User equipment, node, and communication method

Abstract

The present invention provides a user equipment that performs wireless communication with a master node and a secondary node using dual connectivity in a mobile communication system, the user equipment comprising: a reception unit that receives, from the master node, information indicating a wireless quality condition that is to be satisfied for the user equipment to perform a deactivation process for a secondary cell group of the secondary node; and a control unit that measures the wireless quality for the secondary cell group and evaluates whether or not the wireless quality condition is satisfied. The control unit performs the deactivation process for the secondary cell group in response to the satisfaction of the wireless quality condition.

Description

User equipment, node, and communication method

[0001] The present disclosure relates to a user device, a node, and a communication method.

[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).

[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 (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 PSCell.

[0004] Release 17 of the 3GPP standard introduces specifications for deactivating SCGs. Deactivating an SCG in an active state is generally performed in the following procedure: First, the UE sends a measurement report message including measurement results of the radio quality of each cell to the MN. Second, the MN instructs the UE to deactivate the SCG using a radio resource control (RRC) message based on the measurement report message. Third, the UE deactivates the SCG in response to the instruction. Deactivating the SCG transitions the SCG from an active state to an inactive state, and wireless communication using the SCG is stopped.

[0005] Such control has the problem that it is difficult to shorten the time from when the radio quality for the SCG deteriorates in the UE until radio communication using the SCG is stopped.

[0006] 3GPP Technical Specification: TS 38.300 V17.3.0 (2022-12)

[0007] A user equipment according to a first aspect is a user equipment that performs wireless communication with a master node and a secondary node using dual connectivity in a mobile communication system, and includes: a receiving unit that receives, from the master node, information indicating a wireless quality condition that must be satisfied in order for the user equipment to perform a deactivation process for a secondary cell group of the secondary node; and a control unit that measures wireless quality for the secondary cell group and evaluates whether the wireless quality condition is satisfied. The control unit executes the deactivation process for the secondary cell group in response to the wireless quality condition being satisfied.

[0008] A node according to a second aspect is a node that operates as the master node in a mobile communication system in which a user equipment performs wireless communication with a master node and a secondary node using dual connectivity, and includes: a control unit that sets a secondary cell group of the secondary node to the user equipment; and a transmission unit that transmits to the user equipment information indicating a wireless quality condition that must be satisfied for the user equipment to perform a deactivation process for the secondary cell group.

[0009] A communication method according to a third aspect is a communication method used by a user equipment that performs wireless communication with a node using dual connectivity in a mobile communication system, and includes the steps of receiving, from the node, information indicating a wireless quality condition that must be satisfied in order for the user equipment to perform a deactivation process for a secondary cell group configured for the user equipment; measuring wireless quality for the secondary cell group and evaluating whether the wireless quality condition is satisfied; and performing the deactivation process for the secondary cell group in response to the wireless quality condition being satisfied.

[0010] A communication method according to a fourth aspect is a communication method used in a node that performs wireless communication with a user equipment using dual connectivity in a mobile communication system, and includes the steps of: setting a secondary cell group in the user equipment; and transmitting to the user equipment information indicating a wireless quality condition that must be satisfied for the user equipment to perform a deactivation process for the secondary cell group.

[0011] 1 is a diagram showing an example of the configuration of a mobile communication system according to an embodiment; FIG. 2 is a diagram showing 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 showing 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 for explaining a terahertz (THz) wave cell according to an embodiment; FIG. 5 is a diagram for explaining dual connectivity (DC) according to an embodiment; FIG. 6 is a diagram showing a general procedure for setting and activating an SCG; FIG. 7 is a diagram showing a general procedure for deactivating an SCG; FIG. 8 is a diagram showing an example of the configuration of a UE (user equipment) according to an embodiment; FIG. 9 is a diagram showing an example of the configuration of a node according to an embodiment; FIG. 10 is a diagram showing an example of the system operation according to the first embodiment; FIG. 11 is a diagram for explaining a bandwidth portion (BWP); FIG. 12 is a diagram showing an example of the system operation according to a second embodiment; FIG. 13 is a diagram showing a specific example of a reference signal (Fast tracking RS) according to a third embodiment; FIG. 14 is a diagram showing an example of the system operation according to the third embodiment;

[0012] 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.

[0013] (1) First Embodiment The first embodiment will be described with reference to FIGS. 1 to 10. FIG.

[0014] (1.1) System Configuration Example Fig. 1 is a diagram showing a configuration example of a mobile communication system according to an embodiment. The mobile communication system according to the embodiment is a system conforming to the 3GPP standard. For example, the mobile communication system according to the embodiment may be a fifth generation (5G) system or a sixth generation (6G) system.

[0015] 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).

[0016] 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).

[0017] 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.

[0018] 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").

[0019] 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.

[0020] FIG. 2 is a diagram showing an example of the configuration of a protocol stack of a U-plane radio interface that handles data.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] The PDCP layer performs header compression / decompression, encryption / decryption, and the like.

[0026] 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.

[0027] 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).

[0028] 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.

[0029] 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.

[0030] 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").

[0031] (1.2) DC Using a Terahertz Wave Cell FIG. 4 is a diagram for explaining a terahertz (THz) wave cell according to an embodiment.

[0032] The mobile communication system according to the 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.

[0033] 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].

[0034] Dual connectivity (DC) is one method for stably controlling small cells in a mobile communication system. FIG. 5 is a diagram for explaining dual connectivity (DC) according to an embodiment. In the 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 a 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.

[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] The mobile communication system supports activation and deactivation of SCG to enable reduction of power consumption of UE100 in which DC is configured. SCG activation / deactivation can be indicated by an RRC reconfiguration message from MN200M to UE100. While the SCG is deactivated, all SCG SCells are in an inactive state. While the SCG is deactivated, UE100 does not need to transmit a physical uplink shared channel (PUSCH), a sounding reference signal (SRS), and a channel quality indicator (CSI) report in the SCG. Also, while the SCG is deactivated, UE100 does not need to monitor a physical downlink shared channel (PDCCH) or receive a downlink shared channel (DL-SCH) in the SCG. However, the UE 100 can continue radio link monitoring (RLM) and measurement reporting for the PSCell. When activating the SCG, the UE 100 can skip the random access procedure if the timing advance (TA) with the PSCell is valid.

[0039] FIG. 6 shows the general procedure for setting up and activating an SCG.

[0040] In step S11, the UE 100 transmits a measurement report message including measurement results of the radio quality of each cell to the MN 200M. The radio quality may be any index related to radio quality, and is, for example, at least one of RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), and SINR (Signal to Interference & Noise Ratio). The Measurement Report message is an RRC message transmitted and received in the RRC layer. The Measurement Report message may be transmitted periodically or in response to an event trigger. The MN 200M receives the Measurement Report message and determines to set an SCG for the UE 100 based on the Measurement Report message.

[0041] In step S12, MN200M may send an SN (S-Node) Addition Request message to SN200S to request preparation of resources for DC operation for UE100.

[0042] In step S13, in response to receiving the SN Addition Request message, SN200S may send an SN (S-Node) Addition Request Ack (Acknowledge) message to MN200M to acknowledge the preparation of resources for DC operation for UE100.

[0043] In step S14, MN200M transmits an RRC Reconfiguration message to UE100 to set up an SCG in UE100. The RRC Reconfiguration message is an RRC message transmitted and received at the RRC layer. UE100 receives the RRC Reconfiguration message. Here, it is assumed that the initial state of the SCG is an inactive state.

[0044] In step S15, the UE 100 transmits an RRC Reconfiguration Complete message to the MN 200M, indicating that the configuration (addition) of the SCG based on the RRC Reconfiguration message has been completed. The RRC Reconfiguration Complete message is an RRC message transmitted and received at the RRC layer. The MN 200M receives the RRC Reconfiguration Complete message.

[0045] Thereafter, it is assumed that the radio quality of the SCG (PSCell) improves in the UE 100, and the radio quality of the SCG (PSCell) becomes capable of communication.

[0046] In step S16, the UE 100 transmits a Measurement Report message including the measurement result of the radio quality of the PSCell to the MN 200M. The UE 100 may transmit the Measurement Report message to the MN 200M when the radio quality of the PSCell improves as a trigger. The MN 200M receives the Measurement Report message.

[0047] In step S17, MN200M transmits an RRC Reconfiguration message for activating the SCG to UE100. UE100 receives the RRC Reconfiguration message and starts activating the SCG. The SCG activation process includes communication preparations such as channel state information (CSI) measurement, automatic gain control (AGC), and beam management.

[0048] In step S18, the UE 100 transmits an RRC Reconfiguration Complete message to the MN 200M. The MN 200M receives the RRC Reconfiguration Complete message.

[0049] In step S19, UE100 starts wireless communication (data communication) with SN200S using the activated SCG.

[0050] FIG. 7 illustrates the general procedure for deactivating an SCG.

[0051] In step S21, the SCG set in the UE 100 is in an active state, and the UE 100, the MN 200M, and the SN 200S are performing DC communication. Here, the UE 100 performs wireless communication (data communication) with the SN 200S using the activated SCG.

[0052] Here, it is assumed that the radio quality of the SCG (PSCell) in the UE 100 deteriorates, and it becomes difficult to continue the radio communication using the SCG (PSCell).

[0053] In step S22, the UE 100 transmits a measurement report message including the measurement results of the radio quality of each cell to the MN 200M, for example, on the MCG. The MN 200M receives the Measurement Report message. The node 200 recognizes the deterioration of the radio quality of the SCG (PSCell) in the UE 100 based on the Measurement Report message.

[0054] In step S23, MN200M may send an SN Modification Request message to SN200S to request deactivation of the SCG configured in UE100.

[0055] In step S24, in response to receiving the SN Modification Request message, SN200S may send an SN Modification Request Ack message to MN200M to acknowledge the deactivation of the SCG configured in UE100.

[0056] In step S25, MN200M transmits to UE100 an RRC Reconfiguration message for deactivating the SCG configured in UE100. UE100 receives the RRC Reconfiguration message.

[0057] In step S26, the UE 100 transmits an RRC Reconfiguration Complete message to the MN 200M. The MN 200M receives the RRC Reconfiguration Complete message.

[0058] In step S27, UE100 deactivates the SCG in response to receiving the RRC Reconfiguration message in step S25. For example, UE100 stops PDCCH monitoring for the SCG (PSCell). Meanwhile, MN200M stops DL transmission processing (PDCCH transmission, PDSCH transmission) on the SCG. As a result, wireless communication using the SCG is stopped.

[0059] In the operation shown in FIG. 7, when the SCG radio quality in UE 100 deteriorates, communication on the SCG becomes impossible. However, MN 200M cannot grasp the deterioration of the SCG radio quality until it receives the Measurement Report message in step S22. Therefore, SN 200S can continue the DL transmission process on the SCG even after the SCG radio quality deteriorates. Furthermore, UE 100 can continue PDCCH monitoring on the SCG until it receives the RRC Reconfiguration message in step S25. Such an operation has the problem of wasting resources and power consumption.

[0060] For example, the delay from when the SCG (PSCell) radio quality in UE 100 deteriorates to when the Measurement Report message is transmitted may be approximately 10 ms, and the delay from when MN 200M receives the Measurement Report message to when it transmits an RRC Reconfiguration message to UE 100 may be approximately 10 ms. In this case, resources and power consumption may be wasted for approximately 20 ms. Therefore, it is desirable to be able to quickly deactivate the SCG when the radio quality of the SCG (PSCell) no longer satisfies the specified quality.

[0061] (1.3) Example of Configuration of User Equipment FIG. 8 is a diagram illustrating an example of the configuration of the UE 100 (user equipment) according to the embodiment.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] The UE 100 configured in this manner performs wireless communication with the MN 200M and the SN 200S using DC. The receiving unit 110 receives information from the MN 200M indicating wireless quality conditions that must be satisfied in order for the UE 100 to perform a deactivation process for the SCG of the SN 200S. The control unit 130 measures the wireless quality for the SCG (PSCell) and evaluates whether the wireless quality conditions are satisfied. Then, the control unit 130 performs a deactivation process for the SCG in response to the wireless quality conditions being satisfied. In the first embodiment, the deactivation process includes a process of transitioning an SCG in an active state to a deactivated state.

[0066] As a result, when the radio quality of the SCG (PSCell) satisfies the radio quality condition (for example, when the radio quality deteriorates below a predetermined quality), the UE 100 can autonomously perform the deactivation process for the SCG. Therefore, it is possible to speed up the deactivation of the SCG.

[0067] The deactivation process may include a process of transitioning a bandwidth portion (BWP) in a non-dormant state in a PSCell that is a primary cell of the SCG to a dormant state. An example of using a dormant BWP will be described in a second embodiment.

[0068] In the embodiment, the transmitting unit 120 transmits a notification regarding the deactivation process to the node 200 in response to the wireless quality condition being satisfied. This allows the node 200 to understand that the UE 100 will perform the deactivation process based on the notification. Therefore, wireless communication using the activated SCG can be smoothly started. The notification may be a newly introduced MAC CE. Because the MAC CE is transmitted and received at the MAC layer, it can be transmitted faster than a Measurement Report message.

[0069] In the embodiment, the transmission unit 120 transmits a notification regarding the deactivation process to the MN 200M on the MCG. This allows the notification to be transmitted to the network 5 even if the wireless quality of the MCG deteriorates. Therefore, wireless communication using the SCG can be stopped smoothly and quickly.

[0070] In the embodiment, the control unit 130 stops monitoring the PDCCH for the SCG when the wireless quality condition is satisfied or when an acknowledgment (HARQ ACK) to the notification regarding the deactivation process is received from the MN 200M. This makes it possible to prevent the above-mentioned waste of resources and power consumption from occurring.

[0071] (1.4) Example of Node Configuration Fig. 9 is a diagram showing an example of the configuration of a node 200 (base station) according to this embodiment. The node 200 may be a MN 200M or a SN 200S.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] The node 200 configured in this manner operates as MN200M in a mobile communication system in which UE100 performs wireless communication with MN200M and SN200S using DC. The control unit 230 sets the SCG of SN200S to UE100. The transmission unit 210 transmits to UE100 information indicating a wireless quality condition that must be satisfied in order for UE100 to perform a deactivation process for the SCG. As a result, UE100 can autonomously perform a deactivation process for the SCG when the wireless quality for the SCG satisfies the wireless quality condition.

[0077] In the embodiment, the receiving unit 220 receives a notification regarding the deactivation process from the UE 100 in response to the radio quality condition being satisfied in the UE 100. This allows the node 200 (MN 200M) to know that the UE 100 will perform the deactivation process based on the notification.

[0078] In the embodiment, the control unit 230 stops the DL transmission process (PDCCH transmission, PDSCH transmission) on the SCG when receiving a notification regarding the deactivation process or when transmitting an acknowledgment (HARQ ACK) in response to the notification to the UE 100. This allows the DL transmission process to be stopped earlier than in the general procedure shown in Fig. 7, thereby making it possible to suppress the waste of resources and power consumption as described above.

[0079] (1.5) System Operation Example Fig. 10 is a diagram showing an example of system operation according to the first embodiment. In Fig. 10, non-essential steps are indicated by dashed lines. Furthermore, duplicated explanations of operations similar to those in Fig. 6 will be omitted.

[0080] In step S101, MN200M may send an SN Addition Request message to SN200S to request preparation of resources for DC operation for UE100.

[0081] In step S102, in response to receiving the SN Addition Request message, SN200S may send an SN Addition Request Ack message to MN200M to acknowledge the preparation of resources for DC operation for UE100.

[0082] In step S103, the UE 100 may receive a reference signal from each cell, measure radio quality based on the reference signal, and transmit a Measurement Report message including the measurement result to the MN 200M. Here, the Measurement Report message includes the measurement result of the THz wave cell. The receiving unit 220 of the MN 200M receives the Measurement Report message.

[0083] In step S104, MN200M may request activation of the SCG and may send a message (e.g., an SN Modification Request message) to SN200S to configure conditional SCG deactivation for UE100. SN200S receives the message. The message may include an identifier of UE100, specifically, an identifier for identifying UE100 on the inter-node interface. The message may include information notifying that the SCG deactivation is conditional or information requesting the configuration of conditional SCG deactivation. When SN200S requests the configuration of conditional SCG deactivation, it may include configuration information for conditional SCG deactivation in the message.

[0084] In step S105, the SN 200S may transmit a message (e.g., an SN Modification Request Ack message) indicating acknowledgment of the message of step S104 to the MN 200M. The MN 200M receives the message. The message may include information about resources (e.g., SCG and bearers) prepared by the SN 200S, such as information about the PSCell and information about the SCell of the SCG. The message may include configuration information about the reference signal of the SCG (PSCell). This information may be transmitted from the MN 200M to the UE 100 in step S106.

[0085] In step S106, MN 200M generates an RRC Reconfiguration message and transmits the RRC Reconfiguration message to UE 100. UE 100 receives the RRC Reconfiguration message.

[0086] The RRC Reconfiguration message includes information for configuring an SCG and configuration information for conditional SCG deactivation. The information for configuring the SCG includes information on a PSCell and information on an SCell of the SCG. In the illustrated example, the information for configuring the SCG and the configuration information for conditional SCG deactivation are transmitted in one RRC Reconfiguration message, but these pieces of information may be transmitted in separate RRC Reconfiguration messages. Furthermore, the configuration information for conditional SCG deactivation may include information for configuring a frequency and / or a cell ID (cell index) of the PSCell.

[0087] The configuration information for conditional SCG deactivation includes information indicating a radio quality condition that must be satisfied in order for the UE 100 to activate the corresponding SCG.

[0088] The information indicating the radio quality condition may include at least one radio quality threshold among an RSRP threshold, an RSRQ threshold, and an SINR threshold. Satisfying the radio quality condition for the SCG (PSCell) may mean at least one of the following: the RSRP of the SCG (PSCell) is below the RSRP threshold, the RSRQ of the SCG (PSCell) is below the RSRQ threshold, and the SINR of the SCG (PSCell) is below the SINR threshold.

[0089] The information indicating the radio quality condition may include a threshold value of the duration of a state in which a radio problem is detected in a lower layer (for example, a PHY layer) in the UE 100. In this case, satisfying the radio quality condition for the SCG (PSCell) may mean that the duration of the state in which a radio problem is detected for the SCG (PSCell) reaches the threshold value.

[0090] The information indicating the radio quality condition may include a threshold value of the number of times retransmission continues (i.e., the number of times UL data transmission failures continue) in the UE 100. In this case, satisfying the radio quality condition for the SCG (PSCell) may mean that the number of times retransmission continues for the SCG (PSCell) (i.e., the number of times UL data transmission failures continue for the SCG (PSCell)) has reached the threshold value.

[0091] The information indicating the radio quality condition may include a threshold value of a time during which UL data transmission cannot be performed based on the detection of an interference wave in the UE 100. For example, when the SCG (PSCell) is operated in an unlicensed band, the UE 100 performs carrier sense for the SCG (PSCell) and performs UL data transmission only when there is an available channel, and does not perform UL data transmission when there is no available channel. In this case, satisfying the radio quality condition for the SCG (PSCell) may mean that the time during which UL data transmission using carrier sense cannot be performed reaches a threshold value.

[0092] In step S107, the UE 100 generates an RRC Reconfiguration Complete message and transmits the RRC Reconfiguration Complete message to the MN 200M. The MN 200M receives the RRC Reconfiguration Complete message.

[0093] The initial state of the SCG configured in the UE 100 is the active state (step S108). The UE 100 starts radio quality measurement for the SCG (specifically, the PSCell) based on the configuration information for conditional SCG deactivation.

[0094] In step S109, the UE 100 receives a reference signal of the PSCell and measures the radio quality of the PSCell based on the reference signal. The reference signal of the PSCell may be a demodulation reference signal (DMRS) included in an SSB (SS / PBCH Block) transmitted by the PSCell, or a tracking reference signal (TRS), which is a type of CSI-RS. The measurement of the radio quality may include at least one of measuring the duration of a state in which a radio problem is detected, measuring the number of retransmissions that continue (i.e., the number of times UL data transmission failures continue), and measuring the time during which UL data transmission cannot be performed.

[0095] In step S110, the UE 100 determines whether the radio quality condition set in step S106 is satisfied. For example, the UE 100 compares the measurement result (RSRP, RSRQ, and / or SINR) of step S109 with the radio quality threshold set in step S106, and determines that the radio quality condition is satisfied if the measurement result is below the radio quality threshold. If it is determined that the radio quality condition is not satisfied (step S110: NO), the process returns to step S109.

[0096] On the other hand, if it is determined that the radio quality condition is satisfied (step S110: YES), in step S111, the UE 100 deactivates the SCG. For example, the control unit 130 of the UE 100 stops processing such as PDCCH monitoring for the SCG. Note that the SCG deactivation may be performed when an acknowledgment (HARQ ACK) to the notification in step S112 is received.

[0097] In step S112, UE 100 triggers the transmission of an SCG deactivation notification and transmits the SCG deactivation notification to MN 200M. The SCG deactivation notification may be a newly introduced MAC CE. Alternatively, the SCG deactivation notification may be a notification included in UCI transmitted on PUCCH, a PDCP Control PDU, or an RRC message. MN 200M receives the SCG deactivation notification. In response to receiving the SCG deactivation notification, MN 200M recognizes that the SCG of UE 100 has become unavailable. The SCG deactivation notification may include an index (which may be a cell ID) of each cell of the deactivated SCG. The index may refer to each entry of the cell list of the SCG configured in the RRC Reconfiguration message of step S106.

[0098] The SCG deactivation notification may include information on the timing when the SCG deactivation (i.e., step S108) was performed. The timing information may be the radio frame number when the SCG deactivation was performed, or may be expressed by any one or a combination of a system frame number, a subframe number, a slot number, and a symbol number. The timing information may be time information when the SCG deactivation was performed. The timing information may be the elapsed time from when the SCG deactivation was performed until the SCG deactivation notification was transmitted, and may be expressed in seconds (e.g., milliseconds) or in the number of radio frames (e.g., the number of slots). Such timing information allows the node 200 to know when DL reception in the SCG stopped, and to efficiently identify data packets to be retransmitted when retransmitting data transmitted in DL during that period in the MCG.

[0099] Prior to transmitting the SCG deactivation notification, the following processing may be performed in the PHY layer and the MAC layer. Specifically, UE 100 transmits an SR (Scheduling Request) to MN 200M, MN 200M transmits an UL grant for a BSR (Buffer Status Report) to UE 100, UE 100 transmits the BSR to MN 200M, and MN 200M transmits an UL grant for PUSCH transmission to UE 100. Then, UE 100 transmits the SCG deactivation notification based on the UL grant for PUSCH transmission.

[0100] In step S113, the MN 200M may send a message (e.g., an SN Modification Request message) to the SN 200S to notify that the UE 100 has deactivated the SCG. The SN 200S receives the message. The message may include an identifier of the UE 100, specifically, an identifier for identifying the UE 100 on the node-to-node interface.

[0101] In step S114, the SN 200S may send a message indicating approval for the message of step S113 (for example, an SN Modification Request Ack message) to the MN 200M. The MN 200M receives the message.

[0102] In step S115, SN200S stops DL transmission to UE100 using SCG.

[0103] In this operation example, an example has been described in which UE100 sends an SCG deactivation notification to MN200M, but the SCG deactivation notification may also be sent to SN200S on the SCG (e.g., PSCell) before deactivating the SCG.

[0104] In this operation example, MN200M transmits a message to SN200S for setting conditional SCG deactivation in UE100, and SN200S transmits a response message to the message. Meanwhile, SN200S may autonomously transmit a message to MN200M for setting conditional SCG deactivation in UE100. In this case, the message may include information notifying that the SCG is to be deactivated as a conditional SCG or information requesting the setting of conditional SCG deactivation. When SN200S requests the setting of conditional SCG deactivation, it may include setting information for conditional SCG deactivation in the message.

[0105] (2) Second Embodiment With reference to FIGS. 11 and 12, the second embodiment will be described, focusing mainly on the differences from the first embodiment.

[0106] (2.1) BWP FIG. 11 is a diagram for explaining BWP.

[0107] Bandwidth adaptation (BA) allows the transmission and reception bandwidth of the UE 100 to be adjusted without being required to be as large as the bandwidth of the cell. A portion of the cell bandwidth (which may also be called the "system bandwidth" or "carrier bandwidth") is called a BWP. In BA, the node 200 configures one or more BWPs for the UE 100 within the cell and notifies the UE 100 which of the configured BWPs is currently active. BWPs include an initial BWP used for initial access and a dedicated BWP that is individually configured for the UE 100. The bandwidth and subcarrier spacing of each BWP are variably configurable.

[0108] In the illustrated example, three different BWPs are set in the UE 100, and an example is shown in which the active BWP is switched between these BWPs. １ has a width of 40 [MHz] and a subcarrier spacing of 15 [kHz], and BWP ２ has a width of 10 MHz and a subcarrier spacing of 15 kHz, and BWP ３ has a width of 20 MHz and a subcarrier spacing of 60 kHz.

[0109] In each of the UL and DL, there is only one BWP in the active state, and the rest are in the inactive state. In the inactive BWP, the UE 100 does not monitor the PDCCH and does not transmit the PUCCH, the PRACH, and the UL-SCH (PUSCH).

[0110] In the current 3GPP technical specifications, in the case of carrier aggregation (CA), the node 200 can configure a BWP in a dormant state (dormant BWP) for an SCell. When the active BWP of an activated SCell is a dormant BWP, the UE 100 stops PDCCH monitoring and SRS / PUSCH / PUCCH transmission in the SCell, but continues to perform CSI measurement, AGC, and beam management. PDCCH / DCI is used to control entering and leaving the dormant BWP for the SCell. Note that the dormant BWP is one of the dedicated BWPs of the UE 100 configured by the node 200 via dedicated RRC signaling.

[0111] In the second embodiment, it is assumed that the dormant BWP can be set in the PSCell.

[0112] (2.2) System Operation Example The UE 100 according to the second embodiment performs wireless communication with the MN 200M and the SN 200S using DC, as in the first embodiment. In the second embodiment, the deactivation process for the SCG includes a dormant exit process for switching a BWP in a dormant state in the PSCell to a non-dormant state. Specifically, according to the second embodiment, the UE 100 exits the dormant state for the BWP in the dormant state in the PSCell in the active state in response to the wireless quality condition set by the MN 200M being satisfied.

[0113] Fig. 12 is a diagram showing an example of system operation according to the second embodiment. In Fig. 12, non-essential steps are indicated by dashed lines. Furthermore, duplicated explanations of operations similar to those in the first embodiment will be omitted.

[0114] The operations from step S201 to step S205 are the same as those in the first embodiment described above.

[0115] In step S206, the MN 200M transmits an RRC Reconfiguration message to the UE 100. The UE 100 receives the RRC Reconfiguration message. In the second embodiment, the RRC Reconfiguration message includes information for configuring an SCG and configuration information for a conditional dormant BWP transition. The configuration information for a conditional dormant BWP transition includes information indicating a radio quality condition that must be satisfied in order to transition the active BWP of a corresponding active PSCell to a dormant state. The information indicating the radio quality condition is similar to that in the first embodiment, but may include, for example, at least one radio quality threshold among an RSRP threshold, an RSRQ threshold, and an SINR threshold.

[0116] In the second embodiment, the initial state of the active BWP of the PSCell configured in the UE 100 is a non-dormant state. The UE 100 starts radio quality measurement for the PSCell based on the configuration information for transition to a conditional dormant BWP. When the active BWP of the PSCell is a non-dormant BWP, the UE 100 transitions the non-dormant BWP of the PSCell to a dormant state if a radio quality condition is satisfied for the PSCell. In step S207, the UE 100 transmits an RRC Reconfiguration Complete message to the MN 200M. The MN 200M receives the RRC Reconfiguration Complete message.

[0117] The initial state of the SCG set in the UE 100 in step S206 is the active state (step S208).

[0118] In step S209, the UE 100 receives a reference signal of the PSCell and measures the radio quality of the PSCell based on the reference signal. The measurement of the radio quality may include at least one of measuring the duration of a state in which a radio problem is detected, measuring the number of retransmissions (i.e., the number of UL data transmission failures), and measuring the time during which UL data transmission cannot be performed.

[0119] In step S210, the UE 100 determines whether the radio quality condition set in step S206 is satisfied. For example, the UE 100 compares the measurement result (RSRP, RSRQ, and / or SINR) of step S209 with the radio quality threshold set in step S206, and determines that the radio quality condition is satisfied if the measurement result exceeds the radio quality threshold. If it is determined that the radio quality condition is not satisfied (step S210: NO), the process returns to step S209.

[0120] On the other hand, when it is determined that the radio quality condition is satisfied (step S210: YES), in step S211, the UE 100 transitions the active BWP of the PSCell to a dormant state (i.e., switches from a non-dormant state to a dormant state).

[0121] In step S212, the UE 100 triggers transmission of a PSCell BWP sleep transition notification and transmits the PSCell BWP sleep transition notification to the MN 200M. The MN 200M receives the PSCell BWP sleep transition notification. The PSCell BWP sleep transition notification may be a newly introduced MAC CE. Alternatively, the PSCell BWP sleep transition notification may be a notification included in UCI transmitted on the PUCCH, a PDCP Control PDU, or an RRC message.

[0122] The PSCell BWP Dormant Transition Notification may include information on the timing at which the PSCell BWP Dormant Transition (i.e., step S211) was implemented. The timing information may be the radio frame number at which the PSCell BWP Dormant Transition was implemented, or may be expressed as any one or a combination of a system frame number, a subframe number, a slot number, and a symbol number. The timing information may also be time information at which the PSCell BWP Dormant Transition was implemented. The timing information may be the elapsed time from the implementation of the PSCell BWP Dormant Transition to the transmission of the PSCell BWP Dormant Transition Notification, and may be expressed in seconds (e.g., milliseconds) or the number of radio frames (e.g., the number of slots). Such timing information allows the MN 200M to know when DL reception in the SCG (PSCell) stopped, and to efficiently identify data packets to be retransmitted when the MCG retransmits data transmitted in the DL during that period.

[0123] Prior to transmission of the PSCell BWP dormant transition notification, the following processing may be performed in the PHY layer and the MAC layer. Specifically, the UE 100 transmits an SR to the MN 200M, the MN 200M transmits an UL grant for a BSR to the UE 100, the UE 100 transmits a BSR to the MN 200M, and the MN 200M transmits an UL grant for PUSCH transmission to the UE 100. Then, the UE 100 transmits the PSCell BWP dormant transition notification based on the UL grant for PUSCH transmission.

[0124] In step S213, the MN 200M may transmit a message (e.g., an SN Modification Request message) to the SN 200S to notify that the UE 100 has transitioned to dormant for the active BWP of the PSCell. The SN 200S receives the message. The message may include an identifier of the UE 100, specifically, an identifier for identifying the UE 100 on the node-to-node interface.

[0125] In step S214, the SN 200S may send a message indicating approval for the message of step S213 (for example, an SN Modification Request Ack message) to the MN 200M. The MN 200M receives the message.

[0126] In step S215, SN200S stops DL transmission to UE100 using SCG.

[0127] In this operation example, an example has been described in which the UE 100 transmits a PSCell BWP dormant transition notification to the MN 200M. However, the PSCell BWP dormant transition notification may be transmitted to the SN 200S on the PSCell before the active BWP of the PSCell transitions to the dormant state.

[0128] (3) Third Embodiment A third embodiment will be described with reference to Figures 13 and 14, focusing on differences from the above-described embodiments. The third embodiment is based on the first embodiment. However, the third embodiment may also be based on the second embodiment.

[0129] In the above-described embodiment, the UE 100 detects that the radio quality of the PSCell satisfies a predetermined quality and performs SCG deactivation or transition to dormant BWP. Here, in order to quickly detect that the radio quality of the PSCell satisfies a predetermined quality, it is desirable that the UE 100 can constantly measure the radio quality of the PSCell. In the above-described embodiment, the UE 100 measures the radio quality (RSRP, etc.) using the SSB or TRS (CSI-RS) as a reference signal, but these reference signals are transmitted discretely in time. Therefore, at the timing when the SSB or CSI-RS is not transmitted, the UE 100 cannot perform radio communication measurement, and a delay may occur when detecting that the radio quality of the PSCell satisfies a predetermined quality.

[0130] Therefore, in the third embodiment, the SN 200S continuously transmits a reference signal (also referred to as a "Fast Tracking RS") used for measuring radio quality in the time direction on the PSCell. The SN 200S may transmit the Fast Tracking RS based on a request and / or setting from the MN 200M. The UE 100 receives the Fast Tracking RS that is continuously transmitted in the time direction on the PSCell. The UE 100 measures the radio quality of the PSCell based on the Fast Tracking RS.

[0131] 13 is a diagram showing a specific example of a fast tracking RS according to the third embodiment. The fast tracking RS according to the third embodiment is allocated in some frequency resources of the bandwidth of the PSCell.

[0132] In the example of (1) in Fig. 13, the fast tracking RS is arranged in one or more resource blocks at the center of the bandwidth of the PSCell, or in one or more subcarriers at the center of the bandwidth of the PSCell. In the example of (2) in Fig. 13, the fast tracking RS is arranged in one or more resource blocks at one end of the bandwidth of the PSCell, or in one or more subcarriers at one end of the bandwidth of the PSCell. In the example of (3) in Fig. 13, the fast tracking RS is arranged in one or more resource blocks at both ends of the bandwidth of the PSCell, or in one or more subcarriers at both ends of the bandwidth of the PSCell.

[0133] Fig. 14 is a diagram showing an example of system operation according to the third embodiment. In Fig. 14, non-essential steps are indicated by dashed lines. Furthermore, duplicated explanations of operations similar to those in the first embodiment will be omitted.

[0134] The operations from step S301 to step S308 are the same as those in the first embodiment described above.

[0135] Specifically, in step S306, MN 200M transmits an RRC Reconfiguration message to UE 100. UE 100 receives the RRC Reconfiguration message.

[0136] In the third embodiment, the RRC Reconfiguration message may include setting information related to a Fast Tracking RS in addition to the information described in the first embodiment. The setting information related to the Fast Tracking RS includes at least one of information indicating the presence or absence of a Fast Tracking RS, information indicating the position of the Fast Tracking RS on the frequency axis (e.g., resource block number, subcarrier number, and / or ARFCN (Absolute Radio-Frequency Channel Number)), and information assisting in demodulation of the Fast Tracking RS (e.g., a root sequence number indicating a signal sequence of a reference signal).

[0137] Alternatively, the SN 200S or the MN 200M may broadcast the configuration information regarding the fast tracking RS in a system information block (SIB).

[0138] Then, in step S309, the SN 200S transmits a fast tracking RS that is stationary on the time axis in the PSCell that is the target of fast detection. The UE 100 receives the fast tracking RS on the PSCell.

[0139] In step S310, the UE 100 measures the radio quality of the PSCell based on the Fast Tracking RS.

[0140] In step S311, the UE 100 determines whether or not the wireless quality condition set in step S306 is satisfied. If it is determined that the wireless quality condition is not satisfied (step S311: NO), the process returns to step S310.

[0141] When it is determined that the radio quality condition is satisfied (step S311: YES), in step S312, the UE 100 deactivates the SCG.

[0142] The operations from step S313 to step S316 are the same as those in the first embodiment described above.

[0143] (4) Other Embodiments The first to third embodiments described above may be implemented independently, or two or more of the embodiments may be combined and implemented.

[0144] In the above-described embodiment, an example in which the SCG cells are THz-wave cells has been mainly described, but the SCG cells are not limited to THz-wave cells. For example, the SCG cells may be mmW cells.

[0145] The UE 100 may be a Mobile Termination (MT) of an Integrated Access and Backhaul (IAB) node. In this case, the IAB MT (UE 100) may be connected to a first node, and the first node may be connected to a second node. The first node may transmit a notification indicating a radio link failure of a backhaul link between the first node and the second node to the IAB MT (UE 100). Upon receiving the notification, the IAB MT (UE 100) may determine that a radio quality condition is satisfied and may perform SCell deactivation (or dormant BWP transition).

[0146] 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, the 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 of the steps in the operations may be deleted, or additional steps may be added to the process.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] (5) Supplementary Notes The following are additional notes regarding the features of the above-described embodiment.

[0151] (Supplementary Note 1) A user equipment that performs wireless communication with a master node and a secondary node using dual connectivity in a mobile communication system, comprising: a receiver that receives, from the master node, information indicating a wireless quality condition that must be satisfied in order for the user equipment to perform a deactivation process for a secondary cell group of the secondary node; and a controller that measures wireless quality for the secondary cell group and evaluates whether the wireless quality condition is satisfied, and the controller executes the deactivation process for the secondary cell group in response to the wireless quality condition being satisfied.

[0152] (Supplementary Note 2) The user equipment according to Supplementary Note 1, wherein the deactivation process includes a process of transitioning the secondary cell group in an active state to a deactivated state.

[0153] (Supplementary Note 3) The user equipment according to Supplementary Note 1 or 2, wherein the deactivation process includes a process of transitioning a bandwidth portion in a non-dormant state in a primary cell of the secondary cell group to a dormant state.

[0154] (Supplementary Note 4) The user equipment according to any one of Supplementary Notes 1 to 3, further comprising: a transmitter configured to transmit a notification regarding the deactivation process to the master node in response to the wireless quality condition being satisfied.

[0155] (Supplementary Note 5) The user device according to Supplementary Note 4, wherein the control unit completes the deactivation process when sending the notification or when receiving an acknowledgement response to the notification from the master node.

[0156] (Supplementary Note 6) The user equipment according to any one of Supplementary Notes 1 to 5, wherein the receiving unit receives a reference signal that is continuously transmitted in a time direction from the secondary node on a primary cell of the secondary cell group, and the control unit measures the radio quality based on the reference signal.

[0157] (Supplementary Note 7) A node operating as a master node in a mobile communication system in which a user equipment performs wireless communication with a master node and a secondary node using dual connectivity, the node comprising: a control unit that sets a secondary cell group of the secondary node to the user equipment; and a transmission unit that transmits to the user equipment information indicating a wireless quality condition that must be satisfied for the user equipment to perform a deactivation process for the secondary cell group.

[0158] (Supplementary Note 8) The node according to Supplementary Note 7, wherein the deactivation process includes a process of transitioning the secondary cell group in an active state to a deactive state.

[0159] (Supplementary Note 9) The node according to Supplementary Note 7 or 8, wherein the deactivation process includes a process of transitioning a bandwidth portion in a non-dormant state in a primary cell of the secondary cell group to a dormant state.

[0160] (Supplementary Note 10) The node according to any one of Supplementary Notes 7 to 9, further comprising: a receiving unit configured to receive, in response to the wireless quality condition being satisfied in the user equipment, a notification regarding the deactivation process from the user equipment.

[0161] (Supplementary Note 11) The node according to Supplementary Note 10, wherein the controller stops downlink data transmission on the secondary cell group upon receiving the notification or upon transmitting an acknowledgement to the notification to the user equipment.

[0162] (Supplementary Note 12) A communication method used by a user equipment that performs wireless communication with a node using dual connectivity in a mobile communication system, the communication method comprising: a step of receiving, from the node, information indicating a wireless quality condition that must be satisfied in order for the user equipment to perform a deactivation process for a secondary cell group configured for the user equipment; a step of measuring a wireless quality for the secondary cell group and evaluating whether the wireless quality condition is satisfied; and a step of performing the deactivation process for the secondary cell group in response to the wireless quality condition being satisfied.

[0163] (Supplementary Note 13) A communication method used in a node that performs wireless communication with a user equipment using dual connectivity in a mobile communication system, the communication method comprising: a step of setting a secondary cell group in the user equipment; and a step of transmitting to the user equipment information indicating a radio quality condition that must be satisfied for the user equipment to perform a deactivation process for the secondary cell group.

[0164] 1: Network 10: RAN 20: CN 100: UE 110: Receiving unit 120: Transmitting unit 130: Control unit 140: Wireless communication unit 200: Node 210: Transmitting unit 220: Receiving unit 230: Control unit 240: NW communication unit 250: Wireless communication unit 300: CN device

Claims

1. A user equipment that performs wireless communication with a master node and a secondary node using dual connectivity in a mobile communication system, comprising: a receiving unit that receives from the master node information indicating a wireless quality condition that must be satisfied in order for the user equipment to perform a deactivation process for a secondary cell group of the secondary node; and a control unit that measures wireless quality for the secondary cell group and evaluates whether the wireless quality condition is satisfied, and the control unit executes the deactivation process for the secondary cell group in response to the wireless quality condition being satisfied.

2. The user equipment according to claim 1, wherein the deactivation process includes a process of transitioning the secondary cell group in an active state to a deactivated state.

3. The user equipment according to claim 1, wherein the deactivation process includes a process of transitioning a bandwidth portion in a non-dormant state in a primary cell of the secondary cell group to a dormant state.

4. The user equipment according to claim 1, further comprising a transmission unit configured to transmit a notification regarding the deactivation process to the master node in response to the wireless quality condition being satisfied.

5. The user device according to claim 4, wherein the control unit completes the deactivation process when sending the notification or when receiving an acknowledgment for the notification from the master node.

6. The user equipment according to claim 1, wherein the receiving unit receives a reference signal transmitted continuously in a time direction from the secondary node on a primary cell of the secondary cell group, and the control unit measures the radio quality based on the reference signal.

7. A node that operates as a master node in a mobile communication system in which a user equipment performs wireless communication with a master node and a secondary node using dual connectivity, the node comprising: a control unit that sets a secondary cell group of the secondary node to the user equipment; and a transmission unit that transmits to the user equipment information indicating a radio quality condition that must be satisfied for the user equipment to perform a deactivation process for the secondary cell group.

8. The node according to claim 7, wherein the deactivation process includes a process of transitioning the secondary cell group in an active state to a deactivated state.

9. The node according to claim 7, wherein the deactivation process includes a process of transitioning a bandwidth portion in a non-dormant state in a primary cell of the secondary cell group to a dormant state.

10. The node according to claim 7, further comprising a receiving unit configured to receive a notification regarding the deactivation process from the user equipment in response to the radio quality condition being satisfied in the user equipment.

11. The node according to claim 10, wherein the control unit stops downlink data transmission on the secondary cell group upon receiving the notification or upon transmitting an acknowledgment to the notification to the user equipment.

12. A communication method used by a user equipment that performs wireless communication with a node using dual connectivity in a mobile communication system, comprising the steps of: receiving information from the node indicating a wireless quality condition that must be satisfied for the user equipment to perform a deactivation process for a secondary cell group set in the user equipment; measuring wireless quality for the secondary cell group and evaluating whether the wireless quality condition is satisfied; and performing the deactivation process for the secondary cell group in response to the wireless quality condition being satisfied.

13. A communication method used in a node that performs wireless communication with a user equipment using dual connectivity in a mobile communication system, the communication method comprising: a step of setting a secondary cell group in the user equipment; and a step of transmitting to the user equipment information indicating a radio quality condition that must be satisfied for the user equipment to perform a deactivation process for the secondary cell group.

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