Communication device, base station, and communication method
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Filing Date
- 2024-08-08
- Publication Date
- 2026-05-11
Abstract
Description
Communication device, base station, and communication method CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on and claims the benefit of priority from patent application serial number 2023-130208, filed August 9, 2023, the entire contents of which are incorporated herein by reference.
[0002] The present disclosure relates to a communication device, a base station, and a communication method.
[0003] In a mobile communication system that complies with the technical specifications of 3GPP (registered trademark; the same applies hereinafter) (Third Generation Partnership Project), a standardization project for mobile communication systems, the introduction of L1 (Layer 1) / L2 (Layer 2) triggered mobility (LTM) is planned (see, for example, Non-Patent Document 1). In LTM, a base station changes the serving cell of a communication device by transmitting a cell switch command to the communication device via a media access control control element (MAC CE) based on an L1 measurement report received from the communication device. Compared to a cell change based on a radio resource control (RRC) message, the communication device can dynamically perform a cell change and reduce mobility delay.
[0004] In LTM, for example, early synchronization, in which a communication device synchronizes with a candidate cell before receiving a cell change command, and LTM execution, in which a communication device executes a cell change in response to a cell change command based on an L1 measurement report, can be performed.
[0005] In performing LTM, it has been agreed that both a method of performing a random access procedure between a communication device and a base station (hereinafter referred to as RACH-based LTM) and a method of performing uplink transmission by a communication device without performing a random access procedure between the communication device and a base station (hereinafter referred to as RACH-less LTM) are supported.
[0006] Currently, when RACH-less LTM is performed, it is under consideration whether or not to include an uplink grant in the cell change command (MAC CE) to perform uplink transmission to the target cell.
[0007] 3GPP TSG-RAN WG2 Meeting #121, R2-2302039, “38.300 running CR for introduction of NR further mobility enhancements”
[0008] A communication device according to a first aspect includes: a receiver that receives a Radio Resource Control (RRC) message including configuration information related to Layer 1 / Layer 2 Triggered Mobility (LTM) from a base station; and a cell change command Medium Access Control (MAC) Control Element (CE) from the base station, the RRC message including information for identifying the configuration information and instructing a cell change. A controller that, when receiving the cell change command MAC CE, determines to perform a cell change to a target cell corresponding to the information for identifying the configuration information without a Random Access (RA) procedure. When performing the cell change to the target cell without the RA procedure, the controller performs uplink transmission to the target cell. Resources in the time domain for the uplink transmission are determined using a time domain resource allocation table determined based on information included in the configuration information.
[0009] A base station according to a second aspect includes: a transmitter unit that transmits a Radio Resource Control (RRC) message including configuration information related to Layer 1 / Layer 2 Triggered Mobility (LTM) to a communication device, and transmits a cell change command Medium Access Control (MAC) Control Element (CE) to the communication device, the RRC message including information for identifying the configuration information and instructing a cell change; and a controller that includes, in the configuration information, information for determining a time domain resource allocation table that is used to determine resources in the time domain for uplink transmission to the target cell when the communication device performs a cell change to the target cell corresponding to the information for identifying the configuration information without a Random Access (RA) procedure based on reception of the cell change command MAC CE.
[0010] A communication method according to a third aspect is a communication method executed by a communication device. The communication method includes the steps of receiving a Radio Resource Control (RRC) message from a base station, the RRC message including configuration information related to Layer 1 / Layer 2 triggered mobility (LTM), and receiving a cell change command Medium Access Control (MAC) Control Element (CE) from the base station, the RRC message including information for identifying the configuration information and instructing a cell change, determining, when the cell change command MAC CE is received, to perform a cell change to a target cell corresponding to the information for identifying the configuration information without a random access (RA) procedure, and performing uplink transmission to the target cell when the cell change to the target cell is performed without the RA procedure. Resources in the time domain for the uplink transmission are determined using a time domain resource allocation table determined based on information included in the configuration information.
[0011] Objects, features, advantages, etc. of the present disclosure will become clearer from the following detailed description taken in conjunction with the accompanying drawings. Fig. 1 is a diagram illustrating a configuration of a mobile communication system according to an embodiment. Fig. 2 is a diagram illustrating an example configuration of a protocol stack according to an embodiment. Fig. 3 is a diagram illustrating an overview of LTM. Fig. 4 is a diagram illustrating a configuration of a UE according to an embodiment. Fig. 5 is a diagram illustrating a configuration of a base station according to an embodiment. Fig. 6 is a sequence diagram illustrating an example operation according to an embodiment. Fig. 7 is a table illustrating an example operation according to an embodiment.
[0012] 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] However, when performing uplink transmission to a target cell based on an uplink grant, a method for determining resources for the uplink transmission (e.g., resources in the time domain) is not specified. Therefore, when performing RACH-less LTM, the communication device may not be able to properly perform uplink transmission, and cell change to the target cell may fail in LTM.
[0014] Therefore, one object is to provide a communication device, a base station, and a communication method that enable uplink transmission to be performed appropriately when RACH-less LTM is performed.
[0015] (System Configuration) First, the configuration of a mobile communication system 1 according to this embodiment will be described with reference to Fig. 1. The mobile communication system 1 is, for example, a system that complies with the 3GPP Technical Specification (TS). In the following, the mobile communication system 1 will be described using as an example a 5th Generation System (5G system) of the 3GPP standard, i.e., a mobile communication system based on NR (NR (New Radio) radio access).
[0016] The mobile communication system 1 includes a network 10 and a user equipment (UE) 100 that communicates with the network 10. The network 10 includes a next generation radio access network (NG-RAN) 20, which is a 5G radio access network, and a 5G core network (5GC) 30, which is a 5G core network.
[0017] The UE 100 is a communication device that communicates via the base station 200. The UE 100 may be a device used by a user. The UE 100 may be a mobile device such as a mobile phone terminal such as a smartphone, a tablet terminal, a laptop PC, a communication module, or a communication card. The UE 100 may be a vehicle (e.g., a car, a train, etc.) or a device provided therein. The UE 100 may be a transport vehicle other than a vehicle (e.g., a ship, an airplane, etc.) or a device provided therein. The UE 100 may be a sensor or a device provided therein. The UE 100 may be called a terminal, a terminal device, a mobile station, a mobile terminal, a mobile device, a mobile unit, a subscriber station, a subscriber terminal, a subscriber device, a subscriber unit, a wireless station, a wireless terminal, a wireless device, a wireless unit, a remote station, a remote terminal, a remote device, or a remote unit. The UE 100 is an example of a terminal, and the terminal may include factory equipment, etc.
[0018] The NG-RAN 20 includes multiple base stations 200. Each base station 200 manages at least one cell. A cell constitutes the smallest unit of a communication area. One cell belongs to one frequency (carrier frequency). The term "cell" may refer to wireless communication resources or to the communication target of the UE 100. Each base station 200 can perform wireless communication with the UE 100 located in its own cell. The base station 200 communicates with the UE 100 using a RAN protocol stack. Details of the protocol stack will be described later. The base station 200 is also connected to other base stations 200 (which may be referred to as neighboring base stations) via an Xn interface. The base station 200 communicates with neighboring base stations via the Xn interface. The base station 200 provides NR user plane and control plane protocol termination for the UE 100 and is connected to the 5GC 30 via an NG interface. Such an NR base station 200 is sometimes referred to as a gNodeB (gNB).
[0019] The 5GC 30 includes a core network device 300. The core network device 300 includes, for example, an AMF (Access and Mobility Management Function) and / or a UPF (User Plane Function). The AMF performs mobility management for the UE 100. The UPF provides functions specialized for U-plane processing. The AMF and the UPF are connected to the base station 200 via an NG interface.
[0020] (Configuration Example of Protocol Stack) Next, a configuration example of a protocol stack according to this embodiment will be described with reference to FIG.
[0021] The protocol of the wireless section between UE 100 and base station 200 includes 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 radio resource control (RRC) 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 the UE 100 and the PHY layer of the base station 200 via a physical channel.
[0023] The MAC layer performs data priority control, retransmission processing using Hybrid ARQ (HARQ), random access procedures, etc. Data and control information are transmitted between the MAC layer of UE 100 and the MAC layer of base station 200 via a transport channel. The MAC layer of base station 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 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 base station 200 via logical channels.
[0025] The PDCP layer performs header compression / decompression and encryption / decryption.
[0026] A Service Data Adaptation Protocol (SDAP) layer may be provided as an upper layer above the PDCP layer. The SDAP layer maps IP flows, which are units for Quality of Service (QoS) control by the core network, to radio bearers, which are units for QoS control by an Access Stratum (AS).
[0027] The RRC layer controls logical channels, transport channels, and physical channels according to the establishment, re-establishment, and release of radio bearers. RRC signaling for various settings is transmitted between the RRC layer of the UE 100 and the RRC layer of the base station 200. When an RRC connection exists between the RRC of the UE 100 and the RRC of the base station 200, the UE 100 is in an RRC connected state. When there is no RRC connection between the RRC of the UE 100 and the RRC of the base station 200, the UE 100 is in an RRC idle state. When the RRC connection between the RRC of the UE 100 and the RRC of the base station 200 is suspended, the UE 100 is in an RRC inactive state.
[0028] The NAS layer, which is located above the RRC layer in the UE 100, performs session management and mobility management for the UE 100. NAS signaling is transmitted between the NAS layer of the UE 100 and the NAS layer of the core network device 300.
[0029] The UE 100 has an application layer and the like in addition to the radio interface protocol.
[0030] (Radio Frame Configuration) In a 5G system, downlink transmission and uplink transmission are configured within a radio frame having a duration of 10 ms. For example, a radio frame is represented by a system frame number (SFN) ranging from 0 to 1023. For example, a radio frame is configured with 10 subframes. For example, one subframe may be 1 ms. Furthermore, one subframe may be configured with one or more slots. For example, the number of symbols that make up one slot is 14 for a normal CP (Cyclic Prefix) and 12 for an extended CP. Furthermore, the number of slots that make up one subframe varies depending on the set subcarrier spacing. For example, for a normal CP, if the subcarrier spacing is set to 15 kHz, the number of slots per subframe is 1 (i.e., 14 symbols); if the subcarrier spacing is set to 30 kHz, the number of slots per subframe is 2 (i.e., 28 symbols); if the subcarrier spacing is set to 60 kHz, the number of slots per subframe is 4 (i.e., 56 symbols); and if the subcarrier spacing is set to 120 kHz, the number of slots per subframe is 8 (i.e., 128 symbols). Furthermore, if the subcarrier spacing is set to 60 kHz for an extended CP, the number of slots per subframe is 4 (i.e., 48 symbols). That is, the number of slots constituting one subframe is determined based on the subcarrier spacing set by the base station 200. Furthermore, the number of symbols constituting one subframe is determined based on the subcarrier spacing set by the base station 200. That is, the number of symbols constituting a 1 ms subframe is determined based on the subcarrier spacing set by the base station 200, and the length of each symbol (length in the time direction) changes.
[0031] (LTM) In a mobile communication system 1 conforming to the technical specifications of 3GPP, introduction of L1 (Layer 1) / L2 (Layer 2) triggered mobility (LTM) is planned. As shown in Fig. 3, in LTM, the following operations can be performed.
[0032] Step S10: LTM Preparation The UE 100 in the RRC connected state may perform the following operation as an operation for LTM preparation.
[0033] Step S11: The UE 100 transmits a measurement report message to the base station 200. The base station 200 determines to use the LTM and starts candidate cell preparation.
[0034] Step S12: The base station 200 transmits an RRC reconfiguration message including LTM candidate cell configuration of one or more candidate cells.
[0035] Step S13: The UE 100 stores the LTM candidate cell configuration. The UE 100 transmits an RRC reconfiguration complete (RRCReconfigurationComplete) message to the base station 200.
[0036] Step S20: Early synchronization The UE 100 may perform the following operation as the early synchronization operation.
[0037] Step S21: Before receiving the cell switching command, the UE 100 performs downlink (DL) synchronization with the candidate cell. The UE 100 may perform DL synchronization based on a synchronization signal (SS) and a physical broadcast channel (PBCH) block (SSB).
[0038] Step S22: Before receiving the cell switch command, the UE 100 performs timing advance (TA) acquisition. The UE 100 may perform TA acquisition based on a PDCCH order (specifically, a PDCCH ordered RACH). The PDCCH order may be triggered only by the source cell.
[0039] Step S30: LTM execution The UE 100 may execute the following operation as the LTM execution operation.
[0040] Step S31: The UE 100 performs L1 measurement on the candidate cell configured by the LTM candidate cell configuration. The UL 100 transmits a lower-layer measurement report based on the L1 measurement to the base station 200.
[0041] Step S32: The base station 200 determines to perform a cell change to the target cell. The base station 200 transmits a MAC CE that triggers the cell change by including a candidate configuration index of the target cell. The UE 100 switches the configuration of the target cell.
[0042] Step S33: If the cell change needs to include the execution of a random access (RA) procedure, the UE 100 executes the RA procedure toward the target cell.
[0043] Step S40: LTM Completion The UE 100 may perform the following operation as an operation for completing LTM.
[0044] Step S41: The UE 100 indicates that the cell change to the target cell has been successfully completed.
[0045] It should be noted that UE 100 may execute steps S20 to S40 multiple times for subsequent LTM cell switching based on the configuration provided in step S12 without releasing the configuration.
[0046] Incidentally, it has been agreed that in performing LTM, both a method of performing an RA procedure between the UE 100 and the base station 200 (hereinafter referred to as RACH-based LTM as appropriate) and a method of the UE 100 performing uplink transmission without performing an RA procedure between the UE 100 and the base station 200 (hereinafter referred to as RACH-less LTM as appropriate) are supported. Currently, when the RACH-less LTM is performed, it is under consideration whether or not to include an uplink grant (UL grant) in the cell change command (MAC CE) in order to perform uplink transmission to the target cell.
[0047] However, when performing uplink transmission to a target cell based on an uplink grant, a method for determining resources for the uplink transmission (e.g., resources in the time domain) is not specified. Therefore, when performing RACH-less LTM, the UE 100 may not be able to properly perform uplink transmission, and there is a concern that cell change to the target cell in LTM may fail. In one embodiment described later, an operation for enabling proper uplink transmission when performing RACH-less LTM will be described.
[0048] Furthermore, when the uplink grant is provided to the UE 100 using MAC CE or when a process for cell change is executed in the UE 100, there is a concern that a delay may occur before uplink transmission to the target cell is executed, compared to when the uplink grant is provided to the UE 100 using downlink control information (DCI). As a result, a problem may occur in which uplink transmission cannot be executed using resources in the time domain allocated by the uplink grant. In an embodiment described later, an operation for enabling appropriate execution of uplink transmission when RACH-less LTM is executed will be described.
[0049] (Configuration of User Equipment) The configuration of the UE 100 according to the embodiment will be described with reference to Fig. 4. The UE 100 includes a communication unit 110 and a control unit 120.
[0050] The communication unit 110 performs wireless communication with the base station 200 by transmitting and receiving radio signals to and from the base station 200. The communication unit 110 has at least one transmission unit 111 and at least one reception unit 112. The transmission unit 111 and the reception unit 112 may be configured to include multiple antennas and RF (Radio Frequency) circuits. The antenna converts a signal into radio waves and radiates the radio waves into space. The antenna also receives radio waves in space and converts the radio waves into a signal. The RF circuit performs analog processing of the signal transmitted and received via the antenna. The RF circuit may include a high-frequency filter, an amplifier, a modulator, a low-pass filter, etc.
[0051] The control unit 120 performs various controls in the UE 100. The control unit 120 controls communication with the base station 200 via the communication unit 110. The operations of the UE 100 described above and below may be operations controlled by the control unit 120. The control unit 120 may include at least one processor capable of executing a program and a memory that stores the program. The processor may execute the program to perform the operations of the control unit 120. The control unit 120 may include a digital signal processor that performs digital processing of signals transmitted and received via the antenna and the RF circuit. The digital processing includes processing of a RAN protocol stack. The memory stores the program executed by the processor, parameters related to the program, and data related to the program. The memory may include at least one of read-only memory (ROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), random access memory (RAM), and flash memory. All or a portion of the memory may be contained within the processor.
[0052] In the UE 100 configured as described above, the receiver 112 receives a cell change command triggering a cell change from the base station 200 via a MAC CE. The controller 120 controls uplink transmission to the target cell, which is performed without an RA procedure between the UE 100 and the target cell, based on the cell change command. When the cell change command includes an uplink grant for performing the uplink transmission, the controller 120 determines resources in the time domain for the uplink transmission. For example, when the cell change command includes an uplink grant for performing the uplink transmission, the controller 120 may determine (use) a TDRA table for LTM to determine resources in the time domain for the uplink transmission. This allows the UE 100 to determine resources in the time domain for the uplink transmission using the determined TDRA table for LTM, thereby enabling appropriate uplink transmission when performing RACH-less LTM.
[0053] (Configuration of Base Station) The configuration of the base station 200 according to this embodiment will be described with reference to Fig. 5. The base station 200 includes a communication unit 210, a network communication unit 220, and a control unit 230.
[0054] The communication unit 210 receives, for example, a radio signal from the UE 100 and transmits the radio signal to the UE 100. The communication unit 210 has at least one transmission unit 211 and at least one reception unit 212. The transmission unit 211 and the reception unit 212 may be configured to include an RF circuit. The RF circuit performs analog processing of signals transmitted and received via an antenna. The RF circuit may include a high-frequency filter, an amplifier, a modulator, a low-pass filter, etc.
[0055] The network communication unit 220 transmits and receives signals to and from the network. For example, the network communication unit 220 receives signals from adjacent base stations connected via an Xn interface, which is an interface between base stations, and transmits the signals to the adjacent base stations. The network communication unit 220 also receives signals from the core network device 300 connected via an NG interface, and transmits the signals to the core network device 300.
[0056] The control unit 230 performs various controls in the base station 200. The control unit 230 controls, for example, communication with the UE 100 via the communication unit 210. The control unit 230 also controls, for example, communication with a node (e.g., a neighboring base station, the core network device 300) via the network communication unit 220. The operations of the base station 200 described above and below may be controlled by the control unit 230. The control unit 230 may include at least one processor capable of executing a program and a memory that stores the program. The processor may execute the program to perform the operations of the control unit 230. The control unit 230 may include a digital signal processor that performs digital processing of signals transmitted and received via the antenna and the RF circuit. The digital processing includes processing of a RAN protocol stack. The memory stores programs executed by the processor, parameters related to the programs, and data related to the programs. All or a part of the memory may be included in the processor.
[0057] (Operation Example) An operation example will be described with reference to Figures 6 and 7. Previous descriptions may be omitted. The UE 100 is in an RRC connected state with a cell (source cell) managed by the base station 200. Hereafter, the UE 100 performs communication with the base station 200 in the source cell until a cell change to a target cell is performed.
[0058] Step S101: The transmitter 111 of the UE 100 transmits a measurement report (message) to the base station 200. The receiver 212 of the base station 200 receives the measurement report from the UE 100.
[0059] The control unit 230 of the base station 200 determines whether to use LTM. The control unit 230 may determine whether to use LTM based on, for example, a measurement report. If the control unit 230 determines to use LTM, it starts candidate cell preparation.
[0060] As candidate cell preparation, the control unit 230 may select a candidate cell for the target cell in LTM based on the measurement report. The control unit 230 may select a candidate cell, for example, from among cells managed by the base station 200. The control unit 230 may also generate setting information related to LTM (hereinafter, LTM setting information). The control unit 230 may include the generated LTM setting information in, for example, an RRC reconfiguration message. That is, the control unit 230 may instruct the UE 100 to perform LTM (an operation related to LTM) by including the LTM setting information in the RRC reconfiguration message. The UE 100 may perform LTM (an operation related to LTM) when the LTM setting information is included in the RRC reconfiguration message.
[0061] The control unit 230 may include, in the LTM setting information (e.g., LTM-Config), at least any one of information for example, a list for releasing a candidate cell (hereinafter referred to as an LTM candidate release list (e.g., ltm-CandidateToReleaseList)) and a list for adding or changing a candidate cell (hereinafter referred to as an LTM addition change list (e.g., ltm-CandidateToAddModList)). The LTM addition change list may be a list configured by information of one or more candidate cells (e.g., LTM-Candidate). The candidate cell information may include, for example, at least any one of the following information:
[0062] - Identifier of the candidate cell (e.g., ltm-CandidateId) - Configuration information related to the candidate cell (e.g., ltm-CandidateConfig) - Information indicating whether the configuration information related to the candidate cell is a complete configuration (Complete Configuration) or a differential configuration (Delta-Configuration) (e.g., ltm-ConfigComplete) - Configuration information for setting information to be used for early synchronization (e.g., ltm-EarlyUlSyncConfig) - Cell identifier for not performing L2 reset when changing cells (e.g., ltm-NoResetID) - List for adding / changing information to be used for early synchronization (e.g., ltm-Candidate-Tci-States-ToAddModList) - Identifier for canceling (deleting) information used for early synchronization (for example, ltm-Candidate-Tci-States-ToReleaseList) The candidate cell identifier may be an identifier of the candidate cell setting. Furthermore, the setting information regarding the candidate cell (hereinafter, candidate cell setting information) may include an RRC setting (which may be an RRC reconfiguration or an RRC reconfiguration message) set in the UE 100. Furthermore, the candidate cell setting information may include cell group setting information (for example, CellGroupConfig) including serving cell setting information (for example, ServingCellConfig) and the like. Note that the candidate cell setting information may correspond to the LTM candidate cell setting included in the RRC reconfiguration message in the above-mentioned step S12.
[0063] Step S102: The transmitter 211 of the base station 200 transmits an RRC reconfiguration message including the LTM setting information to the UE 100. The receiver 112 of the UE 100 receives the RRC reconfiguration message from the base station 200. The controller 120 of the UE 100 stores the LTM setting information.
[0064] Step S103: The transmitter 111 of the UE 100 transmits an RRC reconfiguration completion message to the base station 200. The receiver 212 of the base station 200 receives the RRC reconfiguration completion message from the UE 100.
[0065] Step S104: As an early synchronization operation, downlink synchronization with each candidate cell may be performed. The control unit 120 of the UE 100 performs downlink synchronization based on, for example, an SSB transmitted from each candidate cell.
[0066] Step S105: Uplink synchronization may be performed as an operation of early synchronization. The transmission unit 211 of the base station 200 may transmit, for example, to the UE 100, a physical downlink control channel (PDCCH) order (i.e., downlink control information (DCI)) that starts an RA procedure for early synchronization in each candidate cell configured for the UE 100 by the candidate cell configuration information. The reception unit 112 of the UE 100 may receive the PDCCH order from the base station 200. Note that the PDCCH order in early synchronization may be a PDCCH order (PDCCH ordered-RACH for TA Acquisition without RAR) used to acquire a TA value without an RA response.
[0067] The control unit 120 of the UE 100 may start the RA procedure based on the PDCCH order. The control unit 120 may control the RA procedure based on setting information for setting information used for early synchronization (hereinafter, early synchronization setting information).
[0068] In each candidate cell, the transmitter 111 of the UE 100 transmits an RA preamble (message 1) on a physical random access channel (PRACH) to the base station 200. The receiver 212 of the base station 200 receives the RA preamble from the UE 100 in each candidate cell.
[0069] The control unit 230 of the UE 100 may use an RA preamble based on the early synchronization setting information, or may use an RA preamble based on information included in the PDCCH order. For example, the control unit 230 of the base station 200 may include a preamble index in the PDCCH order, and may further include an SSB index. The preamble index indicates which RA preamble to use. The SSB index indicates the SSB used to determine the RACH opportunity for PRACH transmission. The control unit 120 of the UE 100 may determine the RA preamble based on the preamble index (and the SSB index). The control unit 120 may use, for example, other information included in the PDCCH order and / or other information included in the early synchronization setting information to transmit the RA preamble.
[0070] The control unit 230 of the base station 200 calculates a timing advance (TA) value based on the RA preamble from the UE 100. The control unit 230 may execute control to omit transmission of an RA response (i.e., message 2) that is a response to the RA preamble.
[0071] Step S106: After performing L1 measurement in each candidate cell configured by the candidate cell configuration information, the transmitter 111 of UE 100 transmits an L1 measurement report to base station 200. The receiver 212 of base station 200 receives the L1 measurement report from UE 100. The L1 measurement report is a measurement report of a lower layer based on the L1 measurement. The L1 measurement report is transmitted in a layer lower than the RRC layer. Note that the measurement report in step S101 is transmitted in the RRC layer.
[0072] The control unit 230 of the base station 200 determines a target cell in the LTM (i.e., an LTM target cell) based on the L1 measurement report. In addition, the control unit 230 may determine whether to cause the UE 100 to execute a RACH-less LTM in which the UE 100 performs uplink transmission without executing an RA procedure between the UE 100 and the base station 200, or to cause the UE 100 to execute a RACH-based LTM in which the RA procedure between the UE 100 and the base station 200.
[0073] When the control unit 230 calculates the TA value in the target cell by performing early synchronization, the control unit 230 may determine to cause the UE 100 to execute the RACH-less LTM. When the control unit 230 sets a valid value as the TA value in the target cell in a MAC CE for transmitting a cell change command described later, the control unit 230 may determine to cause the UE 100 to execute the RACH-less LTM. On the other hand, when the TA value in the target cell has not been calculated, the control unit 230 may determine to cause the UE 100 to execute the RACH-based LTM. When the control unit 230 sets an invalid value as the TA value in the target cell in the MAC CE, the control unit 230 may determine to cause the UE 100 to execute the RACH-based LTM. In this operation example, the description will proceed assuming that the control unit 230 determines to cause the UE 100 to execute the RACH-less LTM.
[0074] The control unit 230 generates a MAC CE for transmitting the cell change command. This MAC CE may be referred to as an LTM cell change command MAC CE, for example. This MAC CE may also be referred to as a cell change command (i.e., may be a cell change command). Hereinafter, the LTM cell change command MAC CE may be referred to as a cell change command as appropriate. The cell change command may include, for example, at least one of the following information (i.e., fields):
[0075] a target configuration identifier (Target Configuration ID) indicating the index of the candidate target configuration to apply to the LTM cell change; a timing advance command (Timing Advance Command) indicating whether the TA for the LTM target cell is valid; a transmission configuration indication (TCI state ID) state identifier indicating and activating the TCI state for the LTM target cell; an uplink TCI state identifier indicating and activating the uplink TCI state for the LTM target cell (UL TCI state ID); an identifier of the downlink bandwidth portion to be activated in the LTM target cell (DL BWP ID); an identifier of the uplink bandwidth portion to be activated in the LTM target cell (UL BWP ID). The target setting identifier may be the identifier of a candidate cell that will become the target cell after the change, among the identifiers of the candidate cells included in the above-mentioned candidate cell information.
[0076] The Timing Advance Command (field) may indicate whether a TA (TA value) is valid for a target cell (e.g., SpCell) corresponding to the target configuration (i.e., candidate cell configuration information) indicated by the Target Configuration Identifier (field). When a predetermined value (e.g., FFF) is set as the value of this field, this field may indicate that valid timing adjustment is not available for the primary timing advance group (PTAG) of the LTM target cell. In this case, the UE 100 needs to perform an RA procedure to the LTM target cell. That is, the UE 100 performs RACH-based LTM. On the other hand, when a value other than the predetermined value (e.g., FFF) is set as the value of this field, this field indicates an index value (i.e., TA value) used to control the amount of timing adjustment to be applied by the MAC entity of the UE 100. That is, the timing advance command (field) indicates that the RA procedure for the LTM cell change can be skipped. In this case, the UE 100 performs RACH-less LTM. Here, the predetermined value may be defined in advance by a specification or the like and may be a known value between the base station 200 and the UE 100.
[0077] In this operation example, the explanation will be given assuming that the control unit 230 of the base station 200 sets the TA value calculated by executing early synchronization in the timing advance command.
[0078] The control unit 230 may determine whether to include an uplink grant for performing uplink transmission in the cell change command. For example, when the control unit 230 causes the UE 100 to perform RACH-less LTM, the control unit 230 may include an uplink grant in the cell change command. On the other hand, when the control unit 230 causes the UE 100 to perform RACH-based LTM, the control unit 230 may not include an uplink grant in the cell change command. In this operation example, the description will proceed assuming that the control unit 230 includes (determines to include) an uplink grant in the cell change command. Note that the uplink grant includes an index value corresponding to a row index, which will be described later.
[0079] Step S107: The transmitting unit 211 of the base station 200 transmits the cell change command by MAC CE to the UE 100. The receiving unit 112 of the UE 100 receives the cell change command from the base station 200 by MAC CE.
[0080] The control unit 120 of the UE 100 switches the setting of the target cell based on the identifier of the candidate cell (i.e., the target setting identifier) included in the cell change command (MAC CE). For example, the control unit 120 applies the candidate cell setting information associated with the identifier of the candidate cell that is the same as the target setting identifier included in the cell change command (MAC CE).
[0081] The control unit 120 determines whether to perform RACH-based LTM or RACH-less LTM based on a value included in the timing advance command. When a predetermined value (e.g., FFF) is set in the timing advance command, the control unit 120 determines to perform RACH-based LTM. On the other hand, when a value other than the predetermined value (e.g., FFF) is set in the timing advance command, the control unit 120 determines to perform RACH-less LTM. In this operation example, the description will proceed assuming that the control unit 120 has determined to perform RACH-less LTM. Therefore, the control unit 120 of the UE 100 determines to control uplink transmission to the target cell, which is performed without an RA procedure between the UE 100 and the target cell, based on the cell change command. The uplink transmission may be a first uplink transmission to the target cell. The first uplink transmission may be an operation upon completion of LTM.
[0082] The control unit 120 determines whether the cell change command includes an uplink grant for performing uplink transmission. If the cell change command includes an uplink grant, the control unit 120 may perform the operation of step S108 below. The uplink grant may be for the initial uplink transmission to the target cell. Note that if the cell change command does not include an uplink grant, the control unit 120 may perform the operation of step S110, for example, based on the candidate cell configuration information.
[0083] Step S108: The control unit 120 of the UE 100 determines a time domain resource assignment (TDRA) table for LTM (hereinafter, appropriately referred to as an LTM TDRA table) in order to determine resources in the time domain for uplink transmission. The control unit 120 may determine the LTM TDRA table by at least one of the following methods. Note that resources in the time domain may be referred to as time resources.
[0084] In the first method, the control unit 120 determines a dedicated TDRA table for the uplink grant included in the cell change command as the LTM TDRA table.
[0085] The transmitting section 211 of the base station 200 may transmit information for setting an LTM TDRA table, which is a dedicated TDRA table (hereinafter, referred to as LTM TDRA information as appropriate), to the UE 100. The receiving section 112 of the UE 100 receives the LTM TDRA information from the base station 200.
[0086] The LTM TDRA information may be a list of time domain assignments (hereinafter referred to as a TDA list, as appropriate) used to set a time domain relationship between an uplink grant (or a cell change command) and an (initial) uplink transmission. Therefore, the TDA list may be information indicating the setting of an LTM TDRA table. The TDA list may constitute the LTM TDRA table.
[0087] The LTM TDRA information may be information for setting a dedicated TDRA table common to each candidate cell set in the UE 100 as a candidate for the target cell. The control unit 120 of the UE 100 may determine the dedicated TDRA table common to each candidate cell as the LTM TDRA table. Therefore, the LTM TDRA table may be set commonly for each candidate cell. The control unit 230 of the base station 200 may include the LTM TDRA information in a field arranged in parallel to a field in the LTM setting information in which the LTM candidate release list is set, instead of in each candidate cell setting information, for example.
[0088] The LTM TDRA information may be information for setting an individual dedicated TDRA table for each candidate cell set in the UE 100 as a candidate for the target cell. The control unit 120 of the UE 100 may determine the individual dedicated TDRA table of the candidate cell corresponding to the target cell as the LTM TDRA table. Thus, the LTM TDRA table may be set individually for each candidate cell. The control unit 230 of the base station 200 may, for example, include the LTM TDRA information in each candidate cell configuration information. The control unit 120 of the UE 100 may, for example, determine the dedicated TDRA table (i.e., the LTM TDRA information) included in the candidate cell configuration information associated with the identifier of the candidate cell that is the same as the target configuration identifier included in the cell change command as the LTM TDRA table.
[0089] The LTM TDRA information (TDRA list) may include at least one of information such as a slot offset value (K2), a start and length indicator value (SLIV), and a PUSCH mapping type. The slot offset value (K2) may indicate the time (offset) from the slot in which the uplink grant (cell change command) is received to the slot in which the uplink transmission is performed. The SLIV may be an index specifying a valid combination of a start symbol and a length. Instead of the SLIV, the time domain resource allocation may include information indicating a symbol length (e.g., Length: L) allocated for the (first) uplink transmission (e.g., PUSCH) and information indicating an index of the start symbol (e.g., startSymbol: S) for the (first) uplink transmission (e.g., PUSCH).
[0090] Furthermore, a dedicated TDRA table for the uplink grant included in the cell change command may be defined in advance. The dedicated TDRA table, the LTM TDRA table, may be defined in, for example, the 3GPP technical specifications. The control unit 120 may determine the predefined dedicated TDRA table as the LTM TDRA table without receiving LTM TDRA information from the base station 200.
[0091] In addition, in the dedicated TDRA table, taking into consideration a delay time specific to the MAC CE including an uplink grant, for example, the maximum slot offset value may be set to be larger than the maximum slot offset value of the default TDRA table.
[0092] In a second method, the control unit 120 determines, as the LTM TDRA table, a TDRA table that is not dedicated to the uplink grant included in the cell change command but is also used to perform other uplink transmissions. For example, the control unit 120 determines, as the LTM TDRA table, a TDRA table for the physical uplink shared channel (PUSCH). For example, the control unit 120 determines the TDRA table for LTM based on the TDRA table for PUSCH set in candidate cell configuration information associated with the candidate cell corresponding to the target cell.
[0093] The control unit 120 may determine the TDRA table for LTM, for example, based on a time domain resource allocation list (i.e., a TDRA table) included in configuration information used to configure PUSCH parameters. The control unit 120 may determine the TDRA table for LTM, for example, according to the rules specified in the table shown in FIG. 7. Specifically, the control unit 120 may determine the TDRA table for LTM based on a time domain allocation (TDA) list (i.e., a TDRA table) included in at least one of configuration information used to configure cell-specific PUSCH parameters (e.g., PUSCH-ConfigCommon) (hereinafter, cell-specific information) and configuration information used to configure UE-specific PUSCH parameters applicable to a specific BWP (e.g., PUSCH-Config) (hereinafter, UE-specific information). Here, the configuration information used to configure the PUSCH parameters may be included in each of one or more candidate cell configuration information. That is, at least one of the cell-specific information and / or the UE-specific information may be included in each of one or more pieces of candidate cell configuration information. As described above, the control unit 120 of the UE 100 may apply the candidate cell configuration information associated with the identifier of the candidate cell included in the cell change command, among one or more pieces of candidate cell configuration information. That is, the control unit 120 of the UE 100 may apply information included in the candidate cell configuration information associated with the identifier of the candidate cell, based on the identifier of the candidate cell included in the cell change command (e.g., configuration information used to configure PUSCH parameters, cell-specific information, and / or UE-specific information, etc.). The control unit 120 of the UE 100 may determine the information to be applied from the information included in one or more pieces of candidate cell information (e.g., LTM-Candidate), based on the identifier of the candidate cell included in the cell change command.As shown in FIG. 7, when the UE-specific information includes a first TDA list (for example, push-TimeDomainAllocationListForMultiPUSCH or push-TimeDomainAllocationListForMultiPUSCH-17) indicating the setting of TDRA tables for multiple PUSCHs, the control unit 120 may determine the TDRA table set in the first TDA list as the LTM TDRA table, regardless of whether the UE-specific information and the cell-specific information include a second TDA list described later.
[0094] When the UE-specific information includes a second TDA list (e.g., push-TimeDomainAllocationList) used to set the time domain relationship between the PDCCH and the PUSCH, but the UE-specific information does not include the second TDA list, the control unit 120 may determine the TDRA table set in the second TDA list included in the UE-specific information as the LTM TDRA table, regardless of whether the cell-specific information includes the second TDA list.
[0095] When the cell-specific information includes the second TDA list and the UE-specific information does not include the first TDA list or the second TDA list, the control unit 120 may determine the TDRA table set in the second TDA list included in the cell-specific information as the LTM TDRA table.
[0096] When the UE-specific information does not include the first TDA list and the second TDA list and the cell-specific information does not include the second TDA list, the control unit 120 may determine a predefined default TDRA table as the TDRA table for LTM. That is, when a TDRA table for PUSCH is not configured by the candidate cell configuration information (or the LTM configuration information), the control unit 120 may determine a predefined default TDRA table as the TDRA table for LTM.
[0097] Step S109: The control unit 120 of the UE 100 determines the time resource for uplink transmission using the LTM TDRA table.
[0098] The LTM TDRA table may be configured by, for example, a row index and parameters associated with the row index (e.g., a PUSCH mapping type, a slot offset value (K2), a symbol length (L), a start symbol (S), etc.).
[0099] The control unit 120 determines the time resource for uplink transmission using a parameter associated with a row index (e.g., m+1) corresponding to an index value (e.g., m) included in the uplink grant.
[0100] For example, the control unit 120 uses a slot offset value associated with a row index corresponding to an index value included in an uplink grant (hereinafter, referred to as an UL grant) in the LTM TDRA table to determine the time resource. Specifically, the control unit 120 determines a slot shifted by the slot offset value from the slot in which the cell change command is received as the slot for the uplink transmission opportunity.
[0101] When the default TDRA table is used as the LTM TDRA table, the control unit 120 may determine the time resource based on the subcarrier spacing (e.g., μPUSCH) of the uplink bandwidth portion (UL BWP) in the target cell. The control unit 120 may determine a calculation value (e.g., j) for calculating the slot offset value based on the subcarrier spacing, for example.
[0102] The control unit 120 may determine the subcarrier spacing based on the UL BWP identifier included in the cell change command.
[0103] The control unit 120 may determine the subcarrier spacing based on the identifier of the UL BWP included in the candidate cell configuration information. Here, the identifier of the UL BWP included in the candidate cell configuration information may be the identifier of the initial UL BWP of the candidate cell identified by the target configuration identifier included in the cell change command. Alternatively, the identifier of the UL BWP may be the identifier of the UL BWP (e.g., firstActiveUplinkBWP-Id) to be activated at a predetermined timing, which is included in the candidate cell configuration information identified by the target configuration identifier included in the cell change command. The predetermined timing is the time of RRC (re)configuration for the SpCell, and the time of SCell activation for the SCell. The identifier of the UL BWP to be activated at a predetermined timing may be included in the serving cell configuration information (e.g., ServingCellConfig) included in the cell group configuration information (e.g., CellGroupConfig) in the candidate cell configuration information.
[0104] The control unit 120 may determine the slot offset value based on the determined subcarrier spacing. A table specifying the correspondence between the subcarrier spacing and the calculated value may be defined in advance. The control unit 120 may use the table to determine the slot offset value associated with the determined subcarrier spacing as the slot offset value to be used.
[0105] Furthermore, the control unit 120 may determine the time resource by applying an additional delay value Δ in addition to the determined slot offset value.
[0106] The additional delay value may be, for example, a value (i.e., a unique value) predefined for the uplink grant included in the cell change command. For example, a table defining the correspondence between the subcarrier spacing and the additional delay value may be predefined. The control unit 120 may use the table to determine the additional delay value associated with the determined subcarrier spacing as the additional delay value to be applied. The additional delay value may be a slot delay value.
[0107] The receiving unit 112 of the UE 100 may receive information for setting an additional delay value (hereinafter, delay value information) from the base station 200. The additional delay value may be set commonly for each candidate cell by the delay value information. In this case, the control unit 120 of the base station 200 may include the delay value information in a field arranged in parallel with a field in the LTM configuration information in which the LTM candidate release list is set, rather than in each candidate cell configuration information. Alternatively, the additional delay value may be set individually for each candidate cell by the delay value information. In this case, the control unit 230 of the base station 200 may, for example, include the delay value information in each candidate cell configuration information. The control unit 120 may apply an additional delay value based on the delay value information received from the base station 200, even if the additional delay value is predefined. When the control unit 120 has not received delay value information, the control unit 120 may apply a predefined value (e.g., a value described in a technical specification) to the additional delay value.
[0108] The control unit 120 determines, for example, a slot shifted by the slot offset value and the additional delay value from the slot in which the cell change command is received as the slot of the uplink transmission opportunity. Therefore, when the UE 100 transmits an uplink transmission (e.g., a PUSCH) scheduled by the cell change command (uplink grant therein), the additional delay value may be applied in addition to the slot offset value (K2).
[0109] The control unit 120 uses, for example, a start symbol (S) associated with a row index corresponding to an index value included in an uplink grant (hereinafter, referred to as an UL grant) in the LTM TDRA table to determine the time resource. Specifically, the control unit 120 determines the symbol indicated by the start symbol (S) as the symbol at which uplink transmission starts in the slot of the uplink transmission opportunity.
[0110] The control unit 120 uses, for example, a symbol length (L) associated with a row index in the LTM TDRA table that corresponds to an index value included in an uplink grant (hereinafter, referred to as an UL grant) to determine the time resource. Specifically, the control unit 120 determines the symbol length indicated by the symbol length (L) as the length of the uplink transmission.
[0111] Step S110: The control unit 120 of the UE 100 controls the transmission unit 111 to perform uplink transmission using the time resources determined using the LTM TDRA table. The control unit 120 of the UE 100 may determine other resources (e.g., resources in the frequency domain) for uplink transmission based on LTM configuration information (e.g., candidate cell configuration information of a candidate cell corresponding to the target cell (i.e., candidate cell configuration information corresponding to the target configuration identifier included in the cell change command)). The transmission unit 111 of the UE 100 transmits uplink transmission (e.g., initial uplink data) to the base station 200. The reception unit 112 of the base station 200 receives the uplink transmission from the UE 100.
[0112] Note that the control unit 230 of the base station 200 may recognize that the UE 100 has changed the serving cell to the target cell based on reception of a first uplink transmission (e.g., first uplink data) in the target cell. As a result, the control unit 230 may determine that the LTM execution procedure has been successfully executed (i.e., LTM completion has been executed). Furthermore, the control unit 120 of the UE 100 may determine that the LTM execution procedure has been successfully executed (i.e., LTM completion has been executed) when determining that the network 10 (e.g., the base station 200) has successfully received a first uplink transmission (e.g., first uplink data).
[0113] As described above, the receiving unit 112 of the UE 100 receives a cell change command that triggers a cell change from the base station 200 by using a MAC CE. Based on the cell change command, the control unit 120 controls uplink transmission to the target cell that is performed without an RA procedure between the UE 100 and the target cell. When the cell change command includes an uplink grant for performing uplink transmission, the control unit 120 determines a TDRA table for LTM to determine time resources for uplink transmission. This allows the UE 100 to determine time resources for uplink transmission using the determined TDRA table for LTM, thereby enabling appropriate uplink transmission when performing RACH-less LTM.
[0114] Furthermore, the control unit 120 may determine a dedicated TDRA table for the uplink grant included in the cell change command as the TDRA table for LTM. This allows the dedicated TDRA table to define each parameter in consideration of a case where an uplink grant is sent in a cell change command, since the TDRA table is not used for other purposes. This allows the UE 100 to determine time resources for uplink transmission using appropriate parameters, thereby enabling appropriate uplink transmission.
[0115] In particular, because the uplink grant is provided to the UE 100 using a MAC CE or because a process for cell change is performed in the UE 100, there is a concern that a delay may occur before uplink transmission to the target cell is performed, compared to when the uplink grant is provided to the UE 100 using downlink control information (DCI). Specifically, because the uplink grant is provided to the UE 100 using a MAC CE transmitted in the MAC layer, a processing delay occurs in the UE 100, compared to when the uplink grant is provided to the UE 100 using DCI transmitted in a layer lower than the MAC layer. Furthermore, because the UE 100 performs a process for cell change, a delay occurs before the process for starting uplink transmission is started. For this reason, for example, a dedicated TDRA table can be defined that includes, as a parameter, a new slot offset value that takes into account a normal slot offset value and an additional delay value. This allows the UE 100 to properly perform uplink transmission without failure of uplink transmission due to delay.
[0116] Furthermore, the receiving unit 112 may receive, from the base station 200, information for setting a dedicated TDRA table common to each candidate cell set in the UE 100 as a candidate for the target cell. The control unit 120 may determine the dedicated TDRA table common to each candidate cell as the TDRA table for LTM. This makes it possible to save radio resources compared to the case where information for setting an individual dedicated TDRA table for each candidate cell is received.
[0117] Furthermore, the receiving unit 112 may receive, from the base station 200, information for setting an individual dedicated TDRA table for each candidate cell set in the UE 100 as a candidate for the target cell. The control unit 120 may determine the individual dedicated TDRA table of the candidate cell corresponding to the target cell as the TDRA table for LTM. This allows each parameter to be applied to uplink transmission for each cell to be specified, thereby enabling flexible parameter setting.
[0118] Furthermore, the receiving unit 112 may receive configuration information related to the configuration of a candidate cell that is a candidate for the target cell from the base station 200. The control unit 120 may determine the TDRA table for the LTM based on the TDRA table for the PUSCH that is set in the configuration information associated with the candidate cell that corresponds to the target cell. As a result, since the TDRA table for the PUSCH is already specified, it is possible to reduce the impact on existing technical specifications and, ultimately, on the mobile communication system 1, compared to when a dedicated TDRA table is newly specified.
[0119] Furthermore, when a TDRA table for PUSCH is not set by the configuration information, the control unit 120 may determine a predefined default TDRA table as the TDRA table for LTM. The control unit 120 may determine the time resource based on the subcarrier spacing of the uplink bandwidth portion in the target cell. This allows the UE 100 to determine the time resource corresponding to the subcarrier spacing, thereby enabling appropriate uplink transmission.
[0120] Furthermore, the control unit 120 may determine the subcarrier spacing based on an identifier of the uplink bandwidth portion included in the cell change command, thereby enabling the base station 200 to dynamically specify the subcarrier spacing for determining the time resource.
[0121] Furthermore, the control unit 120 may determine the subcarrier spacing based on an identifier of the uplink bandwidth portion included in the configuration information, which makes it possible to reduce the amount of information included in the cell change command and save radio resources.
[0122] Furthermore, the control unit 120 may determine a slot offset value, which is the time from the slot in which the uplink grant is received to the slot in which uplink transmission is performed, based on the index value included in the uplink grant and the TDRA table for LTM. The control unit 120 may determine the time resource by applying an additional delay value in addition to the determined slot offset value. This enables the UE 100 to properly perform uplink transmission without failure of uplink transmission due to delay.
[0123] Furthermore, the additional delay value may be a value predefined for the uplink grant included in the cell change command, which eliminates the need for the base station 200 to notify the UE 100 of the additional delay value, thereby saving radio resources.
[0124] Furthermore, the receiving unit 112 may receive information for setting the additional delay value from the base station 200. This allows the base station 200 to flexibly set the additional delay value according to, for example, the capability of the UE 100, and enables the UE 100 to appropriately perform uplink transmission.
[0125] As described above, the control unit 230 of the base station 200 does not need to include an uplink grant for performing uplink transmission in the cell change command. For example, when the control unit 230 of the base station 200 causes the UE 100 to perform RACH-less LTM, the control unit 230 of the base station 200 may control uplink transmission based on information included in each of one or more pieces of candidate cell configuration information. The control unit 230 of the base station 200 may control uplink transmission by including a ConfiguredGrant setting (which may be an RRC-ConfiguredUplinkGrant setting) in each of one or more pieces of candidate cell configuration information. For example, information included in each of one or more pieces of candidate cell configuration information (i.e., ConfiguredGrant configuration or PhysicalCellGroup configuration) may include information indicating a CS-RNTI (Configured Scheduling Radio Network Temporary Identifier), information indicating resources for uplink transmission (information indicating time resources and / or information indicating resources in the time domain (frequency resources)), information indicating a redundancy version (e.g., information indicating a sequence of redundancy versions), information indicating an MCS (Modulation and Coding scheme), information indicating the number of repetitions of uplink transmission (information indicating the Repetition number), information indicating a time reference SFN (time Reference SFN), and a time offset (time offset) related to the time reference SFN. Here, the type of uplink transmission for which the transmission is configured (i.e., the uplink grant is provided) by the RRC layer (i.e., the ConfiguredGrant setting included in the RRC message) is also referred to as ConfiguredGrant Type 1.
[0126] For example, the information indicating the CS-RNTI may be configured to indicate a retransmission of an uplink transmission. Furthermore, the information indicating a time resource for uplink transmission (i.e., PUSCH transmission) may include information indicating a periodicity and / or an offset for the uplink transmission (PUSCH resource). Furthermore, the information indicating the time reference SFN may indicate an SFN used to determine a resource offset in the time domain. For example, the information indicating the time reference SFN may indicate 0 or 512. The UE 100 may use the SFN of the indicated number (e.g., 0 or 512) closest to the time reference SFN before receiving the ConfiguredGrant configuration. Furthermore, the time offset associated with the time reference SFN may indicate a resource offset relative to the SFN in the time domain (i.e., the time reference SFN). For example, the UE 100 may determine resources in the time domain (e.g., SFNs, slots, and / or symbols) for uplink transmission by adding a time offset associated with the time reference SFN to the time reference SFN. That is, the UE 100 may determine resources in the time domain (e.g., SFNs, slots, and / or symbols) for uplink transmission based on the time reference SFN and / or the time offset associated with the time reference SFN.
[0127] For example, base station 200 may configure (transmit) to UE 100, at SFN "1023", information indicating the time reference SFN set to 512. Here, it is assumed that UE 100 fails to decode the ConfiguredGrant setting transmitted from base station 200 at SFN "1023". Base station 200 may again configure (retransmit) to UE 100, at SFN "0", the SFN next to SFN "1023". UE 100 can identify, based on the information indicating the time reference SFN set to 512, to use 512 (i.e., SFN "512") as a reference for determining a resource offset in the time domain for uplink transmission (i.e., a reference for the time domain offset). In this way, by base station 200 setting information indicating the time reference SFN, it becomes possible to share the time reference SFN for uplink transmission between UE 100 and base station 200 in cases such as when SFN changes from "1023" to "0" (when SFN wraparound occurs).
[0128] Here, when uplink transmission is configured by the RRC layer (i.e., an uplink grant is provided), the UE 100 may store the uplink grant as a configured uplink grant. The UE 100 may consider the configured uplink grant to occur sequentially in time domain resources (e.g., SFNs, slots, and / or symbols) for which the following equation is satisfied. That is, the UE 100 may consider the configured uplink grant to have occurred and perform uplink transmission in the time domain resources.
[0129] [(SFN × numberOfSlotsPerFrame × numberOfSymbolsPerSlot) + (slot number in the frame × numberOfSymbolsPerSlot) + symbol number in the slot] = (timeReferenceSFN × numberOfSlotsPerFrame × numberOfSymbolsPerSlot + timeDomainOffset × numberOfSymbolsPerSlot+S+N×periodicity) modulo (1024 × numberOfSlotsPerFrame × numberOfSymbolsPerSlot)
[0130] That is, the UE 100 may determine time domain resources (i.e., PUSCH resources) for uplink transmission (also referred to as ConfiguredGrant transmission) based on information included in the ConfiguredGrant configuration, and may perform uplink transmission using the determined resources. As described above, the UE 100 may apply candidate cell configuration information associated with an identifier of a candidate cell included in a cell change command, among one or more pieces of candidate cell configuration information. That is, the control unit 120 of the UE 100 may apply information (e.g., ConfiguredGrant configuration) included in the candidate cell configuration information associated with the identifier of the candidate cell based on the identifier of the candidate cell included in the cell change command. The UE 100 may identify the ConfiguredGrant configuration included in the candidate cell configuration information associated with the identifier of the candidate cell based on the identifier of the candidate cell included in the cell change command, and perform uplink transmission to a target cell (e.g., base station 200 of the target cell). Here, the uplink transmission may be performed using the resources in the time domain described above. Also, as described above, the timing advance field included in the cell change command may be set to a value other than a predetermined value (e.g., FFF).
[0131] Here, in the LTM, when the UE 100 attempts to perform uplink transmission based on the ConfiguredGrant setting, there is a possibility that the SFN serving as a reference for uplink transmission may be inconsistent between the UE 100 and the target cell (for example, the base station 200 of the target cell). That is, for the UE 100 that has determined the SFN serving as a reference for uplink transmission based on the information indicating the time reference SFN included in the candidate cell setting information, the base station 200 of the target cell cannot identify which SFN serves as a reference for uplink transmission, and there is a possibility that the uplink transmission from the UE 100 may not be received.
[0132] Here, the UE 100 may determine an SFN used to determine a resource offset in the time domain based on the timing (e.g., SFN, slot, and / or symbol) of receiving the LTM configuration information. For example, the UE 100 may use the closest indicated number (e.g., 0 or 512 indicated using information indicating a time reference SFN) before receiving the LTM configuration information as the SFN used to determine the resource offset in the time domain. That is, the UE 100 may use the closest indicated number SFN before receiving the LTM configuration information as a reference for determining a resource offset in the time domain for uplink transmission (i.e., a reference for the time domain offset). When the UE 100 receives an identifier of a candidate cell included in a cell change command, the UE 100 may use the closest SFN before receiving the LTM configuration information based on information indicating the time reference SFN included in the candidate cell configuration information (i.e., the LTM configuration information) corresponding to the identifier of the candidate cell.
[0133] Furthermore, UE 100 may determine an SFN used to determine a resource offset in the time domain based on the timing (e.g., SFN, slot, and / or symbol) at which the corresponding candidate cell configuration information is applied. For example, UE 100 may use the closest indicated number (e.g., 0 or 512 indicated using information indicating a time reference SFN) before application of the corresponding candidate cell configuration information as the SFN used to determine a resource offset in the time domain. That is, UE 100 may use the closest indicated number SFN before application of the corresponding candidate cell configuration information as a reference for determining a resource offset in the time domain for uplink transmission. For example, when UE 100 receives an identifier of a candidate cell included in a cell change command, UE 100 may use the closest SFN before application of the candidate cell configuration information based on information indicating a time reference SFN included in the candidate cell configuration information (i.e., LTM configuration information) corresponding to the identifier of the candidate cell.
[0134] Furthermore, UE 100 may determine an SFN used to determine a resource offset in the time domain based on the timing (e.g., SFN, slot, and / or symbol) of receiving the cell change command. For example, UE 100 may use the closest indicated number (e.g., 0 or 512 indicated using information indicating a time reference SFN) before receiving the cell change command as the SFN used to determine a resource offset in the time domain. That is, UE 100 may use the closest indicated number SFN before receiving the cell change command as a reference for determining a resource offset in the time domain for uplink transmission. For example, when UE 100 receives an identifier of a candidate cell included in a cell change command, UE 100 may use the closest SFN before receiving the cell change command based on information indicating a time reference SFN included in candidate cell configuration information (i.e., LTM configuration information) corresponding to the identifier of the candidate cell.
[0135] Here, information indicating the time reference SFN may be included in the cell change command. That is, the UE 100 may determine the SFN used to determine the resource offset in the time domain based on the information indicating the time reference SFN included in the cell change command. For example, the UE 100 may determine the SFN used to determine the resource offset in the time domain as described above based on the information indicating the time reference SFN included in the cell change command.
[0136] (Other Embodiments) In the above-described embodiments, an NR-based mobile communication system has been described as an example of the mobile communication system 1. However, the mobile communication system 1 is not limited to this example. The mobile communication system 1 may be a system compliant with the TS of either LTE (Long Term Evolution) or another generation system (e.g., 6th generation) of the 3GPP standard. The base station 200 may be an eNB that provides E-UTRA user plane and control plane protocol termination toward the UE 100 in LTE. The mobile communication system 1 may be a system compliant with the TS of a standard other than the 3GPP standard. The base station 200 may be an IAB (Integrated Access and Backhaul) donor or an IAB node.
[0137] In the above-described embodiment, an NR-based mobile communication system has been described as an example of the mobile communication system 1. However, the mobile communication system 1 is not limited to this example. The mobile communication system 1 may be a system conforming to the TS of either LTE or another generation system (e.g., 6th generation) of the 3GPP standard. The base station 200 may be an eNB that provides E-UTRA user plane and control plane protocol termination for the UE 100 in LTE. The mobile communication system 1 may be a system conforming to the TS of a standard other than the 3GPP standard.
[0138] The steps in the operations of the above-described embodiments do not necessarily have to be executed in chronological order according to the order depicted in the flow diagrams or sequence diagrams. For example, the steps in the operations may be executed in an order different from that depicted in the flow diagrams or sequence diagrams, or may be executed in parallel. Some of the steps in the operations may be deleted, or additional steps may be added to the process. Furthermore, the above-described operational flows are not limited to being executed independently, but may be executed by combining two or more operational flows. For example, some steps of one operational flow may be added to another operational flow, or some steps of one operational flow may be replaced with some steps of another operational flow.
[0139] A program may be provided that causes a computer to execute each process performed by the UE 100 or the base station 200. 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 (Compact Disk Read Only Memory) or a DVD-ROM (Digital Versatile Disc Read Only Memory). Furthermore, circuits that execute each process performed by the UE 100 or the base station 200 may be integrated, and at least a part of the UE 100 or the base station 200 may be configured as a semiconductor integrated circuit (chip set, SoC (System On Chip)).
[0140] In the above-described embodiments, "transmit" may mean performing processing at least one layer in a protocol stack used for transmission, or may mean physically transmitting a signal wirelessly or via a wired connection. Alternatively, "transmit" may mean a combination of performing processing at least one layer and physically transmitting a signal wirelessly or via a wired connection. Similarly, "receive" may mean performing processing at least one layer in a protocol stack used for reception, or may mean physically receiving a signal wirelessly or via a wired connection. Alternatively, "receive" may mean a combination of processing at least one layer and physically receiving a signal wirelessly or via a wired connection. Similarly, "obtain / acquire" may mean obtaining information from stored information, obtaining information from information received from another node, or obtaining information by generating the information. Similarly, 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." Similarly, "include" and "comprise" 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. Similarly, in this disclosure, "or" does not mean an exclusive or, but rather a logical 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 in this disclosure 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.
[0141] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.
[0142] (Additional Notes) Additional notes will be given regarding the features of the above-described embodiment.
[0143] (Supplementary Note 1) A communications device comprising: a receiver unit that receives a cell change command that triggers a cell change from a base station by a media access control (MAC) control element (CE); and a controller that controls uplink transmission to the target cell that is performed without a random access (RA) procedure between the communications device and a target cell based on the cell change command, wherein the controller determines a time domain resource allocation (TDRA) table for Layer 1 / Layer 2 triggered mobility (LTM) to determine resources in the time domain for the uplink transmission when the cell change command includes an uplink grant for performing the uplink transmission.
[0144] (Supplementary Note 2) The communication device according to Supplementary Note 1, wherein the control unit determines a dedicated TDRA table for the uplink grant included in the cell change command as the TDRA table for the LTM.
[0145] (Supplementary Note 3) The communication device according to Supplementary Note 2, wherein the receiving unit receives, from the base station, information for setting the dedicated TDRA table common to each candidate cell set in the communication device as a candidate for the target cell, and the control unit determines the dedicated TDRA table common to each candidate cell as the TDRA table for the LTM.
[0146] (Supplementary Note 4) The communication device according to Supplementary Note 2 or 3, wherein the receiving unit receives from the base station information for setting the dedicated TDRA table individually for each candidate cell set in the communication device as a candidate for the target cell, and the control unit determines the individual dedicated TDRA table of the candidate cell corresponding to the target cell as the TDRA table for the LTM.
[0147] (Supplementary Note 5) The communication device according to any one of Supplementary Notes 1 to 4, wherein the receiving unit receives configuration information regarding configuration of a candidate cell that is a candidate for the target cell from the base station, and the control unit determines the TDRA table for the LTM based on a TDRA table for a Physical Uplink Shared Channel (PUSCH) that is set in the configuration information associated with the candidate cell that corresponds to the target cell.
[0148] (Supplementary Note 6) The communication device according to Supplementary Note 5, wherein the control unit, when a TDRA table for the PUSCH is not set by the configuration information, determines a predefined default TDRA table as the TDRA table for the LTM, and determines the resources based on a subcarrier spacing of an uplink bandwidth portion in the target cell.
[0149] (Supplementary Note 7) The communication device according to Supplementary Note 6, wherein the control unit determines the subcarrier spacing based on an identifier of the uplink bandwidth portion included in the cell change command.
[0150] (Supplementary Note 8) The communication device according to Supplementary Note 6 or 7, wherein the control unit determines the subcarrier spacing based on an identifier of the uplink bandwidth portion included in the configuration information.
[0151] (Supplementary Note 9) The communication device according to any one of Supplementary Notes 1 to 8, wherein the control unit determines a slot offset value, which is a time from a slot in which the uplink grant is received to a slot in which the uplink transmission is performed, based on an index value included in the uplink grant and a TDRA table for the LTM, and the control unit determines the resource by applying an additional delay value in addition to the determined slot offset value.
[0152] (Supplementary Note 10) The communication device according to Supplementary Note 9, wherein the additional delay value is a value predefined for the uplink grant included in the cell change command.
[0153] (Supplementary Note 11) The communication device according to Supplementary Note 9 or 10, wherein the receiving unit receives information for setting the additional delay value from the base station.
[0154] (Supplementary Note 12) A communication method executed in a communication device, comprising: receiving, by a medium access control (MAC) control element (CE), from a base station, a cell change command that triggers a cell change; and controlling, based on the cell change command, uplink transmission to the target cell that is performed without a random access (RA) procedure between the communication device and the target cell, wherein, in the controlling step, if the cell change command includes an uplink grant for performing the uplink transmission, determining a time domain resource allocation (TDRA) table for Layer 1 / Layer 2 triggered mobility (LTM) to determine resources in the time domain for the uplink transmission.
[0155] (Supplementary Note 13) A communications device comprising: a receiver that receives a Radio Resource Control (RRC) message including configuration information related to Layer 1 / Layer 2 Triggered Mobility (LTM) from a base station, and receives a cell change command Media Access Control (MAC) Control Element (CE) from the base station, the RRC message including information for identifying the configuration information and instructing a cell change; and a controller that, when receiving the cell change command MAC CE, determines to perform a cell change to a target cell corresponding to the information for identifying the configuration information without a Random Access (RA) procedure, wherein the controller, when performing the cell change to the target cell without the RA procedure, performs uplink transmission to the target cell, and resources in the time domain for the uplink transmission are determined using a time domain resource allocation table that is determined based on information included in the configuration information.
[0156] (Supplementary Note 14) The communication device according to Supplementary Note 1, wherein the control unit controls the uplink transmission based on a grant set by the configuration information.
[0157] (Supplementary Note 15) The communication device according to Supplementary Note 13 or 14, wherein the configuration information includes information related to an uplink bandwidth portion (BWP), and the uplink BWP is activated based on execution of an RRC configuration or an RRC reconfiguration.
[0158] (Supplementary Note 16) The communications device according to any one of Supplementary Notes 13 to 15, wherein the cell change command MAC CE includes a value used to control an amount of timing adjustment to the uplink transmission.
[0159] (Supplementary Note 17) A base station comprising: a transmitter unit that transmits a Radio Resource Control (RRC) message including configuration information related to Layer 1 / Layer 2 Triggered Mobility (LTM) to a communication device, and transmits a cell change command Media Access Control (MAC) Control Element (CE) including information for identifying the configuration information and instructing a cell change to the communication device; and a controller that includes, in the configuration information, information for determining a time domain resource allocation table that is used to determine resources in the time domain for uplink transmission to the target cell when the communication device performs a cell change to the target cell corresponding to the information for identifying the configuration information based on reception of the cell change command MAC CE without a random access (RA) procedure.
[0160] (Supplementary Note 18) A communication method executed by a communication device, comprising: receiving a Radio Resource Control (RRC) message including configuration information related to Layer 1 / Layer 2 Triggered Mobility (LTM) from a base station, and receiving a cell change command Medium Access Control (MAC) Control Element (CE) from the base station including information for identifying the configuration information and instructing a cell change; determining, when the cell change command MAC CE is received, to perform a cell change to a target cell corresponding to the information for identifying the configuration information without a Random Access (RA) procedure; and performing uplink transmission to the target cell when the cell change to the target cell is performed without the RA procedure, wherein resources in the time domain for the uplink transmission are determined using a time domain resource allocation table determined based on information included in the configuration information.
Claims
1. A communication device (100), A receiving unit (112) receives from a base station (200) a radio resource control (RRC) message containing configuration information related to LTMs, including one or more Layer 1 / Layer 2 triggered mobility (LTM) candidate settings, and a cell change command media access control (MAC) control element (CE) from the base station that contains information for identifying one of the candidate identifiers included in each of the one or more LTM candidate settings and instructs a cell change, The system includes a control unit (120) that, upon receiving the cell change command MAC CE, determines whether to perform a cell change to a target cell corresponding to the LTM candidate setting including the one candidate identifier without a random access (RA) procedure. When the control unit performs a cell change to the target cell without the RA procedure, Based on the information included in the LTM candidate setting, which includes the aforementioned candidate identifier, the time domain resource allocation table is determined. Based on the determined time domain resource allocation table and the information included in the LTM candidate setting, which includes the one candidate identifier, the time domain resources for uplink transmission to the target cell are determined. Communication device.
2. The control unit controls the uplink transmission based on the grant setting included in the LTM candidate setting which includes the one candidate identifier. The communication device according to claim 1.
3. The LTM candidate setting, which includes the aforementioned candidate identifier, includes information regarding the uplink bandwidth portion (BWP), The aforementioned uplink BWP is activated based on the execution of RRC setting or RRC reset. The communication device according to claim 1 or 2.
4. The cell change command MAC CE includes a value used to control the amount of timing adjustment for the uplink transmission. The communication device according to claim 1 or 2.
5. It is a base station, It comprises a transmitting unit and a control unit, The aforementioned transmitting unit A radio resource control (RRC) message containing configuration information about LTMs, including one or more Layer 1 / Layer 2 triggered mobility (LTM) candidate settings, is sent to the communication device. A cell change command media access control (MAC) control element (CE) is transmitted to the communication device, which includes information for identifying one candidate identifier among the candidate identifiers included in each of the one or more LTM candidate settings and which instructs a cell change. The control unit includes in the LTM candidate setting the one candidate identifier information for determining the time domain resource allocation table when a cell change to a target cell corresponding to the LTM candidate setting including the one candidate identifier is performed without a random access (RA) procedure. The determined time domain resource allocation table and the information included in the LTM candidate setting, which includes the one candidate identifier, are used to determine the resources in the time domain for uplink transmission to the target cell. Base station.
6. A communication method performed by a communication device (100), The steps include receiving a radio resource control (RRC) message from a base station (200) that includes configuration information about an LTM, including one or more Layer 1 / Layer 2 triggered mobility (LTM) candidate settings, The steps include receiving a cell change command media access control (MAC) control element (CE) from the base station, which includes information for identifying one candidate identifier among the candidate identifiers included in each of the one or more LTM candidate settings and instructs a cell change, The steps include: when the cell change command MAC CE is received, determining whether to perform a cell change to the target cell corresponding to the LTM candidate setting including the one candidate identifier without a random access (RA) procedure; When performing a cell change to the target cell without the aforementioned RA procedure, The steps include determining a time domain resource allocation table based on the information included in the LTM candidate setting, which includes the aforementioned one candidate identifier, The process includes the step of determining a time domain resource for uplink transmission to the target cell based on the determined time domain resource allocation table and the information included in the LTM candidate setting which includes one candidate identifier. Communication method.