User equipment, source base station, target base station and MBS switching method

Abstract

The present invention discloses a user equipment (UE), a source base station, a target base station and a switching method for a multicast / broadcast service (MBS). The method is partially performed by the source base station, including exchanging MBS service and / or service quality (QoS) related information between the source base station and at least one UE as part of a switching measurement message and / or exchanging MBS service and / or QoS related information with the target base station as part of a switching request message, and is partially performed by the target base station, including exchanging MBS scheduling information and timing information when the target base station starts / stops PDCP SN allocation and / or forwards data to at least the source base station through a switching confirmation message and / or the UE starts / stops PDCP SN allocation and / or forwards data to the source base station through a switching command message, and further includes deciding to support the best MBS mobility for a given UE based on the switching measurement and / or switching request message to be performed and / or configured by the source base station or the target base station.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a user equipment (UE), a source base station, a target base station, and a handover (HO) method for a multicast / broadcast service (MBS), which can provide good communication performance and / or high reliability. Background Art

[0002] A wireless communication network may include a base station that may support communication of a user equipment (UE). The UE may communicate with the base station via downlink and uplink. Downlink refers to the communication link from the base station to the UE, and uplink refers to the communication link from the UE to the base station.

[0003] In 3rd generation partnership project (3GPP) cellular networks, broadcast and multicast services can be delivered through a transport service called multimedia broadcast / multicast service (MBMS). A broadcast multicast service center (BM-SC) server is responsible for disseminating media content to a group of subscribers. When a UE moves out of network coverage, the UE may not be able to use MBMS because the uplink and downlink connections to the BM-SC server are no longer available. MBMS is a point-to-multipoint (PTM) interface specification designed to provide efficient broadcast and multicast service delivery in 3GPP cellular networks. Examples of MBMS interface specifications include those described in the universal mobile telecommunication system (UMTS) and long term evolution (LTE) communication specifications. For broadcast transmissions across multiple cells, the specification defines transmissions on a single frequency network configuration. Intended applications include mobile TV, news, radio broadcasting, file transfer, emergency alerts, etc. When the service is broadcast by MBMS, all cells in a multimedia broadcast / multicast service single frequency network (MBSFN) area transmit the same MBMS service.

[0004] Users access these services and obtain MBMS content through wireless communication devices, such as cellular phones, tablets, laptops, and other devices with wireless transceivers that communicate with base stations within the communication system. The base station provides wireless services to wireless communication devices (sometimes referred to as mobile devices or UEs) within the cell. Users can access at least some multimedia services through the UE using a point-to-point (PTP) connection or PTM transmission. In a 3GPP system, PTP services can be provided using unicast technology, and PTM transmissions can be provided using MBMS communications, transmitted via MBSFN or single cell point to multipoint (SC-PTM) communications. In a system operating according to a revised version of the 3GPP Long Term Evolution (LTE) communication specification, MBMS is provided using eMBMS. Therefore, MBMS services can be provided using unicast services, MBSFN, or SC-PTM in an LTE system. In the Radio Access Network (RAN) meeting #88-e held from June 29 to July 3, 2020, a new work item was approved to target RAN support for multicast / broadcast services (MBS) in 5G. The goal of this work item is to provide support in the RAN to enable common MBS services on 5GS to support different MBS services such as public safety and mission critical, V2X applications, transparent IPv4 / IPv6 multicast transport, IPTV, wireless software delivery, group communication, and IoT applications. One of the main goals of this RAN work item is to study and specify support for basic mobility with service continuity to support 5G new radio (NR) multicast / broadcast services (MBS).

[0005] During the 3GPP RAN2#111-e meeting, there was considerable discussion on NR MBS mobility, with many companies proposing to consider NR legacy handover with lossless characteristics as the baseline for NR MBS mobility due to the high reliability requirements of some NR MBS services. On the other hand, some companies proposed additional enhancements for lossless handover to address packet data convergence protocol (PDCP) sequence number (SN) allocation issues, PDCP count value misalignment, and data gap issues due to missynchronization between source and target gNBs during handover. In addition, during this meeting, some other companies proposed adopting NR dual active protocolsstacks (DAPS) handover to minimize service interruption time during NR MBS mobility; meanwhile, others have proposed to deprioritize DAPS HO due to its heavy signaling on the UE side. DAPS is critical for NR MBS mobility because some NR MBS services, such as V2X and industrial applications (e.g., motion sensors and actuators) require very low service interruption latency during mobility, but some modifications to the current DAPS or new DAPS and handover procedures are required to support low-latency MBS mobility. In addition to this, there are many issues related to MBS mobility in NR, such as nested signaling during handover and the type of information to be exchanged in signaling, as well as QoS handling issues that have not been resolved during the 3GPP RAN2#111-e meeting.

[0006] Therefore, this report proposes a new handover procedure to support MBS mobility with service continuity while guaranteeing the reliability and latency requirements of different MBS services for 5G and tries to address some of the above mentioned issues related to NR MBS mobility while minimizing UE signaling complexity and processing cost. Summary of the invention

[0007] The purpose of the present invention is to propose a user equipment (UE), a source base station, a target base station, and a switching method for a multicast / broadcast service (MBS), which can solve the problems in the prior art, solve the delay and reliability requirements during the MBS mobility process, reduce the UE signaling complexity, reduce processing costs, support service continuity, provide good communication performance, and / or provide high reliability.

[0008] In a first aspect of the present invention, a switching method for a multicast / broadcast service MBS performed by a user equipment UE comprises: determining, by the UE, MBS service and / or quality-of-service (QoS) related information as part of a switching measurement report; and exchanging the MBS service and / or the QoS related information as the part of the switching measurement report between at least two of the UE, a source base station, and a target base station, wherein a switching for UE MBS mobility execution and / or configuration is performed based on the part of the switching measurement report.

[0009] In one embodiment of the present invention, the switching type for executing and / or configuring the UE MBS mobility is selected based on at least one of the following: an indication from the UE including the MBS service and / or the QoS related information; an internal configuration of the source base station; or an indication from the core network.

[0010] In one embodiment of the present invention, the MBS service and / or the QoS related information includes a UE identity (ID), an MBS service ID, a QoS flow ID or a session ID association.

[0011] In one embodiment of the present invention, the internal configuration of the source base station includes UE ID, MBS service ID, QoS flow ID or session ID association.

[0012] In one embodiment of the present invention, the indication of the core network includes UE MBS context message, UEID, MBS service ID, QoS flow ID or session ID association.

[0013] In one embodiment of the present invention, determining by the UE the MBS service and / or the QoS related information as the part of the switching measurement report includes the UE receiving the MBS service and / or the QoS related information from the core network via a multicast radio bearer (MRB) or a unicast data radio bearer (DRB).

[0014] In one embodiment of the present invention, exchanging the MBS service and / or the QoS related information between at least two of the UE, the source base station and the target base station includes the UE indicating the MBS service and / or the QoS related information as the part of the switching measurement report to the source base station.

[0015] In one embodiment of the present invention, exchanging the MBS service and / or the QoS related information between at least two of the UE, the source base station and the target base station includes the source base station forwarding the MBS service and / or the QoS related information of the UE as the part of the switching measurement report to the target base station.

[0016] In one embodiment of the present invention, the source base station is instructed in the handover request signaling to forward the MBS service and / or the QoS related information of the UE to the target base station as the part of the handover measurement report.

[0017] In one embodiment of the present invention, the handover type selected for the UE MBS mobility execution and / or configuration includes lossless handover or lossless and low-delay handover.

[0018] In one embodiment of the present invention, the handover type selected for the UE MBS mobility execution and / or configuration includes the lossless handover or the lossless and low-delay handover according to the UE MBS service reliability and delay level requirements.

[0019] In one embodiment of the present invention, the switching method is characterized in that it also includes the UE receiving a configuration from the source base station, the configuration including at least one of the following: the agreed time for the source base station and the target base station to start / stop packet data convergence protocol (PDCP) sequence number (SN) allocation and / or data forwarding; target pre-allocation permission; uplink time advance command; downlink synchronization information; or MBS bearer scheduling / forwarding configuration; and / or the method also includes the UE receiving a switching command from the source base station, the switching command including target downlink / uplink synchronization information, MBS scheduling information and MBS data forwarding timing information; and / or pre-preparing the UE optimal reception configuration for MBS data, and deciding when to stop receiving downlink data from the source base station, when to release the source base station configuration, and releasing the source base station configuration accordingly.

[0020] In one embodiment of the present invention, the configuration is forwarded by the source base station from the target base station to the UE.

[0021] In one embodiment of the present invention, the configuration is forwarded by the source base station from the target base station to the UE in a handover initiation / command message.

[0022] In one embodiment of the present invention, when the UE receives the configuration from the source base station, the UE performs at least one of the following: synchronizing to the target cell based on the downlink synchronization timing and uplink time advance information provided by the source base station from the target base station; configuring separate entities of medium access control (MAC) configuration, PDCP configuration and / or radio link control (RLC) configuration for the target base station and the source base station; stopping receiving from the source base station after the timing information given in the radio resource control (RRC) configuration, while maintaining the source MAC, PDCP and / or MAC entity until the first packet is received from the target base station; stopping sending uplink (UL) first layer channel state information (CSI) feedback, hybrid automatic repeat request (HARQ) feedback, second layer RLC feedback, robust header compression (RLC) feedback, etc. compression, ROHC) feedback, HARQ data retransmission and / or RLC data retransmission to the source base station; the source base station and / or the target base station sends a switching completion message on a pre-allocated license or fails to switch the wireless link; omits sending a switching completion message and uses the pre-allocated license to perform uplink data transmission to the target base station; or releases the MAC configuration, the PDCP configuration and / or the RLC configuration of the source base station.

[0023] In a second aspect of the present invention, a switching method for a multicast / broadcast service (MBS) performed by a source base station comprises: exchanging MBS service and / or quality-of-service (QoS) related information between the source base station and at least one user equipment (UE) as part of a switching measurement message and / or exchanging the MBS service and / or the QoS related information with a target base station as part of a switching request message; and performing switching for UE MBS mobility execution and / or configuration based on the part of the switching measurement report.

[0024] In one embodiment of the present invention, the switching type for executing and / or configuring the UE MBS mobility is selected based on at least one of the following: an indication from the UE including the MBS service and / or the QoS related information; an internal configuration of the source base station; or an indication from the core network.

[0025] In one embodiment of the present invention, the MBS service and / or the QoS related information includes a UE identity (ID), an MBS service ID, a QoS flow ID or a session ID association.

[0026] In one embodiment of the present invention, the internal configuration of the source base station includes UE ID, MBS service ID, QoS flow ID or session ID association.

[0027] In one embodiment of the present invention, the indication of the core network includes UE MBS context message, UEID, MBS service ID, QoS flow ID or session ID association.

[0028] In one embodiment of the present invention, exchanging the MBS service and / or the quality of service QoS related information between the source base station and at least one user equipment UE as the part of the switching measurement message and / or exchanging the MBS service and / or the quality of service QoS related information with the target base station as the part of the switching request message includes the source base station determining the MBS service and / or the QoS related information as the part of the switching measurement report from the UE.

[0029] In one embodiment of the present invention, exchanging the MBS service and / or the quality of service QoS related information between the source base station and at least one user equipment UE as the part of the switching measurement message and / or exchanging the MBS service and / or the quality of service QoS related information with the target base station as the part of the switching request message includes the source base station forwarding the MBS service and / or the QoS related information from the UE as the part of the switching measurement report to the target base station.

[0030] In one embodiment of the present invention, the source base station is instructed in the handover request signaling to forward the MBS service and / or the QoS related information from the UE to the target base station as the part of the handover measurement report.

[0031] In one embodiment of the present invention, the handover type selected for the UE MBS mobility execution and / or configuration includes lossless handover or lossless and low-delay handover.

[0032] In one embodiment of the present invention, the handover type selected for the UE MBS mobility execution and / or configuration includes the lossless handover or the lossless and low-delay handover according to the UE MBS service reliability and delay level requirements.

[0033] In one embodiment of the present invention, the handover method further includes the source base station receiving a handover request confirmation from the target base station in response to the handover request signaling.

[0034] In one embodiment of the present invention, the switching request confirmation includes a configuration, and the configuration includes at least one of the following: the agreed time for the source base station and the target base station to start / stop packet data convergence protocol (PDCP) sequence number (SN) allocation and / or data forwarding; target pre-allocation permission; uplink time advance command; downlink synchronization information; or MBS bearer scheduling / forwarding configuration.

[0035] In one embodiment of the present invention, when the source base station receives the switching request confirmation, the source base station performs at least one of the following: if low latency and lossless switching is selected and / or configured for UE MBS mobility, executes PDCP SN, and the PDCP SN allocates PDCP service data unit (SDU) data forwarding; or sends an SN status transfer message to the target base station to convey the uplink PDCP SN receiver status and downlink PDCP SN transmitter status of the application PDCP state preservation.

[0036] In one embodiment of the present invention, the uplink PDCP SN receiver status includes at least one of the following: the PDCP SN of the first lost UL PDCP SDU; or a reception status bitmap of an out-of-sequence UL PDCP SDU that the UE needs to retransmit in the target cell.

[0037] In one embodiment of the present invention, the downlink PDCP SN transmitter status indicates the next PDCP SN allocated by the target base station to the new PDCP SDU, and if lossless switching is configured, there is no PDCP SN yet.

[0038] In one embodiment of the present invention, the switching method further includes sending the configuration to the UE by the source base station.

[0039] In one embodiment of the present invention, the configuration is forwarded by the source base station from the target base station to the UE.

[0040] In one embodiment of the present invention, the configuration is forwarded by the source base station from the target base station to the UE in a handover initiation / command message.

[0041] In a third aspect of the present invention, a method for switching a multicast / broadcast service (MBS) performed by a target base station comprises: exchanging MBS service and / or service quality QoS related information between at least two of a user equipment UE, a source base station and the target base station as part of a switching measurement report; and when the target base station starts / stops PDCP SN allocation, exchanging MBS scheduling information and timing information and / or forwarding data to at least the source base station via the switching confirmation message and / or the UE via a switching command message.

[0042] In one embodiment of the present invention, the switching type for executing and / or configuring the UE MBS mobility is selected based on at least one of the following: an indication from the UE including the MBS service and / or the QoS related information; an internal configuration of the source base station; or an indication from the core network.

[0043] In one embodiment of the present invention, the MBS service and / or the QoS related information includes a UE identity (ID), an MBS service ID, a QoS flow ID or a session ID association.

[0044] In one embodiment of the present invention, the internal configuration of the source base station includes UE ID, MBS service ID, QoS flow ID or session ID association.

[0045] In one embodiment of the present invention, the indication of the core network includes UE MBS context message, UEID, MBS service ID, QoS flow ID or session ID association.

[0046] In one embodiment of the present invention, exchanging the MBS service and / or the QoS related information between at least two of the UE, the source base station and the target base station includes forwarding the MBS service and / or the QoS related information from the UE to the target base station by the source base station as the part of the switching measurement report.

[0047] In one embodiment of the present invention, the source base station is instructed in the handover request signaling to forward the MBS service and / or the QoS related information from the UE to the target base station as the part of the handover measurement report.

[0048] In one embodiment of the present invention, the handover type selected for the UE MBS mobility execution and / or configuration includes lossless handover or lossless and low-delay handover.

[0049] In one embodiment of the present invention, the handover type selected for the UE MBS mobility execution and / or configuration includes the lossless handover or the lossless and low-delay handover according to the UE MBS service reliability and delay level requirements.

[0050] In one embodiment of the present invention, when the target base station receives the handover request signaling, the target base station performs at least one of the following: performs admission control on the UE MBS mobility and performs selection of the handover type for the UE MBS mobility execution and / or configuration, if the source base station does not perform the handover type selected for the UE MBS mobility execution and / or configuration; determines and / or decides based on the configuration received in the handover request, the time to start PDCP SN allocation and / or forwards data to the UE according to the time reference provided by the source base station; if the MBS session / service / temporary mobile group identity (TMGI) received by the UE exists in the target base station, initiates UE MSB session joining, or if the MBS session received by the UE does not exist in the target base station, initiating a session establishment request to the core network; if necessary, switching the UE to a new radio bearer, and striving to provide the same QoS flow to the radio bearer mapping and scheduling configuration / forwarding processing of the MBS bearer indicated by the source base station; determining the timing configuration that needs to be synchronized with the UE, and providing the UE with a time proposal command and a pre-allocation grant; or starting to forward the copied MBS downlink data forwarded from the source base station as the start of allocating the PDCP SN to the UE.

[0051] In one embodiment of the present invention, the handover method further includes the target base station sending the handover request acknowledgment (ACK) to the source base station in response to the handover request signaling.

[0052] In one embodiment of the present invention, the switching request confirmation includes a configuration, and the configuration includes at least one of the following: the agreed time for the source base station and the target base station to start / stop packet data convergence protocol (PDCP) sequence number (SN) allocation and / or data forwarding; target pre-allocation permission; uplink time advance command; downlink synchronization information; or MBS bearer scheduling / forwarding configuration.

[0053] In one embodiment of the present invention, the configuration is forwarded by the source base station from the target base station to the UE.

[0054] In one embodiment of the present invention, the source base station forwards the configuration from the target base station to the UE in a handover initiation / command message, and / or the target base station prepares according to the configuration received in the handover request, synchronization / timing information, UE pre-allocated grant allocation, and downlink and uplink timing advance.

[0055] In a fourth aspect of the present invention, a user equipment UE for a multicast / broadcast service MBS comprises: a memory, a transceiver and a processor coupled to the memory and the transceiver. The processor is configured to: determine MBS service and / or service quality QoS related information as part of a handover measurement report; and exchange the MBS service and / or the QoS related information as the part of the handover measurement report between at least two of the UE, a source base station and a target base station, wherein a handover for UE MBS mobility execution and / or configuration is performed based on the part of the handover measurement report.

[0056] In one embodiment of the present invention, the switching type for executing and / or configuring the UE MBS mobility is selected based on at least one of the following: an indication from the UE including the MBS service and / or the QoS related information; an internal configuration of the source base station; or an indication from the core network.

[0057] In one embodiment of the present invention, the MBS service and / or the QoS related information includes UE identification ID, MBS service ID, QoS flow ID or session ID association.

[0058] In one embodiment of the present invention, the internal configuration of the source base station includes UE ID, MBS service ID, QoS flow ID or session ID association.

[0059] In one embodiment of the present invention, the indication of the core network includes UE MBS context message, UEID, MBS service ID, QoS flow ID or session ID association.

[0060] In one embodiment of the present invention, determining, by the processor, the MBS service and / or the QoS related information as the part of the handover measurement report includes the UE receiving the MBS service and / or the QoS related information from the core network via a multicast radio bearer MRB or a unicast data radio bearer DRB.

[0061] In one embodiment of the present invention, exchanging the MBS service and / or the QoS related information between at least two of the UE, the source base station and the target base station includes indicating, by the processor, the MBS service and / or the QoS related information as the part of the switching measurement report to the source base station.

[0062] In one embodiment of the present invention, exchanging the MBS service and / or the QoS related information between at least two of the UE, the source base station and the target base station includes the source base station forwarding the MBS service and / or the QoS related information of the UE as the part of the switching measurement report to the target base station.

[0063] In one embodiment of the present invention, the source base station is instructed in the handover request signaling to forward the MBS service and / or the QoS related information of the UE to the target base station as the part of the handover measurement report.

[0064] In one embodiment of the present invention, the handover type selected for the UE MBS mobility execution and / or configuration includes lossless handover or lossless and low-delay handover.

[0065] In one embodiment of the present invention, the handover type selected for the UE MBS mobility execution and / or configuration includes the lossless handover or the lossless and low-delay handover according to the UE MBS service reliability and delay level requirements.

[0066] In one embodiment of the present invention, the UE also includes the transceiver receiving a configuration from the source base station, the configuration including at least one of the following: the agreed time for the source base station and the target base station to start / stop packet data convergence protocol PDCP sequence number SN allocation and / or data forwarding; target pre-allocation permission; uplink time advance command; downlink synchronization information; or MBS bearer scheduling / forwarding configuration; and / or wherein the transceiver is configured to receive a switching command from the source base station, the switching command including target downlink / uplink synchronization information, MBS scheduling information and MBS data forwarding timing information; and / or wherein the processor is configured to prepare the UE optimal reception configuration for MBS data in advance, and decide when to stop receiving downlink data from the source base station, when to release the source base station configuration, and release the source base station configuration accordingly.

[0067] In one embodiment of the present invention, the configuration is forwarded by the source base station from the target base station to the transceiver.

[0068] In one embodiment of the invention, the configuration is forwarded by the source base station from the target base station to the transceiver in a handover initiation / command message.

[0069] In one embodiment of the present invention, when the transceiver receives the configuration from the source base station, the processor performs at least one of the following: synchronizing to the target cell based on the downlink synchronization timing and uplink time advance information provided by the source base station from the target base station; configuring separate entities of media access control MAC configuration, PDCP configuration and / or radio link control RLC configuration for the target base station and the source base station; stopping receiving from the source base station after the timing information given in the radio resource control RRC configuration, while maintaining the source MAC, PDCP and / or MAC entity until receiving from the target base station to the first group; stop sending uplink UL first layer channel state information CSI feedback, hybrid automatic repeat request HARQ feedback, second layer RLC feedback, robust header compression ROHC feedback, HARQ data retransmission and / or RLC data retransmission to the source base station; the source base station and / or the target base station sends a switching completion message on a pre-allocated license or fails to switch the radio link; omits sending a switching completion message and uses the pre-allocated license to perform uplink data transmission to the target base station; or releases the MAC configuration, the PDCP configuration and / or the RLC configuration of the source base station.

[0070] In a fifth aspect of the present invention, a source base station for a multicast / broadcast service MBS comprises a memory, a transceiver and a processor coupled to the memory and the transceiver. The processor is configured to: exchange MBS service and / or service quality QoS related information between the source base station and at least one user equipment UE as part of a handover measurement message and / or exchange the MBS service and / or the QoS related information with a target base station as part of a handover request message; and perform handover for UE MBS mobility execution and / or configuration based on the part of the handover measurement report.

[0071] In one embodiment of the present invention, the switching type for executing and / or configuring the UE MBS mobility is selected based on at least one of the following: an indication from the UE including the MBS service and / or the QoS related information; an internal configuration of the source base station; or an indication from the core network.

[0072] In one embodiment of the present invention, the MBS service and / or the QoS related information includes UE identification ID, MBS service ID, QoS flow ID or session ID association.

[0073] In one embodiment of the present invention, the internal configuration of the source base station includes UE ID, MBS service ID, QoS flow ID or session ID association.

[0074] In one embodiment of the present invention, the indication of the core network includes UE MBS context message, UEID, MBS service ID, QoS flow ID or session ID association.

[0075] In one embodiment of the present invention, exchanging the MBS service and / or the quality of service QoS related information between the source base station and at least one user equipment UE as the part of the switching measurement message and / or exchanging the MBS service and / or the quality of service QoS related information with the target base station as the part of the switching request message includes determining, by the processor, the MBS service and / or the QoS related information as the part of the switching measurement report from the UE.

[0076] In one embodiment of the present invention, exchanging the MBS service and / or the quality of service QoS related information between the source base station and at least one user equipment UE as the part of the switching measurement message and / or exchanging the MBS service and / or the quality of service QoS related information with the target base station as the part of the switching request message includes forwarding the MBS service and / or the QoS related information from the UE as the part of the switching measurement report to the target base station by the transceiver.

[0077] In one embodiment of the present invention, the transceiver is instructed in handover request signaling to forward the MBS service and / or the QoS related information from the UE to the target base station as the part of the handover measurement report.

[0078] In one embodiment of the present invention, the handover type selected for the UE MBS mobility execution and / or configuration includes lossless handover or lossless and low-delay handover.

[0079] In one embodiment of the present invention, the handover type selected for the UE MBS mobility execution and / or configuration includes the lossless handover or the lossless and low-delay handover according to the UE MBS service reliability and delay level requirements.

[0080] In one embodiment of the present invention, the transceiver is configured to receive a handover request confirmation from the target base station in response to the handover request signaling.

[0081] In one embodiment of the present invention, the switching request confirmation includes a configuration, and the configuration includes at least one of the following: the agreed time for the source base station and the target base station to start / stop packet data convergence protocol PDCP sequence number SN allocation and / or data forwarding; target pre-allocation permission; uplink time advance command; downlink synchronization information; or MBS bearer scheduling / forwarding configuration.

[0082] In one embodiment of the present invention, when the transceiver receives the switching request confirmation, the processor performs at least one of the following: if low latency and lossless switching is selected and / or configured for UE MBS mobility, executes PDCP SN, and the PDCP SN allocates PDCP service data unit SDU data forwarding; or sends an SN status transfer message to the target base station to convey the uplink PDCP SN receiver status and downlink PDCP SN transmitter status of the application PDCP state preservation.

[0083] In one embodiment of the present invention, the uplink PDCP SN receiver status includes at least one of the following: the PDCP SN of the first lost UL PDCP SDU; or the reception status bitmap of the out-of-sequence UL PDCP SDU that the UE needs to retransmit in the target cell.

[0084] In one embodiment of the present invention, the downlink PDCP SN transmitter status indicates the next PDCP SN allocated by the target base station to the new PDCP SDU, and if lossless switching is configured, there is no PDCP SN yet.

[0085] In one embodiment of the present invention, the transceiver is configured to send the configuration to the UE.

[0086] In one embodiment of the present invention, the configuration is forwarded by the transceiver from the target base station to the UE.

[0087] In one embodiment of the invention, the configuration is forwarded by the transceiver from the target base station to the UE in a handover initiation / command message.

[0088] In a sixth aspect of the present invention, a target base station for a multicast / broadcast service MBS comprises a memory, a transceiver and a processor coupled to the memory and the transceiver. The processor is configured to: exchange MBS service and / or service quality QoS related information between at least two of a user equipment UE, a source base station and the target base station as part of a handover measurement report; and when the target base station starts / stops PDCP SN allocation, exchange MBS scheduling information and timing information and / or forward data to at least the source base station via the handover confirmation message and / or the UE through a handover command message.

[0089] In one embodiment of the present invention, the switching type for executing and / or configuring the UE MBS mobility is selected based on at least one of the following: an indication from the UE including the MBS service and / or the QoS related information; an internal configuration of the source base station; or an indication from the core network.

[0090] In one embodiment of the present invention, the MBS service and / or the QoS related information includes UE identification ID, MBS service ID, QoS flow ID or session ID association.

[0091] In one embodiment of the present invention, the internal configuration of the source base station includes UE ID, MBS service ID, QoS flow ID or session ID association.

[0092] In one embodiment of the present invention, the indication of the core network includes UE MBS context message, UEID, MBS service ID, QoS flow ID or session ID association.

[0093] In one embodiment of the present invention, exchanging the MBS service and / or the QoS related information between at least two of the UE, the source base station and the target base station includes forwarding the MBS service and / or the QoS related information from the UE to the transceiver by the source base station as the part of the switching measurement report.

[0094] In one embodiment of the present invention, the source base station is instructed in handover request signaling to forward the MBS service and / or the QoS related information from the UE to the transceiver as the part of the handover measurement report.

[0095] In one embodiment of the present invention, the handover type selected for the UE MBS mobility execution and / or configuration includes lossless handover or lossless and low-delay handover.

[0096] In one embodiment of the present invention, the handover type selected for the UE MBS mobility execution and / or configuration includes the lossless handover or the lossless and low-delay handover according to the UE MBS service reliability and delay level requirements.

[0097] In one embodiment of the present invention, when the target base station receives the handover request signaling, the target base station performs at least one of the following: performs admission control on the UE MBS mobility and performs selection of the handover type for the UE MBS mobility execution and / or configuration, if the source base station does not perform the handover type selected for the UE MBS mobility execution and / or configuration; determines and / or decides based on the configuration received in the handover request, starts PDCP The method comprises: forwarding data to the UE according to the time allocated by the SN and / or forwarding data to the UE according to the time reference provided by the source base station; initiating a UE MSB session join if the MBS session / service / temporary mobile group identity TMGI received by the UE exists in the target base station, or initiating a session establishment request to the core network if the MBS session received by the UE does not exist in the target base station; switching the UE to a new radio bearer if necessary, and striving to provide the same QoS flow to the radio bearer mapping and scheduling configuration / forwarding processing of the MBS bearer indicated by the source base station; determining the timing configuration that needs to be synchronized with the UE, and providing the UE with a time proposal command and a pre-allocation grant; or starting to forward the copied MBS downlink data forwarded from the source base station as the start of allocating the PDCP SN to the UE.

[0098] In one embodiment of the present invention, the transceiver is configured to send the handover request confirmation to the source base station in response to the handover request signaling.

[0099] In one embodiment of the present invention, the switching request confirmation includes a configuration, and the configuration includes at least one of the following: the agreed time for the source base station and the target base station to start / stop packet data convergence protocol PDCP sequence number SN allocation and / or data forwarding; target pre-allocation permission; uplink time advance command; downlink synchronization information; or MBS bearer scheduling / forwarding configuration.

[0100] In one embodiment of the present invention, the configuration is forwarded from the transceiver to the UE by the source base station.

[0101] In one embodiment of the present invention, the source base station forwards the configuration from the transceiver to the UE in a handover initiation / command message, and / or the target base station prepares according to the configuration received in the handover request, synchronization / timing information, UE pre-allocated grant allocation, and downlink and uplink timing advance.

[0102] In a seventh aspect of the present invention, a non-transitory machine-readable storage medium has stored thereon instructions that, when executed by a computer, cause the computer to perform the above method.

[0103] In an eighth aspect of the present invention, a chip includes a processor for calling and running a computer program stored in a memory so that a device equipped with the chip executes the above method.

[0104] In a ninth aspect of the present invention, a computer-readable storage medium having a computer program stored therein causes a computer to execute the above method.

[0105] In a tenth aspect of the present invention, a computer program product includes a computer program, and the computer program causes a computer to execute the above method.

[0106] In an eleventh aspect of the present invention, a computer program causes a computer to execute the above method. BRIEF DESCRIPTION OF THE DRAWINGS

[0107] To further illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For any technician in the field, other drawings can be obtained based on the following drawings without creative work.

[0108] Figure 1 is a block diagram of a user equipment (UE), a source base station, and a target base station communicating in a communication network system according to an embodiment of the present invention.

[0109] Figure 2 is a flowchart of a multicast / broadcast service (MBS) switching method performed by a user equipment (UE) in a communication network system according to an embodiment of the present invention.

[0110] Figure 3 is a flowchart of a handover method for a multicast / broadcast service (MBS) performed by a source base station in a communication network system according to an embodiment of the present invention.

[0111] Figure 4 is a flowchart of a handover method for a multicast / broadcast service (MBS) performed by a target base station in a communication network system according to an embodiment of the present invention.

[0112] Figure 5 is a schematic diagram of a 5G NR baseline switching process according to an embodiment of the present invention.

[0113] Figure 6 2 is a schematic diagram of switching a UE with MBS capability from one NG-RAN to another NG-RAN according to an embodiment of the present invention.

[0114] Figure 7 is a schematic diagram of a proposed handover to support low-latency and reliable MBS mobility according to an embodiment of the present invention.

[0115] Figure 8 is a block diagram of a system for wireless communication according to an embodiment of the present invention. DETAILED DESCRIPTION

[0116] The technical matters, structural features, objectives and effects of the embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. Specifically, the terms used in the embodiments of the present invention are only for the purpose of describing the embodiments of the present invention and are not intended to limit the present invention.

[0117] Some embodiments of the present invention relate to wireless communications, and more specifically to mobility issues for Multicast / Broadcast Service (MBS) in NR systems. MBS is a point-to-multipoint (PTM) interface designed to provide efficient broadcast and multicast service delivery in 3GPP cellular networks.

[0118] As discussed according to the [RP-201308] 3GPP document, NR MBS explicitly requires support for basic mobility with service continuity. Although MBS mobility has been extensively discussed in recent 3GPP meetings, there are still many technical gaps related to MBS mobility that have not been discovered or are still being further discussed in upcoming meetings, such as the handling of QoS requirements during MBS mobility, service interruption delay during MBS mobility, the type of handover selection to be performed / configured to support MBS mobility, the nested signaling during handover, and the type of information exchanged in the signaling during handover. The main goal of some embodiments of the present invention is to address some of these technical gaps. Therefore, some embodiments of the present invention propose a novel handover method with modified handover signaling and procedures to support seamless MBS mobility with service continuity, while taking into account the differences in QoS requirements of different MBS use cases during mobility.

[0119] In the NR MBS mobility framework, most of the proposals submitted to the recent 3GPP RAN2 meeting focused on legacy NR unicast handover (HO) with lossless characteristics as a potential candidate for MBS mobility in NR. Legacy NR unicast handover with lossless characteristics can effectively solve the reliability problem during MBS mobility. However, lossless HO will incur additional (from 25ms to 40ms) service interruption time. Given that some MBS use cases for NR may involve MBS reception during mobility, such as V2X and industrial applications (e.g., motion sensors and actuators) that require very low service interruption latency on top of their reliability requirements, a mechanism to simultaneously handle both latency and reliability issues is very important for efficient MBS mobility. Although, some companies have proposed adopting DAPS to achieve low-latency MBS mobility, DAPS also introduces a lot of signaling to the UE due to receiving signals from both the source and target handover gNBs at the same time.

[0120] In some embodiments of the present invention, a QoS-aware reliable and low-latency handover method is proposed to support MBS mobility with service continuity and guarantee the difference in MBS service QoS requirements during UE handover. In this method, we propose to exchange MBS service and / or QoS related information between the UE, the source base station (such as the source gNB) and the target base station (such as the target gNB) to determine the handover type MBS mobility configured for the UE. In addition, we propose some improvements to the current NR handover, including some modifications to the HO signaling and procedures, such as introducing new types of information to be exchanged during the handover process (e.g., timing related information between the UE, the source and the target gNB) to reduce the service interruption time while keeping the UE signaling complexity, processing cost and power consumption as low as possible (according to the recommendation of [RP-201308] that in order to facilitate the implementation and deployment of NR MBS functions, the complexity of the UE should be minimized and the impact on the device hardware should be avoided).

[0121] Compared with the prior art, the main advantage of some embodiments of the present invention is that it provides a switching method that can solve the delay and reliability requirements during MBS mobility and reduce UE signaling complexity and processing costs as much as possible.

[0122] Other advantages of some embodiments of the present invention include at least one of the following.

[0123] Advantages on the UE side:

[0124] The new method exchanges the target gNB MBS data forwarding timing to the UE in the handover command, and the UE can clearly know when it expects to start receiving MBS DL data from the target gNB. Given such information and other information related to MBS scheduling within the handover command, the UE can prepare the best reception configuration for MBS data in advance and decide when to stop receiving DL data from the source gNB and when to release the source gNB configuration (i.e., avoid the need to continue receiving MBS downlink data from the source gNB and the target gNB until the source gNB connection is released by an explicit release command from the target gNB, such as in DAPS). Such a process can relatively reduce UE signaling complexity, processing costs and minimize UE power consumption.

[0125] The new approach introduces the idea of ​​exchanging target gNB timing advance and downlink synchronization information to the source gNB and UE. Such information can help the UE avoid the need for random access (RACH) procedures during handover execution, which may lead to reduced handover interruption time (and help relax UE processing and signaling complexity).

[0126] New method l introduces the idea of ​​pre-allocating uplink grants from the source gNB and the target gNB, which is new and can help to relatively improve the UE's resilience to handover failure (i.e., the UE can send a handover failure indication or a reconnection request to either the source gNB or the target gNB). The new method introduces a process for the target gNB to send or start forwarding MBSDL data to the UE earlier (instead of waiting to receive a handover complete message like in DAPS), which can relatively help to reduce the UE handover interruption time.

[0127] Advantages on the network side:

[0128] This method introduces new types of information to be exchanged between the source gNB and the target gNB in ​​the handover request message, such as agreed timing information when the target NB will start sending data to the UE about a specific downlink / uplink frame that the source gNB sends / receives to / from the UE. Such timing information can help overcome several issues on the network side, such as the following.

[0129] PDCP SN allocation and count value misalignment issue: PDCP SN allocation and count value maintenance can be done directly on the source gNB and target gNB separately, and

[0130] Based on the agreed time, each node will start / stop downlink / uplink transmission to the UE / User Plane Function (UPF). For example, the source gNB can start allocating PDCP SN from the time it receives the HANDOVER ACK message from the target gNB until the start time of the PDCP SN is allocated by the target gNB provided in the HANDOVER ACK message. This helps maintain the logical connection (PDCP level) between the source gNB and the target gNB during the handover and minimize the MBS data loss on the UE side.

[0131] Data forwarding and data gap issues: All MBS packets (PDCP SDUs) received by the source gNB from the core network (UPF) at the UE handover time (i.e. the time when the source gNB and the target gNB agree to stop / start serving the UE) are forwarded to the target gNB and then to the UE, ensuring that no MBS packet loss occurs on the UE side.

[0132] PDCP Reordering and Duplication Issue: The UE may stop downlink transmission either as per the HANDOVER INITIATION command (i.e., the agreed time when the target gNB will start forwarding data to the UE) or immediately after receiving the first packet from the target gNB. This procedure simplifies the network implementation as the duplication check and in-sequence delivery to the 5G Core is done in the source gNB (i.e., until the agreed time or until the first packet is received from or in the target gNB) which is compatible with the current DAPS procedures requiring a common reordering and duplication functionality (for both source and target gNB) in a single PDCP entity. As Figure 1 As shown, in some embodiments, a user equipment (UE) 10, a source base station 20, and a target base station 30 communicating in a communication network system 40 according to an embodiment of the present invention are provided. The communication network system 40 includes the UE 10, the source base station 20, and the target base station 30. The UE 10 may include a memory 12, a transceiver 13, and a processor 11 coupled to the memory 12 and the transceiver 13. The source base station 20 may include a network node, such as a next generation radio access network (NG-RAN node, access and mobility management function (AMF) node, session data management function (SMF) node, network exposure function (NEF)) / policy control function (PCF) node, user plane function (UPF) node, and application function (AF) node. The source base station 20 may include a memory 22, a transceiver 23, and a processor 21 coupled to the memory 22 and the transceiver 23. The target base station 30 may include a network node such as a next generation radio access network (NG-RAN). Node, access and mobility management function (AMF) node, session data management function (SMF) node, network exposure function (NEF) / policy control function (PCF) node, user plane function (UPF) node and application function (AF) node. The target base station 30 may include a memory 32, a transceiver 33 and a processor 31 coupled to the memory 32 and the transceiver 33. The processor 11 or 21 or 31 may be configured to implement the proposed functions, processes and / or methods described in this description. The radio interface protocol layer may be implemented in the processor 11 or 21 or 31. The memory 12 or 22 or 32 is operably coupled to the processor 11 or 21 or 31 and stores various information to operate the processor 11 or 21 or 31. The transceiver 13 or 23 or 33 is operably coupled to the processor 11 or 21 or 31, and the transceiver 13 or 23 or 33 transmits and / or receives radio signals.

[0133] The processor 11 or 21 or 31 may include an application specific integrated circuit (ASIC), other chipsets, logic circuits and / or data processing devices. The memory 12 or 22 or 32 may include a read-only memory (ROM), a random access memory (RAM), flash memory, a memory card, a storage medium and / or other storage devices. The transceiver 13 or 23 or 33 may include a baseband circuit for processing radio frequency signals. When the embodiment is implemented in software, the techniques described herein may be implemented with modules (e.g., procedures, functions, etc.) that perform the functions described herein. The modules may be stored in the memory 12 or 22 or 32 and executed by the processor 11 or 21 or 31. The memory 12 or 22 or 32 may be implemented within the processor 11 or 21 or 31 or outside the processor 11 or 21 or 31, in which case they may be communicatively coupled to the processor 11 or 21 or 31 in various ways known in the art.

[0134] In some embodiments, the processor 11 is configured to determine MBS service and / or service quality QoS related information as part of a switching measurement report; and exchange the MBS service and / or the QoS related information as the part of the switching measurement report between at least two of the UE 10, the source base station 20 and the target base station 30, wherein a switching for UE MBS mobility execution and / or configuration is performed based on the part of the switching measurement report.

[0135] In some embodiments, the processor 21 is configured to exchange MBS service and / or quality-of-service (QoS) related information between the source base station 20 and at least one user equipment (UE) 10 as part of a switching measurement message and / or exchange the MBS service and / or the QoS related information with the target base station 30 as part of a switching request message; and perform switching for UE MBS mobility execution and / or configuration based on the part of the switching measurement report.

[0136] In some embodiments, the processor 31 is configured to exchange MBS service and / or service quality QoS related information between at least two of the user equipment (UE) 10, the source base station 20 and the target base station 30 as part of the handover measurement report; and when the target base station 30 starts / stops PDCP SN allocation, exchange MBS scheduling information and timing information and / or forward data to at least the source base station 20 via the handover confirmation message and / or the UE 10 passes the handover command message. This can solve the problems in the prior art, solve the delay and reliability requirements during MBS mobility, reduce UE signaling complexity, reduce processing costs, support service continuity, provide good communication performance, and / or provide high reliability.

[0137] Figure 2 A handover method 200 for a multicast / broadcast service (MBS) performed by a user equipment (UE) in a communication network system according to an embodiment of the present invention is illustrated. In some embodiments, the handover method 200 includes: step 202, determining, by the UE, information related to MBS services and / or quality of service (QoS) as part of a handover measurement report, step 204, exchanging the MBS services and / or the QoS related information as the part of the handover measurement report between at least two of the UE, a source base station, and a target base station, wherein a handover for UE MBS mobility execution and / or configuration is performed based on the part of the handover measurement report, step 206: the UE receives a handover command including target downlink / uplink synchronization information, MBS scheduling information, and MBS data forwarding timing information from the source base station, step 208: the UE prepares an optimal reception configuration for MBS data in advance, decides when to stop receiving DL data from the source gNB, when to release the source gNB configuration, and avoids continuing to receive MBS downlink data from both the source gNB and the target gNB until the source gNB connection is released by an explicit release command of the target gNB. Such a process can relatively reduce UE signaling complexity, processing cost, and minimize UE power consumption.

[0138] In one embodiment of the present invention, the handover type for the UE MBS mobility execution and / or configuration is selected based on at least one of the following: an indication of the UE including the MBS service and / or the QoS related information; an internal configuration of the source base station; or an indication of the core network. In one embodiment of the present invention, the MBS service and / or the QoS related information includes a UE identity (ID), an MBS service ID, a QoS flow ID, or a session ID association. In one embodiment of the present invention, the internal configuration of the source base station includes a UE ID, an MBS service ID, a QoS flow ID, or a session ID association. In one embodiment of the present invention, the indication of the core network includes a UE MBS context message, a UE ID, an MBS service ID, a QoS flow ID, or a session ID association. In one embodiment of the present invention, determining by the UE the MBS service and / or the QoS related information as the part of the handover measurement report includes the UE receiving the MBS service and / or the QoS related information from the core network via a multicast radio bearer (MRB) or a unicast data radio bearer (DRB).

[0139] In one embodiment of the present invention, exchanging the MBS service and / or the QoS related information between at least two of the UE, the source base station and the target base station includes indicating, by the UE, the MBS service and / or the QoS related information as the part of the handover measurement report to the source base station. In one embodiment of the present invention, exchanging the MBS service and / or the QoS related information between at least two of the UE, the source base station and the target base station includes the source base station forwarding the MBS service and / or the QoS related information of the UE to the target base station as the part of the handover measurement report. In one embodiment of the present invention, the source base station is indicated in the handover request signaling to forward the MBS service and / or the QoS related information of the UE to the target base station as the part of the handover measurement report. In one embodiment of the present invention, the handover type selected for the UE MBS mobility execution and / or configuration includes lossless handover or lossless and low-latency handover.

[0140] In one embodiment of the present invention, the handover type selected for the UE MBS mobility execution and / or configuration includes the lossless handover or the lossless and low-delay handover according to the UE MBS service reliability and delay level requirements. In one embodiment of the present invention, the handover method is characterized in that it also includes the UE receiving a configuration from the source base station, the configuration including at least one of the following: the agreed time for the source base station and the target base station to start / stop packet data convergence protocol (PDCP) sequence number (SN) allocation and / or data forwarding; target pre-allocation permission; uplink time advance command; downlink synchronization information; or MBS bearer scheduling / forwarding configuration; and / or the method also includes the UE receiving a handover command from the source base station, the handover command including target downlink / uplink synchronization information, MBS scheduling information and MBS data forwarding timing information; and / or pre-preparing the UE optimal reception configuration for MBS data, and deciding when to stop receiving downlink data from the source base station, when to release the source base station configuration, and releasing the source base station configuration accordingly.

[0141] In one embodiment of the present invention, the configuration is forwarded by the source base station from the target base station to the UE in a handover initiation / command message. In one embodiment of the present invention, when the UE receives the configuration from the source base station, the UE performs at least one of the following: synchronize to the target cell based on the downlink synchronization timing and uplink time advance information provided by the source base station from the target base station; configure separate entities of medium access control (MAC) configuration, PDCP configuration and / or radio link control (RLC) configuration for the target base station and the source base station; stop receiving from the source base station after the timing information given in the radio resource control (RRC) configuration, while maintaining the source MAC, PDCP and / or MAC entity until the first packet is received from the target base station; stop sending uplink (UL) first layer channel state information (CSI) feedback, hybrid automatic repeat request (HARQ) feedback, second layer RLC feedback, robust header compression (RLC) feedback, etc. compression, ROHC) feedback, HARQ data retransmission and / or RLC data retransmission to the source base station; the source base station and / or the target base station sends a switching completion message on a pre-allocated license or fails to switch the wireless link; omits sending a switching completion message and uses the pre-allocated license to perform uplink data transmission to the target base station; or releases the MAC configuration, the PDCP configuration and / or the RLC configuration of the source base station.

[0142] Figure 3 The diagram shows a handover method 300 of a multicast / broadcast service (MBS) performed by a source base station in a communication network system according to an embodiment of the present disclosure. In some embodiments, the handover method 300 includes: step 302, exchanging MBS service and / or quality-of-service (QoS) related information between the source base station and at least one user equipment (UE) as part of a handover measurement message and / or exchanging the MBS service and / or the QoS related information with a target base station as part of a handover request message, step 304, performing a handover for UE MBS mobility execution and / or configuration based on the part of the handover measurement report.

[0143] In one embodiment of the present invention, the handover type for the UE MBS mobility execution and / or configuration is selected based on at least one of the following: an indication of the UE including the MBS service and / or the QoS related information; an internal configuration of the source base station; or an indication of the core network. In one embodiment of the present invention, the MBS service and / or the QoS related information includes a UE identity (ID), an MBS service ID, a QoS flow ID, or a session ID association. In one embodiment of the present invention, the internal configuration of the source base station includes a UE ID, an MBS service ID, a QoS flow ID, or a session ID association. In one embodiment of the present invention, the indication of the core network includes a UE MBS context message, a UE ID, an MBS service ID, a QoS flow ID, or a session ID association. In one embodiment of the present invention, exchanging the MBS service and / or the quality of service QoS related information between the source base station and at least one user equipment UE as the part of the switching measurement message and / or exchanging the MBS service and / or the quality of service QoS related information with the target base station as the part of the switching request message includes the source base station determining the MBS service and / or the QoS related information as the part of the switching measurement report from the UE.

[0144] In one embodiment of the present invention, exchanging the MBS service and / or the quality of service QoS related information between the source base station and at least one user equipment UE as the part of the handover measurement message and / or exchanging the MBS service and / or the quality of service QoS related information with the target base station as the part of the handover request message includes forwarding the MBS service and / or the QoS related information from the UE to the target base station by the source base station as the part of the handover measurement report. In one embodiment of the present invention, the source base station is instructed in the handover request signaling to forward the MBS service and / or the QoS related information from the UE to the target base station as the part of the handover measurement report. In one embodiment of the present invention, the handover type selected for the UE MBS mobility execution and / or configuration includes lossless handover or lossless and low-delay handover. In one embodiment of the present invention, the handover type selected for the UE MBS mobility execution and / or configuration includes the lossless handover or the lossless and low-delay handover according to the UE MBS service reliability and delay level requirements. In one embodiment of the present invention, the handover method further comprises the source base station receiving a handover request confirmation from the target base station in response to the handover request signaling. In one embodiment of the present invention, the handover request confirmation comprises a configuration, and the configuration comprises at least one of the following: an agreed time for the source base station and the target base station to start / stop packet data convergence protocol (PDCP) sequence number (SN) allocation and / or data forwarding; a target pre-allocation permission; an uplink time advance command; a downlink synchronization information; or an MBS bearer scheduling / forwarding configuration.

[0145] In one embodiment of the present invention, when the source base station receives the handover request confirmation, the source base station performs at least one of the following: if low-delay and lossless handover is selected and / or configured for UE MBS mobility, a PDCP SN is executed, and the PDCP SN allocates PDCP service data unit (SDU) data forwarding; or an SN status transmission message is sent to the target base station to convey the uplink PDCP SN receiver state and the downlink PDCP SN transmitter state of the application PDCP state preservation. In one embodiment of the present invention, the uplink PDCP SN receiver state includes at least one of the following: the PDCP SN of the first lost UL PDCP SDU; or the reception status bitmap of the out-of-order UL PDCP SDU that the UE needs to retransmit in the target cell. In one embodiment of the present invention, the downlink PDCP SN transmitter state indicates the next PDCP SN assigned by the target base station to the new PDCP SDU, and if lossless handover is configured, there is no PDCP SN. In one embodiment of the present invention, the handover method also includes the source base station sending the configuration to the UE. In one embodiment of the present invention, the configuration is forwarded by the source base station from the target base station to the UE. In one embodiment of the present invention, the configuration is forwarded by the source base station from the target base station to the UE in a handover initiation / command message.

[0146] Figure 4 The diagram shows a switching method 400 for a multicast / broadcast service (MBS) performed by a target base station in a communication network system according to an embodiment of the present invention. In some embodiments, the switching method 400 includes:

[0147] Step 402, exchanging MBS service and / or service quality (QoS) related information between at least two of the user equipment (UE), the source base station and the target base station as part of the handover measurement report, and step 404, exchanging MBS scheduling information and timing information and / or forwarding data to at least the source base station via the handover confirmation message and / or the UE via the handover command message when the target base station starts / stops PDCP SN allocation. This can solve the problems in the prior art, solve the delay and reliability requirements during MBS mobility, reduce UE signaling complexity, reduce processing costs, support service continuity, provide good communication performance, and / or provide high reliability.

[0148] In one embodiment of the present invention, the handover type for the UE MBS mobility execution and / or configuration is selected based on at least one of the following: an indication of the UE including the MBS service and / or the QoS related information; an internal configuration of the source base station; or an indication of the core network. In one embodiment of the present invention, the MBS service and / or the QoS related information includes a UE identity (ID), an MBS service ID, a QoS flow ID, or a session ID association. In one embodiment of the present invention, the internal configuration of the source base station includes a UE ID, an MBS service ID, a QoS flow ID, or a session ID association. In one embodiment of the present invention, the indication of the core network includes a UE MBS context message, a UE ID, an MBS service ID, a QoS flow ID, or a session ID association. In one embodiment of the present invention, exchanging the MBS service and / or the QoS related information between at least two of the UE, the source base station, and the target base station includes forwarding the MBS service and / or the QoS related information from the UE to the target base station by the source base station as the part of the handover measurement report.

[0149] In one embodiment of the present invention, the source base station is instructed in the handover request signaling to forward the MBS service and / or the QoS related information from the UE to the target base station as the part of the handover measurement report. In one embodiment of the present invention, the handover type selected for the UE MBS mobility execution and / or configuration includes lossless handover or lossless and low-latency handover. In one embodiment of the present invention, the handover type selected for the UE MBS mobility execution and / or configuration includes the lossless handover or the lossless and low-latency handover according to the UE MBS service reliability and delay level requirements.

[0150] In one embodiment of the present invention, when the target base station receives the handover request signaling, the target base station performs at least one of the following: performs admission control on the UE MBS mobility and performs selection of the handover type for the UE MBS mobility execution and / or configuration, if the source base station does not perform the handover type selected for the UE MBS mobility execution and / or configuration; determines and / or decides based on the configuration received in the handover request, the time to start PDCP SN allocation and / or forwards data to the UE according to the time reference provided by the source base station; if the MBS session / service / temporary mobile group identity (TMGI) received by the UE exists in the target base station, initiates UE MSB session joining, or if the MBS session received by the UE does not exist in the target base station, initiating a session establishment request to the core network; if necessary, switching the UE to a new radio bearer, and striving to provide the same QoS flow to the radio bearer mapping and scheduling configuration / forwarding processing of the MBS bearer indicated by the source base station; determining the timing configuration that needs to be synchronized with the UE, and providing the UE with a time proposal command and a pre-allocation grant; or starting to forward the copied MBS downlink data forwarded from the source base station as the start of allocating the PDCP SN to the UE.

[0151] In one embodiment of the present invention, the handover method further comprises the target base station sending the handover request acknowledgment (ACK) to the source base station in response to the handover request signaling. In one embodiment of the present invention, the handover request acknowledgment includes a configuration, and the configuration includes at least one of the following: an agreed time for the source base station and the target base station to start / stop packet data convergence protocol (PDCP) sequence number (SN) allocation and / or data forwarding; a target pre-allocation grant; an uplink timing advance command; downlink synchronization information; or an MBS bearer scheduling / forwarding configuration. In one embodiment of the present invention, the configuration is forwarded from the target base station to the UE by the source base station. In one embodiment of the present invention, the source base station forwards the configuration from the target base station to the UE in a handover initiation / command message, and / or the target base station prepares according to the configuration received in the handover request, synchronization / timing information, UE pre-allocation grant allocation, and downlink and uplink timing advance.

[0152] In some embodiments, we will start this section by reviewing the currently standardized traditional or baseline NR handover and discussing how to minimize data loss and service interruption delay for NR unicast services. We will mainly focus on features that aim to reduce data loss during the handover process, such as the lossless handover feature, and procedures that aim to minimize service interruption time, such as the DAPS procedure. We will then point out the limitations and shortcomings of the above handover procedures in addressing the MBS mobility requirements in NR. Finally, we will introduce our proposed handover procedures to overcome these shortcomings and limitations.

[0153] NR baseline switching review:

[0154] Figure 5 The diagram illustrates a 5G NR baseline switching process according to an embodiment of the present invention. Figure 5 Illustrated is an NR baseline handover procedure for a UE receiving unicast services moving from a source gNB to a target gNB in ​​some embodiments. Figure 5 The main steps of the control plane (CP) processing baseline switching include: a) switching preparation phase (step 0 to step 5), b) switching execution phase (step 6 to step 8), and 3) switching completion phase (step 8a to 12). These steps are detailed as follows:

[0155] Step 0: The UE context within the source gNB contains information about roaming and access restrictions, which was provided at connection establishment or at the last Tracking Area (TA) update.

[0156] Step 1: The source gNB configures the UE measurement process and the UE reports according to the measurement configuration.

[0157] Step 2: The source gNB decides to handover the UE based on the measurement report and radio resource management (RRM) information.

[0158] Step 3: The source gNB issues a Handover Request message to the target gNB, passing a transparent RRC container with necessary information to prepare the handover at the target side. This information includes at least the target cell ID, KgNB*, the cell radio network temporary identifier (C-RNTI) of the UE in the source gNB, the RRM configuration including the UE inactivity time, the basic AS (Access Stratum) configuration including antenna information and downlink (DL) carrier frequency, the current QoS flow to data radio bearer (DRB) mapping rules applied to the UE, the System Information Block 1 (SIB1) from the source gNB, the capabilities of the UE for different radio access technologies (RATs), flat packet data unit (PDU) session related information, and may include the measurement information reported by the UE, including beam related information if available. The PDU session related information includes slice information and QoS flow level QoS profile. The source gNB may also request DAPS handover for certain DRBs.

[0159] Step 4: Admission control may be performed by the target gNB. If the slice information is sent to the target gNB, slice-aware admission control shall be performed. If a PDU Session is associated with an unsupported slice, the target gNB shall reject such PDU Session.

[0160] Step 5: The target gNB prepares the handover using L1 / L2 and sends a handover request confirmation to the source gNB, which includes the transparent container to be sent as an RRC message to the UE to perform the handover.

[0161] Step 6: The source gNB triggers Uu handover by sending an RRCReconfiguration message to the UE, which contains the information required to access the target cell: at least the target cell ID, the new C-RNTI, the target gNB security algorithm identifier for the selected security algorithm. It may also include a set of dedicated random access channel (RACH) resources, the association between RACH resources and synchronization signal blocks (SSB(s)), the association between RACH resources and UE-specific channel state information-reference signal (CSI-RS) configuration, common RACH resources, system information of the target cell, etc.

[0162] Step 7: The source gNB sends an SN STATUS TRANSFER message to the target gNB to communicate the uplink PDCP SN receiver status and downlink PDCP SN transmitter status (i.e., for RLC AM) of the DRBs to which PDCP state preservation is applied. The uplink PDCP SN receiver status includes at least the PDCP SN of the first lost UL PDCP SDU and may include a bitmap of the reception status of out-of-sequence UL PDCP SDUs that the UE needs to retransmit in the target cell, if any. The downlink PDCP SN transmitter status indicates the next PDCP SN that the target gNB should assign to the new PDCP SDU, for which no PDCP SN is yet available.

[0163] Step 8: The UE synchronizes with the target cell and completes the RRC handover process by sending an RRCReconfigurationComplete message to the target gNB.

[0164] Step 9: The target gNB sends a PATH SWITCH REQUEST message to the Access and Mobility Management Function (AMF) to trigger the 5GC to switch the DL data path to the target gNB and establish the NG-C interface instance to the target gNB.

[0165] Step 10: 5GC switches the DL data path to the target gNB. The User Plane Function (UPF) sends one or more “end marker” packets to the source gNB for each PDU session / tunnel on the old path, and any U-Plane / TNL resources may then be released to the source gNB.

[0166] Step 11: AMF confirms the PATH SWITCH REQUEST message with a PATH SWITCH REQUEST ACKNOWLEDGMENT message.

[0167] Step 12: After receiving the PATH SWITCH REQUEST ACKNOWLEDGMENT message from the AMF, the target gNB sends UE CONTEXT RELEASE to notify the source gNB of the handover success.

[0168] Baseline switching user plane processing:

[0169] For user plane processing, the following applies; During the handover preparation phase, a user plane tunnel can be established between the source gNB and the target gNB; During the handover execution phase, user data can be forwarded from the source gNB to the target gNB as shown below. The forwarding should be done in order as long as the source gNB receives a packet from the UPF or the source gNB buffer is not flushed.

[0170] In the handover completion phase: the target gNB sends a path switch request message to the AMF to notify the UE that it has obtained access. The AMF then triggers the path switch-related 5GC internal signaling and the actual path switch from the source gNB to the target gNB in ​​the UPF. If the source gNB receives a data packet from the UPF or the source gNB buffer has not been cleared, the source gNB continues to forward the data. For the end marker packet processing, the source gNB receives one or more GTP-U end marker packets from the UPF in each PDU session and copies the end marker packet to each data forwarding tunnel when no more user data packets are forwarded through this tunnel. (As shown in step 10.)

[0171] For user plane bearers configured with Radio Link Control - Unacknowledged Mode (RLC-UM) mode, the PDCP entity including the header compression context is reset, and the COUNT value is set to zero. Since new keys are generated at handover anyway, there is no security reason to retain the COUNT value. On the UE side, all PDCP SDUs that have not yet been sent will be sent to the target cell after handover. PDCP SDUs for which transmission has not yet started can be forwarded to the target gNB over the Xn-AP interface. At the same time, unacknowledged PDCP SDUs will be lost. This minimizes the complexity of handover since no context (i.e. configuration information) needs to be transferred between the source and target gNB. For user plane bearers configured with Radio Link Control - Acknowledged Mode (RLC-AM), the user plane processing follows the procedure described in the lossless handover section.

[0172] Lossless Procedure: For lossless handover, the control plane (CP) is processed as specified in step 7 above. As for the user plane processing, the header compression protocol is reset on the UE side because its context is not forwarded from the source eNB to the target eNB, but the sequence number and COUNT value of the PDCP SDU are not reset. To ensure uplink lossless handover, the PDCP PDUs stored in the PDCP retransmission buffer are retransmitted through the RLC protocol according to the PDCP SN maintained at the time of handover and delivered to the gateway in the correct order. To ensure downlink lossless handover, the source eNodeB forwards the uncompressed PDCP SDUs that the UE has not yet acknowledged to be received to the target eNodeB for retransmission in the downlink.

[0173] DAPS process: For DAPS switching, CP processes as follows.

[0174] Step 7a: For DRBs configured with DAPS, the source gNB sends an EARLY STATUS TRANSFER message. The DL COUNT value conveyed in the EARLYSTATUS TRANSFER message indicates the PDCP SN and hyperframe number (HFN) of the first PDCP SDU forwarded by the source gNB to the target gNB. The source gNB does not stop assigning SNs to downlink PDCP SDUs until it sends the SN STATUS TRANSFER message to the target gNB in ​​step 8b.

[0175] Step 8: In case of DAPS HO, the UE does not leave the source cell after receiving the RRCReconfiguration message. The UE releases the source SRB resources, the security configuration of the source cell, and stops DL / UL reception / transmission with the source node after receiving an explicit release from the target node.

[0176] Step 8a / 8b: In case of DAPS handover, the target gNB sends a HANDOVER SUCCESS message to the source gNB to inform the UE that it has successfully accessed the target cell. In return, the source gNB sends a SN STATUSTRANSFER message for the DRB configured with DAPS. Normal data forwarding is shown below.

[0177] Downlink PDCP SDUs are forwarded with the SN assigned by the source gNB until the SN assignment is handed over to the target gNB in ​​step 8b and the source gNB does not stop sending downlink data packets until it receives the HANDOVER SUCCESS message from the target gNB in ​​step 8a. The source gNB may additionally send an EARLY STATUS TRANSFER message between step 7 and step 8b to notify the discarding of the already forwarded PDCP SDUs. The target gNB does not send forwarded downlink PDCP SDUs to the UE whose COUNT is less than the transmitted DL COUNT value and discards them if no transmission has been attempted. If DAPS is configured, the uplink PDCP SN receiver status and the downlink PDCP SN transmitter status are also transmitted in the SN STATUS TRANSFER message in step 8b for the DRB with RLC-UM.

[0178] For DRBs (i.e. RLC-AM) configured with DAPS that needs to avoid duplication,

[0179] The source gNB shall not stop delivering uplink QoS flows to the UPF until it sends the SN STATUS TRANSFER message in step 8b. The target gNB shall not forward the QoS flows of uplink PDCP SDUs successfully received in sequence to the UPF until it receives the SN STATUS TRANSFER message with the first missing SN in the UL HFN and uplink PDCP SN reception status indicating the start of uplink PDCP SDUs being delivered to the UPF. The target gNB shall not deliver any uplink PDCP SDUs with a UL count lower than the one provided. The source gNB may omit sending the SN STATUS TRANSFER message if none of the DRBs are configured with DAPS or PDCP state preservation shall be used.

[0180] For user plane processing of RLC-AM bearers configured with DAPS:

[0181] For downlink, the following principles apply: During HO preparation, a forwarding tunnel is always established. The source gNB is responsible for allocating downlink PDCP SNs until the SN allocation is handed over to the target gNB and data forwarding occurs. That is, the source gNB does not stop allocating PDCP SNs for downlink packets until it receives the HANDOVER SUCCESS message and sends the SN STATUS TRANSFER message to the target gNB. After the source gNB allocates the downlink PDCP SN, it starts scheduling downlink data on the source radio link and starts forwarding downlink PDCP SDUs with the allocated PDCP SN to the target gNB. For security synchronization, ciphering, and integrity protection, the HFN and PDCP SN are maintained after the SN allocation is handed over to the target gNB. The SN STATUS TRANSFER message indicates the next DL PDCP SN to be assigned to packets that do not yet have a PDCP sequence number, even for RLC-UM. During handover execution, the source gNB and target gNB perform ROHC header compression, ciphering, and adding PDCP headers, respectively. During handover execution, the UE continues to receive downlink data from both the source and target gNB until the source gNB connection is released by an explicit release command from the target gNB. A UE configured with DAPS PDCP maintains independent security and ROHC header decompression associated with each gNB while maintaining common reordering functionality, duplicate detection, discard functionality and in-sequence delivery of PDCP SDUs to upper layers. PDCP SN continuity is supported for both RLC AM and UM DRBs configured with DAPS.

[0182] For uplink: The UE transmits UL data to the source gNB until the random access procedure to the target gNB is successfully completed. Thereafter, the UE switches its UL data transmission to the target gNB. The UE continues to send UL Layer 1 CSI feedback, HARQ feedback, Layer 2 RLC feedback, ROHC feedback, HARQ data retransmissions, and RLC data retransmissions to the source gNB even after switching its UL data transmission. During handover execution, the UE maintains separate security contexts and ROHC header compressor contexts for uplink transmissions to the source gNB and target gNB. The UE maintains a common UL PDCP SN allocation. PDCP SN continuity is supported for both RLC AM and UM DRBs configured with DAPS. During handover execution, the source gNB and target gNB maintain their own security and ROHC header decompressor contexts to process the UL data received from the UE. The establishment of a forwarding tunnel is optional. The HFN and PDCP SN are maintained in the target gNB. The SN STATUS TRANSFER message indicates the first missed UL count that the target should start transmitting towards the 5GC, even for RLC-UM.

[0183] Problem Statement:

[0184] NR MBS use cases include public safety and mission-critical, vehicle-to-everything (V2X) applications, transparent Internet Protocol version 4 (IPv4) / Internet Protocol version 6 (IPv6) multicast delivery, Internet Protocol television (IPTV), software delivery wireless, group communications, and Internet of Things (IoT) applications. Most of these use cases involve the reception of MBS services during inter-node mobility, such as public safety, V2X applications, etc. As shown in Table 1 (R1-2007001), it is clear that most of the above use cases require high reliability, such as V2X applications requiring up to 99.9999% reliability, public safety and mission-critical push-to-talk (MCPTT) services, also requiring up to 99.9999% reliability. In addition, some MBS use cases, such as V2X and industrial applications, for example, motion-related sensors such as industrial actuators, may involve the reception of MBS services during inter-node mobility, which may require service interruption times ranging from 5ms to 0.5ms due to their very strict latency requirements (see also Table 1). While most MBS mobility proposals discussed in recent 3GPP meetings suggest adopting traditional and / or lossless handovers to support MBS mobility in NR, it is clear that adopting such handovers can only guarantee the requirements of MBS reliability-sensitive service applications and use cases. For other time-sensitive use cases, the requirement for alternative handover techniques is very obvious. Although, there are also some proposals to adopt DAPS handover for MBS, which can guarantee very low service interruption latency for MBS applications. However, considering the complexity brought to the UE when performing DAPS handover (i.e., due to simultaneous downlink and uplink transmissions from the source gNB and the target gNB during DAPSHO), it may be necessary to improve the current standardized DAPS HO process to better support MBS services. In order to address these technical limitations and deficiencies, some embodiments of the present invention propose a new handover method involving several changes in the handover process, such as changes in handover signaling, information embedded in handover signaling, and some handover procedures at both the source gNB and the target gNB.

[0185] Table 2: Requirements for different MBS use cases

[0186] MBS Use Cases Delay reliability V2X 5-100ms variable 90% to 99.9999% Live Video 150ms 99.9％ Internet of Things, Software Updates Tolerating Delay Higher reliability is beneficial Industry Applications 0.5ms 99.9999％

[0187] In some embodiments of the present invention, the specific switching process and signaling changes are described as follows.

[0188] Proposed solution:

[0189] Summary of the proposed method: Some embodiments of the present invention provide a method for a handover procedure to support UE mobility when receiving services requiring low interruption latency and / or high reliability, such as 5g MBS. Figure 6The diagram illustrates handover of an MBS-capable UE from one NG-RAN to another NG-RAN according to an embodiment of the present invention. Figure 6 Description, in some embodiments, the method considers a scenario where a UE supporting MBS receives services, requiring low interruption time and / or highly reliable MBS services form a 5g core network, through a multicast radio bearer (MRB) or a unicast data radio bearer (DRB) in a source NG-RAN, and moves to another NG-RAN (i.e., a target NG-RAN) that supports / does not support the services provided to the given UE, such as Figure 6 shown.

[0190] Figure 7 The diagram illustrates a proposed switching according to an embodiment of the present invention to support low-latency and reliable MBS mobility. Figure 6 and Figure 7 Description, in some embodiments, in this method, the UE may indicate its MBS service interest (i.e., identity (ID) or type of MBS service or QoS requirement of MBS service) to the source gNB as part of the HANDOVERMEASUREMENT report. In return, the source gNB may decide on the handover based on part of the HANDOVERMEASUREMENT report and may select the type of handover to be performed / configured for a given UEMBS radio bearer (MRB / DRB) based on one of the following:

[0191] UE indication (service interest information, e.g. service QoS requirements, such as target latency and / or reliability level), and / or source gNB internal configuration which may contain UE and MBS Service ID or QoS Flow ID or Session ID association, and / or Core network indication, e.g. UE MBS Context message from AMF or SMF containing UE identity and MBS Service ID / QoS Flow ID / Session ID association.

[0192] In another approach, the selection of the handover type to be configured for the UE MBS bearer may be performed by the target gNB; in this case, the service correlation ID of interest to the UE and / or the UE and QoS flow or session association related information shall be indicated in the HANDOVER REQUEST signaling forwarded by the source gNB to the target gNB (i.e., over the Xn-AP interface). The handover option type to be selected / configured by the source gNB node or the target gNB node for the UE MBS bearer may include lossless handover or lossless and low latency handover based on the UE MBS service reliability and latency level requirements, as shown in Table 2. The details of the procedures and signaling applicable in the case of lossless and low latency handover compared to the existing unicast DAPS and lossless handover are given as described in the Observations and Recommendations section.

[0193] Table 2: Handover types based on UE MBS use cases

[0194] MBS Use Cases Delay reliability Handover Type (HO) V2X 5-100ms variable 90% to 99.9999% Low latency and lossless HO Live Video 150ms 99.9％ Lossless HO Internet of Things, Software Updates Tolerating Delay Higher reliability is beneficial Lossless HO Industry Applications 0.5ms 99.9999％ Low latency and lossless HO

[0195] After the handover is decided (e.g., by the source gNB), the HANDOVER REQUEST message may be forwarded from the source gNB to the target gNB. Depending on the handover selected / configured, the handover message may include at least one of the following information. The handover message may include UE measurement reports, UE MRB / DRB service / QoS information, UE and MBS service / QoS / session association information, the handover type decided / configured by the source gNB, if low latency handover is selected / configured, a request to the target gNB suggesting it to start allocating PDCP SNs and / or start forwarding data to the UE, time and reference X, where X is, for example, the time reference when the source gNB forwards / receives a specific downlink / uplink frame to / from the UE, the downlink and / or uplink timing advance for a given UE, reference X or the downlink / uplink frame scheduled by the source, the current transmission mode of the MBS (i.e., MRB / DRB), and / or MRB / DRB mapping of QoS flows to the UE MBS bearers at the source gNB and the L1, L2 and / or L3 scheduling information / forwarding process for the given UE MBS bearers.

[0196] In some embodiments, when the target gNB receives the HANDOVER REQUEST message, the target gNB may perform at least one of the following operations.

[0197] The target gNB may perform admission control on the handed-over MBS bearers (MRB / DRB) and may decide / configure the type of handover to be performed for a given MBS bearer if not decided / configured by the source gNB.

[0198] The target gNB may determine / decide based on the configuration received in the HANDOVER REQUEST, the exact time to start PDCP SN allocation and start forwarding data to the UE relative to the time reference X provided by the source gNB (or if low latency handover functionality was selected / configured in the HANDOVER REQUESTACK or locally.)

[0199] The target gNB may prepare based on the configuration received in the HANDOVER REQUEST, synchronization / timing information (e.g., Radio Network Temporary Identifier (RNTI) allocation, i.e., g-RNTI for receiving MBS over MRB or C-RNTI for receiving MBS over DRB, UE pre-allocated grant allocation and downlink and uplink timing advance relative to X.)

[0200] The target gNB may initiate a UE MSB session join if the MBS session / service / TMGI received by the UE exists in the target gNB or initiate a session establishment request to the core network if the MABS session received by the UE does not exist in the target gNB.

[0201] The target gNB may handover the UE to a new radio bearer (MRB / DRB) if required and may strive to provide the same QoS flows for the MRB / DRB mapping and prepare the scheduling configuration / forwarding process for the given MBS bearer indicated by the source gNB.

[0202] The target gNB may determine the timing configuration required to synchronize with a given UE and may provide a Timing Proposal Command and a Pre-allocation Grant for the given UE (or if low latency handover functionality is selected / configured in the HANDOVER REQUEST ACK or locally.)

[0203] The target gNB may start forwarding a copy of the MBS downlink data forwarded from the source gNB as soon as it starts allocating a PDCP SN to the UE (i.e. without waiting for receiving a HANDOVER COMPLETE message from the UE) to reduce the UE handover interruption time (if low latency handover functionality is selected / configured in the HANDOVER REQUESTACK or locally at the target gNB).

[0204] In some embodiments, after the target gNB has prepared all the above configurations, the target gNB will prepare for the handover using the L1, L2, and L3 configurations and will send a HANDOVER REQUEST ACKNOWLEDGMENT to the source gNB. The request includes a transparent container as an RRC message (containing the above configurations, uplink timing advance command, and / or downlink synchronization information) to the UE to perform the handover. In return, the source gNB may perform at least one of the following operations.

[0205] The source gNB may perform PDCP SN allocation PDCP SDU data forwarding as given in the above embodiments (or if low latency and lossless features are selected / configured for the MBS bearer.)

[0206] The source gNB may send a SN STATUS TRANSFER message to the target gNB to communicate the uplink PDCP SN receiver status and the downlink PDCP SN transmitter status of the DRBs (i.e. RLC AM) to which PDCP state preservation is applied. The uplink PDCP SN receiver status includes at least the PDCP SN of the first lost UL PDCP SDU and may include a bitmap of the reception status of out-of-sequence UL PDCP SDUs that the UE needs to retransmit in the target cell, if any. The downlink PDCP SN transmitter status indicates the next PDCP SN that the target gNB should assign to new PDCP SDUs, for which there is no PDCP SN yet (or if lossless handover is configured.)

[0207] In some embodiments, after the source gNB receives a HANDOVER REQUESTACKNOWLEDGMENT containing the configuration forwarded by the target gNB, the source gNB sends a HANDOVER INITIATION / COMMAND message to the UE containing the configuration provided by the target gNB. The provided configuration includes, for example, an agreed time for the source gNB and the target gNB to start / stop PDCP SN allocation and / or data forwarding, a target pre-allocation grant, an uplink timing advance command, downlink synchronization information, and / or MBS bearer scheduling / forwarding configuration. When the UE receives the configuration from the source gNB, the UE may perform at least one of the following.

[0208] The UE may synchronize to the target cell based on the synchronization / timing information provided by the target gNB (i.e., the downlink synchronization timing and uplink timing advance information provided by the source gNB from the target gNB in ​​the handover command container).

[0209] The UE may configure separate MAC configuration, PDCP configuration and / or RLC configuration entities for the target gNB and the source gNB.

[0210] The UE can start receiving MBS data from the target gNB after synchronizing and connecting to the target gNB.

[0211] The UE may stop receiving from the Source gNB (i.e. stop / start forwarding downlink data to the UE based on the time agreed upon by the Source gNB and the Target gNB) after the timing specified by the timing information given in the Handover Command RRC message, although it may maintain the release of the configured MAC RLC and PDCP entities of the Source gNB until the first MBS packet is received from the Target gNB.

[0212] The UE may stop sending UL Layer 1 CSI feedback, HARQ feedback, Layer 2 RLC feedback, ROHC feedback, HARQ data retransmissions and / or RLC data retransmissions to the source gNB.

[0213] The UE may send a Handover Complete message or a Handover Radio Link Failure on the pre-allocated grant of the source / target gNB.

[0214] The UE may omit sending the HANDOVER COMPLETE message and use the pre-allocated grant for uplink data transmission to the target gNB.

[0215] The UE may release the MAC configuration, PDCP configuration and / or RLC configuration of the source gNB.

[0216] Low latency and lossless feature recommendations:

[0217] PDCP SN allocation and misalignment:

[0218] In the current DAPS procedure, downlink PDCP SN allocation is performed by the source gNB until the SN allocation is handed over to the target gNB and data forwarding starts. That is, the source gNB does not stop allocating PDCP SNs for downlink data packets until it receives a HANDOVER SUCCESS message and sends a SN STATUS TRANSFER message to the target gNB. Such a procedure may cause the gNB buffer of the target gNB to be loaded. Because the time when the source gNB stops PDCP SN allocation and starts data forwarding depends entirely on the HANDOVER SUCCESS message received from the target gNB, this may take a long time because this message is also triggered by the target gNB after receiving a HANDOVER COMPLETION message from the UE.

[0219] Example: In some embodiments of the present invention,

[0220] In the newly proposed low latency and lossless handover procedure, the source gNB and target gNB directly assign PDCP SN and maintain count values ​​respectively according to the agreed timing when each node starts / stops downlink / uplink transmission to the UE / UPF, (e.g., the source gNB may start assigning PDCP SN from the time the target gNB receives the HANDOVER ACK message until the start time of PDCP SN assignment by the target gNB provided in the HANDOVER ACK message). Such a procedure helps reduce the dependency of the handover procedure (source gNB) on UE related signaling (i.e., HANDOVER COMPLETION message) as it allows the source gNB to start and stop PDCP SN assignment STATUS transmission (agreed by the target gNB) and start data forwarding (low latency handover) without waiting for the HANDOVER SUCCESS message from the target gNB, which depends on the receipt of HANDOVER COMPLETION from the UE. This also helps reduce handover latency and allows some handover signaling to be omitted (e.g., the UE may send handover completion signaling in some cases, omit it if not required and use the pre-assigned grant for uplink data transmission.)

[0221] PDCP reordering and duplication:

[0222] In the current DAPS configuration, the UE will receive downlink user data from both the source gNB and the target gNB simultaneously. Therefore, the PDCP layer is reconfigured as a common PDCP entity for both the source and target user plane protocol stacks. To ensure in-sequence delivery of DL user data, PDCP (SN) continuity is maintained during the handover process. For this purpose, a common reordering and duplication function (for both source and target gNB) is required in a single PDCP entity.

[0223] Embodiment 1: In some embodiments of the present invention, in the newly proposed low-latency and lossless handover MBS procedure, the UE may stop the downlink as specified in the HANDOVER INITIATION command, (i.e., the agreed time at which the target will start forwarding data to the UE) or immediately after receiving the first packet from the target. This procedure may simplify UE and network implementation because the duplication check and in-order delivery to the 5G core is done by the source gNB (i.e., until the agreed time or until the first packet is received from the target) or the target gNB. This is in contrast to the current DAPS procedure, where a common reordering and duplication functionality (for both the source gNB and the target gNB) is required in a single PDCP entity.

[0224] Data forwarding and data gap:

[0225] In case of DAPS handover, the UE continues to receive downlink data from both the source gNB and the target gNB until the source gNB connection is released by an explicit release command from the target gNB. During the handover completion phase, the resource release of the source gNB is triggered by the target gNB after receiving the HANDOVER COMPLETION message from the UE. Such a procedure may increase the UE reception complexity processing cost and power consumption. In addition, the UE will continue to transmit UL data to the source gNB until the random access procedure to the target gNB is successfully completed; then, the UL data transmission is handed over to the target gNB. This also increases the signaling complexity, processing cost and power consumption of the UE.

[0226] Example 1: In some embodiments of the present invention, in the newly proposed low-latency and lossless handover MBS process, the source gNB can forward all MBS data packets (PDCP SDUs) received from the core network (UPF) to the target gNB during the agreed time (transmission switching period) between the source gNB and the target gNB, and then send them to the UE, ensuring that there is no packet loss on the UE side. By doing so, the UE does not need to wait until the target gNB sends a release command to the source gNB. The UE can stop receiving MBS data from the source gNB as specified in the RRC HANDOVER INITIATION command (i.e., the agreed time for the target gNB to start forwarding data to the UE) without worrying about MBS data loss, because all data will be transmitted from the source gNB to the target gNB within the agreed time, and the target gNB can start sending a copy of this data to the UE as early as possible (i.e., before or at the same time as the UE receives the HANDOVER INITIATION command.) In other words, the UE can stop receiving from the source gNB immediately after receiving the first data packet from the target gNB. Such a process helps to avoid packet loss and relax U processing capabilities and reduce power consumption.

[0227] Example 2: In some embodiments of the present invention, the source gNB may forward in the HANDOVER COMMAND message, including the target gNB timing advance information and the uplink pre-allocation grant. The source gNB may also pre-allocate an uplink grant for the UE to allow the UE to adjust its uplink timing to the target gNB (when handing over to the target gNB). This may allow the UE to avoid / omit the RACH procedure which may relatively reduce handover latency and relax the UE handover signaling complexity.

[0228] Some embodiments of the present invention provide a method for reliable and low-latency switching of multicast / broadcast service mobility with service continuity in 5G NR. The main innovations of the method include:

[0229] 1. Introduce the idea of ​​exchanging MBS service and / or QoS related information between UE, source gNB and target gNB to come up with a decision on the type of handover to be configured for UE MBS mobility.

[0230] 2. Introducing new types of information to be exchanged in the Handover Request message between the source gNB and the target gNB during handover, such as helping the source gNB and the target gNB to overcome the timing related information of PDCP allocation, PDCP count value misalignment, and data gap issues.

[0231] 3. Introduce the exchange of UE and MBS service, QoS flow and / or session identity association information between the UE, source gNB and target gNB, which can allow the target gNB to strive to provide the same QoS flow for MRB / DRB mapping and scheduling configuration / forwarding processing for MBS bearers, similar to the configuration of the source gNB. Given such scheduling configuration information and timing information when the source gNB and target gNB will start and stop sending data to the UE for a given MBS service, the UE is able to prepare the optimal reception configuration for the target configured MBS bearers.

[0232] 4. Introducing the idea of ​​combining PDCP SN allocation and data forwarding in a single signaling, which helps save handover signaling between source gNB and target gNB.

[0233] 5. Introducing the idea of ​​forwarding the duplicate downlink data forwarded from the target gNB as soon as the target gNB starts allocating PDCP SN allocations to the UE (i.e. before or at the same time as the UE receives the HANDOVER INITIATION command from the source gNB), helping the UE to avoid packet loss, relax the UE processing capability, and reduce power consumption.

[0234] 6. Introduce the idea of ​​omitting some handover signaling (e.g., UE can send handover complete signaling in some cases and omit it if not needed and use the pre-allocated grant for uplink data transmission.)

[0235] 7. Introducing the idea of ​​pre-allocating uplink grants from the source gNB and / or the target gNB, which can help increase the UE’s resilience against handover failures (i.e. by allowing the UE to send a handover failure to either the source gNB or the target gNB.)

[0236] In summary, in some embodiments of the present invention, a QoS-aware reliable and low-latency handover method is proposed to support MBS mobility with service continuity and ensure the difference in MBS service QoS requirements during UE handover. In this method, we propose to exchange MBS service and / or QoS related information between the UE, the source base station (such as the source gNB) and the target base station (such as the target gNB) to determine the handover type configured for the UE MBS mobility. In addition, we propose some improvements to the current NR handover, including some modifications to the HO signaling and procedures, such as introducing new types of information to be exchanged during the handover process (e.g., time-related information between the UE, the source and the target gNB), reducing the service interruption time, while keeping the UE signaling complexity, processing cost and power consumption as low as possible.

[0237] Compared with the prior art, the main advantage of some embodiments of the present invention is that a switching method is provided, which can simultaneously solve the delay and reliability requirements during MBS mobility and reduce the UE signaling complexity and processing cost as much as possible.

[0238] Other advantages of some embodiments of the present invention include at least one of the following.

[0239] Advantages on UE side:

[0240] 1. Compared with previous solutions to the problem of delayed service interruption of MBS mobility, such as DAPS handover, in which the UE receives a large amount of signaling due to receiving MBS services from the target gNB and the source gNB until the target gNB indicates that the handover to the source gNB is successful. The new method provides the UE with target gNB timing information, allowing the UE to stop receiving MBS services from the source gNB at any time (at an agreed time specified in the handover command or determined locally by the UE) without worrying about losing MBS data, because all MBS data within the agreed time range will be forwarded from the source gNB to the target gNB as early as possible, and from the target gNB to the UE. Such a process can help relax UE processing capabilities and reduce UE power consumption (i.e., the UE does not need to receive / transmit from / to both the source gNB and the target gNB at the same time to receive MBS mobility with low service interruption time).

[0241] 2. The new method exchanges the target gNB timing advance information to the UE and provides the UE with a pre-allocated uplink grant from the source gNB or the target gNB or both, which allows the UE to avoid / omit the RACH procedure to the target gNB. Such a procedure relatively reduces the UE's handover latency and reduces the complexity of UE signaling. The pre-allocated uplink grant provided by the source gNB and / or the target gNB also helps to improve the UE's resilience to handover failures (i.e., allows the UE to send a handover failure to the source gNB or the target gNB.)

[0242] Advantages on the network side:

[0243] This method introduces new types of information to be exchanged between the source gNB and the target gNB in ​​the handover request message, such as agreed timing information when the target NB will start sending data to the UE about a specific downlink / uplink frame that the source gNB sends / receives to / from the UE. Such timing information can help overcome several issues on the network side, such as the following.

[0244] PDCP SN allocation and count value misalignment issue: PDCP SN allocation and count value maintenance can be done directly on the source gNB and target gNB separately, and according to the agreed time, each node will start / stop downlink / uplink transmission to UE / UPF. For example, the source gNB can start allocating PDCP SN from the time it receives the HANDOVER ACK message from the target gNB until the start time of PDCP SN is allocated by the target gNB provided in the HANDOVER ACK message.

[0245] Data forwarding and data gap issues: During the switching time agreed upon by the source gNB and the target gNB, all MBS data packets (PDCP SDU) received by the source gNB from the core network (UPF) can be forwarded to the target gNB and then sent to the UE, ensuring that there is no packet loss on the UE side.

[0246] PDCP reordering and duplication issues: The UE may stop downlink as specified in the HANDOVER INITIATION command (i.e., the agreed time for the target gNB to start forwarding data to the UE) or immediately after receiving the first packet from the target gNB. This procedure simplifies the network implementation as the duplication check and in-sequence delivery to the 5G Core is done in the source gNB (i.e., until the agreed time or until the first packet is received from or in the target gNB) as opposed to the current DAPS procedure where a common reordering and duplication functionality (for both source and target gNB) is required in a single PDCP entity.

[0247] In summary, in some embodiments, a switching method for a user equipment (UE), a source base station, a target base station, and a multicast / broadcast service (MBS) is provided. The switching method for MBS is partially performed by the source base station, including exchanging MBS service and / or service quality (QoS) related information between the source base station and at least one user equipment (UE) as a switching measurement message and / or the target base station as part of a switching request message, and partially performed by the target base station, including exchanging MBS scheduling information and timing information when the target base station starts / stops PDCP SN allocation and / or data forwarding to at least the source base station through a switching confirmation message and / or the UE through a switching command message, and further includes deciding based on the switching measurement and / or the switching request message that the switching will be performed and / or configured by the source or target base station to support the best MBS mobility for a given UE. This can solve the problems in the prior art, solve the UE delay and reliability requirements during MBS mobility, reduce UE signaling complexity, reduce UE processing costs, support service continuity, provide good communication performance, and / or provide high reliability.

[0248] The commercial benefits of some embodiments are as follows. 1. Able to solve problems in the existing technology. 2. Solve the delay and reliability requirements during MBS mobility. 3. Reduce UE signaling complexity. 4. Reduce processing costs. 5. Support service continuity. 6. Provide good communication performance. 7. Provide high reliability. 8. Some embodiments of the present invention are used by 5G-NR chipset suppliers, V2X communication system development suppliers, automobile manufacturers including cars, trains, trucks, buses, bicycles, motorcycles, helmets, etc., drones, smartphone manufacturers, communication equipment for public safety, AR / VR equipment manufacturers (such as games, conferences / seminars, educational purposes). Some embodiments of the present invention are a combination of "technology / processes" that can be adopted in 3GPP specifications to create a final product. Some embodiments of the present invention propose technical mechanisms.

[0249] Figure 8 is a block diagram of a system for wireless communication according to an embodiment of the present invention. The embodiments described herein may be implemented in a system using any suitably configured hardware and / or software. Figure 8An example system 700 for one embodiment is shown, which includes radio frequency (RF) circuitry 710, baseband circuitry 720, application circuitry 730, memory / storage 740, display 750, camera 760, sensor 770, and input / output (I / O) interface 780, all of which are coupled to each other at least as shown. Application circuitry 730 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The processor may include any combination of general-purpose processors and special-purpose processors such as graphics processors, application processors, etc. The processor may be coupled to the memory / storage and configured to execute instructions stored in the memory / storage to enable various applications and / or operating systems running on the system.

[0250] The baseband circuit 720 may include circuits such as, but not limited to, one or more single-core or multi-core processors. The processor may include a baseband processor. The baseband circuit may handle various radio control functions for implementing communications with one or more radio networks via RF circuits. The radio control functions may include, but are not limited to, signal modulation, encoding, decoding, radio frequency shifting, etc. In some embodiments, the baseband circuit may provide communications compatible with one or more radio technologies. For example, in some embodiments, the baseband circuit may support communications with an Evolved Universal Terrestrial Radio Access Network (EUTRAN) and / or other wireless metropolitan area networks (WMANs), wireless local area networks (WLANs), wireless personal area networks (WPANs). An embodiment in which the baseband circuit is configured to support radio communications of more than one wireless protocol may be referred to as a multi-mode baseband circuit.

[0251] In various embodiments, baseband circuitry 720 may include circuitry that operates with signals that are not strictly considered to be at baseband frequencies. For example, in some embodiments, baseband circuitry may include circuitry that operates with signals having an intermediate frequency between baseband frequencies and radio frequencies. RF circuitry 710 may enable communication with a wireless network using modulated electromagnetic radiation transmitted through a non-solid medium. In various embodiments, RF circuitry may include switches, filters, amplifiers, etc. to facilitate communication with a wireless network. In various embodiments, RF circuitry 710 may include circuitry that operates with signals that are not strictly considered to be at radio frequencies. For example, in some embodiments, RF circuitry may include circuitry that operates with signals having an intermediate frequency between baseband frequencies and radio frequencies.

[0252] In various embodiments, the transmitter circuitry, control circuitry, or receiver circuitry discussed above with respect to a user equipment, eNB, or gNB may be embodied in whole or in part in one or more of the RF circuitry, baseband circuitry, and / or application circuitry. As used herein, "circuitry" may refer to, be part of, or include an application specific integrated circuit (ASIC) executing one or more software or firmware programs, an electronic circuit, a processor (shared, dedicated, or grouped), and / or memory (shared, dedicated, or grouped), combinatorial logic circuitry, and / or other suitable hardware elements that provide the described functionality. In some embodiments, the electronic device circuitry may be implemented in one or more software or firmware modules, or the functionality associated with the circuitry may be implemented by one or more software or firmware modules. In some embodiments, some or all of the constituent elements of the baseband circuitry, application circuitry, and / or memory / storage may be implemented together on a system on a chip (SOC). The memory / storage device 740 may be used to load and store, for example, messages and / or instructions for the system. The memory / storage device for one embodiment may include any combination of suitable volatile memory such as dynamic random access memory (DRAM) and / or non-volatile memory such as flash memory.

[0253] In various embodiments, the I / O interface 780 may include one or more user interfaces designed to implement the interaction between the user and the system, and / or a peripheral component interface designed to implement the interaction between the peripheral components and the system. The user interface may include but is not limited to a physical keyboard or keypad, a touchpad, a speaker, a microphone, etc. The peripheral component interface may include but is not limited to a non-volatile memory port, a universal serial bus (USB) port, an audio jack, and a power interface. In various embodiments, the sensor 770 may include one or more sensing devices to determine environmental conditions and / or location information related to the system. In some embodiments, the sensor may include but is not limited to a gyroscope sensor, an accelerometer, a proximity sensor, an ambient light sensor, and a positioning unit. The positioning unit may also be part of a baseband circuit and / or an RF circuit or interact with it to communicate with components of a positioning network such as a global positioning system (GPS) satellite.

[0254] In various embodiments, display 750 may include displays such as liquid crystal displays and touch screen displays. In various embodiments, system 700 may be a mobile computing device, such as, but not limited to, a laptop computing device, a tablet computing device, a netbook, an ultrabook, a smart phone, etc. In various embodiments, the system may have more or fewer components, and / or different architectures. Where appropriate, the methods described herein may be implemented as a computer program. The computer program may be stored on a storage medium such as a non-transitory storage medium.

[0255] It should be understood by those skilled in the art that each of the units, algorithms, and steps described and disclosed in the embodiments of the present disclosure is implemented using electronic hardware or a combination of software for a computer and electronic hardware. Whether the function is run in hardware or software depends on the conditions of the application and the design requirements of the technical plan. A person skilled in the art can use different ways to implement the functions for each specific application, and such implementation should not exceed the scope of the present disclosure. A person skilled in the art should understand that he can refer to the working process of the system, device, and unit in the above-mentioned embodiments, because the working process of the above-mentioned system, device, and unit is basically the same. For ease of description and simplicity, these working processes will not be described in detail.

[0256] It should be understood that the systems, devices and methods disclosed in the embodiments of the present invention can be implemented in other ways. The above embodiments are exemplary only. The division of units is based only on logical functions, and other divisions actually exist. It is possible that multiple units or elements are combined or integrated in another system. Certain features can also be omitted or skipped. On the other hand, the mutual coupling, direct coupling or communication coupling shown or discussed operates through some ports, devices or units, whether indirectly or communicatively by means of electrical, mechanical or other types of forms. The units used for explanation as separate elements are or are not physically separated. The units used for display are or are not physical units, that is, located in one place or distributed on multiple network units. Some or all of the units are used according to the purpose of the embodiment. In addition, each functional unit in each embodiment can be integrated into a processing unit, physically independent, or integrated into a processing unit together with two or more units.

[0257] If the software functional unit is implemented and used and sold as a product, it can be stored in a readable storage medium in a computer. Based on this understanding, the technical solution proposed in the present disclosure can be basically or partially implemented in the form of a software product. Alternatively, a part of the technical solution that is beneficial to traditional technology can be implemented in the form of a software product. The software product in the computer is stored in a storage medium, and the storage medium contains multiple commands for a computing device (such as a personal computer, a server, or a network device) to run all or some of the steps disclosed in the embodiments of the present disclosure. The storage medium includes a flash drive, a mobile hard drive, a read-only memory (ROM), a random access memory (RAM), a floppy disk, or other types of media capable of storing program code.

[0258] While the present disclosure has been described in connection with what are considered to be the most practical and preferred embodiments, it is to be understood that the present disclosure is not limited to the disclosed embodiments but is intended to cover various arrangements made without departing from the broadest interpretation of the appended claims.

Claims

1. A method for switching a multicast / broadcast service MBS performed by a user equipment UE, characterized in that: include: The UE determines MBS service and / or QoS related information as part of the handover measurement report; The MBS service and / or the QoS related information are exchanged between at least two of the UE, the source base station and the target base station as the part of the handover measurement report, and the time information between the UE, the source base station and the target base station is exchanged during the handover process, and carried in a handover command or a handover request confirmation message, and the carried time information is target downlink / uplink synchronization information, MBS data forwarding timing information, the agreed time for the target base station to start / stop packet data convergence protocol PDCP sequence number SN allocation and / or data forwarding, an uplink time advance command, and downlink synchronization information, wherein the handover for UE MBS mobility execution and / or configuration is performed based on the part of the handover measurement report; and The UE receives a configuration from the source base station, where the configuration includes at least one of the following: The agreed time for the source base station and the target base station to start / stop the PDCP SN allocation and / or the data forwarding; Target pre-allocation permission; The uplink timing advance command; the downlink synchronization information; or MBS bearer scheduling / forwarding configuration; and / or The method further includes receiving, by the UE, the switching command from the source base station, the switching command including the target downlink / uplink synchronization information, the MBS scheduling information and the MBS data forwarding timing information; and / or The UE optimal reception configuration of MBS data is prepared in advance, and it is decided when to stop receiving downlink data from the source base station and when to release the source base station configuration, and the source base station configuration is released accordingly.

2. The switching method according to claim 1, characterized in that: in, A handover type for performing and / or configuring the UE MBS mobility is selected based on at least one of: The indication of the UE includes the MBS service and / or the QoS related information; The internal configuration of the source base station; or Indication of the core network.

3. The switching method according to claim 1, characterized in that: The MBS service and / or the QoS related information includes UE identification ID, MBS service ID, QoS flow ID or session ID association.

4. The switching method according to claim 2, characterized in that: The internal configuration of the source base station includes UEID, MBS service ID, QoS flow ID or session ID association.

5. The switching method according to claim 2, characterized in that: The indication of the core network includes a UE MBS context message, a UE ID, an MBS service ID, a QoS flow ID or a session ID association.

6. The switching method according to claim 1, characterized in that: Determining, by the UE, the MBS service and / or the QoS related information as the part of the handover measurement report includes the UE receiving the MBS service and / or the QoS related information from a core network via a multicast radio bearer (MRB) or a unicast data radio bearer (DRB).

7. The switching method according to claim 1, characterized in that: Exchanging the MBS service and / or the QoS related information between the at least two of the UE, the source base station and the target base station includes indicating, by the UE, the MBS service and / or the QoS related information as the part of the handover measurement report to the source base station.

8. The switching method according to claim 7, characterized in that: Exchanging the MBS service and / or the QoS related information between the at least two of the UE, the source base station and the target base station includes the source base station forwarding the MBS service and / or the QoS related information of the UE to the target base station as the part of the handover measurement report.

9. The switching method according to claim 8, characterized in that: Instruct the source base station in the handover request signaling to forward the MBS service and / or the QoS related information of the UE to the target base station as the part of the handover measurement report.

10. The switching method according to claim 2, characterized in that: The handover type selected for the UE MBS mobility execution and / or configuration includes a lossless handover or a lossless and low-delay handover.

11. The switching method according to claim 10, characterized in that: The handover type selected for the UE MBS mobility execution and / or configuration includes the lossless handover or the lossless and low-delay handover according to UE MBS service reliability and delay level requirements.

12. The switching method according to claim 1, characterized in that: The configuration is forwarded by the source base station from the target base station to the UE.

13. The switching method according to claim 1, characterized in that: The configuration is forwarded by the source base station from the target base station to the UE in a handover initiation / command message.

14. The switching method according to claim 1, characterized in that: When the UE receives the configuration from the source base station, the UE performs at least one of the following: Synchronize to the target cell based on the downlink synchronization timing and uplink time advance information provided by the source base station from the target base station; A separate entity for configuring a media access control MAC configuration, a PDCP configuration and / or a radio link control RLC configuration for the target base station and the source base station; stopping receiving from the source base station after the timing information given in the radio resource control (RRC) configuration while maintaining the source MAC, PDCP and / or MAC entity until a first packet is received from the target base station; Stop sending uplink UL first layer channel state information CSI feedback, hybrid automatic repeat request HARQ feedback, second layer RLC feedback, robust header compression ROHC feedback, HARQ data retransmission and / or RLC data retransmission to the source base station; the source base station and / or the target base station sends a handover completion message on a pre-allocated license or the handover radio link fails; Omit sending the handover completion message and use the pre-allocated grant to perform uplink data transmission to the target base station; or Release the MAC configuration, the PDCP configuration and / or the RLC configuration of the source base station.

15. A method for switching a multicast / broadcast service MBS performed by a source base station, characterized in that: include: MBS service and / or service quality QoS related information is exchanged between the source base station and at least one user equipment UE as part of the handover measurement report and / or the MBS service and / or the QoS related information is exchanged with the target base station as part of the handover request message. During the handover process, time information is exchanged between the UE, the source base station and the target base station, and is carried in the handover command or the handover request confirmation message. The carried time information is target downlink / uplink synchronization information, MBS data forwarding timing information, the agreed time for the target base station to start / stop packet data convergence protocol PDCP sequence number SN allocation and / or data forwarding, uplink time advance command, and downlink synchronization information; as well as performing handover for UE MBS mobility execution and / or configuration based on the portion of the handover measurement report; The handover request confirmation message includes a configuration, and the configuration includes at least one of the following: The agreed time for the source base station and the target base station to start / stop the PDCP SN allocation and / or the data forwarding; Target pre-allocation permission; The uplink timing advance command; The downlink synchronization information; or MBS bearer scheduling / forwarding configuration; and / or The method also includes the source base station sending the handover command to the UE, where the handover command includes the target downlink / uplink synchronization information, MBS scheduling information and the MBS data forwarding timing information.

16. The switching method according to claim 15, characterized in that: in, A handover type for performing and / or configuring the UE MBS mobility is selected based on at least one of: The indication of the UE includes the MBS service and / or the QoS related information; The internal configuration of the source base station; or Indication of the core network.

17. The switching method according to claim 15, characterized in that: The MBS service and / or the QoS related information includes UE identification ID, MBS service ID, QoS flow ID or session ID association.

18. The switching method according to claim 16, characterized in that: The internal configuration of the source base station includes UEID, MBS service ID, QoS flow ID or session ID association.

19. The switching method according to claim 16, characterized in that: The indication of the core network includes a UE MBS context message, a UE ID, an MBS service ID, a QoS flow ID or a session ID association.

20. The switching method according to claim 15, characterized in that: Exchanging the MBS service and / or the quality of service QoS related information between the source base station and at least one user equipment UE as the part of the switching measurement message and / or exchanging the MBS service and / or the quality of service QoS related information with the target base station as the part of the switching request message includes determining, by the source base station, the MBS service and / or the QoS related information as the part of the switching measurement report from the UE.

21. The switching method according to claim 20, characterized in that: Exchanging the MBS service and / or the quality of service QoS related information between the source base station and at least one user equipment UE as the part of the switching measurement message and / or exchanging the MBS service and / or the quality of service QoS related information with the target base station as the part of the switching request message includes the source base station forwarding the MBS service and / or the QoS related information from the UE as the part of the switching measurement report to the target base station.

22. The switching method according to claim 21, characterized in that: Instruct the source base station in handover request signaling to forward the MBS service and / or the QoS related information from the UE to the target base station as the part of the handover measurement report.

23. The switching method according to claim 16, characterized in that: The handover type selected for the UE MBS mobility execution and / or configuration includes a lossless handover or a lossless and low-delay handover.

24. The switching method according to claim 23, characterized in that: The handover type selected for the UE MBS mobility execution and / or configuration includes the lossless handover or the lossless and low-delay handover according to UE MBS service reliability and delay level requirements.

25. The switching method according to claim 22, characterized in that: It also includes the source base station receiving a handover request confirmation from the target base station in response to the handover request signaling.

26. The switching method according to claim 25, characterized in that: When the source base station receives the handover request confirmation, the source base station performs at least one of the following: If low latency and lossless handover is selected and / or configured for UE MBS mobility, performing a PDCP SN that allocates PDCP service data unit (SDU) data forwarding; or An SN status transfer message is sent to the target base station to convey an uplink PDCP SN receiver status and a downlink PDCP SN transmitter status for which PDCP status preservation is applied.

27. The switching method according to claim 26, characterized in that: The uplink PDCP SN receiver status includes at least one of the following: the PDCP SN of the first lost UL PDCP SDU; or Reception status bitmap of out-of-sequence UL PDCP SDUs that the UE needs to retransmit in the target cell.

28. The switching method according to claim 26, characterized in that: The downlink PDCP SN transmitter status indicates the next PDCP SN allocated by the target base station to the new PDCP SDU, and if lossless switching is configured, there is no PDCP SN yet.

29. The switching method according to claim 15, characterized in that: It also includes sending the configuration to the UE by the source base station.

30. The switching method according to claim 29, characterized in that: The configuration is forwarded by the source base station from the target base station to the UE.

31. The switching method according to claim 29, characterized in that: The configuration is forwarded by the source base station from the target base station to the UE in a handover initiation / command message.

32. A method for switching a multicast / broadcast service MBS performed by a target base station, characterized in that: include: MBS service and / or service quality QoS related information is exchanged between at least two of the user equipment UE, the source base station and the target base station as part of the handover measurement report. Time information between the UE, the source base station and the target base station is exchanged during the handover process and carried in the handover command or the handover request confirmation message. The carried time information is target downlink / uplink synchronization information, MBS data forwarding timing information, the agreed time for the target base station to start / stop packet data convergence protocol PDCP sequence number SN allocation and / or data forwarding, uplink time advance command, and downlink synchronization information; as well as When the target base station starts / stops PDCP SN allocation, exchanging MBS scheduling information and timing information and / or forwarding data to at least the source base station via a handover confirmation message; The handover request confirmation message includes a configuration, and the configuration includes at least one of the following: The agreed time for the source base station and the target base station to start / stop the PDCP SN allocation and / or the data forwarding; Target pre-allocation permission; The uplink timing advance command; The downlink synchronization information; or MBS bearer scheduling / forwarding configuration.

33. The switching method according to claim 32, characterized in that: in, A handover type for performing and / or configuring the UE MBS mobility is selected based on at least one of: The indication of the UE includes the MBS service and / or the QoS related information; The internal configuration of the source base station; or Indication of the core network.

34. The switching method according to claim 32, characterized in that: The MBS service and / or the QoS related information includes UE identification ID, MBS service ID, QoS flow ID or session ID association.

35. The switching method according to claim 33, characterized in that: The internal configuration of the source base station includes UEID, MBS service ID, QoS flow ID or session ID association.

36. The switching method according to claim 33, characterized in that: The indication of the core network includes a UE MBS context message, a UE ID, an MBS service ID, a QoS flow ID or a session ID association.

37. The switching method according to claim 36, characterized in that: Exchanging the MBS service and / or the QoS related information between at least two of the UE, the source base station and the target base station includes forwarding, by the source base station, the MBS service and / or the QoS related information from the UE to the target base station as the part of the handover measurement report.

38. The switching method according to claim 37, characterized in that: Instruct the source base station in handover request signaling to forward the MBS service and / or the QoS related information from the UE to the target base station as the part of the handover measurement report.

39. The switching method according to claim 33, characterized in that: The handover type selected for the UE MBS mobility execution and / or configuration includes a lossless handover or a lossless and low-delay handover.

40. The switching method according to claim 39, characterized in that: The handover type selected for the UE MBS mobility execution and / or configuration includes the lossless handover or the lossless and low-delay handover according to UE MBS service reliability and delay level requirements.

41. The switching method according to claim 38, characterized in that: When the target base station receives the handover request signaling, the target base station performs at least one of the following: performing admission control on the UE MBS mobility and performing selection of the handover type for performing and / or configuring the UE MBS mobility, if the source base station does not perform selection of the handover type for performing and / or configuring the UE MBS mobility; determining and / or deciding, based on the configuration received in the handover request, a time to start PDCP SN allocation and / or forwarding data to the UE according to a time reference provided by the source base station; If the MBS session / service / temporary mobile group identity TMGI received by the UE exists in the target base station, initiating UE MSB session joining, or if the MBS session received by the UE does not exist in the target base station, initiating a session establishment request to the core network; If necessary, handover the UE to a new radio bearer and strive to provide the same QoS flow as the radio bearer mapping and scheduling configuration / forwarding process of the MBS bearer indicated by the source base station; determining a timing configuration that needs to be synchronized with the UE, and providing a timing proposal command and a pre-allocated grant to the UE; or The forwarding of the copied MBS downlink data forwarded from the source base station is started as a starting point for allocating the PDCP SN to the UE.

42. The switching method according to claim 38, characterized in that: The target base station also sends the handover request confirmation to the source base station in response to the handover request signaling.

43. The switching method according to claim 32, characterized in that: The configuration is forwarded by the source base station from the target base station to the UE.

44. The switching method according to claim 32, characterized in that: The source base station forwards the configuration from the target base station to the UE in a handover initiation / command message, and / or the target base station prepares according to the configuration received in the handover request, synchronization / timing information, UE pre-allocated grant allocation, and downlink and uplink timing advance.

45. A user equipment UE for multicast / broadcast service MBS, characterized in that: include: Memory; Transceiver; and a processor coupled to the memory and the transceiver; The processor is configured to: Determine MBS service and / or QoS related information as part of the handover measurement report; as well as The MBS service and / or the QoS related information are exchanged between at least two of the UE, the source base station and the target base station as the part of the handover measurement report, and the time information between the UE, the source base station and the target base station is exchanged during the handover process, and carried in a handover command or a handover request confirmation message, and the carried time information is target downlink / uplink synchronization information, MBS data forwarding timing information, the agreed time for the target base station to start / stop packet data convergence protocol PDCP sequence number SN allocation and / or data forwarding, an uplink time advance command, and downlink synchronization information; wherein, the handover for UE MBS mobility execution and / or configuration is performed based on the part of the handover measurement report; The transceiver receives a configuration from the source base station, the configuration comprising at least one of the following: The agreed time for the source base station and the target base station to start / stop the PDCP SN allocation and / or the data forwarding; Target pre-allocation permission; The uplink timing advance command; the downlink synchronization information; or MBS bearer scheduling / forwarding configuration; and / or The transceiver is configured to receive the switching command from the source base station, the switching command including the target downlink / uplink synchronization information, the MBS scheduling information and the MBS data forwarding timing information; and / or The processor is configured to prepare in advance the UE optimal reception configuration for MBS data, and decide when to stop receiving downlink data from the source base station, when to release the source base station configuration, and release the source base station configuration accordingly.

46. ​​The UE according to claim 45, characterized in that in, A handover type for performing and / or configuring the UE MBS mobility is selected based on at least one of: The indication of the UE includes the MBS service and / or the QoS related information; The internal configuration of the source base station; or Indication of the core network.

47. The UE according to claim 45, characterized in that The MBS service and / or the QoS related information includes UE identification ID, MBS service ID, QoS flow ID or session ID association.

48. The UE according to claim 46, characterized in that The internal configuration of the source base station includes UE ID, MBS service ID, QoS flow ID or session ID association.

49. The UE according to claim 46, characterized in that The indication of the core network includes a UE MBS context message, a UE ID, an MBS service ID, a QoS flow ID or a session ID association.

50. The UE according to claim 45, characterized in that Determining, by the processor, the MBS service and / or the QoS related information as the part of the handover measurement report includes the UE receiving the MBS service and / or the QoS related information from a core network via a multicast radio bearer MRB or a unicast data radio bearer DRB.

51. The UE according to claim 45, characterized in that Exchanging the MBS service and / or the QoS related information between the at least two of the UE, the source base station and the target base station includes indicating, by the processor, the MBS service and / or the QoS related information as the part of the handover measurement report to the source base station.

52. The UE according to claim 51, characterized in that Exchanging the MBS service and / or the QoS related information between the at least two of the UE, the source base station and the target base station includes the source base station forwarding the MBS service and / or the QoS related information of the UE to the target base station as the part of the handover measurement report.

53. The UE according to claim 52, characterized in that Instruct the source base station in the handover request signaling to forward the MBS service and / or the QoS related information of the UE to the target base station as the part of the handover measurement report.

54. The UE according to claim 46, characterized in that The handover type selected for the UE MBS mobility execution and / or configuration includes a lossless handover or a lossless and low-delay handover.

55. The UE according to claim 54, characterized in that The handover type selected for the UE MBS mobility execution and / or configuration includes the lossless handover or the lossless and low-delay handover according to UE MBS service reliability and delay level requirements.

56. The UE according to claim 45, characterized in that The configuration is forwarded by the source base station from the target base station to the transceiver.

57. The UE according to claim 45, characterized in that The configuration is forwarded by the source base station from the target base station to the transceiver in a handover initiation / command message.

58. The UE according to claim 45, characterized in that When the transceiver receives the configuration from the source base station, the processor performs at least one of the following: Synchronize to the target cell based on the downlink synchronization timing and uplink time advance information provided by the source base station from the target base station; A separate entity for configuring a media access control MAC configuration, a PDCP configuration and / or a radio link control RLC configuration for the target base station and the source base station; stopping receiving from the source base station after the timing information given in the radio resource control (RRC) configuration while maintaining the source MAC, PDCP and / or MAC entity until a first packet is received from the target base station; Stop sending uplink UL layer 1 channel state information CSI feedback, hybrid automatic repeat request HARQ feedback, layer 2 RLC feedback, robust header compression ROHC feedback, HARQ data retransmission and / or RLC data retransmission to the source base station; The source base station and / or the target base station sends a handover completion message on a pre-allocated license or the handover radio link fails; Omit sending the handover completion message and use the pre-allocated grant to perform uplink data transmission to the target base station; or Release the MAC configuration, the PDCP configuration and / or the RLC configuration of the source base station.

59. A source base station for a multicast / broadcast service MBS, characterized in that: include: Memory; Transceiver; and a processor coupled to the memory and the transceiver; The processor is configured to: MBS service and / or service quality QoS related information is exchanged between the source base station and at least one user equipment UE as part of the handover measurement message and / or the MBS service and / or the QoS related information is exchanged with the target base station as part of the handover request message. During the handover process, time information is exchanged between the UE, the source base station and the target base station, and is carried in the handover command or the handover request confirmation message. The carried time information is target downlink / uplink synchronization information, MBS data forwarding timing information, the agreed time for the target base station to start / stop packet data convergence protocol PDCP sequence number SN allocation and / or data forwarding, uplink time advance command, and downlink synchronization information; as well as performing handover for UE MBS mobility execution and / or configuration based on the portion of the handover measurement report; The handover request confirmation message includes a configuration, and the configuration includes at least one of the following: The agreed time for the source base station and the target base station to start / stop the PDCP SN allocation and / or the data forwarding; Target pre-allocation permission; The uplink timing advance command; The downlink synchronization information; or MBS bearer scheduling / forwarding configuration; and / or The method also includes the source base station sending the handover command to the UE, where the handover command includes the target downlink / uplink synchronization information, MBS scheduling information and the MBS data forwarding timing information.

60. The source base station according to claim 59, characterized in that: in, A handover type for performing and / or configuring the UE MBS mobility is selected based on at least one of: The indication of the UE includes the MBS service and / or the QoS related information; The internal configuration of the source base station; or Indication of the core network.

61. The source base station according to claim 59, characterized in that: The MBS service and / or the QoS related information includes UE identification ID, MBS service ID, QoS flow ID or session ID association.

62. The source base station according to claim 60, characterized in that: The internal configuration of the source base station includes UEID, MBS service ID, QoS flow ID or session ID association.

63. The source base station according to claim 60, characterized in that: The indication of the core network includes a UE MBS context message, a UE ID, an MBS service ID, a QoS flow ID or a session ID association.

64. The source base station according to claim 59, characterized in that: Exchanging the MBS service and / or the quality of service QoS related information between the source base station and at least one user equipment UE as the part of the switching measurement message and / or exchanging the MBS service and / or the quality of service QoS related information with the target base station as the part of the switching request message includes determining, by the processor, the MBS service and / or the QoS related information as the part of the switching measurement report from the UE.

65. The source base station according to claim 64, characterized in that: Exchanging the MBS service and / or the quality of service QoS related information between the source base station and at least one user equipment UE as the part of the switching measurement message and / or exchanging the MBS service and / or the quality of service QoS related information with the target base station as the part of the switching request message includes forwarding the MBS service and / or the QoS related information from the UE as the part of the switching measurement report to the target base station by the transceiver.

66. The source base station according to claim 65, characterized in that: The transceiver is instructed in handover request signaling to forward the MBS service and / or the QoS related information from the UE to the target base station as the part of the handover measurement report.

67. The source base station according to claim 60, characterized in that: The handover type selected for the UE MBS mobility execution and / or configuration includes a lossless handover or a lossless and low-delay handover.

68. The source base station according to claim 67, characterized in that: The handover type selected for the UE MBS mobility execution and / or configuration includes the lossless handover or the lossless and low-delay handover according to UE MBS service reliability and delay level requirements.

69. The source base station according to claim 66, characterized in that: The transceiver is configured to receive a handover request confirmation from the target base station in response to the handover request signaling.

70. The source base station according to claim 69, characterized in that: When the transceiver receives the handover request confirmation, the processor performs at least one of the following: If low latency and lossless handover is selected and / or configured for UE MBS mobility, performing a PDCP SN that allocates PDCP service data unit (SDU) data forwarding; or An SN status transfer message is sent to the target base station to convey an uplink PDCP SN receiver status and a downlink PDCP SN transmitter status for which PDCP status preservation is applied.

71. The source base station according to claim 70, characterized in that: The uplink PDCP SN receiver status includes at least one of the following: the PDCP SN of the first lost UL PDCP SDU; or Reception status bitmap of out-of-sequence UL PDCP SDUs that the UE needs to retransmit in the target cell.

72. The source base station according to claim 70, characterized in that: The downlink PDCP SN transmitter status indicates the next PDCP SN allocated by the target base station to the new PDCP SDU, and if lossless switching is configured, there is no PDCP SN yet.

73. The source base station according to claim 59, characterized in that: The transceiver is configured to send the configuration to the UE.

74. The source base station according to claim 73, characterized in that: The configuration is forwarded by the transceiver from the target base station to the UE.

75. The source base station according to claim 73, characterized in that: The configuration is forwarded by the transceiver from the target base station to the UE in a handover initiation / command message.

76. A target base station for a multicast / broadcast service MBS, characterized in that: include: Memory; Transceiver; and a processor coupled to the memory and the transceiver; The processor is configured to: MBS service and / or service quality QoS related information is exchanged between at least two of the user equipment UE, the source base station and the target base station as part of the handover measurement report. Time information between the UE, the source base station and the target base station is exchanged during the handover process and carried in the handover command or the handover request confirmation message. The carried time information is target downlink / uplink synchronization information, MBS data forwarding timing information, the agreed time for the target base station to start / stop packet data convergence protocol PDCP sequence number SN allocation and / or data forwarding, uplink time advance command, and downlink synchronization information; as well as When the target base station starts / stops PDCP SN allocation, exchanging MBS scheduling information and timing information and / or forwarding data to at least the source base station via a handover confirmation message; The handover request confirmation message includes a configuration, and the configuration includes at least one of the following: The agreed time for the source base station and the target base station to start / stop the PDCP SN allocation and / or the data forwarding; Target pre-allocation permission; The uplink timing advance command; The downlink synchronization information; or MBS bearer scheduling / forwarding configuration.

77. The target base station according to claim 76, characterized in that: in, A handover type for performing and / or configuring the UE MBS mobility is selected based on at least one of: The indication of the UE includes the MBS service and / or the QoS related information; The internal configuration of the source base station; or Indication of the core network.

78. The target base station according to claim 76, characterized in that: The MBS service and / or the QoS related information includes UE identification ID, MBS service ID, QoS flow ID or session ID association.

79. The target base station according to claim 77, characterized in that: The internal configuration of the source base station includes UEID, MBS service ID, QoS flow ID or session ID association.

80. The target base station according to claim 77, characterized in that: The indication of the core network includes a UE MBS context message, a UE ID, an MBS service ID, a QoS flow ID or a session ID association.

81. The target base station according to claim 80, characterized in that: Exchanging the MBS service and / or the QoS related information between at least two of the UE, the source base station and the target base station includes forwarding, by the source base station, the MBS service and / or the QoS related information from the UE to the transceiver as the part of the handover measurement report.

82. The target base station according to claim 81, characterized in that: The source base station is instructed in handover request signaling to forward the MBS service and / or the QoS related information from the UE to the transceiver as the part of the handover measurement report.

83. The target base station according to claim 77, characterized in that: The handover type selected for the UE MBS mobility execution and / or configuration includes a lossless handover or a lossless and low-delay handover.

84. The target base station according to claim 83, characterized in that: The handover type selected for the UE MBS mobility execution and / or configuration includes the lossless handover or the lossless and low-delay handover according to UE MBS service reliability and delay level requirements.

85. The target base station according to claim 82, characterized in that: When the target base station receives the handover request signaling, the target base station performs at least one of the following: performing admission control on the UE MBS mobility and performing selection of the handover type for performing and / or configuring the UE MBS mobility, if the source base station does not perform selection of the handover type for performing and / or configuring the UE MBS mobility; determining and / or deciding, based on the configuration received in the handover request, a time to start PDCP SN allocation and / or forwarding data to the UE according to a time reference provided by the source base station; If the MBS session / service / temporary mobile group identity TMGI received by the UE exists in the target base station, initiating UE MSB session joining, or if the MBS session received by the UE does not exist in the target base station, initiating a session establishment request to the core network; If necessary, handover the UE to a new radio bearer and strive to provide the same QoS flow as the radio bearer mapping and scheduling configuration / forwarding process of the MBS bearer indicated by the source base station; determining a timing configuration that needs to be synchronized with the UE, and providing a timing proposal command and a pre-allocated grant to the UE; or The forwarding of the copied MBS downlink data forwarded from the source base station is started as a starting point for allocating the PDCP SN to the UE.

86. The target base station according to claim 82, characterized in that: The transceiver is configured to send the handover request confirmation to the source base station in response to the handover request signaling.

87. The target base station according to claim 76, characterized in that: The configuration is forwarded from the transceiver to the UE by the source base station.

88. The target base station according to claim 76, characterized in that The source base station forwards the configuration from the transceiver to the UE in a handover initiation / command message, and / or the target base station prepares according to the configuration received in the handover request, synchronization / timing information, UE pre-allocated grant allocation, and downlink and uplink timing advance.

89. A non-transitory machine-readable storage medium having instructions stored thereon, characterized in that: When the instructions are executed by a computer, the computer is caused to perform the method according to any one of claims 1 to 44.

90. A chip, characterized in that: include: The processor is configured to call and run a computer program stored in the memory so that a device equipped with the chip executes a method as claimed in any one of claims 1 to 44.

91. A computer-readable storage medium, characterized in that A computer program is stored, wherein the computer program causes a computer to execute the method according to any one of claims 1 to 44.

92. A computer program product, characterized in that Comprising a computer program, wherein the computer program causes a computer to perform the method as claimed in any one of claims 1 to 44.

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