CN116349301A

CN116349301A - User equipment, source base station, target base station and multicast/broadcast service switching method

Info

Publication number: CN116349301A
Application number: CN202080105946.8A
Authority: CN
Inventors: 艾哈迈德·穆罕默德·米凯尔; 生嘉
Original assignee: JRD Communication Shenzhen Ltd
Current assignee: JRD Communication Shenzhen Ltd
Priority date: 2020-10-15
Filing date: 2020-10-15
Publication date: 2023-06-27
Also published as: WO2022077341A1

Abstract

The present invention discloses a User Equipment (UE), a source base station, a target base station, and a handover method for multicast/broadcast service (MBS). The method is performed in part by a source base station, including exchanging MBS Service and/or Quality of Service (QoS) related information between the source base station and at least one UE as part of a handover measurement message and/or exchanging MBS Service and/or QoS related information with a target base station as part of a handover request message, and is performed in part by the target base station, including exchanging MBS scheduling information and timing information when the target base station starts/stops PDCP SN allocation by a handover confirm message and/or the UE forwards data to at least the source base station by a handover command message, and further including deciding to support optimal mobility for a given UE based on handover measurements and/or handover request messages to be performed and/or configured by the source base station or the target base station.

Description

User equipment, source base station, target base station and multicast/broadcast service switching method

Technical Field

The present invention relates to the field of communication technologies, and in particular, to a User Equipment (UE), a source base station, a target base station, and a Handover (HO) method for multicast/broadcast service (MBS), which may provide good communication performance and/or provide high reliability.

Background

The wireless communication network may include base stations that may support communication for User Equipment (UE). The UE may communicate with the base station via downlink and uplink. Downlink refers to the base station to UE communication link and uplink refers to the UE to base station communication link.

In third generation partnership project (3rd generation partnership project,3GPP) cellular networks, broadcast and multicast services may be transmitted through a transmission service called multimedia broadcast/multicast service (multimedia broadcast/multicast service, MBMS). A broadcast multicast service center (broadcast multicast service center, BM-SC) server is responsible for disseminating media content to a group of subscribers. When the 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 intended to provide efficient broadcast and multicast service delivery in 3GPP cellular networks. Examples of MBMS interface specifications include those described in the universal mobile telecommunications system (universal mobile telecommunication system, UMTS) and long term evolution (long term evolution, LTE) communication specifications. For broadcast transmissions across multiple cells, the specification defines transmissions on a single frequency network configuration. Contemplated applications include mobile television, news, radio broadcasts, file transfers, emergency alerts, and the like. When the service is broadcast by MBMS, all cells within a multimedia broadcast/multicast service single frequency network (multimedia broadcast/multicast service single frequency network, MBSFN) area transmit the same MBMS service.

Users access these services and obtain MBMS content via wireless communication devices, such as cellular telephones, tablet computers, laptop computers, and other devices having 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 a cell. A user may access at least some multimedia services through a UE using a point-to-point (PTP) connection or PTM transmission. In 3GPP systems, PTP services can be provided using unicast techniques, PTM transmissions can be provided using MBMS communications, transmitted via MBSFN or single cell point-to-multipoint (single cell point to multipoint, SC-PTM) communications. In a system operating in accordance with a revision of the 3GPP long term evolution (long term evolution, LTE) communication specification, MBMS is provided using eMBMS. Accordingly, the MBMS service may be provided using a unicast service, an MBSFN, or an SC-PTM in the LTE system. In radio access network (radio access network, RAN) conference #88-e held 29 in 6, 2020 to 3 in 7, 2020, a new work item is approved with the goal of RAN supporting multicast/broadcast service (multicast/broadcast services, MBS) in 5G. The goal of this work item is to provide support in the RAN, enabling generic MBS services on 5GS to support different MBS services, such as public safety and mission critical, V2X applications, transparent IPv4/IPv6 multicast transmission, IPTV, wireless software transmission, group communication and internet of things 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).

During the 3GPP RAN2#111-e conference, considerable discussion of NR MBS mobility is made, and many companies have proposed to consider NR legacy handovers 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 propose additional enhancements for lossless handover for packet data convergence protocol (packet data convergence protocol, PDCP) Sequence Number (SN) allocation problems, PDCP count value misalignment, and data gap problems due to the unsynchronization between source and target gnbs during handover. Furthermore, during this meeting, other companies propose to employ NR double active protocol stack (dual active protocols stacks, DAPS) handover to minimize service interruption time during NR MBS movement; meanwhile, others have proposed to lower the priority of DAPS HO because of the large amount of 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 delays during movement, but require some modifications to the current or new DAPS, requiring handover procedures to support low-delay MBS mobility. Besides, there are many MBS mobility related problems in NR, such as nested signaling during handover and the type of information to be exchanged in signaling, and QoS handling problems not yet solved during 3gpp ran2#111-e conferencing.

Therefore, the present report proposes a new handover procedure to support MBS mobility with service continuity while guaranteeing reliability and delay requirements for different MBS services of 5G, and attempts to solve some of the above problems related to NR MBS mobility while reducing UE signaling complexity and processing cost as much as possible.

Disclosure of Invention

The invention aims to provide a User Equipment (UE), a source base station, a target base station and a switching method for multicast/broadcast service (MBS), which can solve the problems in the prior art, solve the delay and reliability requirements in the MBS moving process, reduce the UE signaling complexity, reduce the processing cost, support the service continuity, provide good communication performance and/or provide high reliability.

In a first aspect of the present invention, a method for switching 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 handover measurement report; and exchanging the MBS service and/or the QoS related information as the portion of the handover measurement report between at least two of the UE, source base station and target base station, wherein a handover for UE MBS mobility enforcement and/or configuration is performed based on the portion of the handover measurement report.

In one embodiment of the invention, the handover type for said UE MBS mobility execution and/or configuration is selected based on at least one of the following: the indication of the UE comprises the MBS service and/or the QoS related information; the 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 comprises a UE Identity (ID), MBS service ID, qoS flow ID or session ID association.

In one embodiment of the invention, the internal configuration of the source base station includes a UE ID, MBS service ID, qoS flow ID or session ID association.

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

In one embodiment of the invention, 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 comprises indicating the MBS service and/or the QoS related information by the UE as the part of the handover measurement report to the source base station.

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

In one embodiment of the invention, the handover type selected for the UE MBS mobility execution and/or configuration comprises a lossless handover or a lossless and low delay handover.

In one embodiment of the invention, selecting the handover type for the UE MBS mobility execution and/or configuration comprises the lossless handover or the lossless and low-delay handover according to UE MBS service reliability and delay level requirements.

In one embodiment of the present invention, the handover method is further comprising the UE receiving a configuration from the source base station, the configuration including at least one of: a contracted time for the source base station and the target base station to start/stop packet data convergence protocol (packet data convergence protocol, PDCP) Sequence Number (SN) allocation and/or data forwarding; target pre-allocation permissions; an uplink time advance command; downlink synchronization information; or MBS bearer scheduling/forwarding configuration; and/or the method further comprises receiving, by the UE, a handover command from the source base station, the handover command containing target downlink/uplink synchronization information, MBS scheduling information, and MBS data forwarding timing information; and/or preparing the optimal receiving configuration of the UE of the MBS data in advance, deciding when to stop receiving the downlink data from the source base station, when to release the source base station configuration, and correspondingly releasing the source base station configuration.

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

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

In one embodiment of the invention, when the UE receives the configuration from the source base station, the UE performs at least one of: synchronizing to a target cell based on downlink synchronization timing and uplink time advance information provided by the source base station from the target base station; separate entities configuring a medium access control (medium access control, MAC) configuration, PDCP configuration and/or radio link control (radio link control, RLC) configuration for the target base station and the source base station; stopping receiving from the source base station after timing information given in a radio resource control (radio resource control, RRC) configuration while maintaining source MAC, PDCP and/or MAC entities until a first packet is received from the target base station; ceasing to transmit Uplink (UL) first layer channel state information (channel state information, CSI) feedback, hybrid automatic repeat request (hybrid automatic repeat request, HARQ) feedback, second layer RLC feedback, robust header compression (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 or fails to switch the wireless link on a pre-allocated permission; omitting sending a switching completion message and carrying out uplink data transmission to the target base station by utilizing the pre-allocated permission; or releasing the MAC configuration, the PDCP configuration and/or the RLC configuration of the source base station.

In a second aspect of the present invention, a handover method of a multicast/broadcast service (MBS) performed by a source base station, comprising: exchanging MBS Service and/or Quality-of-Service (QoS) related information as part of a handover measurement message and/or exchanging the MBS Service and/or the QoS related information as part of a handover request message between the source base station and at least one User Equipment (UE); and performing a handover for UE MBS mobility execution and/or configuration based on the portion of the handover measurement report.

In one embodiment of the invention, exchanging the MBS service and/or the quality of service QoS related information as the part of the handover measurement message and/or exchanging the MBS service and/or the quality of service QoS related information as the part of the handover request message by the target base station comprises determining, by the source base station, the MBS service and/or the QoS related information as the part of the handover measurement report from the UE.

In one embodiment of the invention, exchanging the MBS service and/or the quality of service QoS related information as the part of the handover measurement message and/or exchanging the MBS service and/or the quality of service QoS related information as the part of the handover request message by the target base station between the source base station and at least one user equipment UE comprises forwarding the MBS service and/or the QoS related information from the UE as the part of the handover measurement report by the source base station to the target base station.

In one embodiment of the invention, the source base station is instructed 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 handover request signaling.

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

In one embodiment of the invention, the handover request acknowledgement includes a configuration including at least one of: a contracted time for the source base station and the target base station to start/stop packet data convergence protocol (packet data convergence protocol, PDCP) Sequence Number (SN) allocation and/or data forwarding; target pre-allocation permissions; an uplink time advance command; downlink synchronization information; or MBS bearer scheduling/forwarding configuration.

In one embodiment of the present invention, when the source base station receives the handover request acknowledgement, the source base station performs at least one of: performing PDCP SN, which allocates PDCP service data unit (service data unit, SDU) data forwarding, if low delay and lossless handover is selected and/or configured for UE MBS mobility; or sending an SN status transfer message to the target base station to convey an uplink PDCP SN receiver status and a downlink PDCP SN transmitter status to which PDCP status preservation is applied.

In one embodiment of the present invention, the uplink PDCP SN receiver status includes at least one of: PDCP SN of the first lost UL PDCP SDU; or the UE needs a reception status bitmap of out-of-order UL PDCP SDUs retransmitted in the target cell.

In one embodiment of the invention, the downlink PDCP SN transmitter status indicates that the target base station assigned the next PDCP SN of the new PDCP SDU, if a lossless handover is configured, there is no PDCP SN yet.

In one embodiment of the present invention, the handover method further includes transmitting, by the source base station, the configuration to the UE.

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

In one embodiment of the 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 comprises forwarding the MBS service and/or the QoS related information from the UE by the source base station as the part of the handover measurement report to the target base station.

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: performing admission control on the UE MBS mobility and performing the handover type selected 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; 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; initiating a UE MSB session joining if an MBS session/service/temporary mobile group identity (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 an 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 process of MBS bearers indicated by the source base station; determining a timing configuration which needs to be synchronized with the UE, and providing a time suggestion command and a pre-allocation permission for the UE; or starting to forward the duplicate MBS downlink data forwarded from the source base station as starting to distribute the PDCP SN to the UE.

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

In one embodiment of the invention, the source base station forwards the configuration from the target base station to the UE in a handover initiate/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.

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 are coupled to the memory and the transceiver. The processor is configured to: determining MBS service and/or quality of service QoS related information as part of a handover measurement report; and exchanging the MBS service and/or the QoS related information as the portion of the handover measurement report between at least two of the UE, source base station and target base station, wherein a handover for UE MBS mobility enforcement and/or configuration is performed based on the portion of the handover measurement report.

In one embodiment of the invention, the MBS service and/or the QoS related information comprises a UE identity ID, MBS service ID, qoS flow ID or session ID association.

In one embodiment of the invention, determining, by the processor, the MBS service and/or the QoS related information as the part of the handover measurement report comprises 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.

In one embodiment of the invention, 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 comprises 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.

In one embodiment of the invention, the UE further comprises the transceiver to receive a configuration from the source base station, the configuration comprising at least one of: the source base station and the target base station start/stop the appointed time of packet data convergence protocol PDCP serial number SN allocation and/or data forwarding; target pre-allocation permissions; an uplink time advance command; downlink synchronization information; or MBS bearer scheduling/forwarding configuration; and/or wherein the transceiver is configured to receive a handover command from the source base station, the handover command containing target downlink/uplink synchronization information, MBS scheduling information, and MBS data forwarding timing information; and/or wherein the processor is configured to prepare in advance a UE optimal reception configuration for MBS data and to 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.

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

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 initiate/command message.

In one embodiment of the invention, when the transceiver receives the configuration from the source base station, the processor performs at least one of: synchronizing to a target cell based on downlink synchronization timing and uplink time advance information provided by the source base station from the target base station; configuring separate entities of a medium access control, MAC, configuration, PDCP, 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 timing information given in a radio resource control, RRC, configuration while maintaining source MAC, PDCP and/or MAC entities until a 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 (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 or fails to switch the wireless link on a pre-allocated permission; omitting sending a switching completion message and carrying out uplink data transmission to the target base station by utilizing the pre-allocated permission; or releasing the MAC configuration, the PDCP configuration and/or the RLC configuration of the source base station.

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: exchanging MBS services and/or quality of service QoS related information as part of a handover measurement message and/or exchanging said MBS services and/or said QoS related information as part of a handover request message between said source base station and at least one user equipment UE; and performing a handover for UE MBS mobility execution and/or configuration based on the portion of the handover measurement report.

In one embodiment of the invention, exchanging the MBS service and/or the quality of service QoS related information as the part of the handover measurement message and/or exchanging the MBS service and/or the quality of service QoS related information as the part of the handover request message by the target base station comprises determining, by the processor, the MBS service and/or the QoS related information as the part of the handover measurement report from the UE.

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

In one embodiment of the invention, the transceiver is instructed 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 handover request signaling.

In one embodiment of the invention, the transceiver is configured to receive a handover request acknowledgement of the target base station in response to the handover request signaling.

In one embodiment of the invention, the handover request acknowledgement includes a configuration including at least one of: the source base station and the target base station start/stop the appointed time of packet data convergence protocol PDCP serial number SN allocation and/or data forwarding; target pre-allocation permissions; an uplink time advance command; downlink synchronization information; or MBS bearer scheduling/forwarding configuration.

In one embodiment of the invention, when the transceiver receives the handover request acknowledgement, the processor performs at least one of: if the low-delay and lossless handover is selected and/or configured for the UE MBS mobility, performing PDCP SN, wherein the PDCP SN distributes PDCP service data unit SDU data forwarding; or sending an SN status transfer message to the target base station to convey an uplink PDCP SN receiver status and a downlink PDCP SN transmitter status to which PDCP status preservation is applied.

In one embodiment of the invention, the transceiver is configured to transmit the configuration to the UE.

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

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

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: exchanging MBS services and/or quality of service QoS related information as part of a handover measurement report between at least two of a user equipment UE, a source base station and said target base station; and exchanging MBS scheduling information and timing information and/or forwarding data to at least the source base station via the handover confirm message and/or the UE passing a handover command message when the target base station starts/stops PDCP SN allocation.

In one embodiment of the 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 comprises forwarding the MBS service and/or the QoS related information from the UE by the source base station as the part of the handover measurement report to the transceiver.

In one embodiment of the invention, the source base station is instructed 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 in handover request signaling.

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: performing admission control on the UE MBS mobility and performing the handover type selected 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; 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 Identification (TMGI) received by the UE exists in the target base station, initiating a user equipment (MSB) session to join, 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; 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 process of MBS bearers indicated by the source base station; determining a timing configuration which needs to be synchronized with the UE, and providing a time suggestion command and a pre-allocation permission for the UE; or starting to forward the duplicate MBS downlink data forwarded from the source base station as starting to distribute the PDCP SN to the UE.

In one embodiment of the invention, the transceiver is configured to send the handover request acknowledgement to the source base station in response to the handover request signaling.

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

In one embodiment of the invention, the source base station forwards the configuration from the transceiver to the UE in a handover initiate/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.

In a seventh aspect of the 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-described method.

In an eighth aspect of the present invention, a chip includes a processor for calling and running a computer program stored in a memory to cause a device on which the chip is mounted to perform the above method.

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-described method.

In a tenth aspect of the invention, a computer program product comprises a computer program and the computer program causes a computer to perform the above method.

In an eleventh aspect of the present invention, a computer program causes a computer to execute the above method.

Drawings

In order to further explain the technical solution of the embodiments of the present invention, the drawings required for describing the embodiments will be briefly introduced. It is apparent that the following drawings are merely some embodiments of the present invention. Other figures may be made by anyone skilled in the art without the inventive effort based on the following figures.

Fig. 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.

Fig. 2 is a flowchart of a handover method of a multicast/broadcast service (MBS) performed by a User Equipment (UE) in a communication network system according to an embodiment of the present invention.

Fig. 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.

Fig. 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.

Fig. 5 is a schematic diagram of a 5G NR baseline switching process according to an embodiment of the present invention.

Fig. 6 is a schematic diagram of an MBS-capable UE switching from one NG-RAN to another NG-RAN according to an embodiment of the present invention.

Fig. 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.

Fig. 8 is a block diagram of a system for wireless communication according to an embodiment of the present invention.

Detailed Description

Technical matters, structural features, achieved objects and effects of the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In particular, the terminology used in the embodiments of the invention is for the purpose of describing the embodiments of the invention only and is not intended to be limiting of the invention.

Some embodiments of the present invention relate to wireless communications, and more particularly to mobility problems for multicast/broadcast services (MBS) in NR systems. MBS is a point-to-multipoint (PTM) interface intended to provide efficient broadcast and multicast service delivery in 3GPP cellular networks.

As discussed in accordance with the RP-201308 3gpp document, NR MBS explicitly requires support of basic mobility with service continuity. Despite the extensive discussion of MBS mobility in recent 3GPP conferences, there are many technical gaps related to MBS mobility that remain undiscovered or are still further discussed in the conference to be held, such as QoS requirement handling during MBS mobility, service interruption delays during MBS mobility, types of handover selections to be performed/configured to support MBS mobility, nested signaling during handover, and types of information exchanged in signaling during handover. The primary object of some embodiments of the present invention is to address some of these technical gaps. Thus, 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.

In the NR MBS mobility framework, most proposals submitted to the recent 3gpp RAN2 conference focus on traditional NR unicast Handoffs (HO) with lossless characteristics as potential candidates for MBS mobility in NR. The conventional NR unicast switching with lossless characteristics can effectively solve the reliability problem in the MBS moving process. However, lossless HO may result in additional (from 25 ms to 40 ms) service interruption time. Whereas some MBS use cases for NR may involve MBS reception during mobility, e.g. V2X and industrial applications (e.g. motion sensors and actuators) require very low service interruption delays above their reliability requirements, a mechanism that handles both delay and reliability problems is very important for efficient MBS mobility. Although some companies have proposed using DAPS to achieve low-latency MBS mobility, DAPS may also introduce significant signaling to the UE due to the simultaneous reception of signals from the source and target handover gnbs.

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

Compared with the prior art, the method has the main advantages that the method can solve the delay and reliability requirements in the MBS moving process, and reduce the UE signaling complexity and processing cost as much as possible.

Other advantages of some embodiments of the invention include at least one of the following.

UE side advantage:

the new method exchanges the target gNB MBS data forwarding timing to the UE in the handover command, the UE can clearly know when it expects to start receiving MBS DL data from the target gNB. Given such information, as well as other information related to MBS scheduling within the handover command, the UE may 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, as in the DAPS). Such a procedure may relatively reduce UE signaling complexity, processing costs, and minimize UE power consumption.

The new approach introduces the idea of exchanging target gNB timing advance and downlink synchronization information to the source gNB and UE. Such information may help the UE avoid the need for a Random Access (RACH) procedure during handover execution, which may lead to reduced handover interruption time (and help relax UE processing and signaling complexity).

The new method/introduces the idea of pre-allocating uplink grants from the source and target gnbs, which is new, can help to relatively improve the resilience of the UE to handover failures (i.e. the UE can send a handover failure indication or a reconnection request to either) either the source or target gNB. The new approach introduces a procedure for transmitting or starting forwarding MBS DL data to the UE earlier by the target gNB (rather than waiting to receive a handover complete message in the DAPS), which may be relatively helpful in reducing UE handover interruption time.

Network side advantage:

the method introduces new 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 to send data to the UE regarding the specific downlink/uplink frames the source gNB sends/receives to/from the UE. Such timing information may help overcome several problems on the network side, such as the following.

PDCP SN assignment and count value misalignment problem: PDCP SN allocation and count value maintenance can be done separately directly on the source gNB and target gNB, and

according to the agreed time, each node will start/stop downlink/uplink transmissions to the UE/User Plane Function (UPF). For example, the source gNB may allocate PDCP SNs starting from the time it receives a 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 to maintain a logical connection (PDCP level) between the source gNB and the target gNB during handover and minimizes MBS data loss on the UE side.

Data forwarding and data gap problems: all MBS data 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 forwarded to the UE, ensuring that no MBS data packet loss occurs on the UE side.

PDCP reordering and duplication problem: the UE may stop the downlink as per HANDOVER INITIATION command (i.e., the contracted time when the target gNB will begin forwarding data to the UE) or immediately after receiving the first data packet from the target gNB. This procedure simplifies network implementation because the copy checking and in-order 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), adapting to the current DAPS procedure requires a common reordering and copy function (for both the source gNB and the target gNB) in a single PDCP entity. As shown in fig. 1, in some embodiments, a User Equipment (UE) 10, a source base station 20, and a target base station 30 are provided for communication in a communication network system 40 according to an embodiment of the present invention. 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 network nodes such as a next generation radio access network (NG-RAN node, an access and mobility management function (AMF) node, a session data management function (SMF) node, a Network Exposure Function (NEF))/Policy Control Function (PCF) node, a User Plane Function (UPF) node, and an 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). A node, an access and mobility management function (AMF) node, a session data management function (SMF) node, a Network Exposure Function (NEF)/Policy Control Function (PCF) node, a User Plane Function (UPF) node, and an 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 operatively coupled with 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 operatively coupled to the

processor

11 or 21 or 31, and the

transceiver

13 or 23 or 33 transmits and/or receives radio signals.

The

processor

11 or 21 or 31 may include an Application Specific Integrated Circuit (ASIC), other chipset, logic circuit, and/or data processing device.

Memory

12 or 22 or 32 may include Read Only Memory (ROM), random Access Memory (RAM), flash memory, memory cards, storage media, and/or other storage devices. The

transceiver

13 or 23 or 33 may include baseband circuitry that processes radio frequency signals. When the embodiments are implemented in software, the techniques described herein may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The modules may be stored in

memory

12 or 22 or 32 and executed by

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 external to the

processor

11 or 21 or 31, in which case they can be communicatively coupled to the

processor

11 or 21 or 31 via various means as is known in the art.

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

In some embodiments, the processor 21 is configured to exchange MBS Service and/or Quality of Service (QoS) related information as part of a handover measurement message and/or the target base station 30 as part of a handover request message between the source base station 20 and at least one User Equipment (UE) 10; and performing a handover for UE MBS mobility execution and/or configuration based on the portion of the handover measurement report.

In some embodiments, the processor 31 is configured to exchange MBS service and/or quality of service QoS related information as part of a handover measurement report between at least two of the User Equipment (UE) 10, the source base station 20 and said target base station 30; and exchanging MBS scheduling information and timing information and/or forwarding data to at least the source base station 20 via the handover confirm message and/or the UE10 through a handover command message when the target base station 30 starts/stops PDCP SN allocation. This may solve the problems in the prior art, solve delay and reliability requirements in MBS movement, reduce UE signaling complexity, reduce processing costs, support service continuity, provide good communication performance, and/or provide high reliability.

Fig. 2 illustrates a handover method 200 of a multicast/broadcast service (MBS) performed by a User Equipment (UE) in a communication network system according to an embodiment of the present invention. In some embodiments, the handover method 200 includes: step 202, determining, by the UE, MBS service and/or quality of service QoS related information as part of a handover measurement report, step 204, exchanging the MBS service and/or the QoS related information as the part of the handover measurement report between at least two of the UE, source base station and 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 containing target downlink/uplink synchronization information, MBS scheduling information, and MBS data forwarding timing information from the source base station, step 208: the UE prepares the best reception configuration for MBS data in advance, decides when to stop receiving DL data from the source gNB, and when to release the source gNB configuration, avoiding continuing to receive MBS downlink data source and target gNB from both until the source gNB connection is released by an explicit release command of the target gNB. Such a procedure may relatively reduce UE signaling complexity, processing costs, and minimize UE power consumption.

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

In one embodiment of the invention, 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 comprises indicating the MBS service and/or the QoS related information by the UE as the part of the handover measurement report to the source base station. In one embodiment of the invention, 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 comprises 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 invention, the source base station is instructed in handover request signaling to forward the MBS service of the UE and/or the QoS related information as the part of the handover measurement report to the target base station. In one embodiment of the invention, the handover type selected for the UE MBS mobility execution and/or configuration comprises a lossless handover or a lossless and low delay handover.

In one embodiment of the invention, selecting the handover type for the UE MBS mobility execution and/or configuration comprises the lossless handover or the lossless and low-delay handover according to UE MBS service reliability and delay level requirements. In one embodiment of the present invention, the handover method is further comprising the UE receiving a configuration from the source base station, the configuration including at least one of: a contracted time for the source base station and the target base station to start/stop packet data convergence protocol (packet data convergence protocol, PDCP) Sequence Number (SN) allocation and/or data forwarding; target pre-allocation permissions; an uplink time advance command; downlink synchronization information; or MBS bearer scheduling/forwarding configuration; and/or the method further comprises receiving, by the UE, a handover command from the source base station, the handover command containing target downlink/uplink synchronization information, MBS scheduling information, and MBS data forwarding timing information; and/or preparing the optimal receiving configuration of the UE of the MBS data in advance, deciding when to stop receiving the downlink data from the source base station, when to release the source base station configuration, and correspondingly releasing the source base station configuration.

In one embodiment of the invention, the configuration is forwarded by the source base station from the target base station to the UE in a handover initiate/command message. In one embodiment of the invention, when the UE receives the configuration from the source base station, the UE performs at least one of: synchronizing to a target cell based on downlink synchronization timing and uplink time advance information provided by the source base station from the target base station; separate entities configuring a medium access control (medium access control, MAC) configuration, PDCP configuration and/or radio link control (radio link control, RLC) configuration for the target base station and the source base station; stopping receiving from the source base station after timing information given in a radio resource control (radio resource control, RRC) configuration while maintaining source MAC, PDCP and/or MAC entities until a first packet is received from the target base station; ceasing to transmit Uplink (UL) first layer channel state information (channel state information, CSI) feedback, hybrid automatic repeat request (hybrid automatic repeat request, HARQ) feedback, second layer RLC feedback, robust header compression (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 or fails to switch the wireless link on a pre-allocated permission; omitting sending a switching completion message and carrying out uplink data transmission to the target base station by utilizing the pre-allocated permission; or releasing the MAC configuration, the PDCP configuration and/or the RLC configuration of the source base station.

Fig. 3 illustrates 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 by 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.

In one embodiment of the invention, the handover type for said UE MBS mobility execution and/or configuration is selected based on at least one of the following: the indication of the UE comprises the MBS service and/or the QoS related information; the 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 comprises a UE Identity (ID), MBS service ID, qoS flow ID or session ID association. In one embodiment of the invention, the internal configuration of the source base station includes a UE ID, MBS service ID, qoS flow ID or session ID association. In one embodiment of the invention, the indication of the core network comprises 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 invention, exchanging the MBS service and/or the quality of service QoS related information as the part of the handover measurement message and/or exchanging the MBS service and/or the quality of service QoS related information as the part of the handover request message by the target base station comprises determining, by the source base station, the MBS service and/or the QoS related information as the part of the handover measurement report from the UE.

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

In one embodiment of the present invention, when the source base station receives the handover request acknowledgement, the source base station performs at least one of: performing PDCP SN, which allocates PDCP service data unit (service data unit, SDU) data forwarding, if low delay and lossless handover is selected and/or configured for UE MBS mobility; or sending an SN status transfer message to the target base station to convey an uplink PDCP SN receiver status and a downlink PDCP SN transmitter status to which PDCP status preservation is applied. In one embodiment of the present invention, the uplink PDCP SN receiver status includes at least one of: PDCP SN of the first lost UL PDCP SDU; or the UE needs a reception status bitmap of out-of-order UL PDCP SDUs retransmitted in the target cell. In one embodiment of the invention, the downlink PDCP SN transmitter status indicates that the target base station assigned the next PDCP SN of the new PDCP SDU, if a lossless handover is configured, there is no PDCP SN yet. In one embodiment of the present invention, the handover method further includes transmitting, by the source base station, the configuration to the UE. In one embodiment of the invention, the configuration is forwarded by the source base station from the target base station to the UE. In one embodiment of the invention, the configuration is forwarded by the source base station from the target base station to the UE in a handover initiate/command message.

Fig. 4 illustrates a handover 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 handover method 400 includes:

step 402 of exchanging MBS service and/or quality of service (QoS) related information as part of a handover measurement report between at least two of a User Equipment (UE), a source base station and said target base station, and step 404 of exchanging MBS scheduling information and timing information and/or forwarding data at least to said source base station via said handover confirm message and/or said UE passing a handover command message when said target base station starts/stops PDCP SN allocation. This may solve the problems in the prior art, solve delay and reliability requirements in MBS movement, reduce UE signaling complexity, reduce processing costs, support service continuity, provide good communication performance, and/or provide high reliability.

In one embodiment of the invention, the handover type for said UE MBS mobility execution and/or configuration is selected based on at least one of the following: the indication of the UE comprises the MBS service and/or the QoS related information; the 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 comprises a UE Identity (ID), MBS service ID, qoS flow ID or session ID association. In one embodiment of the invention, the internal configuration of the source base station includes a UE ID, MBS service ID, qoS flow ID or session ID association. In one embodiment of the invention, the indication of the core network comprises 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 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 comprises forwarding the MBS service and/or the QoS related information from the UE by the source base station as the part of the handover measurement report to the target base station.

In one embodiment of the invention, the source base station is instructed 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 handover request signaling. In one embodiment of the invention, the handover type selected for the UE MBS mobility execution and/or configuration comprises a lossless handover or a lossless and low delay handover. In one embodiment of the invention, selecting the handover type for the UE MBS mobility execution and/or configuration comprises the lossless handover or the lossless and low-delay handover according to UE MBS service reliability and delay level requirements.

In one embodiment of the present invention, the handover method further includes the target base station sending the handover request Acknowledgement (ACK) to the source base station in response to the handover request signaling. In one embodiment of the invention, the handover request acknowledgement includes a configuration including at least one of: a contracted time for the source base station and the target base station to start/stop packet data convergence protocol (packet data convergence protocol, PDCP) Sequence Number (SN) allocation and/or data forwarding; target pre-allocation permissions; an uplink time advance command; downlink synchronization information; or MBS bearer scheduling/forwarding configuration. In one embodiment of the invention, the configuration is forwarded by the source base station from the target base station to the UE. In one embodiment of the invention, the source base station forwards the configuration from the target base station to the UE in a handover initiate/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.

In some embodiments, we will begin this section by reviewing the current standardized conventional or baseline NR handoff and discussing how to achieve minimization of data loss and service interruption delays for NR unicast services. We will focus mainly on the characteristics that aim to reduce data loss during handover, such as lossless handover characteristics, and on the procedures that aim to minimize service interruption time, such as DAPS procedures. We will then point out the limitations and drawbacks of the above-described handover procedure in addressing MBS mobility requirements in the NR. Finally, we will introduce our proposed handover procedure to overcome these drawbacks and limitations.

NR baseline switching review:

fig. 5 illustrates a 5G NR baseline switching process according to an embodiment of the present invention. Fig. 5 illustrates an NR baseline handover procedure for a UE receiving unicast service to move from a source gNB to a target gNB in some embodiments is illustrated in fig. 5. The main steps of the Control Plane (CP) handling baseline switching include: a) A handover preparation phase (step 0 to step 5), b) a handover execution phase (step 6 to step 8), and 3) a handover completion phase (steps 8a to 12). The steps are as follows:

step 0 the UE context within the source gNB contains information about roaming and access restrictions, which are provided at connection setup or at last Tracking Area (TA) update.

And step 1, configuring a UE measurement process by the source gNB, and reporting by the UE according to the measurement configuration.

Step 2, the source gNB decides to switch the UE according to the measurement report and the Radio Resource Management (RRM) information.

And 3, the source gNB sends a switching request message to the target gNB, and a transparent RRC container with necessary information is transferred so as to prepare for switching at the target end. The information includes at least a target cell ID, a KgNB, a cell radio network temporary identifier (C-RNTI) of the UE in the source gNB, RRM configuration including UE inactivity time, basic AS (access layer) configuration including antenna information, and Downlink (DL) carrier frequency, current QoS flow to Data Radio Bearer (DRB) mapping rules applied to the UE, system information block 1 (SIB 1) from the source gNB, capabilities of the UE for different Radio Access Technologies (RATs), plane Packet Data Unit (PDU) session related information, and may include 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 handoff for some DRBs.

Step 4: admission control may be performed by the target gNB. If the fragmentation information is sent to the target gNB, fragmentation aware admission control should be performed. If a PDU session is associated with an unsupported slice, the target gNB should reject such a PDU session.

Step 5, the target gNB prepares for handover with L1/L2 and sends a handover request acknowledgement to the source gNB, including a transparent container to be sent as an RRC message to the UE to perform the handover.

Step 6: the source gNB triggers Uu handover by sending an RRCRECONfigure message to the UE, which contains the information needed to access the target cell: at least the target cell ID, the new C-RNTI, the target gNB security algorithm identifier of the selected security algorithm. It may also include a set of dedicated Random Access Channel (RACH) resources, an association between RACH resources and Synchronization Signal Blocks (SSBs), an association (CSI-RS) configuration between RACH resources and UE-specific channel state information-reference signals, common RACH resources, system information of the target cell, etc.

Step 7, the source gNB sends an SN status transfer message to the target gNB to convey the uplink PDCP SN receiver status and downlink PDCP SN transmitter status (i.e., for RLC AM) of the DRB to which the PDCP status preservation applies. 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-order UL PDCP SDUs that the UE needs to retransmit in the target cell, if any. The downlink PDCP SN transmitter status indicates that the target gNB should assign to the next PDCP SN of the new PDCP SDU, there is no PDCP SN yet.

Step 8, the UE synchronizes with the target cell by sending an RRCRECONfigure complete message to the target gNB and completes the RRC handover procedure.

Step 9, the target gNB sends PATH SWITCH REQUEST message to the access and mobility management function (AMF) to trigger 5GC to switch DL data path to target gNB and establish NG-C interface instance gNB to target.

Step 10:5gc switches the DL data path to the target gNB. The User Plane Function (UPF) sends one or more "end mark" packets to the source gNB of each PDU session/tunnel over the old path, and then any U-plane/TNL resources may be released to the source gNB.

Step 11 AMF acknowledges PATH SWITCH REQUEST message with PATH SWITCH REQUEST ACKNOWLEDGMENT message.

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 that the handover was successful.

Baseline handover user plane processing:

for user plane processing, the following applies; in the handover preparation stage, a user plane tunnel can be established between a source gNB and a target gNB; during the handoff execution phase, user data may be forwarded from the source gNB to the target gNB as follows. Forwarding should occur in sequence as long as the source gNB receives a packet from the UPF or the source gNB buffer is not emptied.

And in the handover complete phase: the target gNB sends a path switching request message to the AMF, the AMF informs the UE that the UE has obtained access, and then triggers 5GC internal signaling related to path switching and actual path switching from the source gNB to the target gNB in the UPF. If the source gNB receives a packet from the UPF or if the source gNB buffer is not yet empty, the source gNB continues forwarding the data. For 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 packets into each data forwarding tunnel when no more user data packets are forwarded through the tunnel. (as shown in step 10.)

For a user plane bearer configuring a radio link control-unacknowledged mode (RLC-UM) mode, a PDCP entity including a header compression context is reset, and a COUNT value is set to zero. There is no reason for security to preserve the COUNT value since a new key is generated at the time of handover anyway. On the UE side, all PDCP SDUs that have not yet been transmitted will be transmitted to the target cell after handover. PDCP SDUs that have not yet begun to be transmitted may be forwarded to the target gNB over the Xn-AP interface. Meanwhile, unacknowledged PDCP SDUs will be lost. This minimizes the complexity of the handover since no context (i.e., configuration information) need be transferred between the source and target gnbs. For user plane bearers of radio link control acknowledged mode (RLC-AM) configuration, the user plane processing follows the procedure described in the lossless handover part.

Lossless procedure: for lossless handover, the Control Plane (CP) proceeds in the manner specified in step 7 above. As for the user plane processing, the header compression protocol is reset at 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. In order to ensure uplink lossless handover, PDCP PDUs stored in the PDCP retransmission buffer are retransmitted through RLC protocol according to PDCP SNs maintained during handover, and transferred to the gateway in correct order. To guarantee a downlink lossless handover, the source eNodeB forwards the uncompressed PDCP SDUs that the UE has not acknowledged receipt to the target eNodeB for retransmission in the downlink.

DAPS procedure: for DAPS handoff, the CP processes as follows.

Step 7a: for DRBs configured with DAPS, the source gNB sends EARLY STATUS TRANSFER a message. The DL COUNT value conveyed in the EARLY STATUS TRANSFER message indicates the PDCP SN and the Hyper Frame 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 the downlink PDCP SDUs until the source gNB sends a SN STATUS TRANSFER message to the target gNB in step 8 b.

Step 8: in the case of DAPS HO, the UE does not leave the source cell after receiving the rrcrecon configuration 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.

Step 8a/8b: in the case of a DAPS handoff, the target gNB sends a HANDOVER SUCCESS message to the source gNB to inform the UE that the target cell has been successfully accessed. In return, the source gNB sends SN STATUS TRANSFER a message for the DAPS configured DRB, with normal data forwarding as follows.

The downlink PDCP SDU is forwarded with the SN allocated by the source gNB until the SN allocation is handed over to the target gNB in step 8b, and the source gNB does not stop sending downlink data packets until after receiving the HANDOVER SUCCESS message from the target gNB in step 8 a. The source gNB can additionally send EARLY STATUS TRANSFER messages between step 7 and step 8b to inform discard of already forwarded PDCP SDUs. The target gNB will not send forwarded downlink PDCP SDUs to the UE whose COUNT is less than the transmitted DL COUNT value, discarding them if no transmission has been attempted. If DAPS is configured, the uplink PDCP SN receiver state and the downlink PDCP SN transmitter state are also communicated in the SN STATUS TRANSFER message in step 8b for DRB with RLC-UM.

For DRBs (i.e.rlc-AM) configured with DAPS that need to avoid repetition,

the source gNB does not stop transmitting uplink QoS flows to the UPF until it sends SN STATUS TRANSFER a message in step 8 b. The target gNB does not forward QoS flows of uplink PDCP SDUs successfully received in sequence to the UPF until a SN STATUS TRANSFER message is received, where the first missing SN in the UL HFN and uplink PDCP SN reception state indicates the start of uplink PDCP SDUs to be delivered to the UPF. The target gNB does not transmit any uplink PDCP SDUs with UL counts lower than provided. The source gNB may omit sending SN STATUS TRANSFER the message if none of the DRBs are configured with DAPS or should use PDCP state preservation.

User plane processing for RLC-AM bearers configured with DAPS:

for the downlink, the following principle applies: 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 cease to allocate PDCP SNs to downlink packets until it receives the HANDOVER SUCCESS message and sends SN STATUS TRANSFER message to the target gNB. After the source gNB allocates a downlink PDCP SN, it begins scheduling downlink data on the source radio link and begins forwarding downlink PDCP SDUs along with the allocated PDCP SN to the target gNB. For security synchronization, ciphering and integrity protection, the HFN and PDCP SNs are maintained after the SN allocation is handed over to the target gNB. SN STATUS TRANSFER message indicates that the next DL PDCP SN is allocated to a packet that has not yet had a PDCP sequence number, even for RLC-UM. During handover execution, the source gNB and the target gNB perform ROHC header compression, ciphering, and adding PDCP headers, respectively. During handover execution, the UE continues to receive downlink data from the source and target gnbs until the source gNB connection is released by an explicit release command from the target gNB. The UE configured with DAPS PDCP maintains separate security and ROHC header decompression associated with each gNB while maintaining a common reordering function, repetition detection, discard function, and PDCP SDUs delivered to upper layers in sequence. Both RLC AM and UM DRB configured with DAPS support PDCP SN continuity.

For the uplink: the UE transmits UL data to the source gNB until the random access procedure to the target gNB is successfully completed. After that, 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 retransmission, and RLC data retransmission 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 and target gnbs. The UE maintains a common UL PDCP SN allocation. Both RLC AM and UM DRB configured with DAPS support PDCP SN continuity. During handover execution, the source gNB and the target gNB maintain their own security and ROHC header decompressor contexts to process the UL data received from the UE. The establishment of the forwarding tunnel is optional. The HFN and PDCP SNs are maintained in the target gNB. SN STATUS TRANSFER message indicates that the target should start the first lost UL count to transmit to 5GC, even for RLC-UM.

Statement of problem:

NR MBS examples include public safety and mission critical, internet of vehicles (V2X) applications, transparent Internet protocol version 4 (IPv 4)/Internet protocol version 6 (IPv 6) multicast delivery, internet Protocol Television (IPTV), software delivery wireless, group communication, and Internet of things (IoT) applications. Most of these use cases relate to MBS service reception 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, e.g. V2X applications require up to 99.9999% reliability, public safety and mission critical push-to-talk (MCPTT) services, and also up to 99.9999% reliability. Furthermore, some MBS applications, such as V2X and industrial applications, e.g., motion related sensors, such as industrial actuators, may involve MBS service reception during inter-node movement, which may require service interruption times ranging from 5ms to 0.5ms due to its very stringent delay requirements (see also table 1). While most MBS mobility proposals discussed in recent 3GPP conferences suggest the use of traditional and/or lossless handover to support MBS mobility in NR, it is clear that the use of such handover can only guarantee the requirements of MBS reliability sensitive service applications and use cases, and for other time sensitive use cases the requirements of alternative handover techniques are very clear. Although, some proposals have also been made to use DAPS handoff for MBS applications to ensure very low service interruption delays. However, given the complexity of the UE in performing DAPS handover (i.e., due to simultaneous downlink and uplink transmissions from the source and target gnbs during DAPS HO), it may be desirable to improve the current standardized DAPS HO procedure to better support MBS services. To address these technical limitations and drawbacks, some embodiments of the present invention propose a new handover method involving several changes in the handover procedure, such as changes in the handover signaling, nested information in the handover signaling, and some handover procedures at both the source gcb and the target gcb.

TABLE 2 requirements for different MBS use cases

MBS use case	Delay of	Reliability of
			V2X	5-100ms variable	90 to 99.9999%
Real-time video	150ms	99.9％
			Internet of things and software update	Delay tolerant	Higher reliability is beneficial
Industry application	0.5ms	99.9999％

In some embodiments of the invention, a description of specific handover procedures and signaling changes is as follows.

The proposed solution is:

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 delay and/or high reliability, e.g., 5g MBS. Fig. 6 illustrates handover of an MBS-capable UE from one NG-RAN to another NG-RAN according to an embodiment of the present invention. Fig. 6 illustrates that in some embodiments, the method considers the scenario in which MBS-supporting UEs receive services, requires low outage time and/or highly reliable MBS services to form a 5g core network, through Multicast Radio Bearers (MRBs) or unicast Data Radio Bearers (DRBs) in a source NG-RAN, and moves to another NG-RAN (i.e., target NG-RAN) that supports/does not support the services provided for a given UE, as shown in fig. 6.

Fig. 7 illustrates a proposed handover to support low latency and reliable MBS mobility according to an embodiment of the present invention. As illustrated in fig. 6 and 7, 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 requirements of MBS service) to the source gNB as part of the handover measurement report. In return, the source gNB may decide on a handover according to a portion of the HANDOVER MEASUREMENT report and may select the type of handover to be performed/configured for a given UE MBS radio bearer (MRB/DRB) according to one of the following.

UE indication (service interest information, e.g. service QoS requirements, e.g. target delay and/or reliability level), and/or source gNB internal configuration possibly containing 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 contains UE identity and MBS service ID/QoS flow ID/session ID association.

In another approach, the selection of the handover type configured for the UE MBS bearer may be performed by the target gNB; in this case, the service related ID and/or UE and QoS flow or session related information of interest to the UE should be indicated in HANDOVER REQUEST signaling forwarded by the source gNB to the target gNB (i.e. over the Xn-AP interface). The type of handover option to be selected/configured by the source or target gNB node for the UE MBS bearer may include a lossless handover or a lossless and low delay handover according to the UE MBS service reliability and delay level requirements, as shown in table 2. In contrast to existing unicast DAPS and lossless handoff, detailed information of procedures and signaling applicable in the case of lossless and low-delay handoff is given as described in the observation and advice section.

TABLE 2 Handover types based on UE MBS use case

MBS use case	Delay of	Reliability of	Handover type (HO)
				V2X	5-100ms variable	90 to 99.9999%	Low latency and lossless HO
Real-time video	150ms	99.9％	Lossless HO
				Internet of things and software update	Delay tolerant	Higher reliability is beneficial	Lossless HO
Industry application	0.5ms	99.9999％	Low latency and lossless HO

After deciding to HANDOVER (e.g., by the source gNB), the HANDOVER REQUEST message may be forwarded from the source gNB to the target gNB. Depending on the selected/configured handover, 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, a handover type decided/configured by the source gNB, if a low delay handover is selected/configured, a request is issued to the target gNB suggesting that it starts to allocate PDCP SNs and/or start forwarding data to the UE, time and reference X, e.g., a time reference when the source gNB forwards/receives specific downlink/uplink frames to/from the UE, downlink and/or uplink timing advance of a given UE, reference X or source scheduled downlink/uplink frames, MBS current transmission mode (i.e., MRB/DRB), and/or MRB/DRB mapping of QoS flows to UE bearers at the source gNB and L1, L2 and/or L3 scheduling information/forwarding treatment of a given UE MBS bearer.

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

The target gNB may perform admission control on the handover MBS bearer (MRB/DRB) and, if the source gNB does not decide/configure, may decide/configure the type of handover type to be performed for the given MBS bearer.

The target gNB may be determined/decided based on the configuration received in the HANDOVER REQUEST, the exact time to start PDCP SN allocation and start forwarding data to the UE provides the source gNB with respect to time reference X (or if low latency HANDOVER functionality is selected/configured locally in HANDOVER REQUEST ACK.)

The target gNB may be prepared according to 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 through MRB or C-RNTI for receiving MBS through DRB, UE pre-allocation grant allocation and downlink and uplink timing advanced with respect to X.)

The target gNB may initiate UE MSB session joining if the MBS session/service/TMGI received by the UE is present in the target gNB or initiate a session establishment request to the core network if the target gNB does not have the MABS session received by the UE.

The target gNB may switch the UE to a new radio bearer (MRB/DRB) if desired, and may attempt to provide the same QoS flows for the MRB/DRB mapping and prepare a scheduling configuration/forwarding process for a given MBS bearer indicated by the source gNB.

The target gNB may determine the timing configuration needed to synchronize with the given UE and may provide the given UE with time suggestion commands and pre-allocation grants (or if low latency handover functionality is selected/configured locally or in HANDOVER REQUEST ACK.)

The target gNB may begin forwarding copies of MBS downlink data forwarded from the source gNB once it begins assigning PDCP SNs to the UE (i.e., without waiting for a handover complete message to be received from the UE) to reduce the UE handover interruption time. (if the low latency handover function is selected/configured locally in HANDOVER REQUEST ACK or at the target gNB).

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

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

The source gNB can send SN STATUS TRANSFER a message to the target gNB to convey the uplink PDCP SN receiver status and the downlink PDCP SN transmitter status of the DRB (i.e., RLC AM) applying PDCP state preservation. 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-order UL PDCP SDUs that the UE needs to retransmit in the target cell, if any. The downlink PDCP SN sender status indicates that the target gNB should assign to the next PDCP SN of the new PDCP SDU, there is no PDCP SN yet (or if a lossless handover is configured.)

In some embodiments, after the source gNB receives HANDOVER REQUEST ACKNOWLEDGMENT containing the configuration forwarded by the target gNB, the source gNB sends HANDOVER INITIATION/COMMAND message to the UE containing the configuration provided by the target gNB. The provided configurations include, for example, contracted times for the source and target gnbs to start/stop PDCP SN allocation and/or data forwarding, target pre-allocation grants, uplink time advance commands, downlink synchronization information, and/or MBS bearer scheduling/forwarding configurations. When the UE receives the configuration from the source gNB, the UE may perform at least one of the following.

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 time advance information provided by the source gNB from the target gNB in the handover command container).

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

The UE may start receiving MBS data from the target gNB after synchronizing and connecting to the target gNB.

After the timing information assignment given in the handover command RRC message, the UE may stop receiving from the source gNB (i.e., stop/start forwarding downlink data to the UE based on the time agreed by the source gNB and the target gNB), while it may keep the release of configured MAC RLC and PDCP, the entity of the source gNB configures until the first MBS data packet is received from the target gNB.

The UE may cease sending UL layer 1 CSI feedback, HARQ feedback, layer 2 RLC feedback, ROHC feedback, HARQ data retransmission, and/or RLC data retransmission to the source gNB.

The UE may send a handover complete message or a handover radio link failure on a pre-allocation grant of the source/target gNB.

The UE may omit sending the handover complete message and use the pre-allocated grant for uplink data transmission to the target gNB.

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

Low latency and lossless feature recommendation:

PDCP SN allocation and misalignment:

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 begins. That is, the source gNB does not stop assigning PDCP SNs to downlink data packets until a HANDOVER SUCCESS message is received and a SN STATUS TRANSFER message is sent to the target gNB. Such a process may result in loading the gNB buffer of the target gNB. Because the time for the source gNB to cease PDCP SN allocation and begin data forwarding is entirely dependent on the HANDOVER SUCCESS message received from the target gNB, this may take a long time since this message is also triggered by the target gNB after receiving the HANDOVER COMPLETION message from the UE.

Examples: in some embodiments of the present invention,

during the newly proposed low latency and lossless HANDOVER, the source gNB and the target gNB directly allocate PDCP SNs and maintain count values, respectively, according to agreed timing, when each node starts/stops downlink/uplink transmissions to the UE/UPF (e.g., the source gNB may start allocating PDCP SNs from the time the target gNB receives the HANDOVER ACK message until the start time of allocation of PDCP SNs by the target gNB provided in the HANDOVER ACK message). This procedure helps reduce the dependency of the HANDOVER procedure (source gNB) on UE-related signaling (i.e., HANDOVER COMPLETION messages) because it allows the source gNB to start and stop PDCP SN allocation STATUS transmissions (agreed by target gNB) and start data forwarding (low latency HANDOVER) without waiting for HANDOVER SUCCESS messages from the target gNB, depending on HANDOVER completion received from the UE. This also helps to reduce handover delay and allows omitting some handover signaling (e.g. the UE may in some cases send handover complete signaling, omitting it if not needed and using pre-allocated grants for uplink data transmission.)

PDCP reordering and duplication:

in the current DAPS configuration, the UE will receive downlink user data from both the source gNB and the target gNB. Thus, the PDCP layer is reconfigured as a common PDCP entity for the source and target user plane protocol stacks. To ensure sequential delivery of DL user data, PDCP (SN) continuity is maintained during handover. For this, one common reordering and duplication function (for source and target gnbs) is required in a single PDCP entity.

Example l: in some embodiments of the present invention, during the newly proposed low-latency and lossless handover MBS, the UE may stop the downlink as specified by the HANDOVER INITIATION command (i.e., the contracted time when the target will start forwarding data to the UE) or immediately after receiving the first packet from the target. This process may simplify UE and network implementation because copy checking and in-order delivery to the 5G core is done by either the source gNB (i.e., until the agreed time or until the first packet is received from the target) or the target gNB. In contrast to current DAPS procedures, in current DAPS procedures, a common reordering and duplication function (for both source and target gnbs) is required in a single PDCP entity.

Data forwarding and data gaps:

in the case of a DAPS handoff, the UE continues to receive 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. During the handover complete phase, the resource release of the source gNB is triggered by the target gNB upon receipt of a HANDOVER COMPLETION message from the UE. Such a procedure may increase UE reception complexity processing cost and power consumption. In addition, the UE further continues transmitting the UL data to the source gNB until the random access process to the target gNB is successfully completed; then, the UL data transmission is switched to the target gNB. This also increases the complexity, processing cost and power consumption of the signaling UE.

Example 1: in some embodiments of the present invention, in the newly proposed low-delay and lossless handover MBS process, the source gNB may forward all MBS data packets (PDCP SDUs) received from the core network (UPF) to the target gNB during the time (transmission handover period) agreed between the source gNB and the target gNB, and then send them to the UE, so as to ensure that the UE side will not lose the packets. By doing so, the UE does not need to wait until the target gNB sends a release command to the source gNB. The UE may stop receiving MBS data from the source gNB (i.e., the agreed time for the target gNB to begin forwarding data to the UE) as specified by the RRC HANDOVER INITIATION command without fear of 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 may begin sending a copy of this data to the UE as soon as possible (i.e., before or at the same time as the UE receives HANDOVER INITIATION command), in other words, the UE may stop receiving from the source gNB immediately after receiving the first data packet from the target gNB. Such a procedure helps to avoid packet loss and to relax U processing power and reduce power consumption.

Example 2: in some embodiments of the invention, the source gNB may forward in a HANDOVER COMMAND message, including target gNB timing advance information and uplink pre-allocation grants. The source gNB may also pre-allocate uplink grants for the UE to allow the UE to adjust its uplink timing to the target gNB (upon handover to the target gNB). This may allow the UE to avoid/omit RACH procedures that may relatively reduce handover delay and relax UE handover signaling complexity.

Some embodiments of the present invention provide a method for reliable and low-latency handover for multicast/broadcast service mobility with service continuity in 5G NR. The main innovation points of the method include:

1. the idea of exchanging MBS services and/or QoS related information between UE, source gNB and target gNB is introduced to propose a decision to decide the type of handover to be configured for UE MBS mobility.

2. Novel information to be exchanged, such as timing related information to help the source and target gnbs overcome PDCP allocation, PDCP count misalignment, and data gap issues, is introduced in the handover request message between the source and target gnbs during handover.

3. Introducing the exchange of UE and MBS services, qoS flows, and/or session identity association information between the UE, source gNB, and target gNB may allow the target gNB to strive to provide the same QoS flows for MRB/DRB mapping and scheduling configuration/forwarding processing of MBS bearers, similar to the configuration of the source gNB. Given such scheduling configuration information and timing information when the source gNB and the target gNB will start and stop sending data to the UE for a given MBS service, the UE is able to prepare the best reception configuration for the target configured MBS bearers.

4. The idea of combining PDCP SN allocation and data forwarding in a single signaling is introduced, which helps to save handover signaling between source and target gnbs.

5. The idea of forwarding duplicate downlink data forwarded from the target gNB once the target gNB starts to allocate PDCP SN allocations to the UE (i.e., before or while the UE receives HANDOVER INITIATION command from the source gNB) is introduced to help the UE avoid packet loss, relax UE processing capability, and reduce power consumption.

6. An idea of omitting some handover signaling is introduced (e.g. a UE may send handover complete signaling in some cases and omit it if not needed and use pre-allocation grants for uplink data transmission.)

7. Introducing the idea of pre-allocating uplink grants from the source gNB and/or target gNB may help to increase the resilience of the UE to handover failures (i.e. by allowing the UE to send a handover failure to either the source gNB or the target gNB.)

In summary, in some embodiments of the present invention, a reliable and low-delay switching method for QoS awareness is provided to support MBS mobility with service continuity, and ensure the difference of MBS service QoS requirements in the UE switching process. In this approach, we propose to exchange MBS service and/or QoS related information between UE, source base station (e.g. source gNB) and target base station (e.g. target gNB), deciding on the type of handover configured for UE MBS mobility. Furthermore, we propose improvements to the current NR handover including modifications to the HO signaling and procedures, for example introducing new information to be exchanged during the handover, (e.g. time related information between UE, source and target gnbs), reducing service interruption time while keeping UE signaling complexity, processing costs and power consumption as low as possible.

The main advantage of some embodiments of the present invention compared with the prior art is to provide a handover method, which can simultaneously solve the time delay and reliability requirements in the MBS moving process, and reduce the UE signaling complexity and processing cost as much as possible.

UE side advantage:

1. in contrast to previous solutions to the MBS mobility service outage delay problem, such as DAPS handover, where the UE receives a lot 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 (either at the agreed time specified in the handover command or locally decided by the UE) without fear of losing MBS data, since 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 procedure may help relax UE processing power and UE reduce UE power consumption (i.e., the UE does not need to receive/transmit from/to both the source and target gnbs to receive MBS mobility with low service break times).

2. The new method exchanges target gNB timing advance information to the UE and provides pre-allocated uplink grants to the UE from either the source gNB or the target gNB or both, which allows the UE to avoid/omit mimicking RACH procedures to the target gNB. Such a procedure relatively reduces the handover delay of the UE and reduces the complexity of UE signaling. The pre-allocated uplink grants provided by the source gNB and/or the target gNB also help to improve the resilience of the UE to handover failures (i.e., allow the UE to be able to send a handover failure to either the source gNB or the target gNB.)

Network side advantage:

PDCP SN allocation and count value misalignment problem: PDCP SN allocation and count value maintenance may be done separately directly on the source gNB and target gNB, and each node will start/stop downlink/uplink transmissions to the UE/UPF according to the agreed time. For example, the source gNB may begin assigning PDCP SNs from the time it receives a HANDOVER ACK message from the target gNB until the start time of the PDCP SNs is assigned by the target gNB provided in the HANDOVER ACK message.

Data forwarding and data gap problems: during the handover time agreed by the source gNB and the target gNB, all MBS data packets (PDCP SDUs) received by the source gNB from the core network (UPF) may be forwarded to the target gNB and then sent to the UE, so as to ensure that the UE side will not lose packets.

PDCP reordering and duplication problem: the UE may stop the downlink (i.e., the contracted time for the target gNB to begin forwarding data to the UE) as specified by the HANDOVER INITIATION command, or immediately after receiving the first packet from the target gNB. This procedure simplifies network implementation because the copy checking and in-order 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) corresponding to the current DAPS procedure, where a common reordering and copy function (for both source and target gnbs) is required in a single PDCP entity.

In summary, in some embodiments, a method for switching User Equipment (UE), a source base station, a target base station, and a multicast/broadcast service (MBS) is provided. The handover method of the MBS is performed in part by the source base station including 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 the target base station as part of a handover request message, the performing 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 by a handover confirmation message and/or a UE by a handover command message, and further includes deciding that a handover is to be performed and/or configured by the source or target base station to support optimal MBS mobility for the given UE based on the handover measurement and/or the handover request message. This may solve the problems in the prior art, solve UE delay and reliability requirements during MBS movement, reduce UE signaling complexity, reduce UE processing costs, support service continuity, provide good communication performance, and/or provide high reliability.

The commercial benefits of some embodiments are as follows. 1. The problems in the prior art can be solved. 2. And the delay and reliability requirements in the MBS moving process are solved. 3. And the complexity of UE signaling is reduced. 4. And the processing cost is reduced. 5. Support service continuity. 6. Providing good communication performance. 7. Providing high reliability. 8. Some embodiments of the invention are implemented by 5G-NR chipset vendors, V2X communication system development vendors, automotive manufacturers including cars, trains, trucks, buses, bicycles, motorcycles, helmets, etc., drones, smart phone manufacturers, public safety communication devices, AR/VR device manufacturers (e.g., games, meetings/seminars, educational purposes). Some embodiments of the invention are a combination of "technologies/procedures" that may be employed in the 3GPP specifications to create the end product. Some embodiments of the invention propose a technical mechanism.

Fig. 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 suitable configuration of hardware and/or software. FIG. 8 illustrates an example system 700 for one embodiment that 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 coupled to one another 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. A processor may comprise any combination of general-purpose processors and special-purpose processors, such as graphics processors, application processors, and the like. The processor may be coupled to the memory/storage device and configured to execute instructions stored in the memory/storage device to enable various applications and/or operating systems running on the system.

Baseband circuitry 720 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The processor may comprise a baseband processor. The baseband circuitry may handle various radio control functions that enable communication with one or more radio networks via the RF circuitry. The radio control functions may include, but are not limited to, signal modulation, encoding, decoding, radio frequency shifting, and the like. In some embodiments, baseband circuitry may provide communications compatible with one or more radio technologies. For example, in some embodiments, the baseband circuitry may support communication 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). Embodiments in which the baseband circuitry is configured to support radio communications of more than one wireless protocol may be referred to as multi-mode baseband circuitry.

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, the baseband circuitry may include circuitry that operates with signals having intermediate frequencies between baseband frequencies and radio frequencies. The RF circuitry 710 may use modulated electromagnetic radiation transmitted through a non-solid medium to effect communication with a wireless network. In various embodiments, the RF circuitry may include switches, filters, amplifiers, etc. to facilitate communication with the 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, the RF circuitry may include circuitry that operates with signals having intermediate frequencies between baseband frequencies and radio frequencies.

In various embodiments, the transmitter circuitry, control circuitry, or receiver circuitry discussed above with respect to the user equipment, eNB, or gNB may be embodied in whole or in part in one or more of RF circuitry, baseband circuitry, and/or application circuitry. As used herein, "circuitry" may refer to, be part of, or include the following: an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and/or memory (shared, dedicated, or group) that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable hardware components that provide the described functionality. In some embodiments, the electronic device circuitry may be implemented in or the functions associated with one or more software or firmware modules. In some embodiments, some or all of the baseband circuitry, application circuitry, and/or constituent elements of the memory/storage device may be implemented together on a system on a chip (SOC). Memory/storage 740 may be used to load and store information and/or instructions, for example, for the system. The memory/storage device for one embodiment may comprise any combination of suitable volatile memory, such as Dynamic Random Access Memory (DRAM), and/or non-volatile memory, such as flash memory.

In various embodiments, I/O interface 780 may comprise one or more user interfaces designed to enable user interaction with the system and/or a peripheral interface designed to enable peripheral interaction with the system. The user interface may include, but is not limited to, a physical keyboard or keypad, a touch pad, a speaker, a microphone, and the like. The peripheral device 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 comprise one or more sensing devices to determine environmental conditions and/or location information related to the system. In some embodiments, the sensors may include, but are not limited to, gyroscopic sensors, accelerometers, proximity sensors, ambient light sensors, and positioning units. The positioning unit may also be part of or interact with baseband circuitry and/or RF circuitry to communicate with elements of a positioning network, such as Global Positioning System (GPS) satellites.

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, a ultrabook, a smart phone, and the like. In various embodiments, the system may have more or fewer elements, and/or different architectures. The methods described herein may be implemented as a computer program, as appropriate. The computer program may be stored on a storage medium such as a non-transitory storage medium.

It will 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 are implemented using electronic hardware or a combination of software and electronic hardware for a computer. Whether the function is implemented in hardware or software depends on the conditions of the application and the design requirements of the technical project. One of ordinary skill in the art may implement the functionality for each particular application in different ways without such implementation exceeding the scope of the present disclosure. It will be understood by those of ordinary skill in the art that reference may be made to the operation of the systems, devices and units in the embodiments mentioned above, as the operation of the systems, devices and units mentioned above are essentially the same. For ease of description and simplicity, these operations will not be described in detail.

It should be appreciated that the systems, devices, and methods disclosed in the embodiments of the present invention may be implemented in other ways. The above-described embodiments are merely exemplary. The division of cells is based solely on logic functions, while other divisions actually exist. It is possible that multiple units or elements are combined or integrated in another system. Certain features may be omitted or skipped. On the other hand, the mutual coupling, direct coupling or communicative coupling shown or discussed operates through some ports, devices or units, whether indirectly or communicatively via electrical, mechanical or other types of forms. The units used for illustration as separate elements may or may not be physically separate. The units used for display may or may not be physical units, i.e. located at one site or distributed over a plurality of network units. Some or all of the units are used according to the purpose of the embodiment. Furthermore, each functional unit in each embodiment may be integrated in one processing unit, physically separate, or integrated with two or more units in one processing unit.

If the software functional unit is implemented and used and sold as a product, it may be stored in a readable storage medium in a computer. Based on this understanding, the technical solutions proposed by the present disclosure may be implemented substantially or partly in the form of a software product. Alternatively, a part of the technical solution beneficial to the conventional technology may be implemented in the form of a software product. The software product in the computer is stored in a storage medium containing a plurality of commands for a computing device (e.g., a personal computer, server, or network device) to execute all or some of the steps disclosed in the embodiments of the present disclosure. The storage medium includes a flash drive, a removable hard disk, a Read Only Memory (ROM), a Random Access Memory (RAM), a floppy disk, or other type of medium capable of storing program code.

While the present disclosure has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the present disclosure is not limited to the disclosed embodiment, 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, comprising:

Determining, by the UE, MBS services and/or quality of service QoS related information as part of a handover measurement report; and

exchanging the MBS service and/or the QoS related information as the part of the handover measurement report between at least two of the UE, source base station and 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.

2. The handover method according to claim 1, wherein the handover type for the UE MBS mobility execution and/or configuration is selected based on at least one of:

the indication of the UE comprises the MBS service and/or the QoS related information;

the internal configuration of the source base station; or alternatively

An indication of the core network.

3. The handover method according to claim 1 or 2, wherein the MBS service and/or the QoS related information comprises a UE identity ID, an MBS service ID, a QoS flow ID or a session ID association.

4. A handover method according to claim 2 or 3, characterized in that the internal configuration of the source base station comprises UE ID, MBS service ID, qoS flow ID or session ID association.

5. The handover method according to any of claims 2 to 4, wherein the indication of the core network comprises a UE MBS context message, a UE ID, an MBS service ID, a QoS flow ID or a session ID association.

6. The handover method according to any of claims 1 to 5, wherein determining, by the UE, the MBS service and/or the QoS related information as the part of the handover measurement report comprises 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.

7. The handover method according to any of claims 1 to 6, wherein 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 comprises indicating the MBS service and/or the QoS related information by the UE as the part of the handover measurement report to the source base station.

8. The handover method of claim 7, wherein 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 comprises the source base station forwarding the MBS service and/or the QoS related information of the UE to the target base station as the portion of the handover measurement report.

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

10. The handover method according to any of claims 2 to 9, wherein selecting the handover type for MBS mobility execution and/or configuration of the UE comprises a lossless handover or a lossless and low delay handover.

11. The handover method according to claim 10, wherein selecting the handover type for UE MBS mobility execution and/or configuration comprises the lossless handover or the lossless and low-delay handover according to UE MBS service reliability and delay level requirements.

12. The handover method according to any one of claims 1 to 11, further comprising the UE receiving a configuration from the source base station, the configuration comprising at least one of:

the source base station and the target base station start/stop the appointed time of packet data convergence protocol PDCP serial number SN allocation and/or data forwarding;

target pre-allocation permissions;

an uplink time advance command;

downlink synchronization information; or (b)

MBS bearer scheduling/forwarding configuration; and/or

The method further includes receiving, by the UE, 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

The UE, which has previously prepared MBS data, optimally receives the configuration and decides when to stop receiving downlink data from the source base station, when to release the source base station configuration, and accordingly releases the source base station configuration.

13. The handover method according to claim 12, wherein the configuration is forwarded by the source base station from the target base station to the UE.

14. The handover method according to claim 12 or 13, wherein the configuration is forwarded by the source base station from the target base station to the UE in a handover initiate/command message.

15. The handover method according to any one of claims 12 to 14, wherein when the UE receives the configuration from the source base station, the UE performs at least one of:

synchronizing to a target cell based on downlink synchronization timing and uplink time advance information provided by the source base station from the target base station;

configuring separate entities of a medium access control, MAC, configuration, PDCP, 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 timing information given in a radio resource control, RRC, configuration while maintaining source MAC, PDCP and/or MAC entities until a 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 (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 or fails to switch the wireless link on a pre-allocated permission;

omitting sending a switching completion message and carrying out uplink data transmission to the target base station by utilizing the pre-allocated permission; or alternatively

Releasing the MAC configuration, the PDCP configuration and/or the RLC configuration of the source base station.

16. A method for switching a multicast/broadcast service MBS performed by a source base station, comprising:

exchanging MBS services and/or quality of service QoS related information as part of a handover measurement message and/or exchanging said MBS services and/or said QoS related information as part of a handover request message between said source base station and at least one user equipment UE; and

a handover for UE MBS mobility execution and/or configuration is performed based on the portion of the handover measurement report.

17. The handover method according to claim 16, wherein the handover type for the UE MBS mobility execution and/or configuration is selected based on at least one of:

the internal configuration of the source base station; or alternatively

An indication of the core network.

18. The handover method according to claim 16 or 17, wherein the MBS service and/or the QoS related information comprises a UE identity ID, an MBS service ID, a QoS flow ID or a session ID association.

19. The handover method according to claim 17 or 18, wherein the internal configuration of the source base station includes a UE ID, MBS service ID, qoS flow ID or session ID association.

20. The handover method according to any of claims 17 to 19, wherein the indication of the core network comprises a UE MBS context message, a UE ID, an MBS service ID, a QoS flow ID or a session ID association.

21. The handover method according to any of claims 16 to 20, wherein exchanging the MBS service and/or the quality of service QoS related information as the part of the handover measurement message and/or the target base station exchanging the MBS service and/or the quality of service QoS related information as the part of the handover request message between the source base station and at least one user equipment, UE, comprises determining, by the source base station, the MBS service and/or the QoS related information as the part of the handover measurement report from the UE.

22. The handover method according to claim 21, wherein 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 by the target base station as the part of the handover request message comprises forwarding the MBS service and/or the QoS related information from the UE by the source base station to the target base station as the part of the handover measurement report.

23. The handover method according to claim 22, wherein the source base station is instructed in handover request signaling to forward the MBS service and/or the QoS related information as the part of the handover measurement report from the UE to the target base station.

24. The handover method according to any of claims 17 to 23, wherein selecting the handover type for MBS mobility execution and/or configuration of the UE comprises a lossless handover or a lossless and low delay handover.

25. The handover method of claim 24, wherein selecting the handover type for UE MBS mobility execution and/or configuration comprises the lossless handover or the lossless and low-delay handover according to UE MBS service reliability and delay level requirements.

26. The handover method according to any one of claims 23 to 25, further comprising the source base station receiving a handover request acknowledgement of the target base station in response to the handover request signaling.

27. The handover method of claim 26, wherein the handover request acknowledgement includes a configuration including at least one of:

target pre-allocation permissions;

an uplink time advance command;

downlink synchronization information; or alternatively

MBS bearer scheduling/forwarding configuration.

28. The handover method according to claim 26 or 27, wherein when the source base station receives the handover request acknowledgement, the source base station performs at least one of:

if the low-delay and lossless handover is selected and/or configured for the UE MBS mobility, performing PDCP SN, wherein the PDCP SN distributes PDCP service data unit SDU data forwarding; or alternatively

And sending an SN state transmission message to the target base station to convey an uplink PDCP SN receiver state and a downlink PDCP SN transmitter state which apply PDCP state preservation.

29. The handover method of claim 28, wherein the uplink PDCP SN receiver status includes at least one of:

PDCP SN of the first lost UL PDCP SDU; or alternatively

The UE needs a reception status bitmap of out-of-order UL PDCP SDUs retransmitted in the target cell.

30. The handover method according to claim 28 or 29, wherein the downlink PDCP SN transmitter status indicates that the target base station allocated a next PDCP SN for a new PDCP SDU, if a lossless handover is configured, there is no PDCP SN yet.

31. The handover method according to any one of claims 27 to 30, further comprising transmitting the configuration to the UE by the source base station.

32. The handover method of claim 31, wherein the configuration is forwarded by the source base station from the target base station to the UE.

33. The handover method according to claim 31 or 32, wherein the configuration is forwarded by the source base station from the target base station to the UE in a handover initiate/command message.

34. A method for switching a multicast/broadcast service MBS performed by a target base station, comprising:

exchanging MBS services and/or quality of service QoS related information as part of a handover measurement report between at least two of a user equipment UE, a source base station and said target base station; and

Exchanging MBS scheduling information and timing information and/or forwarding data to at least the source base station via the handover confirm message and/or the UE passing a handover command message when the target base station starts/stops PDCP SN allocation.

35. The handover method according to claim 34, wherein the handover type for the UE MBS mobility execution and/or configuration is selected based on at least one of:

the internal configuration of the source base station; or alternatively

An indication of the core network.

36. The handover method according to claim 34 or 35, wherein the MBS service and/or the QoS related information comprises a UE identity ID, an MBS service ID, a QoS flow ID or a session ID association.

37. The handover method according to claim 35 or 36, wherein the internal configuration of the source base station includes a UE ID, MBS service ID, qoS flow ID or session ID association.

38. The handover method according to any of claims 35 to 37, wherein the indication of the core network comprises a UE MBS context message, a UE ID, an MBS service ID, a QoS flow ID or a session ID association.

39. The handover method of claim 38, wherein 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 comprises forwarding the MBS service and/or the QoS related information from the UE to the target base station as the portion of the handover measurement report by the source base station.

40. The handover method of claim 39, wherein the source base station is instructed in handover request signaling to forward the MBS service and/or the QoS related information as the portion of the handover measurement report from the UE to the target base station.

41. The handover method according to any of claims 35 to 40, wherein selecting the handover type for MBS mobility execution and/or configuration of the UE comprises a lossless handover or a lossless and low delay handover.

42. The handover method of claim 41, wherein selecting the handover type for the UE MBS mobility execution and/or configuration comprises the lossless handover or the lossless and low-delay handover according to UE MBS service reliability and delay level requirements.

43. The handover method as claimed in any one of claims 40 to 42,

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 the handover type selected 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;

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 Identification (TMGI) received by the UE exists in the target base station, initiating a user equipment (MSB) session to join, 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;

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 process of MBS bearers indicated by the source base station;

Determining a timing configuration which needs to be synchronized with the UE, and providing a time suggestion command and a pre-allocation permission for the UE; or alternatively

And starting to forward the duplicate MBS downlink data forwarded from the source base station as starting to distribute the PDCP SN to the UE.

44. The handover method according to any one of claims 40 to 43, further comprising the target base station transmitting the handover request acknowledgement to the source base station in response to the handover request signaling.

45. The handover method of claim 44, wherein the handover request acknowledgement includes a configuration including at least one of:

target pre-allocation permissions;

an uplink time advance command;

downlink synchronization information; or alternatively

MBS bearer scheduling/forwarding configuration.

46. The handover method of claim 45, wherein the configuration is forwarded by the source base station from the target base station to the UE.

47. The handover method according to claim 45 or 46, wherein the source base station forwards the configuration from the target base station to the UE in a handover initiate/command message and/or the target base station prepares synchronization/timing information, UE pre-allocation grant allocation and downlink and uplink timing advance according to the configuration received in a handover request.

48. A user equipment, UE, for a multicast/broadcast service, MBS, comprising:

a memory;

a transceiver; and

a processor is coupled to the memory and the transceiver;

wherein the processor is configured to:

determining MBS service and/or quality of service QoS related information as part of a handover measurement report; and

49. The UE of claim 48, wherein the handover type for the UE MBS mobility execution and/or configuration is selected based on at least one of:

the internal configuration of the source base station; or alternatively

An indication of the core network.

50. The UE of claim 48 or 49, wherein the MBS service and/or the QoS related information comprises a UE identification ID, an MBS service ID, a QoS flow ID or a session ID association.

51. The UE of claim 49 or 50, wherein the internal configuration of the source base station comprises a UE ID, MBS service ID, qoS flow ID or session ID association.

52. The UE of any of claims 49 to 51, wherein the indication of the core network comprises a UE MBS context message, a UE ID, an MBS service ID, a QoS flow ID or a session ID association.

53. The UE of any of claims 48 to 52, wherein determining, by the processor, the MBS service and/or the QoS related information as the part of the handover measurement report comprises 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.

54. The UE of any of claims 48 to 53, wherein 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 comprises 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.

55. The UE of claim 54, wherein 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 comprises the source base station forwarding the MBS service and/or the QoS related information of the UE to the target base station as the portion of the handover measurement report.

56. The UE of claim 55, wherein the source base station is instructed in handover request signaling to forward the MBS service and/or the QoS related information of the UE as the portion of the handover measurement report to the target base station.

57. The handover method according to any of claims 49 to 56, wherein selecting the handover type for MBS mobility execution and/or configuration of the UE comprises a lossless handover or a lossless and low delay handover.

58. The handover method of claim 57, wherein selecting the handover type for the UE MBS mobility execution and/or configuration comprises the lossless handover or the lossless and low-delay handover according to UE MBS service reliability and delay level requirements.

59. The UE of any of claims 48-58, further comprising the transceiver receiving a configuration from the source base station, the configuration comprising at least one of:

target pre-allocation permissions;

an uplink time advance command;

Downlink synchronization information; or (b)

MBS bearer scheduling/forwarding configuration; and/or

Wherein the transceiver is configured to receive 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

Wherein the processor is configured to prepare in advance the UE best reception configuration of 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.

60. The UE of claim 59, wherein the configuration is forwarded by the source base station from the target base station to the transceiver.

61. The UE of claim 59 or 60, wherein the configuration is forwarded by the source base station from the target base station to the transceiver in a handover initiate/command message.

62. The UE of any of claims 59-61, wherein the processor performs at least one of the following when the transceiver receives the configuration from the source base station:

63. A source base station for a multicast/broadcast service MBS, comprising:

a memory;

a transceiver; and

a processor is coupled to the memory and the transceiver;

Wherein the processor is configured to:

64. The source base station of claim 63, wherein the handover type for the UE MBS mobility execution and/or configuration is selected based on at least one of:

the internal configuration of the source base station; or alternatively

An indication of the core network.

65. The source base station according to claim 63 or 64, wherein the MBS service and/or the QoS related information comprises a UE identity ID, an MBS service ID, a QoS flow ID or a session ID association.

66. The source base station of claim 64 or 65, wherein the internal configuration of the source base station comprises a UE ID, MBS service ID, qoS flow ID or session ID association.

67. The source base station according to any of claims 64-66, wherein the indication of the core network comprises a UE MBS context message, a UE ID, an MBS service ID, a QoS flow ID or a session ID association.

68. The source base station according to any of the claims 63-67, characterized in that exchanging the MBS service and/or the quality of service QoS related information as the part of the handover measurement message and/or the target base station exchanging the MBS service and/or the quality of service QoS related information as the part of the handover request message between the source base station and at least one user equipment UE comprises determining, by the processor, the MBS service and/or the QoS related information as the part of the handover measurement report from the UE.

69. The source base station of claim 68, wherein exchanging the MBS service and/or the quality of service QoS related information as the portion of the handover measurement message and/or exchanging the MBS service and/or the quality of service QoS related information as the portion of the handover request message by the target base station comprises forwarding the MBS service and/or the QoS related information from the UE to the target base station as the portion of the handover measurement report by the transceiver.

70. The source base station of claim 69, wherein the transceiver is instructed in handover request signaling to forward the MBS service and/or the QoS related information as the portion of the handover measurement report from the UE to the target base station.

71. The source base station according to any of claims 64 to 70, wherein selecting the handover type for MBS mobility execution and/or configuration of the UE comprises a lossless handover or a lossless and low delay handover.

72. The source base station of claim 71, wherein selecting the handover type for UE MBS mobility execution and/or configuration comprises the lossless handover or the lossless and low-delay handover according to UE MBS service reliability and delay level requirements.

73. The source base station of any one of claims 70 to 72, wherein the transceiver is configured to receive a handover request acknowledgement from the target base station in response to the handover request signalling.

74. The source base station of claim 73, wherein the handover request acknowledgement comprises a configuration comprising at least one of:

Target pre-allocation permissions;

an uplink time advance command;

downlink synchronization information; or alternatively

MBS bearer scheduling/forwarding configuration.

75. The source base station of claim 73 or 74, wherein when the transceiver receives the handover request acknowledgement, the processor performs at least one of:

76. The source base station of claim 75, wherein the uplink PDCP SN receiver status comprises at least one of:

PDCP SN of the first lost UL PDCP SDU; or alternatively

77. The source base station of claim 75 or 76 wherein the downlink PDCP SN transmitter status indicates that the target base station assigned a next PDCP SN for a new PDCP SDU, if a lossless handover is configured, there is no PDCP SN yet.

78. The source base station according to any one of claims 74-77, wherein the transceiver is configured to send the configuration to the UE.

79. The source base station of claim 78, wherein the configuration is forwarded by the transceiver from the target base station to the UE.

80. The source base station of claim 78 or 79, wherein the configuration is forwarded by the transceiver from the target base station to the UE in a handover initiate/command message.

81. A target base station for a multicast/broadcast service MBS, comprising:

a memory;

a transceiver; and

a processor is coupled to the memory and the transceiver;

wherein the processor is configured to:

82. The target base station of claim 81, wherein the handover type for the UE MBS mobility execution and/or configuration is selected based on at least one of:

the internal configuration of the source base station; or alternatively

An indication of the core network.

83. The target base station according to claim 81 or 82, wherein the MBS service and/or the QoS related information comprises a UE identity ID, an MBS service ID, a QoS flow ID or a session ID association.

84. The target base station of claim 82 or 83, wherein the internal configuration of the source base station comprises a UE ID, MBS service ID, qoS flow ID or session ID association.

85. The target base station according to any of claims 82-84, wherein the indication of the core network comprises a UE MBS context message, a UE ID, an MBS service ID, a QoS flow ID or a session ID association.

86. The target base station of claim 85, wherein 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 comprises forwarding the MBS service and/or the QoS related information from the UE to the transceiver as the portion of the handover measurement report by the source base station.

87. The target base station of claim 86, wherein the source base station is instructed in handover request signaling to forward the MBS service and/or the QoS related information as the portion of the handover measurement report from the UE to the transceiver.

88. The target base station according to any of claims 82-87, wherein selecting the handover type for MBS mobility execution and/or configuration of the UE comprises lossless handover or lossless and low delay handover.

89. The target base station of claim 88, wherein selecting the handover type for UE MBS mobility execution and/or configuration comprises the lossless handover or the lossless and low-delay handover according to UE MBS service reliability and delay level requirements.

90. The target base station of any one of claims 87 to 89, wherein,

91. The target base station of any of claims 87-90, wherein the transceiver is configured to send the handover request acknowledgement to the source base station in response to the handover request signaling.

92. The target base station of claim 91, wherein the handover request acknowledgement comprises a configuration comprising at least one of:

Target pre-allocation permissions;

an uplink time advance command;

downlink synchronization information; or alternatively

MBS bearer scheduling/forwarding configuration.

93. The target base station of claim 92, wherein the configuration is forwarded by the source base station from the transceiver to the UE.

94. The target base station according to claim 92 or 93, wherein the source base station forwards the configuration from the transceiver to the UE in a handover initiate/command message and/or the target base station prepares synchronization/timing information, UE pre-allocation grant allocation and downlink and uplink timing advance according to the configuration received in a handover request.

95. A non-transitory machine readable storage medium having instructions stored thereon, which when executed by a computer, cause the computer to perform the method of any of claims 1 to 47.

96. A chip, comprising:

a processor configured to invoke and run a computer program stored in a memory to cause a device on which the chip is installed to perform the method of any of claims 1 to 47.

97. A computer readable storage medium, characterized in that a computer program is stored, wherein the computer program causes a computer to perform the method of any one of claims 1 to 47.

98. A computer program product comprising a computer program, wherein the computer program causes a computer to perform the method of any one of claims 1 to 47.

99. A computer program, characterized in that the computer program causes a computer to perform the method of any one of claims 1 to 47.