The present disclosure relates to wireless communication systems, particularly to handovers.
Background technology
[0002]
In Patent Documents 1 and 2, the handover request message sent from the source radio access network (RAN) node (eg, base station) to the target RAN node during the handover procedure is a plurality of candidate targets. It discloses that it contains a list of cells. Further, Patent Document 2 discloses that when a plurality of candidate target cells are acceptable for handover, the target RAN node returns a handover approval message including handover information about the plurality of candidate target cells to the source RAN node. ing.
[0003]
Non-Patent Documents 1 and 2 disclose conditional handover (CHO) discussed in 3GPP. In some implementations for CHO, the source RAN node (eg, eNodeB (eNB)) sends a handover command containing the conditions for performing the handover (eg, threshold) to the wireless terminal (eg, User Equipment (UE)). .. The wireless terminal maintains the connection with the source RAN node even after receiving the handover command, and starts accessing the target RAN node as soon as the condition (configured condition) set by the handover command is satisfied. That is, conditional handover (CHO) is existing in that the wireless terminal starts accessing the target cell not in response to the reception of the handover command but in response to the satisfaction of the condition set by the handover command. It is different from the handover of.
[0004]
CHO can increase the reliability of delivery of the handover command to the UE by early event triggering (that is, lowering the threshold value that triggers the measurement report by the wireless terminal). As a result, the CHO can reduce the handover failure rate.
[0005]
In CHO, the settings of a plurality of candidate target cells may be sent to the wireless terminal. Candidate target cells may be referred to as potential target cells. For example, the wireless terminal receives a handover command including the setting of a plurality of candidate target cells and the CHO execution threshold value from the source RAN node (e.g., eNB). Then, the wireless terminal measures a plurality of set candidate target cells, and starts access to the candidate cell when the measurement in any of the candidate target cells satisfies the CHO execution threshold value.
Prior art literature
Patent documents
[0006]
Patent Document 1: Japanese Unexamined Patent Publication No. 2010-004295
Patent Document 2: International Publication No. 2011/018890
Non-patent literature
[0007]
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
Non-Patent Document 2: MediaTek Inc., “Conditional Handover Procedures”, R2-1816959, 3GPP TSG RAN WG2 Meeting # 104, Spokane, WA, USA, November 12-16, 2018
Outline of the invention
Problems to be solved by the invention
[0008]
When the target RAN node sends multiple settings for each of the multiple candidate target cells to the source RAN node or the target RAN node to the wireless terminal via the source RAN node, signaling of the RAN node-to-ate interface (eg, X2 interface) Overhead, or RAN node-to-node interface and air interface signaling overhead (between source base station and wireless terminal) increases.
[0009]
One of the objectives to be achieved by the embodiments disclosed herein is an apparatus that contributes to reducing signaling overhead of RAN node-to-node interfaces (and air interfaces) in various mobility procedures, including handovers. To provide methods and programs. It should be noted that this object is only one of the purposes that the embodiments disclosed herein seek to achieve. Other objectives or issues and novel features will be apparent from the description or accompanying drawings herein.
Means to solve problems
[0010]
In the first aspect, the target radio access network node comprises at least one memory and at least one processor coupled to said at least one memory. The at least one processor has a first setting common to the plurality of candidate target cells, each of which is said during the mobility procedure for moving the radio terminal from the source cell to one of the plurality of candidate target cells. A plurality of second settings associated with each one of the plurality of candidate target cells are configured to be transmitted to the radio terminal via the source radio access network node that manages the source cell. The first setting includes at least one setting parameter for allowing the wireless terminal to access or communicate with one of the plurality of candidate target cells. Each second setting includes at least one setting parameter that allows the radio terminal to access or communicate with each candidate target cell.
[0011]
In the second aspect, the wireless terminal includes at least one memory and at least one processor coupled to the at least one memory. Each of the at least one processor has a first setting common to the plurality of candidate target cells during the mobility procedure for moving the radio terminal from the source cell to one of the plurality of candidate target cells. A plurality of second settings associated with each one of the plurality of candidate target cells, and a source radio access network node that manages the source cell from a target radio access network node that manages the plurality of candidate target cells. Configured to receive via. The first setting includes at least one setting parameter for allowing the wireless terminal to access or communicate with one of the plurality of candidate target cells. Each second setting includes at least one setting parameter that allows the radio terminal to access or communicate with each candidate target cell.
[0012]
In a third aspect, the method for the target radio access network node is common to the plurality of candidate target cells during the mobility procedure for moving the radio terminal from the source cell to one of the plurality of candidate target cells. And a plurality of second settings, each associated with one of each of the plurality of candidate target cells, to the radio terminal via a source radio access network node that manages the source cell. Be prepared to send. The first setting includes at least one setting parameter for allowing the wireless terminal to access or communicate with one of the plurality of candidate target cells. Each second setting includes at least one setting parameter that allows the radio terminal to access or communicate with each candidate target cell.
[0013]
In a fourth aspect, the method for the radio terminal is common to the plurality of candidate target cells during the mobility procedure for moving the radio terminal from the source cell to one of the plurality of candidate target cells. One setting and a plurality of second settings each associated with one of the plurality of candidate target cells are managed from the target radio access network node that manages the plurality of candidate target cells. Provided to receive via a source radio access network node. The first setting includes at least one setting parameter for allowing the wireless terminal to access or communicate with one of the plurality of candidate target cells. Each second setting includes at least one setting parameter that allows the radio terminal to access or communicate with each candidate target cell.
[0014]
In the fifth aspect, the program includes an instruction group (software code) for causing the computer to perform the method according to the third or fourth aspect described above when the program is read by the computer.
The invention's effect
[0015]
According to the above aspects, it is possible to provide a device, a method, and a program that contribute to reducing the signaling overhead of the RAN node-to-node interface (and air interface) in various mobility procedures including handover.
A brief description of the drawing
[0016]
FIG. 1 is a diagram showing a configuration example of a wireless communication network according to some embodiments.
FIG. 2 is a sequence diagram showing an example of signaling according to the first embodiment.
FIG. 3 is a diagram showing a specific example of the format of the HANDOVER REQUEST message according to the second embodiment.
FIG. 4 is a diagram showing a specific example of the format of the HANDOVER REQUEST ACKNOWLEDGE message according to the second embodiment.
FIG. 5 is a sequence diagram showing an example of signaling according to the third embodiment.
FIG. 6 is a sequence diagram showing an example of signaling according to the fourth embodiment.
FIG. 7 is a sequence diagram showing an example of signaling according to the fifth embodiment.
FIG. 8 is a block diagram showing a configuration example of a radio access network node according to some embodiments.
FIG. 9 is a block diagram showing a configuration example of a wireless terminal according to some embodiments.
Embodiment for carrying out the invention
[0017]
In the following, specific embodiments will be described in detail with reference to the drawings. In each drawing, the same or corresponding elements are designated by the same reference numerals, and duplicate explanations are omitted as necessary for the sake of clarity of explanation.
[0018]
The plurality of embodiments described below can be implemented independently or in combination as appropriate. These plurality of embodiments have novel features that differ from each other. Therefore, these plurality of embodiments contribute to solving different purposes or problems, and contribute to different effects.
[0019]
The plurality of embodiments shown below will be described mainly for the 3GPP Long Term Evolution (LTE) system and the 5th generation mobile communication system (5G system). However, these embodiments may be applied to other wireless communication systems that support handover of wireless terminals. The term LTE as used herein includes improvements and developments of LTE and LTE-Advanced to enable interworking with the 5G System, unless otherwise noted. In addition to NR (New Radio), the 5G System also includes a network configuration in which LTE eNodeB (eNB) connects to the 5G core network (5GC). LTE eNB at this time is also called Next generation (ng) -eNB. ng-eNB is also called eNB / 5GC because it is an eNB connected to 5GC.
[0020]

FIG. 1 shows a configuration example of a wireless communication network according to a plurality of embodiments including the present embodiment. In the example of FIG. 1, the wireless communication network is RAN node 1, R. Includes AN node 2 and wireless terminal 3.
[0021]
The RAN node 1 may be, for example, LTE eNodeB (eNB) or NR gNodeB (gNB). RAN node 1 is a Central Unit (eg, eNB-CU, or gNB-CU) and one or more Distributed Units (eg, eNB-DUs, or gNB-DUs) in a cloud RAN (C-RAN) deployment. May include. C-RAN is also called CU / DU split. Similarly, the RAN node 2 may be an eNB or gNB and may include a Central Unit (CU) and one or more Distributed Units (DUs). Each RAN node may be an Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (EUTRAN) node or an NG-RAN (Next generation Radio Access Network) node. The EUTRAN node may be eNB or en-gNB. The NG-RAN node may be gNB or ng-eNB. The Radio Access Technology (RAT) of RAN node 1 may be different from that of RAN node 2.
[0022]
RAN node 1 provides at least one cell 11. The RAN node 2 provides a plurality of cells (e.g., four cells 21 to 24). In the example of FIG. 1, the cell 11 provided by the RAN node 1 is the current serving cell of the wireless terminal 3, and the wireless terminal (ie, User Equipment (UE)) 3 is a plurality of cells 11 provided by the RAN node 2. It is handed over to one of the cells of. Therefore, in the following, the RAN node 1 is referred to as a source RAN node, and the RAN node 2 is referred to as a target RAN node. Cell 11 is called a 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 for handover (candidats), and notifies the target RAN node 2. The cell selected by the source RAN node 1 is called the candidate target cell. Hereinafter, as an example, it is assumed that cells 21 to 23 are candidate target cells.
[0023]
The handover of the wireless terminal 3 may be a normal handover or a conditional handover. In a normal handover, the wireless terminal 3 starts access to the target RAN node 2 as soon as it receives an RRC message including a handover instruction from the source RAN node 1. In a normal handover, the source RAN node 1 prefers to move one target cell among a plurality of candidate target cells 21 to 23 which the target RAN node 2 has accepted (Admitted) to the wireless terminal 3. It may be selected and notified to the wireless terminal 3. The normal handover may be, for example, a handover triggered by mobilityControlInfo IE or reconfigurationWithSync IE included in the RRC (Connection) Reconfiguration message. In this case, mobilityControlInfo IE or reconfigurationWithSync IE is a handover instruction that triggers a handover in the wireless terminal 3.
[0024]
On the other hand, in the conditional handover, the source RAN node 1 transmits a handover instruction including the conditions (e.g., threshold value) for the handover execution to the wireless terminal 3 by an RRC message. The wireless terminal 3 maintains the connection with the source RAN node 1 even after receiving the RRC message, and starts accessing the target RAN node 2 as soon as the set condition (configured condition) is satisfied. In the conditional handover, the wireless terminal 3 may receive a handover instruction including the setting of a plurality of candidate target cells 21 to 23 and the CHO execution condition (e.g., threshold value) from the source RAN node (e.g., eNB). The handover instruction including the conditions for performing the handover (e.g., threshold value) may be referred to as conditionalMobilityControlInfo IE. The CHO execution condition (e.g., threshold value) may be common to a plurality of candidate target cells 21 to 23, or may be different for each candidate target cell. Then, the wireless terminal 3 measures (or starts) a plurality of designated candidate target cells 21 to 23, and accesses the candidate cell when the measurement for any of the candidate target cells satisfies the CHO execution threshold value. (Eg Random access) may be started. The measurement for the candidate target cell may be, for example, only the measurement in the candidate target cell when the conditional handover condition (e.g., CHO execution threshold value) is related only to the measurement result of the candidate target cell. On the other hand, if the condition of the conditional handover is related to both the measurement result of the candidate target cell and the source cell (that is, the current primary serving cell (PCell)), the measurement at the candidate target cell and the measurement at PCell. May include.
[0025]
The handover of the wireless terminal 3 in this embodiment can also be referred to as the mobility of the wireless terminal 3. The handover or mobility of the wireless terminal 3 may be an inter-master node (MN) handover at Dual Connectivity (DC) or a secondary node change (Secondary Node (SN) Change) at DC.
[0026]
Further or instead, the handover or mobility of the wireless terminal 3 may be a primary cell (PCell) change of the master cell group (MCG) at the DC. Further or instead, the handover or mobility of the wireless terminal 3 is a change of the primary cell of the secondary cell group (SCG) at the DC (that is, a primary SCG Cell (PSCell) change). ) May be. In these cases, the source RAN node 1 may be the source DU and the target RAN node 2 may be the target DU. Instead, 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.
[0027]
DC may be Multi-Radio Dual Connectivity (MR-DC). MR-DC is Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (E-UTRA)-NR Dual Connectivit (EN-DC), NR-E-UTRA DC (NE-DC), NG-RAN EN-DC ( Includes NGEN-DC) and NR-NR DC (NR DC).
[0028]
FIG. 2 shows an example of signaling in a handover procedure for handing over a wireless terminal 3 from a source cell 11 to one of a plurality of candidate target cells 21 to 23. In step 201, the source RAN node 1 determines that a handover (normal handover or conditional handover) is required and sends a handover request message to the target RAN node 2. If the plurality of cells (e.g., cells 21 to 23) provided by the target RAN node 2 are suitable for handover, the handover request message may indicate a plurality of candidate target cells.
[0029]
In steps 202 and 203, the target RAN node 2 has a first setting common to the plurality of candidate target cells 21 to 23, and a plurality of first settings each associated with one of the plurality of candidate target cells 21 to 23. The setting of 2 is transmitted to the wireless terminal 3 via the source RAN node 1. In other words, in step 203, the wireless terminal 3 has a first setting common to the plurality of candidate target cells 21 to 23, and a plurality of first settings each associated with each one of the plurality of candidate target cells 21 to 23. Receive the setting of 2. Then, the wireless terminal 3 executes the handover using the received common first setting and the plurality of second settings. In the case of conditional handover, the wireless terminal 3 determines whether or not the condition (eg, threshold value) is satisfied for each of the plurality of candidate target cells 21 to 23, and sets a common first setting and condition (eg, threshold value). A (conditional) handover to that cell is performed with the second setting for any one of the satisfied cells.
[0030]
As shown in FIG. 2, for example, the target RAN node 2 may include the first setting and a plurality of second settings in the handover approval (ACKNOWLEDGE) message (step 202). More specifically, in some implementations, the first setting and the plurality of second settings may be stored in the Target To Source Transparent Container included in the handover approval message. The source RAN node 1 may put the information contained in the Target To Source Transparent Container (eg, RRC Handover Command) into an RRC message (eg, RRC Reconfiguration) and transmit it to the wireless terminal 3 (step 203). .. Such an operation may be performed, for example, in the case of conditional handover.
[0031]
Instead, in some implementations, the source RAN node 1 receives a handover approval message from the target RAN node 2 carrying the first setting and the plurality of second settings, and the plurality of candidate target cells 21-23. You may select one target cell from which the wireless terminal 3 is preferably moved. Then, the source RAN node 1 derives the setting of the selected target cell from the first setting and the plurality of second settings, or creates (or prepares) based on these, and selects the selection included in the handover command. The setting of the target cell may be transmitted to the wireless terminal 3 by an RRC message (eg, RRC Reconfiguration). In this case, the first setting and the plurality of second settings are transmitted on the interface between the RAN nodes 1 and 2, but not on the air interface between the RAN node 1 and the wireless terminal 3. You may.
[0032]
The first configuration (common configuration) includes at least one configuration parameter for allowing the wireless terminal 3 to access or communicate with one of a plurality of candidate target cells. Each second configuration (cell specific configuration) includes at least one configuration parameter that allows the wireless terminal 3 to access or communicate with each candidate target cell. The cell specific configuration may be referred to as a dedicated configuration.
[0033]
The first setting and multiple second settings are conditional hands Conditions for performing handover for overrun (eg, threshold (event) and corresponding time-to-trigger (TTT)), conditions for the wireless terminal to exit conditional handover (eg, offset), and validity. ) It is not necessary to include the value of the timer. The value of the valid timer may indicate how long the resource of the candidate target cell is valid. Alternatively, the value of the valid timer is the period (time) during which access to the candidate target cell is permitted, or the period during which the settings for conditional handover (eg, first setting, second setting) are valid (. Time) may be indicated.
[0034]
At least one setting parameter included in the first setting may be related to the setting of the wireless bearer. Specifically, the first setting may include one or more radio bearer settings (e.g., RadioBearerConfig) that are common to a plurality of candidate target cells. In this case, the target RAN node 2 generates a radio bearer configuration for one of the plurality of candidate target cells that allow (or allow) the handover, and the radio bearer for the remaining candidate target cells. The setting may be omitted. Instead, the target RAN node 2 generates a radio bearer setting common to a plurality of candidate target cells that are allowed to accept the handover (or allow the handover), and each of the candidate target cells has an individual radio bearer. You do not have to generate the settings. Further or instead, the target RAN node 2 may additionally generate wireless bearer settings only for candidate target cells that require individual wireless bearer settings. That is, a common radio bearer setting and a radio bearer setting peculiar to the candidate target cell that requires a setting different from the common radio bearer setting may be generated.
[0035]
These one or more radio bearer configurations may include configuration information or parameters for the Packet Data Convergence Protocol (PDCP) for radio bearers, or configuration information or parameters for the Service Data Adaptation Protocol (SDAP). May include. One or more radio bearer configurations may include a list (e.g., srb-ToAddModList) of signaling radio bearers (SRBs) to be added or modified. One or more radio bearer settings may include a list (e.g., drb-ToAddModList) of data radio bearers (DRBs) to be added or modified. One or more radio bearer settings may include a list of DRBs released (e.g., drb-ToReleaseList). These one or more radio bearer settings may include security algorithms indicating security algorithms and keys used for signaling and data radio bearers.
[0036]
Further or instead, at least one setting parameter included in the first setting may include system information (SI). For example, the same SI area identifier (e.g., systemInformationAreaID) may be assigned to a plurality of candidate target cells 21 to 23. In this case, the target RAN node 2 sets the system information for one of the plurality of candidate target cells that are allowed to accept the handover (or allow the handover), and set the same SI area identifier as the one cell. You may omit the system information for the remaining candidate target cells you have. Instead, the target RAN node 2 sets system information in common for a plurality of candidate target cells that are allowed to accept the handover (or allow the handover), and set individual system information for each of the candidate target cells. It does not have to be set. Further or instead, the target RAN node 2 may additionally set the system information only for the candidate target cells that individually require the system information (that is, the SI area identifiers are different). That is, the common system information and the system information peculiar to the candidate target cell that needs to be set differently from the common system information may be set. The system information may be System Information Block Type 1 (SIB1), SIB1 and other SIs, or SIs other than SIB1.
[0037]
Further or instead, at least one configuration parameter included in the first configuration may include security information (e.g., masterKeyUpdate). For example, the same security information may be assigned to a plurality of candidate target cells 21 to 23. In this case, the target RAN node 2 sets security information for one of the plurality of candidate target cells that allow (or allow) the handover, and has the same security policy as that one cell. You may omit the security information for the remaining candidate target cells to which you apply. Instead, the target RAN node 2 sets security information in common for a plurality of candidate target cells that are allowed to accept the handover (or allow the handover), and each of the candidate target cells is individually related to security. You do not have to set the information. Further or instead, the target RAN node 2 may set additional security information only for candidate target cells that individually require security information (for example, different security policies). .. That is, information on common security and information on security specific to candidate target cells different from the information on common security may be set. The security-related information may include information on the security key used in the target cell (e.g., nextHopChainingCount) or NAS layer information.
[0038]
Further or instead, at least one setting parameter included in the first setting may include other setting information (e.g., OtherConfig). For example, the same policy (e.g., configuration setup, release) may be assigned to a plurality of candidate target cells 21 to 23 regarding other settings. In this case, the target RAN node 2 sets other setting information for one of the plurality of candidate target cells that are allowed to accept the handover (or allow the handover), and set the same policy as the one cell. Other configuration information for the remaining candidate target cells to apply may be omitted. Instead, the target RAN node 2 sets other setting information in common for a plurality of candidate target cells that are allowed to accept the handover (or allow the handover), and each of the candidate target cells is individually set. You don't have to. Further or instead, the target RAN node 2 sets additional setting information only for candidate target cells that individually require other setting information (for example, different policies regarding other settings). You may. That is, other common setting information and other setting information specific to the candidate target cell different from the common one may be set. The other setting information (eg, OtherConfig) includes, for example, information on data transmission delay (eg, delayBudgetReportingConfig), information on In-Device Coexistence (IDC) (eg, idc-Config), and preferences for transmission power by the wireless terminal. Information (eg, powerPrefIndicationConfig), detailed location information using GNSS (eg, obtainLocationConfig), bandwidth preference by wireless terminal (eg, bw-PreferenceIndicationTimer), overheating in wireless terminal (overheat) It may include information about (eg, overheatingAssistanceConfig) and information about Multimedia Broadcast and Multicast Service (MBMS) (eg, MBMS interest indication).
[0039]
On the other hand, at least one configuration parameter included in each second configuration may relate to at least one configuration of cell group, Medium Access Control (MAC) entity, logical channel set, and random access. good.
[0040]
The setting parameters (e.g., CellGroupConfig) related to the cell group may include the setting parameters of the master cell group (MCG), the secondary cell group (SCG), or both. A cell group contains one MAC entity, a set of logical channels and multiple associated Radio Link Control (RLC) entities. Further, the cell group includes a primary cell (i.e., Special Cell (SpCell)) and one or more secondary cells (secondary cells (SCells)). SpCell is an MCG Primary Cell or an SCG Primary SCG Cell (PSCell). The settings or parameters for SpCell contained in CellGroupConfig are called SpCellConfig.
[0041]
The setting parameters (e.g., mac-CellGroupConfig) related to the MAC entity may include MAC parameters applicable to the entire cell group.
[0042]
The setting parameters (e.g., rlc-BearerToAddModList) related to the set of logical channels may include the settings of MAC Logical Channels and the corresponding RLC entities.
[0043]
Random access configuration parameters may indicate dedicated random access preamble resources.
[0044]
The condition for executing the handover, the condition for the wireless terminal 3 to leave the conditional handover, and the value of the valid timer may be set by the source RAN node 1 or the target RAN node 2. For example, the source RAN node 1 may set them (i.e. conditions for executing the handover, conditions for the wireless terminal 3 to leave the conditional handover, and a value of the valid timer) and transmit them to the wireless terminal 3. In this case, for example, the source RAN node 1 sends a handover request message including these conditions and values ​​set by the source RAN node 1 to the target RAN node 2, and the target RAN node 2 includes them in the handover command. May be good. Alternatively, the source RAN node 1 includes these conditions and values ​​set by the source RAN node 1 in the RRC message including the handover instruction (apart from the RRC message received from the target RAN node or IE), and includes it. It may be transmitted to the wireless terminal 3. Instead, the target RAN node 2 has them (i.e. conditions for performing handover, The condition for the wireless terminal 3 to leave the conditional handover and the value of the valid timer) may be set and transmitted to the source RAN node 1 by, for example, a handover command, and the source RAN node 1 may transmit this to the wireless terminal 3. .. For example, the source RAN node 1 may transfer the handover command (e.g., conditionalMobilityControlInfo IE) received from the target RAN node 2 as it is. Further, the conditions for executing the handover, the conditions for the wireless terminal 3 to leave the conditional handover, and the value of the valid timer may be set by any of the above methods and transmitted to the wireless terminal 3. For example, the conditions for executing the handover, the conditions for the wireless terminal 3 to leave the conditional handover, and the value of the effective timer may be included in the handover command (e.g., conditionalMobilityControlInfo IE).
[0045]
The first setting does not necessarily have to be common to all candidate target cells 21 to 23. For example, the target RAN node 2 sets a first setting common to cells 21 and 22 and a first setting (or equivalent information) applied to the cell 23, and transmits these to the source RAN node 1. You may. In this case, the target RAN node 2 may send them to the source RAN node 1 as two first settings, or additional information corresponding to one first setting and one first setting. May be sent to source RAN node 1. More specifically, the target RAN node 2 indicates that the two first settings are the first setting common to cells 21 and 22 and the first setting applied to cell 23. It may be specified in. Instead, the target RAN node 2 indicates that the target of the first setting is the cells 21 and 22 (or the cell 23 is not the target), and further, the setting information (or setting parameter) for the cell 23. It may contain additional information corresponding to the first setting applied to cell 23, which may be transmitted to the source RAN node 1.
[0046]
As can be understood from the above description, in the present embodiment, the target RAN node 2 is in the handover procedure for handing over the wireless terminal 3 from the source cell 11 to one of the plurality of candidate target cells 21 to 23. , The first setting common to these candidate target cells and the plurality of second settings each associated with each one of these candidate target cells are transmitted to the wireless terminal 3 via the source RAN node 1. .. The first setting common to a plurality of candidate target cells can reduce the data size of the settings related to the plurality of candidate target cells. Therefore, this can reduce the signaling overhead of the RAN node-to-node interface (and air interface) in the handover procedure.
[0047]

The present embodiment provides an improvement for conditional handover of handover-related messages transmitted on the RAN node-to-node interface. The configuration example of the wireless communication network according to the present embodiment may be the same as the example shown in FIG. Further, in the present embodiment, a plurality of candidate target cells may be provided by a plurality of RAN nodes 2.
[0048]
In some implementations, a new HANDOVER REQUEST message (e.g., CONDITIONAL HANDOVER REQUEST message) may be defined for conditional handover. The new HANDOVER REQUEST message is a list of candidate target cells (eg, target cell list) and the information elements contained in the existing HANDOVR REQUEST message that are required to set the target cell for at least CHO (the information element required for setting the target cell for CHO). eg, UE Context information) may be included. When the source RAN node 1 detects that the wireless terminal 3 has performed a conditional handover, one or more target RAN nodes 2 include additional messages including the remaining information elements contained in the existing HANDOVR REQUEST message. You may send it to. If the source RAN node 1 can identify the target cell to which the wireless terminal 3 moves, the source RAN node 1 may send the additional message only to the target RAN node that provides the target cell. The source RAN node 1 may detect the handover execution by receiving a CHO indication (e.g., measurement report, or CHO triggered indication) from the wireless terminal 3. The CHO display from the wireless terminal 3 may include information (e.g., Cell Global ID, PCI, target cell index) indicating the target cell that executes the handover. Instead, the source RAN node 1 may autonomously determine the conditions for the handover execution for CHO, thereby autonomously detecting the handover execution.
[0049]
Alternatively, in some implementations, existing HANDOVR REQUEST messages may be extended (improved) for conditional handover. FIG. 3 shows that the improved format of the HANDOVER REQUEST message may be defined, for example, as in FIG. In the example of FIG. 3, the improved HANDOVER REQUEST message includes a candidate target cell list information element (IE) in addition to the existing target cell ID information element (IE) (e.g., Target Cell Global ID IE). The target cell ID IE (e.g., Target Cell Global ID IE) may indicate one of a plurality of candidate target cells. Specifically, the target cell ID IE (e.g., Target Cell Global ID IE) may indicate the cell having the highest priority (that is, the cell most suitable for the wireless terminal 3 to move). On the other hand, the candidate target cell list IE may show the rest of a plurality of candidate target cells.
[0050]
A new HANDOVER REQUEST message for conditional handover or an enhanced (improved) HANDOVER REQUEST message for conditional handover may include a new Radio Resource Control (RRC) information element (IE). .. The IE may include the conditions for performing the handover (e.g., threshold and TTT) associated with each candidate target cell. Further or instead, the message may include the condition (e.g., offset) that the wireless terminal leaves the conditional handover, and / or both of the values ​​of the validity timer.

The scope of the claims
[Claim 1]
At least one memory and
With at least one processor coupled to the at least one memory,
Equipped with
The at least one processor has a first setting common to the plurality of candidate target cells, each of which is said during the mobility procedure for moving the radio terminal from the source cell to one of the plurality of candidate target cells. A plurality of second settings associated with each one of the plurality of candidate target cells are configured to be transmitted to the radio terminal via a source radio access network node that manages the source cell.
The first setting includes at least one setting parameter for allowing the wireless terminal to access or communicate with one of the plurality of candidate target cells.
Each second setting includes at least one setting parameter to allow the wireless terminal to access or communicate with each candidate target cell.
Target radio access network node.
[Claim 2]
The at least one setting parameter included in the first setting is related to the setting of the wireless bearer.
The target radio access network node according to claim 1.
[Claim 3]
The at least one configuration parameter included in the first configuration includes parameters for at least one of the Packet Data Convergence Protocol (PDCP) and the Service Data Adaptation Protocol (SDAP) for the wireless bearer.
The target radio access network node according to claim 1 or 2.
[Claim 4]
The at least one setting parameter included in the first setting includes system information.
The target radio access network node according to any one of claims 1 to 3.
[Claim 5]
The at least one configuration parameter included in each second configuration relates to at least one configuration of cell group, logical channel, and random access.
The target radio access network node according to any one of claims 1 to 4.
[Claim 6]
The at least one configuration parameter included in each second configuration includes parameters for Medium Access Control (MAC) entities.
The target radio access network node according to any one of claims 1 to 5.
[Claim 7]
The mobility procedure includes at least one of a handover procedure, a secondary node change (SN Change) procedure in Dual Connectivity (DC), and a primary cell change (PSCell Change) procedure in a secondary cell group.
The target radio access network node according to any one of claims 1 to 6.
[Claim 8]
The mobility procedure includes a handover procedure.
The at least one processor is configured to include the first setting and the plurality of second settings in a handover approval message sent from the target radio access network node to the source radio access network node.
The target radio access network node according to any one of claims 1 to 7.
[Claim 9]
The mobility procedure is a conditional mobility procedure,
The target radio access network node according to any one of claims 1 to 8.
[Claim 10]
It is a wireless terminal
At least one memory and
With at least one processor coupled to the at least one memory,
Equipped with
Each of the at least one processor has a first setting common to the plurality of candidate target cells during the mobility procedure for moving the radio terminal from the source cell to one of the plurality of candidate target cells. A plurality of second settings associated with each one of the plurality of candidate target cells, and a source radio access network node that manages the source cell from a target radio access network node that manages the plurality of candidate target cells. Configured to receive via
The first setting includes at least one setting parameter for allowing the wireless terminal to access or communicate with one of the plurality of candidate target cells.
Each second setting includes at least one setting parameter to allow the wireless terminal to access or communicate with each candidate target cell.
Wireless terminal.
[Claim 11]
The at least one setting parameter included in the first setting is related to the setting of the wireless bearer.
The wireless terminal according to claim 10.
[Claim 12]
The at least one configuration parameter included in the first configuration includes parameters for at least one of the Packet Data Convergence Protocol (PDCP) and the Service Data Adaptation Protocol (SDAP) for the wireless bearer.
The wireless terminal according to claim 10 or 11.
[Claim 13]
The at least one setting parameter included in the first setting includes system information.
The wireless terminal according to any one of claims 10 to 12.
[Claim 14]
The at least one configuration parameter included in each second configuration relates to at least one configuration of cell group, logical channel, and random access.
The wireless terminal according to any one of claims 10 to 13.
[Claim 15]
The at least one configuration parameter included in each second configuration includes parameters for Medium Access Control (MAC) entities.
The wireless terminal according to any one of claims 10 to 14.
[Claim 16]
The mobility procedure is a conditional mobility procedure,
The wireless terminal according to any one of claims 10 to 15.
[Claim 17]
During the mobility procedure for moving the wireless terminal from the source cell to one of the plurality of candidate target cells, the first setting common to the plurality of candidate target cells and each of the plurality of candidate target cells, respectively. It comprises transmitting a plurality of second settings associated with one to the radio terminal via a source radio access network node that manages the source cell.
The first setting includes at least one setting parameter for allowing the wireless terminal to access or communicate with one of the plurality of candidate target cells.
Each second setting includes at least one setting parameter to allow the wireless terminal to access or communicate with each candidate target cell.
The method for the target radio access network node.
[Claim 18]
It is a method for wireless terminals,
During the mobility procedure for moving the radio terminal from the source cell to one of the plurality of candidate target cells, a first setting common to the plurality of candidate target cells and each of the plurality of candidate target cells. It comprises receiving a plurality of second settings, each associated with one, from a target radio access network node that manages the plurality of candidate target cells via a source radio access network node that manages the source cell. ,
The first setting includes at least one setting parameter for allowing the wireless terminal to access or communicate with one of the plurality of candidate target cells.
Each second setting includes at least one setting parameter to allow the wireless terminal to access or communicate with each candidate target cell.
Method.
[Claim 19]
A non-temporary computer-readable medium containing a program that allows a computer to perform methods for a target radio access network node.
The method comprises a first setting common to the plurality of candidate target cells and each of the plurality of candidates during a mobility procedure for moving the wireless terminal from the source cell to one of the plurality of candidate target cells. It comprises transmitting a plurality of second settings associated with each one of the target cells to the radio terminal via a source radio access network node that manages the source cell.
The first setting includes at least one setting parameter for allowing the wireless terminal to access or communicate with one of the plurality of candidate target cells.
Each second setting includes at least one setting parameter to allow the wireless terminal to access or communicate with each candidate target cell.
Non-temporary computer-readable medium.
[Claim 20]
A non-temporary computer-readable medium containing a program that allows a computer to perform methods for wireless terminals.
The method comprises a first setting common to the plurality of candidate target cells and each of the plurality of candidate target cells during a mobility procedure for moving the radio terminal from the source cell to one of the plurality of candidate target cells. A plurality of second settings associated with each one of the candidate target cells are received from the target radio access network node that manages the plurality of candidate target cells via the source radio access network node that manages the source cell. Be prepared to do
The first setting includes at least one setting parameter for allowing the wireless terminal to access or communicate with one of the plurality of candidate target cells.
Each second setting includes at least one setting parameter to allow the wireless terminal to access or communicate with each candidate target cell.
Non-temporary computer-readable medium.