Patent Description:
The 3rd generation partnership project (3GPP (registered trademark), hereinafter the same), which is a standardization project for mobile communication systems, defines the technical specifications of carrier aggregation (CA). CA can be configured for a user equipment (UE) through a node of a network of a mobile communication system (also simply referred to as a "node").

In CA, a plurality of component carriers (CCs) corresponding to a plurality of serving cells are aggregated, enabling the UE to simultaneously receive or transmit over the plurality of CCs (plurality of cells). The plurality of CCs may be contiguous or non-contiguous in the frequency domain. One serving cell is referred to as a primary cell (PCell) and one or more secondary cells (SCells) are configured for the UE together with the PCell to form a set of serving cells.

When CA has been configured, the UE has one radio resource control (RRC) connection to the network. SCells can be added and deleted through RRC signaling. SCells can be activated and deactivated through a medium access control (MAC) control element (CE).

CA is generally configured and activated with the following procedure. First, the UE transmits a measurement report message including a radio quality measurement result of each cell to a node. Second, the node configures SCells for the UE using an RRC message based on the measurement report message. Third, the node activates the SCells of the UE using a MAC CE. Activation of an SCell causes the SCell to transition from an inactive state to an active state, enabling wireless communication using the SCell.

Such three-step control poses the problem that it is difficult to shorten a time period from when radio quality corresponding to an SCell in the UE has improved to when wireless communication using the SCell becomes possible.

<CIT> discloses an apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to receive, from a primary cell, a candidate secondary cell configuration which comprises at least one condition, determine that the at least one condition is fulfilled, and activate, as a response to the determining, the candidate secondary cell into a carrier aggregation or a dual connectivity session of the apparatus.

<CIT> discloses a method for activating a secondary cell, a method for measuring a secondary cell, and a terminal, the method for activating a secondary cell comprising: determining a secondary cell satisfying a self-activation determination condition as a self-activated secondary cell; and activating the self-activated secondary cell.

The present invention provides a user equipment, a node, and communication methods according to the independent claims. Further embodiments of the present invention are disclosed in the dependent claims.

A mobile communication system according to embodiments will be described below with reference to the drawings. In the description of the drawings, the same or similar parts will be denoted by the same or similar reference numerals.

A first embodiment will be described with reference to <FIG>.

<FIG> is a diagram illustrating a configuration example of a mobile communication system according to the 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 5th Generation (<NUM>) System or a 6th Generation (<NUM>) System.

The mobile communication system includes a network (NW) <NUM> and a user equipment (UE) <NUM>. The UE <NUM> is a mobile communication apparatus and performs wireless communication with the NW <NUM>. The UE <NUM> may be an apparatus used by a user and may be, for example, a mobile phone terminal (including a smartphone), a tablet terminal, a laptop personal computer (PC), a communication module (including a communication card or chipset), a sensor or an apparatus provided in a sensor, a vehicle or an apparatus provided in a vehicle (a vehicle UE), an aircraft or an apparatus provided in an aircraft (an aerial UE).

The NW <NUM> includes a radio access network (RAN) <NUM> and a core network (CN) <NUM>. When the mobile communication system is a 5th Generation System (5GS), the RAN <NUM> is called a Next Generation Radio Access Network (NG-RAN) and the CN <NUM> is called a <NUM> Core Network (5GC).

The RAN <NUM> includes a plurality of nodes <NUM> (nodes 200a to 200c in the illustrated example). The nodes <NUM> are connected to each other via inter-node interfaces. The nodes <NUM> are also called base stations. Each node <NUM> may include (i.e., be functionally divided into) a Central Unit (CU) and a Distributed Unit (DU), and the two units may be connected through a fronthaul interface. When the mobile communication system is a 5GS, the nodes <NUM> are called gNBs, the inter-node interfaces are called Xn interfaces, and the fronthaul interface is called an F1 interface.

Each node <NUM> manages one or more cells. The node <NUM> performs wireless communication with the UE <NUM> that has established connections to the cells of the node <NUM>. Each node <NUM> has a radio resource management (RRM) function, a user data (also simply referred to as "data") routing function, a measurement control function for mobility control/scheduling, and the like. Note that a "cell" is used as a term indicating a minimum unit of a wireless communication area. A "cell" is also used as a term indicating a function or resource for wireless communication with the UE <NUM>. One cell belongs to one carrier frequency (also simply referred to as one "frequency").

The CN <NUM> includes a CN apparatus <NUM>. The CN apparatus <NUM> may include a control plane (C-plane) apparatus corresponding to a C-plane and a user plane (U-plane) apparatus corresponding to a U-plane. The C-plane apparatus performs various mobility control, paging, and the like for the UE <NUM>. The C-plane apparatus communicates with the UE <NUM> using Non-Access Stratum (NAS) signaling. The U-plane apparatus performs data transfer control. When the mobile communication system is a 5GS, the C-plane apparatus is called an Access and Mobility Management Function (AMF), the U-plane apparatus is called a User Plane Function (UPF), and the interfaces between the node <NUM> and the CN apparatus <NUM> are called NG interfaces.

<FIG> is a diagram illustrating a configuration example of a radio interface protocol stack of the U-plane that handles data.

The U-plane radio interface protocols include, 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.

The PHY layer performs encoding/decoding, modulation/demodulation, antenna mapping/demapping, and resource mapping/demapping. Data and control information is transferred between the PHY layer of the UE <NUM> and the PHY layer of the node <NUM> via a physical channel. The PHY layer of the UE <NUM> receives downlink control information (DCI) transmitted from the node <NUM> over a physical downlink control channel (PDCCH). Specifically, the UE <NUM> blind decodes the PDCCH using a radio network temporary identifier (RNTI) and acquires successfully decoded DCI as DCI addressed to the UE <NUM>. The DCI transmitted from the node <NUM> is appended with CRC parity bits scrambled by the RNTI.

The MAC layer performs data priority control, retransmission processing through hybrid ARQ (HARQ), and the like. Data and control information is transferred between the MAC layer of the UE <NUM> and the MAC layer of the node <NUM> via a transport channel. The MAC layer of the node <NUM> includes a scheduler. The scheduler determines uplink and downlink transport formats (transport block sizes and modulation and coding schemes (MCSs)) and resources allocated to the UE <NUM>.

The RLC layer transfers data to the RLC layer of the receiving side using the functions of the MAC layer and the PHY layer. Data and control information is transferred between the RLC layer of the UE <NUM> and the RLC layer of the node <NUM> via a logical channel.

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

The SDAP layer performs mapping between an IP flow which is the unit in which the CN <NUM> performs QoS control and a radio bearer which is the unit in which an Access Stratum (AS) performs QoS control. Note that the SDAP need not be present when the RAN is connected to an EPC.

<FIG> is a diagram illustrating a configuration example of a radio interface protocol stack of the C-plane that handles signaling (control signals).

The radio interface protocol stack of the C-plane includes, for example, a Radio Resource Control (RRC) layer and a Non-Access Stratum (NAS) layer instead of the SDAP layer illustrated in <FIG>.

RRC signaling for various configurations is transferred between the RRC layer of the UE <NUM> and the RRC layer of the node <NUM>. The RRC layer controls logical, transport, and physical channels in response to establishment, re-establishment, and release of radio bearers. When there is a connection between the RRC of the UE <NUM> and the RRC of the node <NUM> (RRC connection), the UE <NUM> is in an RRC connected state. When there is no connection between the RRC of the UE <NUM> and the RRC of the node <NUM> (RRC connection), the UE <NUM> is in an RRC idle state. When the connection between the RRC of the UE <NUM> and the RRC of the node <NUM> is suspended, the UE <NUM> is in an RRC inactive state.

The NAS layer (also simply referred to as a "NAS") located above the RRC layer performs session management, mobility management, and the like. NAS signaling is transferred between the NAS layer of the UE <NUM> and the NAS layer of the CN apparatus <NUM>. Note that the UE <NUM> includes an application layer in addition to the radio interface protocols. Each layer lower than the NAS layer is referred to as an AS layer (also simply referred to as an "AS").

<FIG> is a diagram for explaining terahertz (THz) wave cells according to the embodiment.

A mobile communication system according to the embodiment may be a <NUM> system. <NUM> is expected to utilize terahertz (THz) waves. A cell that operates with THz waves is called a THz wave cell. Compared to millimeter waves (mmW), THz waves have higher propagation, higher free space loss, and are more susceptible to the effects of the atmosphere and rainfall. Thus, THz wave cells can be ultra-compact size cells.

In the illustrated example, the diameter of the coverage area of a THz wave cell is about <NUM>, the diameter of the coverage area of a mmW cell that operates with mmW is about <NUM>, and the diameter of the coverage area of a macro cell is about <NUM>. Under this assumption, the UE <NUM> which is moving at, for example, <NUM>/s passes through the coverage area of each THz wave cell in about <NUM>.

Carrier aggregation (CA) is one method for reliably controlling compact size cells in a mobile communication system. In the embodiment, it is assumed that THz wave cells are used as secondary cells (SCells) of CA. It is assumed that a primary cell (PCell) of CA is a macro cell, but the PCell may be a mmW cell.

<FIG> is a diagram for explaining carrier aggregation (CA) according to the embodiment.

CA can be configured for the UE <NUM>, which is in an RRC connected state, through the node <NUM>. In CA, a plurality of component carriers (CCs) corresponding to a plurality of serving cells are aggregated, enabling the UE to simultaneously receive or transmit over the plurality of CCs (plurality of cells). The plurality of CCs may be contiguous or non-contiguous in the frequency domain. One serving cell is referred to as a primary cell (PCell) and one or more secondary cells (SCells) are configured for the UE together with the PCell to form a set of serving cells. When CA has been configured, the UE <NUM> has one RRC connection to the network <NUM>. SCells can be added and deleted through RRC signaling. SCells can be activated and deactivated through a medium access control (MAC) control element (CE).

The mobile communication system supports activation and deactivation of cells to enable a reduction in the power consumption of the UE <NUM> when CA has been configured. When an SCell is inactive, the UE <NUM> does not need to receive a PDCCH or a physical downlink shared channel (PDSCH) over the SCell and cannot perform uplink transmission over the SCell. The UE <NUM> also does not need to perform channel quality indicator (CQI) measurement for the inactive SCell. On the other hand, when an SCell is active, the UE <NUM> receives a PDSCH and a PDCCH over the SCell. The UE <NUM> can perform CQI measurement for the active SCell.

Note that when reconfiguring a set of serving cells, the node <NUM> first activates or deactivates SCells added to the set and does not change the activation state (active or inactive state) of SCells remaining in the set (which have not been changed or reconfigured).

<FIG> is a diagram illustrating a general procedure for adding and activating SCells.

In step S11, the UE <NUM> transmits a Measurement Report message including the radio quality measurement result of each cell to the node <NUM>, for example, over the PCell. The radio quality is, for example, at least one selected from the group consisting of Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), and Signal to Interference & Noise Ratio (SINR). The Measurement Report message is an RRC message transmitted and received in the RRC layer. The Measurement Report message may be transmitted periodically or by an event trigger. The node <NUM> receives the Measurement Report Message.

In step S12, the node <NUM> determines to configure (add) the SCell for the UE <NUM> based on the Measurement Report message and transmits, to the UE <NUM>, an RRC Reconfiguration message for adding the SCell to the UE <NUM>, for example, over the PCell. The RRC Reconfiguration message is transmitted and received in the RRC layer. The UE <NUM> receives the RRC Reconfiguration message.

In step S13, the UE <NUM> transmits an RRC Reconfiguration Complete message indicating completion of adding the SCell based on the RRC Reconfiguration message to the node <NUM>, for example, over the PCell. The RRC Reconfiguration Complete message is transmitted and received in the RRC layer. The node <NUM> receives the RRC Reconfiguration Complete message. At this stage, the added SCell is inactive.

In step S14, the node <NUM> transmits, to the UE <NUM>, a MAC CE for activating the SCell added to the UE <NUM>, for example, over the PCell. The MAC CE is transmitted and received in the MAC layer. The UE <NUM> starts activating the SCell upon receiving the MAC CE. Upon starting the activation of the SCell, the UE <NUM> receives a reference signal of the SCell and performs channel state information (CSI) measurement, automatic gain control (AGC), and beam management to prepare for communication.

In step S15, the UE <NUM> transmits a HARQ ACK indicating successful reception of the MAC CE to the node <NUM>, for example, over a PUCCH of the PCell. The node <NUM> receives the HARQ ACK.

In step S16, the UE <NUM> and the node <NUM> start wireless communication using the SCell when the SCell has become active in the UE <NUM>.

According to such a procedure, it takes, for example, about <NUM> until the UE <NUM> is able to use the SCell after the radio quality of the SCell becomes fit for communication. When the SCell is a THz wave cell, the coverage area of the SCell is even narrower due to the influence of shielding or the like and thus the available time of the SCell is shorter. Therefore, in the procedure of <FIG>, it takes a long time until the activation of the SCell is completed, posing the problem that the time during which data can actually be transmitted and received over the SCell is short.

Here, the following extended functions have been introduced up to Release <NUM> of the 3GPP standard as techniques capable of speeding up SCell activation.

A first extended function is direct SCell activation. In direct SCell activation, the node <NUM> can designate the initial state of an SCell as an active state when adding the SCell to the UE <NUM> using an RRC message. This eliminates the need to transmit and receive the MAC CE for SCell activation in <FIG> and thus can speed up SCell activation.

A second extended function is a technique called dormant BWP. The node <NUM> can configure dormant bandwidth parts (BWPs) for SCells. If an active BWP for an activated SCell is a dormant BWP, the UE <NUM> stops PDCCH monitoring and sounding reference signal (SRS)/PUSCH/PUCCH transmission over the SCell, but continues the execution of CSI measurement, AGC, and beam management. PDCCH/downlink control information (DCI) is used to control entering and leaving a dormant BWP for the SCell. Note that the dormant BWP is one of dedicated BWPs of the UE <NUM> that the network <NUM> has configured via dedicated RRC signaling. An example using dormant BWPs will be described in a second embodiment.

A third extended function is a method of configuring, for an SCell, an aperiodic CSI-RS for tracking (synchronization) for fast SCell activation. Such an aperiodic CSI-RS can support AGC and time/frequency synchronization. A MAC CE is used to trigger (start) SCell activation and trigger an aperiodic CSI-RS for a deactivated SCell.

However, these extended functions have room for improvement to further speed up SCell activation. Note that it is possible to eliminate delays associated with activation by keeping SCells in the active state in advance before the radio quality of the SCells meets a predetermined level of quality, but this poses the problem that the power consumption of the UE <NUM> increases. Thus, a method is preferred that can deactivate an SCell when the radio quality of the SCell does not meet a predetermined level of quality and can quickly activate the SCell when the radio quality of the SCell meets the predetermined level of quality.

<FIG> is a diagram illustrating a configuration example of the UE <NUM> (user equipment) according to the embodiment.

The UE <NUM> includes a receiver <NUM>, a transmitter <NUM>, and a controller <NUM>. The receiver <NUM> and the transmitter <NUM> constitute a wireless communicator <NUM> that performs wireless communication with the node <NUM>.

The receiver <NUM> performs various types of reception under the control of the controller <NUM>. The receiver <NUM> includes an antenna and a reception device. The reception device converts a radio signal received through the antenna into a baseband signal (reception signal) and outputs the baseband signal to the controller <NUM>. The transmitter <NUM> performs various types of transmission under the control of the controller <NUM>. The transmitter <NUM> includes an antenna and a transmission device. The transmission device converts a baseband signal (transmission signal) output from the controller <NUM> into a radio signal and transmits the radio signal through the antenna.

The controller <NUM> performs various types of control and processes in the UE <NUM>. The operations of the UE <NUM> described above and below may also be performed under the control of a controller <NUM>. The controller <NUM> includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used for processing by the processor. The processor may include a baseband processor and a Central Processing Unit (CPU). The baseband processor performs modulation/demodulation, encoding/decoding, or the like on the baseband signal. The CPU executes the programs stored in the memory to perform various processes.

The UE <NUM> configured as such performs wireless communication with the node <NUM> using CA. The receiver <NUM> receives, from the node <NUM>, information indicating a radio quality condition that is to be met for the UE <NUM> to perform an activation process for each SCell configured for the UE <NUM>. The controller <NUM> measures radio quality of the SCell and evaluates whether the radio quality condition is met. The controller <NUM> performs an activation process for the SCell in response to the radio quality condition being met.

This allows the UE <NUM> to autonomously perform an activation process for an SCell when the radio quality of the SCell meets the radio quality condition (the predetermined level of quality). On the other hand, in the related art, the node <NUM> needs to identify that the radio quality of an SCell meets a radio quality condition (a predetermined level of quality) based on a Measurement Report message and instruct the UE <NUM> to activate the SCell and/or switch a dormant BWP to a non-dormant state (cause a dormant BWP to leave a dormant state).

In the embodiment, a radio quality condition is configured for the UE <NUM> and the UE <NUM> can determine whether the radio quality condition is met, such that the UE <NUM> can autonomously perform an activation process for the SCell without transmitting a Measurement Report message to the node <NUM>. Thus, it is possible to further speed up SCell activation.

In the first embodiment, the activation process includes a process for transitioning the SCell from an inactive state to an active state. The activation process may also include a process of causing a dormant BWP in the SCell to leave the dormant state. An example using dormant BWPs will be described in the second embodiment.

In the embodiment, the transmitter <NUM> transmits a notification regarding the activation process to the node <NUM> in response to the radio quality condition being met. Thus, based on the notification, the node <NUM> can determine that the UE <NUM> will perform an activation process. Therefore, wireless communication using the activated SCell can be started smoothly.

In the embodiment, the transmitter <NUM> transmits a notification regarding the activation process to the node <NUM> over the PCell. Thus, the notification can be transmitted to the node <NUM> before activation of the SCell is completed. Therefore, wireless communication using the activated SCell can be started smoothly and quickly.

<FIG> is a diagram illustrating a configuration example of the node <NUM> (base station) according to the embodiment.

The node <NUM> includes a transmitter <NUM>, a receiver <NUM>, the controller <NUM>, and a NW communicator <NUM>. The transmitter <NUM> and the receiver <NUM> constitute a wireless communicator <NUM> that performs wireless communication with the UE <NUM>.

The transmitter <NUM> performs various types of transmission under the control of the controller <NUM>. The transmitter <NUM> includes an antenna and a transmission device. The transmission device converts a baseband signal (transmission signal) output from the controller <NUM> into a radio signal and transmits the radio signal through the antenna. The receiver <NUM> performs various types of reception under the control of the controller <NUM>. The receiver <NUM> includes an antenna and a reception device. The reception device converts the radio signal received through the antenna into a baseband signal (reception signal) and outputs the baseband signal to the controller <NUM>.

The controller <NUM> performs various types of control and processes in the node <NUM>. The operations of the node <NUM> described above and below may also be performed under the control of the controller <NUM>. The controller <NUM> includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used for processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation/demodulation, encoding/decoding, or the like on the baseband signal. The CPU executes the programs stored in the memory to perform various processes.

The NW communicator <NUM> is connected to adjacent nodes via inter-node interfaces. The NW communicator <NUM> is connected to the CN apparatus <NUM> via a node-CN interface.

The node <NUM> configured as such performs wireless communication with the UE <NUM> using CA. The controller <NUM> configures SCells for the UE <NUM>. The transmitter <NUM> transmits to the UE <NUM> information indicating a radio quality condition that is to be met for the UE <NUM> to perform an activation process for each SCell. This allows the UE <NUM> to autonomously perform an activation process for an SCell when the radio quality of the SCell meets the radio quality condition (the predetermined level of quality).

In the embodiment, the receiver <NUM> receives a notification regarding the activation process from the UE <NUM> in response to the radio quality condition being met in the UE <NUM>. For example, the receiver <NUM> receives the notification from the UE <NUM> over the PCell.

<FIG> is a diagram illustrating an operation example of a system according to the first embodiment. In <FIG>, dashed lines indicate non-essential steps. Overlapping description of operations the same as those of <FIG> will be omitted.

In step S101, the receiver <NUM> of the UE <NUM> receives a reference signal from each cell, the controller <NUM> of the UE <NUM> measures radio quality based on the reference signal, and the transmitter <NUM> of the UE <NUM> transmits a Measurement Report message including the measurement result to the node <NUM>, for example, over the PCell. Here, it is assumed that the Measurement Report message includes the measurement results of THz wave cells. The receiver <NUM> of the node <NUM> receives the Measurement Report message.

In step S102, the controller <NUM> of the node <NUM> generates an RRC Reconfiguration message and the transmitter <NUM> of the node <NUM> transmits the RRC Reconfiguration message to the UE <NUM>, for example, over the PCell. The receiver <NUM> of the UE <NUM> receives the RRC Reconfiguration message.

The RRC Reconfiguration message includes configuration information for adding SCells and configuration information for conditional SCell activation. The configuration information for adding SCells may be an sCellToAddModList which is a list of SCells to be added or changed. The sCellToAddModList is a list that has SCell configurations (SCellConfig) as entries. Each SCell configuration (SCellConfig) includes an index of the corresponding SCell (sCellIndex) and a configuration of the corresponding SCell (sCellConfigCommon and sCellConfigDedicated).

The SCell configuration (SCellConfig) may include the configuration information for conditional SCell activation. The configuration information for conditional SCell activation includes information indicating a radio quality condition that is to be met for the UE <NUM> to activate the corresponding SCell. The information indicating the radio quality condition may include at least one radio quality threshold value selected from the group consisting of an RSRP threshold value, an RSRQ threshold value, and an SINR threshold value.

In the first embodiment, the initial state of the SCell added to the UE <NUM> is the inactive state. The controller <NUM> of the UE <NUM> starts radio quality measurement for the SCell based on the configuration information for conditional SCell activation.

In step S103, the controller <NUM> of the UE <NUM> generates an RRC Reconfiguration Complete message and the transmitter <NUM> of the UE <NUM> transmits the RRC Reconfiguration Complete message to the node <NUM>, for example, over the PCell. The receiver <NUM> of the node <NUM> receives the RRC Reconfiguration Complete message.

In step S104, the receiver <NUM> of the UE <NUM> receives a reference signal of each SCell and the controller <NUM> of the UE <NUM> measures radio quality based on the reference signal. The reference signal of the SCell may be a demodulation reference signal (DMRS) included in an SS/PBCH Block (SSB) transmitted by the SCell or may be a Tracking Reference Signal (TRS) which is a type of CSI-RS.

In step S105, the controller <NUM> of the UE <NUM> determines whether the radio quality condition configured in step S102 is met. Specifically, the controller <NUM> of the UE <NUM> compares the measurement result (RSRP, RSRQ, and/or SINR) in step S104 with the radio quality threshold value configured in step S102, and if the measurement result exceeds the radio quality threshold value, determines that the radio quality condition is met. When it is determined that the radio quality condition is not met (NO in step S105), the process returns to step S104.

On the other hand, upon determining that the radio quality condition is met (YES in step S105), the controller <NUM> of the UE <NUM> starts activating the SCell in step S106. The controller <NUM> of the UE <NUM> may perform control for establishing time/frequency synchronization with the SCell. For example, the receiver <NUM> of the UE <NUM> receives an SSB or TRS of the SCell and the controller <NUM> of the UE <NUM> establishes time/frequency synchronization using the SSB or TRS. The controller <NUM> of the UE <NUM> may also perform CSI measurement, AGC, and beam management for the SCell.

In steps S104 and S106, the node <NUM> may transmit the TRS over the SCell at a time (occasion) that the node <NUM> has configured in the UE <NUM> in advance and the UE <NUM> may wake up at the time to receive the TRS. The RRC configuration of step S102 may include information on the time (occasion).

In step S107, the controller <NUM> of the UE <NUM> triggers transmission of an SCell activation notification and the transmitter <NUM> of the UE <NUM> transmits the SCell activation notification to the node <NUM> over the PCell. The receiver <NUM> of the node <NUM> receives the SCell activation notification.

The SCell activation notification may be a newly introduced MAC CE. The SCell activation notification includes an index value (which may be a cell ID) of the activated SCell. However, the SCell activation notification may be a notification included in UCI transmitted over a PUCCH, may be a PDCP Control PDU, or may be a notification included in an RRC message.

Prior to transmitting the SCell activation notification, the following processes may be performed in the PHY layer and the MAC layer. Specifically, the UE <NUM> transmits a Scheduling Request (SR) to the node <NUM>, the node <NUM> transmits a UL grant for a Buffer Status Report (BSR) to the UE <NUM>, the UE <NUM> transmits a BSR to the node <NUM>, and the node <NUM> transmits a UL grant for PUSCH transmission to the UE <NUM>. The UE <NUM> then transmits an SCell activation notification based on the UL grant for PUSCH transmission.

Note that an example in which the UE <NUM> transmits the SCell activation notification to the node <NUM> over the PCell has been described, but the UE <NUM> may also transmit the SCell activation notification to the node <NUM> over the SCell if activation of the SCell is completed. The SCell activation notification may include an index of the activated SCell. The index may refer to each entry in the SCell configuration list configured in the RRC Reconfiguration. The cell ID of the activated SCell may be transmitted instead of the index. Alternatively, in a bitmap-like notification, each bit position may be associated with a respective SCell and each bit (<NUM>/<NUM>) may indicate whether the bit is activated.

In step S108, the transmitter <NUM> of the node <NUM> transmits a HARQ ACK indicating successful reception of the SCell activation notification to the UE <NUM> over a PDCCH of the PCell. The receiver <NUM> of the UE <NUM> receives the HARQ ACK. Note that step S108 need not be performed if the SCell activation notification is UCI.

The node <NUM> identifies that the SCell of the UE <NUM> has become available in response to receiving the SCell activation notification in step S107. In step S109, the node <NUM> performs DL transmission and/or UL granting to the UE <NUM> over the activated SCell and starts wireless communication (data communication) over the SCell.

The second embodiment will be described with reference to <FIG> and <FIG>, focusing on differences from the first embodiment.

With bandwidth adaptation (BA), the transmission and reception bandwidth of the UE <NUM> need not be as large as the bandwidth of the cell and can be adjusted. Parts of the cell bandwidth are called BWPs. In BA, the node <NUM> configures one or more BWPs in the cell for the UE <NUM> and informs the UE <NUM> which of the configured BWPs is currently active. BWPs include an initial BWP used for initial access and dedicated BWPs individually configured for the UE <NUM>. The bandwidth and subcarrier spacing of each BWP can be variably configured.

The illustrated example illustrates an example in which three different BWPs are configured for the UE <NUM> and an active BWP is switched among these BWPs. BWP1 has a width of <NUM> and a subcarrier spacing of <NUM>, BWP2 has a width of <NUM> and a subcarrier spacing of <NUM>, and BWP3 has a width of <NUM> and a subcarrier spacing of <NUM>.

In each of the UL and DL, only one BWP is active and the rest are inactive. In inactive BWPs, the UE <NUM> does not monitor a PDCCH and does not transmit a PUCCH, a PRACH, and an UL-SCH.

In the case of CA, the node <NUM> can configure dormant BWPs for SCells. If an active BWP for an activated SCell is a dormant BWP, the UE <NUM> stops PDCCH monitoring and SRS/PUSCH/PUCCH transmission over the SCell, but continues the execution of CSI measurement, AGC, and beam management. A PDCCH/DCI is used to control entering and leaving a dormant BWP for the SCell. Note that the dormant BWP is one of the dedicated BWPs of the UE <NUM> that the node <NUM> has configured via dedicated RRC signaling.

The UE <NUM> according to the second embodiment performs wireless communication with the node <NUM> using CA the same as, and/or similar to, in the first embodiment. The receiver <NUM> receives, from the node <NUM>, information indicating a radio quality condition that is to be met for the UE <NUM> to perform an activation process for each SCell configured for the UE <NUM>. The controller <NUM> measures radio quality of the SCell and evaluates whether the radio quality condition is met. The controller <NUM> performs an activation process for the SCell in response to the radio quality condition being met. In the second embodiment, the activation process includes a dormant leaving process for switching a dormant BWP to a non-dormant state in the SCell.

According to the second embodiment, the controller <NUM> of the UE <NUM> causes a dormant BWP for the active SCell to leave the dormant state in response to the radio quality condition configured by the node <NUM> being met. Thus, the UE <NUM> can cause a dormant BWP to leave the dormant state without transmitting a Measurement Report message to the node <NUM> and receiving DCI indicating leaving a dormant BWP.

<FIG> is a diagram illustrating an operation example of a system according to the second embodiment. In <FIG>, dashed lines indicate non-essential steps. Overlapping description of operations the same as those of the first embodiment described above will be omitted.

In step S201, the receiver <NUM> of the UE <NUM> receives a reference signal from each cell, the controller <NUM> of the UE <NUM> measures radio quality based on the reference signal, and the transmitter <NUM> of the UE <NUM> transmits a Measurement Report message including the measurement result to the node <NUM>, for example, over the PCell. Here, it is assumed that the Measurement Report message includes the measurement results of THz wave cells. The receiver <NUM> of the node <NUM> receives the Measurement Report message.

In step S202, the controller <NUM> of the node <NUM> generates an RRC Reconfiguration message and the transmitter <NUM> of the node <NUM> transmits the RRC Reconfiguration message to the UE <NUM>, for example, over the PCell. The receiver <NUM> of the UE <NUM> receives the RRC Reconfiguration message.

The RRC Reconfiguration message includes configuration information for adding SCells, configuration information for designating the initial state of the SCell as an active state, configuration information for configuring a BWP (a dedicated BWP) for the SCell, configuration information for setting the BWP to a dormant state, and configuration information for conditionally leaving the dormant BWP. The configuration information for adding SCells may be an sCellToAddModList which is a list of SCells to be added or changed. The sCellToAddModList is a list that has SCell configurations (SCellConfig) as entries. Each SCell configuration (SCellConfig) includes an index of the corresponding SCell (sCellIndex) and a configuration of the corresponding SCell (sCellConfigCommon and sCellConfigDedicated).

The SCell configuration (SCellConfig) may include the configuration information for designating the initial state of the SCell as an active state, the configuration information for configuring a BWP (a dedicated BWP) for the SCell, the configuration information for configuring the BWP to a dormant state, and the configuration information for conditionally leaving the dormant BWP.

The configuration information for conditionally leaving the dormant BWP includes information indicating, when the active BWP of the corresponding active SCell is a dormant BWP, a radio quality condition that is to be met to terminate (leave) the dormant state of the corresponding BWP. The information indicating the radio quality condition may include at least one radio quality threshold value selected from the group consisting of an RSRP threshold value, an RSRQ threshold value, and an SINR threshold value.

In the second embodiment, the initial state of the active BWP of the SCell added to the UE <NUM> is the dormant state. The controller <NUM> of the UE <NUM> starts radio quality measurement for the SCell based on the configuration information for conditionally leaving the dormant BWP.

In step S203, the controller <NUM> of the UE <NUM> generates an RRC Reconfiguration Complete message and the transmitter <NUM> of the UE <NUM> transmits the RRC Reconfiguration Complete message to the node <NUM>, for example, over the PCell. The receiver <NUM> of the node <NUM> receives the RRC Reconfiguration Complete message.

In step S204, the receiver <NUM> of the UE <NUM> receives a reference signal of each SCell and the controller <NUM> of the UE <NUM> measures radio quality based on the reference signal. The reference signal of the SCell may be a DMRS included in an SSB transmitted by the SCell or may be a TRS.

In step S205, the controller <NUM> of the UE <NUM> determines whether the radio quality condition configured in step S202 is met. Specifically, the controller <NUM> of the UE <NUM> compares the measurement result (RSRP, RSRQ, and/or SINR) in step S204 with the radio quality threshold value configured in step S202, and if the measurement result exceeds the radio quality threshold value, determines that the radio quality condition is met. When it is determined that the radio quality condition is not met (NO in step S205), the process returns to step S204.

On the other hand, upon determining that the radio quality condition is met (YES in step S205), the controller <NUM> of the UE <NUM> terminates (leaves) the dormant BWP of the SCell (i.e., switches the dormant BPW to a non-dormant state) in step S206.

In steps S204 and S206, the node <NUM> may transmit the TRS over the SCell at a time (occasion) that the node <NUM> has configured in the UE <NUM> in advance and the UE <NUM> may wake up at the time to receive the TRS. The RRC configuration of step S202 may include information on the time (occasion).

In step S207, the controller <NUM> of the UE <NUM> triggers transmission of an SCell BWP dormant leaving notification and the transmitter <NUM> of the UE <NUM> transmits the SCell BWP dormant leaving notification to the node <NUM> over the PCell. The receiver <NUM> of the node <NUM> receives the SCell BWP dormant leaving notification.

The SCell BWP dormant leaving notification may be a newly introduced MAC CE. The SCell BWP dormant leaving notification includes an index value (which may be a cell ID) of the SCell which has terminated the dormant BWP and/or a BWP ID of the BWP. However, the SCell BWP dormant leaving notification may be a notification included in UCI transmitted over a PUCCH, may be a PDCP Control PDU, or may be a notification included in an RRC message.

Prior to transmitting the SCell BWP dormant leaving notification, the following processes may be performed in the PHY layer and the MAC layer. Specifically, the UE <NUM> transmits a Scheduling Request (SR) to the node <NUM>, the node <NUM> transmits a UL grant for a Buffer Status Report (BSR) to the UE <NUM>, the UE <NUM> transmits a BSR to the node <NUM>, and the node <NUM> transmits a UL grant for PUSCH transmission to the UE <NUM>. The UE <NUM> then transmits an SCell BWP dormant leaving notification based on the UL grant for PUSCH transmission.

Note that an example in which the UE <NUM> transmits the SCell BWP dormant leaving notification to the node <NUM> over the PCell has been described, but the UE <NUM> may also transmit the SCell BWP dormant leaving notification to the node <NUM> over the SCell.

In step S208, the transmitter <NUM> of the node <NUM> transmits a HARQ ACK indicating successful reception of the SCell BWP dormant leaving notification to the UE <NUM> over a PDCCH of the PCell. The receiver <NUM> of the UE <NUM> receives the HARQ ACK. Note that step S208 need not be performed if the SCell BWP dormant leaving notification is UCI.

The node <NUM> identifies that the active BWP of the SCell of the UE <NUM> has become available in response to receiving the SCell BWP dormant leaving notification in step S207. In step S209, the node <NUM> performs DL transmission and/or UL granting to the UE <NUM> over the activated BWP of the SCell and starts wireless communication (data communication) over the activated BWP of the SCell.

A third embodiment will be described with reference to <FIG>, focusing on differences from the embodiments described above. The third embodiment is an embodiment based on the first embodiment described above. However, the third embodiment may also be an embodiment based on the second embodiment described above.

In the third embodiment, the controller <NUM> of the UE <NUM> completes activating the SCell (i.e., makes the SCell ready for data communication) within a predetermined time period from the time of transmitting an SCell activation notification or from the time of receiving a positive acknowledgment (HARQ ACK) to the SCell activation notification from the node <NUM>. On the other hand, the controller <NUM> of the node <NUM> assumes that the activation process is completed within the predetermined time period from the time of receiving an SCell activation notification or from the time of transmitting, to the UE <NUM>, a positive acknowledgment (HARQ ACK) to the SCell activation notification. This allows the node <NUM> to smoothly start data communication over the SCell after activation of the SCell is completed.

In the third embodiment, the transmitter <NUM> of the UE <NUM> transmits information indicating the predetermined time period to the node <NUM> when transmitting the SCell activation notification or before transmitting the SCell activation notification. The receiver <NUM> of the node <NUM> receives information indicating the predetermined time period from the UE <NUM>. This allows the node <NUM> to appropriately determine the time when the UE <NUM> completes activation of the SCell and can smoothly start data communication over the SCell. In the following, the predetermined time period is also referred to as a "time offset.

<FIG> is a diagram illustrating an operation example of a system according to the third embodiment. In <FIG>, dashed lines indicate non-essential steps. Overlapping description of operations the same as those of the first embodiment described above will be omitted.

In step S301, the transmitter <NUM> of the UE <NUM> transmits a Measurement Report message to the node <NUM>, for example, over the PCell. The receiver <NUM> of the node <NUM> receives the Measurement Report message.

In step S302, the transmitter <NUM> of the node <NUM> transmits an RRC Reconfiguration message to the UE <NUM>, for example, over the PCell. The receiver <NUM> of the UE <NUM> receives the RRC Reconfiguration message.

In the third embodiment, the RRC Reconfiguration message may include configuration information for configuring a time offset from the time of transmitting an SCell activation notification (or from a positive acknowledgment for the notification) to when the SCell activation process is completed in addition to the information described in the first embodiment above. The time offset may be in units of milliseconds (e.g., X ms) or may be in units according to the radio frame structure (e.g., X frames, X subframes, X slots, or X OFDM symbols).

In step S303, the transmitter <NUM> of the UE <NUM> transmits an RRC Reconfiguration Complete message to the node <NUM>, for example, over the PCell. The receiver <NUM> of the node <NUM> receives the RRC Reconfiguration Complete message.

In step S304, the controller <NUM> of the UE <NUM> measures radio quality based on a reference signal of the SCell.

In step S305, the controller <NUM> of the UE <NUM> determines whether the radio quality condition configured in step S302 is met. When it is determined that the radio quality condition is not met (NO in step S305), the process returns to step S304.

Upon determining that the radio quality condition is met (YES in step S305), the controller <NUM> of the UE <NUM> starts activating the SCell in step S306.

In step S307, the transmitter <NUM> of the UE <NUM> transmits an SCell activation notification to the node <NUM> over the PCell. The receiver <NUM> of the node <NUM> receives the SCell activation notification.

In the third embodiment, the SCell activation notification may include information indicating the time offset. The UE <NUM> determines a time period it will take to complete the SCell activation at the time of transmitting the SCell activation notification and notifies the node <NUM> of the time period as a time offset.

Alternatively, the UE <NUM> may notify the network <NUM> in advance of information indicating a time offset determined according to the capabilities of the UE <NUM>. For example, the node <NUM> transmits an enquiry message inquiring about the capabilities of the UE <NUM> (a UE Capability Enquiry message) to the UE <NUM>. The UE <NUM> transmits a UE capability information message including time offset information to the node <NUM> in response to receiving the UE Capability Enquiry message.

In step S308, the transmitter <NUM> of the node <NUM> transmits a HARQ ACK indicating successful reception of the SCell activation notification to the UE <NUM> over a PDCCH of the PCell. The receiver <NUM> of the UE <NUM> receives the HARQ ACK. Note that step S308 need not be performed if the SCell activation notification is UCI.

The node <NUM> identifies that the SCell of the UE <NUM> has become available after the time offset from the time of receiving the SCell activation notification or from the time of transmitting the HARQ ACK. The time offset may be a variable time offset configured in step S302, a variable time offset notified of in step S307, or a fixed time offset predefined in technical specifications.

In step S309, the node <NUM> performs DL transmission and/or UL granting to the UE <NUM> over the activated SCell and starts wireless communication (data communication) over the SCell.

A fourth embodiment will be described with reference to <FIG> and <FIG>, focusing on differences from the embodiments described above. The fourth embodiment is an embodiment based on the first embodiment described above. However, the fourth embodiment may also be an embodiment based on the second embodiment described above.

In the embodiments described above, the UE <NUM> detects that the radio quality of the SCell meets the predetermined level of quality and activates the SCell or leaves the dormant BWP. Here, to quickly detect that the radio quality of the SCell meets the predetermined level of quality, it is desirable that the UE <NUM> can constantly measure the radio quality of the SCell. In the embodiments described above, the UE <NUM> measures the radio quality (such as an RSRP) using SSBs or TRSs (CSI-RSs) as reference signals, but these reference signals are transmitted discretely in time. Thus, at times when no SSBs or CSI-RSs are transmitted, the UE <NUM> cannot perform wireless communication measurement and may be delayed in detecting that the radio quality of the SCell meets the predetermined level of quality.

When the SCell is activated, the UE <NUM> establishes time/frequency synchronization using SSBs or TRSs (CSI-RSs) as reference signals and performs processes such as CSI measurement, AGC, and beam management. Thus, at times when no SSBs or CSI-RSs are transmitted, the UE <NUM> cannot perform the processes for SCell activation and may be delayed in SCell activation.

Therefore, in the fourth embodiment, the transmitter <NUM> of the node <NUM> transmits a reference signal (also referred to as a "Fast tracking RS") used for radio quality measurement continuously in the time domain over the SCell. The receiver <NUM> of the UE <NUM> receives the Fast tracking RS transmitted continuously in the time domain over the SCell from the node <NUM>. The controller <NUM> of the UE <NUM> measures the radio quality of the SCell based on the Fast tracking RS. The controller <NUM> of the UE <NUM> may perform a process for SCell activation (e.g., at least one selected from the group consisting of time/frequency synchronization establishment, CSI measurement, AGC, and beam management) based on the Fast tracking RS. This can suppress the delay described above.

<FIG> is a diagram illustrating specific examples of Fast tracking RSs according to the fourth embodiment. Fast tracking RSs according to the fourth embodiment are arranged in some frequency resources in the bandwidth of a cell (SCell).

In the example of (<NUM>) of <FIG>, a Fast tracking RS is arranged in one or more resource blocks in the middle of the bandwidth of the SCell or in one or more subcarriers in the middle of the bandwidth of the SCell. In the example of (<NUM>) of <FIG>, a Fast tracking RS is arranged in one or more resource blocks at one end of the bandwidth of the SCell or in one or more subcarriers at one end of the bandwidth of the SCell. In the example of (<NUM>) of <FIG>, the Fast tracking RS is arranged in one or more resource blocks at both ends of the bandwidth of the SCell or in one or more subcarriers on both sides of the bandwidth of the SCell.

<FIG> is a diagram illustrating an operation example of a system according to the fourth embodiment. In <FIG>, dashed lines indicate non-essential steps. Overlapping description of operations the same as those of the first embodiment described above will be omitted.

In step S401, the transmitter <NUM> of the UE <NUM> transmits a Measurement Report message to the node <NUM>, for example, over the PCell. The receiver <NUM> of the node <NUM> receives the Measurement Report message.

In step S402, the transmitter <NUM> of the node <NUM> transmits an RRC Reconfiguration message to the UE <NUM>, for example, over the PCell. The receiver <NUM> of the UE <NUM> receives the RRC Reconfiguration message.

In the fourth embodiment, the RRC Reconfiguration message may include configuration information regarding a Fast tracking RS in addition to the information described in the first embodiment above. The configuration information regarding a Fast tracking RS includes at least one selected from the group consisting 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., a resource block number, a subcarrier number, and/or an Absolute Radio-Frequency Channel Number (ARFCN)), and information that assists in demodulating the Fast tracking RS (e.g., a root sequence number indicating the signal sequence of the reference signal).

The node <NUM> may broadcast the configuration information regarding a Fast tracking RS in a system information block (SIB) of the PCell.

In step S403, the transmitter <NUM> of the UE <NUM> transmits an RRC Reconfiguration Complete message to the node <NUM>, for example, over the PCell. The receiver <NUM> of the node <NUM> receives the RRC Reconfiguration Complete message.

In step S404, the transmitter <NUM> of the node <NUM> transmits a steady Fast tracking RS on the time axis in the SCell targeted for high speed detection. The receiver <NUM> of the UE <NUM> receives the Fast tracking RS over the SCell.

In step S405, the controller <NUM> of the UE <NUM> measures radio quality based on the Fast tracking RS of the SCell.

In step S406, the controller <NUM> of the UE <NUM> determines whether the radio quality condition set in step S402 is met. When it is determined that the radio quality condition is not met (NO in step S406), the process returns to step S405.

Upon determining that the radio quality condition is met (YES in step S406), the controller <NUM> of the UE <NUM> starts activating the SCell in step S407. Here, the transmitter <NUM> of the node <NUM> transmits a steady Fast tracking RS on the time axis in the SCell targeted for high speed detection (step S408). The controller <NUM> of the UE <NUM> may perform control for establishing time/frequency synchronization with the SCell using the Fast tracking RS. The controller <NUM> of the UE <NUM> may also perform CSI measurement, AGC, and beam management for the SCell using the Fast tracking RS.

In step S409, the transmitter <NUM> of the UE <NUM> transmits an SCell activation notification to the node <NUM> over the PCell. The receiver <NUM> of the node <NUM> receives the SCell activation notification.

In step S410, the transmitter <NUM> of the node <NUM> transmits a HARQ ACK indicating successful reception of the SCell activation notification to the UE <NUM> over a PDCCH of the PCell. The receiver <NUM> of the UE <NUM> receives the HARQ ACK. Note that step S408 need not be performed if the SCell activation notification is UCI.

In step S411, the node <NUM> performs DL transmission and/or UL granting to the UE <NUM> over the activated SCell and starts wireless communication (data communication) over the SCell.

The first to fourth embodiments described above may be implemented independently or two or more of the embodiments may be combined and implemented.

Although examples in which the SCell is a THz wave cell have been mainly described in the embodiments above, the SCell is not limited to a THz wave cell. For example, the SCell may be a mmW cell.

The operational flow of each of the embodiments described above does not necessarily have to be executed in chronological order according to the order described in the flow diagram. For example, the steps of operation may be performed in a different order from that described in the flow diagram or may be performed in parallel. Some steps of operation may be omitted and additional steps may be added to the process.

A program that causes the computer (the UE <NUM>, the node <NUM>) to perform operations according to the embodiments described above may be provided. The program may be recorded on a computer readable medium. The computer readable medium allows installation of the program on a computer. Here, the computer readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, but may be, for example, a recording medium such as a CD-ROM or a DVD-ROM.

Claim 1:
A user equipment (<NUM>) for performing wireless communication with a node (<NUM>) using carrier aggregation in a mobile communication system, the user equipment (<NUM>) comprising:
a receiver (<NUM>) configured to receive, from the node (<NUM>), information indicating a radio quality condition that is to be met for the user equipment (<NUM>) to perform an activation process for a secondary cell configured for the user equipment (<NUM>);
a controller (<NUM>) configured to measure radio quality and evaluate whether the radio quality condition is met; and
a transmitter (<NUM>) configured to transmit a notification regarding the activation process to the node (<NUM>) in response to the radio quality condition being met,
wherein the controller (<NUM>) is configured to
perform the activation process for the secondary cell in response to the radio quality condition being met, and
complete the activation process within a predetermined time period from a time of transmitting the notification or from a time of receiving a positive acknowledgment to the notification from the node (<NUM>),
wherein the transmitter (<NUM>) is configured to transmit information indicating the predetermined time period to the node (<NUM>) when transmitting the notification or before transmitting the notification.