CN115996359A

CN115996359A - Method for cell switching and user equipment

Info

Publication number: CN115996359A
Application number: CN202111215299.9A
Authority: CN
Inventors: 肖芳英; 刘仁茂; 山田升平
Original assignee: Sharp Corp
Current assignee: Sharp Corp
Priority date: 2021-10-19
Filing date: 2021-10-19
Publication date: 2023-04-21
Also published as: WO2023066188A1

Abstract

The invention provides a method for carrying out cell switching executed by a source base station, which comprises the following steps: when the source base station sends the cell switching request message to a target base station, determining whether the target base station supports an MBS session or not based on interface parameter information of a network interface established between the source base station and the target base station, wherein the cell switching request message is used for requesting the target base station to prepare RRC resources for user equipment; if the target base station does not support MBS session, the RRC configuration information related to MBS session configured by the source base station for the user equipment is not carried in the cell switching request message; and changing the RRC configuration information related to the MBS session into the RRC configuration information related to the PDU session supported by the target base station, carrying the changed RRC configuration information in the cell switching request message, and sending the cell switching request message to the target base station.

Description

Method for cell switching and user equipment

Technical Field

The present invention relates to the field of wireless communication technologies, and in particular, 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 a user equipment.

Background

A research project SI (see in particular SP-190625) 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, and examples of applications that have been determined to benefit from this feature include, but are not limited to, public safety, V2X applications, transparent IPv4/IPv6 multicast transmission, IPTV, wireless software transmission, group communication, and internet of things applications. Accordingly, in the third generation partnership project (3rd Generation Partnership Project:3GPP) ran#86, work items (see non-patent document: RP-193248:New WID:NR Multicast and Broadcast Service) that propose NR multicast and broadcast services (NR MBS) are approved. The work item is intended to provide support for target a in the RAN.

The present invention discusses the problems associated with the RAN achieving the above-described objectives.

Disclosure of Invention

The invention aims to provide a method for carrying out cell switching, which can ensure the continuity of MBS service and reduce data loss.

In order to solve the above problems, the present invention provides a method for performing cell handover performed by a source base station, comprising: when the source base station sends the cell switching request message to a target base station, determining whether the target base station supports an MBS session or not based on interface parameter information of a network interface established between the source base station and the target base station, wherein the cell switching request message is used for requesting the target base station to prepare RRC resources for user equipment; if the target base station does not support MBS session, the RRC configuration information related to MBS session configured by the source base station for the user equipment is not carried in the cell switching request message; and changing the RRC configuration information related to the MBS session into the RRC configuration information related to the PDU session supported by the target base station, carrying the changed RRC configuration information in the cell switching request message, and sending the cell switching request message to the target base station.

According to another aspect of the present invention, there is also provided a method for performing a cell handover performed by a user equipment, including: receiving a first RRC reconfiguration message which is generated by a source base station and aims at the user equipment from the source base station, wherein the first RRC reconfiguration message carries a second RRC reconfiguration message which is generated by a target base station, and the first RRC reconfiguration message also comprises mapping relation information between MRB which aims at a multicast broadcast service session (MBS session) and DRB which aims at a PDU session; and reconfiguring the RRC configuration of the user equipment related to the MBS session into 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 relation information, wherein 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 is 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 the instructions when executed by the processor perform the method performed by the user equipment as described above.

Effects of the invention

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

Drawings

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

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

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

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

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

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

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

Detailed Description

The invention is described in detail below with reference to the drawings and the detailed description. 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 well-known techniques, which are not directly related to the present invention, are omitted to prevent confusion of the understanding of the present invention.

The following describes some terms related to the present invention, and specific meanings of the terms may be found in 3GPP related documents, such as TS38.300, TS38.321, TS38.323, TS38.331, etc. In addition, the embodiment of the invention is not limited to broadcast/multicast service, and can be applied to other application scenes.

UE: user Equipment, user Equipment.

RRC: radio Resource Control, radio resource control.

Rrc_connected: and an RRC connected state.

Rrc_inactive: and the RRC is inactive.

Rrc_idle: and RRC idle state.

RAN: radio Access Network, radio access network.

NR: new RAT, new radio Access technology.

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

MBS: multicast/broadcast service.

PDCP Packet Data Convergence Protocol packet data convergence protocol.

RLC Radio Link Control radio link control.

SDU Service Data Unit, service data units. The data packet received or delivered from or to the upper layer by this layer is called an SDU.

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

RB: radio Bearer.

MRB: the MBS radio bearer, i.e. one radio bearer configured for MBS transmission (A radio bearer that is configured for MBS delivery).

MCCH: multicast Control Channel, multicast control channels. The MBS-MCCH is used to transmit control information related to reception of 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 identity.

PTM: point to Multipoint, point-to-multipoint, a delivery (delivery) mode of MBS services. In PTM delivery mode, the RAN node delivers a MBS data packet over the air to a group UE (a RAN node delivers a single copy of MBS data packets over radio to a set of UEs).

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

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

MTCH: multicast Traffic Channel, multicast traffic channels. MBS multicast (or multicast traffic) refers to the same service and the same specific content being provided to a group of specific UEs at the same time. A multicast communication service is delivered to the UE using the multicast session.

A UE in rrc_connected may receive a multicast traffic using PTP and/or PTM.

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

An associated PDU session: a PDU session associated to a multicast session (also called MBS session) for the 5G core network 5GC unicast MBS traffic delivery method (5 GC Individual MBS traffic delivery method) and for signaling related to the user's participation in the multicast session (e.g. join and leave requests).

Associated QoS flows: unicast QoS flows belonging to an associated PDU session, mapped from multicast QoS flows in a multicast MBS session, are used for a 5GC unicast MBS traffic delivery method.

In the present invention, the network, the base station and the RAN are used interchangeably, and the network may be a long term evolution LTE network, an NR network, an enhanced long term evolution LTE network, or other networks defined in a later evolution version of 3 GPP.

In LTE SC-PTM, the base station broadcasts its supported multimedia broadcast multicast service MBMS service and its scheduling information via system information and messages transmitted on the SC-MCCH channel, and radio bearer configuration information for transmitting the MBMS service is predefined. The UE can know the MBMS service supported or ongoing by the current cell or base station by receiving the corresponding system information and the message transmitted on the SC-MCCH. When the UE needs to receive a certain MBMS service, a radio bearer is established according to a predefined parameter and data is received. In this case, the UE can receive the MBMS service without establishing an RRC connection.

In NR MBS, a portion of MBS services (services) may also be scheduled in a similar manner as SC-PTM, so that UEs in RRC idle state and RRC inactive state may also receive the MBS services. However, there is another part of MBS services that require the UE to establish an RRC connection with the base station, which then configures the UE through dedicated RRC signaling (also referred to as dedicated RRC message), and radio bearers receiving these MBS services may also be configured by the base station for the UE through dedicated RRC signaling. Fig. 1 (a) - (c) are schematic diagrams showing specific configurations of radio bearers receiving MBS services. The radio bearer may be an MRB configured with only PTM transmissions, as shown in fig. 1 (a), or a separate MRB (split MRB) of PTM and PTP, as shown in fig. 1 (b), or an MRB configured with only PTP transmissions, as shown in fig. 1 (c). Note that (a) - (c) of fig. 1 only show PDCP entities and RLC entities corresponding to bearers and relationships between the two. In the downlink direction, PDCP PDUs encapsulated by the PDCP entity are delivered to the RLC entity.

For MBS service that UE needs to establish RRC connection with base station, when UE switches from a base station supporting MBS (source base station) to a base station not supporting MBS (target base station), how to ensure continuity of MBS service and reduce data loss is a problem to be solved.

In existing HANDOVER based on an Xn interface, a source base station (or source NG-RAN node) sends a HANDOVER REQUEST (HANDOVER REQUEST) message to a target base station (or target NG-RAN node) for establishing necessary resources in the target base station. The handover request message includes an RRC Context field, where the field is configured to include a handover preparation information message. In handover preparation, a handover preparation information message is used to transmit NR RRC information used by the target base station during handover preparation (is used to transfer the NR RRC information used by the target gNB _)。 The HandoverPrepartionInformation message contains RRCReconfiguration configuration (Contains the RRCReconfiguration configuration as generated entirely by the source gNB) generated entirely by the source base station. The Target base station sends a handover request acknowledgement (HANDOVER REQUEST ACKNOWLEDGE) message to the source base station as a response message, wherein the response message comprises a Target base station (i.e., target NG-RAN node) to source base station (i.e., source NG-RAN node) transparent container (Target NG-RAN node to Source NG-RAN node Transparent Container) field for carrying a handover command message carrying an rrcrecconfiguration message generated by the Target base station, and the source base station will be configured by the Target base station after receiving the handover request acknowledgement message The RRCRECONfigure message generated by the base station is forwarded to the UE. The handover request message is sent by the source base station to the target base station to request preparation of resources for handover; the handover request confirm message is sent by the target base station to inform the source base station of the resources that are ready on the target. When the UE in 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 identify configuration information related to MBS, a rrcrecon configuration message generated by the target base station will include a fullconfigug field, where the fullconfigug field is used to indicate that a complete configuration option is applied to the rrcrecon configuration message. In a complete configuration, the UE will release all DRBs and MRBs, which will not enable service continuity and/or result in data loss.

As shown in fig. 2, in S202, the source base station may determine whether the target base station supports an MBS session based on interface parameter information of a 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 prepare RRC resources for the user equipment. The network interface is, for example, an Xn interface.

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

In S206, the source base station may change the RRC configuration information related to the MBS session into 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 with the cell handover request message. As an example, the source base station may modify information of an MRB configured for an MBS session into information of a DRB mapped to the MRB and transmit to the target base station in a cell handover request message.

The target base station may generate second RRC reconfiguration information based on the RRC reconfiguration information carried in the cell handover request message after receiving the cell handover request message, and send the second RRC reconfiguration information to the source base station in a handover request confirm message that is a response message. In one example, upon receiving a handover request confirm message transmitted by a target base station in response to a cell handover request message, a source base station may generate first RRC reconfiguration information for handover of a user equipment to the target base station based on second RRC reconfiguration information carried in the handover request confirm message, and transmit 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. Upon receiving the handover request confirm message from the target base station, the first RRC reconfiguration message may not be generated but the second RRC configuration message carried in the handover request confirm message may be directly transmitted to the UE.

An embodiment of the operations performed by the source base station and the target base station is 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 configuration information of MBS, such as information of MBS session and configuration information of MRB, etc., in the rrcr configuration included in the handover preparation information message provided to the target base station.

In one embodiment, the source base station includes PDU session related information associated with the MBS session in a handover request message, for example, in a PDU session resource list (PDU Session Resources To Be Setup List) field to be established, where the field includes PDU session resource related information, for example, including a PDU session ID (identifying a PDU session for the UE), a PDU session type, a QoS flow list to be established, where the QoS flow list to be established includes information about a QoS flow to be established, where the QoS flow related information may include a QoS flow identification (identifying a QoS flow in a PDU session), qoS parameters of a QoS flow class, and so on. Configuration information related to the MBS session is deleted in the RRCRECONfigure configuration provided to the target base station, e.g. MRB-ToAddModList (newly modified MRB list) and/or related information such as RLC-BearerConfig associated to the MRB. The target base station configures a corresponding DRB for a PDU session associated with the MBS session included in the PDU session resource list to be established, and forwards the configured DRB information to the UE through the source base station by being included in an rrcrecon configuration message (referred to as a second rrcrecon configuration message or a second RRC reconfiguration message) generated by the target base station. Optionally, when receiving the handover request acknowledgement message, the source base station generates an rrcreconditioning message (referred to as a first rrcreconditioning message or a first RRC reconfiguration message), where the first RRC reconfiguration message includes a field mbstonon bsnode for carrying the second RRC reconfiguration message (a field indicating that the cell handover to be performed is a handover from a base station supporting an MBS session to a base station not supporting an MBS session), and a field MRB-todelease list for indicating that the MRB is released (i.e., MRB information to be released), where MRB-todelease list includes MRB-identities of all MRBs that need to be released. It may be provided that the mbsToNonMBSNode is a condition for configuring mrb-todeleaselist, i.e. mrb-todeleaselist may be configured only if mbsToNonMBSNode is present, and vice versa.

In one embodiment, the source base station includes PDU session related information associated with the MBS session in a handover request message, for example, in a PDU session resource list (PDU Session Resources To Be Setup List) field to be established, where the field includes PDU session resource related information, for example, including a PDU session ID (identifying a PDU session for the UE), a PDU session type, a QoS flow list to be established including QoS flow related information to be established including QoS flow identification (identifying a QoS flow in a PDU session), qoS parameters of QoS flow class, etc. Deleting the configuration information related to the MBS session and/or modifying the configuration information related to the MRB into the corresponding DRB in the RRCRECONfigure configuration provided to the target base station, so that the target base station can treat the DRB as the DRB configured by the source base station for the UE. For example, each MRB is assigned a DRB ID (i.e., DRB-Identity, DRB identification), and the MRB ID (i.e., MRB-Identity, MRB identification) is modified to the corresponding DRB ID; and/or modifying the MBS session identification associated with the MRB into the PDU session identification associated with the MBS session; and/or for MRBs associated only with PTM RLC, modifying the MRB ID to a DRB ID and/or deleting the corresponding G-RNTI and/or deleting the indication identity of the PTM transmission (i.e. the indication identity indicates that the corresponding RLC entity is configured for PTM transmission); and/or deleting configuration information related to the PTM RLC and/or deleting corresponding G-RNTI for MRB of the PTM RLC and the PTP RLC which are simultaneously associated; and/or storing a mapping relationship between the MRB and the DRB. For a PDU session associated with one MBS session, its corresponding source base station QoS flow to DRB mapping refers to the associated QoS flow to DRB mapping for the associated PDU session. The target base station transmits a handover request confirm message as a response message to the source base station. The rrcreconditionconfiguration message provided by the source base station to the target base station is contained in a handover preparation information message carried by the handover request message.

A method of performing a cell handover performed by a user equipment according to an embodiment of the present invention will be described below with reference to fig. 3 to 5.

As shown in fig. 3, in S302, the user equipment receives a first RRC reconfiguration message for the user equipment generated by the source base station from the source base station. The first RRC reconfiguration message carries a second RRC reconfiguration message generated by the target base station, and the first RRC reconfiguration message may further include mapping relationship information between an MRB for a multicast broadcast service session, i.e., an MBS session, and a DRB for a PDU session. As an example, the mapping relation information may be a mapping between a DRB identifier and an MRB identifier, a mapping between an MBS session identifier and a PDU session identifier, or a mapping between a DRB identifier and an MRB identifier and a mapping between an MBS session identifier and a PDU session identifier. The second RRC reconfiguration message is generated by the target base station in response to the cell handover request message transmitted by the source base station and transmitted to the source base station as previously described.

In 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 relation information.

In an embodiment of the present invention, the reconfiguration operation may include at least one of: based on the second RRC reconfiguration message and/or the mapping relation information, reconfiguring the RRC configuration related to the MBS session of the user equipment to an RRC configuration related to the PDU session supported by the target base station, including at least one of the following: replacing the MRB identifier for the MBS session with the DRB identifier mapped to the MRB based on the mapping relation information; based on the mapping relation information, associating the DRB mapped by the MRB to an SDAP entity associated with the MRB; modifying the MBS session identification into a PDU session identification of a PDU session associated with the MBS session based on the mapping relation information; indicating to release user plane resource of MBS session to upper layer; indicating user plane resources for establishing PDU session to an upper layer; indicating, by an upper layer, that user plane resources related to an MBS session are modified to user plane resources of a PDU session associated with a DRB mapped to an MRB for the MBS session; for the MRB configured with the PTM RLC entity, the PTM RLC entity is instructed to release the PTM transmission instruction identification.

The user equipment may perform reconfiguration based on the mapping relation information, for example, at least one of the following may be performed for each DRB indicated by the mapping relation information: if the MRB mapped to the DRB is a separate MRB configured with a PTM RLC entity and PTP RLC, releasing the PTM RLC bearer corresponding to the PTM RLC entity; releasing the PTM transmission indication identification of the PTM RLC entity if the MRB mapped to the DRB is a PTM MRB configured with only the PTM RLC entity; if the MRB mapped to the DRB is a PTM MRB configured with only PTM RLC entities or a PTP MRB configured with only PTP RLC entities, the PTM RLC or PTP RLC entity associated with the MRB mapped to the DRB is associated to the DRB.

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

In another example, when the target base station does not support MBS, the source base station may carry a field for indicating that the target base station does not support MBS sessions in the first RRC reconfiguration message. In this example, the user equipment may also parse out the second RRC reconfiguration and perform the reconfiguration when it is determined that the first RRC reconfiguration includes the field. This example is described below with reference to fig. 4.

In S402, the user equipment may determine, upon receiving the first RRC reconfiguration message, 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 the field, the user equipment may parse the field and parse the second RRC reconfiguration message from the field in S404. However, the user equipment may perform the reconfiguration operation. If the first RRC reconfiguration does not include the above-mentioned fields, no further operations may be performed.

The second RRC reconfiguration message may include DRB change information including information that the target base station indicates a DRB that needs to be changed. The "change" as referred to herein may include various changing operations such as deletion, modification, addition, release, and the like. Accordingly, the DRB change information may include DRB modification information indicating information of DRBs to be modified, newly increased DRB information indicating information of DRBs to be newly increased, and DRB information to be released indicating information of DRBs to be released. Such information may be in the form of a list, e.g., a list of DRB identities that may correspond to the DRBs. At this time, the reconfiguration may be performed according to the flow of fig. 5. Fig. 5 is a flowchart of a specific example of a reconfiguration procedure in a method of cell handover performed by a user equipment according to an embodiment of the present invention.

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

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 based on the mapping relationship information at S506;

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 for the MRB mapped to the DRB at S508.

As described above, the DRB change information includes a new and modified DRB list including information of DRBs required to be newly added or modified by the target base station. At this time, the reconfiguration for 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 modified DRB list: if the MRB mapped to the DRB is associated with the PTM RLC entity, the PTM RLC entity is instructed to release the PTM transmission indication identifier and/or the corresponding group wireless network temporary identifier; reconstructing a PDCP entity mapped to an MRB of the DRB if the RRC reconfiguration information includes a PDCP reconstruction indication; if the RRC reconfiguration information includes a PDCP restoration instruction, causing the PDCP entity mapped to the MRB of the DRB to perform data restoration; if the RRC reconfiguration information comprises PDCP reconfiguration information, reconfiguring the PDCP entity mapped to the MRB of the DRB according to the PDCP reconfiguration information; if the RRC reconfiguration information comprises SDAP reconfiguration information, reconfiguring an SDAP entity mapped to the MRB of the DRB according to the SDAP reconfiguration information; for MBS session corresponding to MRB mapped to the DRB, modifying the MBS session identification to PDU session identification corresponding to the DRB; the MRB identity in the existing RRC configuration of the user equipment is released or discarded.

The DRB change information may further include a to-be-released DRB list including information of DRBs required to be released by the target base station. At this time, the operation in S508 may be performed as follows. And if the DRB is included in the DRB list to be released, releasing the MRB identification of the PDCP entity mapped to the MRB of the DRB. The user equipment may also instruct the SDAP entity to release the MRB mapped to the DRB if the MRB mapped to the DRB is configured with a corresponding SDAP entity.

The following describes embodiments of operations when a UE performs handover

In one embodiment, the UE receives a first rrcrecon configuration message (first RRC reconfiguration message) from the base station (i.e., source base station), which may include MRB change information. The "change" as referred to herein may include various changing operations such as deletion, modification, addition, release, and the like. The MRB change information may include information to release the MRB, and may also include new and modified MRB information to be newly added or modified. The information may be in the form of a list including MRB identities. If MRB-toReleaseList (MRB list information is to be released) is included in the message, for each MRB-Identity (MRB Identity) included in MRB-ToReleaseList, if the MRB-Identity is part of the current UE configuration, the corresponding PDCP entity and MRB-Identity are released, and/or a field tmgi indicating this MRB is released and released to the upper layer. The field TMGI is used to indicate the MBS session associated with the bearer, and the value of the field TMGI is TMGI.

In one embodiment, the UE receives an rrcrecon configuration message from the base station (i.e., source base station), if the rrcrecon configuration message contains a recombi-tion wistsync field and the target base station does not support MBS, for each MRB-Identity of the current configuration, releases the corresponding PDCP entity and MRB-Identity, and/or indicates to the upper layer that this MRB is released and tmgi of the released MRB, and/or releases the RLC entity or RLC bearer associated to the MRB. Wherein the reconfigurationWithSync field contains relevant parameters for synchronous reconfiguration to the target SpCell, tmgi is used to indicate the MBS session with which the bearer is associated. The "target base station does not support MBS" may be replaced by "the UE does not include any MRB configuration in the rrcrecnonconfiguration message including the reconconfiguration withsync field" or "the received rrcrecnonconfiguration message does not include the field MBS supporting for indicating that the base station supports MBS". Alternatively, in the handover procedure, if the target base station supports MBS, an mbsssupport field is included in the rrcrecon configuration message generated by the target base station. Optionally, a field keeper MBS is included in the rrcr configuration message for indicating that the UE retains the configured MBS, if the received rrcr configuration message does not include the field, each MRB-Identity or MRB currently configured, if the MRB-Identity or MRB is not included in the received rrcr configuration message, the corresponding PDCP entity and MRB-Identity are released, and/or tmgi indicating that this MRB is released and the released MRB is released to an upper layer, and/or RLC entity or RLC bearer associated with the MRB is released. Further, specific operations of releasing the RLC bearer may include releasing the RLC entity and releasing the corresponding logical channel.

In the present invention, the user plane resource indicating to release the MBS session to the upper layer and tmgi indicating to the released MRB may be used alternatively, and the resulting embodiment is also within the scope of the present invention.

In an embodiment, the UE reconfigures each MRB mapped to a DRB according to configuration information contained in the second rrcr configuration message, e.g. replaces MRB-Identity of the MRB with DRB-Identity of the DRB to which it is mapped, and/or modifies the MBS session Identity of the MRB associated to the PDU session Identity of said MBS session association, and/or associates an MRB associated SDAP entity (or PDCP entity or RLC entity) mapped to the DRB to said DRB (which may also be expressed as associating said DRB to an MRB associated SDAP entity (or PDCP entity or RLC entity)) and/or indicates to release user plane resources of the MBS session and/or indicates to the upper layer to set up user plane resources of the PDU session, and/or indicates to the upper layer to change the user plane resources of the MBS to the user plane resources of the associated PDU session and/or to release the mrap entity or RLC entity for PTM transmission, and to release the PTM entity or RLC entity for PTM transmission only. The following detailed description:

The UE receives a first rrcreconditioning message from the base station (i.e. the source base station), where the first rrcreconditioning message includes an mrbtopmappingenlist field of a mapping relationship between the MBS session and the associated PDU session and/or a mapping relationship between the MRB ID (i.e. MRB-Identity) and the DRB ID (i.e. DRB-Identity), and the first rrcreconditioning message further includes an mbstodurrcrconfiguration field, where the field is used to carry a second rrcreconditioning message generated by the target base station.

For each DRB-Identity in DRB-ToAddModList (newly modified DRB list) contained in the second rrcrecon configuration message, if the DRB-Identity is not part of the current UE configuration, nor is it mapped to one MRB (i.e. DRB-Identity is not contained in the mrbtopmap list field), the corresponding DRB is established (in particular according to the method of establishing DRB defined in 3GPP technical specification TS 38.331).

For each drb-Identity in drb-ToAddModList contained in the second rrcrecon configuration message, if the drb-Identity is not part of the current UE configuration, but the drb-Identity is mapped to one MRB (i.e., drb-Identity is contained in the mrbtopmap list field), then at least one of the following operations (1-8) is performed:

1) If the MRB mapped to the DRB is a separate MRB (i.e., a PTM RLC and a PTP RLC are associated together), then the PTM RLC bearer is released, including in particular releasing the RLC entity and releasing the corresponding logical channel in accordance with the operation defined in section 5.1.3 of TS 38.322.

2) If the MRB mapped to the DRB associates (i.e. associates only) one PTM RLC entity, releasing the PTM transmission indication identification and/or the corresponding G-RNTI or indicating the PTM RLC entity (or PTM RLC bearer) to release the PTM transmission indication identification and/or the corresponding G-RNTI. The purpose of this operation is to make the UE no longer monitor PTM transmissions of MBS.

3) If the resetishpdcp is set, then at least one of (1 a-1 f) is executed: (1a) If the PDCP entity mapped to the MRB of this DRB is not configured with the cipheringDisable, a master key (K _eNB /K _gNB ) Or a secondary key (S-K) _gNB /S-K _eNB ) Associated encryption algorithm and K _UPenc A key configuration PDCP entity, as indicated in the keyToUse, i.e. the ciphering configuration will apply to all subsequent PDCP PDUs received and transmitted by the terminal;

(1b) If the PDCP entity mapped to the MRB of this DRB is configured with integrity protection, the integrity protection algorithm of the PDCP entity is configured according to the securyconfig, and a master key (K) indicated in the keyToUse is applied _gNB ) Or a secondary key (S-K) _gNB ) Associated K _UPint A secret key;

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

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

(1e) If drb-ContinueEHC-UL is contained in the pdcp-Config, indicating that the lower layer is configured with drb-ContinueEHC-UL; it may be specified that this configuration is not used for DRBs to which MRBs map.

(1f) The PDCP entity re-establishing the MRB mapped to this DRB is described in section 5.1.2 of the 3GPP technical specification TS 38.323 for specific operation. When the ciphering algorithm or key is changed and/or the integrity protection algorithm or key is changed, etc., the base station will instruct the UE to reestablish the PDCP entity.

4) If the recovery PDCP is set, the PDCP entity of the MRB mapped to this DRB is triggered to perform data recovery, and specific operations are described in the 3GPP technical Specification TS 38.323. Note that this operational step may not apply to the DRB to which the associated PDU corresponds. The PDCP entity may be instructed to perform data recovery when the ciphering algorithm or key is not changed and/or the integrity protection algorithm or key is not changed, etc., in order to reduce data loss, it is necessary to retransmit data that has been transmitted but has not yet confirmed that transmission was successful.

5) If the PDCP-Config is included therein, the PDCP entity mapped to the MRB of this DRB is reconfigured according to the received PDCP-Config. When the target base station cannot support or needs to modify the configuration of part of the parameters in the current PDCP-Config, the PDCP-Config including the new PDCP entity configuration information may be transmitted to reconfigure the PDCP entity.

6) If sdap-Config is contained therein, at least one of the following operations (4 a-4 b) is performed:

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

(4b) The SDAP entity of the MRB mapped to this DRB is reconfigured according to the received SDAP-Config, in particular according to the operations defined in TS 37.324. When the target base station cannot support or needs to modify the configuration of part of the parameters in the current SDAP-Config, the SDAP-Config containing the new SDAP entity configuration information may be sent to reconfigure the SDAP entity.

7) If the MRB-associated SDAP entity mapped to this DRB associates an MBS Session, then the PDU-Session is set to the PDU-SessionID of the associated PDU Session and/or the MBS-SessionID is released and/or the user plane resources for this MBS-Session are indicated to the upper layer. The purpose of this operation is to modify the MBS session identity to the associated PDU session identity.

8) Release/discard MRB-Identity.

It should be noted that, embodiments obtained by exchanging the execution sequence of the above operations are also within the scope of the present invention. Further, operations 1 and 2 may not be included in the description above for radio bearer configuration. Operation 1 may be described in the RLC bearer release related description and operation 2 may be described in the RLC bearer addition/modification related description.

For each DRB-Identity corresponding DRB contained in the mrbtopmap list, at least one of the following operations a-C is performed:

a) If the MRB mapped to the DRB is a separate MRB (i.e., one PTM RLC and one PTP RLC are associated at the same time), the PTM RLC bearer is released. Specifically including releasing the RLC entity and releasing the corresponding logical channel as defined in section 5.1.3 of TS 38.322.

B) If the MRB mapped to the DRB associates (i.e. associates only) one PTM RLC entity, the PTM transmission indication identity and/or the corresponding G-RNTI is released (or indicated to be released by the PTM RLC entity).

C) An RLC entity mapped to the MRB association of the DRB is associated to the DRB. For PTP MRB configured with PTP RLC entities only, the RLC refers to PTP RLC, and for PTM MRB configured with PTM RLC entities only, the RLC refers to PTM RLC.

It should be noted that, embodiments obtained by exchanging the execution sequence of the above operations are also within the scope of the present invention.

For MRBs that are not mapped to any DRB (i.e., MRBs corresponding to each MRB-Identity not included in the mrbToDrbMappingList), the MRBs are released, including specifically releasing the PDCP entity and MRB-Identity, indicating the release of the MRBs and tmgi of the released MRBs to the upper layer.

For each DRB-Identity in DRB-ToReleaseList (to release DRB information) contained in the second RRCRECONfigure message, if the DRB-Identity is not part of the current UE configuration, but the DRB-Identity maps to one MRB (i.e., DRB-Identity is contained in the mrbToDrbMappingList field), then at least one of the following operations I-II is performed:

i: MRB-Identity of PDCP entities mapped to this DRB and MRB is released.

II: if an associated SDAP entity is configured for the MRB mapped to this DRB, the release of the MRB mapped to this DRB is indicated to the SDAP entity.

The following describes some of the fields involved in the present invention as follows: DRB-ToAddModList is used to indicate configuration information for a set of added or modified DRBs; the mrbToDrbMappingList is used for indicating the mapping relation between the DRB or MRB-Identity and DRB-Identity to which each MRB is mapped, 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 (e.g. when configuring the MEB), the mrbToDrbMappingList need not contain the MBS session and the associated PDU session, otherwise, the information of the MBS session and the associated PDU session need not be contained, may also be contained in another field mbsSerssionTopdusersuppinglist different from the mrbToDrbMappingList, for indicating the association relation between the MBS session and the associated PDU session; DRB-Identity is used to identify DRBs used by the UE; MRB-Identity is used to identify the MRB used by the UE; the resessablichp is used to indicate that the PDCP entity should be re-established; the cipheringDisabled is used to indicate which encryption algorithm is configured for the radio bearer, which disables encryption; the integrity protection indicates whether integrity protection is configured for this radio bearer; the securityConfig indicates a security algorithm and a key used by a radio bearer configured in the radio beareconfig; the keyToUse indicates that the bearer configured in the radiobearconfig uses the master key or the auxiliary key to derive encryption and integrity protected 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 whether the PDCP entity continues or resets the downstream EHC header compression protocol during PDCP re-establishment; drb-ContinueEHC-UL is used to indicate whether the PDCP entity continues or resets the upstream EHC header compression protocol during PDCP re-establishment; the recovery PDCP is used for indicating that the PDCP should perform recovery according to the operation defined by TS 38.323; the PDCP-Config is used to set configurable PDCP parameters for DRBs or MRBs; the SDAP-Config is used for setting configurable SDAP parameters for DRB or MRB; PDU-session is the identity of the associated PDU session for which the QoS flow maps to this DRB; the mbs-Session is the identity of the PDU Session to which the QoS flow maps to this MRB.

In the present invention, there is a one-to-one mapping between MRB and DRB. DRB-Identity mapping to MRB, DRB-Identity mapping to MRB-Identity, DRB mapping to MRB all indicate that this DRB is mapped from MRB, i.e. DRB-Identity is contained in the mrbToDrbMappingList field.

In the present invention, the field may also be referred to as an information element IE.

In the embodiment of the invention, the PTM RLC entity is also called a PTM associated RLC entity or an RLC entity configured with G-RNTI or an RLC entity associated with G-RNTI or an RLC entity for PTM transmission; the PTP RLC entity is also referred to as PTP associated RLC entity or RLC entity for PTP transmission.

It should be noted that an MBS service (or referred to as an MBS session) may be identified by an MBS identifier, which may be a TMGI and/or a session identifier sessionId, where the TMGI may include a PLMN identifier and/or a service identifier, which 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, microcontroller, embedded processor, or the like. The memory 602 may include, for example, volatile memory (such as random access memory RAM), a Hard Disk Drive (HDD), non-volatile memory (such as flash memory), or other memory systems. The memory 602 has stored thereon program instructions. Which, when executed by the processor 601, may perform one or more of the steps of the methods of the present invention described above with respect to fig. 3-5.

In addition, the computer-executable instructions or programs running on the apparatus according to the present invention may be programs that cause a computer to implement 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 a volatile store such as a random access memory RAM, a Hard Disk Drive (HDD), a nonvolatile store such as a flash memory, or other memory system.

Computer-executable instructions or programs for implementing the functions of the embodiments of the present invention may be recorded on a computer-readable storage medium. The corresponding functions can be realized by causing a computer system to read programs recorded on the recording medium and execute the programs. The term "computer system" as used herein may be a computer system embedded in the device and may include an operating system or hardware (e.g., peripheral devices). The "computer-readable storage medium" may be a semiconductor recording medium, an optical recording medium, a magnetic recording medium, a recording medium storing a program dynamically at a short time, or any other recording medium readable by a computer.

The various features or functional modules of the apparatus used in the embodiments described above may be implemented or performed by circuitry (e.g., single-chip or multi-chip integrated circuits). Circuits designed to perform the functions described herein may include a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. The circuit may be a digital circuit or an analog circuit. Where new integrated circuit technologies are presented as an alternative to existing integrated circuits due to advances in semiconductor technology, one or more embodiments of the present invention may also be implemented using these new integrated circuit technologies.

Furthermore, 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 devices installed indoors or outdoors may be used as terminal devices or communication devices such as AV devices, kitchen devices, cleaning devices, air conditioners, office devices, vending machines, and other home appliances, etc.

As above, the embodiments of the present invention have been described in detail with reference to the accompanying drawings. However, the specific structure is not limited to the above-described embodiment, and the present invention also includes any design modification without departing from the gist of the present invention. In addition, various modifications can be made to the present invention within the scope of the claims, and embodiments obtained by appropriately combining the technical means invented by the different embodiments are also included in the technical scope of the present invention. Further, the components having the same effects described in the above embodiments may be replaced with each other.

Claims

1. A method performed by a user equipment for cell switching, comprising:

receiving a first RRC reconfiguration message which is generated by a source base station and aims at the user equipment from the source base station, wherein the first RRC reconfiguration message carries a second RRC reconfiguration message which is generated by a target base station, and the first RRC reconfiguration message also comprises mapping relation information between MRB which aims at a multicast broadcast service session (MBS session) and DRB which aims at a PDU session; and

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

the second RRC reconfiguration message is generated by the target base station in response to the cell handover request message sent by the source base station and sent to the source base station.

2. The method of claim 1, wherein prior to performing the reconfiguration operation, the method further comprises:

when the first RRC reconfiguration message is received, judging whether the first RRC reconfiguration message comprises a field for indicating that the target base station does not support MBS session; and

and if the first RRC reconfiguration message comprises the field, analyzing the field, and analyzing the second RRC reconfiguration message from the field.

3. The method of claim 1, wherein reconfiguring the RRC configuration of the user equipment related to the MBS session to an RRC configuration related to the PDU session supported by the target base station based on the second RRC reconfiguration message and/or the mapping relation information comprises:

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

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

releasing the PTM transmission indication identification of the PTM RLC entity if the MRB mapped to the DRB is a PTM MRB configured with only the PTM RLC entity;

if the MRB mapped to the DRB is a PTM MRB configured with only PTM RLC entities or a PTP MRB configured with only PTP RLC entities, the PTM RLC or PTP RLC entity associated with the MRB mapped to the DRB is associated to the DRB.

4. The method of any of claims 1-3, wherein the second RRC reconfiguration message includes DRB change information including information that the target base station indicates a DRB that needs to be changed, reconfiguring an RRC configuration of the user equipment related to an MBS session to an RRC configuration related to a PDU session supported by the target base station based on the second RRC reconfiguration message and/or the mapping relation information includes:

determining, for each DRB indicated by the DRB change information, whether the DRB is included in an existing RRC configuration of the user equipment;

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

if there is no MRB mapped to the DRB, establishing the DRB;

if there is an MRB mapped to the DRB, reconfiguration is performed for the MRB mapped to the DRB.

5. The method of claim 4, wherein the DRB change information comprises an additionally modified DRB list, the additionally modified DRB list comprising information that the target base station requires an additionally or modified DRB, the reconfiguring for the MRB mapped to the DRB comprising:

if the DRB is included in the newly modified DRB list, performing at least one of:

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

reconstructing a PDCP entity mapped to an MRB of the DRB if the RRC reconfiguration information includes a PDCP reconstruction indication;

if the RRC reconfiguration information includes a PDCP restoration instruction, causing the PDCP entity mapped to the MRB of the DRB to perform data restoration;

if the RRC reconfiguration information comprises PDCP reconfiguration information, reconfiguring the PDCP entity mapped to the MRB of the DRB according to the PDCP reconfiguration information;

If the RRC reconfiguration information comprises SDAP reconfiguration information, reconfiguring an SDAP entity mapped to the MRB of the DRB according to the SDAP reconfiguration information;

for MBS session corresponding to MRB mapped to the DRB, modifying the MBS session identification to PDU session identification corresponding to the DRB;

the MRB identity in the existing RRC configuration of the user equipment is released or discarded.

6. The method of claim 4, wherein the DRB change information includes a to-be-released DRB list including information of DRBs that the target base station requires to release, and reconfiguring for an MRB mapped to the DRB includes:

if the DRB is included in the list of DRBs to be released, performing:

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

If the MRB mapped to the DRB is configured with a corresponding SDAP entity, the SDAP entity is instructed to release the MRB mapped to the DRB.

7. The method according to any of claims 1-3, wherein reconfiguring the RRC configuration of the user equipment related to MBS sessions to an RRC configuration related to PDU sessions supported by the target base station based on the second RRC reconfiguration message and/or the mapping relation information further comprises:

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

8. A method performed by a source base station for cell switching, comprising:

when the source base station sends the cell switching request message to a target base station, determining whether the target base station supports an MBS session or not based on interface parameter information of a network interface established between the source base station and the target base station, wherein the cell switching request message is used for requesting the target base station to prepare RRC resources for user equipment;

if the target base station does not support MBS session, the RRC configuration information related to MBS session configured by the source base station for the user equipment is not carried in the cell switching request message; and

and changing the RRC configuration information related to the MBS session into the RRC configuration information related to the PDU session supported by the target base station, carrying the changed RRC configuration information in the cell switching request message, and sending the cell switching request message to the target base station.

9. The method of claim 8, further comprising:

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

Upon receiving a handover request confirm message sent by the target base station in response to the cell handover request message, generating first RRC reconfiguration information for handover of the user equipment to the target base station based on second RRC reconfiguration information carried in the handover request confirm message, and sending the generated first RRC reconfiguration information to the user equipment, the second RRC reconfiguration information being generated by the target base station based on RRC reconfiguration information carried in the cell handover request message.

10. A user equipment, comprising:

a processor; and

a memory in which instructions are stored,

wherein the instructions, when executed by the processor, perform the processing method according to any one of claims 1 to 7.