MME notifies the S-GW of the amount of data to be routed to each SgNB. The S-GW notifies the routing function of this information. The routing function performs routing using this amount of data.

[0605] In this way, it is possible to adjust the amount of data routed to each SgNB. In addition, the status of downlink data transmission from the SgNB to the UE is notified from each SgNB to the MeNB, and the downlink data transmission status can be used.

[0606] Alternatively, the routing decision may be made by the MME. Each SgNB notifies the MeNB of information for performing routing, and the MeNB notifies the MME of the information. Alternatively, each SgNB may notify the MME of the information for performing routing. As described above, the MME uses the information to derive, for example, the amount of data to be routed to each SgNB, and notifies the S-GW of the derived amount of data. The S-GW notifies the routing function of the information. The routing function performs routing using the amount of data.

[0607] This makes it possible to adjust the amount of data routed to each SgNB. In addition, since the MME, which is the upper device, determines the routing, control can be simplified when the MME and S-GW are configured in the same device.

[0608] Alternatively, the routing decision may be made by the S-GW. Each SgNB notifies the MeNB of information for performing routing, and the information is notified from the MeNB to the MME, and then from the MME to the S-GW. Alternatively, each SgNB may notify the MME of information for performing routing, and the information may be notified from the MME to the S-GW. Alternatively, each SgNB may notify the S-GW of information for performing routing.

[0609] As described above, the S-GW uses this information to derive, for example, the amount of data to be routed to each SgNB. The S-GW notifies the routing function of this information. The routing function performs routing using this amount of data.

[0610] This makes it possible to adjust the amount of data routed to each SgNB. In addition, the S-GW, which is the upper device of the U-Plane, determines the routing, allowing data routing control to be performed within the U-Plane.

[0611] Alternatively, the routing decision may be made by a node having a routing function. Each SgNB notifies the MeNB of information for performing routing, and the information is notified from the MeNB to the MME, from the MME to the S-GW, and from the S-GW to the node having the routing function. Alternatively, each SgNB may notify the MME of information for performing routing, and the information is notified from the MME to the S-GW, and from the S-GW to the node having the routing function. Alternatively, each SgNB may notify the S-GW of information for performing routing, and the S-GW may notify the node having the routing function of the information for performing routing. Alternatively, each SgNB may notify the S-GW of information for performing routing, and the S-GW may notify the node having the routing function of the information for performing routing. Alternatively, each SgNB may notify the node having the routing function of the information for performing routing.

[0612] As described above, the node having the routing function uses the information to derive, for example, the amount of data to be routed to each SgNB, etc. The node having the routing function performs routing using the amount of data.

[0613] This makes it possible to adjust the amount of data routed to each SgNB. In addition, by having a node with routing functionality determine routing, data routing control can be simplified and malfunctions can be reduced.

[0614] The routing function may be performed for each data. Routing is performed to each SgNB for each data. Alternatively, the same routing may be performed for a predetermined period. Data for a predetermined period is routed to the same SgNB. In this way, flexible routing can be implemented. Routing suitable for the communication quality status of each SgNB is possible.

[0615] An eNB, which is an LTE base station, may be used as the secondary base station for MC. An eNB and a gNB may also be used. The method disclosed in the seventh embodiment may be applied as appropriate. In the seventh embodiment, the New AS sublayer is not used in the secondary base station, so it is possible to use an eNB.

[0616] By using the method disclosed in the seventh embodiment, it becomes possible to set up a plurality of secondary base stations to be connected to one UE. It becomes possible to improve the throughput of communication provided to the UE. Furthermore, by connecting to a plurality of base stations, it becomes possible to improve reliability. Furthermore, since it becomes possible to set up an MC using an SCG bearer, it becomes possible to provide communication that does not go through an MeNB. Therefore, it becomes possible to improve the throughput of communication provided to the UE.

[0617] Variation 1 of Embodiment 7 The details of MC using an SCG bearer when a New AS sublayer protocol exists have not yet been discussed. In this first modification of the seventh embodiment, a method for implementing MC using an SCG bearer when a New AS sublayer protocol exists is disclosed.

[0618] Figure 31 is a diagram showing the architecture of MC using an SCG bearer. The upper network is the NG-CN, the master base station is a base station in NR (gNB), and the secondary base station is a base station in NR (gNB). The NR master base station is called MgNB, and the NR secondary base station is called SgNB. The gNB protocol configuration consists of a New AS sublayer, PDCP, RLC, MAC, and PHY. A New AS sublayer is provided above PDCP.

[0619] In FIG. 31, the master base station is a gNB in ​​NR, but an eNB in ​​which a New AS sublayer is provided in an LTE base station may also be the master base station.

[0620] Figure 31 shows the architecture on the base station side, but the architecture on the UE side is similar, except for the upper network. In one UE, a New AS sublayer and PDCP are configured, as well as RLC, MAC, and PHY for the MgNB, and RLC, MAC, and PHY for each SgNB configured for MC.

[0621] Figure 31 shows the case where an SCG bearer is used. The upper network is connected to the SgNB. Downstream data is routed and transferred by the upper network to the SgNB for MC. The data is mapped to a DRB according to the QoS flow identifier in the New AS sublayer of the SgNB, and processed by PDCP for each mapped DRB.

[0622] The data is processed by PDCP, RLC, MAC, and PHY for each DRB at each SgNB and transmitted to the UE.

[0623] The data received by the UE from each SgNB for MC is processed by the PHY, MAC, RLC, PDCP, and New AS sublayer for each SgNB. The New AS sublayer separates the data into QoS flows using the QoS flow identifier and forwards them to the upper layer.

[0624] For uplink data, in the UE, data from higher layers is mapped to a DRB by the New AS sublayer for the SgNB according to the QoS flow identifier, and is processed by PDCP, RLC, MAC, and PHY for each mapped DRB and transmitted to each SgNB.

[0625] Data received by each SgNB from the UE is processed by PHY, MAC, RLC, and PDCP, and then forwarded to the New AS sublayer, which separates the data into QoS flows using QoS flow identifiers and forwards them to the upper network.

[0626] A method for setting an MC using an SCG bearer is disclosed. An MC is set for each DRB. An MC using an SCG bearer is set for each DRB. When an upper network sets an MC using an SCG bearer in an NG-CN, the following main problems arise.

[0627] Conventionally, one PDU session tunnel (sometimes called an N3 tunnel) is set up for one PDU session between the UPF and gNB, and communication is carried out between the UPF and gNB. However, when an SCG bearer is used, communication from the upper network must be carried out not only to the MgNB but also to the SgNB. In the case of MC using an SCG bearer, communication must be carried out not only to the MgNB but also to multiple SgNBs. In such cases, the problem arises of how to handle the PDU session tunnel.

[0628] In addition, the following other problem arises: Routing must be performed for multiple SgNBs for MC, which raises the issue of where to provide the routing function and what kind of function should be provided as the routing function.

[0629] In addition, other problems arise: The DRB required for the MC must be configured in the SgNB. The problem is how to configure the DRB required for the MC in the SgNB and how to map it from the New AS sublayer in the SgNB.

[0630] In this first modification of the seventh embodiment, a method for solving such a problem will be disclosed.

[0631] Multiple PDU session tunnels can be set for one PDU session between the NG-CN and the RAN. The MgNB decides to set up multiple PDU session tunnels. For example, when an MgNB connected to the NG-CN performs MC using an SCG bearer, it decides to set up multiple PDU session tunnels.

[0632] The MgNB notifies the upper network of a request to add a PDU session tunnel. The request may include PDU session tunnel additional information. The MgNB notifies the UPF, which is a node in the upper network, of the request. The MgNB may notify the AMF or SMF, which is a node in the upper network, of the request, and the AMF or SMF may notify the UPF of the request. Nine examples of PDU session tunnel additional information are disclosed below.

[0633] (1) PDU session identifier.

[0634] (2) PDU session tunnel identifier (which may be an N3 tunnel identifier).

[0635] (3) QoS flow identifier for setting MC.

[0636] (4) Identifier of the SgNB that sets the MC.

[0637] (5) Address of the SgNB that configures the MC.

[0638] (6) Identifier of a node with routing functionality.

[0639] (7) The address of the node that has routing capabilities.

[0640] (8) Information on the required method for maintaining a mapping from a QoS profile to a QoS flow.

[0641] (9) A combination of (1) to (8).

[0642] The above (1) can be any information for identifying a PDU session. Information for identifying a PDU session notified by an upper network when a PDU session is established can also be used. It can indicate which PDU session a PDU session tunnel should be added to.

[0643] The above (2) may be information for identifying a PDU session tunnel that has already been set up. Information for identifying a PDU session tunnel notified from the upper network when a PDU session is established may also be used. It is possible to clearly indicate a PDU session tunnel that has already been set up.

[0644] In the above (3), the number of QoS flows to be MCed may be one or more. It is possible to indicate which QoS flows in the PDU session should be migrated to the added PDU session tunnel.

[0645] The above (4) is sufficient as long as it is information for the upper network to identify the SgNB to which the PDU session tunnel is set. For example, if the routing function is provided in the UPF, a PDU session tunnel can be set between the SgNB with the notified identifier.

[0646] The above (5) is sufficient as long as it is information indicating the address of the SgNB to which the upper network sets up a PDU session tunnel. For example, if the routing function is provided in the UPF, a PDU session tunnel can be set up between the SgNB of the notified address.

[0647] The above (6) may be information for the upper network to identify a node having a routing function for setting up a PDU session tunnel. For example, if a node having a routing function is provided on the RAN side, a PDU session tunnel can be set up between the node having the routing function of the notified identifier and the upper network.

[0648] The above (7) may be information indicating the address of a node with a routing function to which the upper network sets up a PDU session tunnel. For example, if a node with a routing function is installed on the RAN side, a PDU session tunnel can be set up between the node with the notified address and the node with the routing function.

[0649] The above (8) may be information indicating that the mapping method from the QoS profile to the QoS flow that will be transferred to the additionally set PDU session tunnel should be the same as before the additional setting. The upper network may use this information to perform mapping from the QoS profile to the QoS flow. The upper network may also decide whether to set the mapping method to the same as before the additional setting. This allows for settings that are appropriate for the situation of the upper network.

[0650] If the mapping method is to be the same as before the additional setting, the upper network may notify the MgNB of this. The MgNB can set the mapping from the QoS flow identifier in the New AS sublayer to the DRB for the SgNB used for MC to the same setting as before the additional setting. This makes it easier to set the SgNB that sets MC.

[0651] If the mapping method is changed from before the additional configuration, the upper network notifies the MgNB of the information on the mapping relationship from the reconfigured QoS profile to the QoS flow. It is recommended to associate the QoS flow identifier with the QoS profile of the QoS flow and notify the information. The MgNB notifies the information to the SgNB used for MC. The SgNB can use the information to configure mapping from the QoS flow identifier to the DRB in the New AS sublayer.

[0652] If the information in (8) is not included in the PDU session tunnel additional information, the upper network decides whether to set the mapping method to the same as before the additional setting, and if the information in (8) is included in the PDU session tunnel additional information, the upper network may set the mapping method to the same as before the additional setting in accordance with the information in (8).

[0653] This section describes the timing for setting up additional PDU session tunnels. For example, when the MgNB receives an SCG addition request response from the SgNB used for MC, it notifies the upper NW of a request to add a PDU session tunnel. Since the notification can be made when the SgNB used for MC is determined, unnecessary PDU session tunnels do not need to be set up.

[0654] For example, the MgNB notifies the upper NW of a request for adding a PDU session tunnel along with a path switch request. The path switch request may include PDU session tunnel addition information. Since the signaling of the path switch request can be used, the amount of signaling can be reduced.

[0655] The timing for additionally setting up a PDU session tunnel is not limited to this. The PDU session tunnel may be additionally set up after the MgNB determines the MC using the SgNB and before the path switch is performed in the upper NW.

[0656] In response to a PDU session tunnel addition request from the MgNB, the upper network notifies the MgNB of a PDU session tunnel addition request response. The upper network may also notify PDU session tunnel addition request response information. Twelve examples of PDU session tunnel addition request response information are disclosed below.

[0657] (1) Additional settings completed.

[0658] (2) Additional settings rejected.

[0659] (3) Reason for rejecting additional settings.

[0660] (4) PDU session identifier.

[0661] (5) PDU session tunnel identifier before additional configuration.

[0662] (6) The additionally configured PDU session tunnel identifier.

[0663] (7) Correspondence information between the added PDU session tunnel and the SgNB.

[0664] (8) Correspondence information between the added PDU session tunnel and the QoS flow.

[0665] (9) QoS profile of the QoS flow.

[0666] (10) UPF identifier.

[0667] (11) UPF address.

[0668] (12) A combination of (1) to (11).

[0669] The above (6) is sufficient as long as it is information that allows the MgNB to identify the additionally set up PDU session tunnel.

[0670] The additionally configured PDU session tunnel may be configured as a PDU session sub-tunnel, attached to the PDU session tunnel before the additional configuration. One or more PDU session sub-tunnels are configured for the PDU session tunnel. In this way, multiple PDU session tunnels do not need to be configured for one PDU session. The conventional configuration in which one PDU session tunnel is configured for one PDU session can be maintained.

[0671] When a PDU session sub-tunnel is set up, the PDU session sub-tunnel identifier may be used instead of the newly set PDU session tunnel identifier in the example of the PDU session tunnel addition request response information. The PDU session tunnel identifier before the additional setting may also be notified. The PDU session before the additional setting and the newly set PDU session sub-tunnel identifier may be associated and notified.

[0672] The PDU session tunnel identifier may be used as the PDU session sub-tunnel identifier. For example, the PDU session sub-tunnel identifier may be a combination of the PDU session tunnel identifier and a sub-number. For example, the PDU session sub-tunnel identifier may be PDU session tunnel identifier + sub-number. Since only the sub-number needs to be notified as information for identifying the PDU session sub-tunnel, the amount of information can be reduced.

[0673] In addition, when multiple SgNBs are used for MC, it is sufficient to provide a PDU session sub-tunnel for each SgNB, thereby eliminating the need to increase the number of PDU session tunnel identifiers.

[0674] When the MgNB notifies a request for adding a PDU session tunnel together with a path switch request to the upper network, the upper network may notify the path switch request response by including PDU session tunnel addition request response information. This can reduce the amount of signaling.

[0675] By using this method, a PDU session tunnel is additionally set up between the upper NW and the SgNB used for MC. By using the additionally set PDU session tunnel, communication between the upper NW and the SgNB becomes possible. Therefore, it becomes possible to perform MC using an SCG bearer.

[0676] A routing function for multiple SgNBs for MC is required. The location where the routing function is provided and the routing function may be appropriately applied to the routing function disclosed in the seventh embodiment. In the seventh embodiment, the upper network is the EPC, but in this first modification of the seventh embodiment, the upper network may be the NG-CN.

[0677] In the seventh embodiment, since the upper network is an EPC, it is disclosed that the upper network and multiple SgNBs are connected without changing the E-RAB bearer setting. In the present modified example 1 of the seventh embodiment, since the upper network is an NG-CN, the E-RAB bearer setting is not performed, and setting using a QoS flow is performed between the upper network and the RAN.

[0678] The routing function may be provided on the upper network side. For example, the routing function may be provided in the UPF. Alternatively, the routing function may be provided in the functions of the UPF. If the routing function is provided in the UPF, it is recommended to additionally set up a PDU session tunnel between the UPF and each SgNB for MC. The above-mentioned method for additionally setting up a PDU session tunnel is recommended.

[0679] The routing function may be provided separately from the upper network. The routing function may be provided as a node on the RAN side. The routing function may be provided in a node on the RAN side. For example, the routing function may be provided as one of the functions of the SgNB. When providing a routing function in a node on the RAN side, it is recommended to set up an additional PDU session tunnel between the UPF and the node on the RAN side. Even when MC is performed using multiple SgNBs, it is sufficient to set up one additional PDU session tunnel.

[0680] It enables data transfer between the UPF and RAN-side nodes with routing functionality. By simply adding one PDU session tunnel, it is possible to simplify the system configuration, including the upper network.

[0681] For data transfer between the RAN node with routing functionality and the SgNB used for MC, it is advisable to use an interface between base stations, such as Xn.

[0682] One way to provide a routing function in a node on the RAN side is to provide a routing function above the New AS sublayer, i.e., between the New AS sublayer and the upper network. Data from the upper network is routed at the packet data stage before being processed by the New AS sublayer. In addition, packet data from the New AS layer of each SgNB for MC is reordered based on the SN added by the routing function and forwarded to the upper network.

[0683] As another method of providing a routing function in a node on the RAN side, a routing function may be provided between the New AS sublayer and the PDCP. Data from the upper network is routed to the PDCP of each SgNB for MC at the data stage after being processed by the New AS sublayer. In addition, data from the PDCP of each SgNB for MC is reordered based on the SN added by the routing function and forwarded to the New AS layer.

[0684] A DRB may be provided for each SgNB for MC. For example, the DRB can be configured depending on the load status of the SgNB. Alternatively, one DRB may be provided for the SgNB that performs the routing function. Each SgNB for MC will perform data communication within this DRB. The DRB configuration of each SgNB may be configured so that the QoS profiles of all SgNBs for MC become the DRB for the SCG bearer or the desired QoS of the QoS flow.

[0685] When providing a routing function in a node on the RAN side, the question arises as to which gNB should have the routing function. This is because a gNB with a routing function will not necessarily be used as an SgNB in ​​the MC. For this reason, it is a good idea to provide the routing function in the gNB in ​​advance. It is also a good idea to be able to turn the routing function on and off.

[0686] This article describes a method for configuring an SgNB that has a routing function turned on. Hereinafter, an SgNB that has a routing function turned on may be referred to as an R-SgNB.

[0687] The upper network determines the R-SgNB. The AMF or SMF may determine the upper network. For example, the R-SgNB may be determined when a PDU session tunnel is added. The AMF determines the R-SgNB to connect to the UPF using the SgNB identifier for MC included in the PDU session tunnel addition information notified from the MgNB to the AMF. The AMF notifies the MgNB of the R-SgNB identifier. The R-SgNB identifier may also be notified by including it in the PDU session tunnel addition request response information.

[0688] The MgNB notifies the R-SgNB of PDU session tunnel addition request response information. Upon receiving this notification, the R-SgNB can connect to the UPF using the PDU session tunnel added to the PDU session including the QoS flow for MC. The MgNB may notify the R-SgNB of a routing implementation request between the UPF and the SgNB for MC. The implementation request may include information about the SgNB itself and information about the SgNB for MC.

[0689] Information about the own SgNB includes the identifier and address of the own SgNB, etc. Information about the SgNB for MC includes the identifier and address of the SgNB for MC, etc. The R-SgNB that receives the implementation request turns on its routing function and routes the QoS flow data communicated through the PDU session tunnel to the SgNB for MC.

[0690] The MgNB may notify the R-SgNB of the PDU session tunnel addition request response information and the routing implementation request between the UPF and the SgNB for MC together. Alternatively, the R-SgNB may request the routing implementation between the UPF and the SgNB for MC by notifying the PDU session tunnel addition request response information, information about the SgNB itself, and information about the SgNB for MC. Since the notification can be made as a single signaling, the amount of signaling can be reduced.

[0691] The AMF notifies the UPF of the PDU session tunnel addition information including at least one of the R-SgNB's identifier and address. This enables the UPF to connect to the R-SgNB using the PDU session tunnel added to the PDU session including the QoS flow for which MC is performed. Communication between the R-SgNB and the UPF becomes possible. For example, this information may be included in a path switch request notified from the AMF to the UPF.

[0692] Although it has been disclosed that AMF notifies UPF, AMF may also notify UPF via SMF. For example, this is useful when there is no direct interface between AMF and UPF.

[0693] The AMF may notify the MgNB of the R-SgNB's shutdown. The AMF also notifies the UPF of the R-SgNB's shutdown. The MgNB notifies the R-SgNB of a request to stop routing between the UPF and the SgNB for MC. Upon receiving the shutdown request, the R-SgNB turns off its routing function and stops routing.

[0694] The R-SgNB may be reconfigured. The AMF decides to change the R-SgNB connected to the UPF. The AMF notifies the MgNB of the R-SgNB change. This notification may use the notification of R-SgNB configuration mentioned above. It is recommended to notify the changed R-SgNB as the setting target. Information about the R-SgNB before the change may also be notified.

[0695] The MgNB notifies the previous R-SgNB of a request to stop routing between the UPF and the SgNB for MC. Upon receiving this stop request, the R-SgNB turns off the routing function and stops routing. The MgNB notifies the new R-SgNB of a request to implement routing between the UPF and the SgNB for MC. This notification may use the aforementioned notification of routing implementation request to the R-SgNB. Upon receiving the implementation request, the R-SgNB turns on the routing function and performs routing.

[0696] The AMF also notifies the UPF of the change in the R-SgNB. This notification may also be accompanied by a notification of the addition of a PDU session tunnel with the R-SgNB as described above. The changed R-SgNB should be notified as the target of the configuration. Information about the previous R-SgNB may also be notified. The UPF can then use the target PDU session tunnel to change the connection from the previous R-SgNB to the new R-SgNB. Communication between the new R-SgNB and the UPF is then possible.

[0697] The RAN may be provided with a function to stop routing to some SgNBs. The MgNB may notify the R-SgNB of a request to stop routing between the UPF and the SgNB for MC, along with information about the SgNBs for which routing is to be stopped or information about the SgNBs for which routing is to be continued. The R-SgNB that receives the stop request stops routing to the SgNBs to be stopped.

[0698] The MgNB may determine the R-SgNB. The MgNB may notify the upper network of information about the determined R-SgNB. As information about the R-SgNB, at least one of the identifier and address of the SgNB for which the routing function is set may be notified. The information may be notified by including it in the PDU session tunnel addition request information.

[0699] For notifications made by the MgNB to the determined R-SgNB and for notifications of information about the R-SgNB made by the AMF to the UPF, the above-mentioned method disclosed in the method for the upper network to determine the R-SgNB may be applied as appropriate.

[0700] The MgNB may also decide to stop the routing function of the R-SgNB and to reconfigure the R-SgNB. The same method as described above may be applied as appropriate.

[0701] The MgNB may notify the UE of the implementation, suspension, or reconfiguration of the routing function. In the UE, the routing function is provided between the upper layer and the New AS sublayer, or between the upper layer and PDCP. The routing function may be the same as that on the NW side.

[0702] Data routing should be configured and implemented by the MgNB for each UE. This allows the network side to recognize which SgNB is being used. Alternatively, data routing may be configured and implemented by the UE. The UE can determine which SgNB to route to based on its power consumption and load status.

[0703] A function for mapping QoS flows and SgNBs for MC may be provided as a routing function. An upper network device may determine the mapping correspondence. For example, this is effective when the routing function is provided in an upper network, such as a UPF. An AMF as an upper network may determine the mapping correspondence. The AMF notifies the UPF of the mapping correspondence. The UPF performs mapping between the QoS flows and SgNBs using the notified mapping correspondence.

[0704] The AMF may notify the MgNB of the mapping support. The MgNB may notify the UE of the mapping support. In this way, the UE can perform mapping between the QoS flow and the SgNB for MC even for uplink communication.

[0705] A node of the RAN may determine the mapping correspondence. For example, this is effective when a routing function is provided in a node on the RAN side. An MgNB as a node of the RAN may determine the mapping correspondence. The MgNB notifies the R-SgNB of the mapping correspondence. The SgNB performs mapping between the QoS flow and the SgNB using the notified mapping correspondence.

[0706] The MgNB may notify the UE of the mapping support, which enables the UE to perform mapping between the QoS flow and the SgNB for MC for uplink communication as well.

[0707] In this way, an SgNB can be configured for each QoS flow. Packet data for a specific QoS flow can be communicated using a specific SgNB. By configuring the SgNB appropriately according to its load status and processing capacity, throughput can be improved.

[0708] This paper discloses how to configure the DRB required for MC in the SgNB and how to map from the New AS sublayer of the SgNB.

[0709] The MgNB notifies each SgNB for MC of information about the DRB setting. The following are nine examples of information about the DRB setting.

[0710] (1) DRB identifier for MC.

[0711] (2) DRB configuration subject to MC.

[0712] (3) QoS flow identifier mapped to the DRB that is the MC target.

[0713] (4) QoS profile for each QoS flow.

[0714] (5) MC target PDU session identifier.

[0715] (6) An additionally configured PDU session tunnel identifier.

[0716] (7) Identifier of the upper device that establishes the PDU session tunnel.

[0717] (8) Address of the upper device that establishes the PDU session tunnel.

[0718] (9) A combination of (1) to (8).

[0719] Each SgNB configures a DRB for MC using the notified information about the DRB configuration. Each SgNB configures mapping from the New AS sublayer to the configured DRB according to the notified information. The DRB configuration at each SgNB may be different. The DRB identifier may also be different. The MgNB may notify each SgNB for MC of information about the DRB configuration using SgNB reconfiguration complete signaling.

[0720] The MgNB may notify each SgNB for MC of a PDU session tunnel establishment request. The above-mentioned information on the DRB setting may be appropriately applied as information for the PDU session tunnel establishment request. The information on the DRB setting and the PDU session tunnel establishment request may be notified together. The notification may be performed by one signaling. This reduces the amount of signaling.

[0721] Each SgNB notifies the MgNB of the DRB setting response information. The following are eight examples of the DRB setting response information.

[0722] (1) Identifier of own SgNB.

[0723] (2) Address of your own SgNB.

[0724] (3) DRB setting approved.

[0725] (4) DRB setting rejected.

[0726] (5) Reasons for refusal of DRB establishment.

[0727] (6) DRB configuration set by the local SgNB.

[0728] (7) DRB identifier set by the local SgNB.

[0729] (8) A combination of (1) to (7).

[0730] The MgNB configures the UE with an MC. As the MC configuration, the DRB configuration result at each SgNB for the MC may be notified. The method of configuring and notifying the MC from the MgNB to the UE may be appropriately applied to the first variant of the sixth embodiment. As the bearer type, an MCG split bearer is disclosed in the first variant of the sixth embodiment, but an SCG bearer may be applied in this first variant of the seventh embodiment.

[0731] By using this method, the upper network can set up MC using an SCG bearer in the NG-CN. MC can be set up for each DRB. MC can be performed between the UE and MgNB, and between the UE and each SgNB for MC. The throughput of the DRB in which MC is set up can be improved.

[0732] Figure 32 is a conceptual diagram showing the data flow when MC using an SCG bearer is set for each DRB. The mapping relationship between the QoS flows and DRBs before setting up MC is the relationship shown in Figure 21. The DRB where MC is performed is DRB1. QoS flow 1 and QoS flow 2 are mapped to DRB1.

[0733] As shown in Figure 32, the MgNB sets up the DRB1 to the MC using the SCG bearer, so that the MgNB additionally sets up a PDU session tunnel on the SgNB side for the MC. Figure 32 shows a case where a node having a routing function is provided separately from the upper network. Therefore, a PDU session tunnel is additionally set up between the upper network and the node having the routing function. When the routing function is provided in the upper network, a PDU session tunnel is additionally set up between the upper network and each SgNB for the MC.

[0734] The added PDU session tunnel carries out communication between QoS flow 1 and QoS flow 2 that were mapped to the DRB that sets the MC. Packet data mapped to QoS flow 1 and QoS flow 2 in the upper network is communicated using the added PDU session tunnel.

[0735] Data is routed to each SgNB for MC by a node with routing functionality. Each SgNB configures a DRB for MC using information on DRB1 for which MC is configured, notified by the MgNB. Figure 32 shows a case where each SgNB configures the same settings as the DRB1 configured by the MgNB. Figure 32 also shows a case where the DRB identifier is set to the same as the DRB identifier configured by the MgNB.

[0736] The data mapped to QoS Flow 1 and QoS Flow 2 is forwarded to the New AS sublayer of each SgNB, and the New AS sublayer maps the data to DRB1. In this way, each SgNB for MC can process the QoS flows that were mapped to DRB1 where the MC is configured.

[0737] The MgNB may notify each SgNB configuration for performing MC and the DRB configuration set by each SgNB. For this notification, for example, the method of notifying the UE of the DRB configuration from the MgNB disclosed in the sixth embodiment may be applied. The UE can set the DRB configuration set by each SgNB. The same applies to uplink data. In this way, it becomes possible to perform MC for each DRB.

[0738] Figures 33 to 35 are diagrams showing an example of a sequence for setting up an MC using an SGB bearer when the upper network is an NG-CN. Figures 33 to 35 are connected at boundary lines BL3334 and BL3435. Figures 33 to 35 show a case where an MgNB and two SgNBs (SgNB1, SgNB2) are used. The sequences shown in Figures 33 to 35 include the same steps as the sequences shown in Figures 19 and 20 and Figures 29 and 30, so the same step numbers are used for the same steps and common explanations will be omitted.

[0739] In steps ST5501 and ST5502, the MgNB notifies the SgNB1 and SgNB2 of an SgNB addition request. The addition request signaling may include information about the DRB configuration described above. The information about the DRB configuration may include, for example, the identifier and DRB configuration of the DRB to be MC-enabled, the identifier and QoS profile of each QoS flow of the QoS flow mapped to the DRB to be MC-enabled, and the PDU session identifier to be MC-enabled.

[0740] The MgNB may determine a QoS profile setting for each SgNB for which MC is configured so as to satisfy the QoS profile of the QoS flow for which MC is performed.

[0741] The MgNB may notify each SgNB that sets up MC of the DRB configuration requested from each SgNB. The MgNB may set the DRB configuration to be the same as the DRB configuration before setting up. Alternatively, the bearer configuration of the SgNB that sets up MC may be determined so that the bearer configuration satisfies the QoS profile of the QoS flow that performs MC.

[0742] Upon receiving information regarding DRB configuration from the MgNB, the SgNB1 and SgNB2 configure the DRB for mapping the QoS flow to be MC-targeted. In steps ST5503 and ST5504, the SgNB1 and SgNB2 notify the MgNB of an addition request response to the addition request. The addition request response signaling may include the above-mentioned DRB configuration response information. The addition request response may be, for example, a DRB configuration acknowledgement, and the DRB configuration response information may be, for example, a DRB identifier and configuration configured by the local SgNB, an identifier and address of the local SgNB, etc. The AS configuration configured by the local SgNB may also be notified.

[0743] In Step ST5505, the MgNB that has received the SgNB addition request response signaling from each SgNB used for MC notifies the upper network of a request to add a PDU session tunnel in order to set up MC using an SCG bearer. The PDU session tunnel addition request signaling may include the above-mentioned PDU session tunnel addition information. The PDU session tunnel addition information may be, for example, a PDU session identifier to be the target of MC, a PDU session tunnel identifier to be the target of MC, a QoS flow identifier to be the target of MC, an SgNB identifier and address for MC, etc.

[0744] In Step ST5506, the AMF / SMF notifies the UPF of a PDU session tunnel addition request. As described above, the PDU session tunnel addition request signaling may include the above-mentioned PDU session tunnel addition information.

[0745] The UPF, which has been notified of the PDU session tunnel addition request and the PDU session tunnel addition information in Step ST5506, additionally sets up a PDU session tunnel between itself and each SgNB used for MC.

[0746] In Step ST4302, the MgNB notifies the UE of the MC configuration. As the MC configuration, the MgNB notifies the UE of the SCG configuration of each SgNB for MC and the DRB configuration set in each SgNB. As signaling, RRCConnectionReconfiguration for setting up an RRC connection may be used. In addition, the MgNB may notify the UE that the bearer type is an SCG bearer.

[0747] The UE that has received the SCG configuration and DRB configuration of SgNB1 and SgNB2 in Step ST4302 configures MC for the MgNB, SgNB1, and SgNB2 in accordance with the configuration. In Step ST4303, the UE notifies the MgNB of an RRC connection reconfiguration complete (RRCConnectionReconfigurationComplete) including the MC configuration completion.

[0748] The MgNB, which has recognized that the UE has completed the MC setup, notifies SgNB1 in Step ST4207 of signaling indicating that the additional setup of the SCG of each SgNB has been completed, and notifies SgNB2 in Step ST4219 of signaling indicating that the additional setup of the SCG of each SgNB has been completed. SgNB1 and SgNB2 recognize that the connection setup for MC with the UE has been completed.

[0749] The MgNB may notify the SgNB1 and SgNB2 of a PDU session tunnel establishment request using the signaling of the SCG additional setting completion in steps ST4207 and ST4219. The signaling of the SCG additional setting completion may include information about the DRB setting described above as information for the PDU session tunnel establishment request.

[0750] Information regarding DRB configuration includes, for example, the DRB identifier to be the MC target, the QoS flow identifier mapped to the DRB to be the MC target, the PDU session identifier to be the MC target, the additionally configured PDU session tunnel identifier, and the identifier and address of the upper device that establishes the PDU session tunnel.

[0751] As a result, a PDU session tunnel is additionally set up between the AMF / SMF and each SgNB used for MC. Data communication is possible between the SgNB for MC using the SCG bearer and the upper NW.

[0752] In steps ST4208 and ST4220, the UE performs RA processing with SgNB1 and SgNB2 to establish synchronization. In steps ST5201 to ST5203, the SN state and data are transferred from the MgNB to SgNB1. For data transfer, the method disclosed in embodiment 7 may be applied as appropriate.

[0753] In Step ST5508, the MgNB notifies the AMF / SMF of a PDU session tunnel switching request. The MgNB requests that the QoS flow included in the DRB to be the MC target be changed from the PDU session tunnel before MC configuration to the PDU session tunnel additionally configured between the SgNBs used for MC. It is preferable that information for PDU session tunnel switching be included in the PDU session tunnel switching request signaling.

[0754] Eight examples are provided below as information for PDU session tunnel switching.

[0755] (1) QoS flow identifier mapped to the DRB that is the MC target.

[0756] (2) The PDU session identifier for the MC.

[0757] (3) An additionally configured PDU session tunnel identifier.

[0758] (4) Identifier of the upper device that establishes the PDU session tunnel.

[0759] (5) The address of the upper device that establishes the PDU session tunnel.

[0760] (6) Identifier of the SgNB used for MC.

[0761] (7) Address of the SgNB used for MC.

[0762] (8) A combination of (1) to (7).

[0763] As in Step ST5508, in Step ST5509, the AMF / SMF notifies the UPF of a PDU session tunnel switching request. In Step ST5206, the UPF that has received the PDU session tunnel switching request transmits an end marker packet as the last packet data to the MgNB, and uses the information notified in the PDU session tunnel switching request to switch to the PDU tunnel that has been additionally set up with the SgNB used for MC. In Step ST5207, the MgNB forwards the end marker to SgNB1. This allows SgNB1 to recognize that the data from the MgNB has ended.

[0764] The AMF / SMF that notified the UPF of the PDU session tunnel switching request in Step ST5509 notifies the MgNB of a PDU session tunnel switching request response, which allows the MgNB to recognize that the PDU session tunnel between the SgNB1 and SgNB2 for MC has been switched to the additionally set PDU session tunnel.

[0765] The UPF, which has received the MC path switch setting information in Step ST5509, transmits an end marker packet as the last packet data to the MgNB in ​​Step ST5206 and initiates a path switch. In Step ST5207, the MgNB forwards the end marker to the SgNB1. This allows the SgNB1 to recognize that the data from the MgNB has ended.

[0766] In step ST5210, packet data is routed between each SgNB for MC by the routing function provided in the UPF, and in steps ST5211 to ST5214, data communication is performed between SgNB1, SgNB2 and the UPF.

[0767] In this way, when the upper network is NG-CN, it becomes possible to perform MC using an SGC bearer. The MgNB can set MC using an SCG bearer for the UE. The UE can perform MC by connecting to multiple SgNBs for MC.

[0768] As for the data splitting method in the uplink in the MC, the method disclosed in the sixth embodiment may be applied as appropriate. It may be applied to the SgNB used for the MC.

[0769] The method for starting transmission of uplink data from the UE to the base station may be the method disclosed in the sixth embodiment, as appropriate. This method may be applied to the MgNB and the SgNB used for MC.

[0770] A method for returning from an MC setting using an SCG bearer to an MCG bearer is disclosed. When a PDU session tunnel for a PDU session that is the target of MC is set between the MgNB and the upper network, the MgNB releases the PDU session tunnel set in each SgNB and sets the QoS flow included in the DRB that is the target of MC to use the PDU session tunnel set between the MgNB and the upper network.

[0771] If a PDU session tunnel for a PDU session that is the target of MC is not set between the MgNB and the upper NW, the MgNB may set a PDU session tunnel between the MgNB and the upper NW. The MgNB may release the PDU session tunnel set in each SgNB and set it so that the PDU session tunnel set between the MgNB and the upper NW is used for the QoS flow included in the DBR that is the target of MC.

[0772] Furthermore, the MgNB may cancel the MC settings established between each SgNB and the UE. These methods may be appropriately applied by using the above-described methods.

[0773] Another method for setting MC using an SCG bearer is disclosed. MC is set for each QoS flow. The New AS sublayer performs MC using an SCG bearer for one or more QoS flows among the QoS flows mapped to the DRB.

[0774] When the upper network sets up an MC using an SCG bearer for each QoS flow in the NG-CN, the following problems arise in addition to the problems mentioned above.

[0775] In an MgNB, when multiple QoS flows are mapped to one DRB and MCs are set for each QoS flow, some QoS flows will remain mapped to the DRB even after MCs are set. In such cases, data will be processed by PDCP and an SN will be added even after MCs are set.

[0776] When the connection with the UE is transferred from the MgNB to the SgNB by MC using the SCG bearer, data that was being processed in the MgNB needs to be transferred to the SgNB. In this case, it was conventionally possible to transfer the SN status and use that SN to set the PDCP SN in the SgNB. This allows the UE to perform PDCP reordering by the SN.

[0777] However, as mentioned above, when multiple QoS flows are mapped to a DRB that sets an MC, there is a case where not only the data of the QoS flows that set an MC but also the data of the QoS flows that do not set an MC are transferred to the SgNB. In this case, the data of the QoS flows that do not set an MC is also processed by the PDCP of the SgNB, which causes a problem that the data of the QoS flows that set an MC cannot be reordered correctly. The same applies to the uplink.

[0778] To solve this problem, forwarding processing is performed for each QoS flow. It is advisable to limit the data forwarded from the MgNB to the SgNB to QoS flows for which an MC is set. The MgNB determines the data based on the QoS flow identifier attached to the data, and forwards the data to the SgNB if the QoS flow has an MC set, but does not forward the data if the QoS flow does not have an MC set.

[0779] QoS flow data forwarded to the SgNB is processed by the SgNB. QoS flow data that is not forwarded to the SgNB is processed by the MgNB. By performing forwarding processing for each QoS flow in this way, it becomes possible to process data correctly at the SgNB.

[0780] Another method for solving this problem is to set up an additional DRB for a QoS flow that performs MC and map the QoS flow that performs MC to the additional DRB. By setting up the additional DRB as an MC, it becomes possible to set an MC for the QoS flow mapped to the DRB.

[0781] By doing this, after MC is set, no QoS flows mapped to the newly set DRB remain. Therefore, data of the QoS flows that perform MC and are mapped to the newly set DRB is transferred to the SgNB. Since the data of the QoS flows that perform MC is processed by the PDCP of the SgNB, reordering can be performed normally. The same applies to the uplink.

[0782] The method of additionally setting up a DRB for a QoS flow that performs MC and mapping the QoS flow that performs MC to the additionally set up DRB may be appropriately applied using the method of additionally setting up a DRB for a QoS flow that performs MC disclosed in variant example 1 of embodiment 6.

[0783] Figure 36 is a conceptual diagram showing the data flow when MC using an SCG bearer is set for each QoS flow. The mapping relationship between the QoS flow and the DRB before setting the MC is the relationship shown in Figure 21. The DRB where MC is performed is DRB1. QoS flow 1 and QoS flow 2 are mapped to DRB1.

[0784] As shown in Figure 36, the MgNB sets up QoS flow 1 of DRB1 to an MC using an SCG bearer, so that the MgNB additionally sets up a PDU session tunnel on the SgNB side for the MC. Figure 36 shows a case where a node having a routing function is provided separately from the upper network. Therefore, a PDU session tunnel is additionally set up between the upper network and the node having the routing function. When the routing function is provided in the upper network, a PDU session tunnel is additionally set up between the upper network and each SgNB for the MC.

[0785] In the added PDU session tunnel, communication of QoS flow 1 that sets MC is performed. Packet data mapped to QoS flow 1 in the upper network is communicated using the added PDU session tunnel.

[0786] The data is routed to each SgNB for the MC by a node with routing functionality. Each SgNB configures a DRB for the MC using information about DRB1 for which the MC is configured, which is notified by the MgNB. Each SgNB may configure a DRB for the MC using information about the QoS profile of QoS flow 1 for which the MC is configured, which is notified by the MgNB.

[0787] Figure 36 shows a case where each SgNB is configured with a different setting from the DRB1 configured in the MgNB. Also, Figure 36 shows a case where the DRB identifier is set to a DRB identifier (DRBY1) different from the DRB identifier configured in the MgNB.

[0788] The data mapped to QoS flow 1 is forwarded to the New AS sublayer of each SgNB and mapped to DRBY1 in the New AS sublayer. In this way, each SgNB for MC can process QoS flow 1 for which the MC is configured.

[0789] On the other hand, no MC is set for QoS flow 2 in DRB1, and communication for QoS flow 2 is performed on the MgNB side. The MgNB maintains a DRB on the MgNB side for QoS flow 2 in DRB1. The MgNB may reconfigure DRB1. For example, after setting the MC, it is recommended to reconfigure a DRB configuration suitable for QoS flow 2.

[0790] Figure 36 shows a case where the same setting as the DRB1 set in the MgNB is performed. Also, Figure 36 shows a case where the DRB identifier is set to the same DRB identifier (DRB1) as the DRB identifier set in the MgNB.

[0791] Communication of QoS flow 2 is performed using the PDU session tunnel that was established between the upper network and the MgNB before the MC was set up. The data mapped to QoS flow 2 in the upper network is forwarded to the New AS sublayer of the MgNB, and is then mapped to DRB1 in the New AS sublayer. This makes it possible for the MgNB to process QoS flow 2, for which no MC is set up.

[0792] The MgNB may notify the UE of the reconfigured DRB configuration. The MgNB may also notify each SgNB configuration for which MC is to be configured and the DRB configuration configured at each SgNB. For this notification, for example, the method of notifying the UE of the DRB configuration from the MgNB disclosed in the sixth embodiment may be applied. The UE can then reconfigure the DRB configuration configured at the MgNB side, and can also configure the DRB configuration configured at each SgNB. The same applies to uplink data. In this way, it becomes possible to implement MC for each QoS flow.

[0793] The sequence for setting up an MC using an SCG bearer for each QoS flow may be the same as that shown in Figures 26 and 27. Steps ST4902 to ST4913 may be performed to additionally set up a DRB for a QoS flow that performs MC. A DRB for the QoS flow that performs MC is additionally set up, and the QoS flow that performs MC is mapped to the additionally set up DRB. By setting up the additionally set up DRB as an MC, it becomes possible to set up an MC for the QoS flow mapped to the DRB.

[0794] By doing this, after MC is set, no QoS flows mapped to the newly set DRB remain. Therefore, data of the QoS flows that perform MC and are mapped to the newly set DRB is transferred to the SgNB. Since the data of the QoS flows that perform MC is processed by the PDCP of the SgNB, reordering can be performed normally. The same applies to the uplink.

[0795] In Step ST4914, the MgNB starts MC setup using the SCG bearer of the DRB that is additionally set up for the QoS flow that performs MC. In Step ST4915, the MgNB, the SgNB1 and SgNB2 used for MC, the AMF / SMF, the UPF, and the UE perform MC setup processing using the SCG bearer among themselves. Figures 33 to 35 may be applied to this MC setup processing.

[0796] As for the data splitting method in the uplink in the MC, the method disclosed in the sixth embodiment may be applied as appropriate. It may be applied to an SgNB that sets an MC for each QoS flow.

[0797] The method of starting transmission of uplink data from the UE to the base station may be appropriately applied to the method disclosed in the sixth embodiment. This method may be applied to the MgNB and the SgNB that sets the MC for each QoS flow. An SR and BSR may be provided for each QoS flow, and the UE may notify the base station.

[0798] In this way, when the upper network is NG-CN, it becomes possible to perform MC using an SGC bearer. The MgNB can set MC using an SCG bearer for the UE. The UE can perform MC by connecting to multiple SgNBs for MC.

[0799] In addition, the MgNB can perform MC for the UE using an SCG bearer for each QoS flow. Because MC can be performed for each QoS flow, MC control can be performed with finer QoS accuracy than MC for each bearer.

[0800] An eNB, which is an LTE base station, may be used as a base station for MC that is not connected to an upper network. An eNB and a gNB may also be used. The method disclosed in Modification 1 of the seventh embodiment may be applied as appropriate. In Modification 1, a New AS sublayer is not used in a base station for MC that is not connected to an upper network, so it is possible to use an eNB.

[0801] By using the method disclosed in this first modification of the seventh embodiment, even when the upper network is an NG-CN, it is possible to configure a single UE so that it is connected to multiple secondary base stations. This makes it possible to improve the throughput of communications provided to the UE. Furthermore, connecting to multiple base stations can also improve reliability. Furthermore...

Claims

1. A user device; A communication system comprising a plurality of base stations that wirelessly communicate with the user equipment, The plurality of base stations include a master base station and a secondary base station that configure dual connectivity for the user equipment, At least one of the plurality of base stations individually sets SCG configuration information and bearer configuration information. Communication systems.

2. The master base station notifies the secondary base station of QoS-related information including a QoS flow identifier and a QoS profile. The communication system according to claim 1 .

3. The master base station notifies the user equipment of configuration information including a QoS flow identifier. The communication system according to claim 1 .

4. The configuration information includes information indicating a correspondence relationship between a QoS flow and a radio bearer. The communication system according to claim 3.

5. The user equipment or the master base station inserts an end marker at the end of the transmission data in the SDAP layer. The communication system according to claim 1 .

6. The master base station or the secondary base station notifies the user equipment of information regarding whether to perform packet duplication using the dual connectivity or packet duplication using carrier aggregation by RRC signaling. The communication system according to claim 1 .

7. The secondary base station notifies the master base station of a message including information regarding packet duplication. The communication system according to claim 1 .

8. The message includes at least one of information regarding the presence or absence of packet duplication, information regarding a logical channel, and information regarding packet duplication in an SRB.

8. The communication system according to claim 7.

9. A user device; A user equipment in a communication system including a plurality of base stations that wirelessly communicate with the user equipment, The plurality of base stations include a master base station and a secondary base station that configure dual connectivity for the user equipment, A message for individually setting SCG configuration information and bearer configuration information is received from at least one of the plurality of base stations. User equipment.

10. A user device; A base station in a communication system including a plurality of base stations that wirelessly communicate with the user equipment, The plurality of base stations include a master base station and a secondary base station that configure dual connectivity for the user equipment, Set SCG configuration information and bearer configuration information separately Base station.

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