Terminal, wireless communication method, and wireless communication system

Abstract

A terminal according to the present invention: transmits, on the basis of a command by a downlink control channel, a random access preamble which assumes that a random access response will be received; and increases the value of a power ramping counter of the random access preamble on the basis of the value of a random access preamble transmission counter and whether or not a candidate target cell for transition under terminal-driven mobility control by a lower layer and a synchronization signal block or a reference signal for channel state information estimation have changed since a previous random access preamble was transmitted.

Description

Terminal, wireless communication method, and wireless communication system

[0001] The present disclosure relates to a terminal, a wireless communication method, and a wireless communication system that support LTM (L1 / L2 mobility).

[0002] The 3rd Generation Partnership Project (3GPP: registered trademark) is developing specifications for the 5th generation mobile communication system (5G, also known as New Radio (NR) or Next Generation (NG)), and is also developing specifications for the next generation, known as Beyond 5G, 5G Evolution, or 6G.

[0003] For example, 3GPP Release 19 discusses extensions to Layer 1 / Layer 2 mobility (L1 / L2 mobility, specifically, Lower Layer Triggered Mobility (LTM)) (see Non-Patent Document 1). LTM is a technology related to the mobility of a terminal (User Equipment, UE) in Layer 1 or Layer 2, and includes the transition of a UE to another cell (handover (HO)). HO using LTM is realized by a lower layer such as the Medium Access Control layer (MAC).

[0004] In addition, in Conditional LTM, specifically UE-triggered LTM, like conditional handover (CHO), the UE receives a specific execution condition from the radio base station (gNB), monitors the status according to the execution condition, and executes handover to another cell if the execution condition is satisfied. Furthermore, LTM enables HO without a random access procedure (RA procedure) (RACH less HO).

[0005] In the case of RACH less HO, a random access response (RAR) from the gNB to the UE is omitted, so the UE cannot know the timing advance (TA) to be applied in the target cell. Therefore, a method (early TA acquisition) has been specified in which the target cell (which may also be called a target gNB, candidate cell, etc.) acquires a TA for its own cell in advance (Non-Patent Document 2). The TA acquired by the target cell through early TA acquisition is notified to the UE by a Cell Switch Command MAC-CE. In early TA acquisition, early synchronization specified in 3GPP TS38.300 may be performed.

[0006] In the case of LTM, a random access channel (PRACH: Physical Random Access Channel) is specified as a PDCCH ordered RACH without RAR, which transmits a random access preamble in response to a command from a PDCCH (Physical Downlink Control Channel) and can omit the RAR (Non-Patent Document 3). Also, 3GPP Release 19 is considering a PDCCH ordered RACH with RAR, in which the RAR is transmitted from the target cell without omitting the RAR.

[0007] "New WID: NR mobility enhancements Phase 4", RP-234036, 3GPP TSG RAN Meeting #102, 3GPP, December 20233GPP TS 38.401 V18.0.0, 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NG-RAN; Architecture description (Release 18), 3GPP, December 2023 3GPP TS 38.300 V18.1.0, 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; NR and NG-RAN Overall Description; Stage 2 (Release 18), 3GPP, March 2024

[0008] In the case of Conditional LTM, as described above, the RA procedure can be omitted, and the transmission of the Cell Switch Command MAC-CE is also unnecessary. In this case, since the TA cannot be notified to the UE, it is possible to notify the UE of the TA using PDCCH ordered RACH with RAR.

[0009] However, in this case, the control of the power ramping counter (PREAMBLE_POWER_RAMPING_COUNTER) for the random access preamble becomes an issue. Specifically, the value of PREAMBLE_POWER_RAMPING_COUNTER cannot be incremented even when a PDCCH ordered RACH with RAR is executed.

[0010] Therefore, the following disclosure has been made in consideration of the above circumstances, and aims to provide a terminal, a wireless communication method, and a wireless communication system that can appropriately control a counter value for power ramping of a random access preamble while using a PDCCH ordered RACH with RAR in Conditional LTM.

[0011] One aspect of the present disclosure is a terminal including: a transmitter that transmits a random access preamble based on a command via a downlink control channel, the random access preamble being assumed to receive a random access response; and a controller that increases the value of a power ramping counter for the random access preamble based on the value of a random access preamble transmission counter, a candidate cell to which a lower layer will transition through terminal-initiated mobility control, and whether a synchronization signal block or a reference signal for channel state information estimation has changed since the previous random access preamble transmission.

[0012] One aspect of the present disclosure is a terminal (UE200) including: a transmitter (RA execution unit 220) that transmits a random access preamble based on an instruction via a downlink control channel, assuming receipt of a random access response; and a control unit (control unit 240) that assumes that the random access procedure is completed when the random access response is triggered in a candidate cell to which a user equipment initiates mobility control via a lower layer, and identification information of the random access preamble corresponding to the index of the random access preamble is acquired within a specific period of time.

[0013] One aspect of the present disclosure is a terminal including a receiver (RA execution unit 220) that receives a random access response to a random access preamble transmitted based on an instruction via a downlink control channel, and a transmitter that, when the random access response is received, transmits an acknowledgment response indicating that the random access response has been received to a candidate cell to which the terminal will transition based on terminal-initiated mobility control via a lower layer.

[0014] One aspect of the present disclosure is a terminal including: a receiving unit that receives a random access response to a random access preamble transmitted based on an instruction via a downlink control channel; and a transmitting unit that, when the random access response is received, transmits acquired information indicating that a timing adjustment value to be applied to a candidate cell to be transitioned to by terminal-initiated mobility control via a lower layer has been acquired via the random access response to a source cell to be transitioned to by terminal-initiated mobility control via a lower layer.

[0015] One aspect of the present disclosure is a terminal including: a transmitting unit that transmits a random access preamble based on an instruction via a downlink control channel, with the assumption that a random access response will be received; and a control unit that increases the transmission power of the random access preamble and retransmits the random access preamble if a random access response to the random access preamble cannot be received within a specific time from the transmission of the random access preamble.

[0016] One aspect of the present disclosure is a terminal including: a receiving unit that receives a random access response to a random access preamble transmitted based on an instruction via a downlink control channel; and a transmitting unit that, when the random access response is received, transmits an acknowledgment response indicating that a timing adjustment value to be applied to a candidate cell to be transitioned to by terminal-initiated mobility control via a lower layer has been obtained via the random access response to the candidate cell to be transitioned to by terminal-initiated mobility control via a lower layer.

[0017] One aspect of the present disclosure is a terminal that includes a control unit that performs terminal-initiated mobility control by a lower layer and controls transmission of a random access preamble based on an instruction via a downlink control channel, assuming reception of a random access response; and a transmission unit that, if the random access response cannot be received and the random access procedure fails, transmits failure information indicating that the random access procedure has failed to a network.

[0018] One aspect of the present disclosure is a terminal that includes a control unit that performs terminal-initiated mobility control by a lower layer and controls transmission of a random access preamble based on an instruction via a downlink control channel, assuming reception of a random access response, and a transmission unit that transmits capability information indicating capabilities related to transmission of the random access preamble to a network.

[0019] FIG. 1 is a diagram illustrating an overall schematic configuration of a wireless communication system 10. FIG. 2 is a diagram illustrating an example of control using LTM (L1 / L2 mobility). FIG. 3 is a functional block diagram of a gNB 100. FIG. 4 is a functional block diagram of a UE 200. FIG. 5 is a diagram illustrating an example of a RACH sequence according to a PDCCH ordered RACH without RAR. FIG. 6 is a diagram illustrating an example of a RACH sequence according to a PDCCH ordered RACH with RAR. FIG. 7 is a diagram illustrating an example of a definition of Random Access Preamble transmission according to Operation Example 1. FIG. 8 is a diagram illustrating an example of a definition of Random Access Preamble transmission according to Operation Example 2. FIG. 9 is a diagram illustrating an example of a definition of Random Access Preamble transmission according to Operation Example 2. FIG. 10 is a diagram illustrating an example of a RACH sequence according to a PDCCH ordered RACH with RAR according to Operation Example 3. FIG. 11 is a diagram illustrating an example of a RACH sequence according to a PDCCH ordered RACH with RAR according to Operation Example 3. Fig. 12 is a diagram showing a RACH sequence example 3 according to a PDCCH ordered RACH with RAR according to operation example 3. Fig. 13 is a diagram showing a RACH sequence example 1 according to a PDCCH ordered RACH with RAR according to operation example 4. Fig. 14 is a diagram showing a RACH sequence example 2 according to a PDCCH ordered RACH with RAR according to operation example 4. Fig. 15 is a diagram showing a RACH sequence example 3 according to a PDCCH ordered RACH with RAR according to operation example 4. Fig. 16 is a diagram showing an example sequence of a random access report according to operation example 5. Fig. 17 is a diagram showing an example sequence of transmitting UE capability information according to operation example 6. Fig. 18 is a diagram showing an example of the hardware configuration of the gNB 100 and the UE 200. Fig. 19 is a diagram showing an example configuration of a vehicle 2001.

[0020] Hereinafter, embodiments will be described with reference to the drawings. Note that the same or similar reference numerals are used to designate the same functions or configurations, and descriptions thereof will be omitted as appropriate.

[0021] (1) Overall Schematic Configuration of Wireless Communication System Fig. 1 is an overall schematic configuration diagram of a wireless communication system 10 according to this embodiment. The wireless communication system 10 is a wireless communication system conforming to 5G New Radio (NR) and includes a Next Generation-Radio Access Network 20 (hereinafter, NG-RAN 20) and a terminal 200 (User Equipment 200, hereinafter, UE 200).

[0022] The wireless communication system 10 may be a wireless communication system conforming to a method called Beyond 5G, 5G Evolution, or 6G, or may include a wireless communication system conforming to a method called Long Term Evolution (LTE) or 4G. The wireless communication system 10 may support functions related to the Industrial Internet of Things (IIoT) and Ultra-Reliable and Low Latency Communications (URLLC).

[0023] The NG-RAN 20 includes a radio base station 100 (hereinafter, gNB 100). Note that the specific configuration of the radio communication system 10, including the number of gNBs (or eNBs, etc.) and UEs, is not limited to the example shown in FIG. 1 .

[0024] The gNB 100 may also employ a fronthaul (FH) interface defined by the Open Radio Access Network Alliance (O-RAN). The gNB 100 may include an O-RAN Distributed Unit (O-DU) and an O-RAN Radio Unit (O-RU). The gNB 100 can function as a type of NG-RAN node.

[0025] The NG-RAN 20 actually includes multiple NG-RAN nodes, specifically, gNBs (or ng-eNBs), and is connected to a 5G core network (5GC, not shown). The NG-RAN 20 and the 5GC may be simply referred to as a "network." The 5GC may introduce the concept of CUPS (Control and User Plane Separation), which clearly separates the functions of the user plane and the control plane.

[0026] The gNB100 is a radio base station conforming to NR, and performs radio communication conforming to NR with the UE200. The gNB100 may be configured to include a CU (Central Unit) and a DU (Distributed Unit), and the DU may be separated from the CU and installed in a different geographical location. One or more DUs may be connected to the CU. The gNB100 (gNB-CU) may be connected to each other via an Xn interface, and the CU and DU may be connected to each other via an F1 interface (such as an F1-AP). In this embodiment, the CU may be called a communication device or a central device. The DU may be called a distributed device.

[0027] The gNB100 and UE200 are capable of supporting Massive MIMO, which generates more directional beams by controlling radio signals transmitted from multiple antenna elements; Carrier Aggregation (CA), which aggregates and uses multiple component carriers (CCs); and Dual Connectivity (DC), which enables simultaneous communication between the UE and multiple NG-RAN nodes.

[0028] The type of DC may be Multi-RAT Dual Connectivity (MR-DC) that uses multiple radio access technologies, or NR-NR Dual Connectivity (NR-DC) that uses only NR. For example, one gNB may constitute a master node (MN), and one or more other gNBs may constitute secondary nodes (SNs).

[0029] In the wireless communication system 10, not only mobility control of the UE 200 in layer 3 (which may be called L3 Mobility) but also mobility control in layer 1 and / or layer 2 (L1 / L2 Mobility) may be applied. L1 / L2 Mobility may be called LTM, and the name LTM will be mainly used hereinafter.

[0030] L3 Mobility may be interpreted as mobility control at the Radio Resource Control layer (RRC), while L1 / L2 Mobility may be interpreted as mobility control at the Physical layer (PHY), Medium Access Control layer (MAC), Radio Link Control layer (RLC), and Packet Data Convergence Protocol layer (PDCP) (mobility control by lower layers).

[0031] LTM may include network-triggered LTM and UE-triggered LTM (Conditional LTM, UE-triggered LTM).

[0032] In addition, in Conditional LTM (which may also be called UE triggered LTM or UE based LTM), like Conditional Handover (CHO), after the radio base station (gNB) receives a specific execution condition, the UE monitors the status according to the execution condition and executes LTM if the execution condition is satisfied.

[0033] Note that the LTM may include LTM fast failure recovery. LTM fast failure recovery is a mechanism in which, in the event of an LTM failure, the UE 200 performs cell selection, and if the selected cell is an LTM candidate cell, the UE 200 directly applies the configuration of the candidate cell without transmitting an RRC Reestablishment Request to the gNB 100.

[0034] In the wireless communication system 10, handover (HO) without a random access procedure may be applied in LTM. Specifically, the UE 200 can perform RACH-less HO, which is HO without using a random access channel (RACH). RACH-less HO may also be referred to as RACH-less LTM.

[0035] In RACH less HO, the UE 200 can calculate a timing advance (TA) by using the time difference between the reception timing of a signal to be measured (e.g., SSB (Synchronization Signal) / PBCH (Physical Broadcast CHannel) Block) between a source cell (which may be interpreted as a serving cell) at the transition source (handover source) and a target cell (handover destination) at the transition destination (handover destination) (UE based TA measurement). Such a TA may be referred to as a UE measured TA, for example.

[0036] In addition, in the case of RACH-less HO, an uplink grant (UL Grant) that allows the UE 200 to transmit an RRC message (RRC Reconfiguration Complete) after HO completion may be configured in advance. Such an UL Grant that is also applicable to RACH-less HO may be deemed invalid if certain conditions are met.

[0037] In the case of RACH less HO, a random access response (RAR) from the gNB to the UE is omitted, so the UE 200 cannot know the timing adjustment value to be applied in the target cell. Therefore, in the wireless communication system 10, a method (early TA acquisition) in which the target cell (which may also be called a target gNB, a candidate cell, etc.) acquires a TA for its own cell in advance may be applied. The TA acquired by the target cell through early TA acquisition is notified to the UE by a Cell Switch Command MAC-CE. In the early TA acquisition, early synchronization specified in 3GPP TS38.300 may be executed.

[0038] In addition, in the wireless communication system 10, in the case of LTM, for the random access channel (PRACH: Physical Random Access Channel), a random access preamble is transmitted in response to an instruction from the PDCCH (Physical Downlink Control Channel), and a PDCCH ordered RACH without RAR, in which the RAR can be omitted, and a PDCCH ordered RACH with RAR, in which the RAR is transmitted from the target cell without omitting the RAR, may be executed.

[0039] RACH less HO (early TA acquisition) is described in 3GPP TS38.401, Chapter 8.2.1.5, etc. Also, PDCCH ordered RACH without RAR is described in 3GPP TS38.300, Chapter 9.2.3.5.2, etc.

[0040] In a broad sense, the mobility of UE200 may mean the ease of movement and maneuverability of UE200, but in this embodiment, it may also mean minimizing call drops, radio link (including beam) failures, unnecessary handovers, ping-pong states, etc.

[0041] Figure 2 shows an example of control by LTM (L1 / L2 mobility). As shown in Figure 2, MAC included in a lower layer (Layer 1 / Layer 2), rather than RRC included in Layer 3, can perform measurement reporting, handover (HO) decision from a source cell to a target cell (which may include candidates), and timer management for determining whether HO is successful.

[0042] The MAC may report information related to the measurement report, the HO decision, etc. to a higher layer (RRC). The RRC may manage the state of radio resources accompanying the cell transition of the UE 200 based on the report.

[0043] The UE 200 transmits a measurement report (hereinafter, referred to as a Measurement report) including reception qualities for cells including a serving cell and neighboring cells to the network. The procedure by which the UE 200 transmits the Measurement report may be referred to as Measurement reporting. The reception qualities for the cells may include reception qualities of beams from the cells, or may include reception qualities of cells based on beams from the cells.

[0044] The UE 200 may periodically perform measurement reporting. The UE 200 may perform measurement reporting for each event. An entering condition for starting measurement reporting and a leaving condition for terminating measurement reporting may be defined for each event. The entering condition may be interpreted as a condition for determining whether or not to include a measurement report target, and the leaving condition may be interpreted as a condition for determining whether or not to exclude a measurement report target. At least one of the entering condition and the leaving condition may be applied as an execution condition in UE triggered LTM.

[0045] In this embodiment, the channels include a control channel and a data channel, such as a physical downlink control channel (PDCCH), a physical uplink control channel (PUCCH), a physical random access channel (PRACH), and a physical broadcast channel (PBCH).

[0046] The data channels include a physical downlink shared channel (PDSCH) and a physical uplink shared channel (PUSCH).

[0047] The reference signal includes a Demodulation Reference Signal (DMRS), a Sounding Reference Signal (SRS), a Phase Tracking Reference Signal (PTRS), and a Channel State Information-Reference Signal (CSI-RS), and the signal includes a channel and a reference signal. Furthermore, the data may refer to data transmitted via a data channel.

[0048] (2) Functional Block Configuration of Wireless Communication System Next, the functional block configuration of the wireless communication system 10 will be described. Specifically, the functional block configuration of the gNB 100 and the UE 200 will be described. Fig. 3 is a functional block configuration diagram of the gNB 100. Fig. 4 is a functional block configuration diagram of the UE 200.

[0049] (2.1) gNB100 As shown in FIG. 3, the gNB100 includes a radio communication unit 110, a handover processing unit 120, an RA procedure management unit 130, and a control unit 140.

[0050] The wireless communication unit 110 transmits downlink signals (DL signals) conforming to NR, and also receives uplink signals (UL signals) conforming to NR.

[0051] The handover processing unit 120 executes handover of the UE 200. Specifically, the handover processing unit 120 executes handover from a serving cell (source cell) of the UE 200 to another nearby cell (target cell). In particular, in this embodiment, the handover processing unit 120 may execute handover in accordance with L1 / L2 mobility (LTM). Note that the source cell and the target cell may also be referred to as a source radio base station (gNB) and a target radio base station (gNB).

[0052] Handover (HO) may also be called cell transition, cell selection, or cell reselection. Handover may be cell-based, but may also involve changing (switching) some of the beams to another cell.

[0053] The serving cell may be simply interpreted as the cell to which the UE 200 is connected, or more precisely, in the case of an RRC_CONNECTED UE without carrier aggregation (CA), there is only one serving cell that constitutes the primary cell. In the case of an RRC_CONNECTED UE configured with CA, the serving cell may be interpreted as indicating a set of one or more cells including the primary cell and all secondary cells.

[0054] The handover may also include a conditional handover (CHO) and / or a dual active protocol stack (DAPS) handover. CHO can execute a handover initiated by the UE 200 when a specific execution condition is met. If CHO is not applicable, a normal handover may be executed (which may be called CHO recovery). In CHO recovery, the UE 200 executes cell selection after a CHO failure. If a CHO candidate cell is selected, the UE 200 can directly apply a conditional RRC reconfiguration of the selected cell to reconnect without transmitting an RRC Restablishment Request to the candidate target cell.

[0055] The RA procedure management unit 130 manages operations related to a random access procedure (RA procedure) with the UE 200. The RA procedure management unit 130 also sets a timing advance (TA) value and the like.

[0056] Specifically, the RA procedure management unit 130 may manage the RACH (RA procedure method applied to the UE 200. More specifically, the RA procedure management unit 130 may apply either a PDCCH ordered RACH without RAR or a PDCCH ordered RACH with RAR to the UE 200.

[0057] In this embodiment, the RA procedure management unit 130 may receive a random access preamble transmitted from the UE 200. In this embodiment, the RA procedure management unit 130 may configure a receiving unit that receives the random access preamble.

[0058] The RA procedure management unit 130 may receive an acknowledgement response indicating that the UE 200 has received the random access response (RAR) from the UE 200. In this embodiment, the RA procedure management unit 130 may constitute a receiving unit that receives the acknowledgement response.

[0059] The RA procedure management unit 130 may receive failure information indicating that the random access procedure (RA procedure) has failed from the UE 200. In this embodiment, the RA procedure management unit 130 may constitute a receiving unit that receives the failure information.

[0060] In addition, the RA procedure management unit 130 may transmit a timing adjustment value (TA) to the source cell of the UE 200 when the radio communication unit 110 receives an acknowledgement indicating that the gNB 100 has formed a target cell and that the UE 200 has received a random access response (RAR).

[0061] Alternatively, the RA procedure management unit 130 may transmit, to the source cell, an indication indicating that the gNB 100 forms the target cell and that the UE 200 has acquired the TA. The TA may refer to a TA applied in the target cell, and may be a TA included in a PDCCH ordered RACH without RAR or a PDCCH ordered RACH with RAR. In this embodiment, the RA procedure management unit 130 may configure a transmission unit that transmits, to the source cell, at least one of the timing adjustment value and an indication indicating that the UE 200 has acquired the timing adjustment value.

[0062] The RA procedure management unit 130 can set a TA value to be applied to the own cell, etc. (a cell or beam formed by the gNB 100).

[0063] The control unit 140 controls each functional block constituting the gNB 100. In particular, in this embodiment, the control unit 140 can perform mobility control with the UE 200. Specifically, the control unit 140 can perform not only mobility control according to L3 Mobility but also mobility control according to L1 / L2 Mobility (LTM).

[0064] In addition, the control unit 140 can perform control as a CU (source side or target side) or a DU (source side or target side) in a gNB100 having a CU-DU configuration.

[0065] In this embodiment, the control unit 140 may perform early acquisition of a timing adjustment value of a target cell with the UE 200 that performs cell transition to the target cell without performing a random access procedure. Specifically, the control unit 140 may perform early TA acquisition with the UE 200 that performs RACH less HO.

[0066] Furthermore, the control unit 140 may determine whether to activate or deactivate an execution condition for the UE 200 that executes cell transfer regardless of an instruction from the network when an execution condition is satisfied, such as Conditional LTM (UE triggered LTM).

[0067] If the control unit 140 does not receive a random access preamble within a specific time, the control unit 140 may assume that the UE 200 has received a random access response. Specifically, if the control unit 140 does not receive a random access preamble from the UE 200 within a time defined by an ra-ResponseWindow (which may also be referred to as a reception time frame), the control unit 140 may assume that the UE 200 has received an RAR. Here, the state in which the random access preamble is not received from the UE 200 may mean that the UE 200 successfully receives the RAR and does not retransmit the random access preamble with power ramping applied. In other words, if the control unit 140 does not receive a random access preamble from the UE 200 after transmitting the RAR, the control unit 140 may assume that the UE 200 has successfully received the RAR.

[0068] (2.2) UE 200 As shown in FIG. 4, the UE 200 includes a radio communication unit 210, an RA execution unit 220, a handover execution unit 230, and a control unit 240.

[0069] The wireless communication unit 210 transmits an uplink signal (UL signal) conforming to NR. The wireless communication unit 210 also receives an uplink signal (DL signal) conforming to NR.

[0070] The RA execution unit 220 executes a random access procedure (RA procedure) with the gNB 100. Specifically, the RA execution unit 220 may execute the RA procedure in accordance with a PDCCH ordered RACH without RAR or a PDCCH ordered RACH with RAR.

[0071] More specifically, the RA execution unit 220 may transmit a random access preamble to the network (gNB) based on a command via the downlink control channel (PDCCH) on the assumption that a random access response (RAR) will be received. In this embodiment, the RA execution unit 220 may constitute a transmission unit that transmits the random access preamble. The random access preamble may include an index (preamble index) that can identify the random access preamble.

[0072] The RA execution unit 220 may also receive a random access response (RAR) from the network in response to a random access preamble transmitted based on a command via a downlink control channel (PDCCH). In this embodiment, the RA execution unit 220 may constitute a receiving unit that receives the random access response. Note that, although a RACH (which may also be read as an RA procedure) may be initiated by the PDCCH here, other physical channels in the downlink direction may be used instead of the PDCCH.

[0073] When the RA execution unit 220 receives a random access response (RAR) in accordance with the PDCCH ordered RACH with RAR, the RA execution unit 220 may transmit an acknowledgement indicating that the RAR has been received to a candidate cell to which the UE is to transfer in accordance with terminal initiated mobility management (LTM) by a lower layer. In this embodiment, the RA execution unit 220 may constitute a transmission unit that transmits the acknowledgement. Specifically, the LTM here may be interpreted as conditional LTM (UE triggered LTM).

[0074] When the RA execution unit 220 receives the RAR, the RA execution unit 220 may transmit acquired information indicating that a timing adjustment value (TA value, abbreviated as TA as appropriate) to be applied to a candidate cell (which may be referred to as a target cell, target gNB, etc.) to be transferred to by the LTM has been acquired by the RAR to the source cell of the transfer source by the LTM. In this embodiment, the RA execution unit 220 may constitute a transmission unit that transmits the acquired information.

[0075] The RA execution unit 220 may transmit the acquired information by at least one of an uplink physical channel, a control element of a medium access control layer, and a message of a radio resource control layer. For example, the RA execution unit 220 may transmit the acquired information by at least one of a PUCCH, a PUSCH, a MAC CE, and an RRC message.

[0076] When the RA execution unit 220 receives the RAR, the RA execution unit 220 may transmit an acknowledgement indicating that the timing adjustment value to be applied to the candidate cell of the LTM handover destination has been obtained by the RAR to the candidate cell by the LTM. The RA execution unit 220 may transmit the acknowledgement using at least one of a PUCCH, a PUSCH, a MAC CE, or an RRC message. In addition, the acknowledgement indicating that the RAR has been received may also be transmitted using at least one of a PUCCH, a PUSCH, a MAC CE, or an RRC message.

[0077] If the RAR cannot be received and the random access procedure fails, the RA executor 220 may transmit failure information indicating that the random access procedure has failed (random access failure) to the network. In this embodiment, the RA executor 220 may constitute a transmitter that transmits the failure information.

[0078] Specifically, the RA executor 220 may transmit a random access report (RA report) including the failure information to the network.

[0079] The RA execution unit 220 may transmit an RA report including at least one of identification information of a candidate cell to be transferred by LTM, an index of an operating frequency band, and an index of an operating beam. Specifically, the RA report may include an LTM candidate cell ID and an operating frequency band of the cell. Furthermore, the index of an operating beam may be an index of a synchronization signal block (SS (Synchronization Signal) / PBCH (Physical Broadcast CHannel) Block)) or an index of a CSI-RS.

[0080] Furthermore, the RA execution unit 220 may transmit an RA report including the number of times the random access preamble has been transmitted. Specifically, the RA report may include the number of times the random access preamble has been transmitted in the target beam (SSB or CSI-RS) of the LTM candidate cell.

[0081] The RA execution unit 220 may transmit capability information (UE capability information) indicating capabilities related to transmission of the random access preamble to the network. In this embodiment, the RA execution unit 220 may constitute a transmission unit that transmits the capability information. Specifically, the RA execution unit 220 may transmit UE capability information including whether or not PDCCH ordered RACH with RAR is supported.

[0082] The RA execution unit 220 may transmit UE Capability Information indicating a capability for obtaining a timing adjustment value to be applied to a candidate cell for handover by LTM. Specifically, the RA execution unit 220 may transmit UE Capability Information including support for obtaining TA included in the RAR in accordance with a PDCCH ordered RACH with RAR.

[0083] The RA execution unit 220 may transmit UE Capability Information including whether or not the RAR, that is, an acknowledgement indicating that the RAR according to the PDCCH ordered RACH with RAR has been received, is supported.

[0084] Furthermore, the RA execution unit 220 may transmit UE Capability Information including support or non-support of an acknowledgement indicating that the timing adjustment value to be applied to the candidate cell for handover by LTM has been acquired by the PDCCH ordered RACH with RAR.

[0085] The RA execution unit 220 may transmit UE Capability Information including support for transmitting failure information indicating that the RAR according to the PDCCH ordered RACH with RAR cannot be received and the random access procedure has failed. This failure may be referred to as a random access failure.

[0086] The handover execution unit 230 executes handover of the UE 200. Specifically, the handover execution unit 230 may execute handover to a transfer destination cell (NG-RAN node) based on control by the gNB 100.

[0087] The handover execution unit 230 can also execute processes related to normal handover (legacy handover), handover according to LTM (L1 / L2 Mobility), conditional handover (CHO), and DAPS handover. The handover execution unit 230 can also support RACH less HO (RACH less LTM).

[0088] Furthermore, the handover execution unit 230 may execute early TA acquisition in order to execute RACH less HO.

[0089] The handover execution unit 230 may transition to the candidate cell when an execution condition is satisfied. The execution condition may be determined based on the quality of the reference signal (RS), specifically, the value of Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), or Signal-to-Interference plus Noise power Ratio (SINR).

[0090] As described above, handover may be interpreted as transition, cell transition, cell selection, etc. Specifically, the handover execution unit 230 may execute handover based on LTM based on at least one command of layer 1 and / or layer 2.

[0091] The type of the command is not particularly limited, and may be, for example, an L1 / L2 Mobility command (e.g., Cell Switch Command MAC-CE). The L1 / L2 Mobility command may be replaced with another command of the RRC layer.

[0092] The control unit 240 controls each functional block constituting the UE 200. Specifically, the control unit 240 can execute control relating to handover of the UE 200.

[0093] The control unit 240 can also perform L1 / L2 Mobility (LTM), i.e., mobility control of at least one of Layer 1 and Layer 2. Mobility control using L1 / L2 Mobility may include quality measurement of service areas and neighboring cells in Layer 1 or Layer 2, setting of destination candidate cells, cell reselection (transition), handover, and the like. In this way, the control unit 240 can perform handover in accordance with mobility control by a lower layer. Specifically, the control unit 240 can perform LTM and control transmission of a random access preamble based on a command via a downlink control channel (or a PDCCH ordered RACH with RAR) assuming reception of a random access response.

[0094] In particular, in this embodiment, the control unit 240 may increase the value of the power ramping counter for the random access preamble based on the value of the random access preamble transmission counter according to the PDCCH ordered RACH with RAR, the candidate cell to which the LTM is to be transferred, and whether the synchronization signal block (SSB) or the reference signal for channel state information estimation (CSI-RS) has changed since the previous random access preamble transmission.

[0095] Specifically, the control unit 240 may increment the value of the PREAMBLE_POWER_RAMPING_COUNTER by "1" if the value of the PREAMBLE_TRANSMISSION_COUNTER and the state of the SSB or CSI-RS have not changed since the previous random access preamble transmission. In other words, the control unit 240 may increment the value of the power ramping counter if the candidate cell, synchronization signal block, or channel state information estimation reference signal has not changed since the previous random access preamble transmission. Note that the increment does not necessarily have to be "1."

[0096] When the control unit 240 has not acquired identification information (random access preamble ID) of the random access preamble according to the PDCCH ordered RACH with RAR, the control unit 240 may increment the value of a random access preamble transmission counter (PREAMBLE_TRANSMISSION_COUNTER). Specifically, when the control unit 240 cannot acquire from the RAR a random access preamble ID that matches the index (preamble index) of the random access preamble transmitted to the network via the RA execution unit 220, the control unit 240 may determine that reception of the RAR has failed and increment the value of PREAMBLE_TRANSMISSION_COUNTER by "1."

[0097] The control unit 240 may assume that the random access procedure is completed if a random access response (RAR) according to a PDCCH ordered RACH with RAR is triggered in a candidate cell to which LTM is to be transferred and a random access preamble index (preamble index) and corresponding random access preamble identification information (random access preamble ID) are obtained within a specific period.

[0098] Specifically, the control unit 240 may assume that the random access procedure is completed when the control unit 240 acquires the identification information (random access preamble ID) within a random access response reception time frame (ra-ResponseWindow). More specifically, the control unit 240 may assume that the random access procedure according to the PDCCH ordered RACH with RAR is completed when the control unit 240 receives an RAR including the random access preamble ID.

[0099] The control unit 240 may assume that the random access procedure is completed if the index of the random access preamble (preamble index) transmitted by the RA execution unit 220 matches the identification information of the random access preamble (random access preamble ID) included in the random access response. Here, "matching" may mean that the preamble index and the random access preamble ID match in part or in whole.

[0100] If the controller 240 does not receive a random access response to the random access preamble according to the PDCCH ordered RACH with RAR within a specific time (which may be ra-ResponseWindow) from the transmission of the random access preamble, the controller 240 may increase the transmission power of the random access preamble and retransmit the random access preamble. Such an increase in transmission power may be referred to as power ramping.

[0101] (3) Operation of the Wireless Communication System Next, a description will be given of the operation of the wireless communication system 10. Specifically, a description will be given of an operation example in which PDCCH ordered RACH with RAR is applied in Conditional LTM.

[0102] As described above, the wireless communication system 10 may support PDCCH ordered RACH without RAR and PDCCH ordered RACH with RAR for the random access procedure.

[0103] Fig. 5 shows an example of a RACH sequence according to a PDCCH ordered RACH without RAR, and Fig. 6 shows an example of a RACH sequence according to a PDCCH ordered RACH with RAR.

[0104] As shown in Fig. 5, PDCCH ordered RACH without RAR is specified in 3GPP Release-18, while PDCCH ordered RACH with RAR is being considered in 3GPP Release-19, as shown in Fig. 6.

[0105] In PDCCH ordered RACH without RAR, the RA procedure may be initiated by a command via PDCCH, and the UE may obtain the TA value applied to the target cell by an LTM cell switch command (Cell Switch Command MAC-CE) after sending a random access preamble (RACH preamble) to the target gNB. In PDCCH ordered RACH without RAR, the random access response (RAR) can be omitted.

[0106] On the other hand, in a PDCCH ordered RACH with RAR, the UE may obtain the TA value applied to the target cell through RAR.

[0107] (3.1) Operation Example 1 In this operation example, when PDCCH ordered RACH with RAR is applied, the value of PREAMBLE_POWER_RAMPING_COUNTER (random access preamble transmission counter) applied to power ramping of random access preamble transmission may be increased.

[0108] In the case of LTM, the execution condition for cell switching is set in the UE from the network in advance, and if the set execution condition is satisfied, the UE may execute cell switching. In other words, an LTM cell switch command (Cell Switch Command MAC-CE) from the gNB is not required.

[0109] On the other hand, in the case of early TA acquisition (also called early synchronization or early UL sync), the UE transmits a RACH preamble to the target gNB, and the target gNB transfers the determined TA value to the source gNB via F1 / Xn. The source gNB transmits the TA value to the UE using the LTM cell switch command.

[0110] When Conditional LTM is applied, the LTM cell switch command is not required, so how to transmit the TA value to the UE becomes an issue. In the PDCCH ordered RACH (PDCCH ordered RACH without RAR) introduced in LTM of 3GPP Release-18, the UE transmits a RACH preamble to the target gNB but does not receive an RAR from the target gNB.

[0111] Therefore, when performing PDCCH ordered RACH with RAR, the UE may obtain TA from the target gNB using RAR. However, in the case of PDCCH ordered RACH with RAR, how to increment PREAMBLE_POWER_RAMPING_COUNTER becomes an issue. In the case of 3GPP Release-18, PREAMBLE_POWER_RAMPING_COUNTER is incremented by "1" when a re-transmission is instructed from the PDCCH order.

[0112] Fig. 7 shows an example of the provisions of Random Access Preamble transmission according to Operation Example 1. Specifically, Fig. 7 shows an example of the provisions of 3GPP TS38.3.2.1 Chapter 5.1.3 (underlined parts are changed parts).

[0113] In this operation example, if the UE cannot obtain a random access preamble ID that matches the preamble index transmitted by itself from the received RAR within a predetermined period (ra-ResponseWindow), the UE may determine that the RAR reception has failed and increment PREAMBLE_TRANSMISSION_COUNTER. If the PREAMBLE_TRANSMISSION_COUNTER value is greater than 1 and the LTM candidate cells and SSB / CSI-RS have not changed since the previous RACH preamble transmission, the UE may increment PREAMBLE_POWER_RAMPING_COUNTER. The incremented value may be "1".

[0114] (3.2) Operation Example 2 In the case of PDCCH ordered RACH without RAR, the random access procedure (RACH) is completed when the PDCCH ordered RACH is triggered, after Message 1 (RACH preamble) is transmitted.

[0115] On the other hand, in the case of PDCCH ordered RACH with RAR, the question arises as to how the UE determines the completion of the random access procedure (RACH).

[0116] Fig. 8 shows a first specification example of random access preamble transmission according to operation example 2. Fig. 9 shows a second specification example of random access preamble transmission according to operation example 2. Specifically, Fig. 8 and Fig. 9 show examples of the specification in 3GPP TS38.3.2.1 Chapter 5.1.3 (underlined parts are changed parts).

[0117] In this operation example, when a PDCCH ordered RACH with RAR is triggered in a specific LTM candidate cell, the UE may determine that the random access procedure is completed if it can obtain a random access preamble ID that matches the preamble index it transmitted from the received RAR within a predetermined period (ra-ResponseWindow).

[0118] (3.3) Operation Example 3 In the case of PDCCH ordered RACH with RAR, the UE transmits a RACH preamble to the LTM candidate cell and can obtain the TA value from the LTM candidate cell via the RAR. However, there is a possibility that the RAR will not reach the UE. In the case of PDCCH ordered RACH with RAR, there is a problem that the LTM candidate cell cannot confirm whether the RAR has reached the UE because Message 3 does not exist.

[0119] In this operation example, in order to solve such a problem, the following operation examples may be applied. Fig. 10 shows a RACH sequence example 1 according to PDCCH ordered RACH with RAR according to operation example 3. Fig. 11 shows a RACH sequence example 2 according to PDCCH ordered RACH with RAR according to operation example 3. Fig. 12 shows a RACH sequence example 3 according to PDCCH ordered RACH with RAR according to operation example 3.

[0120] (Method 1): After receiving the RAR from the LTM candidate cell, the UE may return an Acknowledgement indicating the reception of the RAR to the LTM candidate cell (this Acknowledgement may be referred to as Message 3). This Acknowledgement may be transmitted using at least one of a PUCCH, a PUSCH, a MAC CE, and an RRC message.

[0121] (Method 2): After the UE acquires the TA value from the LTM candidate cell via RAR, the UE may notify the source gNB that the TA value has been acquired. The notification may be sent using at least one of a PUCCH, PUSCH, MAC CE, or RRC message. The source gNB may notify the target gNB that the UE has acquired the TA value via the F1 / Xn interface.

[0122] (Method 3): If the UE fails to receive an RAR within a predetermined period (ra-ResponseWindow) after transmitting a RACH preamble to the LTM candidate cell, the UE may apply power ramping and transmit a RACH preamble to the LTM candidate cell again. If the UE does not transmit another RACH preamble within a predetermined period (ra-ResponseWindow) after transmitting an RAR to the UE, the LTM candidate cell may consider that the UE has received the RAR.

[0123] (3.4) Operation Example 4 In the case of Conditional LTM (PDCCH ordered RACH without RAR), the source gNB needs to instruct the UE to activate the execution condition after the UE acquires the TA. On the other hand, in the case of PDCCH ordered RACH with RAR, the TA value is notified to the UE directly from the target gNB, which causes a problem that the source gNB cannot recognize whether the UE has acquired the TA value through RAR.

[0124] In this operation example, in order to solve such a problem, the following operation example may be applied. Fig. 13 shows a RACH sequence example 1 according to PDCCH ordered RACH with RAR according to operation example 4. Fig. 14 shows a RACH sequence example 2 according to PDCCH ordered RACH with RAR according to operation example 4. Fig. 15 shows a RACH sequence example 3 according to PDCCH ordered RACH with RAR according to operation example 4. Fig. 15 may be interpreted as a variation of sequence example 1.

[0125] (Method 1): After the UE acquires the TA value through the RAR from the LTM candidate cell, it may return an Acknowledgement indicating that the TA value has been acquired to the target gNB. The target gNB may send an indication indicating that the UE has acquired the TA value or the TA value to the source gNB via the F1 / Xn interface, allowing the source gNB to recognize that the UE has acquired the TA value through the RAR from the LTM candidate cell.

[0126] (Method 2): After the UE acquires the TA value through the RAR from the LTM candidate cell, the UE may notify the source gNB that the TA value has been acquired. The notification may be sent using at least one of a PUCCH, a PUSCH, a MAC CE, and an RRC message.

[0127] (3.5) Operation Example 5 In the case of PDCCH ordered RACH with RAR, if the UE does not receive an RAR from the LTM candidate cell within a predetermined period (ra-ResponseWindow), the UE must apply power ramping and transmit a RACH preamble to the LTM candidate cell again. However, if the UE cannot receive an RAR, it cannot apply power ramping forever. Specifically, if PREAMBLE_TRANSMISSION_COUNTER = preambleTransMax + 1, the UE may determine that the random access procedure has failed (random access failure).

[0128] 16 shows an example of a sequence of a random access report according to operation example 5. In this operation example, the following random access report (RA report) may be executed.

[0129] (Method 1): When a failure of the random access procedure occurs, the UE may record the failure in an RA report.

[0130] The RA report may include the following information:

[0131] - random access purpose meaning failure of PDCCH ordered RACH with RAR - LTM candidate cell ID, frequency, beam index (SSB index, CSI-RS index) of the candidate cell in which the random access failure occurred - cell ID of the source cell that triggered the PDCCH ordered RACH - number of times a RACH preamble was transmitted in the target beam (SSB or CSI-RS) of the LTM candidate cell - indication (BOOLEAN) indicating whether the RSRP of the target beam (SSB or CSI-RS) of the LTM candidate cell exceeds a predetermined threshold during RACH Note that, as shown in Figure 16, the UE may transmit a UEInformationResponse including an RA report in response to a UEInformationRequest transmitted from the network.

[0132] (Method 2): The UE may notify the source gNB that a random access failure has occurred in the LTM candidate cell. The notification may be sent using at least one of a PUCCH, a PUSCH, a MAC CE, or an RRC message.

[0133] When notifying a random access failure, the notification may include the LTM candidate cell ID, frequency, and beam index (SSB index, CSI-RS index) of the candidate cell in which the random access failure occurred. The notification may include the number of times a RACH preamble has been transmitted in the target beam (SSB or CSI-RS) of the LTM candidate cell, or an indication (BOOLEAN) indicating whether the RSRP of the target beam (SSB or CSI-RS) of the LTM candidate cell exceeds a predetermined threshold.

[0134] (3.6) Operation Example 6 Fig. 17 shows an example of a transmission sequence of UE capability information according to Operation Example 6. The UE may report the presence or absence of the following capabilities (UE capability information) for PDCCH ordered RACH with RAR to the network. The UE capability information may be defined for each UE, frequency range (FR), frequency channel (FC), etc. Furthermore, RRC signaling and configuration for reporting the UE capability information may be defined.

[0135] Support for PDCCH ordered RACH with RAR Support for obtaining TA using PDCCH ordered RACH with RAR Support for transmitting Acknowledgement after obtaining TA using PDCCH ordered RACH with RAR Support for notifying that the TA value has been obtained after obtaining TA using PDCCH ordered RACH with RAR Support for notifying random access failure information when PDCCH ordered RACH with RAR or RACH fails According to the above-mentioned operation example, when PDCCH ordered RACH with RAR is applied, it is possible to realize power ramping of the RACH preamble, determination of completion of the RA procedure, determination of whether the RAR has reached the UE, confirmation that the UE has obtained a TA value via the RAR, reporting of RA procedure failure (random access failure) to the network, and reporting of UE capability related to PDCCH ordered RACH with RAR to the network.

[0136] This allows the UE to perform Conditional LTM appropriately and reliably while using PDCCH ordered RACH with RAR.

[0137] (4) Other Embodiments Although the embodiments have been described above, it will be obvious to those skilled in the art that the present invention is not limited to the description of the embodiments, and that various modifications and improvements are possible.

[0138] For example, in the above-described embodiment, the names PDCCH ordered RACH without RAR and PDCCH ordered RACH with RAR are used, but these names may be provisional names, and other names may be used as long as the RACH is initiated by the PDCCH.

[0139] In the above description, configure, activate, update, indicate, enable, specify, and select may be interchangeable. Similarly, link, associate, correspond, and map may be interchangeable, and allocate, assign, monitor, and map may be interchangeable.

[0140] Furthermore, specific, dedicated, UE-specific, and UE-dedicated may be interchangeable. Similarly, common, shared, group-common, UE-common, and UE-shared may be interchangeable.

[0141] In this disclosure, terms such as "precoding," "precoder," "weight (precoding weight)," "Quasi-Co-Location (QCL)," "Transmission Configuration Indication state (TCI state)," "spatial relation," "spatial domain filter," "transmit power," "phase rotation," "antenna port," "antenna port group," "layer," "number of layers," "rank," "resource," "resource set," "resource group," "beam," "beam width," "beam angle," "antenna," "antenna element," "panel," etc. may be used interchangeably.

[0142] Furthermore, the block diagrams (FIGS. 3 and 4) used to explain the above-described embodiments show functional blocks. These functional blocks (components) are realized by any combination of hardware and / or software. Furthermore, the method for realizing each functional block is not particularly limited. That is, each functional block may be realized using a single device that is physically or logically coupled, or may be realized using two or more physically or logically separated devices that are connected directly or indirectly (e.g., wired, wireless, etc.) and these multiple devices. The functional block may also be realized by combining software with the single device or multiple devices.

[0143] Functions include, but are not limited to, judgment, determination, judgment, calculation, computation, processing, derivation, investigation, search, confirmation, reception, transmission, output, access, resolution, selection, selection, establishment, comparison, assumption, expectation, consideration, broadcasting, notifying, communicating, forwarding, configuring, reconfiguring, allocating, mapping, and assignment. For example, a functional block (component) that performs transmission is called a transmitting unit or transmitter. As mentioned above, there are no particular limitations on how each is implemented.

[0144] Furthermore, the above-described gNB100 and UE200 (the devices) may function as a computer that performs processing of the wireless communication method of the present disclosure. Figure 18 is a diagram showing an example of the hardware configuration of the devices. As shown in Figure 18, the devices may be configured as a computer including a processor 1001, a memory 1002, a storage 1003, a communication device 1004, an input device 1005, an output device 1006, a bus 1007, etc.

[0145] In the following description, the term "apparatus" can be interpreted as a circuit, a device, a unit, etc. The hardware configuration of the apparatus may be configured to include one or more of the apparatuses shown in the drawings, or may be configured to exclude some of the apparatuses.

[0146] Each functional block of the device (see FIGS. 3 and 4) is realized by any hardware element of the computer device or a combination of the hardware elements.

[0147] In addition, each function of the device is realized by loading specified software (programs) onto hardware such as processor 1001 and memory 1002, causing processor 1001 to perform calculations, control communication via communication device 1004, and control at least one of reading and writing data in memory 1002 and storage 1003.

[0148] The processor 1001 controls the entire computer by running, for example, an operating system, and may be configured as a central processing unit (CPU) including an interface with peripheral devices, a control unit, an arithmetic unit, and registers.

[0149] The processor 1001 also reads programs (program codes), software modules, data, etc. from at least one of the storage 1003 and the communication device 1004 into the memory 1002 and executes various processes in accordance with these. The programs used are those that cause a computer to execute at least some of the operations described in the above-described embodiments. Furthermore, the various processes described above may be executed by a single processor 1001, or may be executed simultaneously or sequentially by two or more processors 1001. The processor 1001 may be implemented by one or more chips. The programs may be transmitted from a network via a telecommunications line.

[0150] The memory 1002 is a computer-readable recording medium and may be configured by at least one of, for example, a read-only memory (ROM), an erasable programmable ROM (EPROM), an electrically erasable programmable ROM (EEPROM), a random access memory (RAM), etc. The memory 1002 may also be called a register, a cache, a main memory (primary storage device), etc. The memory 1002 may store a program (program code), a software module, etc., capable of executing a method according to an embodiment of the present disclosure.

[0151] Storage 1003 is a computer-readable recording medium, and may be, for example, at least one of an optical disk such as a Compact Disc ROM (CD-ROM), a hard disk drive, a flexible disk, a magneto-optical disk (e.g., a compact disk, a digital versatile disk, a Blu-ray disc), a smart card, a flash memory (e.g., a card, a stick, a key drive), a floppy disk, a magnetic strip, etc. Storage 1003 may also be referred to as an auxiliary storage device. The above-mentioned recording medium may be, for example, a database, a server, or other suitable medium including at least one of memory 1002 and storage 1003.

[0152] The communication device 1004 is hardware (transmission / reception device) for communicating between computers via at least one of a wired network and a wireless network, and is also called, for example, a network device, a network controller, a network card, or a communication module.

[0153] The communication device 1004 may be configured to include a high-frequency switch, a duplexer, a filter, a frequency synthesizer, etc. to realize, for example, at least one of Frequency Division Duplex (FDD) and Time Division Duplex (TDD).

[0154] The input device 1005 is an input device (e.g., a keyboard, a mouse, a microphone, a switch, a button, a sensor, etc.) that receives input from the outside. The output device 1006 is an output device (e.g., a display, a speaker, an LED lamp, etc.) that outputs to the outside. Note that the input device 1005 and the output device 1006 may be integrated into one device (e.g., a touch panel).

[0155] Furthermore, each device such as the processor 1001 and the memory 1002 is connected to a bus 1007 for communicating information. The bus 1007 may be configured using a single bus, or may be configured using different buses between each device.

[0156] Furthermore, the device may be configured to include hardware such as a microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a programmable logic device (PLD), or a field programmable gate array (FPGA), and some or all of the functional blocks may be realized by the hardware. For example, the processor 1001 may be implemented using at least one of these pieces of hardware.

[0157] Furthermore, the notification of information is not limited to the aspects / embodiments described in the present disclosure, and may be performed using other methods. For example, the notification of information may be performed by physical layer signaling (e.g., Downlink Control Information (DCI), Uplink Control Information (UCI)), higher layer signaling (e.g., RRC signaling, Medium Access Control (MAC) signaling, broadcast information (Master Information Block (MIB), System Information Block (SIB))), other signals, or a combination thereof. Furthermore, the RRC signaling may be referred to as an RRC message, and may be, for example, an RRC Connection Setup message, an RRC Connection Reconfiguration message, or the like.

[0158] Each aspect / embodiment described in the present disclosure may be applied to at least one of a system using Long Term Evolution (LTE), LTE-Advanced (LTE-A), SUPER 3G, IMT-Advanced, a 4th generation mobile communication system (4G), a 5th generation mobile communication system (5G), a 6th generation mobile communication system (6G), an xth generation mobile communication system (xG) (where x is, for example, an integer or a decimal), Future Radio Access (FRA), New Radio (NR), W-CDMA (registered trademark), GSM (registered trademark), CDMA2000, Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi (registered trademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE 802.20, Ultra-WideBand (UWB), Bluetooth (registered trademark), or other suitable system, and a next-generation system extended based on these. Furthermore, a combination of multiple systems (e.g., a combination of at least one of LTE and LTE-A with 5G) may also be applied.

[0159] The order of the procedures, sequences, flowcharts, etc. of each aspect / embodiment described in this disclosure may be changed unless it is consistent. For example, the methods described in this disclosure present elements of various steps using an example order, and are not limited to the particular order presented.

[0160] In the present disclosure, a specific operation described as being performed by a base station may also be performed by its upper node in some cases. In a network consisting of one or more network nodes having a base station, it is clear that various operations performed for communication with a terminal may be performed by at least one of the base station and another network node other than the base station (e.g., MME or S-GW, etc., but are not limited to these). Although the above example illustrates a case where there is one other network node other than the base station, a combination of multiple other network nodes (e.g., MME and S-GW) may also be used.

[0161] Information, signals (information, etc.) may be output from a higher layer (or a lower layer) to a lower layer (or a higher layer), or may be input and output via multiple network nodes.

[0162] The input and output information may be stored in a specific location (for example, a memory) or may be managed using a management table. The input and output information may be overwritten, updated, or added. The output information may be deleted. The input information may be transmitted to another device.

[0163] The determination may be made based on a value represented by one bit (0 or 1), a Boolean value (true or false), or a numerical comparison (e.g., comparison with a predetermined value).

[0164] The aspects / embodiments described in this disclosure may be used alone, in combination, or switched depending on the implementation. Notification of predetermined information (e.g., notification that "X is true") is not limited to explicit notification, but may be implicit (e.g., not notifying the predetermined information).

[0165] Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

[0166] Software, instructions, information, etc. may also be transmitted or received over a transmission medium. For example, if software is transmitted from a website, server, or other remote source using wired technologies (such as coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL)), and / or wireless technologies (such as infrared, microwave), then these wired and / or wireless technologies are included within the definition of transmission media.

[0167] The information, signals, etc. described in this disclosure may be represented using any of a variety of different technologies. For example, data, instructions, commands, information, signals, bits, symbols, chips, etc. that may be referred to throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, optical fields or photons, or any combination thereof.

[0168] Note that terms described in this disclosure and terms necessary for understanding this disclosure may be replaced with terms having the same or similar meanings. For example, at least one of a channel and a symbol may be a signal (signaling). Furthermore, a signal may be a message. Furthermore, a component carrier (CC) may be called a carrier frequency, a cell, a frequency carrier, etc.

[0169] As used in this disclosure, the terms "system" and "network" are used interchangeably.

[0170] Furthermore, the information, parameters, etc. described in the present disclosure may be expressed using absolute values, relative values ​​from a predetermined value, or other corresponding information. For example, a radio resource may be indicated by an index.

[0171] The names used for the above-described parameters are not intended to be limiting in any way. Furthermore, the mathematical expressions using these parameters may differ from those explicitly disclosed in this disclosure. The various channels (e.g., PUCCH, PDCCH, etc.) and information elements may be identified by any suitable names, and therefore the various names assigned to these various channels and information elements are not intended to be limiting in any way.

[0172] In this disclosure, terms such as "base station (BS)," "radio base station," "fixed station," "NodeB," "eNodeB (eNB)," "gNodeB (gNB)," "access point," "transmission point," "reception point," "transmission / reception point," "cell," "sector," "cell group," "carrier," and "component carrier" may be used interchangeably. Base stations may also be referred to by terms such as macrocell, small cell, femtocell, and picocell.

[0173] A base station can accommodate one or more (e.g., three) cells (also called sectors). When a base station accommodates multiple cells, the overall coverage area of ​​the base station can be divided into multiple smaller areas, and each smaller area can be provided with communication services by a base station subsystem (e.g., a small indoor base station (Remote Radio Head: RRH)).

[0174] The terms "cell" or "sector" refer to part or all of the coverage area of ​​a base station and / or base station subsystem that provides communication services within that coverage area.

[0175] In the present disclosure, the base station transmitting information to a terminal may be interpreted as the base station instructing the terminal to control or operate based on the information.

[0176] In this disclosure, the terms "Mobile Station (MS)," "user terminal," "User Equipment (UE)," "terminal," etc. may be used interchangeably.

[0177] A mobile station may also be referred to by those skilled in the art as a subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile terminal, wireless terminal, remote terminal, handset, user agent, mobile client, client, or some other suitable terminology.

[0178] At least one of the base station and the mobile station may be referred to as a transmitting device, a receiving device, a communication device, etc. At least one of the base station and the mobile station may be a device mounted on a mobile object, the mobile object itself, etc. The mobile object refers to a movable object, and may move at any speed. Naturally, this also includes cases where the mobile object is stationary. Examples of the mobile object include, but are not limited to, vehicles, transport vehicles, automobiles, motorcycles, bicycles, connected cars, excavators, bulldozers, wheel loaders, dump trucks, forklifts, trains, buses, handcars, rickshaws, ships and other watercraft, airplanes, rockets, satellites, drones (registered trademark), multicopters, quadcopters, balloons, and objects mounted thereon. The mobile object may also be a mobile object that moves autonomously based on an operational command. It may be a vehicle (e.g., a car, an airplane, etc.), an unmanned mobile object (e.g., a drone, an autonomous vehicle, etc.), or a robot (manned or unmanned). At least one of the base station and the mobile station may be a device that does not necessarily move during communication operations. For example, at least one of the base station and the mobile station may be an IoT (Internet of Things) device such as a sensor.

[0179] Furthermore, a base station in the present disclosure may be read as a mobile station (user terminal, the same applies hereinafter). For example, the aspects / embodiments of the present disclosure may be applied to a configuration in which communication between a base station and a mobile station is replaced with communication between multiple mobile stations (which may be called, for example, Device-to-Device (D2D) or Vehicle-to-Everything (V2X)). In this case, the mobile station may be configured to have the functions of a base station. Furthermore, terms such as "uplink" and "downlink" may be read as terms corresponding to terminal-to-terminal communication (for example, "side"). For example, terms such as an uplink channel and a downlink channel may be read as a side channel (or sidelink).

[0180] Similarly, a mobile station in the present disclosure may be interpreted as a base station, in which case the base station may have the functions of a mobile station.

[0181] A radio frame may be composed of one or more frames in the time domain. Each of the one or more frames in the time domain may be called a subframe. A subframe may further be composed of one or more slots in the time domain. A subframe may have a fixed time length (e.g., 1 ms) that is independent of numerology.

[0182] Numerology may be communication parameters that apply to the transmission and / or reception of a signal or channel, such as subcarrier spacing (SCS), bandwidth, symbol length, cyclic prefix length, transmission time interval (TTI), number of symbols per TTI, radio frame structure, specific filtering operations performed by the transceiver in the frequency domain, and specific windowing operations performed by the transceiver in the time domain.

[0183] A slot may consist of one or more symbols in the time domain (such as an Orthogonal Frequency Division Multiplexing (OFDM) symbol, a Single Carrier Frequency Division Multiple Access (SC-FDMA) symbol, etc.) A slot may be a numerology-based time unit.

[0184] A slot may include multiple minislots. Each minislot may consist of one or more symbols in the time domain. A minislot may also be called a subslot. A minislot may consist of fewer symbols than a slot. A PDSCH (or PUSCH) transmitted in a time unit larger than a minislot may be called PDSCH (or PUSCH) mapping type A. A PDSCH (or PUSCH) transmitted using a minislot may be called PDSCH (or PUSCH) mapping type B.

[0185] The radio frame, subframe, slot, minislot, and symbol all represent time units for transmitting signals, and may be referred to by other names corresponding to the radio frame, subframe, slot, minislot, and symbol.

[0186] For example, one subframe may be referred to as a transmission time interval (TTI), multiple consecutive subframes may be referred to as a TTI, or one slot or one minislot may be referred to as a TTI. That is, at least one of the subframe and the TTI may be a subframe (1 ms) in existing LTE, a period shorter than 1 ms (e.g., 1-13 symbols), or a period longer than 1 ms. Note that the unit representing the TTI may be called a slot, minislot, etc., instead of a subframe.

[0187] Here, TTI refers to, for example, the smallest time unit for scheduling in wireless communication. For example, in an LTE system, a base station schedules each user terminal to allocate radio resources (such as frequency bandwidth and transmission power that can be used by each user terminal) in TTI units. Note that the definition of TTI is not limited to this.

[0188] The TTI may be a transmission time unit for a channel-encoded data packet (transport block), a code block, a code word, etc., or may be a processing unit for scheduling, link adaptation, etc. When a TTI is given, the time interval (e.g., the number of symbols) to which a transport block, a code block, a code word, etc. is actually mapped may be shorter than the TTI.

[0189] In addition, when one slot or one minislot is called a TTI, one or more TTIs (i.e., one or more slots or one or more minislots) may be the minimum time unit for scheduling, and the number of slots (minislots) constituting the minimum time unit for scheduling may be controlled.

[0190] A TTI having a time length of 1 ms may be referred to as a regular TTI (TTI in LTE Rel. 8-12), normal TTI, long TTI, regular subframe, normal subframe, long subframe, slot, etc. A TTI shorter than a regular TTI may be referred to as a shortened TTI, short TTI, partial or fractional TTI, shortened subframe, short subframe, minislot, subslot, slot, etc.

[0191] In addition, a long TTI (e.g., a normal TTI, a subframe, etc.) may be interpreted as a TTI having a time length of more than 1 ms, and a short TTI (e.g., a shortened TTI, etc.) may be interpreted as a TTI having a TTI length shorter than the TTI length of a long TTI and equal to or greater than 1 ms.

[0192] A resource block (RB) is a resource allocation unit in the time domain and the frequency domain, and may include one or more consecutive subcarriers in the frequency domain. The number of subcarriers included in an RB may be the same regardless of numerology, for example, 12. The number of subcarriers included in an RB may be determined based on numerology.

[0193] The time domain of an RB may include one or more symbols and may have a length of one slot, one minislot, one subframe, or one TTI, each of which may consist of one or more resource blocks.

[0194] Note that one or more RBs may also be called a physical resource block (PRB), a sub-carrier group (SCG), a resource element group (REG), a PRB pair, an RB pair, etc.

[0195] Furthermore, a resource block may be composed of one or more resource elements (REs). For example, one RE may be a radio resource region of one subcarrier and one symbol.

[0196] A Bandwidth Part (BWP) (which may also be referred to as a fractional bandwidth) may represent a subset of contiguous common resource blocks (RBs) for a given numerology on a given carrier, where the common RBs may be identified by their index relative to a common reference point of the carrier. PRBs may be defined in a given BWP and numbered within that BWP.

[0197] The BWP may include a BWP for UL (UL BWP) and a BWP for DL ​​(DL BWP). One or more BWPs may be configured for a UE within one carrier.

[0198] At least one of the configured BWPs may be active, and the UE may not expect to transmit or receive a predetermined signal / channel outside the active BWP. Note that the terms "cell," "carrier," etc. in this disclosure may be read as "BWP."

[0199] The above-described structures of the radio frame, subframe, slot, minislot, and symbol are merely examples. For example, the number of subframes included in a radio frame, the number of slots per subframe or radio frame, the number of minislots included in a slot, the number of symbols and RBs included in a slot or minislot, the number of subcarriers included in an RB, the number of symbols in a TTI, the symbol length, the cyclic prefix (CP) length, and other configurations may be changed in various ways.

[0200] The terms "connected," "coupled," or any variation thereof, refer to any direct or indirect connection or coupling between two or more elements, and may include the presence of one or more intermediate elements between two elements that are "connected" or "coupled" to each other. The coupling or connection between elements may be physical, logical, or a combination thereof. For example, "connected" may be read as "access." As used in this disclosure, two elements may be considered to be "connected" or "coupled" to each other using one or more wires, cables, and / or printed electrical connections, as well as electromagnetic energy having wavelengths in the radio frequency range, microwave range, and optical (both visible and invisible) range, as some non-limiting and non-exhaustive examples.

[0201] The reference signal may also be abbreviated as Reference Signal (RS) and may be called a pilot depending on the applicable standard.

[0202] As used in this disclosure, the phrase "based on" does not mean "based only on," unless expressly stated otherwise. In other words, the phrase "based on" means both "based only on" and "based at least on."

[0203] The "means" in the configuration of each of the above devices may be replaced with "part," "circuit," "device," etc.

[0204] As used in this disclosure, any reference to an element using a designation such as "first," "second," etc. 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.

[0205] When the terms "include," "including," and variations thereof are used in this disclosure, these terms are intended to be inclusive, similar to the term "comprising." Furthermore, when the term "or" is used in this disclosure, it is not intended to be an exclusive or.

[0206] In this disclosure, where articles are added by translation, such as a, an, and the in English, the disclosure may include that the nouns following these articles are in the plural form.

[0207] As used in this disclosure, the terms "determining" and "determining" may encompass a wide variety of actions. "Determining" and "determining" may include, for example, judging, calculating, computing, processing, deriving, investigating, looking up, searching, inquiring (e.g., searching in a table, database, or other data structure), ascertaining, and the like. "Determining" and "determining" may also include receiving (e.g., receiving information), transmitting (e.g., sending information), input, output, accessing (e.g., accessing data in memory), and the like. Furthermore, "judgment" and "decision" can include regarding resolving, selecting, choosing, establishing, comparing, etc. as having been "judged" or "decided." In other words, "judgment" and "decision" can include regarding some action as having been "judged" or "decided." Furthermore, "judgment (decision)" can be interpreted as "assuming," "expecting," "considering," etc.

[0208] In the present disclosure, the term "A and B are different" may mean "A and B are different from each other." The term may also mean "A and B are each different from C." Terms such as "separate" and "coupled" may also be interpreted in the same way as "different."

[0209] 19 shows an example of the configuration of a vehicle 2001. As shown in Fig. 19, the vehicle 2001 includes a drive unit 2002, a steering unit 2003, an accelerator pedal 2004, a brake pedal 2005, a shift lever 2006, left and right front wheels 2007, left and right rear wheels 2008, an axle 2009, an electronic control unit 2010, various sensors 2021 to 2029, an information service unit 2012, and a communication module 2013.

[0210] The drive unit 2002 is composed of, for example, an engine, a motor, or a hybrid of an engine and a motor. The steering unit 2003 includes at least a steering wheel (also called a handle) and is configured to steer at least one of the front wheels and the rear wheels based on the operation of the steering wheel operated by the user. The electronic control unit 2010 is composed of a microprocessor 2031, memory (ROM, RAM) 2032, and a communication port (IO port) 2033. Signals from various sensors 2021 to 2027 provided in the vehicle are input to the electronic control unit 2010. The electronic control unit 2010 may also be called an ECU (Electronic Control Unit).

[0211] The signals from the various sensors 2021 to 2028 include a current signal from a current sensor 2021 that senses the current of the motor, a rotation speed signal of the front and rear wheels obtained by a rotation speed sensor 2022, an air pressure signal of the front and rear wheels obtained by an air pressure sensor 2023, a vehicle speed signal obtained by a vehicle speed sensor 2024, an acceleration signal obtained by an acceleration sensor 2025, an accelerator pedal depression amount signal obtained by an accelerator pedal sensor 2029, a brake pedal depression amount signal obtained by a brake pedal sensor 2026, a shift lever operation signal obtained by a shift lever sensor 2027, and a detection signal for detecting obstacles, vehicles, pedestrians, etc. obtained by an object detection sensor 2028.

[0212] The information service unit 2012 is composed of various devices, such as a car navigation system, an audio system, speakers, a television, and a radio, for providing (outputting) various types of information, such as driving information, traffic information, and entertainment information, and one or more ECUs for controlling these devices. The information service unit 2012 uses information acquired from external devices via the communication module 2013, etc., to provide various types of multimedia information and multimedia services to the occupants of the vehicle 1.

[0213] The information service unit 2012 may include input devices (e.g., keyboards, mice, microphones, switches, buttons, sensors, touch panels, etc.) that accept input from the outside, and may also include output devices (e.g., displays, speakers, LED lamps, touch panels, etc.) that output to the outside.

[0214] The driving assistance system unit 2030 is composed of various devices that provide functions for preventing accidents and reducing the driver's driving burden, such as millimeter-wave radar, LiDAR (Light Detection and Ranging), cameras, positioning locators (e.g., GNSS, etc.), map information (e.g., high-definition (HD) maps, autonomous vehicle (AV) maps, etc.), gyro systems (e.g., IMU (Inertial Measurement Unit), INS (Inertial Navigation System), etc.), AI (Artificial Intelligence) chips, and AI processors, as well as one or more ECUs that control these devices. The driving assistance system unit 2030 also transmits and receives various information via the communication module 2013 to realize driving assistance functions or autonomous driving functions.

[0215] The communication module 2013 can communicate with the microprocessor 2031 and components of the vehicle 1 via the communication port. For example, the communication module 2013 transmits and receives data via the communication port 2033 to and from a driving unit 2002, a steering unit 2003, an accelerator pedal 2004, a brake pedal 2005, a shift lever 2006, left and right front wheels 2007, left and right rear wheels 2008, an axle 2009, a microprocessor 2031 and memory (ROM, RAM) 2032 in the electronic control unit 2010, and sensors 2021 to 2028, which are provided in the vehicle 2001.

[0216] The communication module 2013 is a communication device that can be controlled by the microprocessor 2031 of the electronic control unit 2010 and can communicate with an external device. For example, it transmits and receives various information to and from the external device via wireless communication. The communication module 2013 may be located either inside or outside the electronic control unit 2010. The external device may be, for example, a base station, a mobile station, or the like.

[0217] The communication module 2013 may transmit at least one of signals from the above-mentioned various sensors 2021 to 2028 input to the electronic control unit 2010, information obtained based on the signals, and information based on input from the outside (user) obtained via the information service unit 2012 to an external device via wireless communication. The electronic control unit 2010, the various sensors 2021 to 2028, the information service unit 2012, etc. may be referred to as input units that accept input. For example, the PUSCH transmitted by the communication module 2013 may include information based on the above-mentioned input.

[0218] The communication module 2013 receives various information (traffic information, traffic signal information, vehicle-to-vehicle information, etc.) transmitted from external devices and displays it on an information service unit 2012 provided in the vehicle. The information service unit 2012 may also be called an output unit that outputs information (for example, outputs information to a device such as a display or speaker based on the PDSCH (or data / information decoded from the PDSCH) received by the communication module 2013). The communication module 2013 also stores the various information received from external devices in a memory 2032 that can be used by the microprocessor 2031. Based on the information stored in the memory 2032, the microprocessor 2031 may control the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, shift lever 2006, left and right front wheels 2007, left and right rear wheels 2008, axles 2009, sensors 2021 to 2028, and the like provided in the vehicle 2001.

[0219] (Additional Note) The above disclosure may be expressed as follows: A first feature is a terminal including: a transmitter that transmits a random access preamble on the assumption that a random access response is received, based on a command via a downlink control channel, and a controller that increases a value of a power ramping counter for the random access preamble, based on a value of a random access preamble transmission counter, and on whether a candidate cell to be transitioned to by terminal-initiated mobility control by a lower layer, and a synchronization signal block or a reference signal for channel state information estimation have changed since the previous random access preamble transmission.

[0220] A second feature is that, in the first feature, the control unit increases a value of the power ramping counter when the candidate cell, the synchronization signal block, or the reference signal for estimating channel state information has not changed since the previous random access preamble transmission.

[0221] A third feature is the first or second feature, wherein the control unit increases a value of the random access preamble transmission counter when identification information of the random access preamble has not been acquired.

[0222] A fourth feature is a terminal including: a transmitter that transmits a random access preamble based on an instruction via a downlink control channel, on the assumption that a random access response will be received; and a controller that assumes that the random access procedure is completed when the random access response is triggered in a candidate cell to which a terminal is to transition by terminal-initiated mobility control via a lower layer, and identification information of the random access preamble corresponding to an index of the random access preamble is acquired within a specific period.

[0223] According to a fifth feature in the fourth feature, the control unit assumes that the random access procedure is completed when the identification information is acquired within a reception time frame of the random access response.

[0224] A sixth feature is, in the fourth or fifth feature, wherein the control unit assumes that the random access procedure is completed if an index of the random access preamble transmitted by the transmission unit matches identification information of the random access preamble included in the random access response.

[0225] A seventh feature is a terminal that includes: a control unit that performs terminal-initiated mobility control by a lower layer, and controls transmission of a random access preamble based on an instruction via a downlink control channel, assuming reception of a random access response; and a transmission unit that, if the random access response cannot be received and the random access procedure fails, transmits failure information indicating that the random access procedure has failed to the network.

[0226] In an eighth feature based on the seventh feature, the transmitting unit transmits a random access report including the failure information to the network.

[0227] A ninth feature is that, in the seventh or eighth feature, the transmitter transmits the random access report including at least one of identification information of a candidate cell to which the mobility control is to be transferred, an index of a frequency band used, and an index of a beam used.

[0228] A tenth feature based on any one of the seventh to ninth features is that the transmitter transmits the random access report including the number of times the random access preamble has been transmitted.

[0229] An eleventh feature is a terminal that includes: a control unit that performs terminal-initiated mobility control by a lower layer, and controls transmission of a random access preamble based on an instruction via a downlink control channel, assuming reception of a random access response; and a transmission unit that transmits capability information indicating capabilities related to transmission of the random access preamble to a network.

[0230] A twelfth feature based on the eleventh feature is that the transmitter transmits the capability information indicating a capability related to acquisition of a timing adjustment value to be applied to a candidate cell as a transfer destination under the mobility control.

[0231] According to a thirteenth feature in the eleventh or twelfth feature, the transmitting unit transmits the capability information including supportability of an acknowledgement response indicating that the random access response has been received.

[0232] A fourteenth feature is that, in the eleventh to fourteenth features, the transmitter transmits the capability information including support or non-support of an acknowledgement response indicating that a timing adjustment value to be applied to a candidate cell to which the mobility control is to be transferred has been obtained by the random access response.

[0233] A fifteenth feature is, in the eleventh to fourteenth features, that the transmitting unit transmits the capability information including whether or not the transmitting unit supports transmission of failure information indicating that the random access procedure has failed because the random access response cannot be received.

[0234] 10 Wireless communication system 20 NG-RAN 100 gNB 110 Wireless communication unit 120 Handover processing unit 130 TA setting unit 140 Control unit 200 UE 210 Wireless communication unit 220 Measurement reporting unit 230 Handover execution unit 240 Control unit 1001 Processor 1002 Memory 1003 Storage 1004 Communication device 1005 Input device 1006 Output device 1007 Bus 2001 Vehicle 2002 Drive unit 2003 Steering unit 2004 Accelerator pedal 2005 Brake pedal 2006 Shift lever 2007 Left and right front wheels 2008 Left and right rear wheels 2009 Axle 2010 Electronic control unit 2012 Information service unit 2013 Communication module 2021 Current sensor 2022 RPM sensor 2023 Air pressure sensor 2024 Vehicle speed sensor 2025 Acceleration sensor 2026 Brake pedal sensor 2027 Shift lever sensor 2028 Object detection sensor 2029 Accelerator pedal sensor 2030 Driving assistance system section 2031 Microprocessor 2032 Memory (ROM, RAM) 2033 Communication port

Claims

1. A terminal comprising: a transmitter that transmits a random access preamble based on a command via a downlink control channel, assuming receipt of a random access response; and a controller that increases the value of a power ramping counter for the random access preamble based on the value of a random access preamble transmission counter and whether a candidate cell to transition to through terminal-initiated mobility control by a lower layer, and a synchronization signal block or a reference signal for channel state information estimation have changed since the previous random access preamble transmission.

2. The terminal according to claim 1, wherein the control unit increases the value of the power ramping counter when the candidate cell and the synchronization signal block or the reference signal for channel state information estimation have not changed since the previous random access preamble transmission.

3. The terminal according to claim 1, wherein the control unit increases the value of the random access preamble transmission counter when identification information of the random access preamble has not been acquired.

4. A wireless communication method in a terminal, comprising: a step of transmitting a random access preamble based on a command via a downlink control channel, on the assumption that a random access response will be received; and a step of increasing the value of a power ramping counter for the random access preamble, based on the value of a random access preamble transmission counter and whether or not a candidate cell to which a user will transition due to terminal-initiated mobility control by a lower layer, and a synchronization signal block or a reference signal for channel state information estimation have changed since the previous random access preamble transmission.

5. A wireless communication system including a terminal and a radio base station, wherein the terminal comprises: a transmitter that transmits a random access preamble based on a command via a downlink control channel, assuming receipt of a random access response; and a controller that increases the value of a power ramping counter for the random access preamble, based on the value of a random access preamble transmission counter and whether a candidate cell to transition to through terminal-led mobility control by a lower layer, and a synchronization signal block or a reference signal for channel state information estimation have changed since the previous random access preamble transmission; and the radio base station comprises a receiver that receives the random access preamble.

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