Communication method, node, and user equipment

Abstract

The present invention provides a communication method for wirelessly communicating, by a user equipment, with a master node and a plurality of secondary nodes in a mobile communication system, the communication method comprising: a step of executing, by the master node, processing of transferring, to at least one of the plurality of secondary nodes, control authority for executing, for the user equipment, configuration and / or control relating to coordinated operation among the plurality of secondary nodes; and a step of executing for the user equipment, by the secondary node(s) having the transferred control authority, the configuration and / or the control relating to the coordinated operation.

Description

Communication method, node, and user device

[0001] The present disclosure relates to a communication method, a node, and a user equipment for use in a mobile communication system.

[0002] The Third Generation Partnership Project (3GPP (registered trademark; the same applies hereinafter)), a standardization project for mobile communication systems, defines technical specifications for Dual Connectivity (DC). In DC, a user equipment (UE) performs wireless communication with a master cell group (MCG) of a master node (MN) and a secondary cell group (SCG) of a secondary node (SN). In DC, the roles of nodes communicating with the UE are divided between the MN and the SN. Except for settings determined independently by the SN, the MN has the initiative (also referred to as "control authority") to configure and control the UE.

[0003] In each of the MCG and SCG, multiple component carriers (CCs) corresponding to multiple serving cells are aggregated, and a UE can simultaneously receive or transmit on multiple CCs (i.e., multiple cells). The multiple CCs may be contiguous or non-contiguous in the frequency direction. One serving cell in each of the MCG and SCG is called a primary cell (PCell), and a set of serving cells is formed by configuring one or more secondary cells (SCells) for the UE together with the PCell. The PCell (SpCell) of the SCG is also called a primary secondary cell (PSCell).

[0004] In the current 3GPP technical specifications, a UE uses only one SN in a DC. On the other hand, Non-Patent Document 1 describes multi-connectivity in which a UE simultaneously uses multiple SNs (i.e., multiple SCGs). However, such multi-connectivity involves the MN configuring and / or controlling multiple SNs, which may increase the load on the MN.

[0005] 3GPP contribution RWS-210143 “Multi Radio Multi Connectivity for Rel-18”

[0006] A communication method according to a first aspect is a communication method for a user device to perform wireless communication with a master node and a plurality of secondary nodes in a mobile communication system, and includes the steps of: the master node performing a process of delegating control authority for configuring and / or controlling the user device regarding cooperative operation between the plurality of secondary nodes to at least one of the plurality of secondary nodes; and the secondary node to which the control authority has been delegated performs configuration and / or control regarding the cooperative operation for the user device.

[0007] A node according to a second aspect is a node that operates as a master node in a mobile communication system in which a user device performs wireless communication with a master node and a plurality of secondary nodes, and is equipped with a control unit that performs processing to delegate control authority for the user device to configure and / or control cooperative operation between the plurality of secondary nodes to at least one of the plurality of secondary nodes.

[0008] A node according to a third aspect is a node that operates as a secondary node in a mobile communication system in which a user device performs wireless communication with a master node and a plurality of secondary nodes, and is provided with a control unit that, when the control authority to configure and / or control the user device regarding cooperative operation between the plurality of secondary nodes is delegated from the master node to the user device, configures and / or controls the cooperative operation.

[0009] A user device according to a fourth aspect is a user device that performs wireless communication with a master node and a plurality of secondary nodes, and is equipped with a wireless communication unit that receives signals for setting and / or controlling the cooperative operation between the plurality of secondary nodes from a secondary node to which the master node has delegated control authority to the user device to set and / or control the cooperative operation between the plurality of secondary nodes.

[0010] 1 is a diagram illustrating an example of the configuration of a mobile communication system according to an embodiment. FIG. 2 is a diagram illustrating an example of the configuration of a protocol stack of a radio interface of a U-plane that handles data. FIG. 3 is a diagram illustrating an example of the configuration of a protocol stack of a radio interface of a C-plane that handles signaling (control signals). FIG. 4 is a diagram illustrating a terahertz (THz) wave cell according to an embodiment. FIG. 5 is a diagram illustrating dual connectivity (DC) according to an embodiment. FIG. 6 is a diagram illustrating an example of a procedure for LTM according to an embodiment. FIG. 7 is a diagram illustrating an example of the configuration of a node (base station) according to an embodiment. FIG. 8 is a diagram illustrating an example of the configuration of a UE (user equipment) according to an embodiment. FIG. 9 is a diagram illustrating an operation scenario of a mobile communication system according to a first embodiment. FIG. 10 is a diagram illustrating an overview of the operation of the mobile communication system according to the first embodiment. FIG. 11 is a diagram illustrating an example of the operation of the mobile communication system according to the first embodiment. FIG. 12 is a diagram illustrating a modified example of the operation of the mobile communication system according to the first embodiment. FIG. 13 is a diagram illustrating an operation scenario of a mobile communication system according to a second embodiment. FIG. 14 is a diagram illustrating an example of the operation of a mobile communication system according to a second embodiment.

[0011] Hereinafter, a mobile communication system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0012] (1) First Embodiment The first embodiment will be described with reference to FIGS. 1 to 11. FIG.

[0013] (1.1) System Configuration Example Fig. 1 is a diagram showing a configuration example of a mobile communication system according to the first embodiment. The mobile communication system according to the first embodiment is a system that complies with the 3GPP standard. For example, the mobile communication system according to the first embodiment may be a fifth-generation (5G) system or a sixth-generation (6G) system.

[0014] The mobile communication system includes a network (NW) 1 and a user equipment (UE) 100. The UE 100 is a mobile communication device that performs wireless communication with the NW 1. The UE 100 may be any device used by a user, and may be, for example, a mobile phone terminal (including a smartphone), a tablet terminal, a notebook PC (Personal Computer), a communication module (including a communication card or chipset), a sensor or a device provided in a sensor, a vehicle or a device provided in a vehicle (Vehicle UE), or an aircraft or a device provided in an aircraft (Aerial UE).

[0015] NW1 includes a radio access network (RAN) 10 and a core network (CN) 20. When the mobile communication system is a 5th generation system (5GS), the RAN 10 is referred to as a Next Generation Radio Access Network (NG-RAN), and the CN 20 is referred to as a 5G Core Network (5GC).

[0016] The RAN 10 includes a plurality of nodes 200 (nodes 200a to 200c in the illustrated example). The nodes 200 are connected to each other via inter-node interfaces. The nodes 200 are also referred to as base stations. The nodes 200 may be configured (i.e., functionally divided) with a CU (Central Unit) and a DU (Distributed Unit), and the two units may be connected by a fronthaul interface. When the mobile communication system is 5GS, the nodes 200 are referred to as gNBs, the inter-node interface is referred to as an Xn interface, and the fronthaul interface is referred to as an F1 interface.

[0017] Each node 200 manages one or more cells. The node 200 performs wireless communication with the UE 100 that has established a connection with its own cell. Each node 200 has a radio resource management (RRM) function, a routing function for user data (also simply referred to as "data"), a measurement control function for mobility control and scheduling, and the like. Note that "cell" is used as a term indicating the smallest unit of a wireless communication area. "Cell" is also used as a term indicating a function or resource for performing wireless communication with the UE 100. One cell belongs to one carrier frequency (also simply referred to as "frequency").

[0018] The CN 20 includes a CN device 300. The CN device 300 may include a C-plane device corresponding to the control plane (C-plane) and a U-plane device corresponding to the user plane (U-plane). The C-plane device performs various mobility controls and paging for the UE 100. The C-plane device communicates with the UE 100 using NAS (Non-Access Stratum) signaling. The U-plane device controls data transfer. When the mobile communication system is 5GS, the C-plane device is referred to as an AMF (Access and Mobility Management Function), the U-plane device is referred to as a UPF (User Plane Function), and the interface between the node 200 and the CN device 300 is referred to as an NG interface.

[0019] FIG. 2 is a diagram showing an example of the configuration of a protocol stack of a U-plane radio interface that handles data.

[0020] The U-plane radio interface protocol includes, for example, a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, and a service data adaptation protocol (SDAP) layer.

[0021] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of UE 100 and the PHY layer of node 200 via a physical channel. The PHY layer of UE 100 receives downlink control information (DCI) transmitted from node 200 on a physical downlink control channel (PDCCH). Specifically, UE 100 performs blind decoding of the PDCCH using a radio network temporary identifier (RNTI) and acquires successfully decoded DCI as DCI addressed to the UE. The DCI transmitted from node 200 has CRC parity bits scrambled by the RNTI added.

[0022] The MAC layer performs data priority control and retransmission processing using Hybrid ARQ (HARQ). Data and control information are transmitted between the MAC layer of UE 100 and the MAC layer of node 200 via a transport channel. The MAC layer of node 200 includes a scheduler. The scheduler determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the resources to be allocated to UE 100.

[0023] The RLC layer transmits data to the RLC layer on the receiving side by using the functions of the MAC layer and the PHY layer. Data and control information are transmitted between the RLC layer of the UE 100 and the RLC layer of the node 200 via logical channels.

[0024] The PDCP layer performs header compression / decompression, encryption / decryption, and the like.

[0025] The SDAP layer maps IP flows, which are units for QoS control by the CN 20, to radio bearers, which are units for QoS control by the AS (Access Stratum). Note that if the RAN is connected to the EPC, SDAP may not be required.

[0026] FIG. 3 is a diagram showing an example of the configuration of a protocol stack of a C-plane radio interface that handles signaling (control signals).

[0027] The protocol stack of the C-plane radio interface includes, for example, an RRC (Radio Resource Control) layer and an NAS (Non-Access Stratum) layer instead of the SDAP layer shown in FIG.

[0028] RRC signaling for various settings is transmitted between the RRC layer of UE100 and the RRC layer of node 200. The RRC layer controls logical channels, transport channels, and physical channels in accordance with the establishment, re-establishment, and release of radio bearers. When there is a connection (RRC connection) between the RRC of UE100 and the RRC of node 200, UE100 is in an RRC connected state. When there is no connection (RRC connection) between the RRC of UE100 and the RRC of node 200, UE100 is in an RRC idle state. When the connection between the RRC of UE100 and the RRC of node 200 is suspended, UE100 is in an RRC inactive state.

[0029] The NAS layer (also simply referred to as "NAS") located above the RRC layer performs session management, mobility management, etc. NAS signaling is transmitted between the NAS layer of the UE 100 and the NAS layer of the CN device 300. Note that the UE 100 also has an application layer in addition to the radio interface protocol. The layer below the NAS layer is referred to as the AS layer (also simply referred to as "AS").

[0030] (1.2) DC Using a Terahertz Wave Cell FIG. 4 is a diagram for explaining a terahertz (THz) wave cell according to the first embodiment.

[0031] The mobile communication system according to the first embodiment may be a 6G system. It is expected that 6G will utilize terahertz (THz) waves. A cell operated using THz waves is called a THz wave cell. Compared to millimeter waves (mmW), THz waves have a stronger tendency to propagate in a straighter direction, have a higher free space loss, and are more susceptible to the effects of the atmosphere and precipitation. Therefore, the THz wave cell may be an ultra-small cell.

[0032] In the illustrated example, the diameter of the coverage area of ​​the THz wave cell is about 10 [m], the diameter of the coverage area of ​​the mmW cell operated at mmW is about 100 [m], and the diameter of the coverage area of ​​the macro cell is about 1000 [m]. Under these assumptions, for example, UE 100 moving at 60 [km / s] passes through the coverage area of ​​each THz wave cell in about 599 [ms].

[0033] Dual connectivity (DC) is one method for stably controlling small cells in a mobile communication system.

[0034] 5 is a diagram for explaining dual connectivity (DC) according to the first embodiment. In the first embodiment, it is assumed that a THz-wave cell is used as a cell of a secondary cell group (SCG). Furthermore, a THz-wave cell may be used as a secondary cell (SCell) of a master cell group (MCG). However, a mmW cell may be used instead of the THz-wave cell.

[0035] A DC may be configured for a UE 100 in an RRC connected state. In the DC, the UE 100 performs wireless communication with a master cell group (MCG) managed by a master node (MN) 200M and a secondary cell group (SCG) managed by a secondary node (SN). The MN 200M and the SN 200S are connected to each other via an inter-node interface. When there is no need to distinguish between the MN 200M and the SN 200S, they are simply referred to as nodes 200. The MN 200M is also referred to as a master gNB (MgNB) when it is a 5G / NR node. The SN 200M is also referred to as a secondary gNB (SgNB) when it is a 5G / NR node. Except for settings independently determined by the SN 200S, the MN 200M has the initiative (control authority) to configure and control the UE 100.

[0036] For example, MN200M transmits a predetermined message (for example, an SN Addition Request message) to SN200S, and MN200M transmits an RRC Reconfiguration message to UE100, whereby SCG is set in UE100 and DC is started. In DC, UE100 in the RRC connected state is assigned radio resources from the respective schedulers of MN200M and SN200S, and performs radio communication using the radio resources of MN200M and the radio resources of SN200S.

[0037] The MN 200M may have a control plane connection with the CN 20. The MN 200M provides the primary radio resources for the UE 100. The MN 200M manages the MCG, which is a group of serving cells associated with the MN 200M. The MCG has a primary cell (PCell) and optionally has one or more secondary cells (SCells). On the other hand, the SN 200S may not have a control plane connection with the CN 20. The SN 200S provides additional radio resources to the UE 100. The SN 200S manages the SCG, which is a group of serving cells associated with the SN 200S. The SCG has a primary / secondary cell (PSCell) and optionally has one or more SCells. The PCell of the MCG and the PSCell of the SCG are sometimes referred to as special cells (SpCells).

[0038] In the current 3GPP technical specification, the UE 100 uses only one SN 200S in the DC. That is, the UE 100 cannot use multiple SNs 200S simultaneously. On the other hand, in the first embodiment, multi-connectivity is assumed in which the UE 100 uses multiple SNs 200S (i.e., multiple SCGs) simultaneously.

[0039] (1.3) Overview of LTM The mobile communication system according to the first embodiment supports LTM (L1 / L2-triggered mobility).

[0040] LTM is a technique for reducing mobility delay compared to a typical handover procedure by triggering cell switching through signaling of lower layers, Layer 1 (L1) and / or Layer 2 (L2). In LTM, first, the node 200 prepares an LTM candidate cell configuration for a candidate cell to switch to and provides the LTM candidate cell configuration to the UE 100 through RRC signaling. Second, the node 200 receives a Layer 1 (L1) measurement report from the UE 100 and transmits a cell switch command indicating the LTM candidate cell configuration to the UE 100 through a MAC Control Element (CE) based on the L1 measurement report. The cell switch trigger is conveyed in the MAC CE including at least a candidate configuration index together with a beam indicator. Third, the UE 100 changes the serving cell in response to the cell switch command. In this way, a cell switch is triggered by selecting an LTM candidate cell configuration as a target configuration by the node 200. An LTM candidate cell configuration can be added, modified and released by the node 200 via RRC signaling.

[0041] The following principles apply to LTM:

[0042] Each LTM candidate cell configuration can be provided as a differential configuration (delta configuration) relative to the reference configuration used to form the complete candidate cell configuration.

[0043] If a full candidate cell configuration is applied, it replaces the current UE configuration at cell switch. A reconfiguration procedure does the replacement but does not necessarily reset the MAC, RLC or PDCP layers.

[0044] The user plane continues without a reset if configured in RRC signaling to avoid additional delays in data recovery.

[0045] - Security is not updated in LTM.

[0046] LTM between subsequent LTM candidate cell configurations can be performed without RRC reconfiguration, i.e., the UE 100 does not release other LTM candidate cell configurations after LTM is triggered.

[0047] In the first embodiment, a scenario is assumed in which the LTM is used to change the PSCell of the UE 100 between the SNs 200 and 205. Details of such a scenario will be described later.

[0048] 6 is a diagram showing an example of an LTM procedure according to the first embodiment. In the illustrated example, it is assumed that the UE 100 performs cell switching from a first cell of the node 200 to a second cell of the node 200. Here, the first cell and the second cell may be configured by different TRPs (Transmission and Reception Points).

[0049] In step S11, UE100 is in an RRC connected state in the cell of node 200.

[0050] In step S12, the UE 100 transmits a Measurement Report message, which is an RRC message, to the node 200.

[0051] In step S13, the node 200 determines to use LTM based on the Measurement Report message and starts preparing the candidate cell.

[0052] In step S14, the node 200 transmits, to the UE 100, an RRC Reconfiguration message including an LTM candidate cell configuration (LTM Candidate Configuration) of one or more candidate cells.

[0053] In step S15, the UE 100 saves the LTM candidate cell setting and transmits an RRC Reconfiguration Complete message to the node 200.

[0054] In step S16, the UE 100 may perform downlink (DL) synchronization and timing advance (TA) acquisition with the candidate cell before receiving the cell switch command.

[0055] In step S17, the UE 100 performs Layer 1 (L1) measurement in the configured candidate cell and transmits a lower layer measurement report (L1 Measurement Report) to the node 200. The L1 Measurement Report may be transmitted and received at L1, which is the PHY layer. The L1 Measurement Report may be transmitted and received at Layer 2 (L2), which includes the MAC layer, the RLC layer, and the PDCP layer. Note that the order of steps S16 and S17 may be reversed.

[0056] In step S18, the node 200 determines to perform cell switching to the target cell (second cell).

[0057] In step S19, the node 200 transmits a Cell Switch Command (MAC CE) including a candidate configuration index of the target cell to the UE 100.

[0058] In step S20, the UE 100 switches to the configuration of the target cell. Specifically, the UE 100 detaches from the source cell (first cell) and applies the configuration of the target cell.

[0059] In step S21, if the cell switching needs to include the execution of a random access procedure, the UE 100 executes the random access procedure for the target cell. Note that, if the UE 100 does not need to acquire the TA of the target cell at the time of the cell switching, the random access procedure may be skipped.

[0060] In step S22, the UE 100 indicates that the cell switch to the target cell has been successfully completed. Thereafter, the UE 100 may perform steps S16 to S22 multiple times for subsequent LTM cell switches based on the configuration provided in step S14.

[0061] (1.4) Example of Node Configuration Fig. 7 is a diagram showing an example of the configuration of the node 200 (base station) according to the first embodiment. The node 200 may be a MN 200M or a SN 200S.

[0062] The node 200 includes a transmitting unit 210, a receiving unit 220, a control unit 230, and a NW communication unit 240. The transmitting unit 210 and the receiving unit 220 configure a wireless communication unit 250 that performs wireless communication with the UE 100.

[0063] The transmitting unit 210 performs various transmissions under the control of the control unit 230. The transmitting unit 210 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmission signal) output by the control unit 230 into a radio signal and transmits it from the antenna. The receiving unit 220 performs various receptions under the control of the control unit 230. The receiving unit 220 includes an antenna and a receiver. The receiver converts a radio signal received by the antenna into a baseband signal (reception signal) and outputs it to the control unit 230.

[0064] The control unit 230 performs various controls and processes in the node 200. The operations of the node 200 described above and below may be operations under the control of the control unit 230. The control unit 230 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in the processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0065] The NW communication unit 240 is connected to adjacent nodes via an inter-node interface, and to the CN device 300 via a node-CN interface.

[0066] The node 200 configured in this manner may operate as the MN 200M when the UE 100 performs wireless communication (i.e., multi-connectivity) with the MN 200M and a plurality of SNs 200S. In the first embodiment, the control unit 230 of the node 200 operating as the MN 200M performs control so as to delegate to at least one of the plurality of SNs 200S the control authority for performing settings and / or control on the UE 100 regarding cooperative operation between the plurality of SNs 200S.

[0067] Alternatively, the node 200 may operate as the SN 200S when the UE 100 performs wireless communication (i.e., multi-connectivity) with the MN 200M and a plurality of SNs 200S. In the first embodiment, the control unit 230 of the node 200 operating as the SN 200S performs settings and / or control related to the cooperative operation for the UE 100 when the control authority for performing settings and / or control related to the cooperative operation between the plurality of SNs 200S for the UE 100 is delegated from the MN 200M.

[0068] (1.5) Example of User Equipment Configuration FIG. 8 is a diagram showing an example of the configuration of the UE 100 (user equipment) according to the first embodiment.

[0069] The UE 100 includes a receiving unit 110, a transmitting unit 120, and a control unit 130. The receiving unit 110 and the transmitting unit 120 configure a wireless communication unit 140 that performs wireless communication with the node 200.

[0070] The receiving unit 110 performs various receptions under the control of the control unit 130. The receiving unit 110 includes an antenna and a receiver. The receiver converts a radio signal received by the antenna into a baseband signal (received signal) and outputs it to the control unit 130. The transmitting unit 120 performs various transmissions under the control of the control unit 130. The transmitting unit 120 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmitted signal) output by the control unit 130 into a radio signal and transmits it from the antenna.

[0071] The control unit 130 performs various controls and processes in the UE 100. The operations of the UE 100 described above and below may be operations controlled by the control unit 230. The control unit 130 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in the processing by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0072] The UE 100 configured in this manner may perform wireless communication (i.e., multi-connectivity) with the MN 200M and a plurality of SNs 200S. The wireless communication unit 140 (receiving unit 110) of the UE 100 receives a wireless signal for setting and / or controlling the cooperative operation from the SN 200S to which the MN 200M has delegated control authority for the UE 100 to set and / or control the cooperative operation between the plurality of SNs 200S.

[0073] (1.6) System Operation Example FIG. 9 is a diagram for explaining an operation scenario of the mobile communication system according to the first embodiment.

[0074] In the illustrated example, the UE 100 performs wireless communication using multi-connectivity with the MN 200M and multiple SNs 200S (SNs 200S #1 and SNs 200S #2). Each SN 200S has a narrower cell coverage than the MN 200M. Specifically, each SN 200S (SCG) operates at a higher frequency than the MN 200M (MCG). For example, the MN 200M (MCG) may operate in the Sub-6 band, and each SN 200S (SCG) may operate in the THz band or mmW band. In the first embodiment, a scenario in which each SN 200S (SCG) operates in the THz band is mainly assumed.

[0075] In such a scenario where the cell coverage of each SN200S (SCG) is narrow, it is preferable to perform multi-connectivity by configuring multiple SCGs in the UE100 and to switch between SCGs as the UE100 moves. However, in such multi-connectivity, the MN200 needs to configure and / or control multiple SN200S, which raises concerns about an increase in the load on the MN200M. In other words, in multi-connectivity, if the MN200M manages all control like a DC, the load on the MN200M increases significantly, which is not preferable. In the first embodiment, the load on the MN200M is reduced by transferring authority from the MN200M to the SN200S.

[0076] FIG. 10 is a diagram showing an outline of the operation of the mobile communication system according to the first embodiment.

[0077] In step S1, the MN 200M delegates to at least one of the plurality of SNs 200S the control authority to configure and / or control cooperation between the plurality of SNs 200S for the UE 100. For example, the MN 200M transmits a first message to at least one of the plurality of SNs 200S to request cooperation between the plurality of SNs 200S.

[0078] In step S2, the SN 200S to which the control authority has been delegated performs configuration and / or control regarding cooperative operation among the plurality of SNs 200S for the UE 100. The SN 200S that has received the first message from the MN 200M may transmit a second message for starting cooperative operation among the plurality of SNs 200S to other SNs 200S included in the plurality of SNs 200S.

[0079] This makes it possible to prevent the load on the MN 200M from increasing even when multi-connectivity is performed.

[0080] In the first embodiment, the cooperative operation between the plurality of SNs 200S is a cell switching operation for switching between the SNs 200S the serving cell of the UE 100. That is, the MN 200M transfers authority to perform mobility control of the UE 100 between the SNs 200S.

[0081] In the first embodiment, a scenario is assumed in which a cell switching operation (mobility control) is performed using the above-mentioned LTM. Specifically, in the first embodiment, after setting cells (TRPs) of multiple SNs 200S in the UE 100, the PSCell of the UE 100 is changed between the SNs 200S using the LTM. In such a scenario, there is a concern that each SN 200S may not know which SN 200S it should cooperate with (TRP cooperation). However, in the first embodiment, the combination of SNs 200S that should cooperate can be identified by the above-mentioned first message and / or second message.

[0082] Fig. 11 is a diagram showing an example of the operation of the mobile communication system according to the first embodiment. In Fig. 11, non-essential steps are indicated by dashed lines.

[0083] In step S101, UE100 is performing wireless communication using dual connectivity (DC) with MN200M and SN200S#1.

[0084] In step S102, the UE 100 may transmit a measurement report message including the measurement result of the radio quality of each cell to the MN 200M. The MN 200M may receive the measurement report message from the UE 100.

[0085] In step S103, the MN200M determines a combination of SN200S to operate in cooperation with each other. For example, the MN200M identifies a cell whose wireless quality satisfies a predetermined condition based on the Measurement Report message of step S102, and determines the SN200S to which the identified cell belongs. Here, it is assumed that the MN200M has determined SN200S#2 as the SN200S to operate in cooperation with SN200S#1. The MN200M may determine SN200S#2 as the SN200S to operate in cooperation with SN200S#1 based on the combination of SN200S (or cell combination) set by the network operator (OAM: Operation, Administration and Management). In the first embodiment, MN200M may determine the cell of SN200S#1 as the source cell of LTM, and may also determine the cell of SN200S#2 as the candidate cell (or target cell) of LTM.

[0086] In step S104, the MN 200M transmits an S-node Pairing Request message, which is a request message (first message) for cooperation, to the SN 200S #1. In the example shown in the figure, the MN 200M transmits the S-node Pairing Request message to the SN 200S #1, but the MN 200M may transmit the S-node Pairing Request message to the SN 200S #2, or may transmit the S-node Pairing Request message to both the SN 200S #1 and the SN 200S #2. In the first embodiment, the S-node Pairing Request message may be a request message requesting a change of the PSCell of the UE 100 between the SNs 200S using the LTM.

[0087] In the illustrated example, the request message for collaboration (first message) is a new message transmitted and received on the inter-node interface, but the request message for collaboration (first message) may be an existing message (e.g., an S-NODE MODIFICATION REQUEST message) defined in the 3GPP technical specifications. The request message for collaboration (first message) may be a request message (e.g., an S-node Xn Establishment Request message) requesting the establishment of an inter-node interface between SN200S.

[0088] The request message for cooperative operation (first message) includes at least one piece of information from the following items 1) to 5).

[0089] 1) Identifier of the target UE 100: The request message for cooperation (first message) may include, for example, an identifier of the UE 100 on the inter-node interface (such as Xn-AP UE ID).

[0090] 2) Identifier of target SN 200S: The request message for collaboration (first message) may include, for example, the node ID of the target SN 200S, in particular, the ID of the SN 200S to be paired.

[0091] 3) Identifier of the target cell (e.g., source cell or candidate cell): The coordination request message (first message) includes, for example, the NCGI (NR Cell Global Identifier) ​​of the target cell, in particular the cell ID of the combining partner.

[0092] 4) Information indicating the type of collaborative operation to be performed: The collaborative operation request message (first message) includes, for example, information indicating the type of collaborative operation to be performed (in the first embodiment, a PSCell change using LTM between SN200S).

[0093] 5) Entire UE context of UE 100: The request message for cooperation (first message) may include the entire UE context, such as that transmitted in an existing Handover Request message, rather than a partial UE context, such as that transmitted in an existing S-NODE ADDITION REQUEST message.

[0094] Thus, the request message for cooperative operation (first message) includes at least one of a UE identifier for identifying UE100, a node identifier for identifying SN200S that is the partner in the cooperative operation, a cell identifier for identifying the cell of SN200S that is the partner in the cooperative operation, a type identifier indicating the type of cooperative operation, and a UE context of UE100.

[0095] In step S105, when SN200S#1 receives the request message from MN200M, if it does not have an inter-node interface with SN200S#2 specified in the request message, it sends a message (e.g., an XN SETUP REQUEST message) to SN200S#2 requesting the establishment of the inter-node interface. If SN200S#1 has established an inter-node interface with SN200S#2 specified in the request message, it does not need to send a message (e.g., an XN SETUP REQUEST message) to SN200S#2 requesting the establishment of the inter-node interface.

[0096] In step S106, when SN200S#2 receives the message from SN200S#1 in step S105, it sends a response message (for example, an XN SETUP RESPONSE message) to SN200S#1 in response to the message, thereby establishing an inter-node interface between SN200S#1 and SN200S#2.

[0097] In step S107, SN200S#1, which has received the request message from MN200M, transmits a request message (for example, an S-node Coordination Request message) to SN200S#2 specified in the request message to start the specified cooperative operation. The request message includes at least one of the information 1) to 5) above, similar to the message in step S104.

[0098] In step S108, SN200S#2, which received the request from SN200S#1 in step S107, accepts the request, performs various settings, and then sends a response message (e.g., an S-node Coordination Response message) to SN200S#1. The response message may include RRC settings for SN200S#2. The RRC settings include at least one of the following a) and b):

[0099] a) Configuration information regarding a cell (candidate cell) managed by SN200S#2: The configuration information may include configuration information of the cell, such as a cell ID, physical layer settings, etc., or may include configuration information of the TRP managed by the cell.

[0100] b) Setting the L1 Measurement Report.

[0101] In step S109, SN200S#1 transmits a response message (for example, an S-node Pairing Response message) to MN200M in response to the request message of step S104. The response message may include the RRC configuration of SN200S#2 (acquired in step S108, which may include the L1 Measurement Report configuration) and / or the RRC configuration of SN200S#1.

[0102] In step S110, MN200M may transmit an RRC Reconfiguration message to UE100. Alternatively, SN200S#1 may transmit the RRC Reconfiguration message to UE100 instead of MN200M. The RRC Reconfiguration message may include configuration information regarding SN200S#1 (e.g., RRC configuration) and / or configuration information regarding SN200S#2 (e.g., RRC configuration and / or L1 Measurement Report configuration). In the first embodiment, the RRC Reconfiguration message may include an LTM candidate cell configuration (LTM Candidate Configuration) in which the cell of SN200S#2 is a candidate cell.

[0103] In step S111, UE100 may store the configuration information in the RRC Reconfiguration message and send an RRC Reconfiguration Complete message to MN200M (or SN200S#1).

[0104] In step S112, SN200S#1 and SN200S#2 are set in UE100, thereby entering a multi-connectivity state. Here, SN200S#1 and SN200S#2 control UE100 in cooperation with each other.

[0105] In step S113, the UE 100 may transmit an L1 Measurement Report to the SN 200S #1. The SN 200S #1 may determine cell switching to the cell of the SN 200S #2 based on the L1 Measurement Report.

[0106] In step S114, SN200S#1 transmits to UE100 a Cell Switch Command (MAC CE) including information indicating the cell of SN200S#2.

[0107] In step S115, UE100 applies the settings of the cell (target cell) of SN200S#2 in response to the Cell Switch Command (MAC CE) and detaches from the cell (source cell) of SN200S#1.

[0108] In step S116, UE100 accesses the cell (target cell) of SN200S#2.

[0109] In step S117, when SN200S#2 detects access of UE100 (connection completion), SN200S#2 may notify SN200S#1 of UE access completion. The notification may include the UE context of UE100. The notification may include the latest RRC setting (contents of RRC Reconfiguration).

[0110] In step S118, SN200S#1 may notify MN200M that the PSCell (PCell) change of UE100 has been completed. The notification may include the UE context of UE100. The notification may include the latest RRC setting (contents of RRC Reconfiguration). The notification may include information such as the node ID of SN200S#2.

[0111] (1.7) Modification of the First Embodiment In the above-described first embodiment, an example was described in which the MN200M determines (specifies) the combination of SN200S to operate in coordination, but the SN200S may also determine the combination of SN200S to operate in coordination.

[0112] Fig. 12 is a diagram showing a modified example of the operation of the mobile communication system according to the first embodiment. In Fig. 12, non-essential steps are indicated by dashed lines.

[0113] In this modified example, in step S120, SN200S#1 determines a combination of SN200S to operate in cooperation with SN200S#1. SN200S#1 may determine SN200S#2 as the SN200S to operate in cooperation with SN200S#1 based on the combination of SN200S (or cell combination) set by the network operator (OAM).

[0114] In step S121, SN200S#1 sends a message (for example, an S-node Pairing Required message) indicating a request for cooperation with SN200S#2 to MN200M. The message includes at least one of the information items 1) to 5) above.

[0115] Then, in step S104, MN 200M transmits an S-node Pairing Request message, which is a request message (first message) for cooperative operation, to SN 200S#1. This message is the same as in the above-described embodiment. Alternatively, in step S104, MN 200M may transmit a response message to SN 200S#1 to permit the request of step S121. Subsequent operations are the same as in the above-described embodiment.

[0116] (2) Second Embodiment With reference to FIGS. 13 and 14, a second embodiment will be described, focusing mainly on the differences from the first embodiment.

[0117] In the above-described first embodiment, an example has been described in which the cooperative operation between a plurality of SNs 200S is a cell switching operation in which the serving cell of the UE 100 is switched between the SNs 200S. In contrast, in the second embodiment, the cooperative operation between a plurality of SNs 200S is an operation in which a certain SN 200S (first secondary node) configures and / or controls, on the UE 100, communication between another SN 200S (second secondary node) and the UE 100 on behalf of the MN 200M. That is, in the second embodiment, the SN 200S functions as a proxy node (also referred to as a "proxy MN") for the MN 200M in order to configure and / or control the other SN 200S. This makes it possible to suppress an increase in the load on the MN 200M even when multi-connectivity is performed.

[0118] FIG. 13 is a diagram for explaining an operation scenario of the mobile communication system according to the second embodiment.

[0119] In the illustrated example, UE 100 is performing wireless communication using multi-connectivity with MN 200M and multiple SNs 200S (SNs 200S#1 to SN200S#3).

[0120] SN200S#1 has a narrower cell coverage than MN200M. Specifically, SN200S#1 operates at a higher frequency than MN200M. For example, MN200M may operate in the Sub-6 band, and SN200S#1 may operate in the mmW band.

[0121] Each of SN200S#2 and SN200S#3 has a narrower cell coverage than SN200S#1. Specifically, each of SN200S#2 and SN200S#3 operates at a higher frequency than SN200S#1. For example, SN200S#1 may operate in the mmW band, and each of SN200S#2 and SN200S#3 may operate in the THz band.

[0122] In such a scenario, MN200M allows SN200S#1 to control SN200S#2 and SN200S#3 (i.e., delegates control authority). SN200S#1, to which control authority has been delegated, sets up and / or controls communications between UE100 and SN200S#2 and SN200S#3 on behalf of MN200M for UE100.

[0123] Fig. 14 is a diagram showing an example of the operation of the mobile communication system according to the second embodiment. In Fig. 14, non-essential steps are indicated by dashed lines.

[0124] In step S201, UE100 is performing wireless communication using dual connectivity (DC) with MN200M and SN200S#1.

[0125] In step S202, the UE 100 may transmit a measurement report message including the measurement result of the radio quality of each cell to the MN 200M. The MN 200M may receive the measurement report message from the UE 100.

[0126] In step S203, the MN200M determines a combination of SN200S to operate in cooperation. For example, the MN200M identifies a cell whose wireless quality satisfies a predetermined condition based on the Measurement Report message of step S202, and determines the SN200S to which the identified cell belongs. Here, it is assumed that the MN200M has determined SN200S#2 as the SN200S to operate in cooperation with SN200S#1. The MN200M may determine SN200S#2 as the SN200S to operate in cooperation with SN200S#1 based on the combination of SN200S (or combination of cells) set by the network operator (OAM). In the second embodiment, the MN200M may determine SN200S#1 as the SN200S (proxy MN) that controls SN200S#2.

[0127] In step S204, MN200M transmits an S-node Pairing Request message, which is a request message (first message) for cooperation, to SN200S#1. In the illustrated example, MN200M transmits the S-node Pairing Request message to SN200S#1, but MN200M may transmit the S-node Pairing Request message to SN200S#2, or may transmit the S-node Pairing Request message to both SN200S#1 and SN200S#2. In the second embodiment, the S-node Pairing Request message may be an operation request to perform SN control as a proxy MN, specifically, a message indicating that SN200S#1 is designated as SN200S (proxy MN) that performs control regarding SN200S#2.

[0128] In the illustrated example, the request message for collaboration (first message) is a new message transmitted and received on the inter-node interface, but the request message for collaboration (first message) may be an existing message (e.g., an S-NODE MODIFICATION REQUEST message) defined in the 3GPP technical specifications. The request message for collaboration (first message) may be a request message (e.g., an S-node Xn Establishment Request message) requesting the establishment of an inter-node interface between SN200S.

[0129] The request message for the cooperative operation (first message) includes at least one of the above-mentioned information 1) to 5). In the second embodiment, the information indicating the type of the cooperative operation to be performed (4) may be information indicating a "proxy MN."

[0130] In step S205, when SN200S#1 receives the request message from MN200M, if it does not have an inter-node interface with SN200S#2 specified in the request message, it sends a message (e.g., an XN SETUP REQUEST message) requesting the establishment of the inter-node interface to SN200S#2. If SN200S#1 has established an inter-node interface with SN200S#2 specified in the request message, it does not need to send a message (e.g., an XN SETUP REQUEST message) requesting the establishment of the inter-node interface to SN200S#2.

[0131] In step S206, when SN200S#2 receives the message from SN200S#1 in step S205, it sends a response message (for example, an XN SETUP RESPONSE message) to SN200S#1 in response to the message, thereby establishing an inter-node interface between SN200S#1 and SN200S#2.

[0132] In step S207, SN200S#1, which has received the request message from MN200M, transmits a request message (for example, an S-node Coordination Request message) to SN200S#2 specified in the request message to start the specified cooperative operation. The request message includes at least one of the information 1) to 5) above, similar to the message in step S204.

[0133] In step S208, SN200S#2, which received the request from SN200S#1 in step S207, accepts the request and performs various settings, and then transmits a response message (e.g., an S-node Coordination Response message) to SN200S#1. The response message may include RRC settings for SN200S#2. The RRC settings may include setting information for a cell (candidate cell) managed by SN200S#2. The setting information may include setting information for the cell, such as a cell ID and physical layer settings.

[0134] In step S209, SN200S#1 sends a response message (e.g., an S-node Pairing Response message) to MN200M in response to the request message of step S204. The response message may include the RRC configuration of SN200S#2 (obtained in step S208) and / or the RRC configuration of SN200S#1.

[0135] In step S210, MN 200M may transmit an RRC Reconfiguration message to UE 100. Alternatively, SN 200S #1 may transmit the RRC Reconfiguration message to UE 100 instead of MN 200M. The RRC Reconfiguration message may include configuration information (e.g., RRC configuration) regarding SN 200S #1 and / or configuration information (e.g., RRC configuration) regarding SN 200S #2.

[0136] In step S211, UE100 may store the configuration information in the RRC Reconfiguration message and send an RRC Reconfiguration Complete message to MN200M (or SN200S#1).

[0137] In step S212, SN200S#1 and SN200S#2 are set in UE100, thereby entering a multi-connectivity state. Here, SN200S#1 and SN200S#2 control UE100 in cooperation with each other.

[0138] In step S213, SN200S#1 performs dual connectivity (DC) with SN200S#2. If a DC has been set between MN200M and SN200S#1, the DC setting between SN200S#1 and SN200S#2 may be performed by inheriting the DC setting. Alternatively, if there is no DC between MN200M and SN200S#1, or if the DC setting between MN200M and SN200S#1 is discarded, the DC setting between SN200S#1 and SN200S#2 may be performed as a new setting.

[0139] In steps S214 to S216, SN200S#1 operates as a proxy MN and performs control related to SN200S#2. For example, SN200S#1 may take the initiative in changing the PSCell of UE100 from SN200S#2 to SN200S#3.

[0140] In step S217, when the UE context and / or RRC settings held by SN200S#1 are updated, SN200S#1 may transmit the UE context and / or RRC settings to MN200M. Also, when the MN200M changes the settings of UE100 and the UE context and / or RRC settings held by MN200M are changed, MN200M may transmit the UE context and / or RRC settings to SN200S#1. This performs synchronization processing so that MN200M and SN200S#1 (proxy MN) hold the same UE context and / or RRC settings.

[0141] In addition, in the second embodiment, SN200S#1 operating as a proxy MN may send a request message to the SN200S to be controlled (e.g., SN200S#2) to request a PSCell change using LTM between SN200S in the first embodiment.

[0142] Also in the second embodiment, the same operation as in the modified example of the first embodiment may be applied.

[0143] (3) Other Embodiments The operational flows in the above-described embodiments do not necessarily have to be executed in chronological order according to the order shown in the flow diagrams. For example, steps in the operations may be executed in an order different from that shown in the flow diagrams, or may be executed in parallel. Furthermore, some steps in the operations may be deleted, or additional steps may be added to the processing.

[0144] A program may be provided that causes a computer (UE 100, node 200) to execute the operations according to the above-described embodiments. The program may be recorded on a computer-readable medium. Using the computer-readable medium, the program can be installed on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM.

[0145] As used in this disclosure, the terms "based on" and "depending on / in response to" do not mean "based only on" or "depending only on," unless expressly stated otherwise. The term "based on" means both "based only on" and "based at least in part on." Similarly, the term "depending on" means both "depending only on" and "depending at least in part on." Furthermore, the terms "include," "comprise," and variations thereof do not mean including only the listed items, but may mean including only the listed items or may include additional items in addition to the listed items. Furthermore, the term "or," as used in this disclosure, is not intended to mean an exclusive or. Furthermore, any reference to elements using designations such as "first," "second," etc., as used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used herein as a convenient method of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed therein or that the first element must precede the second element in some way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall include the plural unless the context clearly indicates otherwise.

[0146] The above describes the embodiments in detail with reference to the drawings, but the specific configuration is not limited to that described above, and various design changes can be made within the scope that does not deviate from the gist of the invention.

[0147] (4) Supplementary Notes The following are additional notes regarding the features of the above-described embodiment.

[0148] (Supplementary Note 1) A communication method for a user device to perform wireless communication with a master node and multiple secondary nodes in a mobile communication system, comprising: a step in which the master node performs a process of delegating control authority for configuring and / or controlling the user device regarding cooperative operation between the multiple secondary nodes to at least one of the multiple secondary nodes; and a step in which the secondary node to which the control authority has been delegated performs configuration and / or control regarding the cooperative operation for the user device.

[0149] (Supplementary Note 2) The communication method according to Supplementary Note 1, wherein the step of performing the delegation process includes the step of transmitting a first message for requesting the cooperative operation from the master node to at least one of the plurality of secondary nodes.

[0150] (Supplementary Note 3) The communication method according to Supplementary Note 2, wherein the first message includes at least one of a user equipment identifier for identifying the user equipment, a node identifier for identifying a secondary node that is a partner in the cooperative operation, a cell identifier for identifying a cell of the secondary node that is a partner in the cooperative operation, a type identifier indicating a type of the cooperative operation, and a user equipment context of the user equipment.

[0151] (Supplementary Note 4) The communication method according to Supplementary Note 2 or 3, further comprising a step in which a first secondary node that has received the first message transmits a second message for initiating the cooperative operation to a second secondary node.

[0152] (Supplementary Note 5) The communication method according to any one of Supplementary Notes 1 to 4, wherein the plurality of secondary nodes include a first secondary node to which the control authority has been delegated and a second secondary node, and the cooperative operation includes a cell switching operation of switching a serving cell of the user equipment from a cell of the first secondary node to a cell of the second secondary node.

[0153] (Supplementary Note 6) The communication method according to Supplementary Note 5, wherein the step of configuring and / or controlling the cooperative operation includes a step in which the first secondary node configures and / or controls the cell switching operation for the user equipment using Layer 1 and / or Layer 2 signaling.

[0154] (Supplementary Note 7) The communication method described in any of Supplementary Notes 1 to 6, wherein the plurality of secondary nodes include a first secondary node to which the control authority has been delegated and a second secondary node, and the step of performing configuration and / or control related to the cooperative operation includes a step in which the first secondary node configures and / or controls communication between the user device and the second secondary node on behalf of the master node.

[0155] (Supplementary Note 8) A node that operates as a master node in a mobile communication system in which a user device performs wireless communication with a master node and multiple secondary nodes, the node comprising a control unit that performs processing to delegate control authority for the user device to perform settings and / or control related to cooperative operations between the multiple secondary nodes to at least one of the multiple secondary nodes.

[0156] (Supplementary Note 9) A node that operates as a secondary node in a mobile communication system in which a user device performs wireless communication with a master node and a plurality of secondary nodes, the node comprising a control unit that, when the control authority for performing settings and / or control regarding cooperative operation between the plurality of secondary nodes is delegated to the user device from the master node, performs settings and / or control regarding the cooperative operation for the user device.

[0157] (Supplementary Note 10) A user device that performs wireless communication with a master node and a plurality of secondary nodes, the user device comprising: a wireless communication unit that receives a signal for setting and / or controlling cooperative operation between the plurality of secondary nodes from a secondary node to which the master node has delegated control authority to the user device to set and / or control the cooperative operation between the plurality of secondary nodes.

[0158] 1: NW 10: RAN 20: CN 100: UE 110: Receiving unit 120: Transmitting unit 130: Control unit 140: Wireless communication unit 200: Node 200M: MN 200S: SN 210: Transmitting unit 220: Receiving unit 230: Control unit 240: NW communication unit 250: Wireless communication unit 300: CN device

Claims

1. A communication method in a mobile communication system for a user device to perform wireless communication with a master node and multiple secondary nodes, comprising: a step in which the master node performs a process of delegating control authority for configuring and / or controlling the cooperative operation between the multiple secondary nodes to at least one of the multiple secondary nodes; and a step in which the secondary node to which the control authority has been delegated performs configuration and / or control regarding the cooperative operation for the user device.

2. The communication method according to claim 1, wherein the step of performing the delegation process includes a step of transmitting a first message for requesting the cooperative operation from the master node to at least one of the plurality of secondary nodes.

3. The communication method according to claim 2, wherein the first message includes at least one of a user equipment identifier for identifying the user equipment, a node identifier for identifying a secondary node with which the cooperative operation is performed, a cell identifier for identifying a cell of the secondary node with which the cooperative operation is performed, a type identifier indicating a type of the cooperative operation, and a user equipment context of the user equipment.

4. The communication method according to claim 2, further comprising a step of a first secondary node receiving said first message transmitting a second message for initiating said cooperative operation to a second secondary node.

5. A communication method according to any one of claims 1 to 4, wherein the plurality of secondary nodes include a first secondary node to which the control authority has been delegated and a second secondary node, and the cooperative operation includes a cell switching operation for switching a serving cell of the user equipment from a cell of the first secondary node to a cell of the second secondary node.

6. The communication method according to claim 5, wherein the step of configuring and / or controlling the cooperative operation includes a step in which the first secondary node configures and / or controls the cell switching operation for the user equipment using layer 1 and / or layer 2 signaling.

7. A communication method as claimed in any one of claims 1 to 4, wherein the plurality of secondary nodes include a first secondary node to which the control authority has been delegated and a second secondary node, and the step of configuring and / or controlling the cooperative operation includes a step of the first secondary node configuring and / or controlling communication between the user equipment and the second secondary node on behalf of the master node with respect to the user equipment.

8. A node that operates as a master node in a mobile communication system in which a user device performs wireless communication with a master node and multiple secondary nodes, the node having a control unit that performs processing to delegate control authority for configuring and / or controlling cooperative operation between the multiple secondary nodes to at least one of the multiple secondary nodes.

9. A node that operates as a secondary node in a mobile communication system in which a user equipment performs wireless communication with a master node and multiple secondary nodes, and that has a control unit that, when control authority for configuring and / or controlling the cooperative operation between the multiple secondary nodes is delegated to the user equipment from the master node, performs the configuration and / or control of the cooperative operation for the user equipment.

10. A user device that performs wireless communication with a master node and multiple secondary nodes, the user device having a wireless communication unit that receives signals for setting and / or controlling the cooperative operation between the multiple secondary nodes from a secondary node to which the master node has delegated control authority to perform such setting and / or control on the user device.

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