WO2023066188A1

WO2023066188A1 - Method for cell handover and user equipment

Info

Publication number: WO2023066188A1
Application number: PCT/CN2022/125624
Authority: WO
Inventors: 肖芳英; 刘仁茂; 山田升平
Original assignee: 夏普株式会社; 肖芳英
Priority date: 2021-10-19
Filing date: 2022-10-17
Publication date: 2023-04-27
Also published as: CN115996359A

Abstract

The present invention provides a method for cell handover executed by a source base station, comprising: when a source base station sends a cell handover request message to a target base station, determining whether the target base station supports an MBS session, on the basis of interface parameter information of a network interface established between the source base station and the target base station, the cell handover request message being used to request the target base station to prepare an RRC resource for user equipment; if the target base station does not support an MBS session, not adding RRC configuration information associated with an MBS session configured by the source base station for the user equipment to the cell handover request message; changing the RRC configuration information associated with the MBS session to RRC configuration information associated with a PDU session supported by the target base station, adding the changed RRC configuration information to the cell handover request message, and sending same to the target base station.

Description

Method for Cell Handover and User Equipment

technical field

The present invention relates to the field of wireless communication technology, and more specifically, the present invention relates to a method for performing cell handover performed by a source user equipment, a method for performing cell handover performed by a source base station, and user equipment.

Background technique

A research project SI (see SP-190625 for details) on 5G Multicast Broadcast Service Architecture Improvement has been approved and is in progress. One of the goals of this SI (referred to as Goal A) is to support generic MBS services in 5GS, identified use cases that could benefit from this feature include (but are not limited to) public safety, V2X applications, transparent IPv4/IPv6 multicast transport , IPTV, wireless software transmission, group communication and IoT applications. Correspondingly, at the 3rd Generation Partnership Project (3rd Generation Partnership Project: 3GPP) RAN#86 plenary meeting, Huawei proposed the work item of NR Multicast and Broadcast Service (NR MBS) (see non-patent literature: RP-193248 : New WID: NR Multicast and Broadcast Service) was approved. This work item is intended to provide support for Objective A in the RAN.

The present invention discusses related issues involved in RAN achieving the above working goals.

Contents of the invention

The purpose of the present invention is to provide a cell switching method that can ensure the continuity of MBS services and reduce data loss.

In order to solve the above problems, the present invention provides a method for cell handover performed by a source base station, including: when the source base station sends the cell handover request message to the target base station, based on the source base station and the target base station The interface parameter information of the network interface established between the base stations is used to determine whether the target base station supports MBS sessions, and the cell handover request message is used to request the target base station to prepare RRC resources for the user equipment; if the target base station does not support MBS session, then do not carry the RRC configuration information related to the MBS session configured by the source base station for the user equipment in the cell handover request message; and change the RRC configuration information related to the MBS session to be related to the target The RRC configuration information related to the PDU session supported by the base station, and the changed RRC configuration information is carried in the cell handover request message and sent to the target base station.

According to another aspect of the present invention, there is also provided a method for cell handover performed by user equipment, including: receiving from a source base station a first RRC reconfiguration message for the user equipment generated by the source base station, the The first RRC reconfiguration message carries the second RRC reconfiguration message generated by the target base station, and the first RRC reconfiguration message also includes the difference between the MRB for the multicast broadcast service session, that is, the MBS session, and the DRB for the PDU session and based on the second RRC reconfiguration message and/or the mapping relationship information, reconfigure the RRC configuration related to the MBS session of the user equipment into a PDU supported by the target base station For session-related RRC configuration, the second RRC reconfiguration message is generated by the target base station in response to a cell switching request message sent by the source base station and sent to the source base station.

According to another aspect of the present invention, there is also provided a user equipment, including: a processor; and a memory storing instructions, wherein, when the instructions are executed by the processor, the instructions executed by the user equipment as described above are executed. method.

Invention effect

According to the present invention, when the target base station does not support the MBS session, the continuity of the MBS service can be guaranteed and data loss can be reduced.

Description of drawings

The above and other features of the present invention will become more apparent from the following detailed description in conjunction with the accompanying drawings, in which:

(a) to (c) of FIG. 1 are schematic diagrams showing specific configurations of radio bearers for receiving MBS services according to the present invention.

Fig. 2 is a flow chart of a method for cell handover performed by a base station according to an embodiment of the present invention.

Fig. 3 is a flowchart of a method for cell handover performed by a user equipment according to an embodiment of the present invention.

Fig. 4 is a flowchart of a process of parsing out a second RRC reconfiguration message in a method for cell handover performed by a user equipment according to an embodiment of the present invention.

Fig. 5 is a flow chart of a specific example of a reconfiguration process in a method for cell handover performed by a user equipment according to an embodiment of the present invention.

Fig. 6 is a structural block diagram of a user equipment for performing a method for performing cell handover according to an embodiment of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the present invention should not be limited to the specific embodiments described below. In addition, for the sake of brevity, detailed descriptions of known technologies that are not directly related to the present invention are omitted to prevent confusion to the understanding of the present invention.

Some terms involved in the present invention are described below, and the specific meanings of the terms can be found in the latest relevant documents of 3GPP, such as TS38.300, TS38.321, TS38.323, TS38.331 and so on. In addition, the embodiments of the present invention are not limited to broadcast/multicast services, and can also be applied to other application scenarios.

UE: User Equipment, user equipment.

RRC: Radio Resource Control, radio resource control.

RRC_CONNECTED: RRC connected state.

RRC_INACTIVE: RRC is inactive.

RRC_IDLE: RRC idle state.

RAN: Radio Access Network, wireless access network.

NR: New RAT, new radio access technology.

MBMS: Multimedia Broadcast/Multicast Service, multimedia broadcast multicast service.

MBS: Multicast/Broadcast Services, multicast/broadcast services.

PDCP: Packet Data Convergence Protocol, packet data convergence protocol.

RLC: Radio Link Control, wireless link control.

SDU: Service Data Unit, service data unit. The data packet that this layer receives or delivers from the upper layer is called SDU.

PDU: Protocol Data Unit, protocol data unit. The data packet that this layer receives or delivers from the lower layer is called PDU. For example, a PDCP data PDU is a data packet obtained by adding a PDCP header to a PDCP SDU.

RB: Radio Bearer, radio bearer.

MRB: MBS radio bearer, that is, a radio bearer configured for MBS transmission (Aradio bearer that is configured for MBS delivery).

MCCH: Multicast Control Channel, multicast control channel. The MBS-MCCH is used to transmit control information related to receiving MBS services.

SC-MCCH: Single Cell Multicast Control Channel, single cell multicast control channel.

TMGI: Temporary Mobile Group Identity, temporary mobile group identity.

PLMN: Public Land Mobile Network, public land mobile network.

RNTI: Radio Network Temporary Identifier, wireless network temporary identifier.

PTM: Point to Multipoint, point to multipoint, a delivery method of MBS business. In the PTM delivery mode, the RAN node delivers a single copy of MBS data packets over radio to a set of UEs via radio (a RAN node delivers a single copy of MBS data packets over radio to a set of UEs).

PTP: Point to Point, point to point, a delivery method of MBS business. In the PTP delivery method, the RAN node delivers copies of multiple MBS data packets to each UE via radio (a RAN node delivers separate copies of MBS data packet over radio to individual UE).

LTE SC-PTM: LTE Single Cell Point to Multipoint, long term evolution single cell point to multipoint.

MTCH: Multicast Traffic Channel, multicast traffic channel. MBS multicast (or multicast communication service) means that the same service and the same specific content are simultaneously provided to a group of specific UEs. A multicast traffic is delivered to the UE using the multicast session.

A UE in RRC_CONNECTED can use PTP and/or PTM to receive a multicast communication service.

G-RNTI: Group RNTI, group RNTI, used to scramble the scheduling and transmission of MTCH (used to scramble the scheduling and transmission of MTCH). NR MBS supports 1-1 mapping between G-RNTI and MBS session (One-to-one mapping between G-RNTI and MBS session is supported in NR MBS).

Associated PDU session: a PDU session associated to a multicast session (also called an MBS session), which is used for the 5GC unicast MBS traffic delivery method (5GC Individual MBS traffic delivery method) of the 5G core network and for communicating with users Signaling related to participating in a multicast session such as join and leave requests.

Associated QoS flow: The unicast QoS flow belonging to the associated PDU session is used for the 5GC unicast MBS traffic delivery method, and the associated QoS flow is mapped from the multicast QoS flow in the multicast MBS session.

In the present invention, network, base station and RAN can be used interchangeably, and the network can be a long-term evolution LTE network, an NR network, an enhanced long-term evolution eLTE network, or other networks defined in subsequent evolution versions of 3GPP.

In LTE SC-PTM, the base station broadcasts the MBMS service and its scheduling information supported by the system information and the message transmitted on the SC-MCCH channel. The radio bearer configuration information used to transmit the MBMS service is predefined . The UE can know the MBMS service that the current cell or base station supports or is in progress by receiving the corresponding system information and the message transmitted on the SC-MCCH. When the UE needs to receive a certain MBMS service, it establishes a radio bearer according to predefined parameters and receives data. In this case, UE can receive MBMS service without establishing RRC connection.

In NR MBS, some MBS services (services) can also be scheduled in a manner similar to SC-PTM, so that UEs in the RRC idle state and RRC inactive state can also receive the MBS services. However, there are another part of MBS services that require the UE to establish an RRC connection with the base station, and then the base station configures for the UE through dedicated RRC signaling (also called a dedicated RRC message), and the radio bearer for receiving these MBS services can also be configured by the base station through dedicated RRC signaling. The order is UE configuration. (a) to (c) of FIG. 1 are schematic diagrams showing specific configurations of radio bearers for receiving MBS services. The radio bearer may be an MRB configured with only PTM transmission (as shown in (a) of Figure 1), or a separate MRB (split MRB) configured with PTM and PTP at the same time (as shown in (b) of Figure 1 ) Or only MRBs for PTP transmission are configured (as shown in (c) of FIG. 1 ). It should be noted that (a)-(c) of FIG. 1 only show the PDCP entity and RLC entity corresponding to the bearer and the relationship between them. In the downlink direction, the PDCP PDU encapsulated by the PDCP entity is delivered to the RLC entity.

For the MBS service that the UE needs to establish an RRC connection with the base station, when the UE switches from a base station that supports MBS (source base station) to a base station that does not support MBS (target base station), how to ensure the continuity of the MBS service and reduce data loss is the key issues that need resolving.

In the existing handover based on the Xn interface, the source base station (or source NG-RAN node) sends a handover request (HANDOVER REQUEST) message to the target base station (or target NG-RAN node) to establish the necessary H. The handover request message includes an RRC Context field, and the field is used to include a HandoverPreparationInformation message. In the handover preparation, the HandoverPreparationInformation message is used to transfer the NR RRC information used by the target base station during the handover preparation (is used to transfer the NR RRC information used by the target gNB). The HandoverPreparationInformation message contains the RRCReconfiguration configuration completely generated by the source base station (Contains the RRCReconfiguration configuration as generated entirely by the source gNB). The target base station sends a handover request confirmation (HANDOVER REQUEST ACKNOWLEDGE) message to the source base station as a response message, which includes the transparent container (Target NG-RAN node) from the target base station (ie, the target NG-RAN node) to the source base station (ie, the source NG-RAN node). to Source NG-RAN node Transparent Container), the field is used to carry the HandoverCommand message, and the HandoverCommand message carries the RRCReconfiguration (RRC reconfiguration) message generated by the target base station, and the source base station receives the handover request confirmation message Then forward the RRCReconfiguration message generated by the target base station to the UE. The handover request message is sent by the source base station to the target base station to request to prepare resources for handover; the handover request confirmation message is sent by the target base station to notify the source base station of the prepared resources on the target. When a UE in the RRC connected state is handed over from a source base station supporting MBS to a target base station not supporting MBS, since the target base station cannot recognize MBS-related configuration information, the RRCReconfiguration message generated by the target base station will contain a fullConfig field, the fullConfig field is used to indicate that the full configuration options are applied to the RRCReconfiguration message. In a full configuration, the UE will release all DRBs and MRBs, which will fail to achieve service continuity and/or cause data loss.

As shown in FIG. 2, at S202, the source base station may determine whether the target base station supports MBS sessions based on the interface parameter information of the network interface established between the source base station and the target base station, and the cell handover request message is used to request the target base station to be The user equipment prepares RRC resources. This network interface is, for example, an Xn interface.

If the target base station does not support the MBS session, then at S204, the source base station does not carry the RRC configuration information related to the MBS session configured by the source base station for the user equipment in the cell handover request message.

In S206, the source base station may change the RRC configuration information related to the MBS session to the RRC configuration information related to the PDU session supported by the target base station, and send the changed RRC configuration information to the target base station in a cell handover request message . As an example, the source base station may modify the information of the MRB configured for the MBS session to the information of the DRB mapped to the MRB, and send it to the target base station in the cell handover request message.

After receiving the cell switching request message, the target base station may generate second RRC reconfiguration information based on the RRC reconfiguration information carried in the cell switching request message, and carry the second RRC reconfiguration information in the switching response message as the response message. Sent to the source base station in a request confirmation message. In an example, when receiving the handover request confirmation message sent by the target base station in response to the cell handover request message, the source base station may generate a user equipment handover request based on the second RRC reconfiguration information carried in the handover request confirmation message. and send the first RRC reconfiguration information to the target base station, and send the generated first RRC reconfiguration information to the user equipment.

If the target base station supports the MBS session, the source base station may send a cell handover request message carrying RRC configuration information related to the MBS session to the target base station at S208. When receiving the handover request acknowledgment message from the target base station, the second RRC configuration message carried in the handover request acknowledgment message may be directly sent to the UE instead of generating the first RRC reconfiguration message.

Embodiments of operations performed by the source base station and the target base station are described below.

When the target base station does not support MBS, in order to achieve service continuity and/or reduce data loss, the source base station should not provide MBS configuration information, such as MBS session information, in the RRCReconfiguration configuration included in the HandoverPreparationInformation message provided to the target base station and MRB configuration information, etc.

In one embodiment, the source base station includes the PDU session-related information associated with the MBS session in the handover request message, for example, in the PDU Session Resources To Be Setup List field to be established, and the field includes Information related to PDU session resources, such as including PDU session ID (identifying a PDU session for UE), PDU session type, list of QoS flows to be established, etc., the list of QoS flows to be established includes related Information, the relevant information of the QoS flow may include a QoS flow identifier (identifying a QoS flow in a PDU session), QoS parameters of the QoS flow level, and the like. In the RRCReconfiguration configuration provided to the target base station, the configuration information related to the MBS session is deleted, for example, mrb-ToAddModList (adding and modifying the MRB list) and/or related information such as RLC-BearerConfig associated to the MRB is deleted. The target base station configures the corresponding DRB for the PDU session associated with the MBS session included in the PDU session resource list to be established, and passes the configured DRB information through the RRCReconfiguration message generated by the target base station (referred to as the second RRCReconfiguration message or In the second RRC reconfiguration message), it is forwarded to the UE via the source base station. Optionally, when the source base station receives the handover request confirmation message, it generates an RRCReconfiguration message (called the first RRCReconfiguration message or the first RRC reconfiguration message), and the first RRC reconfiguration message includes information for carrying the second RRC The field mbsToNonMBSNode of the reconfiguration message (this field is used to indicate that the cell handover to be performed is from the base station that supports MBS sessions to the base station that does not support MBS sessions) and the field mrb-ToReleaseList that is used to indicate the release of MRBs (that is, the MRB information), the mrb-ToReleaseList contains the MRB-Identities of all MRBs that need to be released. It can be stipulated that mbsToNonMBSNode is the condition for configuring mrb-ToReleaseList, that is, only when mbsToNonMBSNode appears, can mrb-ToReleaseList be configured, and vice versa.

In one embodiment, the source base station includes the PDU session-related information associated with the MBS session in the handover request message, for example, in the PDU Session Resources To Be Setup List field to be established, and the field includes Information related to PDU session resources, such as including PDU session ID (identifying a PDU session for UE), PDU session type, list of QoS flows to be established, mapping of source base station QoS flows to DRB, etc., the list of QoS flows to be established contains the relevant information of the QoS flow to be established, and the relevant information of the QoS flow may include a QoS flow identifier (identifying a QoS flow in a PDU session), QoS parameters of the QoS flow level, and the like. In the RRCReconfiguration configuration provided to the target base station, delete the configuration information related to the MBS session and/or modify the configuration information related to the MRB to the corresponding DRB, so that the target base station can use the DRB as the DRB that the source base station has configured for the UE to deal with. For example, assign a DRB ID (that is, drb-Identity, DRB identification) to each MRB, modify the MRB ID (that is, mrb-Identity, MRB identification) to the corresponding DRB ID; and/or modify the MBS session identification associated with the MRB The PDU session identifier associated with the MBS session; and/or for the MRB only associated with the PTM RLC, modify the MRB ID to the DRB ID and/or delete the corresponding G-RNTI and/or delete the PTM transmission indicator (that is, the The above indication indicates that the corresponding RLC entity is configured for PTM transmission); and/or for the MRBs of PTM RLC and PTP RLC associated at the same time, delete the configuration information related to PTM RLC and/or delete the corresponding G-RNTI; and/or Or store the mapping relationship between the MRB and the DRB. For a PDU session associated with an MBS session, its corresponding source base station QoS flow-to-DRB mapping refers to the associated QoS flow-to-DRB mapping of the associated PDU session. The target base station sends a handover request confirmation message to the source base station as a response message. Wherein, the RRCReconfiguration configuration message provided by the source base station to the target base station is included in the HandoverPreparationInformation message carried in the handover request message.

The method for performing cell handover performed by the user equipment according to the embodiment of the present invention will be described below with reference to FIGS. 3 to 5 .

As shown in Fig. 3, at S302, the user equipment receives from the source base station a first RRC reconfiguration message for the user equipment generated by the source base station. The first RRC reconfiguration message carries the second RRC reconfiguration message generated by the target base station, and the first RRC reconfiguration message may also include the MRB for the multicast broadcast service session, that is, the MBS session, and the DRB for the PDU session. Mapping relationship information. As an example, the mapping relationship information may be the mapping between the DRB ID and the MRB ID, or the mapping between the MBS session ID and the PDU session ID, or the mapping between the DRB ID and the MRB ID and the MBS session ID. Mapping between identifiers and PDU session identifiers. As mentioned above, the second RRC reconfiguration message is generated by the target base station in response to the cell switching request message sent by the source base station and sent to the source base station.

At S304, the user equipment may reconfigure the RRC configuration related to the MBS session of the user equipment to the RRC configuration related to the PDU session supported by the target base station based on the second RRC reconfiguration message and/or the mapping relationship information.

In an embodiment of the present invention, the reconfiguration operation may include at least one of the following: based on the second RRC reconfiguration message and/or the mapping relationship information, configuring the RRC related to the MBS session of the user equipment , reconfiguring the RRC configuration related to the PDU session supported by the target base station includes at least one of the following: based on the mapping relationship information, replacing the MRB identifier for the MBS session with the DRB identifier mapped to the MRB; The mapping relationship information associates the DRB to which the MRB is mapped to the SDAP entity associated with the MRB; based on the mapping relationship information, modifies the MBS session identifier to the PDU session identifier of the PDU session associated to the MBS session; upward Instruct the layer to release the user plane resources of the MBS session; instruct the upper layer to establish the user plane resource of the PDU session; instruct the upper layer to modify the user plane resource related to the MBS session into a PDU associated with the DRB mapped to the MRB for the MBS session The user plane resource of the session; for the MRB configured with the PTM RLC entity, instruct the PTM RLC entity to release the PTM transmission indication flag.

The user equipment may perform reconfiguration based on the mapping relationship information. For example, for each DRB indicated by the mapping relationship information, at least one of the following may be performed: if the MRB mapped to the DRB is configured with a PTM RLC entity and a PTP RLC release the PTM RLC bearer corresponding to the PTM RLC entity; if the MRB mapped to the DRB is a PTM MRB that is only configured with a PTM RLC entity, release the PTM transmission indicator of the PTM RLC entity; if mapped to If the MRB of the DRB is a PTM MRB configured only with a PTM RLC entity or a PTP MRB configured only with a PTP RLC entity, then the PTM RLC or PTP RLC entity associated with the MRB mapped to the DRB is associated with the DRB.

For an MRB that is not mapped to any DRB determined based on the mapping relationship between the MRB and the DRB, the user equipment may release information related to the MRB.

In another example, when the target base station does not support the MBS session, the source base station may carry a field in the first RRC reconfiguration message indicating that the target base station does not support the MBS session. In this example, when determining that the first RRC reconfiguration includes this field, the user equipment may parse out the second RRC reconfiguration and perform reconfiguration. This example will be described below with reference to FIG. 4 .

At S402, the user equipment may, when receiving the first RRC reconfiguration message, determine whether the first RRC reconfiguration message includes a field for indicating that the target base station does not support the MBS session.

If the first RRC reconfiguration message includes this field, the user equipment may parse the field at S404, and parse out the second RRC reconfiguration message from the field. However, the user equipment may perform a reconfiguration operation. If the first RRC reconfiguration does not include the above fields, no further operations may be performed.

The second RRC reconfiguration message may include DRB change information, and the DRB change information includes information indicating the DRB that needs to be changed by the target base station. The "change" mentioned here may include various change operations such as deletion, modification, addition, and release. Correspondingly, the DRB change information may include DRB modification information indicating the information of the DRB to be modified, may also include the information of the DRB to be added indicating the information of the DRB to be added, and may also include the requirements of the information indicating the DRB to be released. Release DRB information. Such information may be in the form of a list, for example, a list of DRB identities of corresponding DRBs. At this time, reconfiguration may be performed according to the flow in FIG. 5 . Fig. 5 is a flow chart of a specific example of a reconfiguration process in a method for cell handover performed by a user equipment according to an embodiment of the present invention.

In S502-S504, the user equipment may determine, for each DRB indicated by the DRB change information, whether the DRB is included in the existing RRC configuration of the user equipment.

If the DRB is not included in the existing RRC configuration of the user equipment, the user equipment may determine whether there is an MRB mapped to the DRB at S506 based on the mapping relationship information;

If there is no MRB mapped to the DRB, the user equipment may establish the DRB at S506. If there is an MRB mapped to the DRB, the user equipment may reconfigure the MRB mapped to the DRB at S508.

As mentioned above, the DRB change information includes the newly added and modified DRB list, and the newly added and modified DRB list includes the information of the newly added or modified DRB requested by the target base station. At this time, the reconfiguration of the MRB mapped to the DRB described in S508 above includes performing at least one of the following if the DRB is included in the newly added modified DRB list: if the DRB mapped to the DRB The MRB is associated with the PTM RLC entity, and then instructs the PTM RLC entity to release the PTM transmission indication identifier and/or the corresponding group wireless network temporary identifier; if the RRC reconfiguration information includes a PDCP re-establishment indication, re-establish the MRB mapped to the DRB If the RRC reconfiguration information includes a PDCP recovery indication, make the PDCP entity of the MRB mapped to the DRB perform data recovery; if the RRC reconfiguration information includes PDCP reconfiguration information, then according to the PDCP reconfiguration Configuration information, reconfiguring the PDCP entity of the MRB mapped to the DRB; if the RRC reconfiguration information includes SDAP reconfiguration information, reconfiguring the SDAP entity of the MRB mapped to the DRB according to the SDAP configuration information; For the MBS session corresponding to the MRB mapped to the DRB, modify the MBS session identifier to the PDU session identifier corresponding to the DRB; release or discard the MRB identifier in the existing RRC configuration of the user equipment.

The DRB change information may also include a list of DRBs to be released, and the list of DRBs to be released includes the information of the DRBs required to be released by the target base station. At this time, the operation in S508 can be performed as follows. If the DRB is included in the list of DRBs to be released, release the MRB identifier of the PDCP entity of the MRB mapped to the DRB. If the MRB mapped to the DRB is configured with a corresponding SDAP entity, the user equipment may also instruct the SDAP entity to release the MRB mapped to the DRB.

The following describes an embodiment of the operation when the UE performs handover

In an embodiment, the UE receives a first RRCReconfiguration message (first RRC reconfiguration message) from the base station (ie, the source base station), and the first RRCReconfiguration message may include MRB change information. The "change" mentioned here may include various change operations such as deletion, modification, addition, and release. The MRB change information may include the information about the MRB to be released, and may also include the newly added or modified MRB information to be added or modified. These information may be in the form of a list including MRB identification. If the message contains mrb-ToReleaseList (to release MRB list information), then for each mrb-Identity (MRB identity) contained in mrb-ToReleaseList, if the mrb-Identity is part of the current UE configuration, then Release the corresponding PDCP entity and mrb-Identity, and/or indicate to the upper layer that this MRB is released and the field tmgi of the released MRB. Wherein, the field tmgi is used to indicate the MBS session associated with the bearer, and its value is TMGI.

In one embodiment, the UE receives the RRCReconfiguration message from the base station (namely the source base station), if the RRCReconfiguration message contains the reconfigurationWithSync field and the target base station does not support MBS, for each currently configured mrb-Identity, release the corresponding PDCP entity and mrb-Identity, and/or indicate to the upper layer that this MRB is released and the tmgi of the released MRB, and/or release the RLC entity or RLC bearer associated with the MRB. Wherein, the reconfigurationWithSync field includes related parameters of synchronous reconfiguration to the target SpCell, and tmgi is used to indicate the bearer associated MBS session. The "target base station does not support MBS" can be replaced with "the RRCReconfiguration message received by the UE containing the reconfigurationWithSync field does not contain any MRB configuration" or "the received RRCReconfiguration message does not contain a field indicating that the base station supports MBS mbsSupporting". Optionally, during the handover process, if the target base station supports MBS, an mbsSupporting (MBS support) field is included in the RRCReconfiguration message generated by the target base station. Optionally, a field keepMBS is included in the RRCReconfiguration message to instruct the UE to keep the configured MBS. If the received RRCReconfiguration message does not contain the field, for each mrb-Identity or MRB currently configured, if the mrb-Identity or MRB is not included in the received RRCReconfiguration message, then release the corresponding PDCP entity and mrb-Identity, and/or indicate to the upper layer that this MRB is released and the tmgi of the released MRB, and/or release the associated MRB RLC entity or RLC bearer. In addition, the specific operation of releasing the RLC bearer may include releasing the RLC entity and releasing the corresponding logical channel.

In the present invention, the tmgi indicating to the upper layers to release the user plane resources of the MBS session and the released MRBs can be used alternatively, and the obtained embodiments are also within the protection scope of the present invention.

In one embodiment, the UE reconfigures each MRB mapped to the DRB according to the configuration information contained in the second RRCReconfiguration message, for example, replacing the mrb-Identity of the MRB with the drb-Identity of the DRB to which it is mapped, And/or modify the MBS session identifier associated with the MBS to the PDU session identifier associated with the MBS session, and/or associate the SDAP entity (or PDCP entity or RLC entity) associated with the MRB mapped to the DRB to the DRB ( It can also be expressed as associating the DRB with the SDAP entity (or PDCP entity or RLC entity) associated with the MRB mapped to the DRB, and/or instructing the upper layer to release the user plane resources of the MBS session, and/or instructing the upper layer Establish the user plane resources of the PDU session, and/or indicate to the upper layer to change the user plane resources of the MBS session to the user plane resources of the associated PDU session, and/or release the PTM RLC for the detached MRB associated with both PTM transmission and PTP transmission The entity (or releases the PTM RLC bearer), for the MRB configured with only PTM transmission, releases the PTM transmission indicator. The specific description is as follows:

The UE receives the first RRCReconfiguration message from the base station (that is, the source base station), and the first RRCReconfiguration message includes the mapping relationship between the MBS session and the associated PDU session and/or the MRB ID (that is, MRB-Identity) and the DRB ID (that is, the DRB - the mrbToDrbMappingList field of the mapping relationship between Identity), the first RRCReconfiguration message further includes the mbsToPduRRCReconfig field, and the field is used to carry the second RRCReconfiguration message generated by the target base station.

For each drb-Identity contained in the drb-ToAddModList (newly added and modified DRB list) contained in the second RRCReconfiguration message, if the drb-Identity is not part of the current UE configuration and is not mapped to an MRB (ie drb- Identity is not included in the mrbToDrbMappingList field), then the corresponding DRB is established (according to the method for establishing a DRB defined in 3GPP technical specification TS38.331).

For each drrb-Identity included in the drb-ToAddModList in the second RRCReconfiguration message, if the drb-Identity is not part of the current UE configuration, but the drb-Identity is mapped to an MRB (that is, the drb-Idntity is included in the mrbToDrbMappingList field), perform at least one of the following actions (1-8):

1) If the MRB mapped to the DRB is a separate MRB (that is, a PTM RLC and a PTP RLC are associated at the same time), then release the PTM RLC bearer, including releasing the RLC entity according to the operation defined in Section 5.1.3 of TS38.322 And release the corresponding logical channel.

2) If the MRB mapped to the DRB is associated (that is, only associated) with a PTM RLC entity, release the PTM transmission indicator and/or the corresponding G-RNTI or instruct the PTM RLC entity (or PTM RLC bearer) to release the PTM transmission indicator and /or the corresponding G-RNTI. The purpose of this operation is to make the UE no longer monitor the PTM transmission of the MBS.

3) If reestablishPDCP is set, perform at least one of (1a-1f):

(1a) If the PDCP entity of the MRB mapped to this DRB is not configured with cipheringDisabled, use the encryption algorithm associated with the primary key (K _eNB /K _gNB ) or secondary key (SK _gNB /SK _eNB ) and the K _UPenc cipher The key configures the PDCP entity, as indicated in keyToUse, that is, the encryption configuration will be applied to all subsequent PDCP PDUs received and sent by the terminal;

(1b) If the PDCP entity of the MRB mapped to this DRB is configured with integrityProtection, configure the integrity protection algorithm of the PDCP entity according to securityConfig, and apply the primary key (K _gNB ) or secondary key (SK _gNB ) indicated in keyToUse the associated K _UPint key;

(1c) If drb-ContinueROHC is included in pdcp-Config, it indicates that the lower layer is configured with drb-ContinueROHC;

(1d) If drb-ContinueEHC-DL is included in pdcp-Config, it indicates that the lower layer is configured with drb-ContinueEHC-DL;

(1e) If drb-ContinueEHC-UL is included in pdcp-Config, it indicates that the lower layer is configured with drb-ContinueEHC-UL; it can be stipulated that this configuration is not used for the DRB to which the MRB is mapped.

(1f) Rebuild the PDCP entity of the MRB mapped to this DRB. For specific operations, see section 5.1.2 of 3GPP technical specification TS 38.323. When the encryption algorithm or key is changed and/or the integrity protection algorithm or key is changed, the base station will instruct the UE to re-establish the PDCP entity.

4) If recoverPDCP is set, trigger the PDCP entity of the MRB mapped to this DRB to perform data recovery. For specific operations, see 3GPP technical specification TS 38.323. Note, this operation step may not be applied to the DRB corresponding to the associated PDU. When the encryption algorithm or key has not changed and/or the integrity protection algorithm or key has not changed, etc., in order to reduce data loss, it is necessary to retransmit the data that has been sent but has not been confirmed to be sent successfully, and the PDCP entity can be instructed to perform data recovery .

5) If it contains pdcp-Config, reconfigure the PDCP entity of the MRB mapped to this DRB according to the received pdcp-Config. When the target base station cannot support or needs to modify the configuration of some parameters in the current pdcp-Config, it can send pdcp-Config containing new PDCP entity configuration information to reconfigure the PDCP entity.

6) If sdap-Config is included, do at least one of the following (4a-4b):

(4a) If the SDAP entity of the received PDU session has not been established before receiving the reconfiguration message, indicate the user plane resource of the established PDU session to the upper layer.

(4b) According to the received sdap-Config, reconfigure the SDAP entity of the MRB mapped to this DRB, specifically according to the operation defined in TS37.324. When the target base station cannot support or needs to modify the configuration of some parameters in the current sdap-Config, it can send the sdap-Config containing new SDAP entity configuration information to reconfigure the SDAP entity.

7) If the SDAP entity associated with the MRB mapped to this DRB is associated with an MBS session, set the pdu-session to the PDU-SessionID of the associated PDU session, and/or release the mbs-Session (or MBS-SessionID), and/or Instruct the upper layer to release the user plane resources of this mbs-Session. The purpose of this operation is to modify the MBS session ID to the associated PDU session ID.

8) Release/discard MRB-Identity.

It should be noted that an embodiment obtained by exchanging the execution order of the above operations is also within the protection scope of the present invention. In addition, operations 1 and 2 may not be included in the above description for radio bearer configuration. Operation 1 can be described in the related description of RLC bearer release, and operation 2 can be described in the related description of RLC bearer addition/modification.

For the DRB corresponding to each drb-Identity included in mrbToDrbMappingList, perform at least one of the following operations A-C:

A) If the MRB mapped to the DRB is a separate MRB (that is, a PTM RLC and a PTP RLC are associated at the same time), release the PTM RLC bearer. Specifically, it includes releasing the RLC entity and releasing the corresponding logical channel according to the operations defined in Section 5.1.3 of TS38.322.

B) If the MRB mapped to the DRB is associated (that is, only associated) with a PTM RLC entity, release (or instruct the PTM RLC entity to release) the PTM transmission indicator and/or the corresponding G-RNTI.

C) Associating the RLC entity associated with the MRB mapped to the DRB to the DRB. For a PTP MRB configured only with a PTP RLC entity, the RLC refers to the PTP RLC; for a PTM MRB configured only with a PTM RLC entity, the RLC refers to the PTM RLC.

It should be noted that an embodiment obtained by exchanging the execution order of the above operations is also within the protection scope of the present invention.

For an MRB that is not mapped to any DRB (that is, the MRB corresponding to each mrb-Identity not included in mrbToDrbMappingList), release the MRB, specifically including releasing the PDCP entity and mrb-Identity, and indicate to the upper layer the release of the MRB and the released MRB's tmgi.

For each drb-Identity included in the drb-ToReleaseList (to release DRB information) in the second RRCReconfiguration message, if the drb-Identity is not part of the current UE configuration, but the drb-Identity is mapped to an MRB (ie drb-Idntity is included in the mrbToDrbMappingList field), then perform at least one of the following operations I-II:

I: Release the mrb-Identity of the PDCP entity mapped to this DRB and MRB.

II: If an associated SDAP entity is configured for the MRB mapped to this DRB, instruct the SDAP entity to release the MRB mapped to this DRB.

Some of the fields involved in the present invention are described below: drb-ToAddModList is used to indicate a group of added or modified DRB configuration information; mrbToDrbMappingList is used to indicate the DRB to which each MRB is mapped or the relationship between mrb-Identity and drb-Identity Mapping relationship, the PDU session of the DRB is the associated PDU session of the MBS session of the MRB. If the UE has been configured with the MBS session and the associated PDU session in advance (for example, when configuring the MEB), mrbToDrbMappingList does not need to include MBS session and associated PDU session, otherwise it needs to be included, the information of MBS session and associated PDU session can also be included in another field mbsSessionToPduSessionMappinglist different from mrbToDrbMappingList, which is used to indicate the association relationship between MBS session and associated PDU session ;drb-Identity is used to identify the DRB used by the UE; mrb-Identity is used to identify the MRB used by the UE; reestablishPDCP is used to indicate that the PDCP entity should be reestablished; Encryption is disabled for all radio bearers; integrityProtection indicates whether integrity protection is configured for this radio bearer; securityConfig indicates the security algorithm and key used by the radio bearer configured in RadioBearerConfig; keyToUse indicates that the bearer configured in RadioBearerConfig uses the primary key or secondary key. Key to derive encryption and integrity protection keys; drb-ContinueROHC is used to indicate whether the PDCP entity continues or resets the ROHC header compression protocol during PDCP re-establishment; drb-ContinueEHC-DL is used to indicate that the PDCP entity is during PDCP re-establishment Continue or reset the downlink EHC header compression protocol; drb-ContinueEHC-UL is used to indicate whether the PDCP entity continues or resets the uplink EHC header compression protocol during PDCP re-establishment; recoverPDCP is used to indicate that PDCP should perform recovery according to the operation defined in TS38.323 ;pdcp-Config is used to set configurable PDCP parameters for DRB or MRB; sdap-Config is used to set configurable SDAP parameters for DRB or MRB; pdu-session is the identifier of the associated PDU session that QoS flow maps to this DRB ;mbs-Session is the identifier of the PDU session where the QoS flow is mapped to this MRB.

In the present invention, there is a one-to-one mapping between MRBs and DRBs. Drb-Identity is mapped to MRB, drb-Identity is mapped to mrb-Identity, and DRB is mapped to MRB, which means that the DRB is mapped from MRB, that is, drb-Idntity is included in the mrbToDrbMappingList field.

In the present invention, a field may also be called an information element IE.

In the embodiment of the present invention, the PTM RLC entity is also called the RLC entity associated with PTM or the RLC entity configured with G-RNTI or the RLC entity associated with G-RNTI or the RLC entity used for PTM transmission; the PTP RLC entity is also called PTP The associated RLC entity or the RLC entity used for PTP transport.

It should be noted that an MBS service (or MBS session) can be identified by an MBS identifier, and the MBS identifier can be a TMGI and/or a session identifier sessionId, where the TMGI can include a PLMN identifier and/or a service identifier, so The above service identifier uniquely identifies an MBS service within a PLMN.

As shown in FIG. 6 , the user equipment 600 includes at least a processor 601 and a memory 602 . The processor 601 may include, for example, a microprocessor, a microcontroller, an embedded processor, and the like. The memory 602 may include, for example, a volatile memory (such as a random access memory RAM), a hard disk drive (HDD), a nonvolatile memory (such as a flash memory), or other memory systems. Memory 602 has program instructions stored thereon. When the instruction is executed by the processor 601, one or several steps in the method described above in FIGS. 3-5 of the present invention may be executed.

In addition, the computer-executable instructions or programs running on the device according to the present invention may be programs that cause the computer to realize the functions of the embodiments of the present invention by controlling a central processing unit (CPU). The program or information processed by the program may be temporarily stored in volatile memory (such as random access memory RAM), hard disk drive (HDD), non-volatile memory (such as flash memory), or other memory systems.

Computer-executable instructions or programs for realizing the functions of various embodiments of the present invention can be recorded on computer-readable storage media. The corresponding functions can be realized by causing a computer system to read programs recorded on the recording medium and execute the programs. The so-called "computer system" here may be a computer system embedded in the device, which may include an operating system or hardware (such as peripheral devices). The "computer-readable storage medium" may be a semiconductor recording medium, an optical recording medium, a magnetic recording medium, a recording medium that dynamically stores a program for a short period of time, or any other recording medium readable by a computer.

Various features or functional modules of the devices used in the above-mentioned embodiments may be implemented or executed by circuits (for example, single-chip or multi-chip integrated circuits). Circuits designed to perform the functions described in this specification may include general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic, discrete hardware components, or any combination of the above. A general-purpose processor can be a microprocessor, or it can be any existing processor, controller, microcontroller, or state machine. The above-mentioned circuits may be digital circuits or analog circuits. Where advances in semiconductor technology have resulted in new integrated circuit technologies that replace existing integrated circuits, one or more embodiments of the invention may also be implemented using these new integrated circuit technologies.

In addition, the present invention is not limited to the above-described embodiments. Although various examples of the embodiments have been described, the present invention is not limited thereto. Fixed or non-mobile electronic equipment installed indoors or outdoors can be used as terminal equipment or communication equipment, such as AV equipment, kitchen equipment, cleaning equipment, air conditioners, office equipment, vending machines, and other household appliances.

As above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific structure is not limited to the above embodiments, and the present invention also includes any design changes that do not deviate from the gist of the present invention. In addition, various changes can be made to the present invention within the scope of the claims, and embodiments obtained by appropriately combining technical means invented in different embodiments are also included in the technical scope of the present invention. In addition, components having the same effect described in the above embodiments can be substituted for each other.

Claims

A method for performing cell handover performed by user equipment, comprising:

receiving a first RRC reconfiguration message generated by the source base station for the user equipment from the source base station, the first RRC reconfiguration message carrying a second RRC reconfiguration message generated by the target base station, the first RRC reconfiguration message carrying the second RRC reconfiguration message generated by the target base station, the first RRC reconfiguration message being generated by the target base station, An RRC reconfiguration message also includes mapping relationship information between the MRB for the multicast broadcast service session, that is, the MBS session, and the DRB for the PDU session; and

reconfiguring the RRC configuration related to the MBS session of the user equipment to the RRC configuration related to the PDU session supported by the target base station based on the second RRC reconfiguration message and/or the mapping relationship information,

The second RRC reconfiguration message is generated by the target base station in response to the cell switching request message sent by the source base station and sent to the source base station.
The method according to claim 1, wherein, before performing the reconfiguration operation, the method further comprises:

When receiving the first RRC reconfiguration message, determine whether the first RRC reconfiguration message includes a field for indicating that the target base station does not support MBS sessions; and

If the first RRC reconfiguration message includes the field, parse the field, and parse the second RRC reconfiguration message from the field.
The method according to claim 1, wherein, based on the second RRC reconfiguration message and/or the mapping relationship information, the RRC configuration related to the MBS session of the user equipment is reconfigured to be related to the target The RRC configuration related to the PDU session supported by the base station includes:

For each DRB indicated by the mapping relationship information, perform at least one of the following:

If the MRB mapped to the DRB is a separate MRB configured with a PTM RLC entity and a PTP RLC entity, release the PTM RLC bearer corresponding to the PTM RLC entity;

If the MRB mapped to the DRB is a PTM MRB that is only configured with a PTM RLC entity, release the PTM transmission indicator of the PTM RLC entity;

If the MRB mapped to this DRB is a PTM MRB configured with only PTM RLC entities or a PTP MRB configured only with PTP RLC entities, associate the PTM RLC or PTP RLC entity associated with the MRB mapped to this DRB to this DRB.
The method according to any one of claims 1-3, wherein the second RRC reconfiguration message includes DRB change information, and the DRB change information includes the information indicating that the target base station needs to change the DRB, based on the The second RRC reconfiguration message and/or the mapping relationship information, reconfiguring the RRC configuration related to the MBS session of the user equipment to the RRC configuration related to the PDU session supported by the target base station includes:

For each DRB indicated by the DRB change information, determine whether the DRB is included in the existing RRC configuration of the user equipment;

If the DRB is not included in the existing RRC configuration of the user equipment, based on the mapping relationship information, determine whether there is an MRB mapped to the DRB;

If there is no MRB mapped to the DRB, the DRB is established;

If there is an MRB mapped to the DRB, reconfiguration is performed on the MRB mapped to the DRB.
The method according to claim 4, wherein the DRB change information includes a newly added and modified DRB list, and the newly added and modified DRB list includes the information of the newly added or modified DRB required by the target base station, and the MRB mapped to the DRB Performing reconfiguration involves:

If the DRB is included in the newly added modified DRB list, at least one of the following is performed:

If the MRB mapped to the DRB is associated with the PTM RLC entity, instruct the PTM RLC entity to release the PTM transmission indication identifier and/or the corresponding group wireless network temporary identifier;

If the RRC reconfiguration information includes a PDCP re-establishment indication, re-establish the PDCP entity of the MRB mapped to the DRB;

If the RRC reconfiguration information includes a PDCP recovery indication, enabling the PDCP entity of the MRB mapped to the DRB to perform data recovery;

If the RRC reconfiguration information includes PDCP reconfiguration information, reconfigure the PDCP entity of the MRB mapped to the DRB according to the PDCP reconfiguration information;

If the RRC reconfiguration information includes SDAP reconfiguration information, reconfigure the SDAP entity of the MRB mapped to the DRB according to the SDAP configuration information;

For the MBS session corresponding to the MRB mapped to the DRB, modify the MBS session identifier to the PDU session identifier corresponding to the DRB;

Release or discard the MRB identifier in the existing RRC configuration of the user equipment.
The method according to claim 4, wherein the DRB change information includes a list of DRBs to be released, and the list of DRBs to be released includes the information of the DRBs required by the target base station to be released, and the MRBs mapped to the DRBs are reconfigured include:

If the DRB is included in the DRB list to be released, execute:

Release the MRB identity of the PDCP entity of the MRB mapped to the DRB; and/or

If the MRB mapped to the DRB is configured with a corresponding SDAP entity, instruct the SDAP entity to release the MRB mapped to the DRB.
The method according to any one of claims 1-3, wherein, based on the second RRC reconfiguration message and/or the mapping relationship information, the RRC configuration related to the MBS session of the user equipment is reconfigured. The RRC configuration configured to be related to the PDU session supported by the target base station further includes:

For an MRB that is not mapped to any DRB determined based on the mapping relationship between the MRB and the DRB, information related to the MRB is released.
A method for cell handover performed by a source base station, comprising:

When the source base station sends the cell handover request message to the target base station, determine whether the target base station supports MBS sessions based on the interface parameter information of the network interface established between the source base station and the target base station. The cell handover request message is used to request the target base station to prepare RRC resources for the user equipment;

If the target base station does not support MBS sessions, the cell handover request message does not carry the RRC configuration information related to MBS sessions configured by the source base station for the user equipment; and

changing the RRC configuration information related to the MBS session to the RRC configuration information related to the PDU session supported by the target base station, and carrying the changed RRC configuration information in the cell handover request message and sending it to the target base station .
The method of claim 8, further comprising:

modifying the information of the MRB configured for the MBS session to the information of the DRB mapped to the MRB, and sending it to the target base station in the cell handover request message; and/or

When receiving the handover request acknowledgment message sent by the target base station in response to the cell handover request message, based on the second RRC reconfiguration information carried in the handover request acknowledgment message, generate a handover request for the user equipment the first RRC reconfiguration information to the target base station, and send the generated first RRC reconfiguration information to the user equipment, the second RRC reconfiguration information is carried by the target base station based on the cell Generated by the RRC reconfiguration information in the handover request message.
A user equipment, comprising:

processor; and

memory, storing instructions,

Wherein, the instruction executes the processing method according to any one of claims 1 to 7 when executed by the processor.