Terminal device and radio communications system

Abstract

To allow a terminal device to autonomously perform L1L2 triggered mobility (LTM) before receiving a Cell Switch command, thereby speeding up handover processing and shortening interruption times.SOLUTION: A terminal device acquires, from a connected handover source base station device, first information associating a setting grant related to the resource of the uplink shared channel of a L1L2 triggered mobility (LTM) candidate cell with an uplink beam setting, and information on the condition for LTM implementation associated with the LTM candidate cell. Then, in response to an uplink reference signal transmission instruction, the terminal device transmits an uplink reference signal to a handover destination base station device of the LTM candidate cell, and acquires second information on the uplink beam to be used by the terminal device determined by the LTM candidate cell on the basis of the measurement result of the uplink reference signal. Furthermore, when the conditions for LTM implementation are satisfied, the terminal device identifies a setting grant to be used for uplink transmission from the first information and the second information when LTM is implemented, without starting a random access procedure, and uses the grant to perform uplink transmission to the handover destination candidate base station device.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a terminal device and a wireless communication system. [Background technology]

[0002] In a mobile communication system, as a terminal device moves, a handover is performed to switch the cell (base station device) to which the terminal device is connected. Conventionally, after receiving a handover instruction from the base station device, the terminal device performs a process of establishing a connection by performing a synchronization establishment and setting process in the cell to which the connection is to be switched. This process for switching the connection takes a certain amount of time, and the terminal device cannot communicate user data during the period in which this process is being performed. In contrast, in the method described in Non-Patent Document 1, the handover source base station device provides the terminal device with communication parameters in the radio resource control (RRC) layer for connection with another base station device at the handover destination before the handover is actually performed. Then, the handover source base station device transmits a layer 1 or layer 2 command to the terminal device to instruct the cell switching at the timing when the handover should be performed. In response to receiving the command, the terminal device executes a random access procedure with the handover destination base station device, thereby completing the handover without performing a setting process in the RRC layer thereafter. Such a cell switching technology is called LTM (L1L2 Triggered Mobility) and is intended to suppress deterioration of communication efficiency related to handover. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] 3GPP (registered trademark) Contribution, R2-2209255 Summary of the Invention [Problem to be solved by the invention]

[0004] In the handover process by LTM disclosed in Non-Patent Document 1, the terminal device needs to receive a Cell Switch command from the base station device. However, if the Cell Switch Command cannot be received, the terminal device cannot spontaneously start handover processing, and must execute cell search processing and reconnection processing after detecting RLF (Radio Link Failure). Therefore, the LTM technology of Non-Patent Document 1 has a problem that it cannot shorten the communication interruption time and cannot speed up the handover processing.

[0005] In view of such circumstances, the present disclosure proposes a technology that enables a terminal device to perform LTM before receiving a Cell Switch command, thereby speeding up handover processing and shortening the interruption time. [Means for solving the problem]

[0006] In order to solve the above problem, the present disclosure provides, as an example, a terminal device having a conditional LTM function and communicating with a plurality of base station devices while switching connection destinations, a storage device for storing a program relating to handover; a processor that reads the program from the storage device and executes a handover process; The processor, A process of acquiring, from a connected handover source base station device, first information associating a configuration grant related to an uplink shared channel resource of an LTM candidate cell with an uplink beam configuration, and information on conditions for implementing LTM associated with a handover destination base station device of the LTM candidate cell; A process of transmitting an uplink reference signal to a handover destination base station device of the LTM candidate cell in response to an uplink reference signal transmission instruction from the handover source base station device; A process of acquiring, from the handover source base station device, second information regarding an uplink beam to be used by the terminal device, which is determined by the handover destination base station device of the LTM candidate cell based on the measurement result of the uplink reference signal; A process of determining whether a condition for performing LTM associated with the handover destination candidate base station device is satisfied; When the condition for performing the LTM is satisfied, a process of identifying a configuration grant to be used for uplink transmission from the first information and the second information when performing the LTM without starting a random access procedure; a process of performing uplink transmission to the handover destination candidate base station device by using a configuration grant used for the uplink transmission; We propose a terminal device that executes the above.

[0007] Further features related to the present disclosure will become apparent from the description of the present specification and the accompanying drawings. Also, aspects of the present disclosure may be realized and realized by the elements and combinations of various elements and aspects of the following detailed description and the appended claims. The descriptions in this specification are exemplary and illustrative only and are not intended to limit the scope or application of the present disclosure in any way. Effect of the Invention

[0008] According to the technique disclosed herein, even if a terminal device cannot receive a Cell Switch command, it is possible to perform handover processing, thereby realizing faster processing and shorter interruption time. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating an example of a schematic configuration of a wireless communication system according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a diagram illustrating an example of a schematic configuration of a base station device 100 according to the present embodiment. [Diagram 3] FIG. 2 is a diagram illustrating an example of a schematic configuration of a terminal device 200 according to the present embodiment. [Figure 4]FIG. 2 is a diagram for explaining sequence example 1 of handover processing according to the present embodiment. [Diagram 5] FIG. 11 is a diagram for explaining a second sequence example of a handover process according to the present embodiment. [Figure 6] FIG. 11 is a diagram for explaining a third sequence example of a handover process according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] This embodiment discloses performing LTM (but not RACH) to a candidate cell before a terminal device receives a Cell Switch Command from a handover source base station device. The technology according to this embodiment is not limited to this, but can be applied to, for example, wireless communication in the frequency band FR2 (24.25 GHz to 52.6 GHz). Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the accompanying drawings, functionally identical elements may be indicated by the same numbers. Note that the accompanying drawings show specific embodiments according to the principles of the present disclosure, but these are for understanding the present disclosure and are by no means used to interpret the present disclosure in a limiting manner.

[0011] In the present embodiment, the description is given in sufficient detail for a person skilled in the art to implement the present disclosure, but it should be understood that other implementations and forms are possible, and that changes in configuration and structure and substitutions of various elements are possible without departing from the scope and spirit of the technical ideas of the present disclosure. Therefore, the following description should not be interpreted as being limited thereto.

[0012] <System overview example> FIG. 1 is a diagram showing a schematic configuration example of a wireless communication system according to the present embodiment. The wireless communication system is a cellular communication system configured according to a cellular communication standard such as the fifth generation (5G) of the 3rd Generation Partnership Project (3GPP (registered trademark)) and its successor standards. The wireless communication system includes a plurality of base station devices (base station devices 100_1, 100_2,...) and a terminal device 200.

[0013] In FIG. 1, the terminal device 200 is about to move from within the cell range formed by the base station device (handover source base station device) 100_1 to within the cell range formed by the base station device (handover destination base station device) 100_2. At this time, the terminal device 200 will perform a handover to switch the connected base station device from the handover source base station device 100_1 to the handover destination base station device 100_2. Although only the handover destination base station device 100_2 is shown as a handover destination candidate in FIG. 1, actually, there may be a plurality of handover destination candidates (handover destination base station devices 100_3, 100_4,..., 100_k,...).

[0014] <Regarding the conditions (events) for LTM implementation> In the LTM according to the present embodiment, the terminal device 200 starts connection processing and cell switching processing with the handover destination base station device 100_2 and other handover destination candidate base station devices (handover destination base station device 100_k: k=3, 4, . . . ) without receiving a command (Cell switch command) instructing cell switching from the handover source base station device 100_1. As an example, the terminal device 200 acquires, from the handover source base station device 100_1, information on a condition (event) for starting the cell switching processing and on a cell switching processing to be performed when the condition is determined to be met, and then determines whether the condition is met and performs the cell switching processing according to the condition. For example, it is assumed that the cell switching processing to the handover destination base station device 100_2 is associated with the condition 1, and the cell switching processing to another handover destination candidate base station device (handover destination base station device 100_3) is associated with the condition 2. In this case, when it is determined (confirmed) that condition 1 is met, the terminal device 200 executes a cell switching process to the base station device 100_2. On the other hand, when it is determined (confirmed) that condition 2 is met, the terminal device 200 starts a cell switching process to another handover destination candidate base station device (handover destination base station device 100_3). A plurality of pieces of information on the condition and the cell switching process are included in a message RRC Reconfiguration of an RRC (Radio Resource Control) layer, and a condition set for each candidate cell is included in condExecutionCond. In addition, a communication parameter used for communication with the handover destination candidate base station device is included in condLTMReconfig. These pieces of information are provided from the handover source base station device 100_1 to the terminal device 200.

[0015] <Specific examples of the above conditions (events)> As a condition (event) for performing LTM, for example, a condition related to the radio quality of a communicating cell or a candidate cell (CondEventA3, CondEventA4, CondEventA5, CondEventD1, CondEventT1) may be set. In this case, for example, RRC Reconfiguration includes information such as condExecutionCond=condEventA4 (threshold=threshold 1) and condLTMReconfig=communication parameters for candidate cell 1 for condReconfigId (condition setting identifier)=1, and condExecutionCond=condEventA4 (threshold=threshold 2) and condLTMReconfig=communication parameters for candidate cell 2 for condReconfigId=2, and this information is provided to the terminal device 200. Conventionally, it is considered that the base station device 100 sets information (MeasId) for setting a report of an event occurrence to the terminal device 200 in condExecutionCond. Here, MeasId is associated with an identifier measObjectId used by the terminal device to identify a measurement target of wireless quality and an identifier reportConfigId used by the terminal device to identify a report timing to the base station device. The identifier measObjectId is associated with an NR or LTE frequency to be measured by the terminal device 200. The identifier reportConfigId is associated with a report timing to the base station device 100, for example, an event of condEventA4 and a threshold value related to the event. In this way, the terminal device 200 can recognize an event of wireless quality to be determined from MeasId set in condExecutionCond.

[0016] <Internal configuration example of base station equipment> FIG. 2 is a diagram showing a schematic configuration example of the base station device 100. The base station device 100 includes, for example, a processor 101, a storage device 102, a ROM (Read Only Memory) 103, a RAM (Random Access Memory) 104, and a communication device 105. The processor 101 is a computer including one or more processing circuits such as a general-purpose CPU (Central Processing Unit) or an ASIC (Application Specific Integrated Circuit), and executes the overall processing of the device and each of the above-mentioned processes by reading and executing a program stored in the storage device 102 or the ROM 103. The ROM 103 is a read-only memory that stores information such as a program related to the processing executed by the base station device 100 and various parameters. The RAM 104 functions as a workspace when the processor 101 executes a program, and is a random access memory that stores temporary information. The storage device 102 is, for example, configured by a removable external storage device. The communication device 105 is, for example, configured by a circuit for wireless communication of 5G or its successor standard. Although one communication device 105 is shown in FIG. 2, the base station device 100 may include multiple communication devices. For example, the base station device 100 has wireless communication devices for 5G and its successor standards, and an antenna common to these devices. The base station device 100 may have separate antennas suitable for each standard. The base station device 100 may also have a wired communication device used when communicating with other base station devices or nodes of the core network. The base station device 100 may have separate communication devices 105 for each of a plurality of available frequency bands, or may have a common communication device 105 for at least some of these frequency bands.

[0017] The processor 101 reads programs related to handover stored in the memory device 102 or the ROM 103 and expands them into internal memory (not shown), thereby generating an RRC setting unit 1011, an RA instruction unit 1012, a handover instruction unit 1013, an inter-base station communication unit 1014, a TA maintenance management unit 1015, a PUCCH / PDCCH communication unit 1016, and an uplink beam information determination unit 1017.

[0018] FIG. 2 shows only functions particularly related to this embodiment, and various other functions that the base station device 100 may have are omitted. For example, the base station device 100 naturally has other functions that a base station device conforming to 5G or its successor standards generally has. Furthermore, the functional blocks in FIG. 2 are shown in a schematic manner, and each functional block may be integrated and realized, or may be further subdivided. In addition, each function in FIG. 2 may be realized, for example, by the processor 101 executing a program stored in the ROM 103 or the storage device 102, or may be realized, for example, by a processor present in the communication device 105 executing a predetermined software. Note that the details of the processing performed by each functional unit will not be described here in detail, and only the rough functions will be outlined. In addition, the following describes an overview of the operation in a system consisting of a handover source base station device 100_1, one handover destination base station device 100_2 which is an LTM transition destination candidate, and a terminal device 200. However, when there are multiple LTM transition destination candidates, the handover source base station device 100_1 and the terminal device 200 perform similar operations between each candidate handover destination base station device 100_k.

[0019] The RRC setting unit 1011 of the handover source base station device 100_1 performs, for example, RRC layer setting for the connected terminal device 200. The RRC setting unit 1011 transmits a handover request to other candidate base station devices 100 (such as the handover destination base station device 100_2 and the handover destination base station device 100_3) that provide neighboring cells, acquires communication setting information (communication parameters) therefrom, and notifies the terminal device 200 of the communication setting information and the above-mentioned LTM implementation condition (communication parameters of each candidate cell and LTM implementation condition) by a message of the RRC layer. In this case, the above-mentioned communication setting information (communication parameters) also includes information required when the terminal device 200 executes a random access procedure (such as a sequence for generating an RA preamble and information on radio resources used for transmitting an RA preamble). In this embodiment, the message of the RRC layer is an RRC Configuration message. Then, the RRC setup section 1011 receives an RRC Configuration Complete message from the terminal device 200, and thereby performs connection processing setup between the terminal device 200 and another base station device 100 (handover destination base station device 100_2).

[0020] The RA instruction unit 1012 instructs the terminal device 200 for which the RRC layer setting has been completed to transmit an RA preamble to another base station device 100 (handover destination base station device 100_2) that is a candidate for the handover destination. Here, the instruction to transmit the RA preamble includes a sequence for generating an RA preamble that is unique to the terminal device 200 and a group of sequences that can also be used by other terminal devices 200 that are attempting to connect to the other base station devices 100, and also includes information on radio resources used for transmitting the RA preamble. For example, the RA instruction unit 1012 can instruct the currently connected terminal device 200 to transmit an RA preamble to the handover destination (candidate) base station device 100_2 by a physical downlink control channel (PDCCH) order. In addition, the RA instruction unit 1012 can instruct the terminal device 200 to retransmit the RA preamble as necessary, or, when configured to repeatedly transmit the RA preamble, transmit an instruction to stop transmitting the RA preamble to the terminal device 200.

[0021] The handover instruction unit 1013 of the handover source base station device 100_1 instructs the terminal device 200 to execute handover. The handover instruction unit 1013 of the handover source base station device 100_1 notifies (transfers) the TA value acquired from the handover destination base station device 100_2 (acquired by an inter-base station communication unit 1014 as described later) to the terminal device 200 before transmitting a Cell Switch Command.

[0022] Moreover, the handover instruction unit 1013 of the handover source base station device 100_1 measures a sounding reference signal (SRS) directly transmitted from the terminal device 200 by the handover destination base station device 100_2, and notifies the terminal device 200 of a TCI (Transmission Configuration Indicator) designated based on the measurement result. Here, the TCI is information designating an uplink beam (UL Beam) to be used by the terminal device 200.

[0023] Furthermore, the handover instruction unit 1013 of the handover source base station device 100_1 transmits to the terminal device 200, for example, a Cell switch command including information such as a cell identifier capable of identifying the handover destination base station device 100_2.

[0024] The inter-base station communication unit 1014 of the base station device 100_1 communicates (for example, communication via a dedicated wired line) with each handover destination candidate base station device (handover destination base station device 100_2, 100_3, etc.). The inter-base station communication unit 1014 can, for example, notify the handover destination base station device 100_2, which is the transmission destination of the RA preamble, to cause the connected terminal device 200 to transmit the RA preamble. The inter-base station communication unit 1014 is also used, for example, to receive information for the RA procedure in the handover destination candidate base station device (handover destination base station device 100_2). The inter-base station communication unit 1014 can also receive, for example, a message (message 2 or message 4) to be transmitted from the handover destination base station device 100_2 to the terminal device 200 in the RA procedure. Furthermore, the handover source base station 100_1 can acquire the TA value calculated in the handover destination base station device 100_2 via the inter-base station communication unit 1014. Note that the signal received in the inter-base station communication unit 1014 is transferred to the terminal device 200 via, for example, the RA instruction unit 1012. In addition, the inter-base station communication unit 1014 of the handover source base station device 100_1 acquires uplink beam (UL Beam) information (described later) to be used by the terminal device 200, which is notified from the handover destination base station device 100_2.

[0025] The TA maintenance management unit 1015 of the handover source base station 100_1 manages a TA value to be used when the terminal device 200 transmits an uplink signal to the handover destination base station device 100_2. The TA maintenance management unit 1015 can, for example, set an expiration date or an update period of the TA value, and instruct the terminal device 200 to retransmit an RA preamble so that the TA value is updated when the expiration date expires or the update period arrives. The TA maintenance management unit 1015 can also notify the terminal device 200 of an SRS setting in the handover destination base station device 100_2, and update the TA value by having the terminal device 200 transmit an SRS using the SRS setting. The terminal device 200 can acquire the TA value via the TA maintenance management unit 1015 of the handover destination base station device 100_2. In this case, the base station device 100_2 can transmit an instruction to transmit an RA preamble or an instruction to transmit an SRS to the terminal device 200.

[0026] The PUCCH / PDCCH communication unit 1016 operates, for example, when the base station device 100 becomes the handover destination base station device 100_2. As described above, the handover destination base station device 100_2 can start receiving the PUCCH and transmitting the PDCCH between the handover destination base station device 100_2 and the terminal device 200 when notifying the handover source base station device 100_1 of the TA value.

[0027] For example, when the base station device 100 becomes the handover destination base station device 100_2, the uplink beam information determination unit 1017 measures the uplink reference signal (SRS) transmitted by the terminal device 200, and based on the measurement result, identifies the uplink beam (UL beam) information that the terminal device 200 should use.

[0028] Also, for example, when the base station device 100 becomes the handover destination base station device 100_2, the uplink beam information determination unit 1017 may acquire the measurement result of the downlink reference signal from the handover destination base station device 100_2 measured by the terminal device 200 from the handover source base station device 100_1, and identify the beam (UL Beam) information that the terminal device 200 should use based on the measurement result.

[0029] <Example of the internal configuration of a terminal device> FIG. 3 is a diagram showing a schematic configuration example of the terminal device 200. The terminal device 200 includes, for example, a processor 201, a storage device 202, a ROM (Read Only Memory) 203, a RAM (Random Access Memory) 204, a communication device 205, an input device 206, and an output device 207. The processor 201 is a computer including one or more processing circuits such as a general-purpose CPU (Central Processing Unit) or an ASIC (Application Specific Integrated Circuit), and executes the overall processing of the device and each of the above-mentioned processes by reading and executing a program stored in the storage device 202 or the ROM 203. The ROM 203 is a read-only memory that stores information such as programs and various parameters related to the processing executed by the terminal device 200. The RAM 204 functions as a workspace when the processor 201 executes a program, and is a random access memory that stores temporary information. The storage device 202 is, for example, configured by a removable external storage device. The communication device 205 is configured by, for example, a circuit for wireless communication of 5G or a successor standard. Although one communication device 205 is shown in FIG. 3, the terminal device 200 may include a plurality of communication devices. For example, the terminal device 200 has a wireless communication device for each of 5G and its successor standard, and an antenna common to those devices. The terminal device 200 may also have a communication device conforming to a wireless communication standard other than the cellular communication standard, such as a wireless local area network (LAN) or Bluetooth (registered trademark). Furthermore, the terminal device 200 may have a separate antenna suitable for each standard. The terminal device 200 may also have a separate communication device 105 for each of a plurality of available frequency bands, or may have a common communication device 205 for at least a part of those frequency bands.

[0030] The input device 206 can be configured, for example, by a touch panel or a numeric keypad, and is used when a user performs a predetermined operation or inputs desired information. The output device 207 can be configured, for example, by a display device, and in relation to this embodiment, displays information indicating the communication status, information indicating the success or failure of handover, and the like.

[0031] The processor 201 reads a program related to handover stored in the storage device 202 or the ROM 203, and develops it in an internal memory (not shown), thereby generating an RRC setting unit 2011, an RA (random access) execution unit 2012, an LTM implementation condition determination unit 2015, a handover processing unit 2013, a timer control unit 2016, and a reference signal measurement and notification unit 2014. Note that FIG. 3 shows only functions particularly related to this embodiment, and other various functions that the terminal device 200 may have are omitted from the illustration. For example, the terminal device 200 naturally has other functions that terminal devices conforming to 5G and its successor standards generally have. Also, the functional blocks in FIG. 3 are shown in a schematic manner, and each functional block may be realized as an integrated unit, or may be further subdivided.

[0032] The RRC setup unit 2011 performs a connection setup process with the handover destination (candidate) base station device 100_2 by receiving an RRC layer message from the connected handover source base station device 100_1. The RRC setup unit 2011 holds the setting of the connected handover source base station device 100_1 and the settings of a plurality of handover destination candidate base station devices (handover destination base station devices 100_k: k=2, 3, 4, . . . , n) in parallel.

[0033] The RA executor 2012 receives an instruction to transmit an RA preamble from the handover source base station device 100_1. The instruction to transmit the RA preamble is performed in the PDCCH order. The RA executor 2012 can also receive, for example, an instruction to retransmit the RA preamble or an instruction to stop transmitting the RA preamble. In response to receiving the instruction to transmit the RA preamble, the RA executor 2012 transmits the RA preamble to the handover destination (candidate 1) base station device 100_2. Here, a sequence for generating the RA preamble and information on radio resources for receiving the RA preamble in the handover destination base station device (candidate 1) 100_2 are acquired from the currently connected handover source base station device 100_1. The information on the sequence and radio resources may be acquired from system information transmitted by the handover destination base station device 100_2.

[0034] When the handover processing unit 2013 acquires a TA value and an SRS transmission instruction of the handover destination base station device 100_2 from the handover source base station device 100_1 (for example, by MAC CE, downlink control information (DCI), or RAR), it transmits the SRS directly to the handover destination (candidate 1) base station device 100_2. As described above, the handover destination base station device 100_2 measures the SRS, determines a TCI (Transmission Configuration Indicator) based on the measurement result, and notifies the handover source base station device 100_1 of the TCI. Furthermore, the handover processing unit 2013 receives TCI (beam information) from the handover source base station device 100_1 by using the MAC CE or the physical downlink control channel (PDCCH) / downlink control information (DCI). The beam information is information that identifies the TCI state and spatial relationship (information that indicates the relationship between the UL beam and the DL beam, and is used when the TCI state is not supported).

[0035] Moreover, in response to receiving a Cell Switch command from the currently connected handover source base station device 100_1, the handover processing unit 2013 changes the connection destination to the handover destination base station device 100_2. When the allocation of uplink radio resources in the handover destination base station device 100_2 is notified in the received Cell Switch command, the terminal device 200 can immediately transmit an uplink signal by using the radio resources.

[0036] The reference signal measurement / notification unit 2014 measures a downlink reference signal from the handover destination base station device 100_2 (one of the LTM transfer target candidate cells) and notifies the handover source base station device 100_1 of the measurement result. When there are multiple LTM transfer target candidate cells, the reference signal measurement / notification unit 2014 measures downlink reference signals from all corresponding handover destination base station devices 100_k and notifies the handover source base station device 100_1 of each measurement result.

[0037] Meanwhile, the LTM execution condition determination unit 2015 determines whether the conditions for performing LTM associated with the multiple candidate cells notified from the handover source base station device 100_1 are satisfied. A handover destination to be performed is uniquely determined by the condition match. For example, the conditions for performing LTM are determined such that a threshold included in the communication parameters is set low for a candidate cell with a good (not congested) communication situation, and a threshold is set high for a candidate cell with a bad (congested) communication situation.

[0038] When the LTM execution condition determination unit 2015 determines (confirms) that the conditions for LTM execution are met, the handover processing unit 2013 performs a handover process that does not include RA execution processing on the candidate cell (handover destination base station device 100_k) that satisfies the conditions (details will be described later). For example, when it is determined that the conditions for LTM execution associated with the handover destination base station device 100_2 of candidate 1 are satisfied, the handover processing unit 2013 can spontaneously execute the handover process in the same manner as when the Cell Switch Command is received, even when the Cell Switch Command cannot be received. Therefore, it is not necessary to execute the reconnection process starting from cell search, and cell switching can be performed quickly.

[0039] When the LTM execution condition determination unit 2015 determines that the communication status matches the above-described LTM execution conditions, the handover processing unit 2013 specifies a set grant for uplink transmission according to the information of the acquired uplink beam at the timing based on the TA value, and uses the resources (PUSCH) of the uplink shared channel corresponding to the set grant to transmit uplink data, for example, RRCReconfiguration Complete, to the handover destination base station device 100_2. Then, the handover processing unit 2013 receives the UE Contention Resolution Identity MAC CE or C-RNTI addressed PDCCH from the handover destination base station device 100_2.

[0040] The timer control unit 2016 controls the start and stop of various timers (such as T304). For example, the timer (T304) starts when it is confirmed that the conditions for LTM execution are met and LTM execution is determined, and stops when the UE Contention Resolution Identity MAC CE or C-RNTI addressed PDCCH is received from the connected base station device 100.

[0041] <Operation at RLF detection> As described above, when the terminal device 200 determines (confirms) that the conditions for performing LTM specified by the handover source base station device 100_1 are met, the terminal device 200 starts the cell switching process. On the other hand, when the terminal device 200 detects an RLF (radio link failure), the terminal device 200 may start the cell switching process even if the conditions are not met.

[0042] When providing the terminal device 200 with the condition for performing LTM and information (communication parameters) related to the cell switching process associated with the condition for each candidate cell, the handover source base station device 100_1 also provides information of attemptCondReconfig=True / False. When detecting RLF (radio link failure), the terminal device 200 searches for and selects a cell to be used for communication. When attemptCondReconfig notified together with the information related to the cell switching process is True, the terminal device 200 determines whether the cell selected after the search is a candidate base station device (handover destination base station device 100_k) of the handover destination specified in the cell switching process. When it is determined that the cell is not the handover destination base station device specified in the cell switching process, the terminal device 200 performs reconnection processing as in the past. When the cell is the handover destination base station device specified in the cell switching process (any of the notified candidate cells), the terminal device 200 starts the cell switching process even if the condition is not met. This makes it possible to shorten the instantaneous interruption time. Even in this case, if the cell selected after the search is a base station device of a handover destination candidate designated in the cell switching process, that is, an LTM candidate cell, a configuration grant (uplink resource and uplink beam information) corresponding to the selected downlink reference signal can be specified based on the radio quality of the downlink reference signal (SSB or CSI-RS) of the LTM candidate cell and a UL Beam information table described later, and can be used for uplink transmission when performing LTM. Also, if uplink beam information regarding the selected cell is received before RLF detection, it is possible to specify a configuration grant to be used for uplink transmission from the information of the uplink beam received from the base station device, rather than the radio quality of the downlink reference signal (SSB or CSI-RS) of the LTM candidate cell, and use it for uplink transmission when performing LTM.

[0043] <Handover processing sequence example 1> FIG. 4 is a diagram for explaining sequence example 1 of the handover process according to the present embodiment. The sequence shown in FIG. 4 is an example, and each procedure can be modified as described above. For example, FIG. 4 shows an example in which a unique sequence is notified to the terminal device 200 as a sequence for generating an RA preamble to be transmitted to the handover destination base station device 100_2, but may be replaced with the above-mentioned procedure in which a group of sequences available to the multiple terminal devices 200 is notified. Note that in the example of FIG. 4, it is assumed that a connection is established between the handover source base station device 100_1 and the terminal device 200. Also, in FIG. 4, only the handover destination base station device 100_2 is shown as a base station device of an LTM transfer destination candidate cell, but in reality, there are multiple handover destination base station devices 100_k of LTM transfer destination candidate cells.

[0044] In each step, the operation is performed by each processing unit (such as the RRC setting unit 1011), but since each processing unit is a function realized by the processor 101 or 201 of the base station device 100 or the terminal device 200, the processor 101 or 201 may be the operating unit. In the following description, the processing units of the handover source base station device 100_1 are denoted as an RRC setting unit 1011_1, an RA instruction unit 1012_1, a handover instruction unit 1013_1, an inter-base station communication unit 1014_1, a TA maintenance management unit 1015_1, and a PUCCH / PDCCH communication unit 1016_1. Moreover, the respective processing units of the handover destination base station device 100_2 are denoted as an RRC setting unit 1011_2, an RA instruction unit 1012_2, a handover instruction unit 1013_2, an inter-base station communication unit 1014_2, a TA maintenance management unit 1015_2, and a PUCCH / PDCCH communication unit 1016_2. Furthermore, in each of the following steps, various communications are actually performed by the respective processing units of the base station device and the terminal device controlling the communication device 105 and the communication device 205.

[0045] (i) Step S401 The inter-base station communication unit 1014_1 of the handover source base station device 100_1 transmits a HANDOVER REQUEST message to the inter-base station communication unit 1014_2 of the handover destination base station device 100_2 that forms an adjacent cell and is a candidate for the handover destination of the terminal device 200, or to other base station devices (other candidate cells: the inter-base station communication unit 1014_k of the handover destination base station device 100_k (k=3, 4, ...)).

[0046] (ii) Step S402 When the inter-base station communication unit 1014_2 of the handover destination (candidate 1) base station device 100_2 receives the HANDOVER REQUEST message, it returns a HANDOVER REQUEST ACK message including information on communication parameters to be used when the terminal device 200 connects to the handover source base station device 100_1. The communication parameters include CG (Configured Grant) setting information including information on beam settings, parameters for executing a RA (Random Access) procedure, radio resources (frequency and time resources) to be used, etc. in the handover destination base station device 100_2. Other candidate cell base station devices similarly provide communication parameters to the handover source base station device 100_1.

[0047] (iii) Step S403 The RRC setting unit 1011_1 of the handover source base station device 100_1 notifies the terminal device 200 of an LTM Configuration message including the above-mentioned communication parameters acquired from the handover destination base station device 100_2. At this time, the RRC setting unit 1011_1 provides the terminal device 200 with a condition (event: condition for implementing LTM) enabling implementation of LTM before the terminal device 200 receives a Cell Switch Command. With this process, the terminal device 200 does not need to perform an RRC layer configuration process after being instructed by the RA instruction unit 1012_1 to perform a handover to the handover destination base station device 100_2. When there are multiple handover destination (candidate) base station devices, a similar configuration process is performed for each of them.

[0048] The RRC setting unit 2011 of the terminal device 200 receives, via the LTM Configuration included in the RRC Reconfiguration message, information on the synchronization signal (SS) / physical broadcast channel (PBCH) block (SSB: Synchronization Signal Block) (information on the downlink reference signal: for example, SSB index) transmitted from the base station device of each LTM transition target candidate cell (for example, the handover destination base station device 100_2), information (UL Beam information table) correlating CG (Configured grant) setting information (CG occasion) related to uplink resources, and uplink beam information (TCI).

[0049] For example, when the terminal device 200 receives TCI=1 from the handover destination base station device 100_2 via the handover base station device 100_1, the terminal device 200 uses the uplink resource and uplink beam information (configuration grant) corresponding to the associated SSB index=1 and the first CG configuration information (CG Occasion), and when TCI=2, the terminal device 200 uses the uplink resource and uplink beam information (configuration grant) corresponding to the SSB index=2 and the second CG configuration information to perform uplink transmission to the handover destination base station device 100_2 after performing LTM. Note that multiple TCIs may be associated with one CG configuration information. In this case, for example, when TCI=1 or TCI=2 is received, it is possible to instruct the terminal device 200 to use the uplink resource and uplink beam information (configuration grant) corresponding to the associated SSB index=1 and the first CG configuration information (CG Occasion), and to use the uplink resource and uplink beam information (configuration grant) corresponding to TCI=3 or TCI=4SSB index=2 and the second CG configuration information. This makes it possible to reduce the CG configuration information (CG Occasion) set in the terminal device 200, and to save the uplink radio resources allocated to each terminal device when the congestion level is high, etc.

[0050] (iv) Step S404 The RA instruction unit 1012_1 of the handover source base station device 100_1 transmits a PDCCH order to the terminal device 200, and instructs the terminal device 200 to transmit an RA preamble to the handover destination base station device 100_2 (when there are a plurality of candidate cells, a base station device of any appropriate candidate cell is specified). Here, this instruction (PDCCH order) can include information specifying a sequence to be used by the terminal device 200 to generate an RA preamble and a radio resource from which the RA preamble is to be transmitted. Note that the radio resource from which the RA preamble is to be transmitted may be specified based on system information in the handover destination base station device 100_2 transmitted from the handover destination base station device 100_2 and measured by the terminal device 200, for example. That is, this information does not need to be acquired from the connected handover source base station device 100_1. Also, a sequence to be used when generating an RA preamble may be specified in advance. In one example, information on this sequence may be notified to the terminal device 200 in step S403.

[0051] (v) Step S405 The RA execution unit 2012 of the terminal device 200 transmits an RA preamble to the handover destination base station device 100_2 in accordance with the instruction. The purpose of executing the RA procedure is to suppress deterioration of communication efficiency during handover. When the RA preamble is transmitted, the inter-base station communication unit 1014_1 of the handover source base station device 100_1 may notify the handover destination base station device 100_2 that the terminal device 200 plans to transmit an RA preamble. At this time, the inter-base station communication unit 1014_1 of the handover source base station device 100_1 can notify the handover destination base station device 100_2 of information on a sequence used by the terminal device 200 to generate an RA preamble. This allows the RA instruction unit 1012_2 of the handover destination base station device 100_2 to detect the RA preamble transmitted by the terminal device 200. Note that this process is an example, and the HANDOVER REQUEST in step S401 may implicitly notify that the terminal device 200 plans to transmit an RA preamble. In this case, the handover destination base station device 100_2 may specify a sequence to be used by the terminal device 200 to generate an RA preamble in the HANDOVER REQUEST ACK in step S402. Note that these are only examples, and information on a sequence to be used by the terminal device 200 to generate an RA preamble may be shared between the handover source base station device 100_1 and the handover destination base station device 100_2 by other messages.

[0052] (vi) Step S406 The TA maintenance management unit 1015_2 of the handover destination base station device 100_2 calculates a TA value based on the RA preamble transmitted from the terminal device 200. Then, the inter-base station communication unit 1014_2 notifies the handover source base station device 100_1 of the calculated TA value. Note that this TA value may be managed by both the handover source base station device 100_1 and the handover destination base station device 100_2, or may be managed by one of them. This TA value may be acquired from the handover destination base station device 100_2, for example, in response to the handover source base station device 100_1 deciding to execute handover of the terminal device 200. For example, the inter-base station communication unit 1014_1 of the handover source base station device 100_1 notifies the handover destination base station device 100_2 of the execution of handover. In response to the notification, the TA maintenance management unit 1015_1 acquires the TA value from the handover destination base station device 100_2. In addition, when there are a plurality of handover destination (candidate) base station devices (handover destination base station devices 100_2 to 100_k), the handover source base station device 100_1 may obtain the TA values ​​from all the handover destination (candidate) base station devices.

[0053] At this time point, the terminal device 200 has not yet started handover to the handover destination base station device 100_2. In this state, the handover processing unit 2013 of the terminal device 200 continuously performs measurement (e.g., SSB measurement) of a radio signal from the handover destination base station device 100_2 and notifies the connected handover source base station device 100_1 of the measurement result. The handover instruction unit 1013 of the handover source base station device 100_1 can decide to perform handover according to the measurement result.

[0054] (vii) Step S407 The handover instruction unit 1013_1 of the handover source base station device 100_1 notifies the terminal device 200 of the TA value acquired from the handover destination base station device 100_2, and transmits an uplink reference signal (SRS) transmission instruction. When there are a plurality of handover destination (candidate) base station devices (handover destination base station devices 100_2 to 100_k), the handover source base station device 100_1 notifies the terminal device 200 of the TA values ​​of all the handover destination (candidate) base station devices. The notification of the TA value and the uplink reference signal (SRS) transmission instruction can also be notified to the terminal device 200 at different timings.

[0055] (viii) Step S408 The handover processing unit 2013 of the terminal device 200 transmits a reverse link reference signal (SRS) to the handover destination base station device 100_2. The uplink beam information determination unit 1017_2 of the handover destination base station device 100_2 measures the SRS transmitted by the terminal device 200 to determine (identify) the uplink beam (UL beam) to be used when the terminal device 200 communicates with the handover destination base station device 100_2.

[0056] (ix) Step S409 An uplink beam information determination unit 1017_2 of the handover destination base station device 100_2 specifies uplink beam information to be used in the terminal device 200 by a Transmission Configuration Indicator (TCI). Then, an inter-base station communication unit 1014_2 of the handover destination base station device 100_2 provides the TCI to the handover source base station device 100_1.

[0057] (x) Step S410 The handover instruction unit 1013 of the handover source base station device 100_1 notifies the terminal device 200 of the TCI acquired from the handover destination base station device 100_2 by using, for example, a medium access control element (MAC CE) or downlink control information (DCI).

[0058] (xi) Step S411 The handover instruction unit 1013_1 of the handover source base station device 100_1 transmits a Cell Switch Command to the terminal device 200. The Cell Switch Command can be transmitted by using, for example, a medium access control element (MAC CE) or downlink control information (DCI).

[0059] When the handover processing unit 2013 of the terminal device 200 can receive the Cell Switch Command, the handover destination base station device 100_2 allocates resources for PUSCH, and the handover is completed. Then, the terminal device 200 becomes able to transmit user data to the handover destination base station device 100_2 by using the allocated resources for PUSCH. Note that the terminal device 200 has already executed the RA procedure as described above. Therefore, when the terminal device 200 can receive the Cell Switch Command, it is not necessary to execute the RA procedure again, and the terminal device 200 can immediately transmit user data to the handover destination base station device 100_2 by using the designated radio resources.

[0060] Also, when the Cell Switch Command is received, the handover processing unit 2013 of the terminal device 200 may transmit an acknowledgement (Ack) or the like to the handover source base station device 100_1. Furthermore, when the Cell Switch Command is received, the handover processing unit 2013 may switch the connection destination to the handover destination base station device 100_2 and transmit an Ack, an RRCReconfigurationComplete, or the like to the handover destination base station device 100_2 by using the allocated uplink radio resource. Then, the inter-base station communication unit 1014 of the handover destination base station device 100_2 can transfer the acknowledgement to the handover source base station device 100_1. Thereby, the handover source base station device 100_1 can recognize that the terminal device 200 has switched the connection destination to the handover destination base station device 100_2, and can discard, for example, the context information of the terminal device 200.

[0061] On the other hand, when the handover instruction unit 1013_1 of the handover source base station device 100_1 does not receive the Ack from the terminal device 200, the handover instruction unit 1013_1 may retransmit the Cell Switch Command to ensure that the handover is performed reliably.

[0062] (xii) Step S412 The LTM implementation condition determination unit 2015 of the terminal device 200 determines (confirms) whether the above-mentioned LTM implementation conditions are met (satisfied). Specifically, the LTM implementation condition determination unit 2015 determines whether the LTM implementation conditions corresponding to each LTM transfer target candidate cell notified from the handover source base station device 100_1 are satisfied.

[0063] (xiii) Step S413 When the LTM execution condition determination unit 2015 of the terminal device 200 confirms that the conditions for performing LTM are met, the handover processing unit 2013 decides to execute cell switching processing to the handover destination base station device 100_k of the candidate cell corresponding to the condition match. Note that, when there are multiple candidate cells that meet the conditions for performing LTM, for example, the candidate cell with the shortest distance between the terminal device 200 and each handover destination base station device 100_k may be selected as the switching destination, or the candidate cell with the lowest congestion degree may be selected as the switching destination.

[0064] (xiv) Step S414 When it is confirmed that the conditions for implementing LTM are met, the timer control unit 2016 of the terminal device 200 starts a timer (T304).

[0065] (xv) Step S415 The handover processing unit 2013 of the terminal device 200 identifies the uplink beam (UL beam) specified by the TCI and the configuration grant to be used for uplink transmission from the UL beam information table at a timing based on the TA value, and transmits uplink data, for example, RRCReconfiguration Complete, to the handover destination base station device 100_2 using the uplink beam (UL beam) specified by the TCI using the uplink shared channel resource (PUSCH) according to the identified configuration grant.

[0066] (xvi) Step S416 The handover destination base station device 100_2 which has received the RRCReconfigurationComplete transmits a UE Contention Resolution Identity MAC CE or a C-RNTI addressing PDCCH to the terminal device 200 using the PUCCH / PDCCH communication unit 1016_2.

[0067] (xvii) Step S417 When the UE Contention Resolution Identity MAC CE or C-RNTI addressing PDCCH is received, the timer control unit 2016 of the terminal device 200 stops the timer (T304) started in step S414.

[0068] After the cell switching, the terminal device 200 may hold information condLTMReconfig related to the cell switching process that was not executed. By holding the information related to the cell switching process that was not executed by the terminal device 200 even after the cell switching, it is possible to eliminate the need to newly receive condLTMReconfig from the base station device after the cell switching. Also, information related to whether or not to hold information condLTMReconfig related to the cell switching process that was not executed may be notified to the terminal device 200 from the handover source base station device 100_1 before the cell switching.

[0069] In this manner, it is possible to shorten the period (instantaneous interruption time) during which user data communication is not possible when the terminal device 200 is handed over from the handover source base station device 100_1 to the handover destination base station device 100_2. Furthermore, since it is not necessary to transmit an RA preamble again to the handover destination base station device 100_2 when performing LTM, and uplink data can be transmitted using the TA value, the designated uplink beam, and the configuration grant, it is possible to speed up processing compared to the case of transmitting an RA preamble. This makes it possible to provide, for example, communication services that require low delay and high reliability. Furthermore, by shortening the period (instantaneous interruption time) during which user data communication is not possible, it is possible to suppress a decrease in efficiency of wireless communication.

[0070] <Handover processing sequence example 2> Fig. 5 is a diagram for explaining sequence example 2 of handover processing according to the present embodiment. In sequence example 2 of Fig. 5 as well, it is assumed that a connection is established between the handover source base station device 100_1 and the terminal device 200. Also in sequence example 2 of Fig. 5 as well, as in Fig. 4, only the handover destination base station device 100_2 is shown as the base station device of the LTM transfer destination candidate cell, but actually there are a plurality of handover destination base station devices 100_k of the LTM transfer destination candidate cells. In sequence example 2 of FIG. 5, steps S407 and S409 have been partially changed from sequence example 1 of FIG. 4 to steps S407' and S409', and step S408 has been changed to steps S408-1 and S408-2. However, since the other steps are the same as those in sequence example 1 of FIG. 4, their explanations are omitted.

[0071] (i) Step S407' The handover instruction unit 1013_1 of the handover source base station device 100_1 notifies the terminal device 200 of the TA value acquired from the handover destination base station device 100_2, and transmits a downlink reference signal (e.g., SSB or CSI-RS) measurement result transmission instruction (no uplink reference signal (SRS) transmission instruction is sent). When there are a plurality of handover destination (candidate) base station devices (handover destination base station devices 100_2 to 100_k), the handover source base station device 100_1 notifies the terminal device 200 of the TA values ​​of all the handover destination (candidate) base station devices.

[0072] (ii) Step S408-1 The base station device 100_k of each LTM transfer target candidate cell always outputs a downlink reference signal (for example, SSB or CSI-RS) at a constant period. The handover processing unit 2013 of the terminal device 200 measures each downlink reference signal (SRS) and transmits the measurement result to the handover source base station device 100_1.

[0073] (iii) Step S408-2 The inter-base station communication unit 1014_1 of the handover source base station device 100_1 transmits a downlink reference signal (SSB or CSI-RS) measurement result acquired from the terminal device 200 to the handover destination base station device 100_2.

[0074] The uplink beam information determination unit 1017_2 of the handover destination base station device 100_2 determines (identifies) the uplink beam (UL beam) to be used when the terminal device 200 communicates with the handover destination base station device 100_2 based on the downlink reference signal measurement result by the terminal device 200 (downlink beam information and uplink beam information are paired (due to duality), and if the downlink beam can be identified, the uplink beam can be identified).

[0075] <Handover processing sequence example 3> Fig. 6 is a diagram for explaining sequence example 3 of handover processing according to the present embodiment. In the example of Fig. 6, similarly to Fig. 4, it is assumed that a connection is established between the handover source base station device 100_1 and the terminal device 200. Also in Fig. 6, only the handover destination base station device 100_2 is shown as the base station device of the LTM transfer destination candidate cell, but actually there are a plurality of handover destination base station devices 100_k of the LTM transfer destination candidate cells.

[0076] (i) Steps S601 to S606 The processes from step S601 to step S606 are the same as those from step S401 to step S406 in FIG.

[0077] (ii) Step S607 The handover instruction unit 1013_1 of the handover source base station device 100_1 notifies the terminal device 200 of the TA value acquired from the handover destination base station device 100_2 (unlike step S407, an uplink reference signal (SRS) transmission instruction is not transmitted). When there are a plurality of handover destination (candidate) base station devices (handover destination base station devices 100_2 to 100_k), the handover source base station device 100_1 notifies the terminal device 200 of the TA values ​​of all the handover destination (candidate) base station devices.

[0078] (iii) Step S608 The handover instruction unit 1013_1 of the handover source base station device 100_1 transmits a Cell Switch Command to the terminal device 200. The Cell Switch Command can be transmitted by using, for example, a medium access control element (MAC CE) or downlink control information (DCI).

[0079] (iv) Step S609 The process in step S609 is the same as step S412 in FIG.

[0080] (v) Step S610 The reference signal measurement and notification unit 2014 of the terminal device 200 detects and measures downlink reference signals (SSB or CSI-RS) output from each handover destination base station device 100_k, and selects the reference signal with the best communication quality or the reference signal found first (signal with a predetermined quality (threshold) or higher). Then, based on the information (UL Beam information table) acquired in the above LTM Configuration, the reference signal measurement and notification unit 2014 determines a configuration grant (uplink resource and uplink beam information) corresponding to the index of the selected downlink reference signal (SSB).

[0081] (vi) Step S611 When the reference signal measurement and notification unit 2014 of the terminal device 200 determines the configuration grant, the handover processing unit 2013 determines to execute cell switching processing to the handover destination base station device 100_k of the candidate cell corresponding to the condition match. Note that, when there are multiple candidate cells that match the condition for performing LTM, for example, the candidate cell with the shortest distance between the terminal device 200 and each handover destination base station device 100_k may be selected as the switching destination, or the candidate cell with the lowest congestion degree may be selected as the switching destination.

[0082] (xii) Steps S612 to S615 The processes from step S612 to step S615 are the same as those from step S414 to step S417 in FIG.

[0083] <Summary of the embodiment> (i) A terminal device according to the first embodiment A terminal device having a conditional LTM function and communicating with a plurality of base station devices while switching connection destinations, a storage device for storing a program relating to handover; a processor that reads the program from the storage device and executes a handover process; The processor, A process of acquiring, from a connected handover source base station device, first information associating a configuration grant related to an uplink shared channel resource of an LTM candidate cell with an uplink beam configuration, and information on conditions for implementing LTM associated with a handover destination base station device of the LTM candidate cell; A process of transmitting an uplink reference signal to a handover destination base station device of the LTM candidate cell in response to an uplink reference signal transmission instruction from the handover source base station device; A process of acquiring, from the handover source base station device, second information regarding an uplink beam to be used by the terminal device, which is determined by the handover destination base station device of the LTM candidate cell based on the measurement result of the uplink reference signal; A process of determining whether a condition for performing LTM associated with the handover destination candidate base station device is satisfied; When the condition for performing the LTM is satisfied, a process of identifying a configuration grant to be used for uplink transmission from the first information and the second information when performing the LTM without starting a random access procedure; a process of performing uplink transmission to the handover destination candidate base station device by using a configuration grant used for the uplink transmission; A terminal device that executes the above.

[0084] (ii) A terminal device according to the second embodiment A terminal device having a conditional LTM function and communicating with a plurality of base station devices while switching connection destinations, a storage device for storing a program relating to handover; a processor that reads the program from the storage device and executes a handover process; The processor, A process of acquiring, from a connected handover source base station device, first information associating a configuration grant related to an uplink shared channel resource of an LTM candidate cell with an uplink beam configuration, and information on conditions for implementing LTM associated with a handover destination base station device of the LTM candidate cell; A process of notifying the handover source base station device of a measurement result of a downlink reference signal from the LTM candidate cell; A process of acquiring second information on an uplink beam to be used by the terminal device, which is determined by a handover destination base station device of the LTM candidate cell, from the handover source base station device; A process of determining whether a condition for performing LTM associated with the handover destination candidate base station device is satisfied; When the condition for performing the LTM is satisfied, a process of identifying a configuration grant to be used for uplink transmission from the first information and the second information without starting a random access procedure when performing the LTM; a process of performing uplink transmission to the handover destination candidate base station device by using a configuration grant used for the uplink transmission; A terminal device that executes the above.

[0085] (iii) A terminal device according to the third aspect A terminal device having a conditional LTM function and communicating with a plurality of base station devices while switching connection destinations, a storage device for storing a program relating to handover; a processor that reads the program from the storage device and executes a handover process; The processor, A process of acquiring beam configuration related information that associates a downlink reference signal of an LTM candidate cell with a configuration grant related to an uplink shared channel resource from a connected handover source base station device, and information on LTM implementation conditions associated with a handover destination base station device of the LTM candidate cell; A process of determining whether a condition for performing LTM associated with the handover destination candidate base station device is satisfied; When the condition for performing the LTM is satisfied, a process of specifying a configuration grant related to resources of an uplink shared channel to be used in the handover destination base station device of the LTM candidate cell using the measurement result of the downlink reference signal of the LTM candidate cell and the beam configuration related information; a process of performing uplink transmission to the base station device as the handover destination candidate by using a configuration grant related to the uplink shared channel resource without starting a random access procedure when the LTM is performed; A terminal device that executes the above.

[0086] In the above embodiment, the handover source and handover destination base station devices are described as providing one cell, but these base station devices may provide multiple cells. In the above description, the term "base station device" may be read as "cell". That is, in the above description, terms such as "handover source base station device" are used, but these may be read as "handover source cell". However, it should be noted that the main entity that transmits and receives signals is the base station device that provides each cell. In the above example, the terminal device transmits the SRS, but a different uplink reference signal from the SRS may be used to determine the uplink beam to be used by the terminal device.

[0087] (iv) The functions of the present embodiment and each example can also be realized by software program code. In this case, a storage medium on which the program code is recorded is provided to a system or device, and the computer (or CPU or MPU) of the system or device reads the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-mentioned embodiment, and the program code itself and the storage medium on which it is stored constitute the present disclosure. Examples of storage media for supplying such program code include flexible disks, CD-ROMs, DVD-ROMs, hard disks, optical disks, magneto-optical disks, CD-Rs, magnetic tapes, non-volatile memory cards, and ROMs.

[0088] Also, an operating system (OS) running on a computer may perform all or a part of the actual processing based on the instructions of the program code, and the functions of the above-mentioned embodiments may be realized by the processing. Furthermore, after the program code read from a storage medium is written into a memory on a computer, a CPU of the computer may perform all or a part of the actual processing based on the instructions of the program code, and the functions of the above-mentioned embodiments may be realized by the processing.

[0089] Furthermore, the program code of the software that realizes the functions of the embodiments and each example may be distributed via a network and stored in a storage means such as a hard disk or memory of the system or device, or in a storage medium such as a CD-RW or CD-R, so that when used, the computer (or CPU or MPU) of the system or device reads out and executes the program code stored in the storage means or storage medium.

[0090] The processes and techniques described herein are not inherently related to any particular device, and may be implemented by a combination of components. Various types of general-purpose devices may also be added. A dedicated device may be constructed to execute the functions of the present embodiment and each example. Various functions may also be formed by appropriately combining multiple components disclosed in the present embodiment and each example. For example, some components may be deleted from all the components shown in the embodiment and each example, or components across different examples may be appropriately combined.

[0091] In this disclosure, specific examples are described, but they are in all respects for the purpose of explanation (understanding the technology of the present disclosure) and not for the purpose of limitation. It is understood by those skilled in the art that there are many combinations of hardware, software, and firmware suitable for implementing the technology of the present disclosure. For example, the described software can be implemented in a wide range of program or script languages, such as assembler, C / C++, perl, Shell, PHP, Java (registered trademark), etc.

[0092] Furthermore, in the above-described embodiment, the control lines and information lines are those that are considered necessary for the explanation, and not all of the control lines and information lines in the product are necessarily shown. All of the components may be connected to each other.

[0093] In addition, other implementations of the present disclosure will become apparent to those skilled in the art from consideration of the present embodiments and examples. The specification and examples are exemplary only, with the scope and spirit of the present disclosure being indicated by the following claims. [Explanation of symbols]

[0094] 100 Base station equipment 100_1 Handover source base station 100_2 Handover destination base station 200 Terminal Equipment 101, 201 processors 102, 202 Storage devices 103, 203 ROM 104, 204 RAM 105, 205 Communication devices 206 Input Devices 207 Output Devices 1011, 2011 RRC setting section 1012 RA instruction section 1013 Handover instruction unit 1014 Inter-base station communication unit 1015 TA Maintenance Department 1016 PUCCH / PDCCH Communication Department 2012 RA Executive Committee 2013 Handover processing unit 2015 LTM Execution Condition Judgment Department 2016 Timer control unit

Claims

1. A terminal device having an LTM function and communicating with a plurality of base station devices while switching a connection destination, a storage device for storing a program relating to handover; a processor that reads the program from the storage device and executes a handover process; The processor, A process of acquiring, from a connected handover source base station device, first information associating a configuration grant related to an uplink shared channel resource of an LTM candidate cell with an uplink beam configuration, and information on an LTM implementation condition associated with a handover destination base station device of the LTM candidate cell; A process of transmitting an uplink reference signal to a handover destination base station device of the LTM candidate cell in response to an uplink reference signal transmission instruction from the handover source base station device; A process of acquiring, from the handover source base station device, second information regarding an uplink beam to be used by the terminal device, which is determined by the handover destination base station device of the LTM candidate cell based on the measurement result of the uplink reference signal; a process of determining whether a condition for performing the LTM associated with the handover destination candidate base station device is satisfied; When the condition for performing the LTM is satisfied, a process of identifying a configuration grant to be used for uplink transmission from the first information and the second information when performing the LTM without starting a random access procedure; a process of performing uplink transmission to the handover destination candidate base station device by using a configuration grant used for the uplink transmission; A terminal device that executes the above.

2. A terminal device having an LTM function and communicating with a plurality of base station devices while switching a connection destination, a storage device for storing a program relating to handover; a processor that reads the program from the storage device and executes a handover process; The processor, A process of acquiring, from a connected handover source base station device, first information associating a configuration grant related to an uplink shared channel resource of an LTM candidate cell with an uplink beam configuration, and information on an LTM implementation condition associated with a handover destination base station device of the LTM candidate cell; A process of notifying the handover source base station device of a measurement result of a downlink reference signal from the LTM candidate cell; A process of acquiring, from the handover source base station device, second information regarding an uplink beam to be used by the terminal device, which is determined by a handover destination base station device of the LTM candidate cell; a process of determining whether a condition for performing the LTM associated with the handover destination candidate base station device is satisfied; When the condition for performing the LTM is satisfied, a process of identifying a configuration grant to be used for uplink transmission from the first information and the second information during the LTM without starting a random access procedure; a process of performing uplink transmission to the handover destination candidate base station device by using a configuration grant used for the uplink transmission; A terminal device that executes the above.

3. In claim 1 or 2, The processor executes a process of acquiring a timing advance value of a handover destination base station device of the LTM candidate cell from the handover source base station device before performing LTM.

4. In claim 3, The processor executes a process of determining the timing of the uplink transmission to the handover destination base station device using the timing advance value.

5. In claim 4, The processor transmits an RRCReconfiguration Complete to the handover destination candidate base station device by using a configuration grant to be used for the uplink transmission at the determined timing.

6. A terminal device having a conditional LTM function and communicating with a plurality of base station devices while switching a connection destination, a storage device for storing a program relating to handover; a processor that reads the program from the storage device and executes a handover process; The processor, A process of acquiring beam configuration related information that associates a downlink reference signal of an LTM candidate cell with a configuration grant related to resources of an uplink shared channel from a connected handover source base station device, and information on conditions for performing LTM associated with a handover destination base station device of the LTM candidate cell; a process of determining whether a condition for performing the LTM associated with the handover destination candidate base station device is satisfied; When the condition for performing the LTM is satisfied, a process of specifying a configuration grant related to resources of an uplink shared channel to be used in the handover destination base station device of the LTM candidate cell using the measurement result of the downlink reference signal of the LTM candidate cell and the beam configuration related information; a process of performing uplink transmission to the base station device as a handover destination candidate by using a configuration grant related to resources of the uplink shared channel without starting a random access procedure during LTM; A terminal device that executes the above.

7. In claim 6, The terminal device executes the following process when a radio link failure is detected: using the measurement result of the downlink reference signal and the beam setting related information to identify a configuration grant for resources of the uplink shared channel; and when LTM is implemented, performing uplink transmission to the base station device that is a candidate for handover destination using the configuration grant for resources of the uplink shared channel without initiating a random access procedure.

8. In claim 6, A terminal device, wherein the downlink reference signal is an SSB or a CSI-RS.

9. In claim 2, The beam configuration related information is information associating the downlink reference signals of the plurality of LTM candidate cells with configuration grants related to resources of the plurality of uplink shared channels, A terminal device in which the processor associates multiple downlink reference signals with one of the setting grants and stores the beam setting related information in the storage device.

10. In claim 6, The processor executes a process of acquiring a timing advance value of a handover destination base station device of the LTM candidate cell from the handover source base station device before performing LTM.

11. In claim 10, The processor executes a process of determining the timing of the uplink transmission to the handover destination base station device using the timing advance value.

12. In claim 11, The terminal device, wherein the processor transmits an RRCReconfiguration Complete to the handover destination candidate base station device by using a configuration grant related to resources of the uplink shared channel at the determined timing.

13. A wireless communication system including a plurality of base station devices and at least one terminal device having an LTM function, the system executing a handover from a handover source base station device to a handover destination candidate base station device, The handover source base station device to which the terminal device is connected A process of transmitting, to the terminal device, first information associating a configuration grant related to resources of an uplink shared channel of an LTM candidate cell with an uplink beam configuration, and information on a condition for performing LTM associated with a handover destination base station device of the LTM candidate cell; A process of transmitting an uplink reference signal transmission instruction to the terminal device; A process of transmitting, to the terminal device, second information regarding an uplink beam to be used by the terminal device; The terminal device A process of transmitting an uplink reference signal to a handover destination base station device of the LTM candidate cell in response to the uplink reference signal transmission instruction from the handover source base station device; A process of acquiring, from the handover source base station device, the second information determined by the handover destination base station device of the LTM candidate cell based on a measurement result of the uplink reference signal; a process of determining whether a condition for performing the LTM associated with the handover destination candidate base station device is satisfied; When the condition for performing the LTM is satisfied, a process of identifying a configuration grant to be used for uplink transmission from the first information and the second information when performing the LTM without starting a random access procedure; and performing a process of performing uplink transmission to the handover destination candidate base station device by using the configuration grant used for the uplink transmission. Wireless communication system.

14. A wireless communication system including a plurality of base station devices and at least one terminal device having an LTM function, the system executing a handover from a handover source base station device to a handover destination candidate base station device, The handover source base station device to which the terminal device is connected A process of transmitting, to the terminal device, first information associating a configuration grant related to resources of an uplink shared channel of an LTM candidate cell with an uplink beam configuration, and information on a condition for performing LTM associated with a handover destination base station device of the LTM candidate cell; A process of transmitting second information regarding an uplink beam to be used by the terminal device, which is determined by a handover destination base station device of the LTM candidate cell, to the terminal device; The terminal device A process of notifying the handover source base station device of a measurement result of a downlink reference signal from the LTM candidate cell; a process of determining whether a condition for performing the LTM associated with the handover destination candidate base station device is satisfied; When the condition for performing the LTM is satisfied, a process of identifying a configuration grant to be used for uplink transmission from the first information and the second information during the LTM without starting a random access procedure; and performing a process of performing uplink transmission to the handover destination candidate base station device by using the configuration grant used for the uplink transmission. Wireless communication system.

15. A wireless communication system including a plurality of base station devices and at least one terminal device having an LTM function, the system executing a handover from a handover source base station device to a handover destination candidate base station device, The handover source base station device to which the terminal device is connected Execute a process of transmitting to the terminal device beam configuration related information associating a downlink reference signal of an LTM candidate cell with a configuration grant related to resources of an uplink shared channel, and information on conditions for performing LTM associated with a handover destination base station device of the LTM candidate cell; The terminal device a process of determining whether a condition for performing the LTM associated with the handover destination candidate base station device is satisfied; When the condition for performing the LTM is satisfied, a process of specifying a configuration grant related to resources of an uplink shared channel to be used in the handover destination base station device of the LTM candidate cell using the measurement result of the downlink reference signal of the LTM candidate cell and the beam configuration related information; and performing a process of performing uplink transmission to the base station device that is a handover destination candidate by using a configuration grant related to the uplink shared channel resource without starting a random access procedure when the LTM is performed. Wireless communication system.

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