RU2799077C1 - Terminal - Google Patents

Abstract

FIELD: radio messaging.

SUBSTANCE: invention is related to a terminal that transitions to a target radio base station without receiving a handover command. To achieve the result, the terminal receiving unit is configured to receive the first radio resource control RRC Reconfiguration message from the source radio base station including information about the candidate cell and a transition condition to the candidate cell. The terminal transmission unit is configured to send the radio resource control RRC Reconfiguration Complete message for the first configuration message to the source radio base station. The control unit of the terminal is configured to monitor the transition to candidate cell condition after transmission of the RRC Reconfiguration Complete message and change the candidate cell information and transition condition to the candidate cell based on the second RRC Reconfiguration message received from the source radio base station after transmission of the RRC Reconfiguration Complete message. When the transition condition is met, synchronization with the candidate cell and transition to the target radio base station that configures candidate cell information is performed without receiving a handover command.

EFFECT: simplification of the messaging system and avoiding the costs associated with introduction of new types of messages.

7 cl, 33 dwg

Description

The field of technology to which the invention belongs

[0001]

The present invention relates to a terminal that transitions to a target radio base station without receiving a handover (so-called handover) command.

State of the art

[0002]

The 3rd Generation Partnership Project (3GPP) defines the Long Term Evolution (LTE) communication schemes and defines the LTE-Advanced (hereinafter collectively referred to as LTE) with to further accelerate LTE. In addition, the specification of a successor system to LTE called 5G or New Radio (NR) has been studied in 3GPP.

[0003]

In the normal handover (HO) procedure, the network determines the target radio base station (also referred to as the target cell) based on quality information such as a measurement report transmitted from the terminal, and after preparation for handover, the terminal is transmitted handover command.

[0004]

However, when the terminal passes the corresponding handover point during network handover preparation, the terminal transitions to the target radio base station without receiving a handover command from the source radio base station (also referred to as the source cell). For this reason, there is a problem that a momentary interruption of the radio link may occur.

[0005]

Therefore, in order to solve such a problem, a procedure called conditional NO (Non-Patent Document 1) has been studied.

[0006]

In Conditional NO, the source radio base station notifies the terminal in advance of candidate target cell configuration information including the candidate target cell and a transition condition to the candidate target cell using a Radio Resource Control Reconfiguration (RRC) message. from English radio resource control) (messages "RRC Reconfiguration").

[0007]

When the transition to candidate target cell condition is met, the terminal performs a random access procedure with the target radio base station controlling the candidate target cell and transitions to the target radio base station without waiting for the handover command. As a result, a momentary interruption of the radio link can be avoided.

[0008]

When the random access procedure succeeds, the terminal transmits an RRC reconfiguration complete message (RRC Reconfiguration Complete message) to the target radio base station.

Prior Art Documents

non-patent document

[0009]

Non-Patent Document 1: "New WID: NR Mobility Improvements", RP-190489, 3GPP TSG RAN Meeting No. 83, 3GPP, March 2019

Disclosure of the essence of the invention

[0010]

However, in the conditional HO, the terminal transmits an RRC reconfiguration complete message to the target radio base station, and thus has the following problem.

[0011]

In case of changing the configuration information of the target candidate cell, the source radio base station needs to notify the terminal of the change in the configuration information of the target candidate cell using the new RRC reconfiguration message after receiving the RRC reconfiguration complete message.

[0012]

However, in conditional BUT, since the RRC reconfiguration complete message is transmitted to the target radio base station, the source radio base station cannot notify the terminal of the changed configuration information of the target candidate cell.

[0013]

The present invention has been developed in view of such a situation, and it is an object of the present invention to provide a terminal in which a source radio base station can notify the terminal of the changed configuration information of the candidate target cell even in the case that the terminal performs a random access procedure between the terminal and the target radio base station. and transitions to the target radio base station without receiving the handover command.

[0014]

A terminal (200) according to an aspect of the present invention includes: a receiving unit (220) configured to receive from a source radio base station (100A) a first configuration message including configuration information of a cell subordinate to the target radio base station (100B ); a control unit (240) configured to perform a random access procedure between the terminal (200) and the target radio base station (100B) and move to the target radio base station (100B) without receiving a handover command based on the cell configuration information; and a transmission unit (210) configured to transmit to the source radio base station (100A) a completion message for the first configuration message before starting the random access procedure.

Brief description of the drawings

[0015]

In FIG. 1 is a general schematic diagram of a radio communication system 10.

In FIG. 2 is a functional block diagram of each of gNBs 100A, 100B, and 100C.

In FIG. 3 is a functional block diagram of terminal 200.

In FIG. 4 is a diagram illustrating the sequence of the conditional BUT procedure.

In FIG. 5 is a diagram illustrating the recovery sequence after a radio link failure (RLF) in a normal handover (HO) procedure.

In FIG. 6 is a diagram illustrating the sequence (Operation Example 1) of radio link failure (RLF) recovery in the conditional HO procedure.

In FIG. 7 is a diagram illustrating the sequence (Operation Example 2) of radio link failure (RLF) recovery in the conditional HO procedure.

In FIG. 8 is a diagram illustrating the sequence (Operation Example 3) of radio link failure (RLF) recovery in the conditional HO procedure.

In FIG. 9 shows an image for describing information elements (IE, from the English information elements) in the VarRLF-Report.

In FIG. 10 is a picture for describing information elements (IEs) in an RRC Reconfiguration Complete message ("RRC Reconfiguration Complete").

In FIG. 11A is an image for describing information elements (IEs) in an RRC Setup Complete message.

In FIG. 11B is a picture for describing information elements (IE) in an RRC Setup Complete message.

In FIG. 12 is a picture for describing information elements (IEs) in an RRC Reestablishment Complete message.

In FIG. 13 is a picture for describing information elements (IEs) in an RRC Resume Complete message ("RRC Resume Complete").

In FIG. 14 is a picture for describing information elements (IEs) in a UE Information Request.

In FIG. 15A is an image for describing information elements (IEs) in a UE information response ("UE Information Response").

In FIG. 15B is a picture for describing information elements (IEs) in a UE information response ("UE Information Response").

In FIG. 15C is an image for describing information elements (IEs) in a UE information response ("UE Information Response").

In FIG. 16 is a diagram illustrating the transmission sequence of the RRC reconfiguration complete message in the conditional DO procedure.

In FIG. 17 is a diagram illustrating the HO cancellation sequence (Operation Example 1) in the conditional HO procedure.

In FIG. 18 is a diagram illustrating the BUT cancellation sequence (Operation Example 2) in the conditional BUT procedure.

In FIG. 19 is a diagram illustrating the sequence of changing BUT (Operation Example 1) in the conditional BUT procedure.

In FIG. 20 is a diagram illustrating the sequence of changing the BUT (Operation Example 2) in the conditional BUT procedure.

In FIG. 21 is a diagram illustrating the sequence of changing BUT (Operation Example 3) in the conditional BUT procedure.

In FIG. 22 is a diagram illustrating the workflow of gNB 100A for encapsulating multiple pieces of target candidate cell configuration information.

In FIG. 23 is a diagram for describing the configuration (Configuration Example 1) of the RRC reconfiguration message in the conditional BUT procedure.

In FIG. 24 is a diagram illustrating the configuration (Configuration Example 2) of the RRC reconfiguration message in the conditional BUT procedure.

In FIG. 25 is a diagram illustrating the assignment sequence of the transaction ID (transaction ID) (Operation Example 1) in the conditional NO procedure.

In FIG. 26 is a diagram illustrating the sequence of assigning a transaction ID (Operation Example 2) in the conditional BUT procedure.

In FIG. 27 is a diagram illustrating the recovery sequence after a handover failure (HOF) in a conditional HO procedure.

In FIG. 28 is a diagram illustrating the workflow of a terminal 200 that resumes radio transmission after a radio link failure (RLF) in a conditional HO procedure.

In FIG. 29 is a view illustrating conditions for resuming radio transmission after a radio link failure (RLF) in the conditional HO procedure.

In FIG. 30 is a diagram illustrating an example hardware configuration of each of gNBs 100A, 100B, 100C and terminal 200.

Implementation of the invention

[0016]

Next, embodiments will be described with reference to the drawings. It should be noted that the same functions or configurations are referred to by the same or similar reference numerals and their description is omitted if necessary.

[0017]

(1) General Schematic Configuration of a Radio Communication System FIG. 1 is a general schematic diagram of a radio communication system 10 according to the present embodiment. The radio communication system 10 is a radio communication system according to New Radio (NR) and includes a next generation radio access network (NG-RAN, not shown) and a terminal 200.

[0018]

The NG-RAN includes radio base stations 100A, 100B, and 100C (hereinafter referred to as gNBs 100A, 100B, and 100C). It should be noted that the specific configuration of the radio communication system 10 including a number of gNBs and user equipments (UEs) is not limited to the example illustrated in FIG. 1.

[0019]

The NG-RAN actually includes a plurality of NG-RAN nodes, in particular gNB nodes (or ng-eNB nodes), and is connected to a core network (5GC, not shown) according to NR. It should be noted that NG-RAN and 5GC can be expressed simply as a network.

[0020]

Each of the gNBs 100A, 100B, and 100C is a radio base station according to the NR and performs radio communication with the terminal 200 according to the NR. Each of gNBs 100A, 100B, and 100C and terminal 200 can support Massive MIMO technology, in which a more highly directional beam, carrier aggregation (CA) is generated, in which a plurality of component carriers (CC) are combined for use. carriers), dual connection (DC, eng. dual connectivity) for simultaneously performing communication between a plurality of NG-RAN nodes and a terminal, etc., by controlling a radio signal transmitted from a plurality of antenna elements. It should be noted that the CC is also called the carrier.

[0021]

Each of gNBs 100A, 100B, and 100C forms one or more cells and manages one or more cells. Terminal 200 may perform handoff between cells formed by gNBs 100A, 100B, and 100C. 100B and 100C" or "transition between radio base stations 100A, 100B and 100C". In addition, "cells subordinate to gNBs 100A, 100B, and 100C" means "cells formed by gNBs 100A, 100B, and 100C".

[0022]

"Handover" generally means switching between cells or switching between gNBs, and may include behavior of terminal 200 that causes a connection destination cell or connection destination gNB to change, such as cell reselection.

[0023]

"Target cell" generally means a hop destination cell that terminal 200 is hopping to, and may also include a cell (potential target cell) that terminal 200 can hop to. In addition, "target gNB" usually means a hop destination gNB, to which terminal 200 is transitioning, and may also include a gNB (potential target gNB) to which terminal 200 can transition. In the present embodiment, gNBs 100B and 100C are target gNBs. It should be noted that a cell to which a terminal can transition may also be referred to as a candidate cell. In addition, a gNB to which a terminal may transition may also be referred to as a candidate gNB.

[0024]

Meanwhile, "source cell" means a transition source cell. "Original gNB" means the parent gNB of the transition. In the present embodiment, gNB 100A is the parent gNB.

[0025]

In the radio communication system 10, the terminal 200 performs a conditional handover (hereinafter referred to as conditional handover (HO)) procedure. It should be noted that the conditional HO procedure can be abbreviated to "CHO procedure (from the English. Conditional HO)".

[0026]

In the conditional DO procedure as described below, the source gNB 100A notifies the terminal 200 in advance of one or more transition destination candidate cells (hereinafter referred to as “target candidate cells”) to which the terminal 200 can transition. candidate is satisfied, terminal 200 performs a random access (RA) procedure with target gNB 100B (or target gNB 100C) controlling candidate target cell, and transitions to target gNB 100B (or target gNB 100C) without receiving handover commands from the source gNB.

[0027]

It should be noted that the radio communication system 10 may include an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) instead of NG-RAN. In this case, the E-UTRAN includes a plurality of E-UTRAN nodes, in particular eNB nodes (or en-gNB nodes), and is connected to a core network (evolved packet core (EPC) evolved packet core) according to with LTE.

[0028]

(2) Functional block diagram of the radio communication system

Next, a functional block diagram of the radio communication system 10 will be described. Specifically, a functional block diagram of each of the gNBs 100A, 100B, and 100C and the terminal 200 will be described. Next, only parts relating to features in the present embodiment will be described. Therefore, gNBs 100A, 100B, and 100C and terminal 200 have other functional blocks that are not directly related to features in the present embodiment.

[0029]

In FIG. 2 is a functional block diagram of each of gNBs 100A, 100B, and 100C. Since gNBs 100A, 100B, and 100C have the same configuration, description of gNBs 100B and 100C is omitted. As shown in FIG. 2, gNB 100A includes a transmitting unit 110, a receiving unit 120, a storing unit 130, and a control unit 140.

[0030]

The transmission unit 110 transmits a downlink signal (DL signal, English downlink) in accordance with the NR. The receiving unit 120 receives an uplink signal (UL signal, English uplink) in accordance with NR. Specifically, the transmission unit 110 and the reception unit 120 wirelessly communicate with the terminal 200 via a control channel or a data channel.

[0031]

Transmission unit 110 transmits a signal according to NR to another gNB. Receiver 120 receives a signal according to NR from another gNB.

[0032]

The transmission unit 110 transmits an RRC message, such as an RRC reconfiguration message to be described later, to the terminal 200.

[0033]

In the case where the gNB 100A is the source gNB, the transmission unit 110 transmits an AtoN request, which will be described below, to the target gNB. In the case where the gNB 100A is the target gNB, the transmit unit 110 transmits Ato request acknowledgment, HO cancel, and HO change, which will be described below, to the source gNB. The AtoN request acknowledgment includes configuration information of the target candidate cell subordinate to the target gNB.

[0034]

The receiving unit 120 receives from the terminal 200 an RRC message such as an RRC reconfiguration complete message, an RRC reconfiguration complete message 1 ("RRC Reconfiguration Complete1"), an RRC reconfiguration complete message 2 ("RRC Reconfiguration Complete2"), a configuration complete message RRC ("RRC SetupComplete") or RRC recovery complete message to be described later.

[0035]

In the case where the gNB 100A is the source gNB, the receiving unit 120 receives AtoN request acknowledgment, HO cancel, and HO change, which will be described below, from the target gNB. In the case where the gNB 100A is the target gNB, the receive unit 120 receives the AtoN request, which will be described below, from the source gNB.

[0036]

In the case where the gNB 100A is the source gNB, the storage unit 130 stores the configuration information of the target candidate cell subordinate to the target gNB.

[0037]

The control unit 140 controls each functional unit included in the gNB 100A.

[0038]

In the case where the gNB 100A is the target gNB, the control unit 140 determines to delete the candidate target cell configuration information based on the state of the target candidate cell subordinate to the gNB 100A.

[0039]

In the case where gNB 100A is the target gNB, control unit 140 causes transmitter 110 to transmit to the source gNB a HO cancel instructing the deletion of configuration information of the target candidate cell subordinate to gNB 100A.

[0040]

In the case where gNB 100A is the target gNB, control unit 140 causes transmitter 110 to send HO cancel to source gNB when terminal 200 does not transition within a predetermined time, based on the target candidate cell configuration information subordinate to gNB 100A.

[0041]

In the case where the gNB 100A is the target gNB, the control unit 140 determines a change in the configuration information of the target candidate cell based on the state of the target candidate cell subordinate to the gNB 100A.

[0042]

In the case where the gNB 100A is the target gNB, the control unit 140 causes the transmitter 110 to transmit to the source gNB a change DO instructing to change the configuration information of the target candidate cell subordinate to the gNB 100A.

[0043]

In the case where the gNB 100A is the source gNB, the control unit 140 lists in the RRC reconfiguration message a list including a plurality of configuration information pieces of the target candidate cell subordinate to the target gNB.

[0044]

In FIG. 3 is a functional block diagram of terminal 200. As shown in FIG. 3, the terminal 200 includes a transmission section 210, a reception section 220, a storage section 230, and a control section 240.

[0045]

The transmission unit 120 transmits an uplink signal (UL signal) according to NR. The receiving unit 110 receives a downstream signal (DL signal) according to NR. In particular, the transmitting unit 210 and the receiving unit 220 communicate wirelessly with each of the gNBs 100A-100C via a control channel or a data transmission channel.

[0046]

The transmission unit 210 transmits an RRC message such as an RRC reconfiguration complete message, an RRC reconfiguration complete message 1, an RRC reconfiguration complete message 2, an RRC setup complete message, or an RRC restore complete message to be described later.

[0047]

The receiving unit 220 receives an RRC message, such as an RRC reconfiguration message, which will be described below. [0048]

The storage unit 230 stores the configuration information of the candidate target cell subordinate to the target gNB. The target candidate cell configuration information is included in the RRC reconfiguration message.

[0049]

The control unit 240 controls each functional unit included in the terminal 200. [0050]

The control unit 240 executes the RA procedure between the terminal 200 and the target gNB, and performs a transition to the target gNB without performing an RRC Reestablishment procedure when RLF occurs.

[0051]

The control unit 240 performs transition to the target gNB based on the configuration information of the candidate target cell subordinate to the target gNB without performing the RRC recovery procedure when RLF occurs.

[0052]

The control unit 240 performs the RA procedure between the terminal 200 and the target gNB and transitions to the target gNB without receiving a handover command based on the configuration information of the target candidate cell subordinate to the target gNB.

[0053]

The control unit 240 transitions to the target gNB without performing an RRC recovery procedure when a handover failure (HOF) occurs.

[0054]

The control unit 240 inserts, in the above RRC message such as RRC reconfiguration complete message, RRC reconfiguration complete message 2, RRC configuration complete message, or RRC restore complete message, RLF discovery information including RLF information for notification of occurrence of RLF, cell information in which RLF is detected, location information of the terminal 200 which has detected RLF, and the like.

[0055]

In the case where the receiving unit 220 receives the RRC reconfiguration message including the candidate target cell configuration information, the control unit 240 causes the transmission unit 210 to transmit RRC reconfiguration complete message 1 before starting the RA procedure. It should be noted that after transmission of the RRC reconfiguration complete message 1, the receiving unit 220 receives an RRC reconfiguration message including the changed configuration information of the target candidate cell.

[0056]

In the case where the receiving unit 220 receives the configuration information of the target candidate cell subordinate to the target gNB using the RRC reconfiguration message to which the transaction ID is assigned by the source gNB, the control unit 240 inserts, in the RRC reconfiguration complete message 1, the transaction ID. The control unit 240 causes the transmit unit 210 to send an RRC reconfiguration complete message 1 to the source gNB.

[0057]

In the case where the receiving unit 220 receives the configuration information of the target candidate cell subordinate to the target gNB to which the transaction ID is assigned by the source gNB, the control unit 240 inserts, in the RRC reconfiguration complete message 2, the transaction ID. Upon successful completion of the RA procedure, the control unit 240 causes the transmitter 210 to send an RRC reconfiguration complete message 2 to the target gNB.

[0058]

When a HOF occurs, the control unit 240 stores all or part of the configuration information of the target candidate cell subordinate to the target gNB shared by the terminal 200 and the target gNB, and inserts, in the RRC reconfiguration complete message 2, the stored configuration information. The stored configuration information includes security information, identification information of the terminal 200, and the like. Upon successful completion of the RA procedure, the control unit 240 causes the transmitter 210 to send an RRC reconfiguration complete message 2 to the target gNB.

[0059]

When the transition procedure to the target gNB is performed, the control unit 240 resumes the radio transmission suspended between the terminal 200 and the target gNB.

[0060]

In the transition procedure to the target gNB, the control unit 240 resumes the radio transmission suspended between the terminal 200 and the target gNB when executing the RA procedure.

[0061]

In the transition procedure to the target gNB, in the case where the receiving unit 220 receives a message instructing to resume radio transmission, the control unit 240 resumes the radio transmission suspended between the terminal 200 and the target gNB.

[0062]

(3) Operations of the radio communication system

Next, the operations of the radio communication system 10 will be described. In particular, the conditional BUT procedure will be described first, and then the following operations will be described.

[0063]

• Recovery from a radio link failure (RLF) in a conditional NTO procedure

• RRC Reconfiguration Completion Message Transmission Interval in Conditional NO Procedure

• Handover Cancellation (HTO) in Conditional HTO Procedure

• Changing the handover (HTO) in the conditional HTO procedure

• Configuration of the RRC reconfiguration message in the conditional NDO procedure

• Assigning an identifier (ID) to the transaction in the conditional BUT procedure

• Recovery from a handover failure (HOF) in a conditional HOF procedure

• Resuming radio transmission after a radio link failure (RLF) in a conditional HO procedure

[0064]

(3.1) Conditional NUT procedure

In FIG. 4 is a diagram illustrating the sequence of the conditional BUT procedure. As shown in FIG. 4, when source gNB 100A locates target gNBs 100B and 100C based on the measurement report received from terminal 200, source gNB 100A sends a conditional HBW request (AtoN request) to target gNBs 100B and 100C (S11).

[0065]

When the target gNB 100B receives the AtoN request from the source gNB 100A, the target gNB 100B sends to the source gNB 100A an Ato request response (AtoN request acknowledgment) including cell configuration information (called candidate target cell) subordinate to target gNB 100B ( S13). The candidate target cell configuration information includes candidate target cell information and a transition condition to the candidate target cell.

[0066]

Similarly, when the target gNB 100C receives an AtoN request from the source gNB 100A, the target gNB 100C sends to the source gNB 100A an Ato request response (Ato Ato Request Confirmation) including configuration information of a cell (referred to as a candidate target cell) subordinate to the target gNB 100A. gNB 100C (S13). The candidate target cell configuration information includes candidate target cell information and a transition condition to the candidate target cell.

[0067]

When source gNB 100A receives an AtoN request acknowledgment from each of target gNBs 100B and 100C, source gNB 100A transmits a Radio Resource Control (RRC) reconfiguration message (RRC Reconfiguration message) including a conditional HO configuration (AtoN configuration ) to terminal 200 (S15). The AtoN configuration includes target candidate cell configuration information transmitted from each of the target gNBs 100B and 100C.

[0068]

When the terminal 200 receives the AtoN configuration from the source gNB 100A, the terminal 200 monitors the conditional BUT condition (AtoN condition) (S17). Specifically, the terminal 200 judges whether or not the transition to target candidate cell included in the configuration information of each target candidate cell is met or not.

[0069]

In the case where the terminal 200 judges that the handover condition to the candidate target cell is satisfied due to the movement of the terminal 200 or the like, the terminal 200 determines the start of a handover (HO) to the candidate target cell without receiving a handover command from the source gNB 100A (S19). In the present embodiment, the terminal 200 determines the start of the handover to the target candidate cell subordinate to the target gNB 100B. A candidate target cell as a transition destination for which the transition condition is met is also referred to as an AtoN cell.

[0070]

It should be noted that source gNB 100A can only receive candidate target cell information from each of target gNBs 100B and 100C in step S13. In this case, in step S15, source gNB 100A transmits to terminal 200 an AtoN configuration including target candidate cell information and a condition for triggering a handover (HO) of terminal 200.

[0071]

In this case, in step S17, the terminal 200 judges whether or not the condition for starting HO is met. In the case where the terminal 200 decides that the condition for starting HO is met due to the movement of the terminal 200 or the like, the terminal 200 determines the candidate target cell as the transition destination and starts handover to the candidate target cell in step S19 . The terminal 200 determines the target candidate cell as the transition destination based on, for example, the priority of each target candidate cell specified by the source gNB 100A and the cell state included in each target candidate cell information.

[0072]

When terminal 200 determines the start of HO to a candidate target cell slave to target gNB 100B, terminal 200 performs a random access (RA) procedure between target gNB 100B and terminal 200 and establishes synchronization between target gNB 100B and terminal 200 (S21). Thus, terminal 200 is connected to a 100V target gNB.

[0073]

When the terminal 200 is connected to the target gNB 100B, the terminal 200 transmits an RRC reconfiguration complete message (RRC Reconfiguration Complete message) to the target gNB 100B (S23).

[0074]

(3.2) Recovery from RLF in the conditional DO procedure Next, recovery from RLF in the conditional DO procedure will be described. First, the recovery from RLF in the conventional HO procedure will be described.

[0075]

On fig. 5 is a diagram illustrating the RLF recovery sequence in a conventional HO procedure. As shown in FIG. 5, when source gNB 100A finds target gNB 100B based on the measurement report received from terminal 200, source gNB 100A sends a handover request (HO request) to target gNB 100B (S51).

[0076]

When the target gNB 100B receives the HO request from the source gNB 100A, the target gNB 100B transmits to the source gNB 100A a HO request response (HO request acknowledgment) including information about the cell (referred to as the target cell) subordinate to the target gNB 100B (S53).

[0077]

When the source gNB 100A receives the HO request confirmation from the target gNB 100B, the source gNB 100A transmits an RRC Reconfiguration message including a handover command (HO command) to the terminal 200 (S55). The GO command includes information about the target cell transmitted from the target gNB 100B.

[0078]

When terminal 200 receives a HO command from source gNB 100A, terminal 200 performs a random access (RA) procedure between target gNB 100B and terminal 200 and attempts to establish synchronization between target gNB 100B and terminal 200 (S57).

[0079]

In the case where the RA procedure fails due to the occurrence of RLF during the RA procedure in step S57, the terminal 200 performs cell reselection (S59). In the event that terminal 200 decides to re-establish a connection with a cell subordinate to target gNB 100B, terminal 200 performs an RRC Reestablishment procedure between target gNB 100B and terminal 200.

[0080]

Specifically, the terminal 200 transmits an RRC Reestablishment request message (RRC Reestablishment request message) to the target gNB 100B (S61). When the target gNB 100B receives the RRC restoration request from the terminal 200, the target gNB 100B transmits an RRC restoration message (RRC Reestablishment message) to the terminal 200 (S63). The RRC Restore message includes configuration information used to reestablish an RRC connection between target gNB 100B and terminal 200.

[0081]

When terminal 200 receives an RRC restoration message from target gNB 100B, terminal 200 reestablishes an RRC connection between target gNB 100B and terminal 200 and transmits an RRC restoration complete message (RRC Reestablishment Complete message) (S65).

[0082]

In step S65, the terminal 200 inserts, in the RRC recovery complete message, RLF information to perform RLF notification. The RLF information is included in the RRC recovery complete message to notify the network of the occurrence of RLF between terminal 200 and target gNB 100B.

[0083]

When the target gNB 100B receives an RRC recovery complete message from the terminal 200, the target gNB 100B transmits an RRC reconfiguration message to the terminal 200 (S67). When terminal 200 receives an RRC reconfiguration message from target gNB 100B, terminal 200 performs RRC connection reconfiguration and transmits an RRC reconfiguration complete message to target gNB 100B (S69).

[0084]

(3.2.1) Operation example 1

Next, an example 1 of the recovery operation after RLF in the conditional BUT procedure will be described. In the present operation example, in the case where the RA procedure fails due to the occurrence of RLF in the conditional HO procedure, the terminal 200 reselects the candidate target cell (Ato cell) as the transition destination, performs the RA procedure, and then notifies the network of the occurrence RLF through the use of an RRC reconfiguration complete message ("RRC Reconfiguration Complete" message).

[0085]

In FIG. 6 is a diagram illustrating the sequence (Operation Example 1) of recovery from RLF in the conditional BUT procedure. Steps S101-S109 in FIG. 6 are the same processing as S11-S19 in FIG. 4, and thus their description will be omitted.

[0086]

When terminal 200 determines the start of HO to a target candidate cell slave to target gNB 100B without receiving a handover command from source gNB 100A, terminal 200 performs a random access (RA) procedure between target gNB 100B and terminal 200 and attempts to establish synchronization between target gNB 100V and terminal 200 (S111).

[0087]

In the case where the RA procedure fails due to the occurrence of RLF during the RA procedure in step S111, the terminal 200 reselects the candidate target cell (CHO cell) as the transition destination for which the transition condition is met (S113). In the present embodiment, the terminal 200 reselects a target candidate cell subordinate to the target gNB 100B.

[0088]

When terminal 200 reselects a candidate target cell subordinate to target gNB 100B, terminal 200 performs a random access (RA) procedure between target gNB 100B and terminal 200, and establishes synchronization between target gNB 100B and terminal 200 (S115). Thus, terminal 200 connects to (connects to) a 100V target gNB.

[0089]

When the terminal 200 is connected to the target gNB 100B, the terminal 200 transmits an RRC reconfiguration complete message (RRC Reconfiguration Complete message) to the target gNB 100B (S117).

[0090]

In step S117, the terminal 200 inserts the RLF information into the RRC reconfiguration complete message to perform the RLF notification. The RLF information is included in the RRC reconfiguration complete message to notify the network of the occurrence of RLF between terminal 200 and target gNB 100B. For example, RLF information is represented by one bit. In this case, for example, in a case where RLF occurs, "1" is set as the RLF information, and "0" is set as RLF information in the case where RLF does not occur.

[0091]

As described above, RLF information is included (included) in a message indicating that the conditional handover procedure is completed, that is, that the terminal 200 has applied the target candidate cell configuration information.

[0092]

In step S117, the terminal 200 may include RLF information and RLF discovery information in the RRC reconfiguration complete message. The RLF detection information includes, for example, at least one of cell information such as a cell ID in which RLF is detected (in the present embodiment, a cell subordinate to the target gNB 100B), information (Global Navigation Satellite System (GNSS) information) or the like) of the location of the terminal 200 where RLF is detected, radio access technology (RAT) information used in RLF detection, frequency information used in RLF detection, bandwidth fraction information (BWP, from the English bandwidth part) used in RLF detection, and the location (Global Positioning System (GPS) information or the like) where the RLF is detected.

[0093]

It should be noted that, similar to step S13, source gNB 100A can only receive target candidate cell information from each of target gNBs 100B and 100C in step S103. In this case, the terminal 200 reselects a target candidate cell (Ato cell) as a transition destination based on the priority of each target candidate cell assigned by the source gNBs 100A, the cell state included in each target candidate cell information, and the like. .in step S113.

[0094]

As described above, in the case of recovering from RLF using Ato cell reselection, terminal 200 can jump to the target gNB without performing the RRC recovery procedure and be quickly recovered after RLF.

[0095]

(3.2.2) Operation example 2

Next, an example 2 of the recovery operation after RLF in the conditional BUT procedure will be described. In the present operation example, when terminal 200 receives an RRC reconfiguration message from source gNB 100A in step S105 in Operation Example 1, terminal 200 immediately transmits an RRC reconfiguration complete message 1 (RRC Reconfiguration Complete 1 message).

[0096]

In FIG. 7 is a diagram illustrating the sequence (Operation Example 2) of recovering from RLF in the conditional BUT procedure. Steps S101-S115 in FIG. 7 are the same processing as S101-S115 in FIG. 6, and thus their description will be omitted.

[0097]

As shown in FIG. 7, when terminal 200 receives an RRC reconfiguration message from source gNB 100A, terminal 200 immediately transmits RRC reconfiguration complete message 1 (S105a).

[0098]

When the terminal 200 is connected to the target gNB 100B using the RA procedure in step S115, the terminal 200 sends to the target gNB 100B an RRC reconfiguration complete message 2 (RRC Reconfiguration Complete 2 message) or an RRC setup complete message (RRC Setup Complete message). ) (S117a).

[0099]

It should be noted that the RRC reconfiguration complete message 1 and the RRC reconfiguration complete message 2 have the same configuration as the RRC reconfiguration complete message.

[0100]

In step S117a, the terminal 200 inserts the RLF information into the RRC reconfiguration complete message 2 or the RRC setup complete message to perform the RLF notification. In addition, in step S117a, the terminal 200 may include the RLF information and the RLF detection information in the RRC reconfiguration complete message 2 or the RRC setup complete message.

[0101]

(3.2.3) Operation example 3

Next, an example 3 of the recovery operation after RLF in the conditional BUT procedure will be described. In the present operation example, in the case where the RA procedure fails due to the occurrence of RLF in the conditional HO procedure in the operation example 1, the terminal 200 reselects a transition destination cell (a transition destination cell other than an AtoN cell) other than the target cell. candidate, and performs the RRC recovery procedure.

[0102]

In FIG. 8 is a diagram illustrating the sequence (Operation Example 3) of recovery after RLF in the conditional BUT procedure. Steps S101-S111 in FIG. 8 are the same processing as S101-S111 in FIG. 6, and thus their description will be omitted.

[0103]

It should be noted that in the present operation example, source gNB 100A only finds target gNB 100B based on the measurement report received from terminal 200. Therefore, source gNB 100A transmits an AtoN request to target gNB 100B (S101) and receives an AtoN request acknowledgment including target candidate cell configuration information from target gNB 100B (S103).

[0104]

In the case where the RA procedure fails due to the occurrence of RLF during the RA procedure in step S111, the terminal 200 reselects the target candidate cell (CHO cell) as the transition destination for which the transition condition is met. However, in the case where there is no target candidate cell as a transition destination for which the transition condition is met, the terminal 200 reselects a transition destination cell (a transition destination cell other than the AtoN cell) other than the target candidate cell (S131). In the present embodiment, the terminal 200 reselects the cell subordinate to the target gNB 100C.

[0105]

In the event that terminal 200 decides to re-establish a connection with the cell slave of target gNB 100C, terminal 200 performs an RRC recovery procedure between target gNB 100C and terminal 200.

[0106]

Specifically, terminal 200 sends an RRC recovery request to target gNB 100C (S133). When the target gNB 100C receives the RRC restore request from the terminal 200, the target gNB 100C sends an RRC restore message to the terminal 200 (S135). The RRC Restore message includes configuration information used to reestablish an RRC connection between target gNB 100C and terminal 200.

[0107]

When terminal 200 receives an RRC restoration message from target gNB 100C, terminal 200 restores an RRC connection between target gNB 100C and terminal 200 and transmits an RRC restoration complete message (S137).

[0108]

In step S137, the terminal 200 inserts the RLF information into the RRC recovery complete message to perform the RLF notification. In addition, in step S137, the terminal 200 may include RLF information and RLF detection information in the RRC recovery complete message.

[0109]

(3.2.4) Information Elements (IE)

Next, the IEs of each message used for the above-described RLF notification will be described.

[0110]

In FIG. 9 is an image for describing the information items in the "VarRLF-Report". As shown in FIG. 9, terminal 200 inputs RLF information in "rlf-Report-r16" in "VarRLF-Report". It should be noted that the terminal 200 may insert RLF information and RLF detection information in "rlf-Report-r16" in "VarRLF-Report".

[0111]

In FIG. 10 is a picture for describing information elements (IEs) in an RRC reconfiguration complete message. As shown in FIG. 10, in the case where the RLF information is included in the "VarRLF-Report", the terminal 200 inserts the RLF information in "rlf-lnfoAvailable-r16" in the RRC reconfiguration complete message in step S117 in FIG. 6. It should be noted that the terminal 200 may include RLF information and RLF discovery information in "rlf-lnfoAvailable-r16" in the RRC reconfiguration complete message.

[0112]

As described above, the RRC reconfiguration complete message 2 has the same configuration as the RRC reconfiguration complete message. Therefore, in the case where the RLF information is included in the "VarRLF-Report", the terminal 200 inserts the RLF information in "rlf-lnfoAvailable-r16" in the RRC reconfiguration complete message 2 in step S117a in FIG. 7. It should be noted that the terminal 200 may insert RLF information and RLF detection information in "rlf-lnfoAvailable-r16" in RRC reconfiguration complete message 2.

[0113]

In FIG. 11A and 11B are views for describing information items in an RRC setting complete message. As shown in FIG. 11A, in the case where the RLF information is included in the "VarRLF-Report", the terminal 200 inserts the RLF information in "rlf-lnfoAvailable-r16" in the RRC setup completion message in step S117 in FIG. 7. It should be noted that the terminal 200 may include RLF information and RLF discovery information in "rlf-lnfoAvailable-r16" in the RRC setup complete message.

[0114]

In FIG. 12 is a picture for describing information elements (IEs) in an RRC recovery complete message. As shown in FIG. 12, in the case where the RLF information is included in the "VarRLF-Report", the terminal 200 inserts the RLF information in "rlf-lnfoAvailable-r16" in the RRC recovery complete message in step S137 in FIG. It should be noted that the terminal 200 may include RLF information and RLF detection information in "rlf-lnfoAvailable-r16" in the RRC recovery complete message.

[0115]

In FIG. 13 is a picture for describing information elements (IEs) in an RRC resume complete message. The RRC resume complete message is used by the terminal 200 to notify the network that the radio resume is completed based on the receipt of an RRC message instructing the radio to resume, as described in "(3.9) Radio Resume After RLF in the Conditional BUT Procedure" to be described below. .

[0116]

As shown in FIG. 13, in the case where the RLF information is included in the "VarRLF-Report", the terminal 200 may insert the RLF information in "rlf-lnfoAvailable-r16" in the RRC resume completion message to be used to notify that the radio communication resume is completed after the restoration. after RLF. It should be noted that the terminal 200 may include RLF information and RLF detection information in "rlf-lnfoAvailable-r16" in the RRC resume completion message.

[0117]

In FIG. 14 is a picture for describing information elements (IEs) in a UE Information Request. Terminal 200 may notify the network of the occurrence of RLF based on a request from the network. As shown in FIG. 14, the network requests the RLF notification from the terminal 200 with "rlf-ReportReq-r16" in the UE information request message.

[0118]

In FIG. 15A to 15C are views for describing information elements in a UE Information Response. In the case where the terminal 200 is requested by the network to notify the RLF using the UE information request, the terminal 200 contributes the RLF information to "rlf-Cause-r16" in the UE information response, as shown in FIG. 15A. It should be noted that the terminal 200 may insert RLF information and RLF detection information in "rlf-Cause-r16" in the UE information response.

[0119]

(3.2.5) Other

In the operation examples 1 and 2, the message including the RLF information is a message indicating that the conditional BUT procedure is completed, that is, a message indicating that the configuration information of the target candidate cell has been applied (for example, an RRC reconfiguration complete message, RRC reconfiguration complete message 2 or RRC setup complete message), but the present invention is not limited to this.

[0120]

For example, the message including the RLF information may be the first RRC message sent to the target gNB as the transition destination. In addition, the message including the RLF information may be a message having a specific identifier. The identifier can be a transaction identifier, a packet data convergence protocol (PDCP) sequence number (SN), a PDCP account value, a Radio Link Control (RLC) sequence number (SN), or a process identifier. hybrid automatic repeat request (HARQ process, English hybrid automatic repeat request process).

[0121]

In addition, the terminal 200 may notify the network of the RLF information at a time other than the conditional HO procedure.

[0122]

In the operation examples 1-3, the terminal 200 inserts RLF information and RLF detection information into the same message. However, the present invention is not limited to this, and information may be included in various messages. In addition, the terminal 200 may insert RLF information into the message as directed by the network. Similarly, terminal 200 may include RLF discovery information in the message as directed by the network.

[0123]

In the case where multiple RLFs occur, terminal 200 may include multiple pieces of RLF detection information in the same message, and transmit said message to the target gNB as a transition destination. In addition, terminal 200 may contribute only a specified number of pieces of RLF discovery information (eg, one piece of RLF discovery information) in the same message and transmit the specified message to the target gNB as the transition destination.

[0124]

In the case where a plurality of RLFs occur, the terminal 200 may prioritize the plurality of pieces of RLF detection information. For example, in the case where terminal 200 detects RLF on the same frequency as the frequency used in the cell subordinate to the target gNB as the transition destination, terminal 200 assigns high priority to RLF detection information including information on the indicated frequency. In addition, the terminal 200 may send a plurality of pieces of RLF discovery information to the target gNB as a transition destination according to the priority set by the network.

[0125]

In addition, when multiple pieces of RLF discovery information are included in the same message, if the message exceeds the maximum allowable size, the terminal 200 may remove the RLF discovery information piece from the message. In this case, the terminal 200 may notify the target gNB as the transition destination that some pieces of RLF discovery information have been removed.

[0126]

In addition, in the case that RLF is detected again after generating a message including a plurality of pieces of RLF discovery information, the terminal 200 may regenerate said message.

[0127]

(3.3) RRC reconfiguration completion message transmission interval in the conditional NO procedure

Next, the transmission interval of the RRC reconfiguration complete message in the conditional BUT procedure will be described. In the conditional NO procedure shown in FIG. 4, the terminal 200 transmits an RRC reconfiguration complete message if the RA procedure is successfully completed. On the other hand, in this operation, when the terminal 200 receives the RRC reconfiguration message, the terminal 200 immediately transmits the RRC reconfiguration complete message. That is, the terminal 200 transmits an RRC reconfiguration complete message before starting the RA procedure.

[0128]

In FIG. 16 is a diagram illustrating the transmission sequence of the RRC reconfiguration complete message in the conditional DO procedure. Steps S151-S155 in FIG. 16 are the same processing as S11-S15 in FIG. 4, and thus their description will be omitted.

[0129]

When terminal 200 receives an RRC reconfiguration message including an AtoN configuration from source gNB 100A, terminal 200 immediately obtains target candidate cell configuration information and transmits RRC reconfiguration complete message 1 to source gNB 100A (S155a).

[0130]

When the terminal 200 transmits the RRC reconfiguration complete message 1 to the source gNB 100A, the terminal 200 monitors the state of the AtoN (S157). Specifically, the terminal 200 judges whether or not the transition to target candidate cell included in the configuration information of each target candidate cell is met or not.

[0131]

In the case where the RRC processes are performed in parallel, the processing in the radio base station becomes complicated. Therefore, if the configuration information of the target candidate cell is changed, the terminal 200 must notify the change with an RRC reconfiguration message after receiving the RRC reconfiguration complete message to notify that the RRC connection reconfiguration is completed.

[0132]

Therefore, in the case of changing the configuration information of the target candidate cell, the source gNB 100A notifies the terminal 200 of changing the configuration information of the target candidate cell with the RRC reconfiguration message after receiving the RRC reconfiguration complete message 1 from the terminal 200 in step S155a (S159 ).

[0133]

In step S159, the source gNB 100A inserts the changed target candidate cell configuration information into the RRC reconfiguration message. It should be noted that the source gNB 100A may insert, in the new RRC reconfiguration message, a difference between the changed candidate target cell configuration information and the candidate target cell configuration information transmitted in step S155.

[0134]

The RRC reconfiguration message transmitted in step S155 is also referred to as the first configuration message. The RRC reconfiguration completion message 1 transmitted in step S155a is also referred to as the completion message for the first configuration message. The RRC reconfiguration message transmitted in step S159 is also referred to as the second configuration message.

[0135]

When the terminal 200 receives the RRC reconfiguration message from the source gNB 100A, the terminal 200 immediately obtains the changed target candidate cell configuration information and then transmits the RRC reconfiguration complete message 1 to the source gNB 100A (S159a). The terminal 200 updates the target candidate cell configuration information obtained in step S155 based on the changed target candidate cell configuration information.

[0136]

In the case where the terminal 200 judges that the handover condition to the candidate target cell is satisfied due to the movement of the terminal 200 or the like, the terminal 200 determines the start of a handover (HO) to the candidate target cell without receiving a handover command from the source gNB 100A (S161). In the present embodiment, the terminal 200 determines the start of the handover to the target candidate cell subordinate to the target gNB 100B.

[0137]

When terminal 200 determines the start of HO to the candidate target cell subordinate to target gNB 100B, terminal 200 performs a random access (RA) procedure between target gNB 100B and terminal 200, and establishes synchronization between target gNB 100B and terminal 200 (S163). Thus, terminal 200 is connected to a 100V target gNB.

[0138]

When the terminal 200 is connected to the 100B target gNB, the terminal 200 transmits an RRC reconfiguration complete message 2 or an RRC setup complete message to the 100B target gNB (S165).

[0139]

Note that, in step S159, the source gNB 100A sends an RRC reconfiguration message to the terminal 200 to change the target candidate cell's configuration information, but the present invention is not limited to this. For example, source gNB 100A may also send an RRC reconfiguration message to terminal 200 to change the configuration (UE configuration) of terminal 200 in addition to target candidate cell configuration information.

[0140]

In this case, the source gNB 100A contributes the changed UE configuration to the RRC reconfiguration message. It should be noted that the source gNB 100A may insert, in the RRC reconfiguration message, the difference between the changed UE configuration and the previously transmitted UE configuration.

[0141]

(3.4) Cancellation of NR in the conditional NR procedure

Next, the cancellation of BUT in the conditional BUT procedure will be described. In this operation, the target gNB instructs the source gNB to remove the target candidate cell configuration information after transmitting the candidate target cell configuration information to the source gNB. In the present embodiment, the target gNB 100B instructs the source gNB 100A to delete the target candidate cell configuration information.

[0142]

(3.4.1) Operation example 1

First, example 1 of the BUT cancellation operation in the conditional BUT procedure will be described. In FIG. 17 is a diagram illustrating the HO cancellation sequence (Operation Example 1) in the conditional HO procedure. S201-S207 shown in FIG. 17 are the same processing as S151-S157 shown in FIG. 16, and thus their description will be omitted.

[0143]

Note that the AtoN request acknowledgment transmitted in step S203 is also referred to as the first message. The HO cancel transmitted in step S209 is also referred to as the second message.

[0144]

In the case where the target gNB 100B identifies that the candidate target cell subordinate to the target gNB 100B is in a state unsuitable for the transition of the terminal 200, the target gNB 100B transmits a HO delete (HO cancel) message to the source gNB 100A (S209).

[0145]

In particular, the target gNB 100B may transmit a HO cancel in step S209 in the case where the target gNB 100B determines that the load increases in the candidate target cell subordinate to the target gNB 100B and the candidate target cell is in a state unsuitable for the transition of the terminal 200 .

[0146]

In this case, when a large number of terminals transition to a candidate target cell subordinate to the target gNB 100B, and the number of connected terminals exceeds the maximum number of connected terminals allowed by the candidate target cell, the target gNB 100B can determine that the candidate target cell is in state unsuitable for terminal 200 transition.

[0147]

For example, in call admission control (CAC), in the case where the number of connected terminals exceeds the maximum number of UE contexts in the target candidate cell subordinate to the target gNB 100B, the target gNB 100B determines that the target candidate cell is in a state unsuitable for terminal 200 transition.

[0148]

In addition, in the case where the terminal 200 does not transition to the target candidate cell within a predetermined time based on the configuration information of the target candidate cell subordinate to the target gNB 100B (for example, in the case where the terminal 200 is still in the dormant over a predetermined time), the target gNB 100B may transmit HO cancel in step S209.

[0149]

In addition, in the case where the target gNB 100B receives a UE context release from a gNB or ng-eNB other than the source gNB, the target gNB 100B may send a HO release in step S209.

[0150]

It should be noted that, in step S209, the target gNB 100B may directly transmit the HO cancel to the source gNB 100A. In this case, for example, signaling Xn is used to send the HO cancel. Alternatively, the target gNB 100B may send the HO cancel to the source gNB 100A via the core network. In this case, for example, NG signaling is used to transmit the HO cancel.

[0151]

When the source gNB 100A receives the HO cancel from the target gNB 100B, the source gNB 100A notifies the terminal 200 of the configuration information change of the target candidate cell with an RRC reconfiguration message after receiving the RRC reconfiguration complete message 1 from the terminal 200 in step S205a (S211) .

[0152]

In particular, the source gNB 100A inserts in the RRC reconfiguration message information instructing to delete the configuration information of the candidate target cell subordinate to the target gNB 100B. It should be noted that the source gNB 100A may insert, in the RRC reconfiguration message, an AtoN configuration from which the configuration information of the target candidate cell subordinate to the target gNB 100B is removed.

[0153]

When terminal 200 receives an RRC reconfiguration message from source gNB 100A, terminal 200 immediately transmits RRC reconfiguration complete message 1 to source gNB 100A (S211a). The terminal 200 deletes the configuration information of the candidate target cell subordinate to the target gNB 100B based on the receipt of the RRC reconfiguration message.

[0154]

In the case where the terminal 200 judges that the handover condition to the candidate target cell is satisfied due to the movement of the terminal 200 or the like, the terminal 200 determines the start of a handover (HO) to the candidate target cell without receiving a handover command from the source gNB 100A (S213). In the present embodiment, the terminal 200 determines the start of the HO to the candidate target cell subordinate to the target gNB 100C.

[0155]

When terminal 200 determines the start of HO to a candidate target cell subordinate to target gNB 100C, terminal 200 performs a random access (RA) procedure between target gNB 100C and terminal 200, and establishes synchronization between target gNB 100C and terminal 200 (S215). Thus, terminal 200 connects to target gNB 100C.

[0156]

When the terminal 200 is connected to the target gNB 100C, the terminal 200 transmits an RRC reconfiguration complete message 2 or an RRC setup complete message to the target gNB 100C (S217).

[0157]

(3.4.2) Operation example 2

Next, an example 2 of the BUT cancellation operation in the conditional BUT procedure will be described. In FIG. 18 is a diagram illustrating the BUT cancellation sequence (Operation Example 2) in the conditional BUT procedure. S231-S239 shown in FIG. 18 are the same processing as S201-S209 shown in FIG. 17, and thus their description will be omitted.

[0158]

It should be noted that in the present operation example, source gNB 100A locates only target gNB 100B based on the measurement report received from terminal 200. Therefore, source gNB 100A transmits an AtoN request to target gNB 100B (S231) and receives an AtoN request acknowledgment including candidate target cell configuration information from target gNB 100B(S233).

[0159]

In the event that source gNB 100A detects target gNB 100C present in the vicinity of source gNB 100A, after receiving HO cancel from target gNB 100B, source gNB 100A sends a CHO request to target gNB 100C (S241).

[0160]

When the target gNB 100C receives the AtoN request from the source gNB 100A, the target gNB 100C sends to the source gNB 100A an Ato request acknowledgment including the target candidate cell configuration information subordinate to the target gNB 100C (S243).

[0161]

When the source gNB 100A receives the HO cancel from the target gNB 100B and receives the AtoN request acknowledgment from the target gNB 100C, the source gNB 100A notifies the terminal 200 of the target candidate cell configuration information change with an RRC reconfiguration message after receiving the RRC reconfiguration complete message 1 from terminal 200 in step S235a (S245).

[0162]

Specifically, the source gNB 100A deletes the configuration information of the candidate target cell subordinate to the target gNB 100B and inserts, in the RRC reconfiguration message, the AtoN configuration including the configuration information of the target candidate cell subordinate to the target gNB 100C.

[0163]

When terminal 200 receives an RRC reconfiguration message from source gNB 100A, terminal 200 immediately transmits RRC reconfiguration complete message 1 to source gNB 100A (S245a). The terminal 200 applies the AtoN configuration including the configuration information of the candidate target cell subordinate to the target gNB 100C based on the receipt of the RRC reconfiguration message.

[0164]

In the case where the terminal 200 judges that the handover condition to the candidate target cell is satisfied due to the movement of the terminal 200 or the like, the terminal 200 determines the start of a handover (HO) to the candidate target cell without receiving a handover command from the source gNB 100A (S247). In the present embodiment, the terminal 200 determines the start of the HO to the candidate target cell subordinate to the target gNB 100C.

[0165]

When terminal 200 determines the start of HO to a candidate target cell subordinate to target gNB 100C, terminal 200 performs a random access (RA) procedure between target gNB 100C and terminal 200, and establishes synchronization between target gNB 100C and terminal 200 (S249). Thus, terminal 200 connects to target gNB 100C.

[0166]

When the terminal 200 is connected to the target gNB 100C, the terminal 200 transmits an RRC reconfiguration complete message 2 or an RRC setup complete message to the target gNB 100C (S251).

[0167]

(3.5) Changing the NR in the conditional NR procedure

Next, the change of BUT in the conditional BUT procedure will be described. In this operation, the target gNB instructs the source gNB to change the target candidate cell configuration information after transmitting the candidate target cell configuration information to the source gNB. In the present embodiment, the target gNB 100B instructs the source gNB 100A to change the target candidate cell configuration information.

[0168]

(3.5.1) Operation Example 1

First, example 1 of the BUT change operation in the conditional BUT procedure will be described. In FIG. 19 is a diagram illustrating the sequence of changing BUT (Operation Example 1) in the conditional BUT procedure. S301, S303 and S309-S315 shown in FIG. 19 are the same processing as S11, S13, and S17-S23 shown in FIG. 4, and thus their description will be omitted.

[0169]

Note that the AtoN request acknowledgment transmitted in step S303 is also referred to as the first message. The BUT change transmitted in step S209 is also referred to as the second message.

[0170]

As shown in FIG. 19, in the case where the target gNB 100B identifies a state change of the target candidate cell subordinate to the target gNB 100B, after transmitting configuration information of the target candidate cell to the source gNB 100A using Ato request confirmation in step S303, the target gNB 100B transmits a changing HO (change HO) to the original gNB 100 A (S305).

[0171]

Specifically, the target gNB 100B may transmit a change of BUT in step S305 in the case that the target gNB 100B determines that the download state is changed in the candidate target cell subordinate to the target gNB 100B, and thus the transition condition to the target cell needs to be changed. candidate.

[0172]

It should be noted that, in step S305, the target gNB 100B may directly transmit the BUT change to the source gNB 100A. In this case, for example, signaling Xn is used to send a change in HO. Alternatively, target gNB 100B may transmit the BUT change to source gNB 100A via the core network. In this case, for example, NG signaling is used to convey the change in HO.

[0173]

When the source gNB 100A receives the HO change from the target gNB 100B, the source gNB 100A changes the configuration information of the candidate target cell subordinate to the target gNB 100B and transmits an RRC reconfiguration message including the AtoN configuration to the terminal 200 (S307).

[0174]

(3.5.2) Operation example 2

Next, an example 2 of the BUT change operation in the conditional BUT procedure will be described. In FIG. 20 is a diagram illustrating the sequence of changing the BUT (Operation Example 2) in the conditional BUT procedure. S301-S313 shown in FIG. 20 are the same processing as S301 to S313 shown in FIG. 19, and thus their description will be omitted.

[0175]

As shown in FIG. 20, when terminal 200 receives an RRC reconfiguration message from source gNB 100A, terminal 200 immediately transmits RRC reconfiguration complete message 1 (S307a).

[0176]

When the terminal 200 is connected to the target gNB 100B with the RA procedure in step S313, the terminal 200 transmits an RRC reconfiguration complete message 2 or an RRC setup complete message to the target gNB 100B (S315a).

[0177]

(3.5.3) Operation example 3

Next, an example 3 of the BUT change operation in the conditional BUT procedure will be described. In FIG. 21 is a diagram illustrating the sequence of changing BUT (Operation Example 3) in the conditional BUT procedure. S301, S303, S307, S307a and S309 shown in FIG. 21 are the same processing as S301, S303, S307, S307a, and S309 shown in FIG. 20, and thus their description will be omitted.

[0178]

As shown in FIG. 21, when the target gNB 100B identifies a state change of the target candidate cell subordinate to the target gNB 100B, the target gNB 100B transmits the change of HO to the source gNB 100A (S331).

[0179]

When the source gNB 100A receives the HO change from the target gNB 100B, the source gNB 100A notifies the terminal 200 of the change in the configuration information of the target candidate cell with an RRC reconfiguration message after receiving the RRC reconfiguration complete message 1 from the terminal 200 in step S307a (S333) .

[0180]

Specifically, the source gNB 100A inserts, in the RRC reconfiguration message, an AtoN configuration in which the configuration information of the target candidate cell subordinate to the target gNB 100B is changed.

[0181]

When terminal 200 receives an RRC reconfiguration message from source gNB 100A, terminal 200 immediately transmits RRC reconfiguration complete message 1 to source gNB 100A (S333a). The terminal 200 changes the configuration information of the candidate target cell subordinate to the target gNB 100B based on the receipt of the RRC reconfiguration message.

[0182]

In the case where the terminal 200 judges that the handover condition to the candidate target cell is satisfied due to the movement of the terminal 200 or the like, the terminal 200 determines the start of a handover (HO) to the candidate target cell without receiving a handover command from the source gNB 100A (S335). In the present embodiment, the terminal 200 determines the start of the handover to the target candidate cell subordinate to the target gNB 100B.

[0183]

When terminal 200 determines the start of HO to the candidate target cell subordinate to target gNB 100B, terminal 200 performs a random access (RA) procedure between target gNB 100B and terminal 200, and establishes synchronization between target gNB 100B and terminal 200 (S337). Thus, terminal 200 is connected to a 100V target gNB.

[0184]

When the terminal 200 is connected to the 100B target gNB, the terminal 200 transmits an RRC reconfiguration complete message 2 or an RRC setup complete message to the 100B target gNB (S339).

[0185]

(3.6) Configuration of the RRC reconfiguration message in the conditional NDO procedure

Next, the configuration of the RRC reconfiguration message in the conditional BUT procedure will be described. In this configuration, the RRC reconfiguration message includes configuration information of the candidate target cell subordinate to the target gNB 100B and configuration information of the candidate target cell subordinate to the target gNB 100C. configuration of target candidate cells in an RRC reconfiguration message" is also expressed as "encapsulating a plurality of pieces of configuration information of a plurality of target candidate cells in an RRC reconfiguration message".

[0186]

First, a workflow for encapsulating a plurality of pieces of target candidate cell configuration information will be described. In FIG. 22 is a diagram illustrating a workflow for encapsulating multiple pieces of target candidate cell configuration information. As shown in FIG. 22, source gNB 100A transmits an AtoN request to target gNBs 100B and 100C (S350).

[0187]

When source gNB 100A receives candidate target cell configuration information from each of target gNBs 100B and 100C (S353), source gNB 100A encapsulates two pieces of candidate target cell configuration information in an RRC reconfiguration message (S355).

[0188]

When the source gNB 100A encapsulates a plurality of pieces of configuration information of a plurality of candidate target cells in an RRC reconfiguration message, the source gNB 100A transmits an RRC reconfiguration message to the terminal 200 (S357).

[0189]

(3.6.1) Configuration example 1

Next, the encapsulation of a plurality of configuration information pieces of target candidate cells will be described in detail. In FIG. 23 is a diagram illustrating the configuration (Configuration Example 1) of the RRC reconfiguration message in the conditional BUT procedure.

[0190]

As shown in FIG. 23, a group of downlink-dedicated control channel (DL-DCCH) messages includes an RRC reconfiguration message, an RRC resume message ("RRC Resume" message), an RRC release message ("RRC Resume" message). Release”), RRC restoration (“RRC Reestablishment” message), Security Mode Command, etc.

[0191]

The DL-DCCH is a downlink dedicated control channel used by terminal 200 that has established an RRC connection. The terminal 200 receives the above-described RRC message and the like on the DL-DCCH.

[0192]

In this configuration example, a new information element (IE) is set in a normal RRC reconfiguration message, and configuration information of candidate target cell subordinate to target gNB 100B and configuration information of candidate target cell subordinate to target gNB 100C are included in the IE.

[0193]

Specifically, an RRC reconfiguration list ("RRCReconfigurationList") is set as a new IE in a normal RRC reconfiguration message, and a configuration for cell1 (cell1) and a configuration for cell2 (cell2) are set in the RRC reconfiguration list. It should be noted that the number of configurations for cells is not limited to two.

[0194]

In such a configuration, when source gNB 100A receives the configuration information of the candidate target cell subordinate to the target gNB 100B from the target gNB 100B, the source gNB 100A enters the configuration information of the target candidate cell into the configuration for cell1 in the RRC reconfiguration list. Similarly, when source gNB 100A receives configuration information of a target candidate cell subordinate to target gNB 100C from target gNB 100C, source gNB 100A enters configuration information of the candidate target cell into the configuration for cell2 in the RRC reconfiguration list.

[0195]

Note that the RRC reconfiguration list is also referred to as the AtoN configuration. When the terminal 200 receives the RRC reconfiguration message from the source gNB 100A, the terminal 200 obtains the configuration information of the target candidate cell subordinate to the target gNB 100B and the configuration information of the target candidate cell subordinate to the target gNB 100C from the configuration for cell1 and the configuration for cell2 in the RRC reconfiguration message, respectively.

[0196]

The candidate target cell configuration information may include at least one of the following types of information, in addition to the candidate target cell information and the transition condition to the candidate target cell.

[0197]

Measurement condition

Candidate target cell configuration

Security information (for example, security key update information)

Transaction ID

[0198]

(3.6.2) Configuration example 2

In FIG. 24 is a diagram illustrating the configuration (Configuration Example 2) of the RRC reconfiguration message in the conditional BUT procedure. As shown in FIG. 24, the DL-DCCH message includes an RRC Reconfiguration message, an RRC Resume message, an RRC Release message, an RRC Restore message, a Security Mode Command, an RRC Reconfiguration message 1, and the like.

[0199]

RRC reconfiguration message 1 is a new message different from the normal RRC reconfiguration message, and is an RRC reconfiguration message used in the conditional BUT procedure. It should be noted that the name of the new message is not limited to the name "RRC Reconfiguration Message 1" ("RRC Reconfiguration 1"). In the present configuration example, configuration information of candidate target cell subordinate to target gNB 100B and configuration information of candidate target cell subordinate to target gNB 100C are included in an information element (IE) set in RRC reconfiguration message 1.

[0200]

In particular, the RRC reconfiguration list is specified in the new RRC reconfiguration message 1, and the configuration for cell1 and the configuration for cell2 are specified in the RRC reconfiguration list. It should be noted that the number of configurations for cells is not limited to two.

[0201]

In such a configuration, when source gNB 100A receives the configuration information of the candidate target cell subordinate to the target gNB 100B from the target gNB 100B, the source gNB 100A enters the configuration information of the target candidate cell into the configuration for cell1 in the RRC reconfiguration list. Similarly, when source gNB 100A receives configuration information of a target candidate cell subordinate to target gNB 100C from target gNB 100C, source gNB 100A enters configuration information of the candidate target cell into the configuration for cell2 in the RRC reconfiguration list.

[0202]

When terminal 200 receives RRC reconfiguration message 1 from source gNB 100A, terminal 200 obtains configuration information of candidate target cell subordinate to target gNB 100B and configuration information of candidate target cell subordinate to target gNB 100C from the configuration for cell1 and configuration for cell2 in RRC reconfiguration message 1, respectively.

[0203]

(3.7) Assignment of transaction ID in the conditional DUT procedure Next, assignment of the transaction ID in the conditional DUT procedure will be described. In this operation, the source gNB or target gNB performs the assignment of the transaction ID used in the conditional DO procedure.

[0204]

(3.7.1) Operation Example 1

First, example 1 of the operation of assigning an identifier in the conditional BUT procedure will be described. In this example operation, the source gNB performs the assignment of the transaction ID used in the conditional NFR procedure.

[0205]

In FIG. 25 is a diagram illustrating the assignment sequence of an identifier (Operation Example 1) in the conditional DO procedure. S401, S403, and S409-S413 shown in FIG. 25 are the same processing as S11, S13, and S17-S21 shown in FIG. 4, and thus their description will be omitted.

[0206]

As shown in FIG. 25, when source gNB 100A receives an AtoN request acknowledgment from each of target gNBs 100B and 100C, source gNB 100A inserts the AtoN configuration into the RRC reconfiguration message and assigns a transaction ID to the RRC reconfiguration message (S405).

[0207]

Specifically, the source gNB 100A lists, in the RRC reconfiguration list in the RRC reconfiguration message, the identification information of the target candidate cell subordinate to the target gNB 100B and the identification information of the target candidate cell subordinate to the target gNB 100C, and sets the transaction ID to a predetermined information element (IE) in the RRC reconfiguration message (see FIG. 23). Note that the RRC reconfiguration list is also referred to as the AtoN configuration.

[0208]

It should be noted that the source gNB 100A can list, in the RRC reconfiguration list in the RRC reconfiguration message 1, which is the RRC reconfiguration message and is used in the conditional HO, the identity of the candidate target cell subordinate to the target gNB 100B, and the identity of the target cell -candidate subordinate to target gNB 100C and set a transaction ID for a predefined information element (IE) in RRC reconfiguration message 1 (see FIG. 24).

[0209]

The transaction ID can be from 0 to 3 or a fixed value of 0. In the present embodiment, the transaction ID is from 0 to 3.

[0210]

The source gNB 100A may assign a transaction ID to the RRC reconfiguration list included in the RRC reconfiguration message, ie, a group of encapsulated multiple target candidate cell configuration information, instead of assigning a transaction ID to the RRC reconfiguration message.

[0211]

When the source gNB 100A sets up an RRC reconfiguration message, the source gNB 100A transmits an RRC reconfiguration message to the terminal 200 (S407).

[0212]

When the terminal 200 receives the RRC reconfiguration message from the source gNB 100A, the terminal 200 immediately obtains the target candidate cell configuration information and then transmits the RRC reconfiguration complete message 1 to the source gNB 100A (S407a).

[0213]

In step S407a, the terminal 200 inserts, in the RRC reconfiguration complete message 1, the transaction ID assigned to the RRC reconfiguration message received from the source gNB 100A.

[0214]

The terminal 200 monitors the state of the AtoN (S409), starts HO on the target gNB 100B (S411), and performs the RA procedure (S413) between the target gNB 100B and the terminal 200, and when the terminal 200 connects to the target gNB 100B, the terminal 200 sends message 2 o completion of RRC reconfiguration to target gNB 100B (S415).

[0215]

(3.7.2) Operation example 2

Next, an example 2 of the operation of assigning an identifier in the conditional BUT procedure will be described. In this operation example, the target gNB performs the assignment of the transaction ID to be used in the conditional DO procedure.

[0216]

In FIG. 26 is a diagram illustrating the assignment sequence of an identifier (Operation Example 2) in the conditional DO procedure. S401 and S409-S413 shown in Fig. 26 are the same processing as S11 and S17-S21 shown in Fig. 4, and thus their description will be omitted.

[0217]

As shown in FIG. 26, when the target gNB 100B receives an AtoN request from the source gNB 100A, the target gNB 100B contributes, in acknowledgment of the AtoN request, the target candidate cell configuration information subordinate to the target gNB 100B, and assigns the target gNB 100B configuration information Transaction ID. candidate cell (S431). In particular, the target gNB 100B contributes the transaction ID to the configuration information of the target candidate cell.

[0218]

Similarly, when the target gNB 100C receives an AtoN request from the source gNB 100A, the target gNB 100C contributes, in acknowledgment of the AtoN request, the candidate target cell configuration information subordinate to the target gNB 100C, and assigns the candidate target cell configuration information Transaction ID (S431 ). In particular, the target gNB 100B contributes the transaction ID to the configuration information of the target candidate cell.

[0219]

The transaction ID can be from 0 to 3 or a fixed value of 0. In the present embodiment, the transaction ID is from 0 to 3.

[0220]

When source gNB 100A receives an AtoN request acknowledgment from each of target gNBs 100B and 100C, source gNB 100A inserts the AtoN configuration into the RRC reconfiguration message. In particular, the source gNB 100A lists, in the RRC reconfiguration list in the RRC reconfiguration message, the identification information of the target candidate cell subordinate to the target gNB 100B to which the transaction ID is assigned, and the identification information of the target candidate cell subordinate to the target gNB 100C to which the transaction ID is assigned. transaction ID (see Fig. 23). Note that the RRC reconfiguration list is also referred to as the AtoN configuration.

[0221]

It should be noted that the source gNB 100A can list, in the RRC reconfiguration list in the RRC reconfiguration message 1, which is the RRC reconfiguration message used in the conditional HO, the identity of the target candidate cell subordinate to the target gNB 100B, and the identity of the target cell -candidate subordinate to target gNB 100C (see FIG. 24).

[0222]

When the source gNB 100A sets up an RRC reconfiguration message, the source gNB 100A transmits an RRC reconfiguration message to the terminal 200 (S435).

[0223]

When the terminal 200 receives the RRC reconfiguration message from the source gNB 100A, the terminal 200 immediately obtains the target candidate cell configuration information, and transmits an RRC reconfiguration complete message 1 to the source gNB 100A (S435a).

[0224]

The terminal 200 monitors the state of the AtoN (S437), starts HO on the target gNB 100B (S439), and performs the RA procedure (S441) between the target gNB 100B and the terminal 200, and when the terminal 200 connects to the target gNB 100B, the terminal 200 transmits a completion message 2 reconfiguring RRC to target gNB 100B (S443).

[0225]

In step S443, the terminal 200 inputs, in the RRC reconfiguration complete message 2, the transaction ID included in the configuration information of the target candidate cell subordinate to the target gNB 100B.

[0226]

(3.8) Recovery from HOF in the conditional HOF procedure Next, recovery from HOF in the conditional HOF procedure will be described. This operation is performed in the case where a HOF occurs when the terminal 200 receives a HO command from the source gNB during Atoo state tracking, cancels the AtoN, and preferably transitions to the target gNB. In this case, the terminal 200 maintains all or part of the candidate target cell configuration information subordinate to the target gNB.

[0227]

In FIG. 27 is a diagram illustrating the recovery sequence after HOF in a conventional HO procedure. Steps S501-S507 in FIG. 27 are the same processing as S11-S17 in FIG. 4, and thus their description will be omitted.

[0228]

In the case where source gNB 100A decides to prompt terminal 200 to preferentially transition to a candidate target cell subordinate to target gNB 100B, source gNB 100A transmits a HO request to target gNB 100B (S509). When the target gNB 100B receives the HO request from the source gNB 100A, the target gNB 100B sends an acknowledgment of the HO request to the source gNB 100A (S511).

[0229]

When source gNB 100A receives the HO request acknowledgment from target gNB 100B, source gNB 100A transmits a HO command to terminal 200 (S513). When terminal 200 receives a HO command from source gNB 100A during AtoN status monitoring, terminal 200 attempts to perform a handover procedure between target gNB 100B and terminal 200 (S515).

[0230]

In the case where the handover procedure fails due to the occurrence of a HOF during the handover procedure in step S515, the terminal 200 reselects the target candidate cell (CHO cell) as the transition destination for which the transition condition is met (S517). In the present embodiment, the terminal 200 reselects a target candidate cell subordinate to the target gNB 100B.

[0231]

In step S517, the terminal 200 maintains all or part of the target candidate cell configuration information subordinate to the target gNB 100B. It should be noted that "maintaining all or part of the configuration information of the target candidate cell" can also be expressed as "assuming that all or part of the configuration information of the target candidate cell is applicable" or "assuming that all or part of the configuration information of the candidate target cell is applicable" candidate target cell configuration information is valid."

[0232]

In step S517, the information maintained by the terminal 200 in the target candidate cell configuration information is security information, for example. It should be noted that in the case where the target gNB 100B obtains the identification information of the terminal 200 in advance, the information maintained by the terminal 200 may be the identification information of the terminal 200.

[0233]

Examples of identification information of the terminal 200 include the following information.

[0234]

Short Media Access Control Identifier (Short MAC Identifier)

Cell radio network temporary identifier (C-RNTI)

Implicit radio network temporary identifier (I-RNTI)

When terminal 200 reselects a candidate target cell subordinate to target gNB 100B, terminal 200 performs a random access (RA) procedure between target gNB 100B and terminal 200, and establishes synchronization between target gNB 100B and terminal 200 (S519). Thus, terminal 200 is connected to a 100V target gNB.

[0235]

When the terminal 200 is connected to the target gNB 100B, the terminal 200 transmits an RRC reconfiguration complete message (RRC Reconfiguration Complete message) to the target gNB 100B (S521).

[0236]

In step S521, the terminal 200 may insert, in the RRC reconfiguration complete message, all or part of the target candidate cell configuration information maintained in step S517, and transmit to the target gNB 100B an RRC reconfiguration complete message using Radio Signaling Channel 1 (SRB1 , English signaling radio bearer 1). The terminal 200 may insert all or part of the target candidate cell configuration information maintained in step S517 into an RRC Reestablishment request, and transmit the RRC Reestablishment request to the target gNB 100B using Signaling Radio Channel 0 (SRB0 ), instead of SRB1.

[0237]

Note that SRB0 is a radio transmission channel for the common control channel (CCCH). SRB1 is a radio transmission channel for a dedicated control channel (DCCH).

[0238]

In addition, in step S521, the terminal 200 may insert, in the RRC reconfiguration complete message, information indicating that all or part of the target candidate cell's configuration information is supported, and transmit the RRC reconfiguration complete message to the target gNB 100B.

[0239]

In addition, in step S521, the terminal 200 may insert, in the RRC reconfiguration complete message, information that can be one-to-one mapped with the target candidate cell configuration information maintained in step S517, and transmit the RRC reconfiguration complete message to the target gNB 100V.

[0240]

Thus, for example, the security information or identification information of the terminal 200 is shared between the terminal 200 and the target gNB 100B. Therefore, target gNB 100B can determine if terminal 200 is a terminal that is allowed to transition to target gNB 100B.

[0241]

It should be noted that the application of this operation is not limited to the case where a HOF occurs when the terminal 200 receives a HO command from the source gNB while tracking the AtoN state, cancels the AtoN, and preferably transitions to the target gNB. For example, this operation can be applied even in the case where a HOF occurs, when the terminal 200 monitors the Ato condition, the transition condition to the candidate target cell subordinate to the target gNB is met, and HO is performed on the candidate target cell without receiving a HO command from the source gNB. .

[0242]

(3.9) Resuming radio transmission after RLF in the conditional HO procedure Next, the resumption of radio transmission after RLF in the conditional HO procedure will be described. In this operation, in the case where the terminal 200 reconnects to the target gNB in the conditional HO procedure, the terminal 200 resumes radio transmission channels suspended due to the occurrence of RLF based on a specific condition.

[0243]

It should be noted that the radio channels include a signaling radio channel (SRB, signaling radio bearer) and a data radio channel (DRB, data radio bearer). SRB is for control plane data and DRB is for user plane data. In addition, SRBO, SRB1, SRB2 or SRB3 may be configured as SRB according to usage.

[0244]

SRB0 is the radio channel for CCCH. SRB1-SRB3 are radio bearers for DCCH. DRB is a radio channel for user data.

[0245]

SRB1 is used to send and receive RRC messages and NAS messages before setting SRB2.

[0246]

SRB2 is used to send and receive NAS messages, has a lower priority than SRB1, and is configured by the network after "AS security" is enabled.

[0247]

SRB3 is used to send and receive a specific RRC message on an E-UTRA-NR dual connection (E-UTRA-NR Dual Connectivity (EN-DC)).

[0248]

In the present embodiment, in case RLF is detected when the terminal 200 transitions to the target gNB 100B using the target candidate cell configuration information subordinate to the target gNB 100B, the terminal 200 suspends all radio transmission channels except SRB0 between the target gNB 100V and terminal 200, and reconnects to the target gNB 100V.

[0249]

In FIG. 28 is a diagram illustrating the workflow of a terminal 200 that resumes radio transmission after RLF in a conditional HO procedure. In FIG. 29 is a view illustrating conditions for resuming radio transmission after a radio link failure (RLF) in the conditional HO procedure.

[0250]

As shown in FIG. 28, the terminal 200 reselects the AtoN cell in the conditional HO procedure (S601). Specifically, the terminal 200 reselects a candidate target cell (CHO cell) as a transition destination for which the transition condition is met. In the present embodiment, the terminal 200 reselects a target candidate cell subordinate to the target gNB 100B.

[0251]

When the terminal 200 reselects the target candidate cell subordinate to the target gNB 100B, the terminal 200 starts transitioning to the target gNB 100B based on the target candidate cell configuration information (S603). In this case, all radio transmission channels suspended between target gNB 100B and terminal 200 can be resumed (condition A in FIG. 29).

[0252]

Terminal 200 starts a random access (RA) procedure between target gNB 100B and terminal 200, with transition to target gNB 100B (S605). In this case, all radio transmission channels suspended between target gNB 100B and terminal 200 can be resumed (condition B in FIG. 29).

[0253]

When the RA procedure between the 100B target gNB and the terminal 200 is completed (S607), the terminal 200 establishes synchronization between the 100B target gNB and the terminal 200. Thus, the terminal 200 connects to the 100B target gNB. In this case, all radio channels suspended between target gNB 100B and terminal 200 can be resumed (condition C in FIG. 29).

[0254]

It should be noted that in the case that terminal 200 receives an RRC message instructing to resume radio transmission channels from the network in steps S601 to S607, terminal 200 may resume all radio transmission channels suspended between target gNB 100B and terminal 200 (condition D in FIG. 29).

[0255]

In this case, the terminal 200 may notify the network that the resumption of the radio transmission channels is completed by using a resume complete message ("RRC Resume Complete" message).

[0256]

When the terminal 200 is connected to the target gNB 100B, the terminal 200 transmits an RRC reconfiguration complete message to the target gNB 100B (S609).

[0257]

(4) Action/Effect

According to the embodiment described above, terminal 200 receives from source gNB 100A a first configuration message (RRC reconfiguration message) including configuration information of a target candidate cell subordinate to target gNB 100B. The terminal 200 performs a random access procedure (RA procedure) between the terminal 200 and the target gNB 100B and transitions to the target gNB 100B without receiving a handover command based on the target candidate cell configuration information. The terminal 200 sends, to the source gNB 100A, a completion message (RRC reconfiguration complete message 1) for the first configuration message (RRC reconfiguration message) before starting the random access procedure (RA procedure).

[0258]

With this configuration, source gNB 100A can receive an RRC reconfiguration message from terminal 200. Therefore, source gNB 100A can notify terminal 200 of the changed target candidate cell configuration information.

[0259]

According to the embodiment described above, after transmitting the completion message (RRC reconfiguration complete message 1), the terminal 200 receives, from the source gNB 100A, a second configuration message (RRC reconfiguration message) including the changed configuration information of the target cell - candidate.

[0260]

With this configuration, the terminal 200 can jump to the target gNB 100B based on the changed target candidate cell configuration information. Therefore, it is possible to prevent the terminal 200 from transitioning to the target gNB in a state unsuitable for the terminal 200 to transition.

[0261]

(5) Other embodiments

Although the contents of the present invention have been described in accordance with the embodiment, the present invention is not limited to this description, and it is obvious to those skilled in the art that various modifications and improvements can be made thereto.

[0262]

For example, in the embodiment described above, NR has been described as an example. However, the conditional DO can also be applied to LTE, and the same operation can be performed in LTE.

[0263]

The block diagrams (FIGS. 2 and 3) used to describe the above embodiment illustrate blocks of a functional unit. These functional blocks (structural components) are implemented by the desired combination of at least one of hardware and software. The way to implement each functional block is not limited to special cases. That is, each functional block can be implemented by one device, combined physically or logically. Alternatively, two or more physically or logically separated devices may be directly or indirectly connected (eg, wired or wirelessly) to each other, and each functional block may be implemented by this plurality of devices. Function blocks can be implemented by combining software with one device or multiple devices mentioned above.

[0264]

Functions include evaluation, decision, determination, calculation, computation, processing, inference, exploration, search, confirmation, reception, transmission, inference, access, resolution, selection, selection, establishment, comparison, guess, expectation, consideration, broadcast , notification, communication, forwarding, configuration, reconfiguration, placement (display), assignment, etc. However, the functions are not limited to this. For example, a functional block (structural component) that causes a transmission is called a transmitter or transmitter. For any of the above, as described above, the implementation method is not specifically limited to any one method.

[0265]

In addition, the gNBs 100A, 100B, and 100C and the terminal 200 described above can function as a computer that performs processing of the radio communication method of the present invention. In FIG. 30 is a diagram illustrating an example of a hardware configuration of the device. As shown in FIG. 30, the device may be configured as a computer device, including a processor 1001, a memory 1002, a storage device 1003, a communication device 1004, an input device 1005, an output device 1006, a bus 1007, and the like.

[0266]

In addition, in the following description, the term "device" may be replaced by a circuit, device, block, and the like. A device hardware configuration may be built by including one or more of the devices shown in the figure, or may be built without including some devices.

[0267]

Each functional block of the device is implemented by any of the hardware elements of the computing device or by a combination of hardware elements.

[0268]

Moreover, the processor 1001 performs an operation by downloading predetermined software (computer program) to the hardware such as the processor 1001 and the memory 1002, and implements various device functions by controlling communication by the communication device 1004 and by controlling at least one of the reading and writing data to memory 1002 and storage 1003.

[0269]

The processor 1001, for example, controls the operating system to control the entire computer. The processor 1001 may be configured with a central processing unit (CPU) including an interface with a peripheral device, a control device, an operating device, a register, or the like.

[0270]

Moreover, the processor 1001 reads a computer program (computer program code), a program module, data, or the like. from at least one of the storage device 1003 and the communication device 1004 to the memory 1002 and performs various processing in accordance with them. As the computer program, a computer program is used that is capable of performing at least a part of the operation described in the above embodiments on the computer. Alternatively, the various processing described above may be performed by a single processor 1001, or may be performed simultaneously or sequentially by two or more processors 1001. The processor 1001 may be implemented by one or more chips. Alternatively, the computer program may be transmitted from the network over a telecommunications line.

[0271]

The memory 1002 is a computer-readable recording medium and may be configured, for example, with at least one of read-only memory (ROM), erasable programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), random access memory (RAM), etc. P. The memory 1002 may be referred to as a register, cache, main memory (main storage), and the like. The memory 1002 may store a computer program (computer program codes), program modules, and the like that can execute the method according to an embodiment of the present invention.

[0272]

The drive 1003 is a computer-readable recording medium. Examples of the drive 1003 include at least one of an optical disc such as a compact disc ROM (CD-ROM), a hard disk, a floppy disk, a magneto-optical disk (e.g., a CD, a digital versatile disk, and a Blu-ray ( registered trademark) disk), smart cards, flash memory (such as cards, flash cards and key drives), floppy disks (floppy, registered trademark), magnetic stripe, etc. The drive 1003 may be referred to as an auxiliary storage device. The recording medium may be, for example, a database including at least one of the memory 1002 and the drive 1003, a server, or other suitable medium.

[0273]

The communication device 1004 is a hardware (transmitting and receiving device) capable of communicating between computers through at least one of a wired network and a wireless network. The communication device 1004 is also called, for example, a network device, a network controller, a network card, a communication module, or the like.

[0274]

The communication device 1004 may include a high frequency switch, a duplexer, a filter, a frequency synthesizer, and the like. to implement, for example, at least one of duplex communication with frequency division (FDD, from the English. Frequency Division Duplex) and duplex communication with time division (TDD, from the English. Time Division Duplex).

[0275]

The input device 1005 is an input device (eg, keyboard, mouse, microphone, switch, button, sensor, etc.) that receives input from outside. The output device 1006 is an output device (eg, display, speaker, LED lamp, etc.) that outputs data to the outside. It should be noted that the input device 1005 and the output device 1006 can be combined (eg, in the form of a touch screen).

[0276]

In addition, the respective devices such as the processor 1001 and the memory 1002 are connected to each other via the bus 1007 to exchange information between them. Bus 1007 may be formed with a single bus, or may be formed with separate buses between devices.

[0277]

In addition, 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 (PLU), and a field programmable gate array (FPGA). Field Programmable Gate Array). Some or all of these functional blocks may be implemented in hardware. For example, processor 1001 may be implemented using at least one of these types of hardware.

[0278]

Information notification is not limited to what is described in the above aspect/embodiment, and may be performed using another method. For example, notification of the information may be performed by physical layer signaling (eg, downstream control information (DCI), upstream control information (UCI), higher layer signaling (eg, RRC signaling, medium access control (MAC) signaling), broadcast information (Mineral Information Block (MIB) and System Information Block (SIB)), other signals, or a combination thereof. The RRC signaling may be called, for example, an RRC message, or may be an RRC Connection Setup message, an RRC Connection Reconfiguration message, or the like.

[0279]

Each of the above aspects/embodiments can be applied to at least one of the following: Long Term Evolution (LTE) scheme, LTE-Advanced (LTE-A), SUPER 3G, IMT-Advanced, 4th generation mobile communication system (4G ), 5th Generation Mobile Communications System (5G), Future Radio Access (FRA), New Radio (NR), W-CDMA (Registered Trademark), GSM (Registered Trademark), CDMA2000, Ultra Mobile Broadband (UMB) .Ultra Mobile Broadband), IEEE 802.11 (Wi-Fi (Registered Trademark)), IEEE 802.16 (WiMAX (Registered Trademark)), IEEE 802.20, Ultra Wideband (UWB), Bluetooth (Registered Trademark), system using any another suitable system, and a next generation system that builds on them. In addition, multiple systems may be combined (eg, a combination of at least one of LTE and LTE-Ac 5G).

[0280]

As long as there is no conflict, the order of processing procedures, sequences, flow charts, etc. of each of the above aspects/embodiments in the present invention may be changed. For example, the various steps and sequence of steps of the methods described above are exemplary and are not limited to the specific order mentioned above.

[0281]

The particular operation that is performed by the base station in the present invention may, in some cases, be performed by its higher level node. In a network formed by one or more network nodes having a base station, various operations performed for communication with a terminal may be performed by at least one of the base station and other network nodes other than the base station (for example, MME, S- GW, etc., but not limited to). The above describes an example in which there is one network node other than the base station; however, a combination of many other network nodes (eg, MME and S-GW) may be used.

[0282]

Information and signals (information and the like) may be output from a higher layer (or lower layer) to a lower layer (or higher layer). They can be input and output through multiple network nodes.

[0283]

The input and output information may be stored in a specific location (eg memory) or may be managed in a control table. Information to be input and output can be overwritten, updated or added. Information may be deleted after withdrawal. The entered information can be transferred to another device.

[0284]

The determination can be made by a value (0 or 1) represented by a single bit, or by a Boolean value (Boolean value: TRUE or FALSE), or by comparing numerical values (eg, comparing with a predetermined value).

[0285]

Each aspect/embodiment described in the present invention may be used alone or in combination, or may be switched according to implementation. In addition, notification of predetermined information (eg, notification of "equal to X") is not limited to explicit execution, and it may be performed implicitly (eg, without notification of predetermined information).

[0286]

Instead of being called software, firmware, middleware, microcode, hardware description language, or some other name, software should be interpreted broadly as an instruction, set of instructions, code, code segment, program code, program, subroutine, software module, application, software application, software package, algorithm, subroutine, object, executable file, thread of execution, procedure, function, etc.

[0287]

In addition, software, instructions, information, and the like can be transmitted and received via the transmission medium. For example, when software is transferred from a website, server, or other remote source using at least one of the wired technologies (coaxial cable, fiber optic cable, twisted pair cable, digital subscriber lines) or the like) and wireless technology (infrared, microwaves, etc.), at least one of wired technology and wireless technology are included in the definition of a transmission medium.

[0288]

The information, signals, or the like mentioned above may be represented using any of a variety of different technologies. For example, data, instruction, command, information, signal, bit, symbol, chip, or the like, which may be mentioned throughout the above description, may be represented by voltage, current, electromagnetic wave, magnetic field or magnetic particle, optical field or photons, or a desired combination of them.

[0289]

It should be noted that the terms disclosed in the present invention and terms necessary for understanding the present invention may be replaced by terms having the same or similar meaning. For example, at least one of the channel and the symbol may be a signal (signaling). In addition, the signal may be a message. In addition, a component carrier (CC) may be referred to as a frequency carrier, cell, frequency carrier, or the like.

[0290]

The terms "system" and "network" used in the present invention may be used interchangeably.

[0291]

In addition, the information, parameter, and the like described in the present invention may be represented by an absolute value, may be expressed as a relative value from a predetermined value, or may be represented by corresponding other information. For example, the radio resource may be indicated by an index.

[0292]

The name used for the above parameter is by no means a limiting name. In addition, formulas and the like using these parameters may differ from those expressly disclosed in the present invention. Since the various channels (eg, PUCCH, PDCCH, etc.) and information elements can be identified by any suitable name, the various names assigned to these various channels and information elements should not be limited in any way.

[0293]

In the present invention, it is assumed that "base station (BS)", "radio base station", "fixed station", "NodeB", "eNodeB (eNB)", "gNodeB (gNB)", "access point", "transfer point '', 'reception point', 'transmission/reception point', 'cell', 'sector', 'cell group', 'carrier', 'component carrier', etc. may be used interchangeably. A base station may also be referred to by terms such as macro cell, small cell, femto cell, or pico cell.

[0294]

A base station may contain one or more (eg, three) cells (also referred to as sectors). In a configuration in which a base station accommodates a plurality of cells, the entire coverage area of the base station can be divided into a plurality of smaller areas. In each such smaller area, a communication service may be provided by a base station subsystem (eg, a small indoor base station (RRH, Remote Radio Head)).

[0295]

The term "cell" or "sector" refers to part or all of the coverage area of a base station and/or base station subsystem that provides communication service in that coverage.

[0296]

In the present invention, the terms "mobile station (MS)", "user terminal", "user equipment (UE)", "terminal" and the like can be used interchangeably.

[0297]

Those skilled in the art may refer to a mobile station as a subscriber station, a mobile unit, a subscriber unit, a radio unit, a remote unit, a mobile device, a radio device, a radio communication device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a radio terminal, a remote terminal, a handset. , user agent, mobile client, client, or some other suitable term.

[0298]

At least one of the base station and the mobile station may be called a transmission device, a reception device, a communication device, or the like. It should be noted that at least one of the base station and the mobile station may be a device mounted on a moving object, the moving object itself, or the like. The moving object can be a vehicle (for example, a car, an airplane, or the like), a moving object that moves in an unmanned manner (for example, an unmanned aerial vehicle, a self-propelled vehicle, or the like), or a robot (manned type). or unmanned type). At least one of the base station and the mobile station may be a device that does not necessarily move during a communication operation. For example, at least one of the base station and the mobile station may be an Internet of Things (IoT) device such as a sensor.

[0299]

In addition, the base station in the present invention may be referred to as a mobile station (hereinafter, a user terminal, the like is applicable). For example, each of the aspects/embodiments of the present invention can be applied to a configuration that allows communication between a base station and a mobile station to be replaced by communication between a plurality of mobile stations (which may be called, for example, a "Device-device" (D2D). to-Device), "Vehicle-all objects" (V2X, English Vehicle-to-Everything) or the like). In this case, the mobile station may function as a base station. Words such as "uplink" and "downlink" may also be replaced with wording appropriate for inter-terminal communications (eg, "sidelink"). For example, terms such as uplink, downlink or the like can be understood as a side channel.

[0300]

Similarly, the mobile station in the present invention can be understood as a base station. In this case, the mobile station may function as a base station.

[0301]

A radio frame may be configured with one or more frames in the time domain. One frame or each of a plurality of frames in the time domain may be referred to as a subframe.

[0302]

In addition, a subframe may be configured with one or more slots in the time domain. A subframe may be a fixed time duration (eg, 1 ms) independent of numerology.

[0303]

Numerology may be a communication parameter applied to at least one of the transmission or reception of a particular signal or channel. Numerology can represent, for example, at least one of subcarrier spacing (SCS), bandwidth, symbol length, cyclic prefix length, transmission time interval (TTI, Transmission Time Interval), number of symbols per TTI, a radio frame configuration, specific filtering processing performed by the transceiver in the frequency domain, or specific windowing performed by the transceiver in the time domain.

[0304]

A slot can be configured with one or more symbols (Orthogonal Frequency Division Multiplexing (OFDM) symbols, Single Carrier Frequency Division Multiple Access (SC-FDMA) symbols) etc.) in the time domain. A slot can be a unit of time based on numerology.

[0305]

A slot may include a plurality of minislots. Each minislot may be configured with one or more symbols in the time domain. In addition, a minislot may also be referred to as a subslot. A minislot can be configured with fewer symbols than slots. A PDSCH (or PUSCH) transmitted in a unit of time greater than a minislot may be referred to as a Type A PDSCH (or PUSCH) mapping. A PDSCH (or PUSCH) transmitted using a minislot may be referred to as a Type B PDSCH (or PUSCH) mapping.

[0306]

Each of a radio frame, subframe, slot, minislot, and symbol represents a unit of time for signal transmission. Different names may be used for the radio frame, subframe, slot, minislot, and symbol, respectively.

[0307]

For example, one subframe may be referred to as a transmission time interval (TTI), multiple consecutive subframes may be referred to as a TTI, and one slot or one minislot may be referred to as a TTI. That is, at least one of the subframe or TTI may be a subframe (1 ms) in existing LTE, may be a shorter period than 1 ms (e.g., one to thirteen symbols), or may be a longer period of time, than 1 ms. It should be noted that the unit representing the TTI may also be called a slot, minislot, or the like instead of a subframe.

[0308]

In the present description, TTI means, for example, the minimum unit of scheduling time in radio communication. For example, in an LTE system, a base station performs scheduling to allocate radio resources (frequency bandwidth, transmission power, or the like that can be used in each user terminal) for each user terminal in units of TTI. It should be noted that the definition of TTI is not limited to this.

[0309]

The TTI may be a unit of transmission time such as a data packet encoded on a channel (transport block), a code block, or a codeword, or may be a unit of scheduling processing, link adaptation, or the like. It should be noted that when TTI is given, the time interval (eg, the number of symbols) in which the transport block, code block, codeword, or the like is actually displayed may be shorter than the TTI.

[0310]

It should be noted that in the case where one slot or one minislot is referred to as a TTI, one or more TTIs (ie, one or more slots or one or more minislots) may be the minimum scheduling time unit. In addition, the number of slots (number of mini-slots) that constitutes the minimum unit of scheduling time can be adjusted.

[0311]

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

[0312]

It should be noted that a long TTI (eg, a normal TTI, a subframe, or the like) may be understood as a TTI having a time duration exceeding 1 ms, and a short TTI (eg, a short TTI, or the like) may be understood as a TTI , having a TTI duration less than the duration of the TTI of the long TTI and equal to or greater than 1 ms.

[0313]

A resource block (RB) is a resource allocation block in the time domain and frequency domain and may include one or more consecutive subcarriers in the frequency domain. The number of subcarriers included in the RB may be the same regardless of numerology, such as twelve. The number of subcarriers included in the RB may be determined based on numerology.

[0314]

In addition, the RB time domain may include one or more symbols and may have a duration of one slot, one minislot, one subframe, or one TTI. One TTI, one subframe, and the like may be configured with one or more resource blocks.

[0315]

It should be noted that one or more RBs can be called a physical resource block (PRB, Physical RB), a sub-carrier group (SCG, Sub-Carrier Group), a group of resource elements (REG, Resource Element Group), a PRB pair , a pair of RBs or the like.

[0316]

In addition, a resource block may be configured with one or more resource elements (REs). For example, one RE may represent a radio resource region of one subcarrier and one symbol.

[0317]

Part of the bandwidth (BWP, English bandwidth part) (which may be called a partial bandwidth or the like) may represent a subset of contiguous common resource blocks (RB) for a particular numerology in a particular carrier. Here, the common RB may be indicated by the RB index based on the common carrier reference point. The PRB may be defined in a particular BWP and be numbered within the BWP.

[0318]

The BWP may include a BWP (uplink BWP) for uplink and a BWP (downlink BWP) for downlink. One or more BWPs may be configured on a single carrier for a UE.

[0319]

At least one of the configured BWPs may be active and the UE may not assume that a given signal/channel is transmitted and received outside of the active BWP. It should be noted that "cell", "carrier", etc. in the present invention may be replaced by "BWP".

[0320]

The structures described above such as radio frame, subframe, slot, minislot, and symbol are just examples. For example, configurations such as the number of subframes included in a radio frame, the number of slots per subframe or radio frame, the number of mini-slots included in a slot, the number of symbols and RBs included in a slot or mini-slot, the number of subcarriers included into the RB, the number of characters in the TTI, the length of the character and the length of the cyclic prefix (CP, from the English Cyclic Prefix) can be changed in various ways.

[0321]

The terms "connected", "connected" or any of their options means any direct or indirect connection or connection between two or more elements. In addition, one or more intermediate elements may be present between two elements that are "connected" or "linked" to each other. A connection or relationship between elements can be physical, logical, or combinations thereof. For example, "connection" can mean "access". In the present invention, two elements may be "connected" or "connected" to each other using at least one of one or more wires, cables, printed electrical connections, and, as some non-limiting and non-exhaustive examples, using electromagnetic energy having wavelengths in the radio frequency region, the microwave region, and the optical region (both visible and invisible), and the like.

[0322]

The reference signal may be abbreviated to RS and may be referred to as the pilot signal in accordance with applicable standards.

[0323]

In the context of the present invention, the phrase "based on" does not mean "only based on", unless explicitly stated otherwise. In other words, the phrase "based on" can mean either "based on only" or "based on at least".

[0324]

Any reference to an element using a designation such as "first", "second", etc. used in the present invention does not generally limit the number or order of such elements. Such designations can be used in the present invention as a convenient way to distinguish between two or more elements. Thus, the reference to the first and second elements does not imply that only two elements can be received, or that the first element must in any way precede the second element.

[0325]

In the present invention, the terms "comprise", "including" and variations thereof are intended to be inclusive, similarly to the term "comprising". In addition, the term "or" used in the present invention should not carry the meaning of an exclusive disjunction.

[0326]

Throughout the description, for example, if singular nouns are used in the translation, the presence of the plural of these nouns may be allowed.

[0327]

The terms "definition" and "defining" as used in the present invention can cover a wide range of operations. The terms "determining" and "decision making" may include, for example, evaluating, calculating, computing, processing, inferring, examining, looking up (search or querying) (for example, looking up a table, database, or other data structure), and establishing . In addition, the terms "determining" and "decision making" may include receiving (eg, receiving information), transmitting (eg, transmitting information), input, output, and access (eg, accessing data in memory), and the like. . In addition, the terms "determination" and "decision" may include "permission", "selection", "selection", "establishment", "comparison", etc. In other words, the terms "determination" and "acceptance solutions" may include any operation. In addition, the term "determining (making a decision)" can also be understood as "guess", "expectation", "consideration", etc.

[0328]

In the present invention, the phrase "A and B are different" may mean "A and B are different from each other." It should be noted that this term can mean "Each of A and B is different from C". Terms such as "leave", "associated" or the like can also be interpreted in the same way as "other".

[0329]

Although the present invention has been described in detail above, it will be apparent to those skilled in the art that the present invention is not limited to the embodiments described in this disclosure. The present invention may be implemented with modifications and changes without departing from the spirit and scope of the present invention as defined in the claims. Therefore, the description of the present invention is intended to be illustrative and is not meant to be limiting in any way to the present invention.

Industrial Applicability

[0330]

In the case of the terminal described above, even in the case where the terminal performs the random access procedure between the terminal and the target radio base station and performs a transition to the target radio base station without receiving the handover command, the source radio base station can notify the terminal of the changed target cell configuration information. candidate, which is helpful.

Position number list

[0331]

10 Radio communication system

100A, 100V, 100C gNB

110 Transmission unit

120 Receive block

130 Save block

140 Control unit

200 Terminal

210 Transfer unit

220 Receive block

230 Save block

240 Control unit

1001 Processor

1002 Memory

1003 Accumulator

1004 Communication device

1005 Input device

1006 Output device

1007 Tire.

Claims (32)

1. Terminal containing: a receiving unit, configured to receive, from a source radio base station, a first Radio Resource Control Reconfiguration (RRC Reconfiguration) message including information about a candidate cell and a transition condition to a candidate cell; a transmission unit, configured to transmit, to the source radio base station, a radio resource control reconfiguration complete (RRC Reconfiguration Complete) message for the first configuration message; And a control unit configured to monitor a transition condition to a candidate cell after transmission of the RRC Reconfiguration Complete message; wherein the control unit is configured to change the information about the candidate cell and the transition condition to the candidate cell based on the second RRC Reconfiguration message received from the source radio base station after the transmission of the RRC Reconfiguration Complete message, wherein the control unit is configured, when the transition condition is met, to perform synchronization with the candidate cell and perform a transition to the target radio base station that configures candidate cell information without receiving a handover command. 2. The terminal of claim. 1, in which the transmission unit is configured to send an RRC Reconfiguration Complete message to the source radio station before starting synchronization. 3. The terminal of claim 1, wherein the control unit is configured to delete the candidate cell information and the transition condition to the candidate cell based on the third RRC Reconfiguration message received from the source radio base station after the transmission of the RRC Reconfiguration Complete message. 4. The terminal according to claim 1, wherein the control unit is configured, when the receiving unit receives a handover command before the transition condition is met, to perform a handover procedure. 5. Base radio station, containing: a transmission unit, configured to transmit to the terminal a first radio resource control (RRC Reconfiguration) message including candidate cell information; And a receiving unit configured to receive from the terminal a radio resource control reconfiguration complete (RRC Reconfiguration Complete) message for the first RRC Reconfiguration message, wherein the transmission unit is configured to transmit, to the terminal that monitors the transition to candidate cell condition after transmitting the RRC Reconfiguration Complete message, the second RRC Reconfiguration message including the changed candidate cell information and the changed transition to candidate cell condition after receiving the RRC message ReconfigurationComplete. 6. A radio communication system, comprising: a terminal and a source radio base station, the terminal including: a receiving unit, configured to receive, from a source radio base station, a first Radio Resource Control Reconfiguration (RRC Reconfiguration) message including information about a candidate cell and a transition condition to a candidate cell; a transmission unit, configured to transmit, to the source radio base station, a radio resource control reconfiguration complete (RRC Reconfiguration Complete) message for the first RRC Reconfiguration message; And a control unit configured to monitor the transition condition to the candidate cell after the transmission of the RRC Reconfiguration Complete message, wherein the original radio base station includes: a transmission unit, configured to transmit the first RRC Reconfiguration message to the terminal; And a receiving unit configured to receive an RRC Reconfiguration Complete message from the terminal, wherein the transmission unit of the source radio base station is configured to transmit to the terminal a second RRC Reconfiguration message including the changed candidate cell information and the changed transition condition to the candidate cell after receiving the RRC Reconfiguration Complete message, and the terminal control unit is configured to change the candidate cell information and the transition condition to the candidate cell based on the second RRC Reconfiguration message received from the source radio base station after the transmission of the RRC Reconfiguration Complete message, and wherein the control unit of the terminal is configured, when the transition condition is met, to perform synchronization with the candidate cell and perform a transition to the target radio base station that configures candidate cell information without receiving the handover command. 7. Method of radio communication, containing: a step of transmitting, by the source radio base station, to the terminal a first Radio Resource Control Reconfiguration (RRC Reconfiguration) message including information about the candidate cell and a transition condition to the candidate cell; a step of receiving the first RRC Reconfiguration message by the terminal; a step of transmitting, by the source radio base station terminal, a radio resource control reconfiguration complete (RRC Reconfiguration Complete) message for the first RRC Reconfiguration message; a step of monitoring, by the terminal, a transition condition to a candidate cell after transmission of the RRC Reconfiguration Complete message; a step of receiving, by the source radio base station, the RRC Reconfiguration Complete message; a step of transmitting, by the source radio base station, to the terminal a second RRC Reconfiguration message including the changed candidate cell information and the changed transition condition to the candidate cell after receiving the RRC Reconfiguration Complete message; a step for the terminal to change the candidate cell information and the transition condition to the candidate cell based on the second RRC Reconfiguration message received from the source radio base station after the transmission of the RRC Reconfiguration Complete message; And a step for the terminal to synchronize with the candidate cell, and for the terminal to jump to the target radio base station that configures candidate cell information without receiving a handover command when the jump condition is met.

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