Source radio access network node, user equipment and methods thereof

Abstract

The invention relates to a source radio access network node, user equipment and methods thereof. During a movement procedure for moving the radio terminal from the source cell to one of the candidate target cells, the target RAN node sends to the radio terminal via the source RAN node a first configuration common to the candidate target cells and a plurality of second configurations each associated with a respective one of the candidate target cells. The first configuration comprises at least one configuration parameter for enabling the radio terminal to access one of the candidate target cells or to communicate in the candidate target cell. Each second configuration comprises at least one configuration parameter for enabling the radio terminal to access or communicate in the respective candidate target cell. This helps, for example, reduce the signaling overhead of RAN inter-node interfaces (and air interfaces) during various mobility procedures including handover.

Description

[0001] This application is a divisional application of a Chinese patent application with an application date of October 31, 2019, an application number of 201980093316.0, and an invention title of "Radio Access Network Node and Radio Terminal and Their Methods". Technical Field

[0002] The present invention relates to a radio communication system, and in particular, to handover. Background Art

[0003] Patent Document 1 and Patent Document 2 disclose that: a handover request message sent from a source radio access network (RAN) node (e.g., a base station) to a target RAN node during a handover process includes a list of a plurality of candidate target cells. Patent Document 2 also discloses that: when a plurality of candidate target cells can admit a handover, the target RAN node returns a handover confirmation message to the source RAN node, and the handover confirmation message includes handover information related to the plurality of candidate target cells.

[0004] Non-Patent Document 1 and Non-Patent Document 2 disclose conditional handover (CHO) being discussed in 3GPP. In some implementations of CHO, a source RAN node (e.g., an eNodeB (eNB)) sends a handover command including handover execution conditions (e.g., thresholds) to a radio terminal (e.g., a user equipment (UE)). The radio terminal maintains a connection with the source RAN node even after receiving the handover command, and initiates access to the target RAN node as soon as the conditions configured by the handover command are satisfied. That is, conditional handover (CHO) is different from an existing handover in that: the radio terminal initiates access to a target cell in response to satisfying the conditions configured by the handover command rather than in response to receiving the handover command.

[0005] CHO can improve the reliability of delivering a handover command to a UE by early event triggering (i.e., reducing the threshold for triggering a measurement report of the radio terminal). This allows CHO to reduce the handover failure rate.

[0006] In CHO, configurations of a plurality of candidate target cells can be sent to a radio terminal. The candidate target cells can be referred to as potential target cells. For example, the radio terminal receives a handover command including configurations of a plurality of candidate target cells and a CHO execution threshold from a source RAN node (e.g., an eNB). The radio terminal measures the configured candidate target cells, and initiates access to a candidate cell when the measurement in any candidate target cell satisfies the CHO execution threshold.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2010-004295

[0010] Patent Document 2: International Publication WO2011 / 018890

[0011] Non-Patent Document

[0012] Non-Patent Document 1: Intel Corporation, “Discussion of conditional handover”, R2-1816691, 3GPP TSG RAN WG2 Meeting#104, Spokane, WA, USA, November 12-16, 2018

[0013] Non-Patent Document 2: MediaTek Inc., “Conditional Handover Procedures”, R2-1816959, 3GPP TSG RAN WG2 Meeting#104, Spokane, WA, USA, November 12-16, 2018 SUMMARY OF THE INVENTION

[0014] Problems to be Solved by the Invention

[0015] If a target RAN node sends multiple configurations for each candidate target cell to a source RAN node, or sends them to a radio terminal via the source RAN node, this causes an increase in the signaling overhead of the interface between RAN nodes (e.g., the X2 interface) or the signaling overhead of both the interface between RAN nodes and the air interface (between the source base station and the radio terminal).

[0016] One of the objects to be achieved by the embodiments disclosed herein is to provide a device, method, and program that help reduce the signaling overhead of the interface between RAN nodes (and the air interface) during various mobile procedures including handover. It should be noted that this object is only one of the objects to be achieved by the embodiments disclosed herein. Through the following description and drawings, other objects or problems and novel features will become apparent.

[0017] Solutions to the Problems

[0018] In a first aspect, a target radio access network node includes: at least one memory; and at least one processor coupled to the at least one memory. The at least one processor is configured to, during a handover process for causing a radio terminal to move from a source cell to one of a plurality of candidate target cells, send, via a source radio access network node managing the source cell, to the radio terminal a first configuration common to the plurality of candidate target cells and a plurality of second configurations respectively associated with corresponding candidate target cells among the plurality of candidate target cells. The first configuration includes at least one configuration parameter for enabling the radio terminal to access or communicate in one of the plurality of candidate target cells. Each second configuration includes at least one configuration parameter for enabling the radio terminal to access or communicate in the corresponding candidate target cell.

[0019] In a second aspect, a radio terminal includes: at least one memory; and at least one processor coupled to the at least one memory. The at least one processor is configured to, during a handover process for causing a radio terminal to move from a source cell to one of a plurality of candidate target cells, receive, via a source radio access network node managing the source cell, from a target radio access network node managing the plurality of candidate target cells, the first configuration common to the plurality of candidate target cells and the plurality of second configurations respectively associated with corresponding candidate target cells among the plurality of candidate target cells. The first configuration includes at least one configuration parameter for enabling the radio terminal to access or communicate in one of the plurality of candidate target cells. Each second configuration includes at least one configuration parameter for enabling the radio terminal to access or communicate in the corresponding candidate target cell.

[0020] In a third aspect, a method for a target radio access network node includes: during a handover process for causing a radio terminal to move from a source cell to one of a plurality of candidate target cells, sending, via a source radio access network node managing the source cell, to the radio terminal the first configuration common to the plurality of candidate target cells and the plurality of second configurations respectively associated with corresponding candidate target cells among the plurality of candidate target cells. The first configuration includes at least one configuration parameter for enabling the radio terminal to access or communicate in one of the plurality of candidate target cells. Each second configuration includes at least one configuration parameter for enabling the radio terminal to access or communicate in the corresponding candidate target cell.

[0021] In a fourth aspect, a method for a radio terminal includes: during a handover process for moving the radio terminal from a source cell to one of a plurality of candidate target cells, receiving, via a source radio access network node managing the source cell, from a target radio access network node managing the plurality of candidate target cells, a first configuration common to the plurality of candidate target cells and a plurality of second configurations each associated with a respective candidate target cell among the plurality of candidate target cells. The first configuration includes at least one configuration parameter for enabling the radio terminal to access or communicate in one of the plurality of candidate target cells. Each second configuration includes at least one configuration parameter for enabling the radio terminal to access or communicate in the respective candidate target cell.

[0022] In a fifth aspect, a program includes instructions (software code) which, when loaded into a computer, cause the computer to perform the method according to the third or fourth aspect described above.

[0023] Effects of the invention

[0024] According to the above aspects, a device, a method, and a program can be provided that help reduce the signaling overhead of the RAN node - to - node interface (and air interface) during various handover - including mobility processes. Description of the drawings

[0025] Figure 1 is a diagram showing a configuration example of a radio communication network according to an embodiment;

[0026] Figure 2 is a timing diagram showing an example of signaling according to a first embodiment;

[0027] Figure 3 is a diagram showing a specific example of the format of a handover request (HANDOVER REQUEST) message according to a second embodiment;

[0028] Figure 4 is a diagram showing a specific example of the format of a handover request acknowledge (HANDOVER REQUEST ACKNOWLEDGE) message according to a second embodiment;

[0029] Figure 5 is a timing diagram showing an example of signaling according to a third embodiment;

[0030] Figure 6 is a timing diagram showing an example of signaling according to a fourth embodiment;

[0031] Figure 7 is a timing diagram showing an example of signaling according to a fifth embodiment;

[0032] Figure 8 is a block diagram showing a configuration example of a radio access network node according to an embodiment; and

[0033] Figure 9 is a block diagram showing a configuration example of a radio terminal according to an embodiment. DETAILED DESCRIPTION

[0034] Hereinafter, specific embodiments will be described in detail with reference to the accompanying drawings. Throughout the drawings, the same or corresponding elements are denoted by the same reference numerals, and repeated descriptions are omitted as needed for clarity.

[0035] Each of the embodiments described below can be used alone, or two or more of these embodiments can be appropriately combined with each other. These embodiments include novel features that are different from each other. Therefore, these embodiments contribute to achieving different purposes or solving different problems from each other, and also contribute to obtaining different advantages from each other.

[0036] The following description of the embodiments mainly focuses on 3GPP Long Term Evolution (LTE) systems and 5G systems. However, these embodiments can be applied to other radio communication systems that support handover of radio terminals. Note that unless otherwise specified, the term "LTE" as used in this specification includes LTE and enhanced / evolved LTE-Advanced for providing interworking with 5G systems. A 5G system includes a network deployment where an LTE eNodeB (eNB) is connected to a 5G core network (5GC). This eNB may be referred to as a next-generation (ng)-eNB. The ng-eNB may also be referred to as an eNB / 5GC, which means an eNB connected to the 5GC.

[0037] First Embodiment

[0038] Figure 1 shows a configuration example of a radio communication network according to an embodiment including this embodiment. In Figure 1 the example shown, the radio communication network includes RAN node 1, RAN node 2, and radio terminal 3.

[0039] RAN node 1 can be, for example, an LTE eNodeB (eNB) or an NR gNodeB (gNB). RAN node 1 may include a central unit (e.g., eNB-CU or gNB-CU) and one or more distributed units (e.g., eNB-DU or gNB-DU) in a cloud RAN (C-RAN) deployment. C-RAN is also referred to as CU / DU separation. Similarly, RAN node 2 can be an eNB or a gNB and may include a central unit (CU) and one or more distributed units (DU). Each RAN node can be an evolved universal mobile telecommunications system (UMTS) terrestrial radio access network (EUTRAN) node or a next-generation radio access network (NG-RAN) node. An EUTRAN node can be an eNB or an en-gNB. NG-RAN can be a gNB or an ng-eNB. The radio access technology (RAT) of RAN node 1 can be different from the RAT of RAN node 2.

[0040] RAN node 1 serves at least one cell 11. RAN node 2 serves multiple cells (e.g., four cells 21 to 24). In Figure 1 the example, the cell 11 served by RAN node 1 is the current serving cell of radio terminal 3, and the radio terminal (i.e., user equipment (UE)) 3 switches from cell 11 to any one of the cells served by RAN node 2. Therefore, hereinafter, RAN node 1 is referred to as the source RAN node, and RAN node 2 is referred to as the target RAN node. Cell 11 is referred to as the source cell. The source RAN node 1 selects one or more of the cells 21 to 24 of the target RAN node 2 as candidates for the target cell of the handover and notifies the target RAN node 2 of the one or more cells. The cells selected by the source RAN node 1 are referred to as candidate target cells. Hereinafter, as an example, it is assumed that cells 21 to 23 are candidate target cells.

[0041] The handover of radio terminal 3 can be a normal handover or a conditional handover. In a normal handover, as soon as radio terminal 3 receives an RRC message including a handover indication from source RAN node 1, it initiates access to target RAN node 2. In a normal handover, source RAN node 1 can select a preferred target cell for radio terminal 3 from among the target cells accepted by target RAN node 2 in candidate target cells 21 to 23, and notify radio terminal 3 of this target cell. For example, a normal handover can be a handover triggered by a mobilityControlInfo IE or a reconfigurationWithSync IE included in an RRC (connection) reconfiguration message. In this case, the mobilityControlInfo IE or the reconfigurationWithSync IE is a handover instruction for triggering the handover of radio terminal 3.

[0042] On the other hand, in a conditional handover, source RAN node 1 sends a handover instruction including handover execution conditions (e.g., thresholds) to radio terminal 3 via an RRC message. Radio terminal 3 maintains its connection with source RAN node 1 even after receiving the RRC message, and initiates access to target RAN node 2 as soon as the configured conditions are met. In a conditional handover, radio terminal 3 can receive a handover instruction from the source RAN node (e.g., eNB) including the configuration of multiple candidate target cells 21 to 23 and CHO execution conditions (e.g., thresholds). The handover instruction including handover execution conditions (e.g., thresholds) can be referred to as a conditionalMobilityControlInfo IE. The CHO execution conditions (e.g., thresholds) can be common to multiple candidate target cells 21 to 23, or can be different for each candidate target cell. Radio terminal 3 can perform (or initiate) measurements of the indicated candidate target cells 21 to 23, and initiate access (e.g., random access) to the candidate cell when the measurement of any candidate target cell meets the CHO execution threshold. If the conditions for conditional handover (e.g., CHO execution threshold) are only related to the measurement results of candidate target cells, the measurement of each candidate target cell can be only the measurement in the relevant candidate target cell. On the other hand, if the conditions for conditional handover are related to the measurement results of both candidate target cells and the source cell (i.e., the current primary serving cell (PCell)), the measurement of candidate target cells can include both the measurement in the candidate target cell and the measurement in the PCell.

[0043] The handover of radio terminal 3 in this embodiment can also be referred to as the movement of radio terminal 3. The handover or movement of radio terminal 3 can be a master node (MN) handover in dual connectivity (DC) or a secondary node (SN) change in DC.

[0044] Additionally or alternatively, the handover or movement of radio terminal 3 may be a change of the primary cell (PCell) of the master cell group (MCG) in DC. Additionally or alternatively, the handover or movement of radio terminal 3 may be a change of the primary cell of the secondary cell group (SCG) in DC (i.e., a change of the primary SCG cell (PSCell)). In these cases, the source RAN node 1 may be the source DU, and the target RAN node 2 may be the target DU. Alternatively, the source RAN node 1 may be a combination of the (source) CU and the source DU, and the target RAN node 2 may be a combination of the (target) CU and the target DU.

[0045] DC may be multi-radio dual connectivity (MR-DC). MR-DC includes evolved universal mobile telecommunications system (UMTS) terrestrial radio access (E-UTRA)-NR dual connectivity (EN-DC), NR-E-UTRA DC (NE-DC), NG-RAN EN-DC (NGEN-DC), and NR-NR DC (NR DC).

[0046] Figure 2 An example of signaling in a handover process for handing over radio terminal 3 from source cell 11 to one of a plurality of candidate target cells 21 to 23 is shown. In step 201, the source RAN node 1 determines that a handover is required (normal handover or conditional handover), and sends a handover request message to the target RAN node 2. If a plurality of cells (e.g., cells 21 to 23) served by the target RAN node 2 are suitable for handover, the handover request message may indicate the plurality of candidate target cells.

[0047] In steps 202 and 203, the target RAN node 2 sends a first configuration common to the plurality of candidate target cells 21 to 23 and a plurality of second configurations respectively associated with the corresponding candidate target cells in the plurality of candidate target cells 21 to 23 to the radio terminal 3 via the source RAN node 1. In other words, in step 203, the radio terminal 3 receives the first configuration common to the candidate target cells 21 to 23 and the plurality of second configurations respectively associated with the corresponding target cells in the target cells 21 to 23. Then, the radio terminal 3 uses the received common first configuration and the plurality of second configurations to perform the handover. In the case of conditional handover, the radio terminal 3 determines whether the conditions (e.g., thresholds) are met for each of the candidate target cells 21 to 23, and uses the common first configuration and the second configuration related to any cell that has met the conditions (e.g., thresholds) to perform the (conditional) handover to that cell.

[0048] As Figure 2As shown, by way of example and not limitation, the target RAN node 2 may include the first configuration and a plurality of second configurations in the handover confirmation message (step 202). More specifically, in some implementations, the first configuration and the plurality of second configurations may be stored in a Target To Source Transparent Container included in the handover confirmation message. The source RAN node 1 may put the information included in the target to source transparent container (e.g., RRC handover command) into an RRC message (e.g., RRC reconfiguration) and send the RRC message to the radio terminal 3 (step 203). For example, such an operation may be performed in the case of conditional handover.

[0049] Alternatively, in some implementations, the source RAN node 1 may receive a handover confirmation message carrying the first configuration and a plurality of second configurations from the target RAN node 2, and select a preferred target cell for the radio terminal 3 from among the plurality of candidate target cells 21-23. Then, the source RAN node 1 may derive the configuration of the selected target cell from the first configuration and the plurality of second configurations, or create (or prepare) the configuration of the selected target cell based on the first configuration and the plurality of second configurations, and send the configuration of the selected target cell included in the handover command to the radio terminal 3 via an RRC message (e.g., RRC reconfiguration). In this case, the first configuration and the plurality of second configurations are sent through the inter-RAN node interface between the RAN nodes 1 and 2, but do not need to be sent through the air interface between the RAN node 1 and the radio terminal 3.

[0050] The first configuration (i.e., the common configuration) includes at least one configuration parameter for enabling the radio terminal 3 to access or communicate in one of the plurality of candidate target cells. Each second configuration (i.e., the cell-specific configuration) includes at least one configuration parameter for enabling the radio terminal 3 to access or communicate in the corresponding candidate target cell. The cell-specific configuration may be referred to as a dedicated configuration.

[0051] The first configuration and the plurality of second configurations may not include the handover execution conditions (e.g., thresholds (events) and corresponding trigger times (TTTs)) for conditional handover, or the conditions (e.g., offsets) for the radio terminal to exit conditional handover, or the value of the validity timer. The value of the validity timer may indicate the length of time for which the resources of the candidate target cell are valid. Alternatively, the value of the validity timer may indicate the period (or time) for accepting access to the candidate target cell, or the period (or time) for which the configuration (e.g., the first configuration, the second configuration) for conditional handover is valid.

[0052] At least one configuration parameter included in the first configuration may be related to the configuration of a radio bearer. Specifically, the first configuration may include one or more radio bearer configurations (e.g., RadioBearerConfig) common to a plurality of candidate target cells. In this case, the target RAN node 2 may generate a radio bearer configuration for one of the plurality of candidate target cells that has been approved for handover admission (or accepted the handover), and omit the radio bearer configurations of the remaining candidate target cells. Alternatively, the target RAN node 2 may generate a radio bearer configuration common to the plurality of candidate target cells that have been approved for handover admission (or accepted the handover), and may not generate dedicated radio bearer configurations for each candidate target cell. Additionally or alternatively, the target RAN node 2 may additionally generate radio bearer configurations only for candidate target cells that require dedicated radio bearer configurations. That is, a common radio bearer configuration and radio bearer configurations specific to candidate target cells that require configurations different from the common radio bearer configuration may be generated.

[0053] These one or more radio bearer configurations may include configuration information or parameters for the Packet Data Convergence Protocol (PDCP) for the radio bearer, or may include configuration information or parameters for the Service Data Adaptation Protocol (SDAP). The one or more radio bearer configurations may include a list of signaling radio bearers (SRBs) to be added or modified (e.g., srb-ToAddModList). The one or more radio bearer configurations may include a list of data radio bearers (DRBs) to be added or modified (e.g., drb-ToAddModList). The one or more radio bearer configurations may include a list of DRBs to be released (e.g., drb-ToReleaseList). The one or more radio bearer configurations may include a security configuration indicating the security algorithms and keys to be used for signaling and data radio bearers.

[0054] Additionally or alternatively, at least one configuration parameter included in the first configuration may include system information (SI). For example, the same SI area identifier (e.g., systemInformationAreaID) may be assigned to multiple candidate target cells 21 to 23. In this case, the target RAN node 2 may configure the system information for one of the candidate target cells that has been approved to admit the handover (or accept the handover), and may omit the system information for the remaining candidate target cells having the same SI area identifier as that one cell. Alternatively, the target RAN node 2 configures the system information common to the candidate target cells that have been approved to admit the handover (or accept the handover), and there is no need to configure dedicated system information for each candidate target cell. Additionally or alternatively, the target RAN node 2 may additionally configure the system information only for the candidate target cells that require dedicated system information (i.e., have different SI area identifiers). That is, the common system information and the system information specific to the candidate target cells that require a configuration different from the common system information may be configured. The system information may be System Information Block type 1 (SIB1), a combination of SIB1 and other SI, or SI other than SIB1.

[0055] Additionally or alternatively, at least one configuration parameter included in the first configuration may include security-related information (e.g., masterKeyUpdate). For example, the same security-related information may be assigned to multiple candidate target cells 21 to 23. In this case, the target RAN node 2 may configure the security-related information for one of the candidate target cells that has been approved to admit the handover (or accept the handover), and may omit the security-related information for the remaining candidate target cells applying the same security policy as that one cell. Alternatively, the target RAN node 2 may configure the security-related information common to the candidate target cells that have been approved to admit the handover (or accept the handover), and may not configure dedicated security-related information for each candidate target cell. Additionally or alternatively, the target RAN node 2 may additionally configure the security-related information only for the candidate target cells that require dedicated security-related information (e.g., require different security policies). That is, the common security-related information and the security-related information specific to the candidate target cells that is different from the common security-related information may be configured. The security-related information may include information related to the security key to be used in the target cell (e.g., nextHopChainingCount), or may include NAS layer information.

[0056] Additionally or alternatively, at least one configuration parameter included in the first configuration may include other configuration information (e.g., OtherConfig). For example, regarding this other configuration, the same policy (e.g., setting, configuration release) may be applied to multiple candidate target cells 21-23. In this case, the target RAN node 2 may configure the other configuration information for one of the multiple candidate target cells that have been approved for admission handover (or accepted the handover), and omit the other configuration information for the remaining candidate target cells to which the same policy as that for the one cell is applied. Alternatively, the target RAN node 2 may configure the other configuration information common to the multiple candidate target cells that have been approved for admission handover (or accepted the handover), and may not configure dedicated information for each candidate target cell. Additionally or alternatively, the target RAN node 2 may additionally configure the other configuration information only for the candidate target cells that require dedicated other configuration information (e.g., having a different policy related to the other configuration). That is, the common other configuration information and the other configuration information specific to the candidate target cells and different from the common other configuration information may be configured. The other configuration information (e.g., OtherConfig) may include, for example, information related to data transmission delay (e.g., delayBudgetReportingConfig), information related to in-device coexistence (IDC) (e.g., idc-Config), information related to the transmission power preference of the radio terminal (e.g., powerPrefIndicationConfig), information related to detailed location information using GNSS, etc. (e.g., obtainLocationConfig), information related to the bandwidth preference of the radio terminal (e.g., bw-PreferenceIndicationTimer), information related to overheating of the radio terminal (e.g., overheatingAssistanceConfig), and information related to multimedia broadcast and multicast services (MBMS) (e.g., MBMS interest indication).

[0057] On the other hand, at least one configuration parameter included in each second configuration may be related to the configuration of at least one of a cell group, a media access control (MAC) entity, a logical channel set, and random access.

[0058] Configuration parameters related to a cell group (e.g., CellGroupConfig) may include configuration parameters for a master cell group (MCG) or a secondary cell group (SCG) or both. A cell group includes a MAC entity, a set of logical channels, and multiple associated radio link control (RLC) entities. Additionally, a cell group includes a primary cell (i.e., a special cell (SpCell)) and one or more secondary cells (SCells). The SpCell is the primary cell of the MCG or the primary SCG cell (PSCell) of the SCG. The configuration or parameters of the SpCell included in CellGroupConfig are referred to as SpCellConfig.

[0059] Configuration parameters related to the MAC entity (e.g., mac-CellGroupConfig) may include MAC parameters applicable to the entire cell group.

[0060] Configuration parameters related to a set of logical channels (e.g., rlc-BearerToAddModList) may include the configuration of MAC logical channels and the corresponding RLC entities.

[0061] Configuration parameters related to random access may indicate the resources for dedicated random access preambles.

[0062] The handover execution condition, the condition used for the radio terminal 3 to exit the condition handover, and the value of the validity timer can be configured by the source RAN node 1 or by the target RAN node 2. For example, the source RAN node 1 can configure them (i.e., the handover execution condition, the condition used for the radio terminal 3 to exit the condition handover, and the value of the validity timer) and send them to the radio terminal 3. In this case, for example, the source RAN node 1 can send a handover request message containing these conditions and values configured by the source RAN node 1 to the target RAN node 2, and the target RAN node 2 can include these conditions and values in the handover command. Alternatively, in addition to the RRC message or IE received from the target RAN node and in a manner separate from the RRC message or IE, the source RAN node 1 can also include these conditions and values configured by the source RAN node 1 in the RRC message containing the handover instruction to send these conditions and values to the radio terminal 3. Alternatively, the target RAN node 2 can configure them (i.e., the handover execution condition, the condition used for the radio terminal 3 to exit the condition handover, and the value of the validity timer) and send them to the source RAN node 1 using, for example, the handover command, and the source RAN node 1 can send them to the radio terminal 3. For example, the source RAN node 1 can forward the handover command received from the target RAN node 2 as it is (e.g., the conditionalMobilityControlInfo IE). In addition, the handover execution condition, the condition used for the radio terminal 3 to exit the condition handover, and the value of the validity timer can each be configured by any of the above methods and sent to the radio terminal 3. For example, the handover execution condition, the condition used for the radio terminal 3 to exit the condition handover, and the value of the validity timer can be included in the handover command (e.g., the conditionalMobilityControlInfo IE).

[0063] The first configuration does not necessarily have to be common to all of the candidate target cells 21 to 23. For example, the target RAN node 2 may configure a first configuration common to cells 21 and 22, and also configure a first configuration (or similar information) applied to cell 23, and then send the two to the source RAN node 1. In this case, the target RAN node 2 may send the two as two first configurations or as a first configuration and additional information corresponding to the one first configuration to the source RAN node 1. More specifically, the target RAN node 2 may explicitly indicate to the source RAN node 1 that the two first configurations are the first configuration common to cells 21 and 22 and the first configuration applied to cell 23. Alternatively, the target RAN node 2 may send information indicating that the first configuration is to be applied to cells 21 and 22 (or not applied to cell 23), and configuration information (or configuration parameters) of cell 23 including additional information corresponding to the first configuration to be applied to cell 23 to the source RAN node 1.

[0064] As can be understood from the above description, in this embodiment, during the handover process for handing over the radio terminal 3 from the source cell 11 to one of the candidate target cells 21 to 23, the target RAN node 2 sends, via the source RAN node 1, a first configuration common to these candidate target cells and a plurality of second configurations respectively associated with the corresponding candidate target cells among these candidate target cells to the radio terminal 3. The first configuration common to the plurality of candidate target cells can reduce the data size of the configurations related to the plurality of candidate target cells. This can reduce the signaling overhead of the RAN node - to - node interface (and the air interface) during the handover process.

[0065] Second Embodiment

[0066] This embodiment provides an improvement to the handover - related message sent on the RAN node - to - node interface to accommodate conditional handover. The configuration example of the radio communication network according to this embodiment may be the same as the configuration example Figure 1 shown. Additionally, in this embodiment, a plurality of candidate target cells may be served by a plurality of RAN nodes 2.

[0067] In some implementations, a new handover request message (e.g., a CONDITIONAL HANDOVER REQUEST message) can be defined for conditional handover. The new handover request message can include a list of candidate target cells (e.g., a target cell list), and also include information elements among those included in the existing handover request message that are required for at least the target cell setup used for CHO (e.g., UE context information). If the source RAN node 1 detects that the radio terminal 3 has performed a conditional handover, the source RAN node 1 can send an additional message containing the remaining information elements included in the existing handover request message to one or more target RAN nodes 2. If the source RAN node 1 can identify the target cell to which the radio terminal 3 has moved, the source RAN node 1 can send the additional message only to the target RAN node serving the identified target cell. The source RAN node 1 can detect the handover execution by receiving a CHO indication (e.g., a measurement report or an indication of CHO triggering) from the radio terminal 3. The CHO indication from the radio terminal 3 can include information indicating the target cell to which the handover is directed (e.g., cell global ID, PCI, target cell index). Alternatively, the source RAN node 1 can autonomously determine the handover execution conditions used for CHO, thereby autonomously detecting the handover execution.

[0068] Alternatively, in some implementations, an existing handover request message can be enhanced (or improved) for conditional handover. For example, the format of the improved handover request message can be defined as shown, but is not limited thereto. In Figure 3 the example, the improved handover request message includes, in addition to the existing target cell ID information element (IE) (e.g., the target cell global ID IE), a candidate target cell list information element (IE). The target cell ID IE (e.g., the target cell global ID IE) can indicate one of the multiple candidate target cells. Specifically, the target cell ID IE (e.g., the target cell global ID IE) can indicate the cell with the highest priority (i.e., the cell most suitable for the radio terminal 3 to move to). On the other hand, the candidate target cell list IE can indicate the remainder of the multiple candidate target cells. Figure 3

[0069] The new handover request message used for conditional handover or the enhanced (or improved) handover request message used for conditional handover can include a new radio resource control (RRC) information element (IE). This IE can include handover execution conditions (e.g., thresholds and TTTs) associated with each candidate target cell. Additionally or alternatively, the message can include either or both of the conditions (e.g., offsets) for the radio terminal to exit conditional handover and the value of the validity timer.

[0070] In addition, in some implementations, a new handover request acknowledgement message may be defined for conditional handover (e.g., CONDITIONAL HANDOVER REQUEST ACKNOWLEDGE message). The new handover request acknowledgement message may include a list of candidate target cells that have approved (or accepted) the conditional handover (e.g., the list of admitted target cells), and also includes at least the information elements required for the target cell setup used by CHO among the information elements included in the existing handover request acknowledgement message (e.g., the transparent container from the target NG-RAN node to the source NG-RAN node).

[0071] The new handover request acknowledgement message may include a new RRC information element (IE). This IE may include handover execution conditions (e.g., thresholds and TTT) associated with each candidate target cell. Additionally or alternatively, this IE may include either or both of the conditions (e.g., offsets) used by the radio terminal to exit the conditional handover and the value of the validity timer.

[0072] Alternatively, in some implementations, the existing handover request acknowledgement message may be enhanced (or improved) for conditional handover. For example, the format of the improved handover request acknowledgement message may be defined as shown, but this format is not limited thereto. In the example of Figure 4 , the improved handover request acknowledgement message includes a list of candidate target cells that have approved (or accepted) the conditional handover (e.g., the list information element of admitted target cells). Figure 4 The message formats shown in

[0073] Figure 3 and Figure 4 are merely examples. For example, the candidate target cell list IE in Figure 3 may be referred to as an additional target cell list IE or other target cell list IE.

[0074] Third Embodiment

[0075] This embodiment provides an improvement to the handover-related messages sent on the RAN node interface to accommodate conditional handover. The configuration example of the radio communication network according to this embodiment may be the same as the configuration example shown in Figure 1 . However, in this embodiment, a C-RAN deployment is applied to the target RAN node 2 (e.g., gNB). The target RAN node 2 includes a CU 25 (e.g., gNB-CU) and one or more DUs 26 (e.g., gNB-DU).

[0076] In some implementations, the source RAN node 1 sends a handover instruction including handover execution conditions (e.g., thresholds) to the radio terminal 3 via an RRC message. The radio terminal 3 maintains a connection with the source RAN node 1 even after receiving the RRC message, and initiates access to the target RAN node 2 as soon as the configured conditions are met. In conditional handover, the radio terminal 3 may receive a handover instruction including the configuration of a plurality of candidate target cells 21-23 and a CHO execution threshold from the source RAN node (e.g., gNB). The radio terminal 3 may perform (or initiate) measurements on the indicated candidate target cells 21-23, and initiate access (e.g., random access) to the candidate cell if the measurement in any of the candidate target cells meets the CHO execution threshold. In other words, the radio terminal 3 initiates access to the DU 26 (e.g., gNB-DU) of the target RAN node 2 that manages the candidate cells, and establishes an RRC connection with the CU 25 (e.g., gNB-CU) of the target RAN node 2.

[0077] Figure 5 An example of signaling in the handover process for switching the radio terminal 3 from the source cell 11 to one of a plurality of candidate target cells 21-23 is shown. In step 501, the source RAN node 1 determines that a handover is required (i.e., normal handover or conditional handover), and sends a handover request message (handover request) to the CU 25 of the target RAN node 2. If a plurality of cells (e.g., cells 21-23) served by the target RAN node 2 (one or more DUs 26 thereof) are suitable for handover, the handover request message may indicate the plurality of candidate target cells.

[0078] In step 502, the CU 25 of the target RAN node 2 sends a request message (UE context setup request (UE CONTEXT SETUP REQUEST)) for establishing the context of the radio terminal 3 to the DU 26. The CU 25 may send the request message to each of the plurality of DUs 26 that serve the plurality of candidate target cells. The request message for establishing the context includes a part of the information (e.g., handover preparation information) contained in the handover request message received from the source RAN node 1. The request message for establishing the context may indicate the plurality of candidate target cells for conditional handover. The information on the plurality of candidate target cells may be included in an IE (e.g., CU-to-DU RRC information) containing RRC information. More specifically, the information on the plurality of candidate target cells may be included, for example, in the handover preparation information contained in the IE.

[0079] In step 503, the DU 26 of the target RAN node 2 sends a response message (UE CONTEXT SETUP RESPONSE) to the CU 25. The response message includes a plurality of second configurations each associated with a respective candidate target cell among the plurality of candidate target cells 21-23. The DU 26 of the target RAN node 2 may include, in the response message, the second configurations for each candidate target cell that can accept (or has accepted) the handover, and may not include the second configurations for the candidate target cells that cannot accept (or have rejected) the handover. The plurality of second configurations may be included in an IE (e.g., DU-to-CU RRC information) containing RRC information. More specifically, the plurality of second configurations may be included, for example, in a CellGroupConfig IE contained in the IE.

[0080] In step 504, the CU 25 of the target RAN node 2 sends, via a handover confirmation message (HANDOVER REQUEST ACKNOWLEDGMENT), the first configuration common to the plurality of candidate target cells 21-23 and the plurality of second configurations received from one or more DUs 26 to the source RAN node 1. The CU 25 of the target RAN node 2 may associate the first configuration only with the candidate target cells to which one or more DUs 26 can accept (or have accepted) the handover. In other words, the CU 25 of the target RAN node 2 may associate the first configuration only with the candidate target cells for which the CU 25 has received the second configurations from one or more DUs 26. Although not shown, the source RAN node 1 sends a handover instruction including both the first configuration and the plurality of second configurations to the radio terminal 3 via an RRC message (e.g., RRC RECONFIGURATION).

[0081] In some implementations, a new handover request message (e.g., a conditional handover request message) may be defined for conditional handover. Similarly, an RAN node-to-RAN node RRC message (handover preparation information) (e.g., conditional handover preparation information) included in the handover request message may be newly defined for conditional handover. In addition, a new handover request acknowledgment message (e.g., a conditional handover request acknowledgment message) may be defined for conditional handover.

[0082] In some implementations, C-RAN deployment may also be applied to the source RAN node 1. In this case, the CU of the source RAN node 1 (e.g., gNB-CU) may send a handover instruction to the radio terminal 3 via the DU of the source RAN node 1 (e.g., gNB-DU) based on or in response to an acknowledgment message (e.g., HANDOVER REQUEST ACKNOWLEDGMENT) received from the CU of the target RAN node 2 for a request for conditional handover (e.g., HANDOVER REQUEST). In this case, the CU of the source RAN node 1 may send information that explicitly or implicitly indicates that a conditional handover instruction has been sent or is to be sent to the DU of the source RAN node 1.

[0083] Fourth Embodiment

[0084] This embodiment provides an improvement to handover-related messages sent on the RAN node interface to accommodate conditional handover. An example configuration of the radio communication network according to this embodiment can be the same as Figure 1 the configuration example shown. Additionally, in this embodiment, multiple candidate target cells can be served by multiple RAN nodes 2.

[0085] Figure 6 FIG. is an example of signaling according to this embodiment. In step 601, the source RAN node 1 sends a request to release the resources of the candidate target cell(s) to one or more target RAN nodes 2. This request requests each target RAN node 2 to release the resources of one or more candidate target cells reserved for conditional handover. The source RAN node 1 can send this request to the target RAN node 2 that manages candidate target cells different from the target cell to which the radio terminal 3 is moving. This request can be sent from the source RAN node 1 to the target RAN node 2 via a UE context release message (e.g., HANDOVER CANCEL or UE CONTEXT REMOVAL). In this case, the release reason value attached to (or included in) the UE context release message can be, for example, "handover condition satisfied", "action desired for radio reasons", "handover completed", "normal release", or "candidate target cell found".

[0086] For example, the source RAN node 1 can send the request of step 601 when it detects that the radio terminal 3 has completed a conditional handover. The source RAN node 1 can detect this by receiving a message indicating the success of the handover of the radio terminal 3 (e.g., UE CONTEXT RELEASE message) from any of the target RAN nodes 2. In this case, the release reason value attached to (or included in) the UE context release message can be, for example, "handover condition satisfied", "action desired for radio reasons", "handover completed", "normal release", or "candidate target cell found".

[0087] Alternatively, the source RAN node 1 can send the request of step 601 when it detects that the radio terminal 3 has performed (or initiated) a conditional handover. The source RAN node 1 can detect the handover execution by receiving a CHO indication (e.g., measurement report or indication of CHO trigger) from the radio terminal 3. The source RAN node 1 can autonomously judge the handover execution condition of the CHO and thereby autonomously detect the handover execution.

[0088] According to such an operation, for example, the target RAN node 2 can be allowed to release the resources reserved for the CHO in response to a request from the source RAN node 1 without waiting for the validity timer to expire.

[0089] The request in step 601 can be sent for each candidate target cell, each radio terminal, or each target RAN node.

[0090] The request in step 601 can include an identifier of the corresponding candidate target cell (e.g., target index) to identify one or more candidate cells for which resources can be released. Alternatively, the request in step 601 can include the cell ID of the corresponding candidate cell (e.g., physical cell identifier (PCI), cell global identifier (CGI), or cell identifier (CI)).

[0091] Alternatively, the request in step 601 can include an identifier for conditional handover to identify one or more candidate cells for which resources can be released. The identifier for conditional handover can also be included in the handover request message sent from the source RAN node 1 to the target RAN node 2 to request a conditional handover. This enables the identifier for conditional handover to be associated with one or more candidate target cells.

[0092] On the other hand, if the radio terminal 3 completes a conditional handover to any of the candidate target cells in the candidate target cells, the radio terminal 3 can autonomously release the resources of the other candidate target cells (i.e., radio resource configuration). Alternatively, after the conditional handover is completed, the radio terminal 3 can release the resources of the other candidate target cells in response to a release request received from the network (e.g., the target RAN node 2).

[0093] Fifth Embodiment

[0094] This embodiment provides a specific example of signaling for conditional handover. The configuration example of the radio communication network according to this embodiment can be the same as the Figure 1 configuration example shown. However, in this embodiment, the C-RAN deployment is applied at least to the target RAN node 2 (e.g., gNB). The target RAN node 2 includes a CU 25 (e.g., gNB-CU) and one or more DUs 26 (e.g., gNB-DU). Multiple candidate target cells can be served by one DU 26, or can be served by multiple DUs 26.

[0095] Figure 7This is a diagram showing an example of signaling related to conditional handover. In step 701, the CU 25 of the target RAN node 2 sends a request to one or more target DUs 26 to release the resources of candidate target cells. This request requests each target DU 26 to release the resources of one or more candidate target cells reserved for conditional handover. The CU 25 may send this request to the target DU 26 that manages candidate target cells different from the target cell to which the radio terminal 3 is moving.

[0096] The message to be sent in step 701 to request resource release may be, for example, a UE CONTEXT RELEASE COMMAND message. In this case, the release reason value attached to (or included in) the UE CONTEXT RELEASE COMMAND message may be, for example, "handover condition met", "action desired for radio reasons", "handover completed", or "normal release".

[0097] For example, the CU 25 of the target RAN node 2, in response to receiving a request to release the resources of candidate target cells from the source RAN node 1 (e.g., Figure 6 step 601), may send the request in step 701 to the (one or more) DUs 26.

[0098] According to such an operation, for example, it is possible to allow the target DU 26 to release the resources reserved for conditional movement in response to a request from the CU 25 without waiting for the validity timer to expire.

[0099] On the other hand, in the case where the radio terminal 3 has completed a conditional handover to any one of the candidate target cells, the radio terminal 3 may autonomously release the resources of other candidate target cells (i.e., radio resource configuration). Alternatively, after the conditional handover is completed, the radio terminal 3 may release the resources of other candidate target cells in response to receiving a release request from the network (e.g., the target RAN node 2 or CU 25).

[0100] Figure 7 The process shown can be applied to conditional handover between DUs within a CU. In the case of conditional handover between DUs within a CU, the DU 26 connected to the CU 25 among the multiple DUs 26 is the source DU serving the source cell 11, and the other one or more DUs 26 are the target DUs serving one or more candidate target cells. The CU 25 serves as the source RAN node 1 and the target RAN node 2.

[0101] In the case of conditional handover between DUs within a CU, for example, when CU 25 detects that the radio terminal 3 has completed a conditional handover, it may send the request of step 701. CU 25 can detect the completion of the conditional handover by receiving from any target DU 2 a message indicating the successful conditional handover of the radio terminal 3 (for example, an uplink RRC transfer message carrying an RRC reconfiguration complete (RRCReconfigurationComplete) message). In the case where CU 25 and DU 26 are secondary nodes (SNs) of a dual connection (DC), CU 25 can detect the completion of the conditional handover by receiving from the radio terminal 3 via the master node (MN) a message indicating the successful conditional handover of the radio terminal 3 (for example, an RRC reconfiguration complete message).

[0102] Alternatively, when CU 25 detects that the radio terminal 3 has performed (or initiated) a conditional handover, it may send the request of step 701. CU 25 can detect the execution (or initiation) of the handover by receiving an indication of the initiation of the conditional handover (for example, a measurement report) from either the radio terminal 3 or any target DU 26 among the target DUs 26.

[0103] Sixth Embodiment

[0104] This embodiment provides specific examples of conditional mobility other than conditional handover (CHO). The conditional mobility in this embodiment may be a change of the primary cell (PCell) of the master cell group (MCG) in a dual connection (DC), or a handover between master nodes (MNs) in a DC. Additionally or alternatively, the conditional mobility may be a change of the secondary node (SN) in a DC, or a change of the primary cell of the secondary cell group (SCG) in a DC (i.e., a change of the primary SCG cell (PSCell)). The change of the PCell of the MCG in a DC can be performed in the same process as the conditional handover process in the above embodiment.

[0105] In some implementations, conditional mobility can be performed in a secondary node change (SN change) in DC. For example, a source RAN node (i.e., the source SN) or the MN sends a request message for conditional SN change (e.g., SN addition request (ADDITION REQUEST)) to the target SN. In this case, the request message for conditional SN change can indicate multiple candidate target cells. The target RAN node (e.g., the target SN) sends a first configuration common to multiple candidate target cells (e.g., PSCell candidate cells of the target SN) and multiple second configurations each associated with a corresponding candidate target cell among the multiple candidate target cells to the radio terminal (UE) via the MN. In other words, the radio terminal receives an RRC message of the MN RAT (e.g., LTE RRC connection reconfiguration) containing an RRC message of the SN RAT (e.g., NR RRC reconfiguration) in the MCG cell, and the RRC message of the SN RAT includes a common first configuration and multiple second configurations. Then, the radio terminal performs conditional SN change by using the received common first configuration and the received second configurations.

[0106] In some implementations, conditional mobility can be performed in a primary cell change (i.e., PSCell change) of a secondary cell group (SCG) in DC. Conditional PSCell change can also be referred to as conditional reconfiguration with sync (for PSCell change). For example, the source RAN node (i.e., the SN) sends an RRC message of the SN RAT to the radio terminal (UE), and the RRC message of the SN RAT includes a first configuration common to multiple candidate target cells (i.e., PSCell candidate cells) and multiple second configurations each associated with a corresponding candidate target cell among the multiple candidate target cells. Then, the radio terminal performs conditional PSCell change by using the received common first configuration and the received second configurations. The RRC message of the SN RAT can be sent via a signaling radio bearer (e.g., SRB1) of the MCG served by the master node (MN), or can be directly sent from the SN to the UE by an SRB (e.g., SRB3) of the SCG. In the case of conditional PSCell change, the source RAN node can be considered the same as the target RAN node.

[0107] In some implementations, C-RAN deployment can be applied to the target RAN node (i.e., the target SN) for conditional SN change or conditional PSCell change. The target RAN node (e.g., the target SgNB) includes a CU (e.g., gNB-CU) and one or more DUs (e.g., gNB-DU). In this case, the CU can determine a first configuration common to multiple candidate target cells, and one or more DUs can determine multiple second configurations each associated with a corresponding candidate target cell among the multiple candidate target cells.

[0108] Specifically, the DU may include multiple second configurations in an RRC container (e.g., DU-to-CU RRC information) included in a response message (UE context setup response), which is sent in response to a request message (UE context setup request) from the CU for establishing the context of a radio terminal. More specifically, the DU may include multiple second configurations in the RRC CellGroupConfig IE. Then, the CU may send an RRC message (e.g., RRC reconfiguration for SN change or PSCell change) including the first configuration and the second configuration to the radio terminal.

[0109] Multiple candidate target cells may be served by one DU, or may be served by multiple DUs.

[0110] The conditional PSCell change may be an inter-gNB-DU PSCell change using the MCG SRB. In other words, the RRC signaling between the radio terminal and the CU (i.e., the secondary node (SN)) for the inter-gNB-DU PSCell change may be carried out via the signaling radio bearer (e.g., SRB1) of the MCG served by the master node (MN). Alternatively, the conditional PSCell change may be an inter-gNB-DU PSCell change using the SCG SRB. In other words, the RRC signaling between the UE and the CU (i.e., the secondary node (SN)) for the inter-gNB-DU PSCell change may be carried out via the SRB of the SCG (e.g., SRB3). In the case where the conditional PSCell change is an inter-gNB-DU PSCell change within gNB-CU, it may be considered that the CU of the source RAN node is the same as the CU of the target RAN node, while the DU of the source RAN node is different from the DU of the target RAN node.

[0111] The following provides configuration examples of RAN node 1, RAN node 2, and UE 3 according to the above embodiments. Figure 8 is a block diagram showing a configuration example of RAN node 2 according to the above embodiment. The configuration of RAN node 1 may be the same as Figure 8 the configuration shown. Refer to Figure 8, the RAN node 2 includes a radio frequency (RF) transceiver 801, a network interface 803, a processor 804, and a memory 805. The RF transceiver 801 performs analog RF signal processing to communicate with the radio terminal 3. The RF transceiver 801 may include multiple transceivers. The RF transceiver 801 is coupled to the antenna array 802 and the processor 804. The RF transceiver 801 receives modulated symbol data from the processor 804, generates a transmit RF signal, and supplies the transmit RF signal to the antenna array 802. The RF transceiver 801 also generates a baseband receive signal based on the received RF signal received by the antenna array 802 and supplies the baseband receive signal to the processor 804. The RF transceiver 801 may include an analog beamformer circuit for beamforming. The analog beamformer circuit includes, for example, multiple phase shifters and multiple power amplifiers.

[0112] The network interface 803 is used to communicate with network nodes (e.g., control nodes and transport nodes of a 5G core network). The network interface 803 may include, for example, a network interface card (NIC) compliant with the IEEE 802.3 series.

[0113] The processor 804 performs digital baseband signal processing (i.e., data plane processing) and control plane processing for radio communication. The processor 804 may include multiple processors. The processor 804 may include, for example, a modem processor (e.g., a digital signal processor (DSP)) for performing digital baseband signal processing and a protocol stack processor (e.g., a central processing unit (CPU) or a microprocessing unit (MPU)) for performing control plane processing. The processor 804 may include a digital beamformer module for beamforming. The digital beamformer module may include a multiple-input multiple-output (MIMO) encoder and a precoder.

[0114] The memory 805 is composed of a combination of volatile memory and non-volatile memory. The volatile memory is, for example, static random access memory (SRAM), dynamic RAM (DRAM), or a combination thereof. The non-volatile memory is, for example, mask read-only memory (MROM), electrically erasable programmable ROM (EEPROM), flash memory, a hard disk drive, or any combination thereof. The memory 805 may include a memory configured separately from the processor 804. In this case, the processor 804 may access the memory 805 via the network interface 803 or an I / O interface (not shown).

[0115] The memory 805 may store one or more software modules (computer programs) 806, and the one or more software modules include instructions and data for performing the processing carried out by the RAN node 2 described in the above embodiments. In some implementations, the processor 804 may be configured to load the software module 806 from the memory 805 and execute the loaded software module, thereby performing the processing of the RAN node 2 described in the above embodiments.

[0116] In the case where the RAN node 2 is a CU (for example, an eNB-CU or a gNB-CU), the RAN node 2 does not need to include the RF transceiver 801 (and the antenna array 802).

[0117] Figure 9 FIG. is a block diagram showing a configuration example of the radio terminal 3. The radio frequency (RF) transceiver 901 performs analog RF signal processing to communicate with the RAN nodes 1 and 2. The RF transceiver 901 may include a plurality of transceivers. The analog RF signal processing performed by the RF transceiver 901 includes upconversion, downconversion, and amplification. The RF transceiver 901 is coupled to the antenna array 902 and the baseband processor 903. The RF transceiver 901 receives modulation symbol data (or OFDM symbol data) from the baseband processor 903, generates a transmit RF signal, and supplies the transmit RF signal to the antenna array 902. The RF transceiver 901 also generates a baseband receive signal based on the receive RF signal received by the antenna array 902, and supplies the baseband receive signal to the baseband processor 903. The RF transceiver 901 may include an analog beamformer circuit for beamforming. The analog beamformer circuit includes, for example, a plurality of phase shifters and a plurality of power amplifiers.

[0118] The baseband processor 903 performs digital baseband signal processing (i.e., data plane processing) and control plane processing for radio communication. The digital baseband signal processing includes, for example, (a) data compression / decompression, (b) data segmentation / concatenation, (c) constitution / decomposition of a transmission format (i.e., a transmission frame), (d) channel coding / decoding, (e) modulation (i.e., symbol mapping) / demodulation, and (f) generation of OFDM symbol data (i.e., a baseband OFDM signal) using an inverse fast Fourier transform (IFFT). On the other hand, the control plane processing includes communication management of layer 1 (for example, transmission power control), layer 2 (for example, radio resource management and hybrid automatic repeat request (HARQ) processing), and layer 3 (for example, signaling related to attachment, mobility, and call management).

[0119] The digital baseband signal processing performed by the baseband processor 903 may include signal processing of, for example, the Service Data Adaptation Protocol (SDAP) layer, the Packet Data Convergence Protocol (PDCP) layer, the Radio Link Control (RLC) layer, the MAC layer, and the PHY layer. The control plane processing performed by the baseband processor 903 may also include processing of the Non-Access Stratum (NAS) protocol, the RRC protocol, and MAC CE.

[0120] The baseband processor 903 may perform MIMO encoding and precoding for beamforming.

[0121] The baseband processor 903 may include a modem processor (e.g., DSP) for performing digital baseband signal processing and a protocol stack processor (e.g., CPU or MPU) for performing control plane processing. In this case, the protocol stack processor for performing control plane processing may be integrated with the application processor 904 described below.

[0122] The application processor 904 is also referred to as a CPU, MPU, microprocessor, or processor core. The application processor 904 may include multiple processors (processor cores). The application processor 904 loads system software programs (operating system (OS)) and various application programs (e.g., call application, WEB browser, mail program, camera operation application, and music player application) from the memory 906 or from other memories (not shown), and executes these programs, thereby providing various functions of the radio terminal 3.

[0123] In some implementations, as shown by the dashed line (905) in Figure 9 the baseband processor 903 and the application processor 904 may be integrated on a single chip. In other words, the baseband processor 903 and the application processor 904 may be implemented on a single System on Chip (SoC) device 905. The SoC device may be referred to as a Large Scale Integration (LSI) or a chipset.

[0124] The memory 906 is a volatile memory, a non-volatile memory, or a combination thereof. The memory 906 may include multiple memory devices that are physically independent of each other. The volatile memory is, for example, SRAM, DRAM, or a combination thereof. The non-volatile memory is, for example, MROM, EEPROM, flash memory, a hard disk drive, or any combination thereof. The memory 906 may include, for example, an external memory device that can be accessed from the baseband processor 903, the application processor 904, and the SoC 905. The memory 906 may include an internal memory device integrated within the baseband processor 903, the application processor 904, or the SoC 905. The memory 906 may also include a memory in a Universal Integrated Circuit Card (UICC).

[0125] The memory 906 may store one or more software modules (computer programs) 907, and the one or more software modules include instructions and data for performing the processing performed by the radio terminal 3 described in the above embodiments. In some implementations, the baseband processor 903 or the application processor 904 may load these software modules 907 from the memory 906 and execute the loaded software modules, thereby performing the processing of the radio terminal 3 described with reference to the accompanying drawings in the above embodiments.

[0126] The control plane processing and operations performed by the radio terminal 3 described in the above embodiments may be implemented by elements other than the RF transceiver 901 and the antenna array 902, that is, by the memory 906 storing the software module 907 and at least one of the baseband processor 903 and the application processor 904.

[0127] As referred to above Figure 8 and Figure 9 As described, each processor included in the RAN node 1, RAN node 2, and UE 3 according to the above embodiments executes one or more programs including instructions for causing a computer to execute the algorithms described with reference to the accompanying drawings. Any type of non-transitory computer-readable medium may be used to store these programs and provide these programs to a computer. Non-transitory computer-readable media include any type of tangible storage medium. Examples of non-transitory computer-readable media include: magnetic storage media (such as floppy disks, magnetic tapes, hard disk drives, etc.), magneto-optical storage media (e.g., magneto-optical discs), compact disc read-only memory (CD-ROM), CD-R, CD-R / W, and semiconductor memories (such as mask ROM, programmable ROM (PROM), erasable PROM (EPROM), flash ROM, and random access memory (RAM), etc.). Any type of transitory computer-readable medium may be used to provide these programs to a computer. Examples of transitory computer-readable media include electrical signals, optical signals, and electromagnetic waves. Transitory computer-readable media may provide the programs to a computer via a wired communication line (e.g., wires and optical fibers) or a wireless communication line.

[0128] Other embodiments

[0129] In the condition switching in the above embodiments, the radio terminal 3 can process the timer T30x related to condition switching as follows. In normal handover, the radio terminal 3 starts the timer T304 when receiving an RRC message indicating handover (e.g., an RRC reconfiguration including reconfigurationWithSync). In contrast, in condition switching, even if the radio terminal 3 receives an RRC message indicating handover (e.g., an RRC reconfiguration including reconfigurationWithSync for CHO), the radio terminal 3 does not have to immediately start the timer T30x. When the conditions for condition switching for a certain candidate target cell are met, the radio terminal 3 starts the timer T30x corresponding to the candidate target cell. If the random access in the candidate target cell (e.g., SpCell) is successful, the radio terminal 3 stops the timer T30x. An existing T304 can be used as T30x, or a new timer can be specified as T30x.

[0130] For each measurement report triggering event specified by 3GPP (e.g., event A1, A2, A3, A4, A5, A6, B1, B2, C1, C2, W1, W2, W3, V1, V2, H1 or H2), the above handover execution conditions for condition switching (e.g., thresholds (events) and corresponding trigger times (TTT)) can be added (or defined) as new events.

[0131] Additionally or alternatively, the above handover execution conditions for condition switching can include a parameter that can be replaced with at least one of the parameters included in each measurement report triggering event specified by 3GPP.

[0132] Additionally or alternatively, the above handover execution conditions for condition switching can include: an offset value for at least one of the multiple parameters included in each measurement report triggering event specified by 3GPP.

[0133] The parameters included in the measurement report triggering events specified by 3GPP (e.g., event A1, A2, A3, A4, A5, A6, B1, B2, C1, C2, W1, W2, W3, V1, V2, H1 and H2) can include, for example, but are not limited to at least one of the following:

[0134] Ms: The measurement result of the serving cell without considering any offset; the measurement result of the channel busy rate of the transmission resource pool without considering any offset; or the altitude of the aerial UE without considering any offset when the radio terminal 3 is an aerial UE;

[0135] Hys: The hysteresis value of the event;

[0136] Thresh(1 or 2): Threshold for this event;

[0137] Mn: Measurement result of adjacent cells without considering any offset;

[0138] Ofn: Offset value specific to the frequency of the adjacent cell;

[0139] Ocn: Cell-specific offset of the adjacent cell;

[0140] Mp: Measurement result of the primary cell or the primary SCG cell without considering any offset;

[0141] Ofp: Offset value specific to the frequency of the primary cell or the primary SCG cell;

[0142] Ocp: Cell-specific offset of the primary cell or the primary SCG cell;

[0143] Off: Offset parameter for this event;

[0144] Mcr: Measurement result of the CSI-RS (Channel State Information - Reference Signal) resource without considering any offset;

[0145] Ocr: CSI-RS-specific offset value for CSI-RS;

[0146] Mref: Measurement result of the reference CSI-RS resource; and

[0147] Oref: CSI-RS-specific offset value for the reference CSI-RS resource.

[0148] As the condition (e.g., offset) used for the handover as a radio terminal 3 exit condition, the same condition can be configured for multiple conditional handovers, or different conditions can be configured for these multiple conditional handovers. Similarly, as the value of the validity timer, the same value can be configured for multiple conditional handovers, or different values can be configured for these multiple conditional handovers.

[0149] In conditional handover (CHO), when radio terminal 3 fails (e.g., detects a handover failure) in the handover to a candidate cell that meets the execution condition (e.g., threshold), radio terminal 3 can perform (continue) conditional handover by switching (falling back) to another candidate cell that meets the condition.

[0150] If the radio terminal 3 receives, after receiving a handover command including a CHO execution condition (e.g., a threshold) from the source RAN node 1 and during a period before any candidate target cell satisfies the execution condition, a handover command (i.e., a command for normal handover) that does not include a CHO execution condition (e.g., a threshold) from the RAN node 1, the radio terminal 3 may perform a normal handover according to the received handover command that does not include a CHO execution condition (e.g., a threshold). The normal handover command that does not include a CHO execution condition may be, for example, a mobilityControlInfo IE. In this case, in response to receiving the handover command that does not include a CHO execution condition (e.g., a threshold), the radio terminal 3 may release the previously received CHO execution condition (e.g., a threshold).

[0151] Each of the above-described embodiments may be used alone, or two or more embodiments may be appropriately combined with each other. For example, the second embodiment does not necessarily require the improvements described in the first embodiment or the improvements described in the third embodiment. Similarly, the third embodiment does not necessarily require the improvements described in the first embodiment or the improvements described in the second embodiment. In other words, the first to third embodiments may be used independently of each other, and contribute to solving different purposes or problems from each other, and contribute to achieving different effects from each other.

[0152] In a 5G system (e.g., NR) used as one of the application examples of the above-described embodiments, an RRC reconfiguration including a synchronization process (e.g., random access) with a target cell (e.g., in the case of RRC reconfiguration) such as a handover is also referred to as a reconfiguration with sync (or a reconfiguration with synchronization). That is, conditional handover corresponds to (or includes) a conditional reconfiguration with sync.

[0153] The function described as conditional handover (CHO) in the above-described embodiments may be referred to as pre-conditioned HO, preoared HO, delayed HO, etc.

[0154] The handover (or reconfiguration with sync) including normal handover and conditional handover described in the above-described embodiments may be, for example, but not limited to, handover between gNBs, handover within a gNB (between gNB-DUs), handover between a gNB and an eNB / 5GC (ng-eNB), handover between eNBs / 5GCs, or handover within an eNB / 5GC (between eNB / 5GC-DUs).

[0155] The conditional handover described in the above embodiments may be a handover within a conditional DU (e.g., within a gNB-DU or an eNB-DU). In a handover within a conditional DU, at least one of the multiple candidate target cells is a cell served by the same gNB-DU (or eNB-DU) as the source cell. In this case, the UE context setup request and UE context response messages between the CU (e.g., gNB-CU) and DU (e.g., gNB-DU) of the target RAN node may be a UE context modification request (CONTEXT MODIFICATION REQUEST) message and a UE context modification response (CONTEXT MODIFICATION RESPONSE) message, respectively.

[0156] The user equipment (UE) in the present invention is an entity connected to the network via a wireless interface. It should be noted that the radio terminal (UE) in the present invention is not limited to a dedicated communication device, and the radio terminal (UE) may be any device having the communication functions explained herein.

[0157] The terms "user equipment (UE)" (as a term used by 3GPP), "mobile station", "mobile terminal", "mobile device", and "radio terminal (wireless device)" are generally intended to be synonymous with each other. The UE may include independent mobile stations such as terminals, cellular phones, smart phones, tablet computers, cellular IoT (Internet of Things) terminals, and IoT devices. It should be understood that the terms "UE" and "radio terminal" also cover devices that remain stationary for a long time.

[0158] The UE may, for example, be a device for production or manufacturing and / or energy-related machinery (e.g., devices or machinery such as boilers; engines; turbines; solar panels; wind turbines; hydroelectric generators; thermal generators; nuclear power generators; batteries; nuclear systems and / or related equipment; heavy electric machinery; pumps including vacuum pumps; compressors; fans; blowers; oil pressure equipment; pneumatic equipment; metalworking machinery; robotic arms; robots and / or their application systems; tools; extrusion dies or die-casting dies; reels; conveying equipment; lifting equipment; material handling equipment; textile machinery; sewing machines; printing and / or related machinery; paper-making machinery; chemical machinery; mining and / or construction machinery and / or related equipment; agricultural, forestry, and / or fishery machinery and / or tools; safety and / or environmental protection equipment; tractors; power transmission equipment; and / or application systems of any of the foregoing devices or machinery, etc.).

[0159] The UE may, for example, be transportation equipment (e.g., transportation equipment such as rolling stock; motor vehicles; motorcycles; bicycles; trains; buses; carts; rickshaws; ships and other watercraft; airplanes; rockets; satellites; drones; balloons, etc.).

[0160] A UE can be, for example, an information and communication device (e.g., an information and communication device such as: an electronic computer and related devices; communication and related devices; electronic devices, etc.).

[0161] A UE can be, for example, a trade and / or service industry device, a vending machine, a self-service machine, an office machine or device, a consumer electronic and electronic device (e.g., a consumer electronic device such as: an audio device; a speaker; a radio; a video device; a television, etc.).

[0162] A UE can be, for example, an electrical application system or device (e.g., an electrical application system or device such as: an x-ray system; a particle accelerator; a radioactive isotope device; a sound wave device; an electromagnetic application device; an electronic power application device, etc.).

[0163] A UE can be, for example, an electronic lamp, a lighting fixture, a measuring instrument, an analyzer, a tester, or a measuring or sensing instrument (e.g., a measuring or sensing instrument such as: a smoke alarm; a human body alarm sensor; a motion sensor; a wireless tag, etc.), a watch or clock, a laboratory instrument, an optical device, a medical device and / or system, a weapon, a tableware, or a hand tool, etc.

[0164] A UE can be, for example, a wireless-equipped personal digital assistant or related device (such as a wireless card or module designed to be attached to or inserted into another electronic device (e.g., a personal computer, an electrical measuring machine), etc.).

[0165] A UE can be part of a device or system that provides the applications, services, and solutions described below for the "Internet of Things (IoT)" using various wired and / or wireless communication technologies. IoT devices (or "things") can be equipped with appropriate electronics, software, sensors, and / or network connections, etc., which enable these devices to collect data and exchange data with each other and with other communication devices. IoT devices can include automated devices that follow software instructions stored in internal memory. IoT devices can operate without human supervision or interaction. IoT devices can also remain stationary and / or inactive for long periods of time. IoT devices can be implemented as part of (usually) fixed devices. IoT devices can also be embedded in non-stationary devices (e.g., vehicles), or attached to animals or people to be monitored / tracked. It should be understood that IoT technology can be implemented on any communication device capable of connecting to a communication network for sending / receiving data, regardless of whether such a communication device is controlled by human input or by software instructions stored in memory. It should be understood that IoT devices are sometimes also referred to as machine type communication (MTC) devices, machine-to-machine (M2M) communication devices, or narrowband-IoT (NB-IoT) UEs.

[0166] It should be understood that the UE may support one or more IoT or MTC applications.

[0167] Some examples of MTC applications are listed in Annex B of 3GPP TS22.368 V13.2.0 (2017-01-13), the content of which is incorporated herein by reference. This list is not exhaustive and is intended to indicate some examples of MTC applications. In this list, the service areas of MTC applications include security, tracking and tracing, payment, health, remote maintenance / control, metering, and consumer devices.

[0168] Examples of MTC applications related to security include monitoring systems, fixed-line backup, control of physical access (e.g., to a building), and vehicle / driver safety.

[0169] Examples of MTC applications related to tracking and tracing include queue management, order management, telematics insurance: pay-as-you-drive (PAYD), asset tracking, navigation, traffic information, road tolling, and road traffic optimization / diversion.

[0170] Examples of MTC applications related to payment include point of sale (POS), vending machines, and gaming machines.

[0171] Examples of MTC applications related to health include monitoring vital signs, supporting the elderly or disabled, web access to remote medical sites, and remote diagnosis.

[0172] Examples of MTC applications related to remote maintenance / control include sensors, lighting, pumps, valves, elevator control, vending machine control, and vehicle diagnosis.

[0173] Examples of MTC applications related to metering include electricity, gas, water, heating, grid control, and industrial metering.

[0174] Examples of MTC applications related to consumer devices include digital photo frames, digital cameras, and e-books (eBooks).

[0175] Applications, services, and solutions can be Mobile Virtual Network Operator (MVNO) services / systems, emergency radio communication services / systems, Private Branch Exchange (PBX) services / systems, PHS / digital cordless telecommunications services / systems, Point of Sale (POS) services / systems, advertising call services / systems, Multimedia Broadcast and Multicast Service (MBMS) services / systems, Vehicle-to-Everything (V2X) services / systems, train radio services / systems, location-related services / systems, disaster / emergency wireless communication services / systems, Internet of Things (IoT) services / systems, community services / systems, video streaming services / systems, femtocell application services / systems, Voice over LTE (VoLTE) services / systems, radio tag services / systems, billing services / systems, audio-on-demand services / systems, roaming services / systems, activity monitoring services / systems, telecommunication carrier / communication NW selection services / systems, function restriction services / systems, Proof of Concept (PoC) services / systems, personal information management services / systems, display video services / systems, non-communication services / systems, ad-hoc network / Delay Tolerant Network (DTN) services / systems, and so on.

[0176] The above UE categories are only examples of the applications of the technical ideas and embodiments described in the present invention. The UEs described in the present invention are not limited to these examples, and those skilled in the art can make various modifications to them.

[0177] The above embodiments are only examples of the applications of the technical ideas obtained by the present inventor. These technical ideas are not limited to the above embodiments, and various modifications can be made to them.

[0178] All or part of the above embodiments can be described as, but not limited to, the following supplementary explanations.

[0179] (Supplementary Explanation 1)

[0180] A target radio access network node includes:

[0181] At least one memory; and

[0182] At least one processor, coupled to the at least one memory and configured to send, during a handover process for causing a radio terminal to move from a source cell to one of a plurality of candidate target cells, a first configuration common to the plurality of candidate target cells and a plurality of second configurations each associated with a respective candidate target cell among the plurality of candidate target cells to the radio terminal via a source radio access network node that manages the source cell,

[0183] wherein the first configuration includes at least one configuration parameter for enabling the radio terminal to access or communicate in one of the plurality of candidate target cells, and

[0184] Each second configuration includes at least one configuration parameter for enabling the radio terminal to access a corresponding candidate target cell or communicate in the corresponding candidate target cell.

[0185] (Supplementary Note 2)

[0186] The target radio access network node according to Supplementary Note 1, wherein at least one configuration parameter included in the first configuration is related to the configuration of radio bearers.

[0187] (Supplementary Note 3)

[0188] The target radio access network node according to Supplementary Note 1 or 2, wherein at least one configuration parameter included in the first configuration includes parameters for one or both of the packet data convergence protocol, i.e., PDCP, and the service data adaptation protocol, i.e., SDAP.

[0189] (Supplementary Note 4)

[0190] The target radio access network node according to any one of Supplementary Notes 1 to 3, wherein at least one configuration parameter included in the first configuration includes system information.

[0191] (Supplementary Note 5)

[0192] The target radio access network node according to any one of Supplementary Notes 1 to 4, wherein at least one configuration parameter included in each second configuration is related to the configuration of at least one of cell groups, logical channels, and random access.

[0193] (Supplementary Note 6)

[0194] The target radio access network node according to any one of Supplementary Notes 1 to 5, wherein at least one configuration parameter included in each second configuration includes parameters for the media access control entity, i.e., the MAC entity.

[0195] (Supplementary Note 7)

[0196] The target radio access network node according to any one of Supplementary Notes 1 to 6, wherein the handover process includes at least one of the following processes: a handover process, a process for changing the secondary node, i.e., SN, in dual connectivity, i.e., DC, i.e., SN change, and a process for changing the primary cell of the secondary cell group, i.e., PSCell change.

[0197] (Supplementary Note 8)

[0198] The target radio access network node according to any one of Supplementary Notes 1 to 7, wherein

[0199] The movement process includes a handover process, and

[0200] The at least one processor is configured to include both the first configuration and the second configuration in a handover confirmation message to be sent from the target radio access network node to the source radio access network node.

[0201] (Supplementary Note 9)

[0202] The target radio access network node according to any one of Supplementary Notes 1 to 8, wherein the movement process is a conditional movement process.

[0203] (Supplementary Note 10)

[0204] A radio terminal, comprising:

[0205] At least one memory; and

[0206] At least one processor, coupled to the at least one memory and configured to, during a movement process for causing the radio terminal to move from a source cell to one of a plurality of candidate target cells, receive, via a source radio access network node managing the source cell, a first configuration common to the plurality of candidate target cells and a plurality of second configurations respectively associated with corresponding candidate target cells among the plurality of candidate target cells from a target radio access network node managing the plurality of candidate target cells,

[0207] wherein the first configuration includes at least one configuration parameter for enabling the radio terminal to access or communicate in one of the plurality of candidate target cells, and

[0208] Each second configuration includes at least one configuration parameter for enabling the radio terminal to access or communicate in the corresponding candidate target cell.

[0209] (Supplementary Note 11)

[0210] The radio terminal according to Supplementary Note 10, wherein at least one configuration parameter included in the first configuration is related to the configuration of radio bearers.

[0211] (Supplementary Note 12)

[0212] The radio terminal according to Supplementary Note 10 or 11, wherein at least one configuration parameter included in the first configuration includes parameters for one or both of the packet data convergence protocol (PDCP) and the service data adaptation protocol (SDAP).

[0213] (Supplementary Note 13)

[0214] The radio terminal according to any one of Supplementary Notes 10 to 12, wherein at least one configuration parameter included in the first configuration includes system information.

[0215] (Supplementary Note 14)

[0216] The radio terminal according to any one of Supplementary Notes 10 to 13, wherein at least one configuration parameter included in each second configuration is related to the configuration of at least one of a cell group, a logical channel, and random access.

[0217] (Supplementary Note 15)

[0218] The radio terminal according to any one of Supplementary Notes 10 to 14, wherein at least one configuration parameter included in each second configuration includes a parameter for a media access control entity, i.e., a MAC entity.

[0219] (Supplementary Note 16)

[0220] The radio terminal according to any one of Supplementary Notes 10 to 15, wherein the handover process is a conditional handover process.

[0221] (Supplementary Note 17)

[0222] A method for a target radio access network node, the method comprising:

[0223] During a handover process for causing a radio terminal to move from a source cell to one of a plurality of candidate target cells, sending, via a source radio access network node managing the source cell, a first configuration common to the plurality of candidate target cells and a plurality of second configurations each associated with a respective candidate target cell among the plurality of candidate target cells to the radio terminal,

[0224] wherein the first configuration includes at least one configuration parameter for enabling the radio terminal to access one of the plurality of candidate target cells or communicate in the candidate target cell, and

[0225] each second configuration includes at least one configuration parameter for enabling the radio terminal to access the respective candidate target cell or communicate in the respective candidate target cell.

[0226] (Supplementary Note 18)

[0227] A method for a radio terminal, the method comprising:

[0228] During a handover process for causing a radio terminal to move from a source cell to one of a plurality of candidate target cells, a first configuration common to the plurality of candidate target cells and a plurality of second configurations each associated with a respective candidate target cell among the plurality of candidate target cells are received via a source radio access network node managing the source cell from a target radio access network node managing the plurality of candidate target cells,

[0229] wherein the first configuration includes at least one configuration parameter for enabling the radio terminal to access or communicate in one of the plurality of candidate target cells, and

[0230] each second configuration includes at least one configuration parameter for enabling the radio terminal to access or communicate in the respective candidate target cell.

[0231] (Supplementary Note 19)

[0232] A program for causing a computer to perform a method for a target radio access network node, the method comprising:

[0233] During a handover process for causing a radio terminal to move from a source cell to one of a plurality of candidate target cells, the first configuration common to the plurality of candidate target cells and the plurality of second configurations each associated with a respective candidate target cell among the plurality of candidate target cells are sent to the radio terminal via a source radio access network node managing the source cell,

[0234] wherein the first configuration includes at least one configuration parameter for enabling the radio terminal to access or communicate in one of the plurality of candidate target cells, and

[0235] each second configuration includes at least one configuration parameter for enabling the radio terminal to access or communicate in the respective candidate target cell.

[0236] (Supplementary Note 20)

[0237] A program for causing a computer to perform a method for a radio terminal, the method comprising:

[0238] During a handover process for causing a radio terminal to move from a source cell to one of a plurality of candidate target cells, a first configuration common to the plurality of candidate target cells and a plurality of second configurations each associated with a respective candidate target cell among the plurality of candidate target cells are received via a source radio access network node managing the source cell from a target radio access network node managing the plurality of candidate target cells,

[0239] Among them, the first configuration includes at least one configuration parameter for enabling the radio terminal to access or communicate in one of the multiple candidate target cells, and

[0240] each second configuration includes at least one configuration parameter for enabling the radio terminal to access or communicate in the corresponding candidate target cell.

[0241] This application is based on and claims the benefit of the priority of Japanese Patent Application No. 2019-003561 filed on January 11, 2019, the entire content of which is incorporated herein by reference.

[0242] List of Reference Numerals

[0243] 1 Radio Access Network Node

[0244] 2 Radio Access Network Node

[0245] 3 Radio Terminal

[0246] 11 Source Cell

[0247] 21 - 23 Candidate Target Cells

[0248] 25 Central Unit (CU)

[0249] 26 Distributed Unit (DU)

[0250] 804 Processor

[0251] 805 Memory

[0252] 806 Module

[0253] 903 Baseband Processor

[0254] 904 Application Processor

[0255] 906 Memory

[0256] 907 Module

Claims

1. A method for a source radio access network node, i.e., a source RAN node, the method comprising: Receive a first message from a target RAN node, the first message including conditional mobility reconfiguration information for conditional mobility; Generate an execution condition for configuring a triggering event of conditional mobility; After receiving the first message, generate a second message, the second message including the conditional mobility reconfiguration information and the execution condition; and Send the second message to a user equipment, i.e., UE.

2. A source radio access network node, i.e., a source RAN node, comprising: At least one memory; And At least one processor coupled to the at least one memory and configured to: Receive a first message from a target RAN node, the first message including conditional mobility reconfiguration information; Generate an execution condition for configuring a triggering event of conditional mobility; After receiving the first message, generate a second message, the second message including the conditional mobility reconfiguration information and the execution condition; and Send the second message to a user equipment, i.e., UE.

3. A method performed by a user equipment, i.e., a UE, the method comprising: Receive a second message from a source radio access network node, i.e., source RAN node, the second message including both conditional mobility reconfiguration information and an execution condition for configuring a triggering event of conditional mobility; And After receiving the second message, send a radio resource control reconfiguration complete message, i.e., RRC reconfiguration complete message, to the source RAN node, wherein the conditional mobility reconfiguration information is included in a first message sent from the target RAN node to the source RAN node, and wherein the execution condition of the conditional mobility is generated by the source RAN node.

4. The method according to claim 3, further comprising: Before the target cell meets the execution condition, when the UE receives a normal mobility command without the execution condition, perform normal mobility according to the normal mobility command.

5. A user equipment, i.e., a UE, comprising: At least one memory; And At least one processor coupled to the at least one memory and configured to: Receive a second message from a source radio access network node, i.e., source RAN node, the second message including both conditional mobility reconfiguration information and an execution condition for configuring a triggering event of conditional mobility; And After receiving the second message, send a radio resource control reconfiguration complete message, i.e., RRC reconfiguration complete message, to the source RAN node, wherein the conditional mobility reconfiguration information is included in a first message sent from the target RAN node to the source RAN node, and wherein the execution condition of the conditional mobility is generated by the source RAN node.

6. The UE according to claim 5, wherein, The at least one processor is further configured to: Before the target cell meets the execution condition, when the UE receives a normal mobility command without the execution condition, perform normal mobility according to the normal mobility command.

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