Method and system for multicast data forwarding during mobility procedures in a wireless communication network

Abstract

Methods, apparatuses, and systems for providing multicast handover are disclosed. In one exemplary aspect, the method includes: receiving, by a first radio access node, a multicast stream including data packets of a multicast service; determining, by the first radio access node, whether to initiate a handover process from the first radio access node to a second radio access node for a user equipment; after initiating the handover process, replacing, by the first radio access node, a first portion of the data packet with a flow identifier of a unicast stream; and forwarding, by the first radio access node, the data packet of the multicast service including the flow identifier of the unicast stream to the second radio access node.

Description

Technical Field

[0001] This patent application generally relates to wireless communication. Background Art

[0002] Mobile communication technologies are driving the world towards an increasingly interconnected and networked society. The rapid growth of mobile communication and technological advancements have led to a greater demand for capacity and connectivity. Other aspects such as energy consumption, device cost, spectral efficiency, and latency are also important for meeting the requirements of various communication scenarios. Various technologies are currently being discussed, including new methods for providing higher quality of service, longer battery life, and improved performance. Summary of the Invention

[0003] This patent application describes techniques for multicast data forwarding during a mobility process, which enable reliable transfer mode switching between unicast and multicast.

[0004] In one aspect, a data communication method includes: receiving, by a first radio access node, a multicast stream including data packets of a multicast service; determining, by the first radio access node, whether to initiate a handover process from the first radio access node to a second radio access node for a user equipment; after determining to initiate the handover process, replacing, by the first radio access node, a first part of the data packet with a flow identifier of a unicast stream; and forwarding, by the first radio access node, the data packet of the multicast service including the flow identifier of the unicast stream to the second radio access node.

[0005] In another aspect, a data communication method includes: receiving, by a second radio access node, a multicast stream including data packets of a multicast service from the first radio access node, the data packets of the multicast service including a flow identifier for the user equipment from the first radio access node during a handover process; determining, by the second radio access node, whether the flow identifier indicates a flow for the multicast service; and transmitting, by the second radio access node, the data packets of the multicast service to the user equipment via a unicast stream.

[0006] In yet another aspect, a data communication method includes: receiving, by a target radio access node, data packets of a multicast service during a handover process; determining, by the target radio access node, whether the data packets of the multicast service include a Quality of Service (QoS) Flow Identifier (QFI) indicating that the data packets are forwarded from a source radio access node; and transmitting, by the target radio access node, the data packets to a mobile device in unicast mode after determining that the data packets include the QFI.

[0007] This application describes these and other aspects. Brief Description of the Drawings

[0008] Figure 1Depicts the architecture of a 5G system based on some example embodiments of the disclosed technology.

[0009] Figure 2 Depicts an enhanced 5G system architecture for providing broadcast / multicast services to user equipment based on some example embodiments of the disclosed technology.

[0010] Figure 3 Depicts stages in a process for providing multicast services based on some example embodiments of the disclosed technology.

[0011] Figure 4 Depicts a process for establishing a shared tunnel to transport multicast services in a 5G system based on some example embodiments of the disclosed technology.

[0012] Figure 5 Depicts a process for transporting multicast service data from a core network (CN) to a radio access network (NG-RAN) based on some example embodiments of the disclosed technology.

[0013] Figure 6 Depicts a process for transporting multicast service data during a handover process based on some example embodiments of the disclosed technology.

[0014] Figure 7 Depicts an example of a process for wireless communication based on some example embodiments of the disclosed technology.

[0015] Figure 8 Depicts another example of a process for wireless communication based on some example embodiments of the disclosed technology.

[0016] Figure 9 Depicts another example of a process for wireless communication based on some example embodiments of the disclosed technology.

[0017] Figure 10 Depicts a wireless communication system based on some example embodiments of the disclosed technology.

[0018] Figure 11 Depicts a block diagram of a part of a wireless system based on some example embodiments of the disclosed technology. Detailed Description

[0019] Some features are described using examples of fifth-generation (5G) wireless protocols. However, the applicability of the disclosed technology is not limited to 5G wireless systems.

[0020] The 5G system (5GS) includes multicast / broadcast services. One aspect of these services is multicast discovery and the start and end of multicast services. A user equipment (UE) can operate using both unicast (also referred to as single-cast) and multicast services. When a UE moves from one radio access network (RAN) node to another RAN node, service continuity for broadcast and multicast services is required. Techniques for providing service continuity for broadcast and multicast services are disclosed herein.

[0021] In some example embodiments, a multicast service is a communication service in which the same service and the same content data are provided to a group of authorized UEs simultaneously (i.e., not all UEs within the multicast coverage area are authorized to receive the data). A broadcast service is a communication service in which the same service and the same content data are provided to all UEs within a geographical area simultaneously (i.e., all UEs within the broadcast coverage area are authorized to receive the data).

[0022] Figure 1 An example architecture 100 of the 5G system is depicted. The 5G system architecture consists of network functions (NFs) and other functions described below.

[0023] Functions performed by the access and mobility management function (AMF) 125 include UE mobility management, reachability management, connection management, and other functions. The AMF terminates the radio access network control plane (RAN CP) interface (also referred to as the N2 interface 142) and the non-access stratum (NAS) (also referred to as the N1 interface 137), NAS encryption and integrity protection. The AMF also distributes session management (SM) NAS to the appropriate session management function (SMF) via the N11 interface 127.

[0024] The session management function (SMF) 130 includes user equipment (UE) Internet protocol (IP) address allocation and management, selection and control of the UP function, PDU connection management, etc.

[0025] The user plane function (UPF) 145 is the anchor point for mobility within / across radio access technologies (RATs) and the external protocol data unit (PDU) session point for interconnection with data networks. The UPF also routes and forwards data packets as instructed by the SMF and caches downlink (DL) data when the UE is in the idle mode.

[0026] The Unified Data Management (UDM) 110 manages the subscription profiles of the UEs. The subscription includes data for mobility management (e.g., restricted areas), session management (e.g., Quality of Service (QoS) profiles for each slice of each Data Network Name (DNN)). The subscription data also includes slice selection parameters used by the AMF to select the SMF. The AMF and the SMF obtain the subscription from the UDM, and the subscription data is stored in the Unified Data Repository (UDR). The UDM uses this data when receiving requests from the AMF or the SMF.

[0027] The Policy Control Function (PCF) 115 manages network behavior based on subscriptions and indications from the Application Function (AF) 120. The PCF provides policy rules to be enforced by the Control Plane (CP) functions such as the AMF and / or the SMF. The PCF accesses the UDR to retrieve policy data.

[0028] The Network Exposure Function (NEF) (not shown) may be included in the system for exchanging information between the Core Network (5GC) and external third parties. For example, the AF 120 may store application information in the UDR via the NEF.

[0029] The Multimedia Broadcast Multicast Service (MBMS) was developed for video broadcast and streaming services. Since its initial development, the MBMS system has been updated to support new services such as public safety, Consumer Internet of Things (CIoT), and Vehicle-to-Everything (V2X). With the development and maturity of 5GS, 5GS can provide multicast broadcast services for vertical services.

[0030] Figure 2 An example of an enhanced 5G system architecture 200 for providing broadcast / multicast services to a User Equipment 230 is depicted.

[0031] The Multicast / Broadcast Service Function (MBSF) 235 is a Network Function (NF) for handling the signaling part of the service layer capabilities and provides an interface to the Application Server 245. It can be an independent entity or collocated with the MB-SMF.

[0032] The Multicast / Broadcast Service User Plane (MBSU) 240 processes the payload part of the service layer capabilities and can be an independent entity or collocated with the MBSF or the MB-UPF.

[0033] The SMF and the UPF can be enhanced to support multicast / broadcast services. The AMF can also be enhanced to make the signaling of the multicast / play service between the RAN / UE and the Multicast / Broadcast SMF (MB-SMF) 225 transparent.

[0034] Figure 3 An example of the phases in the process for providing multicast services is depicted.

[0035] In the service subscription phase 310, a subscription is an agreement for a user to receive one or more services provided by an operator. The relationship between the user and the service provider is established during the subscription. The relationship can be stored statically in a Unified Data Repository (UDR) or pushed dynamically from the MBS server to the relevant PCF.

[0036] In the multicast service start phase 320, the MBS server triggers the MBSF to start a session to send multicast data. The MBSF triggers the establishment of an MBS session in the 5GS. The session start occurs independently of the user's activation of the service (i.e., a given user can activate the service before or after the session starts). The session start is the trigger for the establishment of bearer resources for MBMS data transmission.

[0037] In the PDU session establishment phase 330, the UE can initiate a unicast PDU session establishment to retrieve the multicast service configuration or establish an association with the MBSF. This can occur before phase 310. The UE can dynamically subscribe to the multicast service via the established PDU session. In the case where the multicast service starts before the UE joins the multicast service, this phase can also occur after phase 340.

[0038] In the multicast service announcement phase 340, the multicast service announcement / discovery mechanism allows the user to request or be notified of the scope of available multicast services. The announcement is also used to distribute information to the user about the service parameters required for service activation (e.g., one or more IP multicast addresses) and possibly other service-related parameters (e.g., service start time).

[0039] At the multicast join phase 350, the UE initiates a join process to become a member of the multicast group.

[0040] At the data transfer phase 360, data is transferred to the UE.

[0041] Figure 4 An example of a process for establishing a shared tunnel to transfer multicast services in a 5G system is depicted. In some example embodiments, this process occurs after the UE has established a PDU session.

[0042] At 410, the UE initiates a unicast PDU session establishment process. During this process, an MBS-SMF that supports both unicast and multicast is selected based on a specific DNN and Single Network Slice Selection Assistance Information (S-NSSAI). After the establishment process is completed, the UE can retrieve the multicast service configuration.

[0043] At 420, the UE initiates a join request via UP data or a NAS message to join the multicast communication service.

[0044] At 430, when the MB-SMF detects the request, the MB-SSF requests the MBSF to authorize the UE. The MBSF checks whether the UE is allowed to access the service. If so, the MBSF checks whether the multicast context of the multicast group exists (i.e., whether the UE has joined the multicast group). If the multicast context of the multicast group does not exist, the SMF creates it when the first UE joins the multicast group. This check may involve the MBS server, the PCF, and / or the UDM. The MBS server may store the group membership in the UDM or send it to the PCF before 430. Then, the MBSF or the MB-SMF may retrieve this information during the establishment of the association between the MBSF / MB-SMF and the PCF / UDM. If there is no interaction between the MBSF and the PCF / UDM, the MBSF may retrieve the information from the MB-SMF.

[0045] At 440, the MBSF triggers the MB-SMF to establish a virtual QoS (Quality of Service) flow in an existing unicast PDU session or a new unicast PDU session.

[0046] At 450, the MBSF triggers the MB-SMF to establish an MBS flow via a shared tunnel for UEs belonging to the same multicast group under the same NG-RAN node. The virtual flows included in the unicast PDU session are not used to transport the multicast service data. The multicast service data is transported to the NG-RAN node via the MBS flow in the shared tunnel. In some embodiments, a session using a shared channel may be characterized as a multicast / broadcast service (MBS) session that includes one or more MBS QoS flows.

[0047] If there is a shared tunnel for the same multicast service (i.e., before this process, other UEs have joined the multicast group via the NG-RAN node), 450 may be skipped.

[0048] At 460, the information from 440 and / or 450 is provided to the NG-RAN node to bind the shared tunnel and one or more virtual flows linked in the unicast PDU session (e.g., one or more virtual flows may be bound to one or more MBS flows in the shared tunnel). This information may include a flow identifier and / or a TMSI and / or a session identifier.

[0049] If a virtual QoS flow is established within an existing unicast PDU session (i.e., PDU session 1), the SMF allocates a QFI for the virtual QoS flow and also generates a QoS profile. The SMF may maintain a common QoS profile for the virtual flow and the MBS QoS flow. In one example, the common QoS includes QoS parameters (e.g., MGBR, 5QI, etc.), the QFI of the virtual flow, and the identifier of the MBS flow. The identifier of the MBS flow may include at least one of the TMGI, multicast address, or QFI in the MBS flow. The SMF may maintain two separate QoS profiles for the virtual flow and the MBS flow. The QoS parameters included in these two QoS profiles are the same, but the identifiers of the virtual flow and the MBS flow are different. The QoS parameters should be transmitted to the NG-RAN.

[0050] At 470, when the NG-RAN node receives multicast data in a shared tunnel, the NG-RAN may determine to deliver the multicast flow via the broadcast mode or the unicast mode over the radio interface. If the unicast mode is used, the virtual multicast flow is used to deliver the multicast flow via a dedicated data radio bearer (DRB) over the radio interface. If the broadcast mode is used, UEs in the same group of this multicast service receive the multicast data via a shared DRB over the radio interface.

[0051] When the UE moves to another RAN node, operations for service continuity of unicast services may be performed during the handover process. Embodiments of the disclosed techniques may be implemented to provide techniques for ensuring service continuity of multicast services for a mobile UE during the handover process.

[0052] In the context of this patent application, the term "virtual flow" is used to indicate a flow formed between a UE and a core network (5GC) via a radio access network (NG-RAN) in certain cases. Multicast service data is not transmitted via the virtual flow between the NG-RAN and the 5GC, but is transmitted via the MBS flow included in the MBS session using a shared tunnel between the NG-RAN and the 5GC. The NG-RAN may not allocate a flow unless the 5GC notifies the NG-RAN of the flow. Therefore, when the NG-RAN decides to use the unicast mode over the radio interface, the NG-RAN may use the QoS information of the virtual flow that has been generated and sent to the NG-RAN to schedule radio resources without notifying the 5GC of the lack of flow information. The SMF may allocate the virtual flow and send it to the NG-RAN, and the NG-RAN may use the virtual flow over the radio interface.

[0053] When moving from a source NG-RAN to a target NG-RAN in a handover scenario, a UE can receive multicast service data from both the source NG-RAN and the target NG-RAN. However, if both the source NG-RAN and the target NG-RAN send multicast service data to the UE in broadcast mode, neither the source NG-RAN nor the target NG-RAN is responsible for ensuring data delivery to every UE in the same group to avoid packet loss, which can affect service continuity.

[0054] Figure 5 Depicted are processes for transmitting multicast service data from a core network (CN) to a radio access network (NG-RAN) based on some example embodiments of the disclosed technology.

[0055] The first user equipment UEa has a unicast PDU session and a server unicast QoS flow (eg, QF1a, QF2a) is established. The second user equipment UEb has a unicast PDU session and a server unicast QoS flow (eg, QF1b, QF2b) is established.

[0056] The first and second user equipments UEa and UEb are in the same group to receive the same multicast service. The first and second user equipments UEa and UEb reside on the same NG-RAN.

[0057] When the first and second user equipment (UEa) and UEb join a multicast group to receive multicast data, the core network 5GC determines to establish a shared tunnel to transmit the multicast data. In one example, the session using this shared tunnel may include a multicast session. The core network (e.g., 5GC) also establishes a virtual QoS flow (QF) in an existing unicast PDU session or in a new unicast PDU session for each user equipment (UE) belonging to this group. The core network (e.g., 5GC) sends the NG-RAN mapping information between the virtual flow in the existing / new unicast PDU session and the flow in the shared tunnel.

[0058] The core network (e.g., 5GC) assigns a QoS flow identifier (QFI) to the new QoS flow and ensures the uniqueness of the QFI within a PDU session.

[0059] When both the virtual flow and the flow (which can be referred to as the MBS flow) in the shared tunnel have been established and multicast data is being transmitted, the core network 5GC only sends multicast data in the shared tunnel. When the multicast service data arrives at the NG-RAN via the shared tunnel, the NG-RAN decides to use a unicast data radio bearer (DRB) DRB1a or DRB1b or a broadcast DRB to transmit the multicast service over the radio interface. The unicast DRB is dedicated to a particular user equipment UE, while all the user equipment UEs resident in the cell can receive the data transmitted via the broadcast DRB. The NG-RAN can also decide to use both the unicast DRB and the broadcast DBR. In this case, some user equipment UEs (e.g., UEa) can receive the multicast service data via the unicast DRB (e.g., DRB1a), while other user equipment UEs resident in the same cell can receive the multicast service data via the broadcast DRB.

[0060] In some embodiments, as Figure 5 shown, the unicast data radio bearer DRB1a is a unicast DRB for the first user equipment UEa, and the virtual flow for the multicast data is included in the unicast data radio bearer DRB1b. The unicast data radio bearer DRB1b is a unicast DRB for the second user equipment UEb, and the virtual flow for the multicast data is included in the unicast data radio bearer DRB1a.

[0061] Figure 6 Illustrates a process for transmitting multicast service data during a handover process based on some example embodiments of the disclosed technology.

[0062] In the case of a handover where a first user equipment UEa having a multicast service in the source RAN moves from the source RAN to the target RAN, the source RAN can use the broadcast DRB to transmit the multicast service data to all the user equipment UEs having such a service. When the user equipment UEa moves to the edge of the coverage area of the source RAN, the source RAN decides to hand over the user equipment UEa to the target RAN. Two different scenarios may occur during the handover process:

[0063] Scenario 1. In the scenario where the target RAN supports transmitting multicast service data via the broadcast DRB, the target RAN receives the multicast service from the core network 5GC via the shared tunnel. In one example, the shared tunnel can be established before the user equipment UEa moves into the coverage area of the target RAN. In another example, the shared tunnel can be established during the handover process.

[0064] When the source RAN decides to handover the user equipment UEa to the target RAN, and the source RAN discovers that the user equipment UEa has multicast service data to receive, the source RAN implemented based on some embodiments of the disclosed technology may cache the multicast service and then forward the multicast service via a direct or indirect tunnel. In some embodiments, when the source RAN forwards the cached multicast service data, the QFI of the virtual flow mapped to the multicast flow in the multicast session is added to the multicast service data to replace the identifier of the MBS flow in the encapsulation header of the multicast service data. When the target NG-RAN receives the multicast service data identified by the QFI from the source NG-RAN, the target NG-RAN sends the multicast service data received from the source NG-RAN via the unicast data radio bearer DRB1a to the user equipment UEa.

[0065] In some embodiments, the radio access network node (NG-RAN) retrieves information for mapping between the identifier of the virtual flow and the identifier of the multicast flow from the core network. The RAN node may also retrieve QoS information from the core network. During the handover process, the unicast PDU session including the PDU session with the virtual flow will be transferred to the target side, and the context of such a PDU session will be sent to the target NG-RAN. In addition, during the handover process or the MBS session establishment process in combination with the handover process, the mapping between the MBS flow and the virtual flow is sent to the target NG-RAN (i.e., a shared tunnel can be established during the handover process).

[0066] To enable the target NG-RAN to know that all the cached multicast service data has been sent out, the source RAN may generate one or more end markers and forward them to the target RAN via a direct tunnel or an indirect tunnel. When the target RAN receives one or more end markers in the direct or indirect tunnel for data forwarding, the target RAN may determine that all the cached multicast service data has been sent out. When receiving the multicast service data from the 5GC through the shared tunnel, if the broadcast mode via the radio interface is selected, the target RAN may decide that transmitting the multicast service data via the broadcast DRB is not the cached multicast service data. In the case of the broadcast mode via the radio interface, the virtual flow included in the unicast DRB may not be scheduled via the radio interface.

[0067] In some embodiments, the data packets may include (1) multicast service data packets cached in the source RAN and forwarded to the target RAN, and (2) data packets of the unicast stream received from the core network. If the data packets are forwarded from the source RAN to the target RAN, the source RAN generates one or more end markers when all the data packets are forwarded. If the data packets are transmitted from the core network to the target RAN, the core network generates one or more end markers when the transmission of the data packets is completed.

[0068] In some embodiments, the "forwarded" multicast service data to be cached in the source RAN and forwarded to the target RAN is transmitted to the user equipment UE through the unicast mode. In some embodiments, the multicast service data received from the core network (instead of from the source RAN) may be transmitted to the user equipment UE through the unicast mode or the multicast / broadcast mode.

[0069] In some embodiments, the end marker may be generated by the core network 5GC to indicate the termination of the cached packets of the unicast stream. However, the core network 5GC that transmits the multicast service data for a group of user equipment UEs in the shared tunnel may not cache packets for a specific UE and generates an end marker to indicate the termination of the cached packets of the multicast stream for the specific user equipment UE in the group. In some embodiments, in the handover scenario, the multicast service data for the user equipment UE is cached in the source NG-RAN, and thus the end marker is generated by the source NG-RAN to indicate that the cached multicast service data has been transmitted to the target NG-RAN.

[0070] Scenario 2. In the scenario where the target RAN does not support transmitting the multicast service data via the broadcast DRB, the virtual stream within the unicast PDU session is used to transmit the multicast service data from the core network 5GC to the user equipment UE via the target NG-RAN. The target RAN can only use the unicast DRB to transmit the multicast service data. After the handover is completed, there is no shared tunnel and mapping information, and the virtual stream is a normal stream in the target RAN.

[0071] Figure 7Illustrates an example of a process 700 for wireless communication based on some example embodiments of the disclosed technology. At 710, method 700 includes: receiving, by a first radio access node (e.g., source NG-RAN), a multicast stream including data packets of a multicast service. At 720, the method includes: determining, by the first radio access node, whether to initiate a handover process from the first radio access node to a second radio access node (e.g., target NG-RAN) for a user equipment (e.g., UE). At 730, the method includes: after determining to initiate the handover process, replacing, by the first radio access node, a first portion of the data packet with a flow identifier (e.g., QFI) of a unicast stream. At 740, the method includes: forwarding, by the first radio access node, the data packet of the multicast service including the flow identifier of the unicast stream to the second radio access node.

[0072] Figure 8 Illustrates another example of a process 800 for wireless communication based on some example embodiments of the disclosed technology. At 810, method 800 includes: receiving, by a second radio access node (e.g., target NG-RAN), from a first radio access node (e.g., source NG-RAN), a multicast stream including data packets of a multicast service, the data packets of the multicast service including a flow identifier for a user equipment from the first radio access node during a handover process. At 820, the method includes: determining, by the second radio access node, whether the flow identifier indicates a flow for the multicast service. At 830, the method includes: transmitting, by the second radio access node, the data packets of the multicast service to the user equipment via a unicast stream.

[0073] Figure 9 Illustrates another example of a process 900 for wireless communication based on some example embodiments of the disclosed technology. At 910, method 900 includes: receiving, by a target radio access node during a handover process, data packets of a multicast service. At 920, the method includes: determining, by the target radio access node, whether the data packets of the multicast service include a quality of service (QoS) flow identifier (QFI) indicating that the data packets are forwarded from a source radio access node. At 930, the method includes: after determining that the data packets include a QFI, transmitting, by the target radio access node, the data packets to a mobile device in a unicast mode.

[0074] Figure 10FIG. 0 shows an example of a wireless communication system 1000 to which techniques according to one or more embodiments of the present technology may be applied. The wireless communication system 1000 may include one or more base stations (BSs) 1005a, 1005b, one or more wireless devices 1010a, 1010b, 1010c, 1010d, and a core network 1025. The base stations 1005a, 1005b may provide wireless services to the wireless devices 1010a, 1010b, 1010c, and 1010d in one or more wireless sectors. In some embodiments, the base stations 1005a, 1005b include directional antennas that generate two or more directional beams to provide wireless coverage in different sectors.

[0075] The core network 1025 may communicate with one or more base stations 1005a, 1005b. The core network 1025 provides connections to other wireless communication systems and wired communication systems. The core network may include one or more service subscription databases for storing information related to the subscribed wireless devices 1010a, 1010b, 1010c, and 1010d. The first base station 1005a may provide wireless services based on a first radio access technology, while the second base station 1005b may provide wireless services based on a second radio access technology. The base stations 1005a and 1005b may be co-located or may be separately installed on-site depending on the deployment scenario. The wireless devices 1010a, 1010b, 1010c, and 1010d may support multiple different radio access technologies. The techniques and embodiments described in this application may be implemented by the base stations of the wireless devices described in this application.

[0076] Figure 11 FIG. 7 is a block diagram representation of a portion of a wireless site to which one or more embodiments of the present technology may be applied. A wireless device 1105, such as a base station or a wireless device (or UE), may include processor electronics 1110, such as a microprocessor, that implements one or more of the wireless technologies presented in this application. The wireless device 1105 may include transceiver electronics 1115 to transmit and / or receive wireless signals via one or more communication interfaces, such as antennas 1120. The wireless device 1105 may include other communication interfaces for transmitting and receiving data. The wireless device 1105 may include one or more memories (not explicitly shown) configured to store information such as data and / or instructions. In some embodiments, the processor electronics 1110 may include at least a portion of the transceiver electronics 1115. In some embodiments, at least some of the disclosed techniques, modules, or functions are implemented using the wireless device 1105. In some embodiments, the wireless device 1105 may be configured to perform the methods described in this application.

[0077] It should be understood that the present application discloses technologies that can be implemented in various embodiments to establish and manage multicast sessions in various scenarios. The disclosed and other embodiments, modules, and functional operations described in the present application can be implemented in digital electronic circuits, or in computer software, firmware, or hardware (including the structures disclosed in the present application and their equivalent structures), or in combinations of one or more of them. The disclosed embodiments and other embodiments can be implemented as one or more computer program products (i.e., one or more modules of computer program instructions encoded on a computer-readable medium) for execution by, or to control the operation of, a data processing apparatus. The computer-readable medium can be a machine-readable storage device, a machine-readable storage substrate, a storage device, a composition of matter affecting a machine-readable propagated signal, or a combination of one or more of them. The term "data processing apparatus" encompasses all apparatuses, devices, and machines for processing data, including, for example, programmable processors, computers, or multiple processors or multiple computers. In addition to hardware, the apparatus may also include code for creating an execution environment for the computer program being discussed, such as code constituting processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them. A propagated signal is an artificially generated signal, for example, a machine-generated electrical, optical, or electromagnetic signal that is generated to encode information for transmission to a suitable receiver device.

[0078] A computer program (also referred to as a program, software, software application, script, or code) can be written in any form of programming language (including compiled or interpreted languages), and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. The program can be stored in a part of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program being discussed, or in multiple cooperating files (e.g., files that store one or more modules, subroutines, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers located at one site or distributed across multiple sites and interconnected by a communication network.

[0079] The processes and logical flows described in the present application can be executed by one or more programmable processors that execute one or more computer programs to perform functions by operating on input data and generating output. The processes and logical flows can also be executed by dedicated logic circuitry, and the apparatus can also be implemented as dedicated logic circuitry (e.g., an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit)).

[0080] For example, a processor suitable for executing a computer program includes general and special microprocessors, as well as any one or more processors of any type of digital computer. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both. The basic elements of a computer are a processor for executing instructions and one or more storage devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to, one or more mass storage devices (e.g., magnetic disks, magneto-optical disks, or optical disks) for storing data, to receive data from or transfer data to the one or more mass storage devices, or both. However, a computer need not have such devices. Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and memory devices, including, for example, semiconductor memory devices such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROM optical disks. The processor and memory may be supplemented by, or incorporated in, special logic circuitry.

[0081] Some embodiments may preferably implement one or more of the following solutions listed in clause format. The following clauses are supported and further described in the above examples and throughout this application. As used in the following clauses, a wireless terminal may be a user equipment, a mobile station, or any other wireless terminal including fixed nodes such as base stations. A network node includes a base station, which includes a next-generation node B (gNB), an enhanced node B (eNB), or any other device operating as a base station. A resource range may refer to a range of time-frequency resources or blocks.

[0082] Clause 1. A data communication method, comprising: receiving, by a first radio access node, a multicast stream including data packets of a multicast service; determining, by the first radio access node, whether to initiate a handover process from the first radio access node to a second radio access node for a user equipment; after determining to initiate the handover process, replacing, by the first radio access node, a first part of the data packet with a stream identifier of a unicast stream; and forwarding, by the first radio access node, the data packet of the multicast service including the stream identifier of the unicast stream to the second radio access node.

[0083] Clause 2. The method according to clause 1, wherein the first part of the data packet includes an identification of the multicast stream in an encapsulation header of the data packet of the multicast service.

[0084] Clause 3. The method according to clause 1, further comprising, after determining to initiate the handover process, caching, by the first radio access node, the data packet of the multicast service for the user equipment.

[0085] Clause 4. The method according to Clause 3, wherein the first radio access node is further configured to generate one or more end markers when all the data packets have been forwarded.

[0086] Clause 5. The method according to Clause 1, wherein forwarding the data packets of the multicast service to a second radio access node includes transmitting the data packets of the multicast service through a direct tunnel between the first radio access node and the second radio access node.

[0087] Clause 6. The method according to Clause 1, wherein forwarding the data packets of the multicast service to a second radio access node includes transmitting the data packets of the multicast service through indirect tunnels between the first radio access node and the user plane function and between the second radio access node and the user plane function.

[0088] Clause 7. The method according to Clause 6, wherein the user plane function is configured to carry network user traffic.

[0089] Clause 8. The method according to Clause 1, wherein the first radio access node is configured to receive the data packets of the multicast service through a shared tunnel established between the core network and the first radio access node.

[0090] Clause 9. The method according to Clause 1, wherein the first radio access node is configured to receive mapping information between the identifier of the multicast stream and the stream identifier of the unicast stream.

[0091] Clause 10. The method according to any one of Clauses 8-9, wherein the first radio access node is configured to store the mapping information.

[0092] Clause 11. A data communication method, comprising: receiving, by a second radio access node from a first radio access node, a multicast stream including data packets of a multicast service, the data packets of the multicast service including a stream identifier for a user equipment from the first radio access node during a handover process; determining, by the second radio access node, whether the stream identifier indicates a stream for the multicast service; and transmitting, by the second radio access node, the data packets of the multicast service to the user equipment through a unicast stream.

[0093] Clause 12. The method according to Clause 11, further comprising: receiving, by the second radio access node, a first data packet from the core network; determining, by the second radio access node, whether to transmit the first data packet to the user equipment through the unicast stream or through the multicast stream; and transmitting, by the second radio access node, the first data packet to the user equipment through the unicast stream or the multicast stream based on the determination of the transmission of the first data packet.

[0094] Clause 13. The method according to Clause 11, wherein receiving the data packets of the multicast service from the first radio access node includes receiving the data packets of the multicast service through a direct tunnel between the first radio access node and the second radio access node.

[0095] Clause 14. The method according to Clause 11, wherein receiving the data packets of the multicast service from the first radio access node includes receiving the data packets of the multicast service through an indirect tunnel between the first radio access node and the user plane function and between the second radio access node and the user plane function.

[0096] Clause 15. The method according to Clause 14, wherein the user plane function is configured to carry network user traffic.

[0097] Clause 16. The method according to Clause 11, wherein after determining that the flow identifier indicates a flow for the multicast service, a unicast data radio bearer is allocated to the user equipment for the transmission of the data packets of the multicast service.

[0098] Clause 17. The method according to any one of Clauses 1-16, wherein the flow identifier indicating the unicast flow includes a Quality of Service (QoS) Flow Identifier (QFI) configured to identify a QoS flow.

[0099] Clause 18. The method according to any one of Clauses 1-16, wherein the data packets of the multicast service are transmitted through a shared tunnel established between the core network and the first radio access node.

[0100] Clause 19. The method according to Clause 18, wherein the first radio access node and the second radio access node receive mapping information between the identifier of the multicast flow transmitted in the shared tunnel and the flow identifier indicating the unicast flow.

[0101] Clause 20. The method according to Clause 19, wherein the unicast flow is a virtual Quality of Service flow established by the radio access network within a Protocol Data Unit (PDU) session.

[0102] Clause 21. The method according to Clause 19, wherein at least one of the Multicast Broadcast Session Management Function (MB-SMF) or the Multicast Broadcast Service Function (MBSF) is configured to allocate a QFI for the unicast flow within a PDU session.

[0103] Clause 22. The method according to Clause 21, wherein at least one of the Multicast Broadcast Session Management Function (MB-SMF) or the Multicast Broadcast Service Function (MBSF) is configured to establish a multicast flow in a session for the multicast mode.

[0104] Clause 23. The method according to any one of Clauses 21 - 22, wherein the multicast broadcast session management function (MB-SMF) or the multicast broadcast service function (MBSF) is configured to generate quality of service flow parameters and identifiers for the multicast flow and the unicast flow, and transmit the generated parameters and identifiers to a radio access node.

[0105] Clause 24. The method according to Clause 23, wherein the quality of service flow parameters of the multicast flow and the unicast flow are the same as each other.

[0106] Clause 25. The method according to Clause 23, wherein the identifiers of the multicast flow and the unicast flow are different from each other.

[0107] Clause 26. The method according to Clause 23, wherein a first flow is formed on a radio access network between a wireless device and a core network, and the quality of service flow parameters of the first quality of service flow and the second quality of service flow are transmitted to the radio access network.

[0108] Clause 27. The method according to any one of Clauses 1 - 26, wherein during a handover process, a first radio access node includes a source radio network, and a second radio access node includes a target radio network.

[0109] Clause 28. A data communication method, comprising: receiving, by a target radio access node, a data packet of a multicast service during a handover process; determining, by the target radio access node, whether the data packet of the multicast service includes a quality of service (QoS) flow identifier (QFI) indicating that the data packet is forwarded from a source radio access node; and transmitting, by the target radio access node, the data packet to a mobile device in a unicast mode after determining that the data packet includes the QFI.

[0110] Clause 29. The method according to Clause 28, wherein after determining that the data packet includes the QFI, the data packet is transmitted via a unicast data radio bearer.

[0111] Clause 30. The method according to Clause 28, further comprising transmitting the data packet to the mobile device in a multicast mode when an end marker indicating the completion of forwarding of the data packet is received in the data packet from the source radio access node.

[0112] Clause 31. The method according to Clause 30, wherein the transmission of the data packet in the multicast mode is performed via a broadcast data radio bearer.

[0113] Clause 32. A device for wireless communication, comprising a memory and a processor, wherein the processor reads code from the memory and implements the method according to any one of Clauses 1 to 31.

[0114] Clause 33. A computer-readable process storage medium storing code which, when executed by a processor, causes the processor to implement the method according to any one of Clauses 1 to 31.

[0115] Although this patent application contains many details, these details should not be construed as limiting the scope of any invention or what can be claimed, but rather as descriptions of features specific to particular embodiments of a particular invention. Certain features described in the context of separate embodiments in this patent application may also be implemented in combination in a single embodiment. Conversely, the various features described in the context of a single embodiment may also be implemented separately in multiple embodiments or in any suitable sub-combination. Additionally, although the above features may be described as acting in certain combinations and even initially claimed as such, in some cases, one or more features from the claimed combination may be deleted from the combination, and the claimed combination may be directed to a sub-combination or a variant of a sub-combination.

[0116] Likewise, although operations are depicted in the figures in a particular order, this should not be construed as requiring that the operations be performed in the particular order shown or sequentially, or that all illustrated operations be performed to achieve the desired result. Additionally, the separation of various system components in the embodiments described in this patent application should not be construed as requiring such separation in all embodiments.

[0117] Only some embodiments and examples have been described, and other embodiments, improvements, and variations are possible based on what is described and illustrated in this patent application.

Claims

1. A data communication method, comprising: receiving, by a first radio access node, a multicast stream including data packets of a multicast service; determining, by the first radio access node, whether to initiate a handover process from the first radio access node to a second radio access node for a user equipment; after determining to initiate the handover process, replacing, by the first radio access node, a first part of the data packets of the multicast service with a flow identifier of a unicast stream; and forwarding, by the first radio access node, the data packets of the multicast service including the flow identifier of the unicast stream to the second radio access node.

2. The method according to claim 1, wherein, The first part of the data packets includes an identifier of the multicast stream in an encapsulation header of the data packets of the multicast service.

3. The method according to claim 1, further comprising, after determining to initiate the handover process, caching, by the first radio access node, the data packets of the multicast service for the user equipment.

4. The method according to claim 3, wherein The first radio access node is further configured to generate one or more end markers when all data packets are forwarded.

5. The method according to claim 1, wherein Forwarding the data packets of the multicast service to the second radio access node includes transmitting the data packets of the multicast service through a direct tunnel between the first radio access node and the second radio access node.

6. The method according to claim 1, wherein Forwarding the data packets of the multicast service to the second radio access node includes transmitting the data packets of the multicast service through an indirect tunnel between the first radio access node and a user plane function and between the second radio access node and the user plane function.

7. The method according to claim 6, wherein The user plane function is configured to carry network user traffic.

8. The method according to claim 1, wherein, The first radio access node is configured to receive the data packets of the multicast service through a shared tunnel established between a core network and the first radio access node.

9. The method according to claim 1, wherein The first radio access node is configured to receive mapping information between an identifier of the multicast stream and a flow identifier of the unicast stream.

10. The method according to any one of claims 8-9, wherein, The first radio access node is configured to store the mapping information.

11. The method according to any one of claims 8-9, wherein, The flow identifier indicating the unicast stream includes a quality of service (QoS) flow identifier (QFI) configured to identify a QoS flow.

12. The method according to any one of claims 8-9, wherein The data packets of the multicast service are transmitted through a shared tunnel established between a core network and the first radio access node.

13. The method according to any one of claims 8-9, wherein, During the handover process, the first radio access node includes a source radio network, and the second radio access node includes a target radio network.

14. A data communication method, comprising: receiving, by a second radio access node, from a first radio access node, a multicast stream including data packets of a multicast service, the data packets including a flow identifier for a user equipment from the first radio access node during a handover process; determining, by the second radio access node, whether the flow identifier indicates a flow for the multicast service; and transmitting, by the second radio access node, the data packets of the multicast service to the user equipment through a unicast stream, wherein, after determining to initiate the handover process, a first part of the data packets of the multicast service is replaced with the flow identifier of the unicast stream.

15. The method according to claim 14 further comprises: receiving, by the second radio access node, a first data packet from a core network; determining, by the second radio access node, whether to transmit the first data packet to the user equipment through the unicast flow or through the multicast flow; and transmitting, by the second radio access node, the first data packet to the user equipment through the unicast flow or the multicast flow based on the determination of the transmission of the first data packet.

16. The method according to claim 14, wherein, Receiving the data packet of the multicast service from the first radio access node includes receiving the data packet of the multicast service through a direct tunnel between the first radio access node and the second radio access node.

17. The method according to claim 14, wherein, Receiving the data packet of the multicast service from the first radio access node includes receiving the data packet of the multicast service through an indirect tunnel between the first radio access node and the user plane function and between the second radio access node and the user plane function.

18. The method according to claim 17, wherein The user plane function is configured to carry network user traffic.

19. The method according to claim 14, wherein, After determining that the flow identifier indicates a flow for a multicast service, a unicast data radio bearer is allocated to the user equipment for the transmission of the data packet of the multicast service.

20. The method according to any one of claims 14 - 19, wherein The flow identifier indicating the unicast flow includes a quality of service (QoS) flow identifier (QFI) configured to identify a QoS flow.

21. The method according to any one of claims 14-19, wherein, The data packet of the multicast service is transmitted through a shared tunnel established between the core network and the first radio access node.

22. The method according to claim 21, wherein The first radio access node and the second radio access node receive mapping information between the identifier of the multicast flow transmitted in the shared tunnel and the flow identifier indicating the unicast flow.

23. The method according to claim 22, wherein, The unicast flow is a virtual quality of service flow established by a radio access network within a protocol data unit (PDU) session.

24. The method according to claim 22, wherein, At least one of a multicast broadcast session management function (MB-SMF) or a multicast broadcast service function (MBSF) is configured to allocate a QFI for the unicast flow within a PDU session.

25. The method according to claim 24, wherein At least one of the multicast broadcast session management function (MB-SMF) or the multicast broadcast service function (MBSF) is configured to establish a multicast flow in a session for a multicast mode.

26. The method according to claim 24 or 25, wherein The multicast broadcast session management function (MB-SMF) or the multicast broadcast service function (MBSF) is configured to generate quality of service flow parameters and identifiers for the multicast flow and the unicast flow and transmit the generated parameters and identifiers to the radio access node.

27. The method according to claim 26, wherein, The quality of service flow parameters for the multicast flow and the unicast flow are the same as each other.

28. The method according to claim 26, wherein the identifiers for the multicast flow and the unicast flow are different from each other.

29. The method according to claim 26, wherein, A first flow is formed on a radio access network between a wireless device and a core network, and quality of service flow parameters for a first quality of service flow and a second quality of service flow are transmitted to the radio access network.

30. The method according to any one of claims 14-19, wherein During the handover process, the first radio access node includes a source radio network, and the second radio access node includes a target radio network.

31. A data communication method, comprising: Receiving, by a target radio access node, data packets of a multicast service during a handover process; Determining, by the target radio access node, whether the data packets of the multicast service include a Quality of Service (QoS) Flow Identifier (QFI) indicating that the data packets are forwarded from a source radio access node; And After determining that the data packets of the multicast service include the QFI, transmitting, by the target radio access node, the data packets to a mobile device in a unicast mode, wherein, after determining to initiate the handover process, a first part of the data packets of the multicast service is replaced by the QFI.

32. The method according to claim 31, wherein, After determining that the data packets include the QFI, the data packets are transmitted via a unicast data radio bearer.

33. The method according to claim 31, further comprising, after receiving an end marker indicating completion of forwarding of the data packets in the data packets from the source radio access node, transmitting the data packets to the mobile device in a multicast mode.

34. The method according to claim 33, wherein Transmission of the data packets in the multicast mode is performed via a broadcast data radio bearer.

35. A device for wireless communication, comprising a memory and a processor, wherein the processor reads code from the memory and implements the method according to any one of claims 1 to 34.

36. A computer-readable program storage medium having code stored thereon, which, when executed by a processor, causes the processor to implement the method according to any one of claims 1 to 34.

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