Data transmission method and device, network equipment and terminal equipment

Abstract

Provided in an embodiment of the present application are a data transmission method and apparatus, a network device, and a terminal device, the method comprising: after receiving a switching confirmation message sent by a terminal device, a target base station sends data of a first service to the terminal device, the switching confirmation message is used for indicating the terminal equipment to confirm that the terminal equipment is switched from a source base station to the target base station; wherein the data of the first service is sent on the source base station side in a multicast mode, and the data of the first service is sent on the target base station side in a multicast mode or a unicast mode.

Description

[0001] Division Case Explanation

[0002] This application is a divisional application of Chinese Patent Application No. 202080090358.1, with the invention title of "A Data Transmission Method, Apparatus, Network Device, and Terminal Device", which enters the Chinese national phase from the PCT international patent application PCT / CN2020 / 078649 with the filing date of March 10, 2020. Technical Field

[0003] Embodiments of this application relate to the field of mobile communication technologies, and specifically relate to a data transmission method, apparatus, network device, and terminal device. Background Art

[0004] To improve the efficiency of air interface data transmission, the network can determine whether to send service data to a terminal device in a unicast manner or in a multicast manner. During the movement of the terminal device, the terminal device may switch from a base station that supports the multicast mode to another base station that does not support the multicast mode. How to ensure the continuity of service data in this case needs to be solved. Summary of the Invention

[0005] Embodiments of this application provide a data transmission method, apparatus, network device, and terminal device.

[0006] The data transmission method provided by embodiments of this application includes:

[0007] After receiving a handover confirmation message sent by a terminal device, a target base station sends data of a first service to the terminal device, where the handover confirmation message is used to instruct the terminal device to confirm the handover from a source base station to the target base station; wherein, the data of the first service is sent in a multicast manner on the source base station side, and the data of the first service is sent in a multicast manner or a unicast manner on the target base station side.

[0008] The data transmission method provided by embodiments of this application includes:

[0009] A terminal device receives data of a first service sent by a source base station in a multicast manner;

[0010] After the terminal device hands over from the source base station to a target base station, the terminal device sends a handover confirmation message to the target base station and receives the data of the first service sent by the target base station in a multicast manner or a unicast manner.

[0011] The data transmission apparatus provided by embodiments of this application is applied to a target base station, and the apparatus includes:

[0012] A receiving unit, configured to receive a handover confirmation message sent by a terminal device; the handover confirmation message is used to instruct the terminal device to confirm the handover from a source base station to the target base station;

[0013] A sending unit, configured to send data of a first service to the terminal device; wherein, the data of the first service is sent in a multicast manner on the source base station side, and the data of the first service is sent in a multicast manner or a unicast manner on the target base station side.

[0014] The data transmission device provided by an embodiment of the present application is applied to a terminal device, and the device includes:

[0015] A receiving unit, configured to receive data of a first service sent by a source base station in a multicast manner;

[0016] A sending unit, configured to send a handover confirmation message to the target base station after switching from the source base station to the target base station;

[0017] The receiving unit is further configured to receive the data of the first service sent by the target base station in a multicast manner or a unicast manner.

[0018] The network device provided by an embodiment of the present application includes a processor and a memory. The memory is used to store a computer program, and the processor is used to call and run the computer program stored in the memory to execute the above data transmission method.

[0019] The terminal device provided by an embodiment of the present application includes a processor and a memory. The memory is used to store a computer program, and the processor is used to call and run the computer program stored in the memory to execute the above data transmission method.

[0020] The chip provided by an embodiment of the present application is used to implement the above data transmission method.

[0021] Specifically, the chip includes: a processor, configured to call and run a computer program from a memory, so that a device installed with the chip executes the above data transmission method.

[0022] The computer-readable storage medium provided by an embodiment of the present application is used to store a computer program, and the computer program enables a computer to execute the above data transmission method.

[0023] The computer program product provided by an embodiment of the present application includes computer program instructions, and the computer program instructions enable a computer to execute the above data transmission method.

[0024] The computer program provided by an embodiment of the present application, when running on a computer, enables the computer to execute the above data transmission method.

[0025] Through the above technical solution, before handover, the terminal device receives the data of the first service sent by the source base station in a multicast manner; after handover, the terminal device receives the data of the first service sent by the target base station in a multicast or unicast manner, thereby realizing the continuity of service data during the multicast transmission process. Description of the Drawings

[0026] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The schematic embodiments and descriptions thereof of the present application are used to explain the present application and do not constitute an improper limitation of the present application. In the drawings:

[0027] Figure 1 is a schematic diagram of a communication system architecture provided by an embodiment of the present application;

[0028] Figure 2 is a network architecture diagram of a point-to-multipoint transmission mechanism provided by an embodiment of the present application;

[0029] Figure 3 is a schematic flowchart of a data transmission method provided by an embodiment of the present application;

[0030] Figure 4 is a flowchart of handover preparation provided by an embodiment of the present application;

[0031] Figure 5 is a flowchart of handover execution provided by an embodiment of the present application;

[0032] Figure 6 is a schematic diagram of the structural composition of an improved data transmission device provided by an embodiment of the present application Figure 1 ;

[0033] Figure 7 is a schematic diagram of the structural composition of an improved data transmission device provided by an embodiment of the present application Figure 2 ;

[0034] Figure 8 is a schematic structural diagram of a communication device provided by an embodiment of the present application;

[0035] Figure 9 is a schematic structural diagram of a chip of an embodiment of the present application;

[0036] Figure 10 is a schematic block diagram of a communication system provided by an embodiment of the present application. Detailed Embodiments

[0037] Next, the technical solutions in the embodiments of the present application will be described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0038] The technical solutions in the embodiments of the present application can be applied to various communication systems, such as: Long Term Evolution (LTE) systems, LTE Frequency Division Duplex (FDD) systems, LTE Time Division Duplex (TDD) systems, 5G communication systems, or future communication systems, etc.

[0039] Exemplarily, the communication system 100 to which the embodiments of the present application are applied is as Figure 1 shown. The communication system 100 may include a network device 110, and the network device 110 may be a device that communicates with a terminal 120 (or referred to as a communication terminal, terminal). The network device 110 may provide communication coverage for a specific geographical area and may communicate with terminals located within the coverage area. Optionally, the network device 110 may be an evolved base station (Evolutional Node B, eNB or eNodeB) in an LTE system, or a radio controller in a Cloud Radio Access Network (CRAN), or the network device may be a mobile switching center, a relay station, an access point, a vehicle-mounted device, a wearable device, a hub, a switch, a bridge, a router, a network-side device in a 5G network, or a network device in a future communication system, etc.

[0040] The communication system 100 also includes at least one terminal 120 located within the coverage of the network device 110. As used herein, "terminal" includes but is not limited to connecting via a wired line, such as via a Public Switched Telephone Networks (PSTN), a Digital Subscriber Line (DSL), a digital cable, a direct cable connection; and / or another data connection / network; and / or via a wireless interface, such as, for a cellular network, a Wireless Local Area Network (WLAN), a digital television network such as a DVB-H network, a satellite network, an AM-FM broadcast transmitter; and / or another terminal configured to receive / send communication signals; and / or an Internet of Things (IoT) device. A terminal configured to communicate via a wireless interface may be referred to as a "wireless communication terminal", "wireless terminal" or "mobile terminal". Examples of mobile terminals include, but are not limited to, satellite or cellular telephones; Personal Communications System (PCS) terminals that may combine cellular radiotelephones with data processing, fax, and data communications capabilities; PDAs that may include radiotelephones, pagers, Internet / Intranet access, Web browsers, notepads, calendars, and / or Global Positioning System (GPS) receivers; and conventional laptop and / or palmtop receivers or other electronic devices that include radiotelephone transceivers. A terminal may refer to an access terminal, User Equipment (UE), a subscriber unit, a subscriber station, a mobile station, a mobile station, a remote station, a remote terminal, a mobile device, a user terminal, a terminal, a wireless communication device, a user agent, or a user device. The access terminal can be a cellular phone, a cordless phone, a Session Initiation Protocol (SIP) phone, a Wireless Local Loop (WLL) station, a Personal Digital Assistant (PDA), a handheld device with wireless communication capabilities, a computing device or other processing device connected to a wireless modem, a vehicle-mounted device, a wearable device, a terminal in a 5G network, or a terminal in a future evolved PLMN, etc.

[0041] Optionally, the terminals 120 may perform device-to-device (D2D) communication.

[0042] Optionally, the 5G communication system or 5G network may also be referred to as a New Radio (NR) system or NR network.

[0043] Figure 1 Exemplarily, a network device and two terminals are shown. Optionally, the communication system 100 may include multiple network devices, and the coverage range of each network device may include other numbers of terminals. The embodiments of the present application do not limit this.

[0044] Optionally, the communication system 100 may further include other network entities such as a network controller and a mobility management entity. The embodiments of the present application do not limit this.

[0045] It should be understood that in the embodiments of the present application, a device with communication functions in a network / system may be referred to as a communication device. Taking Figure 1 the shown communication system 100 as an example, the communication device may include a network device 110 and a terminal 120 with communication functions. The network device 110 and the terminal 120 may be the specific devices described above and will not be elaborated here; the communication device may also include other devices in the communication system 100, such as other network entities like a network controller and a mobility management entity. The embodiments of the present application do not limit this.

[0046] It should be understood that the terms "system" and "network" are often used interchangeably in this article. The term "and / or" in this article is merely a description of the association relationship between associated objects, indicating that there can be three relationships. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the preceding and following associated objects.

[0047] To facilitate the understanding of the technical solutions of the embodiments of the present application, the following describes the technical solutions related to the embodiments of the present application.

[0048] In the 5G system, a point-to-multipoint transmission mechanism will be introduced. The network architecture of this transmission mechanism is as Figure 2As shown, the network elements included in this network architecture are: Radio Access Network (RAN) nodes, Access and Mobility Management Function (AMF), Session Management Function (SMF), User Plane Function (UPF), Network Exposure Function (NEF), Policy Control Function (PCF), and Application Function (AF). It should be noted that Figure 2 The network architecture shown is only exemplary, and this network architecture may also include more or fewer other network elements. The network side uses a point-to-multipoint transmission method to send service data within the service area of the multicast service. Terminal devices in this service area can receive service data using a multicast tunnel.

[0049] The 5G core network (5GC) supports Protocol Data Unit (PDU) connection services, which refer to services for exchanging PDU data packets between terminal devices and a Data Network (DN). PDU connection services are realized by the terminal device initiating the establishment of a PDU session. After a PDU session is established, a data transmission channel between the terminal device and the DN is established.

[0050] The subscription information of each Single-Network Slice Selection Assistance Information (S-NSSAI) may include a default Data Network Name (DNN) and multiple DNNs. When the terminal device does not provide the DNN of the S-NSSAI when initiating a PDU session establishment request, the AMF will select the default DNN for its S-NSSAI (provided that the subscription information of the S-NSSAI has a default DNN); if there is no default DNN, then the AMF will select the locally configured DNN for the S-NSSAI. If the DNN carried by the terminal device in the PDU session establishment request message is not supported by the network and the AMF fails to select a suitable SMF by querying the NF Repository Function (NRF), the AMF will reject the PDU session establishment request and carry the cause value "DNN is not supported" in the rejection message.

[0051] Each PDU session supports one PDU session type, and the PDU session type can be one of the following: IPv4 type, IPv6 type, IPv4v6 type, Ethernet type, Unstructured type.

[0052] The PDU session is established, modified, and released between the terminal device and the SMF through Non-Access Layer (NAS) Session Management (SM) signaling.

[0053] On the other hand, the network can also initiate the establishment of a PDU session. Specifically: 1) When the application server wants to establish a PDU session connection, it will send a trigger message to the 5GC; 2) When the 5GC receives the PDU session establishment request from the application server, it will send a message to trigger the PDU session establishment to the terminal device; 3) After receiving the message, the terminal device will send it to the corresponding application on the terminal device; 4) The application on the terminal device decides when to initiate the specified PDU session connection according to the content of the trigger message.

[0054] When the terminal device sends a PDU session establishment request message to the network, it provides a PDU session identifier. Here, the PDU session identifier is allocated by the terminal device and is unique within the terminal device. To support the handover between 3GPP and non-3GPP accesses under different networks, the PDU session identifier will be stored in the Unified Data Management (UDM) network element. Whether it is 3GPP access or non-3GPP access, the terminal device establishes multiple PDU session connections to the same DN or multiple PDU session connections to different DNs. The terminal device can establish multiple PDU session connections to the same DN and connect to the DN through different UPFs. Optionally, when the terminal device establishes multiple PDU session connections, the SMF corresponding to each PDU session connection can be different. The service SMF information of each PDU session connection will be registered in the UDM.

[0055] When the terminal device establishes a PDU session, a PDU session will be established for the same service. In this PDU session, both the unicast mode of transmitting service data and the multicast mode of transmitting service data can be supported.

[0056] In the data interface (i.e., the N3 interface) between the core network and the RAN, either a terminal device-specific N3 channel can be used, and the unicast data and multicast data of this terminal device are both transmitted in this specific channel. Or a shared transmission channel can be used, and this transmission channel is shared by multiple terminal data transmissions, and these multiple terminals can belong to the same group. To improve the efficiency of air interface data transmission, the network can decide whether to send service data to the terminal device in the unicast mode or in the multicast mode. During the movement of the terminal device, the terminal device may switch from a base station that supports the multicast mode to another base station that does not support the multicast mode. For this situation, how to ensure the continuity of service data needs to be solved. For this reason, the following technical solutions of the embodiments of the present application are proposed to achieve the continuity of supporting multicast services.

[0057] It should be noted that in the technical solutions of the embodiments of the present application, the description of "multicast" can also be replaced by "groupcast" or "broadcast".

[0058] It should be noted that in the technical solutions of the embodiments of the present application, the description of "base station" can also be replaced by "cell" or "RAN node".

[0059] It should be noted that in the technical solutions of the embodiments of the present application, the description of "tunnel" can also be replaced by "channel" or "channel" or "connection".

[0060] Figure 3It is a schematic flowchart of the data transmission method provided by the embodiment of the present application. As Figure 3 shown, the data transmission method includes the following steps:

[0061] Step 301: The terminal device receives the data of the first service sent by the source base station in a multicast manner.

[0062] In the embodiment of the present application, the source base station refers to the base station that serves the terminal device before handover. The target base station refers to the base station that serves the terminal device after handover. Further, the types of the source base station and the target base station may be the same or different. For example, both the source base station and the target base station are gNBs. For example, the source base station is an eNB and the target base station is a gNB.

[0063] Here, the data of the first service is sent in a multicast manner on the source base station side, that is, the source base station supports multicast data transmission (or supports sending the data of the first service in a multicast manner).

[0064] Step 302: After the terminal device switches from the source base station to the target base station, it sends a handover confirmation message to the target base station and receives the data of the first service sent by the target base station in a multicast or unicast manner.

[0065] Here, after receiving the handover confirmation message sent by the terminal device, the target base station sends the data of the first service to the terminal device, where the handover confirmation message is used to instruct the terminal device to confirm the handover from the source base station to the target base station; the data of the first service is sent in a multicast or unicast manner on the target base station side.

[0066] In the embodiment of the present application, the data of the first service is sent in a multicast manner on the source base station side, which is equivalent to: the data of the first service is sent through a multicast session on the source base station side.

[0067] In the embodiment of the present application, the data of the first service is sent in a multicast or unicast manner on the target base station side, which is equivalent to: the data of the first service is sent through a multicast session or a unicast session on the target base station side.

[0068] It should be noted that a "multicast session" refers to a PDU session used for transmitting multicast service data (that is, a PDU session for transmitting service data in a multicast manner). A "unicast session" refers to a PDU session used for transmitting unicast service data (that is, a PDU session for transmitting service data in a unicast manner).

[0069] In the embodiments of the present application, before sending data of a first service, a target base station needs to establish a PDU session for the first service, and the PDU session can be a multicast session or a unicast session. The following describes the context acquisition of the PDU session by the target base station in different cases.

[0070] Case 1: The target base station receives a first message sent by a core network element, and the first message includes the context of a multicast session.

[0071] In an optional manner, the core network element is an SMF.

[0072] In an optional manner, the first message belongs to an N2 SM message. Further, optionally, the first message carries an indication information, which is used to indicate that the N2 SM message is for multicast transmission.

[0073] After the target base station obtains the context of the multicast session, if the target base station supports sending data of the first service in multicast mode, the data of the first service is sent in multicast mode on the target base station side.

[0074] For the case where the data of the first service is sent in multicast mode on the source base station side and the data of the first service is sent in multicast mode on the target base station side:

[0075] 1) If the multicast session already exists on the target base station side, the context of the multicast session includes at least one of the following: the identifier of the terminal device, the group identifier of the multicast group where the terminal device is located, the identifier of the multicast session, multicast Quality of Service (QoS) flow information; or,

[0076] 2) If the multicast session does not exist on the target base station side, the context of the multicast session includes at least one of the following: the identifier of the terminal device, the group identifier of the multicast group where the terminal device is located, the identifier of the multicast session, multicast QoS flow information, N3 UP address, the tunnel identifier associated with the multicast session.

[0077] Here, the tunnel identifier associated with the multicast session refers to the Core Network Tunnel ID (CN Tunnel ID) of the UPF associated with the multicast session.

[0078] Here, the multicast QoS flow information refers to QoS parameters related to the multicast QoS flow.

[0079] Case 2: The target base station receives a second message sent by a core network element, and the second message includes the context of a unicast session.

[0080] In an optional manner, the core network element is the SMF.

[0081] In an optional manner, the second message belongs to the N2 SM message. Further, optionally, the second message carries an indication information, which is used to indicate that the N2 SM message is for unicast transmission.

[0082] After the target base station obtains the context of the unicast session, the data of the first service is sent in a unicast manner on the target base station side (by default, the target base station supports the unicast manner).

[0083] For the case where the data of the first service is sent in a multicast manner on the source base station side and in a unicast manner on the target base station side:

[0084] The context of the unicast session includes at least one of the following: N3 UP address, the tunnel identifier associated with the unicast session, and unicast QoS flow information.

[0085] Here, the tunnel identifier associated with the unicast session refers to the core network tunnel ID (CN Tunnel ID) of the UPF associated with the unicast session.

[0086] Here, the unicast QoS flow information refers to the QoS parameters related to the unicast QoS flow.

[0087] Case 3: The target base station receives a third message sent by the core network element, and the third message includes the context of the multicast session and the context of the unicast session.

[0088] In an optional manner, the core network element is the SMF.

[0089] In an optional manner, the third message belongs to the N2 SM message.

[0090] After the target base station obtains the context of the unicast session and the multicast session, the data of the first service can be sent in a unicast manner or in a multicast manner on the target base station side. Specifically,

[0091] 1) If the target base station supports the multicast session and accepts the multicast session, the target base station sends a first indication information to the core network element, and the first indication information is used to indicate that the target base station accepts the multicast session and rejects the unicast session. Accordingly, the target base station sends the data of the first service in a multicast manner.

[0092] 2) If the target base station does not support the multicast session or does not accept the multicast session, the target base station sends second indication information to the core network element, where the second indication information is used to indicate that the target base station does not support the multicast session or does not accept the multicast session. Accordingly, the target base station sends the data of the first service in a unicast manner.

[0093] Further, optionally, the target base station may store the context of the multicast session; or, the target base station may also delete the context of the multicast session.

[0094] 3) The target base station stores the context of the multicast session and the context of the unicast session; if the target base station uses the context of the multicast session, the target base station sends third indication information to the core network element, where the third indication information is used to indicate that the target base station uses the context of the multicast session (accordingly, the target base station sends the data of the first service in a multicast manner); or, if the target base station uses the context of the unicast session, the target base station sends fourth indication information to the core network element, where the fourth indication information is used to indicate that the target base station uses the context of the unicast session (accordingly, the target base station sends the data of the first service in a unicast manner).

[0095] In the embodiments of the present application, before the target base station receives the handover confirmation message sent by the terminal device, the service server will send the data of the first service to the source base station, and the source base station may choose to forward the data of the first service to the target base station in a multicast manner or in a unicast manner. The following describes how the data of the first service is forwarded between the source base station and the target base station.

[0096] I) Method 1

[0097] The target base station receives the multicast QoS flow from the service server forwarded by the source base station, where the multicast QoS flow contains the data of the first service; if the target base station does not support the multicast QoS flow, the target base station discards or rejects the multicast QoS flow, or the target base station converts the multicast QoS flow into a unicast QoS flow and sends it to the terminal device.

[0098] II) Method 2

[0099] The target base station receives the unicast QoS flow sent by the source base station, where the unicast QoS flow contains the data of the first service; wherein, the unicast QoS flow is obtained by the core network element converting the multicast QoS flow from the service server.

[0100] III) The target base station receives the unicast QoS flow sent by the source base station, and the unicast QoS flow contains data of the first service; wherein, the unicast QoS flow is obtained by the source base station converting the multicast QoS flow from the service server.

[0101] In the embodiments of the present application, the sending of data flows by the target base station and the source base station may not be synchronized. To ensure that the terminal device can make up for this asynchrony, the PSA UPF may insert a sequence number (Series Number, SN) into the data packets sent to the source base station and the target base station. Specifically, the target base station receives the first data flow forwarded by the source base station from the service server, and receives the second data flow sent by the service server through the multicast tunnel; the data packets in the first data flow carry the first SN, and the data packets in the second data flow carry the second SN; wherein, the first data flow and the second data flow belong to the data flows of the first service.

[0102] Here, if the first SN is equal to the second SN, it means that the first data flow and the second data flow are synchronized. If the first SN is not equal to the second SN, it means that the first data flow and the second data flow are different. The following describes how to schedule data flows to make up for this asynchrony in the case of asynchrony.

[0103] A) If the first SN is less than the second SN, the target base station schedules a third data flow for the terminal device through the unicast tunnel, and the third data flow carries the third SN; the rate of the third data flow is greater than the rate of the first data flow; when the third SN is equal to the second SN, the target base station schedules the second data flow for the terminal device through the multicast tunnel.

[0104] B) If the first SN is less than the second SN, the target base station schedules a third data flow for the terminal device through the multicast tunnel, and the third data flow carries the third SN; the rate of the third data flow is greater than the rate of the first data flow; when the third SN is equal to the second SN, the target base station schedules the second data flow for the terminal device through the multicast tunnel.

[0105] C) If the first SN is greater than the second SN, the target base station performs duplicate detection on the first data flow and the second data flow through a Packet Data Convergence Protocol (PDCP) entity to generate a third data flow; the target base station schedules the third data flow for the terminal device through the multicast tunnel.

[0106] The following further describes the technical solutions of the embodiments of the present application in combination with a specific handover interaction process.

[0107] Figure 4 This is a schematic diagram of the Handover Preparation process provided by the embodiments of this application. As Figure 4 shown, this process includes the following steps:

[0108] Step 400: The source base station decides to trigger redirection through the N2 interface.

[0109] Step 401: The source base station sends a handover request message to the source AMF.

[0110] Here, the handover request message carries at least one of the following information: the identifier of the target base station (Target ID), the transparent container from the source base station to the target base station (Source to Target transparent container), the N2 SM information list (N2 SM info list), and the PDU session identifier.

[0111] Here, the PDU session identifier refers to the identifier of the PDU session to be handed over to the target base station, that is, the identifier of the multicast session.

[0112] In this embodiment, there are several implementation methods for the source base station to forward QoS Flows to the target base station:

[0113] 1) The source base station ignores the capabilities of the target base station and directly forwards the multicast QoS flow to the target base station. If the target base station does not support the multicast QoS flow, the target base station may discard or reject the multicast QoS flow, or regard the multicast QoS flow as a unicast QoS flow (provided that the unicast QoS flow meets the QoS requirements).

[0114] 2) When the source base station knows the capabilities of the target base station, if it is determined that the target base station does not support the multicast QoS flow, the source base station does not forward the multicast QoS flow to the target base station. During the path switch, the SMF converts the multicast QoS flow into a unicast QoS flow and sends it to the target base station.

[0115] 3) When the source base station knows the capabilities of the target base station, if it is determined that the target base station does not support the multicast QoS flow, the source base station does not forward the multicast QoS flow to the target base station. During the path switch, the source base station converts the multicast QoS flow into a unicast QoS flow and sends it to the target base station.

[0116] 4) The source base station only forwards the unicast QoS flow to the target base station.

[0117] Step 402: The source AMF selects the target AMF.

[0118] Here, when the source AMF is unable to serve the UE, the source AMF selects a target AMF.

[0119] Step 403: The source AMF sends a UE context establishment request message (i.e., Namf_Communication_CreateUEContext Request) to the target AMF.

[0120] Step 404: The target AMF sends an SM context update request message (i.e., Nsmf_PDUSession_UpdateSMContext Request) to the SMF.

[0121] Here, the SM context update request message carries at least one of the following information: the identifier of the target base station, the PDU session identifier, the target AMF identifier, N2 SM message (N2 SM Information).

[0122] Here, optionally, the SM context update request message also carries an indication information, which is used to indicate the PDU session of the multicast session and / or the related information of the multicast session (such as group address, group ID).

[0123] Step 405: The SMF selects a UPF (PSA).

[0124] Here, when the target base station does not support the multicast mode, the SMF generates an N2 SM message, which includes at least one of the following information: N3 UP address, tunnel identifier of the UPF, QoS parameters. Further, optionally, the N2 SM message also carries an indication information, which is used to indicate that the N2 SM message is for the target base station and / or the N2 SM message is for unicast transmission.

[0125] Here, the SMF confirms whether the N2 handover (for the indicated PDU session) is received based on the identifier of the target base station and / or the information of the requested multicast session. If the UPF has changed, the SMF selects a UPF (PSA) that supports the multicast session.

[0126] Step 406a: The SMF sends a session modification request message (i.e., N4 Session ModificationRequest) to the UPF (PSA).

[0127] Step 406b: The UPF (PSA) sends a session modification response message (i.e., N4 Session ModificationResponse) to the SMF.

[0128] Step 406c: The SMF sends a session establishment request message (i.e., N4 Session Establishment Request) to the target UPF.

[0129] Step 406d: The target UPF sends a session establishment response message (i.e., N4 Session Establishment Response) to the SMF.

[0130] It should be noted that for the case of multicast handover to multicast (i.e., the source base station uses multicast and the target base station uses multicast): If the multicast session (or the context of the multicast session) already exists on the target base station side, the above steps 405 to 406d can be omitted. If the multicast session (or the context of the multicast session) does not exist on the target base station side, the multicast session is established through the above steps 405 to 406d.

[0131] Step 407: The SMF sends an update SM context response message (i.e., Nsmf_PDUSession_UpdateSMContext Response) to the target AMF.

[0132] Step 408: PDU handover response supervision is performed between the target AMF and the target UPF.

[0133] Step 409: The target AMF sends a handover request message to the target base station.

[0134] Here, the messages exchanged between the above steps 407 to 409 can carry at least one of the following information: N2 SM message, PDU session identifier.

[0135] Step 410: The target base station sends a handover request confirmation message to the target AMF.

[0136] Step 411a: The target AMF sends an update SM context request message (i.e., Nsmf_PDUSession_UpdateSMContext Request) to the SMF.

[0137] Step 411b: The SMF sends a session modification request message (i.e., N4 Session Modification Request) to the target UPF.

[0138] Step 411c: The target UPF sends a session modification response message (i.e., N4 Session Modification Response) to the SMF.

[0139] Step 411d: The SMF sends a session modification request message (i.e., N4 Session Modification Request) to the source UPF.

[0140] Step 411e: The source UPF sends a session modification response message (i.e., N4 Session Modification Response) to the SMF.

[0141] Step 411f: The SMF sends an update SM context response message (i.e., Nsmf_PDUSession_UpdateSMContext Response) to the target AMF.

[0142] Step 412: The target AMF sends a create UE context response message (i.e., Namf_Communication_CreateUEContext Response) to the source AMF.

[0143] In an optional manner, the SMF can choose to establish a multicast session context or a unicast session context for the target base station.

[0144] 1) For the case of multicast handover to multicast (i.e., the source base station uses multicast and the target base station uses multicast): If the multicast session (or the context of the multicast session) already exists on the target base station side, the SMF carries at least one of the following information in the N2 SM message to the target base station: UE ID, group identifier of the multicast group where the UE is located, identifier of the multicast session, multicast QoS flow information. If the multicast session (or the context of the multicast session) does not exist on the target base station side, the SMF carries at least one of the following information in the N2 SM message to the target base station: UE ID, group identifier of the multicast group where the UE is located, identifier of the multicast session, multicast QoS flow information, N3 UP address, tunnel identifier of the UPF associated with the multicast session.

[0145] 2) For the case of multicast handover to unicast (i.e., the source base station uses multicast and the target base station uses unicast): The SMF carries at least one of the following information in the N2 SM message to the target base station: N3 UP address, tunnel identifier of the UPF associated with the unicast session, unicast QoS flow information.

[0146] In another alternative, the SMF provides the context of the multicast session and the unicast session to the target base station (e.g., sends the context to the target base station via the N2SM message). If the target base station can support the multicast session and accepts the multicast session, the target base station instructs the SMF to accept the multicast session and reject the unicast session. Alternatively, the target base station stores the context of the two sessions and indicates to the SMF whether the session it uses is a multicast session or a unicast session. Further, if the target base station does not support the multicast session or does not accept the multicast session, it indicates to the SMF that it does not support or does not accept the multicast session, and the target base station can store or delete the context of the multicast session.

[0147] Figure 5 It is a schematic diagram of the handover execution process provided by the embodiments of this application. As Figure 5 shown, this process includes the following steps:

[0148] Step 501: The source AMF sends a handover command to the source base station.

[0149] Here, the handover command carries at least one of the following information: the target-to-source transparent container from the target base station to the source base station, the PDU session identifier to be handed over, and the identifier of the PDU session with establishment failure.

[0150] Here, the PDU session identifier to be handed over can be the PDU session identifier in the N2 SM information from the target base station in the handover preparation process as Figure 4 shown.

[0151] Step 502: The source base station sends the handover command to the UE.

[0152] Here, the handover command carries the UE container, and the UE container is the container belonging to the UE part in the target-to-source transparent container. The UE container is transparently transmitted from the target base station to the source base station via the AMF and sent by the source base station to the UE.

[0153] Step 502a: The source base station performs uplink RAN status transfer to the source AMF.

[0154] Step 502b: N1N2 message transfer is performed between the source AMF and the target AMF (i.e., Namf_Communication_N1N2Message Transfer).

[0155] Step 502c: The target AMF performs downlink RAN status transfer to the target base station.

[0156] Step 503a: The source base station performs direct data forwarding to the target base station.

[0157] Step 503b: The source base station performs indirect data forwarding to the target base station via the source UPF.

[0158] Here, uplink packets are sent by the target base station to the target UPF and the UPF (PSA). Downlink packets are sent by the UPF (PSA) via the source UPF to the source base station, and the source base station starts forwarding the downlink packets to the target base station, which can be done by direct forwarding (such as in step 3a) or indirect forwarding (such as in step 3b).

[0159] Step 504: The UE sends a Handover Confirm message to the target base station.

[0160] Here, after the UE successfully synchronizes to the target base station, the UE sends a handover confirmation message to the target base station, which indicates that the UE confirms the successful handover.

[0161] For asynchronous data transmission in the source base station and the target base station, the UPF (PSA) can insert an SN into the data packets transmitted to the source base station and the target base station.

[0162] 1) During handover, the source base station forwards the data packets carrying the SN to the target base station.

[0163] 2) After handover, if the SN of the data packets received by the target base station from the source base station is less than the SN of the data packets in the multicast tunnel, the target base station and / or the UPF (PSA) first schedule data for the UE through the unicast tunnel, and switch to the multicast tunnel to schedule data for the UE when the SN of the data packets in the unicast tunnel is equal to the SN of the data packets in the multicast tunnel.

[0164] 3) After handover, if the SN of the data packets received by the target base station from the source base station is greater than the SN of the data packets in the multicast tunnel, the target base station and / or the UPF (PSA) schedule data for the UE through the multicast tunnel and perform duplicate detection at the PDPC layer.

[0165] It should be noted that here it can be assumed that the SN range (i.e., the difference between the SN of the data packets forwarded by the source base station and the SN of the data packets in the multicast tunnel) can cover the buffer size of the UPF (PSA).

[0166] It should be noted that considering the storage cost of UPF (PSA) and the satisfaction of multicast QoS requirements, there is no significant difference in the SN range (i.e., the difference between the SN of the data packet forwarded by the source base station and the SN of the data packet in the multicast tunnel).

[0167] Step 505: The target base station sends a handover notification message to the target AMF.

[0168] This handover notification message indicates that the target base station confirms the successful handover.

[0169] Step 506a: The target AMF sends an N2 information notification (i.e., Namf_Communication_N2InfoNotify) to the source AMF.

[0170] Step 506b: The source AMF sends an N2 information notification confirmation (i.e., Namf_Communication_N2InfoNotify Ack) to the target AMF.

[0171] Step 506c: The source AMF sends a release SM context request message (i.e., Nsmf_PDUSession_ReleaseSMContext Request) to the SMF.

[0172] Step 507: The target AMF sends an update SM context request message (i.e., Nsmf_PDUSession_UpdateSMContext Request) to the SMF.

[0173] Step 508a: The SMF sends a session modification request message (i.e., N4 Session ModificationRequest) to the target UPF.

[0174] Step 508b: The target UPF sends a session modification response message (i.e., N4 Session ModificationResponse) to the SMF.

[0175] Step 509a: The SMF sends a session modification request message (i.e., N4 Session ModificationRequest) to the source UPF.

[0176] Step 509b: The source UPF sends a session modification response message (i.e., N4 Session ModificationResponse) to the SMF.

[0177] Step 510a: The SMF sends a session modification request message (i.e., N4 Session ModificationRequest) to the UPF (PSA).

[0178] Step 510b: The UPF (PSA) sends a session modification response message (i.e., N4 Session Modification Response) to the SMF.

[0179] Step 511: The SMF sends an update SM context response message (i.e., Nsmf_PDUSession_UpdateSMContext Response) to the target AMF.

[0180] Step 512: A registration process is performed between the UE and the network.

[0181] Step 513a: The SMF sends a session release request message (i.e., N4 Session Release Request) to the source UPF.

[0182] Step 513b: The source UPF sends a session release response message (i.e., N4 Session Release Response) to the SMF.

[0183] Step 514a: The source AMF sends a UE context release command (i.e., UE Context Release Command) to the source base station.

[0184] Step 514b: The source base station sends a UE context release command completion message (i.e., UE Context Release Command Complete) to the source AMF.

[0185] Step 515a: The SMF sends a session modification request message (i.e., N4 Session Modification Request) to the target UPF.

[0186] Step 515b: The target UPF sends a session modification response message (i.e., N4 Session Modification Response) to the SMF.

[0187] It should be noted that in the processes shown above in this application Figure 4 and Figure 5 the data (or data packet) refers to the data (or data packet) of the first service, where the first service can be any service, such as a video service.

[0188] Figure 6 The structural composition of the improved data transmission device according to the embodiment of this application is schematically shown Figure 1 , applied to the target base station, as Figure 6 shown, the data transmission device includes:

[0189] A receiving unit 601, configured to receive a handover confirmation message sent by a terminal device; the handover confirmation message is used to instruct the terminal device to confirm a handover from a source base station to the target base station.

[0190] A sending unit 602, configured to send data of a first service to the terminal device; wherein, the data of the first service is sent in a multicast manner on the source base station side, and the data of the first service is sent in a multicast manner or a unicast manner on the target base station side.

[0191] In an optional manner, the data of the first service is sent through a multicast session on the source base station side, and the data of the first service is sent through a multicast session or a unicast session on the target base station side.

[0192] In an optional manner, the receiving unit 601 is further configured to receive a first message sent by a core network element, where the first message includes a context of a multicast session.

[0193] In an optional manner, for the case where the data of the first service is sent in a multicast manner on the source base station side and the data of the first service is sent in a multicast manner on the target base station side:

[0194] If the multicast session already exists on the target base station side, the context of the multicast session includes at least one of the following: an identifier of the terminal device, a group identifier of the multicast group where the terminal device is located, an identifier of the multicast session, multicast QoS flow information; or,

[0195] If the multicast session does not exist on the target base station side, the context of the multicast session includes at least one of the following: an identifier of the terminal device, a group identifier of the multicast group where the terminal device is located, an identifier of the multicast session, multicast QoS flow information, an N3 UP address, a tunnel identifier associated with the multicast session.

[0196] In an optional manner, the receiving unit 601 is further configured to receive a second message sent by a core network element, where the second message includes a context of a unicast session.

[0197] In an optional manner, for the case where the data of the first service is sent in a multicast manner on the source base station side and the data of the first service is sent in a unicast manner on the target base station side:

[0198] The context of the unicast session includes at least one of the following: an N3 UP address, a tunnel identifier associated with the unicast session, unicast QoS flow information.

[0199] In an optional manner, the receiving unit 601 is further configured to receive a third message sent by a core network element, where the third message includes the context of a multicast session and the context of a unicast session.

[0200] In an optional manner, the sending unit 602 is further configured to, if the target base station supports and accepts the multicast session, send a first indication message to the core network element, where the first indication message is used to indicate that the target base station accepts the multicast session and rejects the unicast session.

[0201] In an optional manner, the sending unit 602 is further configured to, if the target base station does not support or does not accept the multicast session, send a second indication message to the core network element, where the second indication message is used to indicate that the target base station does not support or does not accept the multicast session.

[0202] In an optional manner, the apparatus further includes:

[0203] A processing unit (not shown in the figure), configured to store the context of the multicast session; or, delete the context of the multicast session.

[0204] In an optional manner, the apparatus further includes:

[0205] A processing unit (not shown in the figure), configured to store the context of the multicast session and the context of the unicast session;

[0206] The sending unit 602 is further configured to, if the target base station uses the context of the multicast session, send a third indication message to the core network element, where the third indication message is used to indicate that the target base station uses the context of the multicast session; or, if the target base station uses the context of the unicast session, send a fourth indication message to the core network element, where the fourth indication message is used to indicate that the target base station uses the context of the unicast session.

[0207] In an optional manner, the receiving unit 601 is further configured to receive a multicast QoS flow forwarded by the source base station from a service server, where the multicast QoS flow contains data of the first service;

[0208] The apparatus further includes: a processing unit (not shown in the figure), configured to, if the target base station does not support the multicast QoS flow, discard or reject the multicast QoS flow, or convert the multicast QoS flow into a unicast QoS flow and send it to the terminal device.

[0209] In an alternative manner, the receiving unit 601 is further configured to receive a unicast QoS flow sent by the source base station, where the unicast QoS flow includes data of the first service; wherein, the unicast QoS flow is obtained by a core network element converting a multicast QoS flow from a service server.

[0210] In an alternative manner, the receiving unit 601 is further configured to receive a unicast QoS flow sent by the source base station, where the unicast QoS flow includes data of the first service; wherein, the unicast QoS flow is obtained by the source base station converting a multicast QoS flow from a service server.

[0211] In an alternative manner, the receiving unit 601 is further configured to receive a first data stream forwarded by the source base station from a service server, and receive a second data stream sent by the service server through a multicast tunnel; packets in the first data stream carry a first SN, and packets in the second data stream carry a second SN; wherein, the first data stream and the second data stream belong to data streams of the first service;

[0212] The sending unit 602 is further configured to, if the first SN is less than the second SN, schedule a third data stream for the terminal device through a unicast tunnel, where the third data stream carries a third SN; the rate of the third data stream is greater than the rate of the first data stream; in a case where the third SN is equal to the second SN, schedule the second data stream for the terminal device through a multicast tunnel.

[0213] In an alternative manner, the receiving unit 601 is further configured to receive a first data stream forwarded by the source base station from a service server, and receive a second data stream sent by the service server through a multicast tunnel; packets in the first data stream carry a first SN, and packets in the second data stream carry a second SN; wherein, the first data stream and the second data stream belong to data streams of the first service;

[0214] The apparatus further includes: a processing unit (not shown in the figure), configured to, if the first SN is greater than the second SN, perform duplicate detection on the first data stream and the second data stream through a PDCP entity to generate a third data stream;

[0215] The sending unit 602 is further configured to schedule the third data stream for the terminal device through a multicast tunnel.

[0216] Those skilled in the art should understand that the relevant descriptions of the above data transmission apparatus in the embodiments of the present application can be understood with reference to the relevant descriptions of the data transmission method in the embodiments of the present application.

[0217] Figure 7Schematic diagram of the structure of the improved data transmission device according to the embodiments of the present application Figure 2 which is applied to a terminal device, such as Figure 7 as shown, the data transmission device includes:

[0218] a receiving unit 701, configured to receive data of a first service sent by a source base station in a multicast manner;

[0219] a sending unit 702, configured to send a handover confirmation message to the target base station after switching from the source base station to the target base station;

[0220] the receiving unit 701 is further configured to receive the data of the first service sent by the target base station in a multicast manner or a unicast manner.

[0221] In an optional manner, the data of the first service is sent through a multicast session on the source base station side, and the data of the first service is sent through a multicast session or a unicast session on the target base station side.

[0222] Those skilled in the art should understand that the relevant descriptions of the above data transmission device according to the embodiments of the present application can be understood with reference to the relevant descriptions of the data transmission method according to the embodiments of the present application.

[0223] Figure 8 FIG. is a schematic structural diagram of a communication device 800 provided by the embodiments of the present application. The communication device can be a terminal device or a network device. Figure 8 As shown, the communication device 800 includes a processor 810, and the processor 810 can call and run a computer program from a memory to implement the method in the embodiments of the present application.

[0224] Optionally, as Figure 8 shown, the communication device 800 may further include a memory 820. Among them, the processor 810 can call and run a computer program from the memory 820 to implement the method in the embodiments of the present application.

[0225] Among them, the memory 820 can be a separate device independent of the processor 810 or integrated in the processor 810.

[0226] Optionally, as Figure 8 shown, the communication device 800 may further include a transceiver 830. The processor 810 can control the transceiver 830 to communicate with other devices. Specifically, it can send information or data to other devices or receive information or data sent by other devices.

[0227] Among them, the transceiver 830 can include a transmitter and a receiver. The transceiver 830 may further include antennas, and the number of antennas can be one or more.

[0228] Optionally, the communication device 800 may specifically be the network device of the embodiments of the present application, and the communication device 800 may implement the corresponding processes implemented by the network device in the various methods of the embodiments of the present application. For the sake of brevity, details are not described herein again.

[0229] Optionally, the communication device 800 may specifically be the mobile terminal / terminal device of the embodiments of the present application, and the communication device 800 may implement the corresponding processes implemented by the mobile terminal / terminal device in the various methods of the embodiments of the present application. For the sake of brevity, details are not described herein again.

[0230] Figure 9 It is a schematic structural diagram of the chip of the embodiments of the present application. Figure 9 The shown chip 900 includes a processor 910. The processor 910 may call and run a computer program from a memory to implement the methods in the embodiments of the present application.

[0231] Optionally, as Figure 9 shown, the chip 900 may further include a memory 920. Among them, the processor 910 may call and run a computer program from the memory 920 to implement the methods in the embodiments of the present application.

[0232] Among them, the memory 920 may be a separate device independent of the processor 910 or may be integrated in the processor 910.

[0233] Optionally, the chip 900 may further include an input interface 930. Among them, the processor 910 may control the input interface 930 to communicate with other devices or chips. Specifically, it may obtain information or data sent by other devices or chips.

[0234] Optionally, the chip 900 may further include an output interface 940. Among them, the processor 910 may control the output interface 940 to communicate with other devices or chips. Specifically, it may output information or data to other devices or chips.

[0235] Optionally, the chip may be applied to the network device in the embodiments of the present application, and the chip may implement the corresponding processes implemented by the network device in the various methods of the embodiments of the present application. For the sake of brevity, details are not described herein again.

[0236] Optionally, the chip may be applied to the mobile terminal / terminal device in the embodiments of the present application, and the chip may implement the corresponding processes implemented by the mobile terminal / terminal device in the various methods of the embodiments of the present application. For the sake of brevity, details are not described herein again.

[0237] It should be understood that the chip mentioned in the embodiments of the present application may also be referred to as a system-on-chip, system chip, chip system, or system-on-chip.

[0238] Figure 10 is a schematic block diagram of a communication system 1000 provided by an embodiment of the present application. As Figure 10 shown, the communication system 1000 includes a terminal device 1010 and a network device 1020.

[0239] Among them, the terminal device 1010 can be used to implement the corresponding functions implemented by the terminal device in the above method, and the network device 1020 can be used to implement the corresponding functions implemented by the network device in the above method. For the sake of brevity, details are not described herein again.

[0240] It should be understood that the processor in the embodiment of the present application may be an integrated circuit chip with signal processing capabilities. During implementation, the steps of the above method embodiments can be completed by the integrated logic circuit in the hardware of the processor or instructions in software form. The above processor may be a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components. It can implement or execute the various methods, steps and logic block diagrams disclosed in the embodiments of the present application. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc. The steps of the method disclosed in combination with the embodiments of the present application can be directly embodied as being executed and completed by a hardware decoding processor, or executed and completed by a combination of hardware and software modules in the decoding processor. The software module may be located in a mature storage medium in the art such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory, or an electrically erasable programmable memory, a register, etc. The storage medium is located in the memory, and the processor reads the information in the memory and combines its hardware to complete the steps of the above method.

[0241] It can be understood that the memory in the embodiments of the present application can be a volatile memory or a non-volatile memory, or can include both volatile and non-volatile memories. Among them, the non-volatile memory can be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory can be a random access memory (RAM), which is used as an external cache. By way of example but not limitation, many forms of RAM are available, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchlink dynamic random access memory (SLDRAM), and direct rambus random access memory (DR RAM). It should be noted that the memory of the systems and methods described herein is intended to include but not be limited to these and any other suitable types of memory.

[0242] It should be understood that the above memory is by way of example but not limitation. For example, the memory in the embodiments of the present application can also be a static random access memory (SRAM), a dynamic random access memory (DRAM), a synchronous dynamic random access memory (SDRAM), a double data rate SDRAM (DDR SDRAM), an enhanced SDRAM (ESDRAM), a synch link DRAM (SLDRAM), and a direct rambus random access memory (DR RAM), etc. That is to say, the memory in the embodiments of the present application is intended to include but not be limited to these and any other suitable types of memory.

[0243] The embodiments of the present application also provide a computer-readable storage medium for storing a computer program.

[0244] Optionally, the computer-readable storage medium can be applied to the network device in the embodiments of the present application, and the computer program causes the computer to execute the corresponding processes implemented by the network device in the various methods of the embodiments of the present application. For the sake of brevity, it will not be elaborated here.

[0245] Optionally, the computer-readable storage medium can be applied to the mobile terminal / terminal device in the embodiments of the present application, and the computer program causes the computer to execute the corresponding processes implemented by the mobile terminal / terminal device in the various methods of the embodiments of the present application. For the sake of brevity, it will not be elaborated here.

[0246] The embodiments of the present application also provide a computer program product including computer program instructions.

[0247] Optionally, the computer program product can be applied to the network device in the embodiments of the present application, and the computer program instructions cause the computer to execute the corresponding processes implemented by the network device in the various methods of the embodiments of the present application. For the sake of brevity, it will not be elaborated here.

[0248] Optionally, the computer program product can be applied to the mobile terminal / terminal device in the embodiments of the present application, and the computer program instructions cause the computer to execute the corresponding processes implemented by the mobile terminal / terminal device in the various methods of the embodiments of the present application. For the sake of brevity, it will not be elaborated here.

[0249] The embodiments of the present application also provide a computer program.

[0250] Optionally, the computer program can be applied to the network device in the embodiments of the present application. When the computer program runs on the computer, it causes the computer to execute the corresponding processes implemented by the network device in the various methods of the embodiments of the present application. For the sake of brevity, it will not be elaborated here.

[0251] Optionally, the computer program can be applied to the mobile terminal / terminal device in the embodiments of the present application. When the computer program runs on the computer, it causes the computer to execute the corresponding processes implemented by the mobile terminal / terminal device in the various methods of the embodiments of the present application. For the sake of brevity, it will not be elaborated here.

[0252] Those of ordinary skill in the art will realize that the units and algorithm steps of each example described in connection with the embodiments disclosed herein can be implemented in electronic hardware, or in a combination of computer software and electronic hardware. Whether these functions are executed in hardware or software depends on the specific application and design constraints of the technical solution. A professional technician can use different methods for each specific application to implement the described functions, but such implementation should not be considered to exceed the scope of this application.

[0253] Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes of the systems, devices, and units described above can refer to the corresponding processes in the foregoing method embodiments, and will not be elaborated herein.

[0254] In several embodiments provided in this application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division, and there can be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces, and the indirect couplings or communication connections of devices or units can be in electrical, mechanical, or other forms.

[0255] The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they can be located in one place, or can be distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0256] In addition, the functional units in each embodiment of this application can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit.

[0257] When the above-mentioned functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of this application. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical discs that can store program codes.

[0258] As described above, the above are only specific implementation manners of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art within the technical scope disclosed by this application can easily think of changes or substitutions, which should all be covered within the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

Claims

1. A data transmission method, the method comprising: After receiving a handover confirmation message sent by a terminal device, a target base station sends data of a first service to the terminal device, where the handover confirmation message is used to instruct the terminal device to confirm handover from a source base station to the target base station; wherein, the data of the first service is sent in a multicast manner on the source base station side, and the data of the first service is sent in a multicast manner or a unicast manner on the target base station side.

2. The method according to claim 1, wherein The data of the first service is sent through a multicast session on the source base station side, and the data of the first service is sent through a multicast session or a unicast session on the target base station side.

3. The method according to claim 1 or 2, wherein, The method further comprises: The target base station receives a first message sent by a core network element, where the first message includes the context of a multicast session.

4. The method according to claim 3, wherein The case where the data of the first service is sent in a multicast manner on the source base station side and the data of the first service is sent in a multicast manner on the target base station side: If the multicast session already exists on the target base station side, the context of the multicast session includes at least one of the following: the identifier of the terminal device, the group identifier of the multicast group where the terminal device is located, the identifier of the multicast session, multicast quality of service (QoS) flow information; Or, If the multicast session does not exist on the target base station side, the context of the multicast session includes at least one of the following: the identifier of the terminal device, the group identifier of the multicast group where the terminal device is located, the identifier of the multicast session, multicast QoS flow information, N3 UP address, the tunnel identifier associated with the multicast session.

5. The method according to claim 1 or 2, wherein The method further comprises: The target base station receives a second message sent by a core network element, where the second message includes the context of a unicast session.

6. The method according to claim 5, wherein, The case where the data of the first service is sent in a multicast manner on the source base station side and the data of the first service is sent in a unicast manner on the target base station side: The context of the unicast session includes at least one of the following: N3 UP address, the tunnel identifier associated with the unicast session, unicast QoS flow information.

7. The method according to claim 1 or 2, wherein, The method further comprises: The target base station receives a third message sent by a core network element, where the third message includes the context of a multicast session and the context of a unicast session.

8. The method according to claim 7, wherein The method further comprises: If the target base station supports the multicast session and accepts the multicast session, the target base station sends a first indication message to the core network element, where the first indication message is used to instruct the target base station to accept the multicast session and reject the unicast session.

9. The method according to claim 7, wherein The method further comprises: If the target base station does not support the multicast session or does not accept the multicast session, the target base station sends a second indication message to the core network element, where the second indication message is used to instruct the target base station not to support the multicast session or not to accept the multicast session.

10. The method according to claim 9, wherein The method further comprises: The target base station stores the context of the multicast session; or, The target base station deletes the context of the multicast session.

11. The method according to claim 7, wherein The method further comprises: The target base station stores the context of the multicast session and the context of the unicast session; If the target base station uses the context of the multicast session, the target base station sends third indication information to the core network element, where the third indication information is used to indicate that the target base station uses the context of the multicast session; or, If the target base station uses the context of the unicast session, the target base station sends fourth indication information to the core network element, where the fourth indication information is used to indicate that the target base station uses the context of the unicast session.

12. The method according to any one of claims 1 to 11, wherein Before the target base station receives the handover confirmation message sent by the terminal device, the method further includes: The target base station receives the multicast QoS flow from the service server forwarded by the source base station, where the multicast QoS flow contains data of the first service; If the target base station does not support the multicast QoS flow, the target base station discards or rejects the multicast QoS flow, or the target base station converts the multicast QoS flow into a unicast QoS flow and sends it to the terminal device.

13. The method according to any one of claims 1 to 11, wherein Before the target base station receives the handover confirmation message sent by the terminal device, the method further includes: The target base station receives the unicast QoS flow sent by the source base station, where the unicast QoS flow contains data of the first service; wherein, the unicast QoS flow is obtained by the core network element converting the multicast QoS flow from the service server.

14. The method according to any one of claims 1 to 11, wherein, Before the target base station receives the handover confirmation message sent by the terminal device, the method further includes: The target base station receives the unicast QoS flow sent by the source base station, where the unicast QoS flow contains data of the first service; wherein, the unicast QoS flow is obtained by the source base station converting the multicast QoS flow from the service server.

15. The method according to any one of claims 1 to 14, wherein The method further includes: The target base station receives the first data stream from the service server forwarded by the source base station, and receives the second data stream sent by the service server through the multicast tunnel; the data packets in the first data stream carry a first sequence number SN, and the data packets in the second data stream carry a second SN; wherein, the first data stream and the second data stream belong to the data streams of the first service; If the first SN is less than the second SN, the target base station schedules a third data stream for the terminal device through a unicast tunnel, where the third data stream carries a third SN; the rate of the third data stream is greater than the rate of the first data stream; When the third SN is equal to the second SN, the target base station schedules the second data stream for the terminal device through the multicast tunnel.

16. The method according to any one of claims 1 to 14, wherein, The method further includes: The target base station receives the first data stream from the service server forwarded by the source base station, and receives the second data stream sent by the service server through the multicast tunnel; the data packets in the first data stream carry a first SN, and the data packets in the second data stream carry a second SN; wherein, the first data stream and the second data stream belong to the data streams of the first service; If the first SN is greater than the second SN, the target base station performs duplicate detection on the first data stream and the second data stream through a Packet Data Convergence Protocol (PDCP) entity to generate a third data stream; the target base station schedules the third data stream for the terminal device through a multicast tunnel.

17. A data transmission method, the method comprising: A terminal device receives data of a first service sent by a source base station in a multicast manner. After the terminal device switches from the source base station to a target base station, the terminal device sends a handover confirmation message to the target base station and receives the data of the first service sent by the target base station in a multicast manner or a unicast manner.

18. The method according to claim 17, wherein, The data of the first service is sent through a multicast session on the source base station side, and the data of the first service is sent through a multicast session or a unicast session on the target base station side.

19. A data transmission device, applied to a target base station, the device comprising: A receiving unit, configured to receive a handover confirmation message sent by a terminal device; The handover confirmation message is used to indicate that the terminal device confirms switching from a source base station to the target base station; A sending unit, configured to send data of a first service to the terminal device; wherein, the data of the first service is sent in a multicast manner on the source base station side, and the data of the first service is sent in a multicast manner or a unicast manner on the target base station side.

20. A data transmission device, applied to a terminal device, the device comprising: A receiving unit, configured to receive data of a first service sent by a source base station in a multicast manner; A sending unit, configured to send a handover confirmation message to the target base station after switching from the source base station to the target base station; The receiving unit is further configured to receive the data of the first service sent by the target base station in a multicast manner or a unicast manner.

21. A network device, comprising: A processor and a memory, the memory is configured to store a computer program, and the processor is configured to call and run the computer program stored in the memory to execute the method according to any one of claims 1 to 16.

22. A terminal device, comprising: A processor and a memory, the memory is configured to store a computer program, and the processor is configured to call and run the computer program stored in the memory to execute the method according to any one of claims 17 to 18.

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