CN114208286A - Terminal device - Google Patents

Abstract

The terminal (200) has a control unit (240) that performs a process of migrating to the target gNB (100B) without performing a reestablishment process in association with a handover failure; and a transmission unit (210) that transmits a specific message to the target gNB (100B) during the transition to the target gNB (100B). When the handover fails, the control unit (240) maintains the identification information shared between the terminal (200) and the target gNB (100B), and includes the identification information in a specific message.

Description

Terminal device

Technical Field

The present invention relates to a terminal migrating to a target radio base station without using a re-establishment procedure.

Background

The third Generation Partnership Project (3rd Generation Partnership Project: 3GPP) has standardized Long Term Evolution (LTE), and has standardized LTE-Advanced (hereinafter referred to as LTE including LTE-Advanced) for the purpose of further speeding up LTE. In addition, in 3GPP, specifications of a subsequent system of LTE called 5G or New Radio (NR) or the like are also studied.

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

However, when the terminal passes through an appropriate handover point (point) in preparation for handover on the network side, there is a problem that a radio link may be momentarily interrupted because a handover command is not received from a source radio base station (also referred to as a source cell) and the terminal migrates to a target radio base station.

In order to solve such a problem, a procedure called Conditional HO (Conditional handover) has been studied (non-patent document 1).

In the Conditional HO, the source radio base station notifies the terminal of setting information of a target candidate cell including a target candidate cell and a transition condition to the target candidate cell in advance.

And when the migration condition to the target candidate cell is met, the terminal executes the random access process with the target wireless base station managing the target candidate cell without waiting for the switching command and migrates to the target wireless base station. Thereby, a momentary interruption of the wireless link can be avoided.

In addition, a procedure for recovering from a handover failure (HOF) as soon as possible using Conditional HO was also studied.

In this case, the terminal can migrate to the target radio base station and recover from the HOF without performing a Reestablishment procedure (RRC request procedure) with the target radio base station.

Documents of the prior art

Non-patent document

Non-patent document 1: "New WID: NR mobility enhancements, RP-190489,3GPP TSG RAN Meeting #83,3GPP, 3 months of 2019

Disclosure of Invention

However, in the case of applying the cell migration procedure by Conditional HO to the recovery from the HOF, there is a problem as described below.

Specifically, conventionally, when recovering from the HOF, new identification information such as security information is shared between the terminal and the target radio base station in the RRC Reestablishment (RRC request) process, but in the Conditional HO, the RRC request process is not performed, and therefore the new identification information is not shared between the terminal and the target radio base station.

Therefore, when the terminal returns from the HOF using the Conditional HO, the target radio base station cannot authenticate the terminal moving to the target radio base station, and there is a possibility that a malicious terminal moves to the target radio base station.

Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a terminal that can be authenticated on the network side and that migrates to a target radio base station without performing a re-establishment procedure in association with a handover failure.

A terminal (200) according to one embodiment of the present invention includes: a control unit (240) which, in association with a handover failure, performs a procedure of moving to a target radio base station (100B) without performing a reestablishment procedure; and a transmission unit (210) that transmits a specific message to the target radio base station (100B) during the transition to the target radio base station (100B), wherein the control unit (240) maintains identification information shared between the terminal (200) and the target radio base station (100B) when the handover fails, and includes the identification information in the specific message.

Drawings

Fig. 1 is a schematic configuration diagram of the entire wireless communication system 10.

Fig. 2 is a functional block diagram of the gNB100A, 100B, 100C.

Fig. 3 is a functional block diagram of the terminal 200.

Fig. 4 is a diagram showing a timing of a Conditional HO procedure.

Fig. 5 is a diagram showing a recovery timing from a Radio Link Failure (RLF) in a conventional Handover (HO) procedure.

Fig. 6 is a diagram showing a recovery timing from a Radio Link Failure (RLF) in a Conditional HO procedure (operation example 1).

Fig. 7 is a diagram showing a recovery timing from a Radio Link Failure (RLF) in a Conditional HO procedure (operation example 2).

Fig. 8 is a diagram showing a recovery timing from a Radio Link Failure (RLF) in a Conditional HO procedure (operation example 3).

Fig. 9 is a diagram for explaining an Information Element (IE) within the VarRLF-Report.

Fig. 10 is a diagram for explaining an Information Element (IE) within an RRC Reconfiguration Complete (RRC Reconfiguration Complete).

Fig. 11A is a diagram for explaining an Information Element (IE) in RRC Setup Complete (RRC Setup Complete).

Fig. 11B is a diagram for explaining an Information Element (IE) in RRC Setup Complete (RRC Setup Complete).

Fig. 12 is a diagram for explaining an Information Element (IE) within an RRC Reestablishment Complete (RRC message Complete).

Fig. 13 is a diagram for explaining an Information Element (IE) in RRC recovery Complete (RRC Resume Complete).

Fig. 14 is a diagram for explaining an Information Element (IE) of a UE Information Request (UE Information Request).

Fig. 15A is a diagram for explaining an Information Element (IE) in the UE Information Response (UE Information Response).

Fig. 15B is a diagram for explaining an Information Element (IE) in the UE Information Response (UE Information Response).

Fig. 15C is a diagram for explaining an Information Element (IE) in the UE Information Response (UE Information Response).

Fig. 16 is a diagram showing an RRC Reconfiguration Complete (RRC Reconfiguration Complete) transmission timing in the Conditional HO procedure.

Fig. 17 is a diagram showing HO termination timing (operation example 1) in the Conditional HO process.

Fig. 18 is a diagram showing HO termination timing (operation example 2) in the Conditional HO process.

Fig. 19 is a diagram showing HO change timing (operation example 1) in the Conditional HO process.

Fig. 20 is a diagram showing HO change timing (operation example 2) in the Conditional HO process.

Fig. 21 is a diagram showing HO change timing (operation example 3) in the Conditional HO process.

Fig. 22 is a diagram showing the operation flow of the gNB100A encapsulating the setting information of the target candidate cell.

Fig. 23 is a diagram for explaining a configuration (configuration example 1) of RRC Reconfiguration (RRC Reconfiguration) in the Conditional HO procedure.

Fig. 24 is a diagram for explaining a configuration (configuration example 2) of RRC Reconfiguration (RRC Reconfiguration) in the Conditional HO procedure.

Fig. 25 is a diagram showing a transaction id (transaction id) assignment sequence (operation example 1) in the Conditional HO process.

Fig. 26 is a diagram showing a transaction ID assignment sequence (operation example 2) in the Conditional HO process.

Fig. 27 is a diagram showing a recovery timing from a handover failure (HOF) in the Conditional HO procedure.

Fig. 28 is a diagram showing an operation flow of terminal 200 that recovers a radio bearer after a Radio Link Failure (RLF) in the Conditional HO procedure.

Fig. 29 is a diagram for explaining a condition for recovering a radio bearer after a Radio Link Failure (RLF) in a Conditional HO procedure.

Fig. 30 shows an example of the hardware configuration of gNB100A, 100B, and 100C and terminal 200.

Detailed Description

Hereinafter, embodiments will be described based on the drawings. The same or similar reference numerals are given to the same functions and structures, and the description thereof is appropriately omitted.

(1) General overall structure of wireless communication system

Fig. 1 is a schematic configuration diagram of the entire radio communication system 10 according to the present embodiment. The wireless communication system 10 is a wireless communication system based on a New Radio (NR), and includes a Next Generation-Radio Access Network (NG-RAN, not shown) and a terminal 200.

The NG-RAN includes radio base stations 100A, 100B, and 100C (hereinafter, referred to as gnbs 100A, 100B, and 100C). In addition, the specific structure of the wireless communication system 10 including the number of the gnbs and the UEs is not limited to the example shown in fig. 1.

The NG-RAN actually comprises a plurality of NG-RAN nodes, specifically, a gNB (or NG-eNB), connected to a core network (5GC, not shown) according to NR. In addition, NG-RAN and 5GC can also be simply expressed as "network".

Each of gnbs 100A, 100B, and 100C is a radio base station compliant with NR and performs radio communication compliant with NR with terminal 200. Each of the gnbs 100A, 100B, and 100C and the terminal 200 can support massive mimo (massive mimo) in which beams having higher directivity are generated by controlling radio signals transmitted from a plurality of antenna elements, Carrier Aggregation (CA) in which a plurality of Component Carriers (CCs) are bundled, Dual Connectivity (DC) in which communication is simultaneously performed between a plurality of NG-RAN nodes and the terminal, and the like. In addition, the CC may also be referred to as a carrier.

Each of gnbs 100A, 100B, and 100C forms 1 or more cell and manages the cell. Terminal 200 is capable of migrating between cells formed by gnbs 100A, 100B, 100C. In addition, "transition between cells formed by the gnbs 100A, 100B, 100C" may be expressed as "transition between the gnbs 100A, 100B, 100C" or "transition between the radio base stations 100A, 100B, 100C". Further, "cells subordinate to gNB100A, 100B, and 100C" means "cells formed of gNB100A, 100B, and 100C".

The "migration" typically refers to handover between cells or handover between gnbs, but may include behavior of terminal 200 (behavior) such that a connection destination cell or a connection destination gNB is changed, for example, cell reselection.

The "target cell" typically refers to a cell of a migration destination to which the terminal 200 is to migrate, but may also include a cell (potential target cell) to which the terminal 200 is able to migrate. Further, "target gNB (target gNB)" typically refers to a gNB of a migration destination to which the terminal 200 is to migrate, but may also include a gNB (potential target gNB) to which the terminal 200 is able to migrate. In the present embodiment, gnbs 100B, 100C are target gnbs. In addition, a cell to which the terminal can migrate may also be referred to as a candidate cell. Furthermore, a gNB that the terminal can migrate may also be referred to as a candidate gNB.

On the other hand, the "source cell" refers to a cell of the migration party. "Source gNB" refers to the migrating gNB. In this embodiment, gNB100A is the source gNB.

In the wireless communication system 10, the terminal 200 executes a Conditional handover (hereinafter referred to as a Conditional HO) procedure. In addition, the Conditional HO process is sometimes simply referred to as the CHO process.

As described below, in the Conditional HO procedure, source gNB100A notifies terminal 200 of candidates of a cell of a migration destination (hereinafter, referred to as target candidate cells) to be migrated by terminal 200 in advance. When the migration condition to the target candidate cell is satisfied, the terminal 200 performs a Random Access (RA) procedure with the target gNB100B (or the target gNB100C) managing the target candidate cell without receiving a handover command from the source gNB, and migrates to the target gNB100B (or the target gNB 100C).

In addition, wireless communication system 10 may include an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) instead of the NG-RAN. In this case, the E-UTRAN includes a plurality of E-UTRAN nodes, specifically enbs (or en-gbbs), connected with an LTE compliant core network (EPC).

(2) Functional block structure of wireless communication system

Next, a functional block configuration of the radio communication system 10 will be described. Specifically, the functional block structures of the gnbs 100A, 100B, and 100C and the terminal 200 will be described. Hereinafter, only the portions related to the features of the present embodiment will be described. Therefore, of course, the gnbs 100A, 100B, 100C and the terminal 200 have other functional blocks not directly related to the features in the present embodiment.

Fig. 2 is a functional block diagram of the gNB100A, 100B, 100C. Since gNB100A, 100B, and 100C have the same configuration, explanations of gNB100B and 100C are omitted. As shown in fig. 2, gNB100A includes a transmission unit 110, a reception unit 120, a holding unit 130, and a control unit 140.

The transmission unit 110 transmits a downlink signal (DL signal) according to the NR. The receiving unit 120 receives an uplink (UL signal) according to the NR. Specifically, the transmission unit 110 and the reception unit 120 perform wireless communication with the terminal 200 via a control channel or a data channel.

The transmission unit 110 transmits a signal according to the NR to another gNB. The receiving unit 220 receives a signal according to NR from another gNB.

The transmission unit 110 transmits an RRC message such as RRC Reconfiguration (RRC Reconfiguration), which will be described later, to the terminal 200.

When the gNB100A is the source gNB, the transmitter 110 transmits a CHO request (CHO request), which will be described later, to the target gNB. When the gNB100A is the target gNB, the transmitter 210 transmits a CHO request response (CHO request ACK), HO deletion (HO cancellation), and HO modification (HO modification), which will be described later, to the source gNB. The CHO request ACK includes setting information of a target candidate cell subordinate to the target gNB.

The reception unit 120 receives RRC messages such as RRC Reconfiguration Complete (RRC Reconfiguration Complete), RRC Reconfiguration Complete 1(RRC Reconfiguration Complete1), RRC Reconfiguration Complete 2(RRC Reconfiguration Complete2), RRC Setup Complete (RRC Setup Complete), and RRC Reconfiguration Complete (RRC Reconfiguration Complete) from the terminal 200, which will be described later.

When the gNB100A is the source gNB, the receiver 120 receives a CHO request ACK, HO cancel, and HO modification, which will be described later, from the target gNB. When the gNB100A is the target gNB, the receiving unit 120 receives a CHO request, which will be described later, from the source gNB.

When the gNB100A is the source gNB, the holding unit 130 holds setting information of target candidate cells subordinate to the target gNB.

Control unit 140 controls each functional block constituting gNB 100A.

When the gNB100A is the target gNB, the control unit 140 determines deletion of the setting information of the target candidate cell according to the state of the target candidate cell under the gNB 100A.

When the gNB100A is the target gNB, the control unit 140 causes the transmission unit 110 to transmit an HO cancel, which instructs deletion of the setting information of the target candidate cell under the gNB100A, to the source gNB.

When the gNB100A is the target gNB, the control unit 140 causes the transmission unit 110 to transmit HO cancel to the source gNB when the terminal 200 does not transit for a predetermined time period based on the setting information of the target candidate cells under the control of the gNB 100A.

When the gNB100A is the target gNB, the control unit 140 determines a change in the setting information of the target candidate cell according to the state of the target candidate cell under the gNB 100A.

When the gNB100A is the target gNB, the control unit 140 causes the transmission unit 110 to transmit HO modification instructing a change of the setting information of the target candidate cell subordinate to the gNB100A to the source gNB.

When the gNB100A is the source gNB, the control unit 140 includes a list including setting information of target candidate cells subordinate to a plurality of target gnbs in RRC Reconfiguration.

Fig. 3 is a functional block diagram of the terminal 200. As shown in fig. 3, the terminal 200 includes a transmission unit 210, a reception unit 220, a holding unit 230, and a control unit 240.

The transmission unit 210 transmits an uplink (UL signal) according to NR. The receiving unit 220 receives a downlink signal (DL signal) according to the NR. Specifically, transmission unit 210 and reception unit 220 perform radio communication with each of gnbs 100A to 100C via a control channel or a data channel.

The transmitter 210 transmits RRC messages such as RRC Reconfiguration Complete, RRC Reconfiguration Complete1, RRC Reconfiguration Complete2, RRC Setup Complete, and RRC Reestablishment Complete, which will be described later.

The reception unit 220 receives an RRC message such as RRC Reconfiguration described later.

The holding unit 230 holds setting information of target candidate cells subordinate to the target gNB. The setting information of the target candidate cell is included in RRC Reconfiguration.

The control unit 240 controls each functional block constituting the terminal 200.

The control unit 240 performs an RA procedure between the terminal 200 and the target gNB and moves to the target gNB without performing a Reestablishment procedure (RRC request procedure) with RLF.

The control unit 240 performs no RRC Reestablishment (RRC request) procedure with the RLF, and migrates to the target gNB based on the setting information of the target candidate cell under the control of the target gNB.

The control unit 240 performs an RA procedure between the terminal 200 and the target gNB and moves to the target gNB when a handover command is not received, based on the setting information of the target candidate cell under the control of the target gNB.

The control unit 240 performs migration to the target gNB without performing the RRC request procedure with the HOF.

Control unit 240 includes RLF detection information including RLF information notifying occurrence of RLF, information of a cell in which RLF is detected, location information of terminal 200 in which RLF is detected, and the like in the RRC messages of the RRC Reconfiguration Complete, RRC Reconfiguration Complete2, RRC Setup Complete, RRC Reestablishment Complete, and the like.

When the reception unit 220 receives RRC Reconfiguration including the setting information of the target candidate, the control unit 240 causes the transmission unit 210 to transmit RRC Reconfiguration Complete1 before the RA procedure is started. Further, the reception unit 220 receives RRC Reconfiguration including the changed setting information of the target candidate cell after transmission of the RRC Reconfiguration Complete 1.

When the receiving unit 220 receives the setting information of the target candidate cell under the control of the target gNB using the RRC Reconfiguration to which the transaction ID is given by the source gNB, the control unit 240 includes the transaction ID in the RRC Reconfiguration Complete 1. The controller 240 causes the transmitter 210 to transmit the RRC Reconfiguration Complete1 to the source gNB.

When the reception unit 220 receives the setting information of the target candidate cell under the target gNB to which the transaction ID is assigned, the control unit 240 includes the transaction ID in the RRC Reconfiguration Complete 2. After the RA procedure is successful, the control unit 240 causes the transmission unit 210 to transmit the RRC Reconfiguration Complete2 to the target gNB.

The control unit 240 maintains all or a part of the setting information of the target candidate cell under the target gNB shared between the terminal 200 and the target gNB at the time of the HOF, and includes the information in the RRC Reconfiguration Complete 2. The setting information maintained includes Security (Security) information, identification information of the terminal 200, and the like. After the RA procedure is successful, the control unit 240 causes the transmission unit 210 to transmit the RRC Reconfiguration Complete2 to the target gNB.

When the migration procedure to the target gNB is performed, the control unit 240 restores the radio bearer that was stopped between the terminal 200 and the target gNB.

When the RA procedure is performed while moving to the target gNB, the control unit 240 restores the radio bearer that was stopped between the terminal 200 and the target gNB.

When the reception unit 220 receives a message instructing recovery of a radio bearer during migration to the target gNB, the control unit 240 recovers the radio bearer stopped between the terminal 200 and the target gNB.

(3) Operation of a wireless communication system

Next, an operation of the radio communication system 10 will be described. Specifically, the following operations will be described in order of the conventional HO procedure.

Recovery from Radio Link Failure (RLF) during Conditional HO

RRC Reconfiguration Complete transmission timing in the Conditional HO procedure

Handover (HO) termination during Conditional HO,

Change of Handover (HO) during Conditional HO,

RRC Reconfiguration Structure in Conditiononal HO procedure

Assignment of transaction Identifier (ID) in Conditional HO procedure

Recovery from handover failure (HOF) during Conditional HO

Recovery of radio bearers after Radio Link Failure (RLF) during Conditional HO

(3.1) Condition HO procedure

Fig. 4 is a diagram showing a timing of a Conditional HO procedure. As shown in fig. 4, when the source gNB100A finds the target gNB100B, 100C according to the measurement report received from the terminal 200, a Conditional HO request (CHO request: CHO request) is transmitted to the target gNB100B, 100C (S11).

When the target gNB100B receives the CHO request from the source gNB100A, a CHO request acknowledgement (CHO request ACK: CHO request ACK) containing setting information of the cells under the control of the target gNB100B (also referred to as target candidate cells) is transmitted to the source gNB100A (S13). The setting information of the target candidate cell includes information of the target candidate cell and a migration condition to the target candidate cell.

Likewise, when the target gNB100C receives the CHO request from the source gNB100A, a CHO request acknowledgement (CHO request ACK) including setting information of a cell under the control of the target gNB100C (referred to as a target candidate cell) is transmitted to the source gNB100A (S13). The setting information of the target candidate cell includes information of the target candidate cell and a migration condition to the target candidate cell.

When source gNB100A receives the CHO request ACK from target gNB100B, 100C, it transmits a Radio Resource Control (RRC) Reconfiguration message (RRC Reconfiguration: RRC Reconfiguration) containing the Conditional HO configuration (CHO configuration: CHO configuration) to terminal 200 (S15). The CHO configuration includes setting information of target candidate cells transmitted from target gnbs 100B and 100C, respectively.

When the terminal 200 receives the CHO configuration from the source gNB100A, the Conditional HO condition (CHO condition) is monitored (S17). Specifically, the terminal 200 determines whether or not a transition condition to the target candidate cell included in the setting information of each target candidate cell is satisfied.

When the terminal 200 determines that the migration condition to the target candidate cell is satisfied by movement of the terminal 200 or the like, it determines to start Handover (HO) to the target candidate cell without receiving a handover command from the source gNB100A (S19). In the present embodiment, terminal 200 determines to start HO to a target candidate cell subordinate to target gNB 100B. The target candidate cell of the migration destination satisfying the migration condition is also referred to as a CHO cell.

In addition, the source gNB100A may receive information of the target candidate cell only from the target gNB100B, 100C in S13. In this case, the source gNB100A transmits CHO configuration including information of the target candidate cell and a condition for the terminal 200 to trigger Handover (HO) to the terminal 200 in S15.

In this case, the terminal 200 determines in S17 whether a condition for triggering HO is satisfied. When the terminal 200 determines that the condition for triggering HO is satisfied by movement of the terminal 200 or the like, at S19, a target candidate cell of the migration destination is determined, and handover to the target candidate cell is started. For example, terminal 200 determines a target candidate cell to be migrated based on the priority of each target candidate cell given by source gNB100A, the state of a cell included in the information of each target candidate cell, and the like.

When the terminal 200 decides to start HO to a target candidate cell under the control of the target gNB100B, a Random Access (RA) procedure is performed between the target gNB100B and the terminal 200, and synchronization is established between the target gNB100B and the terminal 200 (S21). Thereby, terminal 200 is connected to target gNB 100B.

When the terminal 200 is connected to the target gNB100B, an RRC Reconfiguration Complete message (RRC Reconfiguration Complete) is transmitted to the target gNB100B (S23).

(3.2) recovery from RLF during Conditiononal HO

Next, recovery from RLF during the Conditional HO will be described. First, the recovery from RLF in the conventional HO procedure will be described.

Fig. 5 is a diagram showing a recovery timing from RLF in the conventional HO procedure. As shown in fig. 5, when the source gNB100A finds the target gNB100B according to the measurement report received from the terminal 200, an HO request (HO request) is transmitted to the target gNB100B (S51).

When target gNB100B receives the HO request from source gNB100A, it transmits a HO request acknowledgement (HO request ACK) containing information of a cell (referred to as a target cell) under the control of target gNB100B to source gNB100A (S53).

When the source gNB100A receives the HO request ACK from the target gNB100B, it transmits an RRC Reconfiguration message (RRC Reconfiguration) including a handover command (HO command) to the terminal 200 (S55). The HO command contains information of the target cell transmitted from the target gNB 100B.

When the terminal 200 receives the HO command from the source gNB100A, a Random Access (RA) procedure is performed between the target gNB100B and the terminal 200, and establishment of synchronization is attempted between the target gNB100B and the terminal 200 (S57).

When RLF occurs during the execution of the RA procedure and the RA procedure fails in S57, the terminal 200 performs cell reselection (S59). When terminal 200 decides to reconnect with a cell under the control of target gNB100B, an RRC re-establishment (RRC Reestablishment) procedure is performed between target gNB100B and terminal 200.

Specifically, the terminal 200 transmits an RRC Reestablishment request message (RRC request) to the target gNB100B (S61). When the target gNB100B receives the RRC Reestablishment request (RRC request) from the terminal 200, it transmits an RRC Reestablishment message (RRC request) to the terminal 200 (S63). The RRC request contains setting information for re-establishing an RRC connection (RRC connection) between the target gNB100B and the terminal 200.

When the terminal 200 receives the RRC Reestablishment from the target gNB100B, the RRC connection is reestablished between the target gNB100B and the terminal 200, and an RRC Reestablishment Complete message (RRC Reestablishment Complete) is transmitted (S65).

In S65, terminal 200 includes the RLF information in the RRC request document Complete and performs RLF notification. To notify the network side that RLF has occurred between terminal 200 and target gNB100B, RLF information is contained in RRC request fragment Complete.

When the target gNB100B receives the RRC request Complete from the terminal 200, it transmits RRC Reconfiguration to the terminal 200 (S67). When the terminal 200 receives RRC Reconfiguration from the target gNB100B, it performs Reconfiguration of RRC connection and transmits RRC Reconfiguration Complete to the target gNB100B (S69).

(3.2.1) operation example 1

Next, operation example 1 of recovery from RLF during the Conditional HO will be described. In the present operation example, when RLF occurs during the Conditional HO procedure and the RA procedure fails, the terminal 200 reselects a target candidate cell (CHO cell) of the migration destination, and notifies the network side of the occurrence of RLF using an RRC Reconfiguration Complete message (RRC Reconfiguration Complete) after the RA procedure is performed.

Fig. 6 is a diagram showing a recovery timing from RLF in the Conditional HO procedure (operation example 1). S101 to S109 in fig. 6 are the same processes as S11 to S19 in fig. 4, and therefore, the description thereof is omitted.

When the terminal 200 decides to start HO to a target candidate cell under the control of the target gNB100B without receiving a handover command from the source gNB100A, a Random Access (RA) procedure is performed between the target gNB100B and the terminal 200, and establishment of synchronization is attempted between the target gNB100B and the terminal 200 (S111).

When RLF occurs during execution of the RA procedure and the RA procedure fails in S111, the terminal 200 reselects a target candidate cell (CHO cell) of the migration destination that satisfies the migration condition (S113). In the present embodiment, terminal 200 reselects a target candidate cell subordinate to target gNB 100B.

When the terminal 200 reselects a target candidate cell under the control of the target gNB100B, a Random Access (RA) procedure is performed between the target gNB100B and the terminal 200, and synchronization is established between the target gNB100B and the terminal 200 (S115). Thereby, terminal 200 is connected to target gNB 100B.

When the terminal 200 is connected to the target gNB100B, an RRC Reconfiguration Complete message (RRC Reconfiguration Complete) is transmitted to the target gNB100B (S117).

In S117, terminal 200 includes RLF information in the RRC Reconfiguration Complete and performs RLF notification. In order to notify the network side that RLF has occurred between terminal 200 and target gNB100B, RLF information is included in RRC Reconfiguration Complete. For example, the RLF information is represented by 1 bit. In this case, for example, "1" is set as the RLF information when RLF occurs, and "0" is set as the RLF information when RLF does not occur.

Thus, the RLF information is included in a message indicating that the Conditional HO procedure is completed (i.e., indicating that the terminal 200 applies the setting information of the target candidate cell).

In S117, terminal 200 may include RLF information and RLF detection information in the RRC Reconfiguration Complete. The RLF detection information includes, for example, at least one of cell information such as an identifier of a cell in which RLF is detected (in the present embodiment, a cell under the control of the target gNB 100B), location information of the terminal 200 in which RLF is detected (global navigation satellite system (GNSS) information or the like), Radio Access Technology (RAT) information in which RLF is detected, frequency information used when RLF is detected, bandwidth part (BWP) information used when RLF is detected, and a location (global positioning system (GPS) information or the like) in which RLF is detected.

In addition, as in S13, source gNB100A may receive information of target candidate cells only from target gnbs 100B, 100C in S103. In this case, in S113, terminal 200 reselects a target candidate cell (CHO cell) to be migrated, based on the priority of each target candidate cell given by source gNB100A, the state of the cell included in the information of each target candidate cell, and the like.

As described above, in the case of recovery from RLF using reselection of a CHO cell, the terminal 200 can migrate to the target gNB and recover from RLF early without performing the RRC request process.

(3.2.2) operation example 2

Next, operation example 2 of recovery from RLF during the Conditional HO will be described. In this operation example, in operation example 1, when receiving RRC Reconfiguration from source gNB100A in S105, terminal 200 immediately transmits RRC Reconfiguration Complete message 1(RRC Reconfiguration Complete 1).

Fig. 7 is a diagram showing a recovery timing from RLF in the Conditional HO procedure (operation example 2). S101 to S115 in fig. 7 are the same processes as S101 to S115 in fig. 6, and therefore, the description thereof is omitted.

As shown in fig. 7, when the terminal 200 receives RRC Reconfiguration from the source gNB100A, it immediately transmits RRC Reconfiguration Complete1(S105 a).

When the terminal 200 is connected to the target gNB100B through the RA procedure of S115, an RRC Reconfiguration Complete message 2(RRC Reconfiguration Complete2) or an RRC creation Complete message (RRC Setup Complete) is transmitted to the target gNB100B (S117 a).

The RRC Reconfiguration Complete1 and the RRC Reconfiguration Complete2 have the same configuration as the RRC Reconfiguration Complete.

In S117a, terminal 200 includes RLF information in RRC Reconfiguration Complete2 or RRC Setup Complete, and notifies RLF. Further, in S117a, terminal 200 may include RLF information and RLF detection information in RRC Reconfiguration Complete2 or RRC Setup Complete.

(3.2.3) operation example 3

Next, operation example 3 of recovery from RLF during the Conditional HO will be described. In this operation example, in operation example 1, when RLF occurs during the Conditional HO procedure and the RA procedure fails, the terminal 200 reselects a cell of a migration destination other than the target candidate cell (a cell of a migration destination other than the CHO cell) and performs the RRC Reestablishment procedure.

Fig. 8 is a diagram showing a recovery timing from RLF in the Conditional HO procedure (operation example 3). S101 to S111 in fig. 8 are the same processes as S101 to S111 in fig. 6, and therefore, the description thereof is omitted.

In addition, in the present operation example, source gNB100A finds only target gNB100B from the measurement report received from terminal 200. Therefore, the source gNB100A transmits a CHO request to the target gNB100B (S101), and receives a CHO request ACK including the setting information of the target candidate cell from the target gNB100B (S103).

When RLF occurs during execution of the RA procedure and the RA procedure fails in S111, the terminal 200 reselects a target candidate cell (CHO cell) of the migration destination that satisfies the migration condition. However, if there is no target candidate cell of the migration destination that satisfies the migration condition, the terminal 200 reselects a cell of the migration destination other than the target candidate cell (a migration destination cell other than the CHO cell) (S131). In the present embodiment, terminal 200 reselects a cell under the control of target gNB 100C.

When terminal 200 decides to reconnect with a cell under the control of target gNB100C, an RRC request message procedure is performed between target gNB100C and terminal 200.

Specifically, the terminal 200 transmits an RRC request to the target gNB100C (S133). When the target gNB100C receives the RRC request from the terminal 200, it transmits the RRC request to the terminal 200 (S135). The RRC request includes setting information used between the target gNB100C and the terminal 200 to reestablish the RRC connection.

When the terminal 200 receives the RRC request message from the target gNB100C, the RRC connection is re-established between the target gNB100C and the terminal 200, and the RRC request message Complete is transmitted (S137).

In S137, terminal 200 includes the RLF information in the RRC request Complete and performs RLF notification. In S137, terminal 200 may include the RLF information and the RLF detection information in the RRC request fragment Complete.

(3.2.4) Information Element (IE)

Next, the IE of each message used for the RLF notification will be described.

FIG. 9 is a diagram for explaining the IEs within the VarRLF-Report. As shown in fig. 9, the terminal 200 includes RLF information in RLF-Report-r16 within VarRLF-Report. In addition, the terminal 200 may include the RLF information and the RLF detection information in RLF-Report-r16 within the VarRLF-Report.

Fig. 10 is a diagram for explaining an IE in the RRC Reconfiguration Complete. As shown in fig. 10, when RLF information is included in the VarRLF-Report, the terminal 200 includes the RLF information in RLF-InfoAvailable-r16 within the RRC Reconfiguration Complete in S117 of fig. 6. In addition, the terminal 200 may include the RLF information and the RLF detection information in RLF-InfoAvailable-r16 in the RRC Reconfiguration Complete.

As described above, the RRC Reconfiguration Complete2 has the same structure as the RRC Reconfiguration Complete. Therefore, when the RLF information is contained in the VarRLF-Report, the terminal 200 contains the RLF information in RLF-InfoAvailable-r16 within the RRC Reconfiguration Complete2 in S117a of FIG. 7. In addition, the terminal 200 may include the RLF information and the RLF detection information in RLF-InfoAvailable-r16 within the RRC Reconfiguration Complete 2.

Fig. 11A and 11B are diagrams for explaining the IE in the RRC Setup Complete. As shown in fig. 11A, when RLF information is included in the VarRLF-Report, the terminal 200 includes the RLF information in RLF-InfoAvailable-r16 within the RRC Setup Complete in S117a of fig. 7. In addition, the terminal 200 may include RLF information and RLF detection information in RLF-InfoAvailable-r16 within the RRC Setup Complete.

Fig. 12 is a diagram for explaining an IE in the RRC message Complete. As shown in fig. 12, when the RLF information is included in the VarRLF-Report, the terminal 200 includes the RLF information in RLF-InfoAvailable-r16 within the RRC message Complete in S137 of fig. 8. In addition, the terminal 200 may include the RLF information and the RLF detection information in RLF-InfoAvailable-r16 within the RRC message Complete.

Fig. 13 is a diagram for explaining an IE in RRC recovery Complete (RRC Resume Complete). As described in "(3.9) recovery of radio bearer after RLF in Conditional HO procedure" below, RRC Resume Complete is used by terminal 200 to notify the network of "recovery of radio bearer completed upon reception of RRC message instructing recovery of radio bearer".

As shown in fig. 13, in the case where RLF information is included in VarRLF-Report, the terminal 200 may include the RLF information in RLF-InfoAvailable-r16 within RRC Resume Complete for notifying that the recovery of the radio bearer is completed after the recovery from RLF. In addition, the terminal 200 may include the RLF information and RLF detection information in RLF-InfoAvailable-r16 within the RRC Resume Complete.

Fig. 14 is a diagram for explaining an Information Element (IE) in the UE Information Request (UE Information Request). The terminal 200 can notify the network of the occurrence of RLF according to a request from the network. As shown in fig. 14, the network requests the RLF notification to the terminal 200 using RLF-ReportReq-r16 in the UE Information Request.

Fig. 15A to 15C are diagrams for explaining IEs in the UE Information Response (UE Information Response). When the slave network is requested to be notified of the RLF using the UE Information Request, the terminal 200 includes the RLF Information in RLF-Cause-r16 within the UE Information Response, as shown in FIG. 15A. In addition, the terminal 200 may include the RLF Information and the RLF detection Information in RLF-Cause-r16 within the UE Information Response.

(3.2.5) others

In operation examples 1 and 2, the message including the RLF information is a message (for example, RRC Reconfiguration Complete2, or RRC Setup Complete) indicating that the Conditional HO procedure is completed (that is, indicating that the setting information of the target candidate cell is applied), but is not limited thereto.

For example, the message including the RLF information may be the initial RRC message sent to the target gNB of the migration destination. Further, the message including the RLF information may be a message having a specific identifier. As the identifier, a transaction identifier, a Packet Data Convergence Protocol (PDCP) Sequence Number (SN), a PDCP count value, a Radio Link Control (RLC) Sequence Number (SN), or a hybrid automatic repeat request process (HARQ process) identifier may be cited.

Further, the terminal 200 may notify the RLF information to the network side at a timing other than the Conditional HO procedure.

In operation examples 1 to 3, terminal 200 includes RLF information and RLF detection information in the same message, but the present invention is not limited thereto, and these pieces of information may be included in different messages. Further, in the case where there is an indication from the network, the terminal 200 may include the RLF information in the message. Likewise, in the case where there is an indication from the network, the terminal 200 may include the RLF detection information in the message.

When a plurality of RLFs occur, terminal 200 may include a plurality of RLF detection information in the same message and transmit the RLF detection information to the target gNB of the migration destination. Further, the terminal 200 may transmit to the target gNB of the migration destination only a predetermined number of RLF detection information (for example, one RLF detection information) included in the same message.

When a plurality of RLFs occur, the terminal 200 may give priority to the plurality of RLF detection information. For example, when RLF is detected at the same frequency as that used in the cell under the target gNB of the migration destination, terminal 200 gives high priority to RLF detection information including information of the frequency. Further, the terminal 200 may transmit a plurality of RLF detection information to the target gNB of the migration destination in accordance with the priority designated from the network.

Further, when a plurality of RLF detection information are included in the same message, the terminal 200 may delete a part of the RLF detection information from the message in the case where the maximum size allowed for the message is exceeded. In this case, terminal 200 may notify that part of RLF detection information is deleted to target gNB of the migration destination.

In addition, when RLF is detected again after a message including a plurality of RLF detection information is generated, the terminal 200 may regenerate the message.

(3.3) RRC Reconfiguration Complete Transmission timing in the Conditiononal HO procedure

Next, RRC Reconfiguration Complete transmission timing in the Conditional HO procedure will be described. In the Conditional HO procedure shown in fig. 4, when the RA procedure is successful, the terminal 200 performs RRC Reconfiguration Complete transmission. In contrast, in the present operation, when the terminal 200 receives RRC Reconfiguration, the terminal immediately performs transmission of RRC Reconfiguration Complete. That is, the terminal 200 performs transmission of the RRC Reconfiguration Complete before the start of the RA procedure.

Fig. 16 is a diagram showing an RRC Reconfiguration Complete transmission timing in the Conditional HO procedure. S151 to S155 in fig. 16 are the same processes as S11 to S15 in fig. 4, and therefore, the description thereof is omitted.

When receiving the RRC Reconfiguration including the CHO configuration (CHO configuration) from the source gNB100A, the terminal 200 immediately acquires the setting information of the target candidate cell and transmits the RRC Reconfiguration Complete1 to the source gNB100A (S155 a).

When the terminal 200 transmits the RRC Reconfiguration Complete1 to the source gNB100A, the CHO condition is monitored (S157). Specifically, the terminal 200 determines whether or not a transition condition to the target candidate cell included in the setting information of each target candidate cell is satisfied.

When the RRC processes are executed in parallel, the processing on the radio base station side becomes complicated, and therefore, when changing the setting information of the target candidate cell, the terminal 200 needs to notify the change using the RRC Reconfiguration after receiving the RRC Reconfiguration Complete notifying that the Reconfiguration of the RRC connection is completed.

Therefore, when changing the setting information of the target candidate cell, the source gNB100A receives the RRC Reconfiguration Complete1 from the terminal 200 in S155a, and then notifies the terminal 200 of the change of the setting information of the target candidate cell using the RRC Reconfiguration (S159).

In S159, the source gNB100A includes the changed setting information of the target candidate cell in RRC Reconfiguration. The source gNB100A may include the difference between the changed setting information of the target candidate cell and the setting information of the target candidate cell transmitted in S155 in the new RRC Reconfiguration.

The RRC Reconfiguration transmitted in S155 is also referred to as a 1 st setup message. The RRC Reconfiguration Complete1 transmitted in S155a is also referred to as a completion message for the 1 st setup message. The RRC Reconfiguration transmitted in S159 is also referred to as a 2 nd setup message.

When receiving RRC Reconfiguration from source gNB100A, terminal 200 immediately acquires the changed setting information of the target candidate cell, and transmits RRC Reconfiguration Complete1 to source gNB100A (S159 a). The terminal 200 updates the setting information of the target candidate cell acquired in S155, based on the changed setting information of the target candidate cell.

When the terminal 200 determines that the migration condition to the target candidate cell is satisfied by movement of the terminal 200 or the like, if the handover command is not received from the source gNB100A, it determines to start Handover (HO) to the target candidate cell (S161). In the present embodiment, terminal 200 determines to start HO to a target candidate cell subordinate to target gNB 100B.

When the terminal 200 decides to start HO to a target candidate cell under the control of the target gNB100B, a Random Access (RA) procedure is performed between the target gNB100B and the terminal 200, and synchronization is established between the target gNB100B and the terminal 200 (S163). Thereby, terminal 200 is connected to target gNB 100B.

When the terminal 200 connects to the target gNB100B, it transmits RRC Reconfiguration Complete2 or RRC Setup Complete to the target gNB100B (S165).

In S159, source gNB100A transmits RRC Reconfiguration to terminal 200 in order to change the setting information of the target candidate cell, but the present invention is not limited to this. For example, source gNB100A may transmit RRC Reconfiguration to terminal 200 in addition to the setting information of the target candidate cell in order to change the configuration (UE configuration) of terminal 200.

In this case, the source gNB100A includes the changed UE configuration in the RRC Reconfiguration. In addition, the source gNB100A may include the difference between the UE configuration after the change and the UE configuration transmitted earlier in the RRC Reconfiguration.

(3.4) HO termination during Conditional HO

Next, HO termination in the Conditional HO process will be described. In this operation, the target gNB instructs the source gNB to delete the setting information of the target candidate cell after transmitting the setting information of the target candidate cell to the source gNB. In the present embodiment, target gNB100B instructs source gNB100A to delete the setting information of the target candidate cell.

(3.4.1) operation example 1

First, operation example 1 of HO termination in the Conditional HO process will be described. Fig. 17 is a diagram showing HO termination timing (operation example 1) in the Conditional HO process. S201 to S207 shown in fig. 17 are the same processes as S151 to S157 shown in fig. 16, and therefore, the description thereof is omitted.

In addition, the CHO request ACK transmitted in S203 is also referred to as a 1 st message. The HO cancel transmitted in S209 is also referred to as a 2 nd message.

When the target gNB100B recognizes that the subordinate target candidate cell is in a state unsuitable for terminal 200 migration, an HO cancel message (HO cancel) is transmitted to the source gNB100A (S209).

Specifically, when the target gNB100B determines that the load is increased in the subordinate target candidate cell and that the target candidate cell is in a state unsuitable for the terminal 200 to transition, the HO cancel may be transmitted in S209.

In this case, when a plurality of terminals migrate to a target candidate cell under the control of the target gNB100B and the number of connected terminals exceeds the maximum number of connected terminals allowed by the target candidate cell, the target gNB100B may determine that the target candidate cell is in a state unsuitable for the terminal 200 to migrate.

For example, in Call Admission Control (CAC), when the number of connected terminals exceeds the maximum number of UE contexts in the target candidate cells under the control of the target gNB100B, the target gNB100B determines that the target candidate cell is not suitable for the terminal 200 to transition.

In addition, when the terminal 200 does not transit to the target candidate cell within a predetermined time (for example, when the terminal 200 is in an inactive state even if the predetermined time is exceeded) based on the setting information of the target candidate cell under the control of the target gNB100B, the target gNB100B may transmit HO cancel in S209.

In addition, when the target gNB100B receives a UE context release (UE context release) from a gNB other than the source gNB or ng-eNB, the target gNB100B may transmit an HO cancel in S209.

In addition, in S209, target gNB100B may send HO cancel directly to source gNB 100A. In this case, Xn signaling is used for the transmission of HO cancel, for example. Instead, the target gNB100B may send a HO cancel to the source gNB100A via the core network. In this case, for example, NG signaling is used for transmission of HO cancellation.

When the source gNB100A receives the HO cancel from the target gNB100B, in S205a, the RRC Reconfiguration Complete1 is received from the terminal 200, and then the change of the setting information of the target candidate cell is notified to the terminal 200 using the RRC Reconfiguration (S211).

Specifically, the source gNB100A includes information indicating the deletion of the setting information of the target candidate cell under the control of the target gNB100B in the RRC Reconfiguration. Furthermore, source gNB100A may include, in RRC Reconfiguration, CHO configuration from which the setting information of the target candidate cells under the control of target gNB100B is deleted.

When the terminal 200 receives RRC Reconfiguration from the source gNB100A, it immediately transmits RRC Reconfiguration Complete1 to the source gNB100A (S211 a). Terminal 200 deletes the setting information of the target candidate cell under the control of target gNB100B, according to the reception of RRC Reconfiguration.

When terminal 200 determines that the migration condition to the target candidate cell is satisfied due to movement of terminal 200 or the like, if the handover command is not received from source gNB100A, it determines to start Handover (HO) to the target candidate cell (S213). In the present embodiment, terminal 200 determines to start HO to a target candidate cell subordinate to target gNB 100C.

When the terminal 200 decides to start HO to a target candidate cell under the control of the target gNB100C, a Random Access (RA) procedure is performed between the target gNB100C and the terminal 200, and synchronization is established between the target gNB100C and the terminal 200 (S215). Thereby, terminal 200 is connected to target gNB 100C.

When the terminal 200 is connected to the target gNB100C, RRC Reconfiguration Complete2 or RRC Setup Complete is transmitted to the target gNB100C (S217).

(3.4.2) operation example 2

Next, operation example 2 of HO termination in the Conditional HO process will be described. Fig. 18 is a diagram showing HO termination timing (operation example 2) in the Conditional HO process. S231 to S239 shown in fig. 18 are the same processes as S201 to S209 shown in fig. 17, and therefore, the description thereof is omitted.

In addition, in the present operation example, source gNB100A finds only target gNB100B from the measurement report received from terminal 200. Therefore, the source gNB100A transmits a CHO request to the target gNB100B (S231), and receives a CHO request ACK containing setting information of the target candidate cell from the target gNB100B (S233).

When the source gNB100A finds a target gNB100C located around the source gNB100A after receiving HO cancel from the target gNB100B, a CHO request is transmitted to the target gNB100C (S241).

When the target gNB100C receives the CHO request from the source gNB100A, a CHO request ACK containing setting information of target candidate cells subordinate to the target gNB100C is transmitted to the source gNB100A (S243).

When source gNB100A receives HO cancel from target gNB100B and CHO request ACK from target gNB100C, it notifies terminal 200 of change of setting information of the target candidate cell using RRC Reconfiguration after receiving RRC Reconfiguration Complete1 from terminal 200 in S235a (S245).

Specifically, the source gNB100A deletes the setting information of the target candidate cell under the target gNB100B, and includes the CHO configuration including the setting information of the target candidate cell under the target gNB100C in the RRC Reconfiguration.

When the terminal 200 receives RRC Reconfiguration from the source gNB100A, it immediately transmits RRC Reconfiguration Complete1 to the source gNB100A (S245 a). Terminal 200 applies CHO configuration including setting information of target candidate cells subordinate to target gNB100C, in response to reception of RRC Reconfiguration.

When the terminal 200 determines that the migration condition to the target candidate cell is satisfied by movement of the terminal 200 or the like, if the handover command is not received from the source gNB100A, it determines to start Handover (HO) to the target candidate cell (S247). In the present embodiment, terminal 200 determines to start HO to a target candidate cell subordinate to target gNB 100C.

When the terminal 200 decides to start HO to a target candidate cell under the control of the target gNB100C, a Random Access (RA) procedure is performed between the target gNB100C and the terminal 200, and synchronization is established between the target gNB100C and the terminal 200 (S249). Thereby, terminal 200 is connected to target gNB 100C.

When the terminal 200 is connected to the target gNB100C, RRC Reconfiguration Complete2 or RRC Setup Complete is transmitted to the target gNB100C (S251).

(3.5) HO Change during Conditionional HO

Next, HO change in the Conditional HO process will be described. In this operation, after the target gNB transmits the setting information of the target candidate cell to the source gNB, the source gNB is instructed to change the setting information of the target candidate cell. In the present embodiment, target gNB100B instructs source gNB100A to change the setting information of the target candidate cell.

(3.5.1) operation example 1

First, operation example 1 of HO change in the Conditional HO process will be described. Fig. 19 is a diagram showing HO change timing (operation example 1) in the Conditional HO process. S301, S303, and S309 to S315 shown in fig. 19 are the same processes as S11, S13, and S17 to S23 shown in fig. 4, and therefore, description thereof is omitted.

In addition, the CHO request ACK transmitted in S303 is also referred to as a 1 st message. The HO modification transmitted in S305 is also referred to as a 2 nd message.

As shown in fig. 19, when the state of the target candidate cell is recognized to have changed after the setting information of the subordinate target candidate cell is transmitted to the source gNB100A using the CHO request ACK in S303, the target gNB100B transmits an HO change message (HO modification) to the source gNB100A (S305).

Specifically, when the target gNB100B determines that the load status has changed in the subordinate target candidate cell and the transition condition to the target candidate cell needs to be changed, it may transmit HO modification in S305.

In addition, in S305, target gNB100B may send a HO modification directly to source gNB 100A. In this case, Xn signaling is used for example for the transmission of HO modification. Instead, the target gNB100B may send a HO modification to the source gNB100A via the core network. In this case, for example, NG signaling is used for transmission of HO modification.

When source gNB100A receives HO modification from target gNB100B, it changes the setting information of the target candidate cell under the control of target gNB100B and transmits RRC Reconfiguration including CHO configuration to terminal 200 (S307).

(3.5.2) operation example 2

Next, operation example 2 of HO change in the Conditional HO process will be described. Fig. 20 is a diagram showing HO change timing (operation example 2) in the Conditional HO process. S301 to S313 shown in fig. 20 are the same as S301 to S313 shown in fig. 19, and therefore, the description thereof is omitted.

As shown in fig. 20, when the terminal 200 receives RRC Reconfiguration from the source gNB100A, it immediately transmits RRC Reconfiguration Complete1(S307 a).

When the terminal 200 is connected to the target gNB100B through the RA procedure of S313, the RRC Reconfiguration Complete2 or the RRC Setup Complete is transmitted to the target gNB100B (S315 a).

(3.5.3) action example 3

Next, operation example 3 of HO change in the Conditional HO process will be described. Fig. 21 is a diagram showing HO change timing (operation example 3) in the Conditional HO process. S301, S303, S307a, S309 shown in fig. 21 are the same processes as S301, S303, S307a, S309 shown in fig. 20, and therefore, the description thereof is omitted.

As shown in fig. 21, when the target gNB100B recognizes that the state of the subordinate target candidate cell has changed, the HO modification is transmitted to the source gNB100A (S331).

When the source gNB100A receives the HO modification from the target gNB100B, the RRC Reconfiguration Complete1 is received from the terminal 200 in S307a, and then the change of the setting information of the target candidate cell is notified to the terminal 200 using the RRC Reconfiguration (S333).

Specifically, the source gNB100A includes the CHO configuration after changing the setting information of the target candidate cell under the control of the target gNB100B in the RRC Reconfiguration.

When the terminal 200 receives RRC Reconfiguration from the source gNB100A, it immediately transmits RRC Reconfiguration Complete1 to the source gNB100A (S333 a). Terminal 200 changes the setting information of the target candidate cell under the control of target gNB100B in response to the reception of RRC Reconfiguration.

When terminal 200 determines that the migration condition to the target candidate cell is satisfied due to movement of terminal 200 or the like, if the handover command is not received from source gNB100A, it determines to start Handover (HO) to the target candidate cell (S335). In the present embodiment, terminal 200 determines to start HO to a target candidate cell subordinate to target gNB 100B.

When the terminal 200 decides to start HO to a target candidate cell under the control of the target gNB100B, a Random Access (RA) procedure is performed between the target gNB100B and the terminal 200, and synchronization is established between the target gNB100B and the terminal 200 (S337). Thereby, terminal 200 is connected to target gNB 100B.

When the terminal 200 is connected to the target gNB100B, RRC Reconfiguration Complete2 or RRC Setup Complete is transmitted to the target gNB100B (S339).

(3.6) RRC Reconfiguration Structure in Conditionional HO procedure

Next, the configuration of RRC Reconfiguration in the Conditional HO procedure will be described. In the present configuration, RRC Reconfiguration stores setting information of target candidate cells under the control of target gNB100B and setting information of target candidate cells under the control of target gNB 100C. The phrase "setting information of a plurality of target candidate cells is stored in RRC Reconfiguration" may also be expressed as "setting information of a plurality of target candidate cells is encapsulated in RRC Reconfiguration".

First, an operation flow for encapsulating setting information of a target candidate cell will be described. Fig. 22 is a diagram showing an operation flow of encapsulating the setting information of the target candidate cell. As shown in fig. 22, source gNB100A sends a CHO request to target gnbs 100B, 100C (S350).

When the source gNB100A receives the setting information of the target candidate cell from each of the target gnbs 100B and 100C, the setting information of the target candidate cell is encapsulated in RRC Reconfiguration (S355).

When the source gNB100A encapsulates the setting information of the target candidate cells in RRC Reconfiguration, it transmits the RRC Reconfiguration to the terminal 200 (S357).

(3.6.1) structural example 1

Next, the encapsulation of the setting information of the target candidate cell will be described in detail. Fig. 23 is a diagram for explaining the configuration of RRC Reconfiguration in the Conditional HO procedure (configuration example 1).

As shown in fig. 23, the message group for the downlink dedicated control channel (DL-DCCH) includes RRC Reconfiguration (RRC Reconfiguration), RRC Resume message (RRC Resume), RRC Release message (RRC Release), RRC Reestablishment (RRC Reestablishment), Security Mode Command (Security Mode Command), and the like.

DL-DCCH is a downlink dedicated control channel used in the terminal 200 in which the RRC connection is established. The terminal 200 receives the above-described RRC message and the like via the DL-DCCH.

In the present configuration example, a new Information Element (IE) is set in the conventional RRC Reconfiguration, and the IE includes setting information of a target candidate cell under the control of target gNB100B and setting information of a target candidate cell under the control of target gNB 100C.

Specifically, as a new IE, an RRC Reconfiguration list (rrcconfiguration list) is set in the conventional RRC Reconfiguration, and a configuration for cell1 (configuration for cell1) and a configuration for cell2 (configuration for cell2) are set in the rrcconfiguration list. In addition, the number of configurations (configuration for cells) for the cell is not limited to 2.

In this configuration, when source gNB100A receives the setting information of the target candidate cell under the control of target gNB100B from target gNB100B, the setting information of the target candidate cell is included in configuration for cell1 in rrcreconconfigurationlist. Similarly, when source gNB100A receives the setting information of the target candidate cell under the control of target gNB100C from target gNB100C, the setting information of the target candidate cell is included in configuration for cell2 in rrcreconfigurelist.

In addition, rrcreconconfigurationlist is also referred to as CHO configuration. When terminal 200 receives RRC Reconfiguration from source gNB100A, configuration information of a target candidate cell under target gNB100B and configuration information of a target candidate cell under target gNB100C are acquired from configuration for cell1 and configuration for cell2 in RRC Reconfiguration.

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

Measurement conditions

Structure of target candidate cell

Security information (e.g., update information of security key)

Transaction identifier

(3.6.2) structural example 2

Fig. 24 is a diagram for explaining the configuration of RRC Reconfiguration in the Conditional HO procedure (configuration example 2). As shown in fig. 24, the DL-DCCH message set includes RRC Reconfiguration (RRC Reconfiguration), RRC recovery (RRC Resume), RRC Release (RRC Release), RRC Reestablishment (RRC Reestablishment), Security Mode Command (Security Mode Command), RRC Reconfiguration 1(RRC Reconfiguration1), and the like.

The RRC Reconfiguration1 is a new message different from the conventional RRC Reconfiguration, and is an RRC Reconfiguration message used in the Conditional HO procedure. In addition, the designation of the new message is not limited to RRC Reconfiguration 1. In the present configuration example, the setting information of the target candidate cell under the control of target gNB100B and the setting information of the target candidate cell under the control of target gNB100C are included in the Information Element (IE) set in RRC Reconfiguration 1.

Specifically, an RRC Reconfiguration list (rrcconfiguration list) is set in the new RRC Reconfiguration1, and a configuration for cell1 and a configuration for cell2 are set in the rrcconfiguration list. In addition, the number of configuration for cells is not limited to 2.

In this configuration, when source gNB100A receives the setting information of the target candidate cell under the control of target gNB100B from target gNB100B, the setting information of the target candidate cell is included in configuration for cell1 in rrcreconconfigurationlist. Similarly, when source gNB100A receives the setting information of the target candidate cell under the control of target gNB100C from target gNB100C, the setting information of the target candidate cell is included in configuration for cell2 in rrcreconfigurelist.

When terminal 200 receives RRC Reconfiguration1 from source gNB100A, the setting information of the target candidate cell under the control of target gNB100B and the setting information of the target candidate cell under the control of target gNB100C are acquired from configuration for cell1 and configuration for cell2 in RRC Reconfiguration 1.

(3.7) transaction ID assignment during Condition HO

Next, the assignment of the transaction ID in the Conditional HO process will be described. In this operation, the source gNB or the target gNB performs assignment of a transaction ID used in the Conditional HO process.

(3.7.1) operation example 1

First, operation example 1 of ID assignment in the Conditional HO process will be described. In this example of operation, the source gNB performs the assignment of a transaction ID utilized in the Conditional HO process.

Fig. 25 is a diagram showing an ID assignment sequence (operation example 1) in the Conditional HO process. S401, S403, and S409 to S413 shown in fig. 25 are the same processes as S11, S13, and S17 to S21 shown in fig. 4, and therefore, description thereof is omitted.

As shown in fig. 25, when source gNB100A receives the CHO request ACK from target gnbs 100B, 100C, the CHO configuration is included in the RRC Reconfiguration and the RRC Reconfiguration is given a transaction ID (S405).

Specifically, the source gNB100A includes the identification information of the target candidate cell under the target gNB100B and the identification information of the target candidate cell under the target gNB100C in the rrcreconfigurable list in the RRC Reconfiguration, and sets the transaction ID to a predetermined Information Element (IE) in the RRC Reconfiguration (see fig. 23). In addition, rrcreconconfigurationlist is also referred to as CHO configuration.

Further, source gNB100A may include identification information of a target candidate cell under target gNB100B and identification information of a target candidate cell under target gNB100C in rrcreconfigurelist in RRC Reconfiguration message RRC Reconfiguration1 used in the configured HO, and may set a transaction ID to a predetermined Information Element (IE) in RRC Reconfiguration1 (see fig. 24).

The transaction ID may be one of 0 to 3, or may be a fixed value of 0. In the present embodiment, the transaction ID takes one value of 0 to 3.

Instead of assigning the RRC Reconfiguration, the source gNB100A may assign a transaction ID to the rrcconfigurationlist included in the RRC Reconfiguration, that is, to the group of the encapsulated target candidate cell configuration information.

When the source gNB100A sets RRC Reconfiguration, it transmits the RRC Reconfiguration to the terminal 200 (S407).

When receiving RRC Reconfiguration from source gNB100A, terminal 200 immediately acquires the setting information of the target candidate cell and transmits RRC Reconfiguration Complete1 to source gNB100A (S407 a).

In S407a, the terminal 200 includes the RRC Reconfiguration Complete1 with the transaction ID assigned to the RRC Reconfiguration received from the source gNB 100A.

The terminal 200 performs monitoring of the CHO condition (S409), starts HO to the target gNB100B (S411), and performs RA procedure between the target gNB100B and the terminal 200 (S413), and transmits RRC Reconfiguration Complete2 to the target gNB100B when connected to the target gNB100B (S415).

(3.7.2) operation example 2

Next, operation example 2 of ID assignment in the Conditional HO process will be described. In this operation example, the target gNB performs assignment of a transaction ID used in the Conditional HO process.

Fig. 26 is a diagram showing an ID assignment sequence (operation example 2) in the Conditional HO process. S401 and S437 to S441 shown in fig. 26 are the same processes as S11 and S17 to S21 shown in fig. 4, and therefore, the description thereof is omitted.

As shown in fig. 26, when the target gNB100B receives the CHO request from the source gNB100A, the setting information of the target candidate cell under the control of the target gNB100B is included in the CHO request ACK, and the transaction ID is given to the setting information of the target candidate cell (S431). Specifically, the target gNB100B includes the transaction ID in the setting information of the target candidate cell.

Similarly, when the target gNB100C receives the CHO request from the source gNB100A, the configuration information of the target candidate cell under the control of the target gNB100C is included in the CHO request ACK, and the transaction ID is given to the configuration information of the target candidate cell (S431). Specifically, the target gNB100B includes the transaction ID in the setting information of the target candidate cell.

The transaction ID may be one of 0 to 3, or may be a fixed value of 0. In the present embodiment, the transaction ID takes one value of 0 to 3.

When the source gNB100A receives the CHO request ACK from the target gNB100B, 100C, the CHO configuration is included in the RRC Reconfiguration. Specifically, source gNB100A includes, in rrcreconfigurable list in RRC Reconfiguration, identification information of target candidate cells under target gNB100B to which the transaction ID is assigned and identification information of target candidate cells under target gNB100C to which the transaction ID is assigned (see fig. 23). In addition, rrcreconconfigurationlist is also referred to as CHO configuration.

Further, source gNB100A may include identification information of a target candidate cell under target gNB100B and identification information of a target candidate cell under target gNB100C in RRCReconfigurationList in RRC Reconfiguration message RRC Reconfiguration1 used in the Conditional HO (see fig. 24).

When the source gNB100A sets RRC Reconfiguration, it sends the RRC Reconfiguration to the terminal 200 (S435).

When receiving the RRC Reconfiguration from the source gNB100A, the terminal 200 immediately acquires the setting information of the target candidate cell and transmits the RRC Reconfiguration Complete1 to the source gNB100A (S435 a).

The terminal 200 performs monitoring of the CHO condition (S437), starts HO to the target gNB100B (S439), and performs RA procedure between the target gNB100B and the terminal 200 (S441), and when connecting with the target gNB100B, transmits RRC Reconfiguration Complete2 to the target gNB100B (S443).

In S443, terminal 200 includes the transaction ID included in the setting information of the target candidate cell under the control of target gNB100B in RRC Reconfiguration Complete 2.

(3.8) recovery of HOF from Condition HO procedure

Next, the recovery from the HOF during the Conditional HO will be described. In this operation, the terminal 200 receives an HO command (HO command) from the source gNB during the monitoring of the CHO condition, and then interrupts the CHO to preferentially migrate to the target gNB, thereby generating the HOF. In this case, the terminal 200 maintains all or a part of the setting information of the target candidate cell under the control of the target gNB.

Fig. 27 is a diagram showing a recovery timing from the HOF in the Conditional HO procedure. S501 to S507 in fig. 27 are the same processes as S11 to S17 in fig. 4, and therefore, the description thereof is omitted.

When the source gNB100A decides to preferentially migrate the terminal 200 to a target candidate cell under the control of the target gNB100B, it transmits a HO request to the target gNB100B (S509). When the target gNB100B receives the HO request from the source gNB100A, a HO request ACK is transmitted to the source gNB100A (S511).

When the source gNB100A receives the HO request ACK from the target gNB100B, it transmits a HO command to the terminal 200 (S513). When the terminal 200 receives an HO command from the source gNB100A in the monitoring process of the CHO condition, a handover process is attempted between the target gNB100B and the terminal 200 (S515).

When the HOF occurs during the execution of the handover procedure and the handover procedure fails in S515, the terminal 200 reselects a target candidate cell (CHO cell) of the migration destination satisfying the migration condition (S517). In the present embodiment, terminal 200 reselects a target candidate cell subordinate to target gNB 100B.

In S517, terminal 200 maintains all or a part of the setting information of the target candidate cell under the control of target gNB 100B. Further, "maintaining all or a part of the setting information of the target candidate cell" may be expressed as "regarding that all or a part of the setting information of the target candidate cell can be applied" or "regarding that all or a part of the setting information of the target candidate cell is enabled".

In S517, the information maintained by terminal 200 in the setting information of the target candidate cell is, for example, security information. When target gNB100B has acquired the identification information of terminal 200 in advance, the information maintained by terminal 200 may be the identification information of terminal 200.

The identification information of the terminal 200 includes, for example, the following information.

Short medium access control identifier (short MAC-ID)

Cell radio network temporary identifier (C-RNTI)

Implicit radio network temporary identifier (I-RNTI)

When the terminal 200 reselects a target candidate cell under the control of the target gNB100B, a Random Access (RA) procedure is performed between the target gNB100B and the terminal 200, and synchronization is established between the target gNB100B and the terminal 200 (S519). Thereby, terminal 200 is connected to target gNB 100B.

When the terminal 200 is connected to the target gNB100B, an RRC Reconfiguration Complete message (RRC Reconfiguration Complete) is transmitted to the target gNB100B (S521).

In S521, the terminal 200 may include all or a part of the setting information of the target candidate cell maintained in S517 in the RRC Reconfiguration Complete, and transmit the setting information to the target gNB100B using the signaling radio bearer 1(SRB 1). Instead of SRB1, terminal 200 may include all or part of the setting information of the target candidate cell maintained in S517 in the RRC request, and transmit the setting information to target gNB100B using signaling radio bearer 0(SRB 0).

SRB0 is a radio bearer for a Common Control Channel (CCCH). SRB1 is a radio bearer for the Dedicated Control Channel (DCCH).

In S521, terminal 200 may include information indicating that all or a part of the setting information of the target candidate cell is maintained in the RRC Reconfiguration Complete, and transmit the information to target gNB 100B.

In S521, terminal 200 may include information that can be converted in a one-to-one manner with the setting information of the target candidate cell maintained in S517 in RRC Reconfiguration Complete, and transmit the information to target gNB 100B.

Thereby, for example, security information or identification information of terminal 200 is shared between terminal 200 and target gNB 100B. Therefore, target gNB100B can determine whether terminal 200 is a terminal permitted to migrate to target gNB 100B.

The application of this operation is not limited to the case where the terminal 200 receives the HO command from the source gNB during the monitoring of the CHO condition, interrupts the CHO, and generates the HOF when preferentially moving to the target gNB. For example, this operation can be applied to a case where the terminal 200 monitors the CHO condition, satisfies the transition condition to the target candidate cell under the control of the target gNB, and performs HO to the target candidate cell when no HO command is received from the source gNB, thereby generating the HOF.

(3.9) recovery of radio bearers after RLF in Conditiononal HO procedure

Next, the recovery of the radio bearer after RLF in the Conditional HO procedure will be described. In this operation, when the terminal 200 reconnects to the target gNB during the Condition HO, the radio bearer that was stopped due to the occurrence of RLF is restored (resume) according to a specific Condition.

In addition, the radio bearers include a Signaling Radio Bearer (SRB) and a Data Radio Bearer (DRB). SRB is for control plane data and DRB is for user plane data. In addition, SRBs 0, 1, 2, and 3 may be set in the SRBs according to the use.

SRB0 is a radio bearer for CCCH. SRBs 1 to SRBs 3 are radio bearers for DCCH. The DRB is a radio bearer for user data.

The SRB1 is used for RRC messages and NAS messages before the SRB2 is established.

The SRB2 is used for NAS message transceiving, has lower priority than the SRB1, and is set by the network after the AS security is activated.

The SRB3 is used for transmission and reception of a specific RRC message in E-UTRA-NR Dual Connectivity (EN-DC).

In the present embodiment, when terminal 200 detects RLF when moving to target gNB100B using the setting information of the target candidate cell under the control of target gNB100B, terminal 200 stops (suspend) all radio bearers except SRB0 between target gNB100B and terminal 200, and reconnects to target gNB 100B.

Fig. 28 is a diagram showing an operation flow of terminal 200 for recovering a radio bearer after RLF in the Conditional HO procedure. Fig. 29 is a diagram for explaining a condition for recovering a radio bearer after RLF in a Conditional HO procedure.

As shown in fig. 28, the terminal 200 performs CHO cell reselection during the Conditional HO procedure (S601). Specifically, the terminal 200 reselects a target candidate cell (CHO cell) of the migration destination that satisfies the migration condition. In the present embodiment, terminal 200 reselects a target candidate cell subordinate to target gNB 100B.

When terminal 200 reselects a target candidate cell under the control of target gNB100B, it starts migration to target gNB100B according to the setting information of the target candidate cell (S603). In this case, all radio bearers stopped between target gNB100B and terminal 200 may be restored (condition a of fig. 29).

The terminal 200 starts a Random Access (RA) procedure between the target gNB100B and the terminal 200 with the migration to the target gNB100B (S605). In this case, all radio bearers stopped between target gNB100B and terminal 200 may be restored (condition B of fig. 29).

When the terminal 200 completes the RA procedure between the target gNB100B and the terminal 200 (S607), synchronization is established between the target gNB100B and the terminal 200. Thereby, terminal 200 is connected to target gNB 100B. In this case, all radio bearers stopped between target gNB100B and terminal 200 may be restored (condition C of fig. 29).

Further, when terminal 200 receives an RRC message from the network during S601 to S607, the RRC message instructing the recovery of the radio bearer, all the radio bearers stopped between target gNB100B and terminal 200 can be recovered (condition D in fig. 29).

In this case, the terminal 200 may notify the network of the completion of the recovery of the radio bearer using an RRC recovery Complete message (RRC Resume Complete).

When the terminal 200 is connected to the target gNB100B, RRC Reconfiguration Complete is transmitted to the target gNB100B (S609).

(4) Action and Effect

According to the above-described embodiment, the terminal 200 performs the migration to the target gNB100B without performing the Reestablishment procedure (RRC request procedure) with the handover failure (HOF). Terminal 200 transmits a specific message (RRC Reconfiguration Complete) to target gNB100B during migration to target gNB 100B. When the handover fails (HOF), terminal 200 maintains the identification information shared between terminal 200 and target gNB100B, and includes the identification information in a specific message (RRC Reconfiguration Complete).

With this configuration, identification information is also shared between terminal 200 and target gNB100B at the time of recovery from the HOF.

Therefore, the network side can authenticate the terminal migrating to the target gNB100B, and migration of a malicious terminal to the target radio base station can be avoided.

According to the above-described embodiment, when the handover fails (HOF), terminal 200 maintains the short MAC-ID (short MAC-ID) shared between terminal 200 and target gNB100B, and further includes the short MAC-ID in a specific message (RRC Reconfiguration Complete).

With this configuration, the network side can authenticate a terminal migrating to the target gNB100B, and migration of a malicious terminal to the target radio base station can be avoided.

(5) Other embodiments

While the present invention has been described with reference to the embodiments, it will be apparent to those skilled in the art that the present invention is not limited to the descriptions, and various modifications and improvements can be made.

For example, in the above-described embodiment, NR was described as an example, but the Conditional HO can be applied to LTE, and similar operations can be performed in LTE.

The block diagrams (fig. 2 and 3) used in the description of the above-described embodiments show blocks in units of functions. These functional blocks (components) are realized by any combination of at least one of hardware and software. The method of implementing each functional block is not particularly limited. That is, each functional block may be implemented by one device that is physically or logically combined, or may be implemented by two or more devices that are physically or logically separated and that are directly or indirectly (for example, wired or wireless) connected and implemented by these plural devices. The functional blocks may also be implemented by a combination of software and one or more of the above-described devices.

The functions include judgment, decision, judgment, calculation, processing, derivation, investigation, search, confirmation, reception, transmission, output, access, resolution, selection, establishment, comparison, assumption, expectation, viewing, broadcasting (broadcasting), notification (notification), communication (communicating), forwarding (forwarding), configuration (configuring), reconfiguration (reconfiguring), allocation (allocating, mapping), assignment (assigning), and the like, but are not limited thereto. For example, a function block (a configuration unit) that functions transmission is referred to as a transmission unit (transmitter) or a transmitter (transmitter). In short, as described above, the method of implementation is not particularly limited.

Note that the above-described gNB100A, 100B, 100C and terminal 200 may also function as a computer that performs the processing of the wireless communication method of the present disclosure. Fig. 30 is a diagram showing an example of the hardware configuration of the apparatus. As shown in fig. 30, the apparatus may be a computer apparatus including a processor 1001, a memory 1002(memory), a storage 1003(storage), a communication apparatus 1004, an input apparatus 1005, an output apparatus 1006, a bus 1007, and the like.

In the following description, the term "device" may be replaced with "circuit", "device", "unit", and the like. The hardware configuration of the apparatus may include one or more of the illustrated apparatuses, or may be configured not to include a part of the apparatuses.

The functional blocks of the apparatus are realized by arbitrary hardware elements of the computer apparatus or a combination of the hardware elements.

Furthermore, the functions in the apparatus are realized by the following method: when predetermined software (program) is read into hardware such as the processor 1001 and the memory 1002, the processor 1001 performs an operation to control communication of the communication device 1004 or at least one of reading and writing of data in the memory 1002 and the storage 1003.

The processor 1001 operates, for example, an operating system to control the entire computer. The processor 1001 may be a Central Processing Unit (CPU) including an interface with a peripheral device, a control device, an arithmetic device, a register, and the like.

Further, the processor 1001 reads out a program (program code), a software module, data, or the like from at least one of the memory 1003 and the communication device 1004 to the memory 1002, and executes various processes in accordance therewith. As the program, a program that causes a computer to execute at least a part of the operations described in the above-described embodiments is used. While the various processes described above have been described as being executed by one processor 1001, the various processes described above may be executed simultaneously or sequentially by two or more processors 1001. The processor 1001 may also be mounted by more than one chip. In addition, the program may also be transmitted from the network via a telecommunication line.

The Memory 1002 is a computer-readable recording medium, and may be configured by at least one of a ROM (Read Only Memory), an EPROM (Erasable Programmable ROM), an EEPROM (Electrically Erasable Programmable ROM), a RAM (Random Access Memory), and the like. Memory 1002 may also be referred to as registers, cache, main memory (primary storage), etc. The memory 1002 can store a program (program code), a software module, and the like that can execute the method according to one embodiment of the present disclosure.

The storage 1003 is a computer-readable recording medium, and may be constituted by at least one of an optical disk such as a CD-rom (compact Disc rom), a hard disk drive, a flexible disk, a magneto-optical disk (for example, a compact Disc, a digital versatile Disc, a Blu-ray (registered trademark) Disc, a smart card, a flash memory (for example, a card, a stick, a Key drive), a Floppy (registered trademark) Disc, a magnetic stripe, and the like.

The communication device 1004 is hardware (a transmitting/receiving device) for performing communication between computers via at least one of a wired network and a wireless network, and may be referred to as a network device, a network controller, a network card, a communication module, or the like.

Communication apparatus 1004 may be configured to include a high-Frequency switch, a duplexer, a filter, a Frequency synthesizer, and the like, for example, in order to realize at least one of Frequency Division Duplexing (FDD) and Time Division Duplexing (TDD).

The input device 1005 is an input device (for example, a keyboard, a mouse, a microphone, a switch, a key, a sensor, and the like) that receives an input from the outside. The output device 1006 is an output device (for example, a display, a speaker, an LED lamp, or the like) that outputs to the outside. The input device 1005 and the output device 1006 may be integrally formed (for example, a touch panel).

The processor 1001 and the memory 1002 are connected to each other via a bus 1007 for communicating information. The bus 1007 may be configured by using a single bus, or may be configured by using different buses for each device.

The apparatus may include hardware such as a microprocessor, a Digital Signal Processor (DSP), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), and an FPGA (Field Programmable Gate Array), and a part or all of each functional block may be realized by the hardware. For example, the processor 1001 may also be installed using at least one of these hardware.

Further, the notification of information is not limited to the form/embodiment described in the present disclosure, and may be performed using other methods. For example, the Information may be notified by physical layer signaling (e.g., DCI (Downlink Control Information), UCI (Uplink Control Information)), higher layer signaling (e.g., RRC (Radio Resource Control) signaling, MAC (Medium Access Control) signaling, broadcast Information (MIB (Master Information Block), SIB (System Information Block)), other signals, or a combination thereof).

The forms/embodiments described in this disclosure can also be applied to at least one of LTE (Long Term Evolution), LTE-a (LTE-Advanced), SUPER 3G, IMT-Advanced, fourth generation Mobile communication system (4th generation Mobile communication system: 4G), fifth generation Mobile communication system (5th generation Mobile communication system: 5G), Future Radio Access (Future Radio Access: FRA), New Radio (NR), W-CDMA (registered trademark), GSM (registered trademark), CDMA 2000, Ultra Mobile Broadband (Ultra Mobile Broadband: UMB), IEEE 802.11(Wi-Fi (registered trademark)), IEEE 802.16(WiMAX (registered trademark)), IEEE 802.20, UWB (Ultra-wide band), Bluetooth (registered trademark), and extended systems using other suitable systems. Furthermore, a plurality of systems (for example, a combination of 5G and at least one of LTE and LTE-a) may be combined and applied.

For the processing procedures, timings, flows, and the like of the respective forms/embodiments described in the present disclosure, the order may be changed without contradiction. For example, for the methods described in this disclosure, elements of the various steps are suggested using an illustrative sequence, but are not limited to the particular sequence suggested.

In the present disclosure, a specific operation performed by a base station is sometimes performed by its upper node (upper node) depending on the situation. In a network including one or more network nodes (network nodes) having a base station, it is obvious that various operations performed for communication with a terminal may be performed by at least one of the base station and a network node other than the base station (for example, an MME, an S-GW, or the like is considered, but not limited thereto). In the above, the case where there is one network node other than the base station is exemplified, but the other network node may be a combination of a plurality of other network nodes (e.g., MME and S-GW).

Information and signals (information and the like) can be output from an upper layer (or a lower layer) to a lower layer (or an upper layer). Or may be input or output via a plurality of network nodes.

The input or output information may be stored in a specific location (for example, a memory) or may be managed using a management table. The information that is input or output may be overwritten, updated or appended. The output information may also be deleted. The entered information may also be sent to other devices.

The determination may be made by a value (0 or 1) represented by 1 bit, may be made by a Boolean value (true or false), or may be made by comparison of values (for example, comparison with a predetermined value).

The respective forms/embodiments described in the present disclosure may be used alone or in combination, and may be switched depending on execution. Note that the notification of the predetermined information is not limited to be performed explicitly (for example, notification of "X") but may be performed implicitly (for example, notification of the predetermined information is not performed).

Software, whether referred to as software, firmware, middleware, microcode, hardware description languages, or by other names, should be construed broadly to mean commands, command sets, code segments, program code, programs (routines), subroutines, software modules, applications, software packages, routines, subroutines (subroutines), objects, executables, threads of execution, procedures, functions, and the like.

Further, software, commands, information, and the like may be transmitted and received via a transmission medium. For example, where software is transmitted from a web page, server, or other remote source using at least one of wired technology (coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL), etc.) and wireless technology (infrared, microwave, etc.), at least one of these is included within the definition of transmission medium.

Information, signals, and the like described in this disclosure may also be represented using any of a variety of different technologies. For example, data, commands, instructions (commands), information, signals, bits, symbols (symbols), chips (chips), etc., that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or photons, or any combination thereof.

Further, terms described in the present disclosure and terms necessary for understanding the present disclosure may be replaced with terms having the same or similar meanings. For example, at least one of the channel and the symbol may be a signal (signaling). Further, the signal may also be a message. In addition, a Component Carrier (CC) may be referred to as a Carrier frequency, a cell, a frequency Carrier, and the like.

The terms "system" and "network" as used in this disclosure may be used interchangeably.

Further, information, parameters, and the like described in the present disclosure may be expressed using absolute values, may be expressed using relative values to predetermined values, and may be expressed using other corresponding information. For example, the radio resource may also be indicated by an index.

The names used for the above parameters are in no way limiting. Further, the numerical expressions and the like using these parameters may be different from those explicitly disclosed in the present disclosure. Various channels (e.g., PUCCH, PDCCH, etc.) and information elements may be identified by appropriate names, and thus the various names assigned to these various channels and information elements are not limiting in any respect.

In the present disclosure, terms such as "Base Station (BS)", "wireless Base Station", "fixed Station", "NodeB", "enodeb (enb)", "gnnodeb (gnb)", "access point", "transmission point", "reception point", "cell", "sector", "cell group", "carrier", "component carrier" and the like may be used interchangeably. A base station may also be referred to as a macrocell, a smallcell, a femtocell, a picocell, or the like.

A base station can accommodate one or more (e.g., 3) cells (also referred to as sectors). When 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, and each smaller area can also be provided with a communication service by a base station subsystem (e.g., an indoor small Radio Head (RRH)).

The term "cell" or "sector" refers to a part or the whole of the coverage area of at least one of a base station and a base station subsystem that performs communication service within the coverage area.

In the present disclosure, terms such as "Mobile Station (MS)", "User terminal (User terminal)", "User Equipment (UE)", "terminal" and the like may be used interchangeably.

For a mobile station, those skilled in the art will sometimes also refer to the following terms: a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless communication device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent (user agent), a mobile client, a client, or some other suitable terminology.

At least one of the base station and the mobile station may also be referred to as a transmitting apparatus, a receiving apparatus, a communication apparatus, or the like. At least one of the base station and the mobile station may be a device mounted on a mobile body, the mobile body itself, or the like. The moving body may be a vehicle (e.g., an automobile, an airplane, etc.), may be a moving body that moves in an unmanned manner (e.g., an unmanned aerial vehicle, an autonomous automobile, etc.), or may be a robot (manned or unmanned). At least one of the base station and the mobile station includes 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 IoT (Internet of Things) device such as a sensor.

In addition, the base station in the present disclosure may also be replaced with a mobile station (user terminal, the same applies hereinafter). For example, the embodiments and embodiments of the present disclosure may be applied to a configuration in which communication between a base station and a mobile station is replaced with communication between a plurality of mobile stations (for example, a configuration may be referred to as D2D (Device-to-Device) or V2X (Vehicle-to-all system), and in this case, the mobile station may have a function of the base station.

Likewise, the mobile station in the present disclosure may be replaced with a base station. In this case, the base station may have a function of the mobile station.

A radio frame may consist of one or more frames in the time domain. In the time domain, one or more individual frames may be referred to as subframes.

A subframe may be composed of one or more slots in the time domain. The subframe may be a fixed time length (e.g., 1ms) independent of a parameter set (numerology).

The parameter set may be a communication parameter applied to at least one of transmission and reception of a certain signal or channel. The parameter set may represent, for example, at least one of SubCarrier Spacing (SCS), bandwidth, symbol length, cyclic prefix length, Transmission Time Interval (TTI), number of symbols per TTI, radio frame structure, specific filtering processing performed by the transceiver in the frequency domain, specific windowing processing performed by the transceiver in the Time domain, and the like.

A slot may be composed of one or more symbols (OFDM (Orthogonal Frequency Division Multiplexing) symbols, SC-FDMA (Single Carrier Frequency Division Multiple Access) symbols, etc.) in the time domain. The time slot may be a time unit based on a parameter set.

A timeslot may contain multiple mini-slots. Each mini-slot may be composed of one or more symbols in the time domain. In addition, a mini-slot may also be referred to as a sub-slot. A mini-slot may be composed of a smaller number of symbols than a slot. The PDSCH (or PUSCH) transmitted in a unit of time greater than the mini slot may be referred to as PDSCH (or PUSCH) mapping type (type) a. The PDSCH (or PUSCH) transmitted using the mini-slot may be referred to as PDSCH (or PUSCH) mapping type (type) B.

The radio frame, subframe, slot, mini-slot, and symbol all represent a unit of time when a signal is transmitted. The radio frame, subframe, slot, mini-slot, and symbol may each be referred to by corresponding other terms.

For example, 1 subframe may be referred to as a Transmission Time Interval (TTI), a plurality of consecutive subframes may be referred to as TTIs, and 1 slot or 1 mini-slot may be referred to as a TTI. That is, at least one of the subframe and TTI may be a subframe (1ms) in the conventional LTE, may be a period shorter than 1ms (for example, 1-13 symbols), or may be a period longer than 1 ms. Note that the unit indicating TTI may be a slot, a mini-slot, or the like, instead of a subframe.

Here, the TTI refers to, for example, the minimum time unit of scheduling in wireless communication. For example, in the LTE system, the base station performs scheduling for allocating radio resources (frequency bandwidths, transmission powers, and the like that can be used by each user terminal) to each user terminal in units of TTIs. In addition, the definition of TTI is not limited thereto.

The TTI may be a transmission time unit of a channel-coded data packet (transport block), code block, code word, or the like, or may be a processing unit of scheduling, link adaptation, or the like. When a TTI is given, the time interval (for example, the number of symbols) to which the transport block, code word, and the like are actually mapped may be shorter than the TTI.

In addition, in a case where a 1-slot or a 1-mini-slot is referred to as a TTI, one or more TTIs (i.e., one or more slots or one or more mini-slots) may constitute a minimum time unit for scheduling. Further, the number of slots (mini-slots) constituting the minimum time unit of the schedule can be controlled.

TTIs having a time length of 1ms are also referred to as normal TTIs (TTIs in LTE rel.8-12), normal TTIs (normal TTIs), long TTIs (long TTIs), normal subframes (normal subframes), long (long) subframes, slots, etc. A TTI shorter than a normal TTI may be referred to as a shortened TTI, a short TTI (short TTI), a partial TTI, a shortened subframe, a short (short) subframe, a mini-slot, a sub-slot, a slot, etc.

In addition, for a long TTI (long TTI) (e.g., normal TTI, subframe, etc.), a TTI having a time length exceeding 1ms may be substituted, and for a short TTI (short TTI) (e.g., shortened TTI, etc.), a TTI having a TTI length smaller than that of the long TTI (long TTI) and having a TTI length of 1ms or more may be substituted.

A Resource Block (RB) is a resource allocation unit of time and frequency domains, and may include one or more consecutive subcarriers (subcarriers) in the frequency domain. The number of subcarriers included in the RB may be the same regardless of the parameter set, and may be 12, for example. The number of subcarriers included in the RB may also be decided according to the parameter set.

Further, the time domain of the RB may contain one or more symbols, and may be 1 slot, 1 mini-slot, 1 subframe, or 1TTI in length. The 1TTI, 1 subframe, etc. may be respectively composed of one or more resource blocks.

In addition, one or more RBs may be referred to as Physical Resource Blocks (PRBs), Sub-Carrier groups (SCGs), Resource Element Groups (REGs), PRB pairs, RB peers, and so on.

In addition, a Resource block may be composed of one or more Resource Elements (REs). For example, 1RE may be a 1 subcarrier and 1 symbol radio resource region.

The Bandwidth Part (BWP: Bandwidth Part) (also referred to as partial Bandwidth, etc.) represents a subset of consecutive common rbs (common resource blocks) for a certain parameter set in a certain carrier. Here, the common RB may be determined by an index of an RB with reference to a common reference point of the carrier. PRBs are defined in a certain BWP and are numbered within that BWP.

The BWP may include UL BWP (UL BWP) and DL BWP (DL BWP). One or more BWPs may be set for a UE within 1 carrier.

At least one of the set BWPs may be active (active), and a case where the UE transmits and receives a predetermined signal/channel outside the active BWP may not be assumed. In addition, "cell", "carrier", and the like in the present disclosure may be replaced with "BWP".

The above-described structures of radio frames, subframes, slots, mini slots, symbols, and the like are merely examples. For example, the number of subframes included in the 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 in an RB, the number of symbols in a TTI, the symbol length, the Cyclic Prefix (CP) length, and other configurations may be variously changed.

The terms "connected" and "coupled" or any variation thereof are intended to mean that two or more elements are directly or indirectly connected or coupled to each other, and may include one or more intermediate elements between two elements that are "connected" or "coupled" to each other. The combination or connection between the elements may be physical, logical, or a combination of these. For example, "connect" may be replaced with "Access". As used in this disclosure, two elements may be considered to be "connected" or "coupled" to each other by using at least one of one or more wires, cables, and printed electrical connections, and by using electromagnetic energy or the like having wavelengths in the radio frequency domain, the microwave domain, and the optical (both visible and invisible) domain, as some non-limiting and non-inclusive examples.

The reference signal may be referred to as rs (reference signal) for short, or may be referred to as Pilot (Pilot) according to the applied standard.

As used in this disclosure, a statement "according to" is not intended to mean "solely according to" unless explicitly stated otherwise. In other words, the expression "according to" means both "according to" and "at least according to".

Any reference to an element using the designations "first", "second", etc. used in this disclosure is not intended to limit the number or order of such elements. These designations are used in this disclosure as a convenient way to distinguish between two or more elements. Thus, references to first and second elements do not imply that only two elements are possible here or that in any case the first element must precede the second element.

Where the disclosure uses the terms "including", "comprising" and variations thereof, these terms are meant to be inclusive in the same way as the term "comprising". Also, the term "or" used in the present disclosure means not exclusive or.

In the present disclosure, where articles are added by translation, for example, as in the english language a, an, and the, the present disclosure also includes the case where nouns following the articles are plural.

Terms such as "determining" and "determining" used in the present disclosure may include various operations. The terms "determination" and "decision" may include, for example, determining that an item has been determined (judging), calculated (calculating), processed (processing), derived (deriving), investigated (investigating), searched (looking up) (for example, searching in a table, a database, or another data structure), or confirmed (ascertaining) as an item having been determined or decided. The "determination" and "decision" may include a matter in which reception (e.g., reception information), transmission (e.g., transmission information), input (input), output (output), and access (e.g., access to data in the memory) are performed, and the like. The "judgment" and "decision" may include matters regarding the solution (resolving), selection (selecting), selection (breathing), establishment (evaluating), comparison (comparing), and the like as the "judgment" and "decision". That is, "judgment" and "determination" may include "judgment" and "determination" of any item of action. The "determination (decision)" may be replaced by "assumption", "expectation", "consideration", and the like.

In the present disclosure, the phrase "a and B are different" may also mean "a and B are different from each other". The term "A and B are different from C" may be used. The terms "separate", "coupled", and the like may also be construed as "different" in a similar manner.

While the present disclosure has been described in detail, it should be apparent to those skilled in the art that the present disclosure is not limited to the embodiments described in the present disclosure. The present disclosure can be implemented as modifications and alterations without departing from the spirit and scope of the present disclosure as defined by the claims. Accordingly, the disclosure is intended to be illustrative, and not limiting.

Industrial applicability

According to the above terminal, it is possible to authenticate a terminal that has migrated to a target radio base station without performing a re-establishment procedure due to a handover failure on the network side, and therefore, the terminal is useful.

Description of the reference symbols

10 radio communication system

100A、100B、100C gNB

110 sending part

120 receiving part

130 holding part

140 control part

200 terminal

210 sending part

220 receiving part

230 holding part

240 control part

1001 processor

1002 internal memory

1003 memory

1004 communication device

1005 input device

1006 output device

1007 bus

Claims (2)

1. A terminal, wherein the terminal has:

a control unit that performs a procedure of moving to a target radio base station without performing a reestablishment procedure in association with a handover failure; and

a transmission unit that transmits a specific message to the target radio base station during transition to the target radio base station,

the control unit maintains identification information shared between the terminal and the target radio base station when the handover fails, and includes the identification information in the specific message.

2. The terminal of claim 1, wherein,

the control unit maintains a short MAC-ID, which is a short medium access control identifier shared between the terminal and the target radio base station, and includes the short MAC-ID in the specific message when the handover fails.

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