Communication method and communication apparatus

Abstract

This application provides a communication method and a communications apparatus. According to the communication method and the communications apparatus, in a process in which an access network device serving a trminal is handed over from a source access network device to a target access network device, a user plane function network element may transmit first information to the source access network device. The first information is used to indicate that the user plane fuction network element bicasts downlink packets to the sorce access network device and the target access network device, so that after determining that a data packet received before the first information is set to the terminal, the source access network device triggers an air interface handover, to avoid a packet loss in a handover process, or so that the source access network device synchronizes a PDCP SN of the source access network device with a PDCP SN of the target access network device.

Description

Communication methods and communication devices

[0001] This application claims priority to Chinese Patent Application No. 201810660940.1, filed on June 25, 2018, entitled "Communication Method and Communication Apparatus", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of communications, and more specifically, to communication methods and communication apparatus. Background Technology

[0003] In communication networks, in some scenarios, such as when the communication quality between the radio access network (RAN) currently serving the user equipment (UE) and the UE is poor, it is necessary to switch the UE to another RAN device. The RAN device before the switch can be called the source radio access network (S-RAN) device, and the RAN device after the switch can be called the target radio access network (T-RAN) device.

[0004] Based on the latency requirements of communication networks for downlink data packets, such as the 5G... th In ultra-reliable and low-latency communications (URLLC) scenarios of 5G communication systems, it is necessary to reduce the latency of downlink data packets during the handover process of RAN equipment.

[0005] One proposed method for reducing downlink data packet latency during RAN device handover involves: establishing a path between the T-RAN device and the user plane function (UPF) network element before the RAN device handover, and having the UPF network element simultaneously dual-cast downlink data to both the S-RAN and T-RAN devices. This way, during the handover execution phase, the S-RAN device does not need to forward the UE's downlink data packets to the T-RAN device, thereby reducing downlink data packet transmission latency.

[0006] This method may result in packet loss because when the S-RAN device triggers a UE air interface handover, the downlink packets before the UPF network element starts bicasting are not sent to the UE.

[0007] Summary of the Invention

[0008] This application provides a communication method and a communication device that can help avoid packet loss during UE air interface handover triggered by S-RAN equipment, or help achieve synchronization of PDCP SN between S-RAN and T-RAN.

[0009] In a first aspect, this application provides a communication method, which includes: during the process of a service terminal's access network device switching from a source access network device to a target access network device, a user plane function network element determines to dual-cast downlink messages to both the source and target access network devices; the user plane function network element sends first information to the source access network device, the first information being used to instruct the user plane function network element to dual-cast downlink messages to both the source and target access network devices.

[0010] In this communication method, when the user plane function network element determines to dual-cast downlink packets to the source access network device and the target access network device, it sends a first message to the source access network device to instruct the user plane function network element to dual-cast downlink packets to both the source access network device and the target access network device. This allows the source access network device to trigger UE air interface handover after sending downlink packets received before sending the first message to the UE, thus avoiding packet loss during the handover process due to the S-RAN device no longer forwarding the UE's downlink data packets to the T-RAN device.

[0011] In addition, when the user plane function element determines to dual-cast downlink packets to the source access network device and the target access network device, it sends a first message to the source access network device to instruct the user plane function element to dual-cast downlink packets to both the source access network device and the target access network device. This also allows the source access network device to indicate the PDCP SN of the downlink packet to the target access network device based on the first message, thereby achieving synchronization of the PDCP SN between S-RAN and T-RAN.

[0012] In conjunction with the first aspect, in a first possible implementation, the user plane function network element sends first information to the source access network device, including:

[0013] User plane function network elements dual-cast downlink messages to source access network devices and target access network devices, wherein the downlink message dual-cast by user plane function network elements to source access network devices includes first information.

[0014] In this implementation, carrying the first information in the downlink message of the bicast helps to reduce the complexity of communication between the user plane function network element and the source access network device compared with carrying the first information in a new message or message. It also does not add extra messages between the user plane function network element and the source access device, thus helping to reduce message transmission latency.

[0015] In conjunction with the first possible implementation, in the second possible implementation, the first information is carried in the first N downlink packets of the user plane function network element dual-casting to the source access network device, where N is a positive integer.

[0016] When N is greater than 1, this implementation method can improve the reliability of the source access network device receiving the first information.

[0017] In conjunction with the first aspect, in the third possible implementation, the communication method further includes:

[0018] After sending the first information, the user plane function network element dual-casts downlink messages to both the source access network device and the target access network device.

[0019] Secondly, this application provides a communication method, which includes:

[0020] During the process of the service terminal's access network equipment switching from the source access network equipment to the target access network equipment.

[0021] The source access network device receives first information from the user plane function network element, the first information being used to instruct the user plane function network element to duocast downlink packets to the source access network device and the target access network device;

[0022] The source access network device sends second information to the target access network device, the second information being used to determine the packet data aggregation protocol sequence number of the downlink data in the downlink message.

[0023] The source access network device indicates the second information of the PDCP SN of the downlink message to the target access network device based on the first information, thereby enabling the synchronization of the PDCP SN between S-RAN and T-RAN.

[0024] In conjunction with the second aspect, in the first possible implementation, the communication method further includes:

[0025] After sending the data packets received before the first information to the terminal, the source access network device triggers an air interface handover.

[0026] In conjunction with the first possible implementation, in the second possible implementation, the source access network device triggering air interface handover includes:

[0027] The source access network device sends a handover command message to the terminal; or

[0028] The source access network equipment stops sending downlink data to the terminal.

[0029] In a third possible implementation, combining the second aspect or the first or second possible implementation, the source access network device receives first information from the user plane function network element, including:

[0030] The source access network device receives downlink messages bicast from the user plane function network element to both the source access network device and the target access network device. The downlink messages bicast from the user plane function network element to the source access network device include first information.

[0031] In conjunction with the third possible implementation, in the fourth possible implementation, the first information is carried in the first N downlink packets of the user plane function network element dual-casting to the source access network device, where N is a positive integer.

[0032] In conjunction with the second aspect, or the first or second possible implementation, in the fifth possible implementation, the communication method further includes:

[0033] After receiving the first information, the source access network device receives downlink messages bicast from the user plane function network element to both the source access network device and the target access network device.

[0034] In a sixth possible implementation, combining the second aspect or any of the first to fifth possible implementations, the communication method further includes:

[0035] After receiving a handover command from an access and mobility management function (AM) network element, or after sending a handover request message to an AM network element, the source access network device begins to detect whether it has received the first information.

[0036] Thirdly, this application provides a communication method, which includes:

[0037] During the process of the service terminal's access network equipment switching from the source access network equipment to the target access network equipment.

[0038] The source access network device receives first information from the user plane function network element. The first information is used to instruct the user plane function network element to dual-cast downlink packets to the source access network device and the target access network device.

[0039] After sending the data packets received before the first information to the terminal, the source access network device triggers an air interface handover.

[0040] In this communication method, the source access network device receives first information from the user plane function indicating that the user plane function network element should bicast downlink messages to both the source access network device and the target access network device. Based on the first information, the device can send the downlink messages received before the first information to the UE and trigger the UE air interface handover. This ensures that the source access network device has sent the messages before the bicast started to the terminal device before the terminal device switches to the target access network device, thus avoiding packet loss during the handover process caused by the S-RAN device no longer forwarding the UE's downlink data packets to the T-RAN device.

[0041] In conjunction with the third aspect, in the first possible implementation, the source access network device triggering air interface handover includes:

[0042] The source access network device sends a handover command message to the terminal; or

[0043] The source access network equipment stops sending downlink data to the terminal.

[0044] In conjunction with the third aspect or the first possible implementation, in the second possible implementation, the source access network device receives first information from the user plane function network element, including:

[0045] The source access network device receives downlink messages bicast from the user plane function network element to both the source access network device and the target access network device. The downlink messages bicast from the user plane function network element to the source access network device include first information.

[0046] In this implementation, the first information is carried in the downlink message of the dual-cast, which does not add additional messages for interaction between the user plane function network element and the source access device, thus helping to reduce message transmission latency.

[0047] In combination with the second possible implementation, in the third possible implementation, the first information is carried in the first N downlink packets of the user plane function network element to the source access network device, where N is a positive integer.

[0048] When N is greater than 1, this implementation method can improve the reliability of the source access network device receiving the first information.

[0049] In conjunction with the third aspect or the first possible implementation, in the fourth possible implementation, the communication method further includes:

[0050] After receiving the first information, the source access network device receives downlink messages bicast from the user plane function network element to both the source access network device and the target access network device.

[0051] In conjunction with the third aspect or any of the above possible implementations, in the fifth possible implementation, the communication method further includes:

[0052] After receiving the first information from the user plane function network element, the source access network device sends the second information to the target access network device. The second information is used to determine the packet data aggregation protocol sequence number of the downlink data in the downlink message.

[0053] In conjunction with the third aspect or any of the above possible implementations, in the sixth possible implementation, the communication method further includes:

[0054] After receiving a handover command from an access and mobility management function (AM) network element, or after sending a handover request message to an AM network element, the source access network device begins to detect whether it has received the first information.

[0055] Fourthly, this application provides a communication method, which includes:

[0056] During the process of the service terminal's access network equipment switching from the source access network equipment to the target access network equipment.

[0057] The target access network device receives downlink packets from the user plane function network element, which are then bicast to both the source and target access network devices.

[0058] The target access network device receives the second information from the source access network device. The second information is used to determine the packet data aggregation protocol sequence number of the downlink data in the downlink message.

[0059] The target access network device generates a packet data aggregation protocol message based on the second information and the downlink message.

[0060] In this communication method, the target access network device can receive the PDCP SN from the source access network device and generate a PDCP message based on the PDCP SN.

[0061] In one possible implementation, the communication method further includes: the target access network device buffering downlink packets before receiving the second information.

[0062] Fifthly, a communication device is provided, comprising a module for performing the communication method in the first aspect or any possible implementation thereof.

[0063] In a sixth aspect, a communication device is provided, comprising a module for performing the communication method in the second aspect or any possible implementation thereof.

[0064] In a seventh aspect, a communication device is provided, the communication device including a module for performing the communication method in the third aspect or any possible implementation of the third aspect.

[0065] Eighthly, a communication device is provided, the communication device including a module for performing the communication method in the fourth aspect or any possible implementation of the fourth aspect.

[0066] A ninth aspect provides a communication device comprising a processor and a transmitter, the processor being configured to execute a program, wherein when the processor executes the program, the processor and the transmitter implement the communication method of the first aspect or any possible implementation thereof.

[0067] Optionally, the communication device may also include a memory. The memory is used to store programs executed by the processor.

[0068] Optionally, the communication device may also include a receiver. The receiver is used to receive information from other devices or apparatuses.

[0069] One example of this communication device is a user plane function network element.

[0070] In a tenth aspect, a communication device is provided, comprising a processor, a transmitter, and a receiver, wherein the processor is configured to execute a program, and when the processor executes the program, the processor, the transmitter, and the receiver implement the communication method of the second aspect or any possible implementation thereof.

[0071] Optionally, the communication device may also include a memory. The memory is used to store programs executed by the processor.

[0072] One example of this communication device is an access network device.

[0073] Eleventhly, a communication device is provided, comprising a processor and a receiver, the processor being configured to execute a program, wherein when the processor executes the program, the processor and the receiver implement the communication method of the third aspect or any possible implementation thereof.

[0074] Optionally, the communication device may also include a memory. The memory is used to store programs executed by the processor.

[0075] Optionally, the communication device may also include a transmitter. The transmitter is used to send information to other devices or apparatuses.

[0076] One example of this communication device is an access network device.

[0077] In a twelfth aspect, a communication device is provided, comprising a processor and a receiver, the processor being configured to execute a program, wherein when the processor executes the program, the processor and the receiver implement the communication method of the fourth aspect or any possible implementation thereof.

[0078] Optionally, the communication device may also include a memory. The memory is used to store programs executed by the processor.

[0079] Optionally, the communication device may also include a transmitter. The transmitter is used to send information to other devices or apparatuses.

[0080] One example of this communication device is an access network device.

[0081] In a thirteenth aspect, a computer-readable storage medium is provided that stores program code for execution by a communication device or communication apparatus, the program code including instructions for implementing the communication method in the first aspect or any possible implementation thereof.

[0082] In a fourteenth aspect, a computer-readable storage medium is provided that stores program code for execution by a communication device or communication apparatus, the program code including instructions for implementing the communication method in the second aspect or any possible implementation thereof.

[0083] In a fifteenth aspect, a computer-readable storage medium is provided that stores program code for execution by a communication device or communication apparatus, the program code including instructions for implementing the communication method in the third aspect or any possible implementation thereof.

[0084] In a sixteenth aspect, a computer-readable storage medium is provided that stores program code for execution by a communication device or communication apparatus, the program code including instructions for implementing the communication method in the fourth aspect or any possible implementation of the fourth aspect.

[0085] In a seventeenth aspect, a chip is provided, the chip including a processor and a communication interface for communicating with an external device, the processor for implementing the communication method in the first aspect or any possible implementation of the first aspect.

[0086] Optionally, the chip may further include a memory storing instructions, which the processor executes. When the instructions are executed, the processor implements the communication method in the first aspect or any possible implementation of the first aspect.

[0087] Optionally, the chip can be integrated into a user plane function network element.

[0088] Eighteenth aspect, a chip is provided, the chip including a processor and a communication interface for communicating with an external device, the processor for implementing the communication method in the second aspect or any possible implementation of the second aspect.

[0089] Optionally, the chip may also include a memory storing instructions, which the processor executes. When the instructions are executed, the processor implements the communication method in the second aspect or any possible implementation of the second aspect.

[0090] Optionally, the chip can be integrated into access network equipment.

[0091] In a nineteenth aspect, a chip is provided, the chip including a processor and a communication interface for communicating with an external device, the processor for implementing the communication method in the third aspect or any possible implementation of the third aspect.

[0092] Optionally, the chip may also include a memory storing instructions, which the processor executes. When the instructions are executed, the processor implements the communication method in the third aspect or any possible implementation of the third aspect.

[0093] Optionally, the chip can be integrated into access network equipment.

[0094] In a twentieth aspect, a chip is provided, the chip including a processor and a communication interface for communicating with an external device, the processor for implementing the communication method in the fourth aspect or any possible implementation of the fourth aspect.

[0095] Optionally, the chip may also include a memory storing instructions, which the processor executes. When the instructions are executed, the processor implements the communication method in the third aspect or any possible implementation of the third aspect.

[0096] Optionally, the chip can be integrated into access network equipment. Attached Figure Description

[0097] Figure 1 is a schematic diagram of an application scenario for which the method of indicative service diversion can be applied according to the embodiments of this application;

[0098] Figure 2 is a schematic flowchart of a communication method according to an embodiment of this application;

[0099] Figure 3 is a schematic flowchart of a communication method according to another embodiment of this application;

[0100] Figure 4 is a schematic flowchart of a communication method according to another embodiment of this application;

[0101] Figure 5 is a schematic flowchart of a communication method according to another embodiment of this application;

[0102] Figure 6 is a schematic flowchart of a communication method according to another embodiment of this application;

[0103] Figure 7 is a schematic flowchart of a communication method according to another embodiment of this application;

[0104] Figure 8 is a schematic structural diagram of a communication device according to an embodiment of this application;

[0105] Figure 9 is a schematic structural diagram of a communication device according to another embodiment of this application;

[0106] Figure 10 is a schematic structural diagram of a communication device according to another embodiment of this application;

[0107] Figure 11 is a schematic structural diagram of a communication device according to another embodiment of this application;

[0108] Figure 12 is a schematic structural diagram of a communication device according to another embodiment of this application. Detailed Implementation

[0109] The technical solutions in this application will now be described with reference to the accompanying drawings.

[0110] As shown in Figure 1, the application scenarios in which the method of indicative service offloading can be applied according to the embodiments of this application may include UE 101, RAN device 102, RAN device 103, UPF network element 104, access and mobility management function (AMF) network element 105, and session management function (SMF) network element 106.

[0111] A UE can also be called a terminal device. A terminal device can communicate with one or more core networks (CNs) via RAN equipment. Terminal devices can be referred to as access terminals, terminals, user units, user stations, mobile stations, mobile stations, remote stations, remote terminals, mobile devices, user terminals, wireless network equipment, user agents, or user devices. Terminals can be cellular phones, cordless phones, session initiation protocol (SIP) phones, wireless local loop (WLL) stations, personal digital assistants (PDAs), handheld devices with wireless communication capabilities, computing devices or other devices connected to a wireless modem, in-vehicle equipment, wearable devices or IoT devices, terminal devices in vehicular networks, and any form of terminal device in future networks.

[0112] An example of RAN equipment is a base station (BS). A base station, also known as a base station device, is a device that connects terminals to a wireless network, including but not limited to: a transmission reception point (TRP), a 5G node B (gNB), an evolved node B (eNB), a radio network controller (RNC), a node B (NB), a base station controller (BSC), a base transceiver station (BTS), a home base station (e.g., a home evolved node B, or a home node B, HNB), a base band unit (BBU), a Wi-Fi access point (AP), or a small cell device (pico), etc.

[0113] It should be understood that this document does not limit the specific type of base station. In systems employing different wireless access technologies, the names of devices with base station functionality may differ. For ease of description, in all embodiments of this application, the aforementioned devices providing wireless communication functionality to terminals are collectively referred to as base stations.

[0114] UPF network elements have functions such as message forwarding, encapsulation, and statistics for terminal devices.

[0115] AMF network elements are responsible for the access and mobility management of terminal devices. For example, they are responsible for UE location updates, UE network registration, and UE handover.

[0116] SMF network elements are responsible for the selection and reselection of UPF network elements, the allocation of Internet Protocol (IP) addresses, and the establishment, modification, and release of sessions.

[0117] It should be understood that the embodiments of this application are not limited to the system architecture shown in FIG1. ​​For example, a communication system in which the communication method of the embodiments of this application can be applied may include more or fewer network elements or devices. The devices or network elements in FIG1 may be hardware, or software divided functionally, or a combination of both. The devices or network elements in FIG1 can communicate with each other through other devices or network elements.

[0118] In the communication system shown in Figure 1, UE 101 is currently communicating with UPF network element 104 through RAN device 102, that is, transmitting uplink and downlink data packets.

[0119] In some scenarios, it is necessary to switch UE 101 from RAN device 102 to RAN device 103. For example, RAN device 102 can determine to switch UE 101 to RAN device 103 based on the measurement report reported by UE 101. That is, UE 101 will communicate with UPF network element 104 or other UPF network elements through RAN device 103. Here, RAN device 102 can be called S-RAN device, i.e., source access network device; RAN device 103 can be called T-RAN device, i.e., target access network device.

[0120] Once it is determined that UE 101 needs to be switched from RAN device 102 to RAN device 103, RAN device 102 can interact with RAN device 103 so that RAN device 103 can confirm the packet data unit (PDU) session that is allowed to be switched and the quality of service (QoS) flow contained in the PDU session.

[0121] In addition, RAN device 102 provides information about RAN device 103 to AMF network element 105. This information may include the identity (ID) of RAN device 103 and N3 tunnel information, which is used to establish a data transmission tunnel between the UPF network element and RAN device 103. After obtaining the N3 tunnel information of RAN device 103, the UPF can send downlink messages to RAN device 103 based on this tunnel information.

[0122] AMF network element 105 provides information from RAN device 103 to SMF network element 106. Then, SMF network element 106, based on the information from RAN device 103, sends instruction information or forwarding rules to UPF network element 104 (or other UPF network elements). This instruction information or forwarding rules instructs UPF network element 104 to process and forward uplink and / or downlink data packets. In this embodiment, the SMF network element may instruct UPF network element 104, upon receiving the instruction information or forwarding rules, to begin dual-casting downlink packets to RAN devices 102 and 103.

[0123] AMF network element 105 not only provides SMF network element 106 with information about RAN device 103, but also sends a handover command to RAN device 102, triggering RAN device to perform air interface handover.

[0124] A schematic flowchart of a communication method according to an embodiment of this application is shown in FIG2. The method shown in FIG2 may include S201, S202 and S203.

[0125] It should be understood that Figure 2 illustrates the steps or operations of the method, but these steps or operations are merely examples. Other operations or variations of the operations shown in Figure 2 may also be performed in the embodiments of this application. Furthermore, the steps in Figure 2 may be performed in a different order than those presented in Figure 2, and it is not necessary to perform all the operations shown in Figure 2.

[0126] S201, during the process of the access network device of the serving terminal switching from the source access network device to the target access network device, the user plane function network element determines to dual-cast downlink messages to both the source access network device and the target access network device.

[0127] For example, when a session management function network element sends an instruction or forwarding rule to a user plane function network element, the user plane function network element can determine that it needs to dual-cast downlink packets to both the source access network device and the target access network device after receiving the instruction or forwarding rule.

[0128] The bicasting of downlink messages from a user plane function network element to both the source access network device and the target access network device can be understood as the user plane function network element simultaneously sending downlink messages received from the data network (DN) to both the source access network device and the target access network device.

[0129] For example, the user plane function network element will encapsulate the downlink packets received from the DN and send them to the source access network device and the target access network device.

[0130] For example, the user plane function network element generates a first downlink message and a second downlink message based on the downlink message, sends the first downlink message to the source access network device, and sends the second downlink message to the target access network device.

[0131] For example, a user plane function network element can add different General Packet Radio Service (GPRS) Tunneling Protocol for the User Plane (GTP-U) headers to downlink packets received from the DN, generating a first downlink packet and a second downlink packet, which are then sent to the source access network device and the destination access network device, respectively.

[0132] The user plane function network element can be UPF network element 104, the terminal can be UE 101, the source access network device can be RAN device 102, and the target access network device can be RAN device 103.

[0133] S202, the user plane function network element sends first information to the source access network device, the first information being used to instruct the user plane function network element to dual-cast downlink messages to both the source access network device and the target access network device.

[0134] In other words, after a user plane function network element determines that it can dual-cast downlink packets to both the source access network device and the target access network device, it can send the first information to the source access network device indicating that the user plane function network element is dual-casting downlink packets to both the source access network device and the target access network device.

[0135] Optionally, when the user plane function network element sends the first information to the source access network device of the terminal, the user plane function network element may have already started dual-casting downlink packets to both the source access network device and the target access network device. Correspondingly, the source access network device and the target access network device receive the downlink packets from the user plane function network element.

[0136] In this implementation, the user plane function network element may carry the first information only in the downlink message sent to the source access network device (e.g., the first downlink message mentioned above), or it may carry the first information in both the downlink messages sent to the source access network device and the target access network device (e.g., the first and second downlink messages mentioned above).

[0137] For example, this first information can be carried in the first downlink message that the user plane function network element dual-casts to the source access network device.

[0138] In this implementation, to increase the reliability of the first information transmission, for example, to prevent the source access network device from not receiving the first downlink message of the user plane function network element's bicast, thus resulting in the failure to receive the first information, the user plane function network element can carry the first information in the first N downlink messages sent to the source access network device for bicast.

[0139] In this implementation, user plane function network elements can set an identifier bit in the GTP-U header of the message to indicate the first information.

[0140] For example, a flag bit can be set in the GTP-U header of the second downlink message described in step S201 to indicate the first information.

[0141] For example, a specific flag bit in the GTP-U header can be set to "0" or "1" to instruct the user plane function network element to dual-cast downlink messages to the source access network device and the target access network device, where "0" or "1" is the first information.

[0142] Optionally, the user plane function network element may send first information to the source access network device of the terminal before it begins to dual-cast downlink packets to the source access network device and the target access network device. That is, after sending the first information, the user plane function network element begins to dual-cast downlink packets to the source access network device and the target access network device. Accordingly, the source access network device and the target access network device receive the downlink packets from the user plane function network element.

[0143] For example, a user plane function network element can send one or more first downlink messages carrying first information to the source access network device before the first downlink message of the duocast, to indicate that the duocast is about to start, and the messages sent thereafter are duocast messages.

[0144] S203: After sending the data packets received before the first information to the terminal, the source access network device triggers an air interface handover.

[0145] This air interface switching can refer to Uu interface switching.

[0146] The source access network device triggering an air interface handover may include: the source access network device sending a handover command message to the terminal, instructing the terminal device to begin the handover; and / or, the source access network device stopping sending downlink data to the terminal.

[0147] In this embodiment, a first message is sent from the user plane function network element to the source access network device of the terminal to indicate the start of dual-cast. After receiving the first message from the user plane function network element, the source access network device sends the data packets received before the first message to the terminal and then triggers an air interface handover. This ensures that the source access network device has sent the packets before the start of dual-cast to the terminal device before the terminal device switches to the target access network device, thus avoiding packet loss during the handover process.

[0148] A schematic flowchart of a communication method according to another embodiment of this application is shown in FIG3. The method shown in FIG3 may include S301, S302, S303 and S304.

[0149] It should be understood that Figure 3 illustrates the steps or operations of the method, but these steps or operations are merely examples. Other operations or variations of the operations shown in Figure 3 may also be performed in the embodiments of this application. Furthermore, the steps in Figure 3 may be performed in a different order than those presented in Figure 3, and it is not necessary to perform all the operations shown in Figure 3.

[0150] S301, during the process of the access network device of the serving terminal switching from the source access network device to the target access network device, the user plane function network element determines to dual-cast downlink messages to both the source access network device and the target access network device.

[0151] S302, the user plane function network element sends first information to the source access network device, the first information being used to instruct the user plane function network element to dual-cast downlink messages to both the source access network device and the target access network device.

[0152] Steps S301 and S302 can be referred to the descriptions of S201 and S202 in Figure 2, respectively, and will not be repeated here.

[0153] S303, the source access network device sends second information to the target access network device. This second information is used to determine the PDCP SN of the downlink data in the downlink message bicast by the user plane function network element to both the source and target access network devices. Accordingly, the target access network device receives the second information from the source access network device.

[0154] Alternatively, it can be said that the second information is used by the target access network device to determine the PDCP SN of the downlink data in the downlink message of the user plane function network element dual-cast.

[0155] In other words, after detecting the first information, the source access network device can send the second information to the target access network device, so that the target access network device can determine the PDCP SN of the downlink data in the downlink message received from the user plane function network element based on the second information. The downlink message is a downlink message bicast by the user plane function network element to both the source access network device and the target access network device.

[0156] In some possible implementations, the second information may be carried in a sequence number status transfer (SN status transfer) message sent by the source access network device to the target access network device; in some possible implementations, the second information may include the PDCP SN assigned by the source access network device to the first doublecast message; in some possible implementations, the second information may include the PDCP SN assigned by the source access network device to a message preceding the first doublecast message.

[0157] S304, the target access network device generates a PDCP message based on the second information received from the source access network device and the downlink message received from the user plane function network element. This downlink message includes a downlink message bicast from the user plane function network element to both the source and target access network devices.

[0158] For example, if the second information includes the PDCP SN assigned by the source access network device to the first duocast packet, the target access network device can assign that PDCP SN to the first duocast downlink packet received from the user plane function element. If the second information includes the PDCP SN assigned by the source access network device to a packet preceding the first duocast packet, the target access network device can increment that PDCP SN by 1 and assign it to the first duocast downlink packet received from the user plane function element.

[0159] In this embodiment, the user plane function network element sends first information to the source access network device of the terminal to indicate the start of dual broadcast, thereby enabling the source access network device to synchronize downlink PDCP sequence numbers to the target access network device. The target access network device can send PDCP packets encapsulated according to the sequence number to the terminal, so that the terminal can sort and deduplicate the received packets according to the sequence number in the received PDCP packets.

[0160] In the communication method shown in Figure 3, option S203 in Figure 2 may also be included. In the communication method shown in Figure 2, option S303 and / or S304 in Figure 3 may also be included.

[0161] In the communication method shown in Figure 2 or Figure 3, optionally, the source access network device may begin detecting the first information after receiving a handover command sent by the access and mobility management function (AMU) network element. The handover command indicates that the core network side of the source access network device has completed user plane establishment and update. Alternatively, it may begin detecting the first information after sending a handover request message to the AMU network element. The handover request message requests the core network side to begin user plane establishment and update. Detecting the first information means that the source access network device detects whether the downlink packets received from the user plane function network element include the first information.

[0162] The access and mobility management function network element can be AMF network element 105.

[0163] The following uses the following example: the access and mobility management network element is the AMF network element, the session management function network element is the SMF network element, the user plane function network element is the UFP network element, the source access network device is the S-RAN device, and the target access network device is the T-RAN device. When the UE switches from the S-RAN device to the T-RAN device, the S-RAN device and the T-RAN device exchange signaling messages through the Xn interface. The AMF network element and the SMF network element connected to the RAN device remain unchanged before and after the switch. Taking the first information carried in the GTP-U header of the downlink message of the UPF network element dual-cast as an example, and referring to Figure 4, we introduce a schematic flowchart of a communication method of an embodiment of this application.

[0164] The exchange of signaling messages between S-RAN and T-RAN devices via the Xn interface can refer to the direct exchange of signaling messages between S-RAN and T-RAN devices through their respective Xn interfaces.

[0165] It should be understood that Figure 4 illustrates the steps or operations of the method, but these steps or operations are merely examples. Other operations or variations of the operations shown in Figure 4 may also be performed in the embodiments of this application. Furthermore, the steps in Figure 4 may be performed in a different order than those presented in Figure 4, and it is not necessary to perform all the operations shown in Figure 4.

[0166] S401, after determining that the terminal device meets the handover conditions based on the measurement report received from the terminal device, the S-RAN device sends a handover request message to the T-RAN device.

[0167] S402 After receiving the handover request message, the T-RAN equipment performs admission control to determine the PDU session to be handed over and the QoS flows included in the session.

[0168] In step S403, the T-RAN device sends a Handover Request Acknowledge message to the S-RAN device. This message includes information about the T-RAN device, such as its N3 tunnel information. The message may also include the PDU session identifier accepting the handover and the QoS flow identifiers included in the session.

[0169] In step S404, the S-RAN device sends a Handover Required message to the AMF network element. This message includes information about the T-RAN device. For example, this information may include the T-RAN device's identity (ID) and N3 tunnel information. The message may also include the PDU session identifier accepting the handover and the QoS flow identifiers included in the session.

[0170] S405, the AMF network element sends a PDU session context update request (Nsmf_PDU Session_UpdateSMContextRequest) message to the SMF network element. The message includes the information of the T-RAN device obtained in step S404, as well as the PDU session identifier that can be switched and the QoS flow identifier included in the session.

[0171] In step S406, the SMF network element, based on the information included in the PDU session context update request message received from the AMF network element in step 405, determines that a duocast downlink packet needs to be executed. It then sends an instruction message or forwarding rule to the UPF network element based on the information from the T-RAN device, instructing the UPF to begin duocasting downlink packets to both the S-RAN and T-RAN. The instruction message or forwarding rule is carried in an N4 Session Modification Request message and sent to the UPF network element.

[0172] S407, the AMF network element sends a handover command to the S-RAN, indicating that the S-RAN core network side has completed the handover preparation.

[0173] S408, when the UPF network element receives the indication information or forwarding rules, it can determine to dual-cast downlink messages to the S-RAN and T-RAN devices, and dual-cast downlink messages to the S-RAN and T-RAN devices, wherein the downlink messages carry first information.

[0174] For example, a UPF network element may carry the first information only in the downlink messages sent to the S-RAN device, or it may carry the first information in the downlink messages sent to both the S-RAN device and the T-RAN device.

[0175] For example, this first information can be carried by setting a flag in the GTP-U header of the downlink message.

[0176] For example, a specific flag bit in the GTP-U header can be set to "0" or "1" to instruct the user plane function network element to dual-cast downlink messages to the source access network device and the target access network device, where "0" or "1" is the first information.

[0177] To increase reliability and prevent the S-RAN device from failing to receive the first duocast message and thus failing to complete the UPF network element's instruction to duocast, the UPF network element can carry this first information in the first few downlink duocast messages.

[0178] After receiving a duocast downlink message, the T-RAN device can cache the downlink message.

[0179] S409 After detecting the first information, the S-RAN device sends an SN Status Transfer message to the T-RAN device. This message carries the second information so that the T-RAN device can determine the PDCP SN that can be assigned to the first bicast message based on the second information.

[0180] S410: After receiving the second information from the S-RAN device, the T-RAN device uses the PDCP SN indicated by the second information to encapsulate the buffered downlink message and obtain the PDCP message.

[0181] S411: After the S-RAN device confirms that the data packets received before the first message have been sent to the UE, it triggers the UE to perform an air interface handover. The UE synchronizes with the T-RAN device and completes the RRC handover process, that is, the air interface connection with the S-RAN device is disconnected and an air interface connection is established with the T-RAN device. The T-RAN begins to receive uplink messages from the UE and sends downlink messages to the UE.

[0182] It should be understood that steps S407 and S408 have no sequential relationship; that is, S407 and S408 can be executed simultaneously, or S407 can be executed first, or S408 can be executed first. S411 is executed after S407 and S408 are completed. S411 and S409 have no sequential relationship.

[0183] S412, the T-RAN equipment sends an N2 path switch request to the AMF network element.

[0184] S413 After receiving the N2 path switching request from the T-RAN device, the AMF network element sends a PDU session context update request to the SMF network element, requesting the SMF network element to update the session context.

[0185] S414 After receiving the PDU session context update request from the AMF network element, the SMF network element sends an N4 session modification request to the UPF network element, instructing the UPF network element to stop bicasting downlink packets and only forward the UE's downlink packets to the T-RAN equipment.

[0186] The following uses the following example: the access and mobility management network element is the AMF network element, the session management function network element is the SMF network element, the user plane function network element is the UFP network element, the source access network device is the S-RAN device, and the target access network device is the T-RAN device. When the UE switches from the S-RAN device to the T-RAN device, the S-RAN device and the T-RAN device exchange signaling through the Xn interface. The AMF network element and the SMF network element remain unchanged before and after the switch. The first information is carried in the downlink message sent before the bicast message. Referring to Figure 5, a schematic flowchart of the communication method of an embodiment of this application is introduced.

[0187] The exchange of signaling messages between S-RAN and T-RAN devices via the Xn interface can refer to the direct exchange of signaling messages between S-RAN and T-RAN devices through their respective Xn interfaces.

[0188] It should be understood that Figure 5 illustrates the steps or operations of the method, but these steps or operations are merely examples. Other operations or variations of the operations shown in Figure 5 may also be performed in the embodiments of this application. Furthermore, the steps in Figure 5 may be performed in a different order than those presented in Figure 5, and it is not necessary to perform all the operations shown in Figure 5.

[0189] S501 to S507 can be referenced from S401 to S407, and will not be repeated here.

[0190] S508: When the UPF network element receives the indication information or forwarding rules, it can determine that it will send a bicast downlink message to the S-RAN and T-RAN devices. The UPF network element sends one or more first downlink messages carrying first information to the S-RAN device to indicate that the bicast has started and that the messages sent thereafter are bicast messages.

[0191] The first information can be carried in the first downlink message. For example, if the first downlink message is a GTP data packet, the first information can be set in a specific flag bit in the GTP-U header, such as setting the specific flag bit to "0" or "1". In this case, the first information in the specific flag bit can also be called an end marker. The end marker is used to indicate that duocast is about to start, and the subsequent messages sent are duocast messages. In addition to the specific flag bit, the GTP-U header of the first downlink data packet carrying the first indication information also carries the downlink GTP-U tunnel information of the session associated with the duocast message transmitted between the S-RAN and the UPF network element.

[0192] S509, the UPF network element dual-casts downlink messages to both S-RAN and T-RAN devices.

[0193] After receiving a duocast downlink message, the T-RAN device can cache the downlink message.

[0194] S510 to S515 can be referenced from S409 to S414, and will not be repeated here.

[0195] It should be understood that the communication method shown in Figure 4 or Figure 5 can also be applied to scenarios where one or both of the AMF and SMF network elements are changed. In this scenario, simply replace the changed AMF or SMF network element in Figure 4 or Figure 5 with the changed AMF or SMF network element, respectively.

[0196] The following describes a schematic flowchart of a communication method of an embodiment of this application, using the access and mobility management network element as the AMF network element, the session management function network element as the SMF network element, the user plane function network element as the UFP network element, the source access network device as the S-RAN device, and the target access network device as the T-RAN device. When the UE switches from the S-RAN device to the T-RAN device, the S-RAN device and the T-RAN device exchange signaling messages through the N2 interface. The AMF network element and the SMF network element connected to the RAN device remain unchanged before and after the switch. Taking the first information carried in the GTP-U header of the downlink message of the UPF network element dual-cast as an example, and referring to Figure 6, we will introduce a schematic flowchart of a communication method of an embodiment of this application.

[0197] The exchange of signaling messages between S-RAN and T-RAN devices via the N2 interface refers to the message exchange between the two devices being implemented through the N2 interface. For example, when an S-RAN device sends a message to a T-RAN device, the S-RAN device sends the message to the AMF network element via the N2 interface, and the AMF network element then sends the message to the T-RAN device via the N2 interface.

[0198] It should be understood that Figure 6 illustrates the steps or operations of the method, but these steps or operations are merely examples. Other operations or variations of the operations shown in Figure 6 may also be performed in the embodiments of this application. Furthermore, the steps in Figure 6 may be performed in a different order than those presented in Figure 6, and it is not necessary to perform all the operations shown in Figure 6.

[0199] S601, after determining that the terminal device meets the handover conditions based on the measurement report received from the terminal device, the S-RAN device sends a handover request (Handover Required) to the AMF network element. The handover request message includes information about the T-RAN device, such as the T-RAN device ID carried in the measurement report and the PDU session identifier requesting the handover.

[0200] S602, after receiving the handover request message, the AMF network element sends a PDU session context update request message to the SMF network element. The message includes information about the T-RAN device and the PDU session identifier for which the handover is requested.

[0201] S603, the SMF network element determines the acceptable PDU session based on the information included in the PDU session context update request message received from the AMF network element in step 602, and determines whether an intermediate UPF network element needs to be added based on the UPF selection criteria.

[0202] For ease of description, the embodiments of this application assume that no intermediate UPF network element needs to be added. It should be noted that the method of the embodiments of this application is also applicable to scenarios where an intermediate UPF network element needs to be added.

[0203] S604, the SMF network element sends a PDU session context update response message to the AMF network element, which includes the accepted PDU session identifier information.

[0204] S605, after the AMF network element receives the PDU session context update response message from the SMF network element, it sends a handover request message to the T-RAN device according to the T-RAN ID obtained in step 601. The request message includes the information received by the AMF network element from the SMF network element in step 504.

[0205] S606, the T-RAN device sends a Handover Request Acknowledge message to the AMF network element. The message includes the PDU session identifier accepted by the T-RAN network element, the QoS flow identifier included in the session, and the N3 tunnel information of the T-RAN device.

[0206] S607, the AMF network element sends a PDU session context update request message to the SMF network element. The message includes the N3 tunnel information of the T-RAN device, the PDU session identifier accepted by the T-RAN device for handover, and the QoS flow identifier included in the session.

[0207] In step S608, the SMF network element determines that a duocast downlink packet needs to be executed based on the information included in the PDU session context update request message received from the AMF network element in step 607. It then sends an instruction message or forwarding rule to the UPF network element based on the information from the T-RAN device, instructing the UPF to begin duocasting downlink packets to both the S-RAN and T-RAN. The instruction message or forwarding rule is carried in the N4 session modification request and sent to the UPF network element.

[0208] S609, the AMF network element sends a handover command to the S-RAN, indicating that the S-RAN core network side has completed the handover preparation.

[0209] S610, when the UPF network element receives the indication information or forwarding rules, it can determine to dual-cast downlink messages to the S-RAN and T-RAN devices, and dual-cast downlink messages to the S-RAN and T-RAN devices, wherein the downlink messages carry first information.

[0210] For example, a UPF network element may carry the first information only in the downlink messages sent to the S-RAN device, or it may carry the first information in the downlink messages sent to both the S-RAN device and the T-RAN device.

[0211] For example, this first information can be carried by setting a flag in the GTP-U header of the downlink message.

[0212] For example, a specific flag bit in the GTP-U header can be set to "0" or "1" to instruct the user plane function network element to dual-cast downlink messages to the source access network device and the target access network device, where "0" or "1" is the first information.

[0213] To increase reliability and prevent the S-RAN device from failing to receive the first duocast message and thus failing to complete the UPF network element's instruction to duocast, the UPF network element can carry this first information in the first few downlink duocast messages.

[0214] After receiving a duocast downlink message, the T-RAN device can cache the downlink message.

[0215] S611 After detecting the first information, the S-RAN device sends an SN status transmission message to the T-RAN device, which carries the second information so that the T-RAN device can determine the PDCP SN that can be assigned to the first bicast message based on the second information.

[0216] It should be noted that since the S-RAN and T-RAN devices interact through the N2 interface, the SN status transmission message is also forwarded through the AMF network element. That is, the S-RAN device sends the SN status transmission message to the AMF network element, and the AMF network element then sends it to the T-RAN device.

[0217] S612, after receiving the second information from the S-RAN device, the T-RAN device uses the PDCP SN indicated by the second information to encapsulate the buffered downlink message and obtain the PDCP message.

[0218] S613: After the S-RAN device confirms that the data packets received before the first message have been sent to the UE, it triggers the UE to perform an air interface handover. The UE synchronizes with the T-RAN device and completes the RRC handover process, that is, the air interface connection with the S-RAN device is disconnected and an air interface connection is established with the T-RAN device. The T-RAN begins to receive uplink messages from the UE and send downlink messages to the UE.

[0219] S614, the T-RAN equipment sends a handover notification message to the AMF.

[0220] S615 After receiving the handover notification message from the T-RAN device, the AMF device sends a PDU session context update request to the SMF device, requesting the SMF device to update the session context.

[0221] S616 After receiving the PDU session context update request from the AMF device, the SMF device sends an N4 session modification request to the UPF, instructing the UPF to stop bicasting downlink packets and only send the UE's downlink packets to the T-RAN device.

[0222] It should be understood that steps S609 and S610 have no sequential relationship; that is, S609 and S610 can be executed simultaneously, or S609 can be executed first, or S610 can be executed first. S613 is executed after S610 and S611 are completed. Steps S613 and S611 have no sequential relationship.

[0223] The following uses the access and mobility management network element as the AMF network element, the session management function network element as the SMF network element, the user plane function network element as the UFP network element, the source access network device as the S-RAN device, and the target access network device as the T-RAN device. When the UE switches from the S-RAN device to the T-RAN device, the S-RAN device and the T-RAN device exchange signaling messages through the N2 interface. The AMF network element and the SMF network element remain unchanged before and after the switch. The first information is carried in the downlink message sent before the bicast message. Taking Figure 7 as an example, a schematic flowchart of the communication method of an embodiment of this application is introduced.

[0224] The exchange of signaling messages between S-RAN and T-RAN devices via the N2 interface refers to the message exchange between the two devices being implemented through the N2 interface. For example, when an S-RAN device sends a message to a T-RAN device, the S-RAN device sends the message to the AMF network element via the N2 interface, and the AMF network element then sends the message to the T-RAN device via the N2 interface.

[0225] The first information can be carried in the first downlink message. For example, if the first downlink message is a GTP data packet, the first information can be set in a specific flag bit in the GTP-U header, such as setting the specific flag bit to "0" or "1". In this case, the first information in the specific flag bit can also be called an end marker. The end marker is used to indicate that duocast is about to start, and the subsequent messages sent are duocast messages. In addition to the specific flag bit, the GTP-U header of the first downlink data packet carrying the first indication information also carries the downlink GTP-U tunnel information of the session associated with the duocast message transmitted between the S-RAN and the UPF network element.

[0226] It should be understood that Figure 7 illustrates the steps or operations of the method, but these steps or operations are merely examples. Other operations or variations of the operations shown in Figure 7 may also be performed in the embodiments of this application. Furthermore, the steps in Figure 7 may be performed in a different order than those presented in Figure 7, and it is not necessary to perform all the operations shown in Figure 7.

[0227] S701 to S709 can be referenced from S601 to S609, and will not be repeated here.

[0228] S710 to S711 can be referenced from S508 to S509, and will not be elaborated here.

[0229] S712 to S717 can be referenced from S611 to S616, and will not be repeated here.

[0230] It should be understood that the communication method shown in Figure 6 or Figure 7 can also be applied to scenarios where the AMF network element changes. In this scenario, it is only necessary to replace the message sent by the source access network device to the AMF network element in Figure 6 or Figure 7 with the message sent by the source access network device to the target AMF network element, i.e., the changed AMF network element. The message sent by the source access network device to the target AMF network element is forwarded through the source AMF network element.

[0231] It should be understood that in the communication methods shown in Figures 4 to 7, the UPF network element can refer to the anchor UPF, i.e., the PDU session anchor (PSA). The communication methods shown in Figures 4 to 7 are also applicable to situations where there is an intermediate UPF network element between the access network device and the anchor UPF network element. In this case, the intermediate UPF network element only sends uplink and downlink messages between the access network device and the anchor UPF network element.

[0232] Figure 8 is a schematic block diagram of a communication device 800 according to an embodiment of this application. It should be understood that the communication device 800 is only one example. The communication device of this application embodiment may also include other modules or units, or include modules with functions similar to the various modules in Figure 8, or may not be intended to include all the modules in Figure 8.

[0233] In some implementations, the communication device 800 may be a user plane function network element.

[0234] The processing module 810 is used to determine, during the process of the access network device of the serving terminal switching from the source access network device to the target access network device, a dual-cast downlink message to the source access network device and the target access network device.

[0235] The sending module 820 is used to send first information to the source access network device, the first information being used to instruct the user plane function network element to dual-cast downlink packets to the source access network device and the target access network device.

[0236] Optionally, the sending module is specifically used to: dual-cast downlink messages to the source access network device and the target access network device, wherein the downlink messages dual-cast by the user plane function network element to the source access network device include the first information.

[0237] Optionally, the first information is carried in the first N downlink messages that the communication device double-casts to the source access network device, where N is a positive integer.

[0238] Optionally, the sending module is specifically used to: after sending the first information, to dual-cast downlink messages to the source access network device and the target access network device.

[0239] The communication device 800 can be used to perform the steps executed by the user plane function network elements in the methods described in Figures 2 to 7, which will not be described in detail here for the sake of brevity.

[0240] Figure 9 is a schematic block diagram of a communication device 900 according to an embodiment of this application. It should be understood that the communication device shown in Figure 9 is only an example, and the communication device of this application embodiment may also include other modules or units, or include modules with functions similar to the various modules in Figure 9, or may not include all the modules in Figure 9.

[0241] In some implementations, the communication device 900 may be an access network device.

[0242] The receiving module 910 is used to receive first information from a user plane function network element during the process of the access network device of the serving terminal switching from a source access network device to a target access network device. The first information is used to instruct the user plane function network element to dual-cast downlink messages to the source access network device and the target access network device.

[0243] The sending module 920 is used to send second information to the target access network device after receiving the first information from the user plane function network element. The second information is used to determine the packet data aggregation protocol sequence number of the downlink data in the downlink message.

[0244] Optionally, the receiving module is specifically configured to: receive downlink packets bicast by the user plane function network element to the source access network device and the target access network device, wherein the downlink packets bicast by the user plane function network element to the source access network device include the first information.

[0245] Optionally, the first information is carried in the first N downlink packets that the user plane function network element dual-casts to the source access network device, where N is a positive integer.

[0246] Optionally, the receiving module is specifically configured to: after receiving the first information, receive downlink packets bicast by the user plane function network element to the source access network device and the target access network device.

[0247] Optionally, the communication device 900 further includes a switching module 930, which is used to trigger an air interface switch after sending the data packet received before the first information to the terminal.

[0248] Optionally, the switching module is specifically used to send a switching command message to the terminal; or specifically used to stop sending downlink data to the terminal.

[0249] Optionally, the communication device further includes a detection module 940, which is used to detect whether the first information has been received after receiving a handover command from the access and mobility management function network element or after sending a handover request message to the access and mobility management function network element.

[0250] The communication device 900 can be used to perform the steps in the methods described in Figures 2 to 7 that are executed by the source access network device, and for the sake of brevity, they will not be described in detail here.

[0251] Figure 10 is a schematic block diagram of a communication device 1000 according to an embodiment of this application. It should be understood that the communication device shown in Figure 10 is only an example, and the communication device according to an embodiment of this application may also include other modules or units, or include modules with functions similar to the various modules in Figure 10, or may not be intended to include all the modules in Figure 10.

[0252] In some implementations, the communication device 1000 may be an access network device.

[0253] The receiving module 1010 is used to receive first information from a user plane function network element during the process of the access network device of the serving terminal switching from a source access network device to a target access network device. The first information is used to instruct the user plane function network element to dual-cast downlink messages to the source access network device and the target access network device.

[0254] The switching module 1020 is used to trigger an air interface switch after sending the data packet received before the first information to the terminal.

[0255] Optionally, the switching module is specifically used to send a switching command message to the terminal; or specifically used to stop sending downlink data to the terminal.

[0256] Optionally, the receiving module is specifically configured to: receive downlink packets bicast by the user plane function network element to the source access network device and the target access network device, wherein the downlink packets bicast by the user plane function network element to the source access network device include the first information.

[0257] Optionally, the first information is carried in the first N downlink packets that the user plane function network element dual-casts to the source access network device, where N is a positive integer.

[0258] Optionally, the receiving module is specifically configured to: after receiving the first information, receive downlink packets bicast by the user plane function network element to the source access network device and the target access network device.

[0259] Optionally, the communication device 1000 further includes a detection module 1030, which is used to detect whether the first information has been received after receiving a handover command from the access and mobility management function network element or after sending a handover request message to the access and mobility management function network element.

[0260] Optionally, the communication device 1000 further includes a sending module 1040, used to send second information to the target access network device, the second information being used to determine the packet data aggregation protocol sequence number of the downlink data in the downlink message.

[0261] The communication device 1000 can be used to perform the steps executed by the source access network device in the methods described in Figures 2 to 7, which will not be described in detail here for the sake of brevity.

[0262] Figure 11 is a schematic block diagram of a communication device 1100 according to an embodiment of this application. It should be understood that the communication device shown in Figure 11 is only an example, and the communication device according to an embodiment of this application may also include other modules or units, or include modules with functions similar to the various modules in Figure 11, or may not include all the modules in Figure 11.

[0263] In some implementations, the communication device 1100 may be an access network device.

[0264] The receiving module 1110 is used to receive downlink packets bicast from the user plane function network element to the source access network device and the target access network device during the process of the access network device of the serving terminal switching from the source access network device to the target access network device.

[0265] The receiving module 1110 is further configured to receive second information from the source access network device, the second information being used to determine the packet data aggregation protocol sequence number of the downlink data in the downlink message;

[0266] The processing module 1120 is used to generate a packet data aggregation protocol message based on the second information and the downlink message.

[0267] Optionally, the communication device further includes a caching module 1130 for caching the downlink message before receiving the second information.

[0268] The communication device 1100 can be used to perform the steps executed by the target access network device in the methods described in Figures 2 to 7, which will not be described in detail here for the sake of brevity.

[0269] Figure 12 is a schematic structural diagram of a communication device according to another embodiment of this application. It should be understood that the communication device 1200 shown in Figure 12 is only an example, and the communication device of this application embodiment may also include other modules or units, or include modules with functions similar to the various modules in Figure 12.

[0270] The communication device 1200 may include one or more processors 1210, one or more memories 1220, a receiver 1230, and a transmitter 1240. The receiver 1230 and transmitter 1240 may be integrated together and referred to as a transceiver. The memory 1220 is used to store program code executed by the processor 1210. The processor 1210 may have the memory 1220 integrated within it, or the processor 1210 may be coupled to one or more memories 1220 for retrieving instructions from the memory 1220.

[0271] In one embodiment, processor 1210 can be used to implement the operations or steps that processing module 810 in FIG8 can implement, and transmitter 1240 can be used to implement the operations or steps that sending module 820 in FIG8 can implement.

[0272] In another embodiment, processor 1210 can be used to implement the operations or steps that the switching module 930 and detection module 940 in FIG9 can implement, receiver 1230 can be used to implement the operations or steps that the receiving module 910 in FIG9 can implement, and transmitter 1240 can be used to implement the operations or steps that the sending module 920 in FIG9 can implement.

[0273] In another embodiment, processor 1210 can be used to implement the operations or steps that switching module 1020 and detection module 1030 in FIG10 can implement, receiver 1230 can be used to implement the operations or steps that receiving module 1010 in FIG10 can implement, and transmitter 1240 can be used to implement the operations or steps that sending module 1040 in FIG10 can implement.

[0274] In another embodiment, processor 1210 can be used to implement the operations or steps that processing module 1120 in FIG11 can implement, receiver 1230 can be used to implement the operations or steps that receiving module 1110 in FIG11 can implement, and memory 1220 is used to store program code executed by processor 1210 and to implement the operations or steps that cache module 1130 in FIG11 can implement.

[0275] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0276] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0277] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0278] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0279] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0280] If the aforementioned functions are implemented as 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 portion of the 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 to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0281] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A communication method, characterized in that, include: During the process of the service terminal's access network equipment switching from the source access network equipment to the target access network equipment. The user plane function network element determines to dual-cast downlink packets to the source access network device and the target access network device; The user plane function network element sends first information to the source access network device, the first information being used to instruct the user plane function network element to dual-cast downlink packets to both the source access network device and the target access network device.

2. The communication method according to claim 1, characterized in that, The user plane function network element sends first information to the source access network device, including: The user plane function network element dual-casts downlink messages to both the source access network device and the target access network device. The downlink message dual-cast by the user plane function network element to the source access network device includes the first information.

3. The communication method according to claim 2, characterized in that, The first information is carried in the first N downlink packets that the user plane function network element dual-casts to the source access network device, where N is a positive integer.

4. The communication method according to claim 1, characterized in that, The communication method further includes: After sending the first information, the user plane function network element dual-casts downlink messages to the source access network device and the target access network device.

5. A communication method, characterized in that, include: During the process of the service terminal's access network equipment switching from the source access network equipment to the target access network equipment. The source access network device receives first information from the user plane function network element, the first information being used to instruct the user plane function network element to duocast downlink packets to the source access network device and the target access network device; The source access network device sends second information to the target access network device, the second information being used to determine the packet data aggregation protocol sequence number of the downlink data in the downlink message.

6. The communication method according to claim 5, characterized in that, The communication method further includes: After sending the data packets received before the first information to the terminal, the source access network device triggers an air interface handover.

7. The communication method according to claim 6, characterized in that, The source access network device triggering air interface handover includes: the source access network device sending a handover command message to the terminal; or the source access network device stopping sending downlink data to the terminal.

8. A communication method, characterized in that, include: During the process of the service terminal's access network equipment switching from the source access network equipment to the target access network equipment. The source access network device receives first information from the user plane function network element, the first information being used to instruct the user plane function network element to duocast downlink packets to the source access network device and the target access network device; After sending the data packets received before the first information to the terminal, the source access network device triggers an air interface handover.

9. The communication method according to claim 8, characterized in that, The source access network device triggering air interface handover includes: the source access network device sending a handover command message to the terminal; or the source access network device stopping sending downlink data to the terminal.

10. The communication method according to any one of claims 5 to 9, characterized in that, The source access network device receives first information from the user plane function network element, including: The source access network device receives downlink packets bicast by the user plane function network element to both the source access network device and the target access network device, wherein the downlink packets bicast by the user plane function network element to the source access network device include the first information.

11. The communication method according to claim 10, characterized in that, The first information is carried in the first N downlink packets that the user plane function network element dual-casts to the source access network device, where N is a positive integer.

12. The communication method according to any one of claims 5 to 9, characterized in that, The communication method further includes: After receiving the first information, the source access network device receives downlink packets bicast by the user plane function network element to both the source access network device and the target access network device.

13. The communication method according to any one of claims 5 to 12, characterized in that, The communication method further includes: After receiving a handover command from the access and mobility management function network element, or after sending a handover request message to the access and mobility management function network element, the source access network device begins to detect whether it has received the first information.

14. A communication method, characterized in that, include: During the process of the service terminal's access network equipment switching from the source access network equipment to the target access network equipment. The target access network device receives downlink packets from the user plane function network element, which are then bicast to both the source access network device and the target access network device. The target access network device receives second information from the source access network device, the second information being used to determine the packet data aggregation protocol sequence number of the downlink data in the downlink message; The target access network device generates a packet data aggregation protocol message based on the second information and the downlink message.

15. The communication method according to claim 14, characterized in that, The communication method further includes: Before receiving the second information, the target access network device caches the downlink message.

16. A communication device, characterized in that, include: The processing module is used to determine the dual-cast downlink message to the source access network device and the target access network device during the process of the access network device of the serving terminal switching from the source access network device to the target access network device; The sending module is used to send first information to the source access network device, the first information being used to instruct the user plane function network element to dual-cast downlink packets to the source access network device and the target access network device.

17. The communication device according to claim 16, characterized in that, The sending module is specifically used to: dual-cast downlink messages to the source access network device and the target access network device, wherein the downlink messages dual-cast by the user plane function network element to the source access network device include the first information.

18. The communication device according to claim 17, characterized in that, The first information is carried in the first N downlink messages that the communication device dual-casts to the source access network device, where N is a positive integer.

19. The communication device according to claim 16, characterized in that, The sending module is specifically used to: after sending the first information, to dual-cast downlink messages to the source access network device and the target access network device.

20. A communication device, characterized in that, include: The receiving module is used to receive first information from the user plane function network element during the process of the access network device of the serving terminal switching from the source access network device to the target access network device. The first information is used to instruct the user plane function network element to dual-cast downlink packets to the source access network device and the target access network device. The sending module is used to send second information to the target access network device, the second information being used to determine the packet data aggregation protocol sequence number of the downlink data in the downlink message.

21. The communication device according to claim 20, characterized in that, The communication device further includes a switching module, used to trigger an air interface switch after sending the data packets received before the first information to the terminal.

22. The communication device according to claim 21, characterized in that, The switching module is specifically used to send a switching command message to the terminal; or the switching module is specifically used to stop sending downlink data to the terminal.

23. A communication device, characterized in that, include: The receiving module is used to receive first information from the user plane function network element during the process of the access network device of the serving terminal switching from the source access network device to the target access network device. The first information is used to instruct the user plane function network element to dual-cast downlink packets to the source access network device and the target access network device. The switching module is used to trigger an air interface switch after sending the data packets received before the first information to the terminal.

24. The communication device according to claim 23, characterized in that, The switching module is specifically used to send a switching command message to the terminal; or specifically used to stop sending downlink data to the terminal.

25. The communication device according to any one of claims 20 to 24, characterized in that, The receiving module is specifically used to: receive downlink packets bicast by the user plane function network element to the source access network device and the target access network device, wherein the downlink packets bicast by the user plane function network element to the source access network device include the first information.

26. The communication device according to claim 25, characterized in that, The first information is carried in the first N downlink packets that the user plane function network element dual-casts to the source access network device, where N is a positive integer.

27. The communication device according to any one of claims 20 to 24, characterized in that, The receiving module is specifically used to: after receiving the first information, receive downlink packets bicast by the user plane function network element to the source access network device and the target access network device.

28. The communication device according to any one of claims 20 to 27, characterized in that, The communication device further includes a detection module, which is used to detect whether the first information has been received after receiving a handover command from the access and mobility management function network element or after sending a handover request message to the access and mobility management function network element.

29. A communication device, characterized in that, include: The receiving module is used to receive downlink packets bicast from the user plane function network element to the source access network device and the target access network device during the process of the access network device of the serving terminal switching from the source access network device to the target access network device. The receiving module is further configured to receive second information from the source access network device, the second information being used to determine the packet data aggregation protocol sequence number of the downlink data in the downlink message; The processing module is used to generate a packet data aggregation protocol message based on the second information and the downlink message.

30. The communication device according to claim 29, characterized in that, The communication device further includes a caching module for caching the downlink message before receiving the second information.

31. A computer-readable storage medium, characterized in that, The storage medium stores a program that, when executed, implements the communication method as described in any one of claims 1 to 15.

32. A communication device, characterized in that, include: Hardware associated with program instructions, said hardware being used to execute the communication method according to any one of claims 1 to 15.